A Component Architecture for High-Performance Scientific Computing (open access)

A Component Architecture for High-Performance Scientific Computing

The Common Component Architecture (CCA) provides a means for software developers to manage the complexity of large-scale scientific simulations and to move toward a plug-and-play environment for high-performance computing. In the scientific computing context, component models also promote collaboration using independently developed software, thereby allowing particular individuals or groups to focus on the aspects of greatest interest to them. The CCA supports parallel and distributed computing as well as local high-performance connections between components in a language-independent manner. The design places minimal requirements on components and thus facilitates the integration of existing code into the CCA environment. The CCA model imposes minimal overhead to minimize the impact on application performance. The focus on high performance distinguishes the CCA from most other component models. The CCA is being applied within an increasing range of disciplines, including combustion research, global climate simulation, and computational chemistry.
Date: December 14, 2004
Creator: Bernholdt, D. E.; Allan, B. A.; Armstrong, R.; Bertrand, F.; Chiu, K.; Dahlgren, T. L. et al.
System: The UNT Digital Library
High-efficiency diffractive x-ray optics from sectioned multilayers (open access)

High-efficiency diffractive x-ray optics from sectioned multilayers

We investigate the diffraction properties of sectioned multilayers in Laue (transmission) geometry, at hard x-ray energies (9.5 and 19.5 keV). Two samples are studied, a 200 period W/Si multilayer of 29 nm d-spacing, and a 2020 period Mo/Si multilayer of 7 nm d-spacing, with cross-section depths ranging from 2 to 17 {micro}m. Rocking curves across the Bragg reflections exhibit well-defined interference fringes originating from the depth of the sample. Efficiencies as high as 70% were obtained. This exceeds the theoretical limit for standard zone plates operating in the multi-beam regime, demonstrating that all of the intensity can be directed into a single diffraction order in small-period structures.
Date: December 14, 2004
Creator: Kang, H. C.; Stephenson, G. B.; Liu, C.; Conley, R.; Macrander, A. T.; Maser, J. et al.
System: The UNT Digital Library
Ion charge state fluctuations in vacuum arcs (open access)

Ion charge state fluctuations in vacuum arcs

Ion charge state distributions of cathodic vacuum arcs have been investigated using a modified time-of-flight method. Experiments have been done in double gate and burst gate mode, allowing us to study both systematic and stochastic changes of ion charge state distributions with a time resolution down to 100 ns. In the double gate method, two ion charge spectra are recorded with a well-defined time between measurements. The elements Mg, Bi, and Cu were selected for tests, representing metals of very different properties. For all elements it was found that large stochastic changes occur even at the limit of resolution. This is in agreement with fast changing arc properties observed elsewhere. Correlation of results for short times between measurements was found but it is argued that this is due to velocity mixing rather than due to cathode processes. The burst mode of time-of-flight measurements revealed the systematic time evolution of ion charge states within a single arc discharge, as opposed to previous measurements that relied on data averaged over many pulses. The technique shows the decay of the mean ion charge state as well as the level of material-dependent fluctuations.
Date: December 14, 2004
Creator: Anders, Andre; Fukuda, Kentaro & Yushkov, Georgy Yu
System: The UNT Digital Library
Mechanical Property Data for Fiberboard (open access)

Mechanical Property Data for Fiberboard

The 9975 shipping package incorporates a cane fiberboard overpack for thermal insulation and impact resistance. Mechanical properties (tensile and compressive behavior) have been measured on cane fiberboard and a similar wood-based product following short-term conditioning in several temperature/humidity environments. Both products show similar trends, and vary in behavior with material orientation, temperature and humidity. A memory effect is also seen in that original strength values are only partially recovered following exposure to a degrading environment and return to ambient conditions.
Date: December 14, 2004
Creator: WILLIAM, daugherty
System: The UNT Digital Library
An nth-order, Gaussian Energy Distribution Model for Sintering (open access)

An nth-order, Gaussian Energy Distribution Model for Sintering

Although it is well known that the rate of sintering is governed by deceleratory kinetics, it is often difficult to fit power-law and nth-order reaction models over broad time-temperature ranges. This work shows that a phenomenological model combining a reaction order with an activation energy distribution can correlate surface area as a function of sintering time and temperature over a greater range of those variables. Qualitatively, the activation energy distribution accounts the dependence of free energy on particle size and material defects, while the reaction order accounts for geometric factors such as a distribution of diffusion lengths. The model is demonstrated for sintering of hydroxyapatite using data of Bailliez and Nzihou (Chem. Eng. J. 98 (2004), 141-152).
Date: December 14, 2004
Creator: Burnham, A K
System: The UNT Digital Library
Surface Based Differential Forms (open access)

