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This proposed research addresses one of the long outstanding fundamental problems in materials science, the mechanisms of deformation in amorphous metals. Due to the lack of long-range translational order, details of structural defects and their behaviors in metallic glasses have not been accessible in experiments. In addition, the small dimensions of the amorphous alloys made early by rapid quenching impose severe limit on many standard mechanical and microscopy testing. As a result, the microscopic mechanism of deformation in the amorphous materials has not been established. The recent success in synthesis of bulk metallic glass overcomes the difficulty in standard testing; but the barrier for understanding the defect process and microscopic mechanisms of deformation still remains. Amorphous metals deform in a unique way by shear banding. As a result, there is no work hardening, little macroscopic plasticity, and catastrophic failure. To retain and improve the inherent high strength, large elastic strain, and high toughness in amorphous metals, a variety of synthesis activities are currently underway including making metallic glass matrix composites. These new explorations call for a quantitative understanding of deformation mechanisms in both the monolithic metallic glasses as well as their composites. The knowledge is expected to give insight and …

We present a three-dimensional, time-dependent simulation of a laboratory-scale rod-stabilized premixed turbulent V-flame. The simulations are performed using an adaptive time-dependent low Mach number model with detailed chemical kinetics and a mixture model for differential species diffusion. The algorithm is based on a second-order projection formulation and does not require an explicit sub grid model for turbulence or turbulence chemistry interaction. Adaptive mesh refinement is used to dynamically resolve the flame and turbulent structures. Here, we briefly discuss the numerical procedure and present detailed comparisons with experimental measurements showing that the computation is able to accurately capture the basic flame morphology and associated mean velocity field. Finally, we discuss key issues that arise in performing these types of simulations and the implications of these issues for using computation to form a bridge between turbulent flame experiments and basic combustion chemistry.

We assembled 18 months of transfer logs from a production High Performance Storage System (HPSS) system at the National Energy Research Scientific Computing Center(NERSC) and analyzed them to assess workload behavior and gain some insight into which cache configurations would provide the best service to the users. We found, as expected, that the workload is distributed over file size with a declining number of files as the files get larger, so the amount of space consumed per file size increment is roughly constant up to file sizes of 1 GB. Sixty one percent of file accesses were write accesses. There are a significant number of files written which are never read -- backup files and similar files. For all sizes of files, access frequencies decline with the age of the files. HPSS uses the cache as an I/O buffer for incoming data. At our installation the cache behavior is dominated by the write traffic. Cache lifetimes tend to scale linearly with the size of the cache and inversely with the amount of data flow.

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