Digital Commons Network^™

An Investigation Of Subsequent Yield Phenomena, Joseph George Hoeg

Doctoral Dissertations

"A method utilizing high pressure fluid environments is described whereby a three-dimensional subsequent yield surface was determined for 304 stainless steel. Cylindrical parent specimens of this material were prestrained in axial compression under fluid pressure and then small sub-specimens were sectioned from these parent specimens. Finite element techniques were used to optimize the parent specimen size so that a zone of uniform axial stress would result during the prestraining. Longitudinal strains in this zone were monitored during the prestraining and the sub-specimens were cut from this region in a manner that did not allow the machining to appreciably affect the …

The Diffraction Of Plane Sound Waves By A Perfectly Reflecting Quarter-Plane, Curtis Spaulding Morse

Doctoral Dissertations

No abstract provided.

Rocket Measurements Of Field Aligned Currents And Energy Spectra Of Charged Particles In An Auroral Display, Lawrence Wah Choy

Doctoral Dissertations

No abstract provided.

The Trace Fluorometric Determination Of Polynuclear Aromatic Hydrocarbonsin Natural Water, Richard Edward Keegan

Doctoral Dissertations

No abstract provided.

The Relationship Between Cation Uptake And Organic Acid Accumulation In Apple Leaves, Abdul Wahid Mohammad Al. Hachim

Doctoral Dissertations

No abstract provided.

The Species Composition, Seasonal Succession, Reproduction And Distribution Of Marine Algae From Scituate To Woods Hole, Massachusetts, Douglas Clifton Coleman

Doctoral Dissertations

No abstract provided.

Low-Energy Electron Transport By The Method Of Discrete Ordinates, David E. Bartine

Doctoral Dissertations

"The one-dimensional discrete ordinates code ANISN has been adapted to simulate the transport of low-energy (on the order of a few MeV) electrons. Two different calculational techniques have been utilized for the treatment of electron-electron collisions that result in a small energy transfer. One method treats such collisions by a continuous slowing-down approximation, while the other method treats these collisions by the use of a very approximate cross section. Calculated results obtained with ANISN are compared with experimental data for the transmitted energy and angular distributions for 1-, 2.5-, 4-, and 8- MeV electrons normally incident on aluminum slabs of …

Internal Friction Of Ion Exchanged Li₂O•Al₂O₃•2sio₂ Glasses, A. Ismail A. Abdel-Latif

Doctoral Dissertations

"Li₂O•Al₂O₂•2SiO₂ glass fibers were ion-exchanged from 1 to 300 minutes in a sodium nitrate bath at 366ºC. The internal friction was measured along with the lithium and sodium concentration profiles. As sodium progressively replaced lithium, the alkali internal friction peak became smaller while a new peak (mixed alkali peak) appeared and increased in magnitude. These changes in the internal friction are similar to those that occur upon the addition of a second alkali to glasses prepared by conventional melting. The magnitude of both internal friction peaks in ion exchanged glasses was dependent on the overall glass composition. The magnitude of …

Dynamic Behavior Of Eccentrically Stiffened Plates, Charles Stuart Ferrell

Doctoral Dissertations

"The dynamic behavior of eccentrically stiffened rectangular plates is studied by the finite element method. The addition of stiffeners to a plate structure is a common method of increasing the rigidity of the structure with a minimum of weight increase. However, this stiffened plate configuration does not easily lend itself to analysis. This study is an approach to finding a rational method by which the dynamic behavior of such a stiffened plate structure may be determined. The governing differential equations for the finite element model are derived and the stiffness and mass matrices for the plate and stiffener elements are …

The Effect Of A Knurled Heat Transfer Surface Upon Pool Nucleate Boiling Of Normal Pentane, Jerry James Carr

Doctoral Dissertations

"The effect of knurling a nucleate boiling heat transfer surface was studied. The knurling utilized produced regular, four-sided, adjacent pyramids with an apex angle of 90 degrees. Four knurling densities were used ranging from 416 to 2591 pyramids per square inch. The transfer surface was gold-plated copper and the heaters used were electrically heated, ten-inch long, horizontal cylinders of one-inch diameter. The liquid boiled was normal pentane at its saturation temperature and a pressure of 760 millimeters mercury.

