6 resultados para Open quantum system

em Aston University Research Archive


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This research was conducted at the Space Research and Technology Centre o the European Space Agency at Noordvijk in the Netherlands. ESA is an international organisation that brings together a range of scientists, engineers and managers from 14 European member states. The motivation for the work was to enable decision-makers, in a culturally and technologically diverse organisation, to share information for the purpose of making decisions that are well informed about the risk-related aspects of the situations they seek to address. The research examined the use of decision support system DSS) technology to facilitate decision-making of this type. This involved identifying the technology available and its application to risk management. Decision-making is a complex activity that does not lend itself to exact measurement or precise understanding at a detailed level. In view of this, a prototype DSS was developed through which to understand the practical issues to be accommodated and to evaluate alternative approaches to supporting decision-making of this type. The problem of measuring the effect upon the quality of decisions has been approached through expert evaluation of the software developed. The practical orientation of this work was informed by a review of the relevant literature in decision-making, risk management, decision support and information technology. Communication and information technology unite the major the,es of this work. This allows correlation of the interests of the research with European public policy. The principles of communication were also considered in the topic of information visualisation - this emerging technology exploits flexible modes of human computer interaction (HCI) to improve the cognition of complex data. Risk management is itself an area characterised by complexity and risk visualisation is advocated for application in this field of endeavour. The thesis provides recommendations for future work in the fields of decision=making, DSS technology and risk management.

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A broadly tunable quantum-dot based ultra-short pulse master oscillator power amplifier with different diffraction grating orders as an external-cavity resonance feedback is studied. A broader tuning range, narrower optical spectra as well as higher peak power spectal density (maximun of 1.37 W/nm) from the second-order diffraction beam are achieved compared to those from the first-order diffraction beam in spite of slightly broader pulse duration from the secondorder diffraction. © The Institution of Engineering and Technology 2013.

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A free space quantum key distribution system has been demonstrated. Consideration has been given to factors such as field of view and spectral width, to cut down the deleterious effect from background light levels. Suitable optical sources such as lasers and RCLEDs have been investigated as well as optimal wavelength choices, always with a view to building a compact and robust system. The implementation of background reduction measures resulted in a system capable of operating in daylight conditions. An autonomous system was left running and generating shared key material continuously for over 7 days. © 2009 Published by Elsevier B.V..

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The etiology of primary open-angle glaucoma (POAG) remains the subject of continuing investigation. Despite the many known risk factors and mechanism of damage, the principal treatment objectives in POAG still consist of reduction of intraocular pressure, which although straightforward in many cases, often leaves the clinician with the question of how far to pursue a sufficiently low pressure to prevent further damage. Other risk factors such as hemodynamic insufficiency due to vascular dysregulation and abnormal blood pressure are often overlooked in the day-to-day practice; their harmful effects for glaucoma are, it seems, more potent at night while the patient sleeps and when clinical investigation is most difficult. Although the status of autonomic nervous system is an important determinant of the systemic hemodynamic parameters, this issue is usually ignored by the clinician in the process of glaucoma diagnosis. Consequently, there is a lack of alternative therapies tailored to address associated systemic risk factors for POAG on a case and chronological basis; this approach could be more effective in preventing the progression and visual loss in selected glaucoma cases. © 2004 Elsevier Inc. All rights reserved.