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    Numerical approach to unbiased and driven generalized elastic model

    , Article The Journal of chemical physics ; Vol. 140, Issue. 2 , 2014 , pp. 24106- ; ISSN: 0021-9606 Ghasemi Nezhadhaghighi, M ; Chechkin, A ; Metzler, R ; Sharif University of Technology
    Abstract
    From scaling arguments and numerical simulations, we investigate the properties of the generalized elastic model (GEM) that is used to describe various physical systems such as polymers, membranes, single-file systems, or rough interfaces. We compare analytical and numerical results for the subdiffusion exponent β characterizing the growth of the mean squared displacement 〈 (δh)(2)〉 of the field h described by the GEM dynamic equation. We study the scaling properties of the qth order moments 〈 {divides}δh{divides}(q)〉 with time, finding that the interface fluctuations show no intermittent behavior. We also investigate the ergodic properties of the process h in terms of the ergodicity... 

    Real time simulation of grasping procedure of large internal organs during laparoscopic surgery

    , Article Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS ; Volume 2012 , 2012 , Pages 924-927 ; 1557170X (ISSN) Dehghani Ashkezari, H ; Mirbagheri, A ; Farahmand, F ; Behzadipour, S ; Firoozbakhsh, K ; Sharif University of Technology
    2012
    Abstract
    Surgical simulation systems facilitate safe and efficient training processes of surgical trainees by providing a virtual environment in which the surgical procedure can be repeated unlimitedly in a wide variety of situations. The present study attempted to develop a real time simulation system for the grasping procedure of large internal organs during laparoscopic surgery. A mass-spring-damper model was developed to simulate the nonlinear viscoelastic large deformations of the spleen tissue while interacting with a triple-jaw grasper. A novel collision detection algorithm was designed and implemented to determine the contact points between the tissue and the grasper jaws. Force or... 

    Existence of chaos in the fractional order unified system: The lowest effective dimension

    , Article ELECO 2011 - 7th International Conference on Electrical and Electronics Engineering, 1 December 2011 through 4 December 2011 ; Dec , 2011 , Pages II396-II399 ; 9786050102048 (ISBN) Tavazoei, M. S ; Haeri, M ; Sharif University of Technology
    Abstract
    This paper deals with the existence of chaos in the fractional order unified system. In an earlier published work, based on the numerical simulation results it is claimed that the lowest effective dimension in the fractional order unified system in order to present chaotic behaviors is 2.76. In this paper, it is analytically shown that the fractional order unified system can be chaotic for effective dimensions lower than the claimed lowest effective dimension. Also, the lowest effective dimension for existence of chaos in such a system is analytically determined. Computer simulation results, obtained based on a reliable numerical method, are brought to back up the presented analytical work... 

    Analytical model for sight distance analysis on three-dimensional highway alignments

    , Article Transportation Research Record ; Issue 1523 , 1996 , Pages 1-10 ; 03611981 Hassan, Y ; Easa, S. M ; Abd El Halim, A. O ; Sharif University of Technology
    Abstract
    Existing sight distance models are applicable only to two-dimensional (2-D) separate horizontal and vertical alignments or simple elements of these separate alignments (vertical curve, horizontal curve). A new model is presented for determining the available sight distance on 3-D combined horizontal and vertical alignments. The model is based on the curved parametric elements that have been used in the finite element method. The elements presented are rectangular (4-node, 6-node, and 8-node elements) and triangular. These elements are used to represent various features of the highway surface and sight obstructions, including tangents (grades), horizontal curves, vertical curves, traveled... 

    Expectation propagation for large scale Bayesian inference of non-linear molecular networks from perturbation data

    , Article PloS one ; Volume 12, Issue 2 , 2017 , Pages e0171240- ; 19326203 (ISSN) Narimani, Z ; Beigy, H ; Ahmad, A ; Masoudi Nejad, A ; Fröhlich, H ; Sharif University of Technology
    2017
    Abstract
    Inferring the structure of molecular networks from time series protein or gene expression data provides valuable information about the complex biological processes of the cell. Causal network structure inference has been approached using different methods in the past. Most causal network inference techniques, such as Dynamic Bayesian Networks and ordinary differential equations, are limited by their computational complexity and thus make large scale inference infeasible. This is specifically true if a Bayesian framework is applied in order to deal with the unavoidable uncertainty about the correct model. We devise a novel Bayesian network reverse engineering approach using ordinary... 

