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Energy Optimization of an Arm with Seven Degrees of Freedom Using Imperialistic Competitive Algorithm (ICA) and Designing an Artificial Neural Network
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, M.T (Supervisor) ; Asghari, M (Supervisor)
Abstract
In recent years, great attention has been devoted to the design of artificial arms. The most crucial problem in such a design is the trajectory of movement. In this paper, a seven degree of freedom arm is modeled and simulated. Also, the optimization method named “Imperialistic Competitive Algorithm” has been modified and better performance of the new version is presented. Energy optimization is performed based on trajectory of the arm with angular velocity, angular acceleration and joint angles using modified imperialistic competitive algorithm (ICA). Considering ICA as a fast optimization algorithm, it would be reasonable to use this algorithm for robotic purposes for online answering. The...
Whole cell mechanical property characterization based on mechanical properties of its cytoplasm and bio membrane
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 9 November 2012 through 15 November 2012 ; Volume 2 , November , 2012 , Pages 545-551 ; 9780791845189 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Analysis and investigation of the relation between different parts of biological cells such as biomembrane, cytoplasm and nucleus can help to better understand their behaviors and material properties. In this paper, first, the whole elastic properties of mouse oocyte and embryo cells have been computed by inverse finite element and Levenberg-Marquardt optimization algorithm and second, using the derived mechanical properties and the mechanical properties of its bio membrane from the literature, the mechanical properties of its cytoplasm has been characterized. It has been assumed that the cell behavior is as continues, isotropic, nonlinear and homogenous material for modeling. Matching the...
Wall stress estimation of human heart under the effect of high accelerations
, Article ASME 2013 Summer Bioengineering Conference, SBC 2013 ; Volume: 1 , 2013 ; 9780791855614 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2013
Abstract
Human body is constantly under the influence of acceleration loads in environments such as combat flying. This study investigates the effect of body acceleration on human heart function by using finite element analysis. The nonlinear mechanical behavior of myocardium is modeled by Yeoh hyperelastic model. Stress-strain curves of myocardium are determined based on uniaxial compression tests on bovine heart samples. Nonlinear least square curve fitting is conducted in order to obtain material parameters. Heart geometrical modeling in threedimension is done by segmentation of cardiac MRI images. Obtained material coefficients are assigned to the constructed heart model and appropriate pressure...
Vibration of a microbeam under ultra-short-pulsed laser excitation considering momentum and heating effect
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010, Vancouver, BC ; Volume 10 , 2010 , Pages 195-200 ; 9780791844472 (ISBN) ; Vaghasloo, Y. A ; Ahmadian, M. T ; Moheimani, R ; Sharif University of Technology
2010
Abstract
In this study, vibration of a microbeam excited by an ultrashort- pulsed laser considering the momentum and heating effect of the laser beam is investigated. When the laser impacts the microbeam, portion of the photons is absorbed by the beam and their energy will be transformed into heat while the others are reflected. The momentum change of the absorbed and reflected laser photons is considered and modeled as a distributed force on the beam. The absorbed thermal energy yields non-uniform thermal stress causing the beam to vibrate. According to short duration of laser pulse, the non-Fourier conduction equation which takes into account the finite propagation speed of thermal energy, is...
Vibration control and manufacturing of intelligibly designed axially functionally graded cantilevered macro/micro-tubes
, Article 13th IFAC Workshop on Intelligent Manufacturing Systems, IMS 2019, 12 August 2019 through 14 August 2019 ; Volume 52, Issue 10 , 2019 , Pages 382-387 ; 24058963 (ISSN) ; Ebrahimi Mamaghani, A ; Ahmadian, M. T ; Barari A ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In the last decade, extensive attention is devoted to intelligibly designed materials of macro/micro-structures containing the fluid flow. In this study, intelligent control and vibrational stability of cantilevered fluid conveying macro/micro-tubes utilizing axially functionally graded (AFG) materials are considered. The governing equation of motion of the system is derived based on modified couple stress theory and then is discretized using Galerkin method. A detailed investigation is carried out to elaborate the influence of various parameters such as material properties, axial compressive load, and Pasternak foundation on the dynamical behavior of the system, all of which are influential...
