Engineering Commons^™

Optical Recording Aspects Of Rf Magnetron Sputtered Iron-Garnet Films, J.P. Krumme, V. Doormann, P. Hansen, H. Baumgart, J. Petruzzello, M.P.A. Viegers

Electrical & Computer Engineering Faculty Publications

The intrinsic magneto-optical readout performance in reflection is calculated for bismuth and cobalt-substituted iron-garnet films on a multilayer interference mirror at 800-, 633-, 488-, and 420-nm wavelengths and is compared with that of a trilayer medium composed of an antireflection layer, a rare-earth transition-metal film, and a metallic mirror. It is found, when disregarding inhomogeneities, like irregular domain shape, ripple of the magnetic anisotropy, and surface roughness, that iron garnets are superior to rare-earth transition-metal films at blue to near-ultraviolet wavelengths if operated at thicknesses where optical interference occurs in the magnetic layer. Optical transmittance at these thicknesses is sufficiently …

Nanosecond Optical Quenching Of Photoconductivity In A Bulk Gaas Switch, M. S. Mazzola, K. H. Schoenbach, V. K. Lakdawala, S. T. Ko

Electrical & Computer Engineering Faculty Publications

Persistent photoconductivity in copper-compensated, silicon-doped semi-insulating gallium arsenide with a time constant as large as 30 µs has been excited by sub-band-gap laser radiation of photon energy greater than 1 eV. This photoconductivity has been quenched on a nanosecond time scale by laser radiation of photon energy less than 1 eV. The proven ability to turn the switch conductance on and off on command, and to scale the switch to high power could make this semiconductor material the basis of an optically controlled pulsed-power closing and opening switch.

A Structured Light Method For Sensing Alignment During Automated Truss Assembly, Jayesh K. Champaneri

Electrical & Computer Engineering Theses & Dissertations

A new method using structured light is proposed to obtain visual feedback information for aligning two cylindrical beams. For a robotic system employed to perform alignment operations in real time it is essential that the accompanying vision system does not pose a heavy burden on the computing machinery and reduce the overall speed of operation. The method proposed here involves two stripes of light projected on each cylinder. One picture frame is sufficient to completely determine the position of the cylinder in space. An experiment was conducted to demonstrate the principle of this method. Results showed that the errors involved …

An Arrayed Hot-Film Sensor For Detection Of Laminar Boundary-Layer Flow Disturbance Spatial Characteristics, Michael S. Wusk

Mechanical & Aerospace Engineering Theses & Dissertations

An arrayed hot-film sensor has been developed for use in laminar boundary-layer research for the detection of crossflow or Gortler vortices. This sensor has been developed to detect spatial variations in heat transfer and velocity perturbations which are characteristic of crossflow or Gortler vortices. The sensor is ultimately intended for flight research applications. This thesis describes the sensor, its principles of operation, signal analysis techniques, and experimental results illustrating the spatial detection capabilities of this specialized hot-film device. Discretely placed spheres placed in the boundary layer created alternating regions of undisturbed and disturbed laminar flow over a prototype sensor. Flow …

The Effects Of Low Doses (1 To 500 Kilograys) Of 100-Kev Electrons On Four Polymers, Cynthia Anne Bradbury

Physics Theses & Dissertations

Commercial films of polyetherimide (PEI), polyetheretherimide (PEEI), polyethylene terephthalate (PET), and polycarbonate (PC) were exposed in vacuum to l 00-keV electron radiation to total absorbed doses of l, l 0, l 00, 300, and 500 kilograys. The concentration of radiation-generated radicals, as measured by electron paramagnetic resonance (EPR), increased by over an order of magnitude in all four polymers. Correspondingly, the intensity of the infrared absorption peaks increased uniformly for all doses. Solubility tests resulted in decreased solubility in all polymers. IR, EPR, and solubility suggest dehydrogenation of the aliphatic C-H and phenyl C-H sites. The data indicated that cross …

Viscous Shock Layer Analysis Of Hypersonic Flows Over Long Slender Vehicles, Kam-Pui Lee

Mechanical & Aerospace Engineering Theses & Dissertations

A method for solving the viscous shock-layer equations for hypersonic flows over long slender bodies is presented. The governing equations are solved by employing a spatial-marching implicit finite-difference technique. The two first-order equations, continuity and normal momentum, are solved simultaneously as a coupled set. This method yields a simple and computationally efficient technique.

