基于学习效应及时间转换约束双重作用下项目网络模型研究

The Project Network with Learning Effect and Time-Switch Constraints

具有时间转化约束项目网络是对传统网络的创新,其考虑了时间转换约束对项目网络的影响。但是,在已有时间转换约束项目网络的研究过程中都是假设在整个工期内工作效率是固定不变的,忽略了人为因素。而人在工作过程中具有学习效应,即随着时间的推移人由对活动的生疏逐渐到能够熟练完成活动,在这个过程中工作效率也有了很大的提高。本文在前人研究的基础上,考虑了人的行为因素对具有时间转换约束网络的影响,给出了在人的学习效应和时间转换约束双重作用下的机动时间的计算公式,进而给出工序持续时间的计算公式,并在此基础上建立了网络关键线路的变化模型。最后,通过实例验证了该模型的有效性和合理性。

Network planning technique is an important method in the field of project management. The technique is critical for actual projects. The existing researches mostly focus on the research of float activities with the assumption that current activities can start alter precedence activities come to an end. However, in the actual project a large quantity of activities are restricted by the start time, which leads to the impossibility of an activity starting at any time satisfying the constraints of precedence relations. The project network with the time-switch constraints can solve this problem in the traditional network. The project network with time-switch constraints takes into account of the influence of the time-switch constraints. However, in existing researches this method assumes that the work efficiency of the activity is fixed in the whole duration which ignores the fluctuation of human factors. The learning effect is that as time goes on people are able to gradually complete activities from the unfamiliar state to the familiar one. Work efficiency has been greatly improved in this process over time. We arc especially interested in the learning effect which mainly refers to the change of work efficiency caused by repetitive activities. No researches consider applying the learning effect to the projects with time-switch constraints at present. In this paper, we use learning efficiency to represent the impact of work efficiency on the project with time-switch constraints. As a result, the theory related to the project network with time-switch constraints is enhanced. Based on the research for project network with time-switch constraints, we analyzed the impact of time-switch constraints and learning effect on project network. The formula for network float influenced by these two factors is presented. The duration formula for each activity is proposed in this context. At last, we build a model to calculate the critical path of the network. We begin the first part by introducing the existing research of the learning effect and project network with time-switch constraints. In this section, we propose that the learning effect mainly focuses on the improvement of learning rate and lowering production cost. No research considers applying the learning effect to the project with time-switch constraints. In Section 2, we build the model of project network with time-switch constraints and propose the formula of the above network. According the formula, we quantify network with time-switch constraints with the change of duration and effect on each activity float. In the third part, we analyzes the project network with time-switch constraints and learning effect, and build the model of project network with time-switch constraints and learning effect based on the existing model. In the end of this section, we modify activity duration in the new model. In the last part, a project from the pertinent literature is used as an example. Because of the learning effect, both the duration and the critical path are changed in project network with time-switch constraints model.