Sima Ranjbarfard; Amin Ghodousian; D. Moazzami
Abstract
In this paper, we present a binary-linear optimization model to prevent the spread of an infectious disease in a community. The model is based on the remotion of some connections in a contact network in order to separate infected nodes from the others. By using this model we nd an exact optimal solution ...
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In this paper, we present a binary-linear optimization model to prevent the spread of an infectious disease in a community. The model is based on the remotion of some connections in a contact network in order to separate infected nodes from the others. By using this model we nd an exact optimal solution and determine not only the minimum number of deleted links but also their exact positions. The formulation of the model is insensitive to the number of edges in a graph and can be used (with complete or local information) to measure the resistance of a network before and after an infectious spreads. Also, we propose some related models as generalizations: quarantining problem including resource constraints (time, budget, etc.), maximum rescued nodes-minimum deleted links problem and minimum removed links problem nding a prespeci ed number of nodes with weakest connections.
Hassan Shokouhmand; Mohammad Ali Nazari; Babak Ghaem Panah; Mohammad Reza Aligoodarzi
Abstract
In this paper the effect of site conditions, which are Altitude, Temperature and Relative Humidity and also Heat Dissipation Capacity are investigated on the optimized design of natural draft dry cooling towers with specific kind of heat exchangers, known as Forgo T60 type. A genetic algorithm program ...
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In this paper the effect of site conditions, which are Altitude, Temperature and Relative Humidity and also Heat Dissipation Capacity are investigated on the optimized design of natural draft dry cooling towers with specific kind of heat exchangers, known as Forgo T60 type. A genetic algorithm program has been developed for optimized design of these cooling towers. Objective function includes both cost and performance of the tower. The optimized dimensions of the tower, the number of heat exchangers and mass flow rate of water and air are the results of this optimization program. The results show it is possible to find the variation of the optimized value of each design variable versus the variations of the site conditions and heat dissipation capacity. Also finding an optimum for all design parameters for any site condition is possible; however it is very dependent on how exact the cost analysis is.
Ali Reza Arshadi Khamseh; Seyyed Mohammad Taghi Fatemi Ghomi; Majid Aminnayyeri
Abstract
The paper presents an economical model for double variable acceptance sampling with inspection errors. Taguchi cost function is used as acceptance cost while quality specification functions are normal with known variance. An optimization model is developed for double variables acceptance sampling scheme ...
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The paper presents an economical model for double variable acceptance sampling with inspection errors. Taguchi cost function is used as acceptance cost while quality specification functions are normal with known variance. An optimization model is developed for double variables acceptance sampling scheme at the presence of inspection errors with either constant or monotone value functions. The monotone value functions could be descending or ascending exponentially. In the case that inspection errors have exponentially functions, we can find the best value for inspection errors regarding to the sample number and other economical parameters. Finally sensitivity analysis has done on model parameters and some numerical examples are given to demonstrate how the developed model is applied.
Mohammad Reza Ghasemi; Akbar Azadi
Abstract
One of the major purposes of optimization in civil engineering is to perform a suitable design for the structure. This goal has to fulfill technical criteria and contain the minimum economical costs. Building frames are of the most customary civil engineering structures. Therefore, optimization of these ...
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One of the major purposes of optimization in civil engineering is to perform a suitable design for the structure. This goal has to fulfill technical criteria and contain the minimum economical costs. Building frames are of the most customary civil engineering structures. Therefore, optimization of these types of structures could be of a great concern from the economical viewpoints. One of the current obstacles in such optimization problems is the local convergence debility. Thus, using means of tackling this problem seems necessary. Genetic Algorithm which is one of the optimization methods inspired by nature, has overcome this problem. In order to solve such problems, genetic algorithm needs a multiple analyses of structures. Therefore, in this study attempts were made to introduce and embed new formulae into a newly developed program to handle new techniques for selection and mutation as genetic operations. As for the aspects of application, the introduced techniques were inspected and investigated in the optimization of some planar and special braced steel frames. The outcome through comparisons proclaimed a considerable decrease in numbers of analyses as well as significant increases in the speed of convergence.
Ali Reza Soltankouhi; Khosro Bargi
Abstract
Breakwaters are the important and the costly ones of the marine structures. Composite breakwater is one of the common types in the world. Because of the progress in marine industry in Iran in recent years, designers have noticed this structure. Because of the sensitivity of composite breakwater to environmental ...
