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Piezoelectric Sensor In The Application Of Rolling Bearing Health Monitoring, Yinyin Liu

Mechanical & Aerospace Engineering Theses & Dissertations

A condition-based monitoring concept for rolling element bearings in machinery utilizing a piezoelectric load sensor is investigated in this thesis. The radially polarized cylindrical piezoelectric sensor is modeled in its specific coordinates. The sensor registers the stress occurring in all directions around it. The sensor's behavior due to several typical loads is analyzed. Based on the induced stresses in the sensor, the sensor's output as an electric charge can be obtained using the method of integration.

Considering both the normal and tangential loads distributed on the rolling beating's roller-raceway contact surface, the dynamic stress distribution in the outer raceway was …

Analytical Model Of A Thermomechanical Hot Channel Coupled To A Friction Stir Welding Process, Saptarshi Mandal

Mechanical & Aerospace Engineering Theses & Dissertations

Although fusion welding techniques are well established, recent developments in solid state joining techniques have produced high quality welds in materials that are difficult to fusion weld. Friction Stir Welding (FSW) was developed in 1991 as a robust solid-state joining technique that uses a specially shaped rotating tool to generate heat and plasticize material around the tool. The tool then mixes plasticized material along the joint line to produce the weld. Over the last decade, FSW has become increasingly popular for welding aluminum. The combination of attractive properties of the weld and cost-efficiency has led researchers to investigate the feasibility …

A Numerical Analysis Of A Non-Porous, Flexible Upper Airfoil Surface, Asao Omura

Mechanical & Aerospace Engineering Theses & Dissertations

The aerodynamic behavior of the early Wright brothers' airfoils is an important element of the history of aeronautics. Their fabric-covered wings were not constrained to maintain the airfoil shape of their wooden rib substructures and therefore differences in performance between rigid and flexible Wright airfoil shapes can be expected. The purpose of this thesis was to develop a systematic numerical approach that allows an assessment of the influence of the fabric on the overall aerodynamic behavior of the Wright Model B airfoil. The Model B airfoil was chosen because it is the earliest "production" airfoil and has sufficient documentation to …

Mechanical Properties Of The Integument Of The Common Gartersnake, Thamnophis Sirtalis (Serpentes: Colubridae), Gabriel Rivera

Biological Sciences Theses & Dissertations

The evolution of the ophidian feeding mechanism has involved substantial morphological restructuring associated with the ability to ingest relatively large prey. Previous studies examining the morphological consequences of macrophagy have concentrated on modifications of the skull and cephalic musculature. Although it is evident that macrophagy requires highly compliant skin, the mechanical properties of the ophidian integument have received limited attention, particularly in the context of feeding. I examined mechanical properties of skin along the body axis in male Thamnophis sirtalis (Colubridae). From each of 11 specimens, I examined nine circumferential strips of skin, each spanning 10 ventral scales, spaced at …

Atmospheric Water Vapor Lidar Measurements Using Analog And Photon Counting Techniques, Anuj Maheshkumar Shah

Electrical & Computer Engineering Theses & Dissertations

Atmospheric water vapor measurements are essential for the understanding of Earth's weather and radiation budget, along with the water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a commanding method used for water vapor measurements from aircraft, spaceborne, and ground-based platforms. The new unmanned aerial vehicle (UAV) water vapor DIAL system provides great feasibility due to the weight and size limitations. The system has significantly less weight, power consumption, and noise presence, thus making it great for UAV applications.

