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

Abstract Balloon pre-dilation is usually performed before implantation of a nitinol stent in a femoropopliteal artery in a case of severe blockage or calcified plaque. However, its effect on performance of the nitinol stent in a diseased femoropopliteal artery has not been studied yet. This study compares the outcomes of stenting with pre-dilation and without it by modelling the entire processes of stent deployment. Fatigue deformation of the implanted stent is also modelled under diastolic–systolic blood pressure, repetitive bending, torsion, axial compression and their combination. Reduced level of stress in the stent occurs after stenting with pre-dilation, but causing the increased damage in the media layer, i.e. the middle layer of the arterial wall. Generally, pre-dilation increases the risk of nitinol stent’s fatigue failure. Additionally, the development of in-stent restenosis is predicted based on the stenting-induced tissue damage in the media layer, and no severe mechanical irritation is induced to the media layer by pre-dilation, stent deployment or fatigue loading. 

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Effect of balloon pre-dilation on performance of self-expandable nitinol stent in femoropopliteal artery

Molecular dynamics (MD) and single-crystal plasticity finite-element method (CP FEM) are approaches used to simulate the micro-machining process. At such small-length scales, anisotropic behaviour of material becomes important; the two methods can essentially capture it. Therefore, it is important to understand the fundamental principle behind these methods as well as their capabilities and limitations in order to select the scheme to simulate the micro-machining process. In this paper, the fundamentals of MD and CP FEM are introduced in brief. The applicability of the respective method is further illustrated with the help of examples from the literature. Thereafter, the two methods are compared and discussed in terms of their various aspects and capabilities. This discussion should enrich the reader and assist their choice of an appropriate simulation method.

Small-Scale Machining Simulations

This paper aims to investigate the outcomes of stent deployment in a patient-specific coronary artery using finite-element (FE) method. Hyperelastic models with damage, verified against experimental results, were used to describe stress-stretch responses of arterial layers and plaque. Based on intravital optical coherency tomography imaging of a specific patient’s coronary artery, three-dimensional model of a diseased artery was developed, with two constituent layers (media and adventitia) and plaque, using Mimics. The model was meshed using 3-Matics and then exported to FE software Abaqus. Abaqus CAE was used to create the models for off-the-shelf Resolute Integrity™ drug-eluting coronary stents and tri-folded expansion balloons. The effect of percutaneous coronary intervention on a lumen gain was investigated by simulating the deployment of stent, in comparison with the clinical result.

Finite Element Modelling of Stent Deployment in a Patient-specific Coronary Artery

In this paper finite element analysis (FEA) is used to understand the effect of a non-uniform temperature distribution on the creep and fatigue behaviour of lead-free solder joints in an electronic assembly comprising of a chip resistor mounted on printed circuit board (PCB). Solder joints in surface mount devices (SMDs) operate over a temperature range as extreme as -55degC to 125degC, which is high compared to the melting temperature of solder alloys. Exposure of solder joints to these temperatures can result in thermo-mechanical fatigue. Eutectic or near- eutectic tin-lead alloys have previously been used as an interconnection material, but the ban imposed on the use of toxic materials in electronic products demands new lead-free solder materials. This paper presents the experiments carried out using a thermal camera to obtain the real temperature distribution in the electronic assembly. These temperature distributions were used in FEA of the chip resistor under temperature cycling conditions. Unlike accelerated tests for obtaining reliability data, FEA is quick and less expensive.

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Creep Analysis of a Lead-free Surface Mount Device

In the last two decades, experimental observations demonstrated—and numerical simulations confirmed—that plastic deformation in the small scale, i.e. at the micron or sub-micron scales, is different from that at the macro-scale; this phenomenon is known as size effect. It was observed mostly in indentation, torsion and bending experiments, being ascribed to strong gradients of strain in such deformation processes. The size effect was also reported in uniaxial micro- and nano-pillar compression experiments in spite of their inherent lack of (or limited) macroscopic strain gradients. In the present study, we first review some critical and essential experimental studies that were conducted over the years to analyse various mechanisms that govern deformation in the small scale. In the second part, different modelling approaches describing this phenomenon are briefly reviewed.

https://www.springer.com/cda/content/document/cda_downloaddocument/9783319171173-c2.pdf?SGWID=0-0-45-1501877-p177313492

Vadim V. Silberschmidt

Papers

Effect of balloon pre-dilation on performance of self-expandable nitinol stent in femoropopliteal artery

Small-Scale Machining Simulations

Finite Element Modelling of Stent Deployment in a Patient-specific Coronary Artery

Creep Analysis of a Lead-free Surface Mount Device

Crystalline Deformation in the Small Scale