Evidence For Departure in Self-Similarity: A New Spectral Ratio Method Using Narrowband Coda Envelopes (open access)

Evidence For Departure in Self-Similarity: A New Spectral Ratio Method Using Narrowband Coda Envelopes

This study is motivated by renewed interest within the seismic source community to resolve the long-standing question on energy scaling of earthquakes, specifically, 'Do earthquakes scale self-similarly or are large earthquakes dynamically different than small ones?' This question is important from a seismic hazard prediction point of view, as well as for understanding basic rupture dynamics for earthquakes. Estimating the total radiated energy (ER) from earthquakes requires significant broadband corrections for path and site effects. Moreover, source radiation pattern and directivity corrections can be equally significant and also must be accounted for. Regional studies have used a number of different methods, each with their own advantages and disadvantages. These methods include: integration of squared shear wave moment-rate spectra, direct integration of broadband velocity-squared waveforms, empirical Green's function deconvolution, and spectral ratio techniques. The later two approaches have gained popularity because adjacent or co-located events recorded at common stations have shared path and site effects, which therefore cancel. In spite of this, a number of such studies find very large amplitude variance across a network of stations. In this paper we test the extent to which narrowband coda envelopes can improve upon the traditional spectral ratio using direct phases, allowing a …
Date: March 16, 2007
Creator: Mayeda, K; Malagnini, L & Walter, W R
Object Type: Article
System: The UNT Digital Library
Searching for Double Beta Decay with the Enriched Xenon Observatory (open access)

Searching for Double Beta Decay with the Enriched Xenon Observatory

The Enriched Xenon Observatory (EXO) Collaboration is building a series of experiments to search for the neutrinoless double beta decay of {sup 136}Xe. The first experiment, known as EXO-200, will utilize 200 kg of xenon enriched to 80% in the isotope of interest, making it the largest double beta decay experiment to date by one order of magnitude. This experiment is rapidly being constructed, and will begin data taking in 2007. The EXO collaboration is also developing a technique to identify on an event-by-event basis the daughter barium ion of the double beta decay. If successful, this method would eliminate all conventional radioactive backgrounds to the decay, resulting in an ideal experiment. We summarize here the current status of EXO-200 construction and the barium tag R&D program.
Date: March 16, 2007
Creator: Hall, C.
Object Type: Article
System: The UNT Digital Library
An Infrared Study of the Large-Scale Jet in Quasar PKS 1136-135 (open access)

An Infrared Study of the Large-Scale Jet in Quasar PKS 1136-135

We present Spitzer IRAC imaging of the large-scale jet in the quasar PKS 1136-135 at wavelengths of 3.6 and 5.8 {micro}m, combined with previous VLA, HST, and Chandra observations. We clearly detect infrared emission from the jet, resulting in the most detailed multifrequency data among the jets in lobe-dominated quasars. The spectral energy distributions of the jet knots have significant variations along the jet, like the archetypal jet in 3C 273. The infrared measurements with IRAC are consistent with the previous idea that the jet has two spectral components, namely (1) the low-energy synchrotron spectrum extending from radio to infrared, and (2) the high-energy component responsible for the X-ray flux. The optical fluxes may be a mixture of the two components. We consider three radiation models for the high-energy component: inverse Compton scattering of cosmic microwave background (CMB) photons by radio-emitting electrons in a highly relativistic jet, synchrotron radiation by a second distinct electron population, and synchrotron radiation by ultra high energy protons. Each hypothesis leads to important insights into and constraints on particle acceleration in the jet, as well as the basic physical properties of the jet such as bulk velocity, transporting power, and particle contents.
Date: March 16, 2007
Creator: Uchiyama, Yasunobu; Urry, C.Megan; Coppi, Paolo; Van Duyne, Jeffrey; Cheung, C. C.; Sambruna, Rita M. et al.
Object Type: Article
System: The UNT Digital Library
Search for the rare decay B to pi l+ l- (open access)

Search for the rare decay B to pi l+ l-

The authors have performed a search for the flavor-changing neutral-current decays B {yields} {pi}{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either e{sup +}e{sup -} or {mu}{sup +}{mu}{sup -}, using a sample of 230 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector. They observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be {Beta}(B {yields} {pi}{ell}{sup +}{ell}{sup -}) < 9.1 x 10{sup -8} at 90% confidence level. They also search for the lepton-flavor-violating decays B {yields} {pi}e{sup {+-}} {mu}{sup {-+}} and measure an upper limit on the isospin-averaged branching fraction of {Beta}(B {yields} {pi}e{sup {+-}} {mu}{sup {-+}}) < 9.2 x 10{sup -8} at 90% confidence level.
Date: March 16, 2007
Creator: Aubert, B.
Object Type: Article
System: The UNT Digital Library
Human Health and Ecological Risk Assessment for the Operation of the Explosives Waste Treatment Facility at Site 300 of the Lawrence Livermore National Laboratory, Volume 1: Report of Results (open access)

