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heuristic-methods
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Optimal distribution network reconfiguration considering power quality issues
, Article 2017 IEEE Smart Grid Conference, SGC 2017, 20 December 2017 through 21 December 2017 ; Volume 2018-January , March , 2018 , Pages 1-6 ; 9781538642795 (ISBN) ; Gharebaghi, S ; Safdarian, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Distribution network reconfiguration as a technique for reducing network losses and enhancing voltage profile has attracted attention of many researchers. In spite of impacts network reconfiguration can have on power quality indices, the potentials have not been studied enough. To fill the gap, this paper presents a method to determine optimum network configuration considering voltage profile, network losses, and total harmonic distortion (THD). The proposed method also vouches for radial structure of the network, supplying all loads, and maintaining voltages and currents within allowable bounds. Since network reconfiguration problem is a combinatorial optimization problem, a meta-heuristic...
Solving Location Problem for Vehicle Identification Sensors to Observe or Estimate Path Flows in Larg-Scale Networks
, M.Sc. Thesis Sharif University of Technology ; Shafahi, Yousef (Supervisor)
Abstract
Origin-Destination (OD) demand is one of the important requirements in transportation planning. Estimating OD demand could be an expensive and time consuming procedure. These days using vehicle identification sensors for OD estimation has become very common because of its low cost and high accuracy. In this study, we focus on solving location problems of these sensors with the aim of observe and estimate path flows. These problems have only been solved for small-scale networks until recently due to being computationally expensive. These years two basic models have been introduced : one, without considering time of vehicle ID detection and one, with considering that information. In this...
Design and Dynamics Control of Six Degree of Freedom Microrobot
, M.Sc. Thesis Sharif University of Technology ; Sayyaadi, Hassan (Supervisor)
Abstract
The field of microrobotics has seen tremendous advances in recent years. Potential high impact applications of untethered microrobots such as minimally invasive diagnosis and treatment inside the human body, biological studies or bioengineering, microfluidics, desktop micromanufacturing, and mobile sensor networks for environmental and health monitoring are reported. However, There are significant challenges in microrobotic technology, including energy resources, control systems, reliability and safety, design and manufacturing of micromotors and localization. In this work, overall size scale being micron scale is emphasized where mobile robots able to fit in spaces smaller than a millimeter...
Plastic Analysis of Two Dimensional Frames using Ant Colony Algorithms
, M.Sc. Thesis Sharif University of Technology ; Jahanshahi, Mohsen (Supervisor)
Abstract
In previous decades, easy access to material and low cost human power allow the product process to be performed in a preferred way. The limit in amount of material, economy, and the efficiency of the model has not been influential like these days. Today, the effective use of material and consideration of an economic model have great importance. It is obvious that a process of designing implies optimizing which the range of its using is also continuing in many engineering sciences. Many optimization issues contain discrete nature. Many of searching spaces that we encounter in the real world applications are not necessarily continuous as a condition which has crucial importance for classic...
A Heuristic Method for Solving VRP Problem with Customer Loyalty
, M.Sc. Thesis Sharif University of Technology ; Fazli, Mohammad Amin (Supervisor)
Abstract
This paper is concerned with the Vehicle Routing Problem (VRP) in a fleet with customer loyalty. In this work, we consider priority for customers according to their loyalty and try to declare an objective function which concerns customers' satisfaction along other normal VRP objectives like route optimization
A heuristic approach to the realization of the wide-band optical diode effect in photonic crystal waveguides
, Article Journal of Optics (United Kingdom) ; Volume 15, Issue 7 , June , 2013 ; 20408978 (ISSN) ; Rezaei, M ; Fard, A. P ; Mehrany, K ; Sharif University of Technology
2013
Abstract
In this paper a highly efficient optical diode is demonstrated in photonic crystal waveguides with broken spatial symmetry. The structure is made of isotropic linear materials and does not need high power optical beams or strong magnetic fields. While the proposed structure shows almost complete light transmission (>99%) in one direction, it blocks light transmission in the opposite direction. This unidirectional transmission is retained within a wide range of frequencies (>4% of central frequency). In order to achieve an optical diode effect, the optical mode of the waveguide is manipulated by designing an ultra-compact mode converter and an efficient mode filter. The dimensions of the...
