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

Natural-fibre-reinforced polymer (NFRP) composites are becoming a viable alternative to synthetic fibre based composites in many industrial applications. Machining is often necessary to facilitate assembly of parts in a final product. This study focuses on a comparative experimental analysis of the effects of conventional drilling (CD) and a hybrid ultrasonically-assisted drilling (UAD) of a hemp fibre-reinforced vinyl ester composite laminate. The results obtained indicate that UAD is more efficient when compared to CD for a range of drilling conditions. It yields lower cutting forces and energy resulting in reduced machining-induced damage in the composite, including diminished burr formation and fibre pull-outs. The holes drilled with UAD exhibit improved surface finish and hole quality when compared to those produced with CD. The study demonstrates the applicability of UAD as a viable machining process for improved machinability of heterogeneous NFRP composite materials.

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Machinability of natural-fibre-reinforced polymer composites: conventional vs ultrasonically-assisted machining

Damage evolution in adhesive joints subjected to impact fatigue

Damage in adhesively bonded cfrp joints: sinusoidal and impact fatigue

A new constitutive model, which can account for the solder's microstructure and its evolution, is proposed to describe the creep behaviour of the Sn–Ag eutectic phase. In this model, the threshold stress, being a function of the particle size, volume fraction and distribution of Ag 3 Sn intermetallic compound (IMC), is introduced to build the relationship between the creep behaviour of the Sn–Ag solder and its microstructure. Evolution of the eutectic phase's microstructure is accounted for in terms of the coarsening model. Both the creep strain rate and hydrostatic stress's influence are taken into account in the IMC coarsening model. The proposed model is implemented into the commercial finite element code ABAQUS. The creep deformation due to the applied stress and IMC coarsening are discussed in the case of a flip chip solder joint. The obtained results show that the shape of the solder joint influences the particle distribution caused by heterogeneous coarsening. The solder joint is softened due to microstructure evolution over a long range of time.

Modelling of Ag3Sn coarsening and its effect on creep of Sn-Ag eutectics

Composite materials, with their higher exposure to dynamic loads, have increasingly been used in aerospace, naval, automotive, sports and other sectors over the last few decades. Dynamic Deformation, Damage and Fracture in Composite Materials and Structures reviews various aspects of dynamic deformation, damage and fracture, mostly in composite laminates and sandwich structures, in a broad range of application fields including aerospace, automotive, defense and sports engineering. As the mechanical behavior and performance of composites varies under different dynamic loading regimes and velocities, the book is divided into sections that examine the different loading regimes and velocities. Part one examine low-velocity loading and part two looks at high-velocity loading. Part three then assesses shock and blast (i.e. contactless) events and the final part focuses on impact (contact) events. As sports applications of composites are linked to a specific subset of dynamic loading regimes, these applications are reviewed in the final part. Examines dynamic deformation and fracture of composite materialsCovers experimental, analytical and numerical aspectsAddresses important application areas such as aerospace, automotive, wind energy and defence, with a special section on sport applications

Vadim V. Silberschmidt

Papers

Machinability of natural-fibre-reinforced polymer composites: conventional vs ultrasonically-assisted machining

Damage evolution in adhesive joints subjected to impact fatigue

Damage in adhesively bonded cfrp joints: sinusoidal and impact fatigue

Modelling of Ag3Sn coarsening and its effect on creep of Sn-Ag eutectics

Dynamic Deformation, Damage and Fracture in Composite Materials and Structures