Engineering Commons^™

The Effect Of Texture And Microstructure On Equibiaxial Fracture In Gallium Embrittled Aluminum Sheet, Michael Daniel Grah

Open Access Dissertations

No abstract provided.

Cyclo-Static Scheduling Of Large Grain Dataflow Algorithms On A Local Area Atamm Multicomputing Testbed, Sudeepto Roy

Electrical & Computer Engineering Theses & Dissertations

A strategy for cyclo-statically scheduling deterministic large grain dataflow (LGDF) algorithms for distributed execution on loosely coupled multicomputer architectures is presented in this research. The computational paradigm used is the ODU/NASA developed Algorithm To Architecture Mapping Model (ATAMM), which consists of marked graphs and Gantt chart representations that model the iterative execution of deterministic LGDF algorithms for different values of throughput and computation time. It is postulated that the behavior of these algorithms could be represented by the aggregate execution of an ensemble of cyclically shifted threads of a specific node sequence. Assuming the existence of one or more such …

An Evaluation Of The Implementation Of Total Quality Management In A Service Organization, Charles Stanford Stevens

Engineering Management & Systems Engineering Theses & Dissertations

This research consists of a formative evaluation designed to identify the steps necessary to revitalize a formerly successful Total Quality Management (TQM) process at a U.S. Navy engineering and logistics support organization. The research also developed a methodology to account for the fact that the investigator is a well-informed insider who served as one of the principle change agents for the TQM implementation.

The research is based on the researcher's observation that the major cause for the waning implementation was due to senior management and leadership issues and the organization-wide processes with which they interface. The investigation consisted of an …

Simultaneous Aerodynamic Analysis And Design Optimization, Satish Venkatasubra Mani

Mechanical & Aerospace Engineering Theses & Dissertations

An efficient approach for simultaneous aerodynamic analysis and design optimization is presented. Using this approach, the expensive procedure of performing complete steady— state flow analyses at every design-optimization step is avoided, thus addressing the challenge of incorporating computational fluid dynamics software into efficient gradient—based optimization techniques for aerodynamic design. An adjoint—variable method is introduced to nullify the effect of an increased number of design variables in this problem formulation. This approach is successfully tested on two quasi—one—dimensional nozzle—flow problems: a fully supersonic flow, and also a transonic flow with a normal shock. The algorithm is implemented using the direct Newton—iteration …

A New Adjoint Variable Method For The Sensitivity Analysis Of Dynamic Responses, Krishnamoorthy Ramesh

Mechanical & Aerospace Engineering Theses & Dissertations

A new adjoint variable method has been formulated for finding the sensitivity derivatives of dynamic system responses. Though the method can be based on any step-by-step time marching scheme, the Wilson Theta Method has been chosen as the basis of the new formulation . Wilson Theta Method is an implicit numerical integration scheme for finding the dynamic system responses. The new formulation uses the differential form of equations of motion as given by the Wilson Theta Method in its formulation of the adjoint equation. The conventional methods used for finding the sensitivity derivatives, namely, the direct differentiation technique, the central …

Numerical Simulation Of Two-Dimensional, Spatially Developing Mixing Layers, Robert V. Wilson

Mechanical & Aerospace Engineering Theses & Dissertations

Numerical simulation of a forced, two-dimensional, spatially-developing mixing layer using a control-volume formulation is performed. Three classes of forcing functions are used at the inlet boundary which are; (i) steady boundary conditions, (ii) combinations of the fundamental, first subharmonic, and second subharmonic modes from linear inviscid stability theory, and (iii) a broad spectrum of modes whose velocity power spectrum and transverse turbulence intensity relationship is taken from experiment. The results show that shear layer rollup occurs for time-dependent inlet boundary conditions and that the resulting vortex dynamics are determined from the subharmonic content of the inlet boundary conditions. It is …

Emissions Studies For A Natural Gas-Fired Internal Combustion Engine, Carlos M. Buitrago

