基于关键链的项目风险管理

关键链项目管理方法是约束理论在项目管理上的应用,是近年来项目管理领域的重要创新。与传统的项目管理方法相比,该方法强调在制定项目计划时考虑现实存在的资源约束,在项目执行过程中的动态管理,以及整个项目管理流程的持续改进。文中讨论基于关键链的软件项目管理方法。基于软件过程工作分解结构,预测各项工作在理想工作条件下的工期,考虑人力资源的约束与冲突,建立项目的关键链。通过对各项工作的风险分析,为关键链、非关键链分别设置项目缓冲、输入缓冲,通过对缓冲区的监控来进行风险的控制和管理。     

双约束下关键链项目网络计划技术研究

基于关键链管理思想——"鼓"资源冲突优先调度的原则,在满足紧前约束关系的基础上,提出用FS表示紧前约束和SS表示资源约束的关键链项目网络表示方法,改进了传统的项目网络CPM/PERT技术仅考虑紧前约束的情况。进一步基于资源自由时差的概念论证了关键活动和关键路径理论上的识别思路。     

关键链理论在煤田地质项目进度管理中的运用

在项目合同的履行中进度管理始终放在首位。传统的计划评审技术（PERT）和关键路径法（CPM）等网络规划方法在项目进度管理应用上确般多城陷,没有考虑资源的约束因素,并在实施中很难克服多任务和不确定性因素的影响。而“关键链管理”为我们解决上述问题提供了一种思路,划于关键链在项目进瞍管理中的应用研究,既具有重要的实践意义,又具有理论前沿的开拓性意义。本文通过对关键链在煤田地质项目进度管理中应用的研究,将约束理论和关键链甥吣引入到煤田地质领域,使之与煤田地质项目相结合,提出了在煤田地质领域能够广泛应用的项目进度管理方法,给出了占重要地位的缓冲器砹踅、预警机制设越总结了在煤田地质项目中进行关键链项目进度管理的具体实施步骤。     

关键链方法的研究与应用

通过对关键链技术的研究与分析,将其应用到项目管理中,通过具体的应用实例,证明关键链技术能够平衡解决资源约束问题,明显地改善项目和公司的绩效。     

基于Project 2003的关键链启发式算法

介绍了关键链项目管理的基本方法;针对资源受限项目调度问题,提出了资源冲突时的资源分配原则;以项目工期最小化为目标,以Proiect 2003为辅助工具,提出了一个确定关键链的启发式算法,即在找出关键路径的基础上,从后往前遍历,对发生资源冲突的活动,依资源分配原则修改紧前关系,然后再确定关键链,进而得到了基于关键链项目管理方法的项目调度算法.对算法进行了验证,结果表明算法是有效的.     

基于关键链方法的多项目管理

传统多项目管理中的主要问题表现在级联效应、多任务工作、行为效应等三个方面。本文提出五步骤法将关键链管理中的关键链调度、同步化、缓冲管理应用于多项目管理，建立了关键链多项目管理方法(CCMPM)，并构建了由三个项目组成的多项目环境实例，以工期为评估标准，利用模拟软件Crystal Ball 2000．5模拟项目实施过程，1000次模拟结果显示，经CCMPM优化前后项目平均完工时间为320天／295天，完工保证率为90％的工期为330天／301天。     

接驳缓冲设置中的独立时差策略

加入接驳缓冲后可能导致关键链与非关键链产生资源冲突,非关键链溢出等问题,使得关键链调度计划的制定再次复杂化。为优化接驳缓冲的计算,在根方差法的基础上,运用独立时差这一项目网络提供的隐性安全时间,区分非关键链上的活动;并对非关键链上拥有独立时差的活动,改变Goldratt提出的所有非关键活动最晚执行策略,构建考虑独立时差的接驳缓冲设置方法。通过仿真实验,对采用不同接驳缓冲设置法得到的关键链调度计划进行比较;结果表明,新方法能减少接驳缓冲设置引发的问题,并较好地改善了项目工期,项目执行绩效。     

一种基于关键链的计量进度控制方案

关键链技术是工程进度管理的理论创新,文章充分利用关键链思想尝试将约束理论应用到计量进度控制中,并结合计量工作进度控制特点,以国防科技工业电学一级站计量进度控制实际为例,尝试提出了一种适宜于当前计量市场与型号计量需求的计量进度控制方案。     

对关键链法的几个认识误区

关键链法是在约束理论基础上发展起来的一种新型项目进度管理技术,已有较多文献对其进行了介绍,但也存大一些认识误区。从关键链法的基本思想入手,在关键链与关键路径、时间缓存量的确定方法、时间缓存与虚工序、计划与区间计划等几个重要认识误区做了澄清和解释。     

关键链项目管理中关键链和非关键链的识别

运用动态规划的思想设计了一个启发式算法来识别关键链和非关键链.采用此算法对标准问题库PSPLIB中的问题J301_1.SM进行实例求解,识别出来的两条关键链的长度比文献[11,14]中算法求得的长度缩短了6个单位时间.     

Critical chain project buffer sizing based on resource constraints

Project scheduling is a complex process involving many types of resources and activities that require optimisation. The resource-constrained project scheduling problem is one of the well-known problematic issues when project activities have to be scheduled to minimise the project duration. Consequently, several methods have been proposed for adjusting the buffer size but none of these traditional methods consider buffer sizing accuracy based on resource constraints. The purpose of this paper is to develop a buffer sizing method based on a fuzzy resource-constrained project scheduling problem in order to obtain an appropriate proportionality between the activity duration and the buffer size. Specifically, a comprehensive resource-constrained method that considers both the general average resource constraints (GARC) and the highest peak of resource constraints (HPRC) is proposed in order to obtain a new buffer sizing method. This paper contributes to the research by considering several different aspects. First, this paper adopts a fuzzy method to calculate and obtain the threshold amount. Second, this paper discusses the resource levelling problem and proposes the HPRC method. Third, the proposed method uses a fuzzy quantitative model to calculate the resource requirement. The findings indicate that the project achieved higher efficiency, providing effective protection and an appropriate buffer size.     

