Optimal overlapping and functional interaction in product development

Overlapping of development stages and interaction between different functions are regarded as important strategies for reducing development lead time. However, overlapping typically requires additional costs for rework and functional interaction increases communication time. This paper presents an analytical model to improve project performance by balancing the positive and negative effects of overlapping and functional interaction. We first investigate the progress of downstream development, which is essential to derive the optimal overlapping policies. We find that the downstream progress increases over time when the upstream evolution is fast or linear, but it is indefinite when the upstream evolution is slow. Then, we present optimal overlapping policies taking into account the complexity of downstream progress. The impact of different project properties, such as the dependency between development stages and the opportunity cost of time, on overlapping policies is discussed. Finally, we derive the optimal functional interaction strategy when the optimal overlapping is followed. The methodology is illustrated with a case study at a handset design company.     

基于活动重叠的DSM项目进度优化与仿真

项目活动之间的重叠虽然可以缩短项目工期,但又存在返工风险。为此,本文采用设计结构矩阵(DSM),提出活动超前重叠因子矩阵和活动赶工重叠因子矩阵,结合返工风险矩阵,完整地描述了项目活动的重叠及其对返工的影响。提出了基于活动重叠的混合粒子群项目进度优化方法。通过案例计算表明,该法可以有效缩短项目工期,同时为项目决策者合理选择活动重叠量提供了新思路。     

质量文化传播与工程管理行为耦合演化的系统动力学模型研究

为了研究质量文化建设与工程管理行为以及工程绩效的耦合演化规律,对大型工程中的质量文化建设的动态特性进行了分析,运用系统动力学构建了包括质量文化传播、工作流程、人员调配以及进度压力这四个主要模块相互整合的大型工程耦合演化系统模型。系统仿真的结果表明一些管理行为因忽视了其引发的涟漪效应,导致了质量文化建设和工程建设的失败,而该模型考虑了大型工程存在的返工回路等多种动态反馈,能够帮助工程管理者理解质量文化建设存在的动态复杂性。     

Determination of critical chain project buffer based on information flow interactions

It has been well accepted in the literature that co-dependency between project activity durations is caused by resource tightness and network complexity. However, we show that information flow interaction between activities is the key factor for it. Based on whether there exist spliced relationships between activities, we introduce the concept of rework safety time. We propose a method to compute the rework safety time using the information output and input time factors, rework probability matrix, and rework impact matrix. We achieve the optimization of the critical chain sequencing via the design structure matrix so that the dependency between activities is reduced. The project buffer is then determined by the tail concentration method based on the optimized chain. The empirical results show that, as opposed to the traditional RSEM method, our approach improves the project buffer consumption rate, shortens project duration, reduces project cost, and increases project on-time completion rate.     

A multicriteria decision model for assigning priority classes to activities in project management

Problems related to the management of construction projects are addressed in many studies. Falling behind schedule and being over budget are examples of bad results, due to the uncertainties and the dynamic environment of the construction process. This study proposes a decision model for helping project managers to focus on the main tasks of a project network during the life cycle of a project based on a MCDA (multiple criteria decision analysis) method. The model assigns priorities classes to activities in project management, taking into account several points of view. The model is based on the ELECTRE TRI-C method, which permits activities to be assigned to categories. As the environment is very dynamic, the model was built taking into consideration changes that may occur while a project is being carried out, and therefore the model must be reassessed during the project life cycle. Furthermore, the model supports a decision making environment where responsibilities are distributed amongst project team members and it brings the benefit of developing disciplines that lead to the team??s greater effectiveness. An application of the model, based on a realistic situation, is presented in the context of a construction project in order to demonstrate the use of the model. The results show that by using the model, managers can improve their performance with regard to controlling project activities.     

