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dynamic-behavior
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Modeling of Dynamic Behavior of Fixed Offshore Platforms and their Performance Improvement by Endurance time Method
, Ph.D. Dissertation Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor) ; Mehdigholi, Hamid (Supervisor) ; Tabeshpour, Mohammad Reza (Co-Advisor)
Abstract
In this thesis, multi-degree-of-freedom and finite element methods are utilized to simulate the dynamic behavior of fixed offshore structures under the wave and the earthquake excitations. In the field of seismic loading, seismic response of the platform is determined with the response spectrum analysis (RSA), time history analysis (THA) and endurance time (ET) methods. The accuracy and the computational cost of the ET method are compared with the RSA and THA methods. The results indicate that despite the RSA method, the ET method can estimate the nonlinear behavior of these types of structures. Moreover, in comparison with the THA method, the computational burden decreases to about 5% while...
Modeling of tail dynamic behavior and trajectory control of a fish-robot using fuzzy logic
, Article IEEE International Conference on Robotics and Biomimetics ; 2010 , pp. 885-890 ; ISBN: 9781424493173 ; Dehghani, M. R ; Alasty, A ; Sharif University of Technology
Abstract
To have a complete model of a thunniform Fish-Robot, models of both body and tail are required. The dynamic model of the body is developed according to the parameters of a thunniform Fish-Robot built in MIT University, while, as the main part of this paper, the dynamic model of the tail is developed using fuzzy logic. Using experimental data and table look-up scheme, a fuzzy black box is introduced that gives the value of thrust force generated for any value of the Fish-Robot's input parameters: frequency of tail oscillation, amplitude of tail oscillation and speed of the Fish-Robot. In the second part, a trajectory fuzzy controller is designed for the Fish-Robot. The output of trajectory...
Strain gradient formulation of functionally graded nonlinear beams
, Article International Journal of Engineering Science ; Volume 65 , 2013 , Pages 49-63 ; 00207225 (ISSN) ; Kahrobaiyan, M. H ; Ahmadian, M. T ; Firoozbakhsh, K ; Sharif University of Technology
2013
Abstract
In this paper size-dependent static and dynamic behavior of nonlinear Euler-Bernoulli beams made of functionally graded materials (FGMs) is investigated on the basis of the strain gradient theory. The volume fraction of the material constituents is assumed to be varying through the thickness of the beam based on a power law. As a consequence, the material properties of the microbeam (including length scales) are varying in the direction of the beam thickness. To develop the model, the usual simplifying assumption which considers the length scale parameter to be constant through the thickness is avoided and equivalent length scale parameters are introduced for functionally graded microbeams...
Analysis and enhancement of low-voltage ride-through capability of brushless doubly fed induction generator
, Article IEEE Transactions on Industrial Electronics ; Volume 60, Issue 3 , March , 2013 , Pages 1146-1155 ; 02780046 (ISSN) ; Oraee, H ; Zolghadri, M. R ; Shao, S ; Tavner, P ; Sharif University of Technology
2013
Abstract
This paper discusses the dynamic behavior of the brushless doubly fed induction generator during the grid faults which lead to a decrease in the generator's terminal voltage. The variation of the fluxes, back EMFs, and currents are analyzed during and after the voltage dip. Furthermore, two alternative approaches are proposed to improve the generator ride-through capability using crowbar and series dynamic resistor circuits. Appropriate values for their resistances are calculated analytically. Finally, the coupled circuit model and the generator's speed and reactive power controllers are simulated to validate the theoretical results and the effectiveness of the proposed solutions. Moreover,...
Multivariate curve resolution alternating least-squares as a tool for analyzing crude oil extracted asphaltene samples
, Article Energy and Fuels ; Volume 26, Issue 9 , 2012 , Pages 5663-5671 ; 08870624 (ISSN) ; Hemmateenejad, B ; Sedghamiz, T ; Khosousi, T ; Ayatollahi, S ; Seiedi, O ; Sayyad Amin, J ; Sharif University of Technology
ACS
2012
Abstract
Asphaltene deposition in the early stage of the oil reservoir life and later during any stimulation process emerges critical problems to the petroleum industry. Deposition of asphaltene aggregates raises strict problems in industries and demands markedly a practical and scientific knowledge of the mechanisms of aggregation and precipitation. Fluorescence emission spectroscopy has been widely used to illuminate the fundamental properties of crude oils and asphaltenes. It proposes analysis of some details of equilibrium, dynamic behavior, and aggregation composition of crude oil under specific condition. In this work, the fluorescence spectra of crude-oil extracted asphaltene samples were...
