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    Periodic solution of a certain non-linear third order differential equation

    , Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 181-184 ; 10263098 (ISSN) Mehri, B ; 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  

    A novel minimum time trajectory planning in terrain following flights

    , Article 2003 IEEE Aerospace Conference, Big Sky, MT, 8 March 2003 through 15 March 2003 ; Volume 8 , 2003 , Pages 3755-3762 ; 1095323X (ISSN); 078037651X (ISBN); 9780780376519 (ISBN) Malaek, S. M ; Kosari, A. R ; Sharif University of Technology
    2003
    Abstract
    A new methodology has been proposed to enhance inverse dynamics applications in the process of trajectory planning and optimization in Terrain Following Flights (TFF). The new approach uses least square scheme to solve a general two-dimensional (2D) Terrain Following Flight in a vertical plane. In the mathematical process, Chebyshev polynomials are used to model the geographical data of the terrain in a given route in a manner suitable for the aircraft at hand. The aircraft then follows the modeled terrain with sufficient clearance. In this approach the TF problem is effectively converted to an optimal tracking problem. Results show that. this method provides a flexible approach to solve the... 

    Optimal planning of equipment maintenance and replacement on a variable horizon

    , Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 185-192 ; 10263098 (ISSN) Kianfar, F ; 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... 

    Multirate structures for arbitrary rate error control coding

    , Article 2003 IEEE International Conference on Accoustics, Speech, and Signal Processing, Hong Kong, 6 April 2003 through 10 April 2003 ; Volume 4 , 2003 , Pages 245-248 ; 15206149 (ISSN) Avesti Mehr, A. S ; Nayebi, K ; Kasaei, S ; Sharif University of Technology
    2003
    Abstract
    In this paper, we present the most general form for error control coding using finite field multi-rate filters. This method shows how different types of codes can easily be generated by multi-rate filters and filter banks. In all previous works, codes and syndromes were generated using prefilters. Here we present simple multi-rate structures for encoding and generating syndrome. We show that all kinds of arbitrary rate K/L, circulant linear codes can be generated by these structures. Then we claim that a similar simple structure for syndrome generation in all presented cases exist  

    Playbook: An animation-based game for improving children's creativity and problem solving skills

    , Article 13th ACM SIGCHI Symposium on Engineering Interactive Computing Systems, EICS 2021, 8 June 2021 through 11 June 2021 ; 2021 , Pages 12-16 ; 9781450384490 (ISBN) Farzinnejad, F ; Habibi, J ; Baghaei, N ; Sharif University of Technology
    Association for Computing Machinery, Inc  2021
    Abstract
    In this paper, we describe the design, development and preliminary evaluation of a novel animation tool for smartphones and tablets, with the goal of improving creativity and problem-solving ability among novice users, mainly young children. The user first draws the objects with markers and crayons on paper and takes a photo with their mobile or tablet to import their drawings into the app as game sprites. They then design their animation scene and point to a part of the character and selecting its animation type from existing buttons. Hence the selected part is animated in a vertex shader while ensuring a smooth transition with the non-pointed part. The results of a preliminary evaluation... 

    The new york times test: An intersubjective reconsideration

    , Article IEEE Technology and Society Magazine ; Volume 41, Issue 1 , 2022 , Pages 18-22 ; 02780097 (ISSN) Kafaee, M ; Taqavi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Abstract
    Sometimes, in our capacity as professionals, and under certain circumstances, we find ourselves faced with an ethical problem such as a conflict of interest in which codes of ethics or available ethical problem-solving methods cannot help us decide upon the moral course of action to take. Hence, either the codes or methods are flawed, or we are not using them appropriately. A method claimed to be helpful in such situations is The New York Times Test (NYTT). © 1982-2012 IEEE  

    Asymmetric wave propagation in a transversely isotropic half-space in displacement potentials

