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Disclosure and its Perceived Impact as Mediators of the Long-Term Consequences of Child Sexual Abuse

Description: The primary purpose of the present study was to investigate factors associated with childhood sexual abuse which mediate long-term effects. Of particular interest were the mediators of disclosure and its perceived impact, as well as variables related to the severity of the abuse. Also of interest were impact areas related to a history of molestation which have received little attention in the literature. Five hundred and seventy-five female undergraduates completed an extensive questionnaire with measures of family background, childhood and adult sexual experiences, health status, and psychological variables. Of these subjects, 286 reported at least one incident of child sexual abuse. It was hypothesized that those females with histories of sexual abuse who received a positive response to their disclosure of abuse would demonstrate more adaptive adult functioning as compared to those victims receiving a negative response, or those who never disclosed. Significant differences were not detected among the three groups on the outcome measures. A number of reasons were explored for why these differences may not have been detected in the present investigation. Although differences were not detected for disclosure status, significant differences were detected between females reporting a history of child sexual abuse and those reporting no abuse on all of the outcome measures. Specifically, sexual abuse victims were more likely than nonvictims to be sexually revictimized in adulthood. Potential explanations for this finding were explored in a discriminant function analysis predicting revictimization status. Further, abused females had significantly higher levels of depression, dissociation, and perceptual disturbances when compared to their nonabused peers. Sexual abuse victims also reported more health symptoms across various bodily systems and had more negative attributions about their physical health status. Differences between the abused and nonabused groups on levels of perceptual disturbance and perceived physical health status are particularly noteworthy since previous research ...
Date: October 1992
Creator: Phelan-McAuliffe, Debra
Partner: UNT Libraries

Characterization and refinement of carbide coating formation rates and dissolution kinetics in the Ta-C system

Description: The interaction between carbide coating formation rates and dissolution kinetics in the tantalum-carbon system was investigated. The research was driven by the need to characterize carbide coating formation rates. The characterization of the carbide coating formation rates was required to engineer an optimum processing scheme for the fabrication of the ultracorrosion-resistant composite, carbon-saturated tantalum. A packed-bed carburization process was successfully engineered and employed. The packed-bed carburization process produced consistent, predictable, and repeatable carbide coatings. A digital imaging analysis measurement process for accurate and consistent measurement of carbide coating thicknesses was developed. A process for removing the chemically stable and extremely hard tantalum-carbide coatings was also developed in this work.
Date: October 1, 1996
Creator: Rodriguez, P.J.
Partner: UNT Libraries Government Documents Department

New techniques for the scientific visualization of three-dimensional multi-variate and vector fields

Description: Volume rendering allows us to represent a density cloud with ideal properties (single scattering, no self-shadowing, etc.). Scientific visualization utilizes this technique by mapping an abstract variable or property in a computer simulation to a synthetic density cloud. This thesis extends volume rendering from its limitation of isotropic density clouds to anisotropic and/or noisy density clouds. Design aspects of these techniques are discussed that aid in the comprehension of scientific information. Anisotropic volume rendering is used to represent vector based quantities in scientific visualization. Velocity and vorticity in a fluid flow, electric and magnetic waves in an electromagnetic simulation, and blood flow within the body are examples of vector based information within a computer simulation or gathered from instrumentation. Understand these fields can be crucial to understanding the overall physics or physiology. Three techniques for representing three-dimensional vector fields are presented: Line Bundles, Textured Splats and Hair Splats. These techniques are aimed at providing a high-level (qualitative) overview of the flows, offering the user a substantial amount of information with a single image or animation. Non-homogenous volume rendering is used to represent multiple variables. Computer simulations can typically have over thirty variables, which describe properties whose understanding are useful to the scientist. Trying to understand each of these separately can be time consuming. Trying to understand any cause and effect relationships between different variables can be impossible. NoiseSplats is introduced to represent two or more properties in a single volume rendering of the data. This technique is also aimed at providing a qualitative overview of the flows.
Date: October 1, 1995
Creator: Crawfis, R.A.
Partner: UNT Libraries Government Documents Department

Experimental Study of the Spin Structure of the Neutron (3He) at low Q2: a connection between the Bjorken and Gerasimov-Drell-Hearn Sum Rules

