2024-03-28T15:19:19Zhttps://vtechworks.lib.vt.edu/server/oai/requestoai:vtechworks.lib.vt.edu:10919/112362022-02-22T18:55:24Zcom_10919_5534col_10919_11041
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Liu, Sixin
author
2000-05-02
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.
etd-121999-232244
http://hdl.handle.net/10919/11236
http://scholar.lib.vt.edu/theses/available/etd-121999-232244
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
oai:vtechworks.lib.vt.edu:10919/1080872022-02-03T08:31:26Zcom_10919_5534col_10919_11041
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Taheri Hosseinabadi, Sayedsina
author
2022-02-01
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.
vt_gsexam:33664
http://hdl.handle.net/10919/108087
Topology Identification
Strategic Inestment
Probabalistic Hosting Capacity Analysis
Aggregate Flexibility
Fast and Scalable Power System Learning, Analysis, and Planning
oai:vtechworks.lib.vt.edu:10919/403912022-02-22T19:58:14Zcom_10919_5534col_10919_11041
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Gunn, Reamous Jr.
author
1999-09-14
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.
etd-120399-131826
http://hdl.handle.net/10919/40391
http://scholar.lib.vt.edu/theses/available/etd-120399-131826/
Discipline Referrals
Secondary Schools
Conflict Resolution
The Effects of Conflict Resolution Training on Students with Previous Discipline Referrals
oai:vtechworks.lib.vt.edu:10919/499182023-11-28T04:59:09Zcom_10919_5534col_10919_11041
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Arenburg, Robert Thomas
author
1988
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.
http://hdl.handle.net/10919/49918
Analysis of metal matrix composite structures using a micromechanical constitutive theory
oai:vtechworks.lib.vt.edu:10919/535202023-11-28T04:59:07Zcom_10919_5534col_10919_11041
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Gramoll, Kurt C.
author
1988
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.
http://hdl.handle.net/10919/53520
Thermoviscoelastic characterization and predictions of Kelvar/epoxy composite laminates
oai:vtechworks.lib.vt.edu:10919/390682023-08-13T19:27:16Zcom_10919_5534col_10919_11041
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Zeccolo, Peggy L.
author
1996
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.
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
oai:vtechworks.lib.vt.edu:10919/262112022-02-22T18:55:29Zcom_10919_5534col_10919_11041
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Zhang, Wenyan
author
2007-02-01
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.
etd-02152007-110933
http://hdl.handle.net/10919/26211
http://scholar.lib.vt.edu/theses/available/etd-02152007-110933/
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
oai:vtechworks.lib.vt.edu:10919/307092020-09-28T12:53:56Zcom_10919_5534col_10919_11041
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Read, Frederick R.
author
1997-05-19
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.
etd-81297-152342
http://hdl.handle.net/10919/30709
http://scholar.lib.vt.edu/theses/available/etd-81297-152342/
induction
mentors
mentoring
The Perceived Value of Mentoring by Beginning Usarf Instructors With Formal, Informal and No Mentors
oai:vtechworks.lib.vt.edu:10919/272502023-11-29T02:17:12Zcom_10919_5534com_10919_78363com_10919_5549col_10919_11041col_10919_82827
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Matovic, Dragan
author
2002-04-17
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.
etd-04252002-163659
http://hdl.handle.net/10919/27250
http://scholar.lib.vt.edu/theses/available/etd-04252002-163659/
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
oai:vtechworks.lib.vt.edu:10919/1020342022-06-14T20:51:34Zcom_10919_5534col_10919_11041
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Asgari, Elham
author
2019-08-02
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.
vt_gsexam:21901
http://hdl.handle.net/10919/102034
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
oai:vtechworks.lib.vt.edu:10919/772952022-02-22T20:21:26Zcom_10919_5534col_10919_11041
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Pinto, Ameet John
author
2009-12-07
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.
etd-12212009-094300
http://hdl.handle.net/10919/77295
http://scholar.lib.vt.edu/theses/available/etd-12212009-094300/
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
oai:vtechworks.lib.vt.edu:10919/829202022-02-22T20:21:28Zcom_10919_5534col_10919_11041
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Arca, Hale Cigdem
author
2016-11-01
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.
vt_gsexam:8931
http://hdl.handle.net/10919/82920
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
oai:vtechworks.lib.vt.edu:10919/647362021-04-15T17:10:38Zcom_10919_5534col_10919_11041
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dc
Altizer, Carol Jane
author
1977
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.
http://hdl.handle.net/10919/64736
The role of manipulatives in learning to multiply and factor polynomials
oai:vtechworks.lib.vt.edu:10919/296032020-09-25T20:51:20Zcom_10919_5534col_10919_11041
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Witt, Kathy
author
2011-11-01
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.
etd-11152011-123804
http://hdl.handle.net/10919/29603
http://scholar.lib.vt.edu/theses/available/etd-11152011-123804/
Consolidation and Per Pupil Cost
Consolidation in the Henry County Public School System
oai:vtechworks.lib.vt.edu:10919/282972020-09-25T20:48:38Zcom_10919_5534col_10919_11041
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El-Nainay, Mustafa Y.
author
2009-07-01
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.
etd-07142009-101727
http://hdl.handle.net/10919/28297
http://scholar.lib.vt.edu/theses/available/etd-07142009-101727/
channel allocation
power control
flow routing
cognitive networks
island genetic algorithm
distributed reasoning and learning
dynamic spectrum access
Island Genetic Algorithm-based Cognitive Networks
oai:vtechworks.lib.vt.edu:10919/925882020-10-16T21:18:16Zcom_10919_5534col_10919_11041
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Feng, Xuewen
author
2018-02-06
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.
vt_gsexam:13603
http://hdl.handle.net/10919/92588
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
oai:vtechworks.lib.vt.edu:10919/813842020-09-28T18:24:54Zcom_10919_5534col_10919_11041
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Bonakdar, Mohammad
author
2016-06-29
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.
vt_gsexam:8241
http://hdl.handle.net/10919/81384
Blood-brain barrier
Electroporation
Microfluidics
Drug delivery
Electrical impedance spectroscopy
Microdevices for Investigating Pulsed Electric Fields-Mediated Therapies at Cellular and Tissue Level
oai:vtechworks.lib.vt.edu:10919/733122020-09-28T13:51:14Zcom_10919_5534col_10919_11041
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Zheng, Hanguang
author
2015-04-29
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.
vt_gsexam:5067
http://hdl.handle.net/10919/73312
Die-attachment
nanosilver sintering
copper
processing
characterization
reliability.
Die-Attachment on Copper by Nanosilver Sintering: Processing, Characterization and Reliability
oai:vtechworks.lib.vt.edu:10919/1112562022-07-16T07:12:38Zcom_10919_5534col_10919_11041
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Strozier, Jariah Li'Shey
author
2022-07-14
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.
vt_gsexam:35300
http://hdl.handle.net/10919/111256
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
oai:vtechworks.lib.vt.edu:10919/286842022-02-22T19:39:28Zcom_10919_5534col_10919_11041
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Tan, Roy Patrick
author
2007-08-08
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.
etd-08162007-161911
http://hdl.handle.net/10919/28684
http://scholar.lib.vt.edu/theses/available/etd-08162007-161911/
programming language
software engineering
Sulu
unit testing
software testing
Programming Language and Tools for Automated Testing
oai:vtechworks.lib.vt.edu:10919/385452021-05-25T14:24:53Zcom_10919_5534col_10919_11041
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Kirby, Carl Scott
author
1993-08-05
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.
etd-06072006-124154
http://hdl.handle.net/10919/38545
http://scholar.lib.vt.edu/theses/available/etd-06072006-124154/
A geochemical analysis of municipal solid waste ash
oai:vtechworks.lib.vt.edu:10919/384262021-12-14T21:29:37Zcom_10919_5534col_10919_11041
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Coker, Dianna Ross
author
1993-02-22
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.
etd-06062008-170640
http://hdl.handle.net/10919/38426
http://scholar.lib.vt.edu/theses/available/etd-06062008-170640/
The role of visual-spatial aptitude in accounting coursework
oai:vtechworks.lib.vt.edu:10919/285252022-02-22T19:39:26Zcom_10919_5534col_10919_11041
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Ertel, Richard Brian
author
1999-07-28
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.
etd-080499-141603
http://hdl.handle.net/10919/28525
http://scholar.lib.vt.edu/theses/available/etd-080499-141603/
propagation modeling
antenna arrays
wireless communications
Antenna Array Systems: Propagation and Performance
oai:vtechworks.lib.vt.edu:10919/777792020-09-28T13:27:54Zcom_10919_5534col_10919_11041
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Park, Young Hoon
author
1983
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.
http://hdl.handle.net/10919/77779
An analysis of microbial film fermentor system for production of secondary metabolites
oai:vtechworks.lib.vt.edu:10919/401202023-08-13T19:27:29Zcom_10919_5534col_10919_11041
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Pandya, Ashish
author
1992
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.
etd-10242005-124113
http://hdl.handle.net/10919/40120
http://scholar.lib.vt.edu/theses/available/etd-10242005-124113/
Novel nitrogen containing polymers via Reissert chemistry
oai:vtechworks.lib.vt.edu:10919/1160572024-03-13T09:12:19Zcom_10919_5534col_10919_11041
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Grubb, Christopher Thomas
author
2023-08-16
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.
vt_gsexam:38333
http://hdl.handle.net/10919/116057
Bayesian Statistics
Synthetic Populations
Inference for Populations: Uncertainty Propagation via Bayesian Population Synthesis
oai:vtechworks.lib.vt.edu:10919/747642023-11-28T04:59:14Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Choi, Suk Ho
author
1987
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.
http://hdl.handle.net/10919/74764
Binding mechanism of K88ab pili produced by enterotoxigenic Escherichia coli
oai:vtechworks.lib.vt.edu:10919/517462020-09-28T13:43:48Zcom_10919_5534col_10919_11041
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dc
Akoma, Efua Safiya
author
2014-04-16
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.
vt_gsexam:2372
http://hdl.handle.net/10919/51746
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
oai:vtechworks.lib.vt.edu:10919/291122022-03-29T18:20:24Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Drape, Tiffany A.
author
2011-09-12
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.
etd-09262011-163335
http://hdl.handle.net/10919/29112
http://scholar.lib.vt.edu/theses/available/etd-09262011-163335/
Education
engagement
motivation
integration
Technology
Teaching with Technology in an Agriculture Associate's Degree Program
oai:vtechworks.lib.vt.edu:10919/1165072023-10-20T07:11:23Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Uluer, Mahmud Esad
author
2023-10-18
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).
vt_gsexam:38588
http://hdl.handle.net/10919/116507
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
oai:vtechworks.lib.vt.edu:10919/944172021-12-21T14:49:25Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Trent, Alexis Raven
author
2018-04-16
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.
vt_gsexam:14761
http://hdl.handle.net/10919/94417
Biomimetic interface
medical device
protein surface modification
Fabrication, Characterization and Cellular Interactions of Keratin Nanomaterial Coatings for Implantable Percutaneous Prosthetics
oai:vtechworks.lib.vt.edu:10919/265222020-09-25T20:45:41Zcom_10919_5534col_10919_11041
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dc
Baldwin, Mark W.
author
2008-02-29
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.
etd-03272008-134630
http://hdl.handle.net/10919/26522
http://scholar.lib.vt.edu/theses/available/etd-03272008-134630/
disturbance identification
state-space model
wide-area monitoring
modal analysis
FNET
electromechanics
Modal Analysis Techniques in Wide-Area Frequency Monitoring Systems
oai:vtechworks.lib.vt.edu:10919/1096832023-10-31T19:35:11Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Jahromi Shirazi, Masoud
author
2020-10-22
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.
vt_gsexam:27705
http://hdl.handle.net/10919/109683
Agent-based modeling
Bio-inspired sensing
Flocking
Simultaneous localization and mapping
Sonar
Dynamics of Multi-Agent Systems with Bio-Inspired Active and Passive Sensing
oai:vtechworks.lib.vt.edu:10919/111642022-02-22T18:55:26Zcom_10919_5534col_10919_11041
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Allen, April Diane
author
1999-11-01
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.
etd-04302004-150744
http://hdl.handle.net/10919/11164
http://scholar.lib.vt.edu/theses/available/etd-04302004-150744
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
oai:vtechworks.lib.vt.edu:10919/1097962022-05-05T07:12:10Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Oza, Pratham Rajan
author
2022-05-03
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.
vt_gsexam:34431
http://hdl.handle.net/10919/109796
edge computing
real-time systems
intelligent transportation
smart traffic
Predictable Connected Traffic Infrastructure
oai:vtechworks.lib.vt.edu:10919/1161302023-08-26T07:12:23Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Choi, Jae-Young
author
2023
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.
http://hdl.handle.net/10919/116130
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
oai:vtechworks.lib.vt.edu:10919/403312021-04-26T17:42:19Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Jones, Raymond T.
author
1997-03-20
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.
etd-11102005-141137
http://hdl.handle.net/10919/40331
http://scholar.lib.vt.edu/theses/available/etd-11102005-141137/
technology - electronic
Prediction of educational technology to be found in the public schools of the year 2000: a Delphi study
oai:vtechworks.lib.vt.edu:10919/291862022-03-29T19:22:18Zcom_10919_5534col_10919_11041
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dc
McGinnis, Marvin Harris
author
2002-09-20
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.
etd-10042002-103859
http://hdl.handle.net/10919/29186
http://scholar.lib.vt.edu/theses/available/etd-10042002-103859/
African American Males
Academic achievement
high-stakes tests
Challenges Of Studying Attributes Associated With African American Males Who Are Not Successful With Testing Measures
oai:vtechworks.lib.vt.edu:10919/305162022-02-22T19:58:12Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Phillips, Dennis Ivan
author
1998-04-09
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.
etd-4198-14140
http://hdl.handle.net/10919/30516
http://scholar.lib.vt.edu/theses/available/etd-4198-14140/
Coal processing
coarse coal flotation
fine coal
column flotation
Optimum Processing of 1 mm by Zero Coal
oai:vtechworks.lib.vt.edu:10919/397282021-11-18T18:19:35Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Duncan, Harriet H.
author
1993-03-30
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.
etd-10102005-131611
http://hdl.handle.net/10919/39728
http://scholar.lib.vt.edu/theses/available/etd-10102005-131611/
Meanings and motivations among older adult mall walkers: a qualitative analysis
oai:vtechworks.lib.vt.edu:10919/810042021-04-15T17:10:36Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Bentley, Donald Wade
author
1976
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.
http://hdl.handle.net/10919/81004
A study of variables related to turnover of superintendents in selected North Carolina school systems
oai:vtechworks.lib.vt.edu:10919/876552021-04-15T17:10:37Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Renieri, Michael P.
author
1976
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.
http://hdl.handle.net/10919/87655
Rate and time dependent behavior of structural adhesives
oai:vtechworks.lib.vt.edu:10919/371982022-01-05T18:24:08Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Ruark, Edwin Warren
author
1970
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.
etd-01132010-020032
http://hdl.handle.net/10919/37198
http://scholar.lib.vt.edu/theses/available/etd-01132010-020032/
The response of rat thymus nuclei to thyroid hormones
oai:vtechworks.lib.vt.edu:10919/271182020-09-25T20:38:56Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Sexton, Mildred B.
author
2003-04-17
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.
etd-04222003-114716
http://hdl.handle.net/10919/27118
http://scholar.lib.vt.edu/theses/available/etd-04222003-114716/
Attendance
Year-Round
Behavior
Achievement
A Case Study Of The Effect Of Year Round Education On Attendance, Academic Performance, And Behavior Patterns
oai:vtechworks.lib.vt.edu:10919/1148462023-04-29T07:27:29Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Wong, Steven
author
2023-04-27
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.
vt_gsexam:36795
http://hdl.handle.net/10919/114846
firebrands
wildland-urban interface
wildfires
heat transfer
Quantifying Burning, Heat Transfer, and Material Ignition of Smoldering Firebrand Piles
oai:vtechworks.lib.vt.edu:10919/896262020-09-28T14:01:06Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Alfaydi, Ahmed S.
author
2017-12-04
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.
vt_gsexam:13303
http://hdl.handle.net/10919/89626
servant leadership
job satisfaction
teachers
The Effect of Servant Leadership Style on Teachers' Job Satisfaction
oai:vtechworks.lib.vt.edu:10919/284912020-09-25T20:48:52Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Brown, Patricia Leigh
author
2007-07-24
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.
etd-08022007-093023
http://hdl.handle.net/10919/28491
http://scholar.lib.vt.edu/theses/available/etd-08022007-093023/
service learning
community service
Perceptions of Individual Experiences in a Service Learning Course
oai:vtechworks.lib.vt.edu:10919/306962022-02-22T19:58:12Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Lee, Hyesuk Kwon
author
1997-06-27
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.
etd-7497-163154
http://hdl.handle.net/10919/30696
http://scholar.lib.vt.edu/theses/available/etd-7497-163154/
domain decomposition
least squares problem
finite element methods
Optimization Based Domain Decomposition Methods for Linear and Nonlinear Problems
oai:vtechworks.lib.vt.edu:10919/998992021-11-02T13:31:29Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Kinoshita, Timothy Jon
author
2020-09-03
Although originally conceived as an educational intervention for at-risk students, modern career academies have expanded their scope to programs designed to promote critical thinking, problem solving, and analytical skills to be successful in an advanced career path. Through the integration of career and technical education courses and a rigorous, college preparatory academic curriculum, career academies serve as a key piece of a larger strategy for developing a well- prepared STEM workforce. This study focuses on the Virginia Governor's STEM Academies, a state-wide initiative containing programs designed to expand options for the general student population to acquire STEM literacy and other critical skills, knowledge and credentials that will prepare them for high-demand, high-wage, and high-skill careers. Currently, 22 Academies exist serving students across 36 Virginia School Divisions.
