Digital Commons Network^™

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 …

Naval Airborne Early Warning 1945-1985, Edwin Leigh Armistead

History Theses & Dissertations

Airborne Early Warning (AEW) is the act of carrying a search radar aloft that can actively detect and even control aircraft and ships where a radar mounted on a ship or on land cannot. The United States Navy began research during World War II to counter the low-flying aircraft threat. Development of the AEW aircraft, however, was not complete in time to be of use during this conflict. Initially the Navy used two different aircraft, one carrier-based and the other land-based, to detect such air threats. As technology improved, these different capabilities were combined into a single airframe that contained …

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 …

Bleek: A Dramatic Poem, Gwendolyn Gail Nixon

English Theses & Dissertations

This poem is not about any character in particular. It is a montage of disenfranchised voices which reflect disenchantment with the status quo: a system that continues to see gang members as crazed people who are non-human, a stereotype which perpetuates gang-related killings.

Nevertheless, the poem has some of the qualities of a short story in that it has a beginning, middle, and end, as well as a central character, Bleek, who speaks for the norms of the poem. Through a series of scenes and reflections, Bleek takes us on a journey which is as demoralizing as the one that …

The Falcon: A Play, Harold W. Mckinney Ii

Institute for the Humanities Theses

The Falcon is a historical drama set in medieval France during the reign of Philip the Fair, a tumultuous period of history marked by the fall of the Holy Land to Islam after more than 200 years of struggle by Christian forces to reclaim it, and followed by the gradual exile of the Popes from Rome to Avignon on the outskirts of France.

The play itself focuses on King Philip's repeated clashes with the Papacy, as well as his ruthless attack on the Order of the Knights Templar, whose own fate was interwoven with the fortunes of both Crown and …

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 …

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 …

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 …

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 …

Maternal Perceptions Of The Social Development And Behavior Of Asthmatic Children, Chelley A. Merrell

Psychology Theses & Dissertations

To assess the effects of asthma on the social development and behavior of asthmatic children, 60 mothers of 6- to 13-year-old children (30 mothers of asthmatics, 30 mothers of non-asthmatics) completed the Child Behavior Checklist (CBCL: Achenbach & Edelbrock, 1986) and were administered the Vineland Adaptive Behavior Scale (Vineland: Sparrow, Balla, & Cicchetti, 1984). It was hypothesized that asthmatic children would lag behind non-asthmatic peers in social development, defined as the development of age-appropriate behaviors (i.e., communication, daily living skills, and socialization). In addition, it was hypothesized that asthmatic children would exhibit more internalizing behaviors than non-asthmatic children. There were …

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 …

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.

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 …

A Cipp Evaluation Of The Administrative Associate Training Program Through Sentara, Patricia A. Criswell

Community & Environmental Health Theses & Dissertations

Hospitals are facing change in today's environment. In order to meet these growing challenges, they are responding by providing value added services. Value added services have been defined as reducing inefficiencies and improving quality and service. Operational restructuring in the form of a new concept called patient-focused care has become the paradigm shift and structural revamping at several hospitals across the nation. Sentara Hospitals have adopted this program to improve the clinical and service quality delivered to the patient. An integral component of this new approach is the multiskilling of staff to reduce duplication, inefficiencies, and improve the quality provided …

Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia

Mechanical & Aerospace Engineering Theses & Dissertations

A new composite damping material is investigated, which consists of a viscoelastic matrix and high elastic modulus fiber inclusions. This fiber enhanced viscoelastic damping polymer is intended to be applied to light-weight flexible structures as surface treatment for passive vibration control. A desirable packing geometry for the composite material is proposed, which is expected to produce maximum shear strain in the viscoelastic damping matrix. Subsequently, a micromechanical model is established in which the effect of fiber segment length and relative motion between neighboring fibers are taken into account. Based on this model, closed form expressions for the effective storage and …

A Computer-Based Strategy To Facilitate Organizational Learning Process, Charles B. Keating

Engineering Management & Systems Engineering Theses & Dissertations

This research investigated the development of Organizational Learning Process (OLP) through the application of a computer-based strategy in an organizational setting. OLP is developed from the organizational learning literature as an integration of similar concepts of organizational processes of inquiry essential to organizational learning. These concepts included: organizational dialectic (Argyris and Schon 1978), surfacing and testing mental models (Senge 1990a,1990b), and interpretation process (Daft and Weick 1984). A qualitative research methodology was developed within a participatory action research framework (Whyte 1989). A six phase research project, designed as a computer-based strategy to generate OLP, was applied in an organizational setting. …

