ETDs: Virginia Tech Electronic Theses and Dissertations

Permanent URI for this community

https://hdl.handle.net/10919/5534

Virginia Tech has been a world leader in electronic theses and dissertation initiatives for more than 20 years. On January 1, 1997, Virginia Tech was the first university to require electronic submission of theses and dissertations (ETDs). Ever since then, Virginia Tech graduate students have been able to prepare, submit, review, and publish their theses and dissertations online and to append digital media such as images, data, audio, and video.

University Libraries staff are currently digitizing thousands of pre-1997 theses and dissertations and loading them into VTechWorks. Most of these theses and dissertations are fully available to the public, but we will, in general, honor requests by the item's author to restrict access to Virginia Tech only. See our process for Requesting that Material be Amended or Removed.

To search all Virginia Tech print and digital theses and dissertations, use the University Libraries ETD resource guide.

Materials that are restricted to Virginia Tech only may be requested via your own university or public library's Interlibrary Loan program or through the VTechWorks request form that appears when you try to access the item. You might also be able to obtain a copy of the work through ProQuest's database of theses and dissertations. If you are on a Virginia Tech campus but are unable to find the pre-1997 thesis or dissertation you are seeking in VTechWorks, you may also be able to order a physical copy from library storage. Please check the library catalog at http://www.lib.vt.edu/ for physical copies.

The guidelines that apply to Virginia Tech's graduate students as ETD authors can be found at http://guides.lib.vt.edu/ETDguide.

