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Pressure-induced Breaking of Equilibrium Flux Surfaces in the W7AS Stellarator

Description: Calculations are presented for two shots in the W7AS stellarator which differ only in the magnitude of the current in the divertor control coil, but have very different values of experimentally attainable β (<β> ≈ 2.7% versus <β> ≈ 1.8%). Equilibrium calculations find that a region of chaotic magnetic field line trajectories fills approximately the outer 1/3 of the cross-section in each of these configurations. The field lines in the stochastic region are calculated to behave as if the flux surfaces are broken only locally near the outer midplane and are preserved elsewhere. The calculated magnetic field line diffusion coefficients in the stochastic regions for the two shots are consistent with the observed differences in the attainable β, and are also consistent with the differences in the reconstructed pressure profiles.
Date: April 24, 2007
Creator: A. Reiman, M.C. Zarnstorff, D. Monticello, A. Weller, J. Geiger, and the W7-AS Team
Partner: UNT Libraries Government Documents Department

NUCLEAR WASTE GLASSES CONTINUOUS MELTING AND BULK VITRIFICAITON

Description: This contribution addresses various aspects of nuclear waste vitrification. Nuclear wastes have a variety of components and composition ranges. For each waste composition, the glass must be formulated to possess acceptable processing and product behavior defined in terms of physical and chemical properties that guarantee the glass can be easily made and resist environmental degradation. Glass formulation is facilitated by developing property-composition models, and the strategy of model development and application is reviewed. However, the large variability of waste compositions presents numerous additional challenges: insoluble solids and molten salts may segregate; foam may hinder heat transfer and slow down the process; molten salts may accumulate in container refractory walls; the glass on cooling may precipitate crystalline phases. These problems need targeted exploratory research. Examples of specific problems and their possible solutions are discussed.
Date: March 24, 2008
Creator: AA, KRUGER & PR, HRMA
Partner: UNT Libraries Government Documents Department

Using Cytochrome c{sub 3} to Make Selenium Nanowires

Description: We report on a new method to make nanostructures, in this case selenium nanowires, in aqueous solution at room temperature. We used the protein cytochrome c{sub 3} to reduce selenate (SeO{sub 4}{sup 2{minus}}) to selenium (Se{sup 0}). Cytochrome c{sub 3} is known for its ability to catalyze reduction of metals including U{sup VI} {yields} U{sup IV}, Cr{sup VI} {yields} Cr{sup III}, Mo{sup VI} {yields} Mo{sup IV}, Cu{sup II} {yields} Cu{sup 0}, Pb{sup II} {yields} Pb{sup 0}, Hg{sup II} {yields} Hg{sup 0}. Nanoparticles of Se{sup 0} precipitated from an aqueous solution at room temperature, followed by spontaneous self-assembling into nanowires. Cytochrome c{sub 3} was extracted from the sulfate-reducing bacteria Desulfovibrio vulgaris (strain Holdenborough) and isolated by the procedure of DerVartanian and Legall.
Date: November 24, 1999
Creator: ABDELOUAS,A.; FRANCO,R.; GONG,W.L.; LUTZE,W.; MOURA,I. & SHELNUTT,JOHN A.
Partner: UNT Libraries Government Documents Department

Micro-Grooving and Micro-Threading Tools for Fabricating Curvilinear Features

Description: This paper presents techniques for fabricating microscopic, curvilinear features in a variety of workpiece materials. Micro-grooving and micro-threading tools having cutting widths as small as 13 {micro}m are made by focused ion beam sputtering and used for ultra-precision machining. Tool fabrication involves directing a 20 keV gallium beam at polished cylindrical punches made of cobalt M42 high-speed steel or C2 tungsten carbide to create a number of critically aligned facets. Sputtering produces rake facets of desired angle and cutting edges having radii of curvature equal to 0.4 {micro}m. Clearance for minimizing frictional drag of a tool results from a particular ion beam/target geometry that accounts for the sputter yield dependence on incidence angle. It is believed that geometrically specific cutting tools of this dimension have not been made previously. Numerically controlled, ultra-precision machining with micro-grooving tools results in a close match between tool width and feature size. Microtools are used to machine 13 {micro}m wide, 4 {micro}m deep, helical grooves in polymethyl methacrylate and 6061 Al cylindrical workplaces. Micro-grooving tools are also used to fabricate sinusoidal cross-section features in planar metal samples.
Date: July 24, 2000
Creator: ADAMS,DAVID P.; VASILE,MICHAEL J. & KRISHNAN,A.S.M.
Partner: UNT Libraries Government Documents Department

