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

Biological materials: Structure and mechanical properties

The dynamic thermoelastic response of functionally graded cylinders and plates is studied. Thermomechanical coupling is included in the formulation, and a finite element model of the formulation is developed. The heat conduction and the thermoelastic equations are solved for a functionally graded axisymmetric cylinder subjected to thermal loading. In addition, a thermoelastic boundary value problem using the first-order shear deformation plate theory (FSDT) that accounts for the transverse shear strains and the rotations, coupled with a three-dimensional heat conduction equation, is formulated for a functionally graded plate. Both problems are studied by varying the volume fraction of a ceramic and a metal using a power law distribution.

Thermomechanical analysis of functionally graded cylinders and plates

This paper presents a review of microwave heating applications in environmental engineering A number of areas are assessed, including contaminated soil remediation, waste processing, minerals processing and activated carbon regeneration Conclusions are presented, which identify the areas of potential commercial development as contaminated soil vitrification, volatile organic compounds (VOC) treatment and recovery, waste sludge processing, mineral ore grinding and carbon in pulp gold recovery Reasons are detailed why other areas have not seen investment into and implementation of microwave heating technology These include difficulties associated with the scaling up of laboratory units to industrial capacities and a lack of fundamental data on material dielectric properties This has meant that commercialisation of microwave heating processes for environmental engineering applications has so far been slow In fact, commercialisation is only deemed viable when microwave heating offers additional process-specific advantages over conventional methods of heating

Microwave heating applications in environmental engineering—a review

Multidimensional multiphysics simulation of nuclear fuel behavior

An elastic‐plastic finite element method numerical model has been formulated to study residual stresses developed at graded ceramic‐metal interfaces during cooling. The results were compared with those obtained for sharp (nongraded) interfaces to assess the potential for achieving residual stress reductions. Analyses were conducted for various axisymmetric cylindrical specimen geometries relevant to structural joining, coating, and thick film applications. The graded microstructure was treated as a series of perfectly bonded layers, each having slightly different properties. Constitutive relations for the interlayers were estimated using a modified rule‐of‐mixtures approximation, and strain and stress distributions were calculated for simulated cooling from an assumed fabrication temperature. The results demonstrate the importance of accounting for plasticity when comparing graded and nongraded interfaces. Significant geometrical effects on peak stresses were observed in the graded materials. It is shown ...

Finite element analysis of thermal residual stresses at graded ceramic‐metal interfaces. Part I. Model description and geometrical effects

An elastic‐plastic finite element method numerical model previously developed (see Part I of this article) for predicting thermal residual stresses at graded ceramic‐metal interfaces has been applied to determine interface conditions favorable for achieving residual stress reductions. Using Al2O3‐Ni as a model system, and for a fixed specimen geometry, a study was performed to investigate the effects of different interlayer thicknesses and nonlinear composition profiles on strain and stress distributions established during cooling from an assumed elevated bonding temperature. For each interface condition, relative stress reductions were evaluated by comparing the magnitude of specific stress and strain components important for controlling interface failure with those predicted for a sharp (nongraded) interface. For the geometry considered, stress was reduced by thick graded interlayers and nonlinear composition profiles that distributed the largest property changes over the interlayer region having low elastic modulus and high plasticity. In contrast to the Part I results for a linear composition profile, the optimized interlayer condition effectively reduced the peak near‐surface axial stress component.

Finite element analysis of thermal residual stresses at graded ceramic‐metal interfaces. Part II. Interface optimization for residual stress reduction

/pdf/bison-theory-manual-the-equations-behind-nuclear-fuel-33t4fd0siw.pdf

Richard L. Williamson

Papers

Multidimensional multiphysics simulation of nuclear fuel behavior

Finite element analysis of thermal residual stresses at graded ceramic‐metal interfaces. Part I. Model description and geometrical effects

Finite element analysis of thermal residual stresses at graded ceramic‐metal interfaces. Part II. Interface optimization for residual stress reduction

BISON Theory Manual The Equations behind Nuclear Fuel Analysis

Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling