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Reconciliation (open access)

Reconciliation

The content of my work focused on examining the relationship between certain elements of nature and of human beings and was also based on the question of what true life is. The woodcut process - combined with the other printing techniques such as intaglio, collagraph, and monotype - was adopted as a potentially successful medium for conveying the content of the work. Overlay printing techniques and repeated textures were utilized as well.
Date: March 1996
Creator: Chung, Miok
System: The UNT Digital Library
Recycling Culture and Media (open access)

Recycling Culture and Media

A comparison of classical and contemporary cultures was made by recreating classical sculptural imagery in contemporary recyclable materials. I proposed to use the detritus of modern culture to render sculpture that was ancient in subject, stance, and scale. The intention of this work was to create a visual discourse between cultures by bringing together elements of each, showing points of congruence and disparity.
Date: March 1995
Creator: Drew, Robert S.
System: The UNT Digital Library
An Investigation Into the Relationship Between Media and Content (open access)

An Investigation Into the Relationship Between Media and Content

The purpose of this study was to investigate the relationship between media and content in my work. I began a series of paintings in the fall of 1985 which was based on 35mm transparencies. At this point, the slides were nothing more than a visual aid, a way to augment my technical skills; my chief interest in these paintings was narrative. I was also taking a drawing class at the time, and several times I recycled a transparency I had used with a painting to create a drawing. Sometimes Both versions were relatively successful (though often for very different reasons), other times one version would be more successful than the other. Technical proficiency (or lack of it) did not seem to be the determining factor in these cases.
Date: March 1987
Creator: Crouch, Ron Taylor
System: The UNT Digital Library
Nucleation and dynamics of vortices in type-II superconductors (open access)

Nucleation and dynamics of vortices in type-II superconductors

The one- and two-dimensional Ginzburg-Landau equations are numerically integrated in a slab geometry, which is appropriate for comparison to experimental work done on films. When two-dimensional variations become energetically favorable, a vortex is found to nucleate and move to the center of the film with the Gibbs free energy decreasing during the process. An important process by which the energy is lowered during this nucleation procedure is found to be the savings in condensation energy arising from the shrinking size of the vortex core as it moves to the center of the film. The solutions of the Ginzburg-Landau equations are used to explain anomalies observed experimentally in the tunneling characteristics of thin films of PbIn. Excellent agreement between theory and experiment is found with the Ginzburg-Landau equations correctly predicting the field at which flux would first enter the films. We then use the Clem model of an isolated vortex to model vortex nucleation and dynamics under the influence of a transport current. The entry fields predicted by the model are found to be off by almost a factor of two but have the advantage of requiring simple computer programs for their solution, while the Ginzburg-Landau solutions require substantially more numerical …
Date: March 1, 1977
Creator: Balley, R. E.
System: The UNT Digital Library
Electron Transfer at Sensitized Semiconductor Electrodes (open access)

Electron Transfer at Sensitized Semiconductor Electrodes

Electron transfer from the excited state of sensitizing dyes to the conduction band of semiconductors has been studied through photoelectrochemical techniques. Two systems were analyzed in detail: rhodamine B on ZnO and rose bengal on TiO/sub 2/. Prior to electrochemical experimentation, the adsorption characteristics of these dyes were investigated using ZnO, ZnS, and TiO/sub 2/ single crystals as substrates. Absorbance measurements of the adsorbed dye were taken as a function of the solution concentration of the dye. Adsorption isotherms heats of adsorption were also established; they were similar to literature data reported for adsorption of these dyes on powdered substrates. Using the absorbance data, the quantum efficiency for photoinjection of electrons from rhodamine B into a ZnO electrode was determined to be 2.7 x 10/sup -2/. This value was independent of the dye surface concentration down to 50% coverage of the electrode. With the assumption that not all of the rhodamine B adsorbed on the electrode has the same rate of electron injection, a kinetic model for the time decay of the photocurrent was developed; data were analyzed according to this theory. A rate constant for photoreduction of the adsorbed dye was determined for the reducing agents. 86 references.
Date: March 1977
Creator: Spitler, Mark Thomas
System: The UNT Digital Library
Search for first-generation leptoquarks in the jets and missing transverse energy topology in proton-antiproton collisions at center-of-mass energy 1.96 TeV (open access)

