基于CPM网络的关键链汇人缓冲设置研究

关键链管理作为作为项目管理的新一代技术为项目管理提供了新的工具——缓冲区,研究人员可以利用缓冲区结合应用广泛的甘特图技术和CPM网络技术来研究非确定工期项目的管理,这使得原有理论的可移植性大为增强。然而在关键链缓冲区的研究中,汇入缓冲区计算对象即汇入链的定义一直没有明确的界定,这使得缓冲区的计算存在随意性;在工序前后逻辑关系相对复杂的情况下汇入链的识别就成为一个难点。论文对汇入链的识别和汇入缓冲设置问题展开研究,首先根据汇入链的本质对汇入链进行了定义,并利用CPM网络机动时间的性质给出了汇入链的识别的一般方法。其次研究了CPM双代号网络中缓冲区设置问题,并通过添加带有时间参数的缓冲节点解决了缓冲区的表示问题。最后论文通过算例对基于CPM网络对关键链汇入缓冲区设置的步骤进行说明。     

Program Evaluation and Review Technique (PERT) in Construction Schedule Risk Assessment

Construction project scheduling is one of the most critical factors for project success measurement.Not only for the project planning but for construction process management,the scheduling is the basic tool for communication between the owner and the project manager.By developing the schedule before the project starts,the owner knows in advance that the expected timeline of the project.By preparing construction process scheduling,the owner and general contractor can better manage the subcontractors,sub-trades progress,materials storage and deliveries,labors schedule and equipment set up which will eventually save time,money and hassle.Basically,Critical Path Method(CPM) is commonly used in the construction industry.CPM is a deterministic method that assumes that through the network,there is at least one path that determines the project duration and that the path is the critical path.CPM does not consider the uncertainty in the activities;rather it assumes that each activity can be finished in the given situation.Program Evaluation and Review Technique(PERT) is a stochastic technique which is based on the assumption that the duration of a single activity can be described by a probability density function.PERT takes into account the uncertainty during the construction process and has been created out of the need to plan,schedule and control complex projects with many uncertainties.The PERT approach is stated in some books and papers,but there is no deep investigation on the application in the schedule risk assessment.This paper investigates the PERT work process and takes a valuable try on the construction schedule risk assessment by using case studies.The utilization in the estimate the construction liquidated damage with the uncertainties is performed,which also can be used in the insurance company to calculate the insurance premium.     

矿物微粉对水泥基混合料抗压强度的影响

为了了解矿物微粉对混凝土性能的影响,利用可压缩堆积模型(CPM)计算了不同体系胶凝材料的堆积密实度,研究了矿物微粉级配及其相对掺量对低水胶比水泥基混合料抗压强度的影响。结果表明,胶凝材料的堆积密实度与水泥基混合料的抗压强度有很强的对应关系;当堆积密实度相差不大而化学效应相差较大时,化学效应越大,抗压强度越大。     

A Measure for Companies' Customer Portfolio Management

Purpose/Contribution: Customer portfolio management (CPM) is one of the key areas of customer-relationship and network management in business markets. However, there is scant research about the implementation of this concept in business. This article contributes to this conceptually rich but empirically nascent field of CPM research by (1) conceptualizing customer portfolio management, (2) forming a measure for it, (3) validating the suggested measure, and (4) suggesting implications for future research and management.

Methodology: A CPM construct is proposed based on the synthesizing of the theory and the findings from a qualitative field study of companies' management practices. The suggested construct is formative and consists of the following four dimensions: analysis efforts, analysis design, responsiveness efforts, and responsiveness design. Hence, this conceptualization takes into account both the strength and style of companies' CPM practices. The measure is validated following Diamantopoulos and Winklhofer's (2001) Diamantopoulos, A. and Winklhofer, H. 2001. Index construction with formative indicators: An alternative to scale development. Journal of Marketing Research, 38(2): 269–277. [Crossref], [Web of Science ®] , [Google Scholar] guidelines for developing formative measures. Together with the content validity established in the conceptual phase of the research, the results from a cross-industry survey of 212 companies give support to the construct validity of the suggested CPM measure. Partial least squares modeling is applied in validating the measure.

