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    Streaming algorithms for line simplification

    , Article Discrete and Computational Geometry ; Volume 43, Issue 3 , 2010 , Pages 497-515 ; 01795376 (ISSN) Abam, M. A ; de Berg, M ; Hachenberger, P ; Zarei, A ; Sharif University of Technology
    We study the following variant of the well-known line-simplification problem: we are getting a (possibly infinite) sequence of points p0,p1,p2,... in the plane defining a polygonal path, and as we receive the points, we wish to maintain a simplification of the path seen so far. We study this problem in a streaming setting, where we only have a limited amount of storage, so that we cannot store all the points. We analyze the competitive ratio of our algorithms, allowing resource augmentation: we let our algorithm maintain a simplification with 2k (internal) points and compare the error of our simplification to the error of the optimal simplification with k points. We obtain the algorithms... 

    Analytical solution for the free vibration analysis of delaminated timoshenko beams

    , Article The Scientific World Journal ; Volume 2014 , 2014 ; ISSN: 1537744X Jafari Talookolaei, R. A ; Abedi, M ; Sharif University of Technology
    This work presents a method to find the exact solutions for the free vibration analysis of a delaminated beam based on the Timoshenko type with different boundary conditions. The solutions are obtained by the method of Lagrange multipliers in which the free vibration problem is posed as a constrained variational problem. The Legendre orthogonal polynomials are used as the beam eigenfunctions. Natural frequencies and mode shapes of various Timoshenko beams are presented to demonstrate the efficiency of the methodology  

    Hydrodynamic optimization of marine propeller using gradient and non-gradientbased algorithms

    , Article Acta Polytechnica Hungarica ; Volume 10, Issue 3 , 2013 , Pages 221-237 ; 17858860 (ISSN) Taheri, R ; Mazaheri, K ; Sharif University of Technology
    Here a propeller design method based on a vortex lattice algorithm is developed, and two gradient-based and non-gradient-based optimization algorithms are implemented to optimize the shape and efficiency of two propellers. For the analysis of the hydrodynamic performance parameters, a vortex lattice method was used by implementing a computer code. In the first problem, one of the Sequential Unconstraint Minimization Techniques (SUMT) is employed to minimize the torque coefficient as an objective function, while keeping the thrust coefficient constant as a constraint. Also, chord distribution is considered as a design variable, namely 11 design variables. In the second problem, a modified... 

    An efficient hybrid approach based on K-means and generalized fashion algorithms for cluster analysis

    , Article 2015 AI and Robotics, IRANOPEN 2015 - 5th Conference on Artificial Intelligence and Robotics, Qazvin, Iran, 12 April 2015 ; April , 2015 , Page(s): 1 - 7 ; 9781479987337 (ISBN) Aghamohseni, A ; Ramezanian, R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Clustering is the process of grouping data objects into set of disjoint classes called clusters so that objects within a class are highly similar with one another and dissimilar with the objects in other classes. The k-means algorithm is a simple and efficient algorithm that is widely used for data clustering. However, its performance depends on the initial state of centroids and may trap in local optima. In order to overcome local optima obstacles, a lot of studies have been done in clustering. The Fashion Algorithm is one effective method for searching problem space to find a near optimal solution. This paper presents a hybrid optimization algorithm based on Generalized Fashion Algorithm... 

    Two metaheuristics to solve a multi-item multiperiod inventory control problem under storage constraint and discounts

    , Article International Journal of Advanced Manufacturing Technology ; Volume 69, Issue 5-8 , 2013 , Pages 1671-1684 ; 02683768 (ISSN) Pasandideh, S. H. R ; Niaki, S. T. A ; Mousavi, S. M ; Sharif University of Technology
    In this paper, a multi-item multiperiod inventory control problem with all-unit and/or incremental quantity discount policies under limited storage capacity is presented. The independent random demand rates of the items in the periods are known and the items are supplied in distinct batch sizes. The cost consists of ordering, holding, and purchasing. The objective is to find the optimal order quantities of all items in different periods such that the total inventory cost is minimized and the constraint is satisfied. A mixed binary integer programming model is first developed to model the problem. Then, a parameter-tuned genetic algorithm (GA) is employed to solve it. Since there is no... 

