2024-03-29T15:48:23Zhttps://vtechworks.lib.vt.edu/server/oai/requestoai:vtechworks.lib.vt.edu:10919/1034242021-05-22T07:21:37Zcom_10919_5534col_10919_9291
Harlos, Annellie Rae
Department of Biomedical Engineering and Mechanics
Rowson, Steven
Urban, Jillian
Duma, Stefan M.
2021-05-21T08:00:39Z
2021-05-21T08:00:39Z
2021-05-20
vt_gsexam:30343
http://hdl.handle.net/10919/103424
Cycling is an increasingly popular mode of transportation and a preferred form of exercise worldwide. From 1990 to 2015, commuting via bicycle increased as much as four-fold in cities across North America and Europe. However, this increase in cycling is associated with an increase in cycling related fatalities and head injuries. The best way to prevent severe head injury while cycling is to wear a bike helmet. Bike helmets are designed to decrease the linear acceleration of the head, decreasing the rider's risk of severe head injuries, such as skull fracture. In order to sell a bike helmet, it must meet a minimum standard of protection based on linear acceleration of the head upon impact. However, bike helmet impacts are not completely linear in nature and experience a tangential component through angled impacts of the helmet, resulting in rotational accelerations and shear-strain at the skull-brain interface. This strain cause brain injuries such as concussion. Therefore, recent helmet advancements have aimed to decrease rotational acceleration of the head. To continue the advancement of helmet technology and the subsequent decrease of brain injury risk to riders, investigating the impact conditions of real-world impacts is pertinent. This thesis aimed to increase the current body of knowledge of cycling related head impacts. The first aim was to quantify real-world impact locations and analyze how impact location may influence helmet performance. The second aim of this thesis was to investigate the impact velocities and resulting kinematics of real-world crashes based on the magnitude of corresponding damage conditions. Additionally, this aim analyzed the impact conditions from cases which resulted in concussion. Together these studies aim to provide valuable real-world data to be used for the advancement of helmet technologies and design.
Master of Science
Cycling is an increasingly popular mode of transportation and a preferred form of exercise worldwide. From 1990 to 2015, commuting via bicycle increased as much as four-fold in cities across North America and Europe. However, this increase in cycling is associated with an increase in cycling related fatalities and head injuries. The best way to prevent severe head injury while cycling is to wear a bike helmet. Bike helmets are designed to decrease the linear acceleration of the head, decreasing the rider's risk of severe head injuries, such as skull fracture. In order to sell a bike helmet, it must meet a minimum standard of protection based on linear acceleration of the head upon impact. However, bike helmet impacts are not completely linear in nature and experience a tangential component through angled impacts of the helmet, resulting in rotational accelerations and shear-strain at the skull-brain interface. This strain cause brain injuries such as concussion. Therefore, recent helmet advancements have aimed to decrease rotational acceleration of the head. To continue the advancement of helmet technology and the subsequent decrease of brain injury risk to riders, investigating the impact conditions of real-world impacts is pertinent. This thesis aimed to increase the current body of knowledge of cycling related head impacts. The first aim was to quantify real-world impact locations and analyze how impact location may influence helmet performance. The second aim of this thesis was to investigate the impact velocities and resulting kinematics of real-world crashes based on the magnitude of corresponding damage conditions. Additionally, this aim analyzed the impact conditions from cases which resulted in concussion. Together these studies aim to provide valuable real-world data to be used for the advancement of helmet technologies and design.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
injury biomechanics
concussion
bike helmet
kinematics
Quantifying the Characteristics of Real-World Bicycle Helmet Impacts
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Biomedical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/112362022-02-22T18:55:24Zcom_10919_5534col_10919_11041
Liu, Sixin
Crop and Soil Environmental Sciences
Wilkinson, Carol A.
Veilleux, Richard E.
Stromberg, Erik L.
Griffey, Carl A.
Saghai-Maroof, Mohammad A.
2011-08-22T19:04:14Z
2011-08-22T19:04:14Z
2000-05-02
1999-12-19
2001-01-05
2000-01-05
etd-121999-232244
http://hdl.handle.net/10919/11236
http://scholar.lib.vt.edu/theses/available/etd-121999-232244
Powdery mildew, caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici E'm. Marchal (syn. Erysiphe graminis f. sp. tritici), is one of the major diseases of wheat (Triticum aestivum L.) worldwide. The use of cultivars with resistance to powdery mildew is an efficient, economical and environmentally safe way to control powdery mildew. Race-specific resistance has been extensively used in breeding programs; however, it is ephemeral. Adult plant resistance (APR) to powdery mildew is more durable as demonstrated by the cultivar Massey, which has maintained its APR to powdery mildew since its release in 1981. To develop an efficient breeding strategy, it is essential to understand the genetic basis of APR. The objectives of this study were to identify molecular markers associated with APR to powdery mildew in common wheat Massey and to verify their association using recombinant inbred (RI) lines.
A cross was made between the powdery mildew susceptible cultivar Becker and Massey. One hundred and eighty F2:3 lines were rated for disease severity under natural pressure of powdery mildew in field. Using both restriction fragment length polymorphism (RFLP) and microsatellite markers, three quantitative trait loci (QTL), designated as QPm.vt-1B, QPm.vt-2A and QPm.vt-2B, were identified in the Becker x Massey F2:3 generation. These loci are located on chromosomes 1B, 2A and 2B, respectively, and explained 17%, 29% and 11% of the total variation among F2:3 lines for powdery mildew resistance, respectively. Cumulatively, the three QTLs explained 50% of the phenotypic variation among F2:3 lines in a multi-QTL model. The three QTLs associated with APR to powdery mildew were derived from Massey and displayed additive gene action. QPm.vt-2B also fits a recessive model for APR to powdery mildew.
In the second part of this study, 97 RI lines were developed from the Becker x Massey cross. The RI lines were evaluated for APR to powdery mildew under natural disease pressure for three years. Both single marker analysis and interval mapping confirmed the presence of the three QTLs identified in the F2:3 generation. The three QTLs, QPm.vt-1B, QPm.vt-2A and QPm.vt-2B, accounted for 15%, 26% and 15% of the variation of mean powdery mildew severity of the RI lines over three years. In a multi-QTL model, the three QTLs explained 44% of the phenotypic variation of the RI lines. The RI lines were grouped according to the genotype of the three QTLs, represented by markers GWM304a, KSUD22 and PSP3100, respectively. The RI lines with Massey alleles at all three loci had a mean disease severity of 3.4%, whereas the RI lines with Becker alleles at all three loci had a mean disease severity of 22.3%. These severity values are similar to those of the corresponding parents.
The molecular markers identified and verified as to their association with APR to powdery mildew in Massey have the potential for use in marker-assisted selection for resistance to powdery mildew and in pyramiding powdery mildew resistance genes, as well as facilitating a better understanding of the molecular basis of APR to powdery mildew.
Ph. D.
ETD
Virginia Tech
etd-powdery.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Blumeria graminis f. sp. tritici
Erysiphe graminis f. sp. tritici
wheat
RFLP
SSR
QTL
adult plant resistance
Molecular marker analysis of adult plant resistance to powdery mildew in common wheat
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Crop and Soil Environmental Sciencesopen.accessoai:vtechworks.lib.vt.edu:10919/910742020-09-25T20:33:37Zcom_10919_5534col_10919_9291
Ashayeri, Diane L.
Human Nutrition and Foods
2019-07-03T18:56:49Z
2019-07-03T18:56:49Z
1987
http://hdl.handle.net/10919/91074
This study investigated the effects of ionic strength, pH, gum concentration, and protein type on protein - xanthan gum interactions. Commercial soy sauce and tamari sauce as well as model systems of soy protein isolate and whey protein concentrate were the sources of protein used for evaluation with xanthan gum.
Preliminary research indicated that when either soy sauce or tamari sauce were mixed with xanthan gum, stable solutions with notable viscosity synergisms resulted. The soy protein and whey protein systems were subsequently prepared with a range of 0 to 5% added sodium chloride. Results indicated that an equilibrium existed between proteins and xanthan gum such that increased sodium chloride initially increased solution stability; but when in excess, the sodium chloride led to a loss of protein - xanthan gum solution solubility and in some cases to precipitation. Precipitation was also noted at the pH extremes of 2,3, and 9 and when xanthan gum was present in excess, or at 0.25%.
The effects of sodium chloride, protein type, and pH on the rheological parameters of model solutions were also examined. Higher sodium chloride levels yielded greater viscosity synergisms. Those solutions made.with intact protein were generally higher in apparent viscosity than similar solutions made with hydrolyzed protein. Solutions at pH 5 were generally higher in viscosity than were similar solutions at pH 7.
Several factors that appeared to affect the stability, solubility, and the rheological parameters of protein - xanthan gum solutions were sodium chloride concentration, gum concentration, pH, and protein type.
M.S.
xiii, 186 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 16365616
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1987.A79
Gel permeation chromatography
Proteins -- Research
Rheology
Soyfoods
Soy protein-xanthan gum interaction:stability and rheology
Thesis
Text
M.S.
masters
Virginia Polytechnic Institute and State University
Human Nutrition and Foodsopen.accessoai:vtechworks.lib.vt.edu:10919/1080872022-02-03T08:31:26Zcom_10919_5534col_10919_11041
Taheri Hosseinabadi, Sayedsina
Electrical Engineering
Kekatos, Vasileios
Bansal, Manish
Liu, Chen-Ching
Centeno, Virgilio A.
Saad, Walid
2022-02-02T09:01:37Z
2022-02-02T09:01:37Z
2022-02-01
vt_gsexam:33664
http://hdl.handle.net/10919/108087
With the integration of renewable and distributed energy resources (DER) and advances in metering infrastructure, power systems are undergoing rapid modernization that brings forward new challenges and possibilities, which call for more advanced learning, analysis, and planning tools. While there are numerous problems present in the modern power grid, in this work, this work has addressed four of the most prominent challenges and has shown that how the new advances in generation and metering can be leveraged to address the challenges that arose by them. With regards to learning in power systems, we first have tackled power distribution system topology identification, since knowing the topology of the power grid is a crucial piece in any meaningful optimization and control task. The topology identification presented in this work is based on the idea of emph{prob-to-learn}, which is perturbing the power grid with small power injections and using the metered response to learn the topology. By using maximum-likelihood estimation, we were able to formulate the topology identification problem as a mixed-integer linear program. We next have tackled the prominent challenge of finding optimal flexibility of aggregators in distribution systems, which is a crucial step in utilizing the capacity of distributed energy resources as well as flexible loads of the distribution systems and to aid transmission systems to be more efficient and reliable. We have shown that the aggregate flexibility of a group of devices with uncertainties and non-convex models can be captured with a quadratic classifier and using that classifier we can design a virtual battery model that best describes the aggregate flexibility. For power system analysis and planning, we have addressed fast probabilistic hosting capacity analysis (PHCA), which is studying how DERs and the intermittency that they bring to the power system can impact the power grid operation in the long term. We have shown that interconnection studies can be sped up by a factor of 20 without losing any accuracy. By formulating a penalized optimal power flow (OPF), we were able to pose PHCA as an instance of multiparametric programming (MPP), and then leveraged the nice properties of MPP to efficiently solve a large number of OPFs. Regarding planning in power systems, we have tackled the problem of strategic investment in energy markets, in which we have utilized the powerful toolbox of multiparametric programming to develop two algorithms for strategic investment. Our MPP-aided grid search algorithm is useful when the investor is only considering a few locations and our MPP-aided gradient descent algorithm is useful for investing in a large number of locations. We next have presented a data-driven approach in finding the flexibility of aggregators in power systems. Finding aggregate flexibility is an important step in utilizing the full potential of smart and controllable loads in the power grid and it's challenging since an aggregator controls a large group of time-coupled devices that operate with non-convex models and are subject to random externalities. We have shown that the aggregate flexibility can be accurately captured with an ellipsoid and then used Farkas' lemma to fit a maximal volume polytope inside the aforementioned ellipsoid. The numerical test showcases that we can capture 10 times the volume that conventional virtual generator models can capture.
Doctor of Philosophy
With the integration of renewable and distributed energy resources (DER) and advances in metering infrastructure, power systems are undergoing rapid modernization that brings forward new challenges and possibilities, which call for more advanced learning, analysis, and planning tools. While there are numerous problems present in the modern power grid, in this work, this work has addressed four of the most prominent challenges and has shown that how the new advances in generation and metering can be leveraged to address the challenges that arose by them. With regards to learning in power systems, we first have tackled power distribution system topology identification, since knowing the topology of the power grid is a crucial piece in any meaningful optimization and control task. We next have tackled the prominent challenge of finding optimal flexibility of aggregators in distribution systems, which is a crucial step in utilizing the capacity of distributed energy resources as well as flexible loads of the distribution systems and to aid transmission systems to be more efficient and reliable. For power system analysis and planning, we have addressed fast probabilistic hosting capacity analysis (PHCA), which is studying how DERs and the intermittency that they bring to the power system can impact the power grid operation in the long term. We have shown that interconnection studies can be sped up by a factor of 20 without losing any accuracy. Regarding planning in power systems, we have tackled the problem of strategic investment in energy markets, in which we have utilized the powerful toolbox of multiparametric programming to develop two algorithms for strategic investment. We next have presented a data-driven approach in finding the flexibility of aggregators in power systems. Finding aggregate flexibility is an important step in utilizing the full potential of smart and controllable loads in the power grid and it's challenging since an aggregator controls a large group of time-coupled devices that operate with non-convex models and are subject to random externalities.
ETD
en
Virginia Tech
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
http://creativecommons.org/licenses/by-nc-nd/4.0/
Topology Identification
Strategic Inestment
Probabalistic Hosting Capacity Analysis
Aggregate Flexibility
Fast and Scalable Power System Learning, Analysis, and Planning
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Electrical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/403912022-02-22T19:58:14Zcom_10919_5534col_10919_11041
Gunn, Reamous Jr.
Educational Leadership and Policy Studies
Curcio, Claire Cole Vaught
Parks, David J.
Carlton, Patrick W.
Salmon, Richard G.
Yakimowski-Srebnick, Mary E.
2014-03-14T21:23:19Z
2014-03-14T21:23:19Z
1999-09-14
1999-12-03
2000-07-11
1999-07-11
etd-120399-131826
http://hdl.handle.net/10919/40391
http://scholar.lib.vt.edu/theses/available/etd-120399-131826/
The purpose of this study was to determine the effects of conflict resolution training on the number and severity of discipline referral offenses committed by high school students in one urban school.
Effectiveness was measured by the number and severity of student discipline referrals to the school administration. Additionally, data were gathered and analyzed regarding student perceptions following application of conflict resolution training. The population (N=155) consisted of black and white students in grades nine through 12 who had previously received conflict-related discipline referrals. The samples (n=32) were selected using simple random sampling. Identified students were randomly assigned to one of two groups (treatment v. control). The treatment group received twelve hours of conflict resolution training. In addition, a four hour follow-up training session was conducted 60 days later. The control group did not receive training. Both quantitative and qualitative methodologies were used to determine the effects of conflict resolution training in this study. The independent variables were conflict resolution training, gender, and eligibility. The dependent variables were number of referrals and level of referrals. Data were collected from student discipline records and by conducting focus groups and individual interviews. The quantitative data were analyzed using the Statistical Package for the Social Sciences (SPSS-X). Two three-way analysis of variance (ANOVA) were used to test all hypotheses. When an alpha level of .05 was used, only the interaction between gender and eligibility was significant with respect to both the number and level of discipline referrals. Further analyses were conducted to "tease apart" the interactions.
In order to ascertain participants' perceptions of the effects of conflict resolution training, the qualitative data were content analyzed to record emerging themes. When the data were content analyzed, 10 themes emerged with respect to the participants' perceptions. These themes revealed that participants' perceptions were mostly positive. Participants reported that the training influenced positive changes in their own behavior and the behavior of others.
Ed. D.
Virginia Tech
Dissertation710.PDF
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Discipline Referrals
Secondary Schools
Conflict Resolution
The Effects of Conflict Resolution Training on Students with Previous Discipline Referrals
Dissertation
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Educational Leadership and Policy Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/640712020-09-25T18:19:48Zcom_10919_5534col_10919_9291
Willey, Clarke R.
Economic Entomology and Horticulture
2015-11-13T20:44:24Z
2015-11-13T20:44:24Z
1922
http://hdl.handle.net/10919/64071
6 leaves
application/pdf
en_US
Virginia Agricultural and Mechanical College and Polytechnic Institute
OCLC# 30367304
Creative Commons Public Domain Mark 1.0
http://creativecommons.org/publicdomain/mark/1.0/
LD5655.V855 1922.W555A
Peach twig-borer
Peach -- Diseases and pests
The peach twig borer
Thesis
Text
Master of Science
Master of Science
masters
Virginia Agricultural and Mechanical College and Polytechnic Institute
Economic Entomology and Horticultureopen.accessoai:vtechworks.lib.vt.edu:10919/499182023-11-28T04:59:09Zcom_10919_5534col_10919_11041
Arenburg, Robert Thomas
Engineering Mechanics
Reddy, Junuthula N.
Aboudi, J.
Hendricks, Scott L.
Henneke II, E.G.
Johnson, E.R.
Mook, Dean T.
2014-08-13T14:38:47Z
2014-08-13T14:38:47Z
1988
http://hdl.handle.net/10919/49918
The nonlinear behavior of continuous-fiber-reinforced metal-matrix composite structures is examined using a micromechanical constitutive theory. Effective lamina and laminate constitutive relations based on the Aboudi micromechanics theory are presented. The inelastic matrix behavior is modeled by the unified viscoplasticity theory of Bodner and Partom. The laminate constitutive relations are incorporated into a first-order shear deformation plate theory. The resulting boundary value problem is solved by utilizing the finite element method. · Computational aspects of the numerical solution, such as the temporal integration of the inelastic strains and the spatial integration of bending moments are addressed. Numerical results are presented which illustrate the nonlinear response of metal matrix composites subjected to extensional and bending loads. Experimental data from available literature are in good agreement with the numerical results.
Ph. D.
incomplete_metadata
xi, 179 leaves
application/pdf
Virginia Polytechnic Institute and State University
OCLC# 19719229
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1988.A736
Metallic composites
Composite construction
Structural analysis (Engineering)
Analysis of metal matrix composite structures using a micromechanical constitutive theory
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Engineering Mechanicsopen.accessoai:vtechworks.lib.vt.edu:10919/368402020-09-28T12:58:01Zcom_10919_5534col_10919_9291
Navarra, Kelly R.
Mechanical Engineering
O'Brien, Walter F. Jr.
Gord, J. R.
Rabe, Douglas C.
Dancey, Clinton L.
2014-03-14T20:51:58Z
2014-03-14T20:51:58Z
1997-04-24
1997-04-24
1997-07-16
1997-07-16
etd-61597-17256
http://hdl.handle.net/10919/36840
http://scholar.lib.vt.edu/theses/available/etd-61597-17256/
A new pressure-measurement technique which employs the tools of molecular spectroscopy has recently received considerable attention in the fluid mechanics community. Measurements are made via oxygen-sensitive molecules attached to the surface of interest as a coating, or paint. The pressure-sensitive-paint (PSP) technique is now commonly used in stationary wind-tunnel tests; this thesis presents the extension of the technique to advanced turbomachinery applications. New pressure- and temperature-sensitive paints (TSPs) have been developed for application to a state-of-the-art transonic compressor where pressures up to 2 atm and surface temperatures up to 140° C are expected for the first-stage rotor. PSP and TSP data has been acquired from the suction surface of the first-stage rotor of a transonic compressor operating at its peak-efficiency condition. The shock structure is clearly visible in the pressure image, and visual comparison to the corresponding computational fluid dynamics (CFD) prediction shows qualitative agreement to the PSP data.
Master of Science
Virginia Tech
Thesisetd.PDF
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Pressure-sensitive paint
turbomachinery
optical pressure measurement techniques
luminescence quenching.
Development of the Pressure-Sensitive-Paint Technique for Advanced Turbomachinery Applications
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Mechanical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/535202023-11-28T04:59:07Zcom_10919_5534col_10919_11041
Gramoll, Kurt C.
Engineering Mechanics
Hendricks, Scott L.
Reifsnider, Kenneth L.
Knight Jr., Charles E.
Brinson, H.F.
Dillard, D.A.
2015-06-24T13:35:04Z
2015-06-24T13:35:04Z
1988
http://hdl.handle.net/10919/53520
This study consisted of two main parts, the thermoviscoelastic characterization of Kevlar 49/Fiberite 7714A epoxy composite lamina and the development of a numerical procedure to predict the viscoelastic response of any general laminate constructed from the same material. The four orthotropic material properties, S₁₁, S₁₂, S₂₂, and S₆₆, were characterized by 20 minute static creep tests on unidirectional ([0]₈, [10]₈, and [90]₁₆) lamina specimens. The Time-Temperature-Superposition-Principle (TTSP) was used successfully to accelerate the characterization process. A nonlinear constitutive model was developed to describe the stress dependent viscoelastic response for each of the material properties.
A new numerical procedure to predict long term laminate properties from lamina properties (obtained experimentally) was developed. Numerical instabilities and time constraints associated with viscoelastic numerical techniques were discussed and solved. The numerical procedure was incorporated into a user friendly microcomputer program called Viscoelastic Composite Analysis Program (VCAP), which is available for IBM ‘PC’ type computers. The program was designed for ease of use and includes graphics, menus, help messages, etc. The final phase of the study involved testing actual laminates constructed from the characterized material, Kevlar/epoxy, at various temperature and load levels for 4 to 5 weeks. These results were then compared with the VCAP program predictions to verify the testing procedure (i.e., the applicability of TTSP in characterizing composite materials) and to check the numerical procedure used in the program. The actual tests and predictions agreed, within experimental error and scatter, for all test cases which included 1, 2, 3, and 4 fiber direction laminates.
The end result of the study was the development and validation of a user friendly microcomputer program that can be used by design engineers in industry to predict thermoviscoelastic properties of orthotropic composite materials.
Ph. D.
vii, 293 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 18361233
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1988.G725
Viscoelasticity
Laminated materials
Epoxy compounds -- Testing
Thermoviscoelastic characterization and predictions of Kelvar/epoxy composite laminates
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Engineering Mechanicsopen.accessoai:vtechworks.lib.vt.edu:10919/390682023-08-13T19:27:16Zcom_10919_5534col_10919_11041
Zeccolo, Peggy L.
Public Administration and Policy
Goodsell, Charles T.
Kuhns, C.
Silva, M.C.
Wolf, J. F.
White, O. F.
2014-03-14T21:17:19Z
2014-03-14T21:17:19Z
1996
2007-08-06
2007-08-06
2007-08-06
etd-08062007-094417
http://hdl.handle.net/10919/39068
http://scholar.lib.vt.edu/theses/available/etd-08062007-094417/
The nature, origin and validity of ethics for nursing administrators were studied using a historical design with analytical and conceptual methodologies. This was done for the purpose of clarifying those issues for the practical matter of ethical decision making for nursing administrators. Research in that area has been limited.
An extensive analysis of 491 ethical articles, published from 1900-1989 and classified as personal, professional and administrative ethics; an analysis of the nursing codes of ethics and registration laws; trends in case and statute law; as well as conceptual literature and research provided the base for the facts, reasoned arguments, conclusions, interpretations and recommendations. Validity control features, (e.g., primary sources, multiple types of sources, and historical comparisons of trends) were used to minimize internal and external criticisms, as well as ensure integrity. Inter-rater reliability (90%) was ascertained to establish the consistency of the classifications of the data for the sake of replication.
The results of this research supported the hypothesis that there is a distinctive nature to the ethics for nursing administrators, especially those employed in public organizations. This research also concluded that the ethic of the traditional staff nurse is inappropriate for nursing administrators. Less significant results and conclusions linked nursing administration with fresh ideas such as the public interest, public advocacy, public policy, constitutional competency, utilitarianism, and collective ethical decision making. A new model termed Collective Caring, was introduced as a more valid ethic. The Collective Caring Model has three major components (i.e., caring, cooperation and collectives) enhanced by utilitarianism. Collective Caring should be used to depersonalize the situation and integrate the values of the different collectives, as well as encourage utilitarianism, sharing, caring and cooperating for collective ethical decision making. Nursing administrators would be more critically aware of collective (e.g., public) values and more thoughtful about making ethical decisions. In addition, the effectiveness of the profession would be improved by clarifying and enhancing professional and collective relationships.
Ph. D.
ix, 234 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 35301188
LD5655.V856_1996.Z433.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1996.Z433
The nature, origin, and validity of ethics for nursing administrators
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Public Administration and Policyopen.accessoai:vtechworks.lib.vt.edu:10919/262112022-02-22T18:55:29Zcom_10919_5534col_10919_11041
Zhang, Wenyan
Plant Pathology, Physiology, and Weed Science
Chevone, Boris I.
Grabau, Elizabeth A.
Hess, John L.
Beers, Eric P.
Nessler, Craig L.
2014-03-14T20:07:32Z
2014-03-14T20:07:32Z
2007-02-01
2007-02-15
2008-03-27
2007-03-27
etd-02152007-110933
http://hdl.handle.net/10919/26211
http://scholar.lib.vt.edu/theses/available/etd-02152007-110933/
Vitamin C (ascorbic acid, AsA), an important primary metabolite of plants, functions as an antioxidant, an enzyme cofactor, and a cell-signaling modulator in a wide array of crucial physiological processes including biosynthesis of the cell wall, secondary metabolites and phytohormones, stress resistance, photoprotection, cell division, senescence, and growth. To identify genes that may regulate vitamin C levels in plants, about 3000 activation-tagged Arabidopsis lines were treated with ozone, which is a power oxidizing agent. Two mutants were selected for identification of potential genes involved in the regulation of vitamin C synthesis. A putative F-box gene, VCF1, and a purple acid phosphatase, AtPAP15, were identified for further characterization.
Two homozygous SALK T-DNA knockouts in the open reading frame (ORF) of VCF1 exhibited high tolerance to ozone when treated with 450 ppb for 3 hours and the AsA levels of these mutants were 2 to 3 fold higher than wild-type (wt) plants. Developmental studies, using RT-PCR, indicated that foliar expression of the VCF1 gene increased with plant age from 1 to 5 weeks, whereas AsA decreased during this same period. The expression of VCF1 was higher under a low-light condition in which AsA was reduced considerably. The AsA levels in two VCF1 overexpressing lines were only 50 to 70% of wt plants. These results suggested that the putative F-box gene functions as a negative regulator of leaf ascorbate content.
Overexpression of AtPAP15 with the CaMV 35S promoter resulted in up to 3-fold higher AsA levels than wt plants, where two independent SALK T-DNA insertion mutants in AtPAP15 had 50% less AsA than wt plants. Enzyme activity of bacterially expressed GST:AtPAP15 was greatest with phytate as a substrate indicating that AtPAP15 is a phytase. Phytase catalyzes hydrolysis of phytate (myo-inositol hexakisphosphate) to yield myo-inositol and free phosphate. Thus, AtPAP15 may regulate AsA levels by controlling the input of myo-inositol into this branch of AsA biosynthesis in Arabidopsis. AtPAP15 was expressed in all tested organs in wt plants and suggests that the enzyme may have functions other than phytate degradation during seed germination.
Ph. D.
Virginia Tech
Thesis_Zhang.pdf
In Copyright
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RT-PCR
GUS
TAIL-PCR
activation tagging
AtPAP15
VCF1
ascorbate
Arabidopsis
Identification and Characterization of Genes Involved in Regulation of Ascorbate Metabolic Pathway(s) in Arabidopsis thaliana
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Plant Pathology, Physiology, and Weed Scienceopen.accessoai:vtechworks.lib.vt.edu:10919/307092020-09-28T12:53:56Zcom_10919_5534col_10919_11041
Read, Frederick R.
Adult and Continuing Education
Wiswell, Albert K.
Stout, M.
Belli, Gabriella M.
McKeen, Ronald L.
Stubblefield, Harold W.
2014-03-14T20:22:32Z
2014-03-14T20:22:32Z
1997-05-19
1997-05-19
1997-09-30
1997-09-30
etd-81297-152342
http://hdl.handle.net/10919/30709
http://scholar.lib.vt.edu/theses/available/etd-81297-152342/
The purpose of this study was to determine the value, if any, of a mentoring program for beginning U.S. Army Reserve Forces School instructors, specifically: how mentored and unmentored beginning instructors differ in their perception of a mentorship program, how do mentors improve, if at all, the beginner's instructional practice, how mentors assist the beginner's understanding of the school's operating procedures, and how formally and informally mentored instructors differ in their perception of a mentorship program. Army Reserve instructors teaching the Command and General Staff Course (CGSOC) and the Combined Arms Services Staff Course (CAS3), were the subjects for this study. The total population of 267 instructors was surveyed by questionnaire, 217 (81.3%) usable responses were received. ANOVA and t-test statistic calculations showed a significant difference between the mean responses of instructors with a formal mentor and those with an informal or no mentor. Instructors with formal mentors strongly agree that mentorship is beneficial to beginners and should be part of an induction program. Formal mentors helped improve practice through observation, feedback, counseling, and direct assistance. Instructors with formal mentors state they were provided an orientation into administrative, logistical, and standard operating procedures. Finally, the formally mentored group report they were helped to become better instructors, guided in professional development, given a formal assessment of their instructional abilities, and provided materials to improve practice and maintain competence. The data appear to suggest that a formal mentorship program produces a more prepared beginning instructor.