Description: The authors have presented the motivations in gathering doubly polarized data in the quasi-elastic, resonance and DIS domains. These data were used to calculate the extended GDH integral. The comparison of this quantity with the spin dependent forward Compton amplitude {bar S}{sub 1} is of particular importance for the unification of the two strong interaction descriptions (nucleonic/hadronic vs. partonic) because {bar S}{sub 1} is the first quantity theoretically calculable in the full Q{sup 2} domain of the strong interaction. Such a data taking was made possible because of three major technical achievements: (1) the beam of high duty cycle (100%), high current (up to 70 {micro}A) and high polarization (70%); (2) the {sup 3}He target of high density (above 10 atm) with a polarization of 35% and a length of 40 cm; and (3) the large acceptance (6 msr) and high resolution ({Delta}P/P {approx_equal} 10{sup {minus}4}) spectrometers. These features, available at Jefferson Lab, enabled them to achieve the highest luminosity in the world (about 10{sup 36} s{sup {minus}1} cm{sup {minus}2} with a current of 15 {micro}A) as far as polarized {sup 3}He targets are concerned. Consequently they were able to gather, in a rather short period of time (3 months), a large amount of data covering a large kinematical domain.
Date: October 9, 2000
Creator: Deur, Alexander
Partner: UNT Libraries Government Documents Department

Thermal depinning of a single superconducting vortex

Description: Thermal depinning has been studied for a single vortex trapped in a superconducting thin film in order to determine the value of the superconducting order parameter and the superfluid density when the vortex depins and starts to move around the film. For the Pb film in Pb/Al/Al{sub 2}O{sub 3}/PbBi junction having a gold line, the vortex depins from the artificial pinning site (Au line) and reproducibly moves through the same sequence of other pinning sites before it leaves the junction area of the Pb film. Values of the normalized order parameter {triangle}/{triangle}{sub o} vary from {triangle}/{triangle}{sub o}=0.20 at the first motion of the vortex to {triangle}/{triangle}{sub o}=0.16 where the vortex finally leaves the junction. Equivalently, the value of the normalized superfluid density changes from 4% to 2.5% for this sample in this same temperature interval. For the Nb film in Nb/Al/Al{sub 2}O{sub 3}/Nb junction, thermal depinning occurs when the value of {triangle}/{triangle}{sub o} is approximately 0.22 and the value of {rho}{sub s}/{rho}{sub so} is approximately 5%. These values are about 20% larger than those of a Pb sample having a gold line, but the values are really very close. For the Nb sample, grain boundaries are important pinning sites whereas, for the Pb sample with a gold line, pinning may have been dominated by an array Pb{sub 3}AU precipitates. Because roughly the same answer was obtained for these rather different kinds of pinning site, there is a reasonable chance that this is a general value within factors of 2 for a wide range of materials.
Date: October 1, 1995
Creator: Sok, J.
Partner: UNT Libraries Government Documents Department

Authenticated group Diffie-Hellman key exchange: theory and practice

Description: Authenticated two-party Diffie-Hellman key exchange allows two principals A and B, communicating over a public network, and each holding a pair of matching public/private keys to agree on a session key. Protocols designed to deal with this problem ensure A (B resp.)that no other principals aside from B (A resp.) can learn any information about this value. These protocols additionally often ensure A and B that their respective partner has actually computed the shared secret value. A natural extension to the above cryptographic protocol problem is to consider a pool of principals agreeing on a session key. Over the years several papers have extended the two-party Diffie-Hellman key exchange to the multi-party setting but no formal treatments were carried out till recently. In light of recent developments in the formalization of the authenticated two-party Diffie-Hellman key exchange we have in this thesis laid out the authenticated group Diffie-Hellman key exchange on firmer foundations.
Date: October 3, 2002
Creator: Chevassut, Olivier
Partner: UNT Libraries Government Documents Department

Heavy ion beam propagation through a gas-filled chamber for inertial confinement fusion

Description: The work presented here evaluates the dynamics of a beam of heavy ions propagating through a chamber filled with gas. The motivation for this research stems from the possibility of using heavy ion beams as a driver in inertial confinement fusion reactors for the purpose of generating electricity. Such a study is important in determining the constraints on the beam which limit its focus to the small radius necessary for the ignition of thermonuclear microexplosions which are the source of fusion energy. Nuclear fusion is the process of combining light nuclei to form heavier ones. One possible fusion reaction combines two isotopes of hydrogen, deuterium and tritium, to form an alpha particle and a neutron, with an accompanying release of {approximately}17.6 MeV of energy. Generating electricity from fusion requires that we create such reactions in an efficient and controlled fashion, and harness the resulting energy. In the inertial confinement fusion (ICF) approach to energy production, a small spherical target, a few millimeters in radius, of deuterium and tritium fuel is compressed so that the density and temperature of the fuel are high enough, {approximately}200 g/cm{sup 3} and {approximately}20 keV, that a substantial number of fusion reactions occur; the pellet microexplosion typically releases {approximately}350 MJ of energy in optimized power plant scenarios.
Date: October 1, 1996
Creator: Barboza, N.O.
Partner: UNT Libraries Government Documents Department

