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Aging in large CDF tracking chambers (open access)

Aging in large CDF tracking chambers

The experience of the Collider Detector at Fermilab (CDF) with aging in the large axial drift chamber responsible for tracking in the central region is presented. Premature aging in the Run 1 chamber was observed after only 0.02 C/cm. After cleaning much of the gas system and making modifications to reduce aerosols from the alcohol bubbler, the observed aging rate fell dramatically in test chambers. Considerable effort has been made to better understand the factors that affect aging since the replacement chamber for Run 2 will accumulate about 1.0 C/cm. Current test chambers using the full CDF gas system show aging rates of less than 5%/C/cm.
Date: March 19, 2001
Creator: al., M. Binkley et
System: The UNT Digital Library
Anisotropic flow at the SPS and RHIC (open access)

Anisotropic flow at the SPS and RHIC

The results on directed and elliptic flow for Pb + Pb at the full energy of the SPS (158 GeV/A) and from the first year of Au + Au at RHIC ({radical}s{sub NN} = 130 GeV) are reviewed. The different experiments agree well and a consistent picture has emerged indicating early time thermalization at RHIC.
Date: October 19, 2001
Creator: Poskanzer, Arthur M.
System: The UNT Digital Library
Band anticrossing in GaP1-xNx alloys (open access)

Band anticrossing in GaP1-xNx alloys

None
Date: November 19, 2001
Creator: Wu, J.; Walukiewicz, W.; Yu, K. M.; Ager, J. W., III; Haller, E. E.; Hong, Y. G. et al.
System: The UNT Digital Library
Bayesian Separation of Lamb Wave Signatures (open access)

Bayesian Separation of Lamb Wave Signatures

A persistent problem in the analysis of Lamb wave signatures in experimental data is the fact that several different modes appear simultaneously in the signal. The modes overlap in both the frequency and time domains. Attempts to separate the overlapping Lamb wave signatures by conventional signal processing methods have been unsatisfactory. This paper reports an exciting alternative to conventional methods. Severely overlapping Lamb waves are found to be readily separable by Bayesian parameter estimation. The authors have used linear-chirped Gaussian-windowed sinusoids as models of each Lamb wave mode. The separation algorithm allows each mode to be examined individually.
Date: July 19, 2001
Creator: Kercel, Stephen W.; Klein, Marvin B. & Pouet, Bruno
System: The UNT Digital Library
Beam Extraction from Laser Driven Multi-Charged Ion Source (open access)

Beam Extraction from Laser Driven Multi-Charged Ion Source

A newly proposed type of multicharged ion source offers the possibility of an economically advantageous high-charge-state fusion driver. Multiphoton absorption in an intense uniform laser focus can give multiple charge states of high purity, simplifying or eliminating the need for charge-state separation downstream. Very large currents (hundreds of amperes) can be extracted from this type of source. Several arrangements are possible. For example, the laser plasma could be tailored for storage in a magnetic bucket, with beam extracted from the bucket. A different approach, described in this report, is direct beam extraction from the expanding laser plasma. They discuss extraction and focusing for the particular case of a 4.1-MV beam of Xe{sup 16+} ions. The maximum duration of the beam pulse is limited by the total charge in the plasma, while the practical pulse length is determined by the range of plasma radii over which good beam optics can be achieved. The extraction electrode contains a solenoid for beam focusing. The design studies were carried out first with an envelope code and then with a self-consistent particle code. Results from the initial model showed that hundreds of amperes could be extracted, but that most of this current missed the solenoid …
Date: March 19, 2001
Creator: Anderson, O. A. & Logan, B. G.
System: The UNT Digital Library
Benchmark Analysis of the MIX-COMP-THERM-02 Experiments Using the SCALE/CENTRM Sequence (open access)

Benchmark Analysis of the MIX-COMP-THERM-02 Experiments Using the SCALE/CENTRM Sequence

None
Date: January 19, 2001
Creator: Hollenbach, D.F.
System: The UNT Digital Library
CVD Diamond Detectors for Current Mode Neutron Time-of-Flight Spectroscopy at OMEGA/NIF (open access)

CVD Diamond Detectors for Current Mode Neutron Time-of-Flight Spectroscopy at OMEGA/NIF

