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{sup 17}O NMR Investigation of Oxidative Degradation in Polymers Under Gamma-Irradiation

Description: The {gamma}-irradiated-oxidation of pentacontane (C{sub 50}H{sub 102}) and the polymer polyisoprene was investigated as a function of oxidation level using {sup 17}O nuclear magnetic resonance (NMR) spectroscopy. It is demonstrated that by using {sup 17}O labeled O{sub 2} gas during the {gamma}-irradiation process, details about the oxidative degradation mechanisms can be directly obtained from the analysis of the {sup 17}O NMR spectra. Production of carboxylic acids is the primary oxygen-conta… more
Date: March 8, 2000
Creator: Alam, Todd M.; Celina, Mathias C.; Assink, Roger A.; Clough, Roger Lee & Gillen, Kenneth T.
Partner: UNT Libraries Government Documents Department
open access

Improvements in bis(cyclopentadienyl)magnesium purity as determined with gas chromatography-mass spectroscopy

Description: Bis(cyclopentadienyl)magnesium (MgCp2) is used commonly as a source for doping nitride materials with magnesium. Increased oxygen incorporation known to accompany the use of MgCp2 makes the purity of this precursor an important consideration in nitride CVD. Gas chromatography-mass spectroscopy (GCMS) methods have now been developed for the identification of volatile impurities in MgCp2. Diethylether, an oxygen containing organic compound (CH{sub 3}CH{sub 2}OCH{sub 2}CH{sub 3}), and additional o… more
Date: March 8, 2000
Creator: BARTRAM,MICHAEL E.
Partner: UNT Libraries Government Documents Department
open access

Development of field portable sampling and analysis systems

Description: A rapid field portable sample and analysis system has been demonstrated at the Savannah River Site and the Hanford Site. The portable system can be used when rapid decisions are needed in the field during scoping or remediation activities, or when it is impractical to bring large volumes of water to the lab for analysis.
Date: June 8, 2000
Creator: Beals, D.
Partner: UNT Libraries Government Documents Department
open access

Defect diffusion during annealing of low-energy ion-implanted silicon

Description: We present a new approach for investigating the kinetics of defect migration during annealing of low-energy, ion-implanted silicon, employing a combination of computer simulations and atomic-resolution tunneling microscopy. Using atomically-clean Si(111)-7x7 as a sink for bulk point defects created by 5 keV Xe and Ar irradiation, we observe distinct, temperature-dependent surface arrival rates for vacancies and interstitials. A combination of simulation tools provides a detailed description of … more
Date: March 8, 2000
Creator: Bedrossian, P J; Caturla, M-J & Diaz de la Rubia, T
Partner: UNT Libraries Government Documents Department
open access

Evidence for competing order parameters in the paramagnetic phase of layered manganites.

Description: The magnetic field and temperature dependence of the magnetic susceptibility and magnetization is studied for the ferromagnetic layered manganites SrO(La{sub t{minus}x}Sr{sub x}MnO{sub 3}){sub 2} in the composition range x = 0.32-0.40. In the paramagnetic phase, the susceptibility exhibits an anomalous maximum at an intermediate magnetic field value. The size of this field-induced susceptibility enhancement increases dramatically with x from 10% for x = 0.32 to 160% for x = 0.40. The temperatur… more
Date: November 8, 2000
Creator: Berger, A.; Mitchell, J. F.; Miller, D. J. & Bader, S. D.
Partner: UNT Libraries Government Documents Department
open access

Longitudinal spin dependence of massive lepton pair production

Description: In this paper, the authors summarize recent work in which they demonstrate that the Compton subprocess, q + g {r_arrow} {gamma}* + q also dominates the Drell-Yan cross section in polarized and unpolarized proton-proton reactions for values of the transverse momentum Q{sub T} of the pair that are larger than roughly half of the pair mass Q, Q{sub T} > Q/2. The Drell-Yan process is therefore a valuable, heretofore overlooked, independent source of constraints on the spin-averaged and spin-depe… more
Date: February 8, 2000
Creator: Berger, E. L.; Gordon, L. E. & Klasen, M.
Partner: UNT Libraries Government Documents Department
open access

Quench sensitivity of hot extruded 6061-T6 and 6069-T6 aluminum alloys

Description: The purpose of this study is to investigate the quench sensitivity of mechanical properties of hot extruded 6061 and 6069 aluminum alloys. The relationship between mechanical properties and quench delzty time at various temperatures between 200-500 C was determined. It was concluded that the 6069-T6 was somewhat more quench sensitive than 6061, which may be consistent with the composition difference.
Date: August 8, 2000
Creator: Bergsma, S C; Kassner, M E; Li, X & Rosen, R S
Partner: UNT Libraries Government Documents Department
open access

On combining computational differentiation and toolkits for parallel scientific computing.

Description: Automatic differentiation is a powerful technique for evaluating derivatives of functions given in the form of a high-level programming language such as Fortran, C, or C++. The program is treated as a potentially very long sequence of elementary statements to which the chain rule of differential calculus is applied over and over again. Combining automatic differentiation and the organizational structure of toolkits for parallel scientific computing provides a mechanism for evaluating derivative… more
Date: June 8, 2000
Creator: Bischof, C. H.; Buecker, H. M. & Hovland, P. D.
Partner: UNT Libraries Government Documents Department
open access

Recent plant studies using Victoria 2.0

Description: VICTORIA 2.0 is a mechanistic computer code designed to analyze fission product behavior within the reactor coolant system (RCS) during a severe nuclear reactor accident. It provides detailed predictions of the release of radioactive and nonradioactive materials from the reactor core and transport and deposition of these materials within the RCS and secondary circuits. These predictions account for the chemical and aerosol processes that affect radionuclide behavior. VICTORIA 2.0 was released i… more
Date: March 8, 2000
Creator: Bixler, Nathan E. & Gasser, Ronald D.
Partner: UNT Libraries Government Documents Department
open access

Changes in electron-phonon coupling across a bulk phase transition in copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%).