Search for first-generation leptoquarks in the jets and missing transverse energy topology in proton-antiproton collisions at center-of-mass energy 1.96 TeV

The authors performed a search for the pair production of first-generation leptoquarks using 191 pb{sup -1} of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark, which yields missing transverse energy and several high-E{sub T} jets. Several control regions were studied to check the background estimation from Standard Model sources, with good agreement observed in data. In the leptoquark signal region, 124 events were observed with 118.3 {+-} 14.5 expected from background. Therefore, no evidence for leptoquark production was observed, and limits were set on the cross section times the squared branching ratio. Using the next-to-leading order cross section for leptoquark production, they excluded the mass interval 78 to 117 GeV/c{sup 2} at the 95% confidence level for 100% branching ratio into neutrino plus quark.
Date: March 1, 2004
Creator: Tsybychev, Dmitri
System: The UNT Digital Library
Mass spectrum analysis of K- pi+ from the semileptonic decay D+ --> K- pi+ mu+ nu (open access)

Mass spectrum analysis of K- pi+ from the semileptonic decay D+ --> K- pi+ mu+ nu

The Higgs mechanism preserves the gauge symmetries of the Standard Model while giving masses to the W, Z bosons. Supersymmetry, which protects the Higgs boson mass scale from quantum corrections, predicts at least 5 Higgs bosons, none of which has been directly observed. This thesis presents a search for neutral Higgs bosons, produced in association with bottom quarks. The production rate is greatly enhanced at large values of the Supersymmetric parameter tan {beta}. High-energy p{bar p} collision data, collected from Run II of the Fermilab Tevatron using the D0 detector, are analyzed. In the absence of a signal, values of tan {beta} > 80-120 are excluded at 95% Confidence Level (C.L.), depending on the (CP-odd) neutral Higgs boson mass (studied from 100 to 150 GeV/c{sup 2}).
Date: March 1, 2004
Creator: Massafferri Rodrigues, Andre & /Rio de Janeiro, CBPF
System: The UNT Digital Library
Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy (open access)

Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy

Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively …
Date: March 24, 2004
Creator: Willey, T & Willey, T
System: The UNT Digital Library
Laser Ion Acceleration from the Interaction of Ultra-Intense laser Pulse with thi foils (open access)

Laser Ion Acceleration from the Interaction of Ultra-Intense laser Pulse with thi foils

The discovery that ultra-intense laser pulses (I > 10{sup 18} W/cm{sup 2}) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10{sup 18} W/cm{sup 2}), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U{sub p} = ([1 + I{lambda}{sup 2}/1.3 x 10{sup 18}]{sup 1/2} - 1) m{sub o}c{sup 2}, where I{lambda}{sup 2} is the irradiance in W{micro}m{sup 2}/cm{sup 2} and m{sub o}c{sup 2} is the electron rest mass.At laser irradiance of I{lambda}{sup 2} {approx} 10{sup 20} W{micro}m{sup 2}/cm{sup 2}, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the …
Date: March 12, 2004
Creator: Allen, M
System: The UNT Digital Library
Cooling of highly charged ions in a Penning trap (open access)

Cooling of highly charged ions in a Penning trap

Highly charged ions are extracted from an electron beam ion trap and guided to Retrap, a cryogenic Penning trap, where they are merged with laser cooled Be{sup +} ions. The Be{sup +} ions act as a coolant for the hot highly charged ions and their temperature is dropped by about 8 orders of magnitude in a few seconds. Such cold highly charged ions form a strongly coupled nonneutral plasma exhibiting, under such conditions, the aggregation of clusters and crystals. Given the right mixture, these plasmas can be studied as analogues of high density plasmas like white dwarf interiors, and potentially can lead to the development of cold highly charged ion beams for applications in nanotechnology. Due to the virtually non existent Doppler broadening, spectroscopy on highly charged ions can be performed to an unprecedented precision. The density and the temperature of the Be{sup +} plasma were measured and highly charged ions were sympathetically cooled to similar temperatures. Molecular dynamics simulations confirmed the shape, temperature and density of the highly charged ions. Ordered structures were observed in the simulations.
Date: March 31, 2000
Creator: Gruber, L
System: The UNT Digital Library
Development of vertexing and lifetime triggers and a study of B(s) mixing using hadronic decays at D0 (open access)

Development of vertexing and lifetime triggers and a study of B(s) mixing using hadronic decays at D0

