Loading...
Search for:
angular-velocity
0.004 seconds
Total 40 records
Modelling and Analysis of the Effect of Angular Velocity and Acceleration on Brain Strain Field in Traumatic Brain Injury
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Tagh (Supervisor) ; Zohoor, Hassan (Supervisor)
Abstract
Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. A presentation of a model of what happens in the process has been under study for many years; and yet it remains a question due to physiological, geometrical and computational complications. Although the modeling facilities for soft tissue modeling have improved, the precise CT-imaging of human head has revealed novel details of brain, skull and the interface (the meninges), a comprehensive FEM model of which is still being studied. This study aims to present an optimized model of human head after a comprehensive study of the previous models; which includes the brain, skull, and...
Identification and Control of Robot Manipulators using Cell Phone Sensors
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
The goal of controlling robot manipulators is to perform the mission intended for its end effector. Model-based control is a solution that can achieve the control goal with high speed and accuracy in the presence or absence of environmental obstacles by using the knowledge of the robot model. In this thesis, the Armtin 5 robot model parameters were identified in two steps. In the first step, the gravity and friction parameters and in the second step, the dynamic parameters were estimated. In the estimation of gravity and friction parameters, the non-linear behavior of friction causes the estimated parameters to be accompanied by a large amount of error. Estimation of the parameters was...
Numerical Simulation of Turbulent Flow in Annulus with Rotation of an Inner Cylinder in High Angular Speed
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
In this thesis velocity and temperature fields of concentric cylinders with rotation of inner wall have been investigated numerically. Air enters the gap between cylinders and attains fully developed in both velocity and temperature fields after certain lengths. Adiabatic and constant heat flux boundary conditions have been applied and Nusselt number was calculated. In order to analyze the variations of velocity and temperature fields, different angular velocities at constant axial Reynolds number and different axial velocities at constant angular velocity have been investigated. The turbulent stresses were approximated with k ?? ...
Coupled Vibration Analysis of Directional Drilling String Considering Effect of Drilling Mud
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor) ; Farrahi, Gholamhossein (Co-Advisor)
Abstract
Vibration is one of the most important factors in design, operation and lifetime of drill strings. There for, investigation of vibrations in drill string, like every other rotary machine, is very important. The main goal of this research is developing a nonlinear model for a drill string system dynamics in an inclined well. Effects of drilling mud flow rate, weight on bit, angular velocity along with viscous damping, on the stability and vibration of a drill string are studied. Dynamic equation of the model is developed considering axial displacement and lateral bending geometric nonlinear coupling. The effect of drilling mud flow is modeled using Paidoussis formulations. Equation of motion...
Vibration Analysis of Drill String under Inclined Drilling Including Stick-Slip Phenomenon
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Taghi (Supervisor)
Abstract
Vibration is one of the most important factors in design, operation and lifetime of drill string. Evaluation of vibration in the drill string like other rotating machines is very important and according to the length of drill string, whirling is one of the issues discussed. The aim of this thesis is non-linear analysis of the oblique long drill string. By considering the effects of passing drill mud around drill as well as properties of the drilling mud and stick - slip effect in creating whirling. Therefore, the equations related to kinetic and potential energy of a rotating drill string by taking longitudinal and transverse vibrations are written and by using the Lagrange method, equations...
Investigation of the Influence of Geometry and External Field on Fluid Flow Through Carbon Nanotubes by Molecular Dynamics Simulation
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Water transportation through carbon nanotubes is key for designing nanodevices. The directed transport of water molecules through a rotating charged carbon nanotube (CNT) is investigated by molecular dynamics simulations. It is found that the net flux of continuous unidirectional water flow depended sensitively on the charge distribution, charge density and rotation of the CNT. we find that for a constant charge density, the water flux increases with the increase of the charge difference. Besides, we find that the water flux shows a nonlinear dependence on the angular velocity of the rotation. The rotation of the CNT with low angular velocities, can not generate a continuous water flux. The...
