具有服务等级的可拒绝平行机排序问题

研究了将服务等级与拒绝费用2种模型复合起来的平行机排序问题.设有2台平行机M₁,M₂,加工速度相同;n个工件J₁,J₂,…,J_n分别按列表在线到达,每个工件J_j含有3个参数：加工长度t_j、拒绝费用p_j以及服务等级g_j=1,2.当工件到达时,可以接收加工,占用一定的加工时间;亦可拒绝,付出相应的罚值.目标为被接收工件的最大完工时间与被拒绝工件的总罚值之和最小.进一步,当且仅当g（M_i）≤g_j时,工件J_j可以分配给机器M_i加工,即机器M₁可以加工所有工件,机器M₂只能加工等级为g_j=2的工件,允许中断加工.设计了在线算法PH,并证明其竞争比为1+(√2)/(2)≈1.707,下界为1.618,上下界差约为0.089.     

Two-stage Multisplitting Methods with Overlapping Blocks

Parallel two-stage multisplitting methods with overlap for the solution of linear systems of algebraic equations are studied. It is shown that, under certain hypotheses, the method with overlap is asymptotically faster than that without overlap. Experiments illustrating this phenomenon are presented.     

Parallel Algorithms for Orthotropic Problems

Finite element meshes and node-numberings suitable for parallel solution with equally loaded processors are presented for linear orthotropic elliptic partial differential equations. These problems are of great importance, for instance in the oil and airfoil industries. The linear systems of equations are solved by the conjugate gradient method preconditioned by modified incomplete factorization, MIC. The basic method presented, is based on fronts of uncoupled nodes and unlike earlier methods it has the advantage of no requirement of a specific orientation of the mesh. This method is however, in general, restricted to small degree of anisotropy in the differential equation. Another method, which does not suffer from this limitation, uses rotation of the differential equation and spectral equivalence. The rotation is made in such a way that in the new co-ordinate system, the basic method is applicable. The spectral equivalence property is used for estimation of the condition number of the preconditioned system. Both methods are suitable for implementation on parallel computers. The computer architecture could be single instruction multiple data (SIMD) as well as multiple instruction multiple data (MIMD) with shared or distributed memory. Implementation of the basic method on a shared memory parallel computer shows a significant improvement by use of the MIC method compared with the diagonal scaling preconditioning method.     

Gravity compensation of parallel kinematics mechanism with revolute joints using torsional springs

Abstract

Passive gravity compensation technologies based on counterweight and torsional springs is rarely discussed due to the unavailability of an exact mathematical manipulation to determine the required spring constants to achieve the static balance. This article proposes using these springs for a parallel kinematics mechanism with revolute joints. Either the spring constants or initial spring displacements are determined by a constrained optimization approach aiming at minimizing the total potential energy of the mechanism or the static reaction in the actuation direction at the actuators, along a prescribed trajectory. This results in reduced actuation forces/ torques and hence reduced power consumption.     

CMOS三值逻辑系统探讨

本文探讨了一种新的CMOS三值逻辑系统,建立了一套完备的CMOS三值逻辑基本单元电路。给出了CMOS三进制乘法器及9进制7段字形译码器的设计方案。并分析、讨论了该系统的特点。     

一类流体力学问题的并行计算

概述了二维流体力学程序YGX等在银河-1和银河-2巨型计算机上的向量化和并行化工作,总结了一些具有一般意义的实际经验,给出了程序在计算机上执行所获得的重要测试数据。     

BAORJ的收敛性及最优参数的选取

对文献[1]中的BAORJ格式的收敛性做了进一步的讨论,得出了比文献[1]更为广泛的收敛性条件,并就模型问题得出了最优参数和BAORJ的收敛速度,从而为使用BAORJ格式提供了参考。     

高阶两参数并行Jacobi型方法

提出了解线性代数方程组的高阶两参数并行Jacobi型方法,讨论了它的收敛性,给出了模型问题和类模型问题的最优参数和收敛速度,最后还给出了数值例子以说明方法的有效性。     

结构动力分析并行直接积分算法在YH-1机上的实现

本文给出适合寄存器—寄存器加工方式向量机的有效并行直接积分算法。在YH-1机计算表明,当问题总自由度仅为1600阶时,加速比接近30。结合YH-1机特点,在并行计算中部分使用汇编语言,加速比将提高到50。     

高速科学计算与大规模并行机

本文分析了高速科学计算中的"巨大挑战(Grand Challenges)"问题对大规模并行处理(MPP)系统的需求,比较了向量机与MPP,介绍了MPP的发展现状及关键技术,最后扼要地论述了并行计算模型、并行算法与并行程序环境。本文的目的是促使计算物理学者重视并行算法和并行科学计算软件的研究。