Loading...
Search for:
ahmadian--m--t
0.009 seconds
Total 275 records
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...
Analytical modeling of bending effect on the torsional response of electrostatically actuated micromirrors
, Article Optik ; Volume 124, Issue 12 , June , 2013 , Pages 1278-1286 ; 00304026 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2013
Abstract
This paper presents analytical soltions for the nonlinear problem of electrostatically actuated torsional micromirrors considering the bending of the torsional beams. First the energy method is used for finding the equilibrium equations. Then the explicit function theorem is utilized for finding the equations governing the instability mode of the mirror. These equations are then solved using Homotopy Perturbation Method (HPM) for the especial case of α = 0 where α is a small nondimensional geometrical parameter defining the starting point of the underneath electrodes. Then straight forward perturbation method is applied for finding the pull-in angle and pull-in displacement of the...
Analytical closed form model for static pull-in analysis in electrostatically actuated torsional micromirrors
, Article Journal of Mechanical Science and Technology ; Volume 27, Issue 5 , 2013 , Pages 1443-1449 ; 1738494X (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2013
Abstract
The objective of this work is to create an analytical framework to study the static pull-in and also equilibrium behavior in electrostatically actuated torsional micromirrors. First the equation governing the static behavior of electrostatic torsion micromirrors is derived and normalized. Perturbation method, the method of straight forward expansion is utilized to find the pull-in angle of the mirror. Comparison of the presented results with numerical ones available in the literature shows that the proposed second order perturbation expansion gives very precise approximations for the pull-in angle of the mirror. Then straightforward perturbation expansion method is used again to analytically...
On free vibration of functionally graded euler-bernoulli beam models based on the non-local theory
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 12 , 2012 , Pages 169-173 ; 9780791845288 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
In this paper, the governing equations and boundary conditions of a functionally graded Euler-Bernoulli beam are developed based on the non-local theory of elasticity. Afterward, the free vibration is investigated and the effects of the axial load, the non-local parameter and the power index on the natural frequency of a hinged-hinged beam is assessed. The results indicate that the non-local parameter has a decreasing effect on the frequency while the power index has an increasing effect. It is also noted that the effect of the axial load is increasing too
Adaptive neural fuzzy inference (ANFI) modeling technique for production of marine biosurfactant
, Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 2, Issue PARTS A AND B , 2012 , Pages 47-52 ; 9780791845011 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
In this study; a Sugeno type ANFI model which describes the relationship between the bio surfactant concentration as a model output and the critical medium components as its inputs has been constructed. The critical medium components are glucose, urea,SrCl2 and MgSo4 .The experimental data for training and testing capability of the model obtained by a statistical experimental design which have been captured from literatures. Six generalized bell shaped membership function have been selected for each of input variables and based on the training data ANFI model has been trained using the hybrid learning algorithm. The yielded biosurfactant concentration values from the model prediction shows...
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...
Deformation characterization of mouse oocyte cell using inverse finite element and LevenbergâMarquardt optimization algorithm in needle injection experiment
, Article Proceedings of the ASME Design Engineering Technical Conference, 12 August 2012 through 12 August 2012 ; Volume 2, Issue PARTS A AND B , August , 2012 , Pages 847-852 ; 9780791845011 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
In order to better understand the mechanical properties of biological cells, characterization and investigation of their material behavior is necessary. In this paper hyperelastic Neo-Hookean material is used to characterize the mechanicalproperties of mouse oocyte cell. It has been assumed that the cell behavior is continues, isotropic, nonlinear and homogenous material. Then, by matching the experimental data with finite element (FE) simulation result and using the LevenbergâMarquardt optimization algorithm, the nonlinear hyperelastic model parameters have been extracted. Experimental data of mouse oocyte captured from literatures. Advantage of the developed model is that it can be used to...
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
Prediction of reaction force on external indenter in cell injection experiment using support vector machine technique
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 2 , 2012 , Pages 537-543 ; 9780791845189 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Evaluation of the reaction force on a tool which is used for exertion of force on biomaterials such as biological cells or soft tissues has applications in virtual reality based medical simulators or haptic tools. In this study, two least square based support vector machine (SVM) models have been constructed to predict the indentation or reaction force on mouse oocyte and embryo cells in cell injection experiment. Inputs of these two models are geometrical parameters of indented cell, namely dimple radius (a), dimple depth (w) and radius of the semicircular curve (R). Experimental data for calibration and prediction of the models have been captured from literatures. The performance of the...
Force controlled manipulation of biological cells using a monolithic MEMS based nano-micro gripper
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 2 , 2012 , Pages 193-201 ; 9780791845189 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Nano-micro grippers are able to pick-transport-place the micro or nanometer -sized materials, such as manipulation of biological cells or DNA molecules in a liquid medium. This paper proposes a novel monolithic nano-micro gripper structure with two axis piezoresistive force sensor which its resolution is under nanoNewton. The results of the study have been obtained by the simulation of the proposed gripper structure in Matlab software. Motion of the gripper arm is produced by a voice coil actuator. The behavior of the cell has been derived using the assumptions in the literatures. Moreover, two simple PID controllers, one for control of the gripper motion and another for control of the force...
Static and vibrational analysis of fullerene using a newly designed spherical super element
, Article Scientia Iranica ; Volume 19, Issue 5 , 2012 , Pages 1316-1323 ; 10263098 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Accurate prediction of static and dynamic response of nano structures under external excitations has been one of the interests of scientists in the last decade. Several applications of nano machines make it necessary to analyze their components, such as nano bearing, precisely. In this paper, the static and vibrational behavior of a fullerene as a sensitive part of nano bearing under external forces is simulated by a newly designed spherical super element. This super element is designed in such a way that the user can select as many numbers of nodes as desired, so that it can be implemented in different desired precisions. In this study, a 228-node super element, which is similar to a hollow...
