Engineering Commons^™

Excitation Of Source Electromagnetic Waves At Microwave Frequencies Using Optical Techniques, M. Davarpanah

Doctoral Dissertations

"The coupling efficiencies for the excitation of surface electromagnetic waves (SEW} for both the prism and the grating techniques have been studied experimentally in the microwave frequency range. The grating experiments included studies of the SEW coupling efficiencies as functions of the frequency, the angle of incidence, the grating constant, the number of grating bars, and the position of the grating bar at which the maximum radiation field of the antenna was aimed. For the prism coupling technique, the coupling efficiency was studied as functions of the angle of incidence, the aiming point of the transmitting antenna on the prism …

A Computer Technique For Calculating The Radiological Consequences Of Pressurized Water Reactor Power Plant Hypothetical Accidents, Charles Francis Gill

Doctoral Dissertations

"A closed form analytical method of calculating the radiological consequences of ten pressurized water reactor (PWR) hypothetical accidents was developed. This methodology was used to develop a computer code, DOSES, to compute the gamma-whole body, beta-skin and iodine inhalation thyroid doses at the site boundary, at the low population zone outer boundary and for control room occupancy for the ten PWR hypothetical accidents. The computer code, DOSES, was developed to operate in the conversational remote terminal mode and to provide a mechanism for producing required information for chapter 15 of PWR nuclear power plant safety analysis reports.

The identification of …

Bit Penetration Into Rock - A Finite Element Study, Jaw-Kuang Wang

Doctoral Dissertations

"A finite element approach has been developed to simulate bit penetration from bit-rock interaction to chip formation. A mathematical rock failure model, based on a review of the existing literature on rock tests, has been proposed to represent post-failure rock behavior and applied in the penetration simulations. The finite element program has been developed for two dimensional plane strain problems with non-linear material properties, geometrical nonlinearities and fracture. An anisotropic element as well as variable stiffness and stress release methods have been used. An iteration method, using an incremental approach, has been applied for continuous penetration and modifications of material …

Simulation Of Nonisothermal Absorber-Reactors For Multicomponent Systems, Robert E. Schwab

Doctoral Dissertations

"There are various models available for calculations involving one transferring component with chemical reaction for isothermal conditions using linear equilibrium data. However, the differential equations for multicomponent mass and energy transfer with chemical reaction have not been developed or implemented. This work demonstrates the development of a reliable model describing multicomponent mass and energy transfer in a continuous two-phase absorber-reactor for Non isothermal conditions and demonstrates the feasibility of solving the differential equations numerically. The numerical solution, using nonlinear equilibrium data, is used to obtain the absorber-reactor column specifications"-- Abstract, p. 2

Split-Film Anemometry In A Drag-Reducing Solution, Jack Chosnek

Doctoral Dissertations

"Turbulence measurements were made in the tube flow of mineral oil and a 0.2% solution of polyisobutylene in the same oil. Velocity profiles, axial and radial turbulence intensities, and axial and radial energy spectra were obtained in both fluids using a split-film anemometer probe. In addition, velocity profiles and axial turbulence intensities were obtained in oil using a 0.001-in. cylinder probe, a cone probe and a parabolic-wedge probe. The measurements were made in a one-inch tube at a constant fluid temperature of 30.0°C, in the Reynolds-number range of 4,800 to 50,000.

Four factors influenced the results in a greater manner …

Characterization Of Heat-Treated Nickel And Gold Films On Silicon Single Crystals, Ki Hyun Yoon

Doctoral Dissertations

"An experimental electron impact ionization source was used to determine the presence of various neutral atoms and molecules on metallized and bare surfaces of silicon wafers. The metallization consisted of thin films of nicke l and gold separately and in combination. The major surface contaminates on all samples were found to be F, Na, Cl, K, CO, and CO₂. The surface concentration of these species was found to be sensitive to the sample temperature up to 550 °C, the maximum temperature used in this study.

