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Articles 1681 - 1710 of 1800
Full-Text Articles in Engineering
Binary Molecular Diffusivities In Liquids: Prediction And Comparison With Experimental Data, Ronald Dean Mitchell
Binary Molecular Diffusivities In Liquids: Prediction And Comparison With Experimental Data, Ronald Dean Mitchell
Doctoral Dissertations
"The Eyring rate theory equation has been modified successfully to enable predictions of binary molecular diffusivities for a wide variety of liquid-liquid systems. The activation free energy for binary diffusion has been evaluated in terms of the activation free energies for self diffusion of the solvent and solute. This was accomplished through the use of regular solution theory by relating the bond breaking energy of the jump step to the bond breaking energy in evaporation. Diffusivities estimated by this equation and the equations developed by Olander, by Gainer and Metzner, and by Wilke and Chang were compared with experimental data. …
Optimizing Diesel Engine Efficiency Using The Controllability Of A Variable Ratio Hydrostatic Transmission, Gordon Wright
Optimizing Diesel Engine Efficiency Using The Controllability Of A Variable Ratio Hydrostatic Transmission, Gordon Wright
Doctoral Dissertations
"A linear mathematical model of a diesel engine, hydrostatic transmission, and electric dynamometer system was developed. This model was used as an aid in designing a single input controller which regulates engine speed to optimize efficiency while maintaining constant transmission output speed under changing load conditions. Compensation was necessary to stabilize the system because of positive feedback in the engine control system. The compensated system's response was compared to that which was predicted analytically. The analytical model was then extended to design the control system parameters to operate the engine and transmission in a representative vehicle"--Abstract, page ii.
Voids In Neutron Irradiated Aluminum, Nicholas H. Packan
Voids In Neutron Irradiated Aluminum, Nicholas H. Packan
Doctoral Dissertations
"Void formation in high purity aluminum resulting from irradiation to fluences between 1.5 x 10¹⁹ and 1.6 x 10²² neutrons/cm² (E > 0 .1 MeV) at a temperature of 55 ± 5ºC was studied, primarily by means of transmission electron microscopy. In particular the effects of neutron fluence and flux were examined, as well as the possible influences of both preexisting and transmutation-produced impurities. A very low concentration of voids (about 10¹²/cm³) resulted from irradiation to 1.5 x 10¹⁹ neutrons/cm²; they averaged about 150 Å in diameter. Void concentrations and sizes increased with fluence, reaching values of 6 x 10¹⁴ voids/cm³ …
A Model For Predicting The Energizing Transients Of Station Capacitor Banks, Dennis Oliver Wiitanen
A Model For Predicting The Energizing Transients Of Station Capacitor Banks, Dennis Oliver Wiitanen
Doctoral Dissertations
"A model for predicting the transients associated with energizing ungrounded wye-connected station capacitor banks was developed. The model has the capability of simulating non-simultaneous operation of the breaker poles, pre-insertion resistors, and the presence of previously energized capacitor banks at the same station. To investigate various system representations, a computer solution of the transient response of an arbitrary network and the computer solution of the generalized Thevenin impedance of a complex network are presented. A simple power system is defined and used to investigate the modeling of various system components, using the computer solution methods. Simplification of the model due …
A Simulation And Diagnosis System Incorporating Various Time Delay Models And Functional Elements, David Michael Rouse
A Simulation And Diagnosis System Incorporating Various Time Delay Models And Functional Elements, David Michael Rouse
Doctoral Dissertations
"The application of digital simulation to all phases of digital network design is considered here as oppossed [sic] to development of simulation for one or two restricted parts of the digital process. For this reason a simulator is presented which can be consistent by varying the level of expression from the simulation of architectural structures to such detailed simulation requirements as race analysis of asynchronous sequential circuits. In order to make system simulation more than just an idea, it must be capable of handling large circuits in reasonable times. It is demonstrated that functional simulation has the potential to increase …