As part of a laser fusion diagnostic development program, we have performed pulsed neutron and pulsed laser tests of a CVD diamond detector manufactured from DIAFILM, a commercial grade of CVD diamond. The laser tests were performed at the short pulse UV laser at Bechtel Nevada in Livermore, CA. The pulsed neutrons were provided by DT capsule implosions at the OMEGA laser fusion facility in Rochester, NY. From these tests, we have determined the impulse response to be 250 ps fwhm for an applied E-field of 500 V/mm. Additionally, we have determined the sensitivity to be 2.8 mA/W at 500 V/mm and 4.5 mA/W at 1000 V/mm (2 to 6x times higher than reported values for natural Type IIa diamond). These detector characteristics allow us to conceive of a neutron time-of-flight current mode spectrometer based on CVD diamond. Such an instrument would sit inside the laser fusion target chamber close to TCC, and would record neutron spectra fast enough such that backscattered neutrons and y rays from the target chamber wall would not be a concern. However, the data we have taken show that the Electromagnetic Pulse (EMP) noise could be a limiting factor in performance. Determining the degree to …
Date: June 19, 2001
Creator: Schmid, G. J.; Friensehner, A. F.; Glebov, V. Y.; Hargrove, D. R.; Hatchett, S. P.; Izumi, N. et al.
System: The UNT Digital Library
Data Mining for Security Information: A Survey (open access)

Data Mining for Security Information: A Survey

This paper will present a survey of the current published work and products available to do off-line data mining for computer network security information. Hundreds of megabytes of data are collected every second that are of interest to computer security professionals. This data can answer questions ranging from the proactive, ''Which machines are the attackers going to try to compromise?'' to the reactive, ''When did the intruder break into my system and how?'' Unfortunately, there's so much data that computer security professionals don't have time to sort through it all. What we need are systems that perform data mining at various levels on this corpus of data in order to ease the burden of the human analyst. Such systems typically operate on log data produced by hosts, firewalls and intrusion detection systems as such data is typically in a standard, machine readable format and usually provides information that is most relevant to the security of the system. Systems that do this type of data mining for security information fall under the classification of intrusion detection systems. It is important to point out that we are not surveying real-time intrusion detection systems. Instead, we examined what is possible when the analysis …
Date: April 19, 2001
Creator: Brugger, S T; Kelley, M; Sumikawa, K & Wakumoto, S
System: The UNT Digital Library
Density functional theory study of nitrous oxide decomposition over Fe- and Co-ZSM-5 (open access)

Density functional theory study of nitrous oxide decomposition over Fe- and Co-ZSM-5

Iron- and cobalt-exchanged ZSM-5 are active catalysts for the dissociation of nitrous oxide. In this study, density functional theory was used to assess a possible reaction pathway for the catalytic dissociation of N2O. The active center was taken to be mononuclear [FeO]+ or [CoO]+, and the surrounding portion of the zeolite was represented by a 24-atom cluster. The first step of N2O decomposition involves the formation of [FeO2]+ or [CoO2]+ and the release of N2. The metal-oxo species produced in this step then reacts with N2O again, to release N2 and O2. The apparent activation energies for N2O dissociation in Fe-ZSM-5 and Co-ZSM-5 are 39.4 and 34.6 kcal/mol, respectively. The preexponential factor for the apparent first-order rate coefficient is estimated to be of the order 107 s-1 Pa-1. While the calculated activation energy for Fe-ZSM-5 is in good agreement with that measured experimentally, the value of the preexponential factor is an order of magnitude smaller than that observed . The calculated activation energy for Co-ZSM-5 is higher than that reported experimentally. However, consistent with experiment, the rate of N2O decomposition on Co-ZSM-5 is predicted to be significantly higher than that on Fe-ZSM-5.
Date: December 19, 2001
Creator: Ryder, Jason A.; Chakraborty, Arup K. & Bell, Alexis T.
System: The UNT Digital Library
Design and Analysis of Hybrid Solar Lighting and Full-Spectrum Solar Energy Systems (open access)

Design and Analysis of Hybrid Solar Lighting and Full-Spectrum Solar Energy Systems

This paper describes a systems-level design and analysis of a new approach for improving the energy efficiency and affordability of solar energy in buildings, namely, hybrid solar lighting and full-spectrum solar energy systems. By using different portions of the solar spectrum simultaneously for multiple end-use applications in buildings, the proposed system offers unique advantages over other alternatives for using sunlight to displace electricity (conventional topside daylighting and solar technologies). Our preliminary work indicates that hybrid solar lighting, a method of collecting and distributing direct sunlight for lighting purposes, will alleviate many of the problems with passive daylighting systems of today, such as spatial and temporal variability, glare, excess illumination, cost, and energy efficiency. Similarly, our work suggests that the most appropriate use of the visible portion of direct, nondiffuse sunlight from an energy-savings perspective is to displace electric light rather than generate electricity. Early estimates detailed in this paper suggest an anticipated system cost of well under $2.0/Wp and 5-11 {cents}/kWh for displaced and generated electricity in single-story commercial building applications. Based on a number of factors discussed in the paper, including sunlight availability, building use scenarios, time-of-day electric utility rates, cost, and efficacy of the displaced electric lights, the …
Date: June 19, 2001
Creator: Muhs, J.D.
System: The UNT Digital Library
DSDP3: dual scaling algorithm for general positive semidefinite programming. (open access)

DSDP3: dual scaling algorithm for general positive semidefinite programming.