Surface Based Differential Forms

Higher-order basis functions have been constructed for surface-based differential forms that are used in engineering simulations. These surface-based forms have been designed to complement the volume-based forms present in EMSolve[1], a finite element code. The basis functions are constructed on a reference element and transformed, as necessary, for each element in space. Lagrange polynomials are used to create the basis functions. This approach is a necessary step in creating a hybrid finite-element/integral-equation time-domain code for electromagnetic analysis.
Date: December 14, 2004
Creator: Pingenot, J.; Yang, C.; Jandhyala, V.; Champagne, N.; White, D.; Stowell, M. et al.
System: The UNT Digital Library
A viable supersymmetric model with UV insensitive anomaly mediation (open access)

A viable supersymmetric model with UV insensitive anomaly mediation

We propose an electroweak model which is compatible with the UV insensitive anomaly mediated supersymmetry breaking. The model is an extension of the NMSSM by adding vector-like matter fields which can drive the soft scalar masses of the singlet Higgs field negative and the successful electroweak symmetry breaking is achieved. Viable parameter regions are found to preserve perturbativity of all the coupling constants up to the Planck scale. With this success, the model becomes a perfect candidate of physics beyond the standard model without the FCNC and CP problem. The cosmology is also quite interesting. The lightest neutralino is the wino which is a perfect cold dark matter candidate assuming the non-thermal production from the gravitino decay. There is no gravitino problem because it decays before the BBN era, and thus the thermal leptogenesis works. The cosmological domain wall problem inherent in the NMSSM is absent since the Z_3 symmetry is broken by the QCD instanton effect in the presence of the vector-like quarks. We also briefly comment on a possible solution to the strong CP problem a la the Nelson-Barr mechanism.
Date: December 14, 2004
Creator: Ibe, Masahiro; Kitano, Ryuichiro & Murayama, Hitoshi
System: The UNT Digital Library
Advanced diffusion studies with isotopically controlled materials (open access)

Advanced diffusion studies with isotopically controlled materials

The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.
Date: November 14, 2004
Creator: Bracht, Hartmut A.; Silvestri, Hughes H. & Haller, Eugene E.
System: The UNT Digital Library
Techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides in contaminated subsurface environments (open access)

Techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides in contaminated subsurface environments

Department of Energy (DOE) facilities within the weapons complex face a daunting challenge of remediating huge below inventories of legacy radioactive and toxic metal waste. More often than not, the scope of the problem is massive, particularly in the high recharge, humid regions east of the Mississippi river, where the off-site migration of contaminants continues to plague soil water, groundwater, and surface water sources. As of 2002, contaminated sites are closing rapidly and many remediation strategies have chosen to leave contaminants in-place. In situ barriers, surface caps, and bioremediation are often the remedial strategies of chose. By choosing to leave contaminants in-place, we must accept the fact that the contaminants will continue to interact with subsurface and surface media. Contaminant interactions with the geosphere are complex and investigating long term changes and interactive processes is imperative to verifying risks. We must be able to understand the consequences of our action or inaction. The focus of this manuscript is to describe recent technical developments for assessing the performance of in situ bioremediation and immobilization of subsurface metals and radionuclides. Research within DOE's NABIR and EMSP programs has been investigating the possibility of using subsurface microorganisms to convert redox sensitive toxic metals …
Date: November 14, 2004
Creator: Jardine, P. M.; Watson, D. B.; Blake, D. A.; Beard, L. P.; Brooks, S. C.; Carley, J. M. et al.
System: The UNT Digital Library
Activation Energy for Grain Growth in Aluminum Coatings (open access)

Activation Energy for Grain Growth in Aluminum Coatings

To produce a specific grain size in metallic coatings requires precise control of the time at temperature during the deposition process. Aluminum coatings are deposited using electron-beam evaporation onto heated substrate surfaces. The grain size of the coating is determined upon examination of the microstructure in plan view and cross-section. Ideal grain growth is observed over the entire experimental range of temperature examined from 413 to 843 K. A transition in the activation energy for grain growth from 0.7 to 3.8 eV {center_dot} atom{sup -1} is observed as the temperature increases from <526 K to >588 K. The transition is indicative of the dominant mechanism for grain growth shifting with increasing temperature from grain boundary to lattice diffusion.
Date: October 14, 2004
Creator: Jankowski, Alan Frederic; Ferreira, J. L. & Hayes, Jeffrey P.
System: The UNT Digital Library
Engineering Spectral Control Using Front Surface Filters for Maximum TPV Energy Conversion System Performance (open access)

