Search for: procedures
0.008 seconds
Total 495 records

    Finite element analysis of miniscrew placement in mandibular alveolar bone with varied angulations

    , Article European Journal of Orthodontics ; Volume 37, Issue 1 , August , 2015 , Pages 56-59 ; 01415387 (ISSN) Perillo, L ; Jamilian, A ; Shafieyoon, A ; Karimi, H ; Cozzani, M ; Sharif University of Technology
    Oxford University Press  2015
    Summary Background: Titanium miniscrews are increasingly used as orthodontic anchorage. Various factors are known to affect the stability of miniscrew. Placement angle is one of the most controversial issues in this area. Thus, the aim of this finite element study was to evaluate the influence of placement angle and direction of force on the stability of miniscrews. Materials and methods: Finite element analysis was performed using miniscrews inserted into 1mm of cortical bone and 10mm of trabecular bone at angles of 30, 60, 90, 120, and 150 degrees to the alveolar bone. Force of 2 Newton (N) was applied to the heads of the miniscrews in two directions of 0 and 30 degrees. Results: The... 

    A lagged implicit segregated data reconstruction procedure to treat open boundaries

    , Article Journal of Computational Physics ; Volume 229, Issue 14 , July , 2010 , Pages 5418-5431 ; 00219991 (ISSN) Sani, M ; Saidi, M. S ; Sharif University of Technology
    The problem of treating open boundaries is still a challenging one. Applying fully developed condition is constrained to long enough domains. Without having enough physical evidence about what happens on boundaries, the domain extent could not be shortened and computational costs could not be reduced. From the advent of free (open) boundary conditions, they were confined to mixed finite element procedures. Recent works have extended their application to coupled finite volume solvers based on the shape function data reconstruction. A wider class of flow solvers available, however, rely on the segregated procedure where the velocity components and pressure are solved in succession. Moreover,... 

    How to set up stochastic equations for real world processes: markov–einstein time scale

    , Article Understanding Complex Systems ; 2019 , Pages 165-179 ; 18600832 (ISSN) Rahimi Tabar, M. R ; Sharif University of Technology
    Springer Verlag  2019
    In Chaps. 16 – 21 we address a central question in the field of complex systems: Given a fluctuating (in time or space), sequentially uni- or multi-variant measured set of experimental data (even noisy data), how should one analyse the data non-parametrically, assess their underlying trends, discover the characteristics of the fluctuations, including diffusion and jump parts, and construct stochastic evolution equation for the data? © 2019, Springer Nature Switzerland AG  

    How to set up stochastic equations for real world processes: Markov–einstein time scale

    , Article Understanding Complex Systems ; 2019 , Pages 165-179 ; 18600832 (ISSN) Rahimi Tabar, M. R ; Sharif University of Technology
    Springer Verlag  2019
    In Chaps. 16 – 21 we address a central question in the field of complex systems: Given a fluctuating (in time or space), sequentially uni- or multi-variant measured set of experimental data (even noisy data), how should one analyse the data non-parametrically, assess their underlying trends, discover the characteristics of the fluctuations, including diffusion and jump parts, and construct stochastic evolution equation for the data? © 2019, Springer Nature Switzerland AG  

    Comparing the stability regions for fractional-order PI controllers and their integer-order approximations

    , Article Proceedings of the IEEE Conference on Decision and Control, 15 December 2010 through 17 December 2010, Atlanta, GA ; 2010 , Pages 720-725 ; 01912216 (ISSN) ; 9781424477456 (ISBN) Rahimian, M. A ; Tavazoei, M. S ; Sharif University of Technology
    This paper proposes a scheme for computing the stable regions from which the parameters of a fractional-order PI controller can be selected. In particular, we extend a previously investigated method for plotting the stability regions of PIλ controllers to their integer-order approximations. Next we compare the two stability regions and derive their overlapping sections, which is referred to as the implementable stability region. In order for the final closed-loop system to be stable, the designer must choose the controller parameters from the overlapping section of the two stability regions. The devised scheme we believe can facilitate the design procedure for fractional-order PI... 

