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379 Matching Results
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UV-Photoassisted Etching of GaN in KOH
The etch rate of GaN under W-assisted photoelectrochemical conditions in KOH solutions is found to be a strong function of illumination intensity, solution molarity, sample bias and material doping level. At low e-h pair generation rates, grain boundaries are selectively etched, while at higher illumination intensities etch rates for unintentionally doped (n - 3x 10^12Gcm-3) GaN are 2 1000 .min-l. The etching is diffusion limited under our conditions with an activation energy of - 0.8kCal.mol-1. The etched surfaces are rough, but retain their stoichiometry. PEC etching is found to selectively reveal grain boundaries in GaN under low light illumination conditions. At high lamp powers the rates increase with sample temperature and the application of bias to the PEC cell, while they go through a maximum with KOH solution molarity. The etching is diffusion-limited, producing rough surface morphologies that are suitable in a limited number of device fabrication steps. The surfaces however appear to remain relatively close to their stoichiometric composition.
Date:
November 12, 1998
Creator:
Abernathy, C.R.; Auh, K.H.; Cho, H.; Donovan, S.M.; Han, J.; Lambers, E.S. et al.
Object Type:
Article
System:
The UNT Digital Library
Investigation of Deep Levels in GaInNas
This paper presents and discusses the first Deep-Level transient spectroscopy (DLTS) data obtained from measurements carried out on both Schottky barriers and homojunction devices of GaInNAs. The effect of N and In doping on the electrical properties of the GaNInAs devices, which results in structural defects and interface states, has been investigated. Moreover, the location and densities of deep levels related to the presence of N, In, and N+In are identified and correlated with the device performance. The data confirmed that the presence of N alone creates a high density of shallow hole traps related to the N atom and structural defects in the device. Doping by In, if present alone, also creates low-density deep traps (related to the In atom and structural defects) and extremely deep interface states. On the other hand, the co-presence of In and N eliminates both the interface states and levels related to structural defects. However, the device still has a high density of the shallow and deep traps that are responsible for the photocurrent loss in the GaNInAs device, together with the possible short diffusion length.
Date:
November 12, 1998
Creator:
Abulfotuh, F.; Balcioglu, A.; Friedman, D.; Geisz, J. & Kurtz, S.
Object Type:
Article
System:
The UNT Digital Library
Computer software design description for the integrated control and data acquisition system LDUA system
This Computer Software Design Description (CSDD) document provides the overview of the software design for all the software that is part of the integrated control and data acquisition system of the Light Duty Utility Arm System (LDUA). It describes the major software components and how they interface. It also references the documents that contain the detailed design description of the components.
Date:
August 12, 1998
Creator:
Aftanas, B. L.
Object Type:
Report
System:
The UNT Digital Library
Nanoscale investigation of polarization retention loss in ferroelectric thin films via scanning force microscopy.
Scanning force microscopy (SFM) was applied to direct nanoscale investigation of the mechanism of retention loss in ferroelectric thin films. Experiments were conducted by performing local polarization reversal within an individual grain with subsequent imaging of a resulting domain structure at various time intervals. A conductive SFM tip was used for domain switching and imaging in the SFM piezoresponse mode.
Date:
February 12, 1998
Creator:
Aggarwal, S.; Auciello, O.; Gruverman, A.; Prakash, S. A.; Ramesh, R. & Tokumoto, H.
Object Type:
Article
System:
The UNT Digital Library
Composition and Bonding in Amorphous Carbon Films Grown by Ion Beam Assisted Deposition: Influence of the Assistance Voltage
Amorphous carbon films have been grown by evaporation of graphite with concurrent Ar+ ions bombardment assistance. The ion energy has been varied between 0-800 V while keeping a constant ion to carbon atom arrival ratio. Film composition and density were determined by ion scattering techniques (RBS and ERDA), indicating a negligible hydrogen content and a density dependence with the assistance voltage. The bonding structure of the films has been studied by Raman and X-ray Absorption Near-Edge (XANES) spectroscopy. Different qualitative effects have been found depending on the ion energy range. For ion energies below 300 eV, there is a densification of the carbon layer due to the increase in the sp3 content. For ion energies above 300 eV sputtering phenomena dominate over densification, and thinner films are found with increasing assistance voltage until no film is grown over 600 V. The films with the highest SP3 content are grown with intermediate energies between 200-300 V.
