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modeling-and-optimization
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A parametric study on optimal shape of buckling restrained knee bracing frames
, Article 5th International Conference on Advances in Steel Structures, ICASS 2007, Singapore, 5 December 2007 through 7 December 2007 ; Volume 3 , 2007 , Pages 356-361 ; 9789810593711 (ISBN) ; Mofid, M ; Sharif University of Technology
2007
Abstract
This paper is concerned with the development of buckling-restrained knee bracing frames for seismic design and retrofit of steel frame structures. Analytical models based on the new nonlinear finite element modeling of the system for the moment and shear yielding mode were developed in a structure with buckling-restrained knee-braces. Parametric study was performed with new and practical parameters of the system describing the specification of the system in elastic and inelastic behavior; and the results are shown in form of the appropriate graphs and charts. This study makes an offer to a simple design technique for this type of structure with a bilinear approach, using a nonlinear finite...
A strategic planning model for natural gas transmission networks
, Article Energy Policy ; Volume 35, Issue 11 , 2007 , Pages 5656-5670 ; 03014215 (ISSN) ; Hemmati, M. R ; Sharif University of Technology
2007
Abstract
The design and development of natural gas transmission pipeline networks are multidisciplinary problems that require various engineering knowledge. In this problem, the type, location, and installation schedule of major physical components of a network including pipelines and compressor stations are decided upon over a planning horizon with least cost goal and subject to network constraints. Practically, this problem has been viewed as a conceptual design case and not as an optimization problem that tries to select the best design option among a set of possible solutions. Consequently, conceptual design approaches are usually suboptimal and work only for short-run development planning. We...
Design of robust mixed fuzzy controller for gas metal arc welding process
, Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Sayyaadi, H ; Tadayon, M. A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2006
Abstract
Welding is an important manufacturing process that can be automated and optimized. In this paper we discuss the Gas Metal Arc Welding (GMAW) control and modeling problem. For modeling the process recently developed highly nonlinear fifth order mathematical model is used, for controlling the GMAW process we use a new Mixed Fuzzy Control (MFC) structure. In this work first a Traditional Fuzzy Controller (TFC) is designed from the viewpoint of a Single-Input Single-Output (SISO) system for controlling each state of GMAW process. Then, an appropriate coupling fuzzy controller is also designed according to the characteristics of gas metal arc welding process and incorporated into a TFC. We then...
A Bi-objective home health care routing and scheduling model with considering nurse downgrading costs
, Article International Journal of Environmental Research and Public Health ; Volume 18, Issue 3 , 2021 , Pages 1-24 ; 16617827 (ISSN) ; Kayvanfar, V ; Rafiee, M ; Werner, F ; Sharif University of Technology
MDPI AG
2021
Abstract
In recent years, the management of health systems is a main concern of governments and decision-makers. Home health care is one of the newest methods of providing services to patients in developed societies that can respond to the individual lifestyle of the modern age and the increase of life expectancy. The home health care routing and scheduling problem is a generalized version of the vehicle routing problem, which is extended to a complex problem by adding special features and constraints of health care problems. In this problem, there are multiple stakeholders, such as nurses, for which an increase in their satisfaction level is very important. In this study, a mathematical model is...
Optimized age dependent clustering algorithm for prognosis: A case study on gas turbines
, Article Scientia Iranica ; Volume 28, Issue 3 B , 2021 , Pages 1245-1258 ; 10263098 (ISSN) ; Durali, M ; Abbasian Najafabadi, T ; Saadat Foumani, M ; Sharif University of Technology
Sharif University of Technology
2021
Abstract
This paper proposes an Age-Dependent Clustering (ADC) structure to be used for prognostics. To achieve this aim, a step-by-step methodology is introduced, that includes clustering, reproduction, mapping, and finally estimation of Remaining Useful Life (RUL). In the mapping step, a neural fitting tool is used. To clarify the age-based clustering concept, the main elements of the ADC model is discussed. A Genetic algorithm (GA) is used to find the elements of the optimal model. Lastly, the fuzzy technique is applied to modify the clustering. By investigating a case study on the health monitoring of some turbofan engines, the efficacy of the proposed method is demonstrated. The results showed...
