Digital Commons Network^™

Experimental Investigation Of A Direct Expansion Solar-Assisted Heat Pump, James Yau-Jwo Shen

Mechanical & Aerospace Engineering Theses & Dissertations

A direct expansion solar-assisted heat pump, which uses economical bare solar collectors as evaporator, is designed and operated. The experimental results indicate that marked improvement in thermal performance results if the collector/ evaporator temperature is maintained at o0c to 10°c above the ambient temperature. During the course of this investigation, the system thermal performance is determined under various ambient and operating conditions by measuring the incident solar energy flux, refrigerant flow rate, temperature and pressure at various locations in the system. The heat pump coefficient of thermal performance and solar collector efficiency ranging from 2.0 to 3.0 and 40% to …

Improved Finite Element Methodology For Integrated Thermal-Structural Analysis, Pramote Dechaumphai

Mechanical & Aerospace Engineering Theses & Dissertations

An integrated thermal-structural finite element approach for efficient coupling of thermal and structural analysis is presented. New thermal finite elements which yield exact nodal and element temperatures for one-dimensional linear steady-state heat transfer problems are developed. A nodeless variable formulation is used to establish improved thermal finite elements for one-dimensional nonlinear transient and two-dimensional linear transient heat transfer problems. The thermal finite elements provide detailed temperature distributions without using additional element nodes and permit a common discretization with lower order congruent structural finite elements. The accuracy of the integrated approach is evaluated by comparisons with analytical solutions and conventional finite …

A Pattern Analysis Algorithm For Wind Ambiguity Removal, Jaime R. Tormos

Electrical & Computer Engineering Theses & Dissertations

Some remote sensing devices, such as satellite microwave scatterometers, produce sampled wind vectors that are accurate in speed and streamline direction, but have a directional ambiguity of 180°. The extraction of information from the two dimensional wind vectors is readily handled using pattern analysis techniques. It is shown that there is sufficient information in the spatial relationships of the generated windstream vectors to recognize the driving meteorological wind patterns. This then leads to the resolution of the wind ambiguity problem. This thesis presents the development of a pattern analysis algorithm that generates a measure of the raw data set that …

An Update Of The Tidewater Apprenticeship Information Handbook, Claud R. Divers Iii

OTS Master's Level Projects & Papers

The problem of this study was to review the Tidewater Apprenticeship Information Handbook to update information about the apprentice program and employment outlooks for the various trade areas. This information was compiled for the use of guidance and vocational education personnel for local high schools and community colleges.

A Comparison Of Chemical Applications Using Micromax Spinners And Conventional Sprayer Tips, John P. Downing

OTS Master's Level Projects & Papers

The problem of this study was to determine the effects of Poast chemical sprayed on fall grasses and weeds and their percents of kill on test strips by using a conventional hydraulic sprayer with model 8003 tips and by using a C.D.A. micromax spinner at 2000 R.P.H and at 5000 R.P.H.

A Survey Of The Salaries Of Auto Mechanics In Southeastern Virginia, Michael J. Fanelli

OTS Master's Level Projects & Papers

To answer the problem of this research study the following questions were used as a guide: 1. What kind of salary can a mechanic expect to make? 2. What method of payment is used to compute the mechanic's salary? 3. Determine how auto mechanics' salaries compared with other trades.

Electrical And Structural Properties Of P-N Junctions In Cw Laser Annealed Silicon, M. Maier, D. Bimberg, G. Fernholz, H. Baumgart, F. Phillipp

Electrical & Computer Engineering Faculty Publications

Depth profiles of the electrical quality of ion implanted and cw laser annealed p-n junctions in silicon are obtained for the first time by secondary ion mass spectroscopy. A comparison with the crystallographic properties of the surface and the junction as observed by Nomarski optical microscopy as well as cross-sectional and plan view transmission electron microscopy is made. Samples containing slip dislocations show better insulation and a lower reverse bias current across the p-n junction as compared to samples with a perfect surface in agreement with current-voltage characteristics. Small dislocation loops located at the junction are found to degrade the …

Seeded Oscillatory Growth Of Si Over Sio² By Cw Laser Irradiation, G.K. Celler, L. E. Trimble, K.K. Ng, H.J. Leamy, H. Baumgart

Electrical & Computer Engineering Faculty Publications

Extensive seeded epitaxial growth of crystalline Si over SiO₂ was achieved by an oscillatory regrowth method applied to rectangular Si pads recessed into a thick SiO₂ film. Narrow (≃5 μm) via holes linked the pads with the bulk (100) Si substrate. Oriented single crystals propagated as far as 500 μm from the seeding area, following the long term advance of a scanned focused laser beam.