This thesis discusses a UAV water vapor DIAL system that was designed, developed, and evaluated. The research effort was …

A Statistical Evaluation Of Risk Priority Numbers In Failure Modes And Effects Analysis Applied To The Prediction Of Complex Systems, Anthony W. Dean

Engineering Management & Systems Engineering Theses & Dissertations

Complex systems such as military aircraft and naval ships are difficult to cost effectively maintain. Frequently, large-scale maintenance of complex systems (i.e., a naval vessel) is based on the reduction of the system to its base subcomponents and the use of manufacturer-suggested, time-directed, preventative maintenance, which is augmented during the systems lifecycle with predictive maintenance which assesses the system's ability to perform its mission objectives. While preventative maintenance under certain conditions can increase reliability, preventative maintenance systems are often costly, increase down time, and allow for maintenance-induced failures, which may decrease the reliability of the system (Ebeling, 1997). This maintenance …

Monte Carlo Analysis Of Millimeter-Wave Gan Based Gunn Effect Oscillators, Sridhara Viswanadham

Electrical & Computer Engineering Theses & Dissertations

Gunn diodes are one of the most common high frequency solid-state oscillators at the present time, and are considered as promising devices for millimeter and submillimeter wave applications. Monte Carlo studies of Gunn diodes based on bulk wurtzite GaN have been carried out in this thesis research. Two structures have been examined: (i) devices with conventional single notch structure and (ii) repetitive structures with serial segments to fashion a "multiple domain" device. Wurtzite GaN has been chosen because of the high drift velocity and because analytical expressions for the band structure have recently become available. Performance parameters of interest such …

Evolution Of The Band Structure Of Β-In2 S3−3x O3x Buffer Layer With Its Oxygen Content, N. Barreau, S. Marsillac, J. C. Bernède, L. Assmann

Electrical & Computer Engineering Faculty Publications

The evolution of the band structure of β-In2 S3−3x O3x (BISO) thin films grown by physical vapor deposition, with composition x, is investigated using x-ray photoelectron spectroscopy. It is shown that the energy difference between the valence-band level and the Fermi level remains nearly constant as the optical band gap of the films increases. As a consequence, the difference between the conduction band level and the Fermi level increases as much as the optical band gap of the films. The calculation of the electronic affinity [ ] of the BISO thin films shows that it decreases linearly from 4.65 …

Telling Tales Of The Future: Science Fiction And Star Trek's Exemplary Narratives, Lincoln Geraghty

Reconstruction: Studies in Contemporary Culture

[First paragraph]

Due to its very nature as a science fiction series set in the future one would assume that Star Trek's stories have no connection with contemporary storytelling; that its narrative is as futuristic as its ethos. However, by highlighting how Star Trek uses traditional literary methods to communicate with its audience it can be shown that only a minimum number of exemplary narratives are used to build and develop its ever increasing future narrative of human endeavor in space. Scholars such as Jon Wagner and Jan Lundeen (1998) have examined in close detail Star Trek's mythical …

Animation Studies, Disciplinarity And Discursivity, Paul Ward

Reconstruction: Studies in Contemporary Culture

[First paragraph]

Addressing how knowledge grows, develops and fits together is arguably one of the most testing tasks facing scholars. In a world where knowledge is increasingly viewed as a commodity -- and the teaching of that knowledge is often done in an instrumentalist fashion -- we need to come to a fuller understanding of how knowledge areas inter-relate. Such a mapping needs to move beyond simplistic models of disciplinarity (and its bolted-together variants, such as interdisciplinarity, multidisciplinarity, and the like) and explore the ways that a wide range of people in an equally diverse set of contexts might constitute …

Minutes Of The Virginia Academy Of Science Council Meeting- May 2002, Virginia Journal Of Science

Virginia Journal of Science

Full proceedings of the Council Meeting of the Virginia Academy of Science at Hampton University on May 24, 2002

The Effects Of Intense Submicrosecond Electrical Pulses On Cells, Jingdong Deng, Karl H. Schoenbach, E. Stephen Buescher, Pamela S. Hair, Paula M. Fox, Stephen J. Beebe

Bioelectrics Publications

A simple electrical model for living cells predicts an increasing probability for electric field interactions with intracellular substructures of both prokaryotic and eukaryotic cells when the electric pulse duration is reduced into the submicrosecond range. The validity of this hypothesis was verified experimentally by applying electrical pulses (durations 100 μs– 60 ns, electric field intensities 3–150 kV/cm) to Jurkat cells suspended in physiologic buffer containing propidium iodide. Effects on Jurkat cells were assessed by means of temporally resolved fluorescence and light microscopy. For the longest applied pulses, immediate uptake of propidium iodide occurred consistent with electroporation as the cause of …