We implement a dual scaling algorithm for positive semidefinite programming to handle a broader class of problems than could be solved with previous implementations of the algorithm. With appropriate representations of constraint matrices, we can solve general semidefinite programs and still exploit the structure of large-scale combinatorial optimization problems. Computational results show that our preliminary implementation is competitive with primal-dual solvers on many problems requiring moderate precision in the solution and is superior to primal-dual solvers for several types of problems.
Date: March 19, 2001
Creator: Benson, S.J. & Ye, Y.
System: The UNT Digital Library
Eigenfrequencies of vortex state excitations in magnetic submicron-size disks. (open access)

Eigenfrequencies of vortex state excitations in magnetic submicron-size disks.

None
Date: December 19, 2001
Creator: Guslienko, K. Y.; Ivanov, B. A.; Novosad, V.; Otani, Y.; Shima, H. & Fukamichi, K.
System: The UNT Digital Library
Electronic excitations and chemistry in Nitromethane and HMX (open access)

Electronic excitations and chemistry in Nitromethane and HMX

The nature of electronic excitations in crystalline solid nitromethane under conditions of shock loading and static compression are examined. Density functional theory calculations are used to determine the crystal bandgap under hydrostatic stress, uniaxial strain, and shear strain. Bandgap lowering under uniaxial strain due to molecular defects and vacancies is considered. In all cases, the bandgap is not lowered enough to produce a significant population of excited states in the crystal. Preliminary simulations on the formation of detonation product molecules from HMX are discussed.
Date: June 19, 2001
Creator: Reed, E J; Manaa, M R; Joannopoulos, J D & Fried, L E
System: The UNT Digital Library
Expression profiling and comparative sequence derived insights into lipid metabolism (open access)

Expression profiling and comparative sequence derived insights into lipid metabolism

Expression profiling and genomic DNA sequence comparisons are increasingly being applied to the identification and analysis of the genes involved in lipid metabolism. Not only has genome-wide expression profiling aided in the identification of novel genes involved in important processes in lipid metabolism such as sterol efflux, but the utilization of information from these studies has added to our understanding of the regulation of pathways participating in the process. Coupled with these gene expression studies, cross species comparison, searching for sequences conserved through evolution, has proven to be a powerful tool to identify important non-coding regulatory sequences as well as the discovery of novel genes relevant to lipid biology. An example of the value of this approach was the recent chance discovery of a new apolipoprotein gene (apo AV) that has dramatic effects upon triglyceride metabolism in mice and humans.
Date: December 19, 2001
Creator: Callow, Matthew J. & Rubin, Edward M.
System: The UNT Digital Library
Fault Current Tests of a 5-m HTS Cable (open access)

Fault Current Tests of a 5-m HTS Cable

The first industrial demonstration of a three-phase high-temperature superconducting transmission power cable at the Southwire manufacturing complex is in progress. One crucial issue during operation of the 30-m HTS cables is whether they could survive the fault current (which can be over an order of magnitude higher than the operating current) in the event of a short-circuit fault and how HTS cables and the cryogenic system would respond. Simulated fault-current tests were performed at ORNL on a 5-m cable. This single-phase cable was constructed in the same way as the 30-m cables and is also rated for 1250 A at 7.2 kV ac line-to-ground voltage. Tests were performed with fault-current pulses of up to 15 kA (for 0.5 s) with pulse lengths of up to 5 s (at 6.8 kA). Although a large voltage drop was produced across the HTS cable during the fault-current pulse, no significant changes in the coolant temperature, pressure, or joint resistance were observed. The cable survived 15 simulated fault-current shots without any degradation in its V-I characteristics.
Date: February 19, 2001
Creator: Lue, J.W.
System: The UNT Digital Library
Fundamental Elements of Geologic C02 Sequestration in Saline Aquifers (open access)