Analytical modeling of static behavior of electrostatically actuated nano/micromirrors considering van der Waals forces
, Article Acta Mechanica Sinica/Lixue Xuebao ; Volume 28, Issue 3 , June , 2012 , Pages 729-736 ; 05677718 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
In this paper, the effect of van der Waals (vdW) force on the pull-in behavior of electrostatically actuated nano/micromirrors is investigated. First, the minimum potential energy principle is utilized to find the equation governing the static behavior of nano/micromirror under electrostatic and vdW forces. Then, the stability of static equilibrium points is analyzed using the energy method. It is found that when there exist two equilibrium points, the smaller one is stable and the larger one is unstable. The effects of different design parameters on the mirror's pull-in angle and pull-in voltage are studied and it is found that vdW force can considerably reduce the stability limit of the...
Design and implementation of a new spherical super element in structural analysis
, Article Applied Mathematics and Computation ; Volume 218, Issue 14 , March , 2012 , Pages 7546-7561 ; 00963003 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Finite Element Method (FEM) has proved to be a powerful tool for the analysis of mechanical problems such as finding natural frequency and deformation of structures. Design and implementation of super elements with a purpose in reduction of computational time along with accuracy is one of the challenges facing engineers in the past decade. In this study a newly spherical super element is designed and implemented to some problems. This element is generated in such a way that the user can select as many numbers of nodes as desired. Proper formulation is presented to generate the shape function for each node in this element. Some examples of static and vibration analysis using this element are...
Free vibration analysis of FGM beams with different boundary conditions using RKPM meshless method
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 1, Issue PARTS A AND B , August , 2011 , Pages 1187-1191 ; 9780791854785 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
Abstract
This paper presents free vibration analysis of functionally graded material (FGM) beams with different boundary conditions, using RKPM (Reproducing Kernel Particle Method), which is a meshless method. System of equations of motion is derived by using Lagrange's method under the assumption of Euler-Bernoulli beam theory. Boundary conditions of beam are taken into account by using Lagrange multipliers. It is assumed that material properties of the beam vary continuously in the thickness direction according to the power-law form. RKPM is applied to obtain eigenvalue equation of vibration and natural frequencies are obtained. It should be noted that for special cases where the beam is uniform,...
Multi-objective optimization of functionally graded hollow cylinders
, Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ; Volume 8 , 2011 , Pages 583-590 ; 9780791854945 (ISBN) ; Ahmadian, M. T ; ASME ; Sharif University of Technology
Abstract
In this study, two physical properties of simply supported hollow cylinders made of functionally graded materials are investigated. These two properties are mass and first natural frequency which is desirable to be minimized and maximized respectively in mechanical applications. The functionally graded material properties are assumed to vary continuously through the thickness of the cylinder. In this multi-objective optimization problem the first natural frequency of the FGM cylinders as well as its mass are formulated in terms of the volume fraction of the constituents, then by using Genetic algorithm optimization method the continuous volume fraction function of the constituents has been...
Deformation, stress and natural frequency analysis of the fullerene by finite super element method
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 7 , August , 2011 , Pages 153-158 ; 9780791854846 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
Accurate prediction of static and dynamic response of nano structures is one of the important interests of scientists in the last decade. Nano bearing as an important part of nano machines has been extensively implemented in recognizing and disassembling cancerous cells and building molecular support structures for strengthening bones. For this reason, Molecular Dynamic Method and some experimental methods are implemented in this area. As nano ball bearing is one of the most important components of nano machines, a large number of studies are concentrated to analyze it statically and dynamically. In this paper, a Fullerene is simulated by a spherical super element whose stress, deformation...
Design a new spherical super element to static and modal analysis of spherical structures
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 1, Issue PARTS A AND B , August , 2011 , Pages 493-497 ; 9780791854785 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
Hollow Spherical Structures such as spherical pressure vessels are widely used in industries. Using faster numerical methods to solve these spherical problems has been one of the research interests in the last decade. Super elements are elements capable of producing the same accurate result in comparison with several conventional elements. In this paper, a new spherical super element is designed and implemented to study the static deformation and modal analysis of a spherical structure. In the static analysis mean of the inner radial displacements of the hollow structure under the internal pressure is evaluated. also performing the modal analysis, natural frequencies of the structure under...
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...
Application of a new spherical super element in predicting the deformation of biological cells in microinjection
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 7 , August , 2011 , Pages 41-49 ; 9780791854846 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
Biological cell injection is a sensitive and important work which is implemented in injection of foreign materials into individual cells. Microinjection is significantly developed in the field of drug discovery and genetics so predicting the behavior of cell in microinjection is remarkably important because a tiny excessive manipulation force can destroy the tissue of the biological cell. There are a few analytical methods available to simulate the cell injection, hence the numerical methods such as FEM are suitable to be used to model the microinjection. In this study, a new spherical super element is presented to model the biological cells and deformation of a specific cell under an...
Comparison of deformation analysis of a biological cell under an injection force using analytical, experimental and finite element methods and Artificial Neural Network
, Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ; Volume 2 , 2011 , Pages 499-507 ; 9780791854884 (ISBN) ; Ahmadian, M. T ; ASME ; Sharif University of Technology
Abstract
Biological cell injection is a sensitive and important work which is implemented in injection of foreign materials into individual cells. Microinjection is significantly developed in the field of drug discovery and genetics so predicting the behavior of cell in microinjection is remarkably important because a tiny excessive manipulation force can destroy the tissue of the biological cell. There are a few analytical methods available to simulate the cell injection, hence the numerical methods such as FEM are suitable to be used to model the microinjection. In this study, a new spherical super element is presented to model the biological cells and deformation of a specific cell under an...