There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Carbon nanotube–polymer composites: Chemistry, processing, mechanical and electrical properties

This paper presents a study on polycrystalline diamond (PCD) polished by dynamic friction polishing (DFP) with the aid of advanced dual beam FIB (focused ion beam) microscopy. After disclosing a va...

Analysis of polished polycrystalline diamond using dual beam focused ion beam microscopy

This paper presents a temperature-dependent finite element heat transfer model, incorporating a triangular moving heat source and various cooling conditions, to predict the three-dimensional temperature field in plunge surface grinding. The model was applied to analyse the grinding-hardening of quenchable steel 1045 using dry air and liquid nitrogen as the cooling media. The temperature field variation under such grinding conditions was also measured experimentally. It was found that the temperature history predicted by the model agrees well with the measured results. The model provides a fundamental study as a first step in optimisation and control of the hardened layer thickness and its compositions in grinding-hardening technology.

Temperature Fields in Workpieces during Grinding-Hardening with Dry Air and Liquid Nitrogen as the Cooling Media

This paper establishes a theoretical model to explore the coupled effect of grain boundary (GB) sliding deformation and crack tip dislocation emission on the critical stress intensity factor (SIF) for crack growth in ultrafine-grained and nanocrystalline materials (NCMs). The model postulates that the stress concentration near a crack tip initiates GB sliding. It is found that GB sliding leads to the formation of wedge disclination dipole at the triple junctions of grain boundaries. Under the external load and stress fields produced by wedge disclinations, dislocations are emitted from crack tips but will stop at the opposite GBs. The influence of the wedge disclination dipole and the dislocation emitted from crack tip on the critical SIF for crack growth is investigated. The model prediction shows that the critical SIF varies with the decrement of grain size, and that there is a critical grain size corresponding to a minimum value of SIF. Compared with the pure brittle fracture in NCMs at the grain sizes of tens of nanometers, the combined deformation mechanisms can bring an increase of the critical SIF for crack growth.

Coupled effect of grain boundary sliding and dislocation emission on fracture toughness of nanocrystalline materials

This paper investigates the coating thickness and surface morphology of gold/nickel (Au/Ni) layer on copper (Cu) substrate. A cross-sectioned SEM analysis confirmed that the Au/Ni coating was uniform. The top Au layer with average thickness of 0.7 µm appeared to have a very smooth surface without any defect such as cracks and delamination. However, the thin Au/Ni coating greatly influenced the interfacial structure and material properties of electronic interconnections. In the reference Cu substrate/Sn–Bi–Ag solder system, an island-shaped Cu6Sn5 IMC layer at the interface could be clearly observed at the initial reaction stage. After a prolong reaction, a very thin Cu3Sn IMC layer was formed with excessive growth of the Cu6Sn5 IMC layer which can deteriorate the electronic interconnection life-span. However, in the Au/Ni coated substrate/solder system, a very thin scallop-shaped ternary Ni3Sn4 IMC layer formed without the Cu3Sn IMC layer, indicating that the Au/Ni coating hindered the growth of the IMC layer, which consequently changed the activation energies and refined the microstructure. Additionally, the overall micro-hardness of the Au/Ni coated substrate/solder system is higher than that of the reference solder system.

Effect of thin gold/nickel coating on the microstructure, wettability and hardness of lead-free tin–bismuth–silver solder

Chemo-mechanical polishing (CMP) has been a common method to produce nano-scale surface finish of brittle wafers. This paper provides a relatively comprehensive review on the CMP of silicon, silicon carbide and sapphire including both patents and papers. The discussion includes the limitations and further research directions of the CMP technology, the material removal mechanisms, and the control and optimization of the CMP for brittle wafers. The paper concluded that the usage of mix- or coated- abrasives may improve the CMP in terms of less subsurface damage and higher material removal rate.

Liangchi Zhang

Papers

Analysis of polished polycrystalline diamond using dual beam focused ion beam microscopy

Temperature Fields in Workpieces during Grinding-Hardening with Dry Air and Liquid Nitrogen as the Cooling Media

Coupled effect of grain boundary sliding and dislocation emission on fracture toughness of nanocrystalline materials

Effect of thin gold/nickel coating on the microstructure, wettability and hardness of lead-free tin–bismuth–silver solder

On the chemo-mechanical polishing for nano-scale surface finish of brittle wafers.