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为了解城市公交信息化服务对公交乘客出行方式转移的影响,以上海市杨浦区为例,进行关于公交信息化服务下乘客出行方式转移的调查,获取个人属性、公交出行经历、公交出行评价、出行方式转移意向以及公交信息服务需求等信息。从公交信息使用者角度,重点关注公交信息化服务对乘客出行方式转移的影响,分别构建信息化服务情境下(公交到站时间与计划出发时间相差过大和车辆未在提示的时间内到达)的公交出行方式转移二项logit模型。模型结果表明:乘客平均候车时间、是否经常使用公交到站服务、是否有道路拥挤车辆未按时进站等原因而产生出行延误的经历、公交信息准确性评价与是否有必要提示同公交线路连续班次的到站时间等因素对不同情景下的乘客出行方式转移具有显著影响。 相似文献
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文中分析了公交线路运行中常见的问题,考虑了中途站点的车辆停靠行为对乘客候车时间的影响,建立了一种车辆停靠控制模型。达到了疏散车辆和客流,均衡中途各站待运乘客的候车时间的目的。并结合实例分析验证了模型的实用性。 相似文献
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针对偏远离岛地区公交运营收益低、当地居民出行难的问题,考虑该地区的出行需求空间上分布过疏、时间上需求波动性较大、且高支付意愿高质量服务需求无法被满足等特性,提出需求响应式公交运营模式,并将多条存在部分共线的公交线路进行联合优化。为此,建立了双层规划模型,其中上层模型为公交公司运营决策模型,以公交公司总利润最大为目标,以乘客对需求响应式公交的支付意愿作为约束条件,对公交公司在不同时间窗下的发班频率、所需车辆数及乘客所需支付票价进行联合优化;下层模型为乘客出行方式选择模型,通过对乘客出行方式的选择行为进行分析,基于Logit模型确定选择需求响应式公交出行需求站点的乘客人数。最后,以浙江宁波梅山岛为例进行实证分析。通过比较优化方案和现状下的公交公司收益以及乘客出行时间成本,验证了提出的需求响应式公交运营模式以及双层规划模型的有效性。 相似文献
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随着城市轨道交通的快速发展,乘客对列车的舒适度和安全性提出越来越高的要求。乘客紧急报警器的设计提高了车辆的安全性和可靠性。在紧急情况下,乘客可以通过客室紧急报警对讲器与司机通话。文章提供了一种新型乘客紧急报警器,集成了乘客紧急制动手柄及噪声检测器,减少了车内电气设备。旨在解决车辆内部电气安装空间紧张问题,避免司机误判提高车辆的可靠性,同时达到节约成本的效益。 相似文献
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针对传统的配送车辆路径问题,在传统的运距及容量等限制下,增加客户的混合时间窗和车辆在客户点的服务时间,以惩罚、配送总成本最低为目标,构建出带有混合时间窗的车辆路径问题的数学模型.并引入优良基因及最优个体保护策略改进遗传算法,同时设计参数自适应调整公式调整交叉概率,设计了带混合时间窗的配送车辆路径问题的改进遗传算法,最后由实例证明了VRPMTW模型及遗传算法的有效性. 相似文献
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在快递配送过程中,快递配送中心作为货物集散点,首先要分派车辆到各个配送点(客户)送货和取货,为降低配送成本,提高配送效率,车辆的调度是一个重要的问题.根据快递配送的特点,主要研究的车辆路径问题为配送中心在为各分点进行快递配送时,采用快件送达和收集同时服务的配送策略,假设车辆在各点之间的行驶时间服从正态分布,配送分点有软时间窗约束并且快件收集数量服从泊松分布的条件下,建立了问题的求解模型,并进行了基于遗传算法求解的应用设计.该遗传算法通过基于适应度排名和最佳个体保留的选择策略和自适应交叉概率的参数控制来保证所求结果的优良性,并设计算例用matlab编程进行实验,证明了算法的可行性. 相似文献
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Avraham Shtub 《Journal of Operations Management》1986,6(3-4)
In this article we consider the probability of not completing a project on schedule (or the risk of delays) and its effect on the net present cost of the project. We propose an efficient frontier that points out to management the trade-off between low risk, early start schedules and high risk, late start schedules. Early start schedules minimize the risk of delays at the cost of early investment in project activities and material. Late start schedules delay capital outlays while increasing the risk of not completing the project on its due date.The methodology developed in this study is aimed at strategic level decision making. At this level, decisions are based on incomplete information that calls for stochastic analysis and the introduction of uncertainty. Uncertainty in project management is introduced through stochastic activity duration and stochastic lead times of resources required for the project. The commonly used CPM analysis ignores those aspects of uncertainty. PERT analysis does consider the stochastic nature of activity durations but computes only the probability to complete the project on a given date for a single schedule.A crucial decision at the strategic level of project management is when to schedule activities with high value-added. The decision makers have to trade-off the advantages of delaying such activities, thus reducing the net present cost of the project, with the disadvantages associated with increasing the probability of not completing the project on time.The number of feasible schedules in a real project is typically large and exact analysis of all possible schedules is difficult to perform, if not impossible. This article presents a heuristic procedure that generates an efficient frontier representing the risk of delays versus the net present cost of the project. The efficient frontier is a decision aid for the manager who has to choose the appropriate