Human Health and Ecological Risk Assessment for the Operation of the Explosives Waste Treatment Facility at Site 300 of the Lawrence Livermore National Laboratory, Volume 1: Report of Results

Human health and ecological risk assessments are required as part of the Resource Recovery and Conservation Act (RCRA) permit renewal process for waste treatment units. This risk assessment is prepared in support of the RCRA permit renewal for the Explosives Waste Treatment Facility (EWTF) at Site 300 of the Lawrence Livermore National Laboratory (LLNL). The human health risk assessment is based on U.S. Environmental Protection Agency- (U.S. EPA) approved emissions factors and on California Environmental Protection Agency (CalEPA), California Air Resources Board (CARB) and U.S. EPA assessment and air dispersion models. This risk assessment identifies the receptors of concern and evaluates theoretical carcinogenic risk, and theoretical acute and chronic non-carcinogenic hazard, following those guidelines. The carcinogenic risk to a 30-year resident at the maximum off-site receptor location is 0.0000006 or 0.6 in 1 million. The carcinogenic risk to a 25-year worker at the maximum bystander on-site receptor location is also 0.0000006 or 0.6 in 1 million. Any risk of less than 1 in a million is below the level of regulatory concern. The acute non-carcinogenic hazard for the 30-year resident is 0.01, and the chronic non-carcinogenic hazard is 0.01. The acute non-carcinogenic hazard for the 25-year worker is 0.3, and …
Date: March 16, 2007
Creator: Gallegtos, G M; Daniels, J I & Wegrecki, A M
Object Type: Report
System: The UNT Digital Library
Crystal Growth And Characterization of the Model High-Temperature Superconductor HgBa{sub 2}CuO{sub 4+{delta}} (open access)

Crystal Growth And Characterization of the Model High-Temperature Superconductor HgBa{sub 2}CuO{sub 4+{delta}}

Since the discovery of high-transition-temperature (T{sub c}) superconductivity in La{sub 2-x}Ba{sub x}CuO{sub 4} in 1986, the study of the lamellar copper oxides has remained at the forefront of condensed matter physics. Apart from their unusually high values of T{sub c}, these materials also exhibit a variety of complex phenomena and phases. This rich behavior is a consequence of the lamellar crystal structures, formed of copper-oxygen sheets separated by charge reservoir layers, and of the strong electron-electron correlations in the copper-oxygen sheets. After two decades of intensive research, which has stimulated many valuable new insights into correlated electron systems in general, there remains a lack of consensus regarding the correct theory for high-T{sub c} superconductivity. The ultimate technological goal of room-temperature superconductivity might only be attained after the development of a deeper understanding of the mercury-based compounds HgBa{sub 2}Ca{sub n-1}Cu{sub n}OI{sub 2n+2+{delta}}, which currently exhibit the highest T{sub c}values. One very important issue in this regard is the role of electronic versus chemical and structural inhomogeneities in these materials, and the associated need to separate material-specific properties from those that are essential to superconductivity. Unfortunately, there has been remarkably little scientific work on the mercury-based compounds because sizable crystals have not …
Date: March 16, 2007
Creator: Zhao, Xudong; Yu, Guichuan; Cho, Yong-Chan; Chabot-Couture, Guillaume; Barisic, Neven; Bourges, Philippe et al.
Object Type: Article
System: The UNT Digital Library
Tool Support for Inspecting the Code Quality of HPC Applications (open access)

Tool Support for Inspecting the Code Quality of HPC Applications

The nature of HPC application development encourages ad hoc design and implementation, rather than formal requirements analysis and design specification as is typical in software engineering. However, we cannot simply expect HPC developers to adopt formal software engineering processes wholesale, even while there is a need to improve software structure and quality to ensure future maintainability. Therefore, we propose tools that HPC developers can use at their discretion to obtain feedback on the structure and quality of their codes. This feedback would come in the form of code quality metrics and analyses, presented when necessary in intuitive and interactive visualizations. This paper summarizes our implementation of just such a tool, which we apply to a standard HPC benchmark as ''proof-of-concept.''
Date: March 16, 2007
Creator: Panas, T; Quinlan, D & Vuduc, R
Object Type: Article
System: The UNT Digital Library
Data Package for Past and Current Groundwater Flow and Contamination beneath Single-Shell Tank Waste Management Areas (open access)