Using educational administrative data housed within the Virginia Longitudinal Data System, I examined the Virginia Governor's STEM Academies regarding characteristics of student participation and the relationship between Academy participation and high school and postsecondary outcomes. Using multi-level regression modeling, I found that male students, Asian and Hispanic students, and non-economically disadvantage students have a higher rate of Academy participation. After matching students with propensity score matching on demographic and early academic characteristics, I find that Academy participants are more likely to take Algebra II at an earlier grade, enroll in more Career and Technical Education and dual enrollment courses, and declare a STEM major after enrolling at a postsecondary institution.
This research provides a valuable new contribution to the study of career academies after such educational programs have undergone a paradigm shift to preparing students for high-demand, high-wage, and high-skill careers. By incorporating propensity score matching and multi-level regression model, I employ a statistically rigorous approach that can serve as important benchmarking of the enrollment and academic outcomes of the Virginia Governor's STEM Academies.
vt_gsexam:27255
http://hdl.handle.net/10919/99899
Career Academy
Career
STEM Education
Education Policy
Propensity Score Matching
An Exploration of the Enrollment and Outcomes of the Virginia Governor's STEM Academies
oai:vtechworks.lib.vt.edu:10919/395882022-03-29T17:38:07Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
McCoy, Howard Eugene
author
1999
This study examined the demographic characteristics and education-related experiences of adults age 50 and beyond enrolled in graduate degree programs on the academic campus of Virginia Commonwealth University. The major focus for this study was to identify and examine the experiences of adults age 50 and older enrolled in graduate degree programs.
The population for the study included 113 adults age 50 and older who were enrolled in graduate degree programs on the academic campus of Virginia Commonwealth University between fall 1995 and fall 1996. Surveys were mailed to these potential participants with a total of96 individuals responding. A focus group interview was also conducted in the fall semester of 1996 to gain further insight regarding their experiences; the respondents were eager to share their responses during this session.
The findings in this study revealed that older adults in graduate degree programs at Virginia Commonwealth University were between the ages of 50 to 62, were more often married than not, had no children under the age of eighteen in the household, and most completed their last degree in 1979. The results of the survey revealed that most of the adults did not have negative feelings about their experiences. Overall, these students felt very positive about their educational-related experiences. There were, however, several administrative concerns associated with the selected demographics of gender, occupation, income, marital status, age and major field of study, and .the education-related experiences of these adults. While most respondents agreed that it was very difficult to maintain their family, work and personal life while earning this degree, they were overall satisfied with their experiences and felt challenged even though their socializing time was significantly reduced. The respondents were not as satisfied with the administration and staff because they were not available for support after work hours when they had concerns that needed addressing. They also felt their classrooms were not adequately prepared to accommodate the older learners, especially in regard to having appropriate visual equipment and adequately designed desks for older students.
The data obtained will be useful to Virginia Commonwealth University in making decisions relative to improving existing services, developing innovative programs, designing policies and procedures that will improve recruitment, retention, and completion of adults age 50 and beyond in graduate programs. Further study is needed from this population of students to ascertain whether there are additional experiences that should be examined and explored. A replication of the study may reveal additional information not addressed in this study.
etd-10032007-172214
http://hdl.handle.net/10919/39588
http://scholar.lib.vt.edu/theses/available/etd-10032007-172214/
graduate programs
Education, Higher
adult students 50 and beyond
Education related experiences of adults age 50 and beyond enrolled in graduate degree programs at Virginia Commonwealth University
oai:vtechworks.lib.vt.edu:10919/997132021-10-07T18:54:55Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Li, Yifu
author
2020-08-13
A smart manufacturing network connects machines via sensing, communication, and actuation networks. The data generated from the networks are used in data-driven modeling and decision-making to improve quality, productivity, and flexibility while reducing the cost. This dissertation focuses on improving the data-driven modeling of the quality-process relationship in smart manufacturing networks. The quality-process variable relationships are important to understand for guiding the quality improvement by optimizing the process variables. However, several challenges emerge. First, the big data sets generated from the manufacturing network may be information-poor for modeling, which may lead to high data transmission and computational loads and redundant data storage. Second, the data generated from connected machines often contain inexplicit similarities due to similar product designs and manufacturing processes. Modeling such inexplicit similarities remains challenging. Third, it is unclear how to select representative data sets for modeling in a manufacturing network setting, considering inexplicit similarities. In this dissertation, a data filtering method is proposed to select a relatively small and informative data subset. Multi-task learning is combined with latent variable decomposition to model multiple connected manufacturing processes that are similar-but-non-identical. A data filtering and modeling framework is also proposed to filter the manufacturing data for manufacturing network modeling adaptively. The proposed methodologies have been validated through simulation and the applications to real manufacturing case studies.
vt_gsexam:27061
http://hdl.handle.net/10919/99713
Data Filtering
Distributed Filtering and Modeling
Multi-task Learning
Data Filtering and Modeling for Smart Manufacturing Network
oai:vtechworks.lib.vt.edu:10919/281532022-03-01T19:11:01Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Allport, Christopher Douglas
author
2005-06-23
The purpose of this dissertation was to analyze the susceptibility of capital budgeting decisions to bias. Based on the political nature of many of these decisions, attribute framing effects were analyzed in a capital budgeting decision context. Specifically, two independent variables were analyzed: accounting data and attribute frames. This research proposed that attribute framing effects would be conditional on the nature of the accounting data being considered. When the accounting data elicited a positive or negative evaluative reaction, attribute frames were expected to be unobtrusive to capital budgeting decisions. However, when the accounting data was neutral, eliciting an ambiguous evaluative reaction, attribute frames were predicted to bias these decisions. An experiment was conducted that considered the issue across two types of capital budgeting decisions: accept/reject decisions (dichotomous decision) and strategic alliance judgments (monetary allocations). Experimental findings strongly support the predicted relationships. These results suggest that persuasive descriptions are not effective in capital budgeting contexts when accounting data provides a clear picture as to the investment's future success; however, these tactics may be vitally important when accounting information is unclear about the investment's future success.
etd-06292005-165247
http://hdl.handle.net/10919/28153
http://scholar.lib.vt.edu/theses/available/etd-06292005-165247/
Capital Budgeting
Information Ambiguity
Evaluative Reactions
Attribute Framing
The Influence of Evaluative Reactions to Attribute Frames and Accounting Data on Capital Budgeting Decisions
oai:vtechworks.lib.vt.edu:10919/403962020-09-25T20:53:41Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Long, Xiaojing
author
2010-12-03
Alzheimer's disease~(AD) is the most frequent neurodegenerative dementia and a growing health problem. Early and accurate diagnosis and prediction of AD is crucial because treatment may be most efficacious if introduced as early as possible. Neuropsychological testing, which is clinically used, sometimes fails to recognize probable dementia, especially to recognize the disease at an early time point such as the mild cognitive impairment~(MCI), which is the prodromal stage of AD.
Recently, there has been a realization that magnetic resonance imaging~(MRI) may help diagnoses of AD and MCI. In this dissertation, we introduce an MRI-analysis based algorithm to help diagnose the illness before irreversible neuronal loss has set in, and to help detect brain changes between MCI patients who may convert and may not convert to AD. Given a set of brain MR images, the algorithm first calculates the distance between each pair of images via a registration process. Then images are projected from a high dimensional Euclidean space to a low dimensional Euclidean subspace based on the calculated distances, with a dimension reduction method. Finally classical supervised classification approaches are employed to assign images to appropriate groups in the low dimensional space. The classification accuracy rates we obtained in our experiments are higher than, or at least comparable to, those reported in recently published papers.
Moreover, this algorithm can be extended to explore the pathology distribution of AD. Exploring the distribution of AD pathology is of great importance to reveal AD related regional atrophy at specific stages of the disease and provide insight into longitudinal sequence of disease progression. Calculating distances between different brain structures produces different classification accuracy. Those structures yielding higher classification accuracy are considered as pathological regions. Our experimental results on pathology localization are also compared with the reproduced results using other existing popular algorithms; the observations are consistent.
etd-12072010-174256
http://hdl.handle.net/10919/40396
http://scholar.lib.vt.edu/theses/available/etd-12072010-174256/
pathology localization
disease diagnosis
MRI
mild cognitive impairment
Alzheimer's disease
Image Classification using Pair-wise Registration and Machine Learning with Applications to Neuroimaging
oai:vtechworks.lib.vt.edu:10919/1007472022-06-14T20:51:31Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Strayer, Thomas Edward III
author
2019-05-09
A translational gap exists between the development of an evidence-based health promotion intervention and its eventual implementation in the intended setting. This lack of translation impacts the uptake of health promotion interventions within delivery systems such as the Cooperative Extension Service (Extension). Within this system, Extension educators serve as the intermediaries addressing needs in the communities in which they are employed with support from Extension health specialists. Previous research has shown that educators utilize other peer educators and specialists to learn and adopt health promotion programming, but these studies are over two decades old (e.g., missing technological advances such as Internet and social media) and often focused on a single state Extension system.
The purpose of this research was to understand how evidence-based health promotion intervention information is shared within Cooperative Extension by 1) identifying information sources and channels of Extension specialists and educators while 2) identifying the characteristics of an intervention that aid in the adoption and uptake of these health promotion interventions. The first mixed-methods study aimed to identify information sources and channels used by Extension educators from a national sample and learn their preferences for information delivery. Results of this study (Manuscript 1), identified specialists as the key information source Therefore, the second study (Manuscript 2) focused on Extension health specialists' preferences for information sources and channels while also 1) determine how specialists communicate with educators 2) preliminary thoughts on a dissemination intervention. The final study (Manuscript 3) explored the intervention characteristics that are both educator and specialists deemed most important to their adoption decision-making process.
The results of this dissertation inform the development of a dissemination intervention to bridge the translational gap across Extension. The information sources and channels used and trusted by both Extension educators and specialists are highlighted in this work. Additionally, specialists have given insight for consideration for an online repository that can be used on demand to both facilitate the adoption and uptake of health promotion interventions as needed by Extension Educators.
vt_gsexam:19465
http://hdl.handle.net/10919/100747
Science-to-service gap
knowledge transfer
Cooperative Extension
preventive care
mixed-methods
health promotion
public health
Dissemination of Health Promotion Information in Cooperative Extension: A multi-study exploration of channels, sources, and characteristics that influence intervention uptake
oai:vtechworks.lib.vt.edu:10919/286672022-02-22T19:39:28Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Rainer, Paula L.
author
2012-08-06
The purpose of this study was to examine the characteristics of students with disabilities who contact the school counselor for college information. Self-determination was the theoretical framework guiding this study. Self-determination refers to a student's ability to (a) act autonomously, (b) identify goals, (c) engage in problem solving activities, (d) appraise strengths and limitations, and (e) capitalize on opportunities. The current study used the Education Longitudinal Study (ELS:2002), a nationally representative database that tracks high school students as they transition from high school to postsecondary options.
The dependent variable was whether the student went to the school counselor for college information. The independent variables included student characteristics (i.e., sex, race and ethnicity, socioeconomic status, disability type, self-determination) and school characteristics (i.e., school enrollment, number of school counselors). This study has conveyed significant information about the relationship between students with disabilities and professional school counselors.
The results of this study provided a wealth of information about students with disabilities who contacted the school counselor for college information. This results marks the first time research addressed the characteristics of students with disabilities who visited the school counselor for college information by utilizing the Educational Longitudinal Study (ELS:2002). The recommendations to school counselors as a result of this research are to develop comprehensive school counseling programs that embody the characteristics of students with disabilities. One logistic regression model was conducted to determine the influence of sex, race, socioeconomic status, disability type, and self-determination on whether students with disabilities were likely to visit the counselor for college information. Predicted odds were calculated to demonstrate the statistically significant, predictive quality of the variables on visiting the counselor for college information. The theoretical framework of self-determination demonstrated an important relationship in whether the student visited the counselor for college information. Finally, a Pearson correlation (r) that was used for enrollment and number of school counselor variables produced a positive correlation between the number of school counselors and whether the student visited the counselor for college information.
etd-08142012-110803
http://hdl.handle.net/10919/28667
http://scholar.lib.vt.edu/theses/available/etd-08142012-110803/
self-determination
college information
students with disabilities
school counselors
Students with Disabilities Who Contact the School Counselor for College Information
oai:vtechworks.lib.vt.edu:10919/747152020-09-28T13:24:00Zcom_10919_5534col_10919_11041
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Hedrick, Deborah K.
author
1985
Computer-assisted guidance and information systems have recently gained increased popularity among counselors and students. However, there has been little objective research performed on them. The result has been that counselors are often uncertain about the appropriate usage of these instruments. A popular computer-assisted information system which has received little study is the Virginia VIEW Career Search. The Career Search is an accessing strategy designed to lead the users to access occupational and/or educational information from the Virginia VIEW microfiche. The Career Search was adapted from the Michigan Structured Occupational Search, which was developed using the Department of Labor's (DOL) occupational classification system and the Ohio Vocational Interest Survey's weighting of the DOL's data-people-things classification.
The purpose of this study was to clarify the appropriate usage of the Virginia VIEW Career Search. The study sought information concerning how the Career Search is being used in public schools in Virginia by assessing user satisfaction and determining whether the search does lead the users to access occupational and educational information. Finally, user satisfaction ratings and the results of the Career Search and the Ohio Vocational Interest Survey II (OVIS II) were compared.
The sample consisted of 624 Virginia secondary school students whose school districts use both the Career Search and the OVIS II in their counseling programs. The students completed the Career Search, the OVIS II, and the Student Questionnaire. The Student Questionnaire includes a revision of Zener & Schnuelle's 1972 Feedback Sheet, which had been revised to include a questionnaire which assesses whether users seek occupational/educational information after taking the Career Search. A portion of the Feedback Sheet collected ratings so that satisfaction for the Career Search and OVIS II could be compared. Finally, the results of the Career Search and the OVIS II were compared.
The results of the study indicated that users do access career information after taking the Career Search. One of the most utilized sources of career information is the Virginia VIEW microfiche occupational files. Users were generally satisfied with the Career Search, and felt that it helped them gain insight concerning appropriate careers for themselves, and was a good use of their time. Data was insufficient to make a comparison of the levels of user satisfaction for the Career Search and the OVIS II. The comparison of the results of the two instruments yielded limited data as well. However, approximately fifty percent of the subjects had matched results for the first OVIS II scale on their OVIS II Student Report and one or more occupational titles (viewscripts) generated from using the Career Search.
http://hdl.handle.net/10919/74715
Use of and satisfaction with a career information accessing strategy
oai:vtechworks.lib.vt.edu:10919/284302021-03-23T12:51:27Zcom_10919_5534col_10919_11041
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Biedler, James K.
author
2005-07-14
This research focuses on non-Long Terminal Repeat (non-LTR) retrotransposons in the African malaria mosquito, Anopheles gambiae and other mosquito species. An unprecedented diversity of non-LTRs was discovered by genome analysis of the An. gambiae genome assembly. One hundred and four families were found by a reiterative and comprehensive search using the conserved reverse transcriptase domains of known non-LTRs from a number of organisms as the starting queries. These families range in copy number from a few to approximately 2000 and occupy at least 3% of the genome. An. gambiae non-LTRs represent 8 of the 15 previously defined clades, plus two novel clades, Loner and Outcast, raising the total number of known clades to 17. The first invertebrate L1 clade representatives were also found. All clades except one have families with sequence characteristics suggesting recent activity.
