Sharif Digital Repository

Recently, receptance coupling substructure analysis (RCSA) is used for stability prediction of machine tools through its dynamic response determination. A major challenge is the proper modelling of the substructures joints and determination of their parameters. In this paper, a new approach for predicting tool tip FRF is presented. First, inverse RCSA formulation is extended so that the holder FRFs can be identified directly through experimental modal tests. The great advantage of this formulation is its implementation in arbitrary point numbers along joint length. Therefore, in comparison with previous inverse RCSA approaches, a more realistic joint model can be considered. In addition, due... 

Commute mode choice and number of non-work stops during the commute are joint decisions interacting with each other. If an individual chooses a vehicle for the commute, regarding vehicle's restrictions, there could be some stops. On the other hand, if an individual needs to have some stops, a vehicle can be selected for the commute regarding the number of stops. In this study, to consider the interaction between these decisions, we employed a copula-based joint modeling framework. The data used in this study are drawn from origin-destination travels data of Shiraz-Iran conducted in 1997. The commuting mode choice modeling is undertaken using a multinomial logit model, and the number of... 

Trip destination and mode choice are highly influenced by travelers' perceptions and behaviors; selecting a destination and a vehicle for a trip are two interdependent problems. This paper presents and applies a disaggregate joint model for traveler destination and mode choice. The choice model uses fuzzy set and probability theory to deal with the uncertainty embedded in travelers' perceptions and behaviors. The model is structured as a decision tree in which the fuzzy and non-fuzzy classification of influential variables regarding destination selection and mode choice expand the tree. The most influential explanatory variables among all the variables categorized for travelers' household,... 

Games and their use in rehabilitation have formed a new and rapidly growing area of research. A critical hardware component of rehabilitation programs is the input device that measures the patients' movements. After Microsoft released Kinect, extensive research has been initiated on its applications as an input device for rehabilitation. However, since most of the works in this area rely on a qualitative determination of the joints' movements rather than an accurate quantitative one, detailed analysis of patients' movements is hindered. The aim of this article is to determine the accuracy of the Kinect's joint tracking. To fulfill this task, a model of upper body was fabricated. The... 

Objective: The purpose of this study was to compare the relative stiffness of four common external fixation (XF) configurations used to span and stabilize the knee after knee dislocation. Methods: Synthetic composite femora and tibiae connected with cords were used to simulate a knee. Four configurations of external fixation were tested: anterior femoral pins with monotube (XF1), anterolateral femoral pins with monotube (XF2), anterolateral femoral pins with two connecting rods (XF3), and hinged ring fixator (XF4). Six specimens of each configuration were loaded nondestructively in varus/valgus, anterior-to- posterior shear, flexion/extension, axial compression, internal/external torsion,... 

A large number of offshore platforms of various types have been installed in deep or shallow waters throughout the world. These structures are mainly made of tubular members which are interconnected by using tubular joints. In tubular frames, joints may exhibit considerable flexibility in both elastic and plastic range of response. The resulting flexibility may have marked effects on the overall behavior of offshore platforms.This paper investigates the effects of joint flexibility on local and global behavior of tubular framed structures in linear range of response. A new joint flexibility element is developed on the basis of flexibility matrix and implemented in a finite-element program to... 

We simulated the knee arthrometry test to obtain a deeper understanding of the joint's stability behavior and interpret the arthrometric results more effectively. A 2D sagittal plane finite element model of the lower limb in the standard configuration of knee arthrometry was developed using ANSYS APDL. A detailed model of the knee joint was considered including the femoral articulating contour represented by an ellipse, the tibial plateau represented by a circular arc, and four major knee ligaments and their individual bundles represented by linear and nonlinear tensile springs. A deformable layer of articular cartilage was also considered over the tibial plateau to simulate the bones... 

Based on the force-deflection equation for a beam subjected to lateral point loads, a C2 continuous piecewise bicubic mathematical representation was proposed to model complicated geometrical surfaces, e.g. the articular surfaces of human joints. The method was then extended so that it could be used for mathematical modelling of incomplete nets of data points, as well as smoothing of noisy and/or filtering of erroneous data points. Mathematical techniques were also developed to calculate the required unknown parameters explicitly, with no need to solve the system of equations simultaneously. The performance of the proposed method was evaluated on a number of surface modelling problems,... 

Due to the complexity of the human spinal motion segments, the intervertebral joints are often simulated in the musculoskeletal trunk models as pivots thus allowing no translational degrees of freedom (DOFs). This work aims to investigate, for the first time, the effect of such widely used assumption on trunk muscle forces, spinal loads, kinematics, and stability during a number of static activities. To address this, the shear deformable beam elements used in our nonlinear finite element (OFE) musculoskeletal model of the trunk were either substantially stiffened in translational directions (SFE model) or replaced by hinge joints interconnected through rotational springs (HFE model). Results...