Publications

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Glasses filled with ceramic or metallic powders have been developed for use as seals for solid oxide fuel cells (SOFC's) as part of the U.S. Department of Energy's Solid State Energy Conversion Alliance (SECA) Program. The composites of glass (alkaline earth-alumina-borate) and powders ({approx}20 vol% of yttria-stabilized zirconia or silver) were shown to form seals with SOFC materials at or below 900 C. The type and amount of powder were adjusted to optimize thermal expansion to match the SOFC materials and viscosity. Wetting studies indicated good wetting was achieved on the micro-scale and reaction studies indicated that the degree of reaction between the filled glasses and SOFC materials, including spinel-coated 441 stainless steel, at 750 C is acceptable. A test rig was developed for measuring strengths of seals cycled between room temperature and typical SOFC operating temperatures. Our measurements showed that many of the 410 SS to 410 SS seals, made using silver-filled glass composites, were hermetic at 0.2 MPa (2 atm.) of pressure and that seals that leaked could be resealed by briefly heating them to 900 C. Seal strength measurements at elevated temperature (up to 950 C), measured using a second apparatus that we developed, indicated that seals maintained 0.02 MPa (0.2 atm.) overpressures for 30 min at 750 C with no leakage. Finally, the volatility of the borate component of sealing glasses under SOFC operational conditions was studied using weight loss measurements and found by extrapolation to be less than 5% for the projected SOFC lifetime.

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This paper presents a parallel programming model, Parallel Phase Model (PPM), for next-generation high-end parallel machines based on a distributed memory architecture consisting of a networked cluster of nodes with a large number of cores on each node. PPM has a unified high-level programming abstraction that facilitates the design and implementation of parallel algorithms to exploit both the parallelism of the many cores and the parallelism at the cluster level. The programming abstraction will be suitable for expressing both fine-grained and coarse-grained parallelism. It includes a few high-level parallel programming language constructs that can be added as an extension to an existing (sequential or parallel) programming language such as C; and the implementation of PPM also includes a light-weight runtime library that runs on top of an existing network communication software layer (e.g. MPI). Design philosophy of PPM and details of the programming abstraction are also presented. Several unstructured applications that inherently require high-volume random fine-grained data accesses have been implemented in PPM with very promising results.

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This document describes how to obtain, install, use, and enjoy a better life with OVIS version 2.0. The OVIS project targets scalable, real-time analysis of very large data sets. We characterize the behaviors of elements and aggregations of elements (e.g., across space and time) in data sets in order to detect anomalous behaviors. We are particularly interested in determining anomalous behaviors that can be used as advance indicators of significant events of which notification can be made or upon which action can be taken or invoked. The OVIS open source tool (BSD license) is available for download at ovis.ca.sandia.gov. While we intend for it to support a variety of application domains, the OVIS tool was initially developed for, and continues to be primarily tuned for, the investigation of High Performance Compute (HPC) cluster system health. In this application it is intended to be both a system administrator tool for monitoring and a system engineer tool for exploring the system state in depth. OVIS 2.0 provides a variety of statistical tools for examining the behavior of elements in a cluster (e.g., nodes, racks) and associated resources (e.g., storage appliances and network switches). It calculates and reports model values and outliers relative to those models. Additionally, it provides an interactive 3D physical view in which the cluster elements can be colored by raw element values (e.g., temperatures, memory errors) or by the comparison of those values to a given model. The analysis tools and the visual display allow the user to easily determine abnormal or outlier behaviors. The OVIS project envisions the OVIS tool, when applied to compute cluster monitoring, to be used in conjunction with the scheduler or resource manager in order to enable intelligent resource utilization. For example, nodes that are deemed less healthy, that is, nodes that exhibit outlier behavior in some variable, or set of variables, that has shown to be correlated with future failure, can be discovered and assigned to shorter duration or less important jobs. Further, applications with fault-tolerant capabilities can invoke those mechanisms on demand, based upon notification of a node exhibiting impending failure conditions, rather than performing such mechanisms (e.g. checkpointing) at regular intervals unnecessarily.

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Residents of Southern Nevada have expressed interest in the risks posed by transportation of radioactive materials to the Nevada Test Site for disposal. Residents of the urban sections of Clark County, in particular, are concerned because the trucks carrying this material pass through fairly densely populated areas on both primary and secondary highways. Excellent studies by the Desert Research Institute (Miller, et al, 2005; 2007) measured the external radiation doses from these trucks and provided a benchmark for estimating the doses sustained by the population along the transportation routes. The studies did not, however, assess the doses to the population in the event of an accident involving these trucks. The present study estimates doses to the population along these routes and to various individual receptors, both for routine, incident-free transportation and for transportation accidents.

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A state-based peridynamic material model describes internal forces acting on a point in terms of the collective deformation of all the material within a neighborhood of the point. In this paper, the response of a state-based peridynamic material is investigated for a small deformation superposed on a large deformation. The appropriate notion of a small deformation restricts the relative displacement between points, but it does not involve the deformation gradient (which would be undefined on a crack). The material properties that govern the linearized material response are expressed in terms of a new quantity called the modulus state. This determines the force in each bond resulting from an incremental deformation of itself or of other bonds. Conditions are derived for a linearized material model to be elastic, objective, and to satisfy balance of angular momentum. If the material is elastic, then the modulus state is obtainable from the second Frechet derivative of the strain energy density function. The equation of equilibrium with a linearized material model is a linear Fredholm integral equation of the second kind. An analogue of Poincare's theorem is proved that applies to the infinite dimensional space of all peridynamic vector states, providing a condition similar to irrotationality in vector calculus.

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Sandia National Laboratories, California (SNL/CA) is a government-owned/contractor operated laboratory. Sandia Corporation, a Lockheed Martin Company, operates the laboratory for the Department of Energy's National Nuclear Security Administration (NNSA). The NNSA Sandia Site Office oversees operations at the site, using Sandia Corporation as a management and operating contractor. This Site Environmental Report for 2008 was prepared in accordance with DOE Order 231.1A (DOE 2004a). The report provides a summary of environmental monitoring information and compliance activities that occurred at SNL/CA during calendar year 2008. General site and environmental program information is also included.

We report here the fabrication processes used to manufacture US Party Team First Wall Qualification Mockups along with the detailed microstructural characterization and mechanical properties of the Be/CuCrZr/316L HIP bonds. A companion submission to this conference describes details of the PMTF heat flux testing and the performance of the first US FWQM.

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This document is the final SAND Report for the LDRD Project 102660 - 'Bottomup' meets 'top-down': Self-assembly to direct manipulation of nanostructures on length scales from atoms to microns - funded through the Strategic Partnerships investment area as part of the National Institute for Nano-Engineering (NINE) project.

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Running untrusted user-level code inside an operating system kernel has been studied in the 1990's but has not really caught on. We believe the time has come to resurrect kernel extensions for operating systems that run on highly-parallel clusters and supercomputers. The reason is that the usage model for these machines differs significantly from a desktop machine or a server. In addition, vendors are starting to add features, such as floating-point accelerators, multicore processors, and reconfigurable compute elements. An operating system for such machines must be adaptable to the requirements of specific applications and provide abstractions to access next-generation hardware features, without sacrificing performance or scalability.

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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 conforms to the International Standard on Environmental Management Systems, ISO 14001:2004 and Department of Energy (DOE) Order 450.1. Sandia National Laboratories, California (SNL/CA) has maintained functional environmental programs to assist with regulatory compliance for more than 30 years. During 2005, these existing programs were rolled into a formal environmental management system (EMS) that expands beyond the traditional compliance focus to managing and improving environmental performance and stewardship practices for all site activities. An EMS is a set of inter-related elements that represent a continuing cycle of planning, implementing, evaluating, and improving processes and actions undertaken to achieve environmental policy and goals. The SNL/CA EMS Program conforms to the International Standard for Environmental Management Systems, ISO 14001:2004 (ISO 2004). The site received ISO 14001 certification in September 2006. SNL/CA's EMS Program is applicable to the Sandia, Livermore site only. Although SNL/CA operates as one organizational division of the overall Sandia National Laboratories, the EMS Program is site-specific, with site-specific objectives and targets. SNL/CA (Division 8000) benefits from the organizational structure as it provides corporate level policies, procedures, and standards, and established processes that connect to and support elements of the SNL/CA EMS Program. Additionally, SNL/CA's EMS Program benefits from two corporate functional programs (Facilities Energy Management and Fleet Services Environmental programs) that maintain responsibility for energy management and fleet services for all Sandia locations. Each EMS element is further enhanced with site-specific processes and standards. Division 8000 has several groups operating at Sandia National Laboratories, New Mexico (SNL/NM). Although these groups, from an organizational perspective, are part of Division 8000, they are managed locally and fall under the environmental requirements specific to their New Mexico location. The New Mexico groups in Division 8000 follow the corporate EMS Program for New Mexico operations.

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Under shock loading, metals typically increase in strength with shock pressure initially but at higher stresses will eventually soften due to thermal effects. Under isentropic loading, thermal effects are minimized, so strength should rise to much higher levels. To date, though, study of strength under isentropic loading has been minimal. Here, we report new experimental results for magnetic ramp loading and impact by layered impactors in which the strength of 6061-T6 aluminum is measured under quasi-isentropic loading to stresses as high as 55 GPa. Strength is inferred from measured velocity histories using Lagrangian analysis of the loading and unloading responses; strength is related to the difference of these two responses. A simplified method to infer strength directly from a single velocity history is also presented. Measured strengths are consistent with shock loading and instability growth results to about 30 GPa but are somewhat higher than shock data for higher stresses. The current results also agree reasonably well with the Steinberg-Guinan strength model. Significant relaxation is observed as the peak stress is reached due to rate dependence and perhaps other mechanisms; accounting for this rate dependence is necessary for a valid comparison with other results. © 2009 Elsevier Ltd.

Researchers use constructs from the field of electrical engineering for the modelling and analysis of biological systems, but few exploit parallels between electrical and biological circuits for simulation purposes. The authors discuss the development of BioXyce, a circuit-based biological simulation platform that uses Xyce™, a large-scale electrical circuit simulator, as its simulation engine. BioXyce is capable of simulating whole-cell and multicellular systems. Simulation results for the central metabolism in Escherichia coli K12 and cellular differentiation in Drosophila sp. are presented. © The Institution of Engineering and Technology 2009.

A general approach for manufacturing of micro-scale components from high-strength, nanostructured materials is presented. The approach utilizes severe plastic deformation by large-strain extrusion machining to create the nanostructured material in a high-strength alloy system, and conventional micro-machining to produce the components. Manufacture of small-scale gears from nickel-based superalloy Inconel 718 is illustrated. © 2008 Elsevier B.V. All rights reserved.

Porous materials having multiple scales of porosity afford the opportunity to combine the high surface area and functionality of nanopores with the superior charge/discharge characteristics of wider transport channels. However, the relative volume fractions assigned to nanopores and transport channels must be thoughtfully balanced because the introduction of transport channels reduces the volume available for nanopore functionality. In the present paper, the optimal balance between nanopore capacity and system response time is achieved by adjusting the aperture and spacing of a family of transport channels that provide access to adjacent nanopores during recharge/discharge cycles of materials intended for storage of gas or electric charge. A diffusive transport model is used to describe alternative processes of viscous gas flow, Knudsen gas flow, and ion diffusion or electromigration. The coupled transport equations for the nanopores and transport channels are linearized and solved analytically for a periodic variation in external gas pressure, ion concentration, or electric potential using a separation-of-variables approach in the complex domain. Optimization of these solutions yields closed-form expressions for channel apertures and spacing that provide maximum discharge of gas or electric charge for a fixed system volume and a desired discharge time. © 2009 The American Physical Society.

The ferroelectric-to-ferroelectric phase transition between the high temperature (FE RH) and the low temperature (FE RL) rhombohedral phases in a Nb-doped Pb(Zr 0.95Ti 0.05)O 3 ceramic was investigated with transmission electron microscopy (TEM). Both bright field images and electron diffraction patterns were monitored as a function of temperature as well as dc electric field. A special TEM specimen holder that permits the application of electric voltage up to 600 V was employed for the study of electric field-induced phase transition. It was found that both [1/2](011) c- and [1/2](111)c-type superlattice diffraction spots were present at room temperature when the specimen was under no electric field. The [1/2](111) c-type superlattice spots were observed to disappear during heating above the phase transition temperature. When dc electric fields were applied at room temperature, the [1/2](111) c-type superlattice spots vanished as the electric field-induced FE RL → FE RH phase transition occurred. © 2009 Wiley-Liss, inc.

In ductile metals, sliding contact induces plastic deformation resulting in subsurfaces, the mechanical properties of which are different from those of the bulk. This article describes a novel combination of nanomechanical test methods and analysis techniques to evaluate the mechanical behavior of the subsurfaces generated underneath a wear surface. In this methodology, nanoscratch techniques were first used to generate wear patterns as a function of load and number of cycles using a Hysitron TriboIndenter. Measurements were made on a (001) single crystal plane along two crystallographic directions, <001> and <011>. Nanoindentation was then used to measure mechanical properties in each wear pattern. The results on the (001) single crystal nickel plane showed that there was a strong increase in hardness with increasing applied load that was accompanied by a change in surface deformation. The amount of deformation underneath the wear patterns was examined from focused ion beam cross-sections of the wear patterns. © 2009 Materials Research Society.

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Nanoporous palladium powders are synthesized on milligram to gram scales by chemical reduction of tetrachloro complexes by ascorbate in a concentrated aqueous surfactant at temperatures between -20 and 30 C. Particle diameters are approximately 50 nm, and each particle is perforated by 3 nm pores, as determined by electron tomography. These materials are of potential value for storage of hydrogen isotopes and electrical charge; producing them at large scales in a safe and efficient manner will help realize this. A slightly modified procedure also results in nanoporous platinum.

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