Ed. D.
Virginia Tech
ReadDis.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
induction
mentors
mentoring
The Perceived Value of Mentoring by Beginning Usarf Instructors With Formal, Informal and No Mentors
Dissertation
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Adult and Continuing Educationopen.accessoai:vtechworks.lib.vt.edu:10919/332312021-03-23T14:24:57Zcom_10919_5534col_10919_9291
Heath, Shannon Raelene
English
Graham, Peter W.
Radcliffe, David H.
Anderson, Linda
2014-03-14T20:38:35Z
2014-03-14T20:38:35Z
2007-05-21
2007-05-25
2007-06-01
2007-06-01
etd-05252007-154850
http://hdl.handle.net/10919/33231
http://scholar.lib.vt.edu/theses/available/etd-05252007-154850/
In the eighteenth and early nineteenth centuries, the duel of honor functioned as a formal recourse to attacks on a gentleman's reputation. Concurrently, many notable literary figures such as Samuel Johnson, William Gifford, Thomas Moore, and Lord Byron were involved in literary disputes featuring duels or the threat of physical violence, a pattern indicating a connection between authorship and dueling. This study explicitly examines this connection, particularly as it relates to social acceptance, the gentrification of authorship, and the business of publishing. The act of publishing, putting one's work into the public sphere for consumption as well as critique, created an acute sensitivity to issues of honor because publishing automatically broadcast insults or accusations of dishonorable conduct to the reading public.
This study requires a grounded discussion of complex, interconnected concepts, specifically: masculine identity, social hierarchy, and violence; satire; dueling; and authorship. Discussion moves from a foundational concern with violence and the assertion of social status, to the relationship between status and honor, to specific modes of defending honor, and finally to the attempt to establish authorship as an honorable profession. Although each of these quarrels exhibits physical violence or the threat of physical violence, these examples also exhibit verbal violence through satiric assaults or an exchange of verbal attacks and parries.
As professional writers struggled to overcome the stereotype of the literary hack and gain social respectability, dueling, with either lead or paper bullets, became a way for authors to defend and maintain the fragile social status they had gained.
Master of Arts
Virginia Tech
SRHeathThesisETD.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Wolcot
Byron
Moore
Jeffrey
Pindar
Gifford
Johnson
dueling
satire
Macpherson
“Paper Bullets of the Brain”: Satire, Dueling and the Rise of the Gentleman Author
Thesis
Master of Arts
masters
Virginia Polytechnic Institute and State University
Englishopen.accessoai:vtechworks.lib.vt.edu:10919/364522022-03-28T18:24:41Zcom_10919_5534col_10919_9291
Constantine, Irene Elizabeth
Architecture
Galloway, William U.
Feuerstein, Marcia F.
Schneider, Mark E.
2014-03-14T20:50:48Z
2014-03-14T20:50:48Z
2001-06-15
2007-12-26
2008-02-11
2008-02-11
etd-12262007-155504
http://hdl.handle.net/10919/36452
http://scholar.lib.vt.edu/theses/available/etd-12262007-155504/
Architecture exists through human experience. As the product of the relationship between a building and a person, architecture gains meaning when it is viewed and contemplated by an individual moving throughout a building. Architecture simultaneously engages the body and mind of one who experiences it, and its intentions become visible through a continuous weaving of motion through situations that constitute a place. My thesis examines the interplay between architecture and human action.
Manifest in the following thesis are explorations of the institution of the museum. From its earliest forms to its present day forms, the museum has undergone many changes due to a number of influences. In this thesis I will look at the cultural dynamics that shape museums. Specifically, my critique will be through the lens of its cultural history, my own culturally based observations, and through a design: the demonstration.
One objective of this thesis is to revive the idea of the museum as a place of the muses, where the muses inspire those people who experience the place. I have selected Charleston and its historic setting for the project location of a Museum. This is a place where one might participate in a journey of initiation, education, and cultivation. Through design, I demonstrate a museum, which aims to initiate and encourage self-cultivation by one's experience of the objects in the museum and the space that surrounds the objects. It is perhaps through a perusal of objects contained without authoritative concepts applied that one may acquire knowledge and become inspired.
Master of Architecture
Virginia Tech
constantineMARCHETD.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
matrix
institution
Hunley submarine
artifacts
Charleston
Architecture
muses
museum
Architecture and the Inspiration of the Museum
Thesis
Master of Architecture
masters
Virginia Polytechnic Institute and State University
Architectureopen.accessoai:vtechworks.lib.vt.edu:10919/272502023-11-29T02:17:12Zcom_10919_5534com_10919_78363com_10919_5549col_10919_11041col_10919_82827
Matovic, Dragan
Hospitality and Tourism Management
McCleary, Ken W.
Weaver, Pamela A.
Renaghan, Leo
Murrmann, Suzanne K.
Williams, John A.
2014-03-14T20:10:44Z
2014-03-14T20:10:44Z
2002-04-17
2002-04-25
2003-05-06
2002-05-06
etd-04252002-163659
http://hdl.handle.net/10919/27250
http://scholar.lib.vt.edu/theses/available/etd-04252002-163659/
The primary objective of this study was to explore the relationship among various market structure constructs (consisting of barriers to entry, competition, growth, and market share) and their potential impact on financial performance. By applying theoretical underpinnings from the disciplines of marketing, strategy and industrial organization economics, and adapting them to the unique characteristics of the U.S. lodging industry, the above constructs were linked to produce the Lodging Market Structure (LMS) Model. The study consisted of a cross-sectional analysis using a sample of 67 well-recognized hotel brands operating in the U.S. (representing 63 percent of the national guestroom inventory), covering a four-year period between 1996 and 1999. Correlation and multiple regression analysis were used to examine the hypothesized relationships within the LMS model. This study represented the first comprehensive investigation of the competitive market structure of the U.S. lodging industry.
The key findings of the study indicate that the financial performance of hotel brands in the United States is strongly impacted by competitive market structure. Among the various market structure constructs studied, barriers to entry played the most dominant role in determining the level of financial performance of hotel brands. Based on a strong negative relationship, barriers to entry are very effective in reducing competition in the U.S. lodging industry. Also, of the constructs studied, barriers to entry had the greatest influence on enhancing the market share of incumbent hotel brands. The growth rate of those incumbent brands has a positive relationship with barriers to entry. As competition intensifies, the growth rate of hotel brands slows down. Increases in competition are negatively correlated with a brand's market share. Competition has a strong negative relationship with the financial performance of hotel brands. Market share improves as the growth rate of hotel brands increases. As the growth rate of brands increases, profitability also improves. Likewise, improvements in a hotel brand's market share are positively related to increases in profitability. Lastly, the U.S. lodging market is becoming more competitive, and the industry has reached the mature stage of its lifecycle.
Ph. D.
Virginia Tech
matovic.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
financial performance
competition
market structure
lodging brands
The Competitive Market Structure of the U.S. Lodging Industry and its Impact on the Financial Performance of Hotel Brands
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Hospitality and Tourism Managementopen.accessoai:vtechworks.lib.vt.edu:10919/800462020-09-28T13:30:08Zcom_10919_5534col_10919_9291
Toomhirun, Sontichai
Electrical Engineering
2017-11-09T20:41:33Z
2017-11-09T20:41:33Z
1987
http://hdl.handle.net/10919/80046
Residential demand is a large and important factor of the utility load during the system peak period. And the control of residential demand can make a significant change to the system load of the utility. This research is designed to study the residential end-use appliances under various direct load control schemes. These appliances are water heaters, air conditioners, and space heaters which are the major electrical demand of the residential load. The study will apply the LOADSIM, an Electrical Power Research Institute (EPRI) load simulation program, to conduct load control strategies of these residential appliances. The LOADSIM program can be applied both for cycling and shedding control strategies during a specified control period. In this study, the cycling control is done on an air conditioner and space heater. The water heating control is performed under shedding strategy.
The research has studied the appliance use of four house types under the same weather and control conditions. A total of 100,000 houses have been used in the study. These houses have the same dwelling and appliance characteristics but their house insulations are different. Diversity in house insulations gives different results in terms of load reduction and temperature change due to the load control. For example, a better-insulated house demands less electricity for its appliance than a low-insulated house. This study also uses the EPRl-LOADSIM program to estimate the load reduction and temperature change of each house type under the load control.
Master of Science
xi, 128 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 17604974
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1987.T668
Electric utilities -- Time-of-use pricing
Study of residential demand for electricity as functions of load control schemes and dwelling characteristics
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Electrical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/1020342022-06-14T20:51:34Zcom_10919_5534col_10919_11041
Asgari, Elham
Management
Hunt, Richard A.
Gnyawali, Devi R.
Srivastava, Manish Kumar
Tegarden, Linda F.
Townsend, David M.
2021-01-24T07:00:31Z
2021-01-24T07:00:31Z
2019-08-02
vt_gsexam:21901
http://hdl.handle.net/10919/102034
In my dissertation, I examine varied types of knowledge and how they contribute to innovation generation and selection at both the firm and the industry level using the emerging industry context of small satellites. My research is divided into three papers. In Paper One, I take a supply-demand perspective and examine how suppliers of technology—with their unique knowledge of science and technology—and users of technology—with their unique knowledge of demand—contribute to innovation generation and selection over the industry lifecycle. Results show that the contributions of suppliers and users vary based on unique aspects of innovation, such as novelty, breadth, and coherence – and also over the industry life cycle. In Paper Two, I study how firms overcome science-business tension in their pursuit of novel innovation. I examine unique aspects of knowledge: scientists' business knowledge and CEOs' scientific knowledge. I show that CEOs' scientific knowledge is an important driver of firms' novel pursuits and that this impact is higher when scientists do not have business knowledge. In the third paper, I further examine how scientists with high technological and scientific knowledge—i.e., star scientists—impact firm innovation generation and selection. With a focus on explorative and exploitative innovation, I develop theory on the boundary conditions of stars' impact on firm level outcomes. I propose that individual level contingencies—i.e., stage of employment—and organizational level contingencies—explorative or exploitative innovation—both facilitate and hinder stars' impact on firms' innovative pursuits.
Doctor of Philosophy
In my dissertation, I study innovation at both the firm level and the industry level using the emerging industry context of small satellites. My dissertation divides into three papers. In Paper One, I study unique aspects of innovation at the industry level taking a supply-demand perspective. Since novelty, breadth, and convergence of innovation are all important drivers of the emergence and evolution of industries, I examine how supply side or demand side actors contribute to unique aspects of innovation over the industry life cycle. Results suggest that both suppliers and users of technology make important contributions to innovation, however, their respective contributions vary to novelty, breadth, and convergence of innovation. This impact varies over the industry life cycle. In Paper Two, I study how firms pursue novel innovation as main creator of economic value for firms. Firms need both scientific and technological knowledge in their pursuit of novel innovation. However, firms often struggle to overcome science-business tensions. Focusing on CEOs and scientists as two main drivers of innovation, I study how CEOs’ scientific knowledge and scientists’ business knowledge help firms overcome business-science tension. Results suggest that the likelihood of firms’ novel pursuit is higher when CEOs have scientific knowledge and scientists do not have business knowledge. In Paper Three, I further examine how high-performing scientists—i.e., star scientists—impact explorative and exploitative innovation. I propose that the stage of employment of individuals and goal context of firms are important contingencies that impact how stars impact firm level innovation.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Innovation
Demand-Side Perspective
Industry Evolution
Scientific Knowledge
Business Knowledge
Small Satellite Industry
Topic Modeling
The Impact of Varied Knowledge on Innovation and the Fate of Organizations
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Business, Managementopen.accessoai:vtechworks.lib.vt.edu:10919/530472021-05-04T03:04:27Zcom_10919_5534col_10919_9291
Dunay, Donna W.
Architecture
2015-06-23T19:08:13Z
2015-06-23T19:08:13Z
1975
http://hdl.handle.net/10919/53047
The work is divided into two parts, a verbal section and a visual section. The former is supportive, the latter is the main body of the work. Described, this thesis would be closer to a philosophy of design rather than a polemic or manifesto about design. Although it is concerned with the investigation of aesthetic qualities of single objects, within each project lies a universal concern, the struggle for order. The intent is to address the gap between art and daily life and through the design of the immediate environment bring about a more pleasurable and meaningful set of experiences.
The role of a designer is briefly discussed and the concept of always dealing with two as an approach to design is elaborated. But the important meaning of the work is succinctly expressed in a statement by David Jones, "There is no surrogate for being on the job." The designer must acknowledge the obligation not only to generate new ideas, but translate them into three dimensional realities.
Master of Architecture
vi, 68 leaves
application/pdf
en
Virginia Polytechnic Institute and State University
OCLC# 39010807
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1975.D847
Too (2): offerings of small environments
Thesis
Text
Master of Architecture
masters
Virginia Polytechnic Institute and State University
Architectureopen.accessoai:vtechworks.lib.vt.edu:10919/772952022-02-22T20:21:26Zcom_10919_5534col_10919_11041
Pinto, Ameet John
Civil Engineering
Love, Nancy G.
Bott, Charles B.
Stevens, Ann M.
Novak, John T.
Puri, Ishwar K.
2017-04-06T15:44:36Z
2017-04-06T15:44:36Z
2009-12-07
2009-12-21
2016-10-17
2010-01-15
etd-12212009-094300
http://hdl.handle.net/10919/77295
http://scholar.lib.vt.edu/theses/available/etd-12212009-094300/
This study consists of three research phases. First, we developed corrective action strategies to mitigate the impact of calcium hypochlorite and cadmium pulse shocks for the Plum Island Wastewater Treatment Plant (WWTP) in Charleston, SC. The corrective action strategies were developed in consultation with industrial consultants and operational personnel from the utility. These strategies were tested using a laboratory scale system, which was constructed and operated similar to the parent facility. Two corrective actions were tested for calcium hypochlorite, while only one strategy was tested for the cadmium at the laboratory scale. This study shows that no corrective action strategies are required for an acute hypochlorite stress. This is due to the fact that hypochlorite is highly reactive and dissipates rapidly on contact with the wastewater matrix, thus causing only low level process deterioration. In fact, implementation of corrective action strategies results in greater process deterioration as compared to the non-intervention approach. The corrective action tested for cadmium stress showed potential for reducing the peak impact of the toxin and allowed for faster process recovery as compared to the unstressed control.
For the second phase, the corrective actions were tested at a pilot scale facility operated at the Plum Island wastewater treatment plant. We tested two different corrective action strategies for cadmium, while only one strategy was tested for hypochlorite during the pilot scale study. Similar to the laboratory scale experiments, we conclude that no mitigative approaches are necessary for an acute hypochlorite stress. Additionally, the implementation of mitigative approaches for the pilot scale cadmium stress events resulted in greater process deterioration as compared to the non-intervention approach. In contrast to the laboratory scale experiments, theoretical effluent blending calculations showed that corrective actions may not reduce the impact of the cadmium stress. This was attributed to the lower intensity of process deterioration caused by the simulated cadmium stress. The pilot scale study shows that prior to implementing a corrective action strategy, the operator should determine the probable extent of process deterioration due to the detected chemical contaminant before deciding if a corrective action is needed. The pilot scale study also evaluated the effectiveness of current sensor technologies towards the upstream detection of influent anomalies and reliable monitoring of process performance during an upset event. Multivariate analysis on the rate of change of influent sensor signals was reliably able to detect the presence of both toxins tested during this study.
For the third phase of this research, we investigated the impact of cadmium stress on the structure and function of bioreactor microbial communities. We observed significant increases in post-stress heterotrophic and autotrophic bacterial respiration rates for the bioreactors subjected to cadmium stress. The higher respiration rates were due to an increase in bacterial abundance in the cadmium stressed reactors. We were also able to show that the increase in bacterial abundance was not due to changes in community structure or due to cadmium induced deflocculation. In fact, this study demonstrates that transient cadmium stress reduces predator abundance within the activated sludge community and this reduction in predator grazing was responsible for the increase in bacterial abundance. This research highlights the importance of higher life forms, specifically eukaryotic microorganisms, in regulating bacterial community dynamics in systems undergoing chemical perturbations.
Ph. D.
en_US
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
microbial community
hypochlorite
corrective action
sensors
cadmium
activated sludge
upset event
predator grazing
Upset Events At Wastewater Treatment Plants: Implications for Mitigative Strategy Development and Bioreactor Microbial Ecology
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Civil Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/829202022-02-22T20:21:28Zcom_10919_5534col_10919_11041
Arca, Hale Cigdem
Learning Sciences and Technologies
Edgar, Kevin J.
Davis, Richey M.
Turner, S. Richard
Sriranganathan, Nammalwar
Taylor, Lynne S.
2018-04-26T06:00:32Z
2018-04-26T06:00:32Z
2016-11-01
vt_gsexam:8931
http://hdl.handle.net/10919/82920
Amorphous solid dispersion (ASD) is a popular method to increase drug solubility and consequently poor drug bioavailability. Cellulose ω-carboxyesters were designed and synthesized specifically for ASD preparations in Edgar lab that can meet the ASD expectations such as high Tg, recrystallization prevention and pH-triggered release due to the free -COOH groups. Rifampicin (Rif), Ritonavir (Rit), Efavirenz (Efa), Etravirine (Etra) and Quercetin (Que) cellulose ester ASDs were investigated in order to increase drug solubility, prevent release at low pH and controlled release of the drug at small intestine pH that can improve drug bioavailability, decrease needed drug content and medication price to make it affordable in third world countries, and extent pill efficiency period to improve patient quality of life and adherence to the treatment schedule. The studies were compared with cellulose based commercial polymers to prove the impact of the investigation and potential for the application. Furthermore, the in vitro results obtained were further supported by in vivo studies to prove the significant increase in bioavailability and show the extended release.
The need of new cellulose derivatives for ASD applications extended the research area, the design and synthesis of a new class of polymers, alkyl cellulose ω-carboxyesters for ASD formulations investigated and the efficiency of the polymers were summarized to show that they have the anticipated properties. The polymers were synthesized by the reaction of commercial cellulose alkyl ethers with benzyl ester protected, monofunctional hydrocarbon chain acid chlorides, followed by removal of protecting group using palladium hydroxide catalyzed hydrogenolysis to form the alkyl cellulose wcarboxyalkanoate. Having been tested for ASD preparation, it was proven that the polymers were efficient in maintaining the drug in amorphous solid state, release the drug at neutral pH and prevent the recrystallization for hours, as predicted.
Ph. D.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Cellulose esters
cellulose ether esters
Amorphous solid dispersions
structure-property relationship
anti-HIV
rifampicin
quercetin solubility enhancement
Cellulose Esters and Cellulose Ether Esters for Oral Drug Delivery Systems
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Macromolecular Science and Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/705132021-05-04T03:04:22Zcom_10919_5534col_10919_9291
Gohain, Pradip Kumar
Electrical Engineering
2016-04-21T15:34:58Z
2016-04-21T15:34:58Z
1968
http://hdl.handle.net/10919/70513
Theoretical analysis and comparison of three basic digital data communication systems, namely, amplitude-shift keying (ASK), frequency-shift keying (FSK), and phase-shift keying (PSK), for both binary coded and M-ary coded transmissions are presented in this paper. The analysis is limited to only nonfading received signal in additive Gaussian noise. Both coherent and noncoherent detection schemes are considered. A symbol error-rate or probability of error is used as the performance criterion for comparison purpose.
Master of Science
iii, 74 leaves
application/pdf
en
Virginia Polytechnic Institute
OCLC# 38300972
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1968.G6
Error-rates of digital signaling with coherent and noncoherent detections
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute
Electrical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/832352021-08-18T13:17:27Zcom_10919_5534col_10919_9291
Holmes, David Alexander
Mechanical Engineering
Gabler, Hampton Clay
Southward, Steve C.
Hardy, Warren N.
2018-05-17T08:00:24Z
2018-05-17T08:00:24Z
2018-05-16
vt_gsexam:15225
http://hdl.handle.net/10919/83235
Cross-centerline crashes occur rarely in the United States but are especially severe. This type of crash is characterized by one vehicle departing over a centerline and encountering a vehicle traveling in the opposite direction. In recent years, automakers have started developing and implementing lane departure warning (LDW) on newer vehicles. This system provides the potential to reduce or significantly impact the frequency of cross-centerline crashes. The objective of this thesis was to estimate the potential crash and injury benefits of a LDW system if installed on every vehicle in the US fleet.
This research includes the following 1) a characterization of cross-centerline crashes in the United States today with current and future prevention methods, 2) a reconstruction methodology used for all crashes including rollovers and heavy vehicles, and 3) a simulation model and approach method used to estimate potential benefits of LDW systems on cross-centerline crashes.
Cross over to left crashes account for only 4% of non-junction non-interchange crashes but account for 44% of serious injury crashes of the same type. As part of this research, 42 cross-centerline crashes were reconstructed and simulated as if they had a LDW system installed. Accounting for driver capability to react to a LDW alert, crash reduction benefits ranged from 22 – 30%.Using injury risk curves, the probability of experiencing a MAIS2+ injury in a cross-centerline crash was reduced by 29% when using a LDW system.
Master of Science
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
active safety
car crashes
lane departure warning
The Effect of Lane Departure Warning Systems on Cross-Centerline Crashes
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Mechanical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/647362021-04-15T17:10:38Zcom_10919_5534col_10919_11041
Altizer, Carol Jane
Supervision
2016-02-01T18:34:22Z
2016-02-01T18:34:22Z
1977
http://hdl.handle.net/10919/64736
The purpose of this exploratory research study was to investigate, both theoretically and experimentally, the hypothesis that the manipulation of concrete materials can contribute substantively to the learning of the operation of multiplication of polynomials and its inverse, factorization, in children who are in eighth-grade pre-algebra mathematics classes. The study involved a comparison of the achievement of students who used manipulatives to learn how to multiply and factor polynomials with the achievement of those who did not use manipulatives to learn to operate on the polynomials. The instructional material designed for use by both treatment groups was based on the theory of learning developed by this writer. It was theorized that as students use manipulatives to learn mathematical concepts the actions performed upon the concrete materials would be abstracted or internalized in the mind as operations.
The study involved four teachers and 173 students from two middle schools in the Pulaski County School System, Pulaski, Virginia. The means and standard deviations of the students' scores on both the immediate posttest and retention test were compared as well as inferences made from the data using several analyses of covariance. The Orleans-Hanna Algebra Prognosis Test served as the pretest for this study.
The F ratios from the analyses of covariance conducted on the immediate posttest scores from Experiment I indicated that (1) using the total population of students, there was no statistical difference in mean scores between the manipulative and nonmanipulative groups (p = 0.385); (2) using only Teacher A's students, there was no statistical difference in mean scores between the manipulative and nonmanipulative groups (p = 0.609); and (3) using only Teacher B's students, there was a marginal difference in mean scores between the manipulative and nonmanipulative groups (p = 0.071), favoring the nonmanipulative group.
The F ratios from analyses of covariance conducted on the retention test scores from Experiment I indicated that (1) using the total population of students, there was a statistical difference in mean scores between the manipulative and nonmanipulative groups (p < 0.005), favoring the manipulative groups; (2) using only Teacher A's students, there was a statistical difference in mean scores between the manipulative and nonmanipulative groups (p < 0.009), favoring the manipulative group; (3) using only Teacher B's students there was no statistical difference in mean scores between the manipulative and the nonmanipulative groups (p = 0.241). However, the mean score of Teacher B's manipulative group was higher than the mean score of his nonmanipulative group.
The study was replicated (Experiment II) immediately following Experiment I in two classes taught by Teacher D.* The F ratio from an analysis of covariance conducted on the immediate posttest scores indicated that there was no statistical difference in mean scores between the manipulative and nonmanipulative groups (p = 0.762). The F ratio from an analysis of covariance conducted on the retention test scores indicated that there was no statistical difference in mean scores between the manipulative and nonmanipulative groups (p = 0.143). However, the mean score of the manipulative group was higher than the mean score of the nonmanipulative group.
In summary, there are implications from these findings that the manipulation of concrete materials by students does aid the learning of the mathematical transformation of multiplication of polynomials and its inverse, factorization. This was especially evident for retention of the operations. These findings support the theory of learning conceptualized for this study.
*Teacher C was omitted from the analyses of the data since she taught only a manipulative group.
ED. D.
ix, 211 leaves
application/pdf
en
Virginia Polytechnic Institute and State University
OCLC# 40244494
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1977.A48
The role of manipulatives in learning to multiply and factor polynomials
Dissertation
Text
ED. D.
doctoral
Virginia Polytechnic Institute and State University
Supervisionopen.accessoai:vtechworks.lib.vt.edu:10919/357532020-09-28T12:19:02Zcom_10919_5534col_10919_9291
Hu, Yongxuan
Electrical and Computer Engineering
Lee, Fred C.
Lindner, Douglas K.
Boroyevich, Dushan
2014-03-14T20:48:06Z
2014-03-14T20:48:06Z
2001-11-19
2001-11-19
2002-11-26
2001-11-26
etd-11192001-150026
http://hdl.handle.net/10919/35753
http://scholar.lib.vt.edu/theses/available/etd-11192001-150026/
The High-Intensity-Discharge Lamps (HID), consisting of a broad range of gas discharge lamps, are notable for their high luminous efficacy, good color rendering, and long life. Metal halide lamps have the best combination of the above properties and are considered the most ideal light sources. Recently, there has been an emerging demand to replace the conventional halogen headlamps with the newly introduced small-wattage metal halide HID lamps. However, this lamp demands a highly efficient ballast and very complex control circuitry that can achieve fast turn-on and different regulation modes during the lamp start-up process.
Due to the complex lamp v-i profile and timing control requirements, control circuit built with conventional analog control is unavoidably cumbersome. With the unparalleled flexibility and programmability, digital control shows more advantages in this application. An automotive HID ballast with digital controller is developed to demonstrate the feasibility of the digital control along with some key issues in digital controller selection and design. Results show that the microcontroller-based HID ballast can successfully realize the required control functions and achieve a smooth turn-on process and a fast turn-on time of 8 seconds.
One of the major issues of ballast design is the ballast/HID lamp system stability, which originates from the lamp negative incremental impedance. The lamp small-signal model is presented with simulation and measurements. The negative incremental impedance is attributed to a RHP zero in the small-signal model. A new analysis approach, impedance ratio criterion, is proposed to analyze the system stability. With this approach, it clearly shows how the control configurations and converter and control design affect the system stability. The results can provide guidance and be easily used in control configuration selection and converter and control design. Analysis shows that ballast based on PWM converter without inner current loop is unstable and with inner current loop can stabilized the system. This is the reason why for a microcontroller-based ballast system the inner current loop has to be used.
HID lamp has its special acoustic resonance problem and thus a low-frequency unregulated full-bridge is used following the front-end DC/DC converter. To prevent from lamp re-igniting during each bridge commutation, a minimum current changing slope has to be guaranteed. In order to help design the converter, the ballast/lamp re-ignition analysis is presented. With this analysis, it shows that the output capacitance has to be small enough to ensure adequate current slope during zero crossing. Though some approximation is used to simplify the analysis, the results can provide qualitative guidance in the ballast design.
Master of Science
Virginia Tech
Thesis_Yongxuan_Hu.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
HID Lamp
Ballast
Small-Signal Model
Analysis and Design of High-Intensity-Discharge Lamp Ballast for Automotive Headlamp
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Electrical and Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/296032020-09-25T20:51:20Zcom_10919_5534col_10919_11041
Witt, Kathy
Educational Leadership and Policy Studies
Craig, James Richard
Earthman, Glen I.
Sellers, James L.
Tripp, Norman Wayne
2014-03-14T20:18:35Z
2014-03-14T20:18:35Z
2011-11-01
2011-11-15
2011-12-05
2011-12-05
etd-11152011-123804
http://hdl.handle.net/10919/29603
http://scholar.lib.vt.edu/theses/available/etd-11152011-123804/
In the early 1970s, Henry County, Virginia experienced rapid growth but by the late 1970s the population began to decline. In 1982, talks of building a new high school to consolidate two smaller high schools began with the school to be built on the North Carolina boarder. Between 1993 and 2003 approximately 10,523 jobs were lost in Henry County. At this time Henry County operated 20 public schools. In 2000, Dr. Sharon Dodson became the superintendent of Henry County. She was hired to make schools more efficient by using the best available spaces and closing facilities in need of structural repair. In 2001 the school board voted to close three schools but the board of supervisors refused necessary funding for consolidation. During the 2003/04 school year, the school board had no other choice but to revisit the idea of consolidation. In the fall of 2004, reconfiguration occurred which eliminated four facilities with a fifth building closing in the spring of 2008. Today, Henry County operates 14 schools.
This study examined the politics associated with the consolidation process in Henry County and closure of five facilities. The literature associated with consolidation concerning divisions and schools within a division was reviewed to provide context and better understanding of the consolidation process. Historical case study methods where employed to conduct the study. Data were collected from primary sources and interviews were handled qualitatively. Triangulation verification techniques were used to describe and verify consolidation events in Henry County. The findings express the issues and challenges faced and met by Henry County during consolidation. The events that led to school closings and some course offerings and programs are described. The findings indicate that consolidation can be successful even when some stakeholders reject the idea and plan of consolidation. Continued research in the field of consolidation could possibly benefit educational and community leaders considering reconfiguration within a school division. Additional research comparing the cost of operating a division before and after consolidation of schools may provide insights that educational and community members should consider before embarking on consolidation.