Juan, a non-LTR of the Jockey clade originally discovered in the mosquito Culex pipiens quinquefasciatus (Mouches et al. 1991), has been implicated in horizontal transfer in three non-sibling species of the Aedes genus (Mouches, Bensaadi, and Salvado 1992). PCR was used to obtain sequences from 18 mosquito species of six genera. Phylogenetic analysis demonstrates predominant vertical inheritance of Juan elements among these species. There is strong evidence from sequence analysis supporting the recent activity of Juan in several divergent species. We hypothesize that the sustained activity (versus quick inactivation) of non-LTRs in mosquitoes may contribute to the diversity we observe in the An. gambiae genome today.
Promoter and transcriptional analyses were performed for several families previously identified as potentially active elements based on sequence analysis. RT-PCR results indicate that transcripts are present in An. gambiae cell lines that contain sequences corresponding to 13 of 15 tested non-LTR families. The 5' UTRs of An. gambiae non-LTRs from the I, Jockey, and L1 clades support basal transcription in divergent mosquito cell lines from 3 species. The Jen-1 5'UTR did not support transcription in Ae. aegypti and had low activity in Ae. albopictus. In summary, this research shows that Non-LTRs have been highly successful genomic elements that have flourished in many divergent mosquito species.
etd-07282005-125927
http://hdl.handle.net/10919/28430
http://scholar.lib.vt.edu/theses/available/etd-07282005-125927/
Transposable elements
non-LTR retrotransposons
reverse transcriptase
genome evolution
Non-LTR Retrotransposons in Mosquitoes: Diversity, Evolution, and Analysis of Potentially Active Elements
oai:vtechworks.lib.vt.edu:10919/264372022-03-29T14:46:38Zcom_10919_5534col_10919_11041
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Govindarajan Balakumaran, Soundar Sriram
author
2012-03-01
Modeling of chloride-induced deterioration of bridge decks by using Fick's Second Law of diffusion was performed. The objective of this study is to select suitable input parameters for the model to estimate the service life of bridge decks. Five bridge decks, one in each of the following states, Virginia, Florida, New Jersey, New York, and Minnesota were evaluated.
Data collection process involved visual inspections, damage surveys, corrosion testing including continuity, one-point resistivity, four-point resistivity, half-cell potentials, and three-electrode linear polarization, reinforcement cover depths, chloride samples. The Virginia bridge deck was built with epoxy-coated reinforcement as top reinforcement mat and black bar as the bottom mat. The Florida bridge is a segmental prestressed box girder structure built with black bar. The New Jersey bridge deck was overlaid with latex modified concrete. The New York bridge deck, which was built in 1990, is six inch concrete topping over prestressed adjacent box beams structure with epoxy-coated bar in the negative moment area. The Minnesota bridge was rebuilt in 1984. The deck was rebuilt with epoxy coated reinforcing steel in the top and bottom mats.
The probabilistic Fickian model requires reinforcement cover depths, surface chloride concentration, chloride initiation concentration, and diffusion coefficients as input parameters. The chloride initiation concentration was input via parametric bootstrapping, while the other parameters were input as simple bootstrapping. Chloride initiation concentration was determined from the chloride concentration at the reinforcement bar depths.
The modeling results showed that the deterioration of the Virginia bridge deck was corrosion controlled and the bridge will undergo increasingly severe damage in the future. Florida bridge deck is not undergoing corrosion and will not experience corrosion damage within 100 years. New Jersey bridge deck's service life has been most likely extended by the overlay. Deterioration of the New York bridge was not corrosion controlled, but was related to longitudinal cracking of the topping at match lines of adjacent box beams. Minnesota bridge deck is delaminated and contained a large number of cracks that should be included in service life modeling; otherwise the service life estimate is underestimated.
In addition to service life corrosion performance modeling, analyses were conducted on the relationships and interrelations of resistivity, corrosion potential, corrosion current and chloride at the reinforcing bar depth.
etd-03152012-231349
http://hdl.handle.net/10919/26437
http://scholar.lib.vt.edu/theses/available/etd-03152012-231349/
corrosion
service life
bridge decks
Modeling
deterioration
chloride diffusion
concrete
epoxy
overlay
LTBP
Corrosion Testing and Modeling of Chloride-Induced Corrosion Deterioration of Concrete Bridge Decks
oai:vtechworks.lib.vt.edu:10919/547892023-08-13T19:27:35Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
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Malone, Steven William
author
1989
Smokers require high motivation to quit smoking and to remain smoke-free. Worksites might enhance motivation to be smoke-free by offering incentives to employees who quit smoking.
A pilot study was conducted where one worksite offered a smoking cessation group plus several incentive programs. The incentives included money and public recognition based on individual performance, and dinners based on group performance. After 12 months, 48% of participants remained smoke-free. This result is significantly different [x2(1)= 3.910, p<.05]. from the results of a smoking cessation group conducted a comparable company (here, 18% of participants remained smoke-free).
Another study was designed where one worksite would offer a smoking cessation group, and another worksite would offer an incentive program plus a smoking cessation group. Treatment conditions were randomly assigned. Both worksites were part of the same parent company (General Electric), thus minimizing differences between the companies. Many dimensions of the worksites and of participants at each worksite were assessed to demonstrate comparability between the worksites.
In the incentive condition monetary incentives were offered. Participants received $10 for not smoking for two weeks, four weeks. five weeks. six weeks, eight weeks and ten weeks. They received $20 for not smoking after three, four, five and six months. They received $25 for not smoking after nine months and 12 months. Their exhaled air was assessed on a carbon monoxide detector before receiving monetary rewards. As a result, 54% of the 28 participants were smoke-free after nine months.
In the non-incentive condition, participants were offered the same smoking cessation program but without major incentives. Participants were assessed on the carbon monoxide machine for five of the six consecutive months after the program ended. They were also assessed at the nine-month mark. Here, 44% of the 16 participants were smoke-free after nine months. Both interventions, then, were very successful. As a result none of the hypotheses of this study were supported.
This study did not employ a strong research design, and unforeseen changes in procedures weakened the study's validity. Despite these shortcomings, these interventions have merit. The intervention enabled a high percentage of people to quit smoking. These results might encourage smokers who want to quit. Given the success of these programs, hopefully a well-controlled study will be conducted to ascertain the effects of incentives and rewards upon worksite smoking interventions.
http://hdl.handle.net/10919/54789
Using incentives and rewards in worksite smoking interventions
oai:vtechworks.lib.vt.edu:10919/783232022-02-22T20:21:27Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
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Azadeh Fard, Nasibeh
author
2016-01-15
Risk indicators are metrics that are widely used in risk management to indicate how risky an activity is. Among different types of risk indicators, early warning systems are designed to help decision makers predict and be prepared for catastrophic events. Especially, in complex systems where outcomes are often difficult to predict, early warnings can help decision makers manage possible risks and take a proactive approach. Early prediction of catastrophic events and outcomes are at the heart of risk management, and help decision makers take appropriate actions in order to mitigate possible effects of such events. For example, physicians would like to prevent any adverse events for their patients and like to use all pieces of information that help accurate early diagnosis and interventions.
In this research, first we study risk assessment for occupational injuries using accident severity grade as an early warning indicator. We develop a new severity scoring system which considers multiple injury severity factors, and can be used as a part of a novel three-dimensional risk assessment matrix which includes an incident's severity, frequency, and preventability. Then we study the predictability of health outcome based on early risk indicators. A systems model of patient health outcomes and hospital length of stay is presented based on initial health risk and physician assessment of risk. The model elaborates on the interdependent effects of hospital service and a physician's subjective risk assessment on length of stay and mortality. Finally, we extend our research to study the predictive power of early warning systems and prognostic risk indicators in predicting different outcomes in health such as mortality, disease diagnosis, adverse outcomes, care intensity, and survival. This study provides a theoretical framework on why risk indicators can or cannot predict healthcare outcomes, and how better predictors can be designed. Overall, these three essays shed light on complexities of risk assessments, especially in health domain, and in the contexts where individuals continuously observe and react to the risk indicators. Furthermore, our multi-method research approach provides new insights into improving the design and use of the risk measures.
vt_gsexam:6980
http://hdl.handle.net/10919/78323
Risk Assessment
Risk Indicators
Early Warning Systems
Healthcare
Preventability
Predictability
Essays on Risk Indicators and Assessment: Theoretical, Empirical, and Engineering Approaches
oai:vtechworks.lib.vt.edu:10919/383232023-07-29T03:55:40Zcom_10919_5534col_10919_11041
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Purcell, Steven L.
author
1993
By and large, contemporary design models do little more than acknowledge the art and science of media development, and instead, place inordinate emphasis on media selection. While many texts on instructional design will discuss, in general terms, the circumstances under which media needs to be developed, their primary focus is on the selection and customization (e.g., repurposing videodiscs} of extant materials that support previously adopted goals, objectives, and instructional strategies. Although contemporary instructional design models do acknowledge computer-assisted instruction in general terms as part of the media selection and development processes, they fail to address specifically the development issues confronted when digital video is selected as an integral component of computer-based applications. Practitioners wishing to develop their own instructional materials (particularly those which incorporate digital video) are provided few specific details for creating those products in the context of a systems approach to instructional development. This study examined the essential design tasks involved in incorporating digital video into computer-based applications.
The strategy adopted for this study consisted of the following: 1) The author produced a computer-based application for The Museum of Natural History at Virginia Tech that integrated both digital motion-video sequences and still-image graphics; 2) Each of the development “steps” made by the author was preserved through a set of design notes as well as videotaped records of designer and participant comments; 3) The design notes and videotaped records were subjected to qualitative analyses borrowed from standard ethnographic research procedures; 4) Subsequent considerations for integrating digital video into computer-based applications were abstracted from the analyses and presented as practical guidelines for practitioner-developers pursuing media development.
A “traditional” model of instructional design was also modified to reflect state-of-the-art media development strategies. The model illustrates the general procedure of media development and places it in the context of a larger, systems approach to instructional design. The development steps include defining the product, conducting research, brainstorming ideas, generating design solutions, developing the prototype, testing the prototype, and developing the end-product. The model also illustrated (by way of example) the creation of the computer-based application developed for The Virginia Museum of Natural History at Virginia Tech.
etd-06062008-165453
http://hdl.handle.net/10919/38323
http://scholar.lib.vt.edu/theses/available/etd-06062008-165453/
Integrating digital images into computer-based instruction: adapting an instructional design model to reflect new media development guidelines and strategies
oai:vtechworks.lib.vt.edu:10919/401672021-04-23T21:53:45Zcom_10919_5534col_10919_11041
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Mayo, Kevin A.
author
1994-12-15
A software system is an aggregate of communicating modules, and there are several different types of communication among these modules (direct, indirect, and global). Therefore, understanding the interfaces among these modules can characterize the system and are a major factor in the system's complexity. These interfaces could possibly also show and predict inadequacies in the reliability and maintenance of a system. Interfaces are defined early in the development life cycle at a detailed or high level design stage. Knowing that these interfaces exist and their structure leads us to measure them for an indication of the designed interface complexity. This designed interface complexity can then be utilized for software quality assurance by allowing users to choose from among several designs. With data provided by an Ada software developer, the interface complexity metrics correlated with established metrics, but also found complex interfaces that established metrics missed.
etd-10242005-174027
http://hdl.handle.net/10919/40167
http://scholar.lib.vt.edu/theses/available/etd-10242005-174027/
Definition and evaluation of a synthesis-oriented, user-centered task analysis technique: the Task Mapping Model
oai:vtechworks.lib.vt.edu:10919/393322020-09-25T20:53:34Zcom_10919_5534col_10919_11041
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Wu, Tianyu
author
2012-08-31
Conventional free radical polymerization of n-butyl acrylate with 3-[[2-(methacryloyloxy)ethyl](dimethyl)-ammonio]-1-propanesulfonate (SBMA) and 2-[butyl(dimethyl)amino]ethyl methacrylate methanesulfonate (BDMAEMA MS), respectively, yielded zwitterionomers and cationomers of comparable chemical structures. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) revealed that zwitterionomers promoted more well-defined microphase-separation than cationic analogs. Dynamic mechanical analyses (DMA) of the copolymers showed a rubbery plateau region due to physical crosslinks between charges for zwitterionomers only. We attributed improved microphase-separation and superior elastomeric performance of the zwitterionomers to stronger association between covalently tethered charged pairs.
Zwitterionomer / ionic liquid binary compositions of poly(nBA-co-SBMA) and 1-ethyl-3-methylimidazolium ethylsulfate (EMIm ES) were prepared using both the 'swelling– and the –cast with– methods. Dynamic mechanical analysis revealed that the 'swollen– membranes maintained their thermomechanical performance with up to 18 wt% EMIm ES incorporation, while that of the –cast with– membranes decreased gradually as the ionic liquid concentration in the composite membranes increased. Small-angle X-ray scattering results indicated that the 'swollen– and the –cast with– membranes have different morphologies, with the ionic liquid distributed more evenly inside the –cast with– membranes. Impedance spectroscopy results showed that the –cast with– membranes had better ionic conductivity than the 'swollen– membrane at high ionic liquid concentration, in agreement with our proposed model. The results indicated that the different processing methods had a significant impact on thermomechanical properties, ionic conductivities, as well as morphologies of the zwitterionomer / ionic liquid binary compositions.
Reversible addition-fragmentation chain transfer polymerization (RAFT) strategy afforded the synthesis of well-defined poly(sty-b-nBA-b-sty). 2-(Dimethylamino)ethyl acrylate (DMAEA), a tertiary amine-containing acrylic monomer, exhibited radical chain transfer tendency toward itself, which is undesirable in controlled radical polymerization processes. We employed a higher [RAFT] : [Initiator] ratio of 20 : 1 to minimize the impact of the chain transfer reactions and yielded high molecular weight poly[sty-b-(nBA-co-DMAEA)-b-sty] with relatively narrow PDIs. The presence of the tertiary amine functionality, as well as their quaternized derivatives, in the central blocks of the triblock copolymers afforded them tunable polarity toward polar guest molecules, such as ionic liquids. Gravimetric measurements determined the swelling capacity of the triblock copolymers for EMIm TfO, an ionic liquid. DSC and DMA results revealed the impact of the ionic liquid on the thermal and thermomechanical properties of the triblock copolymers, respectively. Composite membranes of DMAEA-derived triblock copolymers and EMIm TfO exhibited desirable plateau moduli of ~ 100 MPa, and were hence fabricated into electromechanical transducers.
RAFT synthesized poly(sty-b-nBA-b-sty) triblock copolymer phase separates into long-range ordered morphologies in the solid state due to the incompatibility between the poly(nBA) phases and the poly(sty) phases. The incorporation of DMAEA into the central acrylic blocks enabled subsequent quaternization of the tertiary amines into sulfobetaine functionalities. Both DSC and DMA results suggested that the electrostatic interactions in the low Tg central blocks of poly(sty-b-nBA-b-sty) enhanced block copolymer phase separation. SAXS results indicated that the presence of the sulfobetaine functionalities in acrylate phases increased electron density differences between the phases, and led to better defined scattering profiles. TEM results confirmed that the block copolymers of designed molecular weights exhibited lamellar morphologies, and the lamellar spacing increased with the amount of electrostatic interactions for the zwitterionic triblock copolymers.
