Biomedical Engineering and Bioengineering Commons^™

Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as ‘long-range’. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical …

Indentation Fracture Of Bovine Cortical Bone: Acoustic Emission Technique, Ashkan Safari, Ger Reilly, Brendan Mccormack

Conference Papers

Indentation cutting may result in microcracking and main crack growth which was previously reported. In this study, we recorded the AE signals produced by cracking processes during cutting on cortical bone, measuring the cutting force and correlating between load-displacement curves and AE activities.

A Numerical Acoustic Fluid-Structure Simulation Of Therapeutic Ultrasound Angioplasty, Graham Gavin, Finbar Dolan, M.S J. Hashmi, Garrett Mcguinness

Conference Papers

INTRODUCTION Therapeutic ultrasound angioplasty is the delivery of high amplitude ultrasonic displacements to the distal-tip of small diameter wire waveguides with the goal of disrupting atherosclerotic plaques. This is a minimally invasive procedure that may have potential' in the treatment of complicated chronic total occlusions. The disruption of plaque is due to direct contact ablation and also cavitation, pressure waves and acoustic streaming in the fluid surrounding the vibrating waveguide distal-tip [1]. Cavitation appears to play a major role and some authors have suggested that plaque ablation is only evident above the cavitation threshold [2]. Makin and Everbach [3] performed …

A Numerical Acoustic Fluid-Structure Model Of A Therapeutic Ultrasound Angioplasty Device, Graham Gavin, M.S. J. Hashmi, Finbar Dolan, Garrett Mcguinness

Conference Papers

Ultrasonic angioplasty involves the use of ultrasonic vibrations delivered to the distal-tip of small diameter wire waveguides and is an emerging technology the may have potential use in the treatment of complicated atherosclerotic plaques during cardiovascular surgery. Complicated plaques, including chronic total occlusions and calcified lesions, seriously reduce success rates during standard intervention involving guidewire access, followed by balloon dilation or stent delivery. The large amplitude (0-150 μm) wire waveguide distal-tip displacements in the low-frequency ultrasonic (18-45 kHz) range have been shown to disrupt plaque material by direct contact ablation and cavitation, acoustic streaming and pressure wave components in adjacent …

Analysis Of Indentation Loading Of Cortical Bone Using Acoustic Emission Techniques, Ashkan Safari, Ger Reilly, Brendan Mccormack

Conference Papers

In this study, we recorded the number of Acoustic emission (AE) hits and related AE energy during indentation fracture of cortical bone using a PAC PCI-2 card and pico sensor. A threshold value of 43dB was used to filter premature trigger due to background noise. Registered AE hits had more than one count (threshold crossing). Amplifier gain was set at 40dB with a (0.1-1) MHz band pass filter. 8mm cubes of cortical bones were indented in the longitudinal direction at constant crosshead speed of 1 mm min-1 using a large 2D, 50˚ wedge indenter. We hypothesised that signals occurring as …

Development And Performance Characteristics Of An Ultrasound Angioplasty Device, Graham Gavin, Garrett Mcguinness, Finbar Dolan, M.S. J. Hashmi

Conference Papers

INTRODUCTION The effect of atherosclerosis is well documented and many procedures such as balloon angioplasty and stentimplantation have been developed to reopen occluded arteries. However, there are considerable differences in the material properties of various atherosclerotic lesions as they develop. Many authors have suggested that rigid calcified plaques may require specific procedures that target this rigid material through de-bulking or complete removal (Salunke et al, 1997). Ultrasound angioplasty is the delivery of high power low frequency ultrasound via a wire waveguide to the lesion location. This results in distal tip wire displacements of up to 100um peak-to-peak (p-p) at frequencies …

Experimental And Numerical Investigation Of Therapeutic Ultrasound Angioplasty, Graham Gavin, M.S. J. Hashmi, Garrett B. Mcguinness

Other resources

Therapeutic ultrasound angioplasty is an emerging minimally invasive cardiovascular surgical procedure that involves the delivery of ultrasonic displacements to the distal-tip of small diameter wire waveguides. The ultrasonic distal-tip displacements affect atherosclerotic plaque and thrombus by direct contact ablation, pressure wave components and cavitation, in addition to an acoustic streaming event around the distal-tip. This study uses experimental and numerical methods to investigate ultrasonic displacements in wire waveguides and the effect the distal-tip displacements have on the surrounding fluid. An experimental therapeutic ultrasound wire waveguide apparatus is described that delivers displacements to the distal-tip of 1.0 mm and tapered 0.35 …

Distal Placement Of An End-To-Side Bypass Graft Anastomosis A 3-D Computational Study, John Robert Di Cicco

Mechanical & Aerospace Engineering Theses & Dissertations

A three-dimensional computational fluid dynamics study of blood flow through stenotic arteries has been conducted. Flow phenomena, such as separation regions and turbulence, can be found distal to an arterial stenosis. Frequently, a bypass graft using an end-to-side technique is attached to a stenotic artery to restore adequate blood flow. However, a significant percentage of these grafts fail after thirty postoperative days due to intimal hyperplasia development around the distal anastomosis. Moreover, aberrant wall shear rates have been implicated as a factor in the development of intimal hyperplasia. Thus, the present study examines whether placement of the distal end of …