    , Article International Journal of Engineering Science ; Volume 46, Issue 7 , 2008 , Pages 690-710 ; 00207225 (ISSN) Khojasteh, A ; Rahimian, M ; Eskandari, M ; Pak, R. Y. S ; Sharif University of Technology
    2008
    Abstract
    With the aid of a complete representation using two displacement potentials, an efficient and accurate analytical derivation of the fundamental Green's functions for a transversely isotropic elastic half-space subjected to an arbitrary, time-harmonic, finite, buried source is presented. The formulation includes a complete set of transformed stress-potential and displacement-potential relations that can be useful in a variety of elastodynamic as well as elastostatic problems. The present solutions are analytically in exact agreement with the existing solutions for a half-space with isotropic material properties. For the numerical evaluation of the inversion integrals, a quadrature scheme... 

    Some basis-free expressions for stresses conjugate to Hill's strains through solving the tensor equation AX + XA = C

    , Article International Journal of Solids and Structures ; Volume 45, Issue 11-12 , 2008 , Pages 3584-3595 ; 00207683 (ISSN) Asghari, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
    2008
    Abstract
    In the present paper, some new and compact basis-free expressions are derived for representing stresses conjugate to the Lagrangean Hill's strain measures. Solving a tensor equation in the form of AX + XA = C, a rather simple general expression is obtained for the conjugate stresses in the case of distinct principal stretches. The result decomposes the conjugate stresses additively into two parts, such that one part is coaxial with the right stretch tensor while another part is orthogonal to it. An expression for the case of double-coalescent principal stretches is also obtained. As an example of the general results, simple expressions are obtained for the stress conjugate to the logarithmic... 

    Detection and classification mean-shifts in multi-attribute processes by artificial neural networks

    , Article International Journal of Production Research ; Volume 46, Issue 11 , 2008 , Pages 2945-2963 ; 00207543 (ISSN) Akhavan Niaki, S. T ; Abbasi, B ; Sharif University of Technology
    2008
    Abstract
    To monitor the quality of a multi-attribute process, some issues arise. One of them being the occurrence of a high number of false alarms (type I error) and the other an increase in the probability of not detecting defects when the process is monitored by a set of independent uni-attribute control charts. In this paper, based upon the artificial neural network capabilities we develop a new methodology to overcome this problem. We design a perceptron neural network to monitor either the proportions of several types of product nonconformities (instead of using several np charts) or the number of different types of defects (instead of using several c charts) in a product. Moreover, while the... 

    Designing and implementing two internet based exam systems using synchronous and asynchronous models

    , Article 2008 10th International Conference on Advanced Communication Technology, Phoenix Park, 17 February 2008 through 20 February 2008 ; Volume 3 , 2008 , Pages 2135-2139 ; 17389445 (ISSN); 9788955191356 (ISBN) Shirali Shahreza, M. H ; Shirali Shahreza, M ; Sharif University of Technology
    2008
    Abstract
    In this paper, two different systems for taking exams through the Internet are described and analyzed. They have been designed and executed in Yazd and Shahed Universities. These systems enable us to take the multiple-choice and descriptive exams. In these systems, the exam questions are prepared by the instructor of the concerned lesson and placed in the system database. The students who have taken that lesson can be connected to the system from wherever they want. After entering their username and password they can take part in the exam. One of these systems has been created on the basis of the synchronous model and another one has been developed on the basis of the asynchronous model.... 

    Question-based CAPTCHA

    , Article International Conference on Computational Intelligence and Multimedia Applications, ICCIMA 2007, Sivakasi, Tamil Nadu, 13 December 2007 through 15 December 2007 ; Volume 4 , 2008 , Pages 54-58 ; 0769530508 (ISBN); 9780769530505 (ISBN) Shirali Shahreza, M ; Shirali Shahreza, S ; Sharif University of Technology
    2008
    Abstract
    Today there are many Internet sites which require only the entry by human users but unfortunately some computer softwares called bots are designed by some hackers to enter these sites and use their resources through false registration. As a result some systems named CAPTCHA have been introduced to tell apart human users and computer software. This paper introduces a new CAPTCHA method. In this method a simple mathematical problem is generated according to a predefined pattern but instead of some object's name, we put their images. Then the whole problem is saved and shown to the user inform of an image to be answered by him. But since answering this problem requires four abilities of... 

