Sharif Digital Repository

Nowadays evolutionary algorithms help developers to solve many problems in applied science and engineering aspects. So the main goal of this thesis is to apply and verify the ability of evolutionary algorithms and artificial neural networks in optimization of Ethane recovery unit. Algorithms applied in this study are Ant Colony Algorithm, Artificial Immune Systems Algorithm, Incremental Evolutionary Algorithm, Chaotic Based Algorithm, Variable Population Size Genetic Algorithm, Frog Leaping Algorithm, Frog Leaping with Bacterial Optimization Approach and Different types of Particle Swarm Optimization Algorithm. Optimization methods based on local search are also applied in order to compare... 

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... 

Pooling Lead-time risk by splitting replenishment orders simultaneously among multiple suppliers is a sourcing policy that has attracted the attention of academic researchers for some years. While they consider many different assumptions in their models, they don’t pay attention to deterioration items in order splitting models. In this thesis, we have considered order splitting policy about products with constant deteriorating rate and developed two inventory models. In the first model, it is assumed that the whole requirement supply from only one source, whereas in the second two suppliers are accessible. Then after determining the optimal policy, by numerical search and use of MAPLE... 

In this thesis a 2-3PRS hybrid mechanism is presented. This manipulator is consisted of two serially connected parallel 3PRS mechanisms, each mechanism has three degrees of freedom, so that the overall degrees of freedom of the manipulator are six. The relations for position, velocity and acceleration of the mechanism in both forward and inverese kinematics are derived and then singular points are determined. After that, the inverse dynamic equations for one of the 3PRS mechanisms are derived through the Newton-Euler and aslo Lagrange approach and the results are verified. Then the derived Newton-Euler equations are implemented for inverse and forward dynamics of the hybrid manipulator. The... 

Long-term coordinated operation of hydro-thermal power systems has important rule in energy generation planning and management. Therefore a new approach for optimization and long-term planning of hydro-thermal power system is developed. In this research main parameters of the system like inflows and energy are considered as uncertain and so scenario optimization technique is applied. The advantage of this research compare to similar approaches is about applying two objective functions which minimize cost of energy generation and flood control.The Noisy GA and NSGA-II algorithms are used to run the model solving the khouzistan hydro-thermal power system in Iran.The results of this model is... 

Facility location decisions play a prominent role in strategic planning of many firms, companies and governmental organizations. Since in many real-world facility location problems, the data are subject to uncertainty, in this thesis, we consider the P-center problem under uncertainty of demand nodes. Using Bertsimas and Sim approach, we modeled the problem as a linear optimization model. Furthermore, we develop a tabu search algorithm to solve the problem. Finally we designed some experiments to adjust the parameters of tabu search algorithm. We presented the numerical result accordingly  

In this thesis, the classical methods of structural optimization were studied and compared. After a comprehensive study on different methods of structural optimization, a reduced number of methods were selected in order to be used in this research. Exterior penalty function method, linear and quadratic extended penalty function methods were the selected constrained optimization methods. For unconstrained optimization, univariate method, Powell method, steepest descent method, Fletcher-Reeves method, and quasi-Newton methods of DFP and BFGS were used. And from different one-dimensional search methods studied, we used the golden section method. The structures which were optimally designed by... 

Commercial banks have got an important role in our lives and every one can mention veriety functions for them. The more benefits can bring the more risks can couse as the old tradeoff between risk and return. One of the important risks that can bring about lots of problem for banking system is liquidity risk. Being not able to respond customers’ liquidity demand is named the liquidity risk. Banks keep some reserve in cental bank to respond other banks’ liquidity demands in payment system. Shortage of this reserve will cause customer and central bank punishments and penalties. Excess reserve on the other hand has opportunity cost. Hence an optimum amount of liquidity resrve must be held in... 

One of the best methods of gait analysis is to use analytical models. In this project, first, the normal human gait was simulated using a two-dimensional biped model with 7 segments, i.e., a HAT segment representing head, arms and trunk, and 6 segments representing thighs, shanks and feet of the two legs. The foot-ground contact was simulated using a five-point penetration contact model. The elastic impact and friction effects are considered in the ground reaction force modeling. Optimization of the normal human walking model provided constant coefficients for simple PD controllers’ (driving torque) equations that could reasonably reproduce the normal kinematical pattern. Then, in the second... 

In software testing, it is often desirable to find test inputs that exercise specific program features. Good testing means uncovering as many faults as possible with a potent set of tests. Thus, a test series that has the potential to uncover many faults is better than one that can only uncover a few. To find these inputs by hand is extremely time-consuming, especially when the software is complex. Therefore, many attempts have been made to automate the process. There are three major methods to generate software test data: Random test data generation, Symbolic test data generation and Dynamic test data generation. Dynamic test data generation, such as those using genetic algorithms, is... 

n the present study, the optimal design of feeding system in steel sand-mold castings is considered. The first part of this research includes fundamental studies on the physics of shrinkage defect formation during the casting process. The results of these studies lead to new findings on the mechanism of shrinkage defect formation, effect of melt quality on the distribution of defects within the castings and the connection between shrinkage and gases defects. The theoretical analysis of thermal criterion functions for the prediction of shrinkage defects in castings and introducing new criterion function with fewer shortcomings can be accounted as the other finding of this part. A new model... 