Acrylic radicals are more susceptible to radical chain transfer than their styrenic and methacrylic counterparts. Controlled radical polymerization processes (e.g. RAFT, ATRP and NMP) mediate the reactivity of the acrylic radical and enable the synthesis of well-defined linear poly(alkyl acrylate)s. However, functional groups such as tertiary amine and imidazole on acrylic monomers interfere with the controlled radical polymerization of functional acrylates. Model CFR and RAFT polymerization of nBA in the presence of triethylamine and N-methyl imidazole revealed the interference of the functional group on the polymerization of acrylate. Various RAFT agents, RAFT agent to initiator ratios, degree of polymerization and monomer feed concentrations were screened with an imidazole-containing acrylate for optimized RAFT polymerization conditions. The results suggest that the controlled radical polymerization of functional acrylates, such as 2-(dimethylamino)ethyl acrylate and 4-((3-(1H-imidazole-1-yl)propanoyl)oxy)-butyl acrylate (ImPBA), remained challenging.
etd-09132012-105916
http://hdl.handle.net/10919/39332
http://scholar.lib.vt.edu/theses/available/etd-09132012-105916/
electromechanical transducer
zwitterion
functional acrylate
ionic liquid
morphology
RAFT polymerization
block copolymer
Synthesis and Characterization of Zwitterion-Containing Acrylic (Block) Copolymers for Emerging Electroactive and Biomedical Applications
oai:vtechworks.lib.vt.edu:10919/261182022-03-01T19:10:57Zcom_10919_5534col_10919_11041
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Giese, Laura
author
2001-01-12
Riparian forests are integral components of the landscape. The inherent biogeochemical processes that occur in such forests provide numerous benefits to wildlife and society. Maintaining good water quality is a major benefit from riparian forests and therefore, the maintenance, creation, or restoration of riparian forests is indispensable. This study was designed to broaden current knowledge of the complex, interrelated biogeochemical processes and determine indices for riparian forest restoration based on the various carbon pools/fluxes that may represent restoration success.
This study was implemented on the Savannah River Site, an Environmental Research Park, where several riparian forests are recovering from thermal disturbances. The streams in these forests were subjected to thermal discharges that increased flows and resulted in removal of soil and a decline in the amount of woody vegetation. Two of these riparian forests are at different ages post-disturbance and represent different stages of recovery, which provides an exceptional opportunity to study successional processes in riparian forests and enhance restoration efforts.
Linear transects perpendicular to the main stream channels were established in 2 recovering riparian forests of different ages (two areas in Pen Branch ~ 8 years post-disturbance; Fourmile Branch ~ 12 years post disturbance) and an undisturbed (thermally) more mature riparian forest (Meyer's Branch ~ 60 years). Along these transects quantitative data were obtained on above and belowground carbon pools and fluxes.
Carbon pools exhibited a close correlation with riparian forest development. Biomass and carbon pools increased with increasing riparian forest stand age. The importance of the herbaceous carbon pool declined relative to the total above ground biomass, and the root carbon pool increased with forest age/succession. In general, net primary production (NPP) in young riparian forests (~8-10 years) rapidly approached and even exceeded NPP of more mature riparian forests. Once the herbaceous stage of succession was surpassed, the litterfall component of NPP plays a greater role riparian forests. As a woody overstory became established (after ~ 8-10 years), annual litterfall rates as a function of NPP were independent of forest age.
Establishment of woody species occurred ~8 to 10 years after thermal disturbance and litterfall amount in young riparian forests rapidly became comparable to mature riparian forests. Lateral litter movement from the riparian forest toward the stream was less than the amount of litter (carbon pool) deposited from upstream into the riparian forest during a flood event. Overall lateral litter movement supplied less energy to the stream system than vertical inputs. A decline in riparian forest floor biomass was observed with increasing riparian forest development. However, a difference in foliar forest floor percent carbon lended itself to a minimal increase in the forest floor carbon pool with increasing riparian forest age. Woody debris in riparian forests comprised a relatively small carbon pool compared to tree and soil carbon pools.
The species composition of litter appeared to be more of an overriding factor influencing decomposition rates than forest age. The influence of litter quality was evident in the decomposition rates of the different litter composites used in this study. In all 4 sites the litter composite from the mature riparian forest decomposed significantly more than the litter composites from the younger riparian forests. The fairly rapid decomposition of red maple (Acer rubrum L.), which was one of the main components in the mature riparian forest litter composite, influenced the greater decomposition rate. The litter composites from the younger riparian forests were similar and both included more decomposition resistant litter types, specifically waxmyrtle (Myrica cerifera L.) and alder (Alnus serrulata (Ait.) Willd.). Decomposition rates did not differ between the individual successional stages.
Riparian forests are intimately associated with their hydroperiod. During flood events the riparian forest receives inputs of organic matter and sediment, and the amount of deposition may decrease along a distance gradient from the main stream channel. The differential amount of inputs could affect forest productivity. However, in these riparian forests, a distance gradient effect was not observed. Trends in herbaceous biomass were evident along a microtopographic moisture gradient. The ridge and swale microtopography prevalent in the younger riparian forests counteracted a distance from the stream channel gradient effect across the riparian forest.
This study provided knowledge of how carbon pools and fluxes change with riparian forest recovery from disturbance as well as through different seral stages. Implementing the findings of this study will enhance restoration evaluation efforts to ensure that these areas continue to provide the numerous benefits gleamed from them.
etd-02052001-064629
http://hdl.handle.net/10919/26118
http://scholar.lib.vt.edu/theses/available/etd-02052001-064629/
riparian
bottomland hardwood
restoration
forest succession
carbon
Carbon Pools and Fluxes as an Indicator of Riparian Restoration
oai:vtechworks.lib.vt.edu:10919/298842022-03-17T20:51:41Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Rachdawong, Sansanalak
author
1999-11-19
Take-all is the most devastating root disease of wheat worldwide. The causal agent is <I>Gaeumannomyces</I> <I>graminis</I> (Sacc.) Arx & Olivier. Based on morphological characteristics and host ranges, three varieties of <I>G</I>. <I>graminis</I> have been recognized. <I>G</I>. <I>graminis</I> var. <I>tritici</I> Walker (Ggt) is the major causal agent of take-all of wheat and barley and the most economically important take-all pathogen. <I>G</I>. <I>graminis</I> var. <I>avenae</I> (Turner) Dennis (Gga) attack oats and causes take-all patch of turf grasses while <I>G</I>. <I>graminis</I> var. <I>graminis</I> (Ggg) is pathogenic on turf grasses but is non-pathogenic on wheat. Conventional diagnosis of take-all pathogens is based on field symptoms such as blackened roots, stunted growth, and white-heads and morphological characteristics such as hyphopodia type, size of perithecia, asci, and ascospores. These procedures are time-consuming, laborious, and often inconclusive. The objective of this study was to develop a rapid, simple, and specific method for differentiation of <I>G</I>. <I>graminis</I> varieties using PCR and molecular-based technology. Exploitation of genes associated with pathogenicity of <I>G</I>. <I>graminis</I> as markers for the test was proposed. Metabolic activities of <I>G</I>. <I>graminis</I> associated with pathogenesis were investigated, namely, the abilities to produce avenacinase and to oxidize manganese. Avenacinase, an avenacin detoxifying enzyme, was associated with Gga pathogenicity for oats but this enzyme is not important in Ggt pathogenicity for wheat. Manganese oxidation was also correlated with Ggt virulence. In this study, avenacinase-like genes were discovered in Ggt and Ggg and manganese oxidation was confirmed for Ggt, Gga, and Ggg. All isolates of Ggt except isolate ATCC 28230 were manganese oxidizers. Ggg and Gga isolates could oxidize manganese but their precipitation patterns were not as intense or closely correlated with mycelial growth as for Ggt. Pathogenicity assays on oats for Ggt, Gga, and Ggg isolates confirmed that Ggt isolates could not cause disease on oats aside from occasional slight root damage. Root weight was reduced for oat seedlings inoculated with Gga isolates. Comparison of partial sequences of avenacinase-like genes from Ggt and Ggg showed strong homology to that of Gga (94.8% identity to Ggt and 94.6% identity to Ggg). However, the Ggt gene was more closely related to that of Ggg (99.2% identity) than to Gga. DNA restriction endonuclease polymorphisms of the genes supported DNA sequencing information and revealed that there were variations within the genes among Ggt, Gga, and Ggg. Variety-specific electrophoretic patterns were obtained when the genes were digested with <I>Hae</I>III. Ggt, Gga, and Ggg upstream (5') variety-specific primers and a downstream (3') universal primer were designed from the avenacinase and avenacinase-like DNA sequences. PCR amplification with Ggt-, Gga-, and Ggg-specific primers generated fragments of 870, 617, and 1,086 bp, respectively. Each 5'-specific primer showed high specificity for its own DNA template in mixed populations of DNA templates. The optimized PCR procedure was sensitive to DNA template concentration as low as 100 pg. Genomic DNA of sixteen Ggt isolates, seven Gga isolates, and five Ggg isolates were tested. Although all Ggt isolates were originally isolated from wheat, seven isolates produced Ggg-specific fragments. This result corresponded well with <I>Hae</I>III DNA polymorphisms, pathogenicity assay, and manganese oxidizing ability. All but one Gga isolates produced the variety-specific fragment. Ggt- and Gga- specific products were generated from Gga isolate RB-W. Although Ggg-specific fragments were produced from all Ggg isolates, non-specific products were also observed from isolates that were not from wheat origin suggesting some genetic variations due to host ranges. Additionally, no non-specific amplification was obtained from any closely related fungi such as <I>Gaeumannomyces</I> <I>cylindrosporus</I> or <I>Phialophora</I> spp. The test developed in this study is the first test capable of identification of Ggt, Gga, and Ggg in a single PCR tube with a basic PCR protocol. The test is rapid and specific. Interpretation of results is simple and conclusive based on differences in size of each variety-specific fragment.
etd-120299-204831
http://hdl.handle.net/10919/29884
http://scholar.lib.vt.edu/theses/available/etd-120299-204831/
identification
Gaeumannomyces graminis
avenacinase
differentiation
manganese oxidation
PCR
take-all
PCR-Based Test for Differentiating Varieties of <i>Gaeumannomyces graminis</i>, The Take-All Pathogens
oai:vtechworks.lib.vt.edu:10919/648452020-09-28T13:50:22Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Yi, Hui
author
2014-08-27
The data from genome-wide association studies (GWAS) in humans are still predominantly analyzed using single marker association methods. As an alternative to Single Marker Analysis (SMA), all or subsets of markers can be tested simultaneously. This approach requires a form of Penalized Regression (PR) as the number of SNPs is much larger than the sample size. Here we review PR methods in the context of GWAS, extend them to perform penalty parameter and SNP selection by False Discovery Rate (FDR) control, and assess their performance (including penalties incorporating linkage disequilibrium) in comparison with SMA. PR methods were compared with SMA on realistically simulated GWAS data consisting of genotype data from single and multiple chromosomes and a continuous phenotype and on real data. Based on our comparisons our analytic FDR criterion may currently be the best approach to SNP selection using PR for GWAS. We found that PR with FDR control provides substantially more power than SMA with genome-wide type-I error control but somewhat less power than SMA with Benjamini-Hochberg FDR control. PR controlled the FDR conservatively while SMA-BH may not achieve FDR control in all situations. Differences among PR methods seem quite small when the focus is on variable selection with FDR control. Incorporating LD into PR by adapting penalties developed for covariates measured on graphs can improve power but also generate morel false positives or wider regions for follow-up. We recommend using the Elastic Net with a mixing weight for the Lasso penalty near 0.5 as the best method.
vt_gsexam:3635
http://hdl.handle.net/10919/64845
Genome-wide Association Study
penalized regression
false discovery rate
linkage disequilibrium
Assessment of Penalized Regression for Genome-wide Association Studies
oai:vtechworks.lib.vt.edu:10919/296932020-09-25T20:51:29Zcom_10919_5534col_10919_11041
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Sun, Miao
author
2006-11-16
This study focuses on the improvement of the axial buckling capacity of elliptical composite cylinders through the use of a circumferentially-varying lamination sequence. The concept of varying the lamination sequence around the circumference is considered as a viable approach for off-setting the disadvantages of having the cylinder radius of curvature vary with circumferential position, the source of the reduced buckling capacity when compared to a circular cylinder with the same circumference. Post-buckling collapse behavior and material failure characteristics are also of interest. Two approaches to implementing a circumferential variation of lamination are examined. For the first approach the lamination sequence is varied in a stepwise fashion around the circumference. Specifically, each quadrant of the cylinder circumference is divided into three equal-length regions denoted as the crown, middle, and side regions. Eight different cylinders designs, whereby each region is constructed of either a quasi-isotropic or an axially-stiff laminate of equal thickness, are studied. Results are compared to the baseline case of an elliptical cylinder constructed entirely of a quasi-isotropic laminate. Since the thickness of the quasi-isotropic and axially-stiff laminates are the same, all cylinders weight the same and thus comparisons are meaningful. Improvements upwards of 18% in axial buckling capacity can be achieved with one particular stepwise design. The second approach considers laminations that vary circumferentially in a continuous fashion to mitigate the effects of the continuously-varying radius of curvature. The methodology for determining how to tailor the lamination sequence circumferentially is based on the analytical predictions of a simple buckling analysis for simply-supported circular cylinders. With this approach, axial buckling load improvements upwards of 30% are realized. Of all the cylinders considered, very few do not exhibit material failure upon collapse in the post-buckled state. Of those that do not, there is little, if any, improvement in bucking capacity. Results for the pre-buckling, buckling, post-buckling, and material failure are obtained from the finite-element code ABAQUS using both static and dynamic analyses. Studies with the code demonstrate that the results obtained are converged.
etd-11202006-124553
http://hdl.handle.net/10919/29693
http://scholar.lib.vt.edu/theses/available/etd-11202006-124553/
Buckling
Material Tailoring
Elliptical Cylinder
Composite
Material Failure
Stability
Post-buckling
Use of Material Tailoring to Improve Axial Load Capacity of Elliptical Composite Cylinders
oai:vtechworks.lib.vt.edu:10919/1084062022-02-19T08:11:29Zcom_10919_5534col_10919_11041
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Purchase, Jeannie Marie
author
2022-02-17
NSF/ANSI 53 lead-certified point-of-use filters (POUs) have been distributed to consumers in many cities facing water lead crises, including Washington D.C., Flint, MI, Newark, NJ, and University Park, IL. It is expected that these filters would reduce water lead to levels that are safe for consumption as residents wait for municipalities to provide more permanent solutions (e.g., corrosion control, lead service line replacement). These filters are certified by the National Sanitation Foundation (NSF) after meeting the challenges of treating two lab synthesized waters with 150 μg/L of soluble and particulate lead. In Flint, as in Washington, there were initial concerns that the filters would not be effective when exposed to lead levels far above the NSF/ANSI 53 150 μg/L Pb level used for certification. However, the EPA conducted a 2016 study in Flint, MI, with over 240 homes with lead up to 4080 μg/L, revealing that all POUs reduced lead levels below 1 μg/L.
Newark, NJ, in response to Lead and Copper Rule (LCR) violations, distributed over 40,000 NSF/ANSI 53 lead-certified pitcher and faucet POUs to protect consumers from high water lead levels. In the summer of 2019, preliminary tests in some homes with the highest lead in water concentrations revealed that 2 of 3 POUs used in Newark had effluent lead levels above 15 μg/L. The publication of these results caused citywide angst, distrust, and EPA mandated a switch to bottled water. However, a later and more extensive study revealed that 97.5% of homes (n=198) with properly used filters had effluent lead levels below 10 μg/L. As a result, the EPA approved Newark's request to discontinue bottled water distribution and only provide POUs to residents. Nevertheless, the experience indicated that it is vital to understand the limitations of POUs. This dissertation comprises three manuscripts that examine the efficacy of POUs under laboratory and field conditions.
The first manuscript sought to provide perspective into potential causes of the filter failures observed in the field. We conducted an extensive laboratory investigation that examined the performance of 10 pitcher and faucet POU brands under extreme conditions (e.g., up to 200% of rated capacity, influent lead levels ≈ 1000 μg/L). Our tests confirmed successful performance documented in some field testing and replicated underperformance observed in others. In this investigation, we observed structural failures due to poor manufacturing (i.e., leaking units, a filter with a large hole in the media) and performance failures (filtered water >10 μg/L Pb). Some of the performance failures occurred when we tested particulate lead waters, which we created, proving to be very difficult to treat relative to those used for NSF/ANSI testing. While the POUs almost always reduce consumer lead exposure, even when operated beyond their rated capacity, this study highlights instances where treated water could far exceed 10 μg/L lead.
High particulate iron (Fe) and manganese (Mn) concentrations often co-occur with high lead in many low-income, rural communities with small community water systems (CWS) or in homes with private wells. These communities are more likely to depend on POUs for protection from waterborne lead as they typically do not have the funds to maintain and upgrade infrastructure, improve corrosion control, or replace service lines. Waters with high levels of Fe and Mn could potentially impact the performance of the POU lead filters. However, such problems would not be detected in NSF/ANSI certification testing because these constituents are not included within the test water.