Date:
November 12, 1998
Creator:
Albella, J. M.; Banks, J. C.; Climent-Font, A.; Doyle, B. L.; Gago, R.; Jimenez, I. et al.
Object Type:
Article
System:
The UNT Digital Library
Oral History Interview with General Alpha Lyons Bowser, March 12, 1998
Access:
Use of this item is restricted to the UNT Community
Transcript of an interview with General Alpha Lyons Bowser, a Marine Corps veteran (3rd Battalion, 12th Marine Regiment, 3rd Marine Division), concerning his experiences as an artillery officer in the Pacific Theater during World War II. Bowser also discusses his role in planning the Inchon landing, 1950, during the Korean War.
Date:
March 12, 1998
Creator:
Alexander, William J. & Bowser, Alpha Lyons
Object Type:
Book
System:
The UNT Digital Library
Sputter deposited beryllium fuel capsules for NIF
The objective of our effort is to systematically study the properties of films produced under different conditions, with an emphasis on improving surface morphology and microstructure while studying permeability and capsule strength. We have made extensive use of atomic force and electron microscopy to determine the microstructure of the films, along with composition probes (mainly x-ray fluorescence) to quantify the chemical structure. Our studies can be roughly divided into three categories. First, there are those in which the effects of substrate biasing have been investigated. This includes varying the substrate voltage from 0 to 120 V and applying an intermittent bias. Next there are studies of Be combined with boron, a non-soluble dopant Because of it`s low Z this dopant is of particular interest for x-ray related applications. Finally, there are experiments in which pulses of nitrogen are admitted to the vacuum chamber during deposition. The layers of nitride formed tended to disrupt the growth of Be grains, leading to a more fine-grained microstructure. For all these studies, we have most often used hollow plastic spheres for our substrate material. However, there have been some samples deposited on glass spheres or silicon flats.
Date:
February 12, 1998
Creator:
Alford, C.S.
Object Type:
Report
System:
The UNT Digital Library
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 42, Ed. 1 Monday, October 12, 1998
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
October 12, 1998
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 65, Ed. 1 Thursday, November 12, 1998
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
November 12, 1998
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Optimum Condition for Accurate Heat Capacity Measurements in Temperature-Modulated Differential Scanning Calorimetry
We explored the optimum conditions in modulation of the program temperature and sample preparation to obtain absolute values of heat capac- ity from quasi-isothermal measurements of temperature-modulated differen- tial scanning calorimetry. A Mettler-Toledo 820 calorimeter and Perkin-Elmer DSC 7 were used for this work, using saw-tooth modulation as well as sinu- soidal modulation. We adopted a simple model to analyze the temperature response of the calorimeters and calibrated the results more precisely.
Date:
September 12, 1998
Creator:
Androsch, R.J.; Moon, K. & Wunderlich, B.
Object Type:
Article
System:
The UNT Digital Library
Effective cleanup at LLNL: innovative technologies and approaches
At the Lawrence Livermore National Laboratory (LLNL) Livermore Site Superfund Site, ground water restoration efforts have been ongoing since 1989. Based on plans committed to by DOE in the Record of Decision (ROD) for the Site in 1992, ground water cleanup was predicted to take 61 years. What began as conventional pump and treat has evolved into an effective Engineered Plume Collapse strategy that employs a well-stocked tool box of remediation technologies, processes, and methodologies. This �tool box� approach has proven effective in solving the vexing problem of restoring the chlorinated volatile organic compound (CVOC) contaminated aquifers beneath the site. The Engineered Plume Collapse strategy has been used to hydraulically control the plumes on the western and southern boundaries of the site, doubled the pounds of CVOC removed from the subsurface compared to predictions in the ROD plans, and �collapsed� offsite plumes. The three major components of the Engineered Plume Collapse strategy are: (1) collection and use of historical and current chemical and hydrogeologic data to accurately identify areas of contamination in the subsurface and guide decisions about on-going remediation needs, (2) design, construction and operation of small, portable, and inexpensive ground water treatment units to implement pump and treat …
Date:
November 12, 1998
Creator:
Angleberger; Brown, M. G.; K. & Lamarre, A.
Object Type:
Article
System:
The UNT Digital Library
Archer County News (Archer City, Tex.), No. 7, Ed. 1 Thursday, February 12, 1998
Weekly newspaper from Archer City, Texas that includes local, state and national news along with advertising.