Sorption of Cesium From Aqueous Waste Solution on SuperLig 644 Resin

Description: The removal of cesium from aqueous waste solution was investigated in a column setup using SuperLig(R) 644 resin. The resin was significantly coarser in size than those used in previous studies because of hydraulic problems encountered during pilot-scale tests. The bed volume (BV = 140) at the onset of breakthrough surpassed the design requirement of 100 BV at 50 percent breakthrough. The percent of cesium removed by the resin at the onset of breakthrough was 99.96. The elution of cesium with 0.5 M HNO3 was satisfactory with a peak BV of 2.5. The elution BV for C/Co = 0.01 was 10, which is less than the target of 15 BV. The percent of sorbed cesium eluted from the resin was 99.88 percent. In addition, the BV of the various solutions used for the supporting process steps (feed displacement, post-feed displacement rinse, post-elution rinse, and regeneration) of the cesium ion exchange system was sufficient.
Date: August 24, 2004
Creator: ADU-WUSU, KOFI
Partner: UNT Libraries Government Documents Department

DESIGN AND STATUS OF THE VISA II EXPERIMENT.

Description: VISA II is the follow-up project to the successful Visible to Infrared SASE Amplifier (VISA) experiment at the Accelerator Test Facility (ATF) in Brookhaven National Lab (BNL). This paper will report the motivation for and status of the two main experiments associated with the VISA II program. One goal of VISA II is to perform an experimental study of the physics of a chirped beam SASE FEL at the upgraded facilities of the ATF. This requires a linearization of the transport line to preserve energy chirping of the electron beam at injection. The other planned project is a strong bunch compression experiment, where the electron bunch is compressed in the chicane, and the dispersive beamline transport, allowing studies of deep saturation.
Date: March 24, 2004
Creator: ANDONIAN,G. BABZIEN,MLBEN-ZVI,I. YAKIMENKO,Y. ET AL.
Partner: UNT Libraries Government Documents Department

HANFORD REGULATORY EXPERIENCE REGULATION AT HANFORD A CASE STUDY

Description: Hanford has played a pivotal role in the United States' defense for more than 60 years, beginning with the Manhattan Project in the 1940s. During its history, the Hanford Site has had nine reactors producing plutonium for the United States' nuclear weapons program. All the reactors were located next to the Columbia River and all had associated low-level radioactive and hazardous waste releases. Site cleanup, which formally began in 1989 with the signing of the Hanford Federal Facility Agreement and Consent Order, also known as the Tri-Party Agreement, involves more than 1,600 waste sites and burial grounds, and the demolition of more than 1,500buildings and structures, Cleanup is scheduled to be complete by 2035. Regulatory oversight of the cleanup is being performed by the U.S. Environmental Protection Agency (EPA) and the Washington State Department of Ecology(Ecology) under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Revised Code of Washington, 'Hazardous Waste Management.' Cleanup of the waste sites and demolition of the many buildings and structures generates large volumes of contaminated soil, equipment, demolition debris, and other wastes that must be disposed of in a secure manner to prevent further environmental degradation. From a risk perspective, it is essential the cleanup waste be moved to a disposal facility located well away from the Columbia River. The solution was to construct very large engineered landfill that meets all technical regulatory requirements, on the Hanford Site Central Plateau approximately 10kilometers from the river and 100metersabovegroundwater. This landfill, called the Environmental Restoration Disposal Facility or ERDF is a series of cells, each 150x 300 meters wide at the bottom and 20 meters deep. This paper looks at the substantive environmental regulations applied to ERDF, and how the facility is designed to protect the environment and meet regulatory requirements. The paper describes ...
Date: September 24, 2007
Creator: AR, HAWKINS
Partner: UNT Libraries Government Documents Department