Pressure Distribution Around Spherical Distal Ball-Tip In Ultrasound Angioplasty, Graham Gavin, Garrett B. Mcguinness, Finbar Dolan, M.S. J. Hashmi

Conference Papers

INTRODUCTION Ultrasound Angioplasty has been shown to be effective in the removal and re-canalising of blockages in arteries (Siegel RJ, 1993). By delivering therapeutic ultrasound to the blockage, via a wire waveguide to a ball-tip, the lesion or thrombus is affected by pressure waves, micro streaming, cavitation and direct contact with the oscillating ball-tip. Most work to date has concentrated on a spherical ball-tip geometry at the distal end of the wire waveguide (Steffen, 1994 and Rosenschein, 1996). Tip displacements usually lie between 10 - 100m (peak-to peak) and ball tip diameters between 1 - 2mm (Atar, 1999 and Yock, …

Field Effect Control Of Electrokinetic Transport Phenomena In Nanofluidics, Song Xue

Mechanical & Aerospace Engineering Theses & Dissertations

Naturally nanofluidics has applications demanding the samples to be handled in exceedingly small quantities due to the small size of the fluidic channels in nanofluidic devices, such as characterization of single biomolecules. Fluids confined in channels of nanometer characteristic dimensions exhibit physical behaviors not observed in large conduits. Charge properties of the nanochannel wall in contact with an aqueous solution play essential roles in the involved electrokinetic transport phenomena occurring in nanofluidic devices. In addition to tuning the charge properties of the nanofluidic channel wall by adjusting the solution properties such as pH and background salt concentration, field effect transistor …

Microscale Investigation Of Thermo-Fluid Transport In The Transition Fil, Region Of An Evaporating Capillary Meniscus Using A Microgravity Environment, Kenneth D. Kihm, Jeffrey S. Allen, Kevin P. Hallinan, David M. Pratt

Mechanical and Aerospace Engineering Faculty Publications

In order to enhance the fundamental understanding of thin film evaporation and thereby improve the critical design concept for two-phase heat transfer devices, microscale heat and mass transport is to be investigated for the transition film region using state-of-the-art optical diagnostic techniques. By utilizing a microgravity environment, the length scales of the transition film region can be extended sufficiently, from submicron to micron, to probe and measure the microscale transport fields which are affected by intermolecular forces. Extension of the thin film dimensions under microgravity will be achieved by using a conical evaporator made of a thin silicon substrate under …

Comment On "Quadriceps Protects The Anterior Cruciate Ligament", Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

No abstract provided.

Multifield Spectral Analysis Of Human Respiratory Sounds, John William Ray Jr.

Doctoral Dissertations

Computer analysis of human respiratory sounds (phonopneumography) has been attempted since the 1960s with poor results. Steady research efforts by numerous researchers have failed to yield a practical diagnostic tool to replace the physician and the stethoscope. This has been the result of the high degree of variability in proposed analysis parameters from subject to subject.

The purpose of this research is to examine a new approach to phonopneumography by comparing multiple lung fields of the same subject for the same breath in order to develop the diagnostic parameters. This approach has the advantage of allowing the subject to provide …

The Effects Of Machining On Structure And Tribological Properties Of Ultra High Molecular Weight Polyethylene For Artificial Joint Prostheses, Jinshan Song

Masters Theses

Understanding the effect of machining on the structure and property of subsurface layer of ultra high molecular weight polyethylene (UHMWPE) can significantly facilitate the increase in longevity of artificial joints. This study was performed to investigate the machining effects on the polymeric structure and tribological properties. Machining parameters include cutting speed, tool feed rate and depth of cut. Temperature rise was studied during machining to assess the extent of thermal degradation due to machining. Polymeric structure of the semicrystalline polymer was characterized using differential scanning calorimetry (DSC) in terms of melting enthalpy, crystallinity and melting temperature. Surface texture and hardness …

Investigation Of Blood Pressure Measurement Using A Hydraulic Occlusive Cuff, Kusha R. Bhattarai

Dissertations and Theses

This thesis presents an improved oscillotonometric system for the measurement of human blood pressure. The study included:

1. The design of a hydraulic occlusive cuff,

2. The investigation of the wave forms taken from the blood pressure measurements, and

3. The design of a mechanism for the simulation of human blood pressure pulse.

In this study, an experimental system consisting of a rigid shell occlusive cuff, a constant volume displacement pump, a transducer, and a chart recorder was designed and used for data collection.

Milking Machine Efficiency And Shed Husbandry Practices, G R. Olney

Journal of the Department of Agriculture, Western Australia, Series 4

MILKING machine efficiency on dairy farms in the Bridgetown, Greenbushes, Balingup, Boyup Brook and Nannup areas was the subject of a recent testing survey.

During the survey 106 machines were tested and the results assessed statistically to gauge the general level of machine efficiency in these districts.