Ed. D.
Virginia Tech
Witt_K_D_2011.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Consolidation and Per Pupil Cost
Consolidation in the Henry County Public School System
Dissertation
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Educational Leadership and Policy Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/282972020-09-25T20:48:38Zcom_10919_5534col_10919_11041
El-Nainay, Mustafa Y.
Electrical and Computer Engineering
MacKenzie, Allen B.
El-Derini, Mohamed N.
DaSilva, Luiz A.
Bostian, Charles W.
Aly, Hussien H.
Midkiff, Scott F.
Marathe, Madhav V.
2014-03-14T20:14:02Z
2014-03-14T20:14:02Z
2009-07-01
2009-07-14
2009-07-24
2009-07-24
etd-07142009-101727
http://hdl.handle.net/10919/28297
http://scholar.lib.vt.edu/theses/available/etd-07142009-101727/
The heterogeneity and complexity of modern communication networks demands coupling network nodes with intelligence to perceive and adapt to different network conditions autonomously. Cognitive Networking is an emerging networking research area that aims to achieve this goal by applying distributed reasoning and learning across the protocol stack and throughout the network. Various cognitive node and cognitive network architectures with different levels of maturity have been proposed in the literature. All of them adopt the idea of coupling network devices with sensors to sense network conditions, artificial intelligence algorithms to solve problems, and a reconfigurable platform to apply solutions. However, little further research has investigated suitable reasoning and learning algorithms.
In this dissertation, we take cognitive network research a step further by investigating the reasoning component of cognitive networks. In a deviation from previous suggestions, we suggest the use of a single flexible distributed reasoning algorithm for cognitive networks. We first propose an architecture for a cognitive node in a cognitive network that is general enough to apply to future networking challenges. We then introduce and justify our choice of the island genetic algorithm (iGA) as the distributed reasoning algorithm.
Having introduced our cognitive node architecture, we then focus on the applicability of the island genetic algorithm as a single reasoning algorithm for cognitive networks. Our approach is to apply the island genetic algorithm to different single and cross layer communication and networking problems and to evaluate its performance through simulation. A proof of concept cognitive network is implemented to understand the implementation challenges and assess the island genetic algorithm performance in a real network environment. We apply the island genetic algorithm to three problems: channel allocation, joint power and channel allocation, and flow routing. The channel allocation problem is a major challenge for dynamic spectrum access which, in turn, has been the focal application for cognitive radios and cognitive networks. The other problems are examples of hard cross layer problems.
We first apply the standard island genetic algorithm to a channel allocation problem formulated for the dynamic spectrum cognitive network environment. We also describe the details for implementing a cognitive network prototype using the universal software radio peripheral integrated with our extended implementation of the GNU radio software package and our island genetic algorithm implementation for the dynamic spectrum channel allocation problem. We then develop a localized variation of the island genetic algorithm, denoted LiGA, that allows the standard island genetic algorithm to scale and apply it to the joint power and channel allocation problem. In this context, we also investigate the importance of power control for cognitive networks and study the effect of non-cooperative behavior on the performance of the LiGA.
The localized variation of the island genetic algorithm, LiGA, is powerful in solving node-centric problems and problems that requires only limited knowledge about network status. However, not every communication and networking problems can be solved efficiently in localized fashion. Thus, we propose a generalized version of the LiGA, namely the K-hop island genetic algorithm, as our final distributed reasoning algorithm proposal for cognitive networks. The K-hop island genetic algorithm is a promising algorithm to solve a large class of communication and networking problems with controllable cooperation and migration scope that allows for a tradeoff between performance and cost. We apply it to a flow routing problem that includes both power control and channel allocation. For all problems simulation results are provided to quantify the performance of the island genetic algorithm variation. In most cases, simulation and experimental results reveal promising performance for the island genetic algorithm.
We conclude our work with a discussion of the shortcomings of island genetic algorithms without guidance from a learning mechanism and propose the incorporation of two learning processes into the cognitive node architecture to solve slow convergence and manual configuration problems. We suggest the cultural algorithm framework and reinforcement learning techniques as candidate leaning techniques for implementing the learning processes. However, further investigation and implementation is left as future work.
Ph. D.
Virginia Tech
MustafaElNainay_IslandGeneticAlgorithmbasedCognitiveNetworks.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
channel allocation
power control
flow routing
cognitive networks
island genetic algorithm
distributed reasoning and learning
dynamic spectrum access
Island Genetic Algorithm-based Cognitive Networks
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Electrical and Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/925882020-10-16T21:18:16Zcom_10919_5534col_10919_11041
Feng, Xuewen
Plant Pathology, Physiology and Weed Science
Baudoin, Antonius B.
Haak, David C.
Vinatzer, Boris A.
Nita, Mizuho
Schmale, David G. III
2019-08-01T06:00:47Z
2019-08-01T06:00:47Z
2018-02-06
vt_gsexam:13603
http://hdl.handle.net/10919/92588
Development of fungicide resistance in fungal and oomycete pathogens is a serious problem in grape production. Quinoxyfen is a fungicide widely used against grape powdery mildew (Erysiphe necator). In 2013, E. necator isolates with reduced quinoxyfen sensitivity (designated as quinoxyfen lab resistance or QLR) were detected in Virginia. Field trials were conducted in 2014, 2015, and 2016 at the affected vineyard to determine to what extent quinoxyfen might still contribute to disease control. Powdery mildew control by quinoxyfen was good, similar to, or only slightly less, than that provided by myclobutanil and boscalid in all three years. The frequency of QLR in vines not treated with quinoxyfen declined only slowly over the three years, from 65% to 46%. Information about the mode of action of quinoxyfen is limited; previous research suggests that quinoxyfen interferes with the signal transduction process. We profiled the transcriptomes of QLR and sensitive isolates in response to quinoxyfen treatment, providing support for this hypothesis. Additional transcriptional targets of quinoxyfen were revealed to be involved in the positive regulation of the MAPK signaling cascade, pathogenesis, and sporulation activity. Grape downy mildew (Plasmopara viticola), another important grape pathogen, is commonly controlled by phosphite fungicides. A field trial and laboratory bioassays were conducted to determine whether P. viticola isolates from vineyards with suspected control failures showed reduced sensitivity against phosphite fungicides. Prophyt applied at 14-day intervals under high disease pressure provided poor downy mildew control in the field. Next-generation sequencing technologies were utilized to identify 391,930 single nucleotide polymorphisms (SNPs) and generated a draft P. viticola genome assembly at ~130 megabase (Mb). Finally, field isolates of P. viticola collected from a Virginia vineyard with suspected mandipropamid control failure were bioassayed. The EC50 values of the isolates were >240 μg.ml-1 for mandipropamid, well above the field rate. The PvCesA3 gene of two resistant isolates was sequenced revealing that these isolates had a GGC-to-AGC substitution at codon 1105, the same mutation that has been found associated with CAA resistance elsewhere.
PHD
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Erysiphe necator
Plasmopara viticola
grape powdery mildew
grape downy mildew
fungicide resistance
quinoxyfen
Prophyt
mandipropamid
RNA-seq
whole genome sequencing
single nucleotide polymorphism (SNP)
Characterization of fungicide resistance in grape powdery and downy mildew using field trials, bioassays, genomic, and transcriptomic approaches: quinoxyfen, phosphite, and mandipropamid
Dissertation
PHD
doctoral
Virginia Polytechnic Institute and State University
Plant Pathology, Physiology and Weed Scienceopen.accessoai:vtechworks.lib.vt.edu:10919/813842020-09-28T18:24:54Zcom_10919_5534col_10919_11041
Bonakdar, Mohammad
Mechanical Engineering
Davalos, Rafael V.
Verbridge, Scott
Paul, Mark R.
Bickford, Lissett R.
Lee, Yong Woo
2017-12-22T07:00:28Z
2017-12-22T07:00:28Z
2016-06-29
vt_gsexam:8241
http://hdl.handle.net/10919/81384
Recent attempts to investigate living systems from a biophysical point of view has opened new windows for development of new diagnostic methods and therapies. Pulsed electric fields (PEFs) are a new class of therapies that take advantage of biophysical properties and have proven to be effective in drug delivery and treating several disorders including tumors. While animal models are commonly being used for development of new therapies, the high cost and complexity of these models along with the difficulties to control the electric field in the animal tissue are some of the obstacles toward the development of PEFs-based therapies. Microengineered models of organs or Organs-on-Chip have been recently introduced to overcome the hurdles of animal models and provide a flexible and cost-effective platform for early investigation of a variety of new therapies. In this study microfluidic platforms with integrated micro-sensors were designed, fabricated and employed to study the consequences of PEFs at the cellular level. These platforms were specifically used to study the effects of PEFs on the permeabilization of the blood-brain barrier for enhanced drug delivery to the brain. Different techniques such as fluorescent microscopy and electrical impedance spectroscopy were used to monitor the response of the cell monolayers under investigation. Irreversible electroporation is a new focal ablation therapy based on PEFs that has enabled ablation of tumors in a non-thermal, minimally invasive procedure. Despite promising achievements and treatment of more than 5500 human patients by this technique, real-time monitoring of the treatment progress in terms of the size of the ablated region is still needed. To address that necessity we have developed micro-sensor arrays that can be implemented on the ablation probe and give real-time feedback about the size of the ablated region by measuring the electrical impedance spectrum of the tissue.
Ph. D.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Blood-brain barrier
Electroporation
Microfluidics
Drug delivery
Electrical impedance spectroscopy
Microdevices for Investigating Pulsed Electric Fields-Mediated Therapies at Cellular and Tissue Level
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Mechanical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/733122020-09-28T13:51:14Zcom_10919_5534col_10919_11041
Zheng, Hanguang
Materials Science and Engineering
Lu, Guo Quan
Ngo, Khai D.
Guido, Louis J.
Aning, Alexander O.
2016-10-21T06:00:19Z
2016-10-21T06:00:19Z
2015-04-29
vt_gsexam:5067
http://hdl.handle.net/10919/73312
Die-attachment, as the first level of electronics packaging, plays a key role for the overall performance of the power electronics packages. Nanosilver sintering has becoming an emerging solder-free, environmental friendly die-attach technology. Researchers have demonstrated the feasibility of die-attachment on silver (Ag) or gold (Au) surfaces by pressure-less or low-pressure (< 5 MPa) nanosilver sintering. This study extended the application of nanosilver sintering die-attach technique to copper (Cu) surface. The main challenge of nanosilver sintering on Cu is the formation of thick Cu oxide during processing, which may lead to weak joints. In this study, different processes were developed based on the die size: for small-area dice (< 5 * 5 mm2), different sintering atmospheres (e.g. forming gas) were applied to protect Cu surface from oxidation; for large-area dice (> 5 * 5 mm2), a double-print, low-pressure (< 5 MPa) assisted sintering process was developed. For both processes, die-shear tests demonstrated die-shear strength can reach 40 MPa.
The effects of different sintering parameters of the processing were analyzed by different material characterization techniques. With forming gas as sintering atmosphere, not only Cu surface was protected from oxidation, but also the organics in the paste were degraded with nanosilver particles as catalyst. External pressure applied in the processing not only increased the density of sintered Ag, but also enhanced the contact area of sintered-Ag/Cu interface. Microstructure of Ag/Cu interface were characterized by transmission electron microscopy (TEM). Characterization results indicate that Ag/Cu metallic bonds formed at the interface, which verified the high die-shear strength of the die-attachment.
Thermal performance of nanosilver sintered die-attachment on Cu was evaluated. A system was designed and constructed for measuring both transient thermal impedance (Zth) and steady-state thermal resistance (Rth) of insulated gate bipolar transistor (IGBT) packages. The coefficient of variation (CV) of Zth measurement by the system was lower than 0.5%. Lead-free solder (SAC305) was applied in comparison of thermal performance with nanosilver paste. With same sample geometry and heating power level, nanosilver sintered joints on Cu showed in average 12.6% lower Zth and 20.1% lower Rth than SAC305 soldered joints. Great thermal performances of nanosilver sintering die-attachment on Cu were mainly due to the low thermal resistivity of sintered-Ag and the good bonding quality.
Both passive temperature cycling and active power cycling tests were conducted to evaluate the reliability of nanosilver sintered joints on Cu. For passive temperature cycling tests (-40 - 125 C), the die-shear strengths of mechanical samples had no significant drop over 1000 cycles, and nanosilver sintered IGBT on Cu packages showed almost no change on Zth after 800 cycles. For active power cycling test (Tj = 45 - 175 C), nanosilver sintered IGBT on Cu assembly had a lifetime over 48,000 cycles. The failure point of the assembly was the detachment of the wirebonds. Great reliability performances of nanosilver sintered die-attachment on Cu were mainly due to the low mismatch of coefficient of thermal expansion (CTE) between sintered-Ag and Cu. Meanwhile, low inter-diffusion rate between Ag and Cu prevented the interface from the reliability issue related to Kirkendall voids, which often took place in tin (Sn) -based solder joints.
Ph. D.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Die-attachment
nanosilver sintering
copper
processing
characterization
reliability.
Die-Attachment on Copper by Nanosilver Sintering: Processing, Characterization and Reliability
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Materials Science and Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/97102022-02-22T21:46:29Zcom_10919_5534col_10919_9291
Warner, Sandra McCarthy
Geosciences
Burbey, Thomas J.
Blewitt, Geoff
Schreiber, Madeline E.
2011-08-06T14:45:40Z
2011-08-06T14:45:40Z
2000-09-19
2004-01-26
2004-02-11
2004-02-11
etd-01262004-202558
http://hdl.handle.net/10919/9710
http://scholar.lib.vt.edu/theses/available/etd-01262004-202558
The horizontal component of land subsidence is typically assumed to be negligible, although recently, theoretical simulations have shown that horizontal strain is significant. A field based investigation in Mesquite, NV, was undertaken from May to July, 2003, for the purpose of evaluating the significance of horizontal strain during an aquifer test. The hydraulic heads in the aquifer were monitored within a meter of the municipal pumping well used for the aquifer test and also at a distance of approximately 1,470 meters from the pumping well. Aquifer deformation in the horizontal and vertical directions were measured using GPS for the first 22 days of pumping in 10 different locations at radial distances from the well varying from 100 meters to 2500 meters. From 22 to 60 days of the aquifer test, the number of GPS stations monitoring deformation was reduced to five.
Radial displacement was measured at all monitoring stations during the aquifer test, indicating that the aquifer is moving closer to the pumping well. The greatest magnitude displacement measured 140 m from the well was approximately 10 mm at the land surface. A zone of radial compression occurred between the pumping well and the first monitoring station 140 m away from the pumping well. Vertical displacement was measured in decreasing magnitude with increasing distance from the well. Because GPS is not as precise a tool in the vertical direction as it is in the horizontal, the vertical signal of displacement is not as accurate.
Numerical simulations using the BIOT and IBS codes were performed to reproduce the aquifer test and land deformation. The model included six layers representing three hydrogeologic units: a bottom aquifer (four layers) in which pumping occurred , a top aquifer (one layer) in which the monitoring well was screened, and a semi-confining bed (one layer) between the two aquifers that represented an equivalent thickness of interbeds and clays layers. The Biot code was used to simulate radial and vertical movements in an axisymmetrical simulation, while the IBS code was used to simulate only vertical displacement but also provided for the simulation of elastic and inelastic storage and compression.
The vertical distribution of radial displacement was simulated using the BIOT code. At the onset of pumping, the greatest radial displacement occurred in the bottom aquifer in which pumping occurred. At a distance of 2,000 m from the well, the radial displacement was uniform over all depths indicating that the differences in hydraulic diffusivity are not as important a factor at distance from the well.
The change in porosity that occurred as a result of horizontal strain was greatest in the bottom aquifer. Using the strain calculated directly from the GPS measurements at the land surface, vertical strain comprised almost 99% of the volume strain at the land surface. However, when the strain was simulated over the entire aquifer system, the radial and hoop strain contributed more than vertical strain in the bottom aquifer at a radius of 100 m from the pumping well at the onset of pumping until the aquifer reached near equilibrium, at which time vertical strain again dominated.
Master of Science
ETD
Virginia Tech
warneretd.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
aquifer test
GPS
Muddy Creek
subsidence
horizontal deformation
Using GPS to Quantify Three Dimensional Storage and Aquifer Deformation in the Virgin River Valley, NV
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Geosciencesopen.accessoai:vtechworks.lib.vt.edu:10919/872102020-09-25T20:33:18Zcom_10919_5534col_10919_9291
Jones, Letitia Power
Environmental Sciences and Engineering
2019-01-31T18:27:17Z
2019-01-31T18:27:17Z
1982
http://hdl.handle.net/10919/87210
As a consequence of new coal mining practices, coal preparation plants have been inundated with increased loads of coal and clay particles in their wastewaters. Traditionally, the industry has employed primary sedimentation as the fundamental treatment scheme for these sediment-laden blackwaters. This study was undertaken to determine the effects of a combination of coagulant addition and rapid mixing on the settleability of these particles. After initial testing, aluminum sulfate and two low molecular weight cationic polymers, Cyanamid Magnifloc 513C and Cyanamid 515C, were chosen as primary coagulants for use in this work. An artificial wastewater was prepared from finely powdered (62 to <38 microns) raw coal samples and tap water, after initial tests indicated that typical frothing and/or collector agents had no demonstrable effect on coagulant function. Initially determined optimum coagulant dosages, as well as flocculation and sedimentation times, were kept constant while rapid mix intensities were varied at G values of 330 sec⁻¹, 700 sec⁻¹, 2000 sec⁻¹ and 7000 sec⁻¹ for each sample. Using a combination of residual turbidity and particle size analyses to determine the effectiveness of each rapid mix intensity, it was discovered that only the highest mixing intensities and durations (G(t) values) caused floe disintegration due to overmixing. At the lower G(t) matrices floe formation and settleability was consistently good. When aluminum sulfate was used as a coagulant, the wastewater was tested at a high pH of 8.1 to 8.3 and a low pH of 5.5 to observe floe behavior under different conditions of coagulant mechanism. The test results were similar for both pH values except at the lowest mixing intensities where the high pH samples settled well, resulting in low residual turbidities, but the low pH samples had relatively high turbidities.
Master of Science
ix, 99, [2] leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 8749129
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1982.J663
Coal mines and mining -- Waste disposal
Coal washing
Water -- Purification -- Flocculation
The effects of rapid mixing on the coagulation and sedimentation of ultra-fine coal and clay particles
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Environmental Sciences and Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/1112562022-07-16T07:12:38Zcom_10919_5534col_10919_11041
Strozier, Jariah Li'Shey
Sociology
Baldwin, Andrea N.
Precoda, Karl R.
Labuski, Christine
Brown, Letisha
Faulkner, Brandy S.
2022-07-15T08:00:12Z
2022-07-15T08:00:12Z
2022-07-14
vt_gsexam:35300
http://hdl.handle.net/10919/111256
First described by physician William Dietz in 1995, the "Food Insecurity-Obesity Paradox" (FIOP) attempts to explain the biology and behaviors of people who are simultaneously overweight and food-insecure. I was introduced to this theory as a Behavioral Health graduate student and, in that context, was taught to understand it as a fact. My personal experiences as a Black woman, however, alongside ongoing engagement with Black feminist thought and critical medical sociology, have taught me otherwise. This disssertation takes Dietz's theory as a starting point in order to argue that Black women in the US experience fatphobic and racial discrimination while being "cared for" by western institutional medicine. I argue that discourses like the FIOP, though framed as benevolent clinical theories, do more harm than good: not only do they multiply pathologize so-called "fat" Black women by drawing on disparaging stereotypes, but they simultaneously ignore the specific health and wellness needs that emerge at the intersection of weight, size, skin color, gender, ability, and economic class.
My broader dissertation project is an interdisciplinary critique of pathologizing discourses about Black women, including medically "legitimate" ones like the FIOP. Via critical analysis of these discourses, and employing Black feminist and medical sociological perspectives, I explore how stereotypes of Black women correlate with how these women are perceived and treated by physicians and other health professionals. These racialized perceptions and forms of discriminatory medical treatment are instances of what has been labeled, variously, as a racial formation (Omi and Winant, 1997), a matrix of domination (Patricia Hill Collins, 1990) and a racial ideology (Feagin, 2006). These processes are further extended by physicians who use these pathologizing discourses and practices to advance their own careers. Black feminist theorists have described the multiple marginalizations experienced by contemporary Black women in the US and my project places weight and body size within this marginalizing dynamic. After tracing the long history of medical "othering" of Black women by science, I show the persistence of these ideologies in contemporary medical practice. My interviews with Black women investigate their lived experiences of these ideologies and practices, and allow women to speak for themselves in a space that so often speaks for them.
Doctor of Philosophy
Black women's historical experiences in the US, including my own story, are akin to what Black feminist Melissa Harris-Perry in her book, Sister Citizen: Shame, Stereotypes, and Black Women in America (2011), calls the crooked room. Applying Harris-Perry's theorization of the crooked room to how medical institutions operate to cause Black thick women to be so quickly categorized as diseased, I have developed the concept of the Crooked Room of Medicine (CRoM) to describe the mental, emotional, and physical struggles Black women face at the intersection of race and gender stereotypes and false narratives particularly in medical settings.
I utilize and build upon Black feminist theoretical frameworks as well as my own personal narrative to investigate how a society that is built on racialized and gendered systems has implications for how the large Black female body is interpreted as unhealthy and diseased when treated within these social and medical settings. Building on Tressie McMillan Cottom's scholarship, I utilize a methodology of what I call Thick Studies to develop a Gender Race Weight (GRW) matrix from the crooked room of medicine, to map out our experiences and develop a theory that focuses on healing. The result of Black women's disproportionately poor health outcomes is a result of a complex environment of barriers from quality health care, to racism, and stress correlated with the distinct social experiences of Black womanhood in U.S. society (Chinn. Martin, Redmond 2021). The heaviness of generational racialized trauma is still in our DNA (Degruy-Leary 2017). Racism and gender discrimination have profound impacts on the well-being of Black women. I argue for a holistic health treatment that addresses mind, body, emotion, and spirit and for an acknowledgement of Black women's knowledge of health and healing in relation to Black women, weight, and medical space.
ETD
en
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Black feminisms
medical sociology
Thick Studies
embodiment
healing
A Black Feminist's Critique of the Crooked Room of Medicine (CRoM): Innovation of Thick Studies and the Gender, Race, Weight (GRW) Matrix
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Sociologyopen.accessoai:vtechworks.lib.vt.edu:10919/316442020-09-28T12:54:44Zcom_10919_5534col_10919_9291
Cowing, Brandy Ellen
Human Nutrition, Foods, and Exercise
Davis, Barbara A.
Bunce, George Edwin
Talmadge, Robert J.
2014-03-14T20:33:13Z
2014-03-14T20:33:13Z
2000-04-04
2000-04-07
2001-04-14
2000-04-14
etd-04072000-08550041
http://hdl.handle.net/10919/31644
http://scholar.lib.vt.edu/theses/available/etd-04072000-08550041/
The growth of many breast cancers is stimulated by the action of the hormone estrogen. Hormonal therapy used to treat these estrogen-dependent breast cancers acts by interfering with the action of estrogen. Current treatments, such as tamoxifen, are not consistently useful due to development of resistance to these drugs. Tamoxifen treatment can also lead to the development of other gynecological cancers, therefore the discovery of novel treatment options for breast cancer is critical. Vitamin B6 is well documented for its role as a modulator of steroid hormones. Pyridoxal phosphate (PLP), the active form of Vitamin B6, may interfere with the action of the estrogen receptor (ER) by blocking the hormone-binding and/or DNA-binding site of the ER. The objective of this study was to examine the effects of Vitamin B6 supplementation on cell proliferation and estrogen-dependent gene expression in breast cancer cells. To accomplish this, estrogen-dependent (MCF-7 and T-47D) and estrogen-independent (BT-20) breast cancer cells were grown in medium supplemented with 0,100, or 300 µM pyridoxal (PL) in the absence or presence of 0.01µM estradiol. Cell counts and [3H]-thymidine incorporation into DNA were assessed in all cell lines. The expression of pS2, an estrogen-sensitive gene, was performed using RNA extracted from MCF-7 cells. PL supplementation was found to significantly decrease total cell numbers and DNA synthesis in both the estrogen-dependent (ER+) and -independent (ER-) breast cancer cells, but did not alter the expression of pS2. These results indicate that PL significantly impairs growth of breast cancer cells and may be exerting its effects via a steroid-independent mechanism.
Master of Science
Virginia Tech
brandyellen1.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Estrogen
Pyridoxal
Vitamin B6
Breast Cancer
Steroid Hormone
Mammary
Vitamin B6 Decreases Proliferation and DNA Synthesis in Human Mammary Carcinoma Cell Lines In Vitro
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Human Nutrition, Foods, and Exerciseopen.accessoai:vtechworks.lib.vt.edu:10919/286842022-02-22T19:39:28Zcom_10919_5534col_10919_11041
Tan, Roy Patrick
Computer Science
Edwards, Stephen H.
Tegarden, David P.
Pérez-Quiñones, Manuel A.
Arthur, James D.
Ramakrishnan, Naren
2014-03-14T20:15:18Z
2014-03-14T20:15:18Z
2007-08-08
2007-08-16
2007-08-27
2007-08-27
etd-08162007-161911
http://hdl.handle.net/10919/28684
http://scholar.lib.vt.edu/theses/available/etd-08162007-161911/
Software testing is a necessary and integral part of the software quality process. It is estimated that inadequate testing infrastructure cost the US economy between $22.2 and $59.5 billion.
We present Sulu, a programming language designed with automated unit testing specifically in mind, as a demonstration of how software testing may be more integrated and automated into the software development process. Sulu's runtime and tools support automated testing from end to end; automating the generation, execution, and evaluation of test suites using both code coverage and mutation analysis. Sulu is also designed to fully integrate automatically generated tests with manually written test suites. Sulu's tools incorporate pluggable test case generators, which enables the software developer to employ different test case generation algorithms.
To show the effectiveness of this integrated approach, we designed an experiment to evaluate a family of test suites generated using one test case generation algorithm, which exhaustively enumerates every sequence of method calls within a certain bound. The results show over 80\% code coverage and high mutation coverage for the most comprehensive test suite generated.
Ph. D.
Virginia Tech
sulu.zip
thesis.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
programming language
software engineering
Sulu
unit testing
software testing
Programming Language and Tools for Automated Testing
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Computer Scienceopen.accessoai:vtechworks.lib.vt.edu:10919/385452021-05-25T14:24:53Zcom_10919_5534col_10919_11041
Kirby, Carl Scott
Geology
Rimstidt, J. Donald
Craig, James R.
Herman, Janet S.
Ribbe, Paul H.
Zelazny, Lucian W.
2014-03-14T21:14:50Z
2014-03-14T21:14:50Z
1993-08-05
2006-06-07
2006-06-07
2006-06-07
etd-06072006-124154
http://hdl.handle.net/10919/38545
http://scholar.lib.vt.edu/theses/available/etd-06072006-124154/
Bulk chemical analysis of a combined municipal solid waste (MSW) bottom and fly ash from one facility showed most elements enriched over average soil abundances. Eleven minerals were identified using powder X-ray diffraction (XRD). Standard additions using XRD gave the following weight % minerals (±2σ): gypsum, 1.8 ± 1.9; hematite, 3.7 ± 1.7; quartz, 2.3 ± 1.0; spinel, approximately 3.5; halite, 0.5 ± 0.4; calcite 3.5 ± 1.9; rutile, 1.1 ± 1.3. Mullite, sylvite, anhydrite, and wüstite were also identified. The ash contained 18% minerals, 9% structural and adsorbed water, and 72% glass.
Chemical sequential extraction showed that most Cr is present in phases resistant to chemical weathering, while significant Cd and Pb are sequestered in acid soluble (carbonate) phases. Little of these toxic trace metals are water soluble or in exchangeable surface sites.
Batch reactors experiments showed that ash-water solutions were dominated by ions released by soluble salts. Three types of reactions are identified. 1) After rapid exhaustion of soluble salts, sodium and potassium exhibited nearly steady state behavior due to slow release of ions from less-soluble minerals and glasses. 2) Calcium and sulfate concentrations are controlled by either gypsum or anhydrite equilibrium after a few hours. Iron, aluminum, and manganese concentrations rapidly equilibrate with respect to hydroxide or oxide solid phases. 3) Silicon clearly shows temperature dependent kinetic behavior, but its rate of release into solution is slowed by back-reaction of a secondary silicate phase.
Calculation of the CIPW normative minerals for MSW ash showed it to be analogous to a tholeiitic basalt. Over the long term, the concentrations of elements in MSW ash will continue to change and can be predicted by Goldschmidt's concept of ionic potential, and mineralogical changes can be predicted based on weathering of basalts.
Comparisons of literature values showed that field MSW ash leachates contained higher concentrations of soluble salts and lower concentrations of magnesium, iron, zinc, copper, and nickel than uncombusted refuse leachates. Comparison of chromium, cadmium, lead, and arsenic concentrations did not clearly delineate which leachate contains more of these elements.
