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

第12次 아시아ㆍ太平洋 矯政局長會議 參加記

Tungsten as material for plasma-facing components in fusion devices

Thermal plasma technology for the treatment of wastes: a critical review.

Problem Given the number of times in which an unknown event has happened and failed: Required the chance that the probability of its happening in a single trial lies somewhere between any two degrees of probability that can be named. SECTION 1 Definition 1. Several events are inconsistent, when if one of them happens, none of the rest can. 2. Two events are contrary when one, or other of them must; and both together cannot happen. 3. An event is said to fail, when it cannot happen; or, which comes to the same thing, when its contrary has happened. 4. An event is said to be determined when it has either happened or failed. 5. The probability of any event is the ratio between the value at which an expectation depending on the happening of the event ought to be computed, and the value of the thing expected upon it’s 2 happening.

An essay towards solving a problem in the doctrine of chances. [Facsimil]

An emissive probe has been used in the edge region of the CASTOR tokamak in order to test the possibility of direct measurements of the plasma potential. The difference between the floating potential of a cold probe and that of an emissive probe has been found to be approximately 1.3 times the electron temperature, which is less than predicted by the probe theory. Several possible reasons to explain this discrepancy are offered, such as secondary electron emission, uncertainties in the ion temperature, different collecting areas for electrons and ions, etc. The possible impact of a space charge formed by the emitted electrons is also discussed.

https://iopscience.iop.org/article/10.1088/0741-3335/44/5/305/pdf

Measurements with an emissive probe in the CASTOR tokamak

During the past centuries, industrial processes and energy conversion plants have shown no or little care for environmental quality. The result is a huge accumulation of pollution and hazardous by-products, left as a heritage for the present and future generations. Recuperation of by-products or thermal energy is not only motivated by cost saving, but also by resource saving considerations. Environmental awareness is more than staying within the lines of the existing regulations.By the application of a plasma based system to a wide range of possible feedstocks which are CO2 neutral, a clean syngas of high caloric value is produced from the organic substances simultaneously with a non-leachable vitrified lava from the inorganic substances. The results will provide the advanced technology for the environmentally friendly treatment of hazardous wastes, biomass and low grade fuel. The driving force behind the task is to give priority to environmental quality at affordable costs. Thus, the investigation of ways to increase the efficiency of the process is very important. A plasma based remediation system is the only technology that prevents undesired pollution in the by-products and end product (such as syngas or other gases). The problem to be solved is twofold: recuperate clean energy from waste and renewables without pollution at affordable costs. Such a technique fulfils the objectives of sustainable development.Today, one of the main reasons that restricts the use of plasma based methods is the cost of electrical energy. The crucial element is the plasma torch performance. Hence, the physics of modern plasma torches is addressed in detail. The optimistic scenario holds the promise to provide 10?15% of the energy needs for the European Union (EU). Thus, the investigation of ways to increase the efficiency of the process is very important.

https://iopscience.iop.org/article/10.1088/0741-3335/47/5A/016/pdf

Guido Van Oost

Papers

Measurements with an emissive probe in the CASTOR tokamak

Plasma based waste treatment and energy production

Influence of recrystallization on thermal shock resistance of various tungsten grades

Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

Progress in waste utilization via thermal plasma