Jha, Akhilesh K

A special class of nonstationary processes with periodically varying statistics, called cyclostationary (CS), is investigated. These processes are encountered in many engineering problems involving rotating machinery such as turbines, propellers, helicopter rotors, and diesel engines. We analyze a cyclostationary process model in order to show its advantages compared to a traditional stationary process model and present a methodology for calculating the statistics of the response of a linear sys...

Swantek, Steven David

The split Hopkinson pressure bar (SHPB) continues to be one of the most common methods of testing materials at medium rates of strain. Elevated rates of strain, such as those found in impact and explosive applications, have been shown to induce phenomena such as strain hardening and phase transitions that can significantly affect the strength of most materials [14]. Due to its relative simplicity and robustness, the SHPB remains one of the preferred platforms for evaluating mechanical properties...

Wang, Zhenyuan

This dissertation is a systematic study of artificial intelligence (AI) applications for the diagnosis of power transformer incipient fault.The AI techniques include artificial neural networks (ANN, or briefly neural networks - NN), expert systems, fuzzy systems and multivariate regression.The fault diagnosis is based on dissolved gas-in-oil analysis (DGA). A literature review showed that the conventional fault diagnosis methods, i.e. the ratio methods (Rogers, Dornenburg and IEC) and the key ga...

Superczynski, Matthew J.

ABSTRACTSuperconducting Magnetic Energy Storage (SMES) has branched out from its application origins of load leveling, in the early 1970s, to include power quality for utility, industrial, commercial and military applications. It has also shown promise as a power supply for pulsed loads such as electric guns and electromagnetic aircraft launchers (EMAL) as well as for vital loads when power distribution systems are temporarily down. These new applications demand more efficient and compact high p...

Roghair, Craig N.

<center>Recovery From and Effects of a Catastrophic Flood and Debris Flow on the Brook Trout (<i>Salvelinus fontinalis</i>) Population and Instream Habitat of the Staunton River, Shenandoah National Park, Virginia.<p>by<p>Craig N. Roghair<p>Committee Chair: C. Andrew Dolloff<p>Fisheries and Wildlife Sciences<p><b>(Abstract)</b></center><...

Zahid, Kazi

Deployment of antenna arrays is a very promising solution to reduce the Multiple Access Interference (MAI) from high data rate users in the Wideband Code Division Multiple Access (W-CDMA) system. Combining the antenna array with a RAKE receiver, both of which exploits multipath diversity, can significantly improve the system performance. In this research, we investigate the performance of these beamformer-RAKE receivers, also known as two-dimensional (2-D) RAKE receiver, for the reverse link of ...

Miceli, Marybeth

Statistics released in the fall 1989 showed that 238,357 (41%) of the nation s 577,710 bridges are either structurally deficient or functionally obsolete. New materials, such as fiber reinforced polymeric composites (FRP), are being suggested for use in bridge systems to solve some of the current problems. These materials are thought to be less affected by corrosive environmental conditions than conventional civil engineering materials. Therefore they may require less maintenance and provide lon...

El-Taher, Hossam

Copper is applied to many crops as a fungicide/bactericide, including plasticulture tomato growing operations. Field tests have shown that copper is sometimes found in ground water near these fields. Therefore, a laboratory study was undertaken to determine if this copper can result from plasticulture application and to determine the mechanisms that account for the movement through soil to the subsurface. From the factors that may affect this mobility process; TOC, dryness and its temperature cy...

Li, Jing

This thesis presents a geometrically exact curved beam theory, with the assumption that the cross-section remains rigid, and its finite element formulation/implementation. The theory provides a theoretical view and an exact and efficient means to handle a large range of nonlinear beam problems.A geometrically exact curved/twisted beam theory, which assumes that the beam cross-section remains rigid, is re-examined and extended using orthonormal reference frames starting from a 3-D beam theory. Th...

Wongwanich, Yodyot

In spite of advances in industrial automation, manual assembly tasks continue to be an important feature of many industrial operations. In heavy part assembly, some pieces of raw material or equipment are too heavy to be safely handled by an operator. Material handling devices such as Jib cranes or overhead cranes are employed to help operators work safer and, in some cases, faster. However, during full-load productions, these devices could become limited and insufficient resources and hence, de...

Jones, Troy Bland

A new laser based flow interrogation system, capable of simultaneous measurement of planar three-component velocity data, was constructed and tested. The Virginia Tech Doppler Global Velocimeter (DGV) system was designed for use in the Virginia Tech Stability Wind Tunnel as a tool for investigating complex three-dimensional separated flow regions. The systems was designed for robustness, ease of use, and for acquisition of low uncertainty velocity data. A series of tests in the Stability Tunnel ...

Loulizi, Amara

Ground penetrating radar (GPR) technology has been used for the past 20 years for a variety of applications to assess transportation infrastructure. However, the main issue after all these years remains: "How well does GPR work and under what conditions?" Results show that GPR works well for some situations, but is not an appropriate tool for other situations. It is not used currently on a routine basis by the US Departments of Transportation (DOTs) due mainly to difficulties encounter...

Sandu, Simonel Ioan

Nitrification performance of three, fluidized-bed filters was investigated. Each filter contained 10 L of plastic bead medium (near neutral specific gravity and 2-4 mm diameter and length) and was loaded under conditions of various flow rates and ammonia levels. Bead settled depth and biofilter diameter (12.7, 15.2 and 17.8 cm) were the factors differing among the filters. The experiments were conducted with three replicate recirculating systems. Each system included one of the three different b...

Russell, Blair Edward

In the effort to improve oil production riser performance, new materials are being studied. In the present case, a Polymer Matrix Composite (PMC) is being considered as a replacement for carbon steel in flexible risers manufactured by Wellstream Inc., Panama City, Florida. The Materials Response Group (MRG) at Virginia Tech had the primary responsibility to develop the models for long-term behavior, especially remaining strength and life. The MRG is also responsible for the characterization of t...

Xia, Jianjun

FINITE ELEMENT ANALYSIS OF SHIP COLLISIONSJianjun XiaABSTRACTThe serious consequence of ship collisions necessitates the development of regulations and requirements for the subdivision and structural design of ships so that damage and environmental pollution is reduced, and safety is improved. A simplified collision model (SIMCOL) is currently being developed at Virginia Tech to conduct probabilistic analysis of damage in ship collisions and ultimately optimize ship structural designs to improve...

Bourne, Amanda C

Assessing the Contamination Risk of PrivateWell Water Supplies in VirginiaAmanda C. Bourne(ABSTRACT)When well water becomes contaminated to the extent that is does not meet EPA drinking water quality standards, it is considered unsafe for consumption. Nitrate and total coliform bacteria are both health contaminants and are both regulated in public water systems. A nitrate concentration of 10 mg/L or higher is considered unsafe, as is the presence of total coliform bacteria. Well degradation, ina...

SAYED, ALI YAWAR

The effects of lithology, fracturing, and gouge zone mineralization on the geophysical properties of fault zones are not very well understood. In situ seismic data collected over the exhumed San Gregorio Fault at Moss Beach, CA were used to relate in situ compressional wave velocity to internal fault zone properties. This active strike-slip fault is exposed in cross section on an uplifting and actively eroding wave-cut platform. It cuts shallow marine sediments that have been buried to depths of...

Makovec, Kristin Lynne

The problem of magnetic control for three-axis stability of a spacecraft is examined. Twocontrollers, a proportional-derivative controller and a constant coefficient linear quadraticregulator, are applied to the system of equations describing the motion of the spacecraft.The stability of each is checked for different spacecraft configurations through simulations,and the results for gravity-gradient stable and non gravity-gradient stable spacecraft arecompared. An optimization technique is implem...

Britton, Jeremy Paul

ABSTRACTSoil-bentonite cutoff walls are commonly used to contain contaminants in the subsurface. A key property in determining the effectiveness of a cutoff wall is its hydraulic conductivity. There are important difficulties and uncertainties regarding the accuracy of commonly used methods of measuring the hydraulic conductivity of cutoff walls.When predicting contaminant transport through cutoff walls, common practice is to use the average hydraulic conductivity of the wall. There are some cas...

Graves, Arthur S.

Virginia ranks third in fresh market staked tomato (Lycopersicon esculentum Mill.) production with approximately 1,659 hectares on the Eastern Shore. Estimated annual gross value is $30,800,000. Copper and chlorothalonil have long been considered essential to control bacterial and fungal diseases in fresh market tomatoes. High rates of these fungicides on tomatoes grown under plastic mulch have led to concerns about their potential adverse effect on water quality in estuaries adjacent to fields....