Recent Advances in High-Pressure Equation-of-State Capabilities

Description: For many scientific and programmatic applications, it is necessary to determine the shock compression response of materials to several tens of Mbar. In addition, a complete EOS is often needed in these applications, which requires that shock data be supplemented with other information, such as temperature measurements or by EOS data off the principal Hugoniot. Recent developments in the use of fast pulsed power techniques for EOS studies have been useful in achieving these goals. In particular, the Z accelerator at Sandia National Laboratories, which develops over 20 million amperes of current in 100-200 ns, can be used to produce muM-Mbar shock pressures and to obtain continuous compression data to pressures exceeding 1 Mbar. With this technique, isentropic compression data have been obtained on several materials to pressures of several hundred kbar. The technique has also been used to launch ultra-high velocity flyer plates to a maximum velocity of 14 km/s, which can be used to produce impact pressures of several Mbar in low impedance materials and over 10 Mbar in high impedance materials. The paper will review developments in both of these areas.
Date: July 24, 2000
Creator: ASAY,JAMES R.; HALL,CLINT A. & KNUDSON,MARCUS D.
Partner: UNT Libraries Government Documents Department

Condition Monitoring of a Thermally Aged HTPB/IPDI Elastomer by NMR CP Recovery Times

Description: A hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer is commonly used as propellant binder material. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. The aging of these binders can be monitored by mechanical property measurements such as modulus or tensile elongation. These techniques, however, are not easily adapted to binder agents that are dispersed throughout a propellant. In this paper the authors investigated solid state NMR relaxation times as a means to predict the mechanical properties of the binder as a function of aging time. {sup 1}H spin-lattice and spin-spin relaxation times were found to be insensitive to the degree of thermal degradation of the elastomer. Apparently these relaxation times depend on localized motions that are only weakly correlated with mechanical properties. A strong correlation was found between the {sup 13}C cross-polarization (CP) NMR time constant, T{sub cp}, and the tensile elongation at break of the elastomer as a function of aging time. A ramped-amplitude CP experiment was shown to be less sensitive to imperfections in setting critical instrumental parameters for this mobile material.
Date: July 24, 2000
Creator: ASSINK,ROGER A.; LANG,DAVID & CELINA,MATHIAS C.
Partner: UNT Libraries Government Documents Department

Heavy-Duty Emissions Control: Plasma-Facilitated vs Reformer-Assisted Lean NOx Catalysis

Description: Progress has been made in the control of combustion processes to limit the formation of environmentally harmful species, but lean burn vehicles, such as those powered by diesel engines used for the majority of commercial trucking and off-road applications, remain a major source of nitrogen oxides (NOx) and particulate matter (PM) emissions. Tighter control of the combustion process coupled with exhaust gas recirculation has brought emissions in line with 2004 targets worldwide. Additional modifications to the engine control system, somewhat limited NOx control, and PM filters will likely allow the 2007 limits to be met for the on-highway regulations for heavy-duty engines in the United States. Concern arises when the NOx emission limit of 0.2 g/bhphr set for the year 2010 is considered.
Date: August 24, 2003
Creator: Aardahl, C. L.; Rozmiarek, R. T.; Rappe, K. G.; Mendoza, D. P. & Park, P. W.
Partner: UNT Libraries Government Documents Department