Power management strategy for a multi-hybrid fuel cell/energy storage power generation systems
, Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 354-359 ; 9781467301114 (ISBN) ; Hamzeh, M ; Mokhtari, H ; Sharif University of Technology
2012
Abstract
This paper depicts a new configuration for modular hybrid power conversion systems, namely, multi-hybrid generation system (MHGS), and parallel connection at the output, such that the converter of each unit shares the load current equally. This is a significant step towards realizing a modular power conversion system architecture, where smaller units can be connected in any series/parallel grouping to realize any required unit specifications. The supercapacitor (SC) as a complementary source is used to compensate for the slow transient response of the fuel cell (FC) as a main power source. It assists the FC to meet the grid power demand in order to achieve a better performance and dynamic...
Application of nonlocal theory in dynamic pull-in analysis of electrostatically actuated micro and nano beams
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011, Washington, DC ; Volume 7 , 2011 , Pages 255-261 ; 9780791854846 (ISBN) ; Pasharavesh, A ; Fallah, A ; Sharif University of Technology
2011
Abstract
One of the most important phenomena related to electrically actuated micro and nano electromechanical systems (MEMSNEMS) is dynamic pull-in instability which occurs when the electrical attraction and beam inertia forces are more than elastic restoring force of the beam. According to failure of classical mechanics constitutive equations in prediction of dynamic behavior of small size systems, nonlocal theory is implemented here to analyze the dynamic pull-in behavior. Equation of motion of an electrostatically actuated micro to nano scale doubly clamped beam is rewritten using differential form of nonlocal theory constitutive equation. To analyze the nonlocal effect equation of motion is...
A modified DTC for induction motor drive system fed by Indirect Matrix Converter using Active Learning Method
, Article 2011 2nd Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2011, 16 February 2011 through 17 February 2011 ; February , 2011 , Pages 356-361 ; 9781612844213 (ISBN) ; Aghasi, M ; Khaburi, D. A ; Ghorbani, M. J ; Sharif University of Technology
2011
Abstract
This paper presents a high performance Direct Torque Control (DTC) theme for the induction motor using Indirect Matrix Converter (IMC). To improve the dynamic behavior of motor, Active Learning Method (ALM) is implemented on the DTC. The ALM uses its own modeling technique called the ink drop spread (IDS) method. Functionally the IMC is very similar to the Direct Matrix Converter (DMC) but it has separate line and load bridges. In the inverter stage, the classical DTC method is employed. In the rectifier stage, in order to reduce losses caused by snubber circuit the rectifier four-step commutation method is employed. By suitably selecting switching pattern and using Active Learning Method...
Dynamic response of a non-uniform Timoshenko beam, subjected to moving mass
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 229, Issue 14 , October , 2015 , Pages 2499-2513 ; 09544062 (ISSN) ; Mofid, M ; Ghannadiasl, A ; Sharif University of Technology
SAGE Publications Ltd
2015
Abstract
In this article, the dynamic response of a non-uniform Timoshenko beam acted upon by a moving mass is extensively investigated. To this end, the eigenfunction expansion method is adapted to the problem, employing the natural mode shapes of a uniform Timoshenko beam. Moreover, the orthonormal polynomial series expansion method is successfully applied to the coupled set of governing differential equations pertaining to the dynamic behavior of non-uniform Timoshenko beam actuated by a moving mass. Some numerical examples are solved in which the excellent agreement of the two presented methods is illustrated
On the chaotic vibrations of electrostatically actuated arch micro/nano resonators: a parametric study
, Article International Journal of Bifurcation and Chaos ; Volume 25, Issue 8 , July , 2015 ; 02181274 (ISSN) ; Hairi Yazdi, M. R ; Nejat Pishkenari, H ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2015
Abstract
Motivated by specific applications, electrostatically actuated bistable arch shaped micro-nano resonators have attracted growing attention in the research community in recent years. Nevertheless, some issues relating to their nonlinear dynamics, including the possibility of chaos, are still not well known. In this paper, we investigate the chaotic vibrations of a bistable resonator comprised of a double clamped initially curved microbeam under combined harmonic AC and static DC distributed electrostatic actuation. A reduced order equation obtained by the application of the Galerkin method to the nonlinear partial differential equation of motion, given in the framework of Euler-Bernoulli beam...