Weigel, Timothy G.

Modeling the Dynamic Interactions between Wood Pallets and Corrugated Containers during ResonanceTimothy G. Weigel(ABSTRACT)The unit load is the form of most commercial and industrial products during storage and distribution. A simple form of a unit load, a palletized bulk bin is commonly used to transport fruit and vegetables from the point of harvest to processing facilities. These vibration sensitive products are often subjected to damaging vibrations during this period. Most damage occurs du...

Kirkpatrick, Trevor Joe

A model to determine the time to first repair and subsequent rehabilitation of concrete bridge decks exposed to chloride deicer salts that recognizes and incorporates the statistical nature of factors affecting the corrosion process is developed. The model expands on an existing deterministic model using statistical computing techniques, including resampling techniques such as the parametric and simple bootstrap. Emphasis was placed on the diffusion portion of the diffusion-cracking model, but a...

Waldron, Christopher J.

The Route 601 Bridge spans 39 ft over Dickey Creek in Sugar Grove, VA and represents the first use of Strongwells 36 in. double web beam (DWB) as the main load carrying members for a traffic bridge. The bridge was designed for AASHTO HS20-44 and AASHTO alternate military loading with a targeted deflection limit of L/800. For the preliminary design, conservative properties for the 36 in. DWB were assumed based on experience at Virginia Tech with Strongwells 8 in. DWB used in the Toms Creek Bridge...

Xie, Lei

Continuous adjoint methods and optimal control theory are appliedto a pressure-matching inverse design problem of quasi 1-D nozzle flows.Pontryagin s Minimum Principle is used to derive the adjointsystem and the reduced gradient of the cost functional. Theproperties of adjoint variables at the sonic throat and the shocklocation are studied, revealing a logarithmic singularity at thesonic throat and continuity at the shock location. A numericalmethod, based on the Steger-Warming flux-vector-split...

Rambo-Roddenberry, Michelle

The behavior and strength of welded shear studs are subjects of ongoing study. In recent years, research has shown that the American Institute of Steel Construction (AISC) specification equations for shear stud strength are unconservative for studs placed in deck with ribs transverse to the steel beam. Twenty-four solid slab push-out tests, 93 composite slab push-out tests, and bare stud tests were performed to study the effects on stud strength of friction, normal load, position of studs in the...

MacLean, Matthew

This work examines the detailed flow characteristics of direct measuring skin friction gages with computational methods. This type of device uses a small movable head mounted flush to a wall such that the head is assumed to be exposed to the same shear stress from the flow as the surrounding wall. The force caused by the action of the shear stress on the head deflects a flexure system monitored by instruments such as strain gages mounted at the base of a beam.The goal of the study was to develop...

Francis, Justin David

(ABSTRACT)Simulations of the welding process for butt and tee joints using finite element analyses arepresented. The base metal is aluminum alloy 2519-T87 and the filler material is alloy 2319. Thesimulations are performed with the commercial software SYSWELD+®, which includes movingheat sources, material deposit, metallurgy of binary aluminum, temperature dependent materialproperties, metal plasticity and elasticity, transient heat transfer and mechanical analyses. One-waythermo-mechan...

Chretien, Nicolas

Equivalent, three-dimensional elastic moduli are determined from unit cell models of balanced plain weave, 2D braid, 2D triaxial braid and 4x4 twill textile composite materials consisting of interlaced or intertwined yarns. The yarn paths are modeled with undulation portions, in which one yarn passes over and under one or more yarns, and with straight portions. It is assumed that the centerline of a yarn in the undulation portions is described by the sine function, and that the cross-sectional a...

Avci, Onur

The AISI (1996) Specification for the Design of Cold-Formed Steel Structural Members provisions for web-crippling are believed to be conservative for multi-web deck sections. They are based on unfastened specimens and are limited to the use of decks with certain geometric parameters. The unified web crippling equation of the North American (2002) Specification for the Design of Cold-Formed Steel Structural Members (adopted from Canadian S136-94 Specification) is also limited to certain geometric...

Christopher, Jr., Edwin A.

Poor harvesting practices can accelerate soil erosion and decrease water quality and site productivity. Forestry Best Management Practices (BMPs) were developed to protect water quality, primarily by minimizing erosion during and after timber harvests. Although properly employed BMPs mitigate against the immediate potential for soil loss, little information exists regarding their long-term effectiveness.Since 1993, the Virginia Department of Forestry (VDOF) has conducted random water quality aud...