Effects of Hydrogen Implantation into GaN

Description: Proton implantation in GaN is found to reduce the free carrier density through two mechanisms - first, by creating electron and hole traps at around Ec-0.8eV and Ev+0.9eV that lead to compensation in both n- and p-type material, and second, by leading to formation of (AH)O complexes, where A is any acceptor (Mg, Ca, Zn, Be, Cd). The former mechanism is usefid in creating high resistivity regions for device isolation, whereas the latter produces unintentional acceptor passivation that is detrimental to device performance. The strong affinity of hydrogen for acceptors leads to markedly different redistribution behavior for implanted in n- and p-GaN due to the chemical reaction to form neutral complexes in the latter. The acceptors may be reactivated by simple annealing at 2600{degrees}C, or by electron injection at 25-150{degrees}C that produces debonding of the (AH) centers. Implanted hydrogen is also strongly attracted to regions of strain in heterostructure samples during annealing, leading to pile-up at epi-epi and epi-substrate interfaces. II? spectroscopy shows that implanted hydrogen also decorates VG, defects in undoped and n-GaN.
Date: December 24, 1998
Creator: Abernathy, C.R.; Han, J.; Pearton, S.J.; Shul, R.J.; Song, C.Y.; Stavola, M. et al.
Partner: UNT Libraries Government Documents Department

Depth Measurement of Moving Slurry at the Wet End of a Paper Machine

Description: The paper industry has long had a need to better understand and control its papermaking process upstream, specifically at the wet end in the forming section of a paper machine. A vision-based system is under development that addresses this need by automatically measuring and interpreting the pertinent paper web parameters at the wet end in real time. The wet-end characterization of the paper web by a vision system involves a four-dimensional measurement of the slurry in real time. These measurements include the two-dimensional spatial information, the intensity profile, and the depth profile. This paper describes the real-time depth profile measurement system for the high-speed moving slurry. A laser line-based measurement method is used with a high-speed programmable camera to directly measure slurry height. The camera is programmed with a profile algorithm, producing depth data at fast sampling rates. Analysis and experimentation have been conducted to optimize the system for the characteristics of the slurry and laser line image. On-line experimental results are presented.
Date: January 24, 1999
Creator: Abidi, B.R.; Goddard, J.S., Jr.; Hunt, M.A.; Sari-Sarraf, H. & Turner, J.C.
Partner: UNT Libraries Government Documents Department

A METHODOLOGY FOR DETERMINING THE DOSE RATE FOR BOUNDING MASS LIMITS IN A 9977 PACKAGING

Description: The Small Gram Quantity (SGQ) concept is based on the understanding that the hazards associated with the shipment of a radioactive material are directly proportional to its mass. This study describes a methodology that estimates the acceptable masses for several neutron and gamma emitting isotopes that can be shipped in a 9977 Package compliant with the Title 10 of the Code of Federal Regulations, Part 71 (10CFR71) external radiation level limits. 10CFR71.33 states that a shipping application identifies the radioactive and fissile materials at their maximum quantity and provides an evaluation demonstrating compliance with the external radiation standards. Since rather small amounts of some isotopes emit sufficiently strong radiation to produce a large external dose rate, quantifying of the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. A methodology was established for determining the dose rate for bounding mass limits for a set of isotopes in the Model 9977 Shipping Package. Calculations were performed to estimate external radiation levels using the MCNP radiation transport code to develop a set of response multipliers (Green's functions) for 'dose per source particle' for each neutron and photon spectral group. The source spectrum from one gram of each isotope was folded with the response multipliers to generate the dose rate per gram of each isotope in the 9977 shipping package and its associated shielded containers. The maximum amount of a single isotope that could be shipped within the regulatory limits for dose rate at the surface was determined. For a package containing a mixture of isotopes, the acceptability for shipment can be determined by a sum of fractions ...
Date: May 24, 2012
Creator: Abramczyk, G.; Bellamy, S.; Nathan, S. & Loftin, B.
Partner: UNT Libraries Government Documents Department

Comments on "Solubility and Dissolution Thermodynamic Data of Cefpiramide in Pure Solvents and Binary Solvents"

Description: Abstract: Errors are found in the mathematical correlation based on the combined Jouyban-Acree and Modified Apelblat model for describing the variation in the mole fraction solubility of cefpiramide with temperature and solvent composition for the binary aqueous-ethanol solvent system. The equation coefficents given by Tang and coworkers, when substituted into the model equation, do not yield the authors' calculated mole fraction solubilities of cefpiramide.
Date: January 24, 2018
Creator: Acree, William E. (William Eugene)
Partner: UNT College of Arts and Sciences

