A 3D multi-scale skeletal muscle model to predict active and passive responses. Application to intra-abdominal pressure prediction

Computational models have been used extensively to study the behavior of skeletal muscle structures, however few of these models are able to evaluate their 3D active response using as input experimental measurements such as electromyography. Hence, improving the activation mechanisms in simulation models can provide interesting and useful achievements in this field. Therefore, the purpose of this paper was to develop a multi-scale chemo-mechanical material model to consider the active behavior of skeletal muscle in 3D geometries. The model was used to investigate the response of abdominal muscles which represent a challenging scenario due to their complex geometry and anatomical conditions. Realistic muscle geometries and other tissues of the human abdomen, including transverse abdominis (TA), internal oblique (IO), external oblique (EO), rectus abdominis (RA), rectus sheath (RSH), linea alba (LA) and aponeurosis (APO) were considered. Since the geometry of these tissues was obtained from magnetic resonance images, an iterative algorithm was implemented to find the initial stress state that achieve the equilibrium of them with the intra-abdominal pressure. In order to investigate the functionality of the proposed model, the increase of intra-abdominal pressure was calculated during cough in the supine position while the Ca2+ signal for activating the muscles was set in regard to experimentally recorded electrical activity from previous studies. The amount of intra-abdominal pressure calculated by the model is consistent with reported experimental results. This model can serve as a virtual laboratory to analyze the role of the abdominal wall components in different conditions, such as the performance of meshes used for repairing hernia defects

Suppression of axial-torsional vibrations in drilling system described by neutral-type delay differential equations

Vibrations in deep drilling systems lead to efficiency deterioration and may even cause the system failure. In this paper, a controller is designed aiming at mitigation of these vibrations, which is based on a neutral-type time delay model that represents distributed axial and torsional dynamics. First, the stability of the associated linearized dynamics is analyzed using a spectral approach. Furthermore, the open-loop system is shown to be stabilizable by state feedback which supports subsequent controller design. An optimization-based continuous pole placement technique has been employed to design a stabilizing controller, which mitigates steady-state drill-string vibrations. The effectiveness of the controller is shown in a representative case study

Failure Procedure in Adhesive Composite Joints under Different Types of Loading

In this paper, we have used numerical simulation to study failure of adhesive joints in composite plates. To determine the failure load, adhesive joints are subjected to different types of loading and gradual failure of the joint is studied using the finite element method. The composite material failure theory is implemented into the FEM software. Also different geometries for the joint edge are considered and effect of these geometries and fillet chamfer angle on the failure load are investigated

INFINITELY VARIABLE SPEED TRANSMISSION

The infinitely variable speed transmission consists of four similar sets of a mechanism, although any number of the sets of a mechanism can be used in the system. Any set contains of a six-bar mechanism. The lengths of the links were selected by an optimization technique. The input angular velocity of the system is assumed constant, while the output angular velocity is a function of the position of a shift lever. The shift lever is attached to the fixed pivot of the output linkage of the first four-bar. The lengths of the linkage are optimized such that minimum variations in output angular velocity for a range of stepless change of speed ratio is obtained. In order to verify the analysis of the system, a prototype was made and the output velocity curves of the system for different values of speed ratios were obtained experimentally. The experimental results compare favorably with theoretical results

Kinematic Analysis of the Spherically Actuated Platform Manipulator

Abstract-New methods for the inverse and forward kinematic analysis of the novel six Degrees of Freedom (6DOF) parallel manipulator which has only two legs are presented. The actuation of the new mechanism is through two base-mounted spherical actuators. In the inverse pose kinematic, active joint variables are directly calculated with no need for the evaluation of passive joint variables. In the forward pose kinematic, closed form solution adopting a new approach is presented. It is shown that the inverse and forward pose kinematic have sixteen and four different solutions, respectively. Moreover, closed form equations for the rate kinematic analysis are proposed. Finally, two different categories of the singularity points for the new mechanism with their geometrical interpretation are introduced. In one category the mechanism loses one or more DOF while in the other one it gains one or more DOF