Multilateral wells are relatively new alternatives in field development and because they can increase the productivity per well and reduce the cost of field development, they are rapidly replacing old methods. In order to predict the performance of well, three methods are usually used: Analytical methods which use closed-forms models, semi-analytical methods which entails line-source model and numerical methods which is based on techniques such as finite volume or finite difference. In this thesis, line-source model is extended from two dimensional forms to three dimensional forms in order to be used to optimize the path of multilateral wells. Optimization entails direct optimization... 

During the last few years, utilization of distributed generation (DG) in power systems has been widely increased. This trend has magnified studying the effects and impacts of DG on such systems. One of the benefits of DGs in a power system is loss reduction. If determining DG size and place is done properly, the loss of the network can be minimized. Another way of reducing loss in distribution network is by reconfiguring the network. During the reconfiguration, constraints like being radial, avoiding load isolation as well as voltage/current limitations must be taken into consideration. Taking these constraints into account makes reconfiguration an optimization problem. In this project, the... 

In this thesis, our aim was to assess the resource allocation problem in wireless sensor netowroks and to optimize network utility and lifetime. To achieve these aims, it is nesseccary to solve resource allocation problem through optimization methods. Since the central methods need a central node to manage resource allocation, they can not be implemented in sensor networks because the nodes neighbors to this central node drain energy very quickly. Also, since central methods require transmission of all information about network topology to this central node, every change in network topology result in transmission of new network topology informations and therefore, overload for frequent... 

Management decisions, Enhanced Oil Recovery, and reservoir development plans in petroleum industries are based on predictions by reservoir simulation. Due to uncertainties in model parameters or engineering assumptions, the simulation results are not accurate, while they are correct. One remedy is to match simulation results with engineering measurements, typically pressure and flow rate, by adjusting model parameters. In Reservoir Engineering literature, this is called History Matching and is an optimization problem. Common methods of history matching are based on finite difference simulation, and therefore have a very low speed. In addition, these methods usually ignore Geostatistical... 

Conjugate gradient methods are appealing for large scale nonlinear optimization problems, because they avoid the storage of matrices. Recently, a new conjugacy condition proposed by Dai and Liao, considers an inexact line search scheme that reduces to the old one if the line search is exact. Based on this condition, a new conjugate gradient method was proposed that has fast convergence. Later, Yabe and Takano, based on new conjugacy condition and modified secant condition, proposed another conjugate gradient method. This method takes both the available gradient and function value information and achieves a high-order accuracy in approximating the second-order curvature of the objective... 

Optimization always has been a major industrial field of study. Optimization is the process of finding the best result based on some events. In design, construction and maintenance of any kind of engineering system ,engineers must take a lot of decisions in the case of management or engineering at different levels in order to minimize the attempts to reach the optimum conditions and obtain the maximum profit on the other side. high speed of processing and litle time for calculations by using computers is very common nowadays which is caused in many improvements in optimization approaches. In this thesis some different classical optimization methods have been applied on Williams-Otto reactor... 

Purpose of ongoing thesis is providing a tool for suitable modeling, increase efficiency and decrease construction cost of solar absorption heat pump. At first, the solar absorption heat pump is modeled by the thermodynamic laws. Then, this model is converted to the new standard mathematical programming model using exergy and thermodynamic Analysis with considering all technical and economic constrains. This mathematical model is optimized by Genetic algorithm (GA). Because of the nonlinear objective function and the constraint, GA is used as optimization algorithm. After applying GA, optimized parameters of cycle heat exchanger designing and its electricity consumption are calculated.... 

A new method, recently introduced in the literature, is discussed for solving equality constrained nonlinear optimization problems. This method does not use a penalty or a barrier function, or a filter, and yet its global convergence to first-order stationary points can be proved. The method uses different trust regions to cope with the nonlinearities of the objective function and the constraints, and admits inexact SQP steps not lying exactly in the nullspace of the local Jacobian. We implement the method in MATLAb 7.7 software environment and test the resulting program on a collection of CUTEr problems. The numerical results are promising and confirm the global convergence of the method  

Xylitol is a sugar alcohol or polyol that has been used as a food additive and sweetening agent due to Its high sweetening power, anti-cariogenic properties and possibilities for use in diabetic food products, makes xylitol an attractive sucrose substitute in a wide variety of foods and beverages. Xylitol is a five carbon polyol or pentitol obtained by the hydrogenation of xylose. xylitol could be produced from xylose in rice seed coats medium by Saccharomyces cerevisiae. For xylitol production, S.cerevisiae was grown in preculture medium at 30°C and agitated at 120 rpm on a rotary platform shaker. The cells were harvested after 20hr, were centrifuged and transferred to the production...