Gas Phase Chromatography of some Group 4, 5, and 6 Halides

Description: Gas phase chromatography using The Heavy Element Volatility Instrument (HEVI) and the On Line Gas Apparatus (OLGA III) was used to determine volatilities of ZrBr{sub 4}, HfBr{sub 4}, RfBr{sub 4}, NbBr{sub 5}, TaOBr{sub 3}, HaCl{sub 5}, WBr{sub 6}, FrBr, and BiBr{sub 3}. Short-lived isotopes of Zr, Hf, Rf, Nb, Ta, Ha, W, and Bi were produced via compound nucleus reactions at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory and transported to the experimental apparatus using a He gas transport system. The isotopes were halogenated, separated from the other reaction products, and their volatilities determined by isothermal gas phase chromatography. Adsorption Enthalpy ({Delta}H{sub a}) values for these compounds were calculated using a Monte Carlo simulation program modeling the gas phase chromatography column. All bromides showed lower volatility than molecules of similar molecular structures formed as chlorides, but followed similar trends by central element. Tantalum was observed to form the oxybromide, analogous to the formation of the oxychloride under the same conditions. For the group 4 elements, the following order in volatility and {Delta}H{sub a} was observed: RfBr{sub 4} > ZrBr{sub 4} > HfBr{sub 4}. The {Delta}H{sub a} values determined for the group 4, 5, and 6 halides are in general agreement with other experimental data and theoretical predictions. Preliminary experiments were performed on Me-bromides. A new measurement of the half-life of {sup 261}Rf was performed. {sup 261}Rf was produced via the {sup 248}Cm({sup 18}O, 5n) reaction and observed with a half-life of 74{sub -6}{sup +7} seconds, in excellent agreement with the previous measurement of 78{sub -6}{sup +11} seconds. We recommend a new half-life of 75{+-}7 seconds for {sup 261}Rf based on these two measurements. Preliminary studies in transforming HEVI from an isothermal (constant temperature) gas phase chromatography instrument to a thermochromatographic (variable temperature) instrument have been completed. Thermochromatography is a ...
Date: October 1, 1998
Creator: Sylwester, Eric Robert
Partner: UNT Libraries Government Documents Department

Unsaturated Groundwater Flow Beneath Upper Mortandad Canyon, Los Alamos, New Mexico

Description: Mortandad Canyon is a discharge site for treated industrial effluents containing radionuclides and other chemicals at Los Alamos National Laboratory, New Mexico. This study was conducted to develop an understanding of the unsaturated hydrologic behavior below the canyon floor. The main goal of this study was to evaluate the hypothetical performance of the vadose zone above the water table. Numerical simulations of unsaturated groundwater flow at the site were conducted using the Finite Element Heat and Mass Transfer (FEHM) code. A two-dimensional cross-section along the canyon's axis was used to model flow between an alluvial groundwater system and the regional aquifer approximately 300 m below. Using recharge estimated from a water budget developed in 1967, the simulations showed waters from the perched water table reaching the regional aquifer in 13.8 years, much faster than previously thought. Additionally, simulations indicate that saturation is occurring in the Guaje pumice bed an d that the Tshirege Unit 1B is near saturation. Lithologic boundaries between the eight materials play an important role in flow and solute transport within the system. Horizontal flow is shown to occur in three thin zones above capillary barriers; however, vertical flow dominates the system. Other simulations were conducted to examine the effects of changing system parameters such as varying recharge inputs, varying the distribution of recharge, and bypassing fast-path fractured basalt of uncertain extent and properties. System sensitivity was also explored by changing model parameters with respect to size and types of grids and domains, and the presence of dipping stratigraphy.
Date: October 15, 1998
Creator: Dander, D.C.
Partner: UNT Libraries Government Documents Department

A Measurement of the neutron electric form factor at very large momentum transfer using polaried electrions scattering from a polarized helium-3 target