Modeling The Decision Process Of A Joint Task Force Commander, John Anthony Sokolowski

Computational Modeling & Simulation Engineering Theses & Dissertations

The U.S. military uses modeling and simulation as a tool to help meet its warfighting needs. A key element within military simulations is the ability to accurately represent human behavior. This is especially true in a simulation's ability to emulate realistic military decisions. However, current decision models fail to provide the variability and flexibility that human decision makers exhibit. Further, most decision models are focused on tactical decisions and ignore the decision process of senior military commanders at the operational level of warfare. In an effort to develop a better decision model that would mimic the decision process of a …

Use Of Eps-Filled Tires As Lightweight Construction Material, Sethapong Sethabouppha

Civil & Environmental Engineering Theses & Dissertations

The purpose of this research is to study the possibility of recycling discarded automobile tires as a lightweight construction material by injecting expanded polystyrene (EPS) into the hollow space of the tires. The observation from compression tests on used tires revealed that the tread wall of these tires bent toward their own center. This inward deformation should provide confining stress to the contained EPS, and thus the compressive strength of EPS-tire composite was expected to be higher than that of EPS.

To produce EPS-filled tire prototypes for this study, EPS type II, with density of 24 kg/m3, was injected into …

Characterization Of Mouse Prostate Tumor-Infiltrating Leukocytes, Daniel Alan Holterman

Theses and Dissertations in Biomedical Sciences

Prostate cancer is the most common form of non-cutaneous cancer among men in the United States and the second most common cause of cancer-related death among men with approximately 189,000 new cases diagnosed and 30,200 deaths of the disease in 2002. Prostate cancer can be a treatable disease but once it becomes metastatic there are no acceptable therapies. For this reason, immunotherapy has been attempted but the results have been disappointing. The TRAMP model was used to evaluate specific interactions between an intact murine immune system and a prostate tumor that expressed a naturally processed weak tumor antigen. Vaccination trials …

Circulation, Vol. 10, No. 1, Center For Coastal Physical Oceanography, Old Dominion University, Thomas Royer

CCPO Circulation

Spring 2003 issue of CCPO Circulation featuring article "R/V Fay Slover Is Here" by Dr. Thomas Royer

Dynamics Of Phase Transitions On Low-Index Metal Surfaces, Bo Lin

Electrical & Computer Engineering Theses & Dissertations

The surface superheating and phase transitions at the low-index surface of metal were investigated using conventional continuous and 100-ps time-resolved reflection high-energy electron diffraction. Three metal surfaces, In(111), Au(110) and Pb(111), have been investigated in this work. The high temperature behavior of the In(111) surface was investigated using reflection high-energy electron diffraction with 100-ps temporal resolution. The change of surface vacancy density on In(111) is observed from 300 K to near the bulk melting point. The vacancy-formation energy of In(111) surface is estimated from experimental results. The surface vacancy density is observed to increase with temperature; however, the average random …

Fuzzy System Identification Based Upon A Novel Approach To Nonlinear Optimization, Raymond Scott Starsman

Electrical & Computer Engineering Theses & Dissertations

Fuzzy systems are often used to model the behavior of nonlinear dynamical systems in process control industries because the model is linguistic in nature, uses a natural-language rule set, and because they can be included in control laws that meet the design goals. However, because the rigorous study of fuzzy logic is relatively recent, there is a shortage of well-defined and understood mechanisms for the design of a fuzzy system. One of the greatest challenges in fuzzy modeling is to determine a suitable structure, parameters, and rules that minimize an appropriately chosen error between the fuzzy system, a mathematical model, …

Application Of The Traditional Epidemiological Model To Predict Occupational Injury Rates In Manufacturing Industries, Gary A. Morris

