Multisclae Modeling Of Regular Collagenous Soft Tissues

, Ph.D. Dissertation Sharif University of Technology Fallah, Ali (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firozbakhsh, Keikhosro (Supervisor) ; Mohammadi Aghdam, Mohammad (Co-Supervisor)

Abstract

In this study, mechanical behavior of soft tissue is investigated considering its hierarchical structure. The elastic and viscoelastic behavior of tissue is investigated using multisclae methods. To this end, the tissue is considered as nonlinear composite material consists of non fibrillar matrix reinforced by the collagen fibers. A physically motivated constitutive model is proposed to predict the tisues constitutents behavior. The numerical homogenization is preforemd with the aid of the ABAQUS software and the UMAT subroutine. The results of the presented study is validated with the available experimental results in the literature. Results show that the increasing the loading rate can...

Design of an Active Exoskeleton Robot to Assist Human Elbow and Wrist Motion

, M.Sc. Thesis Sharif University of Technology Mohammadi, Esmaeil (Author) ; Zohoor, Hassan (Supervisor) ; Firozbakhsh, Keikhosrow (Co-Advisor)

Abstract

Most elderly and physically disabled people suffer from lack of functionality and dexterity in their elbow or wrist. These disabilities are due to the damages mostly caused by sport surgery, spinal surgery, or stroke. Therefore, design of an assistive exoskeleton robot for upper limb movements seems necessary. The purpose of this study is to design, fabricate and deliver a control algorithm for an assistive wearable robot. The robot has three degrees of freedom in order to help the flexion/extension of elbow and wrist. Dynamic and kinematic model of elbow, forearm, and wrist is developed to determine the amounts of torques which are required in the joint actuators mounted on the robot....

Design and Manufacturing of Wearable System for Assessment Risk Factor in Symmetric Lifting Task

, M.Sc. Thesis Sharif University of Technology Keshavarz Moghadam, Hossein (Author) ; Firoozbakhsh, Keikhosro (Supervisor) ; Narimani, Roya (Supervisor)

Abstract

Low back disorders (LBD) is one of the most musculo-skeletal disorders in industrial environments in which it can impose to the society.Therefore, it is very important to reaserch the causes of LBDs, prevention methods and evaluation risk factor in lifting tasks in order to avoid the prevalence of LBDs in society. There is no doubt heavy lifting has a significant role in emerging of LBDs. Hence, many safety risk assessment tools have been made by researchers.Using assessment tools, we need to know the input parameters corrospending to the assessment tools. Input parameters in assessment tools have been measured in a way of traditional method or by expensive equipment in laboratories. On...

Micromechanics and constitutive modeling of connective soft tissues

, Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 60 , 2016 , Pages 157-176 ; 17516161 (ISSN) Fallah, A ; Ahmadian, M. T ; Firozbakhsh, K ; Aghdam, M. M ; Sharif University of Technology

Elsevier Ltd 2016

Abstract

In this paper, a micromechanical model for connective soft tissues based on the available histological evidences is developed. The proposed model constituents i.e. collagen fibers and ground matrix are considered as hyperelastic materials. The matrix material is assumed to be isotropic Neo-Hookean while the collagen fibers are considered to be transversely isotropic hyperelastic. In order to take into account the effects of tissue structure in lower scales on the macroscopic behavior of tissue, a strain energy density function (SEDF) is developed for collagen fibers based on tissue hierarchical structure. Macroscopic response and properties of tissue are obtained using the numerical...

Micromechanical modeling of rate-dependent behavior of Connective tissues

, Article Journal of Theoretical Biology ; Volume 416 , 2017 , Pages 119-128 ; 00225193 (ISSN) Fallah, A ; Ahmadian, M. T ; Firozbakhsh, K ; Aghdam, M. M ; Sharif University of Technology

Academic Press 2017

Abstract

In this paper, a constitutive and micromechanical model for prediction of rate-dependent behavior of connective tissues (CTs) is presented. Connective tissues are considered as nonlinear viscoelastic material. The rate-dependent behavior of CTs is incorporated into model using the well-known quasi-linear viscoelasticity (QLV) theory. A planar wavy representative volume element (RVE) is considered based on the tissue microstructure histological evidences. The presented model parameters are identified based on the available experiments in the literature. The presented constitutive model introduced to ABAQUS by means of UMAT subroutine. Results show that, monotonic uniaxial test predictions of...

Developing a Biomechanical Model of Lumbar Spine in Order to Evaluating the Behavior of Spine under Physiological and in Vitro Loading Conditions

, M.Sc. Thesis Sharif University of Technology Borghei Nejad, Mustafa (Author) ; Firozbakhsh, Keikhosrow (Supervisor) ; Parnianpour, Mohammad (Co-Advisor)

Abstract

In present study we are going to introduce a biomechanical model of lumbar spine with using finite element method and use it for evaluating the behavior of spine under different loading conditions.Spine as the main part of muskloskeletal system of human body is tolerating various forces during daily activities.So it's important to know about different approaches for studing the loading conditions wich is using for evaluating the behavior of lumbar implants. In other words in order to obtain correct outputs we need to simulate the real condition in the experiments. We can use biomechanical models in order to comparison the different approaches

Modeling and Analysis of a Nano Particle Impinged on a Human Cell in Gene Therapy

, M.Sc. Thesis Sharif University of Technology Rostami, Majid (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firozbakhsh, Kikhosroo (Supervisor) ; Asghari, Mohsen (Supervisor)

Abstract

owning to the side effects and disadvantages of conventional methods of cancers treatments such as chemotherapy, currently, scientists are attempting to find new methods to replace them. Furthermore, many human diseases like SCID and Hemophilia are due to genetic disorders and scientists are also seeking to find permanent treatments instead of available temporary ones for them. in recent years, regarding the obtained achievement, Gene Therapy is being considered as a promising method for both cancers and genetic disorders treatment. But due to low efficiency of this method at this stage, there is an endevour among researchers for a more profound comprehension of the basics of gene therapy to...

Fabrication of Artificial skin with Electrospun of Nanofiber made of PCL and PVA

, M.Sc. Thesis Sharif University of Technology Mohseni, Mina (Author) ; Shamloo, Amir (Supervisor) ; Naghdabadi, Reza (Co-Advisor) ; Vosooghi, Manoochehr (Co-Advisor) ; Firoozbakhsh, Keikhosro (Co-Advisor)

Abstract

The main goal of this project is to fabricate the scaffolds including Polycaprolactone and Polyvinyle alcohol nanofibers in order to use as artificial skin. For this purpose, electrospinning parameters have been optimized for various injection rates and the scaffolds containing different percent of PCL and PVA have been made. By investigating the cell growth on these scaffolds, the one made up PVA/PCL (30% ) has been introduced as the best scaffold. To improve biological properties of chosen scaffold, a layer of collagen was coated. The angiogenesis capacity has been improved by adding Heparin to PVA nanofibers. Based on assay of heparin release, it was shown that Heparin is released within...