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Total 150 records

    Control of diseases epidemic spreading through metapopulation models

    , Article International Journal of Control Theory and Applications ; Volume 8, Issue 2 , 2015 , Pages 769-784 ; 09745572 (ISSN) Afshar, M ; Razvan, M. R ; Sharif University of Technology
    International Sciences Press  2015
    Abstract
    We study a system of ordinary differential equations which describes the metapopulation SIR model. The main target is to control the epidemic spreading using the structure of connections between cities. For this purpose, we formulate optimal control strategy that the control represents a drug treatment and Prevention strategies . Some methods are given in numerical example section such as control through spectral radius of movement matrix or optimal control through travelling between cities. Existence results for the optimal control are studied  

    Application of a new rapid transit network design model to bus rapid transit network design: Case study Isfahan metropolitan area

    , Article Transport ; Volume 30, Issue 1 , Oct , 2013 , pages 93-102 ; 16484142 (ISSN) Kermanshahi, S ; Shafahi, Y ; Bagherian, M ; Sharif University of Technology
    2013
    Abstract
    The problem of Rapid Transit Network Design (RTND) is studied in this paper. Due to the noticeable contribution of rapid transit lines in public transportation network of large urban areas, this problem is interesting to the transportation specialists. On the other hand, the success stories of Bus Rapid Transit (BRT) systems in different countries have motivated us to study BRT network planning. BRT systems can be developed with less investment costs and construction time in comparison with rail-based systems. Therefore, planning Bus Rapid Transit lines, either to develop a new rapid transit network or extend a current one can be an interesting research topic. This problem, like other... 

    Suppression of nonlinear regenerative chatter in milling process via robust optimal control

    , Article Journal of Process Control ; Volume 23, Issue 5 , 2013 , Pages 631-648 ; 09591524 (ISSN) Moradi, H ; Vossoughi, G ; Movahhedy, M. R ; Salarieh, H ; Sharif University of Technology
    2013
    Abstract
    During the milling process, self-excited vibration or chatter adversely affects tool life, surface quality and productivity rate. In this paper, nonlinear cutting forces of milling process are considered as a function of chip thickness with a complete third order polynomial (instead of the common linear dependency). An optimal control strategy is developed for chatter suppression of the system described through nonlinear delay differential equations. Counterbalance forces exerted by actuators in x and y directions are the control inputs. For optimal control problem, an appropriate performance index is defined such that the regenerative chatter is suppressed while control efforts are... 

    Optimization analysis of alternate tube section for pulse tube refrigerators

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Jafarian, A ; Saidi, M. H ; Hannani, S. K ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    In spite of numerous attempts which have been made during the last decade to optimize pulse tube refrigerators, still theoretical and analytical realization of this device needs to be thoroughly explained. In this paper, in addition to the oscillatory flow analysis in the pulse tube refrigerator through a simple analytical model, the performance of the alternate tube section of this device is analyzed using a generalized efficiency, based on the entropy generation rate. In this model, in order to extract the entropy generation rate and the dissipative terms caused by fluid friction and heat flow in alternate tube, simplified momentum and energy equations are solved analytically and velocity... 

    Dynamics of a running below-knee prosthesis compared to those of a normal subject

    , Article Journal of Solid Mechanics ; Volume 5, Issue 2 , 2013 , Pages 152-160 ; 20083505 (ISSN) Mamaghani, A. E ; Zohoor, H ; Firoozbakhsh, K ; Hosseini, R ; Sharif University of Technology
    Islamic Azad University  2013
    Abstract
    The normal human running has been simulated by two-dimensional biped model with 7 segments. Series of normal running experiments were performed and data of ground reaction forces measured by force plate was analyzed and was fitted to some Fourier series. The model is capable to simulate running for different ages and weights at different running speeds. A proportional derivative control algorithm was employed to grant stabilization during each running step. For calculation of control algorithm coefficients, an optimization method was used which minimized cinematic differences between normal running model and that of the experimentally obtained from running cycle data. This yielded the... 