Data Package for Past and Current Groundwater Flow and Contamination beneath Single-Shell Tank Waste Management Areas

This appendix summarizes historic and recent groundwater data collected from the uppermost aquifer beneath the 200 East and 200 West Areas. Although the area of interest is the Hanford Site Central Plateau, most of the information discussed in this appendix is at the scale of individual single-shell tank waste management areas. This is because the geologic, and thus the hydraulic, properties and the geochemical properties (i.e., groundwater composition) are different in different parts of the Central Plateau.
Date: March 16, 2007
Creator: Horton, Duane G.
Object Type: Report
System: The UNT Digital Library
SouthernAppalachian Mountains CESE Final Technical Report (open access)

SouthernAppalachian Mountains CESE Final Technical Report

None
Date: March 16, 2007
Creator: Wilson, J. Larry
Object Type: Report
System: The UNT Digital Library
Structural conformation in a poly (ethylene oxide) film obta inedfrom X-ray emission spectroscopy (XES) (open access)

Structural conformation in a poly (ethylene oxide) film obta inedfrom X-ray emission spectroscopy (XES)

The electronic structure of poly(ethylene oxide) (PEO) in a thin (< 1 {micro}) film sample was experimentally probed by X-ray emission spectroscopy. The emission spectra from this film were much sharper with more resolved fine structure than the spectra from the bulk polymer from which it was cast. Both non-resonant and resonant X-ray emission spectra were simulated using density functional theory (DFT) applied to four different models representing different conformations in the polymer. Calculated spectra were compared with experimental results for the PEO film. It was found that the best fit was obtained with the polymer conformation in PEO electrolytes from which the salt (LiMF6, M=P, As, or Sb) had been removed. This conformation is different from that in the crystalline bulk polymer and implies that film casting, commonly used to form electrolytes for Li polymer batteries, induces the same conformation in the polymer with or without the salt present.
Date: March 16, 2007
Creator: Kashtanov, S.; Zhuang, G.V.; Augustsson, A.; Guo, J.-H.; Nordgren, J.; Luo, Y. et al.
Object Type: Article
System: The UNT Digital Library
A Variable Directional Coupler for an Alternate ILC High-Power RF Distribution Scheme (open access)

A Variable Directional Coupler for an Alternate ILC High-Power RF Distribution Scheme

We describe the design and functionality of an RF directional coupler for which the power division between the output ports is mechanically variable. In an alternate power distribution scheme for the ILC, power is delivered to cavities in pairs, through hybrids. Four pairs, or eight cavities, are fed from one waveguide feed, from which one fourth, one third, and one half of the power is coupled out at consecutive directional couplers. Three such feeds are powered by a single 10 MW klystron. Experience suggests that cavities considered useable will display some variation in the operational accelerating gradient they can sustain. With fixed distribution, the klystron power must be kept below the level at which the weakest cavity out of 24 receives its power limit. This problem can be solved by installing variable attenuators, but that means wasting precious power. With adjustable coupling, distribution can be optimized for more efficient use both of available power and of the accelerating cavities. This novel device, feeding cavities paired by similar performance, can provide such benefit to the ILC.
Date: March 16, 2007
Creator: Nantista, Christopher D. & Adophsen, Chris
Object Type: Article
System: The UNT Digital Library
EFFECT OF ELECTROLYZER CONFIGURATION AND PERFORMANCE ON HYBRID SULFUR PROCESS NET THERMAL EFFICIENCY (open access)

EFFECT OF ELECTROLYZER CONFIGURATION AND PERFORMANCE ON HYBRID SULFUR PROCESS NET THERMAL EFFICIENCY

Hybrid Sulfur cycle is gaining popularity as a possible means for massive production of hydrogen from nuclear energy. Several different ways of carrying out the SO{sub 2}-depolarized electrolysis step are being pursued by a number of researchers. These alternatives are evaluated with complete flowsheet simulations and on a common design basis using Aspen Plus{trademark}. Sensitivity analyses are performed to assess the performance potential of each configuration, and the flowsheets are optimized for energy recovery. Net thermal efficiencies are calculated for the best set of operating conditions for each flowsheet and the results compared. This will help focus attention on the most promising electrolysis alternatives. The sensitivity analyses should also help identify those features that offer the greatest potential for improvement.
Date: March 16, 2007
Creator: Gorensek, M
Object Type: Article
System: The UNT Digital Library