基于现金流均衡目标的多模式项目调度问题研究

Multi-mode Project Scheduling Problems with Cash Flow Balanced Objectives

首先对基于现金流均衡目标的多模式项目调度问题进行界定;随后定义两组0-1决策变量并构建问题的优化模型;鉴于问题的强NP-hard属性,设计专门的模拟退火启发式算法;最后用一个实例对研究进行说明,并计算分析关键参数对目标函数的影响。结果表明:承包商最大累计资金缺口随项目截止日期的延迟、支付比例和预付款比例的提高而减小,随着质量保证金比例的提高而增大。

A contractor needs to spend capital on project-related resources before receiving payment from customers for services delivered at each milestone.However,contractors have varying capital availabilities when implementing different projects.Thus,balancing cash inflows and outflows throughout the project life cycle is critical to project success for contractors.This paper studies multi-mode project scheduling problems with the goal of balancing cash inflows and outflows.We use the event-based method to represent a contractor＇s project schedule in the activity-on-node mode,and distribute project expenses to their beginning and ending activities.The objective of this exercise is to minimize the gap of a contractor＇s cumulative capital flows given the constraint of a fixed project deadline.We define two groups of decision variables in order to determine the modes of performing activities and the actual delivery date of events.A0-1 programming model is established to address cash flow problems.A simulated annealing heuristic algorithm with two nested loops is developed to solve cash flow problems.These two nested loops include inner and outer loops.The inner loop searches for a desirable vector of an event＇s completion time under a given activity＇s performing mode.The outer loop seeks the desirable vector of an event＇s completion time established by the inner loop.The simulation results show desirable solutions for cash problems in innerand outer loops.A contracted superhighway construction project is used as a case study to illustrate the use of our proposed simulated algorithm.This project is able to develop a satisfactory schedule.We compare the developed schedule with the actual schedule regarding key cash flow parameters,including project deadline,payment proportion,advance payment proportion,deposit rate of security payment,and objective function values.A contractor can maximize its cumulative capital gap by reducing the procrastination of project deadline,increasing payment proportion,advancing payment proportion,and increasing deposit rate.The findings of this study can help contractors make better decisions on balancing their cash inflows and outflows,and managing project schedule.