درخت حوزه‌های تخصصی

We have a huge civic project, includes several sub-projects, which are divided into activities. This project is a project to rehabilitate 550,000 hectares of agricultural land in the provinces of Khuzestan and Ilam. The project has been divided according to the plots of land. The Jehad in Tehran is managing the projects. They need project scheduling as well as resource levelling and "lot-sizing". Levelling and lot sizing are the most important issues in utilizing the limited resources. For determining the scope and the size of those sub-projects as well as their parallel activities, so far, many models have been proposed. However, the models are weak either in higher resource utilization or in solving numerically the problems. In this paper, our effort has been concentrated on developing scheduling, resource levelling, and lot sizing model, based on balancing utilization of resources, so that the real size civil project could be solved within an acceptable duration time. This paper proposes a goal programming linear model for simultaneous project scheduling and resource levelling. This model determines the best schedule of sub-activities (optimal "lot size" of each sub-activity) to reach the minimum amount of diversion of resources consumed from the number of resources available for the entire periods of the planning horizon. In fact, if the best "lot sizes" have been taken, then minimum fluctuation of the active resources is reached. The proposed model has been used to schedule a project with 87 activities. This project has been scheduled and, accordingly, the optimal volume (the "lot size") of sub-activities have been determined for each activity at any period of time. In this way, only 4 resources out of a total of 32 resources are in shortage. In contrast, the scheduling of this project, using the CPM, results in a shortage of 13 resources.

According to published reports on the level of internalization of commercial vehicles, it shows that most carmakers pursue a minimal domestic manufacturing policy and less have a policy of increasing domestic manufacturing on their agenda. The most important research gaps are need to study R&D activities in the form of a dynamic system in the automotive industry based on the three variables of supply network capabilities, product innovation and process. The purpose of this study is to provide a dynamic model to investigate the behavior of a commercial vehicle R&D system. The present study is applied in terms of purpose. The basis of the system analysis is previous research as well as information obtained from interviews with automotive industry experts. For this purpose, first the variables affecting the cycle of R&D activities are studied and modeling is presented using the dynamics approach. Also, various policies on the performance of the development research cycle based on the time of knowledge acquisition and product introduction have been simulated and analyzed. The results of system performance simulation show that the weak share of research and development budget along with low and limited market share and lack of proper investment makes the research and development capability at an unfavorable level during the next 10 years. Therefore, it is suggested that the necessary measures in this regard be taken in the fields of product sales marketing along with appropriate investment in research and development.