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Total 186 records

    Manipulation of multibody active objects using simple passive manipulators

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010, Vancouver, BC ; Volume 8, Issue PARTS A AND B , 2010 , Pages 597-603 ; 9780791844458 (ISBN) Beigzadeh, B ; Meghdari, A ; Sohrabpour, S ; Sharif University of Technology
    2010
    Abstract
    In this paper, we study passivity in dynamic manipulation of active objects. Active object is a concept covering a variety of objects, which are not rigid and need to be controlled during manipulation process. In this work, we use multi-link mechanisms with sufficient actuators to be controlled as object and a series of simple 1-DoF passive manipulators to perform such a process. Control of the object, dynamic and motion planning of the system, and stability in presence of impact are significant issues in this study  

    Effect of squeeze-film damping on the dynamic behavior of circular and rectangular microplates

    , Article 2007 International Semiconductor Device Research Symposium, ISDRS, College Park, MD, 12 December 2007 through 14 December 2007 ; January , 2007 ; 1424418917 (ISBN); 9781424418916 (ISBN) Tajalli, A ; Ahmadian, M. T ; Sadeghian, H ; Sharif University of Technology
    2007

    Sensitivity analysis of gas turbine fuel consumption with respect to turbine stage efficiency

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 1 , 2012 , Pages 419-423 ; 9780791845172 (ISBN) Zeinalpour, M ; Mazaheri, K ; Irannejad, A ; Sharif University of Technology
    2012
    Abstract
    In this paper, the effect of turbine stage efficiency on fuel consumption of both gas turbines and aerial engines is assessed quantitatively. At the beginning of the gas generator optimization to decrease the fuel consumption, it is necessary to analyze the sensitivity of fuel consumption to its main components efficiencies. This will guide us which component is more important to be optimized. Here a zero-dimensional analysis has been done to determine the effect of turbine stage efficiency on the fuel consumption. Results of this analysis are evaluated in the context of thermodynamic cycle of a gas turbine generator and an aerial engine. As an example, it is shown that if the efficiency of... 

    Utilization of least square support vector machine (LSSVM) for electrical resistivity prediction of the zn-mn-s nanocrystalline semiconductor films

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3, Issue PARTS A, B, AND C , 2012 , Pages 1099-1104 ; 9780791845196 (ISBN) Abbasi, A. A ; Ahmadian, M. T ; Sharif University of Technology
    2012
    Abstract
    In this investigation, application of the least square support vector machine (LSSVM) for modeling of the electrical resistivity of the magnetic Zn-Mn-S nanocrystalline semiconductor films has been described. The model has been trained based on the experimental data obtained from a published work by Sreekantha Reddy et al. The model inputs are temperature and variations in the concentrations of Zn, Mn. The results indicate that LSSVM is able to be used for accurate prediction of the electrical resistivity of the Zn-Mn-S nanocrystalline semiconductor films  

    Estimation of modulus of elasticity for closed-cell aluminum foam

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3, Issue PARTS A, B, AND C , 2012 , Pages 1285-1289 ; 9780791845196 (ISBN) Ahmadian, M. T ; Gobal, A ; Alkhani, R ; Sharif University of Technology
    2012
    Abstract
    Monodisperse closed cell aluminum foam was analyzed numerically to determine the relationship between its elastic modulus, porosity and pore diameter. It was found a nonlinear relationship exists between porosity, pore diameter and modulus of elasticity. In this regard, an empirical equation is developed and implemented for the prediction of modulus of elasticity versus porosity and pore diameter. Comparing experimental and analytical approaches by other researchers with those obtained in this research shows agreement exists within 1 to 3 percent  

    Coupling effects between torsion and bending in torsional micromirrors under capillary forces

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011, Denver, CO ; Volume 11 , November , 2011 , Pages 51-55 ; 9780791854976 (ISBN) Darvishian, A ; Moeenfard, H ; Ahmadian, M. T ; Sharif University of Technology
    2011
    Abstract
    In the current paper, a general theoretical model for the problem of micromirrors under the effect of capillary forces is presented. The presented model considers the coupling effect between torsion and bending of the torsion beams supporting the micromirror. First, the energy method, the principal of minimum potential energy is utilized for finding the equations governing the micromirror rotation and its deflection. Then using the implicit functions theorem, the equations governing the pull-in angle and pull-in displacement of the micromirror is derived. The results, shows that ignoring the bending effect in micromirrors under the effect of capillary forces, can cause a significant (up to... 

    Fatigue analysis of antiroll bar for periodic and random inputs using various theories and introducing a new method

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009, Lake Buena Vista, FL ; Volume 13 , 2010 , Pages 71-76 ; 9780791843864 (ISBN) Azadi, M ; Zahedi, F ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2010
    Abstract
    In the present paper, fatigue analysis of an antiroll bar is investigated and compared for several criterions by using the finite element method (FEM) and also the experimental results. The validity of some of commonly used criterions in estimating fatigue life including Mcdiarmid and Von Misses theories is examined in which the inputs are considered as periodic data. For random inputs, some other methods are proposed including new suggestions and also a new criterion are established for estimation of fatigue life based on Mcdiarmid and Von Misses criterions. Prediction capability of mentioned new criterion which is evaluated for the antiroll bar, shows better results than other methods... 