    Generating Bell states in invariant stratification spin networks

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2010, Issue 12 , 2010 ; 17425468 (ISSN) Ghojavand, M ; Jafarizadeh, M. A ; Rouhani, S ; Sharif University of Technology
    Abstract
    In this paper, we study the generation of Bell states between distant vertices in a permanently coupled quantum spin network, interacting via invariant stratification graphs. To begin with we establish a class of upper bounds over the achievable entanglement between the reference site and various vertices. We observe that the maximum of these upper bounds is one e-bit. We conclude that the reference site can generate a Bell state with a vertex if the corresponding upper bound of the vertex is one e-bit. Thus for generation of a Bell state this upper bound must be saturated. Taking this into account, we obtain the characteristic constraint of the proper graphs. We introduce a special class of... 

    Optimal lot size with rework, inspection errors and scrap items

    , Article 36th International Conference on Computers and Industrial Engineering, ICC and IE 2006, Taipei, 20 June 2006 through 23 June 2006 ; 2006 , Pages 764-771 Haji, A ; Javadian, N ; Shamsi, R ; Sharif University of Technology
    2006
    Abstract
    The classical economic production quantity (EPQ) model is a well-known and commonly used inventory control technique. A common assumption in the EPQ model is that all units produced are of perfect quality, since in practice non-conforming product or scrap items are possible, this assumption will underestimate the actual required quantity. The objective of this paper is to provide a framework to integrate product of imperfect quality items, inspection errors, rework and scrap items into a single EPQ model. To achieve this objective a suitable mathematical model is defined and the optimal production lot size which minimizes the total cost is obtained  

    A robust multi-objective optimization model for project scheduling considering risk and sustainable development criteria

    , Article Environment, Development and Sustainability ; Volume 23, Issue 8 , 2021 , Pages 11494-11524 ; 1387585X (ISSN) Askarifard, M ; Abbasianjahromi, H. R ; Sepehri, M ; Zeighami, E ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    Abstract
    There is limited research that considers the sustainability aspect of the projects’ schedule. The present study proposes a model to cover this gap by considering sustainable development criteria. A multi-objective model with four objective functions, including minimizing cost, risk, and socio-environmental impacts, has been presented to decrease the project’s delay. Since some of the parameters are considered under conditions of uncertainty for the proximity of problems to real projects, the robust programming method is used to deal with the uncertainty, and the epsilon-constraint method was applied to solve the multi-objective model. Several scenarios are also defined to analyze the... 

    A planar neuro-musculoskeletal arm model in post-stroke patients

    , Article Biological Cybernetics ; Volume 112, Issue 5 , 2018 , Pages 483-494 ; 03401200 (ISSN) Asghari, M ; Behzadipour, S ; Taghizadeh, G ; Sharif University of Technology
    Abstract
    Mathematical modeling of the neuro-musculoskeletal system in healthy subjects has been pursued extensively. In post-stroke patients, however, such models are very primitive. Besides improving our general understanding of how stroke affects the limb motions, they can be used to evaluate rehabilitation strategies by computer simulations before clinical evaluations. A planar neuro-musculoskeletal arm model for post-stroke patients is developed. The main idea is to use a set of new coefficients, Muscle Significance Factors (MSF), to incorporate the effects of stroke in the muscle control performance. The model uses the optimal control theory to mimic the performance of the CNS and a two-link... 

    Optimal trajectory planning for flight through microburst wind shears

    , Article Aerospace Science and Technology ; Volume 15, Issue 7 , October , 2011 , Pages 567-576 ; 12709638 (ISSN) Pourtakdoust, S. H ; Kiani, M ; Hassanpour, A ; Sharif University of Technology
    2011
    Abstract
    Microburst wind shear is a potential hazard for aviation safety, especially in some crucial phases of flight like take-off and landing. Optimal trajectories could be useful for suitable retrieval of transport aircrafts encountering microburst. These types of trajectories are investigated in this paper for landing phase in two scenarios of escape and landing utilizing the most recent realistic analytical model of the microburst. In this regard, a set of complete six degrees of freedom aircraft's equations of motion is taken in a variation formulation of this problem. This approach is particularly useful for determination of optimal escape or approach trajectories constrained with respect to... 

    Incremental labeling in closed-2PM model

    , Article Computers and Electrical Engineering ; Volume 36, Issue 5 , 2010 , Pages 895-901 ; 00457906 (ISSN) Rostamabadi, F ; Ghodsi, M ; Sharif University of Technology
    2010
    Abstract
    We consider an incremental optimal label placement in a closed-2PM map containing points each attached with a label. Labels are assumed to be axis-parallel square-shaped and have to be pairwise disjoint with maximum possible length each attached to its corresponding point on one of its horizontal edges. Such a labeling is denoted as optimal labeling. Our goal is to efficiently generate a new optimal labeling for all points after each new point being inserted in the map. Inserting each point may require several labels to flip or all labels to shrink. We present an algorithm that generates each new optimal labeling in O(lgn+k) time where k is the number of required label flips, if there is no... 