For some of the knurled surfaces the temperature difference required to produce a given heat flux was found to be less than …

Transient Hydraulic Simulation: Breached Earth Dams, D. L. Fread

Doctoral Dissertations

"A conceptual method to alleviate flood damages due to over-topping failures of small earthfill dams is the incorporation of a relatively thin erosion retarding layer within the dam. This paper investigates the reduction in the reservoir release due to the hypothetical erosion retarding layer. In addition, the paper provides a method for the determination of an optimal location of the layer so as to minimize the maximum possible reservoir release due to a gradually breached earth dam. The transient reservoir flow is simulated by a numerical model, based upon the solution of the one-dimensional St. Venant unsteady open-channel flow equations. …

An Age Hardening Study Of Magnesium-Thorium-Manganese Alloys, Kuldip Singh Chopra

Doctoral Dissertations

"The age hardening processes in Mg-3.5 wt.% Th-1.0 wt.% Mn and Mg-1.0 wt.% Th-1.0 wt.% Mn alloys have been studied by light and electron microscopy, and by electron and X-ray diffraction. At aging temperatures of 300ºC and below, G.P. zone formation rapidly hardens these alloys followed by the precipitation of disc shaped plates during averaging. During aging above 300ºC, no G.P. zones form and the disc shaped precipitate grows to very large sizes. The combined results of X-ray and electron diffraction indicate that the disc shaped precipitate has a Mg₃Cd (DO₁₉) type structure. The basal plane of the Mg₃Th discs …

Photoionization Of Photoexcited Cesium, Robert E. Hebner

Doctoral Dissertations

"A new method for obtaining the cross section for photoionization of photoexcited cesium is presented. The salient feature of this experiment is to use three crossed beams, i.e., two light beams intersecting a beam of cesium atoms. The cross section is determined by counting the ions produced by the two step process: Cs (6S) + h[upsilon]₁ --> Cs (6P) ; Cs (6P) + [upsilon]₂ --> Cs⁺ + e⁻ The relative cross section for the second step has been obtained from threshold (5060 Å) to 2500 Å. The excitation light source used in obtaining this cross section was a rf resonance …

Surface Reactions Of Boron With Clean Tungsten Substrates, Thomas A. Flaim

Doctoral Dissertations

"A model developed to predict adsorbate-induced work-function changes for thermionic emitters is shown here to apply to a more general class of electron emission phenomena and a much broader range of adsorbates. This model predicts that chemically, vapor-deposited boron will increase the work function of a clean tungsten substrate at coverages between 0 and 1 monolayer. This is the first time that a single model has been shown to predict both positive and negative work function changes for different adsorbates. The reactions of chemically, vapor-deposited (CVD) boron with clean tungsten substrates were studied using field emission microscopy (FEM) and low …

Activation Volumes Of Carbon Diffusion In F.C.C. Iron-Nickel Alloys, James Raymond Keiser

Doctoral Dissertations

"The disaccommodation technique was used to determine the activation volume of carbon diffusion, ΔV, in six fcc iron-nickel alloys. Measurements were made at temperatures ranging from 68ºC to 90ºC and pressures up to six kilobars on samples having a nickel content between 31 and 63 at. %. A maximum activation volume of 3.9 cm³/mole was found at 34 at. % nickel. The compositional dependence of ΔV is satisfactorily reproduced by a magnetic energy continuum model in which it is assumed that the activation free energy of diffusion is essentially ferromagnetic in origin "--Abstract, page iii.

On-Line Economic Optimization Of A Chemical Reactor, Jesse Daniel Bennett

Doctoral Dissertations

"An economic optimizing control system for a continuous flow stirred tank chemical reactor is designed, simulated, and installed on a pilot scale reactor. The control scheme utilizes a reaction and reactor model to predict on-line the economic optimum of a reactant concentration. In this manner the control system manipulates the reactant flow rate to maintain the optimum concentration during changes in reaction-reactor parameters with time. Typical parameter changes include the decay of reaction catalyst activity. The optimizing controller will function in conjunction with various operating policies including control to maintain a specified production rate"--Abstract, page ii.