Ph. D.
vii, 103 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 29179669
LD5655.V856_1993.K572.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1993.K572
Ash disposal -- Analysis
Fly ash
Refuse and refuse disposal -- Analysis
A geochemical analysis of municipal solid waste ash
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Geologyopen.accessoai:vtechworks.lib.vt.edu:10919/1172662023-12-23T03:00:15Zcom_10919_5534col_10919_9291
He, Chongyu
Computer Science and#38; Applications
Fox, Edward A.
Xie, Zhiwu
Polys, Nicholas Fearing
Chen, Yinlin
2023-12-22T09:00:48Z
2023-12-22T09:00:48Z
2023-12-21
vt_gsexam:39186
https://hdl.handle.net/10919/117266
The intricate task of segmenting and quantifying cell nuclear pores in high-resolution 3D microscopy data is critical for cellular biology and disease research. This thesis introduces a deep learning pipeline crafted to automate the segmentation and quantification of nuclear pores from high-resolution 3D cell organelle images. Our aim is to refine computational methods capable of handling the data's complexity and size, thus improving accuracy and reducing manual labor in biological image analysis. The developed pipeline incorporates data preprocessing, augmentation strategies, random block sampling, and a three-stage post-processing algorithm. It utilizes a 3D U-Net with a VGG-16 backbone, optimized through cyclical data augmentation and random block sampling to tackle the challenges posed by limited labeled data and the processing of large-scale 3D images. The pipeline has demonstrated its capability to effectively learn and predict nuclear pore structures, achieving improvements in validation metrics compared to baseline models. Our experiments suggest that cyclical augmentation helps prevent overfitting, and random block sampling contributes to managing data imbalance. The post-processing phase successfully automates the quantification of nuclear pores without the need for manual intervention. The proposed pipeline offers an efficient and scalable approach to segmenting and quantifying nuclear pores in 3D microscopy images. Despite the ongoing challenges of computational intensity and data volume, the techniques developed in this study provide insights into the automation of complex biological image analysis tasks, with potential applications extending beyond the detection of nuclear pores.
Master of Science
This thesis outlines a computer program developed to automatically segment and count nuclear pores in 3D cell images, aiding cell and disease research. This program aims to handle large, complex image data more effectively, boost accuracy, and cut down the need for manual labor. We created a system that prepares data, applies a technique called augmentation to enrich it, selects specific image sections, and carries out a three-step final analysis. At the core of our program is a 3D U-Net model, a type of deep learning network, that has been enhanced to address the challenges of scarce labeled data and the processing of very large images. The system developed is capable of learning and identifying the structure of nuclear pores in cell images. Our experiments indicate that using augmentation in a cyclical manner during training can prevent overfitting, which is when a model learns the training data too well, and cannot suitably generalize. Selecting certain parts of the images for processing proves helpful with imbalanced data. Additionally, the program can automatically count nuclear pores in the final step. The proposed program is effective for analyzing and counting nuclear pores in 3D cell images and has the potential for broader applications in cell analysis. Despite the challenges of managing large datasets and the significant computational power required, our methods open new possibilities for automating cell studies, with uses extending beyond just nuclear pores.
ETD
en
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
High Resolution Data
3D cell Segmentation
Nuclear Pore
Machine Learning
Deep Learning Approach for Cell Nuclear Pore Detection and Quantification over High Resolution 3D Data
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Computer Science & Applicationsopen.accessoai:vtechworks.lib.vt.edu:10919/193292022-02-03T19:05:01Zcom_10919_5534col_10919_9291
Lambeth, Jacob Nelson
Mechanical Engineering
Ferris, John B.
Tjhung, Tana
Taheri, Saied
2013-04-23T08:00:12Z
2013-04-23T08:00:12Z
2013-04-22
vt_gsexam:601
http://hdl.handle.net/10919/19329
Accurate terrain models provide the chassis designer with a powerful tool to make informed design decisions early in the design process. During this stage, engineers are challenged with predicting vehicle loads through modeling and simulation. The accuracy of these simulation results depends not only on the fidelity of the model, but also on the excitation to the model. It is clear that the terrain is the main excitation to the vehicle [1]. The inputs to these models are often based directly on physical measurements (terrain profiles); therefore, the terrain measurements must be as accurate as possible. A collection of novel methods can be developed to aid in the study and application of 3D terrain measurements, which are dense and non-uniform, including efficient gridding, stochastic modeling, and compact characterization.
Terrain measurements are not collected with uniform spacing, which is necessary for efficient data storage and simulation. Many techniques are developed to help effectively grid dense terrain point clouds in a curved regular grid (CRG) format, including center and random vehicle paths, sorted gridding methods, and software implementation. In addition, it is beneficial to characterize the terrain as a realization of an underlying stochastic process and to develop a mathematical model of that process. A method is developed to represent a continuous-state Markov chain as a collection of univariate distributions, to be applied to terrain road profiles. The resulting form is extremely customizable and significantly more compact than a discrete-state Markov chain, yet it still provides a viable alternative for stochastically modeling terrain. Many new simulation techniques take advantage of 3D gridded roads along with traditional 2D terrain profiles. A technique is developed to model and synthesize 3D terrain surfaces by applying a variety of 2D stochastic models to the topological components of terrain, which are also decomposed into frequency bandwidths and down-sampled. The quality of the synthetic surface is determined using many statistical tests, and the entire work is implemented into a powerful software suite. Engineers from many disciplines who work with terrain surfaces need to describe the overall physical characteristics compactly and consistently. A method is developed to characterize terrain surfaces with a few coefficients by performing a principal component analysis, via singular value decomposition (SVD), to the parameter sets that define a collection of surface models.
Master of Science
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Terrain
Surfaces
Gridding
Modeling
Characterization
Markov Chains
Improved Methods for Gridding, Stochastic Modeling, and Compact Characterization of Terrain Surfaces
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Mechanical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/451452022-02-22T22:01:45Zcom_10919_5534col_10919_9291
Goehring, Lutz Steffen
Veterinary Medical Sciences
Furr, Martin O.
Buechner-Maxwell, Virginia A.
Ahmed, S. Ansar
2014-03-14T21:47:28Z
2014-03-14T21:47:28Z
1998-08-14
1998-10-11
1999-04-11
1998-04-11
etd-101098-101319
http://hdl.handle.net/10919/45145
http://scholar.lib.vt.edu/theses/available/etd-101098-101319/
Equine Protozoal Myeloencephalitis is the most frequently diagnosed neurologic disorder of horses in the united states, which is caused by the protozoan organism Sarcocystis neurona. The disease has a profound impact on the American Horse Industry. This impact includes prolonged and expensive treatment without a guaranteed return to a previous level of use for the individual horse. Poor respponse to and prolonged duration of treatment may suggest an immune mediated impariement of host response. There is limited information about the direct interaction between the pathogen and the host.
In two in vitro experiments we investigated a) whether the presence of the protozoan organism can influence mitogen-stimulated peripheral blood mononuclear cells (PBMCs), suggesting a direct influence of the protozoan organism on cells of the immune system, and b) if cerebrospinal fluid (CSF) from horses with EPM has an effect on mitogen-stimulated PBMCs, suggesting that the microenvironment of the site of infection influences the course of disease.
Experiment 1: Mitogen simulated PBMCs from EPM affected and control horses were co-cultured with fragments of freeze thawed bovine turbinate cells that were infected with S. neurona merozoites. Compared to controls PBMCs co-cultured with S. neurona fragments were the only cells that showed a decreased proliferation (p<0.05). A difference between EPM affected and control horses could not be detected (p>0.05). These results may imply that the persistence of S. neurona infection in the horses CNS is, in part, due to a pathogen-derived mechanism that attentuates the hosts immune response.
Experiment 2: Mitogen stimulated PBMCs from a horse affected with EPM and a control were co-cultured n the presence of CSF from EPM affected and uninfected controls. Prior to co-culture the CSF was fractionated by a filtration process over two microfilter units. An identical volume of NaCl (0.9%) served as a control for the volume of CSF that was added. The proliferation assay revealed a deviation of the response depending on cell donor and CSF fraction used. The effect was independant of the protein concentration of the CSF fraction, and a decrease in lymphocyte proliferation was not caused by increased cellular death. This suggests the presence of subsets within the CSF which have a stimulatory of suppressive influence on the cells in culture. The effect was cell donor dependant which implies a difference in lymphocyte subsets between the two horses that were used.
Master of Science
Virginia Tech
ThesisF2.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Sarcocystis neurona
Equine Protozoal Myeloencephalitis
immune priviledged site
Lymphocyte proliferation assay
Horse
Equine Protozoal Myeloencephalitis. Preliminary Investigation of Protozoan-Host interactions in the horse
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Veterinary Medical Sciencesopen.accessoai:vtechworks.lib.vt.edu:10919/384262021-12-14T21:29:37Zcom_10919_5534col_10919_11041
Coker, Dianna Ross
Business (Accounting)
Brown, Robert M.
Killough, Larry N.
Baldwin, Dirk S.
Franchina, Joseph J.
Singh, Kusum
2014-03-14T21:14:20Z
2014-03-14T21:14:20Z
1993-02-22
2008-06-06
2008-06-06
2008-06-06
etd-06062008-170640
http://hdl.handle.net/10919/38426
http://scholar.lib.vt.edu/theses/available/etd-06062008-170640/
Accounting education research has explained some variation in student performance by aptitude, attitude, and experience variables, as well as gender. The unexplained portion of variance, however, suggests the existence of unidentified variables. This study examines the relationship of visual-spatial aptitude (VSA) to student completion and continuing behaviors and to performance in four accounting courses. VSA is a group of cognitive abilities which facilitate building mental representations and solving problems and which are positively related to performance in mathematics and science courses.
This study hypothesizes that high VSA students will complete Accounting Principles I at a higher rate, continue to Principles II at a higher rate, and perform better in Principles I than will low VSA students. Also hypothesized are gender differences and course differences in the relationship between VSA and performance.
Subjects are students tracked in accounting courses for three semesters. Independent variables include gender, prior bookkeeping coursework, and major, as well as SAT scores, GPA, and scores on two VSA tests--the MAP Planning Test (MAP) and the Mental Rotations Test (MRT). MAP and MRT measures include the number right, the number wrong, and the percentage right. Dependent variables include student completion and continuing status as well as performance scores in each of four courses.
Results indicate that high VSA subjects have a higher completion rate than do low VSA subjects and that completers of Principles I have higher VSA than do droppers. Also, continuers to Principles II have higher VSA than do non continuers.
Results indicate relationships between VSA and Principles I scores. Subjects with high MRT percentages score higher on exams and lower on homework/quizzes than do those with low MRT percentages. Subjects with few MRT wrong have higher exam scores than do those with more MRT wrong.
MAP is related only to Principles II and Intermediate, while MRT is related only to Principles I, II, and Cost. Relationships of VSA to exams are positive and frequent. Relationships to homework/quizzes are negative and less frequent. Computerized practice set scores are rarely related to VSA.
In separate analyses of students taking Principles I, VSA is related to homework and exams for females and only to exams for males. For the smaller sample of students continuing to Principles II, models which contain general aptitude covariates indicate that VSA is only related to female performance and only in Principles I.
Ph. D.
x, 185 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 28689701
LD5655.V856_1993.C647.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1993.C647
Accounting -- Study and teaching (Higher)
Space perception
Visual perception
The role of visual-spatial aptitude in accounting coursework
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Business (Accounting)open.accessoai:vtechworks.lib.vt.edu:10919/432622021-05-04T18:49:14Zcom_10919_5534col_10919_9291
O'Neill, Michael Douglas
Electrical Engineering
2014-03-14T21:38:23Z
2014-03-14T21:38:23Z
1988
2010-06-12
2010-06-12
2010-06-12
etd-06122010-020415
http://hdl.handle.net/10919/43262
http://scholar.lib.vt.edu/theses/available/etd-06122010-020415/
An improved algorithm for the automatic generation of test vectors from chip-level descriptions written in VHDL is described. The method offers an order of magnitude speed improvement over earlier test generation algorithms. The algorithm accepts data flow circuit descriptions written in a subset of VHDL. A fault model which defines faults for the VHDL statements is applied to determine fault cases. Test generation requirements of fault sensitization, value justification, and fault effect propagation are expressed in terms of justification, propagation, and execution goals, rather than in terms of low-level operations. Prolog rules define the way in which the goals are satisfied, using backtracking to select alternative solutions. A method for handling time in absolute, rather than relative, terms is discussed. Comparison of run times for the improved algorithm against those obtained by the previous method is made to demonstrate the speedup. Suggestions for incorporating the algorithm into a test generation system are discussed. A user’s guide is given for the current implementation of the method.
Master of Science
viii, 108 leaves
BTD
application/pdf
Virginia Tech
OCLC# 17796926
LD5655.V855_1988.O645.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1988.O645
Integrated circuits -- Large scale integration
An improved chip-level test generation algorithm
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Electrical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/910552020-09-25T20:33:36Zcom_10919_5534col_10919_9291
Parris, Donald R.
Materials Engineering
2019-07-03T18:56:43Z
2019-07-03T18:56:43Z
1986
http://hdl.handle.net/10919/91055
DC resistance and AC conductance and capacitance have been measured under various conditions in an effort to electrically characterize and make electrical-mechanical correlations for 15 carbon black filled rubber samples.
Resistance, conductance and capacitance have been monitored as functions of uniaxial compressive stress, time, temperature, and mechanical and thermal history. Capacitance and conductance have also been monitored as functions of frequency under various degrees of compressive loading and before and after specific heat treatments.
A direct relationship has been found between sample • conductance and capacitance under any thermal and/or mechanical condition. This is in agreement with previous theories of conduction network formation and percolation. Various conduction mechanisms have been enumerated and an equivalent circuit of a network of lumped R-C "microelements'' has been qualitatively described. Stress, relaxation, frequency, and temperature dependences of the macroscopic parameters measured ( conductivity and capacitance) are discussed in terms of this model.
M.S.
xi, 119 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 13488866
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1986.P377
Rubber -- Electric properties
Carbon-black -- Testing
Composite materials -- Electric properties
Rubber -- Testing
Composite materials -- Testing
Electrical characterization of carbon black filled rubber
Thesis
Text
M.S.
masters
Virginia Polytechnic Institute and State University
Materials Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/414932022-03-04T18:21:10Zcom_10919_5534col_10919_9291
Kunselman, Gary L.
Electrical Engineering
Moore, Daniel J.
Davis, William A.
Elshabini-Riad, Aicha A.
2014-03-14T21:31:13Z
2014-03-14T21:31:13Z
1992-12-15
2009-03-12
2009-03-12
2009-03-12
etd-03122009-040933
http://hdl.handle.net/10919/41493
http://scholar.lib.vt.edu/theses/available/etd-03122009-040933/
Portable communication systems require, in part, high-efficiency radio frequency power amplifiers (RF PA) if battery lifetime is to be conserved. Conventional amplifier classifications and definitions are presented in a unified and concise format. The Bipolar Junction Transistor (BJT) and Metal-Semiconductor Field Effect Transistor (MESFET) are evaluated as active devices in high-efficiency RF PA designs. Two amplifier classes (class CE and class F) meet the system requirements of an 850 MHz operating frequency, a power output of 3 W, a battery supply voltage of 9 Vdc, and a sinusoidal-type signal to be amplified. Both classes are evaluated through recent research literature and simulated using the PSpice® computer simulation program. Class CE and class F are found to provide efficiencies exceeding 80 percent under the given system constraints.</p.
Master of Science
viii, 94 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 27871888
LD5655.V855_1992.K867.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1992.K867
Amplifiers, Radio frequency
Portable radios
Radio -- Receivers and reception
Radio frequency power amplifiers for portable communication systems
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Electrical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/345512020-12-09T13:55:40Zcom_10919_5534col_10919_9291
Gray, David T.
Materials Science and Engineering
Hendricks, Robert W.
Guido, Louis J.
Farkas, Diana
2014-03-14T20:43:30Z
2014-03-14T20:43:30Z
2002-12-20
2003-08-15
2004-02-19
2004-02-19
etd-08152003-103345
http://hdl.handle.net/10919/34551
http://scholar.lib.vt.edu/theses/available/etd-08152003-103345
The main objective of this work is to develop and optimize a process for the fabrication of basic semiconductor devices in silicon using the Modu-lab toolset in the MicrON 636 Whittemore cleanroom facility. This toolset is designed to work with four-inch silicon wafers, in a class 10000 cleanroom. Early work on this process produced functioning devices, with low yield and little to no process control. Three aspects of the process were therefore selected for optimization in this work.
The oxidation of the surface of the silicon wafers could not be made to follow models proposed by and accepted in the literature. By carefully changing the airflow in the oxidation furnace module, the uniformity of the oxide layer and the agreement of the growth with models increases to acceptable levels. Also, the effects of redistribution of dopant species due to growth of the oxide layer and the subsequent thermal processing are examined qualitatively.
Phosphorus diffusion in single-crystal silicon has a complex diffusion mechanism involving charged-vacancies, with concentration-dependent diffusion coefficients. It is therefore a complex mathematical problem to model the diffusion of phosphorus from a solid source within the crystal. An empirical model is proposed that accurately predicts the junction depth and sheet resistance of diffused phosphorus layers within the silicon wafer.
Throughout the course of the process it is necessary to monitor the characteristics of the wafers to assure proper conditions. A semiconductor parameter analyzer has been created for this purpose. Our system uses a Keithley model 2400 source meter, Signatone probe station and four-point probe stage, and a PC to measure DC I-V electrical characteristics of materials and devices. The measurements of sheet resistance, as well as device characterization of resistors, p-n junction diodes, and nMOSFETs provides feedback about the accuracy of processing steps, as well as a pedagogical tool for illustrating semiconductor device physics and operation.
Master of Science
Virginia Tech
fianlvers4.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Transistor
Cleanroom
Silicon
Labview
Semiconductor
Optimization of the Process for Semiconductor Device Fabrication in the MicrON 636 Whittemore Cleanroom Facility
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Materials Science and Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/320722021-12-16T17:43:13Zcom_10919_5534col_10919_9291
Bumann, George Bruce
Fisheries and Wildlife Sciences
Stauffer, Dean F.
Norman, Gary W.
Vaughan, Michael R.
Kirkpatrick, Roy L.
2014-03-14T20:34:40Z
2014-03-14T20:34:40Z
2002-04-12
2002-05-01
2003-07-24
2002-07-24
etd-05012002-114423
http://hdl.handle.net/10919/32072
http://scholar.lib.vt.edu/theses/available/etd-05012002-114423/
Predation accounts for the majority of ruffed grouse mortality beyond the brooding period throughout grouse range. Most studies of ruffed grouse ecology have taken place in the central portion of the species range including the Great Lakes states and southern Canada where aspen (Populus tremuloides) is dominant. Populations in the central range of grouse distribution exhibit 10-year cyclic patterns of decline that have been associated with the invasions of boreal predators such as great horned owls and northern goshawks during crashes in small mammal populations.
I completed an accuracy assessment of field sign to determine the role of scavenging as it related to diagnosing causes of proximate mortality. Potentially large numbers of grouse are scavenged after death, which can alter or completely falsify the reported cause of death.. My results indicated that stand-level and micro-site habitat variables did not influence scavenger detection of ruffed grouse carcasses (P > 0.05). Scavenging was limited to 24 of 64 carcasses and was entirely attributed to mammalian species. Scavenging behavior was related to the condition of the carcass following death (P = 0.003) and the ambient temperature (P = 0.01). As the temperature increased and as a carcasses entrails and muscle became more exposed, the probability of being scavenged increased. Nineteen percent of whole carcasses placed in the field were scavenged and would have been attributed to mammal predation based on the field sign; 56% of 32 mock avian kills were scavenged would have been attributed to mammal predation.
I related indices of predators and weather patterns to trends in ruffed grouse predation. Using data collected at 10 study sites between February, 1997 and December, 2000, I compared predation rates, and animal and weather indices to predation rates, across sites, years, regions, seasons and month combinations pooled across years. Avian predators were the primary predators of ruffed grouse in the Appalachian region (50% of all predation). Predation rates on ruffed grouse were highest in fall (8.3%), due to high predation on juveniles, and spring (7.4%) in association with raptor migration and pre-breeding activity of grouse. Predation patterns and predator abundance did not indicate the occurrence of predator invasions during the years of this study. Predation rates on ruffed grouse were positively related to the presence of rain and negatively related to the average low temperature and number of rabbits and squirrels observed per hour. Observations of owls and Cooper's hawks per hour were correlated with predation rates on grouse while those of red-tailed, red-shouldered and broad-winged hawks were not.
Master of Science
Virginia Tech
Resume.pdf
Bumann.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
ACGRP
scavenging
ruffed grouse
predators
Factors Influencing Predation on Ruffed Grouse in the Appalachians
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Fisheries and Wildlife Sciencesopen.accessoai:vtechworks.lib.vt.edu:10919/285252022-02-22T19:39:26Zcom_10919_5534col_10919_11041
Ertel, Richard Brian
Electrical and Computer Engineering
Reed, Jeffrey H.
Beattie, Christopher A.
Rappaport, Theodore S.
Tranter, William H.
Woerner, Brian D.
2014-03-14T20:14:45Z
2014-03-14T20:14:45Z
1999-07-28
1999-08-04
2000-08-13
1999-08-13
etd-080499-141603
http://hdl.handle.net/10919/28525
http://scholar.lib.vt.edu/theses/available/etd-080499-141603/
Due to the enormous performance gains associated with the use of antenna arrays in wireless networks, it is inevitable that these technologies will become an integral part of future systems. This report focuses on signal propagation modeling for antenna array systems and on its relationship to the performance of these systems. Accurate simulation and analytical models are prerequisite to the characterization of antenna array system performance. Finally, an understanding of the performance of these systems in various environments is needed for effective overall network design.
This report begins with an overview of the fundamentals of antenna array systems. A survey of vector channel models is presented. Angle of arrival and time of arrival statistics for the circular and elliptical (Liberti's Model) models are derived. A generalized optimum output SINR analysis is derived for space-time processing structures in frequency selective fading channels. The hardware and software of the MPRG Antenna Array Testbed (MAAT) is described. A literature review of previous antenna array propagation measurements is given. Antenna array measurement results obtained with the MAAT are used to compare the properties of the received signal vector in the various environmental conditions. The influence of channel parameters on the ability of antenna arrays to separate the signals of two users on the reverse link is studied using simulation. Finally, forward link beamforming techniques are reviewed.
Ph. D.
Virginia Tech
rerteldiss.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
propagation modeling
antenna arrays
wireless communications
Antenna Array Systems: Propagation and Performance
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Electrical and Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/534722021-02-23T17:17:02Zcom_10919_5534col_10919_9291
Rollins, Gilbert Horace
Dairy Husbandry
2015-06-23T19:12:16Z
2015-06-23T19:12:16Z
1948
http://hdl.handle.net/10919/53472
A controlled feeding experiment was conducted to compare the influence of barn-cured and field-cured alfalfa hay out from the same field on milk production and liveweight of dairy cows. Twelve Holstein cows were used in this trial. The double-reversal feeding method was followed. Grain was fed at the same rate to each group of cows. Hay was fed as the only source of roughage, and equal amounts of the two kinds of hay were fed to the two groups of cows. There was practically no difference in the total consumption of the two kinds of hay. Analysis of variance on the amounts of four per cent fat-corrected milk produced revealed highly significant differences at the one per cent level in favor of the barn-cured hay. The hays were sampled at regular intervals for proximate analysis. At the time of feeding the barn-cured hay contained .36 per cent more moisture, 2.63 per cent more protein, .26 per cent more fat, 1.20 per cent less fiber, 2.26 per cent less nitrogen-free extract, and .66 per cent more ash. The cows gained slightly in liveweight when they received the field-cured hay and lost slightly in liveweight when they received the barn-cured hay. Liveweight changes were not significant when analyzed statistically.
Master of Science
[2], 41, [7] leaves
application/pdf
en_US
Virginia Polytechnic Institute
OCLC# 29869496
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1948.R644
Alfalfa as feed
A comparison of the influence of barn-cured and field-cured alfalfa hay on milk production
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute
Dairy Husbandryopen.accessoai:vtechworks.lib.vt.edu:10919/777792020-09-28T13:27:54Zcom_10919_5534col_10919_11041
Park, Young Hoon
Chemical Engineering
Wallis, David A.
Konrad, Kenneth
Michelsen, Donald L.
Yousten, Allan A.
2017-05-24T18:19:09Z
2017-05-24T18:19:09Z
1983
http://hdl.handle.net/10919/77779
Performance of a three-phase fluidized-bed biofilm fermenter system, which is used for the production of a secondary metabolite, is analyzed through computer simulation techniques. Penicillin fermentation was chosen for the model system. From the steady-state analysis, it was found that a complete-mixed contacting pattern is superior to a plug flow pattern in terms of productivity, since less inhibitory effect of the substrate is pronounced in that configuration. Optimum biofilm thickness for the fermenter system was found to be a function of various operating parameters, and should be determined from information on the interactions between fermenter productivity and the operating conditions.
The dynamic analysis has shown that for a given constant oxygen transfer rate in bulk phase, there exist operating conditions optimal for maximizing the volumetric productivity of the fermenter system. When a constant oxygen transfer rate with a k.e.a of 300 hr 1 was used with a complete-mixed contacting pattern, the optimum inlet substrate con- centration and mean residence time were found to be 20 (g glucose/liter) and 10 (hours), respectively. Production phase could be extended by increasing the substrate concentration in the feed stream, but the optimum increasing rate and initiation time of increase are functions of other operating parameters, such as initial inlet substrate concentration, mean residence time, and oxygen transfer rate in the fermentor. An increasing rate of 0.6 g glucose/liter/hr with the initiation time t 0 = 51 was found to be the optimal, for the operating conditions found in the dynamic analysis. The result has also shown that a high total biomass concentration and a high oxygen transfer rate in the fermentor are the most important factors to achieve a high productivity.
Ph. D.
xiv, 239, [2] leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 9494939
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1983.P374
Fermentation -- Simulation methods
Microbial metabolites
Penicillin
Computer simulation
An analysis of microbial film fermentor system for production of secondary metabolites
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Chemical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/463202021-04-23T13:35:50Zcom_10919_5534col_10919_9291
Sanders, Christopher Sun
Political Science
Nelson, Scott G.
Zanotti, Laura
Stivachtis, Yannis A.
2014-03-14T21:52:06Z
2014-03-14T21:52:06Z
2010-12-08
2010-12-20
2011-01-21
2011-01-21
etd-12202010-093229
http://hdl.handle.net/10919/46320
http://scholar.lib.vt.edu/theses/available/etd-12202010-093229/
This thesis uses ideas found in Michel Foucault's Discipline and Punish and related works as a theoretic framework for examining daily life in North Korea to understand what type of disciplinary techniques North Korean citizens are subjected to by the North Korean state. This paper will define several disciplinary strategies discussed by Foucault and then show how these strategies are deployed against the North Korean population through multiple examples. Analysis will demonstrate that these disciplinary strategies prevent political instability and suppress ideas dangerous to the North Korean regime, even while the North Korean regime fails to provide basic services for its population. As a result, the reader will have a better understanding of why the North Korean people seem so disciplined and do not rebel against the North Korean regime in the face of state-made disasters and hardships.
Master of Arts
Virginia Tech
Sanders_CS_T_2010.PDF
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Discipline
Power
Knowledge
Panopticon
Michel Foucault
North Korea
Dictatorships
Totalitarianism
The North Korean Security State: Examining the North Korean Population through Michel Foucault's Theories of Discipline and Punishment
Thesis
Master of Arts
masters
Virginia Polytechnic Institute and State University
Political Scienceopen.accessoai:vtechworks.lib.vt.edu:10919/781712020-09-28T12:29:22Zcom_10919_5534col_10919_9291
Grunert, Jonathan David
Science and Technology Studies
Barrow, Mark V. Jr.
Goodrum, Matthew R.
Wisnioski, Matthew
2017-06-13T19:44:28Z
2017-06-13T19:44:28Z
2014-09-18
2014-10-20
2015-01-22
2015-01-22
etd-10202014-111323
http://hdl.handle.net/10919/78171
http://scholar.lib.vt.edu/theses/available/etd-10202014-111323/
In this project I explore the development of bird illustrations in early American natural history publication. I follow three groups in Philadelphia from 1812 to 1858: institutions, artist-naturalists, and printmakers. Each of these groups modeled a certain normative vision of illustration, promoting, producing, and publishing images that reflected their senses of what constituted good illustration. I argue that no single set of actors in this narrative did work that would become the ultimate standard-bearer for ornithological illustration; rather, all of them negotiated the conflicting interests of their own work as positioned against, or alongside, those who had come before. Their diverse intentions, aesthetic and practical, sat prominently in their separate visions of drawing birds; utility, artistry, and feasibility of the images directed the creation of the illustrations. How they used their ideal ways of depicting birds changed the ways that their successors would confront the practice of illustrating birds.