Wave propagation analysis of a spinning porous graphene nanoplatelet-reinforced nanoshell
, Article Waves in Random and Complex Media ; Volume 31, Issue 6 , 2021 , Pages 1655-1681 ; 17455030 (ISSN) ; Mohammadi, K ; Barouti, M. M ; Habibi, M ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
In this article, wave propagation behavior of a size-dependent spinning graphene nanoplatelet-reinforced composite (GNPRC) cylindrical nanoshell with porosity is presented. The effects of small scale are analyzed based on nonlocal strain gradient theory (NSGT), this accurate theory employs exact length scale parameter and nonlocal constant. The governing equations of GNPRC cylindrical nanoshell coupled with piezoelectric actuator (PIAC) are evolved by minimum potential energy principle and solved by the analytical method. For the first time in the current study, wave propagation-porosity behavior of a GNPRC cylindrical nanoshell coupled with PIAC is examined based on NSGT. The results show...
Unidirectional transport of water through an asymmetrically charged rotating carbon nanotube
, Article Journal of Physical Chemistry C ; Volume 121, Issue 42 , 2017 , Pages 23649-23658 ; 19327447 (ISSN) ; Moosavi, A ; Sharif University of Technology
Abstract
Achieving a high speed, unidirectional water flow through carbon nanotubes (CNTs) is a key factor in designing novel nanofluidic devices. In this study, utilizing molecular dynamics (MD) simulations, we propose a novel nanoscale water pump for directed water transportation using charged rotating CNTs. Two basic conditions for stable water flow, including thermodynamic nonequilibrium and spatial asymmetry, are provided by introducing partial charges on carbon atoms of the channel with asymmetric patterns and its rotation, respectively. We demonstrate that the performance of the water pump is proportional to the gradient of a linear charge distribution and angular velocity of the rotation. Our...
Transformation of sliding motion to rolling during spheres collision
, Article Granular Matter ; Volume 19, Issue 4 , 2017 ; 14345021 (ISSN) ; Kaviani Rad, H ; Jafari Shad, H ; Sharif University of Technology
Abstract
In this research, we have investigated the three-dimensional elastic collision of two balls, based on friction in the tangential plane. Our aim is to offer analytical closed form relations for post collision parameters such as linear and angular velocities, collision time and tangential and normal impulse in three dimensions. To simplify the problem, stick regime is not considered. In other words, balls have a low tangential coefficient of restitution. Sliding, sliding then rolling, and rolling at the beginning of contact are three cases that can occur during impact which have been considered in our research. The normal interaction force is described by the Hertz contact force and...
The size-dependent electromechanical instability of double-sided and paddle-type actuators in centrifugal and Casimir force fields
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1077-1090 ; 10263098 (ISSN) ; Farahani, M ; Kanani, A ; Rach, R ; Keivani, M ; Abadyan, M ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
The present research is devoted to theoretical study of the pull-in performance of double-sided and paddle-type NEMS actuators fabricated from cylindrical nanowire operating in the Casimir regime and in the presence of the centrifugal force. D'Alembert's principle was used to transform the angular velocity into an equivalent static, centrifugal force. Using the couple stress theory, the constitutive equations of the actuators were derived. The equivalent boundary condition technique was applied to obtain the governing equation of the paddle-type actuator. Three distinct approaches, the Duan-Adomian Method (DAM), Finite Difference Method (FDM), and Lumped Parameter Model (LPM), were applied...
Swirl effects on spinning solid propellant rocket motor performance
, Article AIAA/ASME/SAE/ASEE 42nd Joint Propulsion Conference, Sacramento, CA, 9 July 2006 through 12 July 2006 ; Volume 6 , 2006 , Pages 4586-4590 ; 1563478188 (ISBN); 9781563478185 (ISBN) ; Mazaheri, K ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2006
Abstract
Spining is used in some of solid rocket motors to increase the flight trajectory precision or for stability requirements. The angular acceleration due to the spin increases the burning rate of solid propellant and changes the motor performance by increasing the operating pressure and decreasing the burning time. On the other hand, due to the rocket and its grain rotation, the gases injected from propellant surface to the flow field have an initial angular velocity. The angular velocity of each particle increases as it approaches to the center due to the conservation of angular momentum and a reduction in its radial location, although it vanishes close to the central axis due to viscous...