schedule for the project.Most computer packages for project management are based on CPM (especially packages for personal computers). Our heuristic procedure is designed to be used as an extension to CPM analysis. The procedure starts with the early start schedule developed by CPM and, using the computed slacks, tries to delay activities with high value-added one at a time. At each iteration a Monte-Carlo-type simulation is used to approximate the probability of not completing the project on time. This probability is stored along with the net present cost of the project. The result of the analysis is a set of points on the plane representing the probability of not completing the project on time versus the net present cost of the project. Each point corresponds to a specific schedule. Management can choose the most appropriate schedule for implementation based on its attitude towards risk and its financial policy.A simple example is used to illustrate the heuristic procedure. In the example, a project with six activities and two types of resources is analyzed. Five schedules are generated with net present cost ranging from $45,000 to $8,191,000 and the probability of not completing the project on time ranging from 0.0001 to 0.75. Our experience with a real project of 400 activities is reported as well.The heuristic procedure can be implemented easily on advanced “Fourth Generation” packages for project management such as IBM's Application System (AS) or Metier's Artemis system. The heuristic procedure can also be implemented on personal computers by processing the output of any CPM package by the special subroutine that is developed in this study. 相似文献
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针对单一产品、单周期、单一供应商、多配送中心、供应商和需求点位置已知的情况,假定(Q,R)库存检查策略、给定备选地址、无容量约束、各需求点的需求完全独立且均服从正态分布、配送中心级和需求级同时采取中心化安全库存策略、允许配送中心间及同一配送线路内的需求点间通过横向转运对缺货进行瞬间补充、不计缺货成本和转运时间,构建了二层规划模型。上层规划解决选址及需求点的分配问题;下层规划确定配送中心级和需求级的中心化存储方案。发现如果考虑库存持有成本、转运成本等因素的影响,安全库存的集中存放策略并不是聚集在某一个地方,而是在多个地方进行有限、适度的集聚,其成本更低。 相似文献
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工程项目进度管理是工程项目管理的一项极为重要的工作,其能全面反映项目的实施情况。做好施工阶段的项目进度控制管理对保证施工企业履行合同、工程项目按期竣工投入使用发挥着决定性作用。文章对工程项目进度管理的影响因素进行了深入分析,并对影响其的相关因素提出了具体的管理措施。工程项目进度控制、成本控制、质量控制,是项目管理三个核心内容,相铺相成。它是确保施工工程项目按期完成,科学安排资源投入、节约工程成本投资的重要举措。 相似文献
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Stephen E. Bechtold D.B.A. 《Journal of Operations Management》1981,1(4):205-214
The problem considered here is the determination of the minimum full-time workforce and corresponding work schedule to meet arbitrary cyclic staffing requirements where all workers are idle either one or two consecutive periods per cycle. Specialized algorithms are developed which are less complex and consequently more efficient than existing algorithms. The new algorithms are also compared with alternative algorithms on the basis of slack dispersion which is a criterion that has not been previously considered in the literature. The results suggested the existence of a trade-off between the execution efficiency of the algorithms and their slack dispersion characteristics. Some initial framework required for future research is also provided. 相似文献
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以战略管理理论和权变理论为理论基础,选取我国2008-2010年深沪市A股上市公司为样本,对上市公司战略选择与预算编制松弛之间的关系进行初步探讨,研究发现:我国上市公司不仅普遍存在预算编制松弛的现象,而且预算编制松弛程度比较严重,预算可靠性较低;权变理论比代理理论更能有效地解释公司预算编制松弛现象,战略管理理论对预算编制松弛程度的影响有限;公司实施差异化战略程度与预算编制松弛程度显著负相关,国际化战略程度与预算编制松弛程度显著正相关. 相似文献