X-Ray And Neutron Diffraction Study Of The Holmium-Iron System, Michael Fred Simmons

Doctoral Dissertations

"Neutron diffraction and x-ray powder studies have been made of holmium-iron intermetallic compounds. The magnetic moments of Ho and Fe are in good agreement with measured spontaneous magnetization assuming a ferrimagnetic model with the Ho moments antiparallel to the Fe moments. The magnetic moments of the Fe atoms are found to be localized and thus independent of the rare earth content in the alloys. In contrast to HoCo₃, (00ℓ) type magnetic peaks in the neutron diffraction patterns are still prevalent at room temperature and gradually decrease as the Curie temperature is approached. This fact indicates that the easy direction of …

Identification Of Centers Of Influence For Urban Areas, Robert W. Meyer

Doctoral Dissertations

"A method is developed for the identification of the spatial locations about which urban population densities tend to be distributed. The identification of these "influence centers" is based upon the use of available census data. The method is developed for application to any population characteristic which can be logically represented in terms of spatial density. Examples of such characteristics are; total population, population by race, and population by income group. The method is empirically developed and verified for restricted spatial distributions using artifically generated census tract information. These spatial distributions are compatiable with population distributions that are most readily modeled …

Structure And Properties Of Silver Borate Glasses, Edward Nashed Boulos

Doctoral Dissertations

"Clear glasses form in the system Ag₂O-B₂O₃ up to about 35 mol.% (65 wt.%) Ag₂O. Infrared absorption, thermal expansion and density data indicated an analogy to the Na₂O-B₂O₃ system. Pentaborate-triborate group pairs appear to be formed upon the addition of Ag₂O to B₂O₃ up to 20 mol.% Ag₂O and diborate groups from 20 to 33 mol.% Ag₂O. This interpretation is supported by the comparison of the infrared absorption spectra of quenched and crystallized glasses. One crystallization product ,Ag₂O.4B₂O₃, has been identified previously. A new compound starts to appear at 28 mol.% Ag₂O. Silver is generally present as a network modifier …

The Genesis Of Cellular Precipitation In Copper Rich Copper-Indium Alloys, Raymond Albert Fournelle

Doctoral Dissertations

"The morphology of cellular precipitation in a Cu-9.5at.%In alloy has been investigated by light and electron microscopy and x-ray and electron diffraction. Both cellular and general precipitation were observed to occur simultaneously in quenched and aged alloys while only cellular precipitation was observed to occur in isothermally aged alloys. Because of the presence of wide, vacancy depleted precipitate free zones in the vicinity of grain boundaries, general precipitation was observed to have no effect on the early development of cellular precipitation. Hence, the early development of cellular precipitation was found to be identical for both types of heat treatment. By …

Trace Base Metals, Petrography, Rock Alteration Of The Productive Tres Hermanas Stock, Luna County, New Mexico, Peethambaram Doraibabu

Doctoral Dissertations

"Zinc, lead and minor copper-bearing manto-type and vein- type deposits occur in Paleozoic sedimentary rocks adjoining the Tres Hermanas quartz monzonite stock, Luna County, New Mexico. In an attempt to prove or disprove a possible genetic relationship between these mineral deposits and the stock, 99 half-mile or closer orthogonal grid samples from the stock and 22 soil samples from a connecting alluvial area to the north were analysed by atomic absorption technique for trace contents of zinc, lead and copper. Thirty-two of the rock samples were selected on a wider grid and petrographically studied and modal analyses calculated. Argillic, sericitic …

Detection Of Delay Time And Filtering Using Sequency Domain Technique, Earl F. Richards

Doctoral Dissertations

"A procedure is presented by which it is possible to detect a known signal of unknown delay in a noisy medium contaminated by noise. From the results the characteristics of a sequency digital filter which would be required to remove the noise contamination is indicated. The Walsh functions are discussed and the sequency domain, which is analogous to the continuous frequency domain, is used in the spectral analysis of signals. The binary nature of the Walsh functions and their ease of generation makes processing of signals easier than the Fourier analysis approach. The applications of fast forward and inverse Walsh …

Distribution Of Trace Elements In Olivines And Proxenes - An Experimental Study, Melvin Leroy Bird

Doctoral Dissertations

"Olivine, pyroxene,and spinel were crystallized in the ternary system anorthite-forsterite-silica to which trace amounts of the transition metal ions Cr³⁺, Fe²⁺, Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺ had been added. The resulting concentrations of the transition metal ions in the liquid and crystalline phases were determined using the electron microprobe. The results, given as free energies and partition functions, indicate the order of substitution of the dipositive ions in all crystals to be Ni²⁺, Co²⁺, Mn²⁺, Cu²⁺, and Fe²⁺ according to the predictions of crystal field theory. The ion Cr³⁺ substituted in greater or lesser quantities depending on the crystalline phase. …

Response Surface Study Of A Characteristic Chemical Plant, John Thomas Mason Iii

Doctoral Dissertations

"Study of the return on investment response surface of a characteristic chemical plant indicates unimodality in the valid region, but the optimum design condition with this response surface is strongly affected by the correlation used for the investment. The method used for the design of this type of chemical plant incorporates the use of a simulation routine for preliminary estimates"--Abstract, page ii.

