共查询到19条相似文献,搜索用时 125 毫秒
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本文在吸取半定规划松弛和秩二松弛方法的优点,克服其缺点的基础上,针对模型目标函数非凸的特点,提出了图的最大二等分问题的秩二松弛模型。由于该模型变量的数目没有增加,因此该方法对求解大规模问题很有优势。数值实验表明,这种算法无论是与半定规划松弛还是原秩二松弛算法相比,在获得目标函数值相当的情况下,运行时间较短。 相似文献
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压电材料修正后的H-R混合变分原理及其层合板的精确法 总被引:4,自引:1,他引:3
将三维弹性体的Hellinger-Reissner(H-R)混合变分原理引入到具有机-电耦合效应的压电材料静力学问题中,建立了压电材料修正后的H-R混合变分原理,通过变分运算和分部积分得到了压电材料的状态向量方程.给出了四边简支的压电材料层合板静力学状态向量方程的精确求解方法,数值实例的结果证明了方法是正确性的.这里的理论和求解方法同样适应于纯弹性材料板和压电材料板混合的层合板静力学问题的分析.变分原理将有利于压电材料问题相应的半解析法或有限元法的推导. 相似文献
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标准铂电阻温度计由于准确度高、性能稳定、使用方便,因此在对二等标准水银温度计的检定过程中,大有取代一等标准水银温度计的趋势.我国2003年新发布的JJG128-2003《二等标准水银温度计》检定规程直接说明了可以采用二等标准铂电阻温度计对二等标准水银温度计进行检定,使得SPRT的应用更加广泛.我们在送上级部门进行检定时,或者新购买的SPRT,往往只给出固定点电阻比和a8、b8的值,为了更好的解决测量中遇到的实际问题,我们分别用Visual Basic和Excel编制了计算方法,并与ITS1990温标进行了验证。 相似文献
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求解二进制二次规划问题的一种连续化方法 总被引:1,自引:1,他引:0
本文提出了一种求解二进制二次规划问题的连续化方法。首先利用NCP函数方法,将二进制变量转化为等价的非光滑方程,再用凝聚函数法对其进行光滑化处理,从而把原来的组合优化问题转化成了一般的可微非线性规划问题。通过对一些标准考题进行计算,表明了该连续化方法的可行性、高效性以及稳定性。 相似文献
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本文给出了一个求解非线性系统的信赖域方法。通过引入松驰变量将非线性系统问题转化为带非负约束的非线性最优化问题,新算法借助于KKT条件和F-BNCP函数,在每次迭代时,不必求解二次信赖域子问题,只需求解一个线性方程组。在一定的假设条件下,该算法还是全局收敛和局部超线性收敛的。数值试验结果表明该算法是有效的。 相似文献
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提出了解决供应链中生产和航空运输协调调度问题的理论框架.基于对生产调度和航空运输调度彼此制约关系的分析,协调调度问题被分解为两个子调度问题.建立了航空运输子调度问题的整数规划模型,并证明了该问题为NP完全问题.提出了基于倒排调度方法(backward scheduling method)的调度算法解单机生产调度子问题. 相似文献
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A quadratic assignment problem (QAP), which is a combinatorial optimisation problem, is developed to model the problem of locating facilities with material flows between them. The aim of solving the QAP formulation for a facility layout problem (FLP) is to increase a system’s operating efficiency by reducing material handling costs, which can be measured by interdepartmental distances and flows. The QAP-formulated FLP can be viewed as a discrete optimisation problem, where the quadratic objective function is optimised with respect to discrete decision variables subject to linear equality constraints. The conventional approach for solving this discrete optimisation problem is to use the linearisation of the quadratic objective function whereby additional discrete variables and constraints are introduced. The adoption of the linearisation process can result in a significantly increased number of variables and constraints; solving the resulting problem can therefore be challenging. In this paper, a new approach is introduced to solve this discrete optimisation problem. First, the discrete optimisation problem is transformed into an equivalent nonlinear optimisation problem involving only continuous decision variables by introducing quadratic inequality constraints. The number of variables, however, remains the same as the original problem. Then, an exact penalty function method is applied to convert this transformed continuous optimisation problem into an unconstrained continuous optimisation problem. An improved backtracking search algorithm is then developed to solve the unconstrained optimisation problem. Numerical computation results demonstrate the effectiveness of the proposed new approach. 相似文献
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A dynamic sailplane performance problem is investigated using optimal control theory. The problem is to minimize the total flight time between successive thermals subject to zero altitude loss. From the original nonlinear optimal control problem, a singular linear/quadratic problem is derived and solved. A relationship between the original optimal control problem and a certain parameter optimization problem is explored, and it is shown that the solution to this parameter optimization provides a lower bound for the minimum flight time of the original optimal control problem. The parameter optimization solution is adopted as the reference trajectory for the linear/quadratic problem. Finally, the linear/quadratic problem is shown to provide a good approximation to the original optimal control problem at a small fraction of the computing cost. 相似文献
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Stress intensity solutions for the interaction between a hole edge crack and a line crack 总被引:2,自引:0,他引:2
The principle of superposition is used to solve the problem and the original problem is converted into two particular hole edge crack problems. The remote stresses are applied at infinity in the first problem. Meantime, a dislocation distribution is assumed outside the hole contour in the second problem. Singular integral equation is proposed for the solution of the second problem, in which the right hand side of the integral equation is obtained from the solution of the first problem. The first problem as well as the elementary solution of the second problem are solved by means of the rational mapping approach. Finally, numerical examples with the calculated results of stress intensity factors are presented. 相似文献
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Optimisation of automatic tool changer (ATC) indexing problem, where cutting tools are allocated to the stations on a turret magazine of a CNC machine, is one of the challenging problems in machining. The aim of the problem is to minimise the total indexing time of ATC. This problem becomes even more challenging if duplication of cutting tools is allowed and a bidirectional ATC is used. The problem has a unique feature which has not been stressed yet by other researchers, that is, although ATC indexing (master problem) is the main optimisation problem, objective function evaluation of this problem is a standalone optimisation problem (sub problem) indeed. Although an approximation algorithm does not guarantee optimality for the master problem, the subproblem must be solved optimally; otherwise, deficiencies arising from ill-defined objective function might be encountered. Considering this interesting future, a novel methodology, which employs a shortest path algorithm, is developed. Thus, the subproblem of this complicated problem can be optimally solved. Moreover, two metaheuristics, based on threshold accepting and descent first improvement greedy methodologies, are proposed for generating efficient solutions. Finally, several benchmarking instances are generated and solved to test the proposed algorithms. 相似文献
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对高校教室调度问题进行研究,能使教室和课程达到一种合理的优化配置。类似问题的研究在制造业或生产系统中都占有非常重要的地位。研究首先采用三元组方式,将教室调度问题描述为一类具有机器适用限制的并行多机问题,以最小化Cmax(即集中时间提高教室利用效率)和滞后时间总和为调度目标,建立了对应的数学模型。根据问题的特性,设计了包含分派规则和遗传算法的启发式调度算法求解该类问题。研究结合问题特性在编码,个体适应度函数,交叉及变异等方面进行了设计。以实例分析验证了所设计算法的可行性和有效性。 相似文献