    Optimizing shipment, ordering and pricing policies in a two-stage supply chain with price-sensitive demand

    , Article Transportation Research Part E: Logistics and Transportation Review ; Volume 45, Issue 4 , 2009 , Pages 564-571 ; 13665545 (ISSN) Sheikh Sajadieh, M ; Akbari Jokar, M. R ; Sharif University of Technology
    Elsevier Ltd  2009
    Abstract
    In this paper we focus on a two-stage supply chain consisting of one vendor and one buyer. We develop an integrated production-inventory-marketing model to determine the relevant profit-maximizing decision variable values. The model proposed is based on the joint total profit of both the vendor and the buyer, and it finds out the optimal ordering, shipment and pricing policies. We are able to ascertain the optimal decision variable values employing an analytical solution procedure. The numerical evidence suggests that it is more beneficial for the buyer and the vendor to cooperate with each other when the demand is more price sensitive. © 2008 Elsevier Ltd. All rights reserved  

    Dynamic optimization in chemical processes using region reduction strategy and Control Vector Parameterization with an Ant Colony Optimization algorithm

    , Article Chemical Engineering and Technology ; Volume 31, Issue 4 , 2008 , Pages 507-512 ; 09307516 (ISSN) Asgari, S. A ; Pishvaie, M. R ; Sharif University of Technology
    2008
    Abstract
    Two different approaches of the dynamic optimization for chemical process control engineering applications are presented. The first approach is based on discretizing both the control region and the time interval. This method, known as the Region Reduction Strategy (RRS), employs the previous solution in its next iteration to obtain more accurate results. Moreover, the procedure will continue unless the control region becomes smaller than a prescribed value. The second approach is called Control Vector Parameterization (CVP) and appears to have a large number of advantages. In this approach, control action is generated in feedback form, i.e., a set of trial functions of the state variables... 

    New approach for strategic bidding of gencos in energy and spinning reserve markets

    , Article Energy Conversion and Management ; Volume 48, Issue 7 , 2007 , Pages 2044-2052 ; 01968904 (ISSN) Soleymani, S ; Ranjbar, A. M ; Shirani, A. R ; Sharif University of Technology
    2007
    Abstract
    In restructured and de-regulated power systems, generating companies (Gencos) are responsible for supplying electricity for both energy and reserve markets, which usually operate simultaneously. In this condition, the question is how much and for what price must each Genco generate for each market to maximize its profit, so this paper intends to answer to this question. In this paper, first, the combined energy and reserve markets are considered, and the Nash equilibrium points are determined. Then, the bidding strategies for each Genco at these points will be presented. The bids for the energy and 10 min spinning reserve (TMSR) markets are separated in the second stage, and again, the... 

    Static and dynamic neural networks for simulation and optimization of cogeneration systems

    , Article 2006 ASME 51st Turbo Expo, Barcelona, 6 May 2006 through 11 May 2006 ; Volume 4 , 2006 , Pages 615-623 ; 0791842398 (ISBN); 9780791842393 (ISBN) Zomorodian, R ; Khaledi, H ; Ghofrani, M. B ; The International Gas Turbine Institute ; Sharif University of Technology
    2006
    Abstract
    In this paper, the application of neural networks for simulation and optimization of the cogeneration systems has been presented. CGAM problem, a benchmark in cogeneration systems, is chosen as a case study. Thermodynamic model includes precise modeling of the whole plant. For simulation of the steady sate behavior, the static neural network is applied. Then using dynamic neural network, plant is optimized thermodynamically. Multi layer feed forward neural networks is chosen as static net and recurrent neural networks as dynamic net. The steady state behavior of CGAM problem is simulated by MFNN. Subsequently, it is optimized by dynamic net. Results of static net have excellence agreement... 

