Search for: optimal-systems
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    Expand the shares together: envy-free mechanisms with a small number of cuts

    , Article Algorithmica ; Volume 81, Issue 4 , 2019 , Pages 1728-1755 ; 01784617 (ISSN) Seddighin, M ; Farhadi, M ; Ghodsi, M ; Alijani, R ; Tajik, A. S ; Sharif University of Technology
    Springer New York LLC  2019
    We study the problem of fair division of a heterogeneous resource among strategic players. Given a divisible heterogeneous cake, we wish to divide the cake among n players to meet these conditions: (I) every player (weakly) prefers his allocated cake to any other player’s share (such notion is known as envy-freeness), (II) the allocation is dominant strategy-proof (truthful) (III) the number of cuts made on the cake is small. We provide methods for dividing the cake under different assumptions on the valuation functions of the players. First, we suppose that the valuation function of every player is a single interval with a special property, namely ordering property. For this case, we... 

    Expand the shares together: envy-free mechanisms with a small number of cuts

    , Article Algorithmica ; 2018 ; 01784617 (ISSN) Seddighin, M ; Farhadi, M ; Ghodsi, M ; Alijani, R ; Tajik, A. S ; Sharif University of Technology
    Springer New York LLC  2018
    We study the problem of fair division of a heterogeneous resource among strategic players. Given a divisible heterogeneous cake, we wish to divide the cake among n players to meet these conditions: (I) every player (weakly) prefers his allocated cake to any other player’s share (such notion is known as envy-freeness), (II) the allocation is dominant strategy-proof (truthful) (III) the number of cuts made on the cake is small. We provide methods for dividing the cake under different assumptions on the valuation functions of the players. First, we suppose that the valuation function of every player is a single interval with a special property, namely ordering property. For this case, we... 

    Performance evaluation of water resources systems using system dynamics approach: Application to the Aras River Basin, Iran

    , Article World Environmental and Water Resources Congress 2012: Crossing Boundaries, Proceedings of the 2012 Congress ; 2012 , Pages 2367-2377 ; 9780784412312 (ISBN) Jood, M. S ; Abrishamchi, A ; Sharif University of Technology
    ASCE  2012
    System Dynamics approach is a powerful tool in water resources systems simulation for evaluating proposed plans and policies in development projects. In Aras River basin, existing water resources do not suffice increasing demand in the near future, thus construction of new reservoirs is under study. In this study, system dynamics approach is used to simulate the water resources system of Darehrood sub basin located in eastern part of Aras River basin. Performance indices are used to evaluate the alternative plans and policies.. Reliability, resiliency and vulnerability, the three performance indices used in study, are estimated using maximum value and mean value estimators mentioned in the... 

    Optimal design of the volute for a turbocharger radial flow compressor

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 6 , July , 2015 , Pages 993-1002 ; 09544100 (ISSN) Mojaddam, M ; Hajilouy Benisi, A ; Movahhedy, M. R ; Sharif University of Technology
    SAGE Publications Ltd  2015
    In this research, design methods of radial flow compressor volutes are reviewed; the main criteria in volute primary designs are recognized and the most effective ones are selected. The effective parameters, i.e., spiral cross-section area, circumferential area distribution, exit cone, and tongue area of the compressor volute are parametrically studied to identify the optimum values. A numerical model has been prepared and verified through experimental data which are obtained from the designed turbocharger test rig. Different volutes are modeled and numerically evaluated using the same impeller and vane-less diffuser. For each model, the volute total pressure ratio, static pressure recovery... 

    Optimal design of multiphase composites under elastodynamic loading

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 300 , 2016 , Pages 265-293 ; 00457825 (ISSN) Tavakoli, R ; Sharif University of Technology
    Elsevier  2016
    An algorithm is proposed to optimize the performance of multiphase structures (composites) under elastodynamic loading conditions. The goal is to determine the distribution of material in the structure such that the time-averaged total stored energy of structure is minimized. A penalization strategy is suggested to avoid the checkerboard instability, simultaneously to generate near 0-1 topologies. As a result of this strategy, the solutions of presented algorithm are sufficiently smooth and possess the regularity of H1 function space. A simple method for the continuum adjoint sensitivity analysis of the corresponding PDE-constrained optimization problem is presented. It is general and can be... 