The second manuscript validated anecdotal reports of premature POU failure due to clogging in rural communities with high iron concentrations in their water. POU pitcher filters were tested with waters containing high lead and iron up to 100% of their rated capacity, or until they clogged as defined by a 75% reduction in initial flowrate. Iron levels above the 0.3 mg/L Secondary Maximum Contaminant Level (SMCL) resulted in rapid clogging, markedly increasing treatment costs, and decreasing consumer satisfaction. At 0.3 mg/L Fe, half of the 6 POU filters tested were clogged at between 38-68% of their rated capacity. When considering the cost of using POU filters vs. purchasing bottled water, the POU devices were often more cost-effective at iron levels at or below 0.3 mg/L. However, as iron concentrations increased, bottled water often became cost-effective depending on the circumstance. The presence of iron did not have an adverse effect on lead removal but significantly affected the cost and reduced flow rates in treating water.
The third manuscript presents a two-phase field study that sought to monitor the long-term filter performance in residential homes in New Orleans and Enterprise, LA. Previous field studies have captured POU removal efficiencies in single event (grab) samples; however, this study quantified filter performance for all the water treated up to POU practical capacity (i.e., filter life) based on consumer judgment regarding acceptable flow rate. The first phase was a rigorously controlled study that tested the POUs (100-gal capacity) at up to 200% of their rated capacity in two New Orleans unoccupied homes. Historically, the first home had consistently high lead levels (10-25 μg/L) even after flushing for > 8 min. Duplicate POUs treated that water to below 5 μg/L at up to 100% capacity, with only two exceptional samples with 12 μg/L Pb in 10-gallon batches of the treated water. The second home had a disturbed lead service line (LSL), resulting in varying concentrations of influent particulate lead ranging from 9-3000 μg/L. The duplicate POUs had difficulty producing water lead levels <10 μg/L before reaching filter capacity, with eight exceedances prior to 100% capacity. This work demonstrated that flushing alone for extended periods (>8 minutes) is not guaranteed to reduce lead levels in all homes with LSLs and highlights some limitations of POU filters in treating water with high levels of particulate lead.
The second phase of the field study monitored POU faucet filter performance in the homes of 21 residents in New Orleans (8) and Enterprise (13), LA. New Orleans is a large urban area with low to moderate water lead levels with many partial LSL replacements. Enterprise (population <300) is a rural, low-income community with an unincorporated water system with moderate to high water lead, iron, and manganese levels. Overall, the POUs consistently reduced lead to <1 μg/L, iron <171 μg/L, and manganese <180 μg/L. Enterprise's high influent concentrations of iron significantly impacted filter capacity due to reduced flow and clogging. Enterprise homes saw an average 62% flowrate reduction, and most of the homes did not reach 50% of the filter's rated capacity before consumers decided the filters were clogged. Most New Orleans residents did not experience clogging, and the homes that did saw only a 16% flow rate reduction. Overall, the New Orleans POUs were 2.3X faster in treating water by the study's end than Enterprise. There was no simple correlation between average iron concentration and days of filter life amongst residents in Enterprise as would be expected given variations in the volume of water used daily and consumer subjectivity in deciding when to end the study due to clogging. However, residents in Enterprise and similar communities would likely need to purchase 2-4 times as many filter cartridges due to clogging when compared to cities like New Orleans with lower iron concentrations. This study shows how POUs have promise for the removal of Pb and Fe in residential homes, but clogging has emerged as an important practical limitation to widespread successful POU deployment.
This dissertation highlighted the multifaceted nature of the question: "How well do POU filters work and under what conditions?" Overall, the POUs have shown their ability to reduce water lead levels effectively <5 μg/L, with a few exceptions primarily attributed to particulate lead and manufacturing quality control issues. However, when treating waters with high levels of iron and other contaminants, POU clogging can cause consumer dissatisfaction and make purchasing bottled water a more favorable solution than POU filters.
vt_gsexam:33800
http://hdl.handle.net/10919/108406
lead
iron
point of use filter
particulates
clogging
bottled water
Practical Application of NSF/ANSI 53 Lead Certified Filters: Investigating Lead Removal, Clogging and Consumer Experience
oai:vtechworks.lib.vt.edu:10919/776262022-03-29T14:21:47Zcom_10919_5534col_10919_11041
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Xie, Xuping
author
2017-05-12
This dissertation uses spatial filtering to develop a large eddy simulation reduced order model (LES-ROM) framework for fluid flows. Proper orthogonal decomposition is utilized to extract the dominant spatial structures of the system. Within the general LES-ROM framework, two approaches are proposed to address the celebrated ROM closure problem. No phenomenological arguments (e.g., of eddy viscosity type) are used to develop these new ROM closure models.
The first novel model is the approximate deconvolution ROM (AD-ROM), which uses methods from image processing and inverse problems to solve the ROM closure problem. The AD-ROM is investigated in the numerical simulation of a 3D flow past a circular cylinder at a Reynolds number $Re=1000$. The AD-ROM generates accurate results without any numerical dissipation mechanism. It also decreases the CPU time of the standard ROM by orders of magnitude.
The second new model is the calibrated-filtered ROM (CF-ROM), which is a data-driven ROM. The available full order model results are used offline in an optimization problem to calibrate the ROM subfilter-scale stress tensor. The resulting CF-ROM is tested numerically in the simulation of the 1D Burgers equation with a small diffusion parameter. The numerical results show that the CF-ROM is more efficient than and as accurate as state-of-the-art ROM closure models.
vt_gsexam:11302
http://hdl.handle.net/10919/77626
Reduced Order Modeling
Large Eddy Simulation
Approximate Deconvolution
Data-Driven Modeling
Stochastic Reduced Order Model
Spatial Filtering
Finite element method
Numerical Analysis
Large Eddy Simulation Reduced Order Models
oai:vtechworks.lib.vt.edu:10919/802992020-09-28T13:59:34Zcom_10919_5534col_10919_11041
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Bhuiyan, Md Hasanuzzaman
author
2017-11-09
Networks (or graphs) are an effective abstraction for representing many real-world complex systems. Analyzing various structural properties of and dynamics on such networks reveal valuable insights about the behavior of such systems. In today's data-rich world, we are deluged by the massive amount of heterogeneous data from various sources, such as the web, infrastructure, and online social media. Analyzing this huge amount of data may take a prohibitively long time and even may not fit into the main memory of a single processing unit, thus motivating the necessity of efficient parallel algorithms in various high-performance computing (HPC) platforms. In this dissertation, we present distributed and shared memory parallel algorithms for some important network analytic problems.
First, we present distributed memory parallel algorithms for switching edges in a network. Edge switch is an operation on a network, where two edges are selected randomly, and one of their end vertices are swapped with each other. This operation is repeated either a given number of times or until a specified criterion is satisfied. It has diverse real-world applications such as in generating simple random networks with a given degree sequence and in modeling and studying various dynamic networks. One of the steps in our edge switch algorithm requires generating multinomial random variables in parallel. We also present the first non-trivial parallel algorithm for generating multinomial random variables.
Next, we present efficient algorithms for assortative edge switch in a labeled network. Assuming each vertex has a label, an assortative edge switch operation imposes an extra constraint, i.e., two edges are randomly selected and one of their end vertices are swapped with each other if the labels of the end vertices of the edges remain the same as before. It can be used to study the effect of the network structural properties on dynamics over a network. Although the problem of assortative edge switch seems to be similar to that of (regular) edge switch, the constraint on the vertex labels in assortative edge switch leads to a new difficulty, which needs to be addressed by an entirely new algorithmic approach. We first present a novel sequential algorithm for assortative edge switch; then we present an efficient distributed memory parallel algorithm based on our sequential algorithm.
Finally, we present efficient shared memory parallel algorithms for generating random networks with exact given degree sequence using a direct graph construction method, which involves computing a candidate list for creating an edge incident on a vertex using the Erdos-Gallai characterization and then randomly creating the edges from the candidates.
vt_gsexam:12662
http://hdl.handle.net/10919/80299
Network Science
Parallel Algorithms
High Performance Computing
Edge Switch
Random Networks
Parallel Algorithms for Switching Edges and Generating Random Graphs from Given Degree Sequences using HPC Platforms
oai:vtechworks.lib.vt.edu:10919/394352021-04-20T18:30:57Zcom_10919_5534col_10919_11041
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Hartman, Richard Donald
author
1992-03-15
The problem of optimal guidance design for the low altitude, subsonic, vertical plane approach maneuver of an air vehicle constrained to maintain view of a fixed final position is studied using a nonlinear, constrained, optimal control problem formulation. Multiple, competing optimization criteria are included separately as performance goals and in combination as state equality constraints for design tradeoff analysis. In conjunction with vehicle flight constraints, a sensor line-of -sight (LOS) angle limit is imposed as a control variable inequality constraint to provide a sensor field of regard influence on the guidance design. Numerical results are provided that illustrate the optimal guidance for different performance criteria, the sensor LOS profile along the optimal maneuvers, and the influence of the sensor limit on the guidance law design. A near-optimal, closed-loop feedback guidance law that incorporates the sensor constraint is developed based on neighboring extremals.
etd-09202005-091019
http://hdl.handle.net/10919/39435
http://scholar.lib.vt.edu/theses/available/etd-09202005-091019/
Optimal maneuver guidance with sensor line of sight constraint
oai:vtechworks.lib.vt.edu:10919/377802022-02-22T19:58:13Zcom_10919_5534col_10919_11041
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Rius, Agustin Gregorio
author
2009-04-28
Dairy herds are major contributors to N pollution because 70% of the N intake is lost to the environment and 30% or less is retained in milk protein. Plasma amino acids (AA) that are not used for protein synthesis in mammary glands (MG) are catabolized in post splanchnic tissues (liver plus gastrointestinal tract, pancreas, spleen, portal system, and associated adipose tissue) and two thirds of the net supply of essential AA (EAA) are cleared in splanchnic tissues. Thus, increasing AA capture in MG would be expected to reduce AA catabolism and thereby increase efficiency of AA utilization. The objectives of the work presented in this dissertation were to test the effect of energy and N intake on cell regulatory mechanisms, nutrient kinetics, milk, milk protein yield, and N efficiency in dairy cows.
The aim of the first study was to test whether metabolizable protein (MP) and dietary energy exerted independent effects on milk protein synthesis and postabsorptive N efficiency. Forty mid-lactation cows (32 multiparous Holstein and 8 primiparous Holstein x Jersey cross-breds) were used in a complete randomized design with a 2 x 2 factorial arrangement of diets. Cows were assigned to one of four dietary treatments: high-energy, high-protein (HE/HP); high-energy, low-protein (HE/LP); low-energy, high-protein (LE/HP); and low-energy, low-protein (LE/LP). Energy concentrations were 1.55 (HE/HP and HE/LP) or 1.44 (LE/HP and LE/LP) Mcal NEL/kg DM according to the NRC model. Changes in predicted MP were achieved by feeding diets with 6.6 (HE/HP and LE/HP) or 4.6% (HE/LP and LE/LP) ruminally undegradable protein (DM basis). Ruminally degradable protein was held constant at 10.1% of DM. All cows were fed HE/HP diet from day 1 to 21 followed by the respective treatments from day 22 to 43 (n=10). Milk protein yield was reduced as dietary energy was reduced. There were no interactions between dietary energy and protein for either milk or protein yield. Milk urea N was significantly affected by energy and protein with an interaction (HE/HP=17.2, HE/LP=12.2, LE/HP=21.0, LE/LP=12.2 mg/dl). Nitrogen efficiency was affected by energy and protein supplies with no interaction and ranged from a low of 31% (LE/HP) to a high of 43% (HE/LP). Although energy and protein independently affected milk and protein yield the tissue and cellular mechanisms that regulate milk production were not studied.
The second experiment studied cellular mechanisms in MG that contributed to the regulation of protein synthesis in the presence of energy or protein supply. We hypothesized that metabolism of AA in the MG is controlled by systemic and local tissue adaptations and when combined with altered mammary cell function controlled milk protein yield. Six primiparous mid-lactation Holstein cows with rumen cannulas were randomly assigned to abomasal infusions of casein and starch using a 2 x 2 factorial arrangement. The design was a replicated incomplete 4 x 4 Latin-square. All animals received the same basal diet (17.6% CP and 1.58 Mcal NEL/kg DM) throughout the study. Cows were restricted to 70% of ad libitum intake and infused abomasally for 36 h with water, starch (2 kg/d), casein (0.86 kg/d), or the combination (2 kg/d starch + 0.86 kg/d casein) using peristaltic pumps. Milk weights, milk samples, and arterial and venous blood samples were collected during the last 8 h of infusions. Mammary biopsy samples were collected and tissue protein prepared to evaluate cell signaling. Animals infused with casein had increased arterial concentrations of NEAA and EAA, as well as net uptake and clearance; however, milk protein yield did not increase. Animals infused with starch however, exhibited reduced arterial concentrations of NEAA and EAA but increased clearance and net uptake of most AA. Additionally, infusions of starch increased circulating concentration of insulin, IGF-I, and glucose as well as the rate of mammary plasma flow. Abomasal infusions of starch activated mammary activity of ribosomal protein S6 irrespective of other treatments. However, mammary tissue mTOR increased activity in response to casein only when starch was present during the infusions. These results suggest that cell signaling activation responded to different nutritional stimuli. Milk and protein yield increased in animals infused with starch. Therefore, MG positively responded to energy supply and engaged local and intracellular regulatory mechanisms to achieve that response. Understanding these adaptations could be beneficial in the development of mathematical representations for nutrients utilization in lactating animals. These two studies supported our hypotheses that regulatory mechanism are activated during limiting supply of AA to sustain protein synthesis in MG. The accuracy of mathematical models for lactating animals would increase if effects of energy on AA metabolism and cell signaling related to protein synthesis were included in the representation of milk protein synthesis.
etd-05112009-141923
http://hdl.handle.net/10919/37780
http://scholar.lib.vt.edu/theses/available/etd-05112009-141923/
Protein metabolism
mammary gland
cow
Nitrogen Efficiency and Regulation of Protein Synthesis in Lactating Dairy Cows
oai:vtechworks.lib.vt.edu:10919/388312020-09-25T20:53:27Zcom_10919_5534col_10919_11041
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Sarkar, Sourish
author
2012-07-23
This work considers inventory systems with two demand classes, where advance demand information is available. Three related scenarios are presented: three-stage production-inventory systems are studied in first two, whereas pure inventory systems are studied in the last scenario.
In the first scenario, continuous review production-inventory systems are considered, where only one class provides advance demand information and early demand fulfillment is permitted. A new approach for production replenishment and order fulfillment in such systems is proposed, which combines the benefits of early fulfillment with Kanban-based pull systems. Simulation is used to compare the performance of the resulting policy with two other policies for a variety of scenarios (depending on the arrival rates, system utilizations, cost structures, arrival ratio, priority levels and amount of the advance demand information). A simulation-based lower bound on the optimal cost is established for some specific scenarios. The proposed policy outperforms the existing policies in every setting considered. Also, the proposed policy has added advantage of both retaining the benefit at high system utilizations and increasing the benefit up to the maximum level of advance demand information provided. A small fraction of customers providing advance demand information with early fulfillment acceptable is shown to have higher benefit than all customers providing same advance demand information with no early fulfillment.
In second scenario, both classes provide advance demand information in production-inventory systems, though only one class accepts early fulfillment. Different levels of system utilization, arrival ratio and backorder cost are considered in the simulation experiments to show the superiority of early fulfillment. Also, experiments suggest that lowering the expected supply lead time may be more beneficial than increasing the demand lead time by the same amount for production-inventory systems with utilization dependent supply lead times.