Mechanical & Aerospace Engineering Theses & Dissertations

Since 1991, a University owned truck has been operating with natural gas. In order to improve emissions performance a different fuel management strategy was developed. With the help of Siemens Automotive in Newport News, VA, a liquid fuel injector was modified to handle natural gas. The basic engine was tested to determine the benefits in emissions that the multi-point injection system can have over the single point injection system that had been used previously. Pre-catalyst, raw exhaust-gas data for the more important pollutants were taken and analyzed in both systems under different loads and intake manifold pressures. In addition, to …

Acoustic Correlates Of Vowel Perception As Determined From Synthesis Experiments With Multi-Tone Stimuli, Zhongjiang Zhang

Electrical & Computer Engineering Theses & Dissertations

An essential requirement of speech signal processing is to extract information (features or parameters) from the speech signal which encode the information carried by the signal. The objective of this thesis work was to examine and evaluate two feature sets as acoustic correlates for vowel perception. They are formants and DCTCs. Formants are the frequencies of spectral peaks of the speech signal. DCTCs are the Discrete Cosine Transform Coefficients of the magnitude spectrum and are thus features which encode the global spectral shape of speech signal.

There are different opinions regarding which feature set is a more accurate representation for …

Computation Of The Aerodynamic Characteristics Of A Subsonic Transport Aircraft Using A Panel Method, Lillianne Plaster Whitelock Troeger

Mechanical & Aerospace Engineering Theses & Dissertations

An advanced low-order panel method, VSAERO, is applied to a full-configuration transport aircraft. Wing pressure distributions as well as lift, drag, and pitching moment coefficients calculated for the full computational configuration are compared with experimental data. In addition, partial configurations are evaluated computationally to determine the relevance of certain complex aircraft components to the computations. It is shown that the wing-surface pressure distributions and pitching moment coefficient are well predicted by VSAERO. The lift coefficient is consistently overpredicted by the code.

Simulation Of Vertical Tail Buffet In Internal Vortex Breakdown Flows, Mark William Flanagan

Mechanical & Aerospace Engineering Theses & Dissertations

Computational simulation of vertical tail buffet in an internal vortex breakdown flow is considered. The fiuid-flow problem is formulated using the full, compressible, unsteady Navier-Stokes equations which are solved using an implicit, flux-difference splitting, finite volume scheme. The fluid-flow problem is solved in a configured circular duct using quasi-axisymmetric assumptions to simplify the flow equations. A plate is placed transverse to the incoming flow. Solution of the flow in the duct is performed with and without a rigid plate, and with and without an elastic plate. The elastic response of the plate is calculated assuming that it is a cantilever …

Accurate Evaluation Of Homogeneous And Nonhomogeneous Gas Emissivities, Kam-Pui Lee

Mechanical & Aerospace Engineering Theses & Dissertations

Spectral transmittance and total band absorptance of selected infrared bands of carbon dioxide and water vapor are calculated by using the line-by-line and quasi-random band models and these are compared with available experimental results to establish the validity of the quasi-random band model. Various wide-band model correlations (such as Edwards and Balakrishnan, Tien and Lowder, and Felske and Tien) are employed to calculate the total band absorptance and total emissivity of these two gases under homogeneous and nonhomogeneous conditions. These results are compared with available experimental results under identical conditions. From these comparisons. it is found that the quasi-random band …

A Study Of Spiking And Relaxation Oscillations In Nd:Yag Laser Using Measured Laser Parameters, Ramesh K. Shori

Dissertations and Theses

It was shown analytically and experimentally that when the cavity losses are perturbed, the output intensity experiences an amplitude modulation or becomes a regular train of spikes, with the frequency depending on both the frequency of perturbation as well as pump power. Coupled nonlinear rate equations including the cavity perturbation term, are solved numerically by a Runga-Kutta method using experimentally-measured parameter values for Nd: Y AG laser. A continuously pumped Nd: Y AG laser was used to verify this theory.