A Three-Dimensional Mathematical Simulator Of Multiphase Systems In A Petroleum Reservoir, Leonard Koederitz
A Three-Dimensional Mathematical Simulator Of Multiphase Systems In A Petroleum Reservoir, Leonard Koederitz
Doctoral Dissertations
"A generalized digital analysis for calculating three phase, three dimensional flow in reservoirs is developed. The computerized mathematical model is applicable to depletion drive, gas injection, water injection, and/or aquifer drive systems with modifications specific to the simulation criterion of that type of drive and includes fluid compressibility effects, gravity drainage and capillary pressure. The simulation allows arbitrary consideration of reservoir heterogeneity, geometry, well locations and rates of production. An innovation to the alternating direction technique for linear differential equations discussed by Brian is developed and employed in order to render the method of solution applicable to non-linear differential equations. …
An Investigation Of The Stiffness Of Shafts With Integral Disks, Richard King Riley
An Investigation Of The Stiffness Of Shafts With Integral Disks, Richard King Riley
Doctoral Dissertations
"The results of an investigation of the effect of an integral disk on the torsional elastic stiffness of an axisymmetric shaft are presented. Various configurations of disk diameters and widths on a shaft of specified diameter were investigated, using a finite element method of calculation verified by experimentation. The finite element method is presented for the elastic solution of a general axisymmetric body under all possible axisymmetric load conditions. The axisymmetric body is idealized as an assemblage of triangular cross-sectioned torii representing both the normal and shear properties. The elastic stiffness is used to obtain the equilibrium equations of the …
An Investigation Of Nucleate And Film Boiling Heat Transfer From Copper Spheres, William David Hardin
An Investigation Of Nucleate And Film Boiling Heat Transfer From Copper Spheres, William David Hardin
Doctoral Dissertations
"This study consisted primarily of a laboratory investigation involving nucleate and film boiling heat transfer from copper spheres with saturated liquid nitrogen at atmospheric pressure. An initial study was directed towards obtaining reproducible boiling heat flux versus ΔT curves in the nucleate boiling region from surface conditions created by single and/or multiple glass bead peenings. The variables of bead size, nozzle line operating pressure, and distance a copper surface should be placed from the nozzle outlet were checked. The results indicated that a final peening of the surface with 0.0017-0.0035 inch diameter glass beads, a nozzle line pressure of approximately …
Anodic Dissolution Of Zinc In Potassium Iodide-Potassium Iodate Solutions, Chi-Chiu Yao
Anodic Dissolution Of Zinc In Potassium Iodide-Potassium Iodate Solutions, Chi-Chiu Yao
Doctoral Dissertations
"The anodic dissolution of Zn was studied in KI-KIO₃ solutions at 25ºC. In I⁻ solutions, it was found that the apparent valence of Zn ions going into solution is approximately two. Smaller values are obtained in IO₃⁻ solutions, with the most pronounced changes occurring in the higher concentrations. An empirical equation is derived relating the apparent valence (or anode efficiency) to the current density and concentrations of IO₃⁻ and I⁻. An anodic dissolution mechanism is proposed"--Abstract, page 1.
Simulation Of A Gas Storage Reservoir With Leakage By A Two-Dimensional Layered Mathematical Model, Steven William Ohnimus
Simulation Of A Gas Storage Reservoir With Leakage By A Two-Dimensional Layered Mathematical Model, Steven William Ohnimus
Doctoral Dissertations
"A generalized mathematical model was developed for two-dimensional compressible fluid flow accounting for the effects of relative permeability capillary pressure, and gravity drainage in addition to the reservoir properties of rock heterogenity and reservoir geometry. The generalized model developed was applied to an aquifer gas storage reservoir in which vertical leakage occurred from the main reservoir to two adjacent overlaying zones. The experimental results of Thomas, et al. were utilized in applying the model to gas storage injection/withdrawal periods yielding reasonable results for the three layers"--Abstract, page ii.