    Comments on “Hydroelastic impact of a horizontal floating plate with forward speed” [J. Fluids Struct. 60 (2016) 97–113]

    , Article Journal of Fluids and Structures ; Volume 81 , 2018 , Pages 378-382 ; 08899746 (ISSN) Moradi, H ; Rahbar Ranji, A ; Haddadpour, H ; Sharif University of Technology
    Academic Press  2018
    Abstract
    This comment concerns the mathematical errors in the recent work of Wang et al. (2016). The corrected equations are presented. Deflections and critical values of compressive force and forward speed are modified. © 2018 Elsevier Ltd  

    Designing gear-shift pattern for an electric vehicle to optimize energy consumption

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Vol. 11 , 2010 , pp. 837-846 ; ISBN: 9780791844489 Rahimi, M. A ; Salehi, R ; Alasty, A ; Sharif University of Technology
    Abstract
    In this paper optimization of energy consumption in an electric vehicle is presented. The main idea of this optimization is based on selecting the best gear level in driving the vehicle. Two algorithms for optimization are introduced which are based on fuzzy rules and fuzzy controllers. In first algorithm, fuzzy controller simulates energy consumption in different gear levels, and chooses the optimum gear level. While in second method, fuzzy controller detects the optimum gear level by measuring the vehicle's average speed and acceleration. To investigate the performance of these controllers, a model of TOSAN vehicle is developed and the controllers outputs are checked in simulation of TOSAN... 

    Characterization of the effect of disturbance on the hydro-mechanical behavior of a highly collapsible loessial soil

    , Article Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 ; Vol. 1, issue , 2014 , p. 261-266 Haeri, S. M ; Khosravi, A ; Ghaizadeh, S ; Garakani, A. A ; Meehan, C. L ; Sharif University of Technology
    Abstract
    Highly collapsible loessial soils are characterized by an open void structure that can experience significant settlement upon loading. In the field, these partially saturated Aeolian deposits are particularly susceptible to wetting-induced collapse. Due to difficulties in preparing undisturbed specimens from highly collapsible soils, previous studies have generally performed laboratory tests on reconstituted specimens with different water contents and densities, and the effect of disturbance on the initial state of the soil was ignored. Disturbance in highly collapsible soil specimens may significantly affect the natural composition of the soil matrix, the non-homogeneous distribution of... 

    Toward searching possible oscillatory region in order space for nonlinear fractional-order systems

    , Article Journal of Computational and Nonlinear Dynamics ; Vol. 9, issue. 2 , 2014 Tavazoei, M. S ; Sharif University of Technology
    Abstract
    Finding the oscillatory region in the order space is one of the most challenging problems in nonlinear fractional-order systems. This paper proposes a method to find the possible oscillatory region in the order space for a nonlinear fractional-order system. The effectiveness of the proposed method in finding the oscillatory region and special order sets placed in its boundary is confirmed by presenting some examples  

    Investigation of the mechanical behaviors of carbon nanotubes under electrostatic actuation using the modified couple stress theory

    , Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 21, Issue 10 , Oct , 2013 , Pages 930-945 ; 1536383X (ISSN) Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    2013
    Abstract
    The paper presents size-dependant mechanical behaviors of carbon nanotubes under electrostatic actuation using modified couple stress theory. The behaviors of the carbon nanotubes with different geometries and boundary conditions are studied in detail. The results reveal that application of this theory results in higher pull-in voltages for both cantilever and doubly clamped boundary conditions  

    Modeling and stability analysis of truncated high density lipoprotein (HDL) system using MARTINI coarse grain technique

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3 A , November , 2013 ; 9780791856215 (ISBN) Damirchi, B ; Rouhollahi, A ; Sohrabi, S ; Mehr, S. M. N ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Abstract
    Lipoproteins are biochemical compounds containing both proteins and lipids. These particles carry chemicals like cholesterol and triglycerides that are not soluble in aqueous solutions. This paper presents modeling of lipoprotein system using coarse grain molecular dynamics technique and stability analysis of this system in a water solution like blood. A high density lipoprotein (HDL) that consists of two annular monomers is modeled. Also there are lipid bilayers located in center of the rings, so the whole HDL and lipid bilayers are called lipoprotein system. First, all atom model is provided and then coarse-grain model is obtained using MARTINI technique. Modeling of the system in all atom... 

    A novel approach for compensating the significance of tubule's architecture in urine concentrating mechanism of renal medulla

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3 B , 2013 ; 9780791856222 (ISBN) Sohrabi, S ; Mehr, S. M. N ; Falsafi, P ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Abstract
    Many theories and mathematical simulations have been proposed concerning urine concentrating mechanism (UCM). The WKM and region approach are the two most valuable methods for compensating the effect of tubule's architecture in renal medulla. They both have tried to simulate tubule's confinement within a particular region mathematically in one spatial dimension. In this study, continuity, momentum and species transport equations along with standard expressions for transtubular solutes and water transports on tubule's membrane were solved numerically in three spatial dimensions which practically is the main significance of our novel approach. Model structure has been chosen as simple as... 