Browse

Now showing 1 - 20 of 149

Adapting selected soil and water engineering technology to Thailand conditions
Weerasopone, Kraisorn (Virginia Polytechnic Institute and State University, 1973)
Techniques were developed for the purpose of applying soil and water conservation structure designs utilized in the United States for use in Thailand. Design parameters currently being used in the United States were first studied and evaluated as to their development and application. The range of application of the various soil and water conservation structures were determined. This process included an evaluation of the soil types, land use, topography, and climatic factors in terms of their effect on the types of soil and water conservation structure designs to be utilized. Since the parameters may act separately or in various combinations, design limits are essential for each one. In the second step of the study, all available survey data applicable in characterizing these same parameters in Thailand were assembled and analyzed for each region. From this analysis, design ranges and the limits for each factor were estimated, based on the research and experience in the United States. Particular attention focused on the research of Beasley and the research compiled in the Engineering Field Manual. Finally, these estimated design values for Thailand's conditions were substituted in United States formulae. From these substitutions, other design procedures for model designs of several major engineering soil and water conservation structures were developed.
Aflatoxin in corn drying
Reid, John F. (Virginia Polytechnic Institute and State University, 1982)
Relationships defining conditions conducive for aflatoxin production by Aspergillus f!avus were coupled with a non-equilibrium corn drying model and used to determine constant drying conditions indicating a potential for aflatoxin development. Airflow rates of 0.8 to 16 m³/min/m³ in 18, 20, 22% initial wet-basis moisture content corn were simulated in a drying model at temperatures from 12.7 to 40.6°C and relative humidities from 5 to 95%. The potential for aflatoxin development was expressed in terms of the critical relative humidities at a given temperature and airflow rate. All relative humidities simulated above the critical relative humidity also indicated a potential for aflatoxin development. Typical drying conditions for high airflow, low temperature drying systems found in Virginia were simulated to identify potential aflatoxin problems. A sensitivity analysis evaluated the importance of temperature, time, and relative humidity on the drying conditions indicating a potential for aflatoxin development. The critical relative humidities for aflatoxin development reached high levels when drying was simulated at high airflow rates and/or low initial corn moisture contents. The results of the sensitivity analysis performed indicated that relatively small changes in the criteria for potential aflatoxin development significantly affected the critical relative humidities. The time criterion for initial aflatoxin development used in the model exhibited the greatest sensitivity. Drying data from drying tests performed in November, 1981 were used to validate the corn drying model.
Allowable bending strength enhancement of 2 by 4 lumber by tension and compression proofloading
Heatwole, Edwin L. (Virginia Polytechnic Institute and State University, 1987)
Research has established that correlations exist between bending and tension, and bending and compression strength of lumber. Because of this correlation, improvement in bending strength may be realized from proofloading in tension or compression. The data utilized in a reliability analysis was from Galligan et al. (1986) that characterized the properties of 2-inch softwood dimension lumber with regressions and probability distributions. Randomly selected groups of 2 by 4 1650f-1.5E Hem-fir and No.2 KD Southern Pine were evaluated for bending strength. One group from each species was selected as a control and tested in bending. The other groups were proofloaded in tension and compression at two stress levels and the survivors were tested in bending to failure. Based on the concept of equal reliability and utilizing the load distributions from Thurmond (1986), the tensile and compressive proofloaded strength distributions were compared to the control. The probability of failure for the control group is found, then with an iterative approach, the bending strength values of the proofloaded sample distribution are artificially altered by a factor K until the probabilities of failure for the proofloaded and control groups are similar. The K is a shift factor relating the amount the proofloaded strength distribution must be shifted on the x-axis to give the same reliability as the control. Simple 5th percentile comparisons, the advanced first order second moment (AFOSM) and numerical integration analysis methods were used to evaluate increases in allowable bending strength from proofloading in tension and compression. Proofloading in tension or in compression both produced significant increases in allowable bending strength for the Hem-fir grade. Proofloading in tension to a target 15 percent breakage level, or 2,838. psi, yielded for the survivors an increase of 72 percent in allowable bending strength. The allowable bending strength increased 60 percent due to a compressive proofloading to a target 15 percent breakage level. The allowable bending strength increased as the proofloading level increased for both tension and compression proofloading with the Hem-fir grade. The southern pine visual stress grade did not show a consistent trend between proofloading level and improvement in allowable bending strength. The lack of a trend between proofloading level and allowable bending strength was attributed to possible sampling error. The fifth percentile analysis method, the AFOSM method and numerical integration method were compared. For lumber strength comparisons, a simple fifth percentile analysis was not the preferred method. The AFOSM method and the numerical integration method provided identical results in terms of their application in adjusting allowable bending stresses. It was not possible to show that the approximate AFOSM method can be used exclusively in lieu of the numerical integration method for reliability calculations.
