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Articles 5521 - 5550 of 5718
Full-Text Articles in Entire DC Network
Realistic Impulsive P Wave Source In An Infinite Elastic Medium, Joseph Hugo Hemmann
Realistic Impulsive P Wave Source In An Infinite Elastic Medium, Joseph Hugo Hemmann
Doctoral Dissertations
"The generally assumed instantaneous impulsive pressure sources for an elastic P wave in an infinite medium lead to basic contradictions, a step function source yielding infinite displacements as the shear modulus goes to zero, and the total energy radiated by a delta function (or any derivative of the delta function) source being infinite. By noting that the character of the solution in the elastic region must match the acoustic case near the source, a realistic impulsive pressure source is postulated which has a finite time history. The elastic field produced by this source is then obtained in closed form. A …
Structures And Relationships Of Some Perovskite-Type Compounds, Christian Michel
Structures And Relationships Of Some Perovskite-Type Compounds, Christian Michel
Doctoral Dissertations
"A model for crystallographic transitions in perovskites is proposed. The model consists of regular octahedra sharing corners and topologically able to rotate without distortion around their three-fold axes. This model, with R3̄c symmetry (18e position) can be described in terms of a continuous rotation of angle, w, of octahedra from two ideal symmetry forms: the hexagonal close-packed and the cubic face-centered configurations. A parametric relation is derived between w and the rhombohedral cell angle, α, or the corresponding hexagonal axial ratio c/a . A wide range of atomic structures based on a framework of regular or slightly distorted octahedra sharing …
Substitution And Photolytic Rearrangements In Three-Member Ring Compounds, Joseph Terril Bohanon
Substitution And Photolytic Rearrangements In Three-Member Ring Compounds, Joseph Terril Bohanon
Doctoral Dissertations
"An investigation into the substitution and photolytic rearrangements of 1,2,3-triphenylcyclopropenes was conducted. Triphenylcyclopropenyl t̲-butyl ether was found to undergo alkyl group exchange with refluxing methanol, ethanol, or 2-propanol to yield the corresponding 1,2,3-triphenylcyclopropenyl alkyl ether when a trace impurity of a 1,2,3-triphenylcyclopropenium halide is present to catalyse the reaction. This forms hydrogen halide with solvent. Upon standing for long periods of time, the 1,2,3-triphenylcyclopropenyl ethers were observed to partially rearrange to new products. A sample of 1,2,3-triphenylcyclopropenyl methyl ether was subjected to photolysis in hexane and yielded 3-methoxy-1,2-diphenylindene, 2,3- diphenylindenone, tolane, benzoic acid, 1,2,3-triphenylpropen-1-one and a polymer. Samples of 1,2,3-triphenylcyclopropene, …
Mhd Waves In The Inner Magnetosheath, Jiann Tsorng Horng
Mhd Waves In The Inner Magnetosheath, Jiann Tsorng Horng
Doctoral Dissertations
No abstract provided.
The Energy Spectrum And Flux Of Fast Neutrons In The Atmosphere, Richard Norbert St. Onge
The Energy Spectrum And Flux Of Fast Neutrons In The Atmosphere, Richard Norbert St. Onge
Doctoral Dissertations
No abstract provided.
High Temperature Optical Pumping And The Hyperfine Structure Of Nitrogen, Roger Edward Weiss
High Temperature Optical Pumping And The Hyperfine Structure Of Nitrogen, Roger Edward Weiss
Doctoral Dissertations
No abstract provided.
Investigation Of Auroral Phenomena By Sounding Rocket, Wentworth Edwards Potter
Investigation Of Auroral Phenomena By Sounding Rocket, Wentworth Edwards Potter
Doctoral Dissertations
No abstract provided.
Response Of The Rat Ovary To Continuous Light: Effects Of Light Frequency, Intensity And Duration Of Exposure, Helen Haynes Lambert
Response Of The Rat Ovary To Continuous Light: Effects Of Light Frequency, Intensity And Duration Of Exposure, Helen Haynes Lambert
Doctoral Dissertations
No abstract provided.
