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    A model for flexi-bar to evaluate intervertebral disc and muscle forces in exercises

    , Article Medical Engineering and Physics ; Volume 38, Issue 10 , 2016 , Pages 1076-1082 ; 13504533 (ISSN) Abdollahi, M ; Nikkhoo, M ; Ashouri, S ; Asghari, M ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    This study developed and validated a lumped parameter model for the FLEXI-BAR, a popular training instrument that provides vibration stimulation. The model which can be used in conjunction with musculoskeletal-modeling software for quantitative biomechanical analyses, consists of 3 rigid segments, 2 torsional springs, and 2 torsional dashpots. Two different sets of experiments were conducted to determine the model's key parameters including the stiffness of the springs and the damping ratio of the dashpots. In the first set of experiments, the free vibration of the FLEXI-BAR with an initial displacement at its end was considered, while in the second set, forced oscillations of the bar were... 

    Instability of nanocantilever arrays in electrostatic and van der waals interactions

    , Article Journal of Physics D: Applied Physics ; Volume 42, Issue 22 , 2009 ; 00223727 (ISSN) Ramezani, A ; Alasty, A ; Sharif University of Technology
    2009
    Abstract
    The structural instability of an array of cantilevers, each of which interacts with two neighbouring beams through electrostatic and van der Waals forces, is studied. Distributed and lumped parameter modelling of the array result in a set of coupled nonlinear boundary value problems and a set of coupled nonlinear equations, respectively. These coupled nonlinear systems are solved numerically for different numbers of beams in the array to obtain the pull-in parameters. The pull-in parameters converge to constant values with an increase in the number of beams in the array. These constants, which are important in the design of cantilever arrays, are compared for the distributed and lumped... 

    Numerical and One Dimensional Modeling of Cardiovascular System Along with Lumped Parameter Modeling of the Heart

    , M.Sc. Thesis Sharif University of Technology Salehi, Sarah (Author) ; Firoozabadi, Bahar (Supervisor) ; Saidi, Mohammad Saeed (Co-Advisor)
    Abstract
    Cardiovascular diseases are major causes of morbidity and mortality in the world. In order to prevent or reduce these diseases, engineers and scientists are concerned to find solutions. In this way, it is important to know about the blood flow and its changes in various diseases. By using simulation methods, diagnosis can be very easier. In this study, a system of arterial tree consisting of 93 systemic arteries along with 7 pulmonary arteries is considered. In other words, this model contains 100 systemic and pulmonary arteries that encompass central and peripheral arteries. Other parts of this model are cerebral vasculature and coronary arteries. Cerebral arteries, also called circle of... 

    Dynamics of bistable initially curved shallow microbeams: Effects of the electrostatic fringing fields

    , Article IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM ; July , 2014 , p. 1279-1283 Tajaddodianfar, F ; Yazdiو M. H ; Pishkenariو H. N ; Sharif University of Technology
    Abstract
    Effects of fringing electrostatic fields on the behavior of a double clamped initially curved microbeam are investigated. Galerkin's decomposition method is applied on the governing Euler-Bernoulli equation with distributed electrostatic force to obtain the lumped-parameter model of the system. The resulting single degree of freedom model is obtained with the Palmer's formula as a model for the fringing field effects. To derive an applied form of the fringing field effect in lumped model, we have used Genetic Algorithms as an optimization method. Then using the lumped model, we have investigated the system nonlinear dynamics. Comparison of the obtained bifurcation diagrams with the... 

    Numerical and 1-D modeling of pulmonary circulation along with lumped parameter modeling of the heart

    , Article 2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013 ; December , 2013 , Pages 93-97 Salehi, S. S ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    A one dimensional model of the pulmonary arterial network along with systemic circulation was introduced to quantify the human pulmonary artery hemodynamics. A lumped parameter model of the right ventricle was used as the inlet boundary condition. A time varying elastance related the volume and pressure of the right ventricle was imposed in the model. By using a four element Windkessel model, blood flow rate throughout the right ventricle was in hand. An asymmetric structured tree was chosen as the outlet boundary conditions. Simulation was based on solving one-dimensional equations of conservation of mass and momentum by using finite volume method. Blood flow rate, pressure and velocity... 

    Nonlinear dynamic analysis and chaotic behavior in atomic force microscopy

    , Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 1 A , 2005 , Pages 129-136 ; 0791847381 (ISBN); 9780791847381 (ISBN) Pishkenari, H. N ; Jalili, N ; Alasty, A ; Meghdari, A ; Sharif University of Technology
    American Society of Mechanical Engineers  2005
    Abstract
    The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. In this paper, the nonlinear dynamical behavior of the AFM is studied. This is achieved by modeling the microcantilever as a single mode approximation (lumped-parameters model) and considering the interaction between the sample and cantilever in the form of van der Waals potential. The resultant nonlinear system is then analyzed using Melnikov method, which predicts the regions in which only periodic and quasi-periodic motions exist, and also predicts the regions that chaotic... 