In the course of the mass spectrometric study, it was found that crystallites …

Effect Of Photoneutrons On Transients Of Beryllium Reflected Reactors, Safdar Ahmad Ali

Doctoral Dissertations

"An analytical model is developed to account for the photoneutron sources present in a beryllium reflector. The time-dependent, two- dimensional and three energy-group diffusion equations are written with an additional photoneutron source term. Then an approximate flux composed of two spatial shapes chosen beforehand, each having an unknown time coefficient, is inserted into time-dependent multigroup equations and the weighted residual criterion is applied. This yielded multimode kinetics equations with generalized definitions for conventional matrix parameters: generation time, reactivity, delayed neutron and delayed photoneutron fraction matrices.

Two transients are analyzed for the University of Missouri Research Reactor: simulation of rod drop …

Use Of Adaptive Linear Equalization And Maximum-Likelihood Sequence Estimation In Conjunction With Filtering To Improve Qpsk Communication In Intersymbol And Interchannel Interference Channels, Srinivasa H. R. Raghavan

Doctoral Dissertations

"At high data rates, bandwidth is more constraining than transmitting power. Twice the data can be transmitted in a given bandwidth by using quadrature phase-shift keyed (QPSK) modulation schemes as opposed to biphase phase-shift keyed (PSK) systems, with a corresponding factor of two increase in power required for identical bit-error-rate performance. At high data rates intersymbol interference due to media dispersion degrades receiver performance . Other degradation results from interchannel interference, co-channel interference and noise may also be present in typical situations.

Equalization is a technique by which the receiver performance in the presence of intersyrnbol interference can be improved. …

Application Of Voltammetry To Copper Electrodeposition, Louis Francis Toth Jr.

Doctoral Dissertations

"A study was undertaken to determine the feasibility of using voltammetry and scanning electron microscopy techniques to characterize copper deposition from an acid-sulfate electrolyte. The main process variables investigated were temperature and addition agents (chloride ion, glue, separan or thiourea) at different concentrations, over a range of current densities. Cathodes employed were either polycrystalline titanium or copper. Some long-time copper deposits were also made using Ti cathodes and the orientations of these deposits were determined by x-ray diffraction.

Observations of copper crystals produced during voltammetry scans, on a Ti cathode, indicated that a characteristic morphology was associated with each type …

Development Of Helicopter Flight Path Models Utilizing Modern Control Techniques, Alfred Fermelia

Doctoral Dissertations

"The nonlinear set of equations which represents helicopter motion are linearized about a prescribed nominal state. Once the linearized system is obtained it is validated by comparing the output of the nonlinear system to that of its linearized counterpart. Having obtained a linear model, linear system theory may then be applied in order to investigate the stability and control characteristics of the aircraft.

General techniques for simulating helicopter pilot response for inclusion in a flight path simulation program have been devised. To provide the desired flight goal, a nominal flight trajectory is obtained from an existing nonlinear model. With this …

Design, Fabrication, And Application Of Uniformly Distributed Rc Networks For Use In Electronic Circuits, Michael Flynn Kavanaugh

Doctoral Dissertations

"In the design of electronic circuits, both linear and non-linear, one of the goals is the reduction of the number of elements needed to complete the design. By using distributed RC networks a reduction in the number of elements by at least 50% is usually possible. This dissertation discusses several distributed RC networks, develops detailed design procedures for each, and applies them in the design of electronic circuits.

The indefinite admittance matrix (IAM) for the DRURC (double-resistive uniformly distributed RC network) and the URC (single-resistive uniformly distributed RC network) , which have been previously derived, are used as the starting …

Optimizing Underground, Trackless Loading And Hauling Systems, Richard Lee Bullock

Doctoral Dissertations

"Determining the optimum system and equipment to be utilized in today's underground trackless haulage mine is a complex problem which was dealt with in this research by systems simulation. The computer program developed by the Caterpillar Tractor Company served as the starting point for simulating the equipment's capabilities to move material over a course in a prescribed time. Extensive time studies of the unsimulated events lead to structuring this program in the deterministic mode since it was felt to be more acceptable to the operating management which would eventually use the technique. Every phase of the simulation was successfully validated …

Corrosion And Electrochemical Behavior Of Indium And Indium-Bismuth Alloys In Hydrochloric Acid, Yar Ming Wang

Doctoral Dissertations

"The corrosion of In-Bi alloys was studied using X-ray, scanning electron microscopy, atomic absorption spectroscopy, and cyclic voltammetry techniques.