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 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 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 …
A.C. Hall Effect Measurements On Very High Resistivity Materials Exhibiting Electrode Polarization, James Dale Boyd
A.C. Hall Effect Measurements On Very High Resistivity Materials Exhibiting Electrode Polarization, James Dale Boyd
Doctoral Dissertations
"A variable frequency, a.c. Hall effect measurement technique has been designed for mobility studies in very high resistivity (>10⁹ ohm·cm) materials exhibiting electrode space charge polarization effects. It incorporates a neutralized input capacitance preamplifier detector which reduces the total input shunting capacitance, including the sample interelectrode capacitances, to a very low, definable value (<0.1 pf) and thereby provides very high and well defined a.c. detector input impedances (4 x 10⁹ and 7 x 10⁹ ohms at 600 and 200 Hz, respectively). Lumped parameter equivalent circuits have been defined to approximate the electrical behavior of sample materials in the measurement configuration. These equivalent circuits, together with independent measurements of the detector input and sample impedances, allow one to correct the detected Hall voltage and obtain the true value from which mobility data may be derived. The validity of these circuits has been established by independent a.c. and d.c. measurements on photoconductive CdS (dark resistivity >10¹⁰ ohm·cm) which exhibited maximum differences of less than 4%. The existing literature has been critically reviewed and the measurement criteria established by this study have been applied to resolve differences in reported data and to suggest improvements in the resolution of previously employed experimental …
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, …
Characterizing Topologies By Continuous Selfmaps, Derald David Rothmann
Characterizing Topologies By Continuous Selfmaps, Derald David Rothmann
Doctoral Dissertations
"Various topological spaces are examined in an effort to describe topological spaces from a knowledge of their class of continuous selfmaps or their class of autohomeomorphisms. Relationships between topologies and their continuous selfmaps are considered. Several examples of topological spaces are given and their corresponding classes of continuous selfmaps are described completely. The problem, given a set X and a topology U when does there exist a topology V either weaker or stronger than U such that the class of continuous selfmaps of (X,V) contains the class of continuous selfmaps of (X,U), is considered. M* and S** spaces are defined …
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 …
Low-Lying Levels In Some Spherical And Rotational Nuclides By Coulomb Excitation And Radiative Capture Of Thermal Neutrons, Donald Allan Mcclure
Low-Lying Levels In Some Spherical And Rotational Nuclides By Coulomb Excitation And Radiative Capture Of Thermal Neutrons, Donald Allan Mcclure
Doctoral Dissertations
"The work presented in this dissertation was performed in order to obtain additional information on the level schemes and decay properties of several nuclei in an attempt to explain the observations in terms of an applicable nuclear model. Various nuclear models are discussed in Section II. A general review from the classical point of view of the Coulomb excitation reaction is discussed in Section III and the thermal-neutron-capture reaction is outlined in Section IV. The experimental equipment and procedure is discussed in Section V in which the ramper method of energy determination is outlined. This method allows the measurement of …
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 …
MöSsbauer Effect Studies Of Ferroelectric Phase Transitions In The Pbzro₃ - Pbtio₃ - Bifeo₃ Ternary System, James P. Canner
MöSsbauer Effect Studies Of Ferroelectric Phase Transitions In The Pbzro₃ - Pbtio₃ - Bifeo₃ Ternary System, James P. Canner
Doctoral Dissertations
"The Mössbauer Effect was used to measure the phase transitions in the following ferroelectric compounds: 95% PbZ4₀.₈Ti₀.₂ - 5% BiFeO₃ [and] 95% PbZ4₀.₇Ti₀.₃ - 5% BiFeO₃ and in the antiferroelectric compound: 95% PbZrO₃ - 5% BiFeO₃. The parameters obtained were the area under the resonance peak, the isomer shift, and the electric quadrupole splitting, all as a function of temperature. The ionicity, electric field gradient, and Debye temperature were determined for room temperature. The data are discussed in terms of the lattice vibration model of ferroelectrics and antiferroelectrics, and the structural phase transitions as recently defined for these compounds. The …
Noble Gases: A Record Of The Early Solar System, E. C. Alexander
Noble Gases: A Record Of The Early Solar System, E. C. Alexander
Doctoral Dissertations
"Analyses of the noble gases in samples of iron meteorites are presented which indicate the following: 1. The inclusions of iron meteorites contain noble gases with a wide range of isotopic compositions. 2. The noble gas concentration and isotopic anomalies arc often grossly inhomogeneously distributed within a given inclusion and vary from inclusion to inclusion in a meteorite. 3. Silicate inclusions appear to be the most promising samples for I-Xe and Pu-Xe dating. 4. Graphite and troilite in addition to the silicate inclusion contain significant radiogenic ¹²⁹Xe anomalies. 5. The total I-Xe (and in the case of Toluca silicates total …