Flows past hyperboloids and sphere cones with body half angles of five to 35 degrees are considered. The flow conditions included are from high Reynolds numbers at low altitudes to low Reynolds numbers at high altitudes. Detailed comparisons have been made with other predictions and experimental data …

Calculations Of Three-Dimensional Transonic Flows Using The Implicit Formulation Of The Isenthalpic Euler Equations With Flux Vector Splitting, Frank E. Cannizzaro

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical method for solving three-dimensional transonic flows using the isenthalpic formulation of the Euler equations is developed. The method uses van Leer's flux vector splitting to solve the implicit formulation of the governing equations, which are applied to a cell centered finite-volume scheme. A three factor spatial approximate factorization is implemented in solving the implicit part of the governing equations. Time marching to a steady state solution requires short computational times due to the relative efficiency of the basic method. Computational times are further reduced by the implementation of the multigrid acceleration technique, which provided converged solutions in approximately …

Effect Of Fabric On Stress-Strain Relation, Volume Change, And Dynamic Shear Modulus Of Ottawa Sand, Ming-Tarng Chen

Civil & Environmental Engineering Theses & Dissertations

To evaluate the effect of fabric on stress-strain behavior, volume change, and the dynamic shear modulus of Ottawa sand, four series of tests on hollow cylindrical specimens were performed by a torsional simple shear/resonant apparatus. All specimens were first isotropically consolidated, and then sheared along the different stress paths while keeping the mean effective stress constant. The test results showed that depositional fabric had a slight influence on the stress-strain behavior, and one half-cycle of pre-shearing created a clear anisotropy on the stress-strain response. The intermediate principal stress had a dominant effect on volume change characteristics but it might not …

Application Of Advanced Grid Generation Techniques For Flow Field Computations About Complex Configurations, Monchai Kathong

Mechanical & Aerospace Engineering Theses & Dissertations

In the computation of flow fields about complex configurations, it is very difficult to construct a boundary-fitted coordinate system. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the "multiple grids" or "zonal grids" approach, and its applications are investigated in this study. The method is a conservative approach and provides conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-stage Runge-Kutta time integration. The code is vectorized and programmed …

Numerical Simulation Of Turbulent Flows Past Three-Dimensional Cavities, Shivakumar Srinivasan

Mechanical & Aerospace Engineering Theses & Dissertations

Computations have been performed to simulate turbulent supersonic, transonic, and subsonic flows past three-dimensional deep, transitional, and shallow cavities. Simulation of these self sustained oscillatory flows has been generated through time accurate solutions of Reynolds averaged full Navier-Stokes equations using the explicit MacCormack scheme. 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 performed for the instantaneous pressure values on the cavity floor. Comparison with experimental data is made in terms of the mean …

Atamm Multicomputer System Design, William Robert Tymchyshyn

Electrical & Computer Engineering Theses & Dissertations

The Algorithm To Architecture Mapping Model, or ATAMM, is a graph theoretic design methodology that has been created to resolve design and performance issues involved with concurrent processing. Petri-net marked graphs are used to represent the computational environment.

This thesis describes the development of a multicomputer system which will operate within the bounds specified by the ATAMM model. The system is first designed and implemented using the framework of standard multicomputer design theory. A validation is then performed by the comparison of the system's computational performance to results predicted by ATAMM. This validation is shown to be successful for three …

A Finite Element Formulation For The Large Deflection Random Response Of Thermally Buckled Structures, James Eugene Locke

Mechanical & Aerospace Engineering Theses & Dissertations

The effects of temperature and acoustic loading are included in a theoretical finite element large deflection formulation for thin, isotropic plate and beam type structures. Thermal loads are applied as steady-state temperature distributions, and acoustic loads are taken to be stationary and Gaussian with zero mean and uniform magnitude and phase over the surface of the structure. Material properties are considered to be independent of temperature. Also, inplane and rotary inertia terms are assumed to be neglegible, and all inplane edge conditions are taken to be immovable. For the random vibration analysis, cross correlation terms are included.