An Evaluation Of Nutrient Sources To Onslow Bay, North Carolina, Larry P. Atkinson, Leonard J. Pietrafesa, Eileen E. Hofmann

CCPO Publications

Hydrographic and current meter data from Onslow Bay, North Carolina, were examined to determine the relative importance of various nutrient sources.

Upwelled Gulf Stream water is the major source of nutrients while rivers represent a minor, if not insignificant, source. In the summer during stratified conditions, the upwelled water penetrates across the shelf, but in the winter the upwelled water is restricted to the outer shelf. Nitrate flux across the 40 m isobath was calculated from continuous temperature and current records. Flux during the summer of 1976 was 2 μM m² sec^-1 which is considerably less than flux …

Smallest Cubic And Quartic Graphs With A Given Number Of Cutpoints And Bridges, Gary Chartrand, Farrokh Saba, John K. Cooper Jr., Frank Harary, Curtiss E. Wall

Mathematics & Statistics Faculty Publications

For positive integers b and c, with c even, satisfying the inequalities b+1≤c≤2b, the minimum order of a connected cubic graph with b bridges and c cutpoints is computed. Furthermore, the structure of all such smallest cubic graphs is determined. For each positive integer c, the minimum order of a quartic graph with c cutpoints is calculated. Moreover, the structure and number of all such smallest quartic graphs are determined.

Picosecond Laser Pulse Irradiation Of Crystalline Silicon, K. L. Merkle, H. Baumgart, R.H. Uebbing, F. Phillipp

Electrical & Computer Engineering Faculty Publications

Morphology changes introduced by picosecond laser pulses at λ = 532 nm and 355 nm in (111) and (100) silicon samples are studied by means of optical and high-voltage electron microscopy. Depending on energy fluence, orientation and wavelength, amorphous or highly defective regions may be created. From an analysis of damage thresholds and damage depth distributions it is concluded that melting and energy confinement precedes the formation of the structural changes.

Design And Analysis Of A Hybrid Thermoelectric Solar Collector, Kay Eddie Shaheen

Mechanical & Aerospace Engineering Theses & Dissertations

A conventional flat-plate collector is modified by imbedding thermoelectric power generators between the absorber plate and flow tubes in parallel finned-tube passes. As solar energy cascades through these generators a temperature differential between the hot and cold junctions of the device produces direct current electricity. Energy not converted to electric power is converted away for use in domestic space and/or water heating.

A parametric study is performed on the steady-state model via computer program in order to find values of design variables that maximize electric power production for purposes of driving pumps, fans, and ·controlling devices. The results of this …

Experimental Investigation Of A Rectangular Surface Thermal Plume, Li-Cheng Chu

Mechanical & Aerospace Engineering Theses & Dissertations

An experimental investigation of the three dimensional mean temperature distribution of a rectangular buoyant surface thermal plume has been conducted for a range of buoyancies, velocity ratios, Reynolds numbers, and for various turbulence generating screens in the crossflow. This study has been motivated by a concern about the applicability of laboratory model data for predicting prototype plume behavior.

A large scale model has been built to study a buoyant, rectangular surface thermal plume which enters at right angles to a constant temperature uniform crossflow of depth equal to that of the plume. A large water tank and flume with weir …

A Direct Formulation And Computer-Implementation Of A Symbolic Network Analysis Algorithm, Timothy James Knerr

Electrical & Computer Engineering Theses & Dissertations

An algorithm for the symbolic analysis of linear, time-invariant, active or passive networks is presented. The algorithm incorporates the best features of earlier numerical and topological methods of symbolic analysis. A hybrid set of equations is formulated for a closed linear graph and arranged in matrix form. A numerical evalu­ation procedure for the determinant of this hybrid matrix results in an efficient method of symbolic analysis. A proof of the algorithm based on determinant evaluation by a permutation product expansion provides insight into relationships with other methods of symbolic analysis. A computer program implementation of the algorithm is described and …

Water Wave Refraction With Non-Linear Theory, Im Sang Oh

OES Theses and Dissertations

Two different kinds of wave refraction models are formulated in the present study using Stokes' third order wave theory. One type of model is utilized in a parametric study employing several different topographies. Wave trajectories obtained from this model, when obtained by using first and third order wave theory with and without the consideration of energy dissipation, show considerable differences. These differences are examined in more detail for a bottom of constant slope: (1) An approximate 10% difference occurs between the refraction coefficients obtained using the first and the third order wave theory. (2) Considerably different ray trajectories are detected …

Analysis Of Aerothermodynamic Environment Of A Titan Aerocapture Vehicle, Hsing Chow