    Diagnosis of coronary artery disease using data mining techniques based on symptoms and ECG features

    , Article European Journal of Scientific Research ; Volume 82, Issue 4 , Aug , 2012 , Pages 542-553 ; 1450216X (ISSN) Alizadehsani, R ; Habibi, J ; Hosseini, M. J ; Boghrati, R ; Ghandeharioun, A ; Bahadorian, B ; Sani, Z. A ; Sharif University of Technology
    EuroJournals, Inc  2012
    The most common heart disease is Coronary artery disease (CAD). CAD is one of the main causes of heart attacks and deaths across the globe. Early diagnosis of this disease is therefore, of great importance. A large number of methods have thus far been devised for diagnosing CAD. Most of these techniques have been conducted on the basis of the Irvine dataset (University of California), which not only has a limited number of features but is also full of missing values and thus lacks reliability. The present study was designed to seek a new set, free from missing values, comprising features such as the functional class, dyspnea, Q wave, ST elevation, ST depression, and T inversion. Information... 

    Color quantization with clustering by F-PSO-GA

    , Article Proceedings - 2010 IEEE International Conference on Intelligent Computing and Intelligent Systems, ICIS 2010, 29 October 2010 through 31 October 2010 ; Volume 3 , 2010 , Pages 233-238 ; 9781424465835 (ISBN) Alamdar, F ; Bahmani, Z ; Haratizadeh, S ; Sharif University of Technology
    Color quantization is a technique for processing and reduction colors in image. The purposes of color quantization are displaying images on limited hardware, reduction use of storage media and accelerating image sending time. In this paper a hybrid algorithm of GA and Particle Swarm Optimization algorithms with FCM algorithm is proposed. Finally, some of color quantization algorithms are reviewed and compared with proposed algorithm. The results demonstrate Superior performance of proposed algorithm in comparison with other color quantization algorithms  

    Diagnosis of coronary artery disease using cost-sensitive algorithms

    , Article Proceedings - 12th IEEE International Conference on Data Mining Workshops, ICDMW 2012 ; 2012 , Pages 9-16 ; 9780769549255 (ISBN) Alizadehsani, R ; Hosseini, M. J ; Sani, Z. A ; Ghandeharioun, A ; Boghrati, R ; Sharif University of Technology
    One of the main causes of death the world over are cardiovascular diseases, of which coronary artery disease (CAD) is a major type. This disease occurs when the diameter narrowing of one of the left anterior descending, left circumflex, or right coronary arteries is equal to or greater than 50 percent. Angiography is the principal diagnostic modality for the stenosis of heart vessels; however, because of its complications and costs, researchers are looking for alternative methods such as data mining. This study conducts data mining algorithms on the Z-Alizadeh Sani dataset which has been collected from 303 random visitors to Tehran's Shaheed Rajaei Cardiovascular, Medical and Research... 

    An improved constant-factor approximation algorithm for planar visibility counting problem

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2 August 2016 through 4 August 2016 ; Volume 9797 , 2016 , Pages 209-221 ; 03029743 (ISSN) ; 9783319426334 (ISBN) Alipour, S ; Ghodsi, M ; Jafari, A ; Sharif University of Technology
    Springer Verlag  2016
    Given a set S of n disjoint line segments in ℝ2, the visibility counting problem (VCP) is to preprocess S such that the number of segments in S visible from any query point p can be computed quickly. This problem can trivially be solved in logarithmic query time using O(n4) preprocessing time and space. Gudmundsson and Morin proposed a 2-approximation algorithm for this problem with a tradeoff between the space and the query time. They answer any query in Oε(n1−α) with Oε(n2+2α) of preprocessing time and space, where α is a constant 0 ≤ α ≤ 1, ε > 0 is another constant that can be made arbitrarily small, and Oε(f(n)) = O(f(n)nε). In this paper, we propose a randomized approximation algorithm... 