Master of Science
en_US
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
ornithology
Philadelphia
illustration
natural history
Aesthetics for Birds: Institutions, Artist-Naturalists, and Printmakers in American Ornithologies, from Alexander Wilson to John Cassin
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Science and Technology Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/451162021-05-14T15:53:26Zcom_10919_5534col_10919_9291
Ramachandran, Sridhar
Industrial and Systems Engineering
2014-03-14T21:47:14Z
2014-03-14T21:47:14Z
1991
2009-10-10
2009-10-10
2009-10-10
etd-10102009-020147
http://hdl.handle.net/10919/45116
http://scholar.lib.vt.edu/theses/available/etd-10102009-020147/
This thesis is concerned with the analysis of a Rectilinear Distance Location Allocation Problem, where the costs are directly proportional to rectilinear distances and the amount shipped. The problem is formulated as a Mixed Integer Bilinear Programming Problem and as a Discrete Location Allocation Problem. Using linear programming relaxations constructed via the Reformulation-Linearization Technique (RLT), the latter formulation is shown to provide stronger lower bounds and is therefore adopted for implementation. In addition, cutting planes are developed to further strengthen the linear programming relaxation. The special structure of the resulting linear program is exploited in order to get a quick lower bound via a suitable Lagrangian dual formulation. This lower bounding scheme is embedded within a finitely convergent Branch and Bound algorithm that enumerates over the location decision variable space. An illustrative example and computational experience are provided to demonstrate the efficacy of the proposed algorithm.
Master of Science
viii, 78 leaves, illustrations; 28
BTD
application/pdf
en
Virginia Tech
OCLC# 24344726
LD5655.V855_1991.R363.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Combinatorial enumeration problems
LD5655.V855 1991.R363
A reformulation-linearization based implicit enumeration algorithm for the rectilinear distance location-allocation problem
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Industrial and Systems Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/401202023-08-13T19:27:29Zcom_10919_5534col_10919_11041
Pandya, Ashish
Chemistry
Gibson, Harry W.
Dorn, Harry C.
McGrath, James E.
Marand, Hervé L.
Riffle, Judy S.
Tanko, James M.
2014-03-14T21:22:05Z
2014-03-14T21:22:05Z
1992
2005-10-24
2005-10-24
2005-10-24
etd-10242005-124113
http://hdl.handle.net/10919/40120
http://scholar.lib.vt.edu/theses/available/etd-10242005-124113/
Novel A-A and A-B difunctional monomers were synthesized by utilizing Reissert compound chemistry and via the use of bis(α-aminonitrile)s. These monomers were produced in high yields with preformed heterocyclic nuclei which included benzothiazole, isoquinoline and quinoline. Acylated linear polyamine derivatives were obtained by the step growth condensation polymerization of open chain bis(Reissert compound)s with suitable dihaloalkanes; intrinsic viscosities of up to 0.48 dl/g were obtained in unoptimized runs. The constitutional repeat unit of these polymers consists of four independent structural variables and thus provides versatility for tailor made macromolecular syntheses.
Novel bis(Schiff base) monomers based on 1,4-trans-diamino cyclohexane were synthesized and these could be used either directly in the production of poly(azomethine aryl ether)s or synthesis of diamines and dicarboxylic acids containing the trans cyclohexyl moiety.
Novel aromatic diamine based bis(α-aminonitrile)s were synthesized from commercially available diamines and are currently being used in the syntheses of post-reaction modifiable co-polyamides.
A novel and unique product of rearrangement of benzothiazole Reissert compounds was isolated and characterized. It was postulated that the reaction proceeds via a bimolecular reaction between 2-cyanobenzothiazole and the’ ring opened azomethinethiophenoxide followed by an intramolecular acyl transfer and eventual reaction with methyl iodide leading to a novel benzothiazine.
A novel nucleophilic aromatic substitution reaction was discovered which involved the reaction of a masked carbonyl carbanion synthon with activated aromatic fluorides. Hitherto unknown poly(aryl ketone sulfone)s were synthesized when this chemistry was extended with the use of bis(α-aryl aminonitrile)s.
A novel quinodimethane was synthesized in quantitative yield by an intramolecular dehydrocyanation. Its structural features are unique in that one end is substituted by a donor moiety while the other end is captodative: this makes it attractive in the fields where electrical conductance and non linear optical (NLO) applications are important.
Ph. D.
xv, 256 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 30909491
LD5655.V856_1992.P363.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1992.P363
Polymerization
Novel nitrogen containing polymers via Reissert chemistry
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Chemistryopen.accessoai:vtechworks.lib.vt.edu:10919/451602022-03-14T21:49:23Zcom_10919_5534col_10919_9291
Huang, Ching-Yang
Civil Engineering
Barker, Richard M.
Holzer, Siegfried M.
Plaut, Raymond H.
2014-03-14T21:47:33Z
2014-03-14T21:47:33Z
1988-02-05
2010-10-13
2010-10-13
2010-10-13
etd-10132010-020103
http://hdl.handle.net/10919/45160
http://scholar.lib.vt.edu/theses/available/etd-10132010-020103/
A finite element program for analyzing the nonlinear behavior of moving contact problems has been developed and used for the analysis of a single sheet pile interlock (Chan and Barker (1985), Wu and Barker (1986). In this study, the program is modified to simulate a sheet pile pull-out test with a new finite element mesh. The improved mesh contains a full-length sheet pile with both of its interlocks connected to two half-length sheet piles. The results are presented and compared with the results of the pull-out tests which were conducted by O'Neil and McDonald at WES (1985). The comparison is not completely satisfactory because the initial slack between interlocks is not modeled. Nonetheless, the general behavior of sheet piles under tensile load is correctly predicted by the finite element program.
For easier interpretation of the output from the finite element analysis, the computer graphics software AutoCAD (Auto desk, 1986) is adopted to serve as a postprocessor. Several features of AutoCAD such as overlaying, zooming, and macro instructions are utilized to serve this purpose. Some intermediate programs are also developed for the communication between the finite element program and AutoCAD.
Master of Science
ix, 117 leaves
BTD
application/pdf
Virginia Tech
OCLC# 18115861
LD5655.V855_1988.H936.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1988.H936
Cofferdams
Comparison and results of sheet pile interlock analysis
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Civil Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/532772023-10-30T19:39:00Zcom_10919_5534col_10919_9291
Taan, Aly H.
Architecture
Rott, Hans Christian
Kilper, Dennis J.
Choudhury, Salahuddin
Dunay, Robert J.
2015-06-23T19:10:16Z
2015-06-23T19:10:16Z
1990
http://hdl.handle.net/10919/53277
iii, 24 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 22588440
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1990.T325
Plazas -- Lebanon -- Beirut -- Designs and plans
Place de Matyrs (Beirut, Lebanon)
Beirut (Lebanon) -- Buildings, structures, etc. -- Designs and plans
A wall within a wall
Thesis
Text
Master of Architecture
Master of Architecture
masters
Virginia Polytechnic Institute and State University
Architectureopen.accessoai:vtechworks.lib.vt.edu:10919/1109232023-09-18T19:23:21Zcom_10919_5534col_10919_9291
Hines, Deena Sbitany
Human Nutrition, Foods and Exercise
Williams, Jay H.
Tegarden, David P.
Anderson, Angela Suzanne
Hedrick, Valisa E.
2022-06-24T08:00:56Z
2022-06-24T08:00:56Z
2022-06-23
vt_gsexam:35159
http://hdl.handle.net/10919/110923
In female college soccer players, there is no protocol for assessing fatigue. A total of 40 members of the Virginia Tech Women's Soccer team participated in the countermovement jump assessment to find a reliable way to gauge player fatigue and readiness in these athletes. These were tested by assessing the within and between-day similarity of a countermovement jump test as a measure of neuromuscular performance by comparing multiple jump heights during jumps performed within a single day and on separate days. Additionally, to determine the responsiveness of countermovement jump height as a marker of fatigue, we compared jump heights before and after activities thought to induce fatigue and competitive matches. All subjects wore a STATSports APEX unit that includes an 18Hz GPS, 952 Hz accelerometer, and 952 Hz gyroscope situated on the upper back over the second thoracic vertebra using a manufacturer-provided vest. After each training session or match, the data was downloaded using the manufacturer's software (APEXA). A custom MATLAB program was then used to calculate CMJ height from vertical acceleration. Results showed that CMJ heights were very reliable both within and between testing days. CMJ heights were found to accurately decrease following both high-load training sessions and a competitive soccer match. For both activities, the decrease in performance was dependent on the amount of load experienced. Lastly, CMJ height did not recover the day following high training load sessions. Across a training week, CMJ consistently decreased each day. This was followed by a recovery in performance following two off days. The results suggest that the use of a trunk-mounted, GPS-embedded accelerometer and a novel three-jump protocol is responsive to assess CMJ height. In addition, it is responsive to estimating fatigue following soccer activity.
Master of Science
In female college soccer players, there is no protocol for assessing fatigue. A total of 40 members of the Virginia Tech Women's Soccer team participated in the countermovement jump assessment to find a reliable way to gauge player fatigue and readiness in these athletes. We hypothesized that countermovement jump heights would not vary between jumps executed on the same day and on different days. We also hypothesized pre-training countermovement jump heights would vary across a 7-day training session with reductions dependent on the prior days' physical demands and would be reduced following a competitive soccer match, also dependent on each player's physical demands. These were tested by assessing the within and between-day reliability of a vertical jump test as a measure of performance by comparing multiple countermovement jump heights during jumps performed within a single day and comparing jumps on separate days. Additionally, to determine the feasibility of countermovement jump height as a marker of fatigue, we compared jump heights before and after activities thought to induce fatigue and competitive matches. All subjects wore a STATSports APEX unit that includes an 18Hz GPS, 952 Hz accelerometer, and 952 Hz gyroscope situated on the upper back over the second thoracic vertebra using a manufacturer-provided vest. After each training session or match, the data was downloaded using the manufacturer's software (APEX) and a custom MATLAB program was then used to calculate CMJ height from vertical acceleration. Results showed that CMJ heights were very reliable both within and between testing days. CMJ heights were found to decrease following both high-load training sessions and following a competitive soccer match. For both activities, the decrease in performance was dependent on the amount of load experienced. Lastly, CMJ height did not recover the day following a high training load sessions. Across a training week, CMJ consistently decreased each day. This was followed by a recovery in performance following two off days. The results suggest that the use of a trunk-mounted, GPS-embedded accelerometer and a novel three-jump protocol is reliable to assess CMJ height. In addition, it is feasible to estimating fatigue following soccer activity.
ETD
en
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
countermovement jump
fatigue
soccer
reliability
applicability
accelerometer
The Feasibility of Accelerometer-Derived Measures of Vertical Jump Height as a Marker of Neuromuscular Performance in Collegiate Soccer Players
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Human Nutrition, Foods, and Exerciseopen.accessoai:vtechworks.lib.vt.edu:10919/1040212022-02-09T14:56:14Zcom_10919_5534col_10919_71751col_10919_9291
Brabble, Jessica Marie
History
Dufour, Monique S.
Heflin, Ashley Shew
Barrow, Mark V. Jr.
Gitre, Edward J. K.
2021-06-25T08:00:57Z
2021-06-25T08:00:57Z
2021-06-24
vt_gsexam:30807
http://hdl.handle.net/10919/104021
This project examines two organizations--the Better Babies Bureau and the Children's Bureau--created by Progessive women in the early twentieth century to combat high infant mortality rates, improve prenatal and postnatal care, and better child welfare. The Better Babies Bureau, founded in 1913 by journalists from the Woman's Home Companion magazine, and the Children's Bureau, founded as a federal agency in 1912, used similar campaigns to raise awareness of these child welfare problems in the early 1900s; where they differed, however, is in their ultimate goals. The Children's Bureau sought to improve long-term medical care and infant mortality rates for women regardless of race or socioeconomic status; I analyze how they worked directly with midwives and health officials to provide better care for mothers and children. The Better Babies Bureau, in comparison, catered specifically to white women through prize-based contests and eugenics rhetoric. Through their better baby contests, they promoted the idea that disabilities and defects should be eliminated in children in order to create a better future. By the late 1910s, these two organizations were utilizing nationwide campaigns to appeal to mothers through either consumerism or health conferences. I argue that although the Better Babies Bureau made a greater cultural impact, the Children's Bureau made a longer lasting—and farther reaching—impact on infant mortality rates by making healthcare more accessible for both rural and urban women.
Master of Arts
In the early twentieth century, many Americans became concerned with the number of children dying before age one. This thesis examines two different organizations that were created in an attempt to reduce these infant mortality rates, improve prenatal and postnatal care, and better child welfare. These two organizations, the Children's Bureau and the Better Babies Bureau, were created and run by Progressive women who took vastly different approaches to raising awareness of these problems. The Children's Bureau worked directly with health and government officials to improve child welfare and healthcare. Meanwhile, the Better Babies Bureau utilized contests to convince mothers that defects and disabilities needed to be eliminated in their children. In this thesis, I argue that the Children's Bureau was ultimately far more effective by appealing to a wider audience, creating a plan for long-term medical care, and improving access to prenatal and postnatal care for women.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
eugenics
progressivism
child welfare
infant mortality
Save the Babies: Progressive Women and the Fight for Child Welfare in the United States, 1912-1929
Thesis
Master of Arts
masters
Virginia Polytechnic Institute and State University
Historyopen.accessoai:vtechworks.lib.vt.edu:10919/1160572024-03-13T09:12:19Zcom_10919_5534col_10919_11041
Grubb, Christopher Thomas
Statistics
House, Leanna L.
Datta, Jyotishka
Higdon, David
Van Mullekom, Jennifer H.
2023-08-17T08:00:09Z
2023-08-17T08:00:09Z
2023-08-16
vt_gsexam:38333
http://hdl.handle.net/10919/116057
In this dissertation, we develop a new type of prior distribution, specifically for populations themselves, which we denote the Dirichlet Spacing prior. This prior solves a specific problem that arises when attempting to create synthetic populations from a known subset: the unfortunate reality that assuming independence between population members means that every synthetic population will be essentially the same. This is a problem because any model which only yields one result (several very similar results), when we have very incomplete information, is fundamentally flawed. We motivate our need for this new class of priors using Agent-based Models, though this prior could be used in any situation requiring synthetic populations.
Doctor of Philosophy
Typically, statisticians work with parametric distributions governing independent observations. However, sometimes operating under the assumption of independence severely limits us. We motivate the move away from independent sampling via the scope of Agent-based Modeling (ABM), where full populations are needed. The assumption of independence, when applied to synthesizing populations, leads to unwanted results; specifically, all synthetic populations generated from the sample sample data are essentially the same. As statisticians, this is clearly problematic because given only a small subset of the population, we clearly do not know what the population looks like, and thus any model which always gives the same answer is fundamentally flawed. We fix this problem by utilizing a new class of distributions which we call spacing priors, which allow us to create synthetic populations of individuals which are not independent of each other.
ETD
en
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Bayesian Statistics
Synthetic Populations
Inference for Populations: Uncertainty Propagation via Bayesian Population Synthesis
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Statisticsembargooai:vtechworks.lib.vt.edu:10919/421522022-03-04T18:25:58Zcom_10919_5534col_10919_9291
Galagedera, Nandadeva Lalith
Civil Engineering
Weyers, Richard E.
Al-Qadi, Imadeddin L.
Drew, Donald R.
Walker, Richard D.
2014-03-14T21:34:13Z
2014-03-14T21:34:13Z
1991-09-09
2009-04-18
2009-04-18
2009-04-18
etd-04182009-041358
http://hdl.handle.net/10919/42152
http://scholar.lib.vt.edu/theses/available/etd-04182009-041358/
Waterproofing membranes have been used on bridge decks for almost three decades in order to prevent chloride ingress into concrete. However, the performance of these membranes have yet to be adequately evaluated. Therefore, this research was carried out primarily to evaluate the integrity and effectiveness of standard preformed membranes placed on concrete bridge decks.
The actual conditions of a bridge deck were simulated in the laboratory using scaled-down reinforced concrete specimens. Forty-eight outdoor and twelve indoor specimens were cast. Three types of standard preformed membranes (Bithuthene 5000, Royston lOA, and Protecto Wrap M400-A), punctured with holes of various sizes and frequencies per unit area, were placed on the specimens. All of the specimens were overlaid with 2.5 inches of hot-mix asphalt, except four outdoor (control) specimens and three indoor specimens.
Master of Science
xi, 136 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 25140600
LD5655.V855_1991.G343.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1991.G343
Concrete bridges
Integrity and effectiveness of standard preformed membranes placed on concrete bridge decks
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Civil Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/768562020-09-28T12:25:32Zcom_10919_5534col_10919_9291
Izquierdo-Roman, Alondra
Biomedical Engineering
Rylander, Christopher G.
Wang, Ge
Robertson, John L.
2017-04-04T19:49:45Z
2017-04-04T19:49:45Z
2011-08-11
2011-08-23
2016-09-30
2011-08-31
etd-08232011-171329
http://hdl.handle.net/10919/76856
http://scholar.lib.vt.edu/theses/available/etd-08232011-171329/
Tissue optical clearing aims to increase the penetration depth of near-collimated light in biological tissue to enhance optical diagnostic, therapeutic, and cosmetic procedures. Previous studies have shown the effects of chemical optical clearing on tissue optical properties. Drawbacks associated with chemical clearing include the introduction of potentially toxic exogenous chemicals into the tissue, poor site targeting, as well as slow transport of the chemicals through tissue. Thus, alternative clearing methods have been investigated. Mechanical compression is one such alternative tissue optical clearing technique. The mechanisms of action of mechanical compression may be similar to those of chemical clearing, though they have yet to be investigated systematically. This research describes the design and execution of a number of procedures useful for the quantification of the tissue optical clearing effects of localized mechanical compression. The first experimental chapter presents the effects of compression on image resolution and contrast of a target imaged through ex vivo biological tissue. It was found that mechanical optical clearing allowed recovery of smaller targets at higher contrast sensitivity when compared to chemical clearing. Also, thickness-independent tissue clearing effects were observed. In the second experimental chapter, dynamic changes in tissue optical properties, namely scattering and absorption coefficients (?s' and ?a, respectively) were monitored during a controlled compression protocol using different indentation geometries. A reduction in ?s' and ?a was evident for all indentation geometries, with greater changes occurring with smaller surface area. Results indicate that localized mechanical compression may be harnessed as a minimally-invasive tissue optical clearing technique.
Master of Science
en_US
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
biological tissue
resolution
compression
contrast
diffuse reflectance spectroscopy
mechanical loading
Localized Mechanical Compression as a Technique for the Modification of Biological Tissue Optical Properties
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Biomedical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/747642023-11-28T04:59:14Zcom_10919_5534col_10919_11041
Choi, Suk Ho
Food Science and Technology
Eigel, W.N.
Pierson, M.D.
Palmer, J.K.
Kornegay, E.T.
Smith, D.F.
2017-01-30T21:24:26Z
2017-01-30T21:24:26Z
1987
http://hdl.handle.net/10919/74764
Binding of K88ab pili by brush border membrane and mucus from pig small intestine was characterized by inhibition assay and Western blot. In Western blot, K88ab pili were bound by two major brush border membrane polypeptides with molecular weight of 61,500 and 57,000 in addition to numerous minor polypeptides and a major mucus polypeptide with molecular weight of 27,500. The results from Western blot assays with periodate oxidized and carbamylated brush border membrane and inhibition assay with brush border membrane glycopeptide suggest that amino groups (rather than carbohydrate) present on the protein moiety are a part of the recognition site for K88ab pili of receptor polypeptides in brush border membrane. Differences were obtained in the binding patterns of K88ab pili when brush border membranes were prepared from small intestines obtained from 2-, 21-, and 42-day-old piglets as well as adult hogs. Binding of K88ab pili by mucus polypeptides was greater when prepared from small intestines obtained from 2-day-old piglets than from piglets of other ages and adult hogs.
In inhibition assay, most fractions from sow milk and colostrum inhibited binding of K88ab pili. After gel filtration of colostral whey, fractions which contained IgG, IgA, and IgM produced the strongest inhibition of K88ab binding. Among fractions prepared from cow milk, casein and skim milk significantly inhibited binding of K88ab pili. In Western blot, α<sub>s1</sub>-casein, immunoglobulin chains, and MFGM polypeptides in sow milk and colostrum were shown to be able to bind K88ab pili. Additionally, α<sub>s1</sub>-casein was the major protein in bovine milk responsible for binding K88ab pili. In dot blot assay, IgG as well as brush border membrane could strongly bind K88ab pili. However, bovine α<sub>s1</sub>-casein showed only weak binding of K88ab pili. Binding of K88ab pili to these proteins and brush border membrane was inhibited by carbamylation and by addition of 100 mM D-galactosamine. The results suggest that the K88ab-binding proteins in milk and colostrum compete to bind K88ab pili with the receptors in the brush border membrane and that mechanisms involved in binding of K88ab pili by these proteins is similar to that by brush border membrane.
Ph. D.
viii, 110 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 17429319
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1987.C565
Escherichia coli infections
Intestines -- Microbiology
Binding mechanism of K88ab pili produced by enterotoxigenic Escherichia coli
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Food Science and Technologyopen.accessoai:vtechworks.lib.vt.edu:10919/517462020-09-28T13:43:48Zcom_10919_5534col_10919_11041
Akoma, Efua Safiya
Sociology
Agozino, Onwubiko
Graves, Ellington T.
Polanah, Paulo S.
Harrison, Anthony Kwame
2015-04-22T08:01:13Z
2015-04-22T08:01:13Z
2014-04-16
vt_gsexam:2372
http://hdl.handle.net/10919/51746
America has continued to be increasingly diverse in culture and ethnicities. As such, these diverse populations require those in health and mental health fields to adjust to the cultural differences that arise. Central to these conversations is the impact of the acculturation process on immigrant populations. Researchers posit the stress of immigration and the acculturation process leads to increased rates of mental illness (Lang, Munoz, Bernal and Sorenson 1982; Masten, Penland and Nayani 1994; Neff and Hoppe 1993). Assuming that the acculturation process impacts first generation immigrants most, this study investigated U.S. born Blacks with and without Caribbean descent and Caribbean born Blacks residing in the U.S. to determine if nativity status and generational status impacts rates of mental illness. Using the National Survey of American Life (NSAL) dataset which is one of three research projects conducted from 2001 to 2003 by the Program for Research on Black Americans (PBRA), as part of the Research Center for Group Dynamics project, analyses were conducted to determine if relationships existed for these groups. Results indicated that mental illness is dependent on country of origin and U.S. born Blacks do self-report mental illnesses significantly more than Caribbean Blacks. Caribbean Blacks who are first generation in the U.S. are significantly less likely to report mental illness than second generation Caribbean Blacks. Differences in gender, work, number of years living in the U.S., age at immigration and wealth and poverty indicators all show some relationships with mental illnesses.
Ph. D.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Blacks
Caribbean descent
Caribbean Blacks
mental illness
U.S. residency
mental health
ethnic origin
generational status
Rates of Mental Illnesses, Nativity and Generational Status in the U.S.: Heterogeneity among Caribbean Born Blacks, Blacks of Caribbean Descent and U.S. Born Blacks
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Sociologyopen.accessoai:vtechworks.lib.vt.edu:10919/291122022-03-29T18:20:24Zcom_10919_5534col_10919_11041
Drape, Tiffany A.
Agricultural and Extension Education
Westfall-Rudd, Donna M.
Chang, Mido
Doolittle, Peter
Rudd, Rick D.
2014-03-14T20:16:50Z
2014-03-14T20:16:50Z
2011-09-12
2011-09-26
2011-10-13
2011-10-13
etd-09262011-163335
http://hdl.handle.net/10919/29112
http://scholar.lib.vt.edu/theses/available/etd-09262011-163335/
Students in any educational setting need to learn how to integrate and successfully use technology to be successful in a future career. While no one educational system can teach every skill, faculty can help integrate technology and model skills that students will need later in life. Using Rogers' Diffusion of Innovations as a model, the researcher examined technology integration and how it affected engagement, motivation, and learning in the classroom setting. The purpose of this study was to investigate the phenomenon of technology integration in an agriculture associate's degree program and evaluate the program from the faculty and student perspective. Ninety-six students enrolled in an agriculture associate's degree program served as the case study group. A qualitative approach guided the inquiry of the study and was represented through observations, participant interviews, and video collection using Noldus Observer.
Findings indicated that technology integration was being implemented in a purposeful way and the faculty work together to make decisions regarding what to integrate for the students' use in their courses. Technology integration decisions were supported by the faculty and program leader. Students viewed the technology as beneficial to their learning while enrolled in the program and as an asset when they graduated. Students reported that they felt as though technology was helping them remain engaged and motivated in the program. Students who participated in the recommend that the faculty use the course management system more efficiently to streamline content to students and the faculty use more features that the system offers such as chat and discussion boards. Students expressed a belief that these practices would help keep students more engaged during class time and help them locate resources more efficiently. It is recommended that faculty work to offer a blended learning experience in the classroom, with group work or guided practice. Finally, as an alternative to traditional assessment, it is recommended that faculty members in the program encourage students to work with technology outside of class to create videos or podcasts to illustrate what they are learning.
Ph. D.
Virginia Tech
Drape_TA_D_2011.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Education
engagement
motivation
integration
Technology
Teaching with Technology in an Agriculture Associate's Degree Program
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Agricultural and Extension Educationopen.accessoai:vtechworks.lib.vt.edu:10919/761932020-09-28T13:29:37Zcom_10919_5534col_10919_9291
Shaikh, Asif Manzoor
Industrial Engineering and Operations Research
2017-03-10T19:28:56Z
2017-03-10T19:28:56Z
1982
http://hdl.handle.net/10919/76193
A simulation model is developed in SLAM II to study and analyze conveyor systems.. The adequacy of the model is tested by applying it to a conveyor layout as well as some variant designs. 1he problem of modeling large systems is reduced by decomposing the system into smaller segments (subsystems). Different types of conveyors are considered. Programming modules are prepared for feasible conveyor types and segments. These simulation modules are integrated into a system.
Master of Science
vi, 209, [1] leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 8706489
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1982.S524
Materials management -- Simulation methods
Conveying machinery
A generalized simulation model for the design of a conveyor system
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Industrial Engineering and Operations Researchopen.accessoai:vtechworks.lib.vt.edu:10919/518472020-09-28T14:08:38Zcom_10919_5534col_10919_9291
Swiatocha, Andrea Leigh
Architecture
Emmons, Paul F.
Kelsch, Paul J.
Piedmont-Palladino, Susan C.
2015-04-29T08:00:45Z
2015-04-29T08:00:45Z
2013-10-02
vt_gsexam:1058
http://hdl.handle.net/10919/51847
Humans are designed to move. Movement is a key component of physical and mental maturation in children. It can take place in various settings, with different levels of intensity. During the developmental years of a child, it is imperative that a child is active. Most often movement and play are thought to occur outdoors. The idea of the"playground" activity does not have to be isolated to the outdoors. Children should be encouraged to be physically active in structured play, allowed free play with peers for social and emotional development, as well as learn through hands-on experiments that are important for their cognitive development. Play is how children experience their world and create new discoveries about themselves and others.
This thesis will be explored through the design of an elementary school for Alexandria, VA. An elementary school creates the perfect setting for which these elements of movement and learning to combine. This thesis explores the way in which the movement of the outdoor school yard can occur within the school building. The school grounds serve as demonstration to the community for active learning. Incorporating active design through elevation changes, material changes and the transition between indoor and outdoor allow the school to be a model for "learning through movement." This school also begins to address the larger issues of our society's unhealthy lifestyle by designing three levels of active design for the community, building, and individual child.
Master of Architecture
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Learning
Movement
School
Active Design
Community
Learning through Movement
Thesis
Master of Architecture
masters
Virginia Polytechnic Institute and State University
Architectureopen.accessoai:vtechworks.lib.vt.edu:10919/705092020-09-28T14:16:24Zcom_10919_5534col_10919_9291
Barnes, Jeffrey Robert
Business Administration
2016-04-21T15:34:56Z
2016-04-21T15:34:56Z
1968
http://hdl.handle.net/10919/70509
v, 117 leaves.
application/pdf
en_US
Virginia Polytechnic Institute
OCLC# 20144697
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1968.B35
Hospitals -- Business management. -- Virginia
Hospitals -- Accounting. -- Virginia
Budgetary philosophy and procedures in community, general, nonprofit hospitals in the state of Virginia
Thesis
Text
Master of Science
Master of Science
masters
Virginia Polytechnic Institute
Business Administrationopen.accessoai:vtechworks.lib.vt.edu:10919/1165072023-10-20T07:11:23Zcom_10919_5534col_10919_11041
Uluer, Mahmud Esad
Mining Engineering
Noble, Christopher Aaron
Amini, Seyed Hassan
Karfakis, Mario G.
Shahab, Shima
Keles, Serhat
2023-10-19T08:00:38Z
2023-10-19T08:00:38Z
2023-10-18
vt_gsexam:38588
http://hdl.handle.net/10919/116507
Respirable coal mine dust (RCMD) is one of the biggest occupational health hazards. Dusty mining environments can cause life-threatening respiratory health problems for coal miners known as black lung. Over the last 20 years, the flooded bed dust scrubber (FBS) has been employed as an integral component of dust control strategies for underground continuous mining operations. These units have been shown to be effective and robust in mining environments; however, several technical challenges and knowledge gaps limit their performance and efficiency. Despite the capability of the FBS, there are numerous technical challenges that limit its performance and efficiency. In particular, the static panel filter, instrumental in most scrubber designs, is fundamentally limited in collection efficiency and causes numerous operational challenges including rapid clogging. Furthermore, the current design of the filter panel is not capable of evenly wetting the entire surface area. This allows dust-laden air to pass through the filter media and decreases the cleaning capability of the FBS. In this research, both a lab-scale and a full-scale vibration-enhanced FBS with a liquid-coated filter panel were designed, manufactured, and tested. The results confirmed that a vibration-induced filter panel enhances dust collection performance and reduces mesh clogging. In addition, laboratory-scale mesh clogging tests showed that a hydrophilic mesh provided superior clogging mitigation and better performance. Typical results from bench-scale tests showed notable improvements in dust collection efficiencies by over 6% in wet condition and over 7% in dry condition while reducing mass accumulation in the filter by almost 10% in wet condition and over 40% in dry condition. The prototype testing was less conclusive, with deviations between the static mesh and vibrating mesh depending on the mesh density and operating conditions. Nevertheless, with the highest mesh density tested (30-layer), the vibrating mesh notably outperformed the static mesh with superior collection efficiency and reduced airflow loss. The system was further analyzed to investigate the size-by-size recovery of dust particles to various endpoints in the scrubber, under both vibrating and static conditions. Results show that while a majority of the particles are recovered into the demister sump, nearly a quarter of the dust mass is recovered upstream of the screen. In addition, the data confirm that vibration prompts notable improvements to collection efficiency, particularly in the finest size class (- 2.5 micron).
