Publications

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Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed very well with the OH flame height. Flame height predictions using Roper's analysis for circular port burners agreed with measured reaction zone heights when using values for the characteristic diffusion coefficient and/or diffusion temperature somewhat different from those recommended by Roper. The fact that Roper's analysis applies to inverse diffusion flames is evidence that inverse diffusion flames are similar in structure to normal diffusion flames.

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Sandia National Laboratories has developed a portfolio of programs to address the critical skills needs of the DP labs, as identified by the 1999 Chiles Commission Report. The goals are to attract and retain the best and the brightest students and transition them into Sandia - and DP Complex - employees. The US Department of Energy/Defense Programs University Partnerships funded ten laboratory critical skills development programs in FY04. This report provides a qualitative and quantitative evaluation of these programs and their status. 3

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This Quality Assurance Project Plan (QAPP) applies to the Environmental Monitoring Program at the Sandia National Laboratories/California. This QAPP follows DOE Quality Assurance Management System Guide for Use with 10 CFR 830 Subpart A, Quality Assurance Requirements, and DOE O 414.1C, Quality Assurance (DOE G 414.1-2A June 17, 2005). The Environmental Monitoring Program is located within the Environmental Operations Department. The Environmental Operations Department is responsible for ensuring that SNL/CA operations have minimal impact on the environment. The Department provides guidance to line organizations to help them comply with applicable environmental regulations and DOE orders. To fulfill its mission, the department has groups responsible for waste management; pollution prevention, air quality; environmental planning; hazardous materials management; and environmental monitoring. The Environmental Monitoring Program is responsible for ensuring that SNL/CA complies with all Federal, State, and local regulations and with DOE orders regarding the quality of wastewater and stormwater discharges. The Program monitors these discharges both visually and through effluent sampling. The Program ensures that activities at the SNL/CA site do not negatively impact the quality of surface waters in the vicinity, or those of the San Francisco Bay. The Program verifies that wastewater and stormwater discharges are in compliance with established standards and requirements. The Program is also responsible for compliance with groundwater monitoring, and underground and above ground storage tanks regulatory compliance. The Program prepares numerous reports, plans, permit applications, and other documents that demonstrate compliance.

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Stakeholders often have competing interests when selecting or planning new power plants. The purpose of developing this preliminary Electricity Portfolio Simulation Model (EPSim) is to provide a first cut, dynamic methodology and approach to this problem, that can subsequently be refined and validated, that may help energy planners, policy makers, and energy students better understand the tradeoffs associated with competing electricity portfolios. EPSim allows the user to explore competing electricity portfolios annually from 2002 to 2025 in terms of five different criteria: cost, environmental impacts, energy dependence, health and safety, and sustainability. Four additional criteria (infrastructure vulnerability, service limitations, policy needs and science and technology needs) may be added in future versions of the model. Using an analytic hierarchy process (AHP) approach, users or groups of users apply weights to each of the criteria. The default energy assumptions of the model mimic Department of Energy's (DOE) electricity portfolio to 2025 (EIA, 2005). At any time, the user can compare alternative portfolios to this reference case portfolio.

A laser safety and hazard analysis is presented, for the Coherent(r) driven Acculite(r) laser central to the Sandia Remote Sensing System (SRSS). The analysis is based on the 2000 version of the American National Standards Institute's (ANSI) Standard Z136.1, for Safe Use of Lasers and the 2000 version of the ANSI Standard Z136.6, for Safe Use of Lasers Outdoors. The trailer (B70) based SRSS laser system is a mobile platform which is used to perform laser interaction experiments and tests at various national test sites. The trailer based SRSS laser system is generally operated on the United State Air Force Starfire Optical Range (SOR) at Kirtland Air Force Base (KAFB), New Mexico. The laser is used to perform laser interaction testing inside the laser trailer as well as outside the trailer at target sites located at various distances. In order to protect personnel who work inside the Nominal Hazard Zone (NHZ) from hazardous laser exposures, it was necessary to determine the Maximum Permissible Exposure (MPE) for each laser wavelength (wavelength bands) and calculate the appropriate minimum Optical Density (ODmin) necessary for the laser safety eyewear used by authorized personnel. Also, the Nominal Ocular Hazard Distance (NOHD) and The Extended Ocular Hazard Distance (EOHD) are calculated in order to protect unauthorized personnel who may have violated the boundaries of the control area and might enter into the laser's NHZ for testing outside the trailer. 4Page intentionally left blank