Analysis and computer program for non-prismatic continuous beam and floor section
Maghsood, Javad (Virginia Polytechnic Institute, 1967)
This thesis is based on research by the VPI Agricultural Engineering Department in residential floor structures. Slope-deflection equations and computer programs were developed for theoretically analyzing continuous non-prismatic T-beams. Residential floor systems were treated as a series of three-span continuous T-beams. Cross-sectional area of the stem of the T-beam was doubled over interior supports and for 3 ft. on either side. Computer programs were used for calculating moment, shear, deflection, and rotation over supports for beams with simply supported ends and with one end cantilevered. The computer was also used for determining span ratios that would result in equal maximum deflections when all three spans were subjected to uniformly distributed loads. Several tests were conducted on a full-scale 8 ft. by 48 ft. floor section. Deflection from the experimental tests on continuous joist alone and with plywood subfloor were statistically compared with theoretical deflections. In one case the theoretical equation did not adequately describe the center span and had to be rewritten in order to show no significant difference between theoretical and experimental deflection. In one experiment symmetrical end spans did not act as replicates of each other 2 in which case the maximum experimental deflection was significantly larger than the theoretical deflection. In all other cases there was no significant difference in theoretical and experimental deflections. It would require 33.9% more timber in nominal 2 in. thick lumber as simple beams to provide equal strength and stiffness as the experimental three-span continuous beam.
Analysis of a dynamic pressure measuring system
Blevins, Roger Allen (Virginia Tech, 1970-05-05)
A dynamic pressure measuring system composed of long connecting tube, transducer, D-C amplifier and galvanometer oscillograph were used in a wind study conducted by the Department of Agricultural Engineering, Virginia Polytechnic Institute. The instrumentation was used to measure and record dynamic pressures due to wind velocity. Data recorded in that study indicated velocity head pressure oscillations on some surfaces of the test structure in excess of 100 Hz. This investigation was undertaken to see if the recorded oscillations could have been generated in the measuring system or if they were truly windpressure variations. Components of the pressure measuring system were modeled by transfer functions. From these transfer functions, a system operational transfer function was determined and used to define system frequency response. The frequency analysis indicated the system was severely limited in response by the oscillating air column constrained within the interconnecting tube. The usable frequency range of the system (+ 10% tolerable amplitude error allowable) was found to go from zero to 34.2 Hz. By eliminating the air column this frequency range could have been extended to 99.4 Hz. Phase shifts in these frequency ranges were found to be negligible. Transducers were mounted rigidly to exterior walls of the test structure. The measured fundamental natural frequencies of these walls (transducer mountings) were found to be well within the usable frequency range of the instrumentation; and, therefore, a source of vibration pickup. To improve the measuring system reliability, recommendations were made to eliminate the air column and stiffen the transducer mountings.
Analysis of shaker unit parameters to separate whole-tree wood chips
Weeks, Gregory Andrew (Virginia Polytechnic Institute and State University, 1988)
The quality of whole-tree wood chips has been the focus of much attention during the past few years because of the increased use of lower grade wood über in pulp production. The need to up-grade the quality has resulted in the use of some form of screening system to separate acceptable wood chips from unwanted material at most pulp mills. In order to upgrade the chip quality, a study was conducted to determine the effect of selected parameters of a separation system with an inclined, vibrating screen on screening efficiency. The parameters studied included screen aperture size and frequency of oscillation. Two screen sizes (3/8 and 1/4 inch apertures) and four different frequencies (1.25, 1.50, 1.75, and 2.00 Hertz) were considered. All other shaker unit parameters were held constant. Statistical analysis revealed that the lowest frequency resulted in the highest screening efficiencies for both the pin chips and fines categories. Screening efficiencies were higher with 3/8 inch screen as opposed to 1/4 inch screen, for all frequencies considered, but at 1.25 Hertz, the screening efficiency of fines was only 6 percent better with 3/8 inch screen. This analysis revealed that the lowest acceleration vectors produced the best screening efficiencies. Velocity and acceleration vectors were directly related to frequency of oscillation since all other parameters were held constant for this study. A Programmer’s Hierarchical Interactive Graphics System (PHIGS) program was developed to graphically simulate the screen motion and to analyze the maximum velocity and acceleration vectors of the upper swing arm (input link). By interactively changing the shaker unit parameters, the screen motion was animated and viewed, with the calculated vectors used in the statistical analysis.
An analysis of winter ventilation for poultry laying houses
Parker, Blaine Frank (Virginia Tech, 1952-09-03)
None
Application of a nonpoint source pollution model to a small watershed in Virginia
Wang, Yang (Virginia Tech, 1991)
