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

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

An immersed boundary method with direct forcing for the simulation of particulate flows

The Maxwell-Stefan approach to mass transfer

Discrete particle simulation of particulate systems: A review of major applications and findings

A vanadium phosphate catalyst precursor (P/V = 1.2) was prepared using an organic medium. The precursor was calcined at 400°C and portions were subjected to further treatments before being placed under reaction conditions (430°C, 1.2% butane/air feed) for 72–95 h. The changes in activity and selectivity with time on stream were monitored, and catalysts were characterized before and after reaction by XRD, IR, B.E.T. surface area, and redox titrometry. No general correlation between solid state properties and reactivity was found. None of the pretreatments caused catalyst performance to stabilize before 48 h on stream. Severely reducing (butane, 480°C) or oxidizing (air, 480°C) treatments were particularly deleterious to selectivity. The treatments leading to the best catalytic performance were to simply run under reaction conditions or to wash the catalyst in boiling methanol. The washing appeared to remove an inert surface phase.

Pretreatment and activation of a vanadium phosphate catalyst for butane oxidation to maleic anhydride.

Mathematical modelling of diffusion and reaction in blocked zeolite catalysts

Significance
Using CFD-DEM simulations, a wet agglomerate of particles was placed in a void region of a dry vigorously fluidized bed to understand how wet agglomerates grow or breakup and how liquid spreads when agglomerates interact with dry fluidized particles. In the CFD-DEM model, cohesive and viscous forces arising from liquid bridges between particles were modeled, as well as a finite rate of liquid bridge filling. The liquid properties were varied between different simulations to vary Bond number (surface tension forces/gravitational forces) and Capillary number (viscous forces/surface tension forces) in the system. Resulting agglomerate behavior was divided into regimes of (i) the agglomerate breaking up, (ii) the agglomerate retaining its initial form, but not growing, and (iii) the agglomerate retaining its initial form and growing. Regimes were mapped based on Bo and Ca. Implications of agglomerate behavior on spreading of liquid to initially dry particles were investigated. This article identifies a new way to map agglomerate growth and breakup behavior based on Bo and Ca. In modeling both liquid forces and a finite rate of liquid transfer, it identifies the complex influence viscosity has on agglomeration by strengthening liquid bridges while slowing their formation. Viewing Ca as the ratio of bridge formation time to particle collision and separation time capture why agglomerates with high Ca struggle to grow. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2520–2527, 2017

Sankaran Sundaresan

Papers

Pretreatment and activation of a vanadium phosphate catalyst for butane oxidation to maleic anhydride.

Mathematical modelling of diffusion and reaction in blocked zeolite catalysts

Growth and breakup of a wet agglomerate in a dry gas–solid fluidized bed

Effect of boundaries on trickle‐bed hydrodynamics

Pretreatment and activation of a vanadium phosphate catalyst for butane oxidation to maleic anhydride