The progress and industrialization of human societies in the past century have intensified the concentration of greenhouse gases and led to climatic change of the different parts of the world. The sign of this climatic change is the long-lasting change in the meteorological parameters. Drought is a serious hydrological phenomenon that may happen due to not receiving rainfall in a vast region and in any climatic conditions. This phenomenon has considerable effects on the economy of environment and water sources. Thus, the study of the climatic impacts of drought can play an important role in the planning and management of water source systems, especially during a period of climatic drought. Paying attention to the climatic change and its effects on water sources is of great importance. Unfortunately, it is not studied sufficiently in our country. In this research, we aim to identify the effects of climatic changes on the time and place distribution pattern of drought using system Dynamic approach. This approach is used to study several factors and dual relation of the climatic changes with the time and place trends of drought simultaneously.

This paper deals with the Modeling and control of a continuous-How fermentation process for the production of alcohol The Dynamic behavior of fermentors has been developed from mass balance and leads to nonlinear differential equations. Based on the proposed model, two computer algorithms are provided to control output alcohol concentration at the desired value by input flow rate manipulation. The first algorithm is based on a conventional PID (Proportional-Integral-Derivative), in which its parameters are determined in a trial and error procedure. The second algorithm is based on optimal controllers. In this way, the difference between output alcohol concentration and desired value is minimized by flow rate manipulation. Minimization (optimization) is done based on the MARQUARDT procedure. The advantages of this method over the conventional PID controller are its higher speed and lack of overshoot.

This paper presents the different systems that used in suspension and generaly study the benefits and harmful effects of this systems. The first step in analysis of a system is presentation of a sutable physical model. The main aim of model is not necessary a complex model, but is a model that explain the relationsheeps between variabilities of system conditions really, and provide the aims of disigner. From these physical models can be used in analysis of stability, ride quality and stiffness coefficient of sprins, and damping coefficient, influency of road unevenness.

The purpose of this study is to Modeling the factors affecting supply chain optimality based on the system Dynamics technique in the power industry. The present study uses a hybrid approach to develop a qualitative-quantitative approach to formulate and validate the factors influencing the supply chain optimality. To elaborate and identify the optimal factors, from content analysis and thematic analysis using Novio software to construct themes, a qualitative model of factors influencing supply chain optimality was designed. On the optimality of the supply chain, 23 experts and experts in the electricity industry with purposive sampling method were selected. In the quantitative part, the system Dynamics method was used for Modeling, and then the data collected was analyzed by Venice software. This simulation was carried out over a one year period and represents a long-term horizon. Then the results of this simulation were presented and interpreted on the variables studied. Determining the relationships between variables and the types of variables can lead to a better understanding of the issue and to making appropriate decisions on the supply chain optimality problem.

This paper deals with the problem of optimizing two-stage structure decision making units (DMUs) where the activity and the performance of two-stage DMU in one period e ect on its efficiency in the next period. To evaluate such systems the e ect of activities in one period on ones in the next term must be considered. To do so, here a Dynamic DEA approach presented to measure the performance of such network units. According to the results of proposed Dynamic model the inefficiencies of DMUs improve considerably. Additionally, in models which measure efficiency score, undesirable outputs are mostly treated as inputs, which do not reect the true production process. This paper proposes an alternative method in dealing with bad outputs. Statistical analysis of sub-efficiencies, i.e. efficiency score of each stage, during all periods represents useful information about the total performance of the stage over all periods.

Human resource management is regarded as a fundamental process for effective labor application to ensure desired performance in the project. The project goals are met only through human resource management, and the project success relies on it. Construction is a labor-intensive industry that heavily depends on human resources. Moreover, construction projects are naturally complex and Dynamics. One of the effective human resource management practices that greatly affects the project workflow and progress is to obtain required labor. System Dynamics is applied to model the labor requirements of the construction projects', considering project Dynamics. System Dynamics is used as a research tool to provide useful insights for human resource planners to ensure that the project will be delivered on time and within the budget. The labor need of the construction projects is investigated based on project progress. A causal loop diagram is obtained, and the Stock-Flow model is developed for estimating the labor need of the construction projects. The proposed model consists of subsystems including the human resources, project workflow, project performance indexes, and policies. The required data are collected for a housing project executed in Iran. Finally, the Dynamic model of the labor need of construction projects is built. The model has been validated using standard testing methods of system Dynamics models. Simulation results show that the required labor in construction projects has fluctuations over time. These fluctuations affect the labor supplying process. Two policies have been proposed to reduce the fluctuations of the labor need of construction projects including hiring policy at different times and employment of different groups of the labor in terms of experience and skills. Although both policies improve the system, each one of them has different effects on project performance. By using the model, the required labor based on project progress can be determined. The opportunity can be given to decision-makers to plan for timely supply of project labor.

Maintaining and promoting unity plays a crucial role in the direction and operation of the full capacity of social system during a process of development. However, most of the communities undergoing development process face a lot of challenges, each one posing a serious threat to integration and community cohesion. The critical question is that what causes challenge social cohesion in the development process and how to maintain cohesion in the development process. Using thematic analysis, national development plans, reports compiled by international organizations in different periods as well as theoretical discussions on development were analyzed, and by identifying the main themes and the relationships between them, a Dynamic model of maintaining cohesion during a process of development was drawn. The main themes of promoting Dynamic cohesion in the society during development process were identified and formulated through the paradigmatic model of Strauss under four main categories of revising strategy of development planning, controlling consequences in development process, and redefining elements related to agents of development and ultimately contextual items.

Management can achieve the long term goals in a system by means of a Dynamic framework. This article considers the problem of social development in macro level. Since social development has a Dynamic and multidimensional nature, the system Dynamics method has been used in this article. In system Dynamics approach, sustainability of social system is not increasing or decreasing in a system, moreover, it is not a static goal, making it impossible to achieve it. In this regard, four indicators of social development that is, population means, employment, water, and food are utilized for Dynamic evaluation Modeling. This model evaluates social development in Iran over the period 1989-2009 and predicts it until 2019. The results indicate there is a relationship between social development components.