Overlapping design and build cycles in product development

Product development time is a major component of the total time it takes to bring a product to market. Overlapping is the process of starting a downstream operation (such as manufacturing) before completing the upstream operation (such as design). There is an inherent risk in overlapping as a build-assembly may not be compatible with a subsequent assembly, requiring reconciliation work on the overlapped tasks. The ensuing trade-off between this risk, and the project time saved, is shown to possess some unique characteristics among different modes of overlapping. We study the optimization model of the trade-off in general, and analyze some special cases to establish interesting insights on overlapping. These include: advantage of overlapping in different scenarios, special properties of optimal overlap, and impact of parameter values on overlapping decisions. We show that several properties of a single overlap can be extended to multiple overlaps, and establish a limit to overlapping based on administrative cost of implementing overlap and shapes of cost functions. The critical role of the administrative cost (of coordinating overlaps) is also borne out by the model.     

A market-based multi-agent system model for decentralized multi-project scheduling

We consider a multi-project scheduling problem, where each project is composed of a set of activities, with precedence relations, requiring specific amounts of local and shared (among projects) resources. The aim is to complete all the project activities, satisfying precedence and resource constraints, and minimizing each project schedule length. The decision making process is supposed to be decentralized, with as many local decision makers as the projects. A multi-agent system model, and an iterative combinatorial auction mechanism for the agent coordination are proposed. We provide a dynamic programming formulation for the combinatorial auction problem, and heuristic algorithms for both the combinatorial auction and the bidding process. An experimental analysis on the whole multi-agent system model is discussed.     

Simultaneous engineering approach to an integrated design and process planning

To support integration of design and process planning, a reference model has been developed. This reference model represents the basis for a new methodology for integrated design and process planning which enables a Simultaneous Engineering approach in the early stages of product development. The reference model consists of four partial models. These are the activity model, the information model, the technical system model and the model of integrating methods. Using these models, the methodology enables a concurrent processing of design and process planning activities with regard to different components of a product. Furthermore, the methodology covers planning methods as well as execution methods, to support early transmission of information to downstream activities and a feedback of information to upstream activities within the process chain of design and process planning.     

基于技术创新的资金约束供应链融资策略分析

新兴技术进入竞争市场时,供应链成员往往存在资金约束,为了尽早占据市场份额、获得更高的利润流,上下游企业有意愿进行供应链的内外部融资。文章对上游企业存在资金约束、下游核心企业资金充裕的供应链融资策略进行决策分析。研究表明:上下游的融资策略会使上游企业得到帕累托改进,且随上游企业自有资金的增大,下游企业的利率阈值逐渐减小;存在最优融资利率使得下游企业的期望利润达到最大。在上下游企业财务不透明的前提下,存在下游企业的融资利率区间使上游企业有隐藏真实资金状况以期获得更低融资利率的动机,文章基于博弈论的信息甄别模型给出了相应的激励合同对上游企业的期望利润进行修正,诱使上游企业提供真实的资金状况。     

An exact approach for relating recovering surgical patient workload to the master surgical schedule

No other department influences the workload of a hospital more than the Department of Surgery and in particular, the activities in the operating room. These activities are governed by the master surgical schedule (MSS), which states which patient types receive surgery on which day. In this paper, we describe an analytical approach to project the workload for downstream departments based on this MSS. Specifically, the ward occupancy distributions, patient admission/discharge distributions and the distributions for ongoing interventions/treatments are computed. Recovering after surgery requires the support of multiple departments, such as nursing, physiotherapy, rehabilitation and long-term care. With our model, managers from these departments can determine their workload by aggregating tasks associated with recovering surgical patients. The model, which supported the development of a new MSS at the Netherlands Cancer Institute–Antoni van Leeuwenhoek Hospital, provides the foundation for a decision support tool to relate downstream hospital departments to the operating room.     