The Sandia National Laboratories, California (SNL/CA) Environmental Management System (EMS) Program Manual documents the elements of the site EMS Program. The SNL/CA EMS Program was developed in accordance with Department of Energy (DOE) Order 450.1 and incorporates the elements of the International Standard on Environmental Management Systems, ISO 14001.

Electromagnetic induction is a classic geophysical exploration method designed for subsurface characterization--in particular, sensing the presence of geologic heterogeneities and fluids such as groundwater and hydrocarbons. Several approaches to the computational problems associated with predicting and interpreting electromagnetic phenomena in and around the earth are addressed herein. Publications resulting from the project include [31]. To obtain accurate and physically meaningful numerical simulations of natural phenomena, computational algorithms should operate in discrete settings that reflect the structure of governing mathematical models. In section 2, the extension of algebraic multigrid methods for the time domain eddy current equations to the frequency domain problem is discussed. Software was developed and is available in Trilinos ML package. In section 3 we consider finite element approximations of De Rham's complex. We describe how to develop a family of finite element spaces that forms an exact sequence on hexahedral grids. The ensuing family of non-affine finite elements is called a van Welij complex, after the work [37] of van Welij who first proposed a general method for developing tangentially and normally continuous vector fields on hexahedral elements. The use of this complex is illustrated for the eddy current equations and a conservation law problem. Software was developed and is available in the Ptenos finite element package. The more popular methods of geophysical inversion seek solutions to an unconstrained optimization problem by imposing stabilizing constraints in the form of smoothing operators on some enormous set of model parameters (i.e. ''over-parametrize and regularize''). In contrast we investigate an alternative approach whereby sharp jumps in material properties are preserved in the solution by choosing as model parameters a modest set of variables which describe an interface between adjacent regions in physical space. While still over-parametrized, this choice of model space contains far fewer parameters than before, thus easing the computational burden, in some cases, of the optimization problem. And most importantly, the associated finite element discretization is aligned with the abrupt changes in material properties associated with lithologic boundaries as well as the interface between buried cultural artifacts and the surrounding Earth. In section 4, algorithms and tools are described that associate a smooth interface surface to a given triangulation. In particular, the tools support surface refinement and coarsening. Section 5 describes some preliminary results on the application of interface identification methods to some model problems in geophysical inversion. Due to time constraints, the results described here use the GNU Triangulated Surface Library for the manipulation of surface meshes and the TetGen software library for the generation of tetrahedral meshes.

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Currently, the critical particle properties of pentaerythritol tetranitrate (PETN) that influence deflagration-to-detonation time in exploding bridge wire detonators (EBW) are not known in sufficient detail to allow development of a predictive failure model. The specific surface area (SSA) of many PETN powders has been measured using both permeametry and gas absorption methods and has been found to have a critical effect on EBW detonator performance. The permeametry measure of SSA is a function of particle shape, packed bed pore geometry, and particle size distribution (PSD). Yet there is a general lack of agreement in PSD measurements between laboratories, raising concerns regarding collaboration and complicating efforts to understand changes in EBW performance related to powder properties. Benchmarking of data between laboratories that routinely perform detailed PSD characterization of powder samples and the determination of the most appropriate method to measure each PETN powder are necessary to discern correlations between performance and powder properties and to collaborate with partnering laboratories. To this end, a comparison was made of the PSD measured by three laboratories using their own standard procedures for light scattering instruments. Three PETN powder samples with different surface areas and particle morphologies were characterized. Differences in bulk PSD data generated by each laboratory were found to result from variations in sonication of the samples during preparation. The effect of this sonication was found to depend on particle morphology of the PETN samples, being deleterious to some PETN samples and advantageous for others in moderation. Discrepancies in the submicron-sized particle characterization data were related to an instrument-specific artifact particular to one laboratory. The type of carrier fluid used by each laboratory to suspend the PETN particles for the light scattering measurement had no consistent effect on the resulting PSD data. Finally, the SSA of the three powders was measured using both permeametry and gas absorption methods, enabling the PSD to be linked to the SSA for these PETN powders. Consistent characterization of other PETN powders can be performed using the appropriate sample-specific preparation method, so that future studies can accurately identify the effect of changes in the PSD on the SSA and ultimately model EBW performance.