The Vibrational Modes Of Spheroidal Cavities In Elastic Solids, David Stewart

Doctoral Dissertations

"A general analysis of all possible cavity shapes is given with a discussion of the mathematical difficulties involved for the various cases. Special emphasis is given to cavity shapes describable in terms of the coordinate surfaces of coordinate systems separating the scalar wave equation. 112 such shapes are identified and discussed. Free boundary condition equations for spheres and spheroids are derived in complete generality in terms of potentials. The difference in the vibrations of a solid and those of a cavity of the same shape is discussed and made clear. The impossibility of deriving a frequency equation for uniform radial …

Theory Of Nucleation Of Water Properties Of Some Clathrate Like Cluster Structures, Mehdi Daee

Doctoral Dissertations

"The tranquility of classical homogeneous nucleation theory has been disturbed by the introduction of statistical mechanical correction factors to a basically thermodynamic theory. These factors, which appear to be essential, destroy much of the agreement with experiment in the case of water vapor. A molecular model for the pre-nucleation water clusters is proposed with a view toward resolving some of these difficulties. As a first step, the Properties of a few specific cluster configurations have been examined. Clathrate-like structures containing 16 to 57 water molecules are discussed. The hydrogen bonds were treated as simple harmonic oscillators for the purpose of …

Homogeneous Nucleation Of Water Vapor In Inert Gas Atmospheres, Arthur Henry Biermann

Doctoral Dissertations

"The homogeneous nucleation of water vapor in atmospheres of helium, neon, argon, krypton, and xenon was studied using an expansion type cloud chamber. A strong dependence of the nucleation rate on the particular inert carrier gas was observed. At present the only dependence upon the nature of the carrier gas included in classical nucleation theories is a small factor arising from kinetic considerations which is in the wrong direction to explain the observations. To explain the dependence of the rate on the nature of the carrier gas, a molecular cluster model is assumed allowing inert gas atoms to occupy the …

Use Of The Turbulence Kinetic Energy Equation In Analyzing Turbulent Near Wakes, James Edward Auiler

Doctoral Dissertations

"A general method is presented for analyzing turbulent flow fields in the near wake regions of two-dimensional and axisymmetric bodies. The governing partial differential equations of continuity, momentum and turbulence kinetic energy are expressed in elliptic form in terms of the dependent variables stream function, vorticity and turbulence kinetic energy. An iterative finite-difference technique is used to solve the governing equations simultaneously. Numerical solutions are obtained for the following physical problems: 1. Laminar near wake: Only stream function and vorticity are considered for laminar flow. Solutions are compared with available analytical results for uniform flow over a sphere. 2. Turbulent …

A Measurement Of Complex Viscosity With Large Amplitudes, Kuo-Shein Shen

Doctoral Dissertations

"In order to study the viscoelastic properties of polymer solutions and greases, a dynamic apparatus was built for making measurements of complex viscosity. Characteristic impedance was measured by a force transducer, an accelerometer and a phase meter. Large amplitudes to 0.5 inch can be obtained with this apparatus. The largest amplitude used was 1.27 x10⁻¹ cm. The frequency range was 30 Hz - 1500Hz. The lowest dynamic viscosity to be measured was 0.5 poise. In order to determine the capabilities of the instrument, complex viscosities of polymer solutions and greases were measured. The polymer solutions studied were polyisobutylene (PIB) L-80, …

Statistical Study Of Rock Drilling By Hypervelocity Jets From Explosive Shaped Charges, John William Brown

Doctoral Dissertations

"The drilling effect in rock of hypervelocity jets from explosive shaped charges was investigated experimentally to supplement a rapid excavation concept. The effects of the design factors of the charge and the mechanical properties of eight rock types were studied. Experiments were both designed and analyzed upon statistical principles. A full factorial experimental design was used for each of seven rock types. An analysis of variance and the k-ratio least significant-difference test were applied to the results.

The optimum design of shaped charges for drilling was found to be independent of rock type and rock properties. For composition C-4 charges …