Buffer sizing approach with dependence assumption between activities in critical chain scheduling

The critical chain/buffer management (CC/BM) methodology, proposed by E.M. Goldratt [1997. Critical chain. New York: The North River Press], introduced the concept of buffers to protect the critical chain against the disruptions. The buffer sizes reflect the uncertainty in the estimation of project duration and affect the project scheduling performance. However, the most current buffer sizing approaches make the assumption that project activity durations are independent. In this paper, the effects of the dependence between activities on project duration performances are analysed, a method for determining buffer sizes with dependence assumption between activities is introduced. Specifically, two definitions reflecting dependence, which are the dependence degree and the dependence factor, are integrated into the formulation of buffer sizing approach. The suggested method is tested and compared with the methods with independence assumption, the root square error method, the adaptive procedure with resource tightness and the adaptive procedure with density. The results indicate that the methods with independence assumption may underestimate the buffer size when at least one of the two definitions is at a high level, while the suggested method can provide better protection in such circumstances.     

Optimisation of critical chain sequencing based on activities’ information flow interactions

One critique for the classic critical chain sequencing methods is that only resource constraints and logical relationships between activities are considered, while interactions of information flows are ignored. However, information flow interactions exist between almost all project activities and bring about big rework risk and rework costs in project management, especially for the long-term projects tied up with big amount of money. In this paper, we propose a new approach to sequence a project’s critical chain by considering activities’ information flow. Specifically, we use the design structure matrix to measure directions and intensities of information flows between activities. The criterion for critical chain sequencing is then to minimise the total coordination cost while considering the influence of feedbacks. The simulation results show that, as opposed to the traditional critical chain sequencing methods, our approach shortens average rework time and reduces the cost.     

基于活动重心定理的关键链识别法

针对关键链识别这一关键链调度理论的基本问题,建立了以活动重心为优先规则的两阶段关键链识别启发式求解方法。并运用数理统计学假设检验方法,以Patterson110问题集为样本,将新构建的算法与三种基于较好优先规则的启发式算法进行了比较,统计数据说明论文构建的迭代重心法有一定的先进性,同时极大地简化了关键链的识别过程。     

A robust scheduling for the multi-mode project scheduling problem with a given deadline under uncertainty of activity duration

The problem of this paper deals with the multi-mode project scheduling problem under uncertainty of activity duration where only the renewable resources are taken into account and a given deadline has to be met at the cost of recruiting additional resources. A heuristic algorithm is employed to solve this problem, and to maintain the robustness of the baseline schedule, the concept of critical chain project management (CCPM) is applied in which a new definition to resource buffer is considered. A simulation methodology is used to determine the size and location of resource buffers in the schedules in which three different buffer sizes and three different uncertainty levels are considered. Results and analysis of the simulation outcomes illustrate that resource buffers are useful and should be simulated by the CCPM schedules, as they help to decrease the total duration of the project during implementation and meet the deadline of the project with more assurance.     

基于多项目关键链的ETO型企业计划管理方法

在ETO型制造企业计划管理中存在着多项目环境、工期不确定性、项目延迟以及人为因素影响等问题.根据多项目关键链原理,提出了包含以计划模板建立、计划编制、控制三个部分的计划管理流程;每个部分又划分为若干个步骤;针对步骤分别详细设计了具体应用方法.最后构造了以某大型变压器制造企业为背景的3个产品并行的多项目环境,并采用Crystal Ball软件模拟了该环境,评估结果显示优化后产品平均周期时间比优化前缩短了2.7d.     

Estimation of the critical constants of long-chain normal alkanes

Correlations between the critical constants of normal alkanes and the number of carbon atoms in a molecule have been considered. In an approximation of a self-consistent field for a polymeric fluid, an equation of state of the van der Waals type has been written, and the dependences of the critical constants of chain molecules on the number of mers have been obtained. It has been found that for an infinitely long alkyl chain, the limiting values of the critical temperature, the critical pressure, and the critical density are equal to, respectively, 1135 K, 0 M Pa, and 0 kg · m^–3. A method of pulse heating of a wire probe immersed in the substance under investigation has been used to measure the dependence of the temperature of the attainable superheatT ^* of low-density polyethylene on the pressure p and the duration of heating pulset ^*. Extrapolation has been used to obtain an estimation of the attainable-superheat temperature of polyethyleneT ^*(p=0,t ^*=0)= 1175 K, which can be treated as the critical temperature of polyethylene.     

Modelling and simulation of energy consumption of ceramic production chains with mixed flows using hybrid Petri nets

Ceramic production chain consisting of discrete flow and continuous flow energy-intensive processes consumes substantial amounts of energy. This study aims to evaluate energy consumption performance and energy-saving potentials of the ceramic production chain. According to the energy consumption characteristics of manufacturing processes and process interaction constraints in a ceramic production chain, an approach integrating the first-order hybrid Petri net (FOHPN) model, an objective linear programming model and a sensitivity analysis is proposed. The FOHPN model will simulate the energy consumption patterns of the ceramic production chain. Meanwhile, multi-objective linear programming model and sensitivity analysis will suggest the optimal specific energy consumption (SEC) of the production chain and identify the influences of input parameters (i.e. production rate of a process) on the SEC in the optimal production scheme. Finally, a real case study from bathroom ceramic plant validates the approach. It provides a tool for modelling and simulation of energy consumption of ceramic production chains with mixed flows and helps operators to perform energy-saving actions in the ceramic enterprise.