Engineering Commons^™

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 …

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 …

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 …

Identification Of Linear Systems With Delay Via A Learning Model, Hugh Francis Spence

Doctoral Dissertations

"The effects of input delay on an identification scheme using a learning model are investigated. The parameter adjustment laws for the learning model are derived through Lyapunov methods similar to those used for the model reference adaptive control systems of Parks. For no measurement noise or delay mismatch between the learning model and system, the parameters are adjusted to bring the error between model and plant to zero. When there is delay mismatch between the inputs of the learning model and the unknown system, the convergence of the parameters of the learning model to those of the unknown system is …

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 …

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 …

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 …

Development And Application Of Cartesian Tensor Mathematics For Kinematic Analysis Of Spatial Mechanisms, Robert Myrl Crane

Doctoral Dissertations

"The complexity of spatial mechanisms in themselves and the absence of an attractive analytical tool for their study has left this field of engineering analysis largely unexplored. In recent years several analytic methods have emerged. One of the most attractive of these is the tensor method. Literature surveys reveal that the tensor method is largely unexploited in the U.S.A., with regard to spatial mechanisms as well as simpler kinematic problems. The purpose of this work is to develop tensor mathematics for application to the kinematic analysis of spatial mechanisms. Methods are developed for position solutions and the determination of velocities …

Effect Of Axial Dispersion On Interphase Mass Transfer In Packed Absorption Columns, Virendra Kumar Mathur

Doctoral Dissertations

"A steady state approach was followed in this investigation to determine the effects of liquid and gas flow rates, packing size and packing height on the interphase mass transfer coefficient and gas phase axial mixing Peclet numbers. Experiments were performed on the absorption of carbon dioxide from a mixture of carbon dioxide and nitrogen in a packed column. Absorption was performed using 1/4, 3/8 and l/2 inch Raschig rings, with a packing height of 3 feet and also using 3/8 inch Raschig rings with a packing height of 5 feet. The liquid and gas flow ranges used were 2865 to …

An Sem Surface Study Of Nucleate Pool Boiling Heat Transfer To Saturated Liquid Nitrogen Reduced Pressures From 0.1 To 0.9, David Virgil Porchey

Doctoral Dissertations

"This study constituted an examination of both nucleate boiling and maximum heat flux characteristics of liquid nitrogen boiling from characterized surfaces. Several textures of gold plated copper surfaces were studied in addition to silver and silver oxide surfaces. Data were taken over a wide range of reduced pressures. All surfaces were examined using a Scanning Electron Microscope (SEM). Data and micrograph comparison revealed that both surface chemistry and surface roughness affect the nucleate boiling characteristics of liquid nitrogen. These effects are separated from each other showing that nucleate boiling is a function of both surface chemistry and topography. Surface roughness …

A Study Of The Anodic Oxidation Of 1, 3-Butadiene On Platinum And Gold Electrodes, Arun Kumar Agrawal

Doctoral Dissertations

"The anodic oxidation of 1,3-butadiene on Pt and Au electrodes was studied at 70°C in solutions of H₂SO₄, K₂SO₄, K₂CO₃, and KOH with pH's ranging from 0.35 to 12.5. Reaction rates (current) were measured as a function of potential, pH, temperature, and butadiene partial pressure. A transition region (apparently a shift in the rate determining step) in case of Pt was observed in the Tafel plots. The coulombic efficiencies of oxidation to CO₂ were 85 percent in 1 N H₂SO₄ on Pt, 93 percent in 1 N KOH on Pt, and 72 percent in 1 N KOH on Au"--Abstract, Page …

Investigation Of Liquid Carryover In The Girdler-Sulfide Process For Production Of Heavy Water At The Aec Savannah River Plant, Samuel Clark Allen