Engineering Spectral Control Using Front Surface Filters for Maximum TPV Energy Conversion System Performance

Energy conversion efficiencies of better than 23% have been demonstrated for small scale tests of a few thermophotovoltaic (TPV) cells using front surface, tandem filters [1, 2]. The engineering challenge is to build this level of efficiency into arrays of cells that provide useful levels of energy. Variations in cell and filter performance will degrade TPV array performance. Repeated fabrication runs of several filters each provide an initial quantification of the fabrication variation for front surface, tandem filters for TPV spectral control. For three performance statistics, within-run variation was measured to be 0.7-1.4 percent, and run-to-run variation was measured to be 0.5-3.2 percent. Fabrication runs using a mask have been shown to reduce variation across interference filters from as high as 8-10 percent to less than 1.5 percent. Finally, several system design and assembly approaches are described to further reduce variation.
Date: October 14, 2004
Creator: Rahmlow, T. D., Jr.; Lazo-Wasem, J.; Gratrix, E.; Azarkevich, J.; Brown, E.; DePoy, D. et al.
System: The UNT Digital Library
Extended CO Solid: A New Class of High Energy Density Material (open access)

Extended CO Solid: A New Class of High Energy Density Material

Covalently bonded extended phases of molecular solids made of first- and second-row elements at high pressures are a new class of materials with advanced optical, mechanical and energetic properties. The existence of such extended solids has recently been demonstrated using diamond anvil cells in several systems, including N{sub 2}, CO{sub 2},and CO. However, the microscopic quantities produced at the formidable high-pressure/temperature conditions have limited the characterization of their predicted novel properties including high-energy content. In this paper, we present the first experimental evidence that these extended low-Z solids are indeed high energy density materials via milligram-scale high-pressure synthesis, recovery and characterization of polymeric CO (p-CO). Our spectroscopic data reveal that p-CO is a random polymer made of lactonic entities and conjugated C=C with an energy content rivaling or exceeding that of HMX. Solid p-CO explosively decomposes to CO{sub 2} and glassy carbon and thus might be used as an advanced energetic material.
Date: October 14, 2004
Creator: Lipp, M. J.; Evans, W. J.; Baer, B. J. & Yoo, C.
System: The UNT Digital Library
Implications of Wall Recycling and Carbon Source Locations on Core Plasma Fueling and Impurity Content in DIII-D (open access)

Implications of Wall Recycling and Carbon Source Locations on Core Plasma Fueling and Impurity Content in DIII-D

Measurement and modeling of the 2-D poloidal D{alpha} intensity distribution in DIII-D low and medium density L-mode and ELMy H-mode plasmas indicate that hydrogen neutrals predominantly fuel the core from the divertor X-point region. The 2-D distribution of neutral deuterium and low-charge-state carbon were measured in the divertor and the high-field side midplane scrape-off layer (SOL) using tangentially viewing cameras. The emission in the high-field SOL at the equatorial plane was found to be three to four orders of magnitude lower than at the strike points in the divertor, suggesting a strong divertor particle source. Modeling using the UEDGE/DEGAS codes predicted the poloidal fueling distribution to be dependent on the direction of the ion Bx{Delta}B drift. In plasmas with the Bx{Delta}B drift into the divertor stronger fueling from the inner divertor than from the outer is predicted, due to a lower-temperature and higher-density plasma in the inner leg. UEDGE simulations with carbon produced by both physical and chemical sputtering at the divertor plates and walls only are in agreement with a large set of diagnostic data. The simulations indicate flow reversal in the inner divertor that augments the leakage of carbon ions from the divertor into the core.
Date: October 14, 2004
Creator: Groth, M.; Porter, G. D.; Boedo, J. A.; Brooks, N. H.; Fenstermacher, M. E.; Groebner, R. J. et al.
System: The UNT Digital Library
Observation of a multiply ionized plasma with index of refraction greater than one (open access)

Observation of a multiply ionized plasma with index of refraction greater than one

We present clear experimental evidence showing that the contribution of bound electrons can dominate the index of refraction of laser created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms show that this results from the dominant contribution of low charge ions to the index of refraction. This usually neglected bound electron contribution can a.ect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.
Date: October 14, 2004
Creator: Filevich, J.; Rocca, J. J.; Marconi, M. C.; Moon, S. J.; Nilsen, J.; Scofield, J. H. et al.
System: The UNT Digital Library
Picosecond 14.7 nm interferometry of high intensity laser-produced plasmas (open access)

Picosecond 14.7 nm interferometry of high intensity laser-produced plasmas

We have developed a compact, 14.7 nm, sub-5 ps x-ray laser source at LLNL together with a Mach-Zehnder type Diffraction Grating Interferometer built at Colorado State University for probing dense, high intensity laser-produced plasmas. The short wavelength and pulse length of the probe reduces refraction and absorption effects within the plasma and minimizes plasma motion blurring. This unique diagnostic capability gives precise 2-D density profile snapshots and is generating new data for rapidly evolving laser-heated plasmas. A review of the results from dense, mm-scale line focus plasma experiments will be described with detailed comparisons to hydrodynamic simulations.
Date: October 14, 2004
Creator: Dunn, J.; Filevich, J.; Smith, R. F.; Moon, S. J.; Rocca, J. J.; Keenan, R. et al.
System: The UNT Digital Library
Pybus -- A Python Software Bus (open access)

Pybus -- A Python Software Bus

A software bus, just like its hardware equivalent, allows for the discovery, installation, configuration, loading, unloading, and run-time replacement of software components, as well as channeling of inter-component communication. Python, a popular open-source programming language, encourages a modular design on software written in it, but it offers little or no component functionality. However, the language and its interpreter provide sufficient hooks to implement a thin, integral layer of component support. This functionality can be presented to the developer in the form of a module, making it very easy to use. This paper describes a Pythonmodule, PyBus, with which the concept of a ''software bus'' can be realized in Python. It demonstrates, within the context of the ATLAS software framework Athena, how PyBus can be used for the installation and (run-time) configuration of software, not necessarily Python modules, from a Python application in a way that is transparent to the end-user.
Date: October 14, 2004
Creator: Lavrijsen, Wim T.L.P.
System: The UNT Digital Library
Reflection-Based Python-C++ Bindings (open access)

Reflection-Based Python-C++ Bindings

Python is a flexible, powerful, high-level language with excellent interactive and introspective capabilities and a very clean syntax. As such, it can be a very effective tool for driving physics analysis. Python is designed to be extensible in low-level C-like languages, and its use as a scientific steering language has become quite widespread. To this end, existing and custom-written C or C++ libraries are bound to the Python environment as so-called extension modules. A number of tools for easing the process of creating such bindings exist, such as SWIG and Boost. Python. Yet, the process still requires a considerable amount of effort and expertise. The C++ language has few built-in introspective capabilities, but tools such as LCGDict and CINT add this by providing so-called dictionaries: libraries that contain information about the names, entry points, argument types, etc. of other libraries. The reflection information from these dictionaries can be used for the creation of bindings and so the process can be fully automated, as dictionaries are already provided for many end-user libraries for other purposes, such as object persistency. PyLCGDict is a Python extension module that uses LCG dictionaries, as PyROOT uses CINT reflection information, to allow /cwPython users to access …
Date: October 14, 2004
Creator: Generowicz, Jacek; Lavrijsen, Wim T.L.P.; Marino, Massimo & Mato, Pere
System: The UNT Digital Library
Saturation of Stimulated Brillouin Backscattering in Two-dimensional Kinetic Ion Simulations (open access)

Saturation of Stimulated Brillouin Backscattering in Two-dimensional Kinetic Ion Simulations

None
Date: October 14, 2004
Creator: Cohen, B. I.; Divol, L.; Langdon, A. B. & Williams, E. A.
System: The UNT Digital Library
Synthesis and Thermal Stability of Amorphous Be-B-X Alloy Coatings (open access)

Synthesis and Thermal Stability of Amorphous Be-B-X Alloy Coatings

Amorphous Be-B-X alloys are vapor deposited as coatings. The microstructure and hardness of the Be-B-X coatings are examined using transmission electron microscopy and nanoindentation, respectively. Whereas a Be-B-2.5 at.% Cu amorphous coating is found to crystallize to a cubic Be-33 at.% B phase at 673 K, a coating of Be-B-1.8 at.% Fe-0.4 at.% Cr-0.3 at.% Co does not crystallize until at a higher temperature of 748 K. The hardness of the amorphous Be-B-X coating increases with B content but is less than its crystalline counterparts.
Date: October 14, 2004
Creator: Jankowski, Alan Frederic; Wall, M. A. & Nieh, T. G.
System: The UNT Digital Library
Algebraic sub-structuring for electromagnetic applications (open access)

