Parametric Optimization of Inductively Driven Liner Compression Driver System

Thesis (Master's)--University of Washington, 2016-06

Improved Techniques for Video Compression and Communication

Thesis (Ph.D.)--University of Washington, 2016-06

Low-bandwidth telerehabilitation for patients who have undergone total knee replacement: preliminary results

We have developed a low-bandwidth, Internet-based telerehabilitation system to provide outpatient rehabilitation to patients who have undergone total knee arthroplasty. The preliminary efficacy of this treatment programme in terms of both physical and functional objective outcome measures was assessed on 21 patients. Subjects receiving a six-week rehabilitation programme were randomized to the telerehabilitation system or the usual face-to-face method. The physical and functional improvements in the telerehabilitation group were similar to those in the control group. There was a non-significant trend for greater improvements in the telerehabilitation group for most outcome measurements. The telerehabilitation programme was well received by patients. The results of this study provide evidence for the efficacy of low-bandwidth telerehabilitation consultations.

Hall-Petch parameters for tension and compression in cast Mg

The flow stress in tensile and compressive deformation has been determined in cast Mg, for a wide range of grain sizes between 36 mum and 1.5 mm. The grain size was varied by alloying Mg with small amounts of Zr. It was found that the 0.2% offset flow stress, sigma(y) (MPa), varies with the grain size, d (m), as sigma(y) = 17.7 + 0.25 d(-1/2) in tension, while sigma(y) = -2.3 + 0.39 d(-1/2) in compression. Possible reasons for the difference between tension and compression are discussed.

A diffusion and T2 relaxation MRI study of the ovine lumbar intervertebral disc under compression in vitro

The ovine lumbar intervertebral disc is a useful model for the human lumbar disc. We present preliminary estimates of diffusion coefficients and T-2 relaxation times in a pilot MRI study of the ovine lumbar intervertebral disc during uniaxial compression in vitro, and identify factors that hamper the ability to accurately monitor the temporal evolution of the effective diffusion tensor at high spatial resolution.

Hall-Petch parameters in tension and compression in cast Mg-2Zn alloys

The flow stress in tension and compression has been measured as a function of plastic strain in Mg-2Zn castings with grain sizes ranging from 55 to 340 mum. Hall-Petch parameters have been calculated and are compared to those previously reported. In contrast to the behaviour of pure Mg grain refined with Zr and of hot-worked and recrystallised pure Mg and Mg-Zn alloys, the cast material shows little tension/compression asymmetry of the flow stress. The possible effects of texture and of twinning are noted. (C) 2004 Elsevier B.V. All rights reserved.

The effect of bandwidth on the quality of transmitted pediatric echocardiograms

Background: Remote access to pediatric cardiology diagnostic services is enabled by real-time transmission of echocardiographic images. Several transmission bandwidths have been used but there has been little analysis of image quality provided by different bandwidths. We designed a study of the quality of transmitted images at various bandwidths. Methods: Two echocardiographers viewed randomly a series of 13 recorded pediatric echocardiographic images either directly or after transmission using 1 of 4 bandwidths: 256; 384; 512; or 768 kbps. An image clarity scoring scale was used to assess image quality of cardiac structures. Results: Measurable differences were found in image quality with different transmission bandwidths; 512 kbps was the minimum for consistently clear imaging of all cardiac structures examined. Conclusion: Bandwidth greater than 512 kbps confers sharper images subjectively although this could not be quantified by our methods.

The effect of finite bandwidth squeezed light on entanglement creation in the Dicke model

We analyse the relation between local two-atom and total multi-atom entanglements in the Dicke system composed of a large number of atoms. We use concurrence as a measure of entanglement between two atoms in the multi-atom system, and the spin squeezing parameter as a measure of entanglement in the whole n-atom system. In addition, the influence of the squeezing phase and bandwidth on entanglement in the steady-state Dicke system is discussed. It is shown that the introduction of a squeezed field leads to a significant enhancement of entanglement between two atoms, and the entanglement increases with increasing degree of squeezing and bandwidth of the incident squeezed field. In the presence of a coherent field the entanglement exhibits a strong dependence on the relative phase between the squeezed and coherent fields, that can jump quite rapidly from unentangled to strongly entangled values when the phase changes from zero to pi. We find that the jump of the degree of entanglement is due to a flip of the spin squeezing from one quadrature component of the atomic spin to the other component when the phase changes from zero to pi. We also analyse the dependence of the entanglement on the number of atoms and find that, despite the reduction in the degree of entanglement between two atoms, a large entanglement is present in the whole n-atom system and the degree of entanglement increases as the number of atoms increases.