Doctoral Dissertations

"An investigation of the causes of liquid carryover in the Girdler-Sulfide process for the production of heavy water was carried out using 12 samples of carbon collected over a one-year time period. Organic impurities from the feedwater were concentrated by adsorption on carbon. Studies of methods for the drying of carbon showed that freeze drying resulted in the minimum reproducible moisture retention without gross loss of the adsorbed organic materials. Rotary vacuum evaporation and air drying of beds of carbon were proven to be less efficient. A study was made of the variables which affect extraction efficiency by the Soxhlet …

Linear Regression Models Of Sound Velocity In The North Atlantic Ocean Below A Critical Depth, Richard Roland Kunkel

Doctoral Dissertations

"Sound velocity models currently in use by the U. S. Navy require difficult data sampling at great expense. This study is to investigate the feasibility of a sound velocity model dependent only upon position that would be valid for a selected, reasonably large, near homogeneous area of the ocean. The most important position parameters are latitude, longitude, and depth. To accomplish this objective a critical depth of 2500 meters was established for an 8° by 20° rectangle of the Sargasso Sea which lies within the North Atlantic Ocean. The critical depth is defined as the depth at which the characteristics …

Mass Transfer From Spherical Gas Bubbles And Liquid Droplets Moving Through Power-Law Fluids In The Laminar Flow Regime, Cheng-Chun Huang

Doctoral Dissertations

"Continuous phase mass transfer coefficients are presented for internally circulating spheres of a Newtonian fluid traveling through a power-law type continuous phase in to so-called creeping-flow region. The Nakano and Tien stream functions allow the Sherwood number to be determined as a function of the Peclet number, power-law index, and a viscosity ratio parameter. The Hirose and Moo-Young relation is shown to be a limiting case of this solution. Mass transfer rates increase as the fluids become more pseudoplastic and/or the continuous phase consistency index increases, all other factors held constant"--Abstract, page ii.

Numerical Simulation Of Forward Combustion In A Radial System, Tommie C. Wilson

Doctoral Dissertations

"A generalized mathematical model is described for the thermal recovery of oil in a radial system in which there are conductive heat losses to the surrounding formations, three phase fluid flow, conductive-convective heat transfer within the producing formation, combustion, and aqueous-phase changes considered. The mathematical form of the temperature equation requires that numerical solutions be obtained with a digital computer for which the numerical approximations of the partial differential equations are presented and the results discussed. The analysis is applied to field size simulations of a forward combustion project to permit direct field analyses of significant importance for accurate reproductions …

Some Effects Of Oh Groups On Sodium Silicate Glasses, Mokhtar Sayed Maklad

Doctoral Dissertations

"Glasses of various compositions in the Na₂O-SiO₂ system were prepared with different levels of OH concentration. Phase separation kinetics, thermal expansion, radiation induced optical absorption, and internal friction of these glasses were studied. The increase in OH content in these glasses was found to (a) enhance the rate of phase separation; (b) increase thermal expansion above the glass temperature and change the dilatometric softening temperature in a way that depends on microstructure; (c) increase the radiation induced optical absorption bands associated with positive hole centers and decrease those associated with electron trap centers; and, (d) decrease the low temperature alkali …

The Cathodic Reduction Of Maleic Acid, Show Yih Hsieh

Doctoral Dissertations

"The electrochemical reduction of maleic acid (0.0003 to 0.3 M) was studied on Hg, 0.5% Bi(Hg) amalgam, 5.0% Bi(Hg) amalgam, and Bi cathodes in 1 n H₂SO₄-K₂SO₄-KOH electrolytes (pH 0.3 to 4.0) at 60°C. The maleic acid was converted to succinic acid with high efficiencies (86 to 100%) on all cathodes. Polarization curves with linear Tafel sections were found. All the cathodes had similar kinetic parameters...A reaction mechanism consistent with the experimental observations is proposed..."--Abstract, pages ii-iii.