Doctor of Philosophy
Coal mine dust is an unintended and unavoidable consequence of coal extraction operations that poses significant health and safety risks. The inhalation of small, respirable dust particles can cause incurable lung diseases, including silicosis and coal workers' pneumoconiosis known as black lung. To minimize occupational hazards of underground coal mine dust, the Mine Safety and Health Administration (MSHA) periodically brings legislation to the industry. The recent respirable dust rule mandates reducing the maximum allowable respirable dust concentrations in the mine environment to below 1.5 mg/m3 at the working face and below 0.5 mg/m3 at intake entries. In order to comply with these regulations, modern mining techniques utilize several dust mitigation strategies, and the flooded-bed dust scrubber (FBS) is one such technology used extensively on continuous miners. The conventional static panel filter, instrumental in most scrubber designs, however, is fundamentally limited in collection efficiencies due to a high clogging rate and a tradeoff between mesh density and airflow rate. Moreover, poorly wetted areas allow dust-laden air to pass through the filter media. To overcome these deficiencies, a novel liquid-coated vibrating mesh panel is introduced in this research. A laboratory-scale dust scrubber unit and a full-scale unit with a vibration-enhanced mesh screen panel were manufactured and employed to investigate the efficacy of the concept as compared to that of a static mesh. A series of experimental design studies were employed to determine the effective vibrational parameters, scrubber operational parameters, and the impact of mesh variations on dust collection and clogging mitigation. Optimized results from this research were also evaluated against those of a static mesh to determine performance improvement while investigating the mechanisms controlling dust collection and particle department through the scrubber system. Results from the laboratory study show that vibrating mesh conditions, higher water flow rates, and a hydrophilic mesh screen panel led to an improvement in the cleaning efficiency of the scrubber system. Compared to a static-mesh to FBS, the vibrating-mesh FBS showed a significant reduction in pressure drop across the mesh screen indicating lower air loss through the test duration. Overall, the findings confirm that vibrating mesh conditions have the ability to improve filter clogging issues while maintaining high collection efficiencies which can lead to better and healthier working conditions and prolonged operational time with less frequent maintenance. This research supports further technological advancement in mine dust mitigation technologies.
ETD
en
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Respirable coal mine dust
Flooded bed dust scrubber
Vibrating mesh filter
Filter surface modification
Vibration Enhanced Flooded Bed Dust Scrubber with Liquid-Coated Mesh Screen
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Mining Engineeringembargooai:vtechworks.lib.vt.edu:10919/909292020-09-25T20:33:31Zcom_10919_5534col_10919_9291
Grenoble, B. Alex
Mining Engineering
2019-07-03T16:42:36Z
2019-07-03T16:42:36Z
1985
http://hdl.handle.net/10919/90929
The mining of coal within 110 feet below a previously mined seam creates interaction effects which can be detrimental to work in the lower seam. These interaction effects are characterized by zones of very high stress and result in floor and roof instability and pillar crushing.
Recent developments in the field of ground control make it possible to determine with a certain degree of confidence the location of these zones and estimate the degree to which the interaction will affect the lower seam. This information has been incorporated into a software package for microcomputers which will predict lower seam problems and suggest design criteria for minimizing the difficulties which will be encountered.
M.S.
viii, 128 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 12783136
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1985.G736
Mining engineering -- Data processing
Ground control (Mining)
Digital computer simulation
Microcomputer simulation of near seam interaction
Thesis
Text
M.S.
masters
Virginia Polytechnic Institute and State University
Mining Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/944172021-12-21T14:49:25Zcom_10919_5534col_10919_11041
Trent, Alexis Raven
Materials Science and Engineering
Van Dyke, Mark
Goldstein, Aaron S.
Whittington, Abby R.
Foster, Earl Johan
2019-10-09T06:00:30Z
2019-10-09T06:00:30Z
2018-04-16
vt_gsexam:14761
http://hdl.handle.net/10919/94417
Implantable medical devices face numerous complications when interfacing with soft tissue, and are plagued by negative responses from host tissue. One such class devices are percutaneous osseointegrated prosthetics (POP). POP consist of a bone anchored titanium post that extrudes through the skin and attaches to an external prosthetic. Compared to the traditional socket interface, POPs offer better stability, limb functionality, and osseoperception for both upper and lower prosthetic limbs. Although the POP surgery technique is well established, the main disadvantage to this technology remains the titanium (Ti) - skin interface. Some of the complications that can arise include epithelial downgrowth, mechanical tearing, and infection. Various types of coatings, surface structure, and antibiotic release technologies have been used to coat Ti in an effort to mitigate POP's associated obstacles, but these methods have failed to translate into published clinical studies and mainstream medical use.
One potential solution may be to mimic an interface already found in the human body, the fingernail-skin interface, which is infection-free and mechanically stable. The same keratins that make up the cortex of human hair fibers are found in the fingernail. These cortical human hair keratins can be extracted and purified, and fingernail-specific dimeric complexes coated onto Ti surfaces using silane coupling chemistry. Keratin has been used in other studies for its cell adhesion and differentiation properties, and it has been suggested that the Leu-Asp-Val (LDV) amino acid motif is the primary site responsible for cellular attachment.
In the present work, keratins extracted from human hair fibers and recombinant keratin nanomaterials (KN) were used to create biomimetic coatings on silanized Ti surfaces. These coatings were characterized and investigated for surface topography, elemental composition, cell adhesion motifs, and cell adhesion. Both keratin substrates showed the ability to create uniform coatings that retain a protein conformation that exhibits cell adhesion motifs. The coatings exhibit the ability to support cell adhesion of both epithelial and connective tissue cells. Application of fluid shear stress was used to test the mechanical adhesion strength of cells on keratin coatings. The structure, biochemical stability and sustained cellular adhesion of these coatings support keratin's capacity to provide a stable interface between POPs and skin. Side-by-side studies of extracted and recombinant keratins reveals that the recombinant form of these materials may provide distinct advantages for their use in POP devices.
Overall, this study confirmed that a uniform, silane-coupled keratin coating was feasible. We demonstrated the substrates contain a biological function in terms of cellular adhesion and phenotypic changes in skin-relevant cells. These results support the biomimetic function of keratin on silanized Ti, which may provide a suitable coating to translate percutaneous medical device coating applications toward clinical use.
Ph. D.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Biomimetic interface
medical device
protein surface modification
Fabrication, Characterization and Cellular Interactions of Keratin Nanomaterial Coatings for Implantable Percutaneous Prosthetics
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Materials Science and Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/344262022-03-28T19:40:30Zcom_10919_5534col_10919_9291
Stroop, Richard Henry Lee
Electrical and Computer Engineering
Athanas, Peter M.
Patterson, Cameron D.
Dietrich, Carl B.
2014-03-14T20:43:01Z
2014-03-14T20:43:01Z
2012-08-07
2012-08-08
2012-09-17
2012-09-17
etd-08082012-154538
http://hdl.handle.net/10919/34426
http://scholar.lib.vt.edu/theses/available/etd-08082012-154538/
Software defined radios (SDRs) have changed the paradigm of slowly designing custom radios, instead allowing designers to quickly iterate designs with a large range of functionality. With the help of environments like the open-source project, GNU Radio, a designer can prototype radios with greatly improved productivity. Unfortunately, due to software performance limitations, there is no way to achieve the range of radio designs made possible with actual physical radio hardware. In order for SDRs to become more prevalent in radio prototyping and development, accelerators must be added to high-throughput and computationally intensive portions. Custom DSPs, GPUs, and FPGAs have all been added to SDRs to try and expand their computational capabilities. One difficulty in this is that by adding these accelerators, the "instant gratification" dynamic of the GNU Radio is lost.
In this thesis, an enhanced GNU Radio flow is presented that seamlessly augments the GNU Radio software-only model with FPGAs, yet preserves the GNU Radio dynamics by providing full-custom radio hardware/software structures in seconds. By delegating portions of a GNU Radio flow graph to networked FPGAs, a larger class of software-defined radios can be implemented. Assembly of the signal processing structures within the FPGAs is accomplished using an enhanced flow where modules are customized, placed, and routed in a fraction of the time required by the vendor tools. With rapid FPGA assembly, a GNU Radio designer retains the ability to perform "what-if" experiments, which in turn greatly enhances productivity.
Due to the modular nature of GNU Radio and of the FPGA designs, a modular assembly of the FPGA hardware is used. In the flow presented here, optimized hardware library components are designed by a domain expert, and stored as compact placed-and-routed modules. When a designer requests the assembly of one or more components within a given FPGA via a GNU Radio Python script, the necessary library components are accessed and translated to an appropriate location within the chip. Then the ports of the modules are stitched together using a custom FPGA router. This process reduces the large compile times of hardware for an FPGA to reasonable software-like times.
To the radio designer, the complexity of the underlying hardware is abstracted away, making it appear as if everything compiles and runs in software, allowing many iterations to be realized quickly. Radio design can continue at the speeds that GNU Radio designers are accustomed to but with the range of possible waveforms and general functionality extended.
Master of Science
Virginia Tech
Stroop_RHL_T_2012.pdf
In Copyright
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Field programmable gate arrays
SDR
qFlow
GNU Radio
Enhancing GNU Radio for Run-Time Assembly of FPGA-Based Accelerators
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Electrical and Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/413622021-10-12T19:27:16Zcom_10919_5534col_10919_9291
Scott, Jennifer Claire
Biology
2014-03-14T21:30:35Z
2014-03-14T21:30:35Z
1994
2009-03-03
2009-03-03
2009-03-03
etd-03032009-040633
http://hdl.handle.net/10919/41362
http://scholar.lib.vt.edu/theses/available/etd-03032009-040633/
Growth rates, age-frequency distributions, and mortality rates of six mussel species were examined at four sites in the Clinch River, Virginia and Tennessee, to identify potentially impacted sites in the upper river. The bioaccumulation of copper in mussel shells also was examined as a possible contributing factor to the declining mussel fauna.
Higher growth rates observed at Hackneys site, river kilometer (RK) 433.7, may have been due to the discharge of domestic sewage from the town of Cleveland into the Clinch River. However, a sewage treatment facility was constructed in 1986 which removed the source of enrichment. Growth rates of female Lampsilis fasciola were significantly less than growth rates of male L. fasciola after 3 years of age, probably due to the onset of sexual maturity.
Age-class distributions revealed an absence of recruited juveniles at the Slant site (RK 359.3) after 1977 to 1979 for four mussel species examined. Substantial erosion of stream banks in tributaries of the Clinch River and deposition of sediment in the Clinch River were observed at Slant, indicating a potential cause of decline. Mean annual mortality rates of adult mussels were extraordinarily high for all species at all sites, which confirms the overall decline of freshwater mussels in the upper Clinch River.
There were no statistically significant differences in accumulation of copper in shells of L. fasciola among sites or sexes. Although Appalachian Power Company’s Clinch River Plant (CRP) had a history of high copper levels in the effluent discharge, it is apparently not the cause of reduced recruitment at the Slant site, located 72 km downstream. As indicated by this research, water quality or habitat conditions of the upper Clinch River continue to be insufficient to sustain freshwater mussels. The CRP has improved the effluent discharge to contain less than 12 μg Cu/L, which should improve conditions directly downstream; however, erosion of stream banks, sewage treatment facilities, and agricultural and urban runoff, continue to contribute to the demise of a rich freshwater mussel fauna.
Master of Science
xiii, 142 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 31256434
LD5655.V855_1994.S398.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1994.S398
Unionidae -- Mortality -- Clinch River (Va and Tenn)
Unionidae -- Clinch River (Va and Tenn) -- Growth
Population demographics of six freshwater mussel species (Bivalvia: Unionidae) in the upper Clinch river, Virginia and Tennessee
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Biologyopen.accessoai:vtechworks.lib.vt.edu:10919/760362020-09-28T13:29:28Zcom_10919_5534col_10919_9291
Ko, Chan Uk
Chemical Engineering
2017-03-09T21:35:23Z
2017-03-09T21:35:23Z
1985
http://hdl.handle.net/10919/76036
The investigation of structure-property behavior of extruded cast films prepared from blends of thermotropic liquid crystalline copolyesters with polyethylene terephthalate (PET). Data were obtained which showed not only the temperature dependence of the moduli and stress-strain behavior but also the orientation effects that must be prevalent in order to explain the differences between the moduli measured parallel and perpendicular to the extrusion direction. Only at high liquid crystal polymer (LCP) compositions is the modulus particularly increased. The modulus enhancement with lower LCP content and utilization of process variables are discussed. Specifically, the extruder gear pump speed did not enhance Young's modulus at the same LCP content as extensively as did the effect of extruder screw speed. Also a study to synthesize and characterize new segmented copolymers that could produce unusual film properties are discussed. The approach involved the synthesis of high Tg (220 C) isotropic poly (aryl ether sulfone) oligomers of varying segment molecular weights. The thermal and mechanical studies of the copolymers have been carried out to probe the potential of these copolymers for signs of liquid crystalline character and to note their ability to thermally crystallize as well as to crystallize by solvent or strain inducement. Along these lines, thermal analysis, polarizing hot-stage microscopy, wide angle x-ray scattering and mechanical testing were utilized in this investigation
Master of Science
ix, 156 leaves
application/pdf
en_US
Virginia Polytechnic Institute and State University
OCLC# 12655557
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1985.K6
Polymers -- Experiments
Liquid crystals -- Experiments
Studies of blends containing liquid crystalline polymers with PET and related investigations of hydroquinone/biphenol polysulfone systems
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Chemical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/265222020-09-25T20:45:41Zcom_10919_5534col_10919_11041
Baldwin, Mark W.
Electrical and Computer Engineering
Liu, Yilu
Conners, Richard W.
Centeno, Virgilio A.
Brown, Gary S.
Prather, Carl L.
2014-03-14T20:08:33Z
2014-03-14T20:08:33Z
2008-02-29
2008-03-27
2009-04-11
2008-04-11
etd-03272008-134630
http://hdl.handle.net/10919/26522
http://scholar.lib.vt.edu/theses/available/etd-03272008-134630/
The advent of synchronized wide-area frequency measurements obtained from frequency disturbance recorders and phasor measurement units has presented the power industry with special opportunities to study power system dynamics. I propose the use of wide-area frequency measurements in identifying system disturbances based on power system post-event modal properties.
In this work, power system dynamics are examined from an internal system energy viewpoint. Since an electric power system is composed of coupled rotating machines (large generators) which have air gap magnetic fields that are essentially static, or quasi-static, the power system may be modeled as a system with energy stored in quasi-static magnetic fields. The magnetic fields in the machines do change with time but may be modeled as static as far as wave propagation is concerned. The dynamic model that I develop treats this magnetic energy specifically as potential energy. Each rotating machine also contains an inertia due to the mass and motion of its rotor train and so each machine contains a rotational kinetic energy. Thus the internal system energy for a power system dynamic model may be considered to be contained in potential (magnetic) and kinetic (rotating mass) energies. This notion of internal energy lends itself to the use of a state-space model where each system state is associated with either a kinetic energy or a potential energy. An n-machine system would have a total of 2n states and would thus be a 2n-th order system. For many power system disturbances, I postulate that a linearized version of this model may be used to examine system natural response in terms of frequency and phasor measurements. The disturbances that I will investigate include generator and line outages. For any particular outage, the power system exhibits a very specific natural response in terms of its kinetic and potential energies. Kinetic energy in the system is directly related to each specific machine's rotational speed. I propose that the kinetic energy corresponds directly with bus frequencies through a linear transformation. Likewise magnetic field energy in each machine corresponds directly with a torque angle. The potential energy in the system thus corresponds directly with bus angles through a linear transformation.
The primary focus of this work is on frequency deviation modal characteristics – specifically damped oscillation frequencies, mode shapes, and damping ratios. This work presents how specific disturbances on a power system will lead to specific oscillation frequencies in the deviation quantities and that these oscillation frequencies may be used to identify the disturbance. The idea of disturbance identification stems out of previous work done in locating disturbances by using a distributed parameter (DP) model of an electric power system. This DP model, which assumes a wave-like motion of frequency and phase quantities, was used to locate disturbances via a triangulation method. This present work, instead of using a DP model of the power system, assumes lumped parameters and focuses on disturbance identification strictly via modal characteristics – particularly oscillation frequency in the frequency deviations. This model is not concerned with geographic location but focuses on system topology, loading, and machine mass as lumped parameters. Advantages of disturbance identification include mainly reliability enhancements but can also be used in marketing applications.
The state-space model used to realize this theory is verified via simulation using small, "academic" systems which should prove useful in classroom settings. Additionally the model is verified on a larger test system in order prove its validity and potential usefulness on large power systems.
Ph. D.
Virginia Tech
MB_dissertation_r4.pdf
In Copyright
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disturbance identification
state-space model
wide-area monitoring
modal analysis
FNET
electromechanics
Modal Analysis Techniques in Wide-Area Frequency Monitoring Systems
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Electrical and Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/1096832023-10-31T19:35:11Zcom_10919_5534col_10919_11041
Jahromi Shirazi, Masoud
Engineering Science and Mechanics
Abaid, Nicole
Ross, Shane D.
Cramer, Mark S.
Tarazaga, Pablo Alberto
Leonessa, Alexander
2022-04-16T06:00:13Z
2022-04-16T06:00:13Z
2020-10-22
vt_gsexam:27705
http://hdl.handle.net/10919/109683
Active sensors, such as radar, lidar and sonar, emit a signal into the environment and gather information from its reflection. In contrast, passive sensors such as cameras and microphones rely on the signals emitted from the environment. In the current application of active sensors in multi-agent autonomous systems, agents only rely on their own active sensing and filter out any information available passively. However, fusing passive and active sensing information may improve the accuracy of the agents. Also, there is evidence that bats who use biosonar eavesdrop on a conspecific's echolocation sound, which shows a successful example of implementing active and passive sonar sensor fusion in nature. We studied the effect of such information fusion in the framework of two problems: the collective behavior in a multi-agent system using the Vicsek model and the canonical robotics problem of Simultaneous Localization And Mapping (SLAM). Collective behavior refers to emergence of a complex behavior in a group of individuals through local interaction. The Vicsek model is a well-established flocking model based on alignment of individuals with their neighbors in the presence of noise. We studied the aligned motion in a group in which the agents employ both active and passive sensing. Our study shows that the group behavior is less sensitive to measurement accuracy compared to modeling precision. Therefore, using measurement values of the noisier passive sonar can be beneficial. In addition, the group alignment is improved when the passive measurements are not dramatically noisier than active measurements. In the SLAM problem, a robot scans an unknown environment building a map and simultaneously localizing itself within that map. We studied a landmark-based SLAM problem in which the robot uses active and passive sensing strategies. The information provided passively can improve the accuracy of the active sensing measurements and compensate for its blind spot. We developed an estimation algorithm using Extended Kalman Filter and employed Monte Carlo simulation to find a parameter region in which fusing passive and active sonar information improves the performance of the robot. Our analysis shows this region is aligned within the common range of active sonar parameters.
Doctor of Philosophy
Group behavior is a fascinating phenomenon in animal groups such as bird flocks, fish schools, bee colonies and fireflies. For instance, many species of fireflies synchronize their flashing when they bio-luminesce. This synchronization pattern is a group behavior created as a result of local interaction formed by sensing individuals in the group. The research question for this dissertation is inspired by comes from group behavior in bats. Bats use echolocation to perceive the environment. They make a sound and listen to the echo of the sound coming back from objects and by analyzing the echo, they can get information about their surroundings. It has been observed that bats may also use the echo of other bats' sound to perceive their environment. In other words they use two different sensors, one is called active sonar since they actively make the sound and listen to its echoes, and the other one is called passive sonar since they just passively listen to the sound generated by other bats. If this information is useful, can we exploit that in design of engineered systems? We investigated these questions using numerical simulation to solve two test bed problems. The first problem is based on a mathematical flocking model in which the individuals in the group align through local interaction. We found out that eavesdropping improves the alignment of the group within a range of parameters in the model which are relevant to the sensing capabilities of the sonar sensors. The other problem is a canonical robotics problem known as the simultaneous localization and mapping (SLAM). In this problem, a robot searches an unknown environment and creates a map of the environment (mapping) and reports the path it takes within the map (localization). We found out that when the robot uses both passive and active sonar, depending on the accuracy of the two sensing approaches, it can improve the accuracy of both the generated map and the robot's path.
ETD
Virginia Tech
In Copyright
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Agent-based modeling
Bio-inspired sensing
Flocking
Simultaneous localization and mapping
Sonar
Dynamics of Multi-Agent Systems with Bio-Inspired Active and Passive Sensing
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Engineering Mechanicsopen.accessoai:vtechworks.lib.vt.edu:10919/1109862022-06-30T14:53:28Zcom_10919_5534col_10919_9291
Thomas, Allen King
Agricultural Education
2022-06-29T19:26:39Z
2022-06-29T19:26:39Z
1947
http://hdl.handle.net/10919/110986
12 unnumbered pages, 177 leaves
application/pdf
en
Virginia Polytechnic Institute
OCLC# 29947942
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1947.T564
Hay -- Virginia
Pastures -- Virginia
Hay and pasture production in Virginia: organized subject matter, factual data, job analyses, and related information on the important jobs in the hay and pasture enterprise in Virginia for the use of teachers and students of Vocational Agriculture
Thesis
Text
M.S.
Virginia
United States
M.S.
masters
Virginia Polytechnic Institute
Agricultural Educationopen.accessoai:vtechworks.lib.vt.edu:10919/111642022-02-22T18:55:26Zcom_10919_5534col_10919_11041
Allen, April Diane
Environmental Design and Planning
Green, William R.
Fine, Elizabeth C.
Beamish, Julia O.
Casto, Marilyn D.
McLain-Kark, Joan H.
2011-08-22T19:01:19Z
2011-08-22T19:01:19Z
1999-11-01
2004-04-30
2004-05-04
2004-05-04
etd-04302004-150744
http://hdl.handle.net/10919/11164
http://scholar.lib.vt.edu/theses/available/etd-04302004-150744
The purpose of this study was to discover the various meanings that the Pulaski Theatre held for the residents of Pulaski and the theatre's social importance to the town. The following research objectives directed this study: 1) to document the theatre's history from the time it was built in 1911 until the present day, 2) to uncover memories or feelings associated with the theatre, and 3) to determine if design features of the theatre building influenced those feelings/memories. In documenting the history of the theatre, design features of the original 1911 building were examined as well as changes over time. To determine if design features of the building influenced the feelings/memories that were associated with the structure it was important first to discover which architectural and design features people remembered, if any, and then to determine if these design features reflected a meaningful association, i.e. sense of place to participants. Also of interest was whether this association or sense of place would be similar or different for all.
Participants were fifteen males and females aged 43 to 82 who had attended the theatre over time. All participants grew up in Pulaski and six had lived there their entire lives. Both African Americans and Caucasians participated.
Subjects were asked to draw a picture of the theatre that expressed their experience of the space. After the drawing, they were asked to discuss the picture and its meaning to them. Clare Cooper Marcus and others used this environmental autobiography technique as a method to bring a person's experiences of a place to a conscious level. Tape-recorded interviews were conducted and transcribed by the researcher to discover memories of the theatre and the meaning of the theatre to the participants.
Data were analyzed by coding to look for emerging themes or categories that relate to the research question. Of interest was whether or not the Pulaski Theatre represented a sense of place to residents and if that sense of place varied for different participants.
Document research was conducted through old newspapers and artifacts in the Raymond Ratcliffe Museum (the historic museum in Pulaski), documents from scrapbooks, architectural plans, and the files of the Town of Pulaski.
Themes that were identified from the research were (1) the structure was an integral part of the community, (2) the theatre was a reflection of the community's social norms and roles, such as segregation, and (3) the theatre interior contributed to the social atmosphere of the space.
The theatre building, while transformed over time, retained a presence in the town and memories associated with it across time were significant in creating a sense of place in the community. The theatre was remembered as a setting that brought excitement and stimulation to children and adults for many years. Participants felt "at home" in the theatre, having favored sections of the theatre where they routinely sat. School children attending the weekly matinees in the summer and African Americans sitting in their special section of the balcony developed a special identity with that particular space within the theatre. Even after segregation, many African Americans continued to sit in the balcony where they had sat for many years and felt at home. The unique characteristics of these spaces were dependent on the people that frequented them rather than the architecture of the building. The sense of place was one of personal relationships and emotional attachments rather than of bricks and mortar. Memories of the theatre were stories of groups or individuals and their interactions in the space. The building represented these individuals and what they brought to this place and time. The Pulaski Theatre played a great role in interactions with friends and neighbors and was significant in reflecting a sense of place in this community.
Ph. D.
ETD
Virginia Tech
CHAPTERSIIIandIV.pdf
CHAPTERSIandII.pdf
CHAPTERV.pdf
frontmatter.pdf
backmatter.pdf
In Copyright
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Small-town
Theater
Sense of Place
Social importance
Pulaski
The Social Importance of a Small-town Theater: A Case Study of the Pulaski Theatre, Pulaski, Virginia
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Environmental Design and Planningopen.accessoai:vtechworks.lib.vt.edu:10919/1097962022-05-05T07:12:10Zcom_10919_5534col_10919_11041
Oza, Pratham Rajan
Electrical and Computer Engineering
Chantem, Thidapat
Heaslip, Kevin Patrick
Wang, Yue J.
Gerdes, Ryan M.
Yu, Guoqiang
2022-05-04T08:00:17Z
2022-05-04T08:00:17Z
2022-05-03
vt_gsexam:34431
http://hdl.handle.net/10919/109796
While increasing number of vehicles on urban roadways create uncontrolled congestion, connectivity among vehicles, traffic lights and other road-side units provide abundant data that paves avenues for novel smart traffic control mechanisms to mitigate traffic congestion and delays. However, increasingly complex vehicular applications have outpaced the computational capabilities of on-board processing units, therefore requiring novel offloading schemes onto additional resources located by the road-side. Adding connectivity and other computational resources on legacy traffic infrastructure may also introduce security vulnerabilities. To ensure that the timeliness and resource constraints of the vehicles using the roadways as well as the applications being deployed on the traffic infrastructure are met, the transportation systems needs to be more predictable. This dissertation discusses three areas that focus on improving the predictability and performance of the connected traffic infrastructure. Firstly, a holistic traffic control strategy is presented that ensures predictable traffic flow by minimizing traffic delays, accounting for unexpected traffic conditions and ensuring timely emergency vehicle traversal through an urban road network. Secondly, a vehicular edge resource management strategy is discussed that incorporates connected traffic lights data to meet timeliness requirements of the vehicular applications. Finally, security vulnerabilities in existing traffic controllers are studied and countermeasures are provided to ensure predictable traffic flow while thwarting attacks on the traffic infrastructure.
Doctor of Philosophy
Exponentially increasing vehicles especially in urban areas create pollution, delays and uncontrolled traffic congestion. However, improved traffic infrastructure brings connectivity among the vehicles, traffic lights, road-side detectors and other equipment, which can be leveraged to design new and advanced traffic control techniques. The initial work in this dissertation provides a traffic control technique that (i) reduces traffic wait times for the vehicles in urban areas, (ii) ensures safe and quick movements of emergency vehicles even through crowded areas, and (iii) ensures that the traffic keeps moving even under unexpected lane closures or roadblocks.
As technology advances, connected vehicles are becoming increasingly automated. This allows the car manufacturers to design novel in-vehicle features where the passengers can now stream media-rich content, play augmented reality (AR)-based games and/or get high definition information about the surroundings on their car's display, while the car is driven through the urban traffic. This is made possible by providing additional computing resources along the road-side that the vehicles can utilize wirelessly to ensure passenger's comfort and improved experience of in-vehicle features. In this dissertation, a technique is provided to manage the computational resources which will allow vehicles (and its passengers) to use multiple features simultaneously.
As the traffic infrastructure becomes increasingly inter-connected, it also allows malicious actors to exploit vulnerabilities such as modifying traffic lights, interfering with road-side sensors, etc. This can lead to increased traffic wait times and eventually bring down the traffic network. In the final work, one such vulnerability in traffic infrastructure is studied and mitigating measures are provided so that the traffic keeps moving even when an attack is detected.
In all, this dissertation aims to improve safety, security and overall experience of the drivers, passengers and the pedestrians using the connected traffic infrastructure.