    A new approach to find the optimal solution for base stock policies

    , Article Journal of Applied Sciences ; Volume 9, Issue 4 , 2009 , Pages 789-793 ; 18125654 (ISSN) Shenas, N. Y ; Eshraghniaye Jahromi, A ; Modarres, M ; Sharif University of Technology
    In this study, the cost function of the defined system is derived first. Then, we prove this function is convex in the system's base stock level. Finally, based on the convexity of the cost function, the optimal solution for the base stock model is determined. For demonstrating the applicability of the proposed method, we resort to solving an example. © 2009 Asian Network for Scientific Information  

    Revenue management approach to stochastic capacity allocation problem

    , Article European Journal of Operational Research ; Volume 192, Issue 2 , 2009 , Pages 442-459 ; 03772217 (ISSN) Modarres, M ; Sharifyazdi, M ; Sharif University of Technology
    To formulate stochastic capacity allocation problems in a manufacturing system, the concept and techniques of revenue management is applied in this research. It is assumed the production capacity is stochastic and hence its exact size cannot be forecasted in advance, at the time of planning. There are two classes of "frequent" and "occasional" customers demanding this capacity. The price rate as well as the penalty for order cancellation caused by overbooking is different for each class. The model is developed mathematically and we propose an analytical solution method. The properties of the optimal solution as well as the behavior of objective function are also analyzed. The objective... 

    Economically optimal uncertainty set characterization for power system operational flexibility

    , Article IEEE Transactions on Industrial Informatics ; Volume 15, Issue 10 , 2019 , Pages 5456-5465 ; 15513203 (ISSN) Pourahmadi, F ; Hosseini, S. H ; Fotuhi Firuzabad, M ; Sharif University of Technology
    IEEE Computer Society  2019
    Assessing the operational flexibility of the grid with high penetration of renewable resources remains an issue of critical importance. Operational flexibility insufficiency may bring about two major problems: 1) there may exist no feasible solution for operation under uncertain conditions due to insufficient available flexibility capacity; 2) even if the solution feasibility criterion is ensured, dispatch limitations of the flexible resources may force the system operating point to deviate from the optimal economic point with increased redispatch. In this paper, an optimal uncertainty set at the unit commitment time scale is proposed and characterized as a reliable operational metric. A... 

    Applying simulated annealing to cellular manufacturing system design

    , Article International Journal of Advanced Manufacturing Technology ; Volume 32, Issue 5-6 , 2007 , Pages 531-536 ; 02683768 (ISSN) Arkat, J ; Saidi, M ; Abbasi, B ; Sharif University of Technology
    Cell formation and cellular layout design are the two main steps in designing a cellular manufacturing system (CMS). In this paper, we will present an integrated methodology based on a new concept of similarity coefficients and the use of simulated annealing (SA) as an optimization tool. In comparison with the previous works, the proposed methodology takes into account relevant production data, such as alternative process routings and the production volumes of parts. The SA-based optimization tool is parallel in nature and, hence, can reduce the computation time significantly, so it is capable of handling large-scale problems. Finally, the SA-based procedure is compared with a genetic... 

    A system dynamics approach to analyze water resources systems

    , Article 31st IAHR Congress 2005: Water Engineering for the Future, Choices and Challenges, 11 September 2005 through 16 September 2005 ; 2005 , Pages 4991-5000 ; 8987898245 (ISBN); 9788987898247 (ISBN) Bagheri, A ; Baradarannia, M.R ; Sarang, A ; Hjorth, P ; Byong-Ho J ; Sang I.L ; Won S.I ; Gye-Woon C ; Sharif University of Technology
    Korea Water Resources Association  2005
    Several mathematical modeling approaches are used to model water resources systems such as deterministic and non-deterministic, lumped and distributed, steady and dynamic, simulation and optimization approaches. All these modeling paradigms - categorized as open systems - assume that the input conditions to the system will not change during their operation. What is happening in the real world is somewhat different. Due to their dynamic behaviors, real world events exert feedbacks from their outputs to their inputs which may cause the input conditions vary with time. This is the main focus of the system dynamics theory which has been introduced in this paper to be applied in water resources... 