Mechanical & Aerospace Engineering Theses & Dissertations

The extent of convective and rad1ative heating for a Titan entry vehicle is invest1gated. The flow in the shock layer is assumed to be axisymmtric, steady, viscous, and compressible. It is further assumed that the gas is in chemical and local thermodynamic equilibrium and tangent slab approximation is used for the rad1ative transport. The effect of slip boundary conditions on the body surface and at the shock wave are included in the analysis of high altitude entry conditions. The implicit finite difference technique is used to .solve the viscous shock layer equations for a 45-degree sphere cone at zero angle …

The African Foreign Policy Of The German Democratic Republic, Heide R. Kersey

Graduate Program in International Studies Theses & Dissertations

This thesis describes the different activities sponsored by the German Democratic Republic to achieve its foreign policy goals in Africa from the late 1950s to the present. The GDR's foreign policy goals and their interaction with each other are examined. Types of GDR activities covered include solidarity assistance, contact building in Africa, United Nations diplomacy, propaganda, cultural foreign policy, trade policy, and military aid. This thesis demonstrates that the role of the GDR in Africa must be understood in the context of the Soviet Union's and the Warsaw Pact states' support of proletarian internationalism and solidarity. However, through its activities …

Effects Of The Dental Hygiene Curriculum On Student Creativity, Linda Kathryn Martin

Dental Hygiene Theses & Dissertations

This investigation examined the influence of the dental hygiene curriculum on student creativity throughout the two years of dental hygiene study. A secondary purpose was to determine if various accredited dental hygiene programs differentially affect creativity in students. Torrance Tests of Creative Thinking was used to measure creativity in students from three dental hygiene programs in Virginia. Data were organized according to a 3 X 4 factorial research design, using dental hygiene programs and academic semester levels as attribute independent variables. Fluency, Flexibility, Originality and Total scores of the Torrance Tests of Creative Thinking were the dependent variables.

Two-way analysis …

Petroleum-Utilizing Bacteria: The Biological Line Defense Against Oil Pollution, Steven W. Sokolowski

Biological Sciences Theses & Dissertations

A silica gel-petroleum (SGP) medium was developed which is reliable, approximately the same cost as that of the corresponding agar-based petroleum medium, and can be made sufficiently firm to use in streaking or the spread-plate technique. Advantages of the medium include: the incorporation of all of the major ions of seawater in accordance with Dittmar's Law (the salinity of which can easily be varied from 0 to 35 parts per thousand); a wide workable pH range (5.5 to 11.6); negligable pH drift(~ 0.2 pH units after 166 days); the elimination of all but negligable amounts of syneresis, the ability to …

Photoelastic Investigation Of Load Transfer In Eccentrically Loaded Single Lap Joints, Stephen Antrim Hann

Mechanical & Aerospace Engineering Theses & Dissertations

Photoelastic models of three eccentrically loaded single lap joints were analyzed. The adherends of each joint were identical and the bondlines differed in thickness and material properties. The adherends were analyzed for both cylindrical plate behavior and geometrical nonlinearity and the load transfer efficiency was examined. For all three models it was found that over 98% of the shank behaves as a cylindrical plate and that a geometrically nonlinear analysis yields bending stresses substantially lower than a linear analysis and that a relatively thick, low modulus bondline can increase load transfer efficiency.

The Use Of Microscopic Vegetative Characteristics And Leaf Characteristics And Leaf Deterioration Rates In The Formulation Of Keys Of Some Wetland Plants, Bruce Foy Williams

Biological Sciences Theses & Dissertations

Leaves of Spartina alterniflora, Spartina patens, Spartina cynosuroides, Distichlis spicata, Phragmites communis, Juncus roemerianus, Scirpus robustus, Typha latifolia, Iva frutescens, and Baccharis halimifolia were examined microscopically. Characteristics of each species were then used to develop identification keys. In addition, leaf fragments were buried in the marsh substrate to simulate a dredging and/or filling operation. At weekly intervals during each season of the year, a leaf fragment of each species was processed and examined to see if it could be identified.

Mining The Deep Seabed Implications For International Law And American Foreign Policy, Steven H. Fitzgerald

Graduate Program in International Studies Theses & Dissertations

Whether or not the United States may someday face a mineral shortage, the need for a coherent, unified minerals policy is critical to national objectives and national security. Deep-sea mining may be the answer to American (and world) mineral needs in the twenty-first century. However, there are numerous problems which must be dealt with and resolved in the near future, in order to enable the U.S. (and the world community) to take advantage of vast undersea resources. Deep-sea mining requires the development of technology, tremendous capital investments, and years of labor before production can begin. U.S. policy makers must decide …

Goertler Instability In Compressible Boundary Layers Along Curved Surfaces With Suction And Cooling, Alok K. Verma