    A comprehensive multimodality heart motion prediction algorithm for robotic-assisted beating heart surgery

    , Article International Journal of Medical Robotics and Computer Assisted Surgery ; Volume 15, Issue 2 , 2019 ; 14785951 (ISSN) Mansouri, S ; Farahmand, F ; Vossoughi, G ; Alizadeh Ghavidel, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    Background: An essential requirement for performing robotic-assisted surgery on a freely beating heart is a prediction algorithm that can estimate the future heart trajectory. Method: Heart motion, respiratory volume (RV) and electrocardiogram (ECG) signal were measured from two dogs during thoracotomy surgery. A comprehensive multimodality prediction algorithm was developed based on the multivariate autoregressive model to incorporate the heart trajectory and cardiorespiratory data with multiple inherent measurement rates explicitly. Results: Experimental results indicated strong relationships between the dominant frequencies of heart motion with RV and ECG. The prediction algorithm... 

    A recursive approach for analysis of snake robots using Kane's equations

    , 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 7 B , 2005 , Pages 855-861 ; 0791847446 (ISBN) Tavakoli Nia, H ; Pishkenari, H. N ; Meghdari, A ; Sharif University of Technology
    This paper presents a recursive approach for solving kinematic and dynamic problem in snake-like robots using Kane's equations. An n-link model with n-nonholonomic constraints is used as the snake robot model in our analysis. The proposed algorithm which is used to derive kinematic and dynamic equations recursively enhances the computational efficiency of our analysis. Using this method we can determine the number of additions and multiplications as a function of n. The proposed method is compared with the Lagrange and Newton-Euler's method in three different aspects: Number of operations, CPU time and error in the computational procedures. Copyright © 2005 by ASME  

    A finite volume central differencing scheme for simulation of the shut down procedure of a hydraulic system

    , Article International Journal of Fluid Power ; Volume 3, Issue 2 , 2002 , Pages 17-27 ; 14399776 (ISSN) Mazaheri, K ; Farahani, R. H ; Sharif University of Technology
    A new central differencing finite volume scheme is investigated for solution of unsteady hydraulic problems as water hammer in pipe systems. Special time stepping procedure similar to Runge-Kutta algorithm is used to stabilize this second order scheme. It is monotonized by adding dissipative terms including second and fourth derivatives of the conserved variables, with coefficients proportional to derivatives of pressure or volumetric flow, which keeps the second order of accuracy in smooth flow regions. The one-dimensional unsteady incompressible equations are solved for a water hammer situation, and results are compared to existing analytical solutions. Results are also compared with... 

    Review on different experimental techniques developed for recording force-deformation behaviour of soft tissues; with a view to surgery simulation applications

    , Article Journal of Medical Engineering and Technology ; Volume 41, Issue 4 , 2017 , Pages 257-274 ; 03091902 (ISSN) Afshari, E ; Rostami, M ; Farahmand, F ; Sharif University of Technology
    Different experimental techniques which have been developed to obtain data related to force-deformation behaviour of soft tissues play an important role in realistically simulating surgery processes as well as medical diagnoses and minimally invasive procedures. Indeed, an adequate quantitative description of soft-tissue-mechanical-behaviour requires high-quality experimental data to be obtained and analysed. In this review article we will first scan the motivations and basic technical issues on surgery simulation. Then, we will concentrate on different experimental techniques developed for recording force-deformation (stress-strain) behaviour of soft tissues with focussing on the in-vivo... 

    Development of an Integrated Solar Energy System for a Typical Educational Building

    , M.Sc. Thesis Sharif University of Technology Motavaselian, Ali Mohammad (Author) ; Saboohi, Yadollah (Supervisor)
    In the present thesis, A Computer software has been developed to evaluate technical and economic aspects of photovoltaic systems, off-grid and on-grid configuration, in urban areas where the electricity grid is accessible. As a case study the building of Energy Engineering faculty with annual demand of electricity in lighting section equals to 80048 kWh was considered. Regarding incident radiation and PV system characteristics with the aid of utilizability concept, a technical evaluation has been performed then life-cycle saving index was considered as a criterion for choosing an optimum nominal size of the system. Results show that for current electricity tariff of educational buildings ... 

