Publications

Abstract not provided.

We report the implementation of an iterative scheme for calculating the Optimized Effective Potential (OEP). Given an energy functional that depends explicitly on the Kohn-Sham wave functions, and therefore, implicitly on the local effective potential appearing in the Kohn-Sham equations, a gradient-based minimization is used to find the potential that minimizes the energy. Previous work has shown how to find the gradient of such an energy with respect to the effective potential in the zero-temperature limit. We discuss a density-matrix-based derivation of the gradient that generalizes the previous results to the finite temperature regime, and we describe important optimizations used in our implementation. We have applied our OEP approach to the Hartree-Fock energy expression to perform Exact Exchange (EXX) calculations. We report our EXX results for common semiconductors and ordered phases of hydrogen at zero and finite electronic temperatures. We also discuss issues involved in the implementation of forces within the OEP/EXX approach.

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Abstract not provided.

Polysilane materials exhibit large photo-induced refractive index changes under low incident optical fluences, making them attractive candidates for applications in which rapid patterning of photonic device structures is desired immediately prior to their use. This agile fabrication strategy for integrated photonics inherently requires that optical exposure, and associated material response, occurs in nonlaboratory environments, motivating the study of environmental conditions on the photoinduced response of the material. The present work examines the impact of atmosphere on the photosensitive response of poly(methylphenylsilane) (PMPS) thin films in terms of both photoinduced absorption change and refractive index modification. Material was subjected to UV light exposure resonant with the lowest energy optical transition associated with the conjugated Si-Si backbone. Exposures were performed in both aerobic and anaerobic atmospheres (oxygen, air, nitrogen, and 5% H2/95% N 2). The results clearly demonstrate that the photosensitive response of this model polysilane material was dramatically affected by local environment, exhibiting a photoinduced refractive index change, when exposed under an oxygen containing atmosphere, that was twice that observed under anaerobic conditions. This effect is discussed in terms of photo-oxidation processes within the polysilane structure and in the context of the need for predictable photosensitive refractive index change in varied photoimprinting environments.

We present a series of related robust optimization models for placing sensors in municipal water networks to detect contaminants that are maliciously or accidentally injected. We formulate sensor placement problems as mixed-integer programs, for which the objective coefficients are not known with certainty. We consider a restricted absolute robustness criteria that is motivated by natural restrictions on the uncertain data, and we define three robust optimization models that differ in how the coefficients in the objective vary. Under one set of assumptions there exists a sensor placement that is optimal for all admissible realizations of the coefficients. Under other assumptions, we can apply sorting to solve each worst-case realization efficiently, or we can apply duality to integrate the worst-case outcome and have one integer program. The most difficult case is where the objective parameters are bilinear, and we prove its complexity is NP-hard even under simplifying assumptions. We consider a relaxation that provides an approximation, giving an overall guarantee of near-optimality when used with branch-and-bound search. We present preliminary computational experiments that illustrate the computational complexity of solving these robust formulations on sensor placement applications.

Sandia National Laboratories Airworthiness Assurance Nondestructive Inspection Validation Center (AANC) provides independent and quantitative evaluations of new and enhanced inspection, to developers, users, and regulators of aircraft. Wayne State University (WSU) has developed and patented an inspection technique using high-power ultrasonic excitation and infrared technology to detect defects in a variety of materials. AANC and WSU are working together as part of the FAA Sonic Infrared Technology Transfer Program. The ultimate goal of the program is to implement Sonic IR in the aviation field where appropriate. The capability of Sonic IR imaging to detect cracks in components commonly inspected with magnetic particle or liquid penetrant inspection in the field is of interest to industry. © 2006 American Institute of Physics.

Oxygen-enhanced and oxygen-fired pulverized coal combustion is actively being investigated to achieve emission reductions and reductions in flue gas cleanup costs, as well as for coal-bed methane and enhanced oil recovery applications. To fully understand the results of pilot scale tests and to accurately predict scale-up performance through CFD modeling, accurate rate expressions are needed to describe coal char combustion under these unconventional combustion conditions. In the work reported here, the combustion rates of two pulverized coal chars have been measured in both conventional and oxygen-enriched atmospheres. A combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation. Highvale subbituminous coal and a high-volatile eastern United States bituminous coal have been investigated, over oxygen concentrations ranging from 6 to 36 mol% and gas temperatures of 1320-1800 K. The results from these experiments demonstrate that pulverized coal char particles burn under increasing kinetic control in elevated oxygen environments, despite their higher burning rates in these environments. Empirical fits to the data have been successfully performed over the entire range of oxygen concentrations using a single-film oxidation model. Both a simple nth-order Arrhenius expression and an nth-order Langmuir-Hinshelwood kinetic equation provide good fits to the data. Local fits of the nth-order Arrhenius expression to the oxygen-enriched and oxygen-depleted data produce lower residuals in comparison to fits of the entire dataset. These fits demonstrate that the apparent reaction order varies from 0.1 under near-diffusion-limit oxygen-depleted conditions to 0.5 under oxygen-enriched conditions. Burnout predictions show good agreement with measurements. Predicted char particle temperatures tend to be low for combustion in oxygen-depleted environments. © 2005 The Combustion Institute.