AGNPS, a nonpoint source pollution model, was selected to stimulate sediment yield and chemical loadings from Owl Run watershed. The model was validated to demonstrate its applicability to Virginia Piedmont conditions. The validation was carried out by comparing simulation results with measured data including runoff, sediment yield, and nitrogen and phosphorus loadings to downstream water bodies. Statistical measures, including simple linear regression, determination of root mean square errors, and test on differences between simulated and measured data, were used in this study to evaluate errors. Results from these statistical procedures indicated that the errors between simulated and measured results are within acceptable limits. An annualization procedure was used to provide the basis for evaluating the long-term impact of various BMP’s. Critical areas in the watershed, which are responsible for majority of the pollutant loadings, were identified by the model using the annulization procedure. A FORTRAN program was developed to convery critical areas for individual events to “annualized critical areas” so that evaluations were made on long-term basis. BMPs currently installed in Owl Run watershed and several alternative BMP implementation scenarios were simulated. Their impacts on reducing pollutant loadings and their cost effectiveness were evaluated by using the AGNPS model and the annualization procedure. The current BMP scenario will eventually reduce sediment yield, total nitrogen, and total phosphorus loadings by 26%, 32%, and 32% respectively. Some of the proposed scenarios can reduce these pollutant loadings by up to 59%, 66%, and 67% respectively.
The application of electricity to agriculture
Somerville, Frank Meriwether (Virginia Agricultural and Mechanical College and Polytechnic Institute, 1926)
Artificial curing of mechanically harvested Virginia-type peanuts
Williams, Everett C. (Virginia Polytechnic Institute, 1960)
The purpose of this research was to obtain information on the requirements for successfully drying mechanically harvested Virginia peanuts by artificial means. The work was performed at the Tidewater Research Station, Holland, Virginia. It was performed in bulk-type bins which were seven feet deep. Two tests, which consisted of four treatments and four replications each, were conducted. One of the replication bins in each treatment was divided into one-foot depth sections. The drying tests were conducted using intermittent heat which was designed to give the prescribed temperature rise when the ambient relative humidity was above 75 percent. The drying potential ranged from 12 cfm/ft³ and a 10 F temperature rise to 9 cfm/ft³ and a 3 F temperature rise. Original moisture contents of the peanuts tested were 43 percent and 31 percent. Weights of the bins were taken during the tests, thereby permitting the calculation of the moisture contents at any time. Drying rate curves were obtained from this. Quality analyses of the peanuts after drying were performed in order to determine the best drying treatment. These included: Fat Acidity, Shelling Damage, and Damaged Kernels from Commercial Grade. The Shelling Damage Tests showed that the lowest drying potential was best. The Fat Acidity Test indicated that the drying potential in all of the treatments was satisfactory when drying Virginia peanuts with an original moisture of 31 percent in a seven-foot depth. However, it appeared that the potential was not adequate to dry peanuts with a 43 percent moisture content in a depth greater than five feet. No information was obtained from the damaged kernels in the commercial grade. The resistance to air flow and the analyses of quality of the end product gave no indication that the sectioning of the bins had any effect on drying as compared with the full depth bins. This can be important in later research from the standpoint of obtaining additional data on drying rates and progression of the drying layer through bulk type bins of Virginia peanuts.
Assessment of groundwater vulnerability to pesticide contamination in Albemarle and Louisa counties, Virginia
Shukla, Sanjay (Virginia Tech, 1995)
Groundwater contamination potential by pesticide was evaluated in Albemarle and Louisa counties of the Thomas Jefferson Planning District in Virginia. A qualitative method was developed to perform an assessment of pesticide contamination potential, using an existing pesticide screening model. The Attenuation Factor (AF), was selected for assessment of groundwater vulnerability to pesticide contamination in Albemarle and Louisa counties. Input data availability, consideration of the major transport processes, and ease of its linkage with a suitable geographic information system (GIS) were the main factors considered for selection of the AF model. The input data requirement of the AF model includes soil, hydrogeologic, and pesticide chemical characteristics. An extensive database was developed to perform AF model simulations within a GIS. The database developed for this study included map databases (resolution = 1/9 ha) for landuse, soils, groundwater recharge, and groundwater depth, and non-spatial (relational tables) databases for pesticide chemical characteristics, SCS curve number, and soil properties. A total of 12 landuse categories were identified for Albemarle and Louisa counties. Groundwater recharge, an input to the AF model, was estimated using a water balance model. Runoff and evapotranspiration components of the water balance model were estimated using SCS curve number (CN), and Thornthwaite’s methods, respectively. Forty years of climatological data records were used for estimating groundwater recharge. Two types of groundwater depths, spatially varying and a constant depth of 2 m, were used for computing AF, The groundwater depth was mapped using the information available in groundwater well completion reports. All the data layers were overlaid within a GIS for spatial computation of AF for actual and 2m groundwater depth. This spatial (map) database was categorized into five categories of pollution potential namely, high, medium, low, very low, and