Search for: multi-objective-optimizations
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    Thermoeconomic analysis and multi-objective optimization of an integrated solar system for hydrogen production using particle swarm optimization algorithm

    , Article Journal of Thermal Engineering ; Volume 7, Issue 4 , 2021 , Pages 746-760 ; 21487847 (ISSN) Keykhah, S ; Assareh, E ; Moltames, R ; Taghipour, A ; Barati, H ; Sharif University of Technology
    Yildiz Technical University  2021
    This study aims to investigate the hydrogen production process using an integrated system based on solar energy. This system includes an evacuated tube collector to absorb solar energy as input energy of the system. A parametric analysis was conducted to determine the most important design parameters and evaluate these parameters' impact on the system's objective functions. For identifying the optimum system conditions, multi-objective optimization was performed using particle swarm optimization (PSO) algorithm. The results obtained from the parametric analysis show that an increment in the collector mass flow rate and the turbine inlet temperature, as well as a decrement in the collector... 

    Multi-objective optimization approach for green design of methanol plant based on CO2-efficeincy indicator

    , Article Journal of Cleaner Production ; 2014 ; ISSN: 09596526 Taghdisian, H ; Pishvaie, M. R ; Farhadi, F ; Sharif University of Technology
    The aim of the present work is to propose an eco-design method for sustainable development of methanol production by implementing a multi-objective optimization model based on CO2-efficiency. Two different approaches for the methanol production, i.e. a conventional reference methanol case (RMC) and proposed green integrated methanol case (GIMC) were compared from the view point of eco-design. Using life cycle assessment and process simulation, the environmental features as well as operational decision variables of the RMC and GIMC were assessed. Based on the inventory analysis of LCA, it was found that carbon dioxide is the major emitted pollutant from methanol production. Thus the... 

    A goal programming approach for optimal PMU placement

    , Article International Review on Modelling and Simulations ; Volume 6, Issue 2 , April , 2013 , Pages 490-497 ; 19749821 (ISSN) Khiabani, V ; Hamidi, M ; Farahmand, K ; Aghatehrani, R ; Sharif University of Technology
    This article proposes a multi-objective goal programming based approach with two objectives of maximizing the reliability and minimizing the placement cost of Phasor Measurement Units (PMUs) for full observability in power systems. The weighted sum goal programming formulation incorporates the reliability of individual PMUs and finds a placement to resolve the conflicting objectives of minimum number of PMUs cost-wise and maximum level of system-wide reliability. This multi-objective problem is formulated as a nonlinear goal programming model in which weights are associated with the objectives. The model is solved for several weight scenarios for the IEEE 14, 30, 57 and 118 bus test systems.... 

    Application of a Modified NSGA Method for Multi-Objective Static Distributed Generation Planning

    , Article Arabian Journal for Science and Engineering ; Volume 36, Issue 5 , 2011 , Pages 809-825 ; 13198025 (ISSN) Soroudi, A ; Ehsan, M ; Sharif University of Technology
    The characteristics of integrating distributed generation (DG) in a distribution network have changed. These electrical resources are used as an alternative energy source to the main grid. The technical and economical benefits of such units are achieved only when they are optimally sized and placed in the network. In this paper, a static mixed integer non-linear model for distributed generation planning is defined and solved using a modified NSGA method (Non-dominated Sorting Genetic Algorithm). Different DG technologies are considered and the objective functions for minimization are defined as the total active loss, investment and operational costs, and environmental pollution. The method... 

    Bi-objective reliability optimization of owitch-oode k-out-of-n series–parallel systems with active and cold standby components having failure rates dependent on the number of components

    , Article Arabian Journal for Science and Engineering ; Volume 42, Issue 12 , 2017 , Pages 5305-5320 ; 13198025 (ISSN) Miriha, M ; Akhavan Niaki, S. T ; Karimi, B ; Zaretalab, A ; Sharif University of Technology
    This paper discusses a bi-objective reliability optimization of a switch-mode active and cold standby k-out-of-n series–parallel system in which a switch is installed to add a redundant component when one of the components fails. The system failure rate is not only dependent on the number of its working components, but reduces when more monitory resources are allocated. As the bi-objective optimization problem is shown to belong to the class of NP-hard problems, a multi-objective meta-heuristic algorithm, namely multi-objective evolutionary algorithm based on decomposition (MOEA/D) with a novel solution structure is developed to solve large-scale problems. Since there is no benchmark... 