Description: Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. Of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q{sup 2} and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized {sup 3}He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. G{sup n}{sub E} was measured to be 0.0242 ± 0.0020(stat) ± 0.0061(sys) and 0.0247 ± 0.0029(stat) ± 0.0031(sys) at Q{sup 2} = 1.7 and 2.5 GeV{sup 2}, respectively.
Date: October 1, 2010
Creator: Kelleher, Aidan
Partner: UNT Libraries Government Documents Department

Hot electron dynamics in graphene

Description: Graphene, a two-dimensional (2D) honeycomb structure allotrope of carbon atoms, has a long history since the invention of the pencil [Petroski (1989)] and the linear dispersion band structure proposed by Wallace [Wal]; however, only after Novoselov et al. successively isolated graphene from graphite [Novoselov et al. (2004)], it has been studied intensively during the recent years. It draws so much attentions not only because of its potential application in future electronic devices but also because of its fundamental properties: its quasiparticles are governed by the two-dimensional Dirac equation, and exhibit a variety of phenomena such as the anomalous integer quantum Hall effect (IQHE) [Novoselov et al. (2005)] measured experimentally, a minimal conductivity at vanishing carrier concentration [Neto et al. (2009)], Kondo effect with magnetic element doping [Hentschel and Guinea (2007)], Klein tunneling in p-n junctions [Cheianov and Fal’ko (2006), Beenakker (2008)], Zitterbewegung [Katsnelson (2006)], and Schwinger pair production [Schwinger (1951); Dora and Moessner (2010)]. Although both electron-phonon coupling and photoconductivity in graphene also draws great attention [Yan et al. (2007); Satou et al. (2008); Hwang and Sarma (2008); Vasko and Ryzhii (2008); Mishchenko (2009)], the nonequilibrium behavior based on the combination of electronphonon coupling and Schwinger pair production is an intrinsic graphene property that has not been investigated. Our motivation for studying clean graphene at low temperature is based on the following effect: for a fixed electric field, below a sufficiently low temperature linear eletric transport breaks down and nonlinear transport dominates. The criteria of the strength of this field [Fritz et al. (2008)] is eE = T2/~vF (1.1) For T >√eE~vF the system is in linear transport regime while for T <√eE~vF the system is in nonlinear transport regime. From the scaling’s point of view, at the nonlinear transport regime the temperature T and electric field E are also ...
Date: October 20, 2011
Creator: Ling, Meng-Cheieh
Partner: UNT Libraries Government Documents Department

Surfaces of Intermetallics: Quasicrystals and Beyond

Description: The goal of this work is to characterize surfaces of intermetallics, including quasicrystals. In this work, surface characterization is primarily focused on composition and structure using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) performed under ultrahigh vacuum (UHV) conditions.
Date: October 26, 2012
Creator: Yuen, Chad
Partner: UNT Libraries Government Documents Department

Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N -> {Delta} Transition

Description: Qweak will determine the weak charge of the proton, Q{sup p}{sub W}, via an asymmetry measurement of parity-violating elastic electron-proton scattering at low four momentum transfer to a precision of 4%. Q{sup p}{sub W} has a firm Standard Model prediction and is related to the weak mixing angle, sin{sup 2} {Theta}{sub W}, a well-defined Standard Model parameter. Qweak will probe a subset of new physics to the TeV mass scale and test the Standard Model. The details of how this measurement was performed and the analysis of the 25% elastic dataset will be presented in this thesis. Also, an analysis of an auxiliary measurement of the parity-violating asymmetry in the N -> {Delta} transition is presented. It is used as a systematic inelastic background correction in the elastic analysis and to extract information about the hadronic parity violation through the low energy constant, d{sub Delta}. The elastic asymmetry at Q{sup 2} = 0.0252 ± 0.0007 GeV{sup 2} was measured to be A{sub ep} = -265 ± 40 ± 22 ± 68 ppb (stat., sys., and blinding). Extrapolated to Q{sup 2} = 0, the value of the proton's weak charge was measured to be Q{sup p}{sub W} = 0.077 ± 0.019 (stat. and sys.) ± 0.026 (blinding). This is within 1 {sigma} of the Standard Model prediction of Q{sup p}{sub W} = 0.0705 ± 0.0008. The N -> {Delta} inelastic asymmetry at Q{sup 2} = 0.02078 ± 0.0005 GeV{sup 2} and W = 1205 MeV was measured to be A{sub inel} = -3.03 ± 0.65 ± 0.73 ± 0.07 ppm (stat., sys., and blinding). This result constrains the low energy constant to be d{sub {Delta}} = 5.8 ± 22g{sub {pi}}, and, if the result of the G0 experiment is included, d{sub {Delta}} = 5.8 ± 17g{sub {pi}}. This result rules out ...
Date: October 16, 2012
Creator: Leacock, John
Partner: UNT Libraries Government Documents Department

