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

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

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

https://cyberleninka.org/article/n/309915.pdf

A critical review on solvent extraction of rare earths from aqueous solutions

Dependence of the crystal structure of the Nd-rich phase on oxygen content in an Nd–Fe–B sintered magnet

Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of Al/Mg Dissimilar Friction Stir Welding Joints

Precipitation behavior of Laves phase in steel X12CrMoWVNbN10-1-1 during short-term (≤400 h) creep exposure was investigated using a transmission electron microscope (TEM) and an ultra high resolution thermal field emission scanning electron microscope (UHR-FESEM). The results demonstrate that Laves phase precipitates are detected in the creep specimens exposed for such a short-term of 400 h at 600 °C and 204 h at 650 °C. Stacking faults are observed in them and the selected area electron diffraction patterns of the phase are characteristic of streaked. There are two mechanisms of the nucleation and growth for Laves phase, one of which is that Laves phases occur alone on martensite lath boundaries and they are coherent with a grain but grow into the adjacent grain which has no rational orientation relationship with them. The other one is that Laves phases are formed in the regions adjacent to M23C6 particles, and then they grow at the expense of the Cr-rich M23C6 carbides in close vicinity. It is established that the former one is the dominant formation mechanism for Laves phase in steel X12CrMoWVNbN10-1-1. Laves phases prefer to locate on the prior austenite grain boundaries and the martensite lath boundaries. The mean diameter and the number density of the phase show significant change with temperature, but slightly change with stress. Moreover, it is proved that the formation of Laves phase in this steel is a thermodynamically possible process. The nucleation process has not finished after heat-treatment and the number of nuclei for Laves phase formed in the steel decreases with raising the temperature.

Lanting Zhang

Papers

Dependence of the crystal structure of the Nd-rich phase on oxygen content in an Nd–Fe–B sintered magnet

Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of Al/Mg Dissimilar Friction Stir Welding Joints

Precipitation behavior of Laves phase in 10%Cr steel X12CrMoWVNbN10-1-1 during short-term creep exposure

Synthesis of filled skutterudite compound La0.75Fe3CoSb12 by spark plasma sintering and effect of porosity on thermoelectric properties

Thermal expansion and elastic moduli of the silicide based intermetallic alloys Ti5Si3(X) and Nb5Si3