    Prediction of pore facies using GMDH-type neural networks: a case study from the South Pars gas field, Persian Gulf basin

    , Article Geopersia ; Volume 8, Issue 1 , March , 2018 , Pages 43-60 ; 22287817 (ISSN) Sfidari, E ; Kadkhodaie, A ; Ahmadi, B ; Ahmadi, B ; Faraji, M. A ; Sharif University of Technology
    University of Tehran  2018
    Pore facies analysis plays an important role in the classification of reservoir rocks and reservoir simulation studies. The current study proposes a two-step approach for pore facies characterization in the carbonate reservoirs with an example from the Kangan and Dalan formations in the South Pars gas field. In the first step, pore facieswere determined based on Mercury Injection Capillary Pressure (MICP) data in corporation with the Hierarchical Clustering Analysis (HCA) method. Each pore facies represents a specific type of pore geometry indicating the interaction between the primary rock fabric and its diagenetic overprints. In the next step, polynomial meta-models were established based... 

    Reliability optimization of tools with increasing failure rates in a flexible manufacturing system

    , Article Arabian Journal for Science and Engineering ; Volume 44, Issue 3 , 2019 , Pages 2579-2596 ; 2193567X (ISSN) Karimi, B ; Akhavan Niaki, S. T ; Haleh, H ; Naderi, B ; Sharif University of Technology
    Springer Verlag  2019
    Tool reliability is one of the most important issues in a flexible manufacturing system. If a tool fails to operate correctly, the performance of the manufacturing system is reduced, the due date may be violated, or the product quality falls behind the standards. This paper develops a bi-objective mathematical model for tool selection in a flexible manufacturing system in order to optimize both reliability and cost. The tools in these environments are considered to have increasing failure rates as they are used over time; a case closer to reality. This paper aims to evaluate the availability of different tools used in a production system, in which the reliability of a tool is dependent on... 

    Multi-objective optimization of a projectile tip for normal penetration

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 26, Issue 10 , 2013 , Pages 1225-1234 ; 10252495 (ISSN) Khalkhali, A ; Roshanfekr, S ; Toraabi, M ; Sharif University of Technology
    The main purpose of the present work is multi-objective shape optimization of a projectile tip for impacting and normal penetrating. Velocity drop, weight and inner volume of projectile have been considered as three conflicting objective functions. For this purpose, at the first step, finite element modeling was done using ABAQUS/Explicit and projectile penetration was examined in different geometric dimensions. Hammersley sequence sampling was employed for designing computer experiments. In the next step, results of the FEM were employed as raw data for MLF-type neural network training to achieve a mathematical model which is able to describe velocity drop behavior. Projectile weight and... 

    Optimum design process of vibration absorber via imperialist competitive algorithm

    , Article International Journal of Structural Stability and Dynamics ; Volume 12, Issue 3 , 2012 ; 02194554 (ISSN) Hoseini, R ; Salehipoor, H ; Sharif University of Technology
    This paper deals with the optimum design of vibration absorbers utilized to reduce undesirable random vibrational effects that are originated in linear structures. Analytical expressions, for the case of nonstationary white-noise accelerations, are derived. The criterion is different from most conventional optimum design criteria, since it is based on minimizing the displacement or the acceleration variance of the main structure responses, without considering performances required against failure. In this study, in order to control the structural vibrations induced on a mechanical structure excited by nonstationary based acceleration random process, the MOO (multi-objective optimum) design... 

    Multi-objective optimization of functionally graded hollow cylinders

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ; Volume 8 , 2011 , Pages 583-590 ; 9780791854945 (ISBN) Nabian, M ; Ahmadian, M. T ; ASME ; Sharif University of Technology
    In this study, two physical properties of simply supported hollow cylinders made of functionally graded materials are investigated. These two properties are mass and first natural frequency which is desirable to be minimized and maximized respectively in mechanical applications. The functionally graded material properties are assumed to vary continuously through the thickness of the cylinder. In this multi-objective optimization problem the first natural frequency of the FGM cylinders as well as its mass are formulated in terms of the volume fraction of the constituents, then by using Genetic algorithm optimization method the continuous volume fraction function of the constituents has been... 