Reliability assessment of distribution system with the integration of photovoltaic and energy storage systems
, Article Sustainable Energy, Grids and Networks ; Volume 28 , 2021 ; 23524677 (ISSN) ; Esmaeili Nezhad, A ; Moeini Aghtaie, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
With the current focus on energy and the environment, efficient integration of renewable energies, especially solar energy into power systems, is becoming indispensable. Moreover, to fully capture solar potentials and to recognize the unique characteristics associated with solar energy in power systems reliability assessment, a profound investigation is needed. Accordingly, this paper attempts to establish a comprehensive analytical approach for modeling the reliability of a hybrid system (Photovoltaic (PV) system with Energy Storage System (ESS)). To this end, the output of the PV system is modeled by a multi-state model, and the ESS system is modeled as a two-state Markov model. Moreover,...
Modeling and optimization of an integrated multi-generation solar system with variable heat to power ratio for supplying residential and industrial demands
, Article Renewable Energy ; Volume 174 , 2021 , Pages 786-798 ; 09601481 (ISSN) ; Fathi, A ; Saboohi, Y ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The paper aims to present a supply model to satisfy the required household final energy carriers, freshwater and industrial cooling loads for a deprived area of access that is located in hot and humid climate. To this aim, a multi-generation hybrid solar thermophotovoltaic integrated system with capability of adjusting heat to power ratio dynamically is introduced. Appropriate analytical tools are developed to obtain the optimal capacity of any systems and energy flows subject to the technology and demand constraints, the financial limitation and the constraints defined by the politicians and local government. The demand constraints are identified through the field studies and the comfort...
Velocity field reconstruction in the mixing region of swirl sprays using general regression neural network
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 127, Issue 1 , 2005 , Pages 14-23 ; 00982202 (ISSN) ; Soltani, M. R ; Morad, M. R ; Ashjaee, M ; Sharif University of Technology
2005
Abstract
A general regression neural network technique is proposed for design optimization of pressure-swirl injectors. Phase doppler anemometry measurements for velocity distributions are used to train the neural network. An overall optimized value for the width of the probability is determined. The velocity field in the extrapolation regime is reconstructed with an accuracy of 93%. Excellent agreement between the predicted values and the measurements is obtained. The results indicate that the capability of performing designand optimization studies for pressure-swirl injectors with sufficient accuracy exists by applying modest amount of data in conjunction with an overall optimized value for the...
Assessment of a parallel evolutionary optimization approach for efficient management of coastal aquifers
, Article Environmental Modelling and Software ; Volume 74 , December , 2015 , Pages 21-38 ; 13648152 (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
This study presents a parallel evolutionary optimization approach to determine optimal management strategies of large-scale coastal groundwater problems. The population loops of evolutionary algorithms (EA) are parallelized using shared memory parallelism to address the high computational demands of such applications. This methodology is applied to solve the management problems in an aquifer system in Kish Island, Iran using a three-dimensional density-dependent groundwater numerical model. EAs of continuous ant colony optimization (CACO), particle swarm optimization, and genetic algorithm are utilized to solve the optimization problems. By implementing the parallelization strategy, a...
Dynamic Simulation of the Biped Normal and Amputee Human Gait
, M.Sc. Thesis Sharif University of Technology ; Farahmand, Farzam (Supervisor) ; Zohour, Hassan (Supervisor)
Abstract
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...