U.S. Battleship Operations in World War I, 1917-1918

Description: This dissertation is an examination of the operations of U.S. battleships in World War I. The study examines tactical cooperation between units of the U.S. Atlantic Fleet and the British Grand Fleet and relations between the two navies; the efficiency of U.S. battleships in terms of both personnel and material; and the strategic ideas of U.S. naval leaders governing the use of capital ships. The manuscript is based primarily on records of the Department of the Navy in the National Archives and Admiralty records at the Public Record Office. Also important are the private papers of principal naval leaders, located at the Library of Congress and the National Maritime Museum in Greenwich, U.K. The published memoirs of several of the participants are also utilized. The first chapter examines Anglo-American naval relations and traces diplomatic events leading to the U.S. Navy Department's decision to dispatch dreadnought battleships to European waters. The following two chapters discuss the amalgamation of Battleship Division Nine into the British Grand Fleet. Chapter IV examines the gunnery efficiency of U.S. battleships serving with the Grand Fleet. Chapter V reviews Anglo-American planning for a possible German battle cruiser raid against the Atlantic convoys. Chapter VI deals with the movement of Battleship Division Six to Berehaven, Ireland. Chapter VII discusses the use of pre-dreadnought battleships as training ships, convoy escorts, and troop transports. The study concludes that U.S. battleships made a subsidiary, but important contribution toward victory at sea. The addition of U.S. battleships allowed the Allies to protect Scandinavian commerce and the supply lines from the United States from German surface raiders while also maintaining superiority in the North Sea.
Date: October 1995
Creator: Jones, Jerry W., 1964-
Partner: UNT Libraries

Oxygen potential of uranium--plutonium oxide as determined by controlled- atmosphere thermogravimetry

Description: The oxygen-to-metal atom ratio, or O/M, of solid solution uranium- plutonium oxide reactor fuel is a measure of the concentration of crystal defects in the oxide which affect many fuel properties, particularly, fuel oxygen potential. Fabrication of a high-temperature oxygen electrode, employing an electro-active tip of oxygen-deficient solid-state electrolyte, intended to confirm gaseous oxygen potentials is described. Uranium oxide and plutonium oxide O/M reference materials were prepared by in situ oxidation of high purity metals in the thermobalance. A solid solution uranium-plutonium oxide O/M reference material was prepared by alloying the uranium and plutonium metals in a yttrium oxide crucible at 1200$sup 0$C and oxidizing with moist He at 250$sup 0$C. The individual and solid solution oxides were isothermally equilibrated with controlled oxygen potentials between 800 and 1300$sup 0$C and the equilibrated O/ M ratios calculated with corrections for impurities and buoyancy effects. Use of a reference oxygen potential of -100 kcal/mol to produce an O/M of 2.000 is confirmed by these results. However, because of the lengthy equilibration times required for all oxides, use of the O/M reference materials rather than a reference oxygen potential is recommended for O/M analysis methods calibrations. (auth)
Date: October 1, 1975
Creator: Swanson, G.C.
Partner: UNT Libraries Government Documents Department

Measurement of the Electric and Magnetic Elastic Structure Functions of the Deuteron at Large Momentum Transfers

Description: The deuteron elastic structure functions, A(Q{sup 2}) and B(Q{sup 2}), have been extracted from cross section measurements of elastic electron-deuteron scattering in coincidence using the Continuous Electron Beam Accelerator and Hall A Facilities of Jefferson Laboratory. Incident electrons were scattered off a high-power cryogenic deuterium target. Scattered electrons and recoil deuterons were detected in the two High Resolution Spectrometers of Hall A. A(Q{sup 2}) was extracted from forward angle cross section measurements in the squared four-momentum transfer range 0.684 ≤ Q{sup 2} ≤ 5.90 (GeV/c){sup 2}. B(Q{sup 2}) was determined by means of a Rosenbluth separation in the range 0.684 ≤ Q{sup 2} ≤ 1.325 (GeV/c){sup 2}. The data are compared to theoretical models based on the impulse approximation with the inclusion of meson-exchange currents and to predictions of quark dimensional scaling and perturbative quantum chromodynamics. The results are expected to provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.
Date: October 1, 1999
Creator: Suleiman, Riad
Partner: UNT Libraries Government Documents Department

