An Improved Algorithm for the Multi-commodity Location Problem

Distribution systems designs commonly require the optimal location decisions of regional ware-houses or distribution centers which function as intermediate facilities between plants and customers. This paper deals with such a location problem in which the facilities can handle one of several commodities. We term this problem the multi-commodity facility location problem. A branch and bound algorithm is proposed for solving this problem. Improved bounds are developed for increasing the efficiency of the algorithm. Computational results are provided.     

Kth最短路径的Bellman改进算法

基于对Bellm an算法的改进,得到了求解k th最短路的新算法.改进算法的优势在于从Bellm an算法只能解决最短路问题拓展到求解k th最短路问题,而且可以考虑权重为负数的情况.与传统算法相比,新算法更易于理解.     

An Improved Algorithm for the Capacitated Facility Location Problem

In this paper we consider the classical capacitated facility location problem. A branch and bound algorithm is presented which measurably improves upon the recent results of Akinc and Khumawala. The use of a specialized Lagrangean relaxation results in significantly tighter bounds than those for the traditional continuous relaxation. These bounds, when combined with penalties derived from the Lagrangean relaxation, enable many integer variables to be fixed at specific values. This results in fewer branches, and indeed for certain test problems taken from the literature, branching is not required. Average computation time for a battery of test problems from the literature has been reduced (conservatively) by a factor of 3.     

一种改进的禁忌搜索算法及其在选址问题中的应用

本文研究了选址问题中无容量限制的p-中值问题,在Rolland等人提出的有效禁忌搜索算法基础上,提出了一种以目标函数变化量作为评价函数的改进禁忌搜索算法,并进行了理论分析,然后将其与有效禁忌搜索算法作了性能比较.通过比较三个公共测试数据集的计算结果,验证了本文提出的禁忌搜索算法的可行性和有效性.     

一种改进的公交配流模型与算法

对两种经典的公交配流模型进行了对比分析,指出了在考虑拥挤影响时两种模型进行公交配流各自存在的缺点．随后对两种模型存在的不足进行了原因分析,并在此基础上对Spiess和Florian提出的线性规划模型及算法进行了改进．改进的模型运用了“最优策略”和“有效频率”的思想, 考虑了拥挤对站点乘客等车时间的影响．模型用MSA（相继平均法）算法进行求解,最后在一个简单网络上进行对比分析,表明改进后的模型能够较合理地求解考虑站点拥挤的公交配流问题．     

A Note on the Two-Dimensional Rectangular Cutting-Stock Problem

The concept of orthogonality in the Two-Dimensional Rectangular Cutting-Stock Problem is introduced. None of the published approaches for solving this problem permit non-orthogonal cutting patterns. An example is given to show that this may prevent the optimal cutting pattern from being obtained. The application of orthogonality to the problem of obtaining the minimum area rectangular enclosure of a number of rectangles is also discussed.     

Application of Heuristic Techniques to the Cutting-Stock Problem for Worktops

This paper addresses a cutting-stock problem which arises in the manufacture of furniture. An heuristic has been developed to schedule the cutting of worktops of varying shapes and sizes from available raw material.The work was carried out for a local manufacturing company. Interface software written at that company allows the program to be integrated into their computer system in such a way that it can easily be run by the user.Details of the heuristic are given, together with results of some numerical experiments designed to test the robustness of the algorithm and to give some guidance as to the optimal batch size and dimensions of the raw material.Performance of the algorithm in situ supports the results of numerical experiments, the computer solution giving some improvements over the previously obtained manual solution with respect to trim loss without incurring an unacceptable build-up of offcuts.     

求解TSP问题的改进离散蝴蝶优化算法

针对离散蝴蝶优化算法求解TSP问题时精度低和收敛速度慢等问题,提出一种改进离散蝴蝶优化算法.为了提升搜索效率,利用贪婪机制初始化种群,同时结合2-opt算子、改进的2-opt算子和模拟退火等策略来提高寻优能力.通过标准TSPLIB数据库中几十个实例仿真实验,并与一些经典、新型的智能算法比较,结果表明提出的算法在寻优能力和鲁棒性方面表现优越.     

一种求解约束优化问题的改进差分进化算法

针对在处理约束优化问题时约束条件难以处理的问题,提出了一种求解约束优化问题的改进差分进化算法.即在每代进化前将群体分为可行个体和不可行个体两类,对不可行个体,用差量法将其逐个转化为可行个体,并保持种群规模不变,经过一序列的进化后,计算所有可行个体的适应度并找到问题的最优解.对5个经典函数进行了优化测试,测试结果表明提出的算法对求解约束优化问题是有效的.     

