Sharif Digital Repository

Multi-disciplinary design optimization (MDO) of a surface to air flying vehicle has been done in this research, on the basis of flight simulation. The MDO problem have five disciplines consists of aerodynamic, propulsion, guidance, control, and fire control. Multiple campaign scenarios are defined. The MDO problem has 31 design variables and two objective functions. The objective functions are flying vehicle weight and miss distance. A new meta-heuristic algorithm has been designed to solve multi-objective optimization problems. The new algorithm has been called Multi-objective Adaptive Real-coded Memetic Algorithm (MARCOMA). The MARCOMA can solve large-scale and multi-objective problems and... 

Emergency Shut Down systems are considered as one of the prominent protection layers in industries. In the situation that the process variables exist acceptable limits, the SIS brings the process in a safe state. According to standards, separate design and operation have been defined for BPCS and SIS. In this research, safety issues related to one of the gas refinery unit has been investigated. In fact, the unit does not have shut down system and all the safety loops are defined as DCS. In the first step, the Safety Integrated Levels of the loops which must be defined in shut down system have been specified by using Modified Calibrated Risk Graf. In next step, philosophy of shut down levels... 

Supply chain as one of the most important and critical parts of the production process; could have significant effect on efficiency and productivity of the firms.Integration of supply chain (components from upstream to downstream of production system) has been recently noticed and considered remarkably since it could have a considerable impact on functional variables in supply chain systems such as: cost reduction, responsiveness, service level and decision making process. On the one hand, in the last decade, new trends in global economics and the ongoing pattern in multinationals to outsource their manufacturing process have made the integration process challenging and difficult. On the... 

The 6DOF modelling and robust attitude control of two tethered satellites using tether tension moments is studied in this thesis. In this regard, the coupled rotational and translational dynamics of two satellites connected by a tether in the presence of Earth’s gravitational perturbation, aerodynamic drag, solar radiation pressure and third body effects (Sun and Moon) and also uncertainties in some of physical parameters of system and sensor’s outputs is modelled. Moreover, the tether attachment point to the satellites is different from their center of mass and its effect on dynamics of the system is taken into consideration. Then, the attitude of both satellites are controlled using robust... 

Gas turbines and centrifugal compressors are the preferred means of compressing the gas in pipeline systems. Both gas turbines and centrifugal compressors exhibit performance characteristics that depend on the operating point imposed on them by the pipeline operation. Simulation of gas turbine-driven centrifugal compressors is necessary for a variety of applications in the general area of pipeline simulation. This research focuses on modeling of twin shaft gas turbine dynamic and steady state performance. For this purpose, it was necessary to evaluate the thermodynamic working process of the gas turbine by using an in-house computer code. At design point, the calculations are solely based on... 

Economics is the science of using scarce resources, which helps to identify the optimal use of economic resources. Enhancement of productivity leads more efficient use of resources in economics sectors. Identification of ways and means of improving productivity is an important policy issue which requires an analysis of the effects of determinants of productivity. In the present research work, Total Factor Productivity (TFP) has been econometrically estimated; based on production function theory. Application of this concept indicates that the elasticities of total value-added (i.e. GDP minus oil rents) with respect to physical capital and labor are 0.8 and 0.2 respectively. It is further... 

In recent years, GPUs have become a popular choice for high-performance general-purpose systems. However, since general-purpose applications do not always utilize processing and memory resources efficiently, energy consumption in these systems has not been managed effectively. As the variety of resources within GPUs continues to increase, the problem of low utilization has become more critical. Past solutions have focused on integrating resources and using multi-tasking, but these methods have limitations in terms of performance and security. Therefore, this research proposes new methods for improving the resource utilization and energy efficiency of GPUs. This dissertation first examines... 

Determining the best location for new wells is a complex problem that depends on reservoir and fluid properties, well and surface equipment specifications, and economic criteria. Various approaches have been proposed for this problem. Among those, direct optimization using the simulator as the evaluation function, although accurate, is in most cases infeasible due to the number of simulations required. This study proposes a hybrid optimization technique (HGA) based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. Hybridization of the GA with these helper methods introduces hill-climbing into the stochastic search and also makes use...