Health Services Research Dissertations

This study was designed to test the usefulness of the Traditional Epidemiological Model of disease causation in modeling occupational injury rates and the presence of occupational illness in the manufacturing industry. More specifically, this research involved use of the agent, host, and environment constructs of the Traditional Epidemiological Model to examine the effects of five environmental-related workplace health and safety practices on occupational injury and illness. Data from the National Occupational Exposure Survey (NOES), conducted by the National Institute for Occupational Safety and Health (NIOSH) in 1981–1983, were used to ascertain the presence of specific workplace characteristics and to calculate …

Field Emission Based Sensors Using Carbon Nanotubes, Changkun Dong

Physics Theses & Dissertations

A number of sensitive applications would be greatly benefited by the development of better cold cathodes that employ the electron field emission process. Among the many kinds of field emitters that could be tried, carbon nanotubes (CNT) have a number of distinct advantages because of their unique geometrical structure, chemical inertness, mechanical stiffness, and high thermal and electrical conductivities. This dissertation describes research in which CNT cathodes were fabricated and their emission characteristics were measured.

Multi-walled carbon nanotubes (MWNT) were grown by chemical vapor deposition (CVD) on various substrates: Ni and Hastelloy gauze, 304 stainless steel (SS) plates, and Ni-coated …

The Relationship Between Non-Completers' Decisions To Leave Certificate Programs Before Earning Certificates And Their Career Goals, Elizabeth M. Lohman

Theses and Dissertations in Urban Services - Urban Education

The primary purpose of this research was to conduct a systematic study that investigated ways other than awarding certificates of completion to determine the effectiveness of community colleges' occupational-technical certificate programs. These programs are designed to provide students with the skills necessary to enter the workforce or receive promotions in existing employment, and they attract students whose primary goals are to gain the skills necessary to be more productive workers.

This study was designed to assess the effectiveness of fifteen occupational-technical certificate programs at Tidewater Community College (TCC) according to the institution's mission statement and to identify ways to encourage …

Numerical Studies On Supersonic Mixing And Combustion Phenomena, Tarek M. Abdel-Salam

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to investigate the mixing, combustion, and flow characteristics of different scramjet-combustor configurations. Three-dimensional models for the combustors have been used. Numerical results are obtained using a finite volume computational fluid dynamics (CFD) code with unstructured grids with sizes between 200,000 and 400,000 cells.

In the first part of the current study, the effects of the side angle of the fuel injectors in both mixing and combustion processes are investigated. Raised (compression) and relieved (expansion) wall-mounted ramps are used with side angles of 0 (unswept), 5, and 10 degrees. Results are obtained for nonreacting flows as …

Parallel Implementation Of A Face Recognition [Sic] System Based On Modular Pca Approach, Rajkiran Gottumukkal

Electrical & Computer Engineering Theses & Dissertations

This thesis describes research in automated methods for the recognition of human faces. The research is driven by the need to design a method, which would ensure high accuracy under the conditions of facial expression, illumination and pose variations. The resulting method is able to cope with uncontrolled nature of facial expression, illumination and head rotations. The main novelty of this work is the idea that some of the local facial features do not vary even when the facial expression, illumination and pose vary. This idea is applied to the existing principle component analysis lPCA) method to arrive at a …

Creating Enterprise Simulations Using High Level Architecture, Anton R. Lidums

Electrical & Computer Engineering Theses & Dissertations

Despite an established need, there are two remaining roadblocks to building distributed simulations and enterprise simulation systems. First, commercial simulation packages and engineering modeling tools are not readily distributable across multiple computers and have traditionally had very little impetus for utilizing a distributable format. Second, although HLA simulations have been built and there are tools to facilitate those efforts, very little has been done or written that specifically describes a "non-standard" integration implementation in sufficient detail to make the process reusable or repeatable. This thesis introduces a proof of concept prototype that was developed to integrate simulations. The paper presents …