A Binary Segmentation Approach for Boxing Ribosome Particles in Cryo EM Micrographs

Description: Three-dimensional reconstruction of ribosome particles from electron micrographs requires selection of many single-particle images. Roughly 100,000 particles are required to achieve approximately 10 angstrom resolution. Manual selection of particles, by visual observation of the micrographs on a computer screen, is recognized as a bottleneck in automated single particle reconstruction. This paper describes an efficient approach for automated boxing of ribosome particles in micrographs. Use of a fast, anisotropic non-linear reaction-diffusion method to pre-process micrographs and rank-leveling to enhance the contrast between particles and the background, followed by binary and morphological segmentation constitute the core of this technique. Modifying the shape of the particles to facilitate segmentation of individual particles within clusters and boxing the isolated particles is successfully attempted. Tests on a limited number of micrographs have shown that over 80 percent success is achieved in automatic particle picking.
Date: June 24, 2003
Creator: Adiga, Umesh P. S.; Malladi, Ravi; Baxter, William & Glaeser, Robert M.
Partner: UNT Libraries Government Documents Department

Underground Corrosion of Activated Metals in an Arid Vadose Zone Environment

Description: The subsurface radioactive disposal site located at the Idaho National Engineering and Environmental Laboratory contains neutron-activated metals from nonfuel nuclear-reactor- core components. A long-term corrosion test is being conducted to obtain site-specific corrosion rates to support efforts to more accurately estimate the transfer of activated elements in an arid vadose zone environment. The tests use nonradioactive metal coupons representing the prominent neutron-activated material buried at the disposal location, namely, Type 304L stainless steel, Type 315L stainless steel, nickel-chromium alloy (UNS NO7718), beryllium, aluminum 6061-T6, and a zirconium alloy, (UNS R60804). In addition, carbon steel (the material presently used in the cask disposal liners and other disposal containers) and a duplex stainless steel (UNS S32550) (the proposed material for the high- integrity disposal containers) are also included in the test program. This paper briefly describes the test program and presents the early corrosion rate results after 1 year and 3 years of underground exposure.
Date: October 24, 2001
Creator: Adler Flitton, M.K; Mizia, R.E. & Bishop, C.W.
Partner: UNT Libraries Government Documents Department

The Ghanaian Approach to the Development of an Effective Waste Management Regime

Description: In Ghana, radioactive waste is generated mainly from spent sealed sources, various nuclear applications--diagnostic and therapeutic procedures in medicine and measurement and processing techniques in industry. The radionuclide composition in the waste arising from industry, research and teaching includes 14C, 137Cs, 60Co, 241Am, 3H, 32P, 125I, 192Ir, 131I, 99m Tc, 35S and 90Sr. Ghana is strengthening its radioactive waste management infrastructure, which include the development of a legal framework by providing laws, regulations and guidelines and allocating responsibilities of waste generators, the National Radioactive Waste Management Centre (NRWMC), and the Radiation Protection Board (RPB). The radioactive waste management regulations which is in it's final stage of promulgation set up the basic technical and organizational requirements to be complied with by waste generators and operators of waste management facilities and make provisions for penalties for non-compliance with the regulations. With the installation of a 30 kW Research Reactor for neutron activation analysis, 185 TBq 60Co facility for the treatment of cancer at the Korle-bu teaching hospital, 1850 TBq 60Co facility for irradiation of medical and agricultural products and 192Ir sources for industrial radiography, radioactive waste is expected to increase in the near future. At present, waste management is limited exclusively to decay, storage and permissible discharge for liquid waste. Radiation sources and radioactive waste inventory have also been established using the Regulatory Authority Information System (RAIS) and the Sealed Radiation Sources Registry System (SRS). Considering the gradual increase in the generation of radioactive waste, there the need to strengthen the infrastructure for the management of radioactive waste in Ghana. A new working group made up of scientists and technicians with experience in working with ionizing radiation has been formed. This paper will outline the measures being put in place by the NRWMC and the new working group in establishing the appropriate ...
Date: February 24, 2003
Creator: Adu, P. S.; Gbadago, J. K. & Glover, E. T.
Partner: UNT Libraries Government Documents Department

