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1,747 Matching Results
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Cancellation of the Chromatic Effects with proper Field Profile
N/A
Date:
April 1, 2004
Creator:
A., Ruggiero
Object Type:
Report
System:
The UNT Digital Library
Simulation of a Production Facility with an Automated Transport System
A model was needed to assess material throughput and validate the conceptual design of a production facility, including equipment lists and layout. The initial desire was to use a commercially available discrete event simulation package. However, the available software was found to be too limited in capability. Database interface software was used to develop autonomous intelligent manufacturing workstations and material transporters. The initial Extend model used to assess material throughput and develop equipment lists for the preconceptual design effort was upgraded with software add-ons from Simulation Dynamics, Inc. (SDI). Use of the SDI database interface allowed the upgraded model to include: 1. a material mass balance at any level of detail required by the user, and 2. a transport system model that includes all transport system movements, time delays, and transfers between systems. This model will assist in evaluating transport system capacity, sensitive time delays in the system, and optimal operating strategies. An additional benefit of using the SDI database interface is dramatically improved run time performance. This allows significantly more runs to be completed to provide better statistics for overall plant performance. The model has all system and process parameters entered into sub-component accessible tables. All information for the …
Date:
April 7, 2004
Creator:
ABRAMCZYK, GLENN
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
Electric Utility Infrastructure Vulnerabilities: Transformers, Towers, and Terrorism
None
Date:
April 9, 2004
Creator:
Abel, Amy; Parfomak, Paul W. & Shea, Dana A.
Object Type:
Report
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
Production of e+e- Pairs Accompanied by Nuclear Dissociation in Ultra-peripheral Heavy Ion Collisions
We present the first data on e{sup +}e{sup -} pair production accompanied by nuclear breakup in ultra-peripheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order corrections to the pair production cross section should be enhanced. We compare the pair kinematic distributions with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED); the latter includes the photon virtuality. The cross section, pair mass, rapidity and angular distributions are in good agreement with both calculations. The pair transverse momentum, p{sub T}, spectrum agrees with the QED calculation, but not with the equivalent photon approach. We set limits on higher-order contributions to the cross section. The e{sup +} and e{sup -} p{sub T} spectra are similar, with no evidence for interference effects due to higher-order diagrams.
Date:
April 7, 2004
Creator:
Adams, J.; Adler, C.; Aggarwal, M. M.; Ahammed, Z.; Allgower, C.; Amonett, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Centrality and pseudorapidity dependence of charged hadron production at intermediate p{sub T} in Au+Au collisions at {radical}s{sub NN} = 130 GeV
We present STAR measurements of charged hadron production as a function of centrality in Au + Au collisions at {radical}s{sub NN} = 130 GeV. The measurements cover a phase space region of 0.2 < p{sub T} < 6.0 GeV/c in transverse momentum and -1 < {eta} < 1 in pseudorapidity. Inclusive transverse momentum distributions of charged hadrons in the pseudorapidity region 0.5 < |{eta}| < 1 are reported and compared to our previously published results for |{eta}| < 0.5. No significant difference is seen for inclusive p{sub T} distributions of charged hadrons in these two pseudorapidity bins. We measured dN/d{eta} distributions and truncated mean p{sub T} in a region of p{sub T} > p{sub T}{sup cut}, and studied the results in the framework of participant and binary scaling. No clear evidence is observed for participant scaling of charged hadron yield in the measured p{sub T} region. The relative importance of hard scattering process is investigated through binary scaling fraction of particle production.
Date:
April 15, 2004
Creator:
Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D.; Arkhipkin, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Centrality and pseudorapidity dependence of charged hadron production at intermediate p{sub t} in Au+Au collisions at {radical}s{sub NN} = 130 GeV
We present STAR measurements of charged hadron production as a function of centrality in Au + Au collisions at {radical}s{sub NN} = 130 GeV. The measurements cover a phase space region of 0.2 < p{sub T} < 6.0 GeV/c in transverse momentum and 11 < {eta} < 1 in pseudorapidity. Inclusive transverse momentum distributions of charged hadrons in the pseudorapidity region 0.5 < |{eta}| < 1 are reported and compared to our previously published results for |{eta}| < 0.5. No significant difference is seen for inclusive p{sub T} distributions of charged hadrons in these two pseudorapidity bins. We measured dN/d{eta} distributions and truncated mean p{sub T} in a region of p{sub T} > P{sub T}{sup cut}, and studied the results in the framework of participant and binary scaling. No clear evidence is observed for participant scaling of charged hadron yield in the measured pT region. The relative importance of hard scattering process is investigated through binary scaling fraction of particle production.
Date:
April 15, 2004
Creator:
Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson, B. D.; Arkhipkin, D. et al.
Object Type:
Article
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
Large batch dimensional metrology demonstrated in the example of a LIGA fabricated spring.
Deep x-ray lithography in combination with electroforming is capable of producing high precision metal parts in small lot series. This study deals with a high aspect ratio structure with overall dimensions on the order of 10 mm x 7 mm x 1.5 mm, with the smallest line width being 150 {micro}m. The lateral deviation from the design is to be kept to a minimum, preferably below 5 {micro}m. To ensure adequate quality control, a semi-automated metrology technique has been established to measure all parts. While the paper will give a brief overview of all involved techniques, it focuses on the method to measure the top and bottom of the parts and the top of geometries following the process. The instrument used is a View Engineering Voyager V6x12 microscope, which is fully programmable. The microscope allows direct measurement of geometries but also is capable of saving all captured data as point clouds. These point clouds play a central role when evaluating part geometry. After measuring the part, the point cloud is compared to the computer aided design (CAD) contour of the part, using a commercially available software package. The challenge of proper edge lighting on a nickel alloy part is evaluated …
Date:
April 1, 2004
Creator:
Aigeldinger, Georg; Skala, Dawn M. & Ceremuga, Joseph T.