    Determination of residual stresses in autofrettaged compound tubes for different geometries

    , Article 2007 ASME Pressure Vessels and Piping Conference, PVP 2007, San Antonio, TX, 22 July 2007 through 26 July 2007 ; Volume 5 , 2008 , Pages 53-61 ; 0277027X (ISSN); 0791842835 (ISBN); 9780791842836 (ISBN) Mohammadi, M ; Farrahi, G. H ; Hoseini, S. H ; Sharif University of Technology
    2008
    Abstract
    In this paper, using numerical solutions of bore and outer radius hoop residual stresses in various tube geometries for autofrettage prior to shrink fit and shrink fit prior to autofrettage design are investigated, and the results are compared with monobloc autofrettaged and shrunk fit tubes. Both of the former compound tubes induce more compressive bore hoop residual stresses than a monobloc autofrettage and shrunk fit case. Furthermore, in geometries in which maximum bore hoop residual stresses are induced, the outer radius experiences acceptably low tensile residual stresses. Bore hoop residual stresses increase with increase of tube outer radius; however the rate of increasing decreases.... 

    SimDiv: A new solution for protein comparison

    , Article Lecture Notes in Electrical Engineering ; Volume 6 , 2008 , Pages 467-483 ; 18761100 (ISSN); 9780387749341 (ISBN) Sayyadi, H ; Salehi, S ; Ghodsi, M ; Sharif University of Technology
    2008
    Abstract
    The number of known proteins is increasing every day; tens of thousands have been studied and categorized by now. In this chapter, we propose amodel for protein matching or extracting similar parts of two given proteins. We focus on the computational geometric approach and the graph matching method that are used to model and compare the sequence and 3D structure of proteins. The remainder ofthis chapter is organized as follows. We first have a glance at the related works. There are two major methods used in the literature: Delaunay tetrahedralization and similarity flooding.We explain the required information in the next section as background knowledge, and then propose a new idea in Sect.... 

    Assisted passive snake-like robots: Conception and dynamic modeling using Gibbs-Appell method

    , Article Robotica ; Volume 26, Issue 3 , 2008 , Pages 267-276 ; 02635747 (ISSN) Vossoughi, G ; Pendar, H ; Heidari, Z ; Mohammadi, S ; Sharif University of Technology
    2008
    Abstract
    In this paper, we present a novel structure of a snake-like robot. This structure enables passive locomotion in snake-like robots. Dynamic equations are obtained for motion in a horizontal plane, using Gibbs-Appell method. Kinematic model of the robot include numerous nonholonomic constraints, which can be omitted at the beginning by choosing proper coordinates to describe the model in Gibbs-Appell framework. In such a case, dynamic equations will be significantly simplified, resulting in considerable reduction of simulation time. Simulation results show that, by proper selection of initial conditions, joint angles operate in a limit cycle and robot can locomote steadily on a passive... 

    Optimization of a process synthesis superstructure using an ant colony algorithm

    , Article Chemical Engineering and Technology ; Volume 31, Issue 3 , 2008 , Pages 452-462 ; 09307516 (ISSN) Raeesi, B ; Pishvaie, M. R ; Rashtchian, D ; Sharif University of Technology
    2008
    Abstract
    The optimization of chemical syntheses based on superstructure modeling is a perfect way for achieving the optimal plant design. However, the combinatorial optimization problem arising from this method is very difficult to solve, particularly for the entire plant. Relevant literature has focused on the use of mathematical programming approaches. Some research has also been conducted based on meta-heuristic algorithms. In this paper, two approaches are presented to optimize process synthesis superstructure. Firstly, mathematical formulation of a superstructure model is presented. Then, an ant colony algorithm is proposed for solving this nonlinear combinatorial problem. In order to ensure... 

    Unreliability of frequency-domain approximation in recognising chaos in fractional-order systems

    , Article IET Signal Processing ; Volume 1, Issue 4 , December , 2007 , Pages 171-181 ; 17519675 (ISSN) Tavazoei, M. S ; Haeri, M ; Sharif University of Technology
    2007
    Abstract
    The effects of using frequency-domain approximation in numerical simulation of fractional-order systems are analytically studied. The main aim in the study is to determine the number, location and stability property of the equilibriums in a fractional-order system and its frequency-based approximating counterpart. The comparison shows that the original fractional-order system and its frequency-based approximation may differ from each other in some or all issues considered in the study. Unfortunately, these differences can lead to wrong consequences in some special cases such as detecting chaos in the fractional-order systems. It is shown that using the frequency-domain approximation methods... 

