模糊搭接网络计划图的新算法

改进了模糊网络时间参数的运算方法,使得模糊数比较大小时不再受隶属度值的影响,且模糊数的加减法运算也避免了模糊数值与展宽的负值现象.同时提出了搭接网络的新画法,将工序间的搭接关系转化为节点之间的搭接关系,解决了单代号搭接网络中的悖论现象,从而使网络图中工序时间参数的计算更加方便、准确.改进后的网络计划图能够更加科学地科学指导工程项目的实施,具有准确性与灵活性,能够有效避免因为工程脱离计划而造成的损失.     

绘制统筹网络图的一个标号算法及应用

本文给出了一个绘制统筹网络图的有效算法，称之为标号算法．利用标号算法可使计算机在只接收到各工序间紧前紧后关系的数据后，便可生成网络优化中必需的网络图形．利用该算法我们还建立了网络优化计算机辅助设计系统，该方法和计算机辅助设计系统，目前已在山东省兴隆庄煤矿井下的拆除和安装工程中得到了具体应用，收到了良好的效果．     

一个绘制统筹图的算法

统筹图又叫计划网络图。任给一个其元素叫做工序（或作业或活动）的有限偏序集，要绘制它的一个最优统筹图，限含虚工序数目为最少者，是一个尚未从理论上解决的问题。本文讨论了虚工序产生的原因和如何减少虚工序数量的一些途径；指出了高度为二的编序集其最优统筹图含虚工序数目达到最大且等于该偏序集框图的边数的充分必要条件；本文给出了一个绘制最优统筹图的近似算法，此算法弥补了文[2]和[3]所给算法的一些不足之处。     

基于时间Petri网的供应链网络关键路径分析

讨论了供应链网络中如何选择优化路径的问题,提出采用时间P etri网对供应链网络关键路径建模的方法.此方法根据顾客需要货物的情况,有条件地选取供应链网络图中可跨越活动和可替换分支,将网络图分别描述成Ebs图和Ew f图,结合时间P etri网的可达算法,求得Ebs和Ew f的关键路径.通过基本供应链的分析,得到网络的优化路径.     

网络图修改方法的两个创新

随着社会的不断向前发展，网络图的应用越来越广泛。比如项目管理中的网络图、电网中的控制图和交通运输中的控制图等都是常见的网络图。网络图越复杂，修改起来越麻烦，本提出的网络图修改方法的两个创新能大大提高网络图修改方法的效率。网络图修改的第一个创新是网络图节点的高效删除．第二个创新是平行工序变为顺序工序的自动实现。     

偏序集最小顶点割算法与最小费用赶工问题

在网络计划问题中,一项大的工程由许多工序合成。工序与工序之间存在着一定的前后关系,每个工序有着自己的正常加工时间和通过赶工所能达到的最短加工时间以及每赶工一天的赶工费用。设一项工程的正常工期为T天,通过对所有可能的工序赶工,整个工程能达到的最短工期为S天。本文的问题是,对于任意给定的t(S t相似文献   

网络图自动生成算法研究

本文针对当前项目管理软件中网络图绘制的缺陷 ,对网络图自动生成的算法作了新的探索 ,提出的算法力求使生成的网络图逻辑关系清楚 ,布局合理 ,直观清晰 ,对改进项目管理软件在此方面的不足甚至对整个项目管理软件的研究有重要意义 .本算法亦有一些遗留问题需进一步研究 .     

基于CPM原理和Dijkstra算法的SPM网络计划模型及性质

CPM(关键路线法)网络计划适用于分析工序间存在严格紧前关系(任意工序只能在它的所有紧前工序都结束时才能开始)的进度计划.针对工序间不存在严格紧前关系(任意工序只要其紧前工序中的一个结束它就可以开始)的进度计划,以CPM原理和Dijkstra算法为基础,提出SPM(最短路线法)网络计划以及拟机动时间概念,根据不同的建模原理,建立了两个SPM网络计划模型,并给出了其建立方法以及各模型拟机动时间的求法,分析了每个模型的性质,最后通过算例对其中的一类模型进行了验证.     

基于均衡使用的通用教练机使用计划编排算法

为确保教练机在飞行训练中的均衡使用,构造描述"训练任务"衔接关系的时序网络模型,以此将教练机均衡使用问题转化为时序网络图上寻找教练机执飞"训练任务"的路径计划问题,通过建立满足教练机均衡使用要求的目标函数,为"训练任务"随机赋予教练机编号生成"训练任务"路径计划,进而设计模拟退火算法获取教练机使用计划方案.选取国内某飞行航校"10架教练机、37个训练任务"的训练计划进行分析,结果表明:算法能够提高教练机使用的均衡性;随着训练任务之间衔接松散度的增加,教练机使用计划方案的均衡更好.     

箭线网络图的唯一性特征和最优箭线图判定

提出箭线网络图由完全工序关系唯一确定、最优箭线图实工序子图唯一确定等结论和由相交紧前工序集直和分解得出的基准箭线图作最优箭线图和判定最优箭线图的概念和方法.     

A new method for constructing a minimal PERT network

A project is an enterprise consisting of several activities which are to be carried out in some specific order. The activities and the order in which they need to be carried out can be represented by a PERT network. The PERT technique is a traditional, well-known approach to the expert of project management. When networks are used, it often becomes necessary to draw dummy activities. Since the computation of project completion time is proportional to the number of arcs, including dummy arcs, it is desirable to draw a network with as few dummy activities as possible.In this paper, we propose a new method for constructing, for a given project scheduling problem, a PERT network having as small as possible the number of dummy arcs by using some results on line graphs. This algorithm deals with the existence of transitive arcs. The paper contains illustrative examples, proofs of some theoretical results as well as a comparative study with a similar algorithm known in the literature. Computational results showed the superiority of our algorithm.     