Object Type:
Report
System:
The UNT Digital Library
Small Column Ion Exchange Analysis for Removal of Cesium from SRS Low Curie Salt Solutions Using Crystalline Silicotitanate (CST) Resin
Savannah River Technology Center (SRTC) researchers modeled ion exchange removal of cesium from dissolved salt waste solutions. The results assist in evaluating proposed configurations for an ion exchange process to remove residual cesium from low curie waste streams. A process for polishing (i.e., removing small amounts) of cesium may prove useful should supernate draining fail to meet the Low Curie Salt (LCS) target limit of 0.1 Ci of Cs-137 per gallon of salt solution. Cesium loading isotherms and column breakthrough curves for Low Curie dissolved salt solutions were computed to provide performance predictions for various column designs.
Date:
April 20, 2004
Creator:
Aleman, Sebastian E. & Hamm, L. L.
Object Type:
Report
System:
The UNT Digital Library
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 14, Ed. 1 Thursday, April 1, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
April 1, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 15, Ed. 1 Thursday, April 8, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
April 8, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 16, Ed. 1 Thursday, April 15, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
April 15, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 17, Ed. 1 Thursday, April 22, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
April 22, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 18, Ed. 1 Thursday, April 29, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
April 29, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
SMART SCREENING SYSTEM (S3) IN TACONITE PROCESSING
The conventional vibrating machines used in processing plants have had undesirable high noise and vibration levels. They also have had unsatisfactorily low screening efficiency, high energy consumption, high maintenance cost, low productivity, and poor worker safety. These conventional vibrating machines have been used in most every processing plant. Most of the current material separation technology uses heavy and inefficient electric motors with an unbalance rotating mass to generate the shaking. In addition to being excessively noisy, inefficient, high-maintenance, these vibrating machines are often the bottleneck in the entire process. Furthermore, these motors along with the vibrating machines and supporting structure shake other machines and structure in the vicinity. The latter increases maintenance costs while reducing worker health and safety. The conventional vibrating fine screens at taconite processing plants have had the same problems as those listed above. This has resulted in lower screening efficiency, higher energy and maintenance cost, and lower productivity and workers safety concerns. The focus of this work is on the design of a high performance screening machine suitable for taconite processing plants. SmartScreens{trademark} technology uses miniaturized motors, based on smart materials, to generate the shaking. The underlying technologies are Energy Flow Control{trademark} and Vibration Control by …
Date:
April 1, 2004
Creator:
Allaei, Daryoush & Mohammed, Asim Syed
Object Type:
Report
System:
The UNT Digital Library
Compact Optical Technique for Streak Camera Calibration
The National Ignition Facility is under construction at the Lawrence Livermore National Laboratory for the U.S. Department of Energy Stockpile Stewardship Program. Optical streak cameras are an integral part of the experimental diagnostics instrumentation. To accurately reduce data from the streak cameras a temporal calibration is required. This article describes a technique for generating trains of precisely timed short-duration optical pulses that are suitable for temporal calibrations.
Date:
April 2004
Creator:
Allen, Curt; Davies, Terence; Janson, Frans; Justin, Ronald; Marshall, Bruce; Sweningsen, Oliver et al.
Object Type:
Article
System:
The UNT Digital Library
FILTER COMPONENT ASSESSMENT--CERAMIC CANDLES--
Efforts at Siemens Westinghouse Power Corporation (SWPC) have been focused on development of hot gas filter systems as an enabling technology for advanced coal and biomass-based gas turbine power generation applications. SWPC has been actively involved in the development of advanced filter materials and component configuration, has participated in numerous surveillance programs characterizing the material properties and microstructure of field tested filter elements, and has undertaken extended, accelerated filter life testing programs. This report summarizes the results of SWPC's filter component assessment efforts, identifying the performance and stability of porous monolithic, fiber reinforced, and filament wound ceramic hot gas candle filters, potentially for {ge}3 years of viable pressurized fluidized-bed combustion (PFBC) service operating life.
Date:
April 23, 2004
Creator:
Alvin, M. A.
Object Type:
Report
System:
The UNT Digital Library
House and Senate Chaplains
This report
Date:
April 7, 2004
Creator:
Amer, Mildred
Object Type:
Report
System:
The UNT Digital Library
House Ethics Rules Changes in the 108th Congress
None
Date:
April 2, 2004
Creator:
Amer, Mildred
Object Type:
Report
System:
The UNT Digital Library
Southwest Retort, Volume 56, Number 8, April 2004
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
April 2004
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Measurement of total ion flux in vacuum Arc discharges
A vacuum arc ion source was modified allowing us to collections from arc plasma streaming through an anode mesh. The mesh had ageometric transmittance of 60 percent, which was taken into account as acorrection factor. The ion current from twenty-two cathode materials wasmeasured at an arc current of 100 A. The ion current normalized by thearc current was found to depend on the cathode material, with valuesinthe range from 5 percent to 11 percent. The normalized ion current isgenerally greater for light elements than for heavy elements. The ionerosion rates were determined fromvalues of ion currentand ion chargestates, which were previously measured in the same experimental system.The ion erosion rates range from 12-94 mu g/C.
Date:
April 12, 2004
Creator:
Anders, Andre; Oks, Efim M.; Yushkov, Georgy Yu. & Brown, Ian G.
Object Type:
Article
System:
The UNT Digital Library
Coming to Washington, DC? Sources of Information on Temporary Housing
This report will introduce a newcomer to the Washington, DC, metropolitan area to sources of general interest, neighborhoods, housing, and public transportation.
Date:
April 23, 2004
Creator:
Anderson, J. Michael
Object Type:
Report
System:
The UNT Digital Library