Developing a feed forward multilayer neural network model for prediction of CO2 solubility in blended aqueous amine solutions
, Article Journal of Natural Gas Science and Engineering ; Volume 21 , November , 2014 , Pages 19-25 ; ISSN: 18755100 ; Mazinani, S ; Davardoost, F ; Mokhtare, A ; Najibi, H ; Van der Bruggen, B ; Darvishmanesh, S ; Sharif University of Technology
Abstract
Absorption of carbon dioxide (CO2) in aqueous solutions can be improved by the addition of other compounds. However, this requires a large amount of equilibrium data for solubility estimation in a wide ranges of temperature, pressure and concentration. In this paper, a model based on an artificial neural network (ANN) was proposed and developed with mixtures containing monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), methanol, triethanolamine (TEA), piperazine (PZ), diisopropanolamine (DIPA) and tetramethylensulfone (TMS) to predict solubility of CO2 in mixed aqueous solution (especially in binary and ternary mixtures) over wide...
Optimal production control and marketing plan in two-machine unreliable flexible manufacturing systems
, Article International Journal of Advanced Manufacturing Technology ; Vol. 73, issue. 1-4 , 2014 , pp. 487-496 ; ISSN: 02683768 ; Karimi, B ; Kianfar, F ; Sharif University of Technology
Abstract
In this paper, we have developed a production planning and marketing model in unreliable flexible manufacturing systems with inconstant demand rate that its rate depends on the level of advertisement on that product. The proposed model is more realistic and useful from a practical point of view. The flexible manufacturing system is composed of two machines that produce a single product. Markovian models frequently have been used in modeling a wide variety of real-world systems under uncertainties. Therefore, in this paper, the inventory balance equation is represented by a continuous-time model with Markov jump process to take into account machines breakdown. The objective is to minimize the...
Numerical study of the effects of process parameters on tool life in a cold radial forging process
, Article Scientia Iranica ; Vol. 21, issue. 2 , 2014 , p. 339-346 ; Movahhedy, M. R ; Sharif University of Technology
Abstract
Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axles, and for creating internal profiles in tubes. Due to very large forging loads, the tool should withstand high stress and wear. Therefore, the success of the forging process depends upon recognition of the die failure factors and optimization of the tool working conditions that enhance tool life. In this study, the effect of process parameters on tool life in the cold radial forging process is investigated using nonlinear three dimensional finite element modeling. Wear and mechanical fatigue are considered as the main modes of tool failure, and a parametric study on the...
Frequency domain identification of the Nomoto model to facilitate Kalman filter estimation and PID heading control of a patrol vessel
, Article Ocean Engineering ; Volume 72 , November , 2013 , Pages 344-355 ; 00298018 (ISSN) ; Ghorbani, M. T ; Sharif University of Technology
2013
Abstract
This paper presents a detailed frequency-domain system identification method applied to identify steering dynamics of a coastal patrol vessel using a data analysis software called CIFER. Advanced features such as the Chirp-Z transform and composite window optimization are used to extract high quality frequency responses. An accurate, robust and linear transfer function model is derived for yaw and roll dynamics of the vessel. To evaluate the accuracy of the identified model, time domain responses from a 45-45 zig-zag test are compared with the responses predicted by the identified model. The identified model shows excellent predictive capability and is well suited for simulation and...
Analyzing price, warranty length, and service capacity under a fuzzy environment: Genetic algorithm and fuzzy system
, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 975-982 ; 10263098 (ISSN) ; Shavandi, H ; Sharif University of Technology
2013
Abstract
In this article, we propose a bi-objective model for the pricing-queuing problem under a fuzzy environment. We consider two objectives: maximizing the profit function and minimizing the waiting time in queue. Imagine a firm which sells a product in a channel providing after sales services. The sales price and warranty length affect customer demand. We formulate the demand function as a fuzzy system considering the sales price and warranty length. The firm optimizes the sales price and warranty length, as well as waiting time, in the queue of after sales services, to maximize its revenues and minimize waiting time. To solve the derived model, we develop a hybrid solution method of a fuzzy...