Vibration control and manufacturing of intelligibly designed axially functionally graded cantilevered macro/micro-tubes
, Article 13th IFAC Workshop on Intelligent Manufacturing Systems, IMS 2019, 12 August 2019 through 14 August 2019 ; Volume 52, Issue 10 , 2019 , Pages 382-387 ; 24058963 (ISSN) ; Ebrahimi Mamaghani, A ; Ahmadian, M. T ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In the last decade, extensive attention is devoted to intelligibly designed materials of macro/micro-structures containing the fluid flow. In this study, intelligent control and vibrational stability of cantilevered fluid conveying macro/micro-tubes utilizing axially functionally graded (AFG) materials are considered. The governing equation of motion of the system is derived based on modified couple stress theory and then is discretized using Galerkin method. A detailed investigation is carried out to elaborate the influence of various parameters such as material properties, axial compressive load, and Pasternak foundation on the dynamical behavior of the system, all of which are influential...
Vibration and buckling analysis of functionally graded beams using reproducing kernel particle method
, Article Scientia Iranica ; Vol. 21, Issue 6 , 2014 , pp. 1896-1906 ; e-ISSN : 23453605 ; Ahmadian, M. T ; Farrahi, G. H ; Sharif University of Technology
Abstract
This paper presents vibration and buckling analysis of functionally graded beams with different boundary conditions, using reproducing kernel particle method (RKPM). Vibration of simple Euler-Bernoulli beam using RKPM is already developed and reported in the literature. Modeling of FGM beams using theoretical method or finite element technique is not evolved with accurate results for power law form of FGM with large power of "n" value so far. Accuracy of the RKPM results is very good and is not sensitive to n value. System of equations of motion is derived using Lagrange's method under the assumption of Euler-Bernoulli beam theory. Boundary conditions of the beam are taken into account using...
Vibration analysis of FGM rings using a newly designed cylindrical superelement
, Article Scientia Iranica ; Volume 25, Issue 3B , 2018 , Pages 1179-1188 ; 10263098 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
Rings are widely used in mechanical equipment, and their fitness may undergo some damage under severe vibration. In these structures, functionally graded rings can be used to optimize the resistance, energy consumption, and fitness. Due to their complexity, the finite-element analysis may be implemented using special elements. Enhancement of accuracy and minimization of time consumption play an important role in the analysis of these rings. In this study, a new cylindrical superelement for the FGM rings is designed and implemented to facilitate the vibration analysis of the rings. The power-law distribution is used for the modeling of the FGM rings in the thickness direction. Natural...
Vibration analysis of electrostatically actuated nonlinear microbridges based on the modified couple stress theory
, Article Applied Mathematical Modelling ; Volume 39, Issue 21 , November , 2015 , Pages 6694-6704 ; 0307904X (ISSN) ; Ahmadian, M. T ; Firoozbakhsh, K ; Sharif University of Technology
Elsevier Inc
2015
Abstract
In this paper natural frequency of electrostatically actuated microbridges is investigated based on the modified couple stress theory. Nonlinear formulation of Euler-Bernoulli microbeam is derived using Hamilton's principle. By considering the von-Karman strain, the nonlinearities caused by the mid-plane stretching are included in the formulation. To confirm the model, results of static deflection and natural frequency of microbeams are calculated using modified couple stress theory and compared to those evaluated based on the classical theory and experimental observations. At first, from experimental results of static deflection of a microcantilever, estimation for length scale parameter of...
