Digital Commons Network^™

Application Of Shape Sensitivity Analysis For Computation Of Transient Free-Surface Flows, Frank Nicolas Michel

Mechanical & Aerospace Engineering Theses & Dissertations

Shape sensitivity analysis is introduced into a numerical scheme simulating a transient free-surface flow and applied to the case of a fluid advancing through a bed of cylinders. For this incompressible Newtonian flow, viscous forces are dominant. A penalty function finite element formulation is used to solve the problem. Coordinates of nodes on the moving boundary are chosen as design variables and an analytical formulation of the gradient of the finite element algebraic system, with respect to these variables, is derived.

In a numerical example, the results obtained with and without sensitivity analysis are compared. The efficiency and accuracy of …

Non-Linear Dynamics And Control For Thermal Room Models, Milind Prabhakar Oak

Mechanical & Aerospace Engineering Theses & Dissertations

Heating, Ventilation and Air Conditioning (HVAC) building operations with emphasis on reduced energy costs and occupant comfort require a dynamic control of short response (minutes) elements of HVAC systems. Hence, it is imperative to acquire better methods of non-linear modeling for prescription of thermal controls which will regulate space conditions over wide parameter ranges without undue cycling or steady state errors. A first step towards this goal is identification and inclusion of short response dynamics elements in the HVAC systems model while retaining essential non-linearities. A single zone environmental chamber is modeled in the heating mode. In the model, …

Changes In Caloric Content As A Result Of Sub-Lethal Stress In Neanthes Virens (Sars), Phyllis J. Friello

Biological Sciences Theses & Dissertations

Neanthes virens were subjected to a toxicity test with 1.8, 3.4, 6.7 and 11.0 mg/1 Cd²⁺. Worms were withdrawn on Days 1, 4, 7, 10 and 14 from each of five replicate tanks and their caloric content determined by bomb calorimetry. Analyses of variance and covariance showed no significant differences in worm caloric content with withdrawal day or cadmium concentration.

In a second experimental series, a sediment toxicity test with Neanthes virens was conducted in contaminated sediments from two sites, as well as reference sediments from a control site. Caloric content of the worms was measured by bomb …

Optical Machine Recognition Of Lower-Case Greek Characters Of Any Size, Ivan X. D. D'Cunha

Electrical & Computer Engineering Theses & Dissertations

An algorithm utilizing a syntactic approach and a criterion based on normalized moments is defined for the reliable, automatic, machine recognition of handwritten and printed Greek characters of any size and font. In this approach a binary image of the character in question is obtained initially; its skeleton is then produced by utilizing a standard thinning algorithm. The classification process then incorporates the topological features of the characters such as existence of closed curves, number of intersections, number and location of free ends, axial symmetry, and the criteria derived from normalized moments to uniquely identify each pattern. Experiments conducted demonstrated …

Synthesis Of An Efficient Band Mechanism For Robots And Prosthetic Devices, Run Chen Zhou

Mechanical & Aerospace Engineering Theses & Dissertations

A noncircular pulley has been applied to improve the system efficiency of an electrical-powered elbow prosthesis. The dynamics of the motor and the prosthetic arm have been incorporated into the kinematic synthesis relationships for determining the pulley profile that maximizes the efficiency of the elbow prosthesis.

The nonlinear dynamic equations have been solved by the code Differential Equation (DE) while determining the motor power and efficiency which are the criteria in the nonlinear programming problem. The optimal design variables for determining the pulley profile along with some simulation results have been obtained from an optimization program (based on the Generalized …

Electrostatic Effects On Airborne Asbestos Monitoring, Roxanne Francis

Biological Sciences Theses & Dissertations

The affects of electrostatic forces on the Membrane Filter Method (MFM) used for air-borne asbestos monitoring have been investigated for many years. Several studies have indicated that these forces interfere with the collection of asbestos fibers on the membrane filter, which results in an underestimated analysis of the airborne concentration. By varying the electroconductivity of the extension cowls on the filter cassettes, it was speculated that the significance of the electrostatic forces could be statistically analyzed. Four sets of filter cassettes with grounded conductive (GC) extension cowls, ungrounded conductive (UC) extension cowls, grounded nonconductive (GN) extension cowls, and ungrounded nonconductive …