A dependent project evaluation and review technique: A Bayesian network approach

The Program Evaluation and Review Technique (PERT) dates back to 1959. This method evaluates the uncertainty distribution of a project’s completion time given the uncertain completion times of the activities/tasks comprised within it. Each activity’s uncertainty was defined originally by a unique two parameter beta PERT distribution satisfying what is known to be the PERT mean and PERT variance. In this paper, a three-parameter PERT family of bounded distributions is introduced satisfying that same mean and variance, generalizing the beta PERT distribution. Their additional flexibility allows for the modeling of statistical dependence in a continuous Bayesian network, generalizing in turn the traditional PERT procedure where statistical independence is assumed among beta PERT activity durations. Through currently available Bayesian network software and the construction of that PERT family herein, the coherent monitoring of remaining project completion time uncertainty given partial completion of a project may become more accessible to PERT analysts. An illustrative example demonstrating the benefit of monitoring of remaining project completion time uncertainty as activities complete in that Bayesian fashion shall be presented, including expressions and algorithms for the specification of the three prior parameters for each activity in the project network to adhere to classical the PERT mean and PERT variance and a degree of statistical dependence between them.     

Estimating a Project's Completion Time Distribution Using Intelligent Simulation Methods

Other researchers have indicated the theoretical problems of using the PERT techniques commonly described in elementary operational research and operations management texts. Monte Carlo simulation has often been suggested as an alternative means of analyzing PERT networks but simulating a network of real world proportions is often assumed to be prohibitively expensive. This paper measures the accuracy and cost of standard PERT and simulation methods for real world sized problems. In addition, several computational heuristics are described and tested that indicate that simulation is a viable alternative. The results indicate that intelligent simulation of PERT networks is considerably more accurate than standard PERT analysis and is definitely not cost prohibitive.     

PERT问题的新算法

本文给出了一种通过求解最长路径解决 PERT问题的新算法 .其优点是 ,编制运算程序之前 ,无需做出系统作业的网络图 ,因此 ,使用起来更加方便     

A rule for slack allocation proportional to the duration in a PERT network

In this paper, we define a new rule for the resolution of the slack allocation problem in a PERT network. This problem exists of allocating existing extra time in some paths among the activities belonging to those paths. The allocation rule that we propose assigns extra time to the activities proportionally to their durations in such a way that no path duration exceeds the completion time of the whole project. This time allocation enables us to make a schedule for the PERT project under study. We give two characterizations of the rule and we compare it with others that have been previously defined in the literature.     

A new probabilistic approach to the path criticality in stochastic PERT

The notion of critical path is a key issue in the temporal analysis of project scheduling in deterministic setting. The very essence of the CPM consists in identifying the critical path, i.e., the longest path in a project network, because this path conveys information on how long it should take to complete the project to the project manager. The problem how can a stochastic counterpart of the deterministic critical path be defined is an important question in stochastic PERT. However, in the literature of stochastic PERT this question has so far almost been ignored, and the research into the random nature of a project duration has mainly been concentrated on the completion time in stochastic PERT in which any concrete special path is not specified. In the present paper we attempt to take first steps to fill this gap. We first developed a probabilistic background theory for univariate and bivariate marginal distributions of path durations of stochastic PERT whose joint path durations are modelled by multivariate normal distribution. Then, a new probabilistic approach to the comparison of path durations is introduced, and based on this comparison we define the concept of probabilistically critical path as a stochastic counterpart of the deterministic critical path. Also, an illustrative simple example of PCP and numerical results on the established probability bounds are presented.     

A Multivariate Approach to Estimating the Completion Time for PERT Networks

Stochastic PERT is typically treated as a critical path problem, with the critical path having a univariate probability distribution. A method has been developed to treat the PERT problem as a multivariate problem taking into consideration correlation among paths, thereby providing a more accurate analysis of the network and its corresponding probabilities for completion time.     

Multi-objective time–cost trade-off in dynamic PERT networks using an interactive approach

We develop a multi-objective model for the time–cost trade-off problem in a dynamic PERT network using an interactive approach. The activity durations are exponentially distributed random variables and the new projects are generated according to a renewal process and share the same facilities. Thus, these projects cannot be analyzed independently. This dynamic PERT network is represented as a network of queues, where the service times represent the durations of the corresponding activities and the arrival stream to each node follows a renewal process. At the first stage, we transform the dynamic PERT network into a proper stochastic network and then compute the project completion time distribution by constructing a continuous-time Markov chain. At the second stage, the time–cost trade-off problem is formulated as a multi-objective optimal control problem that involves four conflicting objective functions. Then, the STEM method is used to solve a discrete-time approximation of the original problem. Finally, the proposed methodology is extended to the generalized Erlang activity durations.     

节点有自环的网络流数学模型

以网络流中节点有自环的情形为对象进行研究,把节点分开为入点和出点,节点自环转换为流量相同,方向相反的两条弧,改进了网络流数学模型.改进后的数学模型在处理原来网络流中节点发生异常情况时,即节点不遵守流量守恒条件时,其节点自环的流能够起特殊的调节作用.在描述网络流异常状态时,给出了网络流状态周期的阶跃性质.通过网络模型对应的邻接矩阵对网络流进行计算和监控,给出一个节点环流的应用实例.