施工项目中设计风险元传递模型研究

针对设计变更对项目实施的影响,本文将影响施工项目的设计变更原因称为项目的设计风险元,基于广义项目风险元传递理论建立系统动力学模型,动态研究设计风险元传递过程。通过模型模拟分析不同时间、不同程度的设计风险元对项目工期和项目费用影响程度,当设计风险元发生后,设计审批及设计过程将影响项目工期;受施工工序影响设计风险元造成实际施工速度不饱和,使得施工效率低下形成窝工;由于设计风险元导致的返工造成施工项目的工期延误和成本超支。此模型为风险管理者或项目管理者在设计风险管理方面提供了有力依据。     

Bid calculation for construction projects: Regulations and incentive effects of unit price contracts

The Austrian contract awarding system for construction projects is characterized by the unit price contract being an important contract type. The bid price is a decisive criterion for the selection of the construction company that performs a project, and the bid price is calculated from the unit prices and the specified production volumes of the project activities. Since the actual production volumes can differ from the specified volumes, the actual payment can differ from the bid price according to these deviations. In practice there can be asymmetric information on the production volumes. This leads to an incentive for the bidders to “skew” the bid calculation by asymmetric allocation of overhead costs to project activities.In this paper we analyze this agency-theoretical situation and develop a model that decides on the allocation of overhead costs to project activities in order to maximize the actual payment for a predetermined bid price. We also present a case study and comment on the implications of the model for the contract awarding system in the construction industry.     

不确定环境下基于时间、费用及鲁棒性权衡的多目标项目调度优化

项目调度中的时间和费用是两个重要的指标,而在不确定环境下进度计划的鲁棒性则是保证项目平稳实施的关键。本文研究不确定环境下的多目标项目调度优化问题,以优化项目的工期、鲁棒值和成本为目标安排各活动的开始时间。基于此,作者构建多目标项目调度优化模型,将模型分解为三个子模型分析目标间的权衡关系,然后设计非劣排序遗传算法进行求解,应用精英保留策略和基于子模型权衡关系的优化策略优化算法,进行算法测试和算例参数敏感性分析。最后,应用上述方法研究一个项目实例,计算得到非劣解集,实例的敏感性分析结果进一步验证了三个目标间的权衡关系,据此提出资源的有效利用策略。本文的研究可以为多目标项目调度制定进度计划提供定量化决策支持。     

Pricing and horizontal information sharing in a supply chain with capacity constraint

This paper aims to explore manufacturers horizontal information sharing strategy under competition. The model framework is based on a two-echelon supply chain composed of one upstream supplier and two downstream manufacturers with asymmetric capacity constraint. Analysis of the model establishes manufacturers’ information sharing strategies under different conditions and shows how supplier’s pricing decision can shape manufacturers’ information sharing incentives.     

Production scheduling with alternative process plans

This paper deals with a scheduling problem with alternative process plans that was motivated by a production of wire harnesses where certain parts can be processed manually or automatically by different types of machines. Only a subset of all the given activities will form the solution, so the decision whether the activity will appear in the final schedule has to be made during the scheduling process. The problem considered is an extension of the resource constrained project scheduling problem (RCPSP) with unary resources, positive and negative time-lags and sequence dependent setup times. We extend classic RCPSP problem by a definition of alternative branchings, represented by the Petri nets formalism allowing one to define alternatives and parallelism within one data structure. For this representation of the problem, an integer linear programming model is formulated and the reduction of the problem, using time symmetry mapping, is shown. Finally, a heuristic algorithm based on priority schedule construction with an unscheduling step is proposed for the nested version of the problem and it is used to solve the case study of the wire harnesses production.     