Algebraic sub-structuring for electromagnetic applications

Algebraic sub-structuring refers to the process of applying matrix reordering and partitioning algorithms to divide a large sparse matrix into smaller submatrices from which a subset of spectral components are extracted and combined to form approximate solutions to the original problem. In this paper, we show that algebraic sub-structuring can be effectively used to solve generalized eigenvalue problems arising from the finite element analysis of an accelerator structure.
Date: September 14, 2004
Creator: Yang, Chao; Gao, Weiguo; Bai, Zhaojun; Li, Xiaoye; Lee, Lie-Quan; Husbands, Parry et al.
System: The UNT Digital Library
The CKM matrix and CP violation (open access)

The CKM matrix and CP violation

The status of CP violation and the CKM matrix is reviewed. Direct CP violation in B decay has been established and the measurement of sin 2{beta} in {psi}K modes reached 5% accuracy. I discuss the implications of these, and of the possible deviations of the CP asymmetries in b {yields} s modes from that in {psi}K. The first meaningful measurements of {alpha} and {gamma} are explained, together with their significance for constraining both the SM and new physics in B-{bar B} mixing. I also discuss implications of recent developments in the theory of nonleptonic decays for B {yields} {pi}K rates and CP asymmetries, and for the polarization in charmless B decays to two vector mesons.
Date: September 14, 2004
Creator: Ligeti, Zoltan
System: The UNT Digital Library
Cost Optimization of Non-Scaling Ffag Latices for Muon Acceleration. (open access)

Cost Optimization of Non-Scaling Ffag Latices for Muon Acceleration.

Fixed Field Gradient (FFAG) accelerators are a promising idea for reducing the cost of acceleration for muon accelerators as well as other machines. This paper presents an automated method for designing these machines to certain specifications, and uses that method to find a minimum cost design. The dependence of this minimum cost on various input parameters to the system is given. The impact of the result on an FFAG design for muon acceleration is discussed.
Date: September 14, 2004
Creator: Berg, J. S. & Palmer, R. B.
System: The UNT Digital Library
Directed assembly of discrete gold nanoparticle groupings usingbranched DNA scaffolds (open access)

Directed assembly of discrete gold nanoparticle groupings usingbranched DNA scaffolds

The concept of self-assembled dendrimers is explored for the creation of discrete nanoparticle assemblies. Hybridization of branched DNA trimers and nanoparticle-DNA conjugates results in the synthesis of nanoparticle trimer and tetramer complexes. Multiple tetramer architectures are investigated, utilizing Au-DNA conjugates with varying secondary structural motifs. Hybridization products are analyzed by gel electrophoresis, and discrete bands are observed corresponding to structures with increasing numbers of hybridization events. Samples extracted from each band are analyzed by transmission electron microscopy, and statistics compiled from micrographs are used to compare assembly characteristics for each architecture. Asymmetric structures are also produced in which both 5 and 10 nm Au particles are assembled on branched scaffolds.
Date: September 14, 2004
Creator: Claridge, Shelley A.; Goh, Sarah L.; Frechet, Jean M.J.; Williams, Shara C.; Micheel, Christine M. & Alivisatos, A. Paul
System: The UNT Digital Library
Electron Model of an FFAG Muon Accelerator. (open access)

Electron Model of an FFAG Muon Accelerator.

Parameters are derived for the lattice and RF system of an electron model of a non-scaling FFAG ring for accelerating muons. The model accelerates electrons from about 10 to about 20 MeV, and has about 15 m circumference. Magnet types and dimensions, spacing, half apertures, about 12 mm by 20 mm, and number of cells are presented. The tune variation with momentum covers several integers, similar to that in a full machine, and allows the study of resonance crossing. The consequences of misaligned magnets are studied by simulation. The variation of orbit length with momentum is less than 36 mm, and allows the study of acceleration outside a bucket. A 100 mm straight section, in each of the cells, is adequately long for an RF cavity operating at 3 GHz. Hamiltonian dynamics in longitudinal phase space close to transition is used to calculate the accelerating voltage needed. Acceleration is studied by simulation. Practical RF system design issues, e.g. RF power, and beam loading are estimated.
Date: September 14, 2004
Creator: Keil, E.; Berg, J. S. & Sessler, A. M.
System: The UNT Digital Library