Fundamental Elements of Geologic C02 Sequestration in Saline Aquifers

Geologic sequestration represents a promising strategy for isolating CO{sub 2} waste streams from the atmosphere. Successful implementation of this approach hinges on our ability to predict the relative effectiveness of subsurface CO{sub 2} migration and sequestration as a function of key target-formation and cap-rock properties, which will enable us to identify optimal sites and evaluate their long-term isolation performance. Quantifying this functional relationship requires a modeling capability that explicitly couples multiphase flow and kinetically controlled geochemical processes. We have developed a unique computational package that meets these criteria, and used it to model CO{sub 2} injection at Statoil's North-Sea Sleipner facility, the world's first saline-aquifer storage site. The package integrates a state-of-the-art reactive transport simulator (NUFT) with supporting geochemical software and databases (SUPCRT92). In our Sleipner study, we have quantified--for the first time--the influence of intra-aquifer shales and aquifer/cap-rock composition on migration/sequestration balance, sequestration partitioning among hydrodynamic, solubility, and mineral trapping mechanisms, and the isolation performance of shale cap rocks. Here, we review the fundamental elements of geologic CO{sub 2} sequestration in saline aquifers as revealed from model XSH of our Sleipner study; this model, unlike CSH and DSH, does not address the complicating (yet advantageous) presence of intra-aquifer shales.
Date: November 19, 2001
Creator: Johnson, J. W.; Nitao, J. J. & Steefel, C. I.
System: The UNT Digital Library
Fusion Ignition Research Experiment Vacuum Vessel Design and Configuration (open access)

Fusion Ignition Research Experiment Vacuum Vessel Design and Configuration

The design status of the vacuum vessel for the Fusion Ignition Research Experiment (FIRE) is presented. The purpose and configuration of the various components of the vessel are described, along with the results of preliminary structural analysis. It appears that a vessel can be designed to meet the requirements within the rather restricted space constraints.
Date: July 19, 2001
Creator: Nelson, B. E.
System: The UNT Digital Library
Future Accelerators, Muon Colliders, and Neutrino Factories (open access)

Future Accelerators, Muon Colliders, and Neutrino Factories

Particle physics is driven by five great topics. Neutrino oscillations and masses are now at the fore. The standard model with extensions to supersymmetry and a Higgs to generate mass explains much of the field. The origins of CP violation are not understood. The possibility of extra dimensions has raised tantalizing new questions. A fifth topic lurking in the background is the possibility of something totally different. Many of the questions raised by these topics require powerful new accelerators. It is not an overstatement to say that for some of the issues, the accelerator is almost the experiment. Indeed some of the questions require machines beyond our present capability. As this volume attests, there are parts of the particle physics program that have been significantly advanced without the use of accelerators such as the subject of neutrino oscillations and many aspects of the particle-cosmology interface. At this stage in the development of physics, both approaches are needed and important. This chapter first reviews the status of the great accelerator facilities now in operation or coming on within the decade. Next, midrange possibilities are discussed including linear colliders with the adjunct possibility of gamma-gamma colliders, muon colliders, with precursor neutrino factories, …
Date: December 19, 2001
Creator: Carrigan, Richard A., Jr.
System: The UNT Digital Library
A highly portable, rapidly deployable system for eddy covariance measurements of CO2 fluxes (open access)

A highly portable, rapidly deployable system for eddy covariance measurements of CO2 fluxes

To facilitate the study of flux heterogeneity within a region, the authors have designed, built, and field-tested a highly portable, rapidly deployable, eddy covariance CO{sub 2} flux measurement system. The system is built from off-the-shelf parts and was assembled at a minimal cost. The unique combination of features of this system allow for a very rapid deployment with a minimal number of field personnel. The system is capable of making high precision, unattended measurements of turbulent CO{sub 2} fluxes, latent heat (LE) fluxes, sensible heat fluxes (H), and momentum transfer fluxes. In addition, many of the meteorological and ecosystem variables necessary for quality control of the fluxes and for running ecosystem models are measured. A side-by-side field comparison of the system at a pair of established AmeriFlux sites has verified that, for single measurements, the system is capable of CO{sub 2} flux accuracy of about {+-} 1.2 {micro}mole/m{sup 2}/sec, LE flux accuracy of about {+-} 15 Watts/m{sup 2}, H flux accuracy of about {+-} 7 Watts/m{sup 2}, and momentum transfer flux accuracy of about {+-} 11 gm-m/sec/sec. System deployment time is between 2 and 4 hours by a single person. The system was measured to draw between 30 and 35 …
Date: September 19, 2001
Creator: Billesbach, David P.; Fischer, Marc L.; Torn, Margaret S. & Berry, Joe A.
System: The UNT Digital Library
History of the APS Topical Group on Shock Compression of Condensed Matter (open access)