Date:
February 12, 1998
Creator:
Armstrong, Sonny
Object Type:
Newspaper
System:
The Portal to Texas History
Archer County News (Archer City, Tex.), No. 11, Ed. 1 Thursday, March 12, 1998
Weekly newspaper from Archer City, Texas that includes local, state and national news along with advertising.
Date:
March 12, 1998
Creator:
Armstrong, Sonny
Object Type:
Newspaper
System:
The Portal to Texas History
MEASURING GLOBAL OBSERVABLES WITH PHENIX.
When the Relativistic Heavy-Ion Collider (RHIC) begins operations, it will be capable of colliding nuclei of various sizes, from protons up to Au, at center-of-mass energies of 200 to 500 GeV per nucleon pair. Some of these collisions are expected to produce a new state of matter, the quark-gluon plasma (QGP), in which quarks are no longer confined to individual hadrons and in which chiral symmetry has been restored. Numerous predictions have been made as to how a phase transition to a QGP would affect the particle spectra produced in these collisions (see, for example, a recent review by Harris and Mueller). The PHENIX physics philosophy is to detect and systematically study the QGP via a simultaneous measurement of many different probes/signatures of the plasma, as a function of the energy density achieved in the nucleus-nucleus collision. To achieve this goal, the PHENIX detector has been designed as a multi-purpose spectrometer, capable of concurrently measuring hadrons, leptons and photons, as well as global properties of the collision, e.g. energy density, as will be detailed below.
Date:
June 12, 1998
Creator:
BENNETT,M.J. FOR THE PHENIX COLLABORATION
Object Type:
Article
System:
The UNT Digital Library
An evaluation of the management system verification pilot at Hanford
The Chemical Management System (CMS), currently under development at Hanford, was used as the ''test program'' for pilot testing the value added aspects of the Chemical Manufacturers Association's (CMA) Management Systems Verification (MSV) process. The MSV process, which was developed by CMA's member chemical companies specifically as a tool to assist in the continuous improvement of environment, safety and health (ESH) performance, represents a commercial sector ''best practice'' for evaluating ESH management systems. The primary purpose of Hanford's MSV Pilot was to evaluate the applicability and utility of the MSV process in the Department of Energy (DOE) environment. However, because the Integrated Safety Management System (ISMS) is the framework for ESH management at Hanford and at all DOE sites, the pilot specifically considered the MSV process in the context of a possible future adjunct to Integrated Safety Management System Verification (ISMSV) efforts at Hanford and elsewhere within the DOE complex. The pilot involved the conduct of two-hour interviews with four separate panels of individuals with functional responsibilities related to the CMS including the Department of Energy Richland Operations (DOE-RL), Fluor Daniel Hanford (FDH) and FDH's major subcontractors (MSCS). A semi-structured interview process was employed by the team of three ''verifiers'' …
Date:
November 12, 1998
Creator:
BRIGGS, C.R.
Object Type:
Report
System:
The UNT Digital Library
Electron-Anode Interactions in Particle-in-Cell Simulations of Applied-B Ion Diodes
Particle-in-cell simulations of applied-B ion diodes using the QUICKSILVER code have been augmented with Monte Carlo calculations of electron-anode interactions (reflection and energy deposition). Extraction diode simulations demonstrate a link between the instability evolution and increased electron loss and anode heating. Simulations of radial and extraction ion diodes show spatial non-uniformity in the predicted electron loss profile leading to hot spots on the anode that rapidly exceed the 350-450 {degree}C range, known to be sufficient for plasma formation on electron-bombarded surfaces. Thermal resorption calculations indicate complete resorption of contaminants with 15-20 kcal/mole binding energies in high-dose regions of the anode during the power pulse. Comparisons of parasitic ion emission simulations and experiment show agreement in some aspects; but also highlight the need for better ion source, plasma, and neutral gas models.
Date:
November 12, 1998
Creator:
Bailey, J. E.; Cuneo, M. D.; Johnson, D. J.; Mehlhorn, T. A.; Pointon, T. D.; Renk, T. J. et al.
Object Type:
Article
System:
The UNT Digital Library
Project W-320 high vacuum 241-AY-102 annulus ventilation system operability test report
This report documents the test results of OTP-320-001, Tank 241-AY-102 Annulus Ventilation System Testing. Included in the appendices are: (1) Supporting documentation prepared to demonstrate the structural integrity of the tank at high annulus vacuum (<20 INWG), and (2) a report that identifies potential cross connections between the primary and annulus ventilation systems. These cross connections were verified to be eliminated prior to the start of testing.
Date:
March 12, 1998
Creator:
Bailey, J. W.