A swarm based method for solving transit network design problem
, Article Australasian Transport Research Forum, ATRF 2013 - Proceedings ; 2013 ; Massah, S ; Kermanshahi, S ; Sharif University of Technology
Australasian Transport Research Forum
2013
Abstract
In this study, a Discrete Particle Swarm Optimization (DPSO) algorithm is assimilated to solve the Transit Network Design Problem (TNDP). First, A Mixed Integer Model is developed for the TNDP. The solution methodology utilized here is made of two major elements. A route generation module is firstly developed to generate all the feasible transit lines. Through the second part, a DPSO algorithm is utilized to select the optimal set of lines from the constructed ones. The objective function is to maximize coverage index while satisfying the operator cost upper level constraints. The efficacy and accuracy of the implemented algorithms is compared with ones obtained by an enumeration process as...
A hybrid Nelder-Mead simplex and PSO approach on economic and economic-statistical designs of MEWMA control charts
, Article International Journal of Advanced Manufacturing Technology ; Volume 65, Issue 9-12 , 2013 , Pages 1339-1348 ; 02683768 (ISSN) ; Noorossana, R ; Niaki, S. T. A ; Ershadi, M. J ; Sharif University of Technology
2013
Abstract
Economic design of a control chart involves determining its basic parameters such that a cost function is minimized. This design when statistical performance measures are also considered is referred to as the economic-statistical design. In this paper, a simplex-based Nelder-Mead algorithm is used in combination with a particle swarm meta-heuristic procedure to solve both the economic and economic-statistical designs of a MEWMA control chart. The application results on extensive simulation experiments show that the particle swarm can lead the Nelder-Mead algorithm to better results. Furthermore, a comparative study is performed on the performances of three different algorithms of the...
Probabilistic heuristics for hierarchical web data clustering
, Article Computational Intelligence ; Volume 28, Issue 2 , 2012 , Pages 209-233 ; 08247935 (ISSN) ; Haghir Chehreghani, M ; Abolhassani, H ; Sharif University of Technology
Abstract
Clustering Web data is one important technique for extracting knowledge from the Web. In this paper, a novel method is presented to facilitate the clustering. The method determines the appropriate number of clusters and provides suitable representatives for each cluster by inference from a Bayesian network. Furthermore, by means of the Bayesian network, the contents of the Web pages are converted into vectors of lower dimensions. The method is also extended for hierarchical clustering, and a useful heuristic is developed to select a good hierarchy. The experimental results show that the clusters produced benefit from high quality
Pool and accuracy based stream classification: A new ensemble algorithm on data stream classification using recurring concepts detection
, Article Proceedings - IEEE International Conference on Data Mining, ICDM, 11 December 2011 through 11 December 2011, Vancouver, BC ; 2011 , Pages 588-595 ; 15504786 (ISSN) ; 9780769544090 (ISBN) ; Ahmadi, Z ; Beigy, H ; Sharif University of Technology
Abstract
One of the main challenges of data streams is the occurrence of concept drift. Concept drift is the change of target (or feature) distribution, and can occur in different types: sudden, gradual, incremental or recurring. Because of the forgetting mechanism existing in the data stream learning process, recurring concepts has received much attention recently, and became a challenging problem. This paper tries to exploit the existence of recurring concepts in the learning process and improve the classification of data streams. It uses a pool of concepts to detect the reoccurrence of a concept using two methods: a Bayesian, and a heuristic method. Two approaches are used in the classification...