The D0 detector underwent a major upgrade to maximize its ability to fully exploit Run II at the Fermilab Tevatron, the world's highest energy collider. The upgrade included a completely new central tracking system with an outer scintillating fiber tracker and an inner silicon vertex detector all within a 2T superconducting solenoid. This thesis describes the development of high level trigger algorithms including vertexing, impact parameter significance and invariant mass, that utilize tracks from these detectors. One of the main physics goals of Run II is the observation of B{sub s} oscillations. This measurement, which cannot be performed at the B factories, will significantly constrain the ''unitarity triangle'' associated with Cp violation and so probe the Standard Model of particle physics. Furthermore this is an interesting measurement as the study of mixing in meson systems has a long history for revealing new physics. The second part of this thesis presents a study of the hadronic decay B{sub s} {yields} D{sub s}{pi}. This important mode provides the best proper time resolution for B{sub s} mixing and is reconstructed for the first time at D0. Projections on the sensitivity to B{sub s} oscillations are then presented.
Date: March 1, 2005
Creator: Barnes, Christopher P.
System: The UNT Digital Library
Bio-Aerosol Detection Using Mass Spectrometry: Public Health Applications (open access)

Bio-Aerosol Detection Using Mass Spectrometry: Public Health Applications

I recently spent a summer as an intern at the Lawrence Livermore National Laboratory. I worked on a project involving the real-time, reagentless, single cell detection of aerosolized pathogens using a novel mass spectrometry approach called Bio-Aerosol Mass Spectrometry (BAMS). Based upon preliminary results showing the differentiation capabilities of BAMS, I would like to explore the development and use of this novel detection system in the context of both environmental and clinical sample pathogen detection. I would also like to explore the broader public health applications that a system such as BAMS might have in terms of infectious disease prevention and control. In order to appreciate the potential of this instrument, I will demonstrate the need for better pathogen detection methods, and outline the instrumentation, data analysis and preliminary results that lead me toward a desire to explore this technology further. I will also discuss potential experiments for the future along with possible problems that may be encountered along the way.
Date: March 5, 2004
Creator: Ludvigson, L D
System: The UNT Digital Library
Search for New Physics in Dielectron Events in 1.96-TeV Proton - Anti-proton Collisions (open access)

Search for New Physics in Dielectron Events in 1.96-TeV Proton - Anti-proton Collisions

The authors have searched for new physics beyond the Standard Model of elementary particle physics in dielectron decay mode at the CDF (Collider Detector at Fermilab) experiment in {bar p}p collisions at {radical}s = 1.96 TeV. The data were collected during the 2002-2003 runs corresponding to an integrated luminosity of 200 pb{sup -1}. Many extensions of the Standard Model have been proposed. Grand Unified Theories (GUT) assumes a larger gauge symmetry group and predict new gauge bosons. GUT has hierarchy problem in it and there have been many attempts to solve the hierarchy problem. Solutions for the hierarchy problem are supersymmetry, technicolor, large extra dimensions, warped extra dimensions and little Higgs models. The authors analyze the differential distribution of dielectron events in terms of their invariant mass and no significant excess is found in very high mass region. They present a 95% confidence level limit on the production cross section times branching ratio for new resonant particles decaying into an electron pair as a function of invariant mass. New resonant particles include new neutral gauge boson Z', Randall-Sundrum graviton, R-parity violating sneutrino, and technicolor particles. They also present limits on the effective Planck scale of large extra dimensions.
Date: March 1, 2004
Creator: Ikado, Koji & U., /Waseda
System: The UNT Digital Library
Inertial Conference Fusion Semiannual Report October 1999 - March 2000, Volume 1, Number 1 (open access)

Inertial Conference Fusion Semiannual Report October 1999 - March 2000, Volume 1, Number 1