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Two 100 kW min-1 (1.67 kW h-1) Li-ion battery energy storage systems (BESS) are described. The systems include a high-power Li-ion battery and a 100 kW power conditioning system (PCS). The battery consists of 12 modules of 12 series-connected Saft Li-ion VL30P cells. The stored energy of the battery ranges from 1.67 to 14 kW h-1 and has an operating voltage window of 515-405 V (dc). Two complete systems were designed, built and successfully passed factory acceptance testing after which each was deployed in a field demonstration. The first demonstration used the system to supplement distributed microturbine generation and to provide load following capability. The system was run at its rated power level for 3 min, which exceeded the battery design goal by a factor of 3. The second demonstration used another system as a stand-alone uninterrupted power supply (UPS). The system was available (online) for 1146 h and ran for over 2 min. © 2005 Elsevier B.V. All rights reserved.

Molecular dynamics (MD) computer simulations of liquid water adsorbed on the muscovite (001) surface provide a greatly increased, atomistically detailed understanding of surface-related effects on the spatial variation in the structural and orientational ordering, hydrogen bond (H-bond) organization, and local density of H 2O molecules at this important model phyllosilicate surface. MD simulations at constant temperature and volume (statistical NVT ensemble) were performed for a series of model systems consisting of a two-layer muscovite slab (representing 8 crystallographic surface unit cells of the substrate) and 0 to 319 adsorbed H 2O molecules, probing the atomistic structure and dynamics of surface aqueous films up to 3 nm in thickness. The results do not demonstrate a completely liquid-like behavior, as otherwise suggested from the interpretation of X-ray reflectivity measurements 1 and earlier Monte Carlo simulations. 2 Instead, a more structurally and orientationally restricted behavior of surface H 2O molecules is observed, and this structural ordering extends to larger distances from the surface than previously expected. Even at the largest surface water coverage studied, over 20% of H 2O molecules are associated with specific adsorption sites, and another 50% maintain strongly preferred orientations relative to the surface. This partially ordered structure is also different from the well-ordered 2-dimensional ice-like structure predicted by ab initio MD simulations for a system with a complete monolayer water coverage. 3 However, consistent with these ab initio results, our simulations do predict that a full molecular monolayer surface water coverage represents a relatively stable surface structure in terms of the lowest diffusional mobility of H 2O molecules along the surface. Calculated energies of water adsorption are in good agreement with available experimental data. 4 © 2005 American Chemical Society.

Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest for large aperture space-based telescopes. Dimensional adjustments of adaptive polymer films are achieved via charge deposition and require a detailed understanding of the piezoelectric material responses which are expected to suffer due to strong vacuum UV, γ-, X-ray, energetic particles and atomic oxygen under low earth orbit exposure conditions. The degradation of PVDF and its copolymers under various stress environments has been investigated. Initial radiation aging studies using γ- and e-beam irradiation have shown complex material changes with significant crosslinking, lowered melting and Curie points (where observable), effects on crystallinity, but little influence on overall piezoelectric properties. Surprisingly, complex aging processes have also been observed in elevated temperature environments with annealing phenomena and cyclic stresses resulting in thermal depoling of domains. Overall materials performance appears to be governed by a combination of chemical and physical degradation processes. Molecular changes are primarily induced via radiative damage, and physical damage from temperature and AO exposure is evident as depoling and surface erosion. Major differences between individual copolymers have been observed providing feedback on material selection strategies. © 2045 Materials Research Society.

To generate data for comparison with the predictions of continuum sintering models for multi-material systems, several types of concentric cylinder samples were sintered to produce damage during sintering. The samples consisted of an outer ring of pressed ceramic powder (alumina or zinc oxide), the center of which was either fully or partially filled with a cylinder that consisted of either the same powder pressed to a higher green density (fully filled) or of previously densified 99% alumina (fully or partially filled). In addition, slots of various lengths were cut in some of the rings, from the outer surface parallel to the cylinder axis, which were then fully filled with dense alumina center cylinders and sintered. The types of sintering damage produced as the shrinkage of the rings was constrained by the center cylinders which shrank less or not at all, included shape deformation, cracking and possible density gradient formation. Comparisons of shrinkage measurements on rings fully filled with dense alumina center cylinders indicated that while the presence of the center cylinder increased the thickness and width shrinkage for both materials, the overall densification of the rings was impeded due to the decrease in circumferential shrinkage. This effect was more severe for the zinc oxide rings. The shape of the cross sections of the rings that were sintered either fully or partially filled with dense alumina center cylinders also showed differences depending on their composition.

An integrated 3D Direct Chill (DC) casting model was used to simulate the heat transfer, fluid flow, solidification, and thermal stress during casting. Temperature measurements were performed in an industrial casting facility to setup and validate the model. The key features such as heat transfer between cooling water and the ingot surface as a function of surface temperature, cooling water flow rate, air gaps caused by mold and bottom block design were also considered in the model. An elasto-viscoplastic constitutive model, which was determined based on mechanical testing, was used to calculate the evolution of stress during casting. The stress evolution was compared at various locations and correlated with physical phenomena associated with the casting process. An Ingot Cracking Index, which represents the ingot hot cracking propensity, was established based on the ratio of stress to strength. The Index calculation results were consistent with observations in industrial casting practice.

Surface heat transfer coefficients representing the various regimes of water cooling during the Direct Chill (DC) casting of aluminum 3004 alloy ingots have been calculated using the inverse heat transfer technique. ProCAST, a commercial casting simulation package, which includes heat transfer, fluid flow, solidification, and inverse heat transfer, was used for this effort. Thermocouple data from an experimental casting run, and temperature-dependent thermophysical properties of the alloy were used in the calculation. The use of a structured vs. unstructured mesh was evaluated. The calculated effective heat transfer coefficient, which is a function of temperature and time, covers three water cooling regimes, i.e., convection, nucleate boiling, and film boiling, and the change of water flow rate with time.

Molecular dynamics simulations are used to study the spreading of binary polymer nanodroplets in a cylindrical geometry. The polymers, described by the bead-spring model, spread on a flat surface with a surface-coupled Langevin thermostat to mimic the effects of a corrugated surface. Each droplet consists of chains of length 10 or 100 monomers with ∼350 000 monomers total. The qualitative features of the spreading dynamics are presented for differences in chain length, surface interaction strength, and composition. When the components of the droplet differ only in the surface interaction strength, the more strongly wetting component forms a monolayer film on the surface even when both materials are above or below the wetting transition. In the case where the only difference is the polymer chain length, the monolayer film beneath the droplet is composed of an equal amount of short chain and long chain monomers even when one component (the shorter chain length) is above the wetting transition and the other is not. The fraction of short and long chains in the precursor foot depends on whether both the short and the long chains are in the wetting regime. Diluting the concentration of the strongly wetting component in a mixture with a weakly wetting component decreases the rate of diffusion of the wetting material from the bulk to the surface and limits the spreading rate of the precursor foot, but the bulk spreading rate actually increases when both components are present. This may be due to the strongly wetting material pushing out the weakly wetting material as it moves toward the precursor foot. © 2005 American Chemical Society.