In third scenario, pure inventory systems are considered, where the demand classes provide different amount of advance demand information, and only one class accepts early fulfillment. The structure of an optimal policy is analytically characterized for periodic review systems under some specific conditions.
etd-07262012-232200
http://hdl.handle.net/10919/38831
http://scholar.lib.vt.edu/theses/available/etd-07262012-232200/
production and inventory control
advance demand information
multiple demand classes
Use of Advance Demand Information in Inventory Management with Two Demand Classes
oai:vtechworks.lib.vt.edu:10919/269402020-09-25T20:37:41Zcom_10919_5534col_10919_11041
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Strickler, Mark Rosen
author
2009-04-01
The study investigated the degree to which the personal values, morals, or ethics of educational leaders enter into their decision making processes. A review of the literature suggests that leadership preparation programs for educators do not adequately equip aspiring administrators for the ethical challenges in a global society. The scholarship of John Dewey and Donald Willower in the field of educational leadership laid the groundwork for the dual methodology pilot study conducted with high school administrators and retired superintendents. Retired division superintendents from Virginia were interviewed to yield a database of thematic strands for developing ethical construct statements. Demographic data was collected in the first portion of the survey. In the second portion of the instrument, respondents indicated strength of relevance for each of twenty valuation statements applied to each of the four ethical scenarios. The third section ended by respondents assigning one of four value labels to each of the ethical scenarios. Implications for further research include early administration to members of new leadership preparation cohorts for comparison at program completion.
etd-04172009-091459
http://hdl.handle.net/10919/26940
http://scholar.lib.vt.edu/theses/available/etd-04172009-091459/
Educational Leadership
Values
Decision-making
Ethics
Morals
Educational Leaders' Decision-Making: Presence, Influence, and Strength of Personal Values, Morals, and Ethics
oai:vtechworks.lib.vt.edu:10919/541802023-08-13T19:27:36Zcom_10919_5534col_10919_11041
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Greene, William H.
author
1989
A study has been performed focusing on the calculation of sensitivities of displacements, velocities, accelerations, and stresses in linear, structural, transient response problems. One significant goal of the study was to develop and evaluate sensitivity calculation techniques suitable for large-order finite element analyses. Accordingly, approximation vectors such as vibration mode shapes are used to reduce the dimensionality of the finite element model. Much of the research focused on the accuracy of both response quantities and sensitivities as a function of number of vectors used.
Two types of sensitivity calculation techniques were developed and evaluated. The first type of technique is an overall finite difference method where the analysis is repeated for perturbed designs. The second type of technique is termed semianalytical because it involves direct, analytical differentiation of the equations of motion with finite difference approximation of the coefficient matrices. To be computationally practical in large-order problems, the overall finite difference methods must use the approximation vectors from the original design in the analyses of the perturbed models. In several cases this fixed mode approach resulted in very poor approximations of the stress sensitivities. Almost all of the original modes were required for an accurate sensitivity and for small numbers of modes, the accuracy was extremely poor. To overcome this poor accuracy, two semi-analytical techniques were developed. The first technique accounts for the change in eigenvectors through approximate eigenvector derivatives. The second technique applies the mode acceleration method of transient analysis to the sensitivity calculations. Both result in accurate values of the stress sensitivities with a small number of modes. In both techniques the computational cost is much less than would result if the vibration modes were recalculated and then used in an overall finite difference method.
http://hdl.handle.net/10919/54180
Computational aspects of sensitivity calculations in linear transient structural analysis
oai:vtechworks.lib.vt.edu:10919/383762021-04-20T18:31:13Zcom_10919_5534col_10919_11041
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Herndon, James Ben
author
1993-10-15
Administrators, faculty, and researchers have assumed that advising needs and preferences for advising styles are similar across student population segments and do not consider the relationship of student attributes or the institutional setting to academic advising. Crookston (1972) presented two advising styles--developmental advising, which reflects a concern for the student's total education, and prescriptive advising, which is primarily focused on formal academic matters. In order to better understand the preference for advising relationships among college students, a model of developmental advising was formulated by Winston and Sandor (1984b). However, because of the increased numbers of special student populations such as women and minorities, it is difficult to ascertain the extent to which advising styles are received and desired by most students.
etd-06062008-170041
http://hdl.handle.net/10919/38376
http://scholar.lib.vt.edu/theses/available/etd-06062008-170041/
Advising styles preferred by African-American students enrolled in a two-year commuter college
oai:vtechworks.lib.vt.edu:10919/382952021-05-15T07:10:21Zcom_10919_5534col_10919_11041
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Goins, Lester Keith
author
1994-04-05
With serious skill shortages in the field of marketing expected during this time period, the increase in marketing opportunities will reinforce the importance of marketing education (U. S. Department of Labor, 1989). "Marketing education programs must be structured to match the diversity of marketing dealing with the principles, concepts, attitudes, and skills necessary to prepare students to work in retail, service, and other business environments." (National Marketing Education Curriculum Framework, 1987, p. 7).
The attitudes counselors have toward marketing education can have a major impact on course enrollment and students' planning of schedules including a combination of both academic and vocational courses (Washburn & McEwen, 1989). To date no evidence was found in the literature that shows what high school counselors think about the overall marketing education program.
The purpose of this study was to determine selected Virginia's secondary school counselors' perceptions towards Virginia's Marketing Education program. A mail survey was developed and distributed to 186 schools offering a Marketing Education program in Virginia.
When completing Section 1 of the survey instrument, participants supplied information concerning selected demographic variables. Data obtained from Section 1 were used to determine if differences existed between these selected demographic variables and Virginia's secondary school counselors' attitudes toward Virginia's Marketing Education program. When completing Section 2, participants used a 5-item Likert-type scale to indicate their attitudes toward Virginia's Marketing Education program. When completing Section 3--Virginia's secondary school counselors' knowledge of Virginia's Marketing Education program--participants selected true, false, or don't know to indicate their knowledge of Virginia's Marketing Education program.
Two hundred and eighty-five counselors in 62% of the schools offering a Marketing Education program in Virginia participated in the study. Research question 1 found that most of the counselors responding have a positive attitude toward Virginia's Marketing Education programs. Research question 2, seeking information on what secondary school counselors know about Marketing Education found that even though their attitudes may be positive, they are not knowledgeable about the Marketing Education program.
Research question 3 concerning selected demographic variables in relation to counselors' attitudes toward and knowledge of Marketing Education found that very small differences exist between the selected demographic variables and Virginia's secondary school counselors' attitudes toward and knowledge of Virginia's Marketing Education program. Conclusions and discussion, considerations for the study, recommendations, and suggestions for future research were described.
etd-06062008-164742
http://hdl.handle.net/10919/38295
http://scholar.lib.vt.edu/theses/available/etd-06062008-164742/
Selected secondary school counselors' perceptions of Virginia's marketing education programs
oai:vtechworks.lib.vt.edu:10919/387202021-12-14T18:46:50Zcom_10919_5534col_10919_11041
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Thompson, Thomas P.
author
1977
This study represents an attempt to develop a multivariate predictive model of professional job satisfaction. The model consists of socio-demographic work related, role conflict and bureaucratic variables. Multiple correlation and regression techniques are used in the data analysis. The sample consists of 308 professional fisheries biologists who were members of the American Fisheries Society in 1974.
The predictive model tested in this study was comprised of 14 independent variables related to social and demographic characteristics, role conflict and bureaucratic characteristics.
The results of this Study show that age, income, education, length of service and residence have a negligible impact on job satisfaction, Person-role conflict, intra-sender conflict, inter-sender conflict, and role overload comprise role conflict. These variables jointly explain 18 percent of variance in job satisfaction.
A multidimensional measure of perceptions of bureaucracy including technical qualifications, procedures, division of labor, hierarchy, and impersonality jointly explain 26 percent of the variance in job satisfaction.
etd-07082010-020250
http://hdl.handle.net/10919/38720
http://scholar.lib.vt.edu/theses/available/etd-07082010-020250/
A formulation and test of a multivariate predictive model of professional job satisfaction
oai:vtechworks.lib.vt.edu:10919/762112021-04-15T17:10:33Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Cilley, Richard Norman
author
1977
The purpose of this study was to compare the inadequacies of instructional space of public secondary vocational automotive mechanics laboratories in Virginia vocational technical centers and comprehensive high schools based upon the perceptions of automotive mechanics teachers. In addition, relationships of the rank orders of inadequacies were compared with the variables or (1) age or facility, (2) amount of teaching experience, (3) amount of trade experience, and (4) class size.
One hundred full-time teachers were utilised in this study. Twenty teachers were selected for the pre-survey and all one hundred teachers were utilized to gather data for the survey.
The following seven general questions were used to carry out the purpose of the study.
1. What are the inadequacies, in rank order, of the instructional space in automotive mechanics laboratories in vocational technical centers and in comprehensive high schools as perceived by teachers in these two types of schools?
2. What is the relationship between the rankings of inadequacies made by automotive mechanics teachers concerning instructional space in automotive mechanics laboratories in vocational technical centers and by teachers in comprehensive high schools?
3. What is the relationship between the rankings or inadequacies made by automotive mechanics teachers concerning instructional space in automotive mechanics laboratories by teachers housed in oldest facilities and by those teachers housed in newest facilities?
4. What is the relationship between the rankings of inadequacies made by automotive mechanics teachers concerning instructional space in automotive mechanics laboratories by teachers possessing the most teaching experience and by those teachers possessing the least teaching experience?
5. What is the relationship between the rankings or inadequacies made by automotive mechanics teachers concerning instructional space in automotive mechanics laboratories by teachers possessing the most trade experience and by those teachers possessing the least trade experience?
6. What is the relationship between the rankings of inadequacies made by automotive mechanics teachers concerning instructional space in automotive mechanics laboratories by teachers possessing the largest class size and by those teachers possessing the smallest class size?
7. What other factors contribute to inadequate instructional space 1n automotive meclumics laboratories?
The Spearman Rank-Order Correlation Coefficient method was utilized to compare data in this study. The levels of significance were tested at the .05 level.
Based upon the findings or this study the following conclusions were reached:
The rankings of inadequacies by automotive mechanics teachers in vocational technical centers and in comprehensive high schools were similar in the following areas:
1. Rankings of inadequacies.
2. Teachers housed in oldest facilities.
3. Teachers housed in newest facilities.
4. Teachers with least teaching experience.
5. Teachers with most trade experience.
6. Teachers with large class size.
7. Teachers with small class size.
The rankings were dissimilar in the following areas:
1. Teachers with most teaching experience.
2. Teachers with least trade experience.
http://hdl.handle.net/10919/76211
A comparison of inadequacies of instructional space of public secondary vocational automotive mechanics laboratories in Virginia vocational technical centers and comprehensive high schools as percived by automotive mechanics teachers
oai:vtechworks.lib.vt.edu:10919/377022021-05-12T07:08:05Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Lamanna, John Joseph
author
1993-04-15
Seriously emotionally disturbed adolescents in residential placement tend to act out aggressively. Such behavior often creates an atmosphere of intimidation and fear which contributes to the high stress, sense of incompetence, and frequent turn over of youth care staff. Formal training for these practitioners is limited in scope and availability. The training program, Therapeutic Crisis Intervention (TCI) (Budlong I 1983) which was the focus of this study, was designed to train youth care workers to deal with aggressive youth. It was anticipated that the program would increase youth care workers perceived sense of competence and reduce their perceived level of job stress.
The Occupational Stress Inventory (OST) and the Correctional Institution Environment Scale (CIES) were used to measure reported perceptions of competence. The Maslach Burnout Inventory (MBI) was used to measure reported perceptions of job stress.
Fifty one subjects, from four residential centers, were randomly assigned to a training group, a training group with follow-up, or a control group. A four way ANOVA was used to analyze main effects and single interactive effects of the classification variables (i.e., age, educational attainment and experience) with training.
In general, the analysis provided the following conclusions: (1) Neither reported self efficacy nor reported job stress were significantly impacted by TCI Training; (2) Although younger participants receiving training without follow-up reported a greater sense of depersonalization (i.e., higher perceived stress) and a lower sense of competence in using supportive skills than their older counterparts, younger participants who received follow-up in addition to the training, reported a lower sense of depersonalization (i.e., lower perceived stress) and a higher sense of competence in using support skills than their older counterparts; (3) Older participants reported lower levels of depersonalization after receiving training. Implications for these findings are discussed.
etd-05042006-164525
http://hdl.handle.net/10919/37702
http://scholar.lib.vt.edu/theses/available/etd-05042006-164525/
Effects of a crisis training program on reported job stress and self efficacy of youth care workers managing seriously emotionally disturbed adolescents in placement
oai:vtechworks.lib.vt.edu:10919/286152020-09-25T20:49:02Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Nam, Jong-Hoon
author
2005-07-29
The hair cell, a specialized cell in the inner ear, is responsible for hearing and balance. The hair cell is an exquisite sensor that captures mechanical stimuli and generates neurosensory signals. A theory called gating theory has been developed and widely used to analyze the experimental data of hair cell transduction. Despite increasing knowledge about molecular structures of hair cells, the mechanical model in the gating theory remained simple. Efforts to make the most of the recent findings regarding the hair cell structures led to the development of hair cell finite element (FE) model (Cotton & Grant, 2000, 2004a, b). I have extended this approach by adding channel kinetics and structural dynamics to the FE structural model of the hair cell.
I have expanded the previous static and passive model to a dynamic and active model. It is the most detailed hair cell structural model and includes up-to-date knowledge of the hair cell structure such as the stereocilia and various extracellular links. In order to observe the dynamic response of hair bundles in the endolymph fluid, I have included fluid drag in the model. Link nonlinearity has been added to reflect recent observations (Tsuprun 2003). The lateral links stiffen as they stretch and prevent contact between stereocilia when they compress. In addition to these structural features, I added channel kinetics such as the fast adaptation. In my study, the Ca²⁺ diffusion kinetics plays a key role in the hair cell adaptations. The Ca²⁺ association rate to the fast adaptation modulator is postulated to govern the fast adaptation. I assumed that two factors--the tip link tension and the Ca²⁺ concentration at the tip of stereocilia govern the hair cell mechanoelectric transduction.
My dissertation comprises three parts--structure, dynamics and mechanotransduction of hair cells. First, the mechanical properties of hair bundle were sought by comparing my FE model with other experiments. The quantified Young's modulus of stereocilia and the stiffness of tip link agree well with other recent estimates. The stiffness of other structural elements (upper lateral and shaft links) was newly estimated through this effort. Second, I established equations of motion for the hair bundle in the fluid. Two possible loading conditions to the hair bundle were simulated. Two different hair bundles were subjected to a point load and a load induced by fluid flow. The results showed that some vestibular hair cells' transduction might be dominated by the fluid-induced force. Finally, I observed the hair cell transduction in various stimulus conditions. The results showed that the hair cell's sensitivity highly depends on the stimulus method. The fluid-jet stimulus activated fewer channels than the glass fiber and made the hair cell less sensitive. A faster stimulus opened more channels and made the hair cell more sensitive. The resting tension in the tip link, which is believed to be controlled by the Ca²⁺ concentration, also affected the hair cell sensitivity. A higher resting tension, equivalent to a lower Ca²⁺ concentration, tended to make the hair cell more sensitive.