The nature of …

Self Consistent Model Of The Glow Discharge, Hao Chen

Electrical & Computer Engineering Theses & Dissertations

The strong spatial variation of the electric field intensity in the vicinity of the cathode of a gas discharge requires the use of microscopic methods to describe the nonequilibrium behavior of the electron dynamics in this region. A one-dimensional Monte Carlo code was developed. It allows one to obtain the distribution of the electron drift velocity and rate coefficients for a given electric field intensity in the cathode fall. The results of this calculation are used to find the density distribution of charged particles in this region and consequently, by means of Poisson's equation, a corrected electric field intensity. In …

Investigation Of Supersonic Chemically Reacting And Radiating Channel Flow, Mortaza Mani

Mechanical & Aerospace Engineering Theses & Dissertations

The two-dimensional time dependent Navier-Stokes equations are used to investigate supersonic flows undergoing finite rate chemical reaction and radiation interaction for a hydrogen-air system. The explicit multi-stage finite volume technique of Jameson is used to advance the governing equations in time until convergence is achieved. The chemistry source term in the species equation is treated implicitly to alleviate the stiffness associated with fast reactions. The multi-dimensional radiative transfer equations for a nongray model are provided for a general configuration, and then reduced for a planer geometry. Both pseudo-gray and nongray models are used to represent the absorption-emission characteristics of the …

A Simulation Study Of A Space-Borne Optical Disk Mass Memory System, Kenny G. Chen

Electrical & Computer Engineering Theses & Dissertations

Issues concerning space-borne applications of an optical disk mass memory system (ODMMS) are investigated through computer simulation. The simulation model is developed according to a current description of the ODMMS with certain application constraints. The results are examined in terms of system modularity, multi-user data rate buffering, disk module access, and read/write file management. The conditions and requirements for future disk controller designs are indicated in the simulation results.

Integral Equation Solution Of The Full Potential Equation For Three-Dimensional, Steady, Transonic Wing Flows, Li-Chuan Chu

Mechanical & Aerospace Engineering Theses & Dissertations

An integral equation method for solving the full potential equation has been developed for three dimensional transonic vortex-wing flows. This method is capable of capturing shocks using the Murman-Cole type of finite difference scheme and is capable of predicting accurate and force-free wake shape as well.

Reading the full potential equation as Poisson's equation, the solution for the velocity field has been expressed in terms of an integral equation using Green's theorem. The solution consists of a surface integral of vorticity distribution on the wing and its free-vortex sheets and a volume integral of source distribution within a computational region …

Full-Potential Integral Solutions For Steady And Unsteady Transonic Airfoils With And Without Embedded Euler Domains, Hong Hu

Mechanical & Aerospace Engineering Theses & Dissertations

The integral equation solution of the full-potential equation is presented for steady and unsteady transonic airfoil flow problems. The method is also coupled with an embedded Euler domain solution to treat flows with strong shocks for steady flows.

For steady transonic flows, three integral equation schemes are well developed. The first two schemes are based on the integral equation solution of the full-potential equation in terms of the velocity field. The Integral Equation with Shock-Capturing (IE-SC) and the Integral Equation with Shock-Capturing Shock-Fitting (IE-SCSF) schemes have been developed. The IE-SCSF scheme is an extension of the IE-SC scheme, which consists …

Large Planar Maneuvers For Articulated Flexible Manipulators, Li-Farn Yang

Mechanical & Aerospace Engineering Theses & Dissertations

An articulated flexible manipulator carried on a translational cart is maneuvered by an active controller to perform certain position control tasks. The nonlinear dynamics of the articulated flexible manipulator are derived and a transformation matrix is formulated to localize the nonlinearities within the inertia matrix. Then a feedback linearization scheme is introduced to linearize the dynamic equations for controller design. Through a pole placement technique, a robust controller design is obtained by properly assigning a set of closed loop desired eigenvalues to meet performance requirements. Numerical simulations for the articulated flexible manipulators are given to demonstrate the feasibility and effectiveness …