Calculated activation energy values indicated that the corrosion of In-Bi alloys was activation controlled. The effect of amine mixtures on the corrosion of In and In₂Bi (ß₁ phase) was studied. Morphological studies revealed that the porosity of the resulting physical surface structure was influential in determining the corrosion rate. In deaerated 3N HCl solutions, the selective dissolution of indium was the predominant mechanism in the corrosion of In-Bi alloys. The corrosion was always accompanied by a phase change …

Influence Of Initial Turbulence Intensity On The Heat And Moisture Transfer Through A Recirculated Air Curtain, Nguyen Quang Van

Doctoral Dissertations

"An air curtain is a directed jet of air separating a controlled space from an environment of different temperature and humidity. This investigation describes the development and verification of an eddy viscosity model which accounts for the influence of the initial turbulence intensity on the transfer of heat and moisture across a recirculated air curtain. The control of the turbulence intensity at the nozzle exit of an air curtain permits control of heat and moisture transfer and therefore the energy required to operate the air curtain.

Both theoretical and experimental studies were made of the recirculated air curtain. An explicit …

State-Space Analysis And Synthesis Of Active Rlc Networks, Wen-Pao Lee

Doctoral Dissertations

"This dissertation provides theoretical foundations for the state-space analysis and synthesis of linear active RLC networks containing all four types of controlled sources. The analysis portion is concerned with an explicit representation of the state model and the order of complexity of a general linear active RLC network. The problem considered in the synthesis portion is the realization of a given A-matrix with an active nondegenerate RLC-ladder network or an active RLC network without any particular structure.

The general active RLC network state model representations are explicitly expressed in terms of the fundamental circuit submatrices, the network element submatrices, and …

Phase Equilibria And Transformations In Potassium Sulfate, Chromate, Molybdate, And Tungstate, Roy Richard Ramey

Doctoral Dissertations

"Thermal expansion and transformations of K₂SO₄, K₂CrO₄, K₂MoO₄, and K₂WO₄ were studied by high temperature diffractometry, differential thermal analysis, and dilatometry. K₂SO₄ and K₂CrO₄ transform from an orthorhombic to a hexagonal structure at 580°C and 670°C respectively, with initiation of the transformation probably related to increased amplitude of S-O tetrahedral vibrations. K₂MoO₄ and K₂WO₄ transform from a monoclinic to an orthorhombic structure at 300° and 370°C respectively. A minor K₂MoO_{4 …}

The Effect Of Contact Angle, Surface Roughness, And Adsorption Of Heterogeneous Nucleation Of Condensing Water, Prafulla Chandra Mahata

Doctoral Dissertations

"Condensation of water vapor on various surfaces was studied experimentally. It was found that supersaturations as high as 25% were required to initiate condensation on hydrophobic surfaces. The supersaturation data agreed qualitatively with the Volmer theory of heterogeneous nucleation. The influence of adsorption of water vapor was found to be small. Surface roughness caused a little reduction in the critical supersaturation"--Abstract, page iii.

Process Optimization By Flow Sheet Simulation, Larry Dale Gaines

Doctoral Dissertations

"PROPS, (Process Optimization System), has been used to simulate and optimize the Universal Oil Products solid phosphoric acid catalyst process for producing gasoline. PROPS, a modified version of CHESS (Chemical Engineering Simulation System), performs a complete design and economic evaluation of the process for each set of independent variables. The computational time during optimization was reduced by the use of a regression equation to determine K-values as a function of temperature and pressure. K-value data used for the regression was generated from the Chao-Seader correlation using mixtures of the gasoline components to be encountered during optimization. The regression equation produces …