    MOCSA: a multi-objective crow search algorithm for multi-objective optimization

    , Article 2nd Conference on Swarm Intelligence and Evolutionary Computation, CSIEC 2017, 7 March 2017 through 9 March 2017 ; 2017 , Pages 60-65 ; 9781509043293 (ISBN) Nobahari, H ; Bighashdel, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    In this paper, an extension of the recently developed Crow Search Algorithm (CSA) to multi-objective optimization problems is presented. The proposed algorithm, called Multi-Objective Crow Search Algorithm (MOCSA), defines the fitness function using a set of determined weight vectors, employing the max-min strategy. In order to improve the efficiency of the search space, the performance space is regionalized using specific control points. A new chasing operator is also employed in order to improve the convergence process. Numerical results show that MOCSA is closely comparable to well-known multi-objective algorithms. © 2017 IEEE  

    A new strategy for optimal fuel core loading pattern design in PWR nuclear power reactors

    , Article Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007, Monterey, CA, 15 April 2007 through 19 April 2007 ; 2007 ; 0894480596 (ISBN); 9780894480591 (ISBN) Mohseni, N ; Boroushaki, M ; Ghofrani, M. B ; Raji, M. H ; Sharif University of Technology
    Most of the strategies yet implemented to optimize fuel loading pattern design in the nuclear power reactors, are based on maximizing the core effective multiplication factor (Keff) in order to extract maximum energy and to reduce the local power peaking factor (Pq) from a set value. However, a new optimization criterion would be of interest in order to maximize the burn-up of the plutonium content (Pu) in the fuel assemblies. In this research we have developed a new strategy based on multi objective optimization, to optimize fuel core loading pattern for a VVER-1000 reactor. In this approach we simultaneously have reduced the Pq, maximized Keff and also minimized the plutonium content in... 

    Multi-objective node placement considering non-uniform event pattern

    , Article Wireless Personal Communications ; Volume 97, Issue 4 , 2017 , Pages 6189-6220 ; 09296212 (ISSN) Mohtashami, H ; Movaghar, A ; Teshnehlab, M ; Sharif University of Technology
    Ease of use, high flexibility and variety of applications have made wireless sensor networks very popular. Node placement in a sensor network is very critical since it affects important network attributes such as coverage, lifetime, and reliability. Therefore, controlled node placement is necessary for achieving specific network features with minimum number of nodes. Since node placement is an NP-hard problem, many placement algorithms have been proposed based on heuristic and meta-heuristic methods. Most of those algorithms assume a uniform event pattern (UEP) throughout the area under investigation. However, in practice some networks deal with non-uniform event pattern (NEP). Optimization... 

    Multi-skilled project scheduling with level-dependent rework risk; three multi-objective mechanisms based on cuckoo search

    , Article Applied Soft Computing Journal ; Volume 54 , 2017 , Pages 46-61 ; 15684946 (ISSN) Maghsoudlou, H ; Afshar Nadjafi, B ; Akhavan Niaki, S. T ; Sharif University of Technology
    Elsevier Ltd  2017
    In many projects, multi-skilled workforces are able to perform different tasks with different quality levels. In this paper, a real-life version of the multi-skilled resource constrained project scheduling problem is investigated, in which the reworking risk of each activity depends on the assigned level of multi-skilled workforces. The problem is formulated mathematically as a bi-objective optimization model to minimize total costs of processing the activities and to minimize reworking risks of the activities, concurrently. In order to solve the resulting problem, three cuckoo-search-based multi-objective mechanisms are developed based on non-dominance sorting genetic algorithm,... 

    The development of a novel multi-objective optimization framework for non-vertical well placement based on a modified non-dominated sorting genetic algorithm-II

    , Article Computational Geosciences ; Volume 23, Issue 5 , 2019 , Pages 1065-1085 ; 14200597 (ISSN) Rostamian, A ; Jamshidi, S ; Zirbes, E ; Sharif University of Technology
    Springer International Publishing  2019
    A single-objective well placement problem is one of the classical optimization problems in oilfield development and has been studied for many years, by researchers worldwide. However, the necessity to face practical applications and handle insufficient data in a single-objective optimization leads to the introduction of a multi-objective optimization framework, which consequently allows an engineer to manage more information. In this study, for the very first time, a multi-objective well placement optimization framework, based on a Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is utilized with a similarity-based mating scheme. To represent the power of this mating procedure, it is... 