Small-scale oriented elasticity modeling of functionally graded rotating micro-disks with varying angular velocity in the context of the strain gradient theory
, Article Acta Mechanica ; Volume 232, Issue 6 , 2021 , Pages 2395-2416 ; 00015970 (ISSN) ; Asghari, M ; Kargarzadeh, A ; Badiee, M ; Sharif University of Technology
Springer
2021
Abstract
During the varying angular speed timespans of the start or shutdown of rotating machinery, the machinery components may be subjected to intense mechanical loadings which should be taken into account by its fabricator in the designing processes. In the microscale rotating systems, where the angular velocity is typically very high, the importance of this issue is much higher. In this paper, a comprehensive strain-gradient elasticity formulation is presented for functionally graded rotating micro-disks under the effects of varying angular velocity. The gradation of the constituent material along the radial direction can be a helpful option to mitigate the stresses in rotating micro-disks under...
Slipping and rolling on an inclined plane
, Article European Journal of Physics ; Volume 32, Issue 4 , 2011 , Pages 1049-1057 ; 01430807 (ISSN) ; Aghamohammadi, A ; Sharif University of Technology
2011
Abstract
In the first part of the paper, using a direct calculation two-dimensional motion of a particle sliding on an inclined plane is investigated for general values of friction coefficient (μ). A parametric equation for the trajectory of the particle is also obtained. In the second part of the paper, the motion of a sphere on the inclined plane is studied. It is shown that the evolution equation for the contact point of a sliding sphere is similar to that of a point particle sliding on an inclined plane whose friction coefficient is 7/2 μ. If μ > 2/7 tanθ, for any arbitrary initial velocity and angular velocity, the sphere will roll on the inclined plane after some finite time. In other cases, it...
Sifs for radial cracks in annular discs under internal and external shrinkage pressure and constant angular velocity
, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 7 , 2007 , Pages 653-659 ; 0791843017 (ISBN) ; Gowhari Anaraki, A. R ; Hardy, S. J ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007
Abstract
Finite element method has been implemented to predict stress intensity factors (SIFs) for radial cracks in annular discs under constant angular velocity. Effects of internal and external uniform pressure on the SIFs have also been considered. Linear elastic fracture mechanics finite element analyses have been performed and results are presented in the form of crack configuration factors for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations. The extensive range of crack configuration factors obtained from the analyses is then used to develop equivalent prediction equations via a statistical multiple...
Rotation rate estimation in parametrically excited micro gyroscopes
, Article Mechatronics ; Volume 31 , October , 2015 , Pages 264-275 ; 09574158 (ISSN) ; Salarieh, H ; Alasty, A ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
This paper reports the estimation of angular velocity in micro gyroscopes with parametric excitation. The identification procedure is done into two consecutive steps: In the first step, the physical parameters of the gyroscope (stiffness, damping, and actuator parameters) are estimated via continuous time Extended and Unscented Kalman filter. In the second step, a separate Kalman filter is dedicated to estimate the time varying rotation rate, using the output of the first step. Using numerical simulations, it is found that by introducing an artificial noise in the observer equations and tuning its variance, arbitrary temporal variation of angular velocity can be well tracked by the proposed...