Absorption Imaging Studies On Intrinsic Gaas, John Samuel Kenney

Electrical & Computer Engineering Theses & Dissertations

A diagnostic technique has been developed which allows recording of the temporal and spatial development of electric field structures in GaAs photoconductive switches. The optical method is based on the Franz-Keldysh effect. Measurements were performed with a Nd:YAG activation laser and a GaAs laser diode as the probe laser. At low applied voltages a 100 atm wide region of high electric field is seen at the cathode only. With increasing voltage strong domain like structures emerge at the anode also. A calibration measurement shows that the electric fields in these domains are well above 50 kV/cm. At a threshold voltage, …

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen

Electrical & Computer Engineering Theses & Dissertations

Fiber optic sensors are widely used in today's technological applications, providing many advantages that conventional sensors lack. In particular, there is a demand in hypersonic applications to develop microphones to measure acoustic pressure that performs in high temperature and noisy surroundings. This thesis analyzes fiber optic lever microphones (FOLM), since they perform at high temperatures. An FOLM system is an intensity modulated sensor, which is simple to implement and is small in size. Two models of the FOLM have been fabricated and calibrated. The first model uses a seven-element fiber array while the second uses a single-fiber to transmit and …

Light Injection From An Active Cladding To The Core Of A Fiber Optic Fluorosensor, Alvin Leon Bryant

Electrical & Computer Engineering Theses & Dissertations

A fluorosensor works on the basis of light injection from the clad into the core of an optical fiber. The sensitivity of such a sensor depends on the efficiency of light injection. Conditions necessary for a high injection efficiency are experimentally determined. The refractive index difference between the core and the clad,ⁿcore ^-nclad, must be maximized to achieve a high injection efficiency. Since an air clad has the least refractive index, a bare core fiber will have a maximum efficiency. Standard optical fibers used for communication employ a minimum value for ⁿcore ^-nclad, in order …

Study Of Algebraic Reynolds Stress Models For The Computation Of Secondary Motion In Channels, Tomas Chylek

Mechanical & Aerospace Engineering Theses & Dissertations

A three-dimensional computer code for solving Reynolds equations of turbulent flow at high Reynolds numbers in generalized curvilinear coordinates is used to study the engineering applications of several variants of linear and nonlinear second moment algebraic Reynolds stress models based on pressure-strain correlation of Launder, Recce and Rodi (1975) and Speziale, Sarkar and Gatski (1991). A new form of algebraic Reynolds stress equation in generalized curvilinear coordinates is derived based on simplification of Reynolds stress transport equations. Two implicit and two explicit implementations are explored in three different geometries of straight channel flows. The predictions of secondary motion driven by …

Materialism And The Self, Kathleen Shirley Micken

Theses and Dissertations in Business Administration

Materialism has been called the most significant macro development in modern consumer behavior. Despite its importance, research about the construct is rather new. Two scales have been developed to measure materialism, one proposed by Belk, the other by Richins and Dawson.

The purpose of this dissertation is threefold. First, it extends the materialism research program by investigating the relationship between materialism and one's self concept. Hypotheses which drive the research posit that people who are more materialistic have lower self-esteem, are less likely to be self-actualized, are extrinsically rather than intrinsically motivated, and are likely to be high self-monitors. The …

Boundary Layer Influences On The Subsonic Near-Wake Of A Family Of Three-Dimensional Bluff Bodies, Charles Willliam Alcorn

Mechanical & Aerospace Engineering Theses & Dissertations

A study is reported on subsonic bluff body near-wake flows. It has been determined that one family of bluff bodies, namely slanted-base ogive cylinders, can experience either a closed recirculating near-wake, or a longitudinal vortex near-wake depending on the base slant-angle and the Reynolds number. This suggests a dependence of near-wake parameters on the state of the boundary layer ahead of separation. This report addresses the influence of the boundary layer on the near-wake of slanted-base bluff bodies. Experiments were conducted in two facilities, the 6-inch Magnetic Suspension and Balance System (MSBS) at NASA Langley Research Center and the Old …

A Framework For Data Sharing In Computer Supported Cooperative Environments, Mohamed Youssef Eltoweissy

Computer Science Theses & Dissertations

Concurrency control is an indispensable part of any information sharing system. Co-operative work introduces new requirements for concurrency control which cannot be met using existing applications and database management systems developed for non-cooperative environments. The emphasis of concurrency control in conventional database management systems is to keep users and their applications from inadvertently corrupting data rather than support a workgroup develop a product together. This "insular" approach is necessary because applications that access the database have been built with the assumptions that they have exclusive access to the data they manipulate and that users of these applications are generally oblivious …

Boundary Value Problems In Rectilinearly Anisotropic Thermoelastic Solids, Gilbert Kerr