Water Quality Modeling Of The Tualitin River, Christopher John Berger

Dissertations and Theses

Water quality problems related to excessive algal growth, high nutrient loading, and low flows have been occurring along Oregon's Tualatin River. The Tualatin River is 86 miles long and has a drainage basin of 711 square miles. The drainage basin incorporates forest, agricultural, and urban areas. Located in the Portland metropolitan area, these problems have been acerbated by the effects of urban growth. To help analyze pollution control alternatives, a river model study, funded by the Oregon Department of Environmental Quality (DEQ}, was undertaken. An in-stream model of hydraulics and water quality was developed. The Corps of Engineer's CE-QUAL-W2 model, …

Modeling Of Flow And Water Quality In Henry Hagg Lake Near Forest Grove, Oregon, Michael T. Knutson

Dissertations and Theses

Increased population growth in Washington County, Oregon, has helped cause the water quality of the Tualatin River to decline. Henry Hagg Lake is a storage reservoir which was built to augment summer low flows in the Tualatin River. Hagg Lake also supplies the Tualatin River Basin with both irrigation and municipal water in the summer. Using the U.S. Army Corps of Engineer's model CE-QUAL-W2 (a two-dimensional hydrodynamic and water quality model) , a model of Henry Hagg Lake was created. The model was calibrated using water quality and hydraulic data for 1990 at the Hagg Lake outflow in Scoggins Creek. …

Analytical Modeling Of Aquifer Decontamination By Pulsed Pumping When Contaminant Transport Is Affected By Rate-Limited Sorption And Desorption, Thomas A. Adams, Robert C. Viramontes

Theses and Dissertations

This research explores radially convergent contaminated transport in an aquifer towards an extraction well. This thesis presents the equations governing the transport of a contaminant during aquifer remediation by pulsed pumping. Contaminant transport is assumed to be affected by radial advection, dispersion, and sorption/desorption. Sorption is assumed to be either equilibrium or rate-limited, with the rate-limitation described by either a first-order law, or by Fickian diffusion of contaminant through layered, cylindrical, or spherical immobile water regions. The equations are derived using an arbitrary initial distribution of contaminant in both the mobile and immobile regions, and they are analytically solved in …

Capabilities Of Air Force Wastewater Treatment Plants In Complying With Projected Regulatory Requirements, Steven R. Ford

Theses and Dissertations

One of the major environmental regulations that directly affects the Air Force is the Federal Water Pollution Control Act (FWPCA). The 1972 FWPCA amendments set forth a series of national goals regarding water quality. The main mechanism for achieving these goals was the National Pollutant Discharge Elimination System (NPDES). NPDES is a program requiring dischargers to limit the quantity of pollutants discharged into the receiving waters. This research effort predicts changes in future NPDES permit requirements, and evaluated the capabilities of Air Force wastewater treatment plants (WWTPs) in meeting those future requirements. It was found that future permit requirements will …

Repair Process Improvement At The Ogden Air Logistics Center, Landing Gear Division: A Case Study In The Application Of The Theory Of Constraints, David A. Maddox, Susan L. Martz

Theses and Dissertations

This study explored the nature and extent of success that resulted from the implementation of the Theory of Constraints (TOC) in a depot repair environment. The actions taken to implement TOC were determined. Performance measures which defined success were identified and data were collected and summarized to demonstrate performance before and after implementation of TOC concepts. Improvements in flowdays and work-in-process (WIP) were determined to be attributable to the TOC effort. In addition, the unique characteristics of probabalistic repair and supply system variability were noted as those characteristics that posed the greatest challenges to implementing TOC in a remanufacturing environment. …

An Investigation Of Integrated Product Development Teams Of The F-22 Program, Gary F. Wagner, Randall L. White

Theses and Dissertations

This study investigated Integrated Product Development (IPD) at the F-22 System Program Office (SPO). A literature review revealed the key IPD characteristics of organizational structure, communication, intense up-front planning, training, integrated management tools, and lessons learned. The research method was twenty-two personal interviews of SPO subjects selected from four IPD teams, the front office, and functional support divisions. Key findings included an emphasis on up-front planning to establish an organizational and contractual structure which empowered workers to develop their products. Also, constant communication with all other functions and teams was stressed while training was primarily done while transitioning to IPD. …

Analysis Of Best Management Practices For Storm Water Compliance At Air Force Airfields, Peter A. Ridilla, Bradley T. Hoagland