Audit scheduling with overlapping activities and sequence-dependent setup costs

Audit firms are faced with the complex job of scheduling auditors to audit tasks. The scheduling becomes more complex as the firm needs to consider real life issues in determining an optimal schedule. Among these issues are the setup times and costs emanating from changing the assignments of the auditors and the lead and lag relationships between the audit tasks.Audit scheduling with overlapping activities and sequence-dependent setup cost has not been treated in literature. This paper presents a formulation and a solution approach for this audit scheduling problem. First, the problem is represented by an activity network with lead/lag relationships. Then the network is analyzed to determine the early and late finish times of activities. An integer linear program (ILP), which uses the early and late finish times of activities to reduce the number of decision variables, is formulated. A four-auditor two-engagement example is used to illustrate the ILP model and its solution. The results indicate that incorporating the setup cost and the overlapping of activities yields lower cost schedules leading to sizable savings in the cost of audits. The proposed treatment is of merit in providing realistic schedules that can be easily implemented     

Project Scheduling under Time Dependent Costs – A Branch and Bound Algorithm

In a given project network, execution of each activity in normal duration requires utilization of certain resources. If faster execution of an activity is desired then additional resources at extra cost would be required. Given a project network, the cost structure for each activity and a planning horizon, the project compression problem is concerned with the determination of optimal schedule (duration) of performing each activity while satisfying given restrictions and minimizing the total cost of project execution. This paper considers the project compression problem with time dependent cost structure for each activity. The planning horizon is divided into several regular time intervals over which the cost structure of an activity may vary. But the cost structure of the activities remains the same (constant) within a time interval. Key events of the project attract penalty for finishing earlier or later than the corresponding target times. The objective is to find an optimal project schedule minimizing the total project cost. We present a mathematical model for this problem, develop some heuristics and an exact branch and bound algorithm. Using simulated problems we provide an insight into the computational performances of heuristics and the branch and bound algorithm.     

Multiple schedules and measures of resource constrained float

The conventional analysis of a resource constrained network produces a single schedule. A measure of float for each activity can be defined by examining the sequences of activities, incorporating the linkages implied by the sharing of resources in this particular schedule. However, the resultant floats are specific to one schedule and the analysis ignores the flexibility inherent in many resource constrained networks. It is often possible to employ alternative resource allocations resulting in schedules with identical overall durations but different timings for individual activities; in one schedule an activity may be critical but in another it may have significant float. A systematic exploration of alternative schedules reveals the flexibility of the network and the consequent variation in activities' floats. This paper defines new parameters describing these characteristics of activities in resource constrained networks. The practical value of the parameters is demonstrated in an example in which the measures of float guide the project planner to an alternative schedule, avoiding a critical dependency on a problematic activity and reducing the risk to the project at no additional cost.     

Controlling job arrivals with processing time windows into Batch Processor Buffer

We consider a two-stage manufacturing system composed of a batch processor and its upstream processor. Jobs exit the upstream processor and join a queue in front of the batch processor, where they wait to be processed. The batch processor has a finite capacity Q, and its processing time is independent of the number of jobs loaded into the batch processor. In certain manufacturing systems (including semiconductor wafer fabrication), a processing time window exists from the time instance the job exits the upstream processor till the time instance it enters the batch processor. If a job is not processed before reaching the end of its processing time window, job rework or validation is required. We model this drawback by assigning a reward R for each successfully processed job by the upstream processor, and a penalty C for each job that reaches the end of its processing time window without being processed by the batch processor. We initially assume an infinite job source in front of the serial processor and also assume that the batch processor is operated under a threshold policy. We provide a method for controlling the production of the serial processor, considering the processing time window between the upstream processor and the downstream batch processor. We then show how the serial processor control policy can be modified when the serial processor also experiences intermittent job arrival.     

Managing uncertainty in major equipment procurement in engineering projects

A better management of time uncertainty in major equipment procurement in engineering construction projects can significantly contribute to project performance. A survey study shows that time buffer is a popularly used approach to protect project schedule from activity duration variation and uncertainty. The problem is that there are repetitive time allowances inserted in the procurement supply chain process and these time buffers are used ineffectively, thus leading to considerable time wastage. Relevant lessons from supply chain management and critical chain project management are combined and applied to create an enhanced critical supply chain management model for major equipment procurement to achieve better management of time uncertainty. This model does not perceive uncertainty purely as a threat, but also as an opportunity to reduce procurement cycle times.