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 …

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 …

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 …

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 …

Experimental Study Of Electron Density And Confinement Time In An Electrostatically-Plugged Cusp Device Using A Microwave Interferometer, Robert Louis Hayward

Masters Theses

"The average electron density and electron confinement time in an electrostatically plugged magnetic spindle cusp device are studied using a 20 GHz microwave interferometer. The results are compared with the predictions from approximate theoretical equations. With a magnetic induction in the point cusp of 5000 Gauss, a plasma is produced by injecting a 5 mA, 500 eV electron beam into hydrogen gas at 10^-5 Torr. The measured electron density is 2 x 10^-10 cm^-3 and the measured confinement time is 80 ysec, which agree to within a factor of two with values predicted by theory"--Abstract, page ii.

Decoupled Explosive Charge Effects On Blasting Performance, Roberto Ucar

Masters Theses

"This investigation was performed to determine the burden at which hard rock would break utilizing decoupled and unstemmed charges when the free surface parallel to the borehole was the wall of an open hole. This open hole was created by burn cuts and by drilling holes of 7-7/8 in. and 12 in. diameter. Additional tests were performed using partially stemmed charges where the stemming was the same size as the explosive charge.

The explosive used was a 0.75 lb. slurry charge, 1.5 in. diameter and 10 in. long. The diameter and depth of the borehole were 2 in. and …

Variables Affecting The Rate Of Solution Of Mold Inoculants In Cast Iron, Jose Osorno Fonnegra

Masters Theses

"The purpose of this investigation was to measure the effectiveness of an inoculant alloy reacting with molten cast iron in a reaction chamber properly located in the gating system.

The chemical composition of the gray iron was held constant while several metallurgical factors were varied to produce test samples with different cementite thicknesses. These chill depths were measured as an indication of the inoculation effectiveness.

Appreciable differences in chilling tendency were observed within the different variables studied. The results indicate that pouring temperature, as well as the other variables studied, are of considerable importance when dealing with inoculation of gray …

Characterization Of Two Mexican Raw Dolomites For Refractory Brick Production, Rodolfo Trevino Cantu

Masters Theses

"Two Mexican dolomites were characterized in order to discover their suitability for production of refractory brick.

The results were compared with other dolomites from American Companies. Some samples were burned in a gas fired Laboratory Furnace and others were obtained in the burned state after processing in Industrial Rotary Kilns.

The characterization procedures included X-Ray Diffraction, Scanning Auger Microprobe, DTA and TGA techniques, Chemical Analysis and Bulk Density measurements.

The procedure to control the quality of the dead-burned dolomite at the industrial level was established taking as the main criteria, bulk density, hydration susceptibility, and impurity levels"--Abstract, page ii.

Innovative Industrial Arts Programs At The Junior High/Middle School And The Continuation Of Those Programs At The Senior High School Level In Iowa, James L. Thiesse

Dissertations and Theses @ UNI

The purpose of this study was to determine the percentage of junior high/middle schools in the State of Iowa using selected. newly developed industrial arts curriculums and to determine if the senior high schools serviced by them were continuing to expand upon that base of knowledge.

Objectives of the Study.

1. To determine the percentage of Iowa junior high/ middle schools using one or more of the selected newly developed industrial arts curriculums.

2. To determine the percentage of senior high schools in Iowa which were using or building upon one of the selected industrial arts curriculums.

3. To inquire …