Liquid phase epitaxial growth of GaAs

Description: Research into new semiconductor materials for measurement of electromagnetic radiation over a wide range of energies has been an active field for several decades. There is a strong desire to identify and develop new materials which can lead to improved detectors. Such devices are expected to solve problems that cannot be solved using the semiconductor materials and device structures which have been traditionally used for radiation detection. In order for a detector which is subjected to some type of irradiation to respond, the radiation must undergo an interaction with the detector. The net result of the radiation interaction in a broad category of detectors is the generation of mobile electric charge carriers (electrons and/or holes) within the detector active volume. This charge is collected at the detector contacts and it forms the basic electrical signal. Typically, the collection of the charge is accomplished through the imposition of an electric field within the detector which causes the positive and/or negative charges created by the radiation to flow in opposite directions to the contacts. For the material to serve as a good radiation detector, a large fraction (preferably 100%) of all carriers created by the interacting incident radiation must be collected. Charge trapping by deep level impurities and structural defects can seriously degrade detector performance. The focus of this thesis is on far infrared and X-ray detection. In X-ray detector applications of p-I-n diodes, the object is to measure accurately the energy distribution of the incident radiation quanta. One important property of such detectors is their ability to measure the energy of individual incident photons with high energy resolution.
Date: October 1, 1997
Creator: Wynne, D. I.
Partner: UNT Libraries Government Documents Department

Phase identification in reactive sintering of molybdenum disilicide composites

Description: Molybdenum disilicide has been predominantly used for furnace heating elements, but recently there has been interest in its use for high temperature structural applications. The reason for this increased interest stems from its desirable characteristics which are a high melting point, relatively low density, good oxidation resistance, relatively good thermal conductivity and electronically conductive. The melting point of MoSi{sub 2} is approximately 2030{degrees}C as compared to a melting point of 1340{degrees}C for the Ni-based superalloys. This could potentially give MoSi{sub 2} a big advantage over the Ni-based superalloys in turbine applications because the operating temperature can be increased resulting in an increase in turbine efficiency and reduced emissions. The relatively low density (6.25g/cm{sup 3}) compared to the Ni-based superalloys (8.9 g/cm{sup 3}) is an important advantage in turbine applications because of the need for low weight. Good oxidation resistance stems from the ability of MoSi{sub 2} to form a protective SiO{sub 2} surface layer when exposed to oxygen. Another advantageous feature of MoSi{sub 2} is its thermal conductivity which is superior to Ni-based superalloys at low temperatures and comparable to the Ni-based superalloys at high temperatures. This allows heat to be dissipated at a rate better than ceramics and comparable to metals. MoSi{sub 2} is electrically conductive allowing it to be electro discharge machined. This is desirable since conventional ceramics are not generally conductive and cannot be electro discharge machined.
Date: October 1, 1996
Creator: Alba, J., Jr.
Partner: UNT Libraries Government Documents Department

Thermodynamic and kinetic studies of some Group III and Group V elements and alloys by solid state electrochemical techniques

Description: The Gibbs free energy of forming gallium sesquioxide and indium sesquioxide are measured using a CO$sub 2$--CO--O$sub 2$ gas reference electrode and calcia stabilized zirconia as the solid electrolyte. The free energies are: $delta$G$sup 0$/sub f/($beta$-Ga$sub 2$O$sub 3$(c)) equals -(265,309 +- 152) + (82.47 +- 0.16) (T/K) cal mol$sup -1$ and $delta$G$sup 0$/sub f/(In$sub 2$O$sub 3$ (c)) equals -(223,160 +- 137) + (79.47 +- 0.12) (T/K) cal mol$sup -$.$sup 1$ A solid state galvanic cell is employed to measure gallium activities in Ga--Sb liquid alloys. Results show moderate negative deviations from ideality in the composition range 0.039 less than x/sub Ga/ less than 0.833. Partial molar enthalpies and entropies are calculated, and agree wih calorimetric data. Results are combined with calorimetric data to calculate the liquidus temperatures of the Ga--Sb system, which are in excellent agreement with measurements. Effect of short-range ordering is also investigated. Coulometric titration techniques are used to investigate the solubility and diffusivity of oxygen in liquid indium. Dissolved atomic oxygen is found to follow Henry's law and a saturation solubility of x$sub 0$/sup sat/ equals 3.3 x 10$sup -3$ is determined at 908$sup 0$K. From a galvanostatic response of an indium electrode, an oxygen diffusivity of 2.2 x 10$sup -6$ cm$sup 2$ s$sup -1$ is found, in good agreement with other available data. (LK)
Date: October 1, 1975
Creator: Anderson, T.J.
Partner: UNT Libraries Government Documents Department