Gorder, Joel Steven

While there are no federal mandates for states to establish watershed managementframeworks, many states see the benefits of doing so and have established suchapproaches. The main advantage of statewide watershed management over traditionalresource management is the cost effectiveness and the formation of integrated solutionsto water quality problems. Statewide watershed frameworks provide a geographic focusand partnerships in order to develop comprehensive solutions to water quality problems.Wat...

de Leon, Raymond F.

There has been a growing interest and support by many state and local programs to address aquatic resource protection and restoration at a watershed level. The desire by many programs to implement watershed management programs has become more than just a need, rather a necessity to ensure suitable water resources. However, many challenges arise when developing and sustaining watershed programs. One such challenge is that watershed programs are resource intensive. These programs require significa...

Kitchin, Patricia Lee III

A statistic that summarizes an entire data set without losing any information about the family of distributions or the model is often called a sufficient statistic. Generally, one would like to use the statistic that contains the most information about the parameter space. Sometimes there are several sufficient statistics. At other times the only sufficient statistic is the entire data set. A large data set can be difficult to work with. In this case, can one use a statistic that, though not suf...

Gupta, Surabhi

Communication systems have an important role to play in managing the safe and efficient operation of the National Airspace System (NAS). The users of the NAS, from the commercial transport aircraft to hobby airplanes can all benefit from the recent advances in digital communication technology especially as the capacity of the analog voice systems is surpassed by the growth in air traffic. One of the benefits of the new digital data links being developed is to allow delivery of real time weather ...

Regmi, Binaya

The development and use of web-enabled tools for watershed modeling and decision-making have gained popularity lately with the increase in internet speed and accessibility. Most of the web-enabled tools available today address the watershed problems related to a narrow discipline like hydrology, or ecology etc. This thesis presents the work done in the development of a web-enabled integrated system, named WebL2W, which can address watershed problems in a more holistic approach.WebL2W integrates ...

Masoud, Ziyad Nayif

Ship-mounted cranes are used to transfer cargo from large container ships to smaller lighters when deep-water ports are not available. The wave-induced motion of the crane ship produces large pendulations of hoisted cargo and causes operations to be suspended.In this work, we show that in boom type ship-mounted cranes, it is possible to reduce these pendulations significantly by controlling the slew and luff angles of the boom. Such a control can be achieved with the heavy equipment that is alre...

Scott, David Andrew

Short-rotation woody crops are becoming important supplies of hardwood fiber, but littleis known about the early nutritional needs of these systems, especially on different site types.The study objectives were, on two young (ages 3-6) sweetgum plantations with contrasting soiltypes, to 1) determine the plant growth and foliar nutrition response to repeated nitrogen (N)fertilizer applications, 2) determine soil N supply, plant N demand, foliar N resorption, and soil and fertilizer uptake efficien...

Small, Ron

Anglers unlawfully introduced gizzard shad Dorosoma cepedianum into Claytor Lake, Virginia in the late 1980s, apparently with the intention of improving the sportfishery by adding an additional clupeid prey resource. This study examined the trophic interactions between larval shad and resident zooplanktivorous fishes, in an attempt to discover the potential for trophic competition and negative impacts to these fish species.Ichthyoplankton sampling in 1997 and 1998 showed that peak abundances of ...

Shukla, Sanjay

Long-term watershed and field nitrogen (N) balances were used in this study to quantify the surface (baseflow) and ground water lag times and effects of BMPs on N discharge from a Virginia Coastal Plain watershed. Ten-year water quantity/quality data (1986-1996) collected at the Nomini Creek (NC) watershed were used. Field (Field-N) and watershed (Watershed-N) scale N models were developed for computing the N balances. BMPs evaluated in this study included no-till corn and split N application. T...

King, Marquea D.

Toxoplasma gondii is a protozoan parasite that causes life-threatening disease in congenitally infected infants and immunocompromised patients, such as those inflicted with AIDS. Toxoplasmic encephalitis (TE) is a common presenting condition in an AIDS infection. People become infected with T. gondii by ingesting tissue cysts in undercooked meats or by ingesting oocysts excreted by cats. Methylmercury (MeHg) is a well-documented neurotoxicant that accumulates in the brain and causes severe menta...

