Sharif Digital Repository

This paper introduces three geometric features, from deformed shape of a soft tissue, which demonstrate good correlation with probing force and maximum local stress. Using FEM simulation, 2D and 3D model of an in vivo porcine liver was built for different probing tasks. Maximum deformation angle, maximum deformation depth and width of displacement constraint of the reconstructed shape of the deformed body were calculated. Two neural networks were trained from these features and the calculated interaction forces. The features are shown to have high potential to provide force estimation either for haptic devices or to assess the damage to the tissue in large deformations of up to 40%  

A robotic system with 6 DOF mobility was proposed for reduction of femoral shaft fractures based on Stewart platform. A plan for implementing the platform on bone fragments was introduced and a step by step strategy for performing the reduction procedure, based on the system's inverse kinematic solution, was proposed. The efficacy of the system was evaluated in some case studies and it was shown that it can be locked to act as an external fixator  

The purpose of this research was to address the design of augmented cones used in revision knee arthroplasty surgeries to fill the large bone defects in metaphyseal regions. A parametric finite element study was performed to investigate the effect of the geometrical design variables of the cone on its biomechanical performance. The model included a nonhomogeneous voxel-based representation for bone, a parametric model of the cone, a standard femoral component of the revision knee arthroplasty, and a cement layer between the cone and implant. Sixteen designs of the cone were analyzed by changing its upper and lower radii, which resulted in different cone angles and cone thicknesses. The... 

Background: Many deficiencies of minimally invasive robotic surgery systems can be eliminated by using automated laparoscopic tools with force measurement and control capability. Method: A fully modular, automated laparoscopic instrument with a proximal force sensory system was designed and fabricated. The efficacy of the instrument was evaluated experimentally when functioning in an autonomous force-controlled grasping scheme. Results: The designed instrument was shown to work easily with standard laparoscopic tools, with the whole distal part detachable for autoclave sterilization. The root mean squared error (RMSE) of the actual pinch force from the target ramp was 0.318 N; it was 0.402 N... 

A transverse-plane hyperelastic micromechanical model of brain white matter tissue was developed using the embedded element technique (EET). The model consisted of a histology-informed probabilistic distribution of axonal fibers embedded within an extracellular matrix, both described using the generalized Ogden hyperelastic material model. A correcting method, based on the strain energy density function, was formulated to resolve the stiffness redundancy problem of the EET in large deformation regime. The model was then used to predict the homogenized tissue behavior and the associated localized responses of the axonal fibers under quasi-static, transverse, large deformations. Results... 

To help walking, using assistive devices can be considered to reduce the loads caused by weight and to effectively decrease the propulsive forces. In this study, a mobility Saddle-Assistive Device (S-AD) supporting body weight while walking was evaluated on two healthy volunteers. This device is based on the support of body weight against gravity with the help of a saddle, which is not used in other passive mobility assistive devices. To prove the efficiency of this device, the experimental results obtained while walking with this device were compared with those related to walking without the assistive device. The results showed that this device could significantly reduce the forces and... 

This paper presents a bi-directional closed-form analytical solution, in the framework of nonlinear soft composites mechanics, for top-down hyperelastic characterization of brain white matter tissue components, based on the directional homogenized responses of the tissue in the axial and transverse directions. The white matter is considered as a transversely isotropic neo-Hookean composite made of unidirectional distribution of axonal fibers within the extracellular matrix. First, two homogenization formulations are derived for the homogenized axial and transverse shear moduli of the tissue, based on definition of the strain energy density function. Next, the rule of mixtures and... 

The majority of the people with incomplete spinal cord injury lose their walking ability, due to the weakness of their muscle motors in providing torque. As a result, developing assistive devices to improve their conditionis of great importance. In this study, a combined application of the saddle-assistive device (S-AD) and mechanical medial linkage or thosis was evaluated to improve the walking ability in patients with spinal cord injury in the gait laboratory. This mobile assistive device is called the saddle-assistive device equipped with medial linkage or thosis (S-ADEM). In this device, a mechanical orthosis was used in a wheeled walker as previously done in the literature. Initially,... 

Physical problems caused by fractures, aging, stroke, and accidents can reduce foot power; these, in the long term, can dwindle the muscles of the waist, thighs, and legs. These conditions provide the basis for the invalidism of the harmed people. In this study, a saddle-walker was designed and evaluated to help people suffering from spinal cord injury and patients with lower limb weakness. This S-AD works based on body weight support against the previously report designs. This saddle-walker consisted of a non-powered four-wheel walker helping to walk and a powered mechanism for the sit-to-stand (STS) transfer. A set of experiments were done on the STS in the use of the standard walker and... 

Heat-bath algorithmic cooling (HBAC) techniques are techniques that are used to purify a target element in a quantum system. These methods compress and transfer entropy away from the target element into auxiliary elements of the system. The performance of algorithmic cooling has been investigated under ideal noiseless conditions. However, realistic implementations are imperfect, and for practical purposes, noise should be taken into account. Here we analyze HBAC techniques under realistic noise models. Surprisingly, we find that noise can, in some cases, enhance the performance and improve the cooling limit of HBAC techniques. We numerically simulate the noisy algorithmic cooling for the two... 

