Browsing by Author "Vaughan, David H."
Now showing 1 - 20 of 37
Results Per Page
Sort Options
- Alternative Waste Treatment System for Poultry Processing PlantsRoshdieh, Rana (Virginia Tech, 2010-08-04)The objective of this research was to design an alternative wastewater treatment system for turkey processing plants to recover energy and reduce N and P to allowable discharge levels. The objective included: 1. Determine the quantity and quality of biogas produced from the turkey processing wastewater (TPW) and COD reduction efficiency. 2. Design a waste treatment system and validate proof of concept for simultaneous P and N removal with a goal of attaining effluent concentrations of 0.1 mg/L and 4 mg/L, for P and N, respectively. A lab-scale complete mixed anaerobic digester was used for turkey processing wastewater (TPW) digestion and biogas recovery running for 6 months. Along with the anaerobic digester, a two-sludge system called A2N-SBR consisting of an anaerobic-anoxic sequencing batch reactor and an attached growth post-nitrification reactor was added for biological nitrogen and phosphorus removal running for 3 months. Biogas production yields of 778 + 89 mL/gVSadded and 951.30 mL/g COD were obtained through anaerobic digestion. Also, an energy balance was conducted on a pilot scale digester for a turkey processing plant with wastewater production of 2160 m3/d and using a combined heat and power (CHP) enginefor conversion of biogas to heat and electricity. Although the biogas yield achieved in a complete mixed reactor was relatively lower than yields obtained in previous studies using reactors such as UASB, still a complete mixed reactor can be a good choice for biogas recovery from TPW and can be used for codigestion with some specific turkey processing byproducts for biogas recovery. Nitrogen and phosphorus removal in the A2N-SBR system were 47% and 75%, respectively, and during the study the nitrogen and phosphorus removal mean concentration in effluent did not meet the nutrient limits specified in the objectives. Average TP and TN in the effluent were 3.2 mg/L and 137 mg/L, respectively. Throughout the study, the nitrification reactor biofilm was not completely developed. Incomplete nitrification and poor settling might be the reasons that quality obtained in effluent was low. To improve the process condition in A2N-SBR, online monitoring of pH, dissolved oxygen (DO) and oxidation reduction potential (ORP) can help to optimize each stage in the SBR and stages duration can be set based on the results.
- Application of Edible Coatings in Maintaining Crispness of Breaded Fried FoodsBallard, Tameshia Shaunt'a (Virginia Tech, 2003-09-17)Crispness is one of the most desirable textural characteristics of breaded fried foods. Consumers often judge the quality of breaded fried foods based on the perceived crispness of the product. Furthermore, today's consumers are showing increasing concern over fat intake. As a result, there is great interest in being able to enhance the crispness and reduce the fat uptake in breaded fried foods without sacrificing other quality attributes. To achieve these goals, modifications to both frying equipment and product formulation have been explored in this study. In this study, two edible film coatings, methylcellulose (MC) and whey protein isolate (WPI) were incorporated into the batter and pre-dust to determine their effect on the crispness of breaded fried chicken nuggets held under a heat lamp for varying time intervals. Crispness was evaluated by both objective (ultrasonic non-destructive evaluation system) and subjective methods. An untrained sensory panel was used to obtain subjective measurements of product crispness. Panelists rated product attributes such as crispness, juiciness, oiliness and flavor on a simple intensity scale. Additionally, panelists rated the liking of the products on a nine-point hedonic scale (1=dislike extremely, 9=like extremely). Two pressure sources (nitrogen gas and steam naturally released from the food material) were used to determine their effects on product crispness, texture, pressed juice, moisture content, fat content and color. Products fried with nitrogen gas as the pressurizing medium produced samples that were comparable to or exceeding the quality of products generated by frying with steam, as it relates to product crispness, texture, pressed juice, moisture content, fat content and color. As related to objective crispness, chicken nuggets fried with nitrogen were significantly crispier (p<0.05) than those fried with steam. Coating type and application also had a significant effect on product crispness. Samples coated with MC in the pre-dust were crispier than samples coated with WPI. However, no significant differences were found in product crispness, juiciness, oiliness or flavor, and overall liking among samples tested by the sensory panel. The results of this study demonstrated that applying an edible film coating to the pre-dust and using nitrogen gas as the pressurizing medium can enhance and maintain the crispness of breaded fried foods.