Nonlinear dynamic analysis of a rectangular plate subjected to accelerated/decelerated moving load
, Article Journal of Theoretical and Applied Mechanics ; Volume 53, Issue 1 , 2015 , Pages 151-166 ; 14292955 (ISSN) ; Mohsenzadeh, R ; Kargarnovin, M. H ; Sharif University of Technology
Polish Society of Theoretical and Allied Mechanics
2015
Abstract
In this paper, nonlinear dynamical behavior of a rectangular plate traveled by a moving mass as well as an equivalent concentrated force with non-constant velocity is studied. The nonlinear governing coupled partial differential equations (PDEs) of motion are derived by energy method using Hamilton's principle based on the large deflection theory in conjuncture with the von-Karman strain-displacement relations. Then Galerkin's method is used to transform the equations of motion into a set of three coupled nonlinear ordinary differential equations (ODEs) which then is solved in a semi-analytical way to get the dynamical response of the plate. Also, by using the Finite Element Method (FEM)...
Modeling of tail dynamic behavior and trajectory control of a fish-robot using fuzzy logic
, Article 2010 IEEE International Conference on Robotics and Biomimetics, ROBIO 2010, 14 December 2010 through 18 December 2010 ; 2010 , Pages 885-890 ; 9781424493173 (ISBN) ; Dehghani, M. R ; Alasty, A ; Sharif University of Technology
Abstract
To have a complete model of a thunniform Fish-Robot, models of both body and tail are required. The dynamic model of the body is developed according to the parameters of a thunniform Fish-Robot built in MIT University, while, as the main part of this paper, the dynamic model of the tail is developed using fuzzy logic. Using experimental data and table look-up scheme, a fuzzy black box is introduced that gives the value of thrust force generated for any value of the Fish-Robot's input parameters: frequency of tail oscillation, amplitude of tail oscillation and speed of the Fish-Robot. In the second part, a trajectory fuzzy controller is designed for the Fish-Robot. The output of trajectory...
Contact time study of electrostatically actuated microsystems
, Article Scientia Iranica ; Volume 17, Issue 5 B , SEPTEMBER-OCTOBER , 2010 , Pages 348-357 ; 10263098 (ISSN) ; Rashidian, B ; Ahmadian, M. T ; Sharif University of Technology
2010
Abstract
This paper presents a model to analyze contact phenomenon in microsystems actuated by ramp voltages, which has applications in frequency sweeping. First-order shear deformation theory is used to model dynamical system using finite element method, while finite difference method is applied to model squeeze film damping. The model is validated by static pull-in results. The presented hybrid FEMFDM model is utilized to compute values of contact time and dynamic behavior. Considering this model, effects of different geometrical and mechanical parameters on contact time are studied. The influence of imposing the additional reverse voltage on dynamic characteristics of the system is also...
Optimum operation of single cavity photonic switches
, Article Proceedings of SPIE - The International Society for Optical Engineering, 25 January 2010 through 27 January 2010 ; Volume 7607 , January , 2010 ; 0277786X (ISSN) ; 9780819480033 (ISBN) ; Monem Haghdoost, Z ; Edalatipour, M ; Khorasani, S ; Mehrany, K ; Sharif University of Technology
2010
Abstract
In this work, an optimum frequency is found for the operation of single cavity photonic switches. At this optimum point, the transmission contrast of ON and OFF states takes its highest value, while keeping the device power threshold relatively low and the device speed acceptably high. Then, the dynamic behavior of a typical single cavity all optical switch is investigated in the optimum operation point through temporal Coupled Mode Theory. Switching speed and power are discussed, and the device is shown to be applicable for telecommunication and data processing applications. The analysis is quite general, and can be used for resonant structures, such as photonic crystals and microring...
Experimental investigation of the effect of chordwise flexibility on the aerodynamics of flapping wings in hovering flight
, Article Journal of Fluids and Structures ; Volume 26, Issue 4 , May , 2010 , Pages 544-558 ; 08899746 (ISSN) ; Ebrahimi, A ; Sharif University of Technology
2010
Abstract
Ornithopters or mechanical birds produce aerodynamic lift and thrust through the flapping motion of their wings. Here, we use an experimental apparatus to investigate the effects of a wing's twisting stiffness on the generated thrust force and the power required at different flapping frequencies. A flapping wing system and an experimental set-up were designed to measure the unsteady aerodynamic and inertial forces, power usage and angular speed of the flapping wing motion. A data acquisition system was set-up to record important data with the appropriate sampling frequency. The aerodynamic performance of the vehicle under hovering (i.e., no wind) conditions was investigated. The lift and...