    A numerical method for solving nth-order boundary-value problems

    , Article Applied Mathematics and Computation ; Volume 196, Issue 2 , 2008 , Pages 889-897 ; 00963003 (ISSN) Hesaaraki, M ; Jalilian, Y ; Sharif University of Technology
    2008
    Abstract
    In this paper, we consider the solution of an nth order boundary-value problem. We solve this problem by changing the problem to a system of two integral-differential equations and using the variational iteration method. By giving three examples and comparing with the other methods, the efficiency of the method will be shown. © 2007 Elsevier Inc. All rights reserved  

    Solving the resource availability cost problem in project scheduling by path relinking and genetic algorithm

    , Article Applied Mathematics and Computation ; Volume 196, Issue 2 , 2008 , Pages 879-888 ; 00963003 (ISSN) Ranjbar, M ; Kianfar, F ; Shadrokh, S ; Sharif University of Technology
    2008
    Abstract
    This paper considers a project scheduling problem with the objective of minimizing resource availability costs required to execute the activities in a project by a given project deadline. The project contains activities interrelated by finish-start-type precedence relations with a time lag of zero, which require a set of renewable resources. Two metaheuristics, path relinking and genetic algorithm, are developed to tackle this problem in which a schedule is created with a precedence feasible priority list given to the schedule generation scheme. In these procedures, each new generation of solutions are created using the combination of current solutions. Comparative computational results... 

    A general purpose optimization approach

    , Article 2007 IEEE Congress on Evolutionary Computation, CEC 2007, 25 September 2007 through 28 September 2007 ; 2007 , Pages 4538-4545 ; 1424413400 (ISBN); 9781424413409 (ISBN) Halavati, R ; Showaki, S. B ; Heravi, M. J ; Jashmi, B. J ; Sharif University of Technology
    2007
    Abstract
    Recombination in the Genetic Algorithm (GA) is supposed to extract the component characteristics from two parents and reassemble them in different combinations hopefully producing an offspring that has the good characteristics of both parents and this requires explicit chromosome and recombination operator design. This paper presents a novel evolutionary approach based on symbiogenesis which uses symbiotic combination instead of sexual recombination and using this operator, it requires no domain knowledge for chromosome or combination operator design. The algorithm is benchmarked on three problem sets, combinatorial optimization, deceptive, and fully deceptive, and is compared with standard... 

    Improving performance of a station and smoothin the exit rate in an assembly line

    , Article 2007 IEEE International Conference on Industrial Engineering and Engineering Management, IEEM 2007, 2 December 2007 through 4 December 2007 ; January , 2007 , Pages 1833-1837 ; 1424415292 (ISBN); 9781424415298 (ISBN) Elmi, A ; Nazabadi, M ; Sharif University of Technology
    2007
    Abstract
    Assembly line is the most well-known mass production system which was first used by Henry Ford in automobile industries. Malfunction of a station will have an impact on the whole assembly line. Having a great impact on the performance of the whole assembly line, Interaction of the stations on each other should be considered precisely. In this paper we will use discrete event simulation to improve performance of a station and the whole assembly line by smoothing the exit rate, which is the entrance rate to the next station. At the end of this article, the results for a case problem are illustrated and several conclusions are driven. © 2007 IEEE  

    Quine-McCluskey classification

    , Article 2007 IEEE/ACS International Conference on Computer Systems and Applications, AICCSA 2007, Amman, 13 May 2007 through 16 May 2007 ; 2007 , Pages 404-411 ; 1424410312 (ISBN); 9781424410316 (ISBN) Safaei, J ; Beigy, H ; Sharif University of Technology
    2007
    Abstract
    In this paper the Karnaugh and Quine-McCluskey methods are used for symbolic classification problem, and then these methods are compared with other famous available methods. Because the data in classification problem is very large, some changes should be applied in the original Quine-McCluskey (QMC) algorithm. We proposed a new algorithm that applies the QMC algorithm greedily calling it GQMC. It is surprising that GQMC results are most of the time equal to QMC. GQMC is still very slow classifier and it can be used when the number of attributes of the data is small, and the ratio of training data to the all possible data is high. © 2007 IEEE  