ETD
en
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
edge computing
real-time systems
intelligent transportation
smart traffic
Predictable Connected Traffic Infrastructure
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/1059682022-02-21T16:23:47Zcom_10919_5534col_10919_9291
Chowdhury, Badrul Hasan
Electrical Engineering
2021-10-26T20:09:41Z
2021-10-26T20:09:41Z
1983
http://hdl.handle.net/10919/105968
The application of wind power in various fields of energy requirements has been examined. Specific applications of the three broad classes of wind machines - Small, Intermediate and Large-scale, have been evaluated. Two methodologies were developed which could compute the amount of wind power required of existing Wind Turbine Generators (WTG) when placed in two sites in Virginia. The impacts of placing multiple WTG's in clusters to get higher power levels have been examined in details. A wake interference model has been included to calculate the amount of power reductions in downwind WTG rows.
The advantages evolving out of site dispersal were also investigated. In general terms, arrays of wind farms produce some firm capacity because of the diversity of wind at the dispersed sites. Mostly, arrays of multiple sites tend to fill up the low power output levels of an individual site during the day. Besides, the output from an array consisting of a total of N wind machines, will be more than the output from an identical number of machines in a single site. These aspects of site dispersal have been discussed.
The studies of Clusters and Arrays have been extended to utility interface. Two separate models - an Individual Site model and a Dispersed Site model have been considered for integration. Capacity credit earned for each case was investigated in details using a Reliability model. Wind power was also looked at from the competition against conventional expansion plants point of view. The economics of wind power in terms of capacity and operational cost savings were also examined.
The problems arising out of a possible integration of wind machines have been pointed out and some solutions have been suggested. Computational results are presented in details from the major studies and recommendations for further work have been discussed.
M.S.
xi, 160 leaves
application/pdf
en
Virginia Polytechnic Institute and State University
OCLC# 10185579
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1983.C456
Wind power
Application of wind in large-scale electric power production
Thesis
Text
M.S.
masters
Virginia Polytechnic Institute and State University
Electrical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/1161302023-08-26T07:12:23Zcom_10919_5534col_10919_11041
Choi, Jae-Young
Aerospace and Ocean Engineering
Choi, Seongim C.
Woolsey, Craig A.
Lowe, K. Todd L.
Raj, Pradeep R.
Wang, Kevin G. W.
2023-08-25T16:44:25Z
2023-08-25T16:44:25Z
2023
http://hdl.handle.net/10919/116130
The present study focuses on developing an efficient and stable unmanned aerial system traffic management (UTM) system that utilizes a data-driven target tracking method and a distributed path planning algorithm for multiple Unmanned Aerial Vehicle (UAV) operations with local dynamic networks, which can provide flexible scalability, enabling autonomous operation of a large number of UAVs in dynamically changing environment. Traditional dynamic motion-based target tracking methods often encounter limitations due to their reliance on a finite number of dynamic motion models. To address this, data-driven target tracking methods were developed based on the statistical model of the Gaussian mixture model (GMM) and deep neural networks of long-short term memory (LSTM) model, to estimate instant and future states of UAV for local path planning problems. The estimation accuracy of the data-driven target tracking methods were analyzed and compared with dynamic model-based target tracking methods. A hybrid dynamic path planning algorithm was proposed, which selectively employs grid-free and -based path search methods depending on the spatio-temporal characteristics of the environments. In static environment, the artificial potential field (APF) method was utilized, while the $A^*$ algorithm was applied in the dynamic state environment. Furthermore, the data-driven target tracking method was integrated with the hybrid path planning algorithm to enhance deconfliction. To ensure smooth trajectories, a minimum snap trajectory method was applied to the planned paths, enabling controller tracking that remains dynamically feasible throughout the entire operation of UAVs. The methods were validated in the Software-in-the-loop (SITL) demonstration with the simple PID controller of the UAVs implemented in the software program.
Ph.D.
This dissertation focuses on developing data-driven models for tracking and path planning of Unmanned Aerial Vehicle (UAV) in dynamic environments with multiple operations. The goal is to improve the accuracy and efficiency of Unmanned Aircraft System traffic management (UTM) under such conditions. The data-driven models are based on Gaussian mixture model (GMM) and long-short term memory (LSTM) and are used to estimate the instant and consecutive future states of UAV for local planning problems. These models are compared to traditional target tracking models, which use dynamic motion models like constant velocity or acceleration. A hybrid dynamic path planning approach is also proposed to solve dynamic path planning problems for multiple UAV operations at an efficient computation cost. The algorithm selectively employs a path planning method between grid-free and grid-based methods depending on the characteristics of the environment. In static state conditions, the system uses the artificial potential field method (APF). When the environment is time-variant, local path planning problems are solved by activating the $A^*$ algorithm. Also, the planned paths are refined by minimum snap trajectory to ensure that the path is dynamically feasible throughout a full operation of the UAV along with controller tracking. The methods were validated in the Software-in-the-loop (SITL) demonstration with the simple PID controller of the UAVs implemented in the software program.
ETD
application/pdf
en
Virginia Tech
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
http://creativecommons.org/licenses/by-nc-nd/4.0/
UTM
Trajectory modeling
Path planning
Gaussian mixture model
Deep neural network
Software-In-The-Loop (SITL)
Data-driven Target Tracking and Hybrid Path Planning Methods for Autonomous Operation of UAV
Dissertation
Ph.D.
doctoral
Virginia Polytechnic Institute and State University
Aerospace Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/403312021-04-26T17:42:19Zcom_10919_5534col_10919_11041
Jones, Raymond T.
Educational Administration
Parks, David J.
Earthman, Glen I.
Richards, Robert R.
2014-03-14T21:23:07Z
2014-03-14T21:23:07Z
1997-03-20
2005-11-10
2005-11-10
2005-11-10
etd-11102005-141137
http://hdl.handle.net/10919/40331
http://scholar.lib.vt.edu/theses/available/etd-11102005-141137/
The world is shifting into an unprecedented technological age. Towns such as Blacksburg, Virginia, are now being called "electronic villages" with electronic infrastructure which not only ties together all aspects of the town but also connects the town to the world. Reality becomes "virtual" with information unimpeded by time and distance.
This rapid advancement in electronical technology is having an impact on world educational systems. Those planning the future of education have a need to know what directions this new technology might take in order to interface such technologies with the schools. The purpose of this study was to predict which present and emerging electronic technologies would be in significant use in the K-12 schools of the year 2000.
The Delphi technique was used to gather predictions from an expert panel of teachers, administrators, electronic media specialists, and those working in the technology industries. The predictions were gathered from winter 1994 to fall 1995 for the year 2000, taking into account the need for a reasonably accurate prediction which could be used for those now engaged in short-term planning and those engaged in generating the appropriate technologies for the schools. The types of present and emerging electronic technologies "to be found in K-12 schools of the year 2000 were solicited in round one of the study. Rounds two and three identified which technologies would indeed be in significant usage. Using a scale of 1 to 4 (1= very unimportant, 2= unimportant, 3=important, 4= very important), a group mean and standard deviation were calculated for each identified technology. Those technologies with a mean score of 3.00 or higher in round three were predicted to be those likely or very likely to be used in the K-12 schools of the year 2000.
Ed. D.
x, 145 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 37231103
LD5655.V856_1997.J664.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
technology - electronic
LD5655.V856 1997.J664
Prediction of educational technology to be found in the public schools of the year 2000: a Delphi study
Dissertation
Text
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Educational Administrationopen.accessoai:vtechworks.lib.vt.edu:10919/291862022-03-29T19:22:18Zcom_10919_5534col_10919_11041
McGinnis, Marvin Harris
Educational Leadership and Policy Studies
Parson, Stephen R.
Driscoll, Lisa G.
Dawson, Christina M.
Crockett, Jean B.
Dixon, Benjamin
2014-03-14T20:17:04Z
2014-03-14T20:17:04Z
2002-09-20
2002-10-04
2003-12-12
2002-12-12
etd-10042002-103859
http://hdl.handle.net/10919/29186
http://scholar.lib.vt.edu/theses/available/etd-10042002-103859/
African Americans continue to perform significantly lower on high-stakes measures of educational achievement than do other ethnic groups. Osborn (1997) attributes this low performance by African Americans to their disidentification with the academic discourse. Ickes and Layden (1976), Metalsky, Abramson, and Peterson (1982), Finn (1989), and Belgrave, Johnson, and Carey (1992) relate the poor performance of African Americans to the manner in which they internalize/externalize negative and positive outcomes and the longevity of such outcomes being internalized, which they term locus of control. This study explores the variables of self-esteem, locus of control, test anxiety, reading ability, testing behaviors and the performance of African American males on high-stakes tests of educational achievement. Simultaneously, the study provides a reflection on the challenges faced by a practitioner when he studies an issue of critical concern in his own community.
Ed. D.
Virginia Tech
cchps.pdf
Vita.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
African American Males
Academic achievement
high-stakes tests
Challenges Of Studying Attributes Associated With African American Males Who Are Not Successful With Testing Measures
Dissertation
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Educational Leadership and Policy Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/420142022-02-22T22:01:44Zcom_10919_5534col_10919_9291
O'Kell, Allison Louise
Veterinary Medical Sciences
Grant, David C.
Weinstein, Nicole M.
Panciera, David L.
Troy, Gregory C.
2014-03-14T21:33:30Z
2014-03-14T21:33:30Z
2012-01-27
2012-04-10
2012-05-07
2012-05-07
etd-04102012-124404
http://hdl.handle.net/10919/42014
http://scholar.lib.vt.edu/theses/available/etd-04102012-124404/
Objectives: To determine the effects of prednisone and prednisone plus ultralow-dose aspirin on coagulation in healthy dogs, and to determine intra-individual variation in thromboelastography (TEG).
Animals: 14 healthy experimental dogs and 10 healthy client-owned dogs
Procedures: Prospective, randomized, blinded study. TEG was performed twice three days apart on each experimental dog prior to treatment and intra-individual variation was calculated. Dogs were given prednisone (2 mg/kg/day) plus aspirin (0.5 mg/kg/day) or prednisone (2 mg/kg/day) plus placebo for 14 days, after which TEG and other baseline tests were repeated. Changes from baseline between and within each group were compared using t-tests or Wilcoxon 2 sample tests. Client owned dogs had TEG performed twice three days apart to determine intra-individual variation.
Results: Intra-individual variation in TEG parameters were <10% for MA (maximum amplitude) and angle. For experimental dogs, MA and fibrinogen significantly increased from baseline whereas Ly30 (percent lysis 30 minutes after MA) and antithrombin activity significantly decreased within each group. For the prednisone plus placebo group, Ly60 (percent lysis 60 minutes after MA) significantly decreased from baseline. For all parameters, there was no difference between groups for change from baseline.
Conclusions and Clinical Relevance: Prednisone caused hypercoagulability in healthy dogs evidenced by increased MA and fibrinogen and decreased antithrombin activity. Concurrent use of ultra-low dose aspirin had no effect on measured TEG parameters. Intra-individual variation in some TEG parameters is high and may preclude routine clinical utility.
Master of Science
Virginia Tech
OKell_AO_T_2012.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
thromboelastography
hypercoagulability
canine
The Effects of Prednisone and Prednisone Plus Ultralow-dose Aspirin on Coagulation Parameters in Healthy Dogs
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Veterinary Medical Sciencesopen.accessoai:vtechworks.lib.vt.edu:10919/305162022-02-22T19:58:12Zcom_10919_5534col_10919_11041
Phillips, Dennis Ivan
Mining and Minerals Engineering
Yoon, Roe-Hoan
Palowitch, E. R.
Wicks, Alfred L.
Adel, Gregory T.
Luttrell, Gerald H.
2014-03-14T20:21:56Z
2014-03-14T20:21:56Z
1998-04-09
1998-04-09
1998-05-01
1998-05-01
etd-4198-14140
http://hdl.handle.net/10919/30516
http://scholar.lib.vt.edu/theses/available/etd-4198-14140/
Coal in the finer particle size ranges (below 1 mm) has always suffered from poor cleaning efficiencies. This problem has been exacerbated in recent years with the increased amount of high ash fines due to continuous mining machines and the mining of dirtier coal seams. In the present work, it is proposed to improve overall plant efficiencies by processing coarser coal in column flotation than is now commonly treated by that method. Column flotation for coarse coal is supported by actual lab and plant test data that result in a full-scale column plant installation. The fundamentals of coarse particle detachment from bubbles are reviewed and a new simplified model is developed which better handles cubical and rectangular coal particles.
Much of the lower efficiency of fine coal cleaning is due to poor size separation of the fine-sized raw coal which results in misplaced high ash fines reporting to the coarser size streams. By sending coarser material to column flotation, the finest size separation that takes place in a plant can be as coarse as 0.5 mm or greater. The proper use of wash water in a flotation column then becomes the best mechanism for desliming of the high ash clays. This work quantifies the benefits of removing the high ash fines from the plant product and increasing overall plant yield by increasing the amount of near-gravity coarse material. The resulting yield gain is greater than that obtained from only the increased fine coal recovery. Methods of column operation for improved coarse coal recovery are also evaluated.
Ph. D.
Virginia Tech
DennisPhillips.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Coal processing
coarse coal flotation
fine coal
column flotation
Optimum Processing of 1 mm by Zero Coal
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Mining and Minerals Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/397282021-11-18T18:19:35Zcom_10919_5534col_10919_11041
Duncan, Harriet H.
Family and Child Development
Allen, Katherine R.
Howze, Elizabeth H.
Sporakowski, Michael J.
McAuley, William J.
Travis, Shirley S.
2014-03-14T21:20:45Z
2014-03-14T21:20:45Z
1993-03-30
2005-10-10
2005-10-10
2005-10-10
etd-10102005-131611
http://hdl.handle.net/10919/39728
http://scholar.lib.vt.edu/theses/available/etd-10102005-131611/
This study employed the grounded theory methodology suggested by Strauss and Corbin (1990) to analyze and explore the meaning of and motivation for mall walking among a group of older, rural, independently living adults. Interviews were conducted with 14 respondents aged 62-81 and participant observation was conducted at a rural mall.
Mall walking was initially motivated by three conditions: (a) expert-directed advice, (b) self-determined goals, and (c) the invitation of significant others. Four major factors encouraged continued participation in mall walking: (a) the need to create work roles after retirement, (b) fear due to perceived vulnerability in the community, (c) social supports from family and peers, and (d) a sense of membership in a community of older adults that was generally time and place specific. Members of this mall community shared activities, routines, rituals, beliefs, and a sense of belonging.
Despite medical disorders, all of the respondents said their health was good. After initially responding to medical advice to walk, walkers paid little or no attention to medical problems. These older adults did not continue to mall walk in response to expert medical direction. This finding suggests that health promoting activities should not rely on the continuing influence of medical advice to encourage adherence or ongoing participation in health promoting activities, and should instead attend to the social constructs of health and wellness.
An important implication for future research is the finding that mall walking was a quasi-work activity, not exercise. Walkers created "work" routines and roles that replaced those lost upon retirement. The equation of mall walking with work has implications for both the design and the implementation of health promoting activities for older adults.
Ph. D.
xi, 185 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 29046271
LD5655.V856_1993.D863.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1993.D863
Exercise for older people -- Psychological aspects
Older people -- Recreation
Shopping malls -- Recreational use
Walking -- Psychological aspects
Meanings and motivations among older adult mall walkers: a qualitative analysis
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Family and Child Developmentopen.accessoai:vtechworks.lib.vt.edu:10919/537132021-01-14T20:59:06Zcom_10919_5534col_10919_9291
Phillippe, Maurice Matthew
Agronomy
2015-06-26T20:53:59Z
2015-06-26T20:53:59Z
1940
http://hdl.handle.net/10919/53713
The appearance of synthetic fertilizers on the market has increased the interest in the so-called "minor elements". Much work with water and sand cultures has proven the necessity of these elements for successful plant growth. However, the need for these elements in crop production on field soils has not been studied intensively, nor have we sufficient knowledge as to the effect of our changing fertilizer practices on the necessity for minor elements.
A number of field studies to determine the necessity of boron, manganese, zinc, copper and ether minor elements, when applied singly or in combinations of two or more, have given phenomenal increases in yields under certain plant and soil conditions. Under other conditions there has been no response from their use when applied to the soil either singly or in combinations of two or more elements. It is the purpose of this study to determine under what soil conditions the need of minor elements becomes a part of our soil management problem and what part natural Chilean nitrate of soda plays in preventing and correcting this condition. Also this investigation was developed to give a comparison of yield and growth of various crops grown intensively on a number of soil types where fertilized with purified carriers of nitrogen, phosphorus and potassium and where these elements were supplied from commonly used commercial carriers. Another purpose of this study was to determine how long these soils could be cropped before minor elements would become a limiting factor in crop production as shown by yields and deficiency symptoms.
Master of Science
[3], 40 leaves
application/pdf
en_US
Virginia Agricultural and Mechanical College and Polytechnic Institute
OCLC# 10581133
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V855 1940.P544
Chile saltpeter as fertilizer
Soils -- Trace element content
Trace elements in agriculture
A study of the effect of intensive cropping and the use of pure chemicals on the need for so-called "minor elements" on certain soil types and the effect of natural Chilean nitrate of soda in eliminating this need
Thesis
Text
Master of Science
masters
Virginia Agricultural and Mechanical College and Polytechnic Institute
Agronomyopen.accessoai:vtechworks.lib.vt.edu:10919/252962020-09-28T14:05:01Zcom_10919_5534col_10919_9291
Maloo, Akshay
Computer Science
Marathe, Madhav Vishnu
Eubank, Stephen G.
Vullikanti, Anil Kumar S.
Xie, Dawen
2014-02-05T09:00:13Z
2014-02-05T09:00:13Z
2014-02-04
vt_gsexam:2003
http://hdl.handle.net/10919/25296
Dynamic Behavior Visualizer (DBV) is a visual analytics environment to visualize the spatial and temporal movements and behavioral changes of an individual or a group, e.g. family within a realistic urban environment. DBV is specifically designed to visualize the adaptive behavioral changes, as they pertain to the interactions with multiple inter-dependent infrastructures, in the aftermath of a large crisis, e.g. hurricane or the detonation of an improvised nuclear device. DBV is web-enabled and thus is easily accessible to any user with access to a web browser. A novel aspect of the system is its scale and fidelity. The goal of DBV is to synthesize information and derive insight from it; detect the expected and discover the unexpected; provide timely and easily understandable assessment and the ability to piece together all this information.
Master of Science
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Information Visualization
Visual Analytics
Data Modeling
Networked Models
Dynamic Behavior Visualizer: A Dynamic Visual Analytics Framework for Understanding Complex Networked Models
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Computer Science and Applicationsopen.accessoai:vtechworks.lib.vt.edu:10919/810042021-04-15T17:10:36Zcom_10919_5534col_10919_11041
Bentley, Donald Wade
Educational Administration
2017-12-06T15:20:45Z
2017-12-06T15:20:45Z
1976
http://hdl.handle.net/10919/81004
The purpose of this study was to investigate selected variables and competencies that were related to the turnover in the superintendency in North Carolina and to study the differences in perception as to the level of importance placed on the variables by superintendents and on the competency data by the chairmen of boards of education.
The population of the three study groups included 104 superintendents and 104 board chairmen. The sample selected consisted of 24 superintendents who have not been in a turnover situation in five years, 12 forced turnover superintendents, 12 turnover superintendents who left a position on their own volition and 48 board chairmen that were categorized into study groups corresponding to the superintendency sample.
The data sought included demographic data, value placed on organizational variables in relationship to their part in turnover, level of performance in 15 competency areas, and value placed on each competency.
The results produced by using Statistical Packages for the Social Sciences, Factor Analysis, and Fortran Packages of Analysis of Variance and Scheffe' Multiple Comparison Test indicated that the non-turnover study group and the forced turnover group were in closer agreement on variables and importance placed on competency items.
The variables listed most frequently in importance were:
1. Board of Education performing administrative duties normally assigned to the superintendent.
2. Board of Education failing to work as a unit.
3. Conflict of personality of superintendent and board.
4. Lack of community confidence and support.
5. Involvement in partisan politics by board.
6. Poor support from local governing board.
7. Interference from pressure groups.
8. Intimidation by locally elected or appointed officials.
Board chairmen placed most importance on the following variables: Planning, Plant operations, Instructional leadership, Decision making, and Business management. These areas were those which produced potential areas of conflict and possible turnover agents.
It is recommended that:
1. Boards of education should work closer together to develop guidelines, policies, and procedures to eliminate the overlapping in performance of duties. Separation of duties should be established and followed.
2. The study should be replicated again at a later date to include more study units.
3. The turnover study group should be questioned again at periodic intervals, preferably on a yearly basis, to see if suggestions for improvements are being used.
4. All boards of education should keep on hand a written list of expected competencies for prospective candidates for the superintendency.
5. Prospective superintendents and boards of education should frankly discuss policy and expectation.
6. Educational institutions should provide more extensive training or retraining in fields of competency where weaknesses were indicated such as leadership, planning, decision-making, plant operation, and school-community relationships.
7. Educational institutions need to be supported by state agencies in providing a closer working relationship between classroom activity and field studies.
8. Training sessions in policy making, school law, and duties of board members should be established as part of the requirement for membership on boards of education.
Ed. D.
vii, 183 leave
application/pdf
en
Virginia Polytechnic Institute and State University
OCLC# 40182605
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1976.B45
A study of variables related to turnover of superintendents in selected North Carolina school systems
Dissertation
Text
Ed. D.
doctoral
Virginia Polytechnic Institute and State University
Educational Administrationopen.accessoai:vtechworks.lib.vt.edu:10919/876552021-04-15T17:10:37Zcom_10919_5534col_10919_11041
Renieri, Michael P.
Engineering Mechanics
2019-02-15T21:22:02Z
2019-02-15T21:22:02Z
1976
http://hdl.handle.net/10919/87655
Studies on two adhesives (Metlbond 1113 and 1113-2) identified as having applications in the bonding of composite materials are presented. Constitutive equations capable of describing changes in material behavior with strain rate are derived from various theoretical approaches. It is shown that certain unique relationships exist between these approaches. It is also shown that the constitutive equation derived from mechanical models can be used for creep and relaxation loading.
Modifications to the constitutive equations for constant strain rate loading are proposed. Nonlinear constitutive equations are derived using a nonlinear perturbation technique in conjunction with a modified Bingham model. Using the modified Bingham model, constitutive equations describing loading-unloading behavior are also proposed.
The stress-strain behavior of the adhesives is shown to be significantly rate dependent. Further it is shown that a rate dependent stress-whitening (crazing) phenomenon occurs prior to the maximum stress. A region of elastic behavior, a rate and time dependent region, and a region of perfectly plastic flow are identified in the stress-strain behavior. Information regarding variations of Poisson's ratio with rate and time is also presented.
The elastic limit stress and strain, and maximum stress are shown to be rate dependent and agree well with an empirical equation proposed by Ludwik. Analytical predictions based on modified Ramberg-Osgood equations are shown to agree well with experimental stress-strain-strain rate results. It is shown that the coefficients of these equations are different before and after stress-whitening due to changes in the properties of the adhesives. Analytical predictions based on the modified Bingham model are shown to agree well with the constant strain rate results. It is also shown that the nonlinear model indicates that the coefficients of the modified Bingham model may vary due to the change in material properties before and after stress-whitening.
A creep to failure phenomenon is shown to exist and is correlated with a delayed yield equation proposed by Crochet. Loading-unloading results are presented and are shown to correlate well with the proposed form of the loading-unloading equations for the modified Bingham model.
Experimental results obtained for relaxation tests above and below the glass transition temperature are presented. It is shown that the adhesives obey the time-temperature superposition principle.
Ph. D.
xiii, 199 leaves
application/pdf
en
Virginia Polytechnic Institute and State University
OCLC# 40221297
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1976.R44
Rate and time dependent behavior of structural adhesives
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State Universityopen.accessoai:vtechworks.lib.vt.edu:10919/371982022-01-05T18:24:08Zcom_10919_5534col_10919_11041
Ruark, Edwin Warren
Biochemistry and Nutrition
2014-03-14T21:08:49Z
2014-03-14T21:08:49Z
1970
2010-01-13
2010-01-13
2010-01-13
etd-01132010-020032
http://hdl.handle.net/10919/37198
http://scholar.lib.vt.edu/theses/available/etd-01132010-020032/
The effect of triiodothyronine (L-T₃) on the protein, RNA and DNA fractions of the thymus nuclei of growth-arrested sulfaguanidine-fed rats has been studied.
A single dose of 15 µg of L-T₃ stimulated the incorporation of ¹⁴C-labelled amino acids into total nuclear protein, whole histone and histone fractions. The incorporation of the labelled amino acid into nuclear protein was increased 40 percent over the control 4 hours after the administration of L-T₃. The incorporation of alanine-1-¹⁴C into the total histone fraction reached a maximum 4 hours after the administration of L-T₃ and then decreased 8 and 16 hours after the administration of L-T₃. The incorporation of alanine-1-¹⁴C into histone fraction f₁ reached a maximum at 4 hours after the administration of L-T₃ while the incorporation into fractions f<sub>2a</sub>, f<sub>2b</sub> and f₃ did not reach a maximum until 8 hours after the administration of L-T₃.
Time course studies showed that the protein and RNA moieties of thymus chromatin of rats injected with a single dose of L-T₃ was increased to a maximum at 4 hours. The T<sub>m</sub> of chromatin was increased 2° by L-T₃ administration as early as 2 hours. However, the T<sub>m</sub> of DNA was not affected.
Four hours after the administration of L-T₃ the template efficiency increased 171 percent. The template efficiency of DNA was not affected by L-T₃.
These results demonstrate that thyroid hormones modify the chromatin in such a way that the template efficiency is increased. An hypothesis for the mechanism of thyroid hormone action was presented.
Ph. D.
89 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 22366655
LD5655.V856_1970.R8.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
LD5655.V856 1970.R8
Rats
Thymus
Thyroid hormones
The response of rat thymus nuclei to thyroid hormones
Dissertation
Text
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Biochemistry and Nutritionopen.accessoai:vtechworks.lib.vt.edu:10919/271182020-09-25T20:38:56Zcom_10919_5534col_10919_11041
Sexton, Mildred B.
Educational Leadership and Policy Studies
Curcio, Claire Cole Vaught
Parson, Stephen R.
Cannaday, Billy K. Jr.
Yakimowski-Srebnick, Mary E.
Twiford, Travis W.
2014-03-14T20:10:26Z
2014-03-14T20:10:26Z
2003-04-17
2003-04-22
2004-04-24
2003-04-24
etd-04222003-114716
http://hdl.handle.net/10919/27118
http://scholar.lib.vt.edu/theses/available/etd-04222003-114716/
Given that standards are legislated through the No Child Left Behind Act of 2001 and the Standards of Learning have been implemented in the Commonwealth of Virginia, educational reforms call for extended learning opportunities and a requirement that leaders implement programs that are scientifically research-based which concentrate on the achievement of all students. Year round education is scientifically research based.
The purpose of this study was to compare year round and traditional education at an urban middle school on attendance, academic performance, and behavior patterns. The school had both year round education and traditional education from 1998-2001. This is a unique factor to this study, as no one has compared year round education and traditional education on attendance, academic performance, and behavior patterns in an urban setting with both year round education and traditional education in the same building.
The population in this quantitative quasi-experimental study was 113 grade 8 year round education (87) and traditional education (26) students from one urban middle school in southeastern Virginia, who had been in the programs for three years (grades 3-6). The over- riding research questions were: (1) does year round education make an impact on attendance as measured by grade 8 attendance data after controlling for initial differences in grade 5 attendance? , (2) does year round education have an impact on academic achievement as measured by the SOL after controlling for grade 5 Degrees of Reading Power (DRP)? , (3) does year round education impact students’ behavior patterns as measured by grade 8 out-of-school suspensions (OSS) and in-school-suspensions (SIPS) data?
Two one-way ANCOVAs, two chi squares, and t-tests were conducted to determine the statistical significant differences in attendance, academic performance, and behavior patterns (the first time placements in in-school suspension and out-of school suspension) of year round education and traditional education students with a pre-determined alpha of .05. The results indicated no statistically significant findings.
The conclusions and implications in this study were limited by the size of the sample, lack of random student assignment, students interacting with each other, and students having the same teachers. Year round education provides an educational option for students and families.
Ed. D.
Virginia Tech
Dissertation.pdf
In Copyright
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Attendance
Year-Round
Behavior
Achievement
A Case Study Of The Effect Of Year Round Education On Attendance, Academic Performance, And Behavior Patterns
Dissertation
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Educational Leadership and Policy Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/780652021-08-27T19:45:57Zcom_10919_5534col_10919_9291
Young, Tyler James
Biomedical Engineering
Duma, Stefan M.
Stitzel, Joel D.