We consider four asynchronous parallel algorithms for Implicit Monte Carlo (IMC) thermal radiation transport on spatially decomposed meshes. Two of the algorithms are from the production codes KULL from Lawrence Livermore National Laboratory and Milagro from Los Alamos National Laboratory. Improved versions of each of the existing algorithms are also presented. All algorithms were analyzed in an implementation of the KULL IMC package in ALEGRA, a Sandia National Laboratory high energy density physics code. The improved Milagro algorithm performed the best by scaling almost linearly out to 244 processors for well load balanced problems. © 2005 Elsevier Inc. All rights reserved.

The technique of active capture and transport of virus particles using a biomolecular motor-driven, nanoscale antibody sandwich assay was described. Nanofluidic transport of macromolecules within living cells is achieved using a complex, three-dimensional network of cytoskeletal filaments and motor proteins. It is observed that glutaraldehyde crosslinking successfully linked fluorescent antibodies to MT shuttles. The application of kinesin and Ab-MT as mechanical actuators enables the development of nanofluidic systems that rely only on chemical energy for capturing and separating of target analytes from a complex solution.

Desulfovibrio vulgaris Hildenborough belongs to a class of sulfate-reducing bacteria (SRB) and is found ubiquitously in nature. Given the importance of SRB-mediated reduction for bioremediation of metal ion contaminants, ongoing research on D. vulgaris has been in the direction of elucidating regulatory mechanisms for this organism under a variety of stress conditions. This work presents a global view of this organism's response to elevated growth temperature using whole-cell transcriptomics and proteomics tools. Transcriptional response (1.7-fold change or greater; Z ≥ 1.5) ranged from 1,135 genes at 15 min to 1,463 genes at 120 min for a temperature up-shift of 13°C from a growth temperature of 37°C for this organism and suggested both direct and indirect modes of heat sensing. Clusters of orthologous group categories that were significantly affected included posttranslational modifications; protein turnover and chaperones (up-regulated); energy production and conversion (down-regulated), nucleotide transport, metabolism (down-regulated), and translation; ribosomal structure; and biogenesis (down-regulated). Analysis of the genome sequence revealed the presence of features of both negative and positive regulation which included the CIRCE element and promoter sequences corresponding to the alternate sigma factors σ32 and σ54. While mechanisms of heat shock control for some genes appeared to coincide with those established for Escherichia coli and Bacillus subtilis, the presence of unique control schemes for several other genes was also evident. Analysis of protein expression levels using differential in-gel electrophoresis suggested good agreement with transcriptional profiles of several heat shock proteins, including DnaK (DVU0811), HtpG (DVU2643), HtrA (DVU1468), and AhpC (DVU2247). The proteomics study also suggested the possibility of posttranslational modifications in the chaperones DnaK, AhpC, GroES (DVU1977), and GroEL (DVU1976) and also several periplasmic ABC transporters. Copyright © 2006, American Society for Microbiology. All Rights Reserved.

A process for deposition of silicon oxycarbonitride films from poly(urea)methyl vinyl silazane (PUMVS) by spin coating precursor solutions onto a substrate, followed by polymerization, cross-linking and pyrolysis has been developed. The cross-linked polymer films (350 nm thick), deposited on variety substrates (e.g., silicon, sapphire, zirconia), were pyrolyzed in nitrogen or ammonia environments either in a hot isostatic press or in a tube furnace. Their microstructure was characterized using infrared and Raman spectroscopy. The tribological (friction and wear) behavior was evaluated in dry nitrogen and air with 50% relative humidity using a unidirectional linear wear tester in a ball-on-disk configuration. Wear surfaces, transfer films and wear debris were analyzed by scanning electron micrograph (SEM)/energy dispersive spectroscopy (EDS). © 2006 The American Ceramic Society.

This report summarizes the activities of the Computer Science Research Institute (CSRI) at Sandia National Laboratories during the period January 1, 2003 to December 31, 2003. During this period the CSRI hosted 164 visitors representing 78 universities, companies and laboratories. Of these 78 were summer students or faculty members. The CSRI partially sponsored 5 workshops and also organized and was the primary host for 3 workshops. These 3 CSRI sponsored workshops had 178 participants--137 from universities, companies and laboratories, and 41 from Sandia. Finally, the CSRI sponsored 18 long-term collaborative research projects and 5 Sabbaticals.

This report summarizes the activities of the Computer Science Research Institute (CSRI) at Sandia National Laboratories during the period January 1, 2004 to December 31, 2004. During this period the CSRI hosted 166 visitors representing 81 universities, companies and laboratories. Of these 65 were summer students or faculty. The CSRI partially sponsored 2 workshops and also organized and was the primary host for 4 workshops. These 4 CSRI sponsored workshops had 140 participants--74 from universities, companies and laboratories, and 66 from Sandia. Finally, the CSRI sponsored 14 long-term collaborative research projects and 5 Sabbaticals.