B-factory signals for a warped extra dimension

Description: We study predictions for B-physics in a class of models, recently introduced, with a non-supersymmetric warped extra dimension. In these models few ({approx} 3) TeV Kaluza-Klein masses are consistent with electroweak data due to bulk custodial symmetry. Furthermore, there is an analog of GIM mechanism which is violated by the heavy top quark (just as in SM) leading to striking signals at B-factories: (1) New Physics (NP) contributions to {Delta}F = 2 transitions are comparable to SM. This implies that, within this NP framework, the success of the SM unitarity triangle fit is a ''coincidence''. Thus, clean extractions of unitarity angles via e.g. B {yields} {pi}{pi}, {rho}{pi}, {rho}{rho}, DK are likely to be affected, in addition to O(1) deviation from SM prediction in Bs mixing. (2) O(1) deviation from SM predictions for B {yields} X{sub s}{ell}{sup +}{ell}{sup -} in rate as well as in forward-backward and direct CP asymmetry. (3) Large mixing-induced CP asymmetry in radiative B decays, wherein the SM unambiguously predicts very small asymmetries. Also, with KK masses 3 TeV or less, and with anarchic Yukawa masses, contributions to electric dipole moments of the neutron are roughly 20 times larger than the current experimental bound so that this framework has a ''CP problem''.
Date: August 24, 2004
Creator: Agashe, Kaustubh; Perez, Gilad & Soni, Amarjit
Partner: UNT Libraries Government Documents Department

Developing high brightness and high current beams for HIF injectors

Description: The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to continue pursuing the traditional approach of large surface ionization sources or to adopt a multiaperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source concept, the recent commissioning of the 2-MeV injector for the High Current eXperiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multiaperture approach, we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress in these areas will be discussed as well as plans for future experiments.
Date: May 24, 2002
Creator: Ahle, Larry; Grote, Dave & Kwan, Joe
Partner: UNT Libraries Government Documents Department

Neutrino observations from the Sudbury Neutrino Observatory

Description: The Sudbury Neutrino Observatory (SNO) is a water imaging Cherenkov detector. Its usage of 1000 metric tons of D{sub 2}O as target allows the SNO detector to make a solar-model independent test of the neutrino oscillation hypothesis by simultaneously measuring the solar {nu}{sub e} flux and the total flux of all active neutrino species. Solar neutrinos from the decay of {sup 8}B have been detected at SNO by the charged-current (CC) interaction on the deuteron and by the elastic scattering (ES) of electrons. While the CC reaction is sensitive exclusively to {nu}{sub e}, the ES reaction also has a small sensitivity to {nu}{sub {mu}} and {nu}{sub {tau}}. In this paper, recent solar neutrino results from the SNO experiment are presented. It is demonstrated that the solar flux from {sup 8}B decay as measured from the ES reaction rate under the no-oscillation assumption is consistent with the high precision ES measurement by the Super-Kamiokande experiment. The {nu}{sub e} flux deduced from the CC reaction rate in SNO differs from the Super-Kamiokande ES results by 3.3{sigma}. This is evidence for an active neutrino component, in additional to {nu}{sub e}, in the solar neutrino flux. These results also allow the first experimental determination of the total active {sup 8}B neutrino flux from the Sun, and is found to be in good agreement with solar model predictions.
Date: September 24, 2001
Creator: Ahmad, Q.R.; Allen, R.C.; Andersen, T.C.; Anglin, J.D.; Barton,J.C.; Beier, E.W. et al.
Partner: UNT Libraries Government Documents Department

