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

THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Although nonwovens used in many areas from civil and mechanical engineering to consumer products, research on their mechanical behavior are rather limited in the literature. In this study, a brief ...

https://journals.sagepub.com/doi/pdf/10.1177/1558925020970197

A brief review on the mechanical behavior of nonwoven fabrics

A computational study of fatigue resistance of nitinol stents subjected to walk‐induced femoropopliteal artery motion

Damage and failure in carbon fabric-reinforced polymer (CFRP) composites under low velocity impacts is investigated using explicit finite element analyses. Three-dimensional finite element models are developed to simulate the deformation behaviour of, and damage evolution in CFRP laminates under such loading conditions. In these simulations, the onset and growth of inter-ply delamination is captured by bilinear cohesive zone elements inserted between plies of the composite. Intra-ply fabric fracture is simulated by defining a transverse layer of cohesive elements at the specimen fracture location. The energies associated with dynamic propagation of these damage mechanisms are also captured by the numerical simulations, demonstrating their potential to model the damage modes as well as their interaction. In this study, a novel damage modelling technique based on the cohesive zone method is proposed for interaction of various damage modes, which is more efficient for coupling between failure modes than a co...

Numerical analysis of the interactive damage mechanisms in two-dimensional carbon fabric-reinforced thermoplastic composites under low velocity impacts

Double-cantilever beams (DCBs) are widely used to study mode-I fracture behavior and to measure mode-I fracture toughness under quasi-static loads. Recently, the authors have developed analytical solutions for DCBs under dynamic loads with consideration of structural vibration and wave propagation. There are two methods of beam-theory-based data reduction to determine the energy release rate: (i) using an effective built-in boundary condition at the crack tip, and (ii) employing an elastic foundation to model the uncracked interface of the DCB. In this letter, analytical corrections for a crack-tip rotation of DCBs under quasi-static and dynamic loads are presented, afforded by combining both these data-reduction methods and the authors’ recent analytical solutions for each. Convenient and easy-to-use analytical corrections for DCB tests are obtained, which avoid the complexity and difficulty of the elastic foundation approach, and the need for multiple experimental measurements of DCB compliance and crack length. The corrections are, to the best of the authors’ knowledge, completely new. Verification cases based on numerical simulation are presented to demonstrate the utility of the corrections.

/pdf/analytical-corrections-for-double-cantilever-beam-tests-1p9rrehnbz.pdf

Analytical corrections for double-cantilever beam tests

The spatiotemporal evolution of damage in stochastic rocks is studied in terms of the multi—scale approach with the fractal tree used as an analogue of a discretization scheme for the region under study Such an approach, based on the fractal theory, allows quantitative information on spatial (morphology of fracture surface) and temporal scaling of the failure process to be obtained The numerical simulation for different types of stochasticity has shown that the fractal dimension of the fractured zone is the invariant characteristic of the failure process and depends totally on the stochastic properties of material The analysis of the load vs time—to—fracture relation for a vast interval of loads proved the scale—invariance of the fracture process The multifractal properties of the load distribution near fractures are studied

Vadim V. Silberschmidt

Papers

A brief review on the mechanical behavior of nonwoven fabrics

A computational study of fatigue resistance of nitinol stents subjected to walk‐induced femoropopliteal artery motion

Numerical analysis of the interactive damage mechanisms in two-dimensional carbon fabric-reinforced thermoplastic composites under low velocity impacts

Analytical corrections for double-cantilever beam tests

Multi—Scale Model of Damage Evolution in Stochastic Rocks: Fractal Approach