Vibration analysis of delaminated Timoshenko beams under the motion of a constant amplitude point force traveling with uniform velocity
, Article International Journal of Mechanical Sciences ; Volume 70 , 2013 , Pages 39-49 ; 00207403 (ISSN) ; Jafari Talookolaei, R. A ; Ahmadian, M. T ; Sharif University of Technology
2013
Abstract
A composite beam with single delamination traveled by a constant amplitude moving force is modeled accounting for the Poisson's effect, shear deformation and rotary inertia. The mechanical behavior between the delaminated surfaces is modeled using a piecewise-linear spring foundation. The governing differential equations of motion for such system are derived. Primarily, eigen-solution technique is used to obtain the natural frequencies and their corresponding mode shapes of such beam. Then, the Ritz method is employed to derive the dynamic response of the beam due to the moving force. The obtained results for the free and forced vibrations of beams are verified against reported similar...
Vibration analysis of a rotating FGM cantilever ARM
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 15 , 2010 , Pages 359-365 ; 9780791843888 (ISBN) ; Moeini, S. A ; Kahrobaiyan, M. H ; Ahmadian, M. T ; Sharif University of Technology
Abstract
Functionally graded materials (FGMs) are inhomogeneous composites which are usually made of a mixture of metals and ceramics. Properties of these kinds of materials vary continuously and smoothly from a ceramic surface to a metallic surface in a specified direction of the structure. The gradient compositional variation of the constituents from one surface to the other provides an elegant solution to the problem of high transverse shear stresses that are induced when two dissimilar materials with large differences in material properties are bonded. FGMs have extracted much attention as advanced structural materials in recent years. In this paper, free vibration of a rotating FGM cantilever...
Vibrational analysis of wavy carbon nanotube-reinforced composites
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011, Washington, DC ; Volume 7 , August , 2011 , Pages 371-377 ; 9780791854846 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
Characterization and simulation of carbon nanotubereinforced composites at large scale have been a concern of researchers in the past decade. This is due to the computational complication of considering many embedded carbon nanotubes (CNTs). However a simple meshing of organized CNT distribution in the matrix can ease this obstacle. In this study, a finite element approach is employed to investigate the elastodynamic behavior of a wavy CNTreinforced composite structure. A three dimensional structure with up to 6400 uniformly distributed wavy CNTs is embedded in a polymer matrix. Each wavy nanotube is represented by a set of beam elements. The effect of nanotube waviness and volume fraction...
Vibrational analysis of single-walled carbon nanotubes using beam element
, Article Thin-Walled Structures ; Volume 47, Issue 6-7 , 2009 , Pages 646-652 ; 02638231 (ISSN) ; Ahmadian, M. T ; Vafai, A ; Sharif University of Technology
2009
Abstract
Vibrational analysis of single-walled carbon nanotubes (SWCNTs) is performed using a finite element method (FEM). To this end, the vibrational behavior of bridge and cantilever SWCNTs with different side lengths and diameters is modeled by three-dimensional elastic beams and point masses. The beam element elastic properties are calculated by considering mechanical characteristics of the covalent bonds between the carbon atoms in the hexagonal lattice. The mass of each beam element is assumed as point masses at nodes coinciding with the carbon atoms. Implementing the atomistic simulation approach, the natural frequencies of zigzag and armchair SWCNTs are computed. It is observed that the...
Vibrational analysis of single-layered graphene sheets
, Article Nanotechnology ; Volume 19, Issue 8 , 2008 ; 09574484 (ISSN) ; Ahmadian, M. T ; Naghdabadi, R ; Sharif University of Technology
2008
Abstract
A molecular structural mechanics method has been implemented to investigate the vibrational behavior of single-layered graphene sheets. By adopting this approach, mode shapes and natural frequencies are obtained. Vibrational analysis is performed with different chirality and boundary conditions. Numerical results from the atomistic modeling are employed to develop predictive equations via a statistical nonlinear regression model. With the proposed equations, fundamental frequencies of single-layered graphene sheets with considered boundary conditions can be predicted within 3% difference with respect to the atomistic simulation. © IOP Publishing Ltd
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) ; 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
Using super element and p-approximation for free vibration analysis of composite plates
, Article 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Anaheim, CA, 13 November 2004 through 19 November 2004 ; Volume 255 , 2004 , Pages 81-84 ; 01608835 (ISSN) ; Ahmadian, M. T ; Ghoreishi, S. R ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2004
Abstract
Effective and efficient methods in computational mechanics have been of interest for the designers and engineers in the last decade. A 3D super elements is developed and implemented for the free vibration analysis of the composite plates. These new elements have been constructed by a 2D super elements in the plane direction and p-version finite element in the thickness direction. Results of 2D super elements are comparable to SHELL 63 and results of 3D super elements with cubic polynomial are comparable to SHELL 93. In the thin plates, 2D super element (or SHELL 63) and 3D super elements (or SHELL 93) have same results, but in the thick plates results change drastically. Natural frequencies...
