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738 Matching Results
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PROPOSAL FOR A SILICON VERTEX TRACKER (VTX) FOR THE PHENIX EXPERIMENT.
We propose the construction of a Silicon Vertex Tracker (VTX) for the PHENIX experiment at RHIC. The VTX will substantially enhance the physics capabilities of the PHENIX central arm spectrometers. Our prime motivation is to provide precision measurements of heavy-quark production (charm and beauty) in A+A, p(d)+A, and polarized p+p collisions. These are key measurements for the future RHIC program, both for the heavy ion program as it moves from the discovery phase towards detailed investigation of the properties of the dense nuclear medium created in heavy ion collisions, and for the exploration of the nucleon spin-structure functions. In addition, the VTX will also considerably improve other measurements with PHENIX. The main physics topics addressed by the VTX are: (1) Hot and dense strongly interacting matter--Potential enhancement of charm production; Open beauty production; Flavor dependence of jet quenching and QCD energy loss; Accurate charm reference for quarkonium; Thermal dilepton radiation; High p{sub T} phenomena with light flavors above 10-15 GeV/c in p{sub T}; and Upsilon spectroscopy in the e{sup +}e{sup -} decay channel. (2) Gluon spin structure of the nucleon--{Delta}G/G with charm; {Delta}G/G with beauty; and x dependence of {Delta}G/G with {gamma}-jet correlations. (3) Nucleon structure in nuclei--Gluon shadowing over …
Date:
March 30, 2004
Creator:
AKIBA,Y.
Object Type:
Report
System:
The UNT Digital Library
Hydrogen Storage Properties of Magnesium Base Nanostructured Composite Materials
In this work, nanostructured composite materials have been synthesized using the mechanical alloying process. The new materials produced have been investigated by X-ray diffraction (XRD), transition electron microscope (TEM), scanning electron microscope (SEM) and electron energy dispersion spectrum (EDS) for their phase compositions, crystal structure, grain size, particle morphology and the distribution of catalyst element. Hydrogen storage capacities and the hydriding-dehydriding kinetics of the new materials have been measured at different temperatures using a Sieverts apparatus. It is observed that mechanical alloying accelerates the hydrogenation kinetics of the magnesium based materials at low temperature, but a high temperature must be provided to release the absorbed hydrogen from the hydrided magnesium based materials. It is believed that the dehydriding temperature is largely controlled by the thermodynamic configuration of magnesium hydride. Doping Mg-Ni nano/amorphous composite materials with lanthanum reduces the hydriding and dehydriding temperature. Although the stability of MgH2 can not be easily reduced by ball milling alone, the results suggest the thermodynamic properties of Mg-Ni nano/amorphous composite materials can be alternated by additives such as La or other effective elements. Further investigation toward understanding the mechanism of additives will be rewarded.
Date:
April 30, 2004
Creator:
AU, M
Object Type:
Article
System:
The UNT Digital Library
Electricity: The Road Toward Restructuring
The Public Utility Holding Company Act of 1935 (PUHCA) and the Federal Power Act (FPA) were enacted to eliminate unfair practices and other abuses by electricity and gas holding companies by requiring federal control and regulation of interstate public utility holding companies. Comprehensive energy legislation has passed the House and Senate. The House passed H.R. 6 on April 11, 2003. On July 31, 2003, the Senate suspended debate on S. 14, inserted the text of H.R. 4 (107th Congress) as a substitute, and passed H.R. 6. A conference agreement was reached November 17, 2003, and passed by the House the next day. H.R. 6 includes an electricity title that would, in part, repeal PUHCA, would prospectively repeal the mandatory purchase requirement under PURPA, and would create an electric reliability organization. On June 15, 2004, H.R. 4503, a comprehensive energy policy bill, passed the House.
Date:
September 30, 2004
Creator:
Abel, Amy & Parker, Larry
Object Type:
Report
System:
The UNT Digital Library
Analysis of Premixed Charge Compression Ignition Combustion with a Sequential Fluid Mechanics-Multizone Chemical Kinetics Model
We have developed a methodology for analysis of PCCI engines that applies to conditions in which there is some stratification in the air-fuel distribution inside the cylinder at the time of combustion. Our analysis methodology consists of two stages: first, a fluid mechanics code is used to determine temperature and equivalence ratio distributions as a function of crank angle, assuming motored conditions. The distribution information is then used for grouping the mass in the cylinder into a two-dimensional (temperature-equivalence ratio) array of zones. The zone information is then handed on to a detailed chemical kinetics model that calculates combustion, emissions and engine efficiency information. The methodology applies to situations where chemistry and fluid mechanics are weakly linked. The results of the multi-zone model have been compared to the results obtained from a fully integrated code, in which a chemical kinetics code is directly linked into a fluid mechanics code to calculate chemistry in every cell of the grid. The results show that the multi-zone model predicts burn duration and peak cylinder pressure with good accuracy. However, ignition timing predicted by the multi-zone model is sensitive to the transition angle between the fluid mechanics code and the chemical kinetics code. The …
Date:
September 30, 2004
Creator:
Aceves, S. M.; Flowers, D. L.; Espinosa-Loza, F.; Babajimopoulos, A. & Assanis, D. N.