Experimental investigation, modeling and optimization of membrane separation using artificial neural network and multi-objective optimization using genetic algorithm
, Article Chemical Engineering Research and Design ; Volume 91, Issue 5 , 2013 , Pages 883-903 ; 02638762 (ISSN) ; Shoushtari, N. A ; Mirza, B ; Salahi, A ; Sharif University of Technology
2013
Abstract
In this work, treatment of oily wastewaters with commercial polyacrylonitrile (PAN) ultrafiltration (UF) membranes was investigated. In order to do these experiments, the outlet wastewater of the API (American Petroleum Institute) unit of Tehran refinery, is used as the feed. The purpose of this paper was to predict the permeation flux and fouling resistance, by applying artificial neural networks (ANNs), and then to optimize the operating conditions in separation of oil from industrial oily wastewaters, including trans-membrane pressure (TMP), cross-flow velocity (CFV), feed temperature and pH, so that a maximum permeation flux accompanied by a minimum fouling resistance, was acquired by...
Optimal tuning of sliding mode controller parameters using LQR input trend
, Article IS'2012 - 2012 6th IEEE International Conference Intelligent Systems, Proceedings ; 2012 , Pages 297-303 ; 9781467327824 (ISBN) ; Banazadeh, A ; Ahadi, A ; Sharif University of Technology
2012
Abstract
This paper presents a novel method fortuning the parameters of an sliding mode (SM) controller to obtain near-optimal performance. In order to do so the Linear Quadratic Regulator (LQR) was implemented on a linearized system. The input history of the LQR was used as a reference to obtain an optimal space for sliding mode controller parameters. Afterwards, the optimal space boundaries were dedicated to Genetic Algorithm (GA) to search for the optimal parameter for the nonlinear model. Also, the center of the obtained optimal space was used as an initial guess to the Particle Swarm Optimization (PSO) Algorithm. The proposed algorithm was implemented to regulate SM controller for the attitude...
Sensitivity of a real-time freeway crash prediction model to calibration optimality
, Article European Transport Research Review ; Volume 4, Issue 3 , September , 2012 , Pages 167-174 ; 18670717 (ISSN) ; Hellinga, B ; Sharif University of Technology
2012
Abstract
Background: Real-time crash prediction models are often structured as general log-linear categorical models which must be calibrated using an extensive database. However, there is no method to optimally select the number of categories and the values that define the boundaries between categories when representing continuous measures as categorical variables within the log-linear model. This raises the question of how important the calibration is to the safety impacts estimated when using the crash prediction model. In this paper, we examined the impact that the process used to calibrate the crash prediction model has on estimates of safety impacts of a variable speed limit system. Methods:...
A practical approach to R&D portfolio selection using the fuzzy pay-off method
, Article IEEE Transactions on Fuzzy Systems ; Volume 20, Issue 4 , 2012 , Pages 615-622 ; 10636706 (ISSN) ; Collan, M ; Modarres, M ; Sharif University of Technology
IEEE
2012
Abstract
The objective of this research is to develop a practical research and development (R&D) portfolio selection model that addresses the effective R&D project valuation issue, while tackling R&D uncertainty in portfolio optimization. Fuzzy set theory is employed to capture and model the uncertain project information. To evade the well-known complexities of fuzzy real option valuation, the recently developed fuzzy pay-off method is used to more effectively valuate R&D projects. The resulting problem is formulated as a fuzzy zero-one integer programming model that handles uncertainty of input data in order to determine the optimal portfolio. Two satisfaction measures, which are based on...
Performance analysis of contact baking of flat bread in an indirect-heating oven
, Article Drying Technology ; Volume 30, Issue 9 , May , 2012 , Pages 1014-1023 ; 07373937 (ISSN) ; Feilizadeh, M ; Najafabadi, A. T ; Sharif University of Technology
2012
Abstract
A significant portion of Iranian flat breads are produced in semi-industrial, indirect-heating ovens. Therefore, an efficient oven design and a proper selection of operating conditions are crucial to improve the product quality and reduce energy consumption. In the present study, a mathematical model is developed to simulate a semi-industrial, indirect-heating, continuous oven performance during contact baking of an Iranian flat bread, referred to as Taftoon. Individual modes of heat transfer are considered among various components of the baking system to estimate the system performance and the bread quality in terms of design and operating conditions. The predictions of this model are in...