Tang Wan-yee. / "July 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 192-212). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

Cheung Mei-chun. / "January 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 66-94). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Investigations of radon in natural water and its relation to physical and chemical parameters are outlined in this thesis. In particular, a method for measuring 222Rn in water at low concentrations (~20 mBq.l-1) is described, followed by discussions concerning the design and its application to study both radon and parameters influencing radon levels in natural waters. A topic considered is the impact of fluoride and other aquatic parameters on radon in water. Moreover, variables such as uranium series radionuclides and stable elements in water, bedrock and sediment radioactivity and geology are investigated in two case studies. This was performed by employing radiometric-, chemical-, statistical- and GIS & geostatistical- analyses. The general water chemistry and presence of some elements such as fluoride was observed to influence radon levels in water. Health aspects of radon in drinking water are discussed based on radiation dose assessments. The radiation doses are compared with and added to doses incurred from ingestion of uranium, radium and polonium isotopes in drinking water and inhalation of radon in air in order to estimate total exposures for different age categories. The results may have a potential for future epidemiological studies.

The advent of high-frequency silicon-based technologies has enabled the design of mixed-signal circuits that incorporate analog, RF, and digital circuit components to build cost-effective system-on-a-chip solutions. Emerging applications provide great incentive for continued scaling of transistor performance, requiring careful attention to mismatch, noise, and reliability concerns. If these mixed-signal technologies are to be employed within space-based electronic systems, they must also demonstrate reliability in radiation-rich environments. SiGe BiCMOS technology in particular is positioned as an excellent candidate to satisfy all of these requirements. The objective of this research is to develop predictive modeling tools that can be used to design new mixed-signal technologies and assess their reliability on Earth and in extreme environments. Ultimately, the goal is to illuminate the interaction of device- and circuit-level reliability mechanisms and establish best practices for modeling these effects in modern circuits. To support this objective, several specific areas have been targeted first, including a TCAD-based approach to identify performance-limiting regions in SiGe HBTs, measurement and modeling of carrier transport parameters that are essential for predictive TCAD, and measurement of device-level single-event transients to better understand the physical origins and implications for device design. These tasks provide the foundation for the bulk of this research, which addresses circuit-level reliability challenges through the application of novel mixed-mode TCAD techniques. All of the individual tasks are tied together by a guiding theme: to develop a holistic understanding of the challenges faced by emerging broadband technologies by coordinating results from material, device, and circuit studies.

This thesis is dedicated to the investigation of the structural destabilisation of UO2 single crystal. Irradiations with 470-keV Xe, 500-keV Ce and 500-keV La ions (with corresponding ion range of Rp 85 nm and range straggling of Delta Rp _ 40 nm according to SRIM calculation) have been performed to investigate the destabilisation of UO2 single crystals induce by (i) the radiation damage effects due to the nuclear stopping process of a fission fragment at the end of their trajectories (ballistic contribution) and by (ii) the incorporation of a fission product at high concentration (chemical contribution). The energies and masses of bombarding ions were deliberately chosen so that they would have very similar projected range in UO2 in order to compare the effects induced by solubles (La and Ce) versus non soluble Xe species in UO2. Rutherford Backscattering Spectrometry in channelling geometry (RBS/C) was applied to study the defects induced. Channelling data were analysed afterwards by Monte-Carlo simulation with McChasy code assuming a two-class model of defects comprising (i) the randomly displaced atoms (RDA) and the bent channels (BC) defects. The accumulation of RDA with increasing ion fluence leads to a steep increase (build-up of defects) observed from 4 to 7 dpa regardless of nature of ions and a dramatic increase observed from 300 dpa (corresponding to _ 5 at. % of implanted ions) only for Xe irradiated crystal. The difference due to the soluble versus insoluble species was clearly observed. Such a difference was observed via the dramatic increase of RDA when the crystal is implanted at very high concentration only for crystal implanted with insoluble species. Moreover, the difference is also observed via the higher fraction of RDA created in the crystal irradiated with insoluble element. This phenomenon is mostly due to the size of implanted species in the matrix. Insoluble Xe atoms have the atomic radius which is larger than twice the atomic radius of U sub-lattice while soluble La and Ce atoms have the atomic radii of similar size as compared to U atom. Xe creates a much stronger stress field in UO2 crystal in comparison to La or Ce; a higher fraction of RDA is thus created. Conversely, the accumulation of BC with increasing ion fluence leads to very similar evolution versus ion fluence in all crystals implanted with the three elements . A regular increase of BC versus fluence which reveal the dramatic