Sojourn: A Time In Egypt, Deborah L. Miller

Institute for the Humanities Theses

This work is a chronicle of events and ideas experienced by the author while traveling in the Arab Republic of Egypt in December, 1986 and January, 1987. The illustrations at each chapter head were drawn to help the reader understand the nature of the story of each chapter.

Domain Decomposition For Multigrid, Finite Volume Flow Solvers, Victor Robert Lessard

Mechanical & Aerospace Engineering Theses & Dissertations

Computing the flow fields about three-dimensional complex configurations accurately becomes a difficult task, if it is attempted to generate a single, body fitted grid with proper clustering. The domain decomposition methods, which divide the computational domain into less complex subdomains, are extensively used to decrease the grid generation workload. A domain decomposition technique also allows the use of different solution methods for different subdomains. The objective of this work is to develop a domain decomposition method via overlapping/embedding the component grids, which is to be used by upwind, multigrid, finite volume solution algorithms. A computer code, given the name MaGGiE, …

The Effects Of Bending On The Strain Distributions In A Stiffener-Skin Interface Region, Osvaldo F. Lopez

Mechanical & Aerospace Engineering Theses & Dissertations

An analytical and experimental study to assess the effect of bending on the adhesive strain distributions in a stiffener-skin interface region is described. A one-dimensional beam analysis is derived using a variational approach. Parametric studies are conducted to assess the effects of stiffener, skin, and adhesive thickness and adhesive material nonlinearity on the adhesive layer extensional and shear strain distributions subjected to applied bending. Two experimental methods of measuring through-the-thickness extensional strains in an adhesive are investigated. One method involves measuring the changes in the resistance of a composite strain sensor subjected to applied tension and compression loads. The second …

The Electrical Characteristics Of Semi-Insulating Gallium Arsenide A Material For High Power Switches, David Clifton Stoudt

Electrical & Computer Engineering Theses & Dissertations

An experimental study of the electrical characteristics of semi-insulating gallium arsenide has been performed. The goal of this research was to aid in the development of an electron-beam controlled high-power semiconductor switch. The electrical characteristics were found to be heavily dependent on the deep level configuration of the material being investigated. Two methods of deep level characterization are discussed and their results are compared to the information given by the material manufacturer. Studies were conducted to determine both the steady-state and transient dark current characteristics of the switch. Along with being a function of the applied voltage and the deep …

Navier-Stokes Analysis Of Cold Gas Scramjet Nozzle-Afterbody Flowfields, Walter C. Engelund

Mechanical & Aerospace Engineering Theses & Dissertations

The recent renewal of interest in hypersonic aerodynamics, brought about largely in part due to the development of the National Aerospace Plane (NASP), is resulting in an increased reliance on computational fluid dynamics for flowfield data in this flight regime. The design of the nozzle-afterbody section for a hypersonic transport such as the NASP is currently underway, and is being conducted using both computational fluid dynamics and cold, non-reacting, simulant gas experimental models. In this study, a computational analysis is conducted for the flow through a scramjet nozzle-afterbody test section.

Computations have been performed for a cold gas simulation of …

Comparison Of Digital Controllers Used In Magnetic Suspension And Balance Systems, William Allen Kilgore

Mechanical & Aerospace Engineering Theses & Dissertations

Dynamic systems that were once controlled by analog circuits are now controlled by digital computers. Presented is a comparison of the digital controllers presently used with magnetic suspension and balance systems. The overall response of the systems are compared using a computer simulation of the magnetic suspension and balance system and the digital controllers. The comparisons include responses to both simulated force and position inputs. A preferred digital controller is determined from the simulated responses.

