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Full-Text Articles in Engineering

Studies Of Mixing Processes In Gases And Effects On Combustion And Stability, Frank Paul Kozusko Jr. Jul 1995

Studies Of Mixing Processes In Gases And Effects On Combustion And Stability, Frank Paul Kozusko Jr.

Mathematics & Statistics Theses & Dissertations

Three physical models of laminar mixing of initially separated gases are studied. Two models study the effects of the mixing dynamics on the chemical reactions between the gases. The third model studies the structure and stability of a laminar mixing layer in a binary gas. The three models are:

1. Two ideal and incompressible gases representing fuel and oxidizer are initially at rest and separated across an infinite linear interface in a two dimensional system. Combustion, expected as the gases mix, will lead to a rapid rise in temperature in a localized area, i.e. ignition. The mixing of the ...


Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant Apr 1995

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant

Physics Theses & Dissertations

The demand to improve the corrosion resistance of steel sheet, particularly for use within the automotive industry, has led to a dramatic increase in the use of coated steels in place of cold-rolled sheet steel. Galvanneal steel results from the post annealing of the zinc-coated steel sheet, in which iron and zinc are interdiffused to form an iron-zinc alloy coating. Within this alloy coating, four main iron-zinc phases, Zeta, Delta, Gamma-1, and Gamma may be present. Manufacture of the most suitable coating requires identifying which phases form during the galvannealing process, an understanding of the properties of each phase and ...


Minimizing The Radiated Sound Power With Minimal Structural Modification , Daniel Henry Kruger Jan 1995

Minimizing The Radiated Sound Power With Minimal Structural Modification , Daniel Henry Kruger

Retrospective Theses and Dissertations

In cases where a structure's excitation cannot be altered, the sound radiation from the structure must be minimized by modifying the structure within given design constraints. This dissertation considers minimizing sound radiated by an existing structure with minimal changes to the structure itself. To accomplish this the sound power radiated by a structure was written as a function of the normal surface velocity using the boundary element method. The feasibility of reducing radiated sound power with small patches of constrained layer damping material is proved. Small patches of constrained layer damping material are placed on the structure to effectively ...


Turbulent Scalar Transport Using Two-Point Statistical Closure Theory , Robert Charles Sanderson Jan 1995

Turbulent Scalar Transport Using Two-Point Statistical Closure Theory , Robert Charles Sanderson

Retrospective Theses and Dissertations

The turbulent transport of a passive scalar (Corrsin's problem with diffusion) and of an active scalar in stably stratified fluids is studied using linear analysis (rapid distortion theory or RDT), Kraichnan's direct interaction approximation (DIA) and direct numerical simulation (DNS). The results are compared with each other and with laboratory experiments. The numerical results compare favorably with the experiments of Sirivat and Warhaft, Budwig, Tavoularis and Corrsin and Stillinger and Itsweire of van Atta's group. The RDT study reveals that much of the qualitative behavior observed in experiments, such as the tendency for the system to evolve ...


Preparation And Characterization Of B2s3-Based Chalcogenide Glasses , Jaephil Cho Jan 1995

Preparation And Characterization Of B2s3-Based Chalcogenide Glasses , Jaephil Cho

Retrospective Theses and Dissertations

The discovery of the fast ion conducting B[subscript]2S[subscript]3-based glasses has been one of the most significant development in the field of solid electrolytes. Considerable experimental studies have been done to maximize conductivities and chemical stabilities of these glass systems. Recently, the study of the structure and properties of these glasses compared to their oxide analog has become important;The IR spectra of M[subscript]2S + B[subscript]2S[subscript]3 (M = Li, K, Rb and Cs) and MS + B[subscript]2S[subscript]3 (M = Sr and Ba) thioborate glasses have shown the monotonic increase in tetrahedral ...


Increasing The Efficiency Of A Piezoelectric Aluminum Nitride Microstrip Resonator By Utilizing High Temperature Superconductors , Edward David Goff Jan 1995

Increasing The Efficiency Of A Piezoelectric Aluminum Nitride Microstrip Resonator By Utilizing High Temperature Superconductors , Edward David Goff

Retrospective Theses and Dissertations

High temperature superconductors have potential applications in the field of microwave devices and circuits. To utilize these materials in such a way as to increase the efficiency of these microwave devices would be beneficial for high efficiency/low noise applications. This dissertation accomplishes the following goals: (1) The design and fabrication of an initial device that increases the quality factor, Q, and therefore the efficiency of a high frequency thin film resonator which uses superconducting metal as the device's electrode, (2) the measurement and characterization of this device, (3) the theoretical calculation and predicted performance of this device, and ...