unlikely, based on the numerical values of the AF. For evaluating the contamination potential of pesticides, three pesticide leaching potential scenarios were considered in order to facilitate the evaluation of pesticide leaching under maximum, average and minimum cases of degradation and sorption in the soil. A combination of high, average, and low values of half life and sorption coefficient were selected for three leaching scenarios. A total of six simulations were performed (two groundwater depths and three leaching scenarios) for each pesticide. Toxicity of the pesticides was not considered in the contamination potential assessment in this study. A total of 11 relatively mobile pesticides were identified in Albemarle and Louisa counties, based on the results for various leaching scenarios. Groundwater contamination potential maps were produced for mobile pesticides and the results were discussed. Picloram was identified to be the most mobile pesticide in the two counties. Atrazine, carbofuran, metolachlor, simazine and triclopyr were found to have considerable potential to move to the groundwater. Contamination potential of three herbicides, atrazine, simazine and metolachlor, was predicted to be higher than other pesticides in light of the fact that they are often used in combination (tank mixed) for a wide variety of weed control. Dicamba was found to be the most heavily-used pesticide with regard to its area of application. In light of dicamba's moderate contamination potential and its higher usage amount this herbicide was identified to have a considerable potential to move to the groundwater, especially, in Albemarle County. Other pesticides such as fenarimol, lindane, metalaxyl, and metsulfuron methyl were shown to be relatively more mobile than some other pesticides. However, in light of small application areas for these pesticides, the contamination potential of these pesticides was predicted to be relatively small. In addition to 11 mobile pesticides, a few low mobility pesticides were also identified. Among the low mobility pesticides, diazinon was found to have relatively high contamination potential. Comparison between the contamination potential maps and the groundwater recharge map revealed that most of the high contamination potential areas coincided with the higher groundwater recharge regions in the two counties. Soil characteristics such as organic matter and percent sand and clay were also observed to affect the contamination potential of pesticides. The performance of the AF model was evaluated by using six years of groundwater monitoring data from the Nomini Creek watershed study. Two types of rankings were made, one using the AF model simulation results, while the other ranking was based on the frequency of detection of pesticides in the Nomini Creek watershed. A comparison of the rankings revealed that the AF model performed fairly well in identifying the top few mobile pesticides. Sensitivity analysis was performed to identify the important parameters affecting the contamination potential of pesticides. Results of the sensitivity analysis revealed that considerable uncertainty in the model prediction can be invoked due to the variability in the soil and chemical data. To make a better use of results of this study, it was recommended that groundwater monitoring be performed in the two counties to verify the so that results of this study. The results of this study will provide information about the potential threat to groundwater by pesticides to the citizens and policymakers in the two counties.
Bearing failure detection in farm machinery using low-cost acoustic techniques
Worley, Stacy K. (Virginia Tech, 1994)
Unexpected bearing failures in agricultural equipment can result in considerable inconvenience, potential hazard, and monetary loss. Continuous bearing condition monitoring using vibration and audio spectrum analysis can detect imminent bearing failures before dangerous situations develop. Current application of bearing condition monitoring using vibration signature analysis has focused on fixed industrial applications involving high cost equipment and high shaft speeds. The feasible application of current technology on mobile agricultural equipment requires a lower-cost method of signal sensing and processing. Lower shaft speeds and the use of neural-net based pattern recognition techniques can allow the use of lower-cost transducers necessary for practical adoption on mobile equipment. A test apparatus was developed and constructed to test the feasibility of using a electret microphone as a sensor for monitoring bearing condition through vibration signature analysis. Laboratory experiments designed to evaluate the sensors with test bearings at both an advanced and an early stage of wear were developed. A field-worn bearing that had been removed from a unit of farm machinery was obtained and examined. Twelve new bearings identical in type to the field worn bearing were also examined, altered to simulate an early stage of wear, and re-examined. Identical experiments were conducted on both the field-worn and altered bearings. The signal acquired from a field-worn bearing was compared with the signal acquired from a new bearing using a two-sample, paired t-test for means at an alpha level of 0.05 and a graphical defect frequency analysis. The signals acquired from the altered bearings were compared with the signals acquired from the new bearings using the same statistical and graphical test performed on the field-worn bearings. The goal of the analysis was to evaluate the performance of the microphone by attempting to identify significant frequency patterns that could be used to determine the condition of the test bearing while in operation. Duplicate experiments conducted using the accelerometer provided a comparison of sensor performance. The microphone performed well for bearings at an advanced stage of wear. The sensitivity of the accelerometer resulted in better performance when used with bearings at an early stage of wear.