An Assessment Of The Characteristics And Attrition Rates Of Physical Therapist Assistant Educational Programs, Pamela Ann Bayliss

Community & Environmental Health Theses & Dissertations

The purpose of this study was to determine the student attrition rate in physical therapist assistant programs accredited by the American Physical Therapy Association (APTA) at the time of the study and to identify factors which may affect student attrition. The survey instrument was designed to gather data on student attrition rates for the classes which graduated in 1984, 1985, and 1986 and on program characteristics such as admission policies and curricular requirements. The mean student attrition rates were 32%, 28.6%, and 26.4% in 1984, 1985 and 1986, respectively. There were no significant differences identified via Chi Square (p

Investigating The Method Of Structural Topological Variations For Sensitivity Analysis And Design Optimization, Niki A. Mehta

Mechanical & Aerospace Engineering Theses & Dissertations

The method of structural topological variations is a newly developed technique for analysis of frame structures. It provides a novel method that completely avoids formulating and solving simultaneous equations, required in the finite element displacement method. The principal objective of this thesis is to investigate the method of topological variations as a possible design tool and study its applicability in the sensitivity analysis and in the process of design optimization.

A computer code was developed for this method to obtain its comparative performance against the finite element displacement method. For analysis of large structures involving frequent local modifications, the method …

Determinations Of Molecular Weight And Molecular Weight Distribution Of High Polymers By The Rheological Properties, Joan Y. Z. Huang

Mechanical & Aerospace Engineering Theses & Dissertations

Several methods are reviewed by which the molecular weight (MW) and molecular weight distribution (MWD) of polymeric material were determined from the rheological properties. A poly (arylene ether) polymer with six different molecular weights was used in this investigation. Experimentally measured MW and MWD were conducted by GPC/LALLS (Gel Permeation Chromatography/Low Angle Laser Light Scattering), and the rheological properties of the melts were measured by a Rheometric System Four rheometer. It was found that qualitative information of the MW and MWD of these polymers could be derived from the viscoelastic properties, with the methods proposed by Zeichner and Pate1, and …

Global/Local Stress Analysis Of Composite Structures, Jonathan B. Ransom

Mechanical & Aerospace Engineering Theses & Dissertations

A method for performing a global/local stress analysis is described and its capabilities are demonstrated. The method employs spline interpolation functions which satisfy the linear plate bending equation to determine displacements and rotations from a global model which are used as "boundary conditions" for the local model. Then, the local model is analyzed independent of the global model of the structure. This approach can be used to determine local, detailed stress states for specific structural regions using independent, refined local models which exploit information from less-refined global models. The method presented is not restricted to having a priori knowledge of …

The Composition And Concentrations Of Cyanobacteria In The North Landing River, Virginia And Upper Currituck Sound, North Carolina, Sonja E. Midgette

Biological Sciences Theses & Dissertations

A 12 month study of cyanobacteria composition and concentrations in the North Landing River and upper Currituck Sound was conducted from March 1986 to February 1987. Epifluorescence microscopy and the fluorochrome proflavin were used to determine cell concentrations and vertical, station to station and seasonal distribution of these cells. Cyanobacterial assemblage patterns were coupled with pH, temperature, salinity and water transparency readings.

Cyanobacteria were found to be a persistent and prolific phytoplankton component of both the river and upper sound. For a comparison of vertical distribution for each station, an analysis of variance for. two groups of equal size was …

Software Reliability Models, Syed Afzal Hossain

Mathematics & Statistics Theses & Dissertations

The problem considered here is the building of Non-homogeneous Poisson Process (NHPP) model. Currently existing popular NHPP process models like Goel-Okumoto (G-O) and Yamada et al models suffer from the drawback that the probability density function of the inter-failure times is an improper density function. This is because the event no failure in (0, oo] is allowed in these models. In real life situations we cannot draw sample(s) from such a population and also none of the moments of inter-failure times exist. Therefore, these models are unsuitable for modelling real software error data. On the other hand if the density …