    A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk muscle forces

    , Article Journal of Biomechanics ; 2017 ; 00219290 (ISSN) Shojaei, I ; Arjmand, N ; Meakin, J. R ; Bazrgari, B ; Sharif University of Technology
    Elsevier Ltd  2017
    The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental... 

    A minimally invasive robotic surgery approach to perform totally endoscopic coronary artery bypass on beating hearts

    , Article Medical Hypotheses ; Volume 124 , 2019 , Pages 76-83 ; 03069877 (ISSN) Alamdar, A ; Hanife, S ; Farahmand, F ; Behzadipour, S ; Mirbagheri, A ; Sharif University of Technology
    Churchill Livingstone  2019
    The currently available robotic systems rely on rigid heart stabilizers to perform totally endoscopic coronary artery bypass (TECAB) surgery on beating hearts. Although such stabilizers facilitate the anastomosis procedure by immobilizing the heart and holding the surgery site steady, they can cause damage to the heart tissue and rupture of the capillary vessels, due to applying relatively large pressures on the epicardium. In this paper, we propose an advanced robotic approach to perform TECAB on a beating heart with minimal invasiveness. The idea comes from the fact that the main pulsations of the heart occur as excursions in normal direction, i.e., perpendicular to the heart surface. We... 

    Extraction of hydroxyapatite nanostructures from marine wastes for the fabrication of biopolymer-based porous scaffolds

    , Article Marine Drugs ; Volume 18, Issue 1 , 2020 Gheysari, H ; Mohandes, F ; Mazaheri, M ; Dolatyar, B ; Askari, M ; Simchi, A ; Sharif University of Technology
    MDPI AG  2020
    Three-dimensional porous nanocomposites consisting of gelatin-carboxymethylcellulose (CMC) cross-linked by carboxylic acids biopolymers and monophasic hydroxyapatite (HA) nanostructures were fabricated by lyophilization, for soft-bone-tissue engineering. The bioactive ceramic nanostructures were prepared by a novel wet-chemical and low-temperature procedure from marine wastes containing calcium carbonates. The effect of surface-active molecules, including sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB), on the morphology of HA nanostructures is shown. It is demonstrated that highly bioactive and monophasic HA nanorods with an aspect ratio > 10 can be synthesized in... 

    Design of a gain-scheduling anti-swing controller for tower cranes using fuzzy clustering techniques

    , Article CIMCA 2006: International Conference on Computational Intelligence for Modelling, Control and Automation, Jointly with IAWTIC 2006: International Conference on Intelligent Agents Web Technologies and International Commerce, Sydney, NSW, 28 November 2006 through 1 December 2006 ; 2006 ; 0769527310 (ISBN); 9780769527314 (ISBN) Sadati, N ; Hooshmand, A ; Sharif University of Technology
    IEEE Computer Society  2006
    The main objective of this paper is to design a fast,non-expensive and practical controller for towercranes. The controllers are designed to transfer theloads from point to point, as fast as possible, and at thesame time the load swing is kept small during thetransfer process. Moreover, variations of the systemparameters such as cable length are taken intoconsideration. It is shown how the state feedbackcontrollers along with the gain scheduling could beused for a time varying linear model with varyingparameters. For this reason, linear controllers aredesigned for a number of operating points, where theirparameters are interpolated for conditions in between.In this way, a globally nonlinear... 

    A hybrid algorithm for prediction of varying heart rate motion in computer-assisted beating heart surgery

    , Article Journal of Medical Systems ; Volume 42, Issue 10 , 2018 ; 01485598 (ISSN) Mansouri, S ; Farahmand, F ; Vossoughi, G ; Alizadeh Ghavidel, A ; Sharif University of Technology
    Springer New York LLC  2018
    An essential requirement for performing robotic assisted surgery on a freely beating heart is a prediction algorithm which can estimate the future trajectory of the heart in the varying heart rate (HR) conditions of real surgery with a high accuracy. In this study, a hybrid amplitude modulation- (AM) and autoregressive- (AR) based algorithm was developed to enable estimating the global and local oscillations of the beating heart, raised from its major and minor physiological activities. The AM model was equipped with an estimator of the heartbeat frequency to compensate for the HR variations. The RMS of the prediction errors of the hybrid algorithm was in the range of 165–361 μm for the... 