Object Type:
Report
System:
The UNT Digital Library
News Bulletin (Castroville, Tex.), Vol. 39, No. 11, Ed. 1 Thursday, March 12, 1998
Weekly newspaper from Castroville, Texas that includes local, state, and national news along with extensive advertising.
Date:
March 12, 1998
Creator:
Barnes, Thomas
Object Type:
Newspaper
System:
The Portal to Texas History
News Bulletin (Castroville, Tex.), Vol. 39, No. 46, Ed. 1 Thursday, November 12, 1998
Weekly newspaper from Castroville, Texas that includes local, state, and national news along with extensive advertising.
Date:
November 12, 1998
Creator:
Barnes, Thomas
Object Type:
Newspaper
System:
The Portal to Texas History
Data quality objectives for the B-Cell waste stream classification sampling
This document defines the data quality objectives, (DQOS) for sampling the B-Cell racks waste stream. The sampling effort is concentrated on determining a ratio of Cs-137 to Sr-90 and Cs-137 to transuranics (TRU). Figure 1.0 shows the logic path of sampling effort. The flow chart begins with sample and data acquisition and progresses toward (a) statistical confidence and waste classification boundaries, (b) management decisions based on the input parameters and technical methods available, and (c) grout container volume/weight limits and radiation limits. The end result will be accurately classifying the B-Cell rack waste stream.
Date:
May 12, 1998
Creator:
Barnett, J. M.
Object Type:
Report
System:
The UNT Digital Library
Small Inorganic Scintillators as Neutron Detectors
Small organic scintillators that exhibit pulse shape differences (PSD) in response to charged particles have been investigated as possible neutron detectors in the energy range from 1 to 200 MeV. Neutrons in this energy range can induce reactions such as (n,p) and (n,alpha) in these scintillators, and the cross sections for these reactions vary with energy. Pulse-height and PSD distributions were measured as a function of neutron energy for small crystals of NaI(Tl) and CsI(Tl) at the LANSCE-WNR pulsed spallation neutron source. PSD information indicating the relative numbers of protons and alphas produced can give information about the neutron spectrum in fast-neutron radiation fields such as those encountered in space exploration.
Date:
May 12, 1998
Creator:
Bartle, C. M. & Haight, R. C.
Object Type:
Article
System:
The UNT Digital Library
In-Situ Sample Preparation for Radiochemical Analyses of Surface Water
A new method for improved radionuclide sample analysis of surface water has been demonstrated at the Savannah River Site, a U.S. Department of Energy production facility, currently in standby. The method makes uses of selective solid phase extraction (SPE) disks being placed in a modified portable aqueous sampler.
Date:
November 12, 1998
Creator:
Beals, D.M.; Crandall, B. S. & Fledderman, P. D.
Object Type:
Article
System:
The UNT Digital Library
Elastic wave propagation and attenuation in a double-porosity dual-permeability medium
To account for large-volume low-permeability storage porosity and low-volume high-permeability fracture/crack porosity in oil and gas reservoirs, phenomenological equations for the poroelastic behavior of a double porosity medium have been formulated and the coefficients in these linear equations identified. The generalization from a single porosity model increases the number of independent inertial coefficients from three to six, the number of independent drag coefficients from three to six, and the number of independent stress-strain coefficients from three to six for an isotropic applied stress and assumed isotropy of the medium. The analysis leading to physical interpretations of the inertial and drag coefficients is relatively straightforward, whereas that for the stress-strain coefficients is more tedious. In a quasistatic analysis, the physical interpretations are based upon considerations of extremes in both spatial and temporal scales. The limit of very short times is the one most relevant for wave propagation, and in this case both matrix porosity and fractures are expected to behave in an undrained fashion, although our analysis makes no assumptions in this regard. For the very long times more relevant for reservoir drawdown, the double porosity medium behaves as an equivalent single porosity medium. At the macroscopic spatial level, the pertinent …
Date:
October 12, 1998
Creator:
Berryman, J.G. & Wang, H.F.
Object Type:
Article
System:
The UNT Digital Library
Tax Code Termination Act: A Fact Sheet
This report discusses the Tax Code Termination Act, which would “sunset” (repeal) the Internal Revenue Code of 1986 on December 31, 2002 and would require that any new federal tax system that is adopted be approved not later than July 4, 2002.
Date:
August 12, 1998
Creator:
Bickley, James M.
Object Type:
Report
System:
The UNT Digital Library