Traumatic brain injury caused by +Gz acceleration
, Article ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 21 August 2016 through 24 August 2016 ; Volume 3 , 2016 ; 9780791850138 (ISBN) ; Ahmadian, M.T ; Hoviattalab, M ; Computers and Information in Engineering Division; Design Engineering Division ; Sharif University of Technolgy
American Society of Mechanical Engineers (ASME)
Abstract
Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. This phenomenon has been under study for many years and yet it remains a question due to physiological, geometrical and computational complexity. Although the modeling facilities for soft tissue have improved, the precise CT-imaging of human head has revealed novel details of the brain, skull and meninges. In this study a 3D human head including the brain, skull, and meninges is modeled using CT-scan and MRI data of a 30-year old human. This model is named "Sharif University of Technology Head Trauma Model (SUTHTM)". By validating SUTHTM, the model is then used to study the...
Transparency enhancement of haptic systems based on compensation of device dynamics
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 10, Issue PART A , 2010 , Pages 103-110 ; 9780791843833 (ISBN) ; Ahmadian, M. T ; Vossoughi, G. R ; Motamedi, M ; Sharif University of Technology
Abstract
Transparency is a measure of performance in haptic devices. In order to improve transparency and reduce the difference between the impedance transmitted to the user and the target impedance it is necessary to compensate for the dynamics of the haptic device. Due to stability reasons improvement of transparency is limited. Passivity as a stability criterion has been used widely in design and analysis of haptic devices, Since passivity is a conservative criterion, it acts as an obstacle in improving transparency of the haptic interfaces. In this paper instead of passivity, robust stability of the interaction is studied in the presence of parametric uncertainties due to variations in user hand...
Torsion of strain gradient bars
, Article International Journal of Engineering Science ; Volume 49, Issue 9 , September , 2011 , Pages 856-866 ; 00207225 (ISSN) ; Tajalli, S. A ; Movahhedy, M. R ; Akbari, J ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
The governing differential equation and both classical and non-classical boundary conditions of strain gradient bars are derived using variational approach. A closed-form analytical solution is obtained for static torsion and the characteristic equation, which gives the natural frequencies, is derived and analytically solved for the free torsional vibrations of the strain gradient microbars. A fixed-fixed microbar is considered as a specific case to investigate the torsional size-dependent static and free-vibration behavior of strain gradient microbars. The results of the current model are compared to those of the modified couple stress and classical theories
Torsional sensitivity of the first four modes of an AFM cantilever with a sidewall probe using analytical method
, Article Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009, 30 August 2009 through 2 September 2009, San Diego, CA ; Volume 6 , August-September , 2010 , Pages 617-622 ; 9780791849033 (ISBN) ; Rahaeifard, M ; Ahmadian, M. T ; Sharif University of Technology
2010
Abstract
In this study, using analytical method, the torsional resonant frequency and torsional sensitivity of the first four modes of an AFM cantilever with sidewall probe including a horizontal cantilever and a vertical extension is analyzed and a closed form for torsional sensitivity of the probe is derived. In addition, the effect of relative parameters such as ratio of vertical extension length to horizontal cantilever length is investigated. According to this study, the results show that as contact stiffness increases, the resonant frequencies of all vibration modes increases until they reach constant values at very high values of contact stiffness. It is also can be found that low-order modes...