This first issue of the ''ICF Semiannual Report'' contains articles whose diverse subjects attest to the broad technical and scientific challenges that are at the forefront of the ICF program at LLNL. The first article describes the progress being made at solving the surface roughness problem on capsule mandrels. All NIF capsule options, except machined beryllium, require a mandrel upon which the ablator is deposited. This mandrel sets the baseline sphericity of the final capsule. Problems involving defects in the mandrel have been overcome using various techniques so that 2-mm-size mandrels can now be made that meet the NIF design specification. The second article validates and provides a detailed numerical investigation of the shadowgraph technique currently used to diagnose the surface roughness of a fuel ice layer inside of a transparent capsule. It is crucial for the success of the indirect-drive ignition targets that the techniques used to characterize ice-surface roughness be well understood. This study identifies methods for analyzing the bright band that give an accurate measure of the ice-surface roughness. The third article describes a series of realistic laser and target modifications that can lead to 3-4 times more energy coupling and 10 times greater yield from a …
Date: March 1, 2000
Creator: Hammel, B. A.
System: The UNT Digital Library
Measurement of W + gamma Production in the W to Muon Decay Channel in Proton - Anti-proton Collisions at s**(1/2) = 1.96-TeV (open access)

Measurement of W + gamma Production in the W to Muon Decay Channel in Proton - Anti-proton Collisions at s**(1/2) = 1.96-TeV

The production cross section and the kinematic properties of the decay products of W{gamma} in the W {yields} {mu}{nu} decay channel from p{bar p} collisions at {radical}s = 1.96 TeV are presented. The measurement use the high p{sub T} muon data from the upgraded Collider Detector at Fermilab (CDF). The data were collected between March 2002 and September 2003. The total integrated luminosities are 192 pb{sup -1} with the muon detector which covers the pseudorapidity region of |{eta}| {le} 0.6 and 175 pb{sup -1} with the muon detector covering the region 0.6 {le} |{eta}| {le} 1.0. In the Standard Model the {mu}{nu}{gamma} final states occur due to W{gamma} {yields} {mu}{nu}{gamma} production and via muon Bremsstrahlung, W {yields} {mu}{nu} {yields} {mu}{nu}{gamma}. W bosons are selected in their muon decay mode. Additionally, photons with transverse energy above 7 GeV, pseudorapidity in the central region (|{eta}| < 1.1) and muon-photon angular separation {Delta}R({mu},{gamma}) > 0.7 are selected. The author observes a total of 128 W{gamma} candidates, whereas the Standard Model expectation is 142.4 {+-} 9.5 events. The W{gamma} production cross section is found to be {sigma}(p{bar p} {yields} {mu}{nu}{gamma}) = 16.3 {+-} 2.3(stat.) {+-} 1.8(syst.) {+-} 1.2(lum.) [pb]. The theoretical prediction for this …
Date: March 1, 2005
Creator: Tanimoto, Naho & U., /Okayama
System: The UNT Digital Library
Use of a Superconducting Tunnel Junction for X-Ray Fluorescence Spectroscopy (open access)

Use of a Superconducting Tunnel Junction for X-Ray Fluorescence Spectroscopy

A superconducting tunnel junction (STJ) in combination with a superconducting absorber of radiation may function as a highly resolving x-ray spectrometer. Electronic excitations, or quasiparticles, are created when a superconductor absorbs an x ray and are detected as an excess tunnel current through the junction. The number of quasiparticles created and the magnitude of the excess current is proportional to the energy of the absorbed x ray. This is similar to existing semiconductor-based spectrometers that measure electron-hole pairs, but with 1000 times more excitations. The energy measurement therefore can be up to 30 times more precise with a superconducting detector than with a semiconductor detector. This work describes the development and testing of an STJ spectrometer design for x-ray fluorescence applications. First, the basic principles of the STJ spectrometer are explained. This is followed by detailed simulations of the variance in the number of quasiparticles produced by absorption of an x ray. This variance is inherent in the detector and establishes an upper limit on the resolving power of the spectrometer. These simulations include effects due to the materials used in the spectrometer and to the multilayer structure of the device. Next, the spectrometer is characterized as functions of operating …
Date: March 6, 2001
Creator: Hiller, L
System: The UNT Digital Library
Inertial fusion technology spin-offs-history provides a glimpse of the future (open access)