    True damping and frequency prediction for aeroelastic systems: The PP method

    , Article Journal of Fluids and Structures ; Volume 25, Issue 7 , 2009 , Pages 1177-1188 ; 08899746 (ISSN) Haddadpour, H ; Firouz Abadi, R. D ; Sharif University of Technology
    This paper presents a numerical scheme for stability analysis of the aeroelastic systems in the Laplace domain. The proposed technique, which is called the PP method, is proposed for when the aerodynamic model is represented in the Laplace domain and includes complicated transcendental expressions in terms of the Laplace variable. This method utilizes a matrix iterative procedure to find the eigenvalues of the system and generalizes the other methods such as the P and PK methods for prediction of the flutter conditions. The major advantage of this technique over the other approximate methods is true prediction of subcritical damping and frequency values of the aeroelastic modes. To examine... 

    Modeling of the Flexible Instrument Inside the Vascular Environment for Its Motion Control in Minimally Invasive Procedures

    , M.Sc. Thesis Sharif University of Technology Rezazadeh, Taha (Author) ; Nejat Pishkenari, Hossein (Supervisor)
    Minimally invasive procedures are diagnostic or therapeutic methods that cause minimal injuries and side effects for patients. PCI is a common minimally invasive procedure for diagnosis and curing of cardiovascular disorders. In this procedure, the surgeon can have access to the cardiac vessels by a flexible instrument. However, motion control of this instrument inside the patient's body relies on surgeon's skills and in some cases, is time consuming so that the toxic effects of radiation on patient and surgical team increases. Magnetic flexible instruments are suggested to address this problem. Nevertheless, motion control of the flexible instrument inside the body still has many challenges... 

    Coding advantage decomposition inequality for the space-frequency block codes

    , Article IET Communications ; Vol. 8, Issue. 4 , 2014 , Pages 500-507 ; ISSN: 17518628 Morsali, A ; Tofigh, S ; Mohammadian, Z ; Talebi, S ; Sharif University of Technology
    In this study, the authors present a new criterion which can be used to decompose the coding advantage (CA) of space-frequency block codes (SFBCs). The proposed decomposition separates the CA into two parts, called precoder-CA and channel-CA. The precoder-CA represents the effects of the precoder and the signal constellation, and can be used in the design of the precoder of SFBCs. The channel-CA, on the other hand, gives an indication of the effects of the channel characteristics, and can be utilised for optimising the permutation parameter. The authors have shown that the proposed decomposition method leads to a lower computational complexity for the optimisation procedure compared with the... 

    Design of dual- and quad-band E-CRLH-TLs with arbitrary phase characteristics

    , Article Progress In Electromagnetics Research M ; Vol. 35, issue , 2014 , p. 141-149 Fozi, M ; Nikmehr, S ; Ghurt-Tappeh, M.V ; Bemani, M ; Sharif University of Technology
    In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component  

    Performance evaluation of energy meters in nonses'usoidal environment based on IEEE 1459 standard

    , Article 22nd International Conference and Exhibition on Electricity Distribution, CIRED 2013; Stockholm; Sweden; 10 June 2013 through 13 June 2013 ; Volume: 2013, Issue: 615 , 2013 ; 9781849197328 (ISBN) Youhannaei, M ; Honarmand, M. E ; Ouni, S ; Mehri, R ; Behinh, Y ; Mokhtari, H ; Talebi, J ; Sharif University of Technology
    The objective of this work is to study the effects of harmonics on energy meters. This study is canied out based on IEEE 1459 standard through extensive tests on some energy meters installed at Gil an utility consumers. First, a review on IEEE 1459 standard on power definitions will be given. The definitions are then ervaluated for a compact Fluorescent Lamp (CFL) as a harmonic generating load. Then, the results of the performance e-alnation of two energy meters are presented for different linear and nonlinear loads based on IEEE1459 standard power definitions. Two different test procedures are performed for this putpose. In the first series of tests, a harmonic polluted voltage is applied...