A bibliography concerned with the effect of floor slabs, with and without spandels, on the moment in columns due to vertical or lateral loads
Kolker, Robert Jack (Virginia Tech, 1951-06-05)
The Engineering Index was the primary reference for the articles listed in this bibliography. There are a few articles included which have been taken from various engineering experiment station bulletins. In order to determine the extent of coverage of the Engineering Index, several of the articles which appeared as experiment station bulletins were cross-checked and found listed in the Index. While it is possible that some significant articles may have been omitted from the Index, it is hoped that they were of less importance than any of those which have been listed. The first volume of the Engineering Index appeared in 1884, therefore this bibliography will be limited to those articles listed in the issues of 1884 to May 1951 inclusive. All of the articles published in the United States, Canada, and England, and which were found to be on the campus, were read in a cursory manner in order to determine their applicability to the problem. In each case where the article was read, written additions were made to the abstracts in order that they might be more helpful to anyone using the bibliography. The part of the abstract enclosed with quotation marks was taken from the Index, the rest of the information was added. Photographic copies and English translations of all of the articles listed may be obtained from the publishers of the Engineering Index. It is hoped that this compilation of works on the integral action of beams, columns and slabs will prove helpful to anyone interested in this subject.
Bond graph model and computer simulation of a hydrostatic drive test stand
League, Richard B. (Virginia Polytechnic Institute and State University, 1985)
A hydrostatic drive test stand was constructed to aid in the instruction of the characteristics of hydrostatic transmissions and to develop a time-varying load in a shaft to compare torque transducers. A mathematical model of the device was derived using the bond graph approach and was implemented using the Advanced Continuous Simulation Language (ACSL). The test stand was used to obtain experimental data to try to refine the model parameters. To facilitate the measurement of system flows, a microprocessor-based digital flow indicator was developed. Steady-state tests were performed at various constant pump swashplate angles; for the dynamic tests, the pump swashplate angle was cycled from zero degrees to 6.5 degrees.
Bond graph modeling of hydraulic circuits on a sweet sorghum harvester
Rains, Glen Christopher (Virginia Tech, 1992)
A whole-stalk harvester was developed as part of a sweet sorghum-for-ethanol production system. Gathering chains grasped the stalks as they were cut at the base with a disk-cutter. These stalks were flipped onto a cross conveyor and deposited into an accumulator. Periodically the machine stopped and the accumulator was dumped. All the components on the harvester are powered hydraulically. Five pumps on the harvester supply flow to seven actuator circuits. Power is delivered to the pumps from the tractor PTO via a universal joint driveline. Each of the six existing circuits and one proposed circuit were modeled with bond graphs and implemented for computer analysis using TUTSIM. Model validation was done by comparing simulated and measured driveline torque, line pressure, and return line flow rate in each of the six existing circuits. Data collected on the gathering chains circuit was used to analyze the effect of driveline joint angles on transmitted torque and pump output. Torque measurements at three driveline angles showed a torsional vibration with a primary harmonic at driveline rpm and a secondary at twice driveline rpm. A combination of Cardan joint characteristics, mass unbalance, the secondary couple, and non-linear driveline and V-belt stiffness was used to model the driveline. Resulting simulated torque emulated the experimental very well. Measured pressure in the gathering chains circuit showed relatively low fluctuations at the highest amplitude torsional vibration (highest driveline joint angles). It was concluded that driveline vibration would not significantly affect the gathering chains circuit performance. The cross-conveyor motor circuit simulation showed close agreement to experimental results. Mean predicted flow, pressure, and torque were within 8.9, 7.3, and 7.7 percent of mean measured values. A simulation with a stalk load on the conveyor showed that power requirement increased only 8.0 percent. The accumulator dump circuit was analyzed to determine if the load on the motor would become over-running and cavitate the pump or motor as the stalks were being dumped. Simulation showed that a bundle up to 300 kg could be dumped without over-running the motor, and since this was a larger bundle than the bin could hold, a design modification was not necessary. The disk-cutter circuit was designed based on simulation results for several combinations of motor, pump, and sheave ratio. A 7.3 cm³/rad motor, 2.53 cm³/rad pump , and 2:1 sheave ratio produced the correct disk-cutter speed, and low torsional vibration when cutting the stalks, consequently this combination was selected for the design.
Bracing requirements for post-frame endwalls
Wirt, Donald Lee (Virginia Tech, 1991)
