Publications

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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