Design and verification of a parallel elastic robotic leg.

This paper presents the design and experimental verification of a parallel elastic robotic leg mechanism that aims to capture the dynamics of the linear mass-spring-damper model. The mechanism utilizes a wrapping cam mechanism to linearize the non-linear force resulting from the elongation of the parallel elastic element. Firstly, we explain the desired dynamics of the mass-spring-damper model, including the impact transitions, and the design of the wrapping cam mechanism.

Simulation of turbulence induced sound generation inside stenosed femoral artery models with different severities and eccentricities.

Background And Objectives: Recent developments of low-cost, compact acoustic sensors, advanced signal processing tools and powerful computational resources allow researchers design new scoring systems for acoustic detection of arterial stenoses. In this study, numerical simulations of blood flow inside stenosed arteries are performed to understand the effect of stenosis severity and eccentricity on the turbulence induced wall pressure fluctuations and the generated sound.

Methods: Axisymmetric and eccentric elliptic stenoses of five different severities are generated inside a 6.

Effect of stenosis shape on the sound emitted from a constricted blood vessel.

Effect of stenosis shape on the post-stenotic pressure fluctuations and the sound emitted from a constricted blood vessel is studied numerically. Large eddy simulations are performed using OpenFOAM under pulsatile flow conditions with a non-Newtonian fluid model. Findings indicate that the high slope at the stenosis entrance and overlap of more than one stenosis shorten the length of the flow jet, trigger turbulence, and increase vortical activity, turbulent kinetic energy, and magnitude of pressure fluctuations at the post-stenotic region.

Numerical investigation of wall pressure fluctuations downstream of concentric and eccentric blunt stenosis models.

Pressure fluctuations that cause acoustic radiation from vessel models with concentric and eccentric blunt stenoses are investigated. Large eddy simulations of non-pulsatile flow condition are performed using OpenFOAM. Calculated amplitude and spatial-spectral distribution of acoustic pressures at the post-stenotic region are compared with previous experimental and theoretical results.

Computational analysis for non-invasive detection of stenosis in peripheral arteries.

Atherosclerosis usually affects the entire cardiovascular system, including peripheral blood vessels. Peripheral arterial stenosis may indicate possible serious vascular disorders related to more vital organs. If peripheral arterial stenosis can be discerned at an early stage, it can serve as a warning sign to take precautions, such as using more invasive diagnostic techniques or adopting a healthier life style.

Experimental and numerical investigation on soft tissue dynamic response due to turbulence-induced arterial vibration.

Peripheral arterial occlusive disease is a serious cardiovascular disorder. The arterial occlusion leads to turbulent flow and arterial sound generation on the inner vessel wall. Stenosis-induced vibro-acoustic waves propagate through the surrounding soft tissues and reach the skin surface.

Flow-induced vibration analysis of constricted artery models with surrounding soft tissue.

Arterial stenosis is a vascular pathology which leads to serious cardiovascular diseases. Blood flow through a constriction generates sound and vibration due to fluctuating turbulent pressures. Generated vibro-acoustic waves propagate through surrounding soft tissues and reach the skin surface and may provide valuable insight for noninvasive diagnostic purposes.

Interdependence of pulsed ultrasound and shear stress effects on cell morphology and gene expression.

Fluid shear stress is a key biomechanical regulatory factor in a several biological systems including bone tissue. Bone cells are also regulated by exogenous acoustic vibration, which has therapeutic benefits. In this study, we determined the effects of shear stress and pulsed ultrasound (US), alone and in series on osteoblast morphology and gene expression.

Acoustic radiation from a fluid-filled, subsurface vascular tube with internal turbulent flow due to a constriction.

The vibration of a thin-walled cylindrical, compliant viscoelastic tube with internal turbulent flow due to an axisymmetric constriction is studied theoretically and experimentally. Vibration of the tube is considered with internal fluid coupling only, and with coupling to internal-flowing fluid and external stagnant fluid or external tissue-like viscoelastic material. The theoretical analysis includes the adaptation of a model for turbulence in the internal fluid and its vibratory excitation of and interaction with the tube wall and surrounding viscoelastic medium.

Surface response of a viscoelastic medium to subsurface acoustic sources with application to medical diagnosis.

The response at the surface of an isotropic viscoelastic medium to buried fundamental acoustic sources is studied theoretically, computationally and experimentally. Finite and infinitesimal monopole and dipole sources within the low audible frequency range (40-400 Hz) are considered. Analytical and numerical integral solutions that account for compression, shear and surface wave response to the buried sources are formulated and compared with numerical finite element simulations and experimental studies on finite dimension phantom models.