Theses and Dissertations

This research analyzed storm water best management practices (BMPs) that may a Base Civil Engineers/Environmental Managers in complying with National Pollutant Discharge Elimination System (NPDES) storm water discharge requirements for Air Force airfield pavements. As a result of recent storm water regulations issued by the Environmental Protection Agency, increased emphasis has been placed on preventing and controlling the discharge of pollutants into surface waters of the United States. Based on the results of an American Association of Airport Executives' survey of civilian airports, the types and levels of airfield pollutants were identified. Typical NPDES storm water permit standards were then …

Guidance For The Development Of Air Force Storm Water Sampling Programs, Jerry K. Weldon Iii, Roy T. Willis

Theses and Dissertations

The purpose of this research was to develop sampling guidance that will enable Air Force (AF) installations to conduct cost effective storm water sampling in accordance with current storm water regulations. Data on the techniques used by AF bases to obtain storm water samples for the AF group storm water permit application were collected and analyzed. This information was used to outline management and resource requirements associated with the implementation of NPDES storm water regulations. The use of in-house personnel, automatic sampling equipment, or a contractor to perform the field data collection was examined. An in-house manual approach to storm …

A Predictive Model For The Determination Of The Economic Feasibility Of Construction And Demolition Waste Recycling In The Air Force, Byron L. Dixon

Theses and Dissertations

This study created a model to be used at a CONUS Air Force base to determine the economic feasibility of Construction and Demolition (C&D) waste recycling. Three areas investigated to develop this model: the methods to determine amounts and types of C&D waste generated at a specific location, the markets for recycled C&D wastes, and the recycling methods currently available. From this data, gathered through records searches and interviews, a procedure was developed to perform cost/benefit analyses on the available recycling options. A model was then created based on these calculations which can arm a manager with information to either …

A Risk Assessment Of The Health Liabilities From Exposure To Toxic Metals Found In The Composted Material Of Air Force Municipal Solid Waste, Timothy L. Merrymon

Theses and Dissertations

This thesis assesses the risk of the health liabilities from exposure to toxic metals found in the composted material of Air Force municipal solid waste (MSW). The goal is to determine the probability that the composted MSW could be a health hazard if it were used as a soil amendment. The research limited the assessment of the exposure risk to heavy metals found in raw MSW and its resulting compost. The thesis uses reviews of present literature to examine the food and soil ingestion exposure pathways. These pathways are assessed using the heavy metal concentrations found in MSW compost and …

Photoluminescence Spectroscopy Of Zinc Germanium Diphosphide (Zngep2), Jack E. Mccrae

Theses and Dissertations

Zinc germanium diphosphide (ZnGeP₂) is a chalcopyrite semiconductor with strong nonlinear optical properties and potential application to Air Force interests. The characteristics of this material have been studied using photoluminescence (PL) spectroscopy. The PL spectrum is dominated by transitions from the conduction band to a deep acceptor level, and features in the spectrum suggest that more than one transition is being observed. The PL is partially polarized, and the degree of polarization appears to differ for each feature in the spectrum. The relative PL intensity of these features are seen to depend upon the wavelength of the excitation …

Investigation Of The Sensitivity, Selectivity, And Reversibility Of The Chemically-Sensitive Field-Effect Transistor (Chemfet) To Detect Nitrogen Dioxide, Dimethyl Methylphosphonate, And Boron Trifluoride, Neal T. Hauschild

Theses and Dissertations

This study investigated the sensitivity, selectivity, and reversibility of a chemically-sensitive field-effect transistor (CHEMFET) gas microsensor. Various physical operating parameters were tested to determine which produced the most significant sensitivity, selectivity, and reversibility which were computed from response changes generated from electrical conductivity modulations when exposed to challenge gases. The variable operating parameters included: thinfilm material, film thickness, challenge gas specie, challenge gas concentration, and operating temperature. Copper phthalocyanine and lead phthalocyanine were used as thin films to detect the following challenge gases: nitrogen dioxide, dimethyl methylphosphonate, boron trifluoride, methanol, carbon monoxide, vinyl chloride, and trichloroethylene. Tests revealed that copper …

Evaluation Of The Total Petroleum Hydrocarbon Standard For Cleanup Of Petroleum Contaminated Sites, Rick A. Blaisdell, Mark E. Smallwood