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Purchasers must often make lot sizing decisions when facing price schedules of price-quantity discounts. It is important to determine the supplier's pricing philosophy when establishing a solution procedure.One approach is to evaluate total costs at all of the appropriate break points. This offers limited information: a lot size and a set of total costs. This is especially true in the case of full fixed cost recovery pricing. In actual practice price schedules can be extremely lengthy: indeed, it may be in the supplier's best interests to offer comprehensive discount schedules. This situation complicates the purchaser's decision making process.An efficient alternative, which solves the price-quantity discount problem when the supplier insists on a full fixed cost recovery schedule, is presented. Computations are reduced to a few simple steps; the result is a least total cost lot size for a simple linear package price model given parameters obtained by an appropriate analysis of the supplier's price-quantity discount schedule. A starting point is determined and the choice of the lot size is made using a simple criterion. Rapid convergence is assured, given a reasonably well-behaved schedule. 相似文献
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EPC工程项目进度计划管理是整个工程项目管理的基础和根本的出发点。工程项目进度管理是否科学、有效,直接影响到整个工程项目是否能够实现合同要求中的进度目标,对于保证工程项目的整体质量以及经济效益意义重大。EPC工程项目进度计划管理在实际的工程建设中具有诸多优势。目前在海外石油工程建设方面普遍采用EPC模式,采用这种模式不仅可以有效的节省建设方的人力、物力,也在工期、协调管理、成本控制方面占有较大优势。本文将对海外石油工程建设的特点以及EPC工程进度控制方法进行一定的分析,进一步的探讨进度计划编制原则,更好的促进海外石油工程建设发展。 相似文献
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Ralph St. John 《Journal of Operations Management》1985,5(2):119-128
Much of the current literature in the field of production and inventory control systems stresses the need to revise traditional forms of thinking regarding production processes, the role of inventories for work in process, and the need for reduced lead times or flow times. Group technology, manufacturing cells, and other means of incorporating repetitive manufacturing techniques into traditional job-shop settings constitute the leading edge in system development.Still, there is resistance to these dramatic changes, and traditional “business as usual” methods still predominate. This study attempts to illustrate graphically the cost justification associated with reduction in lead times which generally results from these new concepts. In most job shops today, lead times are much longer than they need to be due to inflation of lead time estimates. Actual lead times for the manufacture of fabricated and assembled products have been shown to be a direct consequence of the planning lead times used in the MRP planning process—a form of self-fulfilling prophesy.The research employs a simulation model of a factory using MRP as a planning tool in a multiproduct, multilevel production environment. Manufacturing costs constitute the dependent variable in the experiments, defined as the sum of material costs (including expedite premiums), direct labor costs (including overtime premiums), inventory carrying costs, and overhead costs. The independent variable being manipulated is the planned lead time offset used in the MRP planning process. Twenty values of planned lead time are evaluated ranging from a value that includes no slack time at all (pure assembly line) up to a value that allows 95% slack (queue) time which, unfortunately, is not uncommon in many job shops today. Stochastic variables in the model include customer demand and actual processing times—the sum of set-up and run times.The result of the study is a cost curve formed over the range of independent lead time variables that is constructed using nonlinear regression techniques. The conclusions from the resultant graph clearly indicate the cost consequences of long lead times, with exponential cost increases beyond the 80–90% queue time level. Total costs are 41% higher at the maximum lead time allowance compared to the minimum. Clearly, this study demonstrates the need for lead time reduction, either through downward adjustment of MRP planned lead times or by introducing new manufacturing concepts. 相似文献