    Performance tradeoff of MVNOs in OFDMA-based virtualized wireless networks

    , Article IEEE Transactions on Vehicular Technology ; 2021 ; 00189545 (ISSN) Robat Mili, M ; Li, S ; Mokhtari, F ; Derakhshani, M ; Ashtiani, F ; Le-Ngoc, T ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    In this paper, we analyze the tradeoff between the profits gained by mobile virtual network operators (MVNOs) in an orthogonal frequency division multiple access (OFDMA)-based virtualized wireless networks (VWNs). In this respect, MVNOs rent the network resources from a mobile network operator (MNO) to create virtual resources based on allocated rates and the cost due to allocated transmit powers in two different strategies: resource-based isolation strategy and rate-based isolation strategy. In resource-based isolation strategy, it is assumed that the whole bandwidth in each base station is divided equally between MVNOs whereas in rate-based isolation strategy, the whole bandwidth in each... 

    A dynamic fuzzy interactive approach for DG expansion planning

    , Article International Journal of Electrical Power and Energy Systems ; Volume 43, Issue 1 , 2012 , Pages 1094-1105 ; 01420615 (ISSN) Esmi Jahromi, M ; Ehsan, M ; Fattahi Meyabadi, A ; Sharif University of Technology
    This paper presents a dynamic multi objective model for distribution network expansion, considering the distributed generators (DGs) and network reinforcements. The proposed model simultaneously optimizes three objective functions namely, total cost, emission cost and technical satisfaction (voltage profile) by finding the optimal schemes of timing, sizing, placement and DG technologies in a long term planning period (dynamic planning). The importance of each objective function can be changed in the interactive steps. The calculation algorithm is based on Chaotic Local Search with Modified Honey Bee Mating Optimization (CLSMHBMO). The effectiveness of the proposed model and the calculation... 

    Bi-objective optimization approaches to many-to-many hub location routing with distance balancing and hard time window

    , Article Neural Computing and Applications ; Volume 32, Issue 17 , 2020 , Pages 13267-13288 Basirati, M ; Akbari Jokar, M. R ; Hassannayebi, E ; Sharif University of Technology
    Springer  2020
    This study addresses a many-to-many hub location-routing problem where the best-found locations of hubs and the best-found tours for each hub are determined with simultaneous pickup and delivery within the hard time window. To find practical solutions, the hubs and transportation fleet have constrained capacity, in which every node can be serviced by multiple allocations with the hard time window and limited tour length. First, a bi-objective optimization model is proposed to balance travel costs among different routes and to minimize the total sum of fixed costs of locating hubs, the costs of handling, traveling, assigning, and transportation costs. The problem is then solved using an... 

    A Green hazardous waste location-routing problem considering the risks associated with transportation and population

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 33, Issue 11 , 2020 Delfani, F ; Kazemi, A ; Seyed hosseini, S. M ; Akhavan Niaki, S. T ; Sharif University of Technology
    Materials and Energy Research Center  2020
    The researches on environmental and sustainability are an active topic, especially in the waste management. As such, the hazardous waste optimization is an active research topic in developing countries which may be integrated with carbon emissions and green subjects. This grand challenge motivates the current research to contribute a new multi-objective optimization model to address the green hazardous waste location-routing problem. The proposed multi-objective optimization model establishes four objectives simultaneously for the first time. In addition to the total cost and the greenhouse gas emissions of the transportation systems as the two main objectives, another objective function... 

    Comparison between different multi-objective approaches to distribution network planning

    , Article IET Conference Publications ; Volume 2013, Issue 615 CP , 2013 ; 9781849197328 (ISBN) Haji, A ; Eini, B. J ; Mirvazand, M ; Safari, M ; Sharif University of Technology
    Distribution companies try to meet different goals such as increasing profitability, reducing investment and improving reliability indices. Therefore, distribution network planning has converted into complex multi-objective optimization problems. Mathematicians and operation research experts have developed many methods which can be used for solving these problems. Despite all efforts to develop applicable approaches for these problems, there is still no general consensus on project selection policy. Evaluating the strengths and weaknesses of each network optimization strategy selection in pragmatic manner is the objective of current research. In this paper, many methods used in network...