In conclusion, I developed a new tool to study the hair cell mechanoelectric transduction. My hair cell computational model enables us (1) to study how the hair cells' morphological variations are related to their function; (2) to investigate the hair cell mechanoelectric transduction at the single channel level, in silico, as opposed to the statistical approach; (3) to test the response of hair cells under in situ force boundary conditions.
etd-08112005-144849
http://hdl.handle.net/10919/28615
http://scholar.lib.vt.edu/theses/available/etd-08112005-144849/
Mechanoelectric transduction
Finite element
Hair cell
A Computational Study on the Structure, Dynamics and Mechanoelectric Transduction of Vestibular Hair cell
oai:vtechworks.lib.vt.edu:10919/770982020-10-16T21:01:25Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Cecere, Thomas E.
author
2012-05-21
Porcine circovirus associated disease (PCVAD) is currently one of the most economically important diseases facing the global swine industry. Porcine circovirus type 2 (PCV2) is the primary and essential causative agent of PCVAD, but development of clinical disease typically requires co-infection with other swine pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV). The specific mechanisms of co-infection that lead to clinical disease are not fully understood, but immune modulation by the co-infecting viruses is thought to play a critical role. The ability of dendritic cells (DC) infected with PRRSV, PCV2 or both to induce regulatory T cells (Tregs) was evaluated in vitro. DCs infected with PCV2 significantly increased CD4+CD25+FoxP3+ Tregs (p<0.05) and DCs co-infected with PRRSV and PCV2 induced significantly higher numbers of Tregs than with PCV2 alone (p<0.05). This Treg induction was found to be dependent on TGF-β and not IL-10. Further investigation of the in vivo swine immune response to acute co-infection with PCV2 and PRRSV failed to detect activation of Tregs in peripheral blood mononuclear cells (PBMCs) or bronchoalveolar lavage samples. The Treg response to in vitro and in vivo PRRSV challenge in pigs persistently infected with PCV2 or vaccinated against PCV2 was evaluated. There was no significant difference in Tregs in PBMCs among chronically PCV2-infected, vaccinated PCV2 challenged or negative control pigs. However, following in vitro infection of monocyte-derived dendritic cells with PCV2, PRRSV, or both viruses, co-cultured lymphocytes from chronically infected and PCV2 vaccinated pigs had significantly (p<0.05) decreased Treg expression in the virus infected groups compared to the negative controls. In separate experiments, pigs vaccinated against PCV2 and subsequently challenged with an attenuated PRRSV strain and its pathogenic parental strain developed increased CD4+CD25+FoxP3+ Tregs (p<0.05) in PBMC samples compared to uninfected controls, and this correlated with increased suppressor activity and IL-10 expression. The findings from these studies indicate that the interaction of PCV2 and PRRSV in swine modulates the host immune response mediated in part through the activity of Tregs. However, the extent to which Tregs orchestrate a dysregulated immune response in the pathogenesis of PCVAD in vivo remains to be determined.
etd-06052012-160901
http://hdl.handle.net/10919/77098
http://scholar.lib.vt.edu/theses/available/etd-06052012-160901/
regulatory T cell
porcine reproductive and respiratory syndrome viru
dendritic cell
porcine circovirus 2
Porcine circovirus associated disease: Modulation of the host immune response to PCV2 and PRRSV by regulatory T cells
oai:vtechworks.lib.vt.edu:10919/536722023-11-28T04:59:09Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Antenucci, Robert Nicholas
author
1988
Refined corn hulls (bran) were hydrolyzed with 30 mM oxalic acid in order to release carbohydrate fragments containing ferulic acid. The fragments which were high in ferulic acid also contained high levels of arabinose, xylose, and galactose, which are characteristic of sugars comprising corn hull hemicellulose side chains. Corn hull hydrolysate fragments were fractionated by chromatography to obtain purified feruloyl oligosaccharides. A The structure of the major feruloyl compounds were characterized by analysis of the products of acid, alkali, and enzyme hydrolysis, in combination with carbon-13 and 2D proton NMR spectroscopy. Three feruloyl oligosaccharides were identified as 5-0-(trans)-feruloyl-L-arabinofuranose (FA), 2-0-β-xylopyranosyl-(5-0-trans-feruloyl arabinofuranose) (FXA), and 0-(6-0-trans-feruloyl-α-D-galactopyranosyl)-(1-4) -O-β-D-xylopyranosyl-(1-2)-L-arabinofuranose (FGXA).
http://hdl.handle.net/10919/53672
Isolation and characterization of ferulic acid carbohydrate esters from corn hull (Zea mays)
oai:vtechworks.lib.vt.edu:10919/272232022-03-29T17:52:44Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Horton, Leanna Marie
author
2012-04-17
Work-related musculoskeletal disorders (WMSDs) remain a substantial problem in the workplace. Rotation, in which workers are rotated between tasks, is widely used as an administrative control, as it is considered to reduce WMSD risk through reducing physical exposures and increasing exposure variation. However, despite its widespread use, there is limited evidence that rotating between tasks is effective in reducing the risk of WMSDs. Inconsistencies in measured outcomes of rotation may be attributed to the variety of parameters involved in determining rotation schedules, including which tasks to include in a schedule, the rate at which workers rotate, and the order in which tasks are performed.
This research assessed the effects of rotation, specifically focusing on rotation frequency and task order, on muscle fatigue and performance when included tasks loaded the same muscle group. Twelve participants completed six experimental sessions in each of three studies, during which repetitive tasks were performed for one hour either with or without rotation. Each study simulated a different task, including static shoulder abduction, box lifting, and a light assembly task. Rotation occurred between lower and higher exertion levels, and each rotation schedule varied in both rotation frequency (rotating every 15 minutes vs. 30 minutes) and task order (starting with the lower vs. higher intensity task). Muscle fatigue was assessed through several measures, including electromyography, and ratings of perceived discomfort. Performance was assessed through the accuracy of shoulder moment output, the accuracy of box placement, or the speed of assembly completion.
As expected, rotation was effective in reducing fatigue compared to higher intensity tasks with no rotation, although it increased fatigue compared to the lower intensity with no rotation. While effects of rotation frequency and task order were seen on some measures, results across all three studies did not indicate consistent effects of either rotation frequency or task order on fatigue or performance. As such, the practical relevance of these rotation parameters and the likely impacts of rotation are not yet clear, and further assessments are needed. Such assessments should ideally involve longer durations, field studies, and/or more direct measures of injury or injury risk.
etd-04242012-143711
http://hdl.handle.net/10919/27223
http://scholar.lib.vt.edu/theses/available/etd-04242012-143711/
Performance
muscle fatigue
task order
rotation frequency
The Effects of Job Rotation Parameters on Localized Muscle Fatigue and Performance: An Investigation of Rotation Frequency and Task Order
oai:vtechworks.lib.vt.edu:10919/403282023-07-29T03:49:40Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Tran, Tuan A.
author
1996
The objective of this work is to investigate new signal processing techniques for optical fiber sensors that utilize the phase information of the electromagnetic field. Research concentrated on Fourier transform spectroscopy as a means for capturing wavelength encoded information from the fiber sensor. Classical spectral analysis utilizing the Fourier transform as a mathematical foundation for relating a time or space signal to its frequency-domain representation was shown to be inadequate for mitigating the bias errors caused by harmonic distortions. A modified spectral estimation algorithm is presented to overcome some of the practical issues while maintaining the high spectral resolution characteristic of the classical technique. This research also showed that unlike in free-space propagation, an optical signal propagating through a fiber waveguide, even over short distances, can experience significant phase modulation noise. A number of chromatic distortion mechanisms including modal interference, mode coupling due to periodic perturbations such as microdeformation and macrobends, and mode field diameter variations are addressed. We treated these issues by employing both theoretical simulation and experimental data. Coupled-mode formalism based upon approximated field solutions is used in the theoretical analysis. An extensive error analysis was also performed to determine how waveguide and noise distortion affect the performance of the spectral estimation algorithm.
etd-11102005-141134
http://hdl.handle.net/10919/40328
http://scholar.lib.vt.edu/theses/available/etd-11102005-141134/
Digital spectral analysis and adaptive processing techniques for phase modulated optical fiber sensors
oai:vtechworks.lib.vt.edu:10919/518132022-02-22T20:39:46Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Philips, Christopher Robin
author
2013-09-02
Integrated pest management (IPM) is defined as an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. Integrated pest management programs use current, comprehensive information on the life cycles of pests and their interactions with host plants and the environment. This information, in combination with available pest control methods, is used to manage pest populations by the most economical means, and with the least possible hazard to people, property, and the environment. True IPM takes advantage of all appropriate pest management options including, as appropriate, the judicious use of pesticides. It is currently estimated the IPM in its full capacity is being practiced on less than ten percent of the agricultural land in the U.S.
The primary objective of this research was to evaluate land management decisions and create new tools to promote a true IPM approach and encourage growers to reevaluate their method of insect control. To accomplish this I developed new predictive tools to reduce or eliminate unnecessary insecticide application intended to target cereal leaf beetle in wheat, and assessed a conservation biological control technique, farmscaping, to determine its true impact on lepidopteran pest suppression in collards.
vt_gsexam:1583
http://hdl.handle.net/10919/51813
Oulema melanopus
cereal leaf beetle
CLB
small grains
wheat
IPM
integrated pest management
degree-days
predictive model
Food webs and phenology models: evaluating the efficacy of ecologically based insect pest management in different agroecosystems
oai:vtechworks.lib.vt.edu:10919/1142352023-04-01T07:31:54Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Sepasdar, Reza
author
2021-10-07
This dissertation studies the micromechanical behavior of high-performance carbon fiber-reinforced polymer (CFRP) composites through high-fidelity numerical simulations. We investigated multiple transverse cracking of cross-ply CFRP laminates on the microstructure level through simulating large numerical models. Such an investigation demands an efficient numerical framework along with significant computational power. Hence, an efficient numerical framework was developed for simulating 2-D representations of CFRP composites' microstructure. The framework utilizes a nonlinear interface-enriched generalized finite element method (IGFEM) scheme which significantly decreases the computational cost. The framework was also designed to be fast and memory-efficient to enable simulating large numerical models. By utilizing the developed framework, the impacts of a few parameters on the evolution of transverse crack density in cross-ply CFRP laminates were studied. The considered parameters were characteristics of fiber/matrix cohesive interfaces, matrix stiffness, $0^{circ}$~plies longitudinal stiffness. We also developed a micromechanical framework for efficient and accurate simulation of damage propagation and failure in aligned discontinuous carbon fiber-reinforced composites under loading along the fibers' direction. The framework was validated based on the experimental results of a recently developed 3-D printed aligned discontinuous carbon fiber-reinforced composite as the composite of interest. The framework was then utilized to investigate the impacts of a few parameters of the constitutive equations on the strength and failure pattern of the composites of interest. This dissertation also contributes towards improving the computational efficiency of CFRP composites' simulations. We exhaustively investigated the cause of a convergence difficulty in finite element analyses caused by cohesive zone models (CZMs) which are commonly used to simulate fiber/matrix interfaces in CFRP composites. The CZMs' convergence difficulty significantly increases the computational burden. For the first time, we explained the root of the convergence difficulty and proposed a simple technique to overcome the convergence issue. The proposed technique outperformed the existing methods in terms of accuracy and computational cost. We also proposed a deep learning framework for predicting full-field distributions of mechanical responses in 2-D representations of CFRP composites based on the geometry of the microstructures. The deep learning framework can be used as a surrogate to the expensive and time-consuming finite element simulations. The proposed framework was able to accurately predict the stress distribution at an early stage of damage initiation and the failure pattern in representations of CFRP composites microstructure under transverse tension.
vt_gsexam:32801
http://hdl.handle.net/10919/114235
Micromechanics
CFRP Composites
FE Simulations
Deep Learning
CNN
Micromechanical Behavior of Fiber-Reinforced Composites using Finite Element Simulation and Deep Learning
oai:vtechworks.lib.vt.edu:10919/387672021-04-26T17:42:15Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Sipon, Ahamad B.
author
1996-08-29
The purpose of this study were: 1) to determine whether support exists for Herzberg's two factor theory in an educational setting in Malaysia; 2) to determine and describe the job satisfaction of polytechnic instructors in Malaysia and 3) to examine the relationships between job satisfaction and selected personal charactoristics contextual characterisitcs, and students perceptions of instructors' teaching effectiveness.
etd-07112007-092857
http://hdl.handle.net/10919/38767
http://scholar.lib.vt.edu/theses/available/etd-07112007-092857/
Herzberg's Theory
job satisfaction
teaching effectiveness
instructors
Malasia
The applicability of Herzberg's two-factor theory to the job satisfaction of Malaysian polytechnic instructors
oai:vtechworks.lib.vt.edu:10919/380812022-03-29T18:09:32Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Hale, Alan A.
author
1996-12-15
Modem high-performance military aircraft are subjected to rapid flight maneuvers which place great operational demands on their compression system by producing highly distorted flow to the compressor. Inlet distortion generally reduces the engine compressor stability margin and may induce compressor surge at high rotational speeds, or rotating stall at lower rotational speeds. Therefore, a computational fluid dynamics (CFD) based compressor simulation would be very useful in the design, test, and analysis process since it gives additional information with inexpensive modifications.
A new CFD simulation called the Turbine Engine Analysis Compressor Code (TEACC) was designed to meet these requirements. This code solves the compressible 3D Euler equations modified to include turbomachinery source terms which simulates the effect of the compressor blades. The source terms are calculated for each blade row by the application of a streamline curvature code. A methodology was developed for calculating turbomachinery source terms and distributing them axially, radially, and circumferentially while maintaining a sensitivity to strong inlet distortion.
TEACC was compared with experimental data from NASA Rotor 1 B, a transonic rotor. Experimental data from Rotor 1 B were available for comparison with TEACC results for a clean inlet and for an inlet distortion produced by a 90-degree, one-per-revolution screen. TEACC results compared very well with experimental data with a clean inlet. Comparison with experimental data with inlet distortion demonstrated TEACC's ability to characterize the compressor overall, and to accurately predict the magnitude and shape of exit total temperature and exit total pressure in the distorted region. TEACC calculated the overall character of exit total pressure and exit total temperature in the nondistorted region, identifying the location of the largest value just after the inlet distortion and the decrease in exit total values through the nondistorted region in the direction of rotation.
etd-06062008-154548
http://hdl.handle.net/10919/38081
http://scholar.lib.vt.edu/theses/available/etd-06062008-154548/
distortion
compressor
three-dimensional
Simulation
A three-dimensional turbine engine analysis compressor code (TEACC) for steady-state inlet distortion
oai:vtechworks.lib.vt.edu:10919/737522020-11-05T20:55:20Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Bivens, Laura R.
author
2016-07-01
A variety of individual and geographic factors influence the mix of formal and informal services utilized by older adults and their families along the continuum of care. This study focuses on a specific rural population in the United States - Central and South Central Appalachia, which experiences the triple jeopardy of vulnerable people (older adults) in vulnerable places (rural Appalachia), with cultural views and beliefs that may negatively impact the care they receive. Using Andersen’s behavioral model of service utilization, Soldo’s supplementation model of care, and Bronfenbrenner’s ecological theory as the theoretical frameworks, data from the Older Families in Rural Communities: Personal and Social Influences on Service Use project and the United States 2000 Census were used to examine the utilization of informal and formal care services and nursing home placement risk in a rural Appalachian population. The main goals of this research were to (a) examine the relationships among individual and geographic characteristics and determine how those relationships affect the utilization of informal-formal care-mix, and (b) determine how the informal-formal care-mix is associated with nursing home placement risk in older adults living in rural southwest Virginia. Two separate analyses were completed in order to address the research objectives. First, a multinomial regression model, including both individual and geographic data, was used to predict care-mix. Second, after calculating the outcome variable “nursing home placement risk” via a derived logistic regression equation, a log-linear analysis with a 3×4 contingency table was computed in order to understand the association between care-mix and nursing home placement risk. Results indicate that disparities in sex and poverty level in an area that already suffers from healthcare disparities significantly affect the type of care an older adult receives. When formal care was utilized, it was more often added to existing informal care systems, supplementing them, rather than replacing them. The type of care-mix individuals received was also associated with nursing home placement risk. Specifically, when informal support was the only source of care, nursing home placement risk was significantly higher than when informal-formal care-mix was received. Research and policy implications for disparity-ridden areas are discussed.
vt_gsexam:7856
http://hdl.handle.net/10919/73752
Appalachia
Nursing Home Placement Risk
Informal Care
Formal Care
Older Adults
Rural
Care Patterns
Individual and Geographic Predictors of Formal and Informal Care Patterns and Nursing Home Placement Risk among Rural Appalachian Elders
oai:vtechworks.lib.vt.edu:10919/379882022-03-14T21:49:27Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Berends, Corey L.
author
1996-08-04
In this study, low density polyethylene (LDPE) and polyethylene terephalate (PETE) resin beads were ground to a coarse powder and exposed to sterilization treatments applied to the food contact surface of packaging materials used in aseptically processed and packaged food. Electron paranlagnetic resonance (EPR) analyzed free radical (-CH2CHCH=CHCHz-) production on the surface of LDPE exposed to heat (107°C) and treatments of heat (107°C) + 30% hydrogen peroxide solution (H20 2). As the temperature was raised from 100° to 200°C, peak intensity of carbon radicals produced gradually increased. The sensitivity of EPR prevented detection of free radicals on LDPE, exposed to H20 2 treatment, due to residual peroxide and H20 condensation on the surface of LDPE. D-limonene was placed in 12ml sealed glass vials containing a sodium citrate buffer solution (pH=3.7), under atmospheric O₂ (21%) conditions. Oxidation of d-limonene, placed in intimate contact with untreated, HzOz treated, and ultraviolet (VV) light (650mW/cm2) treated LDPE for 15 weeks, was measured to determine the capacity of an oxidized polymer to initiate autoxidation. The oxidation of d-limonene in vials containing no polymer was also measured. Production of carvone and carveol were used as an index for oxidation. No polymer and UV treated samples showed significantly (P<0.05) higher levels of calVone and calVeol than samples containing untreated and HzOz treated LDPE. Samples containing no polymer oxidized d-limonene at the highest rate, but not significantly faster than solutions containing UV treated LDPE. Accumulation of carvone and carveol was zero order.
etd-06062008-151152
http://hdl.handle.net/10919/37988
http://scholar.lib.vt.edu/theses/available/etd-06062008-151152/
polymer oxidation
free radicals
hexanal
d-limonene
Stability of aseptically packaged food as a function of oxidation initiated by a polymer contact surface
oai:vtechworks.lib.vt.edu:10919/290202021-11-04T20:36:26Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Belote, R. T.
author
2008-09-05
For this dissertation, I measured how plant communities in Appalachian forests responded to disturbances caused by forest management activities. I had two primary objectives including (1) testing theories of biological diversity and invasions by nonnative species; and (2) providing empirical data that will help guide the sustainable use of forest resources. This work is part of the Southern Appalachian Silviculture and Biodiversity (SASAB) experiment that was established in the early 1990s to investigate ecosystem responses to a gradient of timber harvesting disturbances. Ranging from undisturbed controls to silvicultural clearcuts, the disturbance gradient is replicated at sites located throughout the Appalachian mountains of Virginia and West Virginia. The plant community was sampled across a wide range of spatial scales (2 hectares to 1 m2) using a nested sampling design and was also sampled at three times including pre-disturbance, one year post-disturbance, and ten year post-disturbance.