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Breakwaters are the important and the costly ones of the marine structures. Composite breakwater is one of the common types in the world. Because of the progress in marine industry in Iran in recent years, designers have noticed this structure. Because of the sensitivity of composite breakwater to environmental conditions, also construction costs, difficulty of repair and maintenance and importance of structures on and behind the breakwater, design of composite breakwater must be very accurate. Estimation of optimum dimensions of composite breakwater in different hydraulic and geotechnique conditions of sea is an important problem for engineers. In this research with regard to a nonlinear wave field in front of structure, its dimensions have been optimized in various hydraulic and geotechnique conditions. The results of this research have been expressed in some applied graphs for optimum design of composite breakwaters. By using of these graphs designer can estimate optimum dimensions of structure in various conditions. So, a noticeable reduction in costs will occur. Additionally, results of this research can be used for attentively design of these structures in different environmental conditions of sea.
Mohammad Sa'adat Seresht; Farhad Samadzadegan
Abstract
Nowadays, the subject of vision metrology network design is local enhancement of the existing network. In the other words, it has changed from first to third order design concept. To improve the network, locally, some new camera stations should be added to the network in drawback areas. The accuracy ...
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Nowadays, the subject of vision metrology network design is local enhancement of the existing network. In the other words, it has changed from first to third order design concept. To improve the network, locally, some new camera stations should be added to the network in drawback areas. The accuracy of weak points is enhanced by the new images, if the related vision constraints are satisfied simultaneously. Therefore, the camera placement is an optimization problem that here is solved by using NSGA-II, a multi-objective evolutionary algorithm (MOEA) based on Pareto front concept. Although we have proposed two deterministic ITO and OTI methods and a non-deterministic fuzzy camera placement method in our previous research, here we solved the problem by an MOEA method. The NSGA-II network design method is able to solve the problem in complex cases in which other aforementioned methods are failed or cannot converge to global optimum. In addition, it is a good means to analysis the capabilities of other methods especially in complex network cases. It also gives us several optimal solutions for camera placement, so that designer can select one of them based on his/her experience and environmental restrictions. In this research, we did various tests on a complex example of camera placement by using NSGA-II algorithm. The result demonstrates the high capabilities of the method in solving and analyzing the camera placement in complex close-range photogrammetric networks.
Ahmad Kahrobaian; Hamid Reza Malekmohammadi
Abstract
A new method of optimization on linear parabolic solar collectors using exergy analysis is presented. A comprehensive mathematical modeling of thermal and optical performance is simulated and geometrical and thermodynamic parameters were assumed as optimization variables. By applying a derived expression ...
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A new method of optimization on linear parabolic solar collectors using exergy analysis is presented. A comprehensive mathematical modeling of thermal and optical performance is simulated and geometrical and thermodynamic parameters were assumed as optimization variables. By applying a derived expression for exergy efficiency, exergy losses were generated and the optimum design and operating conditions, were investigated. The objective function (exergy efficiency) along with constraint equations constitutes a four-degree freedom optimization problem. Using Lagrange multipliers method, the optimization procedure was applied to a typical collector and the optimum design point was extracted. The optimum values of collector inlet temperature, oil mass flow rate, concentration ratio and glass envelope diameter are calculated simultaneously by numerical solution of a highly non-linear equations system. To study the effect of changes in optimization variables on the collected exergy, the sensitivity of optimization to changes in collector parameters and operating conditions is evaluated and variation of exergy fractions at this point are studied.
Farhad Kolahan; Mohammad Doustparast; Mojtaba Mamourian
Abstract
In this research, a model for optimal PM planning based on reliability is developed and solved for multi-component systems. In the proposed model, the type of PM actions for each inspection period is determined in such manner that the total weighted related costs are minimized while a minimum required ...
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In this research, a model for optimal PM planning based on reliability is developed and solved for multi-component systems. In the proposed model, the type of PM actions for each inspection period is determined in such manner that the total weighted related costs are minimized while a minimum required system reliability is maintained. The planning horizon is divided into some inspections intervals of equal size. In the beginning of each interval, with respect to the system constraints, one of the following PM actions is suggested for each component: 1) inspection and minimal service, 2) preventive repair and 3) preventive replacement. Each of these activities consumes different resources and has different effect on the system reliability. The PM costs include, repair cost, replacement cost, system downtime cost, and random failure cost. In the optimal PM schedule, the PM actions are determined so that a minimum required reliability is obtained with minimum total PM cost. Since the proposed model has a complex structure, Tabu Search and Simulated Annealing are employed to provide quick solutions. The efficiency of these techniques has been demonstrated by solving a PM scheduling problem for a system with 14 components.