    An enhanced random-walk method for content locating in P2P networks

    , Article 27th International Conference on Distributed Computing Systems Workshops, ICDCSW'07, Toronto, ON, 22 June 2007 through 29 June 2007 ; 2007 ; 0769528384 (ISBN); 9780769528380 (ISBN) Ronasi, K ; Firooz, M. H ; Pakravan, M. R ; Nasiri Avanaki, A ; Sharif University of Technology
    2007
    Abstract
    The important problem of content location in an unstructured distributed network (such as P2P, with no central searching system, graph construction control or file placement regulation) is addressed. The existing methods that are based on either flooding or random walk impose a large traffic load on the network or require a long time to search. In this work, we propose a method that outperforms the existing methods in both of these measures. These advantages are achieved by publishing traces of the contents of each node in its nearby nodes, so that the closer nodes to the target have a stronger trace of it. Such traces are used to rapidly locate the desired content. The superb performance of... 

    Genetic multivariable PID controller based on IMC

    , Article NAFIPS 2007: 2007 Annual Meeting of the North American Fuzzy Information Processing Society, San Diego, CA, 24 June 2007 through 27 June 2007 ; 2007 , Pages 174-177 ; 1424412145 (ISBN); 9781424412143 (ISBN) Kermanshachi, Sh ; Sadati, N ; Institute of Electrical and Electronics Engineers (IEEE) ; Sharif University of Technology
    2007
    Abstract
    A new approach for PID tuning, based on GA (Genetic algorithm) and Internal Model Control (IMC) technique, is presented in this paper. PID tuning is based on using Method. The IMC technique reduces the number of parameters that must be tuned for a multivariable system using PID controller. The algorithm uses GA for optimal determination of IMC variables. Simulation results present the good performance of the proposed method. © 2007 IEEE  

    High resolution simulations of unstable modes in a collisionless disc

    , Article Astronomy and Astrophysics ; Volume 473, Issue 1 , 2007 , Pages 31-40 ; 00046361 (ISSN) Khoperskov, A. V ; Just, A ; Korchagin, V. I ; Jalali, M. A ; Sharif University of Technology
    2007
    Abstract
    We present N-body simulations of unstable spiral modes in a dynamically cool collisionless disc. We show that spiral modes grow in a thin collisionless disk in accordance with the analytical perturbation theory. We use the particle-mesh code SUPERBOX with nested grids to follow the evolution of unstable spirals that emerge from an unstable equilibrium state. We use a large number of particles (up to N = 40 & 106) and high-resolution spatial grids in our simulations (1283 cells). These allow us to trace the dynamics of the unstable spiral modes until their wave amplitudes are saturated due to nonlinear effects. In general, the results of our simulations are in agreement with the analytical... 

    An 8-bit 300MS/S switched-current pipeline ADC in 0.18μm CMOS

    , Article 2007 IEEE International Symposium on Circuits and Systems, ISCAS 2007, New Orleans, LA, 27 May 2007 through 30 May 2007 ; 2007 , Pages 1481-1484 ; 02714310 (ISSN) Sedighi, B ; Sharif Bakhtiar, M ; Sharif University of Technology
    2007
    Abstract
    In this paper, capabilities of switched-current (SI) circuits are utilized to design a high-speed A/D converter. New methods to improve the performance of the SI circuits are introduced. An 8-bit 300MS/s pipeline ADC is design in 0.18um CMOS technology and an ENOB of 7.3b is obtained from simulations. The ADC consumes 40mW from a 1.8V supply. © 2007 IEEE  

    Experimental and theoretical investigation of twin-entry radial inflow gas turbine with unsymmetrical volute under fulland partial admission conditions

    , Article 2007 ASME Turbo Expo, Montreal, Que., 14 May 2007 through 17 May 2007 ; Volume 6 PART B , 2007 , Pages 1099-1107 ; 079184790X (ISBN); 9780791847909 (ISBN) Aghaali, H ; Hajilouy Benisi, A ; Sharif University of Technology
    2007
    Abstract
    In this paper the performance characteristics of turbocharger twin-entry radial inflow gas turbine with unsymmetrical volute and rotor tip diameter of 73.6 mm in steady state and under full and partial admission conditions are investigated. The employed method is based on one dimensional performance prediction which is developed for partial admission conditions. Furthermore this method is developed for unsymmetrical volute of the turbine considering flow specifications. Experimental investigation of the research carried out on special test facility under full and partial admission conditions for a wide range of speed. The comparison of experimental and modeling results shows good agreements.... 