    A solution for transportation planning in supply chain

    , Article Scientia Iranica ; Volume 16, Issue 2 E , 2009 , Pages 149-158 ; 10263098 (ISSN) Modares, A ; Sepehri, M ; Sharif University of Technology
    An advanced optimization system for Vehicle Routing and Scheduling Problems (VRSP), which is one of the Supply Chain Planning modules, is introduced. An object oriented system, Computer Aided Routing and Scheduling (CARS) can handle complicated distribution models using advanced heuristic optimization algorithms. To classify various types of routing and scheduling problems in a structured manner, a classification scheme is introduced based on the main objects of VRSP. Also, the modeling and solution approach in the CARS optimization engine has been elaborated. Main static and dynamic objects of the system as well as their relationships and interactions have been explained. The user interface... 

    A decomposed solution to multiple-energy carriers optimal power flow

    , Article IEEE Transactions on Power Systems ; Vol. 29, issue. 2 , March , 2014 , p. 707-716 ; ISSN: 8858950 Moeini-Aghtaie, M ; Abbaspour, A ; Fotuhi-Firuzabad, M ; Hajipour, E ; Sharif University of Technology
    Presence of energy hubs in the future vision of energy networks creates a great opportunity for system planners and operators to move towards more efficient systems. The role of energy hubs as the intermediate in multi-carrier energy (MCE) systems calls for a generic framework to study the new upcoming technical as well as economical effects on the system performance. In response, this paper attempts to develop a general optimization and modeling framework for coupled power flow studies on different energy infrastructures. This, as a large-scale nonlinear problem, is approached through a robust optimization technique, i.e., multi-agent genetic algorithm (MAGA). The proposed procedure... 

    Redundancy allocation problem of a system with three-state components: A genetic algorithm

    , Article International Journal of Engineering, Transactions B: Applications ; Vol. 27, Issue. 11 , 2014 , pp. 1663-1672 ; ISSN: 1663-1672 Pourkarim Guilani, P ; Sharifi, M ; Niaki, S. T. A ; Zaretalab, A ; Sharif University of Technology
    The redundancy allocation is one of the most important and useful problems in system optimization, especially in electrical and mechanical systems. The object of this problem is to maximize system reliability or availability within a minimum operation cost. Many works have been proposed in this area so far to draw the problem near to real-world situations. While in classic models the system components are assumed to have two states of working and failed, in this paper, parallel components of serial sub-systems are considered to work in three states, each with a certain performance rate. The component states are classified into two working states of working with full performance and working... 

    A platform for optimisation in distributed manufacturing enterprises based on cloud manufacturing paradigm

    , Article International Journal of Computer Integrated Manufacturing ; Vol. 27, Issue 11 , 2 November , 2014 , pp. 1031-1054 ; ISSN: 0951192X Fatahi Valilai, O ; Houshmand, M ; Sharif University of Technology
    The synergy of fundamental factors like changes in governmental policies, global expansions of the manufacturing industries and improvements in technology related to reliability of manufacturing information flow have created the global manufacturing revolution in the first years of the twenty-first century. Although the concept of global manufacturing enterprise has created benefits and opportunities for todays manufacturing enterprises, it has enforced enterprises to endure costs to adopt the global manufacturing solutions. Besides, considering the researches aimed to enable the global manufacturing paradigm, there is still a need for efficient solutions to fulfil the global product... 

    Optimal strategies for price, warranty length, and production rate of a new product with learning production cost

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 2247-2258 ; 10263098 (ISSN) Faridimehr, S ; Niaki, S. T. A ; Sharif University of Technology
    This study investigates optimal strategies for price, warranty length, and production rate of a new product in which both static markets for non-durable and dynamic markets for durable products are involved. The mathematical model incorporates both the demand and the cost functions including production, warranty length, and inventory costs. Using the maximum principle approach, the optimal strategies and interactions among price, warranty length, and production rate in both markets are analyzed using some propositions. The analysis shows that to maximize profits in all cases, the price, the warranty length, and the production rate all must go up simultaneously, or one of them must increase... 