Ionization Of Air Produced By Strong Shocks, Howard Sajon Joyner
Ionization Of Air Produced By Strong Shocks, Howard Sajon Joyner
Doctoral Dissertations
"This dissertation provides theoretical predictions along with experimental results for electron concentrations behind a shock as a function of Mach number over a range from 11 to 20 using a combustion driven shock tube operating in air. These theoretical predictions represent an upper bound for chemical equilibrium. The model for air was 78.0880% nitrogen, 20.949% oxygen, 0.0300% carbon dioxide, 0 .9300% argon, 0.0025%neon, and 0.0005% helium. Also the theory of a double diaphragm shock tube with corresponding pressure ratio vs. Mach number relationships is provided. A computor [sic] program using iterative techniques for a succinct presentation covering the modifications and …
The Deformation Mechanisms In Sublimed Magnesium Under Cyclic Loading, Babu Narian Thakur
The Deformation Mechanisms In Sublimed Magnesium Under Cyclic Loading, Babu Narian Thakur
Doctoral Dissertations
"A detailed study of the deformation processes in sublimed magnesium under reverse bending fatigue in air at room temperature has been undertaken utilizing the light, scanning and transmission electron microscopy. The Principal deformation modes are the basal slip and {10Ī2} twinning. The proportion of twinning increases markedly with the increasing stress level and the number of cycles. The evidence for cross slip is seen on the basal slip bands. The extrusions are seen not only along the basal slip lines but also along the {10Ī2} twin boundaries. In the later stages of fatigue, the extrusions chip off producing a notch …
Microwave Propagation Through Isotropic Inhomogeneous Photoconductive Media, Thomas Van Doren
Microwave Propagation Through Isotropic Inhomogeneous Photoconductive Media, Thomas Van Doren
Doctoral Dissertations
"The electromagnetic field equations for microwave propagation through a rectangular waveguide filled with a lossy, isotropic, linear, inhomogeneous material are derived in matrix form and solved numerically by computer. The theoretical effects of photo-induced conductivity and dielectric constant variations on microwave attenuation, phase shift, and voltage standing wave ratio are plotted for typical examples in the X-band frequency range. The theoretical calculations indicate that a two order-of-magnitude change in the conductivity can produce a 25 db change in the attenuation or a 100 degree change in the angle of the reflection coefficient. The theoretical predictions are verified qualitatively by experiments …
A Method For Determining Transient Stability In Power Systems, Charles A. Gross
A Method For Determining Transient Stability In Power Systems, Charles A. Gross
Doctoral Dissertations
"Given a three phase ac power system consisting of synchronous alternators interconnected by transmission lines and other items of electrical transmission equipment, a method is presented which determines the stability of the system when subjected to a three phase symmetrical fault, and to the subsequent clearing of the fault. It is inherent in the method that an estimation of system stability, assuming an instantaneous clearing of the fault, is available. The critical clearing time is therefore determined. The effect of a speed control loop on the system's largest machine is investigated. The method is applied to two, three, four, and …
A Theoretical Study On The Interpretation Of Resistivity Sounding Data Measured By The Wenner Electrode System, Siew Hung Chan
A Theoretical Study On The Interpretation Of Resistivity Sounding Data Measured By The Wenner Electrode System, Siew Hung Chan
Doctoral Dissertations
"This thesis deals with a theoretical study on the interpretation of resistivity sounding data measured by the Wenner electrode system. The objectives of this investigation are twofold: (i) to derive from the apparent resistivity data some suitable functions from which the resistivity and thickness of each member of the sequence of layers composing the earth may be determined, and (ii) to devise suitable methods for analyzing the resulting functions. In this investigation it is shown that the solution of the boundary value problem associated with an n-layered earth model leads to an integral equation for the Wenner electrode system. This …
Analysis Of The Traveling-Wave Transistor, Vernon Ray Stanley
Analysis Of The Traveling-Wave Transistor, Vernon Ray Stanley
Doctoral Dissertations
"Transmission lines containing independent and dependent distributed sources are considered and the transfer matrices of various active distributed lines are derived. A method is discussed by which a lossy line can be made lossless by the appropriate choice of distributed sources. A steady-state analysis of the uniform traveling wave transistor is given. Considering the device as an active four port network, the transfer matrix is found in closed form and the power gain, output voltage, and input impedance are found. A computer program is written and the frequency response is given for various values of line parameters and terminations. Finally, …
Diffusion Of Iron And Cobalt In Nickel Single Crystals, Charles Frederick Heuer
Diffusion Of Iron And Cobalt In Nickel Single Crystals, Charles Frederick Heuer
Doctoral Dissertations
"Diffusion coefficients of iron-59 in nickel have been determined in the temperature range 815°C to 1200°C. The temperature dependence can be represented by an Arrhenius type relationship,...The effect of the isotopic mass on the diffusion coefficient of cobalt in nickel has also been investigated. The isotope effect parameter, E, was found to vary from .26 to .84 over the temperature range 970.5°C to 1200°C. Both results are consistent with the single vacancy mechanism of diffusion. No evidence of divacancy contributions to the mass transport has been found"--Abstract, Page i.