Effect of granule morphology on breakage behaviour during compression

In the area of dry particle breakage, Discrete Element Method (DEM) simulations have been widely used to analyse the sensitivity of various physical parameters to the behaviour of agglomerates during breakage. This paper looks at the effect of agglomerate shape and structure on the mechanisms and extent of breakage of dry agglomerates under compressive load using DEM simulations. In the simulations, a spherical-shaped agglomerate produced within the DEM code is compared with an irregularly shaped agglomerate, whose structure is that of an actual granule that was characterised with X-ray microtomography (muCT). Both agglomerates have identical particle size distribution, coordination number and surface energy values, with only the agglomerate shape and structure differing between the two. The work here details the breakage behaviour with a number of traditional DEM output parameters (i.e., contact/cluster distributions) with showing vastly different behaviour between the two agglomerates. (C) 2004 Elsevier B.V. All rights reserved.

Rehabilitation after total knee replacement via low-bandwidth telemedicine: the patient and therapist experience

After a total knee replacement, inadequate rehabilitation is associated with poor physical outcomes and a reduced longevity of the knee prosthesis. We have developed a low-bandwidth telemedicine system to enable rehabilitation services to be delivered directly to the home of patients in rural and remote areas. We have examined the experience of clinical physiotherapists and of 31 participants who received treatment via the system. High levels of satisfaction were reported by participants (mean responses >7 on a 10 cm visual analogue scale). The service was found to be effective, safe and easy to use, and it integrated well into current clinical practice. The study demonstrates the potential for delivering physiotherapy services via low-bandwidth Internet connections.

An experimental and finite element poroelastic creep response analysis of an intervertebral hydrogel disc model in axial compression

A hydrogel intervertebral disc (lVD) model consisting of an inner nucleus core and an outer anulus ring was manufactured from 30 and 35% by weight Poly(vinyl alcohol) hydrogel (PVA-H) concentrations and subjected to axial compression in between saturated porous endplates at 200 N for 11 h, 30 min. Repeat experiments (n = 4) on different samples (N = 2) show good reproducibility of fluid loss and axial deformation. An axisymmetric nonlinear poroelastic finite element model with variable permeability was developed using commercial finite element software to compare axial deformation and predicted fluid loss with experimental data. The FE predictions indicate differential fluid loss similar to that of biological IVDs, with the nucleus losing more water than the anulus, and there is overall good agreement between experimental and finite element predicted fluid loss. The stress distribution pattern indicates important similarities with the biological lVD that includes stress transference from the nucleus to the anulus upon sustained loading and renders it suitable as a model that can be used in future studies to better understand the role of fluid and stress in biological IVDs. (C) 2005 Springer Science + Business Media, Inc.

Effect of cyclic pneumatic soft tissue compression on simulated distal radius fractures

We investigated the effect of pneumatic pressure applied to the proximal musculature of the sheep foreleg on load at the site of a transverse osteotomy of the distal radius. The distal radii of 10 fresh sheep foreleg specimens were osteotomized and a pressure sensor was inserted between the two bone fragments. An inflatable cuff, connected to a second pressure sensor, was positioned around the proximal forelimb musculature and the leg then was immobilized in a plaster cast. The inflatable cuff was inflated and deflated repeatedly to various pressures. Measurements of the cuff pressure and corresponding change in pressure at the osteotomy site were recorded. The results indicated that application of pneumatic pressure to the proximal foreleg musculature produced a corresponding increase in load at the osteotomy site. For the cuff pressures tested (109.8-238.4 mm Hg), there was a linear correlation with the load at the osteotomy site with a gradient of 12 mm Hg/N. It is conceivable, based on the results of this study, that a technique could be developed to provide dynamic loading to accelerate fracture healing in the upper limb of humans.

Detecting finite bandwidth periodic signals in stationary noise using the signal coherence spectrum

All signals that appear to be periodic have some sort of variability from period to period regardless of how stable they appear to be in a data plot. A true sinusoidal time series is a deterministic function of time that never changes and thus has zero bandwidth around the sinusoid's frequency. A zero bandwidth is impossible in nature since all signals have some intrinsic variability over time. Deterministic sinusoids are used to model cycles as a mathematical convenience. Hinich [IEEE J. Oceanic Eng. 25 (2) (2000) 256-261] introduced a parametric statistical model, called the randomly modulated periodicity (RMP) that allows one to capture the intrinsic variability of a cycle. As with a deterministic periodic signal the RMP can have a number of harmonics. The likelihood ratio test for this model when the amplitudes and phases are known is given in [M.J. Hinich, Signal Processing 83 (2003) 1349-13521. A method for detecting a RMP whose amplitudes and phases are unknown random process plus a stationary noise process is addressed in this paper. The only assumption on the additive noise is that it has finite dependence and finite moments. Using simulations based on a simple RMP model we show a case where the new method can detect the signal when the signal is not detectable in a standard waterfall spectrograrn display. (c) 2005 Elsevier B.V. All rights reserved.