Fe--12Ni--4Co--2Mo--.05Ti alloy for use at 77$sup 0$K and below

Description: A variant of the maraging class of steels is proposed for application at 77$sup 0$K and below where a combination of very high strength and good toughness is required. The alloy has a composition of Fe-12Ni-4Co-2Mo-0.05Ti where low interstitial content. The as quenched and quenched and aged structures were completely martensitic with a prior austenitic grain size of 10 to 12 $mu$m. This structure had a Y.S. of 138.5 ksi and 154 ksi before and after aging respectively. All aging was done at 444$sup 0$C for 4 hours. The DBTT was shown to lie above 77$sup 0$K as measured by C/sub v/ testing. Based on dilatometric studies of the $alpha$ $Yields$ $gamma$ and $gamma$ $Yields$ $alpha$ transformation temperatures a cycling treatment consisting of reportedly heating to above the A/sub f/ temperature followed by a water quench was utilized to further reduce the prior $gamma$ grain size to approximately 4 to 6 $mu$m. The structure was completely martensitic and possessed a Y.S. of 151 ksi at 77$sup 0$K in the unaged condition with a Y.S./K/sub IC/ ratio of 1.9 while the aged structure showed a Y.S. of 162 ksi with a Y.S./K/sub IC/ ratio of 1.3. C/sub v/ testing showed the DBTT to lie between 77$sup 0$K and 4.2$sup 0$K. Further grain refinement was accomplished by a 2 phase decomposition procedure which resulted in a grain size of 1 to 2 $mu$m. The structure which contained decreasing amounts of austenite with temperature (3.0 percent at R.T. to 1.0 percent at 4.2$sup 0$K) showed the best combination of strength and ductility at 4.2$sup 0$K. A Y.S. of 205 ksi with a Y.S./K/sub IC/ ratio of 0.84 was achieved before aging. The aged structure was brittle at 4.2$sup 0$K with a Y.S. of 218 ksi and a Y.S./K/ sub IC/ ratio of 0.425. ...
Date: October 1, 1975
Creator: Whitaker, B.W.
Partner: UNT Libraries Government Documents Department

Transverse Space-Charge Effects in Circular Accelerators

Description: The particles in an accelerator interact with one another by electromagnetic forces and are held together by external focusing forces. Such a many-body system has a large number of transverse modes of oscillation (plasma oscillations) that can be excited at characteristic frequencies by errors in the external guide field. In Part I we examine one mode of oscillation in detail, namely the quadrupole mode that is excited in uniformly charged beams by gradient errors. We derive self-consistent equations of motion for the beam envelope and solve these equations for the case in which the space-charge force is much less than the external focusing force, i.e., for strong-focusing synchrotrons. We find that the resonance intensity is shifted from the value predicted by the usual transverse incoherent space-charge limit; moreover, because the space-charge force depends on the shape and size of the beam, the beam growth in always limited. For gradient errors of the magnitude normally present in strong-focusing synchrotrons, the increase in beam size is small provided the beam parameters are properly chosen; otherwise the growth may be large. Thus gradient errors need not impose a limit on the number of particles that can be accelerated. In Part II we examine the other modes of collective oscillation that are excited by machine imperfections. For simplicity we consider only one-dimensional beams that are confined by harmonic potentials, and only small-amplitude oscillations. The linearized Vlasov and Poisson equations are used to find the twofold infinity of normal modes and eigenfrequencies for the stationary distribution that has uniform charge density in real space. In practice, only the low-order modes (the dipole, quadrupole, sextupole, and one or two additional modes) will be serious, and the resonant conditions for these modes are located on a tune diagram. These results, which are valid for all beam intensities, ...
Date: October 30, 1968
Creator: Sacherer, Frank James
Partner: UNT Libraries Government Documents Department