Mass And Heat Transfer Through Nonwettable Porous Membranes, Chung-Liang Yeh
Mass And Heat Transfer Through Nonwettable Porous Membranes, Chung-Liang Yeh
Doctoral Dissertations
"Evaporation of water through nonwettable porous membranes has been studied under various pressures with various membrane thicknesses. The results of previous investigations at 1 atmosphere have been correlated into one equation for mass transfer resistance which has also been found to fit approximately new data obtained of 1.5, 2, and 3 atmospheres in this investigation. In the new data fluxes varied from 0.064 to 0.691 lb./ft.²/hr. through glass fiber-Teflon membrane from 0.02 to 0.08 inch in thickness. Temperatures ranged for 80 to 260°F. A more theoretical equation has been developed to explain variations from the equations based on 1 atmosphere …
Models For The Pn Diode And The Npn And Pnp Transistor For Use In Computer Aided Design And Analysis Programs, Glenn Ronald Case
Models For The Pn Diode And The Npn And Pnp Transistor For Use In Computer Aided Design And Analysis Programs, Glenn Ronald Case
Doctoral Dissertations
"This work is concerned with the problem of developing suitable mathematical representations for the pn junction diode and npn and pnp transistors for use in computer aided design and analysis programs. The Ebers-Moll model as used in the Net-1 program has been considerably improved, particularly regarding base resistance prediction, prediction of high forward current behavior, and the addition of reverse breakdown terms. The resulting models show substantial improvement in representation of d-c and transient characteristics. Some improvement in a-c characteristics has also been obtained. Methods of obtaining parameters for the new model and several of the present models, given measured …
Phase Equilibria And Thermodynamic Studies In The System Ca0-Fe0-Fe₂0₃₋Si0₂, Muharrem Timucin
Phase Equilibria And Thermodynamic Studies In The System Ca0-Fe0-Fe₂0₃₋Si0₂, Muharrem Timucin
Doctoral Dissertations
"A study of phase relations and thermodynamic properties of phases in the system CaO-FeO-Fe₂O₃-SiO₂ was conducted at 1450°C and 1550°C. The region of stability of the different phases was determined by microscopic examination of the specimens. The thermodynamic properties of liquid were determined by analyses of quenched samples equilibrated at oxygen pressures from about 10⁻¹¹ to 1 atm. Isothermal phase diagrams were constructed from data for 0, 5, 10, 20, and 30 weight percent silica sections of the CaO-FeO-Fe₂O₃-SiO₂ system, and the effect of temperature and increased silica additions on the oxygen solubility of the liquid oxides was measured. Multicomponent …
Numerical Inversion Of The Laplace Transformation And The Solution Of The Viscoelastic Wave Equations, Abbas Ali Daneshy
Numerical Inversion Of The Laplace Transformation And The Solution Of The Viscoelastic Wave Equations, Abbas Ali Daneshy
Doctoral Dissertations
"In the numerical inversion of Laplace transform two general techniques of inversion are analyzed; a study of the procedures based on an expansion of f̄(s) by a polynomial in 1/s (Salzer's method) provides accurate results for certain ranges of t. A curvature criterion for the selection of the range of points for polynomial interpolation, and a geometric distribution in this interval markedly improves the range and the degree of accuracy of inversion. The results may be further improved by multiplying f̄(s) by 1/s of 1/s². Other procedures are based on approximation of f̄(t). This investigation includes a general review of …
Signal Distortion In A Regenerative Frequency Divider, Carl Ray Ryan
Signal Distortion In A Regenerative Frequency Divider, Carl Ray Ryan
Doctoral Dissertations