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 …
Radiative Lifetime Of The B¹Σ⁺ And B³Σ⁺ States Of Carbon Monoxide, John Robert Rogers
Radiative Lifetime Of The B¹Σ⁺ And B³Σ⁺ States Of Carbon Monoxide, John Robert Rogers
Doctoral Dissertations
"The radiative lifetimes of the B¹Σ⁺ and b³Σ⁺ excited states of carbon monoxide were measured at six different pressures: 10, 25, 50, 75, 100, and 125 microns of Hg. The lifetimes were obtained by observation of the radiative decay of the (0,0), (0,1), (0,2), and (1,1) bands of the Angstrom system and the radiative decay of the (0,1), (0,2), (0,3), and (0,4) bands of the Third Positive system. No pressure dependence of the lifetimes was observed for either system. The average lifetime of the v' = 0 vibrational level of the B¹Σ⁺ state was found to be 24.4 x 10⁻⁹ …
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 …
Statistical Inferences For Location And Scale Parameter Distributions, Robert Henry Dumonceaux
Statistical Inferences For Location And Scale Parameter Distributions, Robert Henry Dumonceaux
Doctoral Dissertations
"The problem of discriminating between two location and scale parameter distributions is investigated. A general test based on a ratio of likelihoods is presented. A test based on a Pearson Goodness of Fit statistic is also considered. Tables are given for discriminating between the normal and exponential, the normal and double exponential, the normal and extreme value, and also between the normal and logistic. For location and scale parameter distributions, two-sided tolerance limits are shown to always be obtainable by Monte Carlo simulation. A method for obtaining confidence intervals on the reliability at a fixed time t is also given. …
Statistical Inferences For The Generalized Gamma Distribution, Harold Walter Hager
Statistical Inferences For The Generalized Gamma Distribution, Harold Walter Hager
Doctoral Dissertations
"Procedures for handling statistical problems with nuisance parameters are considered with special reference to problems in the three parameter generalized gamma distribution. Maximum likelihood estimation of the parameters of this density has been investigated. Properties of these estimates are established which make it possible to make inferences about the parameters. Discrimination between various models for life testing problems is discussed and the robustness of the Weibull model is advanced. The question of the existence of the maximum likelihood estimates of the parameters for all samples is raised. Empiric evidence is presented indicating that they may not exist for all small …
Longitudinal Optical Phonon-Plasmon Coupling In Ionic Semiconductors, Thomas Joseph Mcmahon
Longitudinal Optical Phonon-Plasmon Coupling In Ionic Semiconductors, Thomas Joseph Mcmahon
Doctoral Dissertations
"The coupling of free carriers and lattice vibrational modes is studied in CdS and InSb by room temperature far infrared reflectance measurements. When the free carrier concentration is such that the plasma frequency is at or near the longitudinal optical mode frequency it is shown that while the transverse modes remain fixed, the longitudinal modes mix with the plasma mode and are shifted in a manner similar to that described by Varga in 1965. Using the dielectric function for the coupled system permits the determination of electron effective masses by reflectance measurements with lattice effects excluded. This method allows one …
Vapor Phase Clustering Model For Water, Richard W. Bolander
Vapor Phase Clustering Model For Water, Richard W. Bolander
Doctoral Dissertations
"Although nucleation phenomena are among the most widespread of all naturally occurring phenomena, even the simplest of nucleation processes, homogeneous nucleation, is poorly understood, particularly the homogeneous nucleation of liquid droplets from water vapor. Homogeneous nucleation involves only molecules of a single substance and does not include the complicating effects due to a substrate or piece of foreign matter. The semiphenomenological liquid drop theories developed nearly three decades ago differ in relatively minor details, with the crucial element of the theory being the derivation of the free energy of formation of the clusters. The clusters are viewed as well-defined incompressible …
Hyperfine Splittings And Pressure Shifts Of Lithium-6 And Lithium-7, John Jay Wright
Hyperfine Splittings And Pressure Shifts Of Lithium-6 And Lithium-7, John Jay Wright
Doctoral Dissertations
No abstract provided.
Investigation Of The Effect Of Molecular Geometry On The Electronic Structures Of Styrene And Indene, James Denis Quirk
Investigation Of The Effect Of Molecular Geometry On The Electronic Structures Of Styrene And Indene, James Denis Quirk
Doctoral Dissertations
No abstract provided.
Studies In Atomic Fluorescence Flame Spectroscopy, Donald Romeo Demers
Studies In Atomic Fluorescence Flame Spectroscopy, Donald Romeo Demers
Doctoral Dissertations
No abstract provided.
A Search For High Energy Solar Neutrons, David John Forrest
A Search For High Energy Solar Neutrons, David John Forrest
Doctoral Dissertations
No abstract provided.