Electronic And Photonic Devices: Experimental Investigations Of Hydrogenated Amorphous Silicon Substrate N+/I/P+ Solar Cell And Fundamental Properties Of Quantum Wells With Cylindrical Geometry And Applications To Electronics And Photonics , Er-Xuan Ping Jan 1995

Electronic And Photonic Devices: Experimental Investigations Of Hydrogenated Amorphous Silicon Substrate N+/I/P+ Solar Cell And Fundamental Properties Of Quantum Wells With Cylindrical Geometry And Applications To Electronics And Photonics , Er-Xuan Ping

Retrospective Theses and Dissertations

This thesis consists of two different parts: (I) experimental investigations of hydrogenated amorphous silicon substrate n[superscript]+/i/p[superscript]+ solar cells and, (II) fundamental properties of quantum wells with cylindrical geometry and applications to electronics and photonics;Part I. The substrate structural n[superscript]+/i/p[superscript]+ solar cells based on a-Si:H materials are fabricated by a radio frequency (RF) triode geometric plasma enhanced chemical vapor deposition (PECVD) system. The solar cells have been electrically and optically tested. Two different substrates, tin-oxide coated glass and stainless steel foil, are used. An RF magnetron sputtering system is used to ...


Beam Dynamics In The Cebaf Superconducting Cavities, Zenghai Li Jan 1995

Beam Dynamics In The Cebaf Superconducting Cavities, Zenghai Li

Dissertations, Theses, and Masters Projects

This work is a study of beam dynamics in the CEBAF superconducting cavities under the influence of the fields generated by externally applied RF and beam particles.;A full 3-D modeling of the CEBAF 5-cell superconducting cavity is carried out. Details of the modeling with MAFIA are discussed. Multipole fields due to the asymmetric couplers are studied by means of 3-D Fourier transforms. The cavity steering and focusing of the multipole fields are studied. Experimental measurements of these effects are performed to validate the modeling. Evaluation of the cavity misalignment is discussed. The emittance degradation effects in the CEBAF superconducting ...


Calculations Of The Interactions Of Energetic Ions With Materials For Protection Of Computer Memory And Biological Systems, Myung-Hee Y. Kim Jan 1995

Calculations Of The Interactions Of Energetic Ions With Materials For Protection Of Computer Memory And Biological Systems, Myung-Hee Y. Kim

Dissertations, Theses, and Masters Projects

Theoretical calculations were performed for the propagation and interactions of particles having high atomic numbers and energy through diverse shield materials including polymeric materials and epoxy-bound lunar regolith by using transport codes for laboratory ion beams and the cosmic ray spectrum. Heavy ions fragment and lose energy upon interactions with shielding materials of specified elemental composition, density, and thickness. A fragmenting heavy iron ion produces hundreds of isotopes during nuclear reactions, which are treated in the solution of the transport problem used here. A reduced set of 80 isotopes is sufficient to represent the charge distribution, but a minimum of ...


Modeling X-Ray Scattering Process And Applications Of The Scattering Model , Taher Lutfi Al-Jundi Jan 1995

Modeling X-Ray Scattering Process And Applications Of The Scattering Model , Taher Lutfi Al-Jundi

Retrospective Theses and Dissertations

Computer modeling of nondestructive inspections with x-rays is proving to be a very useful tool for enhancing the performance of these techniques. Two x-ray based inspection techniques are considered in this study. The first is "Radiographic Inspection", where an existing simulation model has been improved to account for scattered radiation effects. The second technique is "Inspection with Compton backscattering", where a new simulation model has been developed;The effect of scattered radiation on a simulated radiographic image can be insignificant, equally important, or more important than the effect of the uncollided flux. Techniques to account for the scattered radiation effects ...


Vortex Lattice Melting In An Anisotropic Type Ii Superconductor , John Anton Fendrich Jan 1995

Vortex Lattice Melting In An Anisotropic Type Ii Superconductor , John Anton Fendrich

Retrospective Theses and Dissertations

The flux line lattice in superconducting single crystals of YBa [subscript]2Cu[subscript]3O[subscript]7-[delta] is shown to undergo a very abrupt melting transition as the temperature and field approach the normal state. The sharpest transitions from the vortex solid to liquid phase, as seen in resistivity measurements, are of the order of 10mK in a temperature of 85K and of the order of 10 Oe in a field of 6T. The discontinuity in the resistivity associated with vortex lattice melting is asymmetrically hysteretic with applied field in clean crystals. The melting transition width for decreasing applied magnetic ...


Compensation And Characterization Of Gallium Arsenide, Randy A. Roush Jan 1995

Compensation And Characterization Of Gallium Arsenide, Randy A. Roush

Electrical & Computer Engineering Theses & Disssertations

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the ...