"A regenerative frequency divider can be constructed with one integrated circuit and a single-pole tuned circuit. The divider can be used as a means for reducing the modulation index of either deterministic or random signals. This reduction in modulation index can simplify many signal processing schemes. This technique can be used up to S-band frequencies. The mathematical model of the regenerative frequency divider corresponds very closely to that of a first order Phase Locked Loop (PLL). The loop gain is determined in part by the nonlinear element used in the feedback loop. The loop gain is also proportional to the …
Spherical Antenna Array, Narong Yoothanom
Spherical Antenna Array, Narong Yoothanom
Doctoral Dissertations
"The far field radiation pattern of an isotropic spherical antenna array with two types of element distributions, a latitude-longitude distribution and an approximately equally-spaced distribution, has been analyzed using Poisson's Sum Formula. Beamwidth expressions of both element distributions are found in various planes. All numerical results are given only for the case of 21 rings"--Abstract, page ii.
X-Ray Determination Of Lattice Parameters And Thermal Expansion Coefficients Of Aluminum, Silver And Molybdenum At Cryogenic Temperatures, Claude Lowell Woodard
X-Ray Determination Of Lattice Parameters And Thermal Expansion Coefficients Of Aluminum, Silver And Molybdenum At Cryogenic Temperatures, Claude Lowell Woodard
Doctoral Dissertations
"A multiple exposure back reflection diffraction camera was designed to mount on the vacuum jacket of a pressurized helium gas "Cryomite". With this design it is possible to obtain six diffraction exposures on a single film at any temperature in the range of 180 to 25°K. temperatures within this range are reached in short intervals and exposure periods are less than 30 minutes in a 2.875 inch (73.03 mm) diameter camera. Some of the advantages of this design are; direct measurements, multiple exposures on a single film, short exposures, direct compensation of film length changes due to evacuation or processing …
Turbulence Measurements In Drag Reducing Flow, Jorge Mario Rodriguez
Turbulence Measurements In Drag Reducing Flow, Jorge Mario Rodriguez
Doctoral Dissertations
"Studies of the frequency response of hot-film wedge probes in viscoelastic fluids established their reliability as measuring devices and demonstrated that the objections raised by Metzner and Astarita (77) are not valid for wedge probes. The structure of turbulence in drag reducing soap and polymer solutions was studied using a hot-film wedge probe. Intensity of turbulence measurements in drag reducing fluids indicate that the structure of trubulence is strongly dependent on the condition of the solution. Rates of energy dissipation calculated at the center of the tube indicate that there is an increase in the rate of energy dissipated in …
Grain Boundary Self-Diffusion In Sodium Chloride, Kenneth Ray Riggs
Grain Boundary Self-Diffusion In Sodium Chloride, Kenneth Ray Riggs
Doctoral Dissertations
"The diffusion of ²²sodium and ³⁶chlorine along tilt and twist grain boundaries in pure and calcium chloride doped sodium chloride bicrystals was investigated. No enhanced diffusion of ²²sodium along the grain boundaries was observed. Between 400°C and 500°C the chlorine grain boundary diffusion parameter, D'Δ, is described by D'Δ = (D'Δ)₀exp (-Qb/kT), where (D'Δ)₀ is approximately 10⁻⁷ cm³/sec and Qb is 1.15 ± .30 eV. The grain boundary angle, the grain boundary character (tilt or twist), and the calcium chloride concentration appear to have no pronounced effect upon the observed chlorine grain boundary diffusion. The ionic movement …
A Study Of The Anodic Oxidation Of Acetylene On Platinum-Gold Alloys, Christopher Kuo-Chieh Wu