    System and method for analysis of involving factors in the demisting cyclone efficiency

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), San Diego, CA ; Volume 15 , November , 2013 ; 9780791856444 (ISBN) Najafabadi, M. M ; Ehteram, M. A ; Ahmadian, M. T ; Barari, A ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Abstract
    In this study a system for real-time analysis of some involving factors in the efficiency of gas-liquid separators is developed based on the weighing method. An ultrasonic atomizer generates water drops in a size range of 1-10 μm with the same frequency during the test. A cyclone separator is selected and effect of the developing flow rate and shape of the mini-riser as a part of connecting assembly to the cyclone separator is investigated. Further an efficient electrostatic precipitator (ESP) with outcome of single-phase airflow is employed in the downstream of the cyclone to separate remaining droplets and produce the same pressure loss during the test. Circular, triangular, rectangular... 

    Slope variation effect on large deflection of compliant beam using analytical approach

    , Article Structural Engineering and Mechanics ; Volume 44, Issue 3 , 2012 , Pages 405-416 ; 12254568 (ISSN) Khavaji, A ; Ganji, D. D ; Roshan, N ; Moheimani, R ; Hatami, M ; Hasanpour, A ; Sharif University of Technology
    2012
    Abstract
    In this study the investigation of large deflections subject in compliant mechanisms is presented using homotopy perturbation method (HPM). The main purpose is to propose a convenient method of solution for the large deflection problem in compliant mechanisms in order to overcome the difficulty and complexity of conventional methods, as well as for the purpose of mathematical modeling and optimization. For simplicity, a cantilever beam of linear elastic material under horizontal, vertical and bending moment end point load is considered. The results show that the applied method is very accurate and capable for cantilever beams and can be used for a large category of practical problems for the... 

    Simulation and optimization of a semi spherical air bearing

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 7, Issue PARTS A, B, C, D , 2012 , Pages 153-159 ; 9780791845233 (ISBN) Saidimanesh, M ; Shahiri, A ; Nikparto, A ; Sharif University of Technology
    2012
    Abstract
    It is important to test the attitude control systems on satellites before they are launched in space. Traditionally this has been done by dropping the satellite, and firing the thrusters before the satellite makes a soft landing in a net. This method only allows a few seconds of testing and does not lend itself to the measurement of pointing accuracy. A better method is to mount the satellite on a spherical air bearing. In this paper behavior of a semi spherical air bearing is studied and analyzed in various conditions. These bearings are used in different applications such as simulation of approximately frictionless condition which is the satellite's situation in space. In this analysis... 

    Expansion of indicial function approximations for 2-D subsonic compressible aerodynamic loads

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 1 , 2012 , Pages 519-528 ; 9780791845172 (ISBN) Farsadi, T ; Javanshir, J ; Sharif University of Technology
    2012
    Abstract
    This article deals with the new generation of proper Mach dependent exponential approximations of the indicial aerodynamic functions toward the aeroelastic formulation of 2-D lifting surface in the subsonic compressible flow. The indicial lift response is a useful starting point in the development of a general time-domain unsteady aerodynamic theory. By definition, an indicial function is the response to a disturbance that is applied instantaneously at time zero and held constant thereafter; that is a disturbance given by a step function. If the indicial response is known, then the unsteady loads to arbitrary changes in angle of attack can be obtained through the superposition of indicial... 

    Simulation of biomanipulation using molecular dynamics

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 9, Issue PARTS A AND B , 2012 , Pages 137-143 ; 9780791845257 (ISBN) Pishkenari, H. N ; Mahboobi, S. H ; Mahjour, M. A ; Meghdari, A ; Sharif University of Technology
    2012
    Abstract
    In this paper, the simulation of biomolecules manipulation using molecular dynamics (MD) is studied. In order to investigate the manipulation behavior, we have used the ubiquitin as biomolecule, a single-walled carbon nanotube (SWCNT) as manipulation probe, a two-layer graphene sheet as substrate. Along this line, a series of simulations are conducted to study the effects of different conditions on the success of manipulation process. These conditions include tip diameter, vertical gap between the tip and substrate, initial orientation of protein, and the tip position with respect to the biomolecule  

    Stability analysis of a rotating stepped shaft via lyapunov criterion

    , Article ASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012, Houston, TX, 9 November 2012 through 15 November 2012 ; Volume 4, Issue PARTS A AND B , 2012 , Pages 701-706 ; 9780791845202 (ISBN) Chekan, J. A ; Merat, K ; Zohoor, H ; Sharif University of Technology
    2012
    Abstract
    In this investigation, the stability analysis of a rotating elastic stepped shaft is studied and the sufficient condition for system stability in the sense of Lyapunov is derived. The model consists of an elastic stepped shaft which is clamped rigidly to a rotary device. From the model's point of view, the entire length of shaft is partitioned into uniform segments with different characteristics. The Lyapunov direct method is applied in this survey where the Hamilton function has been chosen as the candidate Lyapunov function. Since the dynamical mode shapes of the shaft are required for the stability analysis, the shaft has been modeled by the Euler- Bernoulli beam theory and the...