Temperature Variation In Distribution Of Relaxation Times In Aluminosilicate Glasses, David Wayne Moore

Doctoral Dissertations

"The distribution of relaxation times for the alkali peak in a Li₂ O·A1₂O₃ ·2.0SiO₂ glass and for the mixed alkali peak in a 0.5Li₂O·0.5Na₂O·A1₂O₃·2.OSiO₂ glass was studied using the internal friction technique. A lognormal distribution of relaxation times provided the best agreement with the experimental data. The ß parameter of the lognormal distribution function, which is related to the half-height peak width, varied with temperature, indicating that the distribution of relaxation times is dependent upon the activation energy and the activation entropy of the relaxation mechanism. The major contributor to the distribution of relaxation times is a wide distribution in …

Discrimination Of Signal And Noise Events On Seismic Recordings By Linear Threshold Estimation Theory, David Nuse Peacock

Doctoral Dissertations

"The object of this study is the investigation of a linear threshold element technique for identifying surface multiples on a single seismic trace. Traces of seismic events were generated which contained primaries, surface multiples, and various levels of Gaussian random noise. Since it was necessary to separate the events as much as possible, the traces were subjected to pulse-compression deconvolution processing prior to LTE analysis. Mean frequency, peak frequency, amplitude spectrum variance, periodicity, and polarity were employed as pattern parameters. A set of weights was found that would maximize the moment of inertia of the S line distribution of the …

Electrode Reactions In Zinc Electrolysis, Ernest R. Cole

Doctoral Dissertations

"The effects of temperatures from 0°C to 50°C and current densities from 10 asf to 200 asf on the current efficiency in the electrolysis of pure zinc sulfate solutions (65 gpl Zn⁺⁺ - 200 gpl H₂SO₄) were determined. Pure platinum and platinum coated titanium anodes were used with an aluminum cathode. Platinum anodes were not inert at certain combinations of temperature and current density, and platinum acted as a low overvoltage impurity causing resolution of the cathode deposit. Orientation of the zinc deposits was found to vary with temperature and to have a distinct relationship to current efficiency. Preconditioning of …

Penetration In Granite By Shaped Charge Liners Of Various Metals, Hemendra Nath Kalia

Doctoral Dissertations

"The penetration in Missouri red granite by cylindrical charges with metal liners of aluminum 2011 (T-3), aluminum 7075 (T-6), yellow brass, monel, maraging steel (vascomax 250), and copper was measured. Metals having high ductility and moderate compressive strength penetrated deeper than high strength maraging steel. Aluminum required a greater standoff for optimum penetration than the other metal liners tested. Preliminary metallographic studies of the liner metals and slugs showed that the grains had elongated along the slug axis. The metals containing zinc formed very small or no slugs. The granite grains were highly fractured. The holes were discolored and coated …

Iddap -- Interactive Computer Assistance For Creative Digital Design, Richard Franklin Crall

Doctoral Dissertations

"A new computer-aided design program to assist in the initial phases of logical design is described. The program, intended for use via an on-line remote terminal, will allow the designer to study and experiment with design alternatives during the initial creative design phases. An ALGOL-like language is used for specifying the system being designed. In addition to simulating the design, the program allows the user to perform on-line design changes, reorganize data and generate timing diagram information"--Abstract, page ii.

Diffusion And Internal Friction In Sodium-Rubidium Silicate Glasses, Gary L. Mcvay

Doctoral Dissertations

"The internal friction and self diffusion coefficients of sodium and rubidium ions for (1 - X) Na₂O·X Rb₂O·3 SiO₂ glasses have been measured. The diffusion measurements employed radioactive isotopes and a thin sectioning technique and extended from 350 to 500°C. Internal friction measurements were made from -150 to 500°C and at frequencies of 0.05 to 6000 Hz. The maximum height for the mixed alkali internal friction peak occurs at the composition where the sodium and rubidium diffusion coefficients are equal. It is concluded that the mechanism responsible for the mixed alkali peak is a cooperative rearrangement of sodium-rubidium ions and …

