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... 

Groundwater beneath the cities is becoming an important and valuable resource. Conjunctive use of surface and groundwater is likely to become increasingly more common as urban population grows by time. Therefore, one important requirement for urban water management planning is forecasting the groundwater level fluctuations. Unfortunately less experience and information is available to evaluate the fluctuations of groundwater level in urban environment compare to the natural systems, also different processes (sources) are involved in an urban water cycle, which all together make it more complicated to study. Similar to many other megacities, there is a serious lack of hydrogeological and... 

One of the most important problems in using wind energy is the estimation of wind energy potential of a region with acceptable accuracy. To use wind energy and convert it to electrical energy it is necessary to study the economical aspects of wind farm installation, and to choose an appropriate wind turbine to be installed in a region. To do such a study and to choose approperiate wind turbine, annual energy output of different wind turbines should be estimated in that region. The porpuse of this thesis is to develop new methods to estimate annual energy production of a wind turbine by using some of the parameters of wind speed pattern of a region such as wind speed average, wind speed... 

The quality characteristics of both manufacturing and service industries include not only the variables but the attributes as well. While a substantial research have been performed on auto-correlated variables, no attempt has been fulfilled for auto-correlated attributes. Ignoring the imbedded autocorrelation structure in constructing control charts cause not only the in-control run length to decrease, but also the false alarms to increase. To overcome these shortcomings, in this research, an auto-regressive (AR) vector first models the autocorrelation structure of the process data. Then, a modified Elman neural network is developed to generate simulated data using the ARTA algorithm. Next,... 

In this era, competition in economic fields is undeniable. According to huge amount of foreign trades between countries, economic prosperity of each country causes persuasion of foreign investors to come into that country for investment. Stock Exchanges is one sign of economic prosperity in each country, So prediction of the stock exchanges situation is very important. It is noteworthy that according to the importance of prediction in partial level, the necessity of predicting companies stock price is realized. According to the complicated term in this field, linear methods do not have appropriate efficiency for predicting, so nonlinear methods and especially Artificial Neural Networks are... 

Breast Cancer is considered one of the most common cancers among Iranian women. Every year, seven thousands women start suffering from this disease. Since 70 percent of this patients live over 5 years, after this disease starts, there are 70 thousands women who are suffering from the cancer. The average age of getting the disease in Iran is 5 years lower than that of the global level. Studies show that compound containing Chromene and Carboxamides are appropriate candidates for preventing breast cancer. One of the most important fields of researches in Chemistry and Bio-Chemistry is QSAR which is used to relate the structure of molecules to their activities. In this study, molecular... 

Taking into consideration of optimization methods has been increased recently. Optimization methods in engineering that consumes a lot of time and cost have been developed. Optimal design of structures is a matter that grabbed the attention of civil engineers and due to the deficiency of classical methods the modern approaches are being developed. One of the most important structures that are constructed for industrial and transportation purposes are truss structures.Structural control under support excitation is constraining the structure to some structural limitations. The final target in this paper is to apply the modern methods to get the optimal weight of structure under seismic loads.... 

Following the recent developments in the field of decision making, a considerable number of problems involved with stochastic systems can be thought of whose analysis depends on a set of intricate mathematical relations. In such cases, simulation is one of the most popular tools that can be applied toward analysis of behavior of such stochastic systems. Not only does not the simulation model rely on such intricate mathematical relations, it also enjoys the added advantage of being free of any restricting assumptions which may normally be considered in a stochastic system.To analyze such problem, one may aim at determining the best combination of input variables to optimize the system... 

Over time, human needs more groundwater to meet agricultural, industrial, and urban uses; so the study on factor affecting groundwater and groundwater level changes are important for water resource management. However, often forgotten is the fact that accurate and reliable predictions are based on a correct diagnose of the past. One of the questions here is how the climate has changed since the last. Such a question is largely related to detection. Purpose of detecting climate variability and climate change, identifying climate variability and trends in system and describe the factors causing these changes are. Without knowing and understanding these changes and fluctuations, we are not able... 

Three different feedback linearization control methods are applied to nonlinear control of type I diabetes mellitus model. One is exact FBL and the two others are approximate manners based on approximations of the nonlinear system and its duality one-form, utilizing uniform approximation and a homotopy operator, respectively. An extended luenberger observer is also employed to observe the required states of designed compensators. The nonlinear compensators are designed based on a minimal model and applied to the minimal model, as well as Sorensen’s physiological model. In addition to the mentioned close-loop control strategies, a discrete control strategy based on an optimization problem is... 