求解零等待流水车间调度问题的改进蝙蝠算法

针对零等待流水车间调度问题特性,设计了一种蝙蝠算法进行求解.算法模拟蝙蝠捕食搜索行为进行寻优,利用基于最小位置值规则的随机键编码方式来表示问题解,采用基于NEH方法的局部搜索策略和随机交换、插入、逆序操作的变邻域搜索策略来提高局部优化性能,进一步根据Metropolis概率准则接受劣解来避免早熟.通过典型算例对所提算法进行仿真测试并与粒子群算法和RAJ启发式算法进行对比,结果表明所设计算法求解零等待流水车间调度问题的有效性和优越性,是求解流水车间生产调度问题的一种有效工具.     

一种求解TSP问题的多策略改进蚁群算法

蚁群算法是一种求解复杂组合优化问题的启发式仿生进化算法,并是求解TSP问题行之有效的一种随机算法.但此算法仍存在求解精度低、易陷入局部最优及求解效率低的问题,针对该问题提出一种多策略改进蚁群算法.采用最近邻法影响初始信息素的分布,达到降低算法初期较短路径上信息素浓度的目的,并在转移规则变异调整的基础上,结合路径的均值交叉进化策略,增强算法探索全局解空间和避免陷入局部最优的能力.然后,结合迭代和精英策略对信息素更新机制进行改进,进一步提高化算法的求解性能及求解效率,最后,对从TSPLIB数据库选出的8个实例进行求解并与其他算法进行对比,实验结果表明,改进算法在求解旅行商问题时的高效性,且具有较高的运算性能.     

改进的布谷鸟算法求解物流配送中心选址问题

针对基本布谷鸟算法求解物流配送中心选址问题时存在搜索精度低、易陷入局部最优值的缺陷,提出一种改进的布谷鸟算法.算法采用基于寄生巢适应度值排序的自适应方法改进基本布谷鸟算法的惯性权重,以平衡算法的全局开发能力和局部探索能力;利用NEH领域搜索以提高算法的搜索精度和收敛速度;引入停止阻止策略对全局最优寄生巢位置进行变异避免算法陷入局部最优值、增加种群的多样性.通过实验仿真表明,改进的布谷鸟算法在求解物流配送中心选址问题上要优与基本布谷鸟算法以及其它智群算法,是一种有效的算法.     

An Algorithm for the Vehicle-dispatching Problem

The vehicle-scheduling problem involves the design of several vehicle tours to meet a given set of requirements for customers with known locations, subject to a capacity constraint for the vehicles and a distance (or time) constraint for vehicle tours. Three methods of solution are considered in this paper:

1. a
   A branch-and-bound approach.
    
2. b
   The "savings" approach.
    
3. c
   The 3-optimal tour method.
    

The excessive computation time and computer storage required for the first method renders it impracticable for large problems. Ten problems are examined and the results suggest that method C is superior to the other two methods.     

An Algorithm for the Allocation Problem

This paper* sets out a procedure for solving allocation problems, on different lines from procedures based on linear programming.     

改进填充算法在矩形件排样中的应用

矩形件排样的合理性直接影响板材利用率.考虑到下料过程中板材的纤维方向和一刀切等工艺约束,建立了以板材平均利用率最大为目标的数学模型.提出了一种改进填充算法,增加了矩形件的排列方式、扩大了矩形件试排范围,实现了排样的多样性.此外,在改进填充算法的基础上引入了遗传算子,利用遗传算法全局搜索能力强的特点,对矩形件排样顺序进行寻优.最后,采用不同规模的算例验证所建模型和所提算法的合理性与普适性,算例结果表明改进后的算法能够有效提高板材的利用率,可为实际作业提供技术支持及方法借鉴.     

基于改进遗传算法的集合覆盖问题

集合覆盖问题是组合优化中的典型问题,在日常生活中有着广泛的应用.提出了一种改进遗传算法来解决集合覆盖问题.算法对标准遗传算法的改进主要表现在:1)结合启发式算法和随机生成,设计了新的产生初始种群的方法;2)引入修补操作处理不可行解使其转换成可行解;3)对重复个体进行处理再利用;4)对多点交叉进行推广,提出了新的交叉算子;5)针对可行解和不可行解,采取两种自适应多位变异操作.数值实验结果表明该算法对于解决规模较大的集合覆盖问题是有效的.     

求解运输问题的一种算法

文章给出了运输问题的一种算法,该算法计算过程容易掌握,求解具有一次终止性     

求解运输问题的一个算法

给出一个求解问题的数值算法，证明了算法的理论依据，并举例说明算法的应用。     

An Improved Formulation for the Job-Shop Scheduling Problem

This paper presents an extension of an earlier integer programming model developed by other authors to formulate a general n-job, m-machine job-shop problem. The new formulation involves substantially fewer functional constraints at the expense of an increase in the number of upper bound variables. This reduction of functional constraints, together with the imposition of upper and lower bounds on the objective value, significantly reduces the computation time for solving the integer model for the job-shop scheduling problem.