Automatic Speaker Identification Using Reusable And Retrainable Binary-Pair Partitioned Neural Networks, Ashutosh Mishra

Electrical & Computer Engineering Theses & Dissertations

This thesis presents an extension of the work previously done on speaker identification using Binary Pair Partitioned (BPP) neural networks. In the previous work, a separate network was used for each pair of speakers in the speaker population. Although the basic BPP approach did perform well and had a simple underlying algorithm, it had the obvious disadvantage of requiring an extremely large number of networks for speaker identification with large speaker populations. It also requires training of networks proportional to the square of the number of speakers under consideration, leading to a very large number of networks to be trained …

Analysis Of Ingaassb/Aigaassb Photodetectors For Applications At The 2.0 Micron Wavelengths, Phani Pendyala

Electrical & Computer Engineering Theses & Dissertations

The study of an InGaAsSb-based heterojunction avalanche photo detector has been carried out for 2-μm applications. A separate absorption and multiplication structure was used because it minimizes the tunneling component of the dark current in the absorption region, and also provides single-carrier injection into the multiplication region. This is a well-known requirement for reducing the multiplication noise. The primary goal was to evaluate the potential of InGaAsSb-AlGaAsSb photo-detectors for photodetection at the two-micron wavelength.

InGaAsSb is a relatively new material, and, therefore, characterization and photodetector response analysis based on this material are not available in the literature. In this thesis …

Adaptive Segmentation Techniques For Object Region Extraction From Images With Complex Lighting Environment, Deepthi P. Valaparla

Electrical & Computer Engineering Theses & Dissertations

Automated image segmentation of objects in complex lighting environments is a difficult task since it is not possible to pre-define a threshold to distinguish the object from the background. It is ascertained that an effective threshold citation for such objects depends on the negative binomial distribution of the object region with respect to the background lighting. Based on this concept, a novel adaptive threshold selection method for automatic segmentation of the lumen region in endoscopic images is presented in this thesis. More precise lumen region and boundary are obtained by an integrated neighborhood search based region growing procedure whose speed …

Science Comprehension: Effects Of Text Coherence And Reader Aptitudes, Kimberly G. Cottrell

Psychology Theses & Dissertations

There is a significant need to improve reading comprehension as typical textbooks, particularly science textbooks, are often too difficult for the average student to comprehend. The overall purpose of this study was to examine which reader aptitudes, specifically prior domain knowledge, reading ability, metacognitive reading strategy knowledge, and motivation, were most predictive of science text comprehension, and whether these relationships varied as a function of text coherence. Further, the purpose entailed which factors (reading ability, metacognitive reading strategy knowledge, and motivation) may assist low knowledge readers to compensate for knowledge deficits, particularly when reading low-coherence texts. There were 241 undergraduate …

Self-Management And Telework: Assessing The Performance Of A Remote Workforce, Michael C. Mihalecz

Psychology Theses & Dissertations

The role of self-management practices in task and citizenship performance was examined with data from 127 participants employed as teleworkers by eight public and private organizations. A self-management practices instrument was validated. The instrument was then used to investigate the effect of self-management on task and citizenship performance. The use of two self-management practices, goal setting and external aids, successfully predicted both task and citizenship performance, Results of the study provide evidence that the use of self-management may impact several performance domains. Discussion focused on the implications of the results for managing remote workers.

A Combinatorial Technique For Face Detection Based On Color And Statistical Analysis, Harishwaran Hariharan

Electrical & Computer Engineering Theses & Dissertations

Automatic detection of faces from video sequences is an important task in security applications. The number, location, size and orientation of human faces in a video frame are unpredictable and can vary from frame to frame. A face detection algorithm for color images in the presence of varying lighting conditions and complexity in background relying upon color and statistical analysis is presented in this thesis. The new method detects skin regions over the entire image and then classifies the skin regions as faces and non-faces. Segmentation of skin regions is performed by a novel color space merging procedure named Integrated …