Optimizing capacity, pricing and location decisions on a congested network with balking
, Article Mathematical Methods of Operations Research ; Volume 74, Issue 2 , October , 2011 , Pages 233-255 ; 14322994 (ISSN) ; Babri, S ; Berman, O ; Shavandi, H ; Sharif University of Technology
2011
Abstract
In this paper, we consider the problem of making simultaneous decisions on the location, service rate (capacity) and the price of providing service for facilities on a network. We assume that the demand for service from each node of the network follows a Poisson process. The demand is assumed to depend on both price and distance. All facilities are assumed to charge the same price and customers wishing to obtain service choose a facility according to a Multinomial Logit function. Upon arrival to a facility, customers may join the system after observing the number of people in the queue. Service time at each facility is assumed to be exponentially distributed. We first present several...
Influence maximization of informed agents in social networks
, Article Applied Mathematics and Computation ; Volume 254 , 2015 , Pages 229-239 ; 00963003 (ISSN) ; Jalili, M ; Sharif University of Technology
Abstract
Control of collective behavior is one of the most desirable goals in many applications related to social networks analysis and mining. In this work we propose a simple yet effective algorithm to control opinion formation in complex networks. We aim at finding the best spreaders whose connection to a reasonable number of informed agents results in the best performance. We consider an extended version of the bounded confidence model in which the uncertainty of each agent is adaptively controlled by the network. A number of informed agents with the desired opinion value is added to the network and create links with other agents such that large portion of the network follows their opinions. We...
Optimal pinning controllability of complex networks: Dependence on network structure
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 91, Issue 1 , January , 2015 ; 15393755 (ISSN) ; Askari Sichani, O ; Yu, X ; Sharif University of Technology
American Physical Society
2015
Abstract
Controlling networked structures has many applications in science and engineering. In this paper, we consider the problem of pinning control (pinning the dynamics into the reference state), and optimally placing the driver nodes, i.e., the nodes to which the control signal is fed. Considering the local controllability concept, a metric based on the eigenvalues of the Laplacian matrix is taken into account as a measure of controllability. We show that the proposed optimal placement strategy considerably outperforms heuristic methods including choosing hub nodes with high degree or betweenness centrality as drivers. We also study properties of optimal drivers in terms of various centrality...
Yield-driven design-time task scheduling techniques for multi-processor system on chips under process variation: A comparative study
, Article IET Computers and Digital Techniques ; Volume 9, Issue 4 , 2015 , Pages 221-229 ; 17518601 (ISSN) ; Assare, O ; Rahmati, N ; Boroumand, A ; Barati, S ; Goudarzi, M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
Process variation has already emerged as a major concern in design of multi-processor system on chips (MPSoC). In recent years, there have been several attempts to bring variability awareness into the task scheduling process of embedded MPSoCs to improve performance yield. This study attempts to provide a comparative study of the current variation-aware design-time task and communication scheduling techniques that target embedded MPSoCs. To this end, the authors first use a sign-off variability modelling framework to accurately estimate the frequency distribution of MPSoC components. The task scheduling methods are then compared in terms of both the quality of the final solution and the...
Active constrained fuzzy clustering: A multiple kernels learning approach
, Article Pattern Recognition ; Volume 48, Issue 3 , March , 2015 , Pages 953-967 ; 00313203 (ISSN) ; Beigy, H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
In this paper, we address the problem of constrained clustering along with active selection of clustering constraints in a unified framework. To this aim, we extend the improved possibilistic c-Means algorithm (IPCM) with multiple kernels learning setting under supervision of side information. By incorporating multiple kernels, the limitation of improved possibilistic c-means to spherical clusters is addressed by mapping non-linear separable data to appropriate feature space. The proposed method is immune to inefficient kernels or irrelevant features by automatically adjusting the weight of kernels. Moreover, extending IPCM to incorporate constraints, its strong robustness and fast...