Description: We present evidence for a change in electron--phonon coupling across a bulk phase transition. Below the lattice stiffening transition at around 160 K, there is a change in the diffracted peak width observed by neutron and X-ray scattering techniques. Also, the electronic band structure of the copolymer is shifting in binding energy below 160 K, decreasing the density of states near the Fermi level. The value of the effective Debye temperature above the transition temperature is approximately 50… more
Date: November 8, 2000
Creator: Borca, C. N.; Adenwalla, S.; Choi, J.; Robertson, L.; You, H.; Fridkin, V. M. et al.
Partner: UNT Libraries Government Documents Department
open access

Mechanical Testing of EPON SU-8 With SIEM

Description: High aspect ratio structures are often present in MEMS devices and EPON SU-8 is often used to produce such structures because of its low cost. It is essential to know the mechanical properties of SU-8 for producing reliable MEMS products. However, the mechanical properties of SU-8 may depend on the manufacturing process and the size of the structure, which is in the micron domain. Hence, one needs to test specimens that are similar in size to MEMS structures to determine if the mechanical prope… more
Date: June 8, 2000
Creator: Chang, S.; Warren, J. & Chiang, F. P.
Partner: UNT Libraries Government Documents Department
open access

Nucleon Spin Structure Study at Jefferson Lab

Description: I will first review the latest development in the nucleon spin structure study with lepton- nucleon deep inelastic scattering (DIS) from high energy laboratories. I will then concentrate on the progress and plan of study of the nucleon spin structure in the low energy region. With the newly built high luminosity 6 GeV electron beam accelerator and the progress in the highly polarized electron source and highly polarized targets, new experiments are being carried out at Jefferson Lab (CEBAF) to … more
Date: November 8, 2000
Creator: Chen, Jian-ping
Partner: UNT Libraries Government Documents Department
open access

Electron irradiation effect on bubble formation and growth in a sodium borosilicate glass

Description: In this study, the authors studied simultaneous and intermittent electron irradiation effects on bubble growth in a simple sodium borosilicate glass during Xe ion implantation at 200 C. Simultaneous electron irradiation increases the average bubble size in the glass. This enhanced diffusion is also shown by the migration of Xe from bubbles into the matrix when the sample is irradiated by an electron beam after the Xe implantation.
Date: February 8, 2000
Creator: Chen, X.; Birtcher, R. C. & Donnelly, S. E.
Partner: UNT Libraries Government Documents Department
open access

Safety testing of 18650-style Li-Ion cells

Description: To address lithium-ion cell safety issues in demanding power applications, electrical and thermal abuse tests were performed on 18650 sized cells. Video and electrically monitored abuse tests in air included short circuit, forced overcharge, forced reversal, and controlled overheating (thermal) modes. Controlled overheating tests to 200 C were performed in a sealed chamber under a helium atmosphere and the gases released from the cell during thermal runaway were analyzed at regular intervals us… more
Date: June 8, 2000
Creator: Crafts, Chris C.; Borek, Theodore T., III & Mowry, Curtis Dale
Partner: UNT Libraries Government Documents Department
open access

O-d energetics scaling models for Z-pinch-driven hohlraums

Description: Wire array Z-pinches on the Z accelerator provide the most intense laboratory source of soft x-rays in the world. The unique combination of a highly-Planckian radiation source with high x-ray production efficiency (15% wall plug), large x-ray powers and energies ( >150 TW, {ge}1 MJ in 7 ns), large characteristic hohlraum volumes (0.5 to >10 cm{sup 3}), and long pulse-lengths (5 to 20 ns) may make Z-pinches a good match to the requirements for driving high-yield scale ICF capsules with ade… more
Date: June 8, 2000
Creator: Cuneo, Michael E.; Vesey, Roger A.; Hammer, J. H. & Porter, John L.
Partner: UNT Libraries Government Documents Department
open access

Shock certification of replacement subsystems and components in the presence of uncertainty

Description: In this paper a methodology for analytically estimating the response of replacement components in a system subjected to worst-case hostile shocks is presented. This methodology does not require the use of system testing but uses previously compiled shock data and inverse dynamic analysis to estimate component shock response. In the past component shock responses were determined from numerous system tests; however, with limitations on system testing, an alternate methodology for determining comp… more
Date: May 8, 2000
Creator: DOHNER,JEFFREY L. & LAUFFER,JAMES P.
Partner: UNT Libraries Government Documents Department
open access

Taming the Viper: Software Upgrade for VFAUser and Viper

Description: This report describes the procedure and properties of the software upgrade for the Vibration Performance Recorder. The upgrade will check the 20 memory cards for proper read/write operation. The upgrade was successfully installed and uploaded into the Viper and the field laptop. The memory checking routine must run overnight to complete the test, although the laptop need only be connected to the Viper unit until the downloading routine is finished. The routine has limited ability to recognize i… more
Date: August 8, 2000
Creator: DORIN,RANDALL T. & MOSER III,JOHN C.
Partner: UNT Libraries Government Documents Department
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