- Biodiesel fuelWen, Zhiyou; Grisso, Robert D.; Ogejo, Jactone Arogo; Vaughan, David H. (Virginia Cooperative Extension, 2009-05-01)The purpose of this publication is to introduce the basics of biodiesel fuel and address some myths and answer some questions about biodiesel fuel before farmers and fleet owners use this type of fuel.
- A Case-Based Reasoner for Evaluating Crop Rotations in Whole-Farm PlanningBhogaraju, Prabhakar V. (Virginia Tech, 1996-07-31)I have worked on a Case-Based Reasoning (CBR) system that evaluates crop rotations for their soil erosion and risk of insect pest problems. The purpose of this system is to provide decision support for an automated whole-farm planner (CROPS). CROPS (Buick et al., 1992) generates crop rotation plans that can address some of the environmental, economic and legislative pressures facing natural resource managers. To generate and recommend a crop rotation plan CROPS requires estimates on the soil erosion risks and pesticide pollution potential of the crop rotation. In this research I have designed and prototyped a system that can assist CROPS in the process of whole-farm planning by providing information required for determining the soil erosion risks and the pesticide pollution potential of crop rotations. Inputs for the system include: a crop rotation, its tillage and residue management practices, and field conditions. Soil erosion risk is quantified using the C-value. Pest risks are likelihood of pest outbreaks that require control in a crop rotation. CBR was the chosen methodology for system implementation. In CBR, solutions to new problem situations are derived from retrieving and adapting solutions to similar problem situations experienced in the past. The system was prototyped using Esteem™, a CBR development shell, and runs on a PC under the MS. Windows™, operating system.
- Changes in Streambank Erodibility and Critical Shear Stress Due to Surface Subaerial ProcessesHenderson, Marc Bryson (Virginia Tech, 2006-05-11)Previous studies have shown that soil erodibility and critical shear stress are highly influenced by weathering processes such as freeze-thaw cycling and wet-dry cycling. Despite over forty years of research attributing changes in soil properties over time to climate-dependent variables, little quantitative information is available on the relationships between streambank erodibility and critical shear stress and environmental conditions and processes that enhance streambank erosion potential. The goal of this study was to investigate temporal changes in streambank erodibility and critical shear stress due to surface weathering. Soil erodibility and critical shear stress were measured monthly in situ using a multi-angle submerged jet test device. Environmental and soil data were also collected directly at the streambank surface to determine freeze-thaw cycles, soil moisture, soil temperature, bulk density, soil erodibility, critical shear stress, and other atmospheric conditions that could impact bank erosion potential. Statistical tests, including a nonparametric alternative to ANOVA and multiple comparison tests, were used to determine if temporal changes in soil erosion potential were greater than spatial differences. Regression analyses were also utilized to identify the factors contributing to possible changes in soil erodibility, critical shear stress, and bulk density. The nonparametric alternative to ANOVA in combination with Dunn's nonparametric multiple comparison test showed soil erodibility was significantly higher (p=0.024) during the winter (November - March) and the spring/fall (April - May, September - October). Regression analyses showed 70 percent of soil erodibility variance was attributed to freeze-thaw cycling alone. Study results also indicated that bulk density is highly influenced by climate changes since gravimetric water content and freeze-thaw cycles combined explain as much as 86 percent of the variance in bulk density measurements. Results of this study show significant amounts of variation in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes, specifically changes in soil moisture and temperature. These results have potential implications for streambank modeling and restoration projects that assume constant values for soil erodibility. Watershed models and restoration designs should consider the implications of changing soil erodibility during the year in model development and stream restoration designs.
