共查询到19条相似文献,搜索用时 78 毫秒
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研究了在时变环境下,允许从配送中心出发同时访问R个配送点,且兼顾费用与可靠性的选址问题,这里R是预先给定的容量约束.问题本身是NP完备的,给出了一个确定单个配送中心的启发式算法. 相似文献
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电子商务环境下物流配送中心选址及其启发式算法 总被引:1,自引:0,他引:1
电子商务环境下的物流配送中心选址是很复杂的问题,涉及许多因素。考虑电子商务环境下的物流配送特点,将物流配送中心选址模型从变动费用和时间约束的条件上进行修改,建立适用于电子商务环境下的物流配送中心选址模型。与原有模型相比,这些特点使得物流配送中心选址模型在模型的合理性上和实际应用上有了很大的改进。由于选址模型是NP问题,采用启发式算法进行求解。 相似文献
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目前,物流已成为企业第三利润源泉,是现代化生产的重要组成部分,合理的物流网络规划对企业至关重要。其中,配送中心作为联结着需求点和资源点的桥梁,在整个物流网络中起着举足轻重的作用,配送中心的选址问题更是备受关注,精准的选址方案可以提高物流网络的整体效益,节约企业的运作成本。 相似文献
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动车组配送供应链网络优化设计包括供应商招标、配送中心选址、配送路线规划等多方面,是典型的具有NP难性质的MSDLP问题.采用启发式思想,将该复杂问题模型层层分解,剔除0-1变量,得到一系列简单运输问题子模型.实例证明所提设计思想在实际应用中具有清晰的指导性和科学可行性. 相似文献
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动车组配送供应链网络优化设计包括供应商招标、配送中心选址、配送路线规划等多方面,是典型的具有NP难性质的MSDLRP问题。采用启发式思想,将该复杂问题模型层层分解,剔除0-1变量,得到一系列简单运输问题子模型。实例证明所提设计思想在实际应用中具有清晰的指导性和科学可行性。 相似文献
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基于零售点所采取的单周期随机库存控制策略,建立了考虑库存的物流系统选址分配问题的混合整数非线性规划模型.设计了一种求解该模型的启发式算法:先用解析法求出各个零售点的最佳订货量,然后利用Hopfield人工神经网络算法求解各个零售点的最佳配送量,最后通过枚举法确定配送中心的选址以及最佳配送方案.将该启发式算法与分支定界法进行了模拟比较,结果表明该算法具有相对的先进性.最后,用实例对模型与算法进行了数值演算. 相似文献
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Antoon Kolen 《Statistica Neerlandica》2007,61(1):4-15
We describe a genetic algorithm for the partial constraint satisfaction problem. The typical elements of a genetic algorithm, selection, mutation and cross-over, are filled in with combinatorial ideas. For instance, cross-over of two solutions is performed by taking the one or two domain elements in the solutions of each of the variables as the complete domain of the variable. Then a branch-and-bound method is used for solving this small instance. When tested on a class of frequency assignment problems this genetic algorithm produced the best known solutions for all test problems. This feeds the idea that combinatorial ideas may well be useful in genetic algorithms. 相似文献
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This paper presents the location-allocation problem of parking facilities in Mobarakeh Steel Company. The aim is to find the optimal location for the parking facilities and allocate travels between departments to each parking facility. To optimize the cost and facing the transportation demands of all departments, a mathematical model is designed and solved by a commercial software package. Also, the number of vehicles allocated to each parking facility is determined. A hybrid meta-heuristic algorithm combining a genetic algorithm with parallel simulated annealing is developed which can be used even in more complicated structure of the problem. The results show that this hybrid algorithm is highly efficient in solving this kind of problems. 相似文献
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针对车辆路径问题,基于扫描算法第一阶段的解,应用启发式算法中的最近插入算法、凸包算法和最远插入算法求解第二阶段。通过仿真实验,从总里程和算法运行时间两个方面对各算法性能给出评价。结果显示,在应用扫描算法进行聚类后,求解路径排程阶段,凸包算法虽然用时多于其它两种算法,但在里程上有明显优势,最远插入算法与最近插入算法在运行时间上没有显著差别,但在总里程上,前者较好。 相似文献
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《Socio》2023
We study the Maximal Covering Location Problem with Accessibility Indicators and Mobile Units that maximizes the facilities coverage, the accessibility of the zones to the open facilities, and the spatial disaggregation. The main characteristic of our problem is that mobile units can be deployed from open facilities to extend the coverage, accessibility, and opportunities for the inhabitants of the different demand zones. We formulate the Maximal Covering Location Problem with Accessibility Indicators and Mobile Units as a mixed-integer linear programming model. To solve larger instances, we propose a matheuristic (combination of exact and heuristic methods) composed of an Estimation of Distribution Algorithm and a parameterized Maximal Covering Location Problem with Accessibility Indicators and Mobile Units integer model. To test our methodology, we consider the Maximal Covering Location Problem with Accessibility Indicators and Mobile Units model to cover the low-income zones with Severe Acute Respiratory Syndrome Coronavirus 2 patients. Using official databases, we made a set of instances where we considered the poverty index, number of population, locations of hospitals, and Severe Acute Respiratory Syndrome Coronavirus 2 patients. The experimental results show the efficiency of our methodologies. Compared to the case without mobile units, we drastically improve the coverage and accessibility for the inhabitants of the demand zones. 相似文献
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Marc Rysman 《Journal of Economics & Management Strategy》2019,28(1):153-158
This paper discusses the empirical identification of network effects in light of the reflection problem of Manski. I argue that models of indirect network effects present reasonable exclusion restrictions to address the challenges of the reflection problem. 相似文献
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《Socio》2019
Reforming the healthcare delivery system to provide optimum care to sick newborn infants is a critical task in Korea. Motivated by the efforts of the Korean government, we study a capacity allocation model to design an optimal capacity allocation plan for neonatal intensive care units (NICUs). Our model considers the following properties: 1) the hierarchical feature of neonatal care services and 2) the congestion effect in NICU operations. We develop a mathematical model that combines a hierarchical location model with queuing theory. We subsequently apply the proposed model to the problem of allocating capacities to NICUs in Korea. We provide information that can help policymakers draw an initial plan by evaluating various capacity allocation scenarios. We further examine two policy alternatives for improving accessibility to neonatal care. One involves increasing service capacity by adaptively adding resources to NICUs, and the other includes expanding physical service coverage by introducing helicopter transport. The results show that each alternative can contribute toward improving accessibility, and we believe that these findings will have practical implications for developing a better neonatal care system. 相似文献
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《Socio》2020
This paper presents a stochastic optimisation model for locating walk-in clinics for mobile populations in a network. The walk-in clinics ensure a continuum of care for the mobile population across the network by offering a perpetuation of services along the transportation lines, and also establishing referral systems to local healthcare facilities. The continuum of care requirements for different diseases is modelled using coverage definitions that are designed specifically to reflect the adherence protocols for services for different diseases. The risk of not providing the required care under different realisations of health service demand is considered. In this paper, for a multi-disease, multi-service environment, we propose a model to determine the location of roadside walk-in clinics and their assigned services. The objective is to maximise the total expected weighted coverage of the network subject to a Conditional-Value-at-Risk (CVaR) measure. This paper presents developed coverage definitions, the optimisation model and the computational study carried out on a real-life case in Africa. 相似文献