    Complexity of computing the anti-ramsey numbers for paths

    , Article 45th International Symposium on Mathematical Foundations of Computer Science, MFCS 2020, 25 August 2020 through 26 August 2020 ; Volume 170 , 2020 Amiri, S. A ; Popa, A ; Roghani, M ; Shahkarami, G ; Soltani, R ; Vahidi, H ; Sharif University of Technology
    Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing  2020
    The anti-Ramsey numbers are a fundamental notion in graph theory, introduced in 1978, by Erdös, Simonovits and Sós. For given graphs G and H the anti-Ramsey number ar(G, H) is defined to be the maximum number k such that there exists an assignment of k colors to the edges of G in which every copy of H in G has at least two edges with the same color. Usually, combinatorists study extremal values of anti-Ramsey numbers for various classes of graphs. There are works on the computational complexity of the problem when H is a star. Along this line of research, we study the complexity of computing the anti-Ramsey number ar(G, Pk), where Pk is a path of length k. First, we observe that when k is... 

    Efcient Algorithms for Visibility Testing of Objects and Counting

    , Ph.D. Dissertation Sharif University of Technology Alipour, Sharareh (Author) ; Ghodsi, Mohammad (Supervisor)
    Planar visibility computing is defned as determining the region of the plane that is visible from a specifc observer. This concept has many applications in computer graphics, robotic and computer games. In certain visibility problems, counting the number of visible objects in an appropriate time is required. For obtaining a solution fast, current algorithms give an approximated count. In this thesis, we consider visibility testing problem and visibility counting problem.For a given set S = fs1; s2; :::; sng of non-intersecting segments and a query point p in the plane, the visibility testing problem checks the inter-visibility of p and a segment si 2 S and the visibility counting problem... 

    Quantum Walk Application in Search Algorithms

    , M.Sc. Thesis Sharif University of Technology Ghorban Fekr, Hossein (Author) ; Karimipour, Vahid (Supervisor)
    Providing an Algorithm whi? can solve the sear? problem using minimum resources(su? as time, memory and so on)has been ?allenged by computer science experts for many years. By discovering the quantum computer it can be asked that does the quantum algorithm provide a be?er solution to sear? problem? ?e answer is yes. In this thesis the grover’s algorithm, the quantum sear? algorithm using the quantum walk, probabilistic quantum sear? algorithm and finally the two-qubit grover sear? algorithm implementation in physical world will be discussed  

    An ACO algorithm for the graph coloring problem [electronic resource]

    , Article Computational Intelligence Methods and Applications, ICSC Congress on ; 2005 Salari, M. (Majid) ; Eshghi, Kourosh ; Sharif University of Technology
    Ant colony optimization (ACO) is a well-known metaheuristic in which a colony of artificial ants cooperate in exploring good solutions to a combinatorial optimization problem. In this paper, an ACO algorithm is presented for the graph coloring problem. This ACO algorithm conforms to max-min ant system structure and exploits a local search heuristic to improve its performance. Experimental results on DIMACS test instances show improvements over existing ACO algorithms of the graph coloring problem  

    An algorithmic approach for finding deletion correcting codes

    , Article 2011 IEEE Information Theory Workshop, ITW 2011 ; 2011 , Pages 25-29 ; 9781457704376 (ISBN) Khajouei, F ; Zolghadr, M ; Kiyavash, N ; Sharif University of Technology
    A general construction for deletion/insertion correcting codes is proposed by concatenating codes derived from a heuristic maximal independent set algorithm on an appropriately defined graph. Our heuristic algorithm is polynomial with respect to the number of nodes in the graph. This methodology may be used for construction of any length n, s-deletion code. Our experimental results show that cardinalities of our codebooks exceed sizes of all previously known constructions. In fact, they are comparable to Levenshteins lower bound  

    Accuracy versus run time in an adiabatic quantum search

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 82, Issue 5 , 2010 ; 10502947 (ISSN) Rezakhani, A. T ; Pimachev, A. K ; Lidar, D. A ; Sharif University of Technology
    Adiabatic quantum algorithms are characterized by their run time and accuracy. The relation between the two is essential for quantifying adiabatic algorithmic performance yet is often poorly understood.We study the dynamics of a continuous time, adiabatic quantum search algorithm and find rigorous results relating the accuracy and the run time. Proceeding with estimates, we show that under fairly general circumstances the adiabatic algorithmic error exhibits a behavior with two discernible regimes: The error decreases exponentially for short times and then decreases polynomially for longer times.We show that the well-known quadratic speedup over classical search is associated only with the... 