- Characterization of protein microstructure by various chromatographic techniquesPathange, Lakshmi Prasad (Virginia Tech, 2007-02-28)Due to the rising health care costs and with the advent of biogenerics, there is a growing demand to develop new and reliable techniques to characterize proteins and biopharmaceuticals. In addition, characterization aids in understanding the intricate relationship between a protein's structure and its function. To address this challenge, two protein structural parameters, 1) amino acid surface area and 2) amino acid microstructure, were chosen to be investigated. Two chromatographic techniques, 1) ion exchange chromatography (IEC) and 2) immobilized metal affinity chromatography (IMAC), were used to characterize the above-mentioned protein structure parameters. The model protein chosen for our work is T4 lysozyme. The protein consists of 164 amino acids with molecular weight ~ 18 kD. SYBYL 7.1 software was used to generate in silico point mutants. Two categories of protein variants (point mutants) were generated using site-directed protein mutagenesis. The goal for generating point mutants was to obtain mutants that vary in the two structural parameters. The first category point mutants vary in the surface accessibility of a surface accessible histidine residue. The second category point mutants predominantly vary in protein net charge and the amino acid microstructure. In total, seventeen point mutants were generated: 1) category I consists of seven variants that vary predominantly in their histidine surface accessibility, and were obtained by replacing a charged amino acid residue at different locations on the surface of the protein molecule, and 2) category II consists of ten variants that vary in both net charge and charge distribution were obtained by replacing charged and neutral amino acid residues at different locations (different microenvironments) on the protein surface. PCR technique was used to generate the point mutants. Gene and protein sequencing were employed to confirm the veracity of point mutation. CD and Lysozyme activity assays were performed to determine whether or not the 3D structure of all the protein variants was intact. Zonal analysis was used to obtain the binding strength values of all seventeen variants in IMAC with copper as the immobilized metal ions, and gradient elution method was used to obtain the relative retention times (rRT) values of all the variants in IEC. The seven lysozyme variants generated in category I each contains one surface histidine residue. In IMAC, there is a correlation between the surface accessibility of the lone surface histidine and the protein's binding strength with R²⁺= 0.76. In IEC, the correlation between the protein's microstructure, which predominantly consists the surface accessibility of the histidine residue, and the protein's retention times was R²⁺= 0.95. However, there were few outlier variants (e.g. variant K83H) which did not follow the correlations. The variations presented by few outlier variants can be attributed to the presence of intramolecular bonds, which restrict the mobility of the amino acid side chains and subsequently hinder the specific interaction between the amino acid residue and chromatographic media. For category II variants, short and medium range charge perturbations around the sole histidine residue in T4 lysozyme were engineered within 15 Ã distance of histidine. There was a strong correlation (R²⁺ = 0.96) between the theoretical (DeltaDeltaGElec) values, calculated using simple Coulomb's law, and the experimental (DeltaDeltaGB) values, which were obtained by measuring the protein binding strength values using IMAC. Similar correlation (R²⁺= 0.93) was obtained between the change in net charge (-2 to +2 units) and the relative retention times in IEC. Similarly, there were few variants (e.g. S136K, R76D) that did not follow the trends. The deviations of the few outlier variants can be attributed to the presence of unique microstructure effects around the histidine residue. These microstructure effects were quantified in IMAC as (DeltaDeltaGMicro), and in IEC they were quantified by the change in rRT values. In summary, all seventeen variants had different binding strengths and rRT values indicating the variation in the protein structure around the histidine residue. Our work reveals that it is possible to capture the microstructural effects of a protein through the combination of protein molecular modeling and simple chromatographic experiments.
- Cover crop residue effects on machine-induced soil compactionEss, Daniel R. (Virginia Tech, 1994-07-05)Crop production systems which utilize the biomass produced by rye (Secale cereale ) to suppress weed growth and conserve soil moisture have been developed at Virginia Tech. The success of alternative, reduced-input crop production systems has encouraged research into the potential for breaking the traffic-tillage cycle associated with conventional tillage crop production systems. The fragile residues encountered in agricultural crop production, whether incorporated into the soil or distributed on the soil surface, provide minimal protection against compaction by wheeled vehicles. The potential of an intact cover crop to reduce machine-induced effects on soil properties that affect primary crop growth was the subject of this study. A randomized complete block experiment was conducted at the Whitethorne Farm in Montgomery County, Virginia. One set of plots was arranged on a terrace adjacent to the New River in a fine, mixed, mesic, Aquic Argiudolls. Another set of plots was arranged on an upland site, a river terrace tread, in a fine-loamy, mixed, mesic, Typic Hapludults. Three rye cover crop treatments were examined. In one, a live cover crop was completely undisturbed prior to tracking by a wheel-type tractor. In another, the cover crop was chemically desiccated, and in the third treatment, all above-ground biomass was removed from plots prior to machine traffic. The treatments permitted investigation of the effects of crop condition on machine-induced soil compaction and the contribution of root reinforcement to the alteration of soil response to machine traffic. A fall-tilled fallow treatment served as an experimental control. Three levels of traffic were investigated: one pass, three passes, and five passes. Undisturbed soil core samples were analyzed to determine machine-induced effects on dry bulk density, pore size distribution, and saturated hydraulic conductivity. The treatments affected soil response to machine traffic. The cover crop treatments altered the soil-plant microenvironment, affecting soil parameters that influence compactibility. Soil compaction was attenuated by the reinforcing effect of a network of undisturbed roots within the soil. There was no convincing evidence that above-ground biomass contributed directly to the reduction of machine-induced compaction effects. Soil response to machine traffic was limited to the uppermost 15 cm of the soil profile.
