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(1996)ThesisWith the significant outgrowth of hardware technology, the amount of pictorial information has increased remarkably. Due to this increase in image data, the need for an efficient indexing technology arises. In earlier retrieval systems, images are described using plain text and retrieval is based on the text description using conventional information retrieval techniques. These systems are good for retrieval abstract concepts captured in images. However, it suffers the problem of subjectiveness and manual entry of text description. To overcome these limitations content-based retrieval techniques using image features have been proposed. The main features used for image retrieval are shape, texture and colour. The purpose of our work is to develop an efficient content-based retrieval technique based on colour. Researchs on colour feature have shown very successful results. However, these techniques have been applied to the overall image content. The processing time for extracting colour features is another problem. In this paper, we propose three extensions to the basic colour histogram matching technique: (a) the use of hue value of HSI colour space; (b) the use of segmentation for object level; and (c) the use of clustering.
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(1989)ThesisIn this project the preparation of the electrolyte for the all vanadium redox flow battery was investigated using both chemical and electrolytic reduction of ^O,- powder. Oxalic acid and SO^ reduction were found to be unsuitable as only the V(IV) state could be produced directly. With suspended powder hydrolysis, however, vanadium sulphate of any oxidation state, in this case 50% V(IV) plus 50% V(III) in sulphuric acid can readily be prepared from V^O^ powder, thus allowing a significant reduction in the cost of the vanadium battery electrolyte. Results from conductivity and electrolyte stability tests at elevated temperature have led to modification of the electrolyte composition for the vanadium redox cell, from the 2 M V plus 2 M H^SO^, originally employed, to the use of 3 M H^SO^, much higher energy efficiencies and greater electrolyte stability was demonstrated with the 3 M H^SO^ supporting electrolyte. Spectroscopy and electrolyte conductivity have been demonstrated as suitable techniques for state-of-charge monitoring. A number of electrode materials were also evaluated and a Toray graphite bonded to a carbon plastic electrode was selected for further prototype development. Energy efficiencies of between 83 and 86% were obtained for a current density of 30 mA/cm for a temperature range 5 to 45'C, and between 0 and 100% state-of-charge. A wide range of construction materials was tested for long term stability in the vanadium redox electrolyte.
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(1997)ThesisSpace exploration and the rapid growth of the satellite communications industry has promoted substantial research into the effects of ionising radiation on modem electronic technology. The enabling electronics and computer processing has seen a commensurate growth in the use of radiation for diagnostic and therapeutic purposes in medicine. Numerous studies exist in both these fields but an analysis combining the fields of study to ascertain the effects of radiation on medically implantable electronics is lacking. A review of significant ground level radiation sources is presented with particular emphasis on the medical environment. Mechanisms of permanent and transient ionising radiation damage to Metal Oxide Semiconductors are summarised. Three significant sources of radiation are classified as having the ability to damage or alter the behavior of implantable electronics; Secondary neutron cosmic radiation, alpha particle radiation from the device packaging and therapeutic doses of high energy radiation. With respect to cosmic radiation, the most sensitive circuit structure within a typical microcomputer architecture is the Random Access Memory(RAM). A theoretical model which predicts the susceptibility of a RAM cell to single event upsets from secondary cosmic ray neutrons is presented. A previously unreported method for calculating the collection efficiency term in the upset model has been derived along with an extension of the model to enable estimation of multiple bit upset rates. An Implantable Cardioverter Defibrillator is used as a case example to demonstrate model applicability and test against clinical experience. The model correlates well with clinical experience and is consistent with the expected geographical variations of the secondary cosmic ray neutron flux. This is the first clinical data set obtained indicating the effects of cosmic radiation on implantable devices. Importantly, it may be used to predict the susceptibility of future implantable device designs to cosmic radiation. The model is also used as a basis for developing radiation hardened circuit techniques and system design. A review of methods to radiation harden electronics to single event upsets is used to recommend methods applicable to the low power/small area constraints of implantable systems.
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