The Oxidation Kinetics Of Liquid Lead And Lead Alloys, Thomas Edward Weyand

Doctoral Dissertations

"Liquid lead and lead-silver alloys were investigated to determine the rates and products of oxidation in pure oxygen at temperatures of 350 to 600°C. The kinetic data were determined using a Cahn electro-balance. Liquid lead was found to follow a cubic rate of oxidation between 350 and 400°C. A parabolic rate was found at temperatures above 400°C. 0.496% silver and 2.258% silver alloys followed a cubic rate of oxidation from 350 to 550°C and tended to approach a parabolic rate of oxidation above this temperature. Silver additions were found to increase the rate of oxidation as compared to the pure …

A Computer Simulation Of Mine Air Shaft Thermodynamics, Ambyo Sumopandhi Mangunwidjojo

Doctoral Dissertations

"Several earlier investigations have been conducted into various aspects of heat problems in underground mines. The application of general gas laws and thermodynamics in the approach of mine ventilation has been helpful in elucidating certain difficulties associated with the subject. By combining several of the techniques perfected by these researchers and applying Carrier's method of calculation for heat flow from exposed rock strata into a workable plan, a method was developed whereby it is possible to accurately and conveniently predict the quality of working environment at any point within a deep mine. The findings of this study may be of …

Higher Space Mode Analysis Of A Large Cylindrical Pulsed H₂O System, Harold David Hollis

Doctoral Dissertations

"By utilizing a geometrically centered pulsed source internal to a large (B²_g) ≈ 0.002) cylindrical H₂O system, the neutron flux was measured as a function of position and time. A least square fit of the data yielded the fundamental and five higher decay constants and amplitudes of the thermal neutron flux. Symmetrical and enhanced neutron densities were obtained as a result of the internal source. Long waiting times were unnecessary and data acquisition was accelerated.

The decay constants were found to be independent of position, pulse width, counting time and rates, method of normalization, or waiting time. …

Synthesis Heuristics For Large Asynchronous Sequential Circuits, Robert Judson Smith

Doctoral Dissertations

"Many well-known synthesis procedures for asynchronous sequential circuits produce minimal or near-minimal results, but are practical only for very small problems. These algorithms become unwieldy when applied to "large" circuits with, for example, three or more input variables and twenty or more internal states. New heuristic procedures are described which permit the synthesis of very large machines. Although the resulting designs are generally not minimal, the heuristics are able to produce near-minimal solutions orders of magnitude more rapidly than the minimal algorithms. A method for specifying sequential circuit behavior is presented. Input-output sequences define submachines or modules. When properly interconnected, …

Model-Referenced Adaptive Control Of Plants With Noise And Inaccessible State Vector, Donald James Schooley

Doctoral Dissertations

"The problems of process noise, measurement noise, and inaccessible process state vector in the model-referenced system of Shackcloth-Butchart-Parks (SBP) are investigated. Since the system no longer possesses a static equilibrium point, the concept of asymptotic stability does not apply. However, by using Liapunov-like ideas, the error between the plant (process plus controller) and the model is shown to enter a region about the origin if certain bounds are known. A possible technique for reducing the size of this region is to feedback a function of the error into the plant's input. Several methods of circumventing the inaccessible state vector problem …

Use Of The Turbulence Kinetic Energy Equation In Prediction Of Nonequilibrium Turbulent Boundary Layers, William Madison Byrne Jr.

Doctoral Dissertations

"A differential method is proposed for the prediction of a broad range of turbulent boundary layers of engineering and scientific interest. A digital computer program is presented which is applicable to boundary layers with positive, negative, and zero pressure gradient in the main-stream direction as well as boundary layers with suction, blowing or zero mass addition at the wall. The turbulence kinetic energy equation is solved simultaneously with the longitudinal momentum and continuity equations to provide an independent means for determining the effective viscosity which makes allowance for "history" effects in the flow. It is shown that the prediction method …