- Development of a whole-stalk sweet sorghum harvesterRains, Glen Christopher (Virginia Tech, 1989-04-15)Sweet sorghum produces more carbohydrates and more biomass per unit land area than com in the Eastern U. S. Piedmont. An equipment system for harvesting and processing whole-stalk sweet sorghum is being developed, with the expectation that sweet sorghum can be commercialized as an ethanol feedstock. A whole-stalk harvester was designed, constructed, and tested during the 1988 harvest season. The harvester captured a row of stalks between two counter rotating gathering belts, cut them at the base with a disk cutter (basecutter), and, at the rear of the machine, rotated the stalks 90° by capturing the stalk butts between to spring-loaded disks, called the stalk flipper. At a field speed of 6.7 km/h, the machine worked best when the flipper tangential velocity was 24 percent higher than the gathering belt Linear velocity, which was approximately (within six percent) equal to ground speed. The harvester was pulled behind a tractor and powered with a universal joint drive line. Two computer software packages, Computer-Graphic Augmented Design and Manufacturing (CADAM) and Integrated Mechanisms Program (IMP), were used to design the hitch and drive line. Calculated angular accelerations in the 3-joint drive line were excessive during a right or left turn; consequently a constant velocity joint was used at the tractor PTO. The hitch was designed with three position settings. With the hitch in the Field 1 position, the harvester was offset sufficiently to capture a row with the gathering belts. In the travel position, the harvester trailed behind the tractor within the 2.4 m legal road width.
- Development of finish cooking methods for producing low-fat breaded cheese sticksYavuz, Nihat (Virginia Tech, 2010-12-08)Deep-fat fried foods have unique characteristics that attract consumers but their high fat contents must be reduced in order to provide healthy foods along with high quality. In the first part of this study, effects of frying temperature and frying pressure on the quality of partially fried breaded cheese sticks were determined. In the second part, far infrared finish cooking methods were compared to traditional deep-fat frying in terms of product quality. Increasing frying temperature significantly (P<0.05) reduced fat and moisture contents of the samples and increased crispness and exterior hardness. Pressure did not affect crust fat content of the samples significantly (P>0.05). However, increasing frying pressure resulted in the samples having higher moisture contents. Crispness and exterior hardness of pressure-fried cheese sticks were lower than traditional deep-fat fried samples. Increasing frying temperature and pressure resulted in darker sample color. Par-fried far-infrared finish cooked cheese sticks had lower fat contents than deep-fat fried cheese sticks had. Moisture contents of far-infrared finish-cooked samples were higher than those of deep-fat fried samples. Far-infrared finish cooking significantly (P<0.05) reduced crispness and exterior hardness of breaded cheese sticks.
- Development of the Urban Wetland Filter for Managing Phosphorus in StormwaterRosenquist, Shawn E. (Virginia Tech, 2010-03-19)Degradation of surface water quality by excess nutrients in stormwater is a substantial environmental and economic problem in the U.S. Phosphorus (P) is often the limiting nutrient for harmful algal blooms and the best target to prevent degradation. Natural treatment strategies such as constructed wetlands (CW) demonstrate effective and economical P management but obstacles exist to implementation. Biological P removal has large land requirements that limit the use of best management practices (BMP) in high land-value areas. Various BMP also utilize sorption processes (SP) for P removal but variations in performance and finite sorption capacity limit SP as a viable long-term removal strategy. However, by understanding variability and making sorption capacity renewable, SP could provide, with shorter retention times, a space-efficient, long-term removal strategy. This multi-study research program developed the urban wetland filter (UWF), a concept intended to overcome the unique limitations of high land-value areas to natural treatment strategies and provide a low-cost, easily implemented BMP to meet P management goals while harvesting sequestered P for use as a fertilizer. Experimental factors included substrate and influent properties pertinent to understanding performance variation and optimizing microbial iron (Fe) reduction for rejuvenation of sorption capacity. Regarding performance, modeling identified major sources of variability including, by order of importance, magnitude of a solution/substrate concentration gradient, length of the "antecedent dry period" between loadings, and pH. Field-scale results confirmed this multifactor dependence of P-removal while also supporting the inclusion of cast-iron filings in substrate to improve P removal. Regarding rejuvenation, results indicated that microbial Fe reduction is capable of releasing previously sequestered P from substrates. A sufficient carbon source was necessary, but microbial inoculation was not necessary to facilitate Fe reduction, which released most of the previously sequestered P, albeit more slowly than P sequestration. Field-scale results indicated that Fe reduction might occur faster under field conditions, possibly due to humic acids, and that inclusion of cast-iron filings enabled additional P removal after rejuvenation by providing a conservative source of Fe for the creation of new sorption sites; however, cast-iron filings may also limit the release of P during rejuvenation.
