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local-stability
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The Effect of Speed on Kinematic Variability and Dynamic Stability of Trunk in Subjects with and without Nonspecific Low back Pain during a Sagittal Repetitive Flexion Extension Movements
, M.Sc. Thesis Sharif University of Technology ; Parnianpour, Mohammad (Supervisor) ; Narimani, Rouya (Supervisor) ; Sanjari, Mohammad Ali (Co-Advisor)
Abstract
Low back pain is one the most prevalent disease and major economic issue facing modern countries. Epidemiological studies suggest that maximum trunk flexion, the angular velocity of trunk and the rate of repetitive movements (such as flexion-extension), are associated with low-back disorders. From biomechanical point of view, lack of stability during dynamic repetitive movements, increases the risk of injuries. On the other hand, some researchers suggest increasing motor variability could be an intrinsic factor to intervene muscuskeletal disorders during repetitive movements. Pace of repetitive occupational tasks could affect both, motor variability and dynamic stability. The goal of this...
Null Controllability and Stabilizability of Compressible Navier-stokes System in One Dimension
, M.Sc. Thesis Sharif University of Technology ; Hesaraki, Mahmoud (Supervisor)
Abstract
In this thesis we study the exponential stabilization of the one dimensional compressible Navier-Stokes system, in a bounded interval locally around a constant steady state by a localized distributed control acting only in the velocity equation. In fact this is an analysis of a paper that published by Shirshendu Chowdhury, Debayan Maity, Mithily Ramaswamy and Jean-Pierre Raymond in Journal of Differential Equations. We determine a linear feedback law able to stabilize a nonlinear transformed system. Coming back to the original nonlinear system, we obtain a nonlinear feedback law able to stabilize locally this nonlinear system. The result is providing feedback control laws stabilizing...
Effect of Hand-Held Flexible-Bar on Postural Stability and Shoulder Muscle Synergies during Repetitive Planar Hand Exercises
, M.Sc. Thesis Sharif University of Technology ; Parnianpour, Mohammad (Supervisor) ; Hoviattalab, Maryam (Supervisor)
Abstract
Shoulder is one of the most important joints of the body with high degrees of freedom. Synergic analysis of the shoulder muscles shows the joint condition due to applied force or torque. The results of the linear COP parameters and nonlinear analysis indicate the characteristics of subjects postural stability. The flexi-bar is a rehabilitation tool which stimulates the muscles. In this study, the effect of bar on the body has been examined. The modeling is carried out in two horizontal and vertical condition of bar in sixteen separate positions in the upper right side quadrant of the model. Muscle activation and joint stiffness, force and torque were obtained. COP data in AP and ML were...
Fair resource allocation in Ad hoc networks in the presence of delay
, Article INDICON 2008 IEEE Conference and Exhibition on Control, Communications and Automation, Kanpur, 11 December 2008 through 13 December 2008 ; Volume 1 , 2008 , Pages 159-164 ; 9781424427475 (ISBN) ; Haeri, M ; Sharif University of Technology
IEEE Computer Society
2008
Abstract
In this paper, the problem of resource allocation at an Ad hoc network with nodes not using any infrastructure to cooperate with each other is considered. By using a simple interference model in wireless links, the convergence and stability of a fair resource allocation scheme in the absence of delay is investigated. Also, the local stability of the scheme in the presence of upper-bounded delay is verified. Simulations results illustrate the convergence and fairness of this scheme considering different initial states for different sources. The performance of the scheme in the presence of different disturbances for each flow in transient and steady state along with its local stability in the...
Bazykyn Predator-Prey Model
, M.Sc. Thesis Sharif University of Technology ; Hesaraki, Mahmoud (Supervisor)
Abstract
prey and predator model occurs when the growth rate of species decline and increase the growth rate of other species. In the first chapter of this thesis review of basic concepts and theorems are important. In the second quarter, positive solutions in a heterogeneous system model release Bazykin with classic techniques to points most important of which is the case. In the third season, Stability and bifurcation system and predator prey Bazykin model with the function response Bdyngtn- De Angelis to equilibrium the points. In the fourth chapter in the normal form prey and predator system model Bazykin discuss
Welding current and arc voltage control in a GMAW process using ARMarkov based MPC
, Article Control Engineering Practice ; Volume 19, Issue 12 , December , 2011 , Pages 1408-1422 ; 09670661 (ISSN) ; Haeri, M ; Sharif University of Technology
Abstract
A predictive functional controller based on ARMarkov model structure has been designed to control welding current and arc voltage in a GMAW process. The closed loop system performance is investigated through computer simulations and is compared by those achieved from implementing two commonly used controllers i.e. PI and feedback linearization based PID. The local stability of the closed loop system is analyzed in the presence of uncertainties in the linearized model of the process as well as the control parameters. Finally it is shown that the proposed controller performs like a PI controller along with a pre-filter compensator
Numerical study of ignition process in turbulent shear-less methane-air mixing layer
, Article Flow, Turbulence and Combustion ; Volume 99, Issue 2 , 2017 , Pages 411-436 ; 13866184 (ISSN) ; Tabejamaat, S ; Mani, M ; Farshchi, M ; Sharif University of Technology
Springer Netherlands
2017
Abstract
In this work, ignition process in a turbulent shear-less methane-air mixing layer is numerically investigated. A compressible large eddy simulation method with Smagorinsky sub-grid scale model is used to solve the flow field. Also, a thickened flame combustion model and DRM-19 reduced mechanism are used to compute species distribution and the heat release. Non-reacting mean and RMS axial velocity profiles and mean mixture fraction are validated against experimental data. Instantaneous mixture fraction contours show that the large bursts penetrate from the fuel stream into that of the oxidizer and vice versa and a random behaviour in the cross-stream direction. Flame kernel initiation, growth...
The effects of movement speed on kinematic variability and dynamic stability of the trunk in healthy individuals and low back pain patients
, Article Clinical Biomechanics ; Volume 30, Issue 7 , Aug , 2015 , Pages 682-688 ; 02680033 (ISSN) ; Sanjari, M. A ; Mokhtarinia, H. R ; Moeini Sedeh, S ; Khalaf, K ; Parnianpour, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Background: Comparison of the kinematic variability and dynamic stability of the trunk between healthy and low back pain patient groups can contribute to gaining valuable information about the movement patterns and neuromotor strategies involved in various movement tasks. Methods: Fourteen chronic low back pain patients with mild symptoms and twelve healthy male volunteers performed repeated trunk flexion-extension movements in the sagittal plane at three different speeds: 20 cycles/min, self-selected, and 40 cycles/min. Mean standard deviations, coefficient of variation and variance ratio as variability measures; maximum finite-time Lyapunov exponents and maximum Floquet multipliers as...