For one element of the study I tested modern theories of biological invasions and investigated how the forest disturbance gradient interacted with species diversity to influence invasion by nonnative species (Chapter 2). Contrary to popular ecological theories of biotic resistance, the most diverse sites tended to be more easily invaded following intense canopy disturbance. Interestingly, none of the sites in this study were dominated by invasive plants, which led me to ask whether dominant tree species in forests provided resistance to nonnative plant establishment and growth through the quality of the litter they produce. I also asked how might animals that are known to alter litter layers interact with dominant tree species to influence plant invasions. Therefore, I conducted an experiment investigating how changes in litter from dominant tree species and invasions by nonnative earthworms might influence invasibility of forests using forest floor mesocosms (Chapter 3). I found that plant invasion was inhibited by native oak litter even when earthworms were present, suggesting that oak forests may resist plant invasions via oak tree litter. In contrast, plant invasion was greater under invasive tree litter and earthworm activity tended to facilitate invasive plant success only under invasive tree litter.
I was also interested in understanding how disturbance might alter relationships between local and regional diversity. The long-term data of the forest disturbance experiment allowed me to investigate how local species richness is mediated by regional species richness after disturbance and during forest community development (Chapter 4). Local richness depended strongly on regional richness only after disturbance via colonization of species, but this relationship changed during forest aggradation. These results suggest that regional species pools are important to maintain local diversity following disturbance, but that local interactions (through canopy closure of dominant trees) exert control over species diversity during community reorganization.
Lastly, I tested current theories on how diversity influences compositional stability after disturbance (Chapter 5). Disturbance consistently resulted in decreased compositional stability, but diversity was associated with stability in complex ways, which depended on how stability was measured and at what scale. Species-rich areas were in some instances less stable; in other instances areas with intermediate levels of diversity were more stable. These results suggest that disturbance causes shifts in species composition via colonization, but the ways in which diversity of sites influences compositional stability is complex and depends on methods used and the scales of observation. Taken together, these results suggest that disturbance influences invasibility, species saturation, and compositional stability of ecological communities. These properties change immediately following disturbance, and during forest development and canopy closure. Data from this project were useful in testing existing theories of community ecology, and may ultimately prove useful for forest managers as they decide how to protect biodiversity while planning for other uses of forest resources. Overall, these results suggest that colonization of species is the primary process driving plant community patterns in Appalachian forests following disturbance.
etd-09182008-232754
http://hdl.handle.net/10919/29020
http://scholar.lib.vt.edu/theses/available/etd-09182008-232754/
forest management
introduced species
earthworms
diversity-stability
diversity-invasibility
Appalachian Mountains
species richness
silviculture
Diversity, Invasibility, and Stability of Appalachian Forests across an Experimental Disturbance Gradient
oai:vtechworks.lib.vt.edu:10919/282532022-02-22T19:39:24Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Eisenback, Brian Matthew
author
2008-06-27
Prey-mediated effects of imidacloprid were evaluated for Laricobius nigrinus Fender and Sasajiscymnus tsugae Sasaji and McClure after feeding on hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). Two methods were evaluated for detecting imidacloprid in hemlock tissues: a commercially available enzyme linked immunoassay (ELISA) kit and a high performance thin-layer chromatography technique for detecting and quantifying imidacloprid residues in hemlock wood and needle tissues. ELISA is advantageous because of its cost, sensitivity, and ease of use. However, matrix effects in the form of false positives and overestimated imidacloprid concentrations were evident in hemlock wood and needle tissue extracts. Matrix effects could be reduced by dilution with water, effectively raising the lower detection range of the kit from 0.2 to 200 ppb. High performance thin-layer chromatography was accurate, quick, easy to use, and matrix effects were not evident. However, the technique is sensitive in the lower ppm range and tissue samples from field-treated hemlocks are often in the ppb range, making this technique less desirable than more sensitive analytical methods.
Lethal and sublethal effects on both predators were evident after eastern hemlock branches infested with HWA were spiked with imidacloprid in the laboratory. HWA mortality increased with dosage and time, and its 30 d LC50 was determined to be 242 ppb. Both predator species exhibited reduced survivorship and fitness parameters after feeding on HWA from the treated branches. In a topical application bio-assay, 6 d imidacloprid LD50 values for L. nigrinus and S. tsugae were 2.43 and 1.82 µg/g, respectively. Imidacloprid and its major metabolites in hemlock tissues were analyzed by liquid chromatography-tandem mass spectrometry. Imidacloprid recovery from beetle cadavers was correlated with beetle mortality from feeding on treated hemlock branches. Olefin was the primary imidacloprid metabolite recovered from hemlock wood tissues.
When predators fed on HWA from field-treated trees, impacts on survivorship and fitness were variable. In 2005, significantly higher proportions of both species of beetles were affected by feeding on control branches compared with treated branches. In 2006, beetles feeding on HWA from some of the trees treated in the field exhibited longer fliptimes compared with beetles feeding on controls, although beetle mortality was not significant among treatements. In the field, imidacloprid controlled HWA populations 1-3 years post-treatment. Hemlock health improved in the highest dosage group, with significantly greater lengths of new shoots compared with shoots from control trees. Eastern hemlock trees primarily metabolized imidacloprid into the olefin metabolite, which can have increased insecticidal toxicity compared with imidacloprid. Imidacloprid was detected in beetle cadavers after feeding on HWA from treated branches, suggesting that prey-mediated impacts of systemic imidacloprid are possible on nontarget predators. However, because of HWA's sensitivity to imidacloprid, in field situations predators are more likely to be affected by reduced adelgid density and quality.
etd-07102008-125307
http://hdl.handle.net/10919/28253
http://scholar.lib.vt.edu/theses/available/etd-07102008-125307/
biological control
ELISA
Adelges tsugae
Tsuga canadensis
non-target effects
Prey-mediated effects of imidacloprid on Laricobius nigrinus (Coleoptera: Derodontidae) and Sasajiscymnus tsugae (Coleoptera: Coccinellidae), two predators of hemlock woolly adelgid
oai:vtechworks.lib.vt.edu:10919/378062022-03-01T19:10:56Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
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Cai, Rongman
author
2012-05-02
Pseudomonas syringae is a common foliar plant pathogenic bacterium that causes diseases on many crop plants. We hypothesized that today's highly virulent P. syringae crop pathogens with narrow host range might have evolved after the advent of agriculture from ancestral P. syringae strains with wide host range that were adapted to mixed plant communities. The model tomato and Arabidopsis pathogen P. syringae pv. tomato (Pto) DC3000 and its close relatives isolated from crop plants were thus selected to unravel basic principles of host range evolution by applying molecular evolutionary analysis and comparative genomics approaches. Phylogenetic analysis was combined with host range tests to reconstruct the host range of the most recent common ancestor of all analyzed strains isolated from crop plants. Even though reconstruction of host range of the most recent common ancestor of all analyzed strains was not conclusive, support for this hypothesis was found in some sub-groups of strains. The focus of my studies then turned to Pto T1, which was found to represent the most common P. syringae lineage causing bacterial speck disease on tomato world-wide. Five genomes were sequenced and compared to each other. Identical genotypes were found in North America and Europe suggesting frequent pathogen movement between these continents. Moreover, the type III-secreted effector gene hopM1 was found to be under strong selection for loss of function and non-synonymous mutations in the fliC gene allowed to identify a region that triggers plant immunity. Finally, Pto T1 was compared to closely related bacteria isolated from snow pack and surface water in the French Alps. Recombination between alpine strains and crop strains was inferred and virulence gene repertoires of alpine strains and crop strains were found to overlap. Alpine strains cause disease on tomato and have relatively wider host ranges than Pto T1. The conclusion from these studies is that Pto T1 and other crop pathogens may have evolved from ancestors similar to the characterized environmental strains isolated in the French Alps by adapting their effector repertoire to individual crops becoming more virulent on these crops but losing virulence on other plants.
etd-05132012-234836
http://hdl.handle.net/10919/37806
http://scholar.lib.vt.edu/theses/available/etd-05132012-234836/
ancestral state reconstruction
fliC
host range evolution
Pseudomonas syringae
molecular evolution
HopM1
recombination
phylogeography
microevolution
most recent common ancestor
phylogenetic tree
population genetics
New hypotheses about the origin of Pseudomonas syringae crop pathogens
oai:vtechworks.lib.vt.edu:10919/398992021-04-15T17:11:05Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
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Porter, Nancy M.
author
1990
This study was designed to empirically test a conceptual model and measurement of financial well-being as a function of (a) personal characteristics; (b) objective attributes, quantitative indicators of the financial domain and financial management behaviors of respondents; (c) perceived attributes, subjectively assessed life conditions and perceptions of financial situation; and (d) evaluations of financial situation using various reference points as standards of comparison. Two sub-problems were investigated in the study: (a) Which group of attributes, personal characteristics, objective attributes, perceived attributes, or evaluated attributes, significantly explains variance in perceived financial well-being?; and (b) Which individual attributes significantly explain variance in perceived financial well-being?
A mail survey was conducted from October of 1989 through January of 1990 with a randomly selected sample of Virginia citizens (N = 1,500). After an initial mailing and two follow-up mailings, 529 questionnaires were returned of the 1,450 that were received by respondents, providing a 36.5% total return rate (529/1,450). Twenty-three questionnaires were blank or unusable, yielding a useable return rate of 34.9% (506/1,450). Demographic characteristics of the sample were similar to those of the population of Virginia citizens.
Financial well-being, as measured by an adaptation of Cantril's (1965) 11-point self-anchoring striving scale, was the dependent variable. All of the independent variables regressed on the dependent variable produced an R 2 of .71, which was statistically significant (p < .01). Removing each group of attributes individually from the regression equation resulted in a significant (p < .01) decrease in the resulting adjusted R2s as computed by F ratios. All attribute groups were determined to be essential to the measurement of financial wellbeing.
Individual variables with a significant t ratio (p < .05) were the Perceived Attribute Index, Index of Well-Being, and full-time employment status. The results of the study supported the conceptual model. Results clearly verified the measurement of financial well-being as a function of personal characteristics, objective attributes, perceived attributes, and evaluated attributes.
etd-10142005-135742
http://hdl.handle.net/10919/39899
http://scholar.lib.vt.edu/theses/available/etd-10142005-135742/
Testing a model of financial well-being
oai:vtechworks.lib.vt.edu:10919/542282023-08-13T19:27:35Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
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Lampkins, Carlton
author
1989
Fairfax County Public Schools (FCPS) are located in the Commonwealth of Virginia, approximately fifteen miles south of Washington, D.C. This school system is the tenth largest in the United States and it has a student population of approximately 130,000. Because of the size of the FCPS system, it is divided into four administrative areas-Area I, Area II, Area III and Area IV.
Area II of FCPS has a student population of approximately 26,000 students, and of those 26,000 students, approximately 9 percent of them are of Hispanic origin. This English as a Second Language (ESL) population is of special interest to the school system because these students often do not possess the communication skills necessary for matriculation/ graduation. Therefore, their academic performance is frequently below average. This poses problems and raises concern for the educators that serve them.
As a part of FCPS' minority achievement program, which began in 1983, an Area II staff member initiated a two-part training program entitled, "Intensive Spanish for Educators" patterned on a similar program used with Arlington County, Virginia educators. The program carries university credit and provides a forum for the presentation of oral and aural Spanish language skills, as they relate to relevant school situations and Hispanic cultural awareness.
Based on the perceptions of the program participants, this dissertation represents an evaluation of the "Intensive Spanish for Educators" program, utilizing information obtained from on-site observations of class sessions, examination of planning documents/proposals/syllabi/etc., interviews with the program administrator/coordinators, program trainers and randomly selected program participants, and a questionnaire.
The results of this evaluative study indicated that the Intensive Spanish for Educators training program is a worthwhile and valuable program because it provides the opportunity for teachers, pupil personnel staff and administrators to acquire knowledge and skills in an area that can be used on a daily basis, it is well planned and it is sanctioned by the Area II Superintendent. The participants were enthusiastic about being in the program and felt the program should be strongly recommended, but not made mandatory.
http://hdl.handle.net/10919/54228
An evaluative study of the perceptions of school personnel towards a training program involving the comprehension of basic Spanish language and culture
oai:vtechworks.lib.vt.edu:10919/800202023-08-13T19:27:32Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Yock, Carla M.
author
1989
The major purpose of this study was to study the perceptions and expectations of school board members regarding turnover in the superintendency of the public school systems. Data were gathered regarding the frequency of superintendency turnover and compared to board turnover. The study sought to collect data concerning board satisfaction with the superintendent, priority issues the board expected the superintendent to address, the kind of experience board members preferred in their superintendent, the ideal length of superintendency tenure, and at what point school board members think that a superintendent's contract should be terminated. These data were then crosstabbed with selected demographic variables.
Descriptive research methodology was utilized in this study. A nationwide sample of school board members was identified from a list of 53,247 board members provided by the National School Boards Association. The study was completed using a stratified random sampling technique by state. Of the 94,716 board members in the population, 11,992 or 12.6% were surveyed. The response rate was 18%. The study was sponsored by The American School Board Journal, published by the National School Boards Association, the national professional organization for school board members in the United States.
http://hdl.handle.net/10919/80020
Superintendency turnover: a national survey of the perceptions and expectations of school board members
oai:vtechworks.lib.vt.edu:10919/871782020-09-25T20:32:41Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Munday, Edgar Gray
author
1984
Biaxial stress fatigue data is carefully examined in order to determine how much foundation exists for a rational approach to classical stress-based fatigue limit analysis involving biaxial stress components. A review is given of the methods presently in vogue, and new methods are suggested for obtaining equivalent mean and equivalent alternating stresses.
Some groundwork is laid for the consideration of stress gradient influence on fatigue behavior. There are also some observations concerning the Distortional Energy and Tresca criteria and how they are incorporated in fatigue design procedures.
The work is restricted to cases in which the alternating principal stress axes have fixed orientation.
http://hdl.handle.net/10919/87178
Fatigue limit analysis involving biaxial stress components
oai:vtechworks.lib.vt.edu:10919/545122023-08-13T19:27:37Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
dc
Demeio, Lucio
author
1989
In this work, we investigate numerically the evolution of perturbed Vlasov equilibria. according to the full nonlinear system with particular emphasis on analyzing the asymptotic states towards which the system evolves. The simulations are carried out with the numerical code that we have implemented on the Cray X-MP of the Pittsburgh Supercomputing Center and which is based on the splitting scheme algorithm. Maxwellian symmetric and one-sided bump-on-tail and two-stream type of equilibrium distributions are considered: the only distribution which seems to evolve towards a BGK equilibrium is the two-stream while the asymptotic states for the other distributions are better described by superpositions of possible BGK modes. Perturbations with wave-like dependence in space and both symmetric and non-symmetric dependence on velocity are considered.
For weakly unstable modes, the problem of the discrepancy between different theoretical models about the scaling of the saturation amplitude with the growth rate is addressed for the first time with the splitting scheme algorithm. The results are in agreement with the ones obtained in the past with less accurate algorithms and do not exhibit spurious numerical effects present in those.
Finally, collisions are included in the splitting scheme in the form of the Krook model and some simulations are performed whose results are in agreement with existing theoretical models.
http://hdl.handle.net/10919/54512
Nonlinear evolution of Vlasov equilibria
oai:vtechworks.lib.vt.edu:10919/543152020-09-28T13:46:32Zcom_10919_5534col_10919_11041
00925njm 22002777a 4500
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Frank, Lawrence H.
author
1986
http://hdl.handle.net/10919/54315
Effects of visual display and motion system delays on operator performance and uneasiness in a driving simulator
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