A Study Of The Anodic Oxidation Of Acetylene On Platinum-Gold Alloys, Christopher Kuo-Chieh Wu
Doctoral Dissertations
"The anodic oxidation of acetylene on Pt-Au alloys of four compositions (80-20, 60-40, 40-60, and 20-80 Pt-Au) was studied at 80°C in solutions of constant pH and unit normality. Currents were measured as a function of potential and partial pressure of acetylene. The effects of temperature on current in 1 N H₂SO₄ and 1 N NaOH and the coulombic efficiencies for CO₂ production were determined. The experimental results indicated that the alloys can be classified into three groups, Pt-rich, Au-rich, and intermediate compositions. A transition region (change of the mechanism) was found for the Au-rich alloys. The oxidation can be …
Dynamic Response Of Circular Plates To Transient And Harmonic Transverse Loads Including The Effect Of Transverse Shear And Rotary Inertia, Perakatte Joseph George
Dynamic Response Of Circular Plates To Transient And Harmonic Transverse Loads Including The Effect Of Transverse Shear And Rotary Inertia, Perakatte Joseph George
Doctoral Dissertations
"Using an improved theory of plate vibration suggested by R. D. Mindlin which takes into account the effects of transverse shear and rotary inertia, free and forced transverse vibrations of uniform circular plates are studied and the results compared with those obtained using the classical theory of plate vibration. The governing equations are developed in polar coordinates using the equations of elasticity. Frequency equations for axisymmetric and antisymmetric vibrations are derived for solid circular plates under different boundary conditions and for an annular plate rigidly mounted on a shaft. The response of plates to different types of rapidly applied axisymmetric …
A Crystallization Study Of A Tetrasilicic Fluormica Glass, William H. Daniels
A Crystallization Study Of A Tetrasilicic Fluormica Glass, William H. Daniels
Doctoral Dissertations
"The transformation of a synthetic mica composition K₂Mg₅Si₈O₂₀F₄ from amorphous to crystalline structure was studied isothermally at selected temperatures from 560°C to 1150°C. thermal changes associated with the transformation were followed by differential thermal analysis techniques. Structural changes promoted by the isothermal treatments were observed by density measurements, Debye-Scherrer X-ray diffraction techniques, electron replication microscopy, and electron scanning microscopy. Isothermal treatment at 450°C for 9 hours produces structural ordering in quenched K₂Mg₅Si₈O₂₀F₄ glass. Fluorine exerts a significant influence on the transformation temperature; decreasing amounts of fluorine producing increasing transformation temperatures. The crystallizing phase rapidly attains a limiting particle size and …
A Finite Element Method For Geometrically Nonlinear Large Displacement Problems In Thin, Elastic Plates And Shells, Ronald August Melliere
A Finite Element Method For Geometrically Nonlinear Large Displacement Problems In Thin, Elastic Plates And Shells, Ronald August Melliere
Doctoral Dissertations
"A finite element method is presented for geometrically nonlinear large displacement problems in thin, elastic plates and shells of arbitrary shape and boundary conditions subject to externally applied concentrated or distributed loading. The initially flat plate or curved shell is idealized as an assemblage of flat, triangular plate, finite elements representing both membrane and flexural properties. The 'geometrical' stiffness of the resulting eighteen degree-of-freedom triangular element is derived from a purely geometrical standpoint. This stiffness in conjunction with the standard small displacement 'elastic' stiffness is used in the linear-incremental approach to obtain numerical solutions to the large displacement problem. Only …