    Spanning trees with minimum weighted degrees

    , Article Information Processing Letters ; Volume 104, Issue 3 , 2007 , Pages 113-116 ; 00200190 (ISSN) Ghodsi, M ; Mahini, H ; Mirjalali, K ; Oveis Gharan, S ; Sayedi Roshkhar, A. S ; Zadimoghaddam, M ; Sharif University of Technology
    2007
    Abstract
    Given a metric graph G, we are concerned with finding a spanning tree of G where the maximum weighted degree of its vertices is minimum. In a metric graph (or its spanning tree), the weighted degree of a vertex is defined as the sum of the weights of its incident edges. In this paper, we propose a 4.5-approximation algorithm for this problem. We also prove it is NP-hard to approximate this problem within a 2 - ε factor. © 2007 Elsevier B.V. All rights reserved  

    Streaming algorithms for line simplification

    , Article 23rd Annual Symposium on Computational Geometry, SCG'07, Gyeongju, 6 June 2007 through 8 June 2007 ; 2007 , Pages 175-183 ; 1595937056 (ISBN); 9781595937056 (ISBN) Abam, M. A ; De Berg, M ; Hachenberger, P ; Zarei, A ; Sharif University of Technology
    2007
    Abstract
    We study the following variant of the well-known line-simpli- ficationproblem: we are getting a possibly infinite sequence of points p 0,p1,p2,... in the plane defining a polygonal path, and as wereceive the points we wish to maintain a simplification of the pathseen so far. We study this problem in a streaming setting, where weonly have a limited amount of storage so that we cannot store all thepoints. We analyze the competitive ratio of our algorithms, allowingresource augmentation: we let our algorithm maintain a simplificationwith 2k (internal) points, and compare the error of oursimplification to the error of the optimal simplification with k points. We obtain the algorithms with O(1)... 

    A new learning algorithm for the MAXQ hierarchical reinforcement learning method

    , Article ICICT 2007: International Conference on Information and Communication Technology, Dhaka, 7 March 2007 through 9 March 2007 ; 2007 , Pages 105-108 ; 9843233948 (ISBN); 9789843233943 (ISBN) Mirzazadeh, F ; Behsaz, B ; Beigy, H ; Sharif University of Technology
    2007
    Abstract
    The MAXQ hierarchical reinforcement learning method is computationally expensive in applications with deep hierarchy. In this paper, we propose a new learning algorithm for MAXQ method to address the open problem of reducing its computational complexity. While the computational cost of the algorithm is considerably decreased, the required storage of new algorithm is less than two times as the original learning algorithm requires storage. Our experimental results in the simple Taxi Domain Problem show satisfactory behavior of the new algorithm  

    A metaheuristic approach to the graceful labeling problem of graphs

    , Article 2007 IEEE Swarm Intelligence Symposium, SIS 2007, Honolulu, HI, 1 April 2007 through 5 April 2007 ; 2007 , Pages 84-91 ; 1424407087 (ISBN); 9781424407088 (ISBN) Mahmoudzadeh, H ; Eshghi, K ; Sharif University of Technology
    2007
    Abstract
    In this paper, an algorithm based on Ant Colony Optimization metaheuristic is proposed for finding solutions to the well-known graceful labeling problem of graphs. Despite the large number of papers published on the theory of this problem, there are few particular techniques introduced by researchers for gracefully labeling graphs. The proposed algorithm is applied to many classes of graphs, and the results obtained have proven satisfactory when compared to those of the existing methods in the literature. © 2007 IEEE