- Effects of Heat Addition After the Exhaust Valve on a Small Turbocharged Diesel EngineBrandon, Sidney Jordan (Virginia Tech, 2006-04-11)Designers of engines have always looked for ways to improve the power to weight ratio of mobile internal combustion engines. This was especially true in aircraft engine design and engines for various forms of racing. Today designers are looking for ways to make everything from cars to road tractors to farm tractors lighter and thereby more efficient. In addition, in many cases these vehicles only need the maximum power that an engine can produce for a small amount of time. What is needed is a small, lightweight engine with the ability to produce a large amount of power for a short duration. The work here describes one possible method for constructing just such a type of engine. By adding a combustion chamber in the exhaust flow between the engine exhaust valve and the turbine inlet on a turbocharged diesel engine, it should be possible to increase the turbine temperature. This will in turn allow the turbine to deliver more power to the compressor and create a higher inlet pressure and allow the engine to create more power. This paper describes both a computer simulation and an engine with this combustion chamber installed. There were however, problems with both the simulation as well as the test engine. While no quantitative data was obtained from the test engine, some valuable observations were made. The computer simulation yielded results and from these results and observations made while testing the engine with the combustion chamber installed it was determined that this design shows promise of creating an engine with higher specific power.
- Energetics of a sustainable crop-livestock systemKern, James D. (Virginia Tech, 1994-05-15)This study compares the energy utilization of two systems for producing cattle of desirable slaughter weight and grade from weanlings. Both systems produce beef cattle as a primary output; various types of baled hay are produced as a secondary output. One system uses generally accepted, "best management practices" while the other uses experimental, sustainable agriculture techniques. Since the adoption of new practices in agriculture often hinges on economics, an economic comparison is also presented. Beef produced in the sustainable system required 32% less energy per kilogram than that produced in the conventional system. However, baled alfalfa produced in the sustainable system required 8% more energy per kilogram than the alfalfa grown in the conventional system. When all types of hay were considered, the sustainable system used 7% more energy to produce one kilogram of baled hay. To compare the energetics of the two systems on a whole farm basis, the amount of energy required to produce one dollar of return was calculated. The sustainable system required 12.4 megajoules to produce one dollar of return, while the conventional system required 17.1 megajoules to produce the same return. Although economic returns on beef and alfalfa production were comparable in the two systems studied, the conventional system showed greater returns on the whole farm, due to a greater export of baled hay.
- Energetics of low-input corn productionEss, Daniel R. (Virginia Tech, 1990-12-05)This study compares the energy costs of synthesizing, distributing, and applying manufactured nitrogen fertilizer to the overall energy costs associated with nitrogen-fixing legume production and use. The energetics of com silage and com grain production under standard and alternative practices are examined. Economic analyses of crop production practices are used to aid the selection of recommended alternative practices. In corn silage production, cover-cropped treatments had a significant advantage over standard practice treatments in terms of overall energy expenditures for field operations. Cover-cropped no-till treatments required an average energy expenditure of 9026 MJ/ha compared to 19,763 MJ/ha required by the standard-practice no-till treatment. Cover-cropped treatments that used disking to kill the cover crops required an average energy expenditure of 9781 MJ/ha compared to 18,488 MJ /ha required by the standard-practice winter-fallow treatment. Alternative-practice treatments that utilized vetches to provide nitrogen for com production performed significantly better than standard-practice treatments in terms of energy use per unit of crop output. In addition, the alternative hairy vetch - no-till treatment produced a $33/ha greater average net revenue than the standard-practice no-till treatment. Weed control energy requirements for cover-cropped ridge-tillage com grain production were compared. Broadcast application of pre-emergence herbicides required an energy expenditure of 1160 MJ fha. Cultivation of ridges to control weeds consumed 380 MJ/ha. Economic costs of ridge cultivation were $14/ha. Broadcast application of pre-emergence herbicides cost $49/ha.