Theses and Dissertations

This study evaluated the TPH (total petroleum hydrocarbon) cleanup standard for petroleum contaminated soils (PCS). A survey of 13 state regulators was performed to characterize current standards and regulatory viewpoints on the use of a TPH versus a BTEX cleanup standard. The regulatory community considers the BTEX constituents the greatest threat to groundwater, yet expressed concern that the use of a compound specific standard, without an accompanying analysis for TPH, might result in residual soil contamination that may present risk. This study also evaluated the ratio of BTEX TPH in soil over time. Based on JP-4 contaminated site soil data, …

A Decision Support Model Using Life Cycle Cost (Lcc) Analysis To Select Cost-Effective Alternatives For Hazardous Materials, Blaine F. Burley, Kirk A. Phillips

Theses and Dissertations

This research focuses on the development of a decision support model to select cost-effective alternatives for hazardous materials using life cycle cost (LCC) analysis. The model provides an effective decision-making tool to evaluate the economic feasibility of using alternatives for hazardous materials. Given a specific operation, the users of this model can enter site-specific cost data to determine the total LCCs of using baseline hazardous materials (i.e., hazardous materials currently being used in an operation), as well as the total LCCs of using various alternatives. This thesis postulates that the material having the lowest total LCC is considered to be …

A Refinement Of Risk Analysis Procedures For Trichloroethylene Through The Use Of Monte Carlo Method In Conjunction With Physiologically Based Pharmacokinetic Modeling, William J. Cronin Iv, Eric J. Oswald

Theses and Dissertations

This study refines risk analysis procedures for trichloroethylene (TCE) using a physiologically based pharmacokinetic (PBPK) model in conjunction with the Monte Carlo method. The Monte Carlo method is used to generate random sets of model parameters, based on the mean, variance, and distribution types. The procedure generates a range of exposure values for human excess lifetime cancer risk of lxl0 (exp-6), based on the upper and lower bounds and the mean of a 95% confidence interval. Risk ranges were produced for both ingestion and inhalation exposures. Results are presented in a graphical format to reduce reliance on qualitative discussions of …

Development Of An Effectiveness Model Or Metric For The Air Force Environmental Compliance Assessment And Management Program (Ecamp), Craig B. Dezell

Theses and Dissertations

The Department of Defense (DoD) and the Air Force (AF) are committed to being national leaders in protecting and enhancing the environment and achieving environmental compliance. This commitment is exemplified by the Air Force Chief of Staff's goal of no notices of violation (NOVs). However, the number of AF NOVs from 1990-1992 rose from 103 to 178 an increase of 73 percent. A July 1992 AF Inspector General Report also concluded that Environmental Compliance Assessment and Management Program (ECAMP) findings were not being effectively utilized by the Major Commands (MAJCOM). To aid AF leaders in solving these problems, and protecting …

Development Of A Multicriteria Decision Model For Prioritizing Air Force Environmental Restoration Program Projects, Thomas E. Ellingson, T. G. Gallogly

Theses and Dissertations

Cleaning up hazardous and toxic wastes left from past activities has become one of the major goals of the Department of Defense. Within the Air Force, individual major commands (MAJCOMs) annually review numerous projects submitted under the Defense Environmental Restoration Program (DERP) and forward these projects to HQ USAF/CEVR for funding. Until recently, adequate resources have been available to fully fund all projects. However, within the last two years, funding shortfalls have been experienced, and projects have received only partial funding. The Air Force needs a decision support system that will assist in determining funding priorities for these projects. This …

A Strategy For Combining The Pollution Prevention Opportunity Assessment With The Environmental Compliance Assessment And Management Program, Stacy E. Gent

Theses and Dissertations

This research develops a method to allow an installation environmental function to satisfy the assessment requirements of both the Air Force Pollution Prevention and the Environmental Compliance Assessment and Management Program with the implementation of one assessment process. The model developed is designed to achieve the goals of both programs while increasing the efficiency of implementation. The resulting assessment model formulated within this research is applied on a theoretical level to yield preliminary results. These results indicate that the combination of the Pollution Prevention Opportunity Assessment and the environmental compliance assessment required by the Environmental Compliance Assessment and Management Program …