Cawrse, Jason Kyle

The primary objective of this project was to test a full-scale prototype of an actual bridge deck containing GFRP bars as the top mat of reinforcement. The purpose of the tests was to verify that the design would resist the loads for which it was designed and provide assurance that the deck would not unexpectedly fail due to the use of this new material. Behavior of the bridge and deck, such as failure load, failure mode, cracking load, crack widths, deflections, and internal stresses, were exam...

Costigan, John A

In the arena of software development, implementing a software design (no matter how perfect the design) is rarely done right the first time. Consequently, debugging one s own (or someone else s) software is inevitable, and tools that assist in this often-arduous task become very important with respect to reducing the cost of debugging as well as the cost of the software life cycle as a whole. Many tools exist with this aim, but all are lacking in a key area: information visualization. Applying i...

Daqaq, Mohammed F.

We present a virtual simulation of ships and ship-mounted cranes. The simulation is carried out in a Cave Automated Virtual Environment (CAVE). This simulation serves as a platform to study the dynamics of ships and ship-mounted cranes under dynamic sea environments and as a training platform for ship-mounted crane operators. A model of the (Auxiliary Crane Ship) T-ACS 4-6 was built, converted into an OpenGL C++ API, and then ported into the CAVE using DiverseGL (DGL). A six-degrees-of-freedom m...

Fussell, John David

Repairs and modifications were made to a flow velocity measurement system designed to measure a planar area of unsteady three component velocities in a single realization using a velocity measurement technique referred to as Doppler Global Velocimetry (DGV). Several hardware components in the system were modified and new hardware was added. Significant improvements were made to the procedures used in acquiring DGV data as well as the procedures used in reducing the acquired DGV data. Though hard...

Watt, Alisa H.

The purpose of this study was to help explore the assumptions in job analysis literature involving whether holistic or decomposed job analysis items lead to a higher level of cognitive load for raters. The main study, involving 303 undergraduate university students, was a 2 (Type of measure: holistic or decomposed) X 2 (Level of extraneous cognitive load: additional load or no additional load) within-subjects design. The 160 decomposed items analyzed in this study were pilot tested to ensure tha...

Chaffin, Jake Lee

AbstractArsenic is a naturally occurring element, which is toxic to aquatic biota especially in disturbed areas where it may be found at high concentrations. A headwater stream adjacent to an 85 year-old abandoned arsenic mine was investigated to determine the influence of arsenic on stream biota and processes using an upstream (reference) and downstream (mine-influenced) comparative approach. Arsenic concentration was measured monthly at 10 sites along the stream length. Benthic macroinvertebra...

Delabbio, Juliette Lee

In aquaculture, biosecurity consists of policies, procedures and measures used to prevent or control the spread of fish disease. The focus of this research was the practice of biosecurity in the recirculation sector of finfish aquaculture in the United States and Canada. Specifically, this research: 1) identified and characterized finfish recirculation facilities in the United States and Canada; 2) assessed biosecurity utilization in these facilities; 3) examined the relationship between biosecu...

Brewster, Ryan Jude Stephen

Bioremediation of chlorinated aliphatic hydrocarbon (CAH) compounds commonly found at contaminated sites has been an area of focus in recent years. The cometabolic transformation of CAH compounds is important at sites where the redox condition does not favor natural attenuation or populations of indigenous microorganisms are relatively low. At sites where the ground-water system is aerobic, monitored natural attenuation strategies will not meet remediation objectives, or both, enhanced bioremedi...

Kogler, Timothy Michael

Fratricide is one of the most devastating consequences of any military conflict. Target identification failures have been identified as the last link in a chain of mistakes that can lead to fratricide. Other links include weapon and equipment malfunctions, command, control, and communication failures, navigation failures, fire discipline failures, and situation awareness failures. This research examined the effects of degraded vision and combat identification reliability on the time-stressed dec...

Boeving, Charmayne Alexandra

The state of the literature on the psychosocial adjustment of children and adolescents with cancer is primed for novel contributions to the promotion of quality of life and depletion of negative psychosocial outcomes. Many recent studies indicate that this population may be at increased risk for depressed and anxious symptomatology; however, there is a large degree of individual variation. Coping responses have been demonstrated as significant predictors of adjustment outcomes with these patient...