The currently available robotic systems rely on rigid heart stabilizers to perform totally endoscopic coronary artery bypass (TECAB) surgery on beating hearts. Although such stabilizers facilitate the anastomosis procedure by immobilizing the heart and holding the surgery site steady, they can cause damage to the heart tissue and rupture of the capillary vessels, due to applying relatively large pressures on the epicardium. In this paper, we propose an advanced robotic approach to perform TECAB on a beating heart with minimal invasiveness. The idea comes from the fact that the main pulsations of the heart occur as excursions in normal direction, i.e., perpendicular to the heart surface. We... 

The growth of database application usage requires DataBase Management Systems (DBMS) that are accessible, reliable, and dependable. One approach to handle these requirements is replication mechanism. Replication mechanism can be divided into various categories. Some related works consider two categories for replication mechanisms: heterogeneous and homogenous however majority of them classify them in three groups: physical, trigger-based and log based schema. Log-based replication mechanisms are the most widely used category among DBMS vendors. Adapting such approach for heterogeneous systems is a complex task, because of lack of log understanding in the other end. Semantic technologies... 

The assessment of the various impairments in brain damage including spasticity is important. The purpose of this study was to develop a new biomechanical method based on quantification of velocity reduction (VR) suitable for clinical use  

Background: An effective master robot for haptic tele-surgery applications needs to provide a solution for the inversed movements of the surgical tool, in addition to sufficient workspace and manipulability, with minimal moving inertia. Method: A novel 4+1-DOF mechanism was proposed, based on a triple parallelogram linkage, which provided a Remote Center of Motion (RCM) at the back of the user's hand. The kinematics of the robot was analyzed and a prototype was fabricated and evaluated by experimental tests. Results: With a RCM at the back of the user's hand the actuators far from the end effector, the robot could produce the sensation of hand-inside surgery with minimal moving inertia. The... 

Proper modeling of the human arm dynamic, as it interacts with telemanipulation and haptic systems, is important in enhancing the transparency of these systems. In this article, we introduced an adaptive identifier to estimate the impedance characteristic of a human operator as it interacts with a single translational degree of freedom mechanism. The five parameter model, including an extra spring and damper for a better approximation of the dynamic behavior of human arm, has been used. Since the impedance characteristic of human arm differs from one individual to another, it is important to estimate these parameters for each individual and update the controller to enhance the transparency... 

Medical applications of rapid prototyping have an increasing trend, making the future of RP more and more promising. These applications may include design, development, and manufacture of medical devices and instrumentation, as well as implant design, anatomical modeling, surgical planning, surgical implants, and prosthesis fabrication. This paper provides a new methodology for customized hip prosthesis that could provide high accuracy of femoral canal reconstruction via 3D modeling of prosthesis stem, 3D modeling of prosthesis neck, and facilitating the communication between the designer and surgeon. Combining RP technologies and rapid tooling with this novel custom-made hip prosthesis,... 

For simulating the surgical procedures in a virtual environment, it is necessary to propose a suitable virtual environment model which can reflect the real physical tool-tissue interaction behavior and a proper human user interface appropriate dynamic model. In this study, a linear Kelvin-Voigt and a nonlinear Hunt-Crossley models have been utilized to describe human hand dynamics during interaction with a haptic interface. Using the Lyapunov stability criteria, an adaptive neural network based controller being designed for guaranteeing the stability of the entire system, considering a nonlinear model for the environment, an inertia for a virtual tool, a constant time delay for data... 

Background: Kinematic indices (KIs) are frequently used as objective measures to assess the upper extremities motor performance in post stroke patients. The clinimetric analysis of these indices has been mostly limited to their averaged values over different directions of reaching movements. Recent studies indicate direction dependencies of such motor performances due to neural and/or biomechanical causes. The direction dependencies of such indices and their clinimetric parameters remains to be investigated. Methods: An apparatus was built to perform and measure planar point-to-point reaching tasks in 8 directions using a virtual reality environment. 24 stroke and 18 healthy individuals... 

Assistant robots are widely used in laparoscopic surgery to facilitate the camera holding and manipulation task. A variety of a hands-free operator interfaces have been implemented for user control of the robots, including voice commands, foot pedals, and eye and head motion tracking systems. This paper proposes a novel user control interface, based on processing of the laparoscopic images, that enables the robot to automatically adjust the view of the laparoscopic camera without disturbing the surgeon's concentration. An effective marker-free detection method was investigated to track the instrument position in the laparoscopic images in real time so that the robot could center the... 

In this paper design and fabrication of a wrist exoskeleton robot (ROBOWRIST) has been discussed. The robot has 3 degree of freedom, including flexion/extension, abduction/ adduction and pronation/supination based on the anatomical axis of the body. Four stepper motors are responsible for creating the motion. The exoskeleton can be used for neurorehabilitation and also post-surgery of wrist and forearm. Various therapeutic procedures with a precise tracking can be handled using the control algorithms. Each motor has a separate encoder to measure the angular position and send feedback to the controller. The design goal is to construct a reliable robot that is robust and applicable for...