Heuristic algorithm for periodic clock optimisation in scheduling-based latency-insensitive design
, Article IET Computers and Digital Techniques ; Volume 9, Issue 3 , May , 2015 , Pages 165-174 ; 17518601 (ISSN) ; Hessabi, S ; Goudarzi, M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
Delay in communication wires causes design iterations in system-on-chip. Latency-insensitive design copes with this issue by encapsulating each core in a shell wrapper and inserting buffers in the wires to separate the design of core from that of communication wires. Scheduling-based latency-insensitive protocol is a methodology which employs shift registers for periodic clock gating of blocks instead of the shell wrappers. In many cases, the bit sequences inside the shift registers are too long and therefore consume a large area. This study presents a heuristic algorithm that optimises the bit sequences and produces them with shorter lengths compared with the existing method. The algorithm...
Total flow time minimization in a flowshop sequence-dependent group scheduling problem
, Article Computers and Operations Research ; Volume 37, Issue 1 , 2010 , Pages 199-212 ; 03050548 (ISSN) ; Logendran, R ; Skandari, M. R ; Sharif University of Technology
Abstract
We have developed a mathematical programming model for minimizing total flow time of the flow shop sequence dependent group scheduling (FSDGS) problem, typically classified as Fm|fmls, Splk, prmu|∑Cj. As the problem is shown to be strongly NP-hard, a tabu search (TS) algorithm as well as a hybrid ant colony optimization (HACO) algorithm have been developed to heuristically solve the problem. A lower bounding (LB) method based on the Branch-and-Price algorithm is also developed to evaluate the quality of the metaheuristic algorithms. In order to compare the performance of metaheuristic algorithms, random test problems, ranging in size from small, medium, to large are created and solved by...
Optimising multi-item economic production quantity model with trapezoidal fuzzy demand and backordering: Two tuned meta-heuristics
, Article European Journal of Industrial Engineering ; Volume 10, Issue 2 , 2016 , Pages 170-195 ; 17515254 (ISSN) ; Niaki, S. T. A ; Malekian, M. R ; Sadeghi, S ; Sharif University of Technology
Inderscience Enterprises Ltd
2016
Abstract
In this paper, a multi-item economic production quantity model with fuzzy demand is developed in which shortages are backordered and the warehouse space is limited. While the demand is assumed to be a trapezoidal fuzzy number, the centroid defuzzification method is used to defuzzify fuzzy output functions. The Lagrangian relaxation procedure is first employed to solve the problem. Then, the model is extended to a constrained fuzzy integer nonlinear programming, in order to suit real-world situations. As the extended model cannot be solved in a reasonable time using exact methods, two meta-heuristic algorithms, named the genetic algorithm (GA) and the particle swarm optimisation (PSO) each...
Applying portfolio theory-based modified ABC to electricity generation mix
, Article International Journal of Electrical Power and Energy Systems ; Volume 80 , 2016 , Pages 356-362 ; 01420615 (ISSN) ; Mozafari, B ; Ranjbar, A. M ; Soleymani, S ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Portfolio theory has found its model in numerous engineering applications for optimizing the electrical generation mix of an electricity area. However, to have better performance of this theory, this paper presents a new heuristic method as known modified artificial bee colony (MABC) to portfolio optimization problem. Moreover, we consider both dis-patchable and non-dis-patchable constrains variables and energy sources. Note that the proposed MABC method uses a Chaotic Local Search (CLS) to enhance the self searching ability of the original ABC algorithm. Resulting, in this paper a portfolio theory-based MABC model that explicitly distinguishes between electricity generation (energy),...
On the efficiency of artificial neural networks for plastic analysis of planar frames in comparison with genetic algorithms and ant colony systems
, Article Neural Computing and Applications ; 2016 , Pages 1-19 ; 09410643 (ISSN) ; Maleki, E ; Ghiami, A ; Sharif University of Technology
Springer-Verlag London Ltd
Abstract
The investigation of plastic behavior and determining the collapse load factors are the important ingredients of every kinematical method that is employed for plastic analysis and design of frames. The determination of collapse load factors depends on many effective parameters such as the length of bays, height of stories, types of loads and plastic moments of individual members. As the number of bays and stories increases, the parameters that have to be considered make the analysis a complex and tedious task. In such a situation, the role of algorithms that can help to compute an approximate collapse load factor in a reasonable time span becomes more and more crucial. Due to their...