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problem-solving
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Optimal planning of equipment maintenance and replacement on a variable horizon
, Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 185-192 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
In maintenance and replacement planning of an industry, the purchasing of new equipment on the market with some kind of technological improvement over existing equipment should be taken into account. Because of operating cost, ordinary and preventive maintenance expenses may be lower, production rate may be higher and the quality of output may be better, etc. The industry to be considered in this paper is the mining industry and the replaced equipment is the mine shovel. It is assumed that, at most, one new shovel can be purchased before the mine is exhausted. It is possible that the mine is given up before exhausted, because of the disadvantage of the expense and loss of the salvage value...
Periodic solution of a certain non-linear third order differential equation
, Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 181-184 ; 10263098 (ISSN) ; Shadman, D ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
In this paper, the third order differential equation x‴ + ψ (x′)x″ + (κ2 +ø (x))x′ + f(t, x = e(t) is considered. Under certain conditions on the functions appearing in the differential equation, the existence of periodic solutions is proved. Similar problems have been treated by authors in [4,6,7]. However, the method employed here is used by Reissig [1] and the results obtained are, in fact, a generalization of those in [1-3]. The conditions imposed on the nonlinear terms do not require the ultimate boundedness of all solutions. © Sharif University of Technology
What's decidable about availability languages?
, Article 35th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science, FSTTCS 2015, 16 December 2015 through 18 December 2015 ; Volume 45 , 2015 , Pages 192-205 ; 18688969 (ISSN) ; 9783939897972 (ISBN) ; Atig, M. F ; Meyer, R ; Salehi, M. S ; Harsha P ; Ramalingam G ; Sharif University of Technology
Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
2015
Abstract
We study here the algorithmic analysis of systems modeled in terms of availability languages. Our first main result is a positive answer to the emptiness problem: it is decidable whether a given availability language contains a word. The key idea is an inductive construction that replaces availability languages with Parikh-equivalent regular languages. As a second contribution, we solve the intersection problem modulo bounded languages: given availability languages and a bounded language, it is decidable whether the intersection of the former contains a word from the bounded language. We show that the problem is NP-complete. The idea is to reduce to satisfiability of existential Presburger...
A weighted K-means clustering approach to solve the redundancy allocation problem of systems having components with different failures
, Article Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability ; Volume 233, Issue 6 , 2019 , Pages 925-942 ; 1748006X (ISSN) ; Akhavan Niak, S. T ; Miriha, S. M ; Ghare Hasanluo, M ; Javanmard, S ; Sharif University of Technology
SAGE Publications Ltd
2019
Abstract
A nonlinear integer programming model is developed in this article to solve redundancy allocation problems with multiple components having different failure rates in the series–parallel configuration using an active strategy. The main objective of this research is to select the number and the type of each component in subsystems so as the reliability of the system under certain constraints is maximized. To this aim, a weighted K-means clustering method is proposed, in which the analytical network process is employed to assign weights to the components of each cluster. As the proposed model belongs to the class of nondeterministic polynomial-time hardness problems, precise solution methods...
A Boolean network control algorithm guided by forward dynamic programming
, Article PLoS ONE ; Volume 14, Issue 5 , 2019 ; 19326203 (ISSN) ; Goliaei, S ; Foroughmand Araabi, M. H ; Sharif University of Technology
Public Library of Science
2019
Abstract
Control problem in a biological system is the problem of finding an interventional policy for changing the state of the biological system from an undesirable state, e.g. disease, into a desirable healthy state. Boolean networks are utilized as a mathematical model for gene regulatory networks. This paper provides an algorithm to solve the control problem in Boolean networks. The proposed algorithm is implemented and applied on two biological systems: T-cell receptor network and Drosophila melanogaster network. Results show that the proposed algorithm works faster in solving the control problem over these networks, while having similar accuracy, in comparison to previous exact methods. Source...