- Energy loss to the soil surrounding a below-grade solar energy storage pondHolmes, Brian J. (Virginia Tech, 1979-04-15)Several techniques have been proposed for storing collected solar energy. A study was undertaken to investigate energy losses to the soil surrounding a below grade solar energy storage pond. A three dimensional finite element model was developed to approximate the solution of the differential equation of heat transfer. The Crank-Nicholson central difference scheme was used to solve for the time derivative. Four small ponds were constructed at the VPI & SU Swine Center, Blacksburg, Virginia, to study the effect of insulation on heat losses from a warmed water pond. The water in each pond was warmed with an electric resistance immersion heater. The power consumed by each heater was metered. The uninsulated (control) pond was more thoroughly instrumented with thermocouples than were the other three ponds. These thermocouples provided data that were used as input to the computer model as well as data to verify the model. Based on the conditions under which the model was tested, energy losses to the soil from an uninsulated pond were on the order of 26.H-31-7 MJ/day (25-30 k BTU/day). By providing insulation to the ground surface and to a depth of 0.66 m (2 ft) at a distance of 0.33 m (1 ft) from the pond edge, energy loss to the soil was reduced to about 33 percent of the uninsulated case. Insulation of the pond sides and bottom resulted in energy losses that were about 16 percent of those for the uninsulated pond.
- Evaluation of Nutrient and Pathogen Losses From Various Poultry Litter Storage MethodsHabersack, Mathew James (Virginia Tech, 2002-07-23)Considerable concern has developed over the possible pollution from poultry litter storage methods. This study was conducted to evaluate three different storage scenarios; covered stockpiles, uncovered stockpiles, and litter sheds. The stockpiles were monitored over two rainfall simulation events, in both the Ridge and Valley and the Piedmont physiographic provinces, with both surface and subsurface flows analyzed. An observational study, where subsurface water was sampled for a nine-month period was conducted using six litter sheds, three in each of the above provinces. Samples were analyzed for nutrients, fecal coliforms, and solids. Concentrations of NHx, TKN, OP, TP, VSS, and FC in surface runoff from uncovered litter piles were all statistically higher than that from covered piles, with NO3 being the exception. However, increased runoff volumes originating from the covered litter piles caused mass loadings from both covered and uncovered piles to be similar enough that statistical significance was not obtained, except in the case of FC. Soil water samples from litter stockpiles did not show a statistically significant treatment effect for concentration data, but uncovered piles did exhibit higher nitrogen concentration estimates than the covered piles. Sample collection frequency showed a statistically significant increase in the number of samples that could be obtained from the edge lysimeter under uncovered litter piles from the Piedmont experimental site. This result indicates uncovered piles are releasing the precipitation absorbed during the rainfall simulation into the sub-surface environment. In the storage shed study, a greater number of samples were collected per attempt at the Piedmont sheds compared to those at the Ridge and Valley site. While both areas were undergoing a significant drought, Piedmont porous-cup lysimeters yielded samples 63% of the time, compared to 10% for Ridge and Valley lysimeters. Lysimeters located near the edge of the shed were also more likely to yield a sample than those in the center or a background location. Unknown interferences within the litter shed samples prevented three laboratories from obtaining valid nutrient concentrations.
- The experimental determination of rotor blade dynamic bending moments of a 10-kw wind turbineHendricks, David Gerard (Virginia Tech, 1991-05-05)A l0-kW horizontal axis wind turbine was studied to determine the effects of wind shear and gravity on rotor blade bending moments. A drag sphere based wind measuring system was designed to measure rapid fluctuations in wind velocity at two different heights. However, severe power line noise problems with the low level signals forced the use of standard rotating cup anemometry. Rotor blade bending moments were obtained with strain gages mounted on blade extenders near the root of the instrumented blade. Rotor angular position data were obtained with a photocell arrangement. The one per revolution primary bending moment frequency was caused mostly by gravity-induced bending. Also present is the 6 Hz blade natural frequency. A logarithmic atmospheric boundary layer (ABL) profile was used to estimate wind conditions at the upper level. Examination of the bending moment data revealed good agreement with values predicted from the ABL profile (within 4% in the mean) indicating the profile was a good mean approximation. A logarithmic atmospheric boundary layer (ABL) profile was used to estimate wind conditions at the upper level. Examination of the bending moment data revealed good agreement with values predicted from the ABL profile (within 4% in the mean) indicating the profile was a good mean approximation.