The Effect Of Elastic Boundary Conditions On The Dynamic Response Of Rectangular Plates, Terry K. Brewer

Mechanical & Aerospace Engineering Theses & Dissertations

Natural frequencies and forced steady-state harmonic response for the vibration of uniform rectangular plates with edges elastically restrained against rotation and transverse translation are addressed. A single mode Rayleigh-Ritz solution is derived using functions that describe the normal modes of vibration of a beam whose ends are elastically restrained. The finite element solution is obtained for comparison. MACSYMA symbolic manipulation system is implemented as an aid to the mathematical rigor of the Ritz approach and NASTRAN finite element code is used to model the mechanical system. Comparisons are made to published results and the solutions of this study are found …

A Bulk Optically Controlled Semiconductor Switch, Rudolf K.F. Germer, Karl H. Schoenbach, Stephen G.E. Pronko

Bioelectrics Publications

Turn‐on and turn‐off of bulk semiconductor switches, based on excitation and quenching of photoconductivity, respectively, have been demonstrated with copper‐doped II‐VI semiconductor crystals. The increase of the conductivity (turn‐on) was realized with a xenon flash‐lamp pulse of 15‐μs duration. A reduction of the conductivity (turn‐off) was obtained by irradiating the samples with IR light using an 8‐ns Nd:YAG laser pulse (YAG denotes yttrium aluminum garnet). For turn‐on in CdS:Cu the conductivity follows the xenon flash excitation. The turn‐off time constant was 250 ns. ZnS and ZnSe crystals showed a slower response. A memory effect for the IR light was observed.

A Simple Solid-Phase Electrophoretic Procedure For The Separation Of Plasmid Dna, Linda Ann Simurra

Biological Sciences Theses & Dissertations

A method was developed for extraction of plasmid DNA from bacterial cells embedded in agarose blocks. Cell - containing blocks were treated with various lysing reagents and inserted into the wells of an agarose gel. Upon electrophoresis the plasmid DNA migrated out of the embedding block and into the gel leaving intact chromosomal DNA in the well. This method was tested with various organisms and found to be effective for plasmid isolation. In comparison to "traditional" procedures, this new method is less tedious since chemical separation of plasmids is not required prior to electrophoresis. Also, a higher yield of plasmid …

Strains In Si-Onsio2 Structures Formed By Oxygen Implantation: Raman Scattering Characterization, D.J. Olego, H. Baumgart, G.K. Celler

Electrical & Computer Engineering Faculty Publications

Low-temperature Raman scattering measurements were carried out to characterize Si-on-SiO₂ structures formed by oxygen implantation and subsequent furnace or lamp annealing. The experiments were conducted with 413.1 nm laser light to probe only the thin Si layers at the top of the structures. The Raman spectra of the furnace-annealed samples are red shifted and broadened when compared with a virgin Si surface. The shifts and broadenings decrease with increasing annealing temperatures but they are still present in samples annealed above 1250°C for 3 h. No shifts or broadenings affect the Raman peaks of the layers, which were lamp annealed …

Raman Scattering Characterization Of The Microscopic Structure Of Semi-Insulating Polycrystalline Si Thin Films, D.J. Olego, H. Baumgart

Electrical & Computer Engineering Faculty Publications

Raman scattering experiments were carried out to study the microscopic structure of semi-insulating polycrystalline Si (SIPOS) thin films prepared by low-pressure chemical vapor deposition. The samples contain 18, 25, and 30 at. % of oxygen and after growth they were annealed at 900 and 1000°C for 30 min. The Raman spectra show in the vibrational region of the optical frequencies of Si two bands, which arise from scattering in crystalline grains and disordered forms of Si. The behavior of these bands as a function of oxygen content and annealing temperatures was established in detail. The crystallinelike band peaks below the …

An Optically Controlled Closing And Opening Semiconductor Switch, K. H. Schoenbach, V. K. Lakdawala, R. Germer, S. T. Ko

Electrical & Computer Engineering Faculty Publications

A concept for a bulk semiconductor switch is presented, where the conductivity is increased and reduced, respectively, through illumination with light of different wavelengths. The increase in conductivity is accomplished by electron ionization from deep centers and generation of bound holes. The reduction of conductivity is obtained by hole ionization from the excited centers and subsequent recombination of free electrons and holes. The transient behavior of electron and hole density in a high power semiconductor (GaAs:Cu) switch is computed by means of a rate equation model. Changes in conductivity by five orders of magnitude can be obtained.

