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

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Principles of equal-channel angular pressing as a processing tool for grain refinement

羟氨苄青霉素引起大疱性类天疱疮样疹

Progress in structural materials for aerospace systems

Preface * The light metals * Physical metallurgy of aluminium alloys * Wrought aluminium alloys * Cast aluminium alloys * Magnesium alloys * Titanium alloys * Novel alloys and processes * Appendix * Index.

Light Alloys : Metallurgy of the Light Metals

Preface The light metals Physical metallurgy of aluminium alloys Wrought aluminium alloys Cast aluminium alloys Magnesium alloys Titanium alloys New materials and processing methods Appendix Index.

Light Alloys: From Traditional Alloys to Nanocrystals

Origins of hardening in aged Al-Cu-Mg-(Ag) alloys

Nucleation of precipitates in aged Al-Cu-Mg-(Ag) alloys with high Cu:Mg ratios

A new wrought aluminum alloy has been designed having high room temperature strength (e.g., 0.2 pct P.S. 520 MPa) combined with improved creep resistance at temperatures in the range 150° to 220 °C. The alloy is A1-6.3 pct Cu-0.5 pct Mg-0.5 pct Ag-0.5 pct Mn-0.2 pct Zr and it is hardened by a new precipitate which forms on the {111} planes and appears to be highly stable at elevated temperatures. Details are given of the principles underlying the development of the alloy and of the preliminary assessment that has been made of mechanical properties. The alloy, or compositions close to it, also has potential for welded applications.

Ian J. Polmear

Papers

Light Alloys : Metallurgy of the Light Metals

Light Alloys: From Traditional Alloys to Nanocrystals

Origins of hardening in aged Al-Cu-Mg-(Ag) alloys

Nucleation of precipitates in aged Al-Cu-Mg-(Ag) alloys with high Cu:Mg ratios

Design and development of an experimental wrought aluminum alloy for use at elevated temperatures