- Facilitated iron reduction as a possible means of rejuvenating phosphorus removal performance of filtration substratesRosenquist, Shawn E.; Levy, C. L.; Sell, S. T.; Hession, W. Cully; Eick, Matthew J.; Vaughan, David H. (American Society of Agricultural and Biological Engineers, 2011)In order to mitigate nutrient pollution in surface runoff more sustainably, the finite capacity for phosphorus (P) sequestration in best management practices (BMP) that rely heavily on sorption processes must be addressed. These BMP include sand filters, bioretention cells, and several types of constructed wetland. This study investigated facilitated microbial reduction of iron-based filtration substrates to promote controlled release of P previously sequestered by the BMP, P harvest for recycling, and rejuvenation of the substrate sorption capacity. Total dissolved P was well correlated with total dissolved iron during the reduction process, indicating that microbial iron reduction was capable of releasing previously sequestered P from substrates. Furthermore, results indicated that a sufficient carbon source was necessary but addition of a microbial culture was not necessary to facilitate iron reduction. While a large percentage of the previously sequestered P was removed, the process was much slower than initial sequestration of P by adsorption, and further research is needed to promote a more rapid release of P in order to optimize the rejuvenation process for field application.
- Factors Influencing the Amount of Time Spent By Cattle In Streams: Implications for TMDL DevelopmentMasters, Amanda Lynn (Virginia Tech, 2002-07-08)The amount of time cattle spend standing in streams is one input parameter needed by computer models when total maximum daily load (TMDL) plans are being developed. This input parameter is estimated using professionals' best judgment because experimental data are not available, and estimations are generally inconsistent. The goal of this study was to gain a better estimate of the amount of time cows spend in streams, since this has a significant impact on direct fecal coliform loadings to streams. Significant factors influencing the amount of time cattle spend in streams were identified, and a relationship was developed for predicting the amounts of time cattle spend in streams. Five farms were studied in southwest Virginia from August 2001 through February 2002. Camera surveillance systems were set up on two beef farms and three dairy heifer operations, and cattle activity in streams was recorded during daylight hours. Climatic data, pasture characteristics, feed characteristics, and farm management practices were collected from each site, and their relationships with the amount of time cattle spend in streams were investigated. No significant difference (p=0.82) was found between the amount of time beef cattle and dairy heifers spent in streams. Overall, cows spent an average of 10.12 min day-1cow-1 standing in streams during the observation period. Throughout the study period from August to February, cows spent the highest amount of time in streams during the month of November (14.3 min day-1cow-1). Feed, climatic, and pasture parameters were found to influence the amount of time cattle spent in streams. These significant parameters were used to develop an empirical equation for predicting cattle presence in streams. This model may not accurately predict the amount of time spent in streams by cows during warmer summer months, since data was collected during fall and winter months. Other limitations may be encountered when using the model to predict the amount of time lactating dairy cows spend in streams when streams are their sole water source, since they have a much higher water requirement than those cows studied.
- "Gear up and throttle down" to save fuelGrisso, Robert D.; Pitman, Robert M.; Perumpral, John V.; Vaughan, David H.; Roberson, Gary T.; Hoy, Roger M. (Virginia Cooperative Extension, 2009-05-01)This publication explains the fuel-saving technique called "Gear up and throttle-down," or GUTD.
- An improved control strategy for wind-powered refrigerated storage of applesBaldwin, John Derouet Couper (Virginia Tech, 1979-08-07)The need for an improved control strategy for the operation of a wind-powered refrigeration system for the storage of apples was investigated. The results are applicable to other systems which employ intermittently available power sources, battery and thermal storage, and an auxiliary, direct current power supply. Tests were conducted on the wind-powered refrigeration system at the Virginia Polytechnic Institute and State University Horticulture Research Farm in Blacksburg, Virginia. Tests were conducted on the individual components of the system. In situ windmill performance were also conducted. The results of these tests have been presented. An improved control strategy was developed to improve the utilization of available wind energy and to reduce the need for electrical energy from an external source while maintaining an adequate apple storage environment.