When diaphragm action is considered in the design of post-frame buildings, the endwalls may require supplemental reinforcement to replace lost strength and stiffness, due to placement of large doors and openings in the endwalls. The diaphragm design standard, ASAE EP484, does not provide guidelines concerning such endwall reinforcement. Flat steel strapping 1s proposed for use as supplemental reinforcement to replace this lost strength and stiffness. An analysis procedure was developed, with the intention of serving as input to endwall diaphragm design. Using PPSA 3.00 and calibrated endwall data, a computer structural analog was developed that “mimics” the deflection of an actual solid endwall. Sections of the structural analog were removed to represent a centered door opening. Fictitious members representing steel-strap bracing were added to the remaining endwall diaphragm to restore the endwall deflection to that of the same endwall with no door openings. Large corner post uplift values were observed for tall endwalls. For purposes of endwall analysis, it is necessary to distribute corner post uplift forces to the other posts along the adjacent endwall and sidewall. Along with the tabulated results in this research, this analysis procedure provides building designers a tool that will enable them to analyze virtually any endwall-door combination. All that is required is PPSA 3.00 software (or equivalent), a personal computer, and endwall stiffness data.
A comparative study of conventional greens washers and a prototype system recycling wash water with a mathematical model of grit concentration in wash water
Brzozowski, Jan Kazimierz (Virginia Polytechnic Institute and State University, 1977)
A prototype system with wash water recirculation was studied as a possible method of water conservation in the food processing industry. A conventional leafy-greens washer at the Exmore Foods Company, Incorporated, Exmore, Virginia, was compared with a prototype system. Spinach and turnip greens were processed with the two systems. The quality of the product and that of the wash water from both systems was compared by measuring grit content, bacteria contamination, and insect contamination of the product; TSS, VSS, COD, and grit concentrations in the wash water. The results indicated the better performance of prototype system which required only 23 percent of the water used by the conventional washers. The mathematical model developed to describe the grit content in the wash water of the prototype during washing succeeded in producing predicted values generally close to measured values.
Comparison of two hydrological models on a Virginia Piedmont watershed
Fu, Youtong (Virginia Tech, 1994-12-05)
KINEROS and PSRM-QUAL:J two distributed parameter event-based hydrologic models, were applied to Foster Creek Watershed, Louisa County, Virginia. The simulations of the two models were conducted using published data and a ten year database from the Foster Creek Watershed, Louisa County, Virginia. Data management and analysis was supported through the use of PC-VirGIS, a DOS based GIS package developed by the Information Support Systems Laboratory, Virginia Tech. The performance of the two models were based on the criteria established to compare the simulated and recorded peak discharge rates , total runoff volumes and time to peak. Goodness of fit criteria were based on graphic comparison relative error, model efficiency, linear regression, hypothesis testing and variance. Based on these measurements, the simulated results by both models were acceptable. KINEROS generally made better predictions of peak discharge rate and time to peak. Hydrograph shapes also generally matched the recorded sequence more closely. PSRM-QUAL simulated the total runoff volume slightly better than KINEROS. The sensitivity of KINER OS and PSRM-QUAL to the model input parameters was evaluated. For KINEROS, peak discharge rate and runoff volume were very sensitive to changes in rainfall amount, saturated hydraulic conductivity and effective capillary drive. For PSRM-QUAL, peak discharge rate and total runoff volume were very sensitive to changes in SCS CN, initial abstraction coefficient and rainfall amount.
Comparison of Virginia Future Farmers of America receiving the State Farmer degree between 1927-1938 with boys not holding the same degree
Sharitz, Thorold Joseph Brown (Virginia Agricultural and Mechanical College and Polytechnic Institute, 1940)
A computer program for an equation of wind velocity profiles from zero to thirty feet
Ogburn, Charles Brame (Virginia Polytechnic Institute, 1966)
Years of research have been devoted to the understanding of the structure and nature of natural wind and to the development of theories which can be applied to the design of buildings and other structures. Extensive studies of the velocity profile of wind have been made from the ground to the stratosphere, but investigators have concentrated on the winds above thirty feet. It has been from the studies in excess of thirty feet that the most recent concepts for deriving design velocities have been obtained. Structures used in agricultural enterprises are usually low-profile structures being located in the lower thirty feet of the atmosphere. For this reason, this investigation was undertaken to measure the wind velocities in the lower thirty feet of the atmosphere and to develop a computer program whose output would be an equation for the vertical profile of the measured wind velocities. It was felt that this information would be of great value in the study of wind pressure distributions on a prototype building, and also in the wind tunnel model tests of the prototype. Velocity measurements were made with four pitot tubes mounted on a thirty-foot mast at intervals of eight feet along the mast. Velocity pressures were recorded instantaneously from all the pitot tubes by an oscillograph. The data recorded were entered into a computer program for multiple regression coefficients. The output was the intercept, K, and the slope, 1/α, for a velocity profile with an equation of the general form, V = KZ^1/α Where: V = velocity at height Z, K = intercept, 1/α = slope. The statistical analysis on the fit of the profile equation, obtained from the computer, to the velocities recorded for this investigation showed a high significance value. It was concluded that wind velocity measurements could be obtained by pitot tubes with reasonable accuracy in the lower thirty feet of the atmosphere, and that these velocity data could be entered into a computer program which would yield an output of a velocity profile equation that could be used with confidence.

Browse

Browsing ETDs: Virginia Tech Electronic Theses and Dissertations by Department "Agricultural Engineering"

Results Per Page

Sort Options