Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat transfer performance can be applied in many devices for better performances (i.e. energy, heat transfer and other performances). In this paper, a comprehensive literature on the applications and challenges of nanofluids have been compiled and reviewed. Latest up to date literatures on the applications and challenges in terms of PhD and Master thesis, journal articles, conference proceedings, reports and web materials have been reviewed and reported. Recent researches have indicated that substitution of conventional coolants by nanofluids appears promising. Specific application of nanofluids in engine cooling, solar water heating, cooling of electronics, cooling of transformer oil, improving diesel generator efficiency, cooling of heat exchanging devices, improving heat transfer efficiency of chillers, domestic refrigerator-freezers, cooling in machining, in nuclear reactor and defense and space have been reviewed and presented. Authors also critically analyzed some of the applications and identified research gaps for further research. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. Based on results available in the literatures, it has been found nanofluids have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conventional fluids. This can be considered as one of the key parameters for enhanced performances for many of the applications of nanofluids. Because of its superior thermal performances, latest up to date literatures on this property have been summarized and presented in this paper as well. However, few barriers and challenges that have been identified in this review must be addressed carefully before it can be fully implemented in the industrial applications.

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A review on applications and challenges of nanofluids

This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

/pdf/a-benchmark-study-on-the-thermal-conductivity-of-nanofluids-1ahazpqp7s.pdf

A benchmark study on the thermal conductivity of nanofluids

Most explosives are micro- and nanoscale composite material systems consisting of energetic crystals, amorphous particles, binders, and additives whose response to mechanical, thermal, or electromagnetic insults is often controlled by submicrometer-scale heterogeneities and interfaces. Several advanced dynamic atomic force microscopy (AFM) techniques, including phase imaging, force volume mode, and Kelvin probe force microscopy with resonance enhancement for dielectric property mapping, have been used to map the local physical properties of mock explosive materials systems, allowing the identification of submicrometer heterogeneities in electrical and mechanical properties that could lead to the formation of hotspots under electromagnetic or mechanical stimuli. The physical interpretation of the property maps and the methods of image formation are presented. Possible interpretations of the results and future applications to energetic material systems are also discussed.

Nanoscale Characterization of Mock Explosive Materials Using Advanced Atomic Force Microscopy Methods

Multiphase reactive systems can exhibit highly dynamic combustion phenomena that could be better understood by using recently developed high-repetition-rate optical diagnostic and imaging approaches. Here, we present an overview of recent activities using high-speed (5 kHz) OH planar laser-induced fluorescence to visualize and make measurements in several multiphase reactive systems. This technique is used to visualize the dynamically changing OH concentration in the gas phase near the surface of solids, liquids, and gels. In addition to gas-phase OH imaging, condensed phases of various solid propellants, gels, and liquids are found to fluoresce when exposed to the laser radiation centered at 283.2 nm. Simultaneous imaging of condensed phases and gasphase OH radical fluorescence has proven to be particularly useful for various measurements, and several examples are presented.

High speed OH PLIF applied to multiphase combustion (Review)

Evaluation of a CL-20/TATB Energetic Co-crystal

Pyrotechnic time delays are reactive systems that burn for a desired period of time at a specified rate and are commonly used in military applications such as grenades and hand-held signals. Typically, they are manufactured by pressing the reactive powder into a metal housing. This rigid design inherently limits configurability, and they have had reliability issues. Additionally, there has been advocacy for environmentally friendly pyrotechnic ignition delays, by removal of barium chromate (BaCrO4). This study has two distinct objectives. First, determine the viability of two possible replacements, strontium molybdate (SrMoO4) and barium molybdate (BaMoO4), for the harmful component, BaCrO4, in the traditional T-10 delay. This includes combustion characteristics such as burning rate, combustion temperature, and gas generation. Furthermore, thermal characteristics are determined through differential scanning calorimetry (DSC), and combustion products are analyzed with X-ray diffraction (XRD). Second, by us...

Environmentally Friendly Boron-Based Pyrotechnic Delays: An Additive Manufacturing Approach

Current fielded delay formulations face increased scrutiny due to their environmentally hazardous components (i.e., BaCrO4/KClO4), and there is an immediate need for viable replacements. In this work, the W/MnO2 composition is explored as an environmentally benign time delay replacement. Delay performance and aging characteristics are examined at diameters (6.35 and 4.7 mm) similar to those of common delay housings. Measured maximum combustion temperatures ranged from 1466 to 1670 K as a function of mixture stoichiometry. The measured combustion velocities ranged from 0.67 to 1.68 mm/s for 6.35 mm open air pellets, and from 1.62 to 4.61 mm/s when combusted in 6.35 and 4.7 mm ID Al/SS housings. When packing density was increased and decreased from the standard 60% theoretical maximum density, combustion velocity decreased. For all W/MnO2 formulations, the maximum measured gas production was 9.1 mL/g. Accelerated aging was performed for 8 weeks, and negligible changes in combustion characteristics were obse...

Lori J. Groven

Papers

Nanoscale Characterization of Mock Explosive Materials Using Advanced Atomic Force Microscopy Methods

High speed OH PLIF applied to multiphase combustion (Review)

Evaluation of a CL-20/TATB Energetic Co-crystal

Environmentally Friendly Boron-Based Pyrotechnic Delays: An Additive Manufacturing Approach

Performance of W/MnO2 as an Environmentally Friendly Energetic Time Delay Composition