Object Type:
Article
System:
The UNT Digital Library
Analysis of Homogeneous Charge Compression Ignition (HCCI) Engines for Cogeneration Applications
This paper presents an evaluation of the applicability of Homogeneous Charge Compression Ignition Engines (HCCI) for small-scale cogeneration (less than 1 MWe) in comparison to five previously analyzed prime movers. The five comparator prime movers include stoichiometric spark-ignited (SI) engines, lean burn SI engines, diesel engines, microturbines and fuel cells. The investigated option, HCCI engines, is a relatively new type of engine that has some fundamental differences with respect to other prime movers. Here, the prime movers are compared by calculating electric and heating efficiency, fuel consumption, nitrogen oxide (NOx) emissions and capital and fuel cost. Two cases are analyzed. In Case 1, the cogeneration facility requires combined power and heating. In Case 2, the requirement is for power and chilling. The results show that the HCCI engines closely approach the very high fuel utilization efficiency of diesel engines without the high emissions of NOx and the expensive diesel fuel. HCCI engines offer a new alternative for cogeneration that provides a unique combination of low cost, high efficiency, low emissions and flexibility in operating temperatures that can be optimally tuned for cogeneration systems. HCCI engines are the most efficient technology that meets the oncoming 2007 CARB NOx standards for cogeneration …
Date:
April 30, 2004
Creator:
Aceves, S; Martinez-Frias, J & Reistad, G
Object Type:
Article
System:
The UNT Digital Library
Atmospheric Radiation Measurement Program Science Plan Current Status and Future Directions of the ARM Science Program
The Atmospheric Radiation Measurement (ARM) Program has matured into one of the key programs in the U.S. Climate Change Science Program. The ARM Program has achieved considerable scientific success in a broad range of activities, including site and instrument development, atmospheric radiative transfer, aerosol science, determination of cloud properties, cloud modeling, and cloud parameterization testing and development. The focus of ARM science has naturally shifted during the last few years to an increasing emphasis on modeling and parameterization studies to take advantage of the long time series of data now available. During the next 5 years, the principal focus of the ARM science program will be to: • Maintain the data record at the fixed ARM sites for at least the next five years. • Improve significantly our understanding of and ability to parameterize the 3-D cloud-radiation problem at scales from the local atmospheric column to the global climate model (GCM) grid square. • Continue developing techniques to retrieve the properties of all clouds, with a special focus on ice clouds and mixed-phase clouds. • Develop a focused research effort on the indirect aerosol problem that spans observations, physical models, and climate model parameterizations. • Implement and evaluate an operational …
Date:
October 30, 2004
Creator:
Ackerman, TP; Genio, AD Del; Ellingson, RG; Ferrare, RA; Klein, SA; McFarquhar, GM et al.
Object Type:
Report
System:
The UNT Digital Library
Hydrogen Storage in metal-modified single-walled carbon nanotubes
It has been known for over thirty years that potassium-intercalated graphites can readily adsorb and desorb hydrogen at {approx}1 wt% at 77 K. These levels are much higher than can be attained in pure graphite, owing to a larger thermodynamic enthalpy of adsorption. This increased enthalpy may allow hydrogen sorption at higher temperatures. Potassium has other beneficial effects that enable the design of a new material: (a) Increased adsorption enthalpy in potassium-intercalated graphite compared to pure graphite reduces the pressure and increases the temperature required for a given fractional coverage of hydrogen adsorption. We expect the same effects in potassium-intercalated SWNTs. (b) As an intercalant, potassium separates c-axis planes in graphite. Potassium also separates the individual tubes of SWNTs ropes producing swelling and increased surface area. Increased surface area provides more adsorption sites, giving a proportionately higher capacity. The temperature of adsorption depends on the enthalpy of adsorption. The characteristic temperature is roughly the adsorption enthalpy divided by Boltzmann's constant, k{sub B}. For the high hydrogen storage capacity of SWNTs to be achieved at room temperature, it is necessary to increase the enthalpy of adsorption. Our goal for this project was to use metal modifications to the carbon surface of …
Date:
April 30, 2004
Creator:
Ahn, Dr.