The Materials Applications for Homeland Security session at the Materials Science and Technology 2005 (MS&T'05) Conference discussed new countermeasures related to anticipate, prevent, respond to, and recover from acts of terrorism. Examples were given of how science and technology have contributed to counter-terrorism, as with the development of sensor systems and in effects mitigation, where the latter protect people and physical assets in the event of attack. However, it is also important that the S&T community consider the technical capabilities of end-users. Jon MacLaren of the DHS Risk Assessment program discussed the threats to critical infrastructures while Jiann-Yang (Jim) Hwang and Bowen Li of Michigan Technological University described active antibacterial/antifungal coatings made of low-cost vermiculite in which magnesium ions are replaced with copper ions. Dr. John Vitko of the Department of Homeland Security oversees a broad-ranging program from surveillance to forensics and consequence management, from personnel training to development of anti-viral drugs. Vinayak Dravid described bio-chem assay microsensor which offer versatility for sensing biological and chemical threats, and provide significant advantages over alternatives.

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Abstract not provided.

The proposed Yucca Mountain repository, located in southern Nevada, is to be the first facility for permanent disposal of spent reactor fuel and high-level radioactive waste in the United States. Total Systems Performance Assessment (TSPA) analysis has indicated that among the major radionuclides contributing to dose are technetium, iodine, and neptunium, all of which are highly mobile in the environment. Containment of these radionuclides within the repository is a priority for the Yucca Mountain Project (YMP). These proceedings review current research and technology efforts for sequestration of the radionuclides with a focus on technetium, iodine, and neptunium. This workshop also covered issues concerning the Yucca Mountain environment and getter characteristics required for potential placement into the repository.

High-energy photons and neutrons can be used to actively interrogate for heavily shielded special nuclear material (SNM), such as HEU (highly enriched uranium), by detecting prompt and/or delayed induced fission signatures. In this work, we explore the underlying physics for a new type of photon source that generates high fluxes of mono-energetic gamma-rays from low-energy (<500 keV) proton-induced nuclear reactions. The characteristic energies (4- to 18-MeV) of the gamma-rays coincide with the peak of the photonuclear cross section. The source could be designed to produce gamma-rays of certain selected energies, thereby improving the probability of detecting shielded HEU or providing a capability to determine enrichment inside sealed containers. The fundamental physics of such an interrogation source were studied in this LDRD through scaled ion accelerator experiments and radiation transport modeling. The data were used to assess gamma and neutron yields, background, and photofission-induced signal levels from several (p,{gamma}) target materials under consideration.

Wind turbine system reliability is a critical factor in the success of a wind energy project. Poor reliability directly affects both the project's revenue stream through increased operation and maintenance (O&M) costs and reduced availability to generate power due to turbine downtime. Indirectly, the acceptance of wind-generated power by the financial and developer communities as a viable enterprise is influenced by the risk associated with the capital equipment reliability; increased risk, or at least the perception of increased risk, is generally accompanied by increased financing fees or interest rates. This paper outlines the issues relevant to wind turbine reliability for wind turbine power generation projects. The first sections describe the current state of the industry, identify the cost elements associated with wind farm O&M and availability and discuss the causes of uncertainty in estimating wind turbine component reliability. The latter sections discuss the means for reducing O&M costs and propose O&M related research and development efforts that could be pursued by the wind energy research community to reduce cost of energy.

Glass, in various formulations, may be useful as a transparent armor material. Fused quartz (SiO{sub 2}), modified with either B{sub 2}O{sub 3} (13 % wt.) or Na{sub 2}O (15 % wt.), was studied to determine the effect on the dynamic response of the material. Utilizing powder and two-stage light gas guns, plate impact experiments were conducted to determine the effect on strength properties, including the elastic limits and plastic deformation response. Further, the effect of glass modification on known transitions to higher density phases in fused quartz was evaluated. Results of these experiments will be presented and discussed.

The Power Sources Manufacturers Association (PSMA) is pleased to announce the release of the latest Power Technology Roadmap Workshop Report. This Fifth Edition Workshop Report includes presentations and discussions from the workshop as seen by the participants that included many of the industry's most influential members representing end-users, power supply manufacturers, component suppliers, consultants and academia. This report provides detailed projections for the next three to four years of various technologies in a quantitative form. There was special emphasis on how the increasing use of digital technologies will affect the industry in the next four years. The technology trend analysis and the roadmap is provided for the following specific product families expected to be the areas of largest market growth: (1) Ac-dc front end power supplies--1 kW from a single phase ac source; (2) External ac-dc power supplies; (3) Dc-dc bus converters; and (4) Non-isolated dc-dc converters. Bruce Miller, Chairman of PSMA, stated that 'the Power Technology Roadmap Workshop Report is an extensive document that analyzes and provides projections for most major technical parameters for a specific power supply. It is a unique document as it contains technology/parametric trends in a roadmap fashion from a variety of diverse sources, giving significant depth to its content. No such information is available from any other source'. The Power Technology Roadmap Workshop Report is available at no cost as to PSMA Regular and Associate members and at a reduced price to Affiliate members as a benefit of membership. The report will be offered to non-members at a price of $2490. For further information or to buy a copy of the report, please visit the publications page or the PSMA website or contact the Association Office.

Abstract not provided.

Abstract not provided.