Contact time study of microsystems actuated by ramp-input voltages
, Article ASME 2009 International Mechanical Engineering Congress and Exposition, IMECE2009, Lake Buena Vista, FL, 13 November 2009 through 19 November 2009 ; Volume 12, Issue PART A , 2010 , Pages 105-112 ; 9780791843857 (ISBN) ; Rashidian, B ; Ahmadian, M. T ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2010
Abstract
This paper presents a model to analyze contact phenomenon in microsystems, actuated by ramp voltages, which has applications in frequency sweeping. First-order shear deformation theory is used to model dynamical system using finite element method, while finite difference method is applied to model squeeze film damping. The model is validated by static pull-in results. The presented hybrid FEM-FDM model is utilized to compute values of contact time and dynamic behavior. Considering this model, effects of different geometrical and mechanical parameters on contact time are studied. The influence of imposing the additional reverse voltage on dynamic characteristics of the system is also...
Dynamic modeling of a piezo-driven compliant mechanism using modal analysis
, Article ASME 2009 International Mechanical Engineering Congress and Exposition, 13 November 2009 through 19 November 2009 ; Volume 10, Issue PART B , 2010 , Pages 715-720 ; 9780791843833 (ISBN) ; Shahidi, A. R ; Zohoor, H ; Sanikhani, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
Abstract
Dynamic modeling of piezo-driven compliant mechanisms is necessary to predict dynamic behavior of nanopositioning systems, and also to optimize their controlling methods. Dynamic tests on a real system or dynamic analyses on a FEM model is very time consuming when they must be carried out iteratively. According to previous works, obtaining static specifications of model is possible within a reasonable error margin. But all geometric dimensions and mass distribution details of the whole moving parts should be considered to calculate dynamic specifications of the model. In this paper, a functional method is described to obtain dynamic specifications of an planar compliant mechanism, by means...
Dynamic analysis of electrically actuated rectangular microplates with nonlinear plate theory under squeeze-film damping effect
, Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 13, Issue PART A , 2009 , Pages 401-408 ; 9780791848746 (ISBN) ; Moghimi Zand, M ; Ahmadian, M. T ; Sharif University of Technology
2009
Abstract
In this paper, dynamic behavior and pull-in phenomenon of electrically actuated rectangular micro plates under the effect of squeeze-film damping and nonlinear electrostatic force is studied. Finite element method is implemented in order to drive weak formulations of linear and nonlinear micro plate equations of motion based on classical plate theory (CPT) (for thin microplates with moderate nonlinearity) and squeeze-film damping based on Reynolds nonlinear equation. Finally, an efficient reduced-order model contingent on singular value decomposition method (SVD) is used to study dynamic pull-in phenomenon. This model is constructed by the global basis functions achieved from a few runs of...
Time saving simulation of long train derailment
, Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 17 , 2009 , Pages 461-465 ; 9780791848784 (ISBN) ; Jalili, M. M ; Sharif University of Technology
2009
Abstract
This article presents a new method in determining long train derailment. A new strategy for building train models with large number of wagons has been developed. Previous studies have shown that in a train model, some of the details in the model of the wagons neighboring the wagon under study play minor role in dynamic behavior of the spotted wagon. To reduce the size of the overall model, one would tend to eliminate some of the details of the complex neighboring model having minor effect on overall behavior and trade a small approximation in results for large saving in computation time. In this research this idea is used to develop a train model with one full detail wagon model linked in a...
A unified computational method for simulating dynamic behavior of planing vessels
, Article China Ocean Engineering ; Volume 23, Issue 3 , 2009 , Pages 517-528 ; 08905487 (ISSN) ; Jahanbakhsh, E ; Panahi, R ; Karimi, M. H ; Sharif University of Technology
2009
Abstract
High speed planing hulls have complex hydrodynamic behaviors. The trim angle and drafts are very sensitive to speed and location of the center of gravity. Therefore, motion simulation for such vessels needs a strong coupling between rigid body motions and hydrodynamic analysis. In addition, free surface should be predicted with good accuracy for each time step. In this paper, velocity and pressure fields are coupled by use of the fractional step method. On the basis of integration of the two-phase viscous flow induced stresses over the hull, acting loads (forces and moments) are calculated. With the strategy of boundary-fitted body-attached mesh and calculation of 6-DoF motions in each time...