Algorithm for equilibrium transit assignment problem
, Article Transportation Research Record ; Issue 1923 , 2005 , Pages 227-235 ; 03611981 (ISSN) ; Aashtiani, H. Z ; Sharif University of Technology
National Research Council
2005
Abstract
Transit assignment is an important problem in the literature of transportation. Almost all competitive algorithms in this area are strategy based. For uncongested transit networks, the problem may be formulated into an optimization problem for which good solution algorithms exist. A variational inequality formulation of the problem with several solution methods is also presented in the literature for congested networks. This paper is devoted to solving a transit assignment problem based on complementarity formulation using path flows. The solution algorithm exploits the three concepts of decomposition, path generation, and linearization. The procedure has been applied on a large-scale...
The effect of added mass fluctuation on heave vibration of TLP
, Article International Journal of Engineering, Transactions B: Applications ; Volume 18, Issue 3 , 2005 , Pages 219-228 ; 1728-144X (ISSN) ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
Materials and Energy Research Center
2005
Abstract
The resulting motion in waves can be considered as a superposition of the motion of the body in still water and the forces on the restrained body. In this study the effect of added mass fluctuation on vertical vibration of TLP in the case of vibration in still water for both free and forced vibration subjected to axial load at the top of the leg is presented. This effect is more important when the amplitude of vibration is large. Also this is important in fatigue life study of tethers. The structural model used here is very simple. Perturbation method is used to formulate and solve the problem. First and second order perturbations arc used to solve the free and forced vibration respectively
Resource investment problem with discounted cash flows
, Article International Journal of Engineering, Transactions B: Applications ; Volume 18, Issue 1 , 2005 , Pages 53-64 ; 1728-144X (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
Materials and Energy Research Center
2005
Abstract
A resource investment problem is a project-scheduling problem in which the availability levels of the resources are considered as decision variables and the goal is to find a schedule, and resource requirement levels, such that some objective function optimizes. In this paper, we consider a resource investment problem in which the goal is to maximize the net present value of the project cash flows. We call this problem as Resource Investment Problem with Discounted Cash Flows (RIPDCF) and we develop a heuristic method to solve it. Results of several numerical examples show that the proposed method performs relatively well
Financially embedded facility location decisions on designing a supply chain structure: A case study
, Article Systems Engineering ; Volume 21, Issue 6 , 2018 , Pages 520-533 ; 10981241 (ISSN) ; Jalali, S ; Akhavan Niaki, S. T ; Sharif University of Technology
John Wiley and Sons Inc
2018
Abstract
The facility location problem and its related financial issues have a significant impact on the configuration of a supply chain structure (SCS). Although affording the setup cost of facilities requires a huge financial investment, a meticulous planning to recoup it has been neglected by an overwhelming majority of previous studies. To fill this gap, an economical investment plan of facilities is determined by striking a trade-off between the contribution of the stockholders’ capital and the loan arrangement. In the context of a multiperiod three-echelon SCS, the model also determines the optimum location of plants and the best supply and distribution patterns. The model maximizes the fill...
Predictive directional compensator for systems with input constraints
, Article ISA Transactions ; Volume 45, Issue 3 , 2006 , Pages 393-405 ; 00190578 (ISSN) ; Aalam, N ; Sharif University of Technology
ISA - Instrumentation, Systems, and Automation Society
2006
Abstract
Nonlinearity caused by actuator constraint plays a destructive role in the overall performance of a control system. A model predictive controller can handle the problem by implementing a constrained optimization algorithm. Due to the iterative nature of the solution, however, this requires high computation power. In the present work we propose a new method to approach the problem by separating the constraint handling from the predictive control job. The input constraint effects are dealt with in a newly defined component called a predictive directional compensator, which works based on the directionality and predictive concepts. Through implementation of the proposed method, the...