Rowson, Steven
2017-06-13T19:43:41Z
2017-06-13T19:43:41Z
2013-12-09
2013-12-18
2014-01-10
2014-01-10
etd-12182013-105415
http://hdl.handle.net/10919/78065
http://scholar.lib.vt.edu/theses/available/etd-12182013-105415/
The research presented in this thesis aims to improve the knowledge of head impact biomechanics in youth football players by analyzing head impact exposure of youth football players and the performance of youth football helmets. The results of the studies presented provide a foundation for researchers, football leagues, and helmet manufactures to implement changes and modifications that aim to reduce concussion risk in youth athletes. The first study presented in this thesis aims to quantify the head impact exposure of 7 to 8 year old football players and determine the cause of variation in player exposure. To conduct this study, 19 players were instrumented with helmet mounted accelerometers that measured real-time acceleration data on the field. This data was analyzed to determine the magnitude, frequency, and location of each impact sustained by players in the 2011 and 2012 football season. From these data, it was determined that the average 7 to 8 year old player experienced 161 impacts per season, 60% of which were in practice and 40% were in games. The median impact for 7 to 8 year old players was 16 g and 686 rad/s². The magnitude of the 95th percentile impact was 38 g and 2052 rad/s². A total of 125 impacts above 40 g were recorded, 67% of which occurred in practices and 33% occurred in games. It was determined that returning players experienced significantly more impacts per season than first time players and practices had significantly higher magnitude impacts than games. These data can be used to further develop practice modifications that aim to reduce total impacts and high magnitude impacts experienced by youth football players. The second study presented in this thesis aims to quantify differences in youth football helmet performance before and after a football season. Currently, the only requirement regarding helmet recertification and reconditioning states that no helmet older than 10 years will be recertified or reconditioned. Quantitative data is needed to either support or refute this guideline and provide data describing how often youth football helmets should be recertified and reconditioned. To conduct this study, 6 youth Riddell Revolution football helmets, 3 that were new and 3 that had been used for one season, were tested on a drop tower from various heights and impact locations before and after the 2013 football season. It was determined that there was no significant difference in helmet performance before and after a season for new helmets or helmets that had been used for one season. In addition, there was no significant correlation between the frequency of impacts, the 95th percentile impact magnitude, or the product of the frequency and 95th percentile impact magnitude with the change in helmet performance. Future studies should be conducted that analyze the performance of youth football helmets over the course of multiple seasons.
Master of Science
en_US
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Youth
Acceleration
Helmet
Football
Brain injury
Concussion
Head Impact Biomechanics and Helmet Performance in Youth Football
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Biomedical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/370092022-02-03T19:04:55Zcom_10919_5534col_10919_9291
Holland, Michael L.
Mechanical Engineering
Reinholtz, Charles F.
Sturges, Robert H.
Kasarda, Mary E. F.
2014-03-14T20:52:28Z
2014-03-14T20:52:28Z
1998-08-24
1998-08-24
1998-09-02
1998-09-02
etd-8298-34627
http://hdl.handle.net/10919/37009
http://scholar.lib.vt.edu/theses/available/etd-8298-34627/
This thesis is a treatise on optimal assembly methods for double row ball bearings. As with common single row bearings, double row ball bearings, consist of four general components, namely, an inner ring, an outer ring, a complement of balls and a cage or retainer to keep the balls separate. Unlike single row bearings, however, double row ball bearings have two complements of balls in two distinct parallel races. Although this double row configuration is desirable in a number of applications, it makes the bearings more difficult and expensive to assemble. In addition, current manual assembly procedures require a great deal of digital manipulation, leading to concern about carpal tunnel syndrome and other long-term repetitive motion injuries.
This thesis attempts to develop an improved assembly process for all types of double row bearings. Although the work is intended to be general, the Torrington 5203 double row ball bearing is adopted as a specific application example. This bearing's assembly difficulties and additional cost are a result of its manual Conrad assembly method and a rubber O-ring and groove used solely for bearing assembly. In the assembly process, the O-ring supports the upper balls temporarily until the two rings can be aligned concentrically, thus snapping the balls into the bearing races. This thesis addresses the replacement of the rubber O-ring and explores opportunities for bearing assembly automation.
Design synthesis of a retractable or reusable assembly component to replace the rubber O-ring supporting the upper balls during assembly is presented. A large group of design concepts are developed and evaluated, resulting in a small group of feasible designs. These feasible solutions are then tested, and a design that has the potential immediate implementation in an improved manual assembly process is proposed. In addition, two design concepts are presented as candidates for possible implementation in an automated assembly process.
Master of Science
Virginia Tech
Absplus.pdf
ch1.pdf
Ch2.pdf
Ch3.pdf
Ch4.pdf
RefVita.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Ball bearings
Assembly
Torrington
Double Row Bearings
Assembly Optimization for Double Row Ball Bearings
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Mechanical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/787202022-12-13T19:49:20Zcom_10919_5534col_10919_9291
Gaillard, Sarah C.
Mining and Minerals Engineering
Sarver, Emily A.
Keles, Cigdem
Luxbacher, Kramer Davis
2017-08-22T08:00:21Z
2017-08-22T08:00:21Z
2017-08-21
vt_gsexam:12626
http://hdl.handle.net/10919/78720
Diesel particulate matter (DPM) is the solid portion of diesel exhaust, which occurs primarily in the submicron range. It is complex in nature, occuring in clusters and agglomerated chains, and with variable composition depending on engine operating conditions, fuel type, equipment maintenance, etc. DPM is an occupational health hazard that has been associated with lung cancer risks and other respiratory issues. Underground miners have some of the highest exposures to DPM, due to work in confined spaces with diesel powered equipment. Large-opening mines present particular concerns because sufficient ventilation is very challenging. In such environments, reliable DPM sampling and monitoring is critical to protecting miner health. Though complex, DPM is made up primarily of elemental (EC) and organic carbon (OC), which can be summed to obtain total carbon (TC). The Mine Safety and Health Administration (MSHA) currently limits personal DPM exposures in metal/non-metal mines to 160 µg/m3 TC on an 8-hour time weighted average. To demonstrate compliance, exposures are monitored by collecting filter samples, which are sent to an outside lab and analyzed using the NIOSH 5040 Standard Method. To support real-time results, and thus more timely decision making, the Airtec handheld DPM monitor was developed. It measures EC, which is generally well correlated with TC, using a laser absorption technique as DPM accumulates on a filter sample. Though intended as a personal monitor, the Airtec has application as an engineering tool. A field study is reported here which demonstrated the usefulness of the Airtec in tracking temporal and spatial trends in DPM. An approach to sensitizing the monitor to allow "spot checking" was also demonstrated. Since DPM in mine environments generally occurs with other airborne particulates, namely dust generated during the mining process, DPM sampling must be done with consideration for analytical interferences. A common approach to dealing with mineral dust interferences is to use size selectors in the sampling train to separate DPM from dust; these devices are generally effective because DPM and dust largely occur in different size ranges. An impactor-type device (DPMI) is currently the industry standard for DPM sampling, but it is designed as a consumable device. Particularly for continuous monitoring applications, the sharp cut cyclone (SCC) has been suggested as a favorable alternative. In another field study reported here, the effect of aging (i.e., loading as an artifact of sampling) on the DPMI and SCC was investigated. Results suggest the effective cut size of the DPMI will be reduced much more rapidly than that of the SCC with aging — though even in a relatively high dust, high DPM environment, the DPMI performs adequately. In a third field study, the possibility of attachment between DPM and respirable dust particles was investigated. Such a phenomenon may have implications for both reliable sampling and health outcomes. Data collected by transmission electron microscope (TEM) on samples collected in the study mine showed that DPM-dust attachment does indeed occur. Moreover, the study results suggest that respirable particulate sampling — as opposed to submicron sampling, which is currently used — may be favorable for ensuring that oversized DPM is not excluded from samples. This strategy may require additional sample preparation to minimize dust interferences, but methods have been previously developed and were demonstrated here.
Master of Science
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Diesel Particulate Matter
DPM
Monitoring DPM
Transmission Electron Microscope
A Series of Studies to Support and Improve DPM Sampling in Underground Mines
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Mining Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/334672020-09-25T21:00:27Zcom_10919_5534col_10919_9291
Lester, Alanna Paige
Geosciences
Chapman, Martin C.
Matheson, Gordon
Martin, James R. Jr.
Snoke, J. Arthur
2014-03-14T20:39:33Z
2014-03-14T20:39:33Z
2005-06-01
2005-06-07
2005-07-21
2005-07-21
etd-06072005-163816
http://hdl.handle.net/10919/33467
http://scholar.lib.vt.edu/theses/available/etd-06072005-163816/
This study examines the sensitivity of calculated site response in connection with alternative assumptions regarding input motions and procedures prescribed in the IBC 2000 building code, particularly the use of average shear wave velocity in the upper 30 meters as an index for engineering design response spectra. Site specific subsurface models are developed for four sites in and near Columbia, South Carolina using shear wave velocity measurements from cone penetrometer tests. The four sites are underlain by thin coastal plain sedimentary deposits, overlying high velocity Paleozoic crystalline rock. An equivalent-linear algorithm is used to estimate site response for vertically incident shear waves in a horizontally layered Earth model. Non-linear mechanical behavior of the soils is analyzed using previously published strain-dependent shear modulus and damping degradation models.
Two models for material beneath the investigated near-surface deposits are used: B-C outcrop conditions and hard rock outcrop conditions. The rock outcrop model is considered a geologically realistic model where a velocity gradient, representing a transition zone of partially weathered rock and fractured rock, overlies a rock half-space. Synthetic earthquake input motions are generated using the deaggregations from the 2002 National Seismic Hazard Maps, representing the characteristic Charleston source. The U. S. Geological Survey (2002) uniform hazard spectra are used to develop 2% in 50 year probability of exceedance input ground motions for both B-C boundary and hard rock outcrop conditions. An initial analysis was made for all sites using an 8 meter thick velocity gradient for the rock input model. Sensitivity of the models to uncertainty of the weathered zone thickness was assessed by randomizing the thickness of the velocity gradient. The effect of the velocity gradient representing the weathered rock zone increases site response at high frequencies.
Both models (B-C outcrop conditions and rock outcrop conditions) are compared with the International Building Code (IBC 2000) maximum credible earthquake spectra. The results for both models exceed the IBC 2000 spectra at some frequencies, between 3 and 10 Hz at all four sites. However, site 2, which classifies as a C site and is therefore assumed to be the most competent of the four sites according to IBC 2000 design procedures, has the highest calculated spectral acceleration of the four sites analyzed. Site 2 has the highest response because a low velocity zone exists at the bottom of the geotechnical profile in immediate contact with the higher velocity rock material, producing a very large impedance contrast. An important shortcoming of the IBC 2000 building code results from the fact that it does not account for cases in which there is a strong rock-soil velocity contrast at depth less than 30 meters. It is suggested that other site-specific parameters, specifically, depth to bedrock and near-surface impedance ratio, should be included in the IBC design procedures.
Master of Science
Virginia Tech
lesterrevised_mcc.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Earthquake Hazard Analysis
Strong Motion
Site Response
Columbia
South Carolina
IBC 2000
An Examination of Site Response in Columbia, South Carolina: Sensitivity of Site Response to "Rock" Input Motion and the Utility of Vs(30)
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Geosciencesopen.accessoai:vtechworks.lib.vt.edu:10919/1148462023-04-29T07:27:29Zcom_10919_5534col_10919_11041
Wong, Steven
Mechanical Engineering
Lattimer, Brian Y.
Diller, Thomas E.
Qiao, Rui
Huxtable, Scott T.
Case, Scott W.
2023-04-28T08:00:22Z
2023-04-28T08:00:22Z
2023-04-27
vt_gsexam:36795
http://hdl.handle.net/10919/114846
Wildfires pose a growing threat for communities along the wildland-urban interface (WUI) around the world driven by a changing climate and expanding urban areas. One of the primary mechanisms by which fires can spread in the WUI are firebrands, airborne embers capable of acting as ignition sources carried in the airstream. Many studies have been conducted on the generation and transport of firebrands, but limited work has been conducted to quantify the heat transfer of firebrand piles to surfaces. A series of three studies are presented here exploring the heat transfer, burning, and material ignition of firebrands. In the first study, the differences between firebrands from structure and vegetation sources was compared. It was found that an ash layer in the vegetation firebrands reduced the heat and mass transfer. In the second study, impact of the surface geometries that firebrands accumulate on was explored. It was found that wall and corner configurations reduced the heat transfer the most and caused piles to burn from the wall surfaces outwards. Flat plate and decking configurations had the highest heat flux due to the lack of flow obstruction. In the final study, a framework was developed for predicting the material ignition resistance reliability exposed to a smoldering firebrand pile. The exposure was based on empirical relations for the heat flux from piles as a function of pile height, porosity, and wind speed. Cone calorimeter data was used to generate material thermal and ignition properties. With these inputs, the framework was used to predict the potential for material ignition thus circumventing the need for costly firebrand tests. This collection of studies provides evidence of the factors that drive firebrand burning behavior and heat transfer and links those aspects to the potential for ignition of construction materials.
Doctor of Philosophy
Wildland-urban interface (WUI) fires pose a growing threat for communities around the world driven by a changing climate and expanding urban areas. A particularly dangerous way that fires can spread long distances is via firebrands, burning particles that splinter off of trees or buildings that can be blown long distances by the wind. These firebrands can land onto surfaces like buildings and ignite those surfaces, causing new fires called spot fires. The science behind how firebrands ignite new surfaces is not well-developed, and there is no broad tool that can be used to predict whether a material or a building will ignite given certain conditions. The research presented here aims to address that lack of understanding by approaching the problem systematically, breaking down the individual driving elements of firebrand burning. First, the difference in heat transfer and burning behavior between firebrands from structures and from vegetation was explored. Second, the impact of various surface geometries was explored. The surface geometry of where the firebrands accumulate also influences the heat transfer of the firebrands. Finally, a framework for predicting the material reliability of materials to firebrand exposure is presented. Experimental correlations for firebrand burning based on pile parameters were generated and used to predict the heat fluxes from piles. The framework used material ignition data from cone calorimeter experiments to predict how materials would respond under thermal exposure. The framework compares the predicted exposure with the material ignition data to calculate the reliability. This collection of studies provides insight on the many factors that drive firebrand burning behavior and heat transfer and links those aspects to the ignition of materials.
ETD
en
Virginia Tech
Creative Commons Attribution 4.0 International
http://creativecommons.org/licenses/by/4.0/
firebrands
wildland-urban interface
wildfires
heat transfer
Quantifying Burning, Heat Transfer, and Material Ignition of Smoldering Firebrand Piles
Dissertation
Doctor of Philosophy
doctoral
Virginia Polytechnic Institute and State University
Mechanical Engineeringembargooai:vtechworks.lib.vt.edu:10919/896262020-09-28T14:01:06Zcom_10919_5534col_10919_11041
Alfaydi, Ahmed S.
Counselor Education
Alexander, Michael D.
Gratto, John R.
Salmon, Richard G.
Earthman, Glen I.
2019-05-29T06:00:28Z
2019-05-29T06:00:28Z
2017-12-04
vt_gsexam:13303
http://hdl.handle.net/10919/89626
Servant leadership is one of the most important forms of leadership and some authors and experts even consider servant leaders to be among the best leaders. The purpose of this quantitative research study is to examine the relation between teachers’ perceptions of their principals’ servant leadership style and teacher job satisfaction. The target population of the study was teachers in the Al-Salama 2 district in Jeddah, Saudi Arabia. There are eight public schools in this district; all are similar with respect to the school buildings, curricula, number of teachers and students, and their socioeconomic status. Two separate survey instruments were used for this study: Liden et al.’s (2008) Servant Leadership Questionnaire (SLQ), which is a validated survey instrument that identifies seven dimensions of servant leadership characteristics. Mohrman et al.’s (1977) Mohrman–Cooke–Mohrman job satisfaction survey (MCMJSS) also was administered to measure the teachers’ job satisfaction. The data was formatted using Qualtrics survey software and all data were analyzed in SPSS v. 24. The results from the data analysis indicated that teachers do perceive their school leaders’ behavior reflects servant leadership characteristics and also showed a significant positive correlation between teachers’ perceptions of their principals’ servant leadership and their job satisfaction. The findings of this study indicate that the positive correlation between servant leadership and job satisfaction exists in Saudi Arabia. This field of research can continue to examine if this relationship exists as an embedded part of specific cultures or if it is inherently true that those who lead through service contribute to a greater sense of job satisfaction despite any differences in job category, pay scales, or cultural differences. Moreover, the results were consistent with the theoretical framework with respect to servant leadership theory and job satisfaction, and with the results of previous research.
Ph. D.
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
servant leadership
job satisfaction
teachers
The Effect of Servant Leadership Style on Teachers' Job Satisfaction
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Educational Leadership and Policy Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/519472022-02-22T22:01:48Zcom_10919_5534col_10919_9291
Venkatapathi, Sarankumar
Mechanical Engineering
Hin, Celine
Huxtable, Scott T.
von Spakovsky, Michael R.
2015-04-30T06:00:29Z
2015-04-30T06:00:29Z
2013-08-14
vt_gsexam:1300
http://hdl.handle.net/10919/51947
This study seeks to evaluate the temperature effects on the electronic properties of thermoelectric materials, using first principles Density Functional Theory (DFT) calculations by incorporating the temperature effects on structural properties of the material. Using the electronic properties attained, the charge carrier scattering relaxation times were determined. The effect of interface between PbTe and SrTe on the charge carrier mobility was studied by finding out the relative alignment of energy bands at the semiconductor heterojunction. The crystal shape of the SrTe precipitates in the PbTe host matrix was evaluated from the interface energies using the Wulffman construction. We also attempted to develop a relation between the interface energies and electronic band alignment for different interface orientations.
In this research, we incorporated the temperature effects on the structural properties of PbTe to get the temperature dependence of electronic properties like energy bandgap and effective masses of charge carriers. We used the values of bandgap and effective masses to determine the charge carrier scattering relaxation time at different temperatures which is used in evaluating the transport properties of thermoelectric materials like the Seebeck coefficient and electrical conductivity.
Master of Science
ETD
Virginia Tech
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
First-principles calculations
charge carrier effective mass
scattering relaxation time
semiconductor band alignment
Temperature effects on the electronic properties of lead telluride (PbTe) and the influence of nano-size precipitates on the performance of thermoelectric materials. (SrTe precipitates in PbTe bulk material)
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Mechanical Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/330892022-02-03T19:04:55Zcom_10919_5534col_10919_9291
Chansiri, Noppamas
Landscape Architecture
Jacobson, Wendy R.
Wang, Joseph C.
Miller, Patrick A.
2014-03-14T20:38:00Z
2014-03-14T20:38:00Z
1999-05-06
1999-05-21
2000-05-27
1999-05-27
etd-052199-125950
http://hdl.handle.net/10919/33089
http://scholar.lib.vt.edu/theses/available/etd-052199-125950/
This thesis proposes guidelines for reestablishing the historic canal system on Rattanakosin Island, Bangkok as a public space system and a connector of key public spaces. The study examines the historic value and cultural symbolism of the canals through evolutionary morphological analysis, establishing that the canals are primary structural elements in the city, since they have retained the integrity of their physical form over time, and have come to hold cultural meaning for the Thai people. The canals have also accommodated different functions over time, in response to a changing urban context. There is potential for them to accept new functions as recreational spaces, connectors of key public spaces, and as tourist destinations.
Typological analysis of structural characteristics of the canals yields seven canal types that have potential to accommodate public space functions. The study proposes guidelines for the seven canal types that will enhance these potentials and ensure the preservation of the canals' physical form.
Master of Landscape Architecture
Virginia Tech
thesis_body.pdf
thesis_abstract.pdf
thesis_front.pdf
thesis_title.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Canal
Preservation
Morphology
Public Space Typology
The Historic Canal System in Bangkok, Thailand: Guidelines for Reestablishing Public Space Functions
Thesis
Master of Landscape Architecture
masters
Virginia Polytechnic Institute and State University
Landscape Architectureopen.accessoai:vtechworks.lib.vt.edu:10919/358812023-02-09T01:28:39Zcom_10919_5534col_10919_9291
Lu, Qiang
Electrical and Computer Engineering
Conners, Richard W.
Brown, Ezra A.
Kline, D. Earl
Abbott, A. Lynn
2014-03-14T20:48:37Z
2014-03-14T20:48:37Z
1994-10-10
1994-10-10
1998-02-19
1998-02-19
etd-11798-223049
http://hdl.handle.net/10919/35881
http://scholar.lib.vt.edu/theses/available/etd-11798-223049/
This thesis describes the development of a software system for color sorting hardwood edge-glued panel parts. Conceptually, this system can be broken down into three separate processing steps. The first step is to segment color images of each of the two part faces into background and part. The second step involves extracting color information from each region labeled part and using this information to classify each part face as one of a pre-selected number of color classes plus an out class. The third step involves using the two face labels and some distance information to determine which part face is the better to use in the face of an edge-glued panel. Since a part face is illuminated while the background is not, the segmentation into background and part can be done using very simple computational methods. The color classification component of this system is based on the Trichromatic Color Theory. It uses an estimate of a part's 3-dimension (3-D) color probability function, P, to characterize the surface color of the part. Each color class is also represented by an estimate of the 3-D color probability function that describes the permissible distribution of colors within this color class. Let P_omega_i denote the estimated probability function for color class omega_i. Classification is accomplished by finding the color difference between the estimated color probability function for the part and each of the estimated 3-D color probability functions that represent the color classes. The distance function used is the sum of the absolute values of the differences between the elements of the estimated probability function for a class and the estimated probability function of the part. The sample is given the label of the color class to which it is closest if this distance is less than some class specific threshold for that class. If the distance to the class to which the part is closest is larger than the threshold for that class, the part is called an out. This supervised classification procedure first requires one to select training samples from each of the color classes to be considered. These training samples are used to generate P_omega_i for each color class omega_i and to establish the value of the threshold T_i that is used to determine when a part is an out. To aid in determining which part face is better to use in making a panel, the system allows one to prioritize the various color classes so that one or more color classes can have the same priority. Using these priorities, labels for each of the part faces, and the distance from each of the part faces' estimated probability functions to the estimated probability function of the class to which each face was assigned, the decision logic selects which is the ``better'' face. If the two part faces are assigned to color classes that have different priorities, the part face assigned to the color class with higher priority is chosen as the better face. If the two part faces have been assigned to the same color class or to two different classes having the same priority, the part face that is closest to the estimated probability function of the color class to which it has been assigned is chosen to be the better face. Finally, if both faces are labeled out, the part becomes an out part. This software system has been implemented on a prototype machine vision system that has undergone several months of in-plant testing. To date the system has only been tested on one type of material, southern red oak, with which it has proven itself capable of significantly out performing humans in creating high-quality edge-glued panels. Since southern red oak has significantly more color variation than any other hardwood type or species, it is believed that this system will work very well on any hardwood material.
Master of Science
Virginia Tech
ETD.PDF
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
Color Sorting
Image Processing
Vision System
A Real-Time System for Color Sorting Edge-Glued Panel Parts
Thesis
Master of Science
masters
Virginia Polytechnic Institute and State University
Electrical and Computer Engineeringopen.accessoai:vtechworks.lib.vt.edu:10919/284912020-09-25T20:48:52Zcom_10919_5534col_10919_11041
Brown, Patricia Leigh
Educational Leadership and Policy Studies
Twiford, Travis W.
Schreck, John F.
Marks, Deborah
Niles, Jerome A.
Salmon, Richard G.
2014-03-14T20:14:39Z
2014-03-14T20:14:39Z
2007-07-24
2007-08-02
2010-10-07
2007-09-14
etd-08022007-093023
http://hdl.handle.net/10919/28491
http://scholar.lib.vt.edu/theses/available/etd-08022007-093023/
Service Learning is an instructional approach that has been gaining national attention in the past several years. The concept was supported by John Dewey as early as 1915 but not given serious attention by educational leaders until about 30 years ago. Currently, a growing number of schools across the country are incorporating community service activities into the curriculum. In this study, seven individuals who were enrolled in such a course while in high school were interviewed. The purpose of this phenomenological study was to describe the perceptions and experiences of these former high school students while enrolled in a service learning course coupled with the passage of time to reflect upon the experience. The major research questions were: 1. Does service learning foster in students the perception of a more empathetic nature in their understanding of the recipients of the service work? 2. Are the perceptions of the students as to their desire to perform volunteer work in the future affected by service learning experiences? 3. How do students perceive the usefulness of the service learning curriculum as to linking classroom work with the volunteer experience? Service learning was defined generally as a structured elective course that combines classroom instruction with volunteer service in the community. A qualitative design was chosen for the research as this method allowed for a more in depth description of the main focus of the study--the perceptions of these former students. The findings from this study support the inclusion of service learning courses in high schools; however, there was an overall consensus from the seven participants that work must be done by educators in order to provide more structured and viable curriculums for these courses. The participant responses were generally favorable regarding their actual volunteer experiences, supporting the assertion that volunteer work supported by a well designed service learning course increases a student's ability to feel empathy for others along with the desire to be a lifelong volunteer.
Ed. D.
Virginia Tech
Dissertation.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
service learning
community service
Perceptions of Individual Experiences in a Service Learning Course
Dissertation
Doctor of Education
doctoral
Virginia Polytechnic Institute and State University
Educational Leadership and Policy Studiesopen.accessoai:vtechworks.lib.vt.edu:10919/420832022-03-15T14:13:27Zcom_10919_5534col_10919_9291
Hilton-Jones, David
Biology
Cairns, John Jr.
Atkinson, Robert B.
Paterson, Robert A.
Smith, Eric P.
2014-03-14T21:33:45Z
2014-03-14T21:33:45Z
1994-04-15
2009-04-14
2009-04-14
2009-04-14
etd-04142009-040641
http://hdl.handle.net/10919/42083
http://scholar.lib.vt.edu/theses/available/etd-04142009-040641/
Wetland acreage in Southwest Virginia has increased because of formation of wetlands on relic surface mine benches. Prior to the Surface Mining Control and Reclamation Act of 1977 (PL 95-87) once mining operations were completed the sites were abandoned. These areas presented novel landscapes in the rugged Allegheny Plateau physiographic region. Specifically, flat, compacted areas were created. In microdepression of these sites wetlands have formed. This study investigates the macroinvertebrate community associated wetlands of relic surface mining operations. Surveys were conducted to identify what macroinvertebrates utilize these wetlands, to determine how this community was influenced by the physio-chemical characteristics of surface mine wetlands, and to develop design specifications for creating wetlands for current restoration efforts. Nine wetlands were sampled four times between July 1993 and May 1994. Seventy genera of macroinvertebrates were identified. The wetlands represented a range of physical and chemical parameters. The taxa richness appears to be related to these differences. Canonical Correspondence Analysis suggests that for the nine wetlands, the macro invertebrate taxa distribution is best explained by physical features of depth and duration of flooding, chemical parameters of iron, manganese, and sulfate concentration, and a biotic measure of plant litter biomass.
The findings of this study can be applied to ecological restoration. Wetland creation can be incorporated into current surface mine reclamation projects. To maximize the macro invertebrate community of reclamation wetlands, sites must be positioned to avoid water quality problems, excavated to have a deeper portion which will remain inundated during all or most of the year, and have a gradually sloping substrate from the deepest area to the land surface. The final criteria being indirectly related to the macroinvertebrate community by influencing the macrophyte production, richness, and litter.
Master of Science
vii, 56 leaves
BTD
application/pdf
en
Virginia Tech
OCLC# 34087231
LD5655.V855_1994.J664.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
wetlands
LD5655.V855 1994.J664
Macroinvertebrate communities inhabiting surface mine wetlands of southwestern Virginia
Thesis
Text
Master of Science
masters
Virginia Polytechnic Institute and State University
Biologyopen.accessoai:vtechworks.lib.vt.edu:10919/306962022-02-22T19:58:12Zcom_10919_5534col_10919_11041
Lee, Hyesuk Kwon
Mathematics
Gunzburger, Max D.
Cliff, Eugene M.
Heinkenschloss, Matthias
Herdman, Terry L.
2014-03-14T20:22:30Z
2014-03-14T20:22:30Z
1997-06-27
1997-06-27
1997-08-05
1997-08-05
etd-7497-163154
http://hdl.handle.net/10919/30696
http://scholar.lib.vt.edu/theses/available/etd-7497-163154/
Optimization based domain decomposition methods for the solution of partial differential equations are considered. The crux of the method is a constrained minimization problem for which the objective functional measures the jump in the dependent variables across the common boundaries between subdomains; the constraints are the partial differential equations.
First, we consider a linear constraint. The existence of optimal solutions for the optimization problem is shown as is its convergence to the exact solution of the given problem. We then derive an optimality system of partial differential equations from which solutions of the domain decomposition problem may be determined. Finite element approximations to solutions of the optimality system are defined and analyzed as is an eminently parallelizable gradient method for solving the optimality system. The linear constraint minimization problem is also recast as a linear least squares problem and is solved by a conjugate gradient method.
The domain decomposition method can be extended to nonlinear problems such as the Navier-Stokes equations. This results from the fact that the objective functional for the minimization problem involves the jump in dependent variables across the interfaces between subdomains. Thus, the method does not require that the partial differential equations themselves be derivable through an extremal problem.
An optimality system is derived by applying a Lagrange multiplier rule to a constrained optimization problem. Error estimates for finite element approximations are presented as is a gradient method to solve the optimality system. We also use a Gauss-Newton method to solve the minimization problem with the nonlinear constraint.
Ph. D.
Virginia Tech
kwon.pdf
In Copyright
http://rightsstatements.org/vocab/InC/1.0/
domain decomposition
least squares problem
finite element methods
Optimization Based Domain Decomposition Methods for Linear and Nonlinear Problems
Dissertation
Ph. D.
doctoral
Virginia Polytechnic Institute and State University
Mathematicsopen.accessdim///com_10919_5534/100