History of the APS Topical Group on Shock Compression of Condensed Matter

In order to provide broader scientific recognition and to advance the science of shock compressed condensed matter, a group of American Physical Society (APS) members worked within the Society to make this field an active part of the APS. Individual papers were presented at APS meetings starting in the 1940's and shock wave sessions were organized starting with the 1967 Pasadena meeting. Shock wave topical conferences began in 1979 in Pullman, WA. Signatures were obtained on a petition in 1984 from a balanced cross-section of the shock wave community to form an APS Topical Group (TG). The APS Council officially accepted the formation of the Shock Compression of Condensed Matter (SCCM) TG at its October 1984 meeting. This action firmly aligned the shock wave field with a major physical science organization. Most early topical conferences were sanctioned by the APS while those held after 1992 were official APS meetings. The topical group organizes a shock wave topical conference in odd numbered years while participating in shock wavehigh pressure sessions at APS general meetings in even numbered years.
Date: October 19, 2001
Creator: Forbes, J W
System: The UNT Digital Library
Hydrogen Production as a Major Nuclear Energy Application (open access)

Hydrogen Production as a Major Nuclear Energy Application

None
Date: June 19, 2001
Creator: Forsberg, Charles W.
System: The UNT Digital Library
Intelligent Collection Environment for an Interpretation System (open access)

Intelligent Collection Environment for an Interpretation System

An Intelligent Collection Environment for a data interpretation system is described. The environment accepts two inputs: A data model and a number between 0.0 and 1.0. The data model is as simple as a single word or as complex as a multi-level/multidimensional model. The number between 0.0 and 1.0 is a control knob to indicate the user's desire to allow loose matching of the data (things are ambiguous and unknown) versus strict matching of the data (things are precise and known). The environment produces a set of possible interpretations, a set of requirements to further strengthen or to differentiate a particular subset of the possible interpretation from the others, a set of inconsistencies, and a logic map that graphically shows the lines of reasoning used to derive the above output. The environment is comprised of a knowledge editor, model explorer, expertise server, and the World Wide Web. The Knowledge Editor is used by a subject matter expert to define Linguistic Types, Term Sets, detailed explanations, and dynamically created URI's, and to create rule bases using a straight forward hyper matrix representation. The Model Explorer allows rapid construction and browsing of multi-level models. A multi-level model is a model whose elements …
Date: July 19, 2001
Creator: Maurer, W J
System: The UNT Digital Library
Interfacing microbiology and biotechnology. Conference abstracts (open access)

Interfacing microbiology and biotechnology. Conference abstracts

The Interfacing Microbiology and Biotechnology Conference was attended by over 100 faculty, post-docs, students, and research scientists from the US, Europe, and Latin America. The conference successfully stimulated communication and the dissemination of knowledge among scientists involved in basic and applied research. The focus of the conference was on microbial physiology and genetics and included sessions on C1 metabolism, archaeal metabolism, proteases and chaperones, gene arrays, and metabolic engineering. The meeting provided the setting for in-depth discussions between scientists who are internationally recognized for their research in these fields. The following objectives were met: (1) The promotion of interaction and future collaborative projects among scientists involved in basic and applied research which incorporates microbial physiology, genetics, and biochemistry; (2) the facilitation of communication of new research findings through seminars, posters, and abstracts; (3 ) the stimulation of enthusiasm and education among participants including graduate and undergraduate students.
Date: May 19, 2001
Creator: Maupin, Julia A.
System: The UNT Digital Library
Irradiation testing of actinide transmutation fuels in the advanced test reactor. (open access)

Irradiation testing of actinide transmutation fuels in the advanced test reactor.

The first irradiation experiment to evaluate the technical feasibility of proposed acitnide transmutation fuels for the US. Accelerator Transmutation of Waste program is currently under design. The goal of this irradiation experiment is to obtain initial irradiation performance data on candidate transmutation fuel concepts. The candidate fuels include non-fertile variations of (1) metallic alloys, (2) nitrides, (3) oxides, and (4) metal-matrix dispersion fuels. These fuels will be irradiated in the form of rodlets in the Advanced Test Reactor in Idaho beginning in September 2002. it is expected that postirradiation examinations will be performed on these fuels at the {approx} 7 and 20 at.-% burnup levels. This paper presents the design of the irradiation test vehicle and the fuel rodlets; the test matrix of fuel variations, the target test conditions; and the planned postirradiation examinations.
Date: September 19, 2001
Creator: Hayes, S. L.; Meyer, M. K. & Crawford, D. C.
System: The UNT Digital Library