    Combined action of Casimir and electrostatic forces on nanocantilever arrays

    , Article Acta Mechanica ; Volume 212, Issue 3-4 , July , 2010 , Pages 305-317 ; 00015970 (ISSN) Ramezani, A ; Alasty, A ; Sharif University of Technology
    2010
    Abstract
    Cantilever arrays with nearest-neighbor interactions are considered to obtain the pull-in parameters. The interactions between the neighboring beams are a combination of the Casimir force and the electrostatic force with the first-order fringing field correction. A set of coupled nonlinear boundary value problems and a set of coupled nonlinear equations arise in the distributed and lumped parameter modeling of the array, respectively. The models are simulated numerically to obtain the pull-in parameters of the arrays with different number of beams. The pull-in parameters of large arrays converge to constant values, which are independent of the number of beams in the array. The constants... 

    A validated reduced-order dynamic model of nitric oxide regulation in coronary arteries

    , Article Computers in Biology and Medicine ; Volume 139 , 2021 ; 00104825 (ISSN) Moshfegh, H ; Tajeddini, F ; Pakravan, H. A ; Mahzoon, M ; Azadi Yazdi, E ; Bazrafshan Drissi, H ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Nitric Oxide (NO) provides myocardial oxygen demands of the heart during exercise and cardiac pacing and also prevents cardiovascular diseases such as atherosclerosis and platelet adhesion and aggregation. However, the direct in vivo measurement of NO in coronary arteries is still challenging. To address this matter, a mathematical model of dynamic changes of calcium and NO concentration in the coronary artery was developed for the first time. The model is able to simulate the effect of NO release in coronary arteries and its impact on the hemodynamics of the coronary arterial tree and also to investigate the vasodilation effects of arteries during cardiac pacing. For these purposes, flow... 

    A lumped parameter model for exponentially tapered piezoelectric beam in transverse vibration

    , Article Journal of Mechanical Science and Technology ; Volume 33, Issue 5 , 2019 , Pages 2043-2048 ; 1738494X (ISSN) Fakharian, O ; Salmani, H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
    Korean Society of Mechanical Engineers  2019
    Abstract
    Tapered piezoelectric beams, because of their more efficiency to generate power, are required to be analyzed by simple models. In this paper, single degree of freedom (SDOF) relations are used to model transvers vibration of an exponentially tapered piezoelectric beam. For this purpose, first, response of the damped cantilevered Euler–Bernoulli beam with base excitation is obtained. Then, lumped parameters of the beam are extracted in order to calculate the SDOF model response. Comparing the Euler-Bernoulli beam model with the SDOF model shows that the lumped parameter model is not accurate enough to predict the beam’s response. Therefore, a tapering parameter dependent correction factor is... 

    Error estimate in calculating natural frequencies of a vibrating shaft by changing number of segments using lumped parameter model and transfer matrix method

    , Article 7th European Conference on Structural Dynamics, EURODYN 2008, 7 July 2008 through 9 July 2008 ; 2008 ; 9780854328826 (ISBN) Kargarnovin, M. H ; Sharif University of Technology
    University of Southampton, Institute of Sound Vibration and Research  2008
    Abstract
    In this paper using classical beam theory, the dynamical governing differential equations of a vibrating shaft are derived then by using lumped parameter technique and method of transfer matrix (TM) the induced eigen value problem is solved. In calculating natural frequencies of a vibrating shaft under different boundary conditions, primarily the shaft was divided into number of segments. In each segment different number of lumped properties like mass, damping and flexibility on overall massless elastic or rigid shaft were applied. One of the aims of this study was to find out the optimum value for number of segments under different aforementioned conditions. In order to estimate the natural... 

    Prediction of particle deposition in the respiratory track using 3D-1D modeling

    , Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1479-1486 ; 10263098 (ISSN) Monjezi, M ; Dastanpour, R ; Saidi, M. S ; Pishevar, A. R ; Sharif University of Technology
    2012
    Abstract
    Airflow simulation of the whole respiratory system is still unfeasible due to the geometrical complexity of the lung airways and the diversity of the length scales involved in the problem. Even the new CT imaging system is not capable of providing accurate 3D geometries for smaller tubes, and a complete 3D simulation is impeded by the limited computational resources available. The aim of this study is to develop a fully coupled 3D-1D model to make accurate prediction of airflow and particle deposition in the whole respiratory track, with reasonable computational cost and efficiency. In the new proposed method, the respiratory tree is divided into three parts to be dealt with using different... 

    Assessment of nitrate contamination in unsaturated zone of urban areas: the case study of Tehran, Iran

    , Article Environmental Geology ; Volume 57, Issue 8 , 2009 , Pages 1785-1798 ; 09430105 (ISSN) Joekar Niasar, V ; Ataie Ashtiani, B ; Sharif University of Technology
    2009
    Abstract
    Modeling fate of nitrogen in unsaturated and saturated zone is a complex process, which requires detailed geochemical data. Complexities of the process as well as data insufficiencies are two major issues, which make quantitative assessment of the problem more complicated. In this work, a lumped-parameter model (LPM) is proposed that has been evaluated for a data-limited case to study temporal and steady-state behavior of Nitrate and Ammonium in unsaturated zone. The concentration of components in the model are assumed as the depth-averaged concentrations, and dispersive fluxes have been neglected. The case study area is Tehran City aquifer, which is highly contaminated by domestic... 

