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    pH control using the nonlinear multiple models, switching, and tuning approach

    , Article Industrial and Engineering Chemistry Research, Washington ; Volume 39, Issue 5 , 2000 , Pages 1311-1319 ; 08885885 (ISSN) Pishvaie, M. R ; Shahrokhi, M ; Sharif University of Technology
    ACS  2000
    pH control is known to be a challenging problem due to its highly nonlinear nature. Several control strategies are proposed for controlling pH processes among which is the strong acid equivalent scheme. Although this technique is robust to modeling error, the controller performance is degraded if the titration curve undergoes large changes. To overcome this problem, two control schemes that are based on the strong acid equivalent strategy and that use the multiple models, switching, and tuning approach are proposed in this work. For modeling, both fixed and adaptive models are considered. An experimental setup is used to evaluate the performance of the proposed scheme. The effectiveness of... 

    Capacity analysis of a CDMA cellular system with mixed cell sizes and imperfect power control

    , Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 262-267 ; 10263098 (ISSN) Rohi, H ; Aref, M. R ; Kalantary, M. E ; Sharif University of Technology
    Sharif University of Technology  2004
    The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are necessary to increase the capacity of cellular systems. Cell splitting causes a cellular system to have mixed cell sizes. Calculation of the reverse link capacity of CDMA cellular systems with mixed cell sizes and imperfect power control is presented in this paper. When a macro cell is split into micro cells, the capacity of a non-uniform cellular system has been calculated, together with the calculation of micro and neighboring macro cell capacity. The computer simulation results show that with the reduction in radius of a micro cell, its capacity increases, while that of the... 

    Optimal yaw moment control law for improved vehicle handling

    , Article Mechatronics ; Volume 13, Issue 7 , 2003 , Pages 659-675 ; 09574158 (ISSN) Esmailzadeh, E ; Goodarzi, A ; Vossoughi, G. R ; Sharif University of Technology
    A new optimal control law for direct yaw moment control, to improve the vehicle handling, is developed. Although, this can be considered as part of a multi-layer system, for the traction control of a motorized wheels electric vehicle, but the results of this study are quite general and can be applied to other types of vehicles. The dynamic model of the vehicle system is initially developed and, using the well-known optimal control theory, an optimal controller is designed. Two different versions of control laws are considered here and the performance of each version of the control law is compared with the other one. The numerical simulation of the vehicle handling with and without the use of... 

    Optimised analytic designed 2.5 GHz CMOS VCO

    , Article Electronics Letters ; Volume 39, Issue 16 , 2003 , Pages 1160-1162 ; 00135194 (ISSN) Dehghani, R ; Atarodi, S. M ; Sharif University of Technology
    An analytic method for prediction of oscillation amplitude and supply current of differential CMOS oscillators is presented. The validity of this method has been verified by designing an LC CMOS oscillator in a 0.24 μm CMOS technology. The predictions are in good agreement with simulation results over a wide range of supply voltage  

    Height fluctuations and intermittency of V2O5 films by atomic force microscopy

    , Article Journal of Physics Condensed Matter ; Volume 15, Issue 12 , 2003 , Pages 1889-1898 ; 09538984 (ISSN) Iraji Zad, A ; Kavei, G ; Rahimi Tabar, M. R ; Vaez Allaei, S. M ; Sharif University of Technology
    The spatial scaling law and intermittency of the V2O5 surface roughness has been investigated by atomic force microscopy. The intermittency of the height fluctuations has been checked by two different methods, first, by measuring the scaling exponent of the qth moment of height-difference fluctuations i.e. Cq = <|h(x1) - h(x2)|q>, and second, by defining the generating function Z(q, N) and generalized multi-fractal dimension Dq. These methods predict that there is no intermittency in the height fluctuations. The observed roughness and dynamical exponents can be explained by numerical simulation on the basis of the forced Kuramoto-Sivashinsky equation  

    A criterion to evaluate the accuracy of reduced order models of induction generators based on neglecting stator transients

    , Article 5th IFAC Symposium on Power Plants and Power Systems Control 2003, 15 September 2003 through 19 September 2003 ; Volume 36, Issue 20 , 2003 , Pages 509-512 ; 14746670 (ISSN) Rafi, S. B ; Varahram, M. H ; Sharif University of Technology
    IFAC Secretariat  2003
    Various attempts has 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.Among various order reduction methods the most applicable ones are those based on neglecting the stator transients of the machine.In this paper, some of these methods are discussed and a criterion has been introduced to evaluate the accuracy of resultant reduced order models. Copyright © 2003 IFAC  

    Simple models of small-world networks with directed links

    , Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 66, Issue 3 , 2002 ; 1063651X (ISSN) Ramezanpour, A ; Karimipour, V ; Sharif University of Technology
    We investigate the effect of directed short- and long-range connections in a simple model of a small-world network. Our model is one in which we can determine many quantities of interest by an exact analytical method. We calculate the function [formula presented] defined as the number of sites affected up to time T when a naive spreading process starts in the network. As opposed to shortcuts, the presence of unfavorable bonds has a negative effect on this quantity. Hence, the spreading process may not be able to affect all of the network. We define and calculate a quantity identified as the average size of the accessible world in our model. The interplay of shortcuts and unfavorable bonds on... 

    Reaction-diffusion models describing a two-lane traffic flow

    , Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 62, Issue 5 , 2000 , Pages 5940-5947 ; 1063651X (ISSN) Fouladvand, M. E ; Sharif University of Technology
    A unidirectional two-lane road is approximated by a set of two parallel closed one-dimensional chains. Two types of cars, i.e., slow and fast ones are considered in the system. Based on the Nagel-Schreckenberg model of traffic flow [K. Nagel and M. Schreckenberg, J. Phys. 2, 2221 (1992)], a set of reaction-diffusion processes is introduced to simulate the behavior of the cars. Fast cars can pass the slow ones using the passing lane. We write and solve the mean-field rate equations for the density of slow and fast cars, respectively. We also investigate the properties of the model through computer simulations and obtain the fundamental diagrams. A comparison between our results and the... 

    Targeted pulmonary drug delivery in coronavirus disease (COVID-19) therapy: A patient-specific in silico study based on magnetic nanoparticles-coated microcarriers adhesion

    , Article International Journal of Pharmaceutics ; Volume 609 , 2021 ; 03785173 (ISSN) Ebrahimi, S ; Shamloo, A ; Alishiri, M ; Mozhdehbakhsh Mofrad, Y ; Akherati, F ; Sharif University of Technology
    Elsevier B.V  2021
    Since the beginning of the COVID-19 pandemic, nearly most confirmed cases develop respiratory syndromes. Using targeted drug delivery by microcarriers is one of the most important noteworthy methods for delivering drugs to the involved bronchi. This study aims to investigate the performance of a drug delivery that applies microcarriers to each branch of the lung under the influence of a magnetic field. The results show that by changing the inlet velocity from constant to pulsatile, the drug delivery performance to the lungs increases by ∼31%. For transferring the microcarriers to the right side branches (LUL and LLL), placing the magnet at zero height and ∼30° angle yields the best outcome.... 

    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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...