    Prediction of spindle dynamics in milling by sub-structure coupling

    , Article International Journal of Machine Tools and Manufacture ; Volume 46, Issue 3-4 , 2006 , Pages 243-251 ; 08906955 (ISSN) Movahhedy, M. R ; Gerami, J. M ; Sharif University of Technology
    2006
    Abstract
    The Stability of machining process depends on the dynamics of the machine tool, among other things. However, the dynamics of the machine tool changes when the tool is changed. To avoid the need for repeating the measurements, sub-structuring analysis may be used to couple the tool and spindle frequency response functions. A major difficulty in this approach is the determination of joint stiffness and damping between the two sub-structures. In particular, the measurement of rotational responses (RDOFs) at joints is a difficult task. In this research, a simple joint model that accounts for RDOFs is proposed. It is shown that this model avoids RDOF measurement while taking into account the... 

    A new structure for electricity market scheduling

    , Article 2006 International Conference on Power Electronics, Drives and Energy Systems, PEDES '06, New Delhi, 12 December 2006 through 15 December 2006 ; 2006 ; 078039772X (ISBN); 9780780397729 (ISBN) Soleymani, S ; Ranjbar, A. M ; Shirani, A. R ; Sharif University of Technology
    2006
    Abstract
    On pool market structure, the generating units are typically dispatched in order of lowest to highest bid as needed to meet demand requirement as well as considering network constraints. Generally, no account is taken of generating unit's reliability when scheduling them. This paper proposes a new structure for electricity market to consider generating unit's reliability in the scheduling problem. GAMS (General Algebraic Modeling System) language has been used to solve the social welfare maximization problem using CPLEX optimization software with mixed integer programming. ©2006 IEEE  

    Design, modeling and optimization of a novel two DOF polymeric electro-thermal micro-actuator

    , Article Applied Mechanics and Materials ; Vol. 307 , 2013 , pp. 112-116 ; ISSN: 16609336 ; ISBN: 9783037856598 Sheikhbahaie, R ; Alasty, A ; Salarieh, H ; Sharif University of Technology
    Abstract
    In this paper, design, simulation and optimization of a novel electrothermally-activated polymeric microactuator capable of generating combination of bidirectional lateral and rotational motions are presented. The composite structure of this actuator is consisted of a symmetric meandered shape silicon skeleton, a SU8 thermal expandable polymer and a thin film chrome layer heater. This actuator is controlled by applying appropriate voltages on its four terminals. With the purpose of dimension optimization, a numerical parametric study is executed. The modeled actuator which is 1560 ?m long, 156 ?m wide and 30 ?m thick, demonstrates a remarkable lateral displacement of 23 ?m at power... 

    Dynamics of bistable initially curved shallow microbeams: Effects of the electrostatic fringing fields

    , Article IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM ; July , 2014 , p. 1279-1283 Tajaddodianfar, F ; Yazdiو M. H ; Pishkenariو H. N ; Sharif University of Technology
    Abstract
    Effects of fringing electrostatic fields on the behavior of a double clamped initially curved microbeam are investigated. Galerkin's decomposition method is applied on the governing Euler-Bernoulli equation with distributed electrostatic force to obtain the lumped-parameter model of the system. The resulting single degree of freedom model is obtained with the Palmer's formula as a model for the fringing field effects. To derive an applied form of the fringing field effect in lumped model, we have used Genetic Algorithms as an optimization method. Then using the lumped model, we have investigated the system nonlinear dynamics. Comparison of the obtained bifurcation diagrams with the... 

    Response surface methodology for modeling and optimizing the treatment of synthetic starchy wastewater using hydrophilic PES membrane

    , Article Desalination and Water Treatment ; Volume 51, Issue 37-39 , 2013 , Pages 7036-7047 ; 19443994 (ISSN) Hedayati Moghaddam, A ; Shayegan, J ; Sargolzaei, J ; Bahadori, T ; Sharif University of Technology
    Abstract
    In this work, the process of starch removal from starchy wastewater using a hydrophilic polyethersulfone membrane was investigated. The pore size of the membrane was 0.65 μm and the pattern of stream in plate and frame handmade membrane module was cross-flow. To design the layout of the experiments, response surface methodology was applied. The performance of the filtration process was evaluated by calculating the (chemical oxygen demand) COD removal percentage (rejection factor) and permeate flux. In this study, five operative parameters were investigated, including trans-membrane pressure, flow rate and temperature of feed, pH, and the COD concentration of starch wastewater. Two models...