    Optimal and suboptimal sensing sequences in multiuser cognitive radio networks

    , Article 2012 6th International Symposium on Telecommunications, IST 2012, 6 November 2012 through 8 November 2012 ; November , 2012 , Pages 243-248 ; 9781467320733 (ISBN) Shokri Ghadikolaei, H ; Nasiri Kenari, M ; Sharif University of Technology
    Designing proper spectrum decision schemes for cognitive radios (CRs) improves spectral usage efficiency as well as CR network throughput. One of the key effecting factors of the CR network throughput is the spectrum sensing sequences of the secondary users (SUs). In this paper, the SUs throughput maximization through appropriately selecting the sensing sequences of the SUs, called sensing matrix (SM), is investigated. More specifically, first the average throughput of the CR network is evaluated for a given SM in the case of error-free channel sensing. Then, an optimization problem is formulated with the aim to maximize the network throughput by finding the optimal SM. In order to avoid... 

    Using partial tag comparison in low-power snoop-based chip multiprocessors

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 19 June 2010 through 23 June 2010 ; Volume 6161 LNCS , June , 2012 , Pages 211-221 ; 03029743 (ISSN) ; 9783642243219 (ISBN) Shafiee, A ; Shahidi, N ; Baniasadi, A ; Sharif University of Technology
    In this work we introduce power optimizations relying on partial tag comparison (PTC) in snoop-based chip multiprocessors. Our optimizations rely on the observation that detecting tag mismatches in a snoop-based chip multiprocessor does not require aggressively processing the entire tag. In fact, a high percentage of cache mismatches could be detected by utilizing a small subset but highly informative portion of the tag bits. Based on this, we introduce a source-based snoop filtering mechanism referred to as S-PTC. In S-PTC possible remote tag mismatches are detected prior to sending the request. We reduce power as S-PTC prevents sending unnecessary snoops and avoids unessential tag lookups... 

    One for one period policy for perishable inventory

    , Article Computers and Industrial Engineering ; Volume 79 , January , 2015 , Pages 10-17 ; 03608352 (ISSN) Mahmoodi, A ; Haji, A ; Haji, R ; Sharif University of Technology
    Elsevier Ltd  2015
    Recently, for zero ordering cost a new ordering policy named (1, T), in which the time interval between two consecutive orders and the value of the order size are both constant, have been developed for nonperishable products. In this paper, the (1, T) policy is developed for perishable products. Using an analogy among this inventory model, a queueing model with impatient customers, and a finite dam model, the long-run average total cost function of the inventory system is derived. It is observed that the total cost rate is independent from the lead time as is for nonperishable products. Since analyzing the convexity of the model is extremely complicated, a proposition is proved to define a... 

    A weighting scheme and a model for computing alternative pareto optimal solutions of multi objective linear programming problems

    , Article IEEM2010 - IEEE International Conference on Industrial Engineering and Engineering Management, 7 December 2010 through 10 December 2010 ; 2010 , Pages 2110-2115 ; 9781424485031 (ISBN) Maali, Y ; Mahdavi Amiri, N ; Sharif University of Technology
    A new weighted order scheme is presented for finding alternative Pareto optimal solution of multi objective linear programming problems. In developing the weighted scheme, a big M model is proposed. We establish some properties of the ordering scheme and the proposed model and show how to determine proper values of the parameter M. Illustrative examples are worked out to show the effectiveness of the proposed approach and the competitiveness of the obtained solutions as compared to the ones obtained by the weighted maxmin and the weighted aggregation methods  

    New solutions of LR fuzzy linear systems using ranking functions and ABS algorithms

    , Article Applied Mathematical Modelling ; Volume 34, Issue 11 , November , 2010 , Pages 3363-3375 ; 0307904X (ISSN) Ghanbari, R ; Mahdavi Amiri, N ; Sharif University of Technology
    We propose an approach for computing the general compromised solution of an LR fuzzy linear system by use of a ranking function when the coefficient matrix is a crisp m×n matrix. The solution is so that mean values of a compromised solution satisfies the corresponding crisp linear system. We show that if the corresponding crisp system is incompatible, then the fuzzy linear system lacks any solution. Otherwise, we solve a constrained least squares problem to compute a compromised solution. If the optimal value of the constrained least squares problem is zero, then we obtain the LR solution, namely the exact solution, of the system with respect to a ranking function. On the other hand, if the...