Chan Mok-wah, Paul. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves [219-231]). / ACKNOWLEDGEMENTS / SUMMARY / LIST OF ABBREVIATIONS / Chapter CHAPTER 1. --- INTRODUCTION / Chapter 1.1 --- HISTORY --- p.1 / Chapter 1.2 --- RADIATION EXPOSURES OF THE POPULATION --- p.1 / Chapter 1.2.1 --- Introduction --- p.1 / Chapter 1.2.1 --- The Projected Expansion of Medical Exposures --- p.2 / Chapter 1.3 --- RADIATION HAZARDS --- p.6 / Chapter 1.3.1 --- Deterministic Effects --- p.6 / Chapter 1.3.2 --- Stochastic Effects --- p.7 / Chapter 1.3.3 --- Pre-natal Irradiation --- p.9 / Chapter 1.4 --- THE LOCAL SITUATION --- p.9 / Chapter 1.5 --- JUSTIFICATION OF THE STUDY OF LOCAL PATIENT DOSE --- p.10 / Chapter CHAPTER 2. --- THE MEDICAL EXPOSURES IN HONG KONG / Chapter 2.1 --- INTRODUCTION --- p.11 / Chapter 2.2 --- MAN-MADE RADIATION IN HONG KONG --- p.11 / Chapter 2.2.1 --- Occupational Exposure --- p.11 / Chapter 2.2.2 --- Radioactive Fall-out --- p.12 / Chapter 2.2.3 --- Nuclear Medicine --- p.12 / Chapter 2.2.4 --- Diagnostic Radiology --- p.12 / Chapter 2.3 --- THE FUTURE TREND --- p.13 / Chapter 2.4 --- THE CURRENT STUDY --- p.15 / Chapter CHAPTER 3. --- METHODS OF OPTIMISATION / Chapter 3.1 --- INTRODUCTION --- p.17 / Chapter 3.2 --- JUSTIFICATION OF DIAGNOSTIC RADIATION EXPOSURE --- p.17 / Chapter 3.3 --- OPTIMISATION OF DIAGNOSTIC RADIATION EXPOSURE --- p.18 / Chapter 3.4 --- THE CONTROL OF EXPOSURES --- p.19 / Chapter 3.4.1 --- The Control of Occupational Exposure --- p.19 / Chapter 3.4.2 --- The Control of Public Exposure --- p.20 / Chapter 3.4.3 --- The Control of Patient Exposure --- p.20 / Chapter 3.5 --- A PRACTICAL APPROACH TO CONTROL PATIENT EXPOSURES --- p.23 / Chapter 3.5.1 --- Intrumental Approach --- p.23 / Chapter 3.5.2 --- Technical Approach --- p.24 / Chapter 3.5.3 --- Administrative Approach --- p.25 / Chapter 3.6 --- CONCLUSION --- p.26 / Chapter CHAPTER 4. --- METHOD OF STUDY / Chapter 4.1 --- INTRODUCTION --- p.27 / Chapter 4.2 --- A WORKING SCHEME --- p.27 / Chapter 4.3 --- THE MEASUREMENT OF ESD --- p.29 / Chapter 4.3.1 --- Thermoluminescent Dosimetry --- p.29 / Chapter 4.3.2 --- The TL Material Adopted --- p.30 / Chapter 4.3.3 --- Irradiated of TLDs --- p.32 / Chapter 4.3.4 --- Readout of the Exposed TLDs --- p.32 / Chapter 4.3.5 --- Accuracy of Readings --- p.35 / Chapter 4.4 --- MONTE CARLO SIMULATION --- p.36 / Chapter 4.4.1 --- Introduction --- p.36 / Chapter 4.4.2 --- History --- p.38 / Chapter 4.4.3 --- The Principle --- p.38 / Chapter 4.4.4 --- Photon History --- p.40 / Chapter 4.4.5 --- The Use of Monte Carlo simulation in Organ Doses Estimation --- p.47 / Chapter 4.4.6 --- The