Evaluation Of Equilibrium Turbulence For A Hypersonic Boundary Layer At Nonadiabatic Wall Conditions, Cindy W. Albertson

Mechanical & Aerospace Engineering Theses & Dissertations

This paper presents an experimental study to characterize the compressible turbulent boundary layer produced along a flat plate in the NASA Langley 8-Foot High Temperature Tunnel and determine the test conditions necessary to achieve equilibrium turbulence. In addition, the present study extends the data base for equilibrium compressible turbulent boundary layers over quasi-isothermal walls which are far from the adiabatic wall temperature. The measurements consist of pilot pressure, static pressure, and total temperature distributions in the boundary layer. A flat plate measuring 9.7 feet long and 4.3, feet wide was used for the study to provide a naturally turbulent boundary …

A Comparative Analysis Of Selected Adolescent Fears, Martina Griffith Meyer

Psychology Theses & Dissertations

The subject of adolescent fears troubling today's generation was studied with the question of specific fears and methods of questioning. It was hypothesized that direct, close-ended questions related to the fear of nuclear war and the fear of failure would elicit responses of greater fear than would indirect, open-ended questions about the future. It was also hypothesized that there would be sex differences in fearfulness of nuclear war with females indicating more fear. It was also expected that there would be developmental differences with 8th-grade subjects more fearful of nuclear war than 12th-grade subjects, and with the older subjects more …

Explicit And Implicit Calculations Of Turbulent Cavity Flows With And Without Yaw Angle, Guan-Wei Yen

Mechanical & Aerospace Engineering Theses & Dissertations

Computations have been performed to simulate turbulent supersonic flows past three-dimensional deep cavities with and without yaw. Simulation of these self-sustained oscillatory flows have been generated through time accurate solutions of the Reynolds averaged complete Navier-Stokes equations using two different schemes: (1) MacCormack, finite-difference, (2) implicit, upwind, finite-volume schemes. The second scheme, which is approximately 30% faster, is found to produce better time accurate results. The Reynolds stresses have been modeled, using the Baldwin-Lomax algebraic turbulence model with certain modifications. The computational results include instantaneous and time averaged flow properties everywhere in the computational domain. Time series analyses have been …

The Use Of Rhythm In The Acquisition Of Motor Skills, Ann C. Fulop

Psychology Theses & Dissertations

This research assessed whether rhythm aids in the acquisition of motor skills by providing cues for the timing of those skills. The nature of representations of rhythms in memory was also explored. Certain rhythms have stable memory representations, while others have unstable representations. It was hypothesized that rhythms that had stable memory representations would be more beneficial in learning a skill than unstable rhythms. Three groups learned three different rhythms by practicing a tracking task. Three different tracks displayed the three rhythms. Following training, subjects attempted to reproduce the rhythms from memory. The results suggest that rhythms do help in …

Stability Design Of A Slender Column With Curved Longitudinal Stiffeners, Mark S. Lake

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents the results of a stability design study of a slender column with curved longitudinal stiffeners for large space structure applications. The stiffened column concept is attractive because it allows the buckling load of a slender column to be increased at a fairly low cost in increased mass, and at no change in the column packaged size. Linear stability analyses are performed using a "linked-plate" representation of the stiffeners to determine stiffener local buckling stresses. Results from a set of parametric analyses are used to determine an approximate explicit expression for stiffener local buckling in terms of its …

Pet Rock, July A. Jolly

English Theses & Dissertations

This book is an attempt to re-create the essence of what life was like for an American family living in Zambia during the early 197Os. While it must be acknowledged that Pet Rock is semi-autobiographical--after all, my family, like the Petersons, lived in Zambia, and I, like Carrie, was sent away to the United States for school--the events dramatized are nevertheless completely imaginary, as are the characters involved. Even Carrie, who grew directly out of my own emotional remembrance, is not really me. And yet, although it doesn't tell "what actually happened," Pet Rock allows the reader to experience what …

