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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase) This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys

Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off

Study on the in situ composites microstructure of the directionally solidified hypoeutectic Cu-Cr alloys

Silicon solar cell is well known as one of the cleanest and most potential renewable resources. As the major photovoltaic (PV) material in PV industry, multi-crystalline silicon (mc-Si) grown by directional solidification has recently attracted increasing attention because of its low production cost, low pollution and high throughput. Deeper understanding of the physic and optic properties, and preparation methods of the materials will lead to improved device design. This paper briefly presents basic directional solidification theory of multi-crystalline silicon, and reviews recent development of solar-grade multi-crystalline silicon. The directional solidification preparation techniques of high-quality solar-grade multi-crystalline silicon are detailed introduced and summarized. Furthermore, the existing problems and further development direction of directionally solidified multi-crystalline silicon for solar cell are discussed.

Preparation Development of High-Quality Solar-Grade Multi-Crystalline Silicon by Directional Solidification

Herein, a TiAl alloy containing a high Nb concentration with a composition of Ti-45.5Al-7Nb-(W, Cr, B) was prepared by electromagnetic cold crucible zone melting (ECCZM) using a ceramic mould. The microstructure, tensile properties and fracture morphology were analyzed by means of SEM, EDS and TEM. As results, there were three blocky phases, namely α 2 b , γ b , and TiB, and two types of γ/γ interfaces. The tensile tests at room temperature showed that the ultimate tensile strength of the alloy reached a maximum value of 645 MPa. The primary strengthening mechanism of the alloy was the interfacial strengthening of the γ/γ interfaces. The two types of γ/γ interfaces can hinder dislocation movement and allow the dislocations to move under high tensile stress, thus strengthening the alloy without increasing stress concentration. Moreover, the three blocky phases can hinder dislocations through the interface between them and γ lamellae, thereby strengthening the lamellae. Among them the γ b phase plays a coordinated role in controlling the deformation of the lamellar colony. 

Strengthening effect of blocky phases and γ/γ interface in the directional solidified high-Nb-containing TiAl alloy

This paper has systematically studied the evolving process of column crystals of Ti46Al0.5W0.5Si alloys that is directionally solidified by rectangular cold crucible. The results showed that: the solid/liquid interface presented convex to the liquid metal due to the complicated influences by cold crucible. Overheating temperature and new crystal nucleus had great effects on the growth continuity and the stability of column crystals. Furthermore, the precipitation phases have been studied. As a result, the methods for controlling growing process of columnar crystals have been submitted, which are playing a critical role in optimizing experimental parameters and devising the construction-elements of cold crucible.

Columnar Crystal Growth of Ti46Al0.5W0.5Si Alloys Directional Solidified by Rectangular Cold Crucible

To begin a preliminary exploration on the effect of shape, the effect of a novel shaped 29 × 6 mm plate mold on the microstructure and mechanical properties of directionally solidified (DS) Ti-45Al-2Cr-2Nb was investigated. For comparison, Φ15 mm cylindrical molds with an equivalent cross-sectional area were used. Experimental results show that the typical microstructures of the DS region in all samples consist of regular well aligned α 2/γ lamellar structure, B2 phase and Y2O3 particles. Due to the lower strength of flow generated by the shape factor of the mold, the plate sample has coarser lamellae and more B2 phase, but fewer Y2O3 particles. Additionally, the room temperature (RT) fracture toughness and tensile properties of the plate sample are improved.

Hengzhi Fu

Papers

Study on the in situ composites microstructure of the directionally solidified hypoeutectic Cu-Cr alloys

Preparation Development of High-Quality Solar-Grade Multi-Crystalline Silicon by Directional Solidification

Strengthening effect of blocky phases and γ/γ interface in the directional solidified high-Nb-containing TiAl alloy

Columnar Crystal Growth of Ti46Al0.5W0.5Si Alloys Directional Solidified by Rectangular Cold Crucible

Comparison of a Directionally Solidified TiAl Alloy by Φ15 mm Cylindrical and 29 × 6 mm Plate Y 2 O 3 Molds