    Optimal sliding mode control of AFM tip vibration and position during manipulation of a nanoparticle

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings ; Vol. 12, Issue. PART A , 2010 , pp. 205-214 ; ISBN: 9780791843857 Babahosseini, H ; Khorsand, M ; Meghdari, A ; Alasty, A ; Sharif University of Technology
    Abstract
    This research regards to a two-dimensional lateral pushing nanomanipulation using Atomic Force Microscope (AFM). Yet a reliable control of the AFM tip position during the AFM-based manipulation process is a chief issue since the tip can jump over the target nanoparticle and then the process can fail. However, a detailed Modeling and understanding of the interaction forces on the AFM tip is important for prosperous manipulation control and a nanometer resolution tip positioning. In the proposed model, Lund-Grenoble (LuGre) dynamic friction model is used as friction force on the contact surface between the nanoparticle and the substrate. This model leads to a stick-slip behavior of the... 

    Optimal sliding mode control for Atomic Force Microscope tip positioning during nano-manipulation process

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 2285-2296 ; 10263098 (ISSN) Babahosseini, H ; Mahboobi, S. H ; Vakilzadeh, M. K ; Alasty, A ; Meghdari, A ; Sharif University of Technology
    Sharif University of Technology  2013
    Abstract
    This research presents two-dimensional controlled pushing-based nanomanipulation using an Atomic Force Microscope (AFM). A reliable control of the AFM tip position is crucial to AFM-based manipulation since the tip can jump over the target nanoparticle causing the process to fail. However, detailed modeling and an understanding of the interaction forces on the AFM tip have a central role in this process. In the proposed model, the Lund-Grenoble (LuGre) method is used to model the dynamic friction force between the nanoparticle and the substrate. This model leads to the stick-slip behavior of the nanoparticle, which is in agreement with the experimental behavior at nanoscale. Derjaguin... 

    Frequency response behavior of microcantilevers in tapping-mode Atomic Force Microscopy

    , Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010, Montreal, QC ; Volume 4 , 2010 , Pages 469-476 ; 9780791844120 (ISBN) Delnavaz, A ; Mahmoodi, S. N ; Jalili, N ; Zohoor, H ; Sharif University of Technology
    2010
    Abstract
    Distributed-parameters vibration model of microcantilevers in tapping-mode Atomic Force Microscopy (AFM) is developed and is shown to be highly nonlinear. The question of why these nonlinearities are important and how they influence the predicted frequency response behavior of the cantilevers is addressed by comparing the results of developed model with a simple lumpedparameters model that has been extensively studied in the literature so far. The interaction forces between the microcantilever tip and the sample is supposed to be the same in both models and consist of attractive and repulsive interaction force regimes. In addition, experimental measurements are provided for a typical... 

    Linear and nonlinear approaches towards amplitude modulation atomic force microscopy

    , Article Current Applied Physics ; Volume 10, Issue 6 , 2010 , Pages 1416-1421 ; 15671739 (ISSN) Delnavaz, A ; Mahmoodi, S. N ; Jalili, N ; Zohoor, H ; Sharif University of Technology
    2010
    Abstract
    Frequency response behavior of microcantilever is analytically and experimentally investigated in amplitude modulation Atomic Force Microscopy (AFM). AFM microcantilever probe is modeled as a continuous beam, and tip-sample interaction force is considered to include both attractive and repulsive force regimes. The developed model is compared with the linear lumped-parameters model that has been extensively used in the literature so far. Experimental measurements are also provided for the frequency response of a typical microcantilever-sample system to demonstrate the advantages of the developed model over the linear formulation. The results indicate that the nonlinear continuous model is... 

    Optimal sliding mode control of AFM tip vibration and position during manipulation of a nanoparticle

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009, Lake Buena Vista, FL ; Volume 12, Issue PART A , 2010 , Pages 205-214 ; 9780791843857 (ISBN) Babahosseini, H ; Khorsand, M ; Meghdari, A ; Alasty, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2010
    Abstract
    This research regards to a two-dimensional lateral pushing nanomanipulation using Atomic Force Microscope (AFM). Yet a reliable control of the AFM tip position during the AFM-based manipulation process is a chief issue since the tip can jump over the target nanoparticle and then the process can fail. However, a detailed Modeling and understanding of the interaction forces on the AFM tip is important for prosperous manipulation control and a nanometer resolution tip positioning. In the proposed model, Lund-Grenoble (LuGre) dynamic friction model is used as friction force on the contact surface between the nanoparticle and the substrate. This model leads to a stick-slip behavior of the...