By far, the most expensive part of the production optimization process is the evaluation of the objective function because this requires computationally expensive reservoir simulations to be performed.One way to reduce this high computational cost isby using surrogates or proxies for the reservoir simulator. There are different methods for constructing a surrogate that their aims are mimicking the reservoir behavior with high accuracy and low computational cost. In reservoir engineering surrogate modeling has been used for the problem of well placement optimization,while in the context of production optimization it has not yet been investigated in the literature. Moreover, most of surrogate... 

Value at risk of an asset, is the asset’s expected maximum loss for a certain period of time and at a specified confidence level. Value-at-Risk can be calculated in the bank with its inter-nal method or standardized method. when a method have more violation number then bank need to keep more daily capital requirements. under the Basel 2 agreement if the violation of method more than 10 times in year, the Bank uses the standardized method.
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate... 

This effort attempts to study the change point problem in the area of non-linear profiles. Two methods for estimating the time of a single step change is proposed. In the first method a model consisting of two networks which is based on artificial neural networks is proposed. These networks are different only in their training data. One network is trained for ascending segments of the profile and the other is trained for descending segments of the profile. In the second method the maximum likelihood estimator (MLE) of the single step change is analyzed. Due to the complexity of estimating the parameters of the non-linear model by MLE, this estimator is based on the difference between the... 

Generally, predicting the adsorption and Catalytic characteristics of the solids base on the primary principles is impossible; this is only possible for small molecules and single crystal surfaces. On the other hand, phenomenological approaches, which are based on experimental data, are efficient approaches in many cases. The best predictions and designs are done by those who have an extensive information “resources” about the “Reactive Substances- Catalytic-conditions” and are able to “analyze” the data based on the “chemical physical Models”. A Neural network is an extremely simplified model of the human brain that predicts a complex characteristic(s) from a series of primary... 

In gas-condensate reservoirs, when pressure reduces to less than dew point pressure, condensate will form out of the gas phase. Gas recycling is one of the most common methods to enhance the production of gas-condensate reservoirs.The purpose of this thesis is to optimize gas recycling process in a gas condensate reservoir in order to produce the accumulated condesate in the reservoir and maximize reservoir economic efficiency.The parameters that need optimization are:
• Injection gas ratio
• Injection gas allocation amongst injection wells
• Bottomhole pressure of production wells
Genetic algorithm was considered as optimization method and Proxy model is used in order to... 

Due to the significance of exchange rates in economic policy making, different patterns have been proposed so as to explain the behavior, provide ways to model and deliver tools to forecast different exchange rates. Using a novel approach, this thesis tries to investigate the behavior of exchange rates by identifying time series nature of exchange rates, and performing nonlinear test for daily data between years 2003 to2006. In this study, we try to model and forecast the daily exchange rates by the use of Artificial Neural Networks (ANN). We also compare the results with ARIMA model outputs based on measures for forecasting accuracy. 80 percent of the daily data, that is, 1160 days from... 

Optimization methodologies with an emphasis on turbomachinery applications are of great interest. In the present study, a framework is proposed for the multi-objective optimization of a compressor blade using a coupled approximator and optimizer modules, as a mean for lowering the vast computational costs. The proposed framework consists of three main units: a CFD solver, an approximator unit, and an optimizer module. In this regard, a multi-layer perceptron artificial neural network is used as the approximator module while a multi-objective genetic algorithm, the non-dominated sorting genetic algorithm-NSGA II, is employed as the optimizer unit of the framework. In addition, a commercial... 

Nowadays, climate change is one of most important environmental challenges in all over the world. In addition to climate change, population growth, increase in water demand, which surpasses available resources so that the water system cannot meet the demands, and the subsequent growth in the development of water resources plans make watershed management become a challenging issue . In the last decade, due to significant reduction of precipitation, continuous increase in water development plans and utilization of too much water for agricultural and other uses, water inflow to the lake Urmia has reduced. Furthermore, Urmia lake have a strategic location which flows in three provinces of East... 

Measurement is the start point of identification and analysis of a physical quantity. By recording body movements, one obtains an efficient insight of musculoskeletal performance. Furthermore it leads to quantification of physic-structural health of human. In addition this information can be applied to many human related applications such as: balance survey, sport analysis, muscular pathology, physiology method performance evaluation, etc.With reference to statistics of the elderly fall, the large number of medications with bilateral effects such as instability and drowsiness, arthritis resulted from daily movement misconduct, there is a need for a preemptive system to overcome these...