Rotation induced by uniform and non-uniform magnetic fields in a conducting fluid carrying an electric current
, Article RSC Advances ; Volume 6, Issue 113 , 2016 , Pages 112641-112645 ; 20462069 (ISSN) ; Nasiri, M ; Amjadi, A ; Nejati, A ; Sobhani, S.O ; Habibi, M ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
We study the dynamics of a conducting fluid carrying (i) a uniform current in the presence of a non-uniform magnetic field or (ii) carrying a non-uniform current in the presence of a uniform magnetic field, using particle image velocimetry (PIV). Our results show that the average angular velocity of the induced rotation has a power-law dependence on the electric current passing through the fluid with an exponent ≈2/3, in excellent agreement with our simulation results, for the same system. To explain the experimental observations we explore all possibilities for inducing rotation in a fluid carrying an electric current. Our theoretical discussion indicates two scenarios wherein applying...
Reducing the effects of inaccurate fault estimation in spacecraft stabilization
, Article Journal of Aerospace Technology and Management ; Volume 9, Issue 4 , 2017 , Pages 453-460 ; 19849648 (ISSN) ; Alikhani, A ; Fathi Jegarkandi, M ; Sharif University of Technology
Abstract
Reference Governor is an important component of Active Fault Tolerant Control. One of the main reasons for using Reference Governor is to adjust/modify the reference trajectories to maintain the stability of the post-fault system, especially when a series of actuator faults occur and the faulty system can not retain the pre-fault performance. Fault estimation error and delay are important properties of Fault Detection and Diagnosis and have destructive effects on the performance of the Active Fault Tolerant Control. It is shown that, if the fault estimation provided by the Fault Detection and Diagnosis (initial “fault estimation”) is assumed to be precise (an ideal assumption), the...
Optimal stability of a redundant mobile manipulator via genetic algorithm
, Article Robotica ; Volume 24, Issue 6 , 2006 , Pages 739-743 ; 02635747 (ISSN) ; Naderi, D ; Eslami, S ; Sharif University of Technology
2006
Abstract
Once the path of the vehicle and the desired task of the end-effector are predefined, in order to apply the optimal stability criterion, the manipulator should be redundant. In this paper, the goal is to find the position, angular velocity, and angular acceleration of the redundant link of the manipulator such that the entire system becomes optimally stable. By considering the full dynamic interaction between the manipulator and its vehicle, the stability issue becomes more complex. There are some measures of stability and one of them is the tire's upward force. This measure tries to equalize the upward forces of the tires that lead to optimal stability and better steer-ability. Optimizing...
Numerical simulation of centrifugal serpentine micromixers and analyzing mixing quality parameters
, Article Chemical Engineering and Processing: Process Intensification ; Volume 104 , 2016 , Pages 243-252 ; 02552701 (ISSN) ; Madadelahi, M ; Akbari, A ; Sharif University of Technology
Elsevier, B.V
2016
Abstract
Centrifugal microfluidics or the Lab on a CD (LOCD) has developed vast applications in biomedical researches and analyses. Fluid mixing is an application of the LOCD. In this paper, multiple centrifugal micromixers were simulated. Various parameters were originally presumed to have an effect on mixing performance. These parameters include inlet angle, angular velocity, cross-sectional profile, perpendicular length ratio and the number of channels in series. They were each analyzed through simulations. It was gathered that the inlet angle does not significantly affect the mixing quality. Increasing angular velocity steadily increases mixing quality for all geometries. The vertical triangular...
Nonlinear thermoelastic stress analysis of the rotating FGM disk with variable thickness and temperature-dependent material properties using finite element method
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 14 , 2010 , Pages 359-364 ; 9780791843871 (ISBN) ; Damircheli, M ; Sharif University of Technology
Abstract
In this paper, nonlinear radial and hoop thermoelastic stress analysis of rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using the finite element method. In this method, one-dimensional second order elements with three nodes have been used. The geometrical and boundary conditions are in the shape of nonexistence of the pressure (zero radial stress) in both external and internal layers and zero displacement at the internal layer of rotating disk. Furthermore, it's assumed that heat distribution is as second order curve while material properties such as elasticity modulus, Poisson's ratio and thermal expansion coefficient vary by using a...