Electron-Gamma-Shower (EGS4) Code System --- p.51 / Chapter 4.5 --- A LOCAL MATHEMATICAL PHANTOM --- p.52 / Chapter 4.5.1 --- Introduction --- p.52 / Chapter 4.5.2 --- An Ideal Mathematical Phantom --- p.52 / Chapter 4.5.3 --- Choice of Mathematical Phantom Model --- p.53 / Chapter 4.5.4 --- The Development of a Chinese Mathematical Phantom --- p.55 / Chapter 4.5.5 --- Results --- p.56 / Chapter 4.5.6 --- A Comparison --- p.60 / Chapter 4.6 --- A SUMMARY --- p.62 / Chapter CHAPTER 5. --- POPULATION STUDIES / Chapter 5.1 --- INTRODUCTION --- p.63 / Chapter 5.2 --- FREQUENCY SURVEY --- p.63 / Chapter 5.2.1 --- Survey in Private Sectors --- p.63 / Chapter 5.2.2 --- Surveyin Government Sectors --- p.64 / Chapter 5.3 --- DOSE SURVEY --- p.66 / Chapter 5.3.1 --- Selection of Regions and Projections --- p.66 / Chapter 5.3.2 --- Selection of Hospitals and Laboratories --- p.66 / Chapter 5.4 --- SAMPLE SIZE --- p.67 / Chapter CHAPTER 6. --- RESULTS / Chapter 6.1 --- INTRODUCTION --- p.68 / Chapter 6.2 --- SAMPLE SIZE --- p.68 / Chapter 6.3 --- AGE BAND AND SEX DISTRIBUTION --- p.68 / Chapter 6.4 --- THE MEASURED ESD --- p.75 / Chapter 6.4.1 --- Histograms of ESDs by Projection --- p.75 / Chapter 6.4.2 --- A Comparison of ESDs by Projection --- p.89 / Chapter 6.4.3 --- A Comparison of ESDs by Centre --- p.93 / Chapter 6.4.4 --- A Comparison of Collective ESDs by Centre --- p.96 / Chapter 6.5 --- THE ESTIMATED ORGAN DOSES --- p.103 / Chapter 6.5.1 --- Introduction --- p.103 / Chapter 6.5.2 --- Method --- p.103 / Chapter 6.5.3 --- Normalised Organ Doses --- p.105 / Chapter 6.5.4 --- Organ doses per Projection --- p.105 / Chapter 6.5.5 --- A Computerised programme --- p.119 / Chapter 6.6 --- A COMPARISON OF ORGAN DOSES ESTIMATED ON LOCAL AND NRPB MODELS --- p.152 / Chapter CHAPTER 7. --- SOURCES OF UNCERTAINTY / Chapter 7.1 --- UNCERTAINTITIES IN COMPUTATION --- p.156 / Chapter 7.1.1 --- Inaccuracy of the Justaposition of Complex Human Anatomy and the X-ray Beam --- p.156 / Chapter 7.1.2 --- Statistical Uncertainties --- p.156 / Chapter 7.1.3 --- Attenuation Coefficient Uncertainties --- p.157 / Chapter 7.1.4 --- Anatomic Inexactitudes --- p.157 / Chapter 7.2 --- ERRORS CONTRIBUTED BY TLDs --- p.155 / Chapter 7.3 --- TOTAL POSSIBLE ERROR --- p.157 / Chapter 7.4 --- VERIFICATION OF THE RESULTS --- p.158 / Chapter 7.4.1 --- Verification of the Measured ESD --- p.158 / Chapter 7.4.2 --- Verification of the Estimated Organ Doses --- p.158 / Chapter CHAPTER 8. --- HEALTH IMPLICATIONS / Chapter 8.1 --- INTRODUCTION --- p.161 / Chapter 8.2 --- DATA SOURCE --- p.161 / Chapter 8.3 --- ASSUMPTIONS --- p.162 / Chapter 8.4 --- SOMATIC RISK --- p.162 / