Sandia National Laboratories

About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Thin film. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.

Self-limiting lithiation in silicon nanowires.

Abstract: The rates of charging and discharging in lithium-ion batteries (LIBs) are critically controlled by the kinetics of Li insertion and extraction in solid-state electrodes. Silicon is being intensively studied as a high-capacity anode material for LIBs. However, the kinetics of Li reaction and diffusion in Si remain unclear. Here we report a combined experimental and theoretical study of the lithiation kinetics in individual Si nanowires. By using in situ transmission electron microscopy, we measure the rate of growth of a surface layer of amorphous LixSi in crystalline Si nanowires during the first lithiation. The results show the self-limiting lithiation, which is attributed to the retardation effect of the lithiation-induced stress. Our work provides a direct measurement of the nanoscale growth kinetics in lithiated Si, and has implications on nanostructures for achieving the high capacity and high rate in the development of high performance LIBs.

An Approach to Sensitivity Analysis of Computer Models: Part II - Ranking of Input Variables, Response Surface Validation, Distribution Effect and Technique Synopsis

Abstract: This is the second part of a two-part paper presenting a statistical approach to the sensitivity analysis of computer models. In this part consideration is given to response surface construction techniques including identification of possible overfit an..

Detection and correction of silent data corruption for large-scale high-performance computing

Abstract: Faults have become the norm rather than the exception for high-end computing clusters. Exacerbating this situation, some of these faults remain undetected, manifesting themselves as silent errors that allow applications to compute incorrect results. This paper studies the potential for redundancy to detect and correct soft errors in MPI message-passing applications while investigating the challenges inherent to detecting soft errors within MPI applications by providing transparent MPI redundancy. By assuming a model wherein corruption in application data manifests itself by producing differing MPI messages between replicas, we study the best suited protocols for detecting and correcting corrupted MPI messages. Using our fault injector, we observe that even a single error can have profound effects on applications by causing a cascading pattern of corruption which in most cases spreads to all other processes. Results indicate that our consistency protocols can successfully protect applications experiencing even high rates of silent data corruption.

Ice properties of single‐layer stratocumulus during the Mixed‐Phase Arctic Cloud Experiment: 1. Observations

Abstract: [1] During the Department of Energy's Atmospheric Radiation Measurement Program's Mixed-Phase Arctic Cloud Experiment (M-PACE) in fall 2004, the University of North Dakota Citation measured 53 profiles within single-layer stratus clouds by executing spiral ascents and descents over Barrow and Oliktok Point, Alaska, and by flying ramped ascents and descents between. Cloud phase was identified from an algorithm that uses voltage change from the Rosemount ice detector, the size distribution (SD) shape measured by the Forward Scattering Spectrometer Probe (FSSP), and manual identification of particles imaged by the Cloud Particle Imager, the two-dimensional cloud probe (2DC) and the high-volume precipitation sampler (HVPS). Size and mass distribution functions were derived using data from the FSSP, one-dimensional cloud probe, 2DC and HVPS in conjunction with total water content (TWC) measured by the Counterflow Virtual Impactor. With clouds defined as locations where TWC > 0.001 g m−3, there were a total of 513 30-s averaged SDs in single-layer clouds, of which 71% were in mixed-phase parcels, 23% in ice-phase and 6% in liquid-phase. The mixed-phase parcels were dominated by contributions from liquid drops, with the liquid mass fraction fl having averages and standard deviations of 0.89 ± 0.18 with 75% of cases having fl > 0.9. For these single-layer clouds, fl increased with normalized cloud altitude zn, defined as linearly increasing from 0 at cloud base to 1 at cloud top with fl averaging 0.96 ± 0.13 near zn = 1 and 0.70 ± 0.30 near zn = 0. The effective radius of water droplets rew increased with zn, from an average of 6.9 ± 1.8 μm near zn = 0 to 11.4 ± 2.4 μm near zn = 1, whereas the effective radius of ice crystals rei (25.2 ± 3.9 μm) was nearly independent of zn. The averaged cloud droplet number concentration and concentrations of ice crystals with maximum dimensions greater than 53 μm were 43.6 ± 30.5 × 103 L−1 and 2.8 ± 6.9 L−1, respectively, and nearly independent of zn. In contrast to past measurements in mixed-phase clouds combined from many geographical locations where fl increased with temperature, fl decreased from −12° to −3°C as clouds typically consisted of a liquid topped layer with precipitating ice below.