Numerical Study Of Three-Dimensional Separation And Flow Control At A Wing/Body Junction, Balakrishnan Lakshmanan

Mechanical & Aerospace Engineering Theses & Dissertations

The problem of three-dimensional separation and flow control at a wing/body junction has been investigated numerically using a three-dimensional Navier-Stokes code. The numerical code employs an algebraic grid generation technique for generating the grid for unmodified junction and an elliptic grid generation technique for filleted fin junction. The results for laminar flow past a blunt fin/flat plate junction demonstrate that after grid refinement, the computations agree with experiment and reveal a strong dependency of the number of vortices at the junction on Mach number and Reynolds number. The numerical results for pressure distribution, particle paths and limiting streamlines for turbulent …

Hemispheric Effects Of Response Hand And Concurrent Auditory And Visual Information Processing On Task Performance, Paula J. Guerette

Psychology Theses & Dissertations

Previous research (cf. Wickens, Mountford & Schreiner, 1981; Wickens & Sandry, 1982) has suggested that performance is facilitated by maintaining "integrity" between the hemisphere of information input, processing, and motor response. This task-hemispheric integrity has been found to exist during concurrent performance of verbal and spatial tasks, both of which are presented in a visual modality. The present study sought to examine whether task-hemispheric integrity exists during concurrent performance of a verbal and a spatial task when the verbal task is presented in an auditory modality and the spatial task(s) are presented in a visual modality. Fifty-six individuals (28M, 28F) …

The Effects Of Life Stress And Risk-Taking Style On Risk Perception And Driver Performance, Christine B. Philput

Psychology Theses & Dissertations

This study examined the effects of risk-taking style, stress level, and highway environment on driver performance. In Phase I, 50 subjects were assessed for risk-taking style and stress level. In Phase II, the same subjects were presented with slides of traffic situations that varied in terms of risk of accident. This was a paired comparison task in which they rank-ordered ten highway sites, producing a measure of subjective risk. No significant relationships were identified between these subjective risk judgments and objective data regarding those sites (accidents and fatalities), though this is most likely due to problems with the slide presentation. …

Signals Intelligence In World War Ii Ultra And The Air War In Europe, Demetrio J. Perez

Graduate Program in International Studies Theses & Dissertations

(First paragraph) In recent years the study of military intelligence, particularly when viewed from a historical context, has acquired new significance. As military historians attempt to find a correlation between wartime events and the intelligence activities supporting those events, many serious works in this field have emerged. Some accounts of World War II military intelligence deal with the subject in terms of its benefits to the field commander. Others take a more extreme view and argue that major wartime successes resulted more from good intelligence than from good leadership.

An Analysis And Evaluation On Printed Materials Used In Genetic Counseling, Janet L. Macarthur

Community & Environmental Health Theses & Dissertations

The purpose of this study was to examine printed educational materials on five specific genetic disabilities and evaluate them for appropriateness of reading level and for inclusion of several specific issues related to the adequacy of the literature. Publicly available literature was analyzed using the Flesch-Kincaid Readability Formula and content analysis to estimate readability and to test for the presence of a definition of the disorder, a description of the basic genetics of the disorder and its symptomology, references to support groups and references for further information.

The data indicate that a definition of the disorder was included in 85% …

Mine Warfare In The Russian And Soviet Navies, Jeffrey K. Bray

Graduate Program in International Studies Theses & Dissertations

This thesis examines the development of technology, tactics, strategy, and organization of mine warfare in the Russian and Soviet navies from 1807 to the present. The author reviews the trials and tribulations of the development of naval mines and their employment within these two navies. This development has been primarily driven by the needs of war and advances of technology. In spite of occasional setbacks, the Russian and Soviet mine warfare forces continued to provide support to the overall naval and central policies of their respective governments. This support has often been during times of high tension and limited resources. …