Measurements Of Condensation Coefficient Exhibited By Water Drops Grown On Rural Cloud Nuclei, Abbas M. Sinnarwalla

Doctoral Dissertations

"Values of condensation coefficient, ß, were experimentally determined for water drops grown on cloud nuclei in atmospheric air samples. The measured quantities were supersaturation, final drop size (6 to 7.5 µm radius), and time to grow from near dry radius to final radius. The drops were grown in a vertical-flow thermal diffusion chamber, at supersaturations near 0.5 and 1.0%. The final drop sizes were large enough so that ß did not depend upon the size of the nucleus producing a given drop. The average value of ß was 0.025 with a standard deviation of about 0.01"--Abstract, page 2.

Rc-Gyrator Ladder And Rlc Symmetrical Lattice Network Synthesis - A State-Space Approach, Tien Hua

Doctoral Dissertations

"This dissertation presents two network realization procedures using the state-space approach. The first procedure is the realization of a transfer function. A state model (A,B,C,D) is obtained from the given transfer function by inspection, where A is a companion matrix. Through a similarity transformation T, another state model (F,G,H,J) is obtained, where F is a tridiagonal matrix and can be realized by a RC-gyrator ladder network. The input source is inserted in the proper position of the ladder network, and the output is obtained through a summing circuit. It is a unified procedure and uses simple algebraic computation. A general …

Anionic Polymerization Of A Series Of Cyclocarbosiloxanes, William W. Knickmeyer

Doctoral Dissertations

"A study has been made on the anionic polymerization of a series of cyclocarbosiloxanes of the type: [IMAGE] where n was varied from 2 to 8. The polymerization reaction in benzene, was initiated using cesium trihexyl silanolate, a unique organic soluble liquid catalysts. Benzene served as both a solvent and to shift the position of the NMR SiCH₃ polymer peak away from the monomer peak making it feasible to follow the kinetics on a Varian EM-360 Nuclear Magnetic Resonance Spectrometer. Hexamethylphosphoramide (HMPA) was used as a promoter to solvate the initiator ions and thus increasing the polymerization rate. It …

The Morphology Of Cellular Precipitation In Magnesium Rich Magnesium-Aluminum Alloys, Jyong Shi Cho

Doctoral Dissertations

"The morphology of cellular precipitation in a Mg-9wt. %AI alloy has been investigated by light and electron microscopy. A study of the early stages of the cellular precipitation process indicated that cellular precipitate structure forms in Mg-Al alloys by Fournelle and Clark mechanism. "Replacive" motion indicative of the Tu and Turnbull mechanism for cellular precipitation was not seen"--Abstract, page 1.

Structural Behavior Of Cold-Formed Steel Members Made Of Thick Sheets And Plates, Ai-Shen Liu

Doctoral Dissertations

"It is well-known that the current AlSI Specification for the design of cold-formed steel structural members has been developed mainly for thin steel sections. In order to extend the applicability of the specification for the design of cold-formed steel members thicker than 1/4 in., both analytical and experimental investigations have recently been conducted with special emphases on the effects of cold work on the mechanical properties of corners and the strength of bolted connections.

For the effects of cold work, previous investigations have shown that the phenomena of strain hardening and strain aging are main factors which affect the mechanical …

Towards A Design Of Hmo, An Integrated Hardware Microcode Optimizer, James Oliver Bondi

Doctoral Dissertations

"This paper discusses an algorithm for optimizing the density and parallelism of microcoded routines in micro-programmable machines. Besides presenting the algorithm itself, this research also analyzes the algorithm's uses, design integration problems, architectural requirements, and adaptability to conventional machine characteristics. Even though the paper proposes a hardware implementation of the algorithm, the algorithm is viewed as an integral part of the entire microcode generation and usage process, from initial high-level input into a software microcode compiler down to machine-level execution of the resultant microcode on the host machine. It is believed that, by removing much of the traditionally time-consuming and …

A Finite Element Method For Three-Dimensional Analysis Of Metal Forming, Nguyen Don Phu

Doctoral Dissertations

"The importance of metal forming by extrusion was reviewed. A Finite Element Approach was developed to analyze extrusion processes. A brick type linear element and the Upper Bound theorem were used to analyze the extrusion of a cylindrical billet into a square cross-section prism. A minimization technique for a non-linear functional with linear constraints was developed. Different types of boundary conditions were also formulated. A frictionless extrusion was simulated using the computer program developed. Velocity profiles at different sections of the deforming solid were obtained and an average extrusion pressure was predicted for a given area reduction ratio.