Critic learning in multi agent credit assignment problem
, Article Journal of Intelligent and Fuzzy Systems ; Volume 30, Issue 6 , 2016 , Pages 3465-3480 ; 10641246 (ISSN) ; Beigy, H ; Sharif University of Technology
IOS Press
2016
Abstract
Multi-agent systems can be seen as an apparatus for testing the performance of real distributed systems. One problem encountered in multi-agent systems with the learning capability is credit assignment. This paper presents two methods for solving this problem. The first method assigns credit to the agents according to the history of the interaction while the second method assigns credit to the agents according to the knowledge of agents, and thus the shares of the agents are extracted from the feedback of the environment. The computer experiments show that critic learning has a positive impact in credit assignment problem
A memetic algorithm for flexible flow shop sequence dependent group scheduling problem
, Article IIE Annual Conference and Expo 2010 Proceedings, 5 June 2010 through 9 June 2010 ; 2010 ; Salmasi, N ; Logendran, R ; Sharif University of Technology
Institute of Industrial Engineers
2010
Abstract
The focus of this research is on the flexible flow shop sequence dependent group scheduling problem (FFSDGS) with minimization of makespan as the criterion (FFm|fmls, Splk|Cmax). Since the research problem is shown to be NP-hard, a meta-heuristic algorithms based on memetic algorithm is developed to efficiently solve the problem. The performance of the proposed algorithm is compared with the only available meta-heuristic algorithm in the literature, i.e., tabu search (TS). The comparison is performed based on paired t-test and the result shows that the memetic algorithm has a superior performance compared to the TS
Developing a two-stage procedure for Estimating Origin-Destination matrix based on routes and traffic volumes
, Article IEOM 2015 - 5th International Conference on Industrial Engineering and Operations Management, Proceeding, 3 March 2015 through 5 March 2015 ; 2015 ; 9781479960651 (ISBN) ; Mahmoudabadi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Estimating Origin-Destination matrix, named O-D matrix or ODM, is an important issue in transportation planning. Due to need to survey movements on the network, estimating ODM is usually considered as a high-cost measure in transportation planning. In this research work, a two-stage procedure, including solving routing problem and minimizing the difference between observed and estimated traffic volumes on the network, has been developed to estimate the O-D matrix elements. At the first stage, routing problem is solved to determine paths while in the second stage an absolute error function has been defined to determine the number of trips from each origin to destination pairs. The procedure...
A simple geometrical approach for deinterleaving radar pulse trains
, Article Proceedings - 2016 UKSim-AMSS 18th International Conference on Computer Modelling and Simulation, UKSim 2016, 6 April 2016 through 8 April 2016 ; 2016 , Pages 172-177 ; 9781509008889 (ISBN) ; Pezeshk, A. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Some periodic and quasi-periodic pulse trains are emitted by different sources in the environment and a number of sensors receive them through a single channel simultaneously. We are often interested in separating these pulse trains for source identification at sensors. This identification process is termed as deinterleaving pulse trains. Deinterleaving pulse trains has wide applications in communications, radar systems, neural systems, biomedical engineering, and so on. This paper studies the deinterleaving problem with the assumption that both sources and sensors are fixed. In this study, the problem of deinterleaving pulse trains is modeled as a blind source separation (BSS) problem. To...
Secure overlay routing using key pre-distribution: A linear distance optimization approach
, Article IEEE Transactions on Mobile Computing ; Volume 15, Issue 9 , 2016 , Pages 2333-2344 ; 15361233 (ISSN) ; Yousefi'zadeh, H ; Movaghar, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Key pre-distribution algorithms have recently emerged as efficient alternatives of key management in today's secure communications landscape. Secure routing techniques using key pre-distribution algorithms require special algorithms capable of finding optimal secure overlay paths. To the best of our knowledge, the literature of key pre-distribution systems is still facing a major void in proposing optimal overlay routing algorithms. In the literature work, traditional routing algorithms are typically used twice to find a NETWORK layer path from the source node to the destination and then to find required cryptographic paths. In this paper, we model the problem of secure routing using...
A novel stochastic framework based on cloud theory and θ-modified bat algorithm to solve the distribution feeder reconfiguration
, Article IEEE Transactions on Smart Grid ; Volume 7, Issue 2 , 2016 , Pages 740-750 ; 19493053 (ISSN) ; Niknam, T ; Fotuhi Firuzabad, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Distribution feeder reconfiguration (DFR) is a precious operation strategy that can improve the system from different aspects including total cost, reliability, and power quality. Nevertheless, the high complexity of the new smart grids has resulted in much uncertainty in the DFR problem that necessities the use of a sufficient stochastic framework to deal with them. In this way, this paper proposes a new stochastic framework based on cloud theory to account the uncertainties associated with multiobjective DFR problem from the reliability point of view. Cloud theory is constructed based on fuzzy theory and probability idea. In comparison with the Monte Carlo simulation method, cloud models...