Providing a socio-legal analysis of the issues, expert evidence and judgment in Reay and Hope v BNFL plc., the thesis offers an insight into the complexity of the toxic tort. Starting with an overview of the history of Sellafield, the thesis reflects on the scientific and epidemiological concerns surrounding the link between childhood cancer and nuclear installations. Drawing on scientific knowledge and epistemological considerations, the thesis moves on to the difficulties of verifying causation in science and the problems of establishing causation in law. Outlining the role of the expert witness and scientific expert evidence, the thesis proceeds with a case analysis, before broaching the thorny issue of judicial decision making and in particular, the difference between the 'discovery' and 'justification' process. Moving on to the Judgment in Reay and Hope, attention is given to the potential application of probability theory to the judicial decision making process. Lasting just short of one hundred days and including the testimony of numerous scientific experts, Reay and Hope marked new ground in a number of ways; it was the first personal injury claim to test the concept of genetic damage from radiation; the only time that a Queen's Bench Division Judge had been allocated a full-time judicial assistant; and one of the first trials to endorse a satellite video link for examination of international expert witnesses. As far as judicial management is concerned, the case was a forerunner in having Counsels' Opening Statements in writing in advance of the trial, as well as having written daily submissions of key issues from plaintiffs and defendants upon conclusion of oral evidence. The circumstances that led to the trial relate to events in excess of thirty to forty years ago when the fathers of Dorothy Reay and Viven Hope were employed by the Defendants and their predecessors (the United Kingdom Atomic Energy Authority) as fitters for the Sellafield Plant. Intrinsic to the litigation was whether paternal preconception irradiation caused or materially contributed to a predisposition to cancer leading to Dorothy's death from leukaemia and Vivien Hope's non-Hodgkin's lymphoma. As a consequence of the various statutory provisions, the Plaintiffs did not need to prove negligence on the part of the Defendants. In order to succeed the Plaintiffs had to prove on the balance of probabilities that radiation from Sellafield was a material contributory cause of the Plaintiffs' disease. The fundamental issue therefore was causation. In addition to the case analysis, two pieces of empirical research were conducted for the purposes of this thesis. The first, a Social Survey (consisting of thirty four questions) was circulated to 160 members of the Academy of Experts (quantitative research); the second, a letter, involved written communication with sixty five judges from the Queen's Bench Division of the High Court (qualitative research). Underlying this socio-legal case analysis are fundamental questions with regard to existing legal principles, liability and judicial decision making.

No description available.

A new one-dimensional device simulation package developed for the simulation of neutron radiatiol! effects in silicon avalanche photodiodes is described. The software uses a finite difference technique to solve the time-independent semiconductor equations across a user specified structure. Impact ionisation and illumination are included, allowing accurate simulation with minimal assumptions about the device under investigation. The effect of neutron radiation damage is incorporated via the introduction of deep acceptor levels subject to Shockley-Read-Hall statistics. Two models are presented. A reverse reach through model, based on the EG&G C30626E reverse reach through avalanche photo diode originally proposed for use in the CMS electromagnetic calorimeter, and a reach through model, based on widely available commerical devices. A short experimental study on two commercial silicon avalanche photodiodes, a C30719F reverse reach through APD and a C30916E reach through APD, is presented for comparison with the simulation data. To allow full comparison with the simulated predictions, the commercial devices were irradiated at the Rutherford Appleton Laboratory's ISIS facility. The simulated data shows good qualitative agreement with the measurements performed on the commercial devices, quantitative predictions would require exact information about the doping profile. The characteristic behaviour of the devices is predicted over a wide range of conditions both before and after neutron irradiation. The effect of ionised deep acceptors in the bulk of the devices is investigated. The simulation package provides a useful tool for the analysis of semiconductor devices, particularly in areas where a non-ionising radiation damage is prevelent e.g. high energy physics, and provides a good basis for further development.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.