Object Type:
Report
System:
The UNT Digital Library
Sandia National Laboratories Laboratory Directed Research and Development Program Annual Report: 2003
None
Date:
July 30, 2004
Creator:
Al-Ayat, R
Object Type:
Report
System:
The UNT Digital Library
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 39, Ed. 1 Thursday, September 30, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
September 30, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 51, Ed. 1 Thursday, December 30, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
December 30, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Fabrication of Mo/Cu Multilayer and Bilayer Transition Edge Sensors
We are developing cryogenic high-resolution x-ray, {gamma}-ray and neutron spectrometers based on superconducting Mo/Cu transition edge sensors. Here we discuss the sensor design for different applications, present the photolithographic fabrication techniques, and outline future detector development to increase spectrometer sensitivity.
Date:
September 30, 2004
Creator:
Ali, Z. A.; Drury, O. B.; Cunningham, M. F.; Chesser, J. M.; Barbee, T. W., Jr. & Friedrich, S.
Object Type:
Article
System:
The UNT Digital Library
Thermodynamics and Structure of Plutonium Alloys
The goal of this project was to investigate the chemical and structural effects of gallium and impurity elements, iron and nickel, on the phase behavior and crystallography of Pu-Ga alloys. This was done utilizing a theoretical chemical approach to predict binary and ternary alloy energetics, phase stability, and transformations. The modeling results were validated with experimental data derived from the synthesis of selected alloys and advanced characterization tools. The ultimate goal of this work was to develop a robust predictive capability for studying the thermodynamics and the structure-properties relationships in complex materials of high relevance to the Laboratory and DOE mission.
Date:
January 30, 2004
Creator:
Allen, P G; Turchi, P A & Gallegos, G F
Object Type:
Report
System:
The UNT Digital Library
A Hydrologic-Geophysical Method for Characterizing Flow and Transport Processes within the Vadose Zone
The research objective of this project is to analyze the resolution of two different geophysical imaging techniques (electrical resistivity tomography and cross-borehole ground penetrating radar) for monitoring subsurface flow and transport processes within the vadose zone. This is being accomplished through a coupled approach involving large scale unsaturated flow modeling, petrophysical conversion of the resulting hydrologic properties to a geophysical property model and generation of synthetic geophysical data, followed by the inversion of the synthetic geophysical data. The resolution, benefits, and limitations of the geophysical techniques will then be ascertained through analysis and comparison of the images to the original hydrologic model. In addition, increasing levels of complexity will be added to the models as the project progresses through the addition of heterogeneity in the original hydrologic property model, and through uncertainty in the petrophysical relationship that couples the geophysical model to the hydrologic simulation.
Date:
June 30, 2004
Creator:
Alumbaugh, David L. & Brainard, James R.
Object Type:
Report
System:
The UNT Digital Library
Extractor Configurations for a Heavy Ion Fusion Volume Source
In order for volume sources to deliver the current (e.g., 0.8 A of Ar{sup +} per module) and brightness necessary for heavy ion fusion (HIF), they must operate at high current density. Conventional extractor designs for 1 to 2 MeV run into voltage breakdown limitations and cannot easily produce the required current rise time (about one microsecond). We discuss two systems that can overcome these volume-extraction problems. Each uses multichannel preaccelerators followed by a single channel main accelerator. Fast beam switching is done in the low energy beamlet stages. A new design, utilizing concentric ring preaccelerators, was recently described for another application [2]. A more conventional design uses a large number of small round beamlets. In either case, the merging beamlets are angled toward the axis, a feature that dominates other focusing. By suitable adjustment of the individual angles, beam aberrations are reduced. Because of the high current density, the overall structure is compact. Emittance growth from merging of beamlets is calculated and scaling is discussed.
Date:
August 30, 2004
Creator:
Anderson, O. A.
Object Type:
Article
System:
The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 105, No. 273, Ed. 1 Friday, January 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
January 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 105, No. 324, Ed. 1 Tuesday, March 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
March 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 26, Ed. 1 Friday, April 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
April 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 51, Ed. 1 Sunday, May 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
May 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 78, Ed. 1 Wednesday, June 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
June 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 103, Ed. 1 Friday, July 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
July 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 129, Ed. 1 Monday, August 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
August 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 156, Ed. 1 Thursday, September 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
September 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 201, Ed. 1 Tuesday, November 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
November 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 227, Ed. 1 Thursday, December 30, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
December 30, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History