基于仿真分析的随机活动工期鲁棒性项目调度优化

在不确定环境下，项目的计划与控制对项目能否顺利实施十分重要。考虑随机活动工期，研究了如何借助仿真分析确定鲁棒性调度优化的最佳项目输入参数组合。首先，对研究问题进行界定；随后，构建鲁棒性项目调度优化模型，并设计仿真分析流程，建立项目输入参数与仿真指标之间的对应关系；接着，开发了禁忌搜索启发式算法对鲁棒性调度优化模型进行求解，并制定了仿真实施流程；最后，通过一个实际案例对研究进行说明。得到结论：进度计划的鲁棒性随项目计划工期与资源可用量的增大而增大，达到一定值后保持稳定；当选取不同的仿真指标时，得到的最佳输入参数的组合不同，管理者可根据实际需求选取相应的指标。研究能够为不确定条件下鲁棒性项目调度提供指导，有助于项目进度计划鲁棒性的提升。     

带有模糊工期的多模式项目鲁棒优化

研发类项目的活动工期通常是模糊不确定的,且不同的资源投入对应不同的工期,基于此背景对带有模糊工期的多模式项目调度问题进行建模。模型以进度计划鲁棒性最大化为优化目标,考虑时序约束和可更新资源约束。针对问题的NP-hard属性和模型特点设计遗传算法求解,用不同活动规模的标准算例进行计算实验,并用一个实际案例进一步验证说明。案例计算结果优于实际情况,与单模式相比,活动具有多种执行模式时所求满意解的鲁棒值更高。对项目关键参数的分析表明,增加瓶颈资源可用量能够提高项目进度计划鲁棒值。研究成果为项目管理者在不确定环境下制定进度计划提供参考。     

基于Max-npv的项目进度与支付集成优化

以某房地产项目室外基础设施配套工程为对象,对基于Max-npv的支付进度安排问题进行了研究。首先介绍了工程背景资料;其次构建了资金约束下的Max-npv调度问题优化模型,并求解获得满意支付进度安排;最后对理论求解结果与实际情况进行对比分析,项目净现值提升幅度为17.8%,项目最大化资金缺口得到改善。研究为项目支付进度管理定量化决策提供了依据。     

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。     

基于MTO的多目标优化排产模型

针对多订单情况下多产品生产计划安排研究存在不足,提出了一种新的基于订单的计划排期多目标优化模型,目标包括利润最大化与均衡生产,通过各计划期之间产量安排对各资源消耗的偏差最小化来实现均衡生产.模型存在非线性多目标,实现时采用了遗传算法,通过Sheffield GATBX利用MATLAB编程实现.     

基于资源共享的延迟惩罚最小化的多项目调度优化

对可并行进行的多项目调度问题进行定性描述,在共享资源的数量约束下,构建了以多项目延迟惩罚总和为目标函数的优化模型。鉴于问题的强NP-hard属性,为模型设计了迭代循环求解的启发式遗传算法。运用实际案例对研究进行验证,分析关键参数对合同双方项目收益的影响,得到如下结论:与实际进度安排相比,满意进度安排下承包商因延期完工而遭到来自于业主的罚款数额出现了明显的下降;业主的单位延迟罚款费用、共享资源池中的资源数量也会影响承包商对项目的进度安排,并对双方的项目收益产生重要影响。     

基于工程项目SD模型的并行建设策略研究

并行建设对建设工程项目进度和成本的影响具有动态性、反直观和非线性等特征,传统项目管理方法对项目并行建设模式下的决策支持作用已显不足.在分析项目并行建设中不同工作之间的依赖关系、返工、工程变更、质量问题、资源约束、进度压力和组织决策等因素因果关系的基础上,构建了建设工程项目SD模型.以该模型为“策略实验室”,对实际项目进行仿真实验,应用系统结构和行为相结合的方法,对仿真结果进行机理分析,可以得出使建设工程项目的工期和成本最优的并行建设策略.     

双重时间不确定性资源受限项目的预防调度研究北大核心CSSCI

以任务工期和发布时间分别描述项目内部与外部环境不确定性对项目实施的影响,研究了具有双重不确定性约束的项目调度问题。采用模糊数进行参数表示,首先对研究问题进行描述和分析;随后以最大化计划方案的鲁棒性为目标建立了预防调度数学模型;针对该问题的NPhard属性,设计了蚁群优化算法。最后,经算例验证和分析,得到如下结论:相较于传统方法所得到的计划方案,该研究所得到的预防调度方案在最糟糕环境下保证项目顺利完工的概率要高出8%,且完工时间更短。     

双重时间不确定性资源受限项目的预防调度研究

以任务工期和发布时间分别描述项目内部与外部环境不确定性对项目实施的影响,研究了具有双重不确定性约束的项目调度问题。采用模糊数进行参数表示,首先对研究问题进行描述和分析;随后以最大化计划方案的鲁棒性为目标建立了预防调度数学模型;针对该问题的NPhard属性,设计了蚁群优化算法。最后,经算例验证和分析,得到如下结论:相较于传统方法所得到的计划方案,该研究所得到的预防调度方案在最糟糕环境下保证项目顺利完工的概率要高出8%,且完工时间更短。     

变电设备检修进度与成本控制探讨

电力检修成本控制关系着电网运行成本。通过对影响电力检修成本的各个因素进行分析,从进度和资金、进度和资源供应进度与奖罚金不确定性因素对进度影响四方面出发建立数学优化模型,从而对网络计划图优化提出一种可靠的理论依据。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to