Inertial fusion technology spin-offs-history provides a glimpse of the future

The development and demonstration of inertial fusion is incredibly challenging because it requires simultaneously controlling and precisely measuring parameters at extreme values in energy, space, and time. The challenges range from building megajoule (10{sup 6} J) drivers that perform with percent-level precision to fabricating targets with submicron specifications to measuring target performance at micron scale (10{sup -6} m) with picosecond (10{sup -12} s) time resolution. Over the past 30 years in attempting to meet this challenge, the inertial fusion community around the world has invented new technologies in lasers, particle beams, pulse power drivers, diagnostics, target fabrication, and other areas. These technologies have found applications in diverse fields of industry and science. Moreover, simply assembling the teams with the background, experience, and personal drive to meet the challenging requirements of inertial fusion has led to spin-offs in unexpected directions, for example, in laser isotope separation, extreme ultraviolet (EUV) lithography for microelectronics, compact and inexpensive radars, advanced laser materials processing, and medical technology. It is noteworthy that more than 40 R&D 100 awards, the ''Oscars of applied research'' have been received by members of the inertial fusion community over this period. Not surprisingly, the inertial fusion community has created many new …
Date: March 7, 2000
Creator: Powell, H
System: The UNT Digital Library
Lasershot peening--a means to strengthen metals (open access)

Lasershot peening--a means to strengthen metals

Lasershot peening is an emerging modern process that impresses a compressive stress into the surfaces of metals, improving their operational lifetime. Almost everyone is familiar with taking a strip of metal or a wire and bending it multiple times until it breaks. In this situation, when the metal is bent, the surface of outer radius is stretched into a tensile state. Under tension, any flaw or micro-crack will grow in size with each bending of the metal until the crack grows through the entire strip, breaking it into two pieces. Flexure of metal components occurs in most applications. The teeth of a transmission gear flex as they deliver torque in a vehicle. Springs and valves flex every time they transfer loads. If fatigue failure from flexing occurs in the tooth of a transmission gear of light or heavy vehicles, in a fan blade of a diesel engine, in shock-absorbers or safety-related supporting structures, significant loss of assets and potentially loss of human life occurs. Lasershot peening, better than any other technique, has the potential to extend the fatigue lifetime of metal components. In the process, the laser generates a high intensity shock wave at the surface of the metal, straining …
Date: March 1, 2000
Creator: Chen, H. L.
System: The UNT Digital Library
Design and Implementation of a Text Editor Under Music Interactive Operating System (open access)

Design and Implementation of a Text Editor Under Music Interactive Operating System

An interactive text editor is a computer program that allows a user to create and revise a target document such as program statements, manuscript text, and numeric data through an online terminal and the computer. It allows text to be modified and corrected many orders of magnitude faster and more easily than would manual correction. The most important characteristic of the text editor is its convenience for the user. Such convenience requires a simple, mnemonic command language which is easy to use and understand.
Date: March 1984
Creator: Hwa, Shu-Jen
System: The UNT Digital Library
Development of a Text Formatted Under VAX/VMS Operating System (open access)

Development of a Text Formatted Under VAX/VMS Operating System

No matter how extended the use of the computer is, the printed document is still the primary medium for the presentation information, and will continue to be for some time. The use of computing facilities for preparation and production of the document is becoming as prevalent as their use for numeric computation. Commercially, document preparation systems are now a standard facility at research institution, and they have become quite common on each computer program. A conventional document preparation system usually contains two parts: a text editor used to create, enter, update, and maintain the text and control words that comprise the document in its "input" form, and a text formatter used to process that input and produce the final document.
Date: March 1984
Creator: Chow, Perng
System: The UNT Digital Library
Quaternary liquid/liquid equilibria of sodium sulfate, sodium sulfite and water with two solvents: Acetone and 2-propanol (open access)

Quaternary liquid/liquid equilibria of sodium sulfate, sodium sulfite and water with two solvents: Acetone and 2-propanol

Aqueous solutions of sodium sulfate and sodium sulfite are produced from sodium carbonate in flue-gas scrubbers; recovery of these salts often requires multi-effect evaporators; however, a new energy-efficient unit operation called extractive crystallization has been shown to have reduced energy costs. In this process, an organic solvent is added to the aqueous salt solution to precipitate salt. Acetone is a suitable solvent for this process, better than 2-propanol. Liquid/liquid/solid equilibria for ternary systems containing a salt, water, and an organic solvent were measured. Systems investigated were sodium sulfite/water/acetone and sodium sulfite/water/2-propanol. Experiments were conducted at salt saturation covering a temperature range between the lower consolute temperature and 48.6{degrees}C. In the attempt to improve the extractive crystallization process for recovery of sodium sulfate from flue-gas scrubbers, attention was given to a feed containing a mixture of sodium sulfite and sodium sulfate. Liquid-liquid equilibria for quaternary systems containing two salts, water, and an organic solvent were experimentally determined at 35{degrees}C. The systems investigated were sodium sulfate/sodium sulfite/water/acetone and sodium sulfate/sodium sulfite/water/2propanol. The systems were studied at three salt ratios. For each salt ratio, experiments were conducted starting at saturation, water was then added until the one-phase region was reached. Mixtures of the …
Date: March 1, 1994
Creator: Schiozer, A. L.
System: The UNT Digital Library
Chemisorption and catalytic reactivity of cobalt and sulfur monolayers on ordered molybdenum surfaces (open access)