Top quark physics

Description: The top quark, when it was finally discovered at Fermilab in 1995 completed the three-generation structure of the Standard Model (SM) and opened up the new field of top quark physics. Viewed as just another SM quark, the top quark appears to be a rather uninteresting species. Produced predominantly, in hadron-hadron collisions, through strong interactions, it decays rapidly without forming hadrons, and almost exclusively through the single mode t {r_arrow} Wb. The relevant CKM coupling V{sub tb} is already determined by the (three-generation) unitarity of the CKM matrix. Rare decays and CP violation are unmeasurable small in the SM. Yet the top quark is distinguished by its large mass, about 35 times larger than the mass of the next heavy quark, and intriguingly close to the scale of electroweak (EW) symmetry breaking. This unique property raises a number of interesting questions. Is the top quark mass generated by the Higgs mechanism as the SM predicts and is its mass related to the top-Higgs-Yukawa coupling? Or does it play an even more fundamental role in the EW symmetry breaking mechanism? If there are new particles lighter than the top quark, does the top quark decay into them? Could non-SM physics first manifest itself in non-standard couplings of the top quark which show up as anomalies in top quark production and decays? Top quark physics tries to answer these questions. Several properties of the top quark have already been examined at the Tevatron. These include studies of the kinematical properties of top production, the measurements of the top mass, of the top production cross-section, the reconstruction of t{bar t}pairs in the fully hadronic final states, the study of {tau} decays of the top quark, the reconstruction of hadronic decays of the W boson from top decays, the search for flavor changing neutral ...
Date: March 24, 2000
Creator: Ahmadov, A.; Azuelos, G.; Bauer, U.; Belyaev, A.; Berger, E. L.; Sullivan, Z. et al.
Partner: UNT Libraries Government Documents Department

Scalable Analysis Techniques for Microprocessor Performance Counter Metrics

Description: Contemporary microprocessors provide a rich set of integrated performance counters that allow application developers and system architects alike the opportunity to gather important information about workload behaviors. These counters can capture instruction, memory, and operating system behaviors. Current techniques for analyzing data produced from these counters use raw counts, ratios, and visualization techniques to help users make decisions about their application source code. While these techniques are appropriate for analyzing data from one process, they do not scale easily to new levels demanded by contemporary computing systems. Indeed, the amount of data generated by these experiments is on the order of tens of thousands of data points. Furthermore, if users execute multiple experiments, then we add yet another dimension to this already knotty picture. This flood of multidimensional data can swamp efforts to harvest important ideas from these valuable counters. Very simply, this paper addresses these concerns by evaluating several multivariate statistical techniques on these datasets. We find that several techniques, such as statistical clustering, can automatically extract important features from this data. These derived results can, in turn, be feed directly back to an application developer, or used as input to a more comprehensive performance analysis environment, such as a visualization or an expert system.
Date: July 24, 2002
Creator: Ahn, D H & Vetter, J S
Partner: UNT Libraries Government Documents Department

Synthesis, Characterization, and Catalytic Activity of Sulfided Silico-Alumino-Titanate (Si-Al-Ti) Mixed Oxides Xerogels Supported Ni-Mo Catalyst

Description: Layered semicrystalline silico-alumino-titanate (Si-Al-Ti) mixed oxides were synthesized by a modified sol-gel method with hydrothermal synthesis temperatures less than 200 C and autogenic pressure. The solid products are semicrystalline materials with a surface area of 136-367 m{sup 2}/g and a monomodal pore size distribution with an average pore diameter of 3.6-4.7 nrn. The catalytic activity for pyrene hydrogenation in a batch reactor at 300 C and 500 psig was determined for sulfided Ni-Mo supported on the Si-Al-Ti mixed oxide. The activity was a function of the support composition the heat treatment before and after loading the active metals, the addition of organic templates, and different methods of metal loading. The most active sulfided Ni-Mo/Si-Al-Ti catalyst has an activity in the same range as the commercial catalyst, Shell 324, but the metal loading is 37% less than the commercial catalyst.
Date: February 24, 1999
Creator: Al-Adwani, H.A.; Anthony, R.G.; Gardner, T.J. & Thammachote, N.
Partner: UNT Libraries Government Documents Department