Extrusions from …

Numerical Modeling Of The Early Stage Of Cloud Formation In A Simulation Chamber, Adel Nassif Saad

Doctoral Dissertations

"A numerical model has been developed to simulate the growth of cloud droplets by condensation upon a spectrum of hygroscopic nuclei. The model is applicable to cloud simulation chamber conditions as well as to the study of the role of these nuclei on cloud base microstructure.

Equations are given for the growth by condensation of water vapor on a population of hygroscopic nuclei in a volume being cooled by expansion. The equations are integrated simultaneously, using Hamming's modified predictor-corrector method for given initial conditions, to obtain the droplet size distribution, temperature, pressure, supersaturation, and liquid water content. Temperature fluctuations, sedimentation …

Kalman Filter Equalization For Qpsk Communications, Tze-Shen Lee

Doctoral Dissertations

"The discrete complex Kalman filter is considered as an equalizer for quadrature phase shift keyed (QPSK) systems in the presence of additive noise and intersymbol interference (ISI). For a known linear time-invariant channel with finite duration impulse response, the finite n-dimension complex Kalman filter equalizer is able to reduce the degradation caused by ISI. When the channel is unknown, an adaptive Kalman equalizer is used in which the channel complex tap gains are estimated by decision feedback. A two component multipath channel QPSK system is used as an example. Using the Chernoff upper bound to calculate the error probabilities, the …

Surface Elastic Waves In Piezoelectric Semiconductors And Layered Media, Yu-Pin Han

Doctoral Dissertations

"The primary interest of this investigation is to understand the surface elastic wave properties in piezoelectric semiconductors and layered media. Generalized piezoelectric wave equations in piezoelectric semiconductors and layered media are derived. Systems considered are the piezoelectric semiconductor, the two layer piezoelectric insulator-semiconductor, the three layer piezoelectric insulator- gap-semiconductor and the four layer piezoelectric insulator-gap-semiconductor-dielectric substrate. The eigenwave expansion and the iteration methods in the complex domain are used to solve the problems. Mathematically, it represents a solution of the eigenvalue boundary value problem which involves iteration of functions in the complex domain. Solutions obtained are eigenvalues and eigenvectors which …

An Analytical And Experimental Study Of The Dynamic Response Of A Press, Woosoon Bai

Doctoral Dissertations

"This dissertation presents a simplified mathematical model and computer simulation of the vertical motion of a press. The model is verified by comparing simulation results with actual field measurements.

Using this model, the computer simulation is then extended to study the dynamic response of a bolted press, one with loosened anchor bolts, and one which is isolated. Press performance, in terms of acceleration of the press, velocity of its foundation, and forces transmitted to the foundation, is analyzed in relation to the foundation mass and the stiffness of the isolators, where applicable. Comparative performances of the presses secured by the …

In Vitro Studies Of Lipid Uptake By Medical Grade Silicone Rubbers Used For Heart Valve Balls, Shu Hua Wu

Doctoral Dissertations

"Various chemical and physical aspects of high lipid absorption by medical grade silicone rubber and the dynamic mechanical properties of lipid-rubber systems were studied in order to provide an insight into the problem of 'variance' of these materials when subjected to 'in vitro' and 'in vivo' environments. Wide variations of post cure procedures of the silicone rubber were studied. Different post cures did not appreciably affect the mechanical properties of the silicone rubber. Mass transfer studies demonstrated that the diffusion of linolenic acid into a silicone rubber slab is a purely physical diffusion process (D = 3.2 x 10^{-3 …}