    Implementation of a robust algorithm for prediction of forming limit diagrams

    , Article Journal of Materials Engineering and Performance ; Volume 17, Issue 1 , 2008 , Pages 1-6 ; 10599495 (ISSN) Ganjiani, M ; Assempour, A ; Sharif University of Technology
    In this article, a robust algorithm for prediction of forming limit diagrams (FLD) has been presented. The presented model is based on the "Marciniak and Kuczynski" (M-K) theory. Solution to the system of equations has been obtained by applying the Newton's method. Since the Newton's method usually has nonconverging problem, a particular backtracking algorithm has been developed and applied. In this algorithm, a technique for step length selection in the frame of gradient descent method has been implemented. Also for the convergence criterion the so-called "Armijo" condition has been used. For verification of the results, BBC2000 yield function and Swift hardening law for AK steel metal have... 

    The Minimum vulnerability problem

    , Article Algorithmica ; Volume 70, Issue 4 , 2014 , pp 718-731 ; ISSN: 14320541 Assadi, S ; Emamjomeh-Zadeh, E ; Norouzi-Fard, A ; Yazdanbod, S ; Zarrabi-Zadeh, H ; Sharif University of Technology
    We revisit the problem of finding (Formula presented.) paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the (Formula presented.) paths. We provide a (Formula presented.)-approximation algorithm for this problem, improving the best previous approximation factor of (Formula presented.). We also provide the first approximation algorithm for the problem with a sublinear approximation factor of (Formula presented.), where (Formula presented.) is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be... 

    A genetic programming-based learning algorithms for pruning cost-sensitive classifiers

    , Article International Journal of Computational Intelligence and Applications ; Volume 11, Issue 2 , June , 2012 ; 14690268 (ISSN) Nikdel, Z ; Beigy, H ; Sharif University of Technology
    In this paper, we introduce a new hybrid learning algorithm, called DTGP, to construct cost-sensitive classifiers. This algorithm uses a decision tree as its basic classifier and the constructed decision tree will be pruned by a genetic programming algorithm using a fitness function that is sensitive to misclassification costs. The proposed learning algorithm has been examined through six cost-sensitive problems. The experimental results show that the proposed learning algorithm outperforms in comparison to some other known learning algorithms like C4.5 or naïve Bayesian  

    Reconfiguration and capacitor placement in radial distribution systems for loss reduction and reliability enhancement

    , Article 2011 16th International Conference on Intelligent System Applications to Power Systems, ISAP 2011 ; 2011 Rezaei, P ; Vakilian, M ; Hajipour, E ; Sharif University of Technology
    This paper applies different approaches to solve network reconfiguration and capacitor placement/setting problem. First, reconfiguration and capacitor placement is solved for power loss minimization. Second, medium and long-term planning perspective is considered for the problem which takes into account reliability cost in addition to energy losses cost. A heuristic algorithm is used in this study for reliability evaluation considering protection schemes and isolation points in the distribution network. The problems are solved by Harmony Search Algorithm, and it is shown that its performance is much more satisfactory than several other metaheuristic algorithms to solve reconfiguration and... 

    Improved algorithms for partial Curve matching

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 5 September 2011 through 9 September 2011 ; Volume 6942 LNCS , September , 2011 , Pages 518-529 ; 03029743 (ISSN) ; 9783642237188 (ISBN) Maheshwari, A ; Sack, J. R ; Shahbaz, K ; Zarrabi Zadeh, H ; Sharif University of Technology
    Back in 1995, Alt and Godau gave an efficient algorithm for deciding whether a given curve resembles some part of a larger curve under a fixed Fréchet distance, achieving a running time of O(nm log(nm)), for n and m being the number of segments in the two curves, respectively. We improve this long-standing result by presenting an algorithm that solves this decision problem in O(nm) time. Our solution is based on constructing a simple data structure which we call free-space map. Using this data structure, we obtain improved algorithms for several variants of the Fréchet distance problem, including the Fréchet distance between two closed curves, and the so-called minimum/maximum walk problems....