Interference efficiency: A new concept to analyze the performance of cognitive radio networks
, Article 2017 IEEE International Conference on Communications Workshops, ICC Workshops 2017, 21 May 2017 through 25 May 2017 ; 2017 , Pages 1105-1110 ; 9781509015252 (ISBN) ; Musavian, L ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, we develop and analyze a novel performance metric, called interference efficiency (IE), that shows the number of transmitted bits per unit of interference energy imposed on the primary users (PUs) in an underlay cognitive radio network (CRN). Specifically, we develop a framework to maximize the IE of a CRN with multiple secondary users (SUs) while satisfying target constraints on the average interference power on PU receiver, total SUs transmit power and minimum ergodic rate for the SUs. In doing so, we formulate a multiobjective optimization problem (MOP), that aims to achieve the maximum ergodic sum rate of multiple SUs and the minimum average interference power on the...
Effective cache bank placement for GPUs
, Article 20th Design, Automation and Test in Europe, DATE 2017, 27 March 2017 through 31 March 2017 ; 2017 , Pages 31-36 ; 9783981537093 (ISBN) ; Mirhosseini, A ; Roozkhosh, S ; Bakhishi, H ; Sarbazi Azad, H ; ACM Special Interest Group on Design Automation (ACM SIGDA); Electronic System Design Alliance (ESDA); et al.; European Design and Automation Association (EDAA); European Electronic Chips and Systems Design Initiative (ECSI); IEEE Council on Electronic Design Automation (CEDA) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
The placement of the Last Level Cache (LLC) banks in the GPU on-chip network can significantly affect the performance of memory-intensive workloads. In this paper, we attempt to offer a placement methodology for the LLC banks to maximize the performance of the on-chip network connecting the LLC banks to the streaming multiprocessors in GPUs. We argue that an efficient placement needs to be derived based on a novel metric that considers the latency hiding capability of the GPUs through thread level parallelism. To this end, we propose a throughput aware metric, called Effective Latency Impact (ELI). Moreover, we define an optimization problem to formulate our placement approach based on the...
Improved routing and spectrum assignment formulations for optical OFDM networks
, Article 2016 8th International Symposium on Telecommunications, IST 2016, 27 September 2016 through 29 September 2016 ; 2017 , Pages 34-39 ; 9781509034345 (ISBN) ; Pakravan, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Efficient resource allocation in OFDM-based optical networks is directly affected by definition and formulations of Routing and Spectrum Assignment (RSA) problem. In this paper, we propose new Binary Linear Programming (BLP) formulations for the RSA problem that provide more efficient resource allocation in comparison with previous formulations. Unlike the conventional formulations that mainly aim at minimizing used spectrum slots, our formulations simultaneously aim at defragmentation and minimization of the assigned spectrum slots. We show contiguity constraint of the conventional formulations may incorrectly make a feasible solution unattainable. To solve this problem, we remove the...
WiP: Floating xy-yx: An efficient thermal management routing algorithm for 3d nocs
, Article 16th IEEE International Conference on Dependable, Autonomic and Secure Computing, IEEE 16th International Conference on Pervasive Intelligence and Computing, IEEE 4th International Conference on Big Data Intelligence and Computing and IEEE 3rd Cyber Science and Technology Congress, DASC-PICom-DataCom-CyberSciTec 2018, 12 August 2018 through 15 August 2018 ; 2018 , Pages 730-735 ; 9781538675182 (ISBN) ; Shirmohammadi, Z ; Rohbani, N ; Farbeh, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
3D Network-on-Chips (3D NoCs) have higher scalability, higher throughput, and lower power consumption over 2D NoCs. However, the reliability of data transfer in 3D NoCs is seriously threatened by thermal problems. This is due to poor heat dissipation, inappropriate traffic distribution, and cooling restriction for layers away of the chip heat-sink in 3D NoCs. To solve this problem, this paper proposes an efficient deadlock-free and traffic-And thermal-Aware routing algorithm, called Floating XY-YX. The main idea behind Floating XY-YX routing algorithm is twofold: 1) to use XY and YX routing algorithms in consecutive layers in dessicate form, and 2) to evenly load the traffic, which is...