Implications: This study gives an extensive, up-to-date review of customer portfolio management and provides measures for future research on companies' CPM practices and performance. Further, the theory and the field study highlighted several central topics that should be addressed in future CPM studies. The resulting managerial implications derive from the discussion on the key aspects of developing CPM practices in business.     

Time Management in the Cost Evaluation of Limited Resource Programs

Planning, implementing and evaluating an intervention program all hinge around time. A program’s actions are planned according to a forecast of the time required to achieve certain objectives, and the program’s implementation among a group of users is conditioned by its real time application. Similarly, program evaluation needs to take into consideration the time resource when analysing objectively the extent to which a program’s targets have been reached, and when conducting a cost analysis of the program. In limited resource programs, any disparity between the scheduled time and the real time available can have serious consequences, and even undermine a program’s efficacy. Time management, above all where resources are limited, is therefore the linchpin in the planning, implementation and evaluation of an intervention program. In this study we analyse the utility of PERT and CPM as basic tools for the efficient time management of limited resource programs.     

优化参数对CPM-PSWF信号性能的影响

基于椭圆球面波信号的连续相位调制（Continuous Phase Modulation Based on Prolate Spheroidal Wave Function,CPM-PSWF）方法是一种新颖的数字调制方式,调制参数的优化与其调制信号性能有着直接联系。分析不同调制参数对CPM-PSWF信号性能的影响,优化选择调制参数,对获得能量聚集性和功率效率都较高的CPM信号具有重要意义。首先,对基于椭圆球面波信号的CPM信号进行描述;其次,采用韦尔奇(Welch)谱密度估计法,对时间带宽积、调制指数、关联长度等不同参数对CPM-PSWF调制信号的功率谱密度和带宽特性的影响进行了仿真分析。实验结果表明,选用0阶椭圆球面波信号,小时间带宽积、调制指数和符号进制数越小,关联长度越大时,CPM-PSWF信号具有频谱带外高频滚降快、占用带宽小的特点。     

基于突变级数法的钢铁企业环境绩效评价

环境是影响企业经济活动的重要因素,应将其纳入到战略管理和经营决策中去,钢铁企业作为高碳排放、高能耗、高污染的代表尤应如此。借鉴国内外环境绩效评价标准,结合国内钢铁企业生产实践,从源头投入、末端排放、综合利用、关联管理四个方面构建了钢铁企业的环境绩效评价指标体系,并运用突变级数对指标进行耦合,建立了环境绩效评价突变模型,减少了人为对指标赋予权重的主观性,提高了评价模型的科学性。     

等效化简连续型时间-费用权衡问题

大型工程项目中的连续型时间-费用权衡问题是复杂的项目调度问题,特别是非线性问题,需要先用适当的分段线性函数近似逼近原先的非线性时间-费用函数.等效化简是有效减少其计算量,进而使其便于求解的理想方法.针对该问题,本文采用等效化简的方法,把大型问题转化为等价的小型问题,即在不影响解的最优性的前提下,减少问题所涉及的工序数量,并减小工序的工期范围,使原来不可计算的问题变得可以计算,使复杂的问题变得简单.另外,减小工序的工期范围,便于用更精细的分段线性函数来近似逼近原非线性函数,从而提高解的准确性.在该原理的基础上,本文以CPM网络为工具,利用机动时间与网络中路长的关系,寻找求解原问题过程中的冗余工序,以及非冗余工序的冗余工期,并将其去掉,进而实现问题的等效简化.     

一种新颖的Multi-h CPM信号符号速率盲估计算法

针对非合作条件下Multi-h连续相位调制（CPM）信号符号速率的盲估计问题,提出 了一种新颖的预滤波二次谱算法,通过对接收信号滤波然后搜索其二次谱的峰值实现Multi -h CPM信号符号速率的估计,并利用CPM信号的PAM展开表达式解释了算法的原理。仿真实 验结果表明,该算法是无偏的,与基于循环谱分析的算法相比具有运算量小的优点,并且适 用于各种类型的Multi-h CPM信号,同时不需要载波频率和调制指数的先验信息,具有很强 的鲁棒性。