Mechanical & Aerospace Engineering Theses & Dissertations

The Goertler instability of the laminar compressible boundary layer flows along concave surfaces is investigated. The linearized disturbance equations for the three-dimensional, counter-rotating streamwise vortices in two dimensional boundary layers are presented in an orthogonal curvilinear coordinates. The basic approximation of the disturbance equations, that includes the effect of the growth of the boundary layer, is considered and solved numerically. The effect of compressibility on critical stability limits, growth rates, and amplitude ratios of the vortices is evaluated for a range of Mach numbers for Oto 5. The effect of wall cooling and suction of the boundary layer on the …

Thomas Sully (1783-1872): Beginning Portraitist In Norfolk, Beth N. Rossheim

Institute for the Humanities Theses

An examination of the Register of Paintings and Journal of Activities written by Thomas Sully reveals his attempt to begin a painting career in Norfolk, Virginia, 1801-1803. A discussion of portraiture in America in the early 19th century precedes the investigation of the Sully family, their theatrical background and influence on Thomas Sully. Descriptive material on Norfolk is provided as background to a close study of Sully's earliest patrons Several early portraits are presented to demonstrate a progressive sophistication.

The Evolution Of The Fleet Submarine In The United States Navy, Robert P. Kendall

History Theses & Dissertations

This thesis examines the evolution of the United States Navy fleet submarine from the T-class of 1916 through the Tench-class of 1943. The fleet submarine played a major role in the defeat of Japan in World War II by attacking enemy lines of communication and supply, vital to an island empire. The author reviews the trials and errors of submarine construction in the United States Navy. Each succeeding class of submarines is discussed in order to show the progress made, leading to the excellent weapon provided for submarine officers and men with which they destroyed Japanese merchantmen and warships. Japanese- …

The Banker's Briar Patch: The American Banker's Association And The Glass-Owen Bill Of 1913, Robert Drake Scull

History Theses & Dissertations

In order to compete with the British in international finance, leading bankers in the United States began to agitate for a central bank and "elastic" currency at least as early as 1905. Although the Panic of 1907 helped stir interest in banking reform, the political climate was so prejudiced against the banking profession that it became necessary for ABA spokesmen to condemn publicly the proposed legislation in order to insure that it would be passed. Privately, these same bankers worked closely with Woodrow Wilson and helped elect him president in 1912. Wilson returned the favor with the Federal Reserve Act …

Effects Of Multiple Scattering And Surface Albedo On The Photochemistry Of The Troposphere, Tommy Reinhold Robert Augustsson

Mechanical & Aerospace Engineering Theses & Dissertations

A one-dimensional photochemical model of the troposphere containing the species of the nitrogen, oxygen, carbon, hydrogen, and sulfur families has been developed and used to investigate the vertical profiles and the natural (including atmospheric chemical reactions) and anthropogenic sources and sinks of these species. The species continuity equations are solved numerically applying prescribed boundary conditions. The vertical flux is simulated by use of the parameterized eddy diffusion coefficients. Heterogeneous losses (e.g. rainout, gas-to-particle chemistry, and dry deposition), are parameterized to make calculated profiles consistent with measurements. The photochemical model is coupled to a radiative transfer model that calculates the radiation …

Usage And Limitations Of Characteristic Vector Analysis Of Remote Sensing Multispectral Data For The Identification And Quantification Of Water Quality Parameters, Theodore A. Talay

Civil & Environmental Engineering Theses & Dissertations

Recent applications of the technique of characteristic vector analysis to remote-sensing water color data has met with varying degrees of success. It is apparent from these experiments that a more thorough understanding of the informational capability of characteristic vector analysis is needed.

Sound Absorption In N2-H2o Gas Mixtures At Room Temperature And Low Frequency/Pressure Ratios, William Axam Griffin

Mechanical & Aerospace Engineering Theses & Dissertations

This study was motivated by a need to obtain standard values of nitrogen's contribution to sound absorption in the Earth's atmosphere. Specific goals included accurate measurements of sound absorption in nitrogen - water vapor mixtures at room temperature and low frequency/pressure ratios, the determination of the N₂ vibrational relaxation peak location, (f/P)_max, on the f/P axis as a function of humidity, h, and critical evaluation of all results.

The free decay technique was used in a resonance tube to obtain ten sets of sound absorption data in N₂-H₂O gas mixtures and requisite companion …

Low Speed Handling Characteristics Of A Supersonic Transport By Eigenstructure Assignment, Michael Peter Lazar

Mechanical & Aerospace Engineering Theses & Dissertations

A synthesis procedure, based upon optimal regulator theory and eigenvalue/eigenvector assignment technique, was used in the design of a low-speed lateral control system for the SCAT-15F supersonic transport. Emphasis was placed on reducing the lateral acceleration at the pilot's station. Control laws were designed to make the aircraft handling characteristics acceptable with the exception of the lateral acceleration. It was found that a compromise between the roll performance requirements and the peak lateral acceleration requirement is needed for a successful SCAT-15F design.