Mathematics & Statistics Theses & Dissertations

The boundary value problems which are considered are the type that arise due to the presence of a Griffith crack (or cracks) in an anisotropic thermoelastic solid. The thermoelastic field, in such materials, when the infinitesimal theory is employed, is governed by a set of elliptic partial differential equations. The general solution of these equations is expressed in terms of arbitrary analytic functions whose real parts, in turn, are expressed in terms of Fourier type integrals or Fourier series. Integral transform techniques are then used to determine the stress intensity factors (and other pertinent information) for various crack geometries. In …

Multilevel Parallel Communications, Sanjay Khanna

Computer Science Theses & Dissertations

The research reported in this thesis investigates the use of parallelism at multiple levels to realize high-speed networks that offer advantages in throughput, cost, reliability, and flexibility over alternative approaches. This research specifically considers use of parallelism at two levels: the "upper" level and the "lower" level. At the upper level, N protocol processors perform functions included in the transport and network layers. At the lower level, M channels provide data and physical layer functions. The resulting system provides very high bandwidth to an application. A key concept of this research is the use of replicated channels to provide a …

Studies On Nonequilibrium Phenomena In Supersonic Chemically Reacting Flows, Rajnish Chandrasekhar

Mechanical & Aerospace Engineering Theses & Dissertations

This study deals with a systematic investigation of nonequilibrium processes in supersonic combustion. The two-dimensional, elliptic Navier-Stokes equations are used to investigate supersonic flows with nonequilibrium chemistry and thermodynamics, coupled with radiation, for hydrogen-air systems. The explicit, unsplit MacCormack finite-difference scheme is used to advance the governing equations in time, until convergence is achieved.

For a basic understanding of the flow physics, premixed flows undergoing finite rate chemical reactions are investigated. Results obtained for specific conditions indicate that the radiative interactions vary substantially, depending on reactions involving HO$\sb2$ and NO species, and that this can have a noticeable influence on …

Three-Dimensional Transport Simulations Of The Dispersal Of Volcanic Aerosol From Mount Pinatubo, T. Duncan A. Fairlie

Mechanical & Aerospace Engineering Theses & Dissertations

A global finite-difference model that simulates the large-scale dynamics of the Earth's stratosphere and mesosphere is combined with a global spectral transport model to investigate aspects of the initial dispersal of the volcanic aerosol plume from the Mount Pinatubo eruption in 1991. Results of the modelling study are found to compare well with observations of the volcanic plume made from satellite instruments. Dynamical quantities, diagnosed from the simulated fields are used to provide insight into the evolution of the volcanic plume. Lagrangian trajectory analysis is used to help assess the performance of the Eulerian transport model and to highlight small-scale …

Development Of A Knowledge Based System For Wastewater Pipeline Failure Risk Assessment, Adam Mayanzani Ngaliga

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this thesis was to study and analyze the wastewater pipeline failure risk assessment process, and then design and develop an effective and efficient wastewater pipeline risk assessment tool for the Hampton Roads Sanitation District, in Virginia, U.S.A. A knowledge based system was developed using an expert system building shell (Xi-Plus).

The system design is based on the knowledge elicited from the experts and literature in sanitary pipeline failure risk evaluation. The knowledge base contains both heuristics and procedural rules. The system interprets the information provided by the user and reasons from that information to reach conclusions on …

A Multivariate Quality Control Approach For Automated Manufacturing Systems, Hisham Naim Ashur

Engineering Management & Systems Engineering Theses & Dissertations

In today's competitive manufacturing environment, effective and practical statistical quality control approaches are essential. A successful process control approach needs to provide on line real time monitoring of quality related characteristics.

No longer acceptable is an approach that analyzes quality related data only after the product is produced. A statistical process control approach that monitors the process during production and that reports trouble spots before bad products are made is necessary in an automated manufacturing environment.

An automated manufacturing environment is characterized by high volume production runs and short production cycles. Traditional statistical process control approaches are not capable of …

The Influence Of Reynolds Number And Atmospheric Effects On Aircraft Wake Vortices Near The Ground, Zhongquan Charlie Zheng

Mechanical & Aerospace Engineering Theses & Dissertations

Aircraft wakes represent potential hazards which can control aircraft spacing and thus limit airport capacity. Wake vortex trajectories and strengths are altered radically by interactions with the ground plane and by atmospheric conditions. This work has been concerned with developing more accurate numerical predictions. A two-dimensional, unsteady numerical-theoretical study is presented which has included viscous effects, the influence of stratification, crosswind and turbulence on vortex behavior near the ground plane, using a vorticity-streamfunction formulation.

A two-parameter perturbation procedure has been developed which uses analytic solutions for the initial flow field to accommodate the ground effect region in the numerical simulation. …