Dynamic Allocation Of Responsibility Between Operators With Different Models Of System Information Using Computer-Mediated Communication, Michele Terranova

Psychology Theses & Dissertations

This research focused on the effectiveness of two operator teams for dynamic control of a process simulation. The responsibility for system optimization and failure detection was shared by the operators through computer-mediated communication. System information was displayed to both operators by one of three mental models of the systems: an alphanumeric/separable representation, a graphic/integral system representation, or both representations. The following team-display configurations were used: primary operator with graphic display, support operator with alphanumeric (GRAL); primary operator with alphanumeric display, support operator with graphic (ALGR); both operators with alphanumeric displays (BOAL); both operators with graphic displays (BOGR); and both operators …

Model Of Hot-Film Sensor With Substrate Effects, David Mcalpine Judge

Electrical & Computer Engineering Theses & Dissertations

A detailed mathematical model is constructed to investigate the frequency response of a hot-film anemometer system. Since several diverse factors affect the frequency response, the analysis is broken down into three main parts. Each part is a detailed mathematical model. The first model consists of the ordinary differential equations which govern the electronics of the feedback system and heat transfer of the sensor. An important simplification in this model is that the rate of heat conduction from the sensor to its substrate is constant.

In the second model the unsteady state heat transfer properties of the substrate are examined by …

An Application Of Global Optimization Algorithm For Modal Parameter Identification, Chung-Men Chen

Mechanical & Aerospace Engineering Theses & Dissertations

Single-mode projection filters for modal parameter identification for flexible structures are introduced. An effective two-dimensional global optimization method using interval analysis is combined with the projection filters to facilitate identification for modal frequency and damping. A numerical simulation of a ten-mode structure is presented to illustrate the feasibility of the new method. The projection filters are practical for parallel processing implementation.

Computer-Aided Analysis And Design Of Rectangular Buried Tank Walls And Its Safety Factor Evaluation Based On Yield Line Analysis, Rakiya J. Fatoohi

Civil & Environmental Engineering Theses & Dissertations

This thesis presents the results of a study that determines the true safety factor of underground square reinforced concrete tank walls.

The walls are analyzed and designed by elastic method. The amount and distribution of the reinforcement was determined by use of the alternate design method (working stress) in compliance with all ACI code requirements. The wall's ultimate moment was computed by use of yield line theory assuming non-isotropic reinforcement. The ultimate value of the earth pressure was computed and compared with the elastic analysis and design values to give the true safety factor.

The results of this study indicate …

Development Of Load Carrying Thermoplastic Components For An Automotive Emergency Braking System, Joseph Gerard Sikora

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis describes a classical approach to plastic parts' design leading to the development of load carrying fiber reinforced thermoplastic components for use in an automotive emergency braking system. The control arms that are the focus of this study are designed to withstand the static loads characteristic of the loads experienced by an automotive emergency braking system. The present study is particularly significant as a case study because the design involves development of load carrying components for use in the harsh automotive environment.

Beginning with a fundamental concept for the control arms, basic design criteria, and a limited insight into …

A Study Of Flow Separation In Transonic Flow Using Inviscid And Viscous Cfd Schemes, James Andrew Rhodes

Mechanical & Aerospace Engineering Theses & Dissertations

A comparison of flow separation in transonic flows is made using various computational schemes which solve the Euler and the Navier-Stokes equations of fluid mechanics. The flows examined are computed using several simple two-dimensional configurations including a backward facing step and a bump in a channel. Comparison of the results obtained using shock fitting and flux vector splitting methods are presented and the results obtained using the Euler codes are compared to results on the same configurations using a code which solves the Navier-Stokes equations.