Chemisorption and catalytic reactivity of cobalt and sulfur monolayers on ordered molybdenum surfaces

Complex Co/Mo sulfide catalysts are modelled by the chemisorption of layers on Mo single crystal surfaces. Growth and structure of overlayers on flat, stepped and kinked surfaces were investigated. Growth of Co overlayers on clean and S covered Mo surfaces was studied using AES and CO chemisorption; results reveal that Co grows as a flat monolayer on clean Mo surfaces. Co multilayers then form 3-D islands. When Co is deposited on S covered surfaces, the S overlayer migrates to the top; this topmost overlayer reduces CO adsorption capacity. While growth mode of Co overlayers are similar on flat and stepped surfaces, the number and type of ordered Co and S structures on flat and stepped surfaces are different. In the case of Co, an ordered (3 {times} 1) structure is formed on Mo(910) and (28,4,1) surfaces; this structure does not develop on clean (100) surface. Only one of two possible (3 {times} 1) Co domains are formed on Mo(910) and Mo(28,4,1) surfaces. These domains have one side of (3 {times} 1) unit cell parallel to the step edges, suggesting that Co adsorbs at the step edges. The (3 {times} 1) structure does not form on Mo(911) surface, indicating that step …
Date: March 1, 1992
Creator: Knight, C. C.
System: The UNT Digital Library
Signal and noise analysis of a-Si:H radiation detector-amplifier system (open access)

Signal and noise analysis of a-Si:H radiation detector-amplifier system

Hydrogenated amorphous silicon (a-Si:H) has potential advantages in making radiation detectors for many applications because of its deposition capability on a large-area substrate and its high radiation resistance. Position-sensitive radiation detectors can be made out of a 1d strip or a 2-d pixel array of a Si:H pin diodes. In addition, signal processing electronics can be made by thin-film transistors on the same substrate. The calculated radiation signal, based on a simple charge collection model agreed well with results from various wave length light sources and 1 MeV beta particles on sample diodes. The total noise of the detection system was analyzed into (a) shot noise and (b) 1/f noise from a detector diode, and (c) thermal noise and (d) 1/f noise from the frontend TFT of a charge-sensitive preamplifier. the effective noise charge calculated by convoluting these noise power spectra with the transfer function of a CR-RC shaping amplifier showed a good agreement with the direct measurements of noise charge. The derived equations of signal and noise charge can be used to design an a-Si:H pixel detector amplifier system optimally. Signals from a pixel can be readout using switching TFTs, or diodes. Prototype tests of a double-diode readout scheme …
Date: March 1, 1992
Creator: Cho, Gyuseong
System: The UNT Digital Library
Energy development and CO{sub 2} emissions in China (open access)

Energy development and CO{sub 2} emissions in China

The objective of this research is to provide a better understanding of future Chinese energy development and CO{sub 2} emissions from burning fossil fuels. This study examines the current Chinese energy system, estimates CO{sub 2} emissions from burning fossil fuels and projects future energy use and resulting CO{sub 2} emissions up to the year of 2050. Based on the results of the study, development strategies are proposed and policy implications are explored. This study first develops a Base scenario projection of the Chinese energy development based upon a sectoral analysis. The Base scenario represents a likely situation of future development, but many alternatives are possible. To explore this range of alternatives, a systematic uncertainty analysis is performed. The Base scenario also represents an extrapolation of current policies and social and economic trends. As such, it is not necessarily the economically optimal future course for Chinese energy development. To explore this issue, an optimization analysis is performed. For further understanding of developing Chinese energy system and reducing CO{sub 2} emissions, a Chinese energy system model with 84 supply and demand technologies has been constructed in MARKAL, a computer LP optimization program for energy systems. Using this model, various technological options and …
Date: March 1, 1993
Creator: Xiaolin Xi
System: The UNT Digital Library