    A parametric study on residual stresses and forging load in cold radial forging process

    , Article International Journal of Advanced Manufacturing Technology ; Volume 33, Issue 1-2 , 2007 , Pages 7-17 ; 02683768 (ISSN) Ameli, A ; Movahhedy, M. R ; Sharif University of Technology
    2007
    Abstract
    In this work, a comprehensive study of radial forging process is presented through 2-D axisymmetric and 3-D finite element simulations while considering internal tube profile. The tube used in this investigation has four internal helical grooves along its length. The material is modeled with the elastic-plastic behavior, and sliding-sticking friction model is utilized to model the die-workpiece and mandrel-workpiece contacts. The numerical results in the 2-D case are compared with available experimental data. Residual stresses in the forged product, stress concentration around the grooves, pressure distribution on the hammers and mandrel and maximum forging load are studied. The effects of... 

    Incremental learning of planning operators in stochastic domains

    , Article 33rd Conference on Current Trends in Theory and Practice of Computer Science, SOFSEM 2007, Harrachov, 20 January 2007 through 26 January 2007 ; Volume 4362 LNCS , 2007 , Pages 644-655 ; 03029743 (ISSN); 9783540695066 (ISBN) Safaei, J ; Ghassem Sani, G ; Sharif University of Technology
    Springer Verlag  2007
    Abstract
    In this work we assume that there is an agent in an unknown environment (domain). This agent has some predefined actions and it can perceive its current state in the environment completely. The mission of this agent is to fulfill the tasks (goals) that are often assigned to it as fast as it can. Acting has lots of cost, and usually planning and simulating the environment can reduce this cost. In this paper we address a new approach for incremental induction of probabilistic planning operators, from this environment while the agent tries to reach to its current goals. It should be noted that there have been some works related to incremental induction of deterministic planning operators and... 

    Formalizing compatibility and substitutability in communication protocols using I/O-constraint automata

    , Article 2nd IPM International Symposium on Fundamentals of Software Engineering, FSEN 2007, Tehran, 17 April 2007 through 19 April 2007 ; Volume 4767 LNCS , 2007 , Pages 49-64 ; 03029743 (ISSN); 9783540756972 (ISBN) Niamanesh, M ; Jalili, R ; Sharif University of Technology
    Springer Verlag  2007
    Abstract
    A communication protocol consists of a sequence of messages used by peer entities to communicate. Each entity in a network is equipped by at least one protocol stack. Due to the need for on-the-fly reconfiguration of protocol stack in future communication and computation devices, formalizing substitutability and compatibility of protocol entities are important in correctness assessment of dynamic reconfiguration. In this paper, we extend Constraint Automata and propose I/O-Constraint Automata to model behavior of protocols and propose enough formalism for substitutability and compatibility relations between protocols. We introduce input-blocking property of communication protocols, and show... 

    A new approach to reduce the dynamic order of induction generators

    , Article International Journal of Power and Energy Systems ; Volume 27, Issue 4 , 2007 , Pages 315-319 ; 10783466 (ISSN) Varahram, M. H ; Behzadi Rafi, S ; Sharif University of Technology
    Acta Press  2007
    Abstract
    Various attempts have been made to derive linearized, reduced order models of induction generators. Due to the fact that there is usually numerous number of these machines in wind power plants, these models provide great facilities in calculations, and therefore are used widely in power system transient stability studies. In this paper, some of these methods are discussed and compared and then a method known as "balanced realizations" is used to reduce the dynamic order of the machine. Computer simulation shows that the last method markedly improves the accuracy of the resulting reduced order model. The improvement is demonstrated by comparing the response characteristics predicted by each... 

    An 8-bit switched-resistor pipeline ADC

    , Article 2007 IEEE International Symposium on Circuits and Systems, ISCAS 2007, New Orleans, LA, 27 May 2007 through 30 May 2007 ; 2007 , Pages 1963-1966 ; 02714310 (ISSN) Sedighi, B ; Sharif Bakhtiar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2007
    Abstract
    In this paper a new technique called switched-resistor is used as an alternative to switched-capacitor circuits in a low-voltage low-power high-speed A/D converter. Simulation results for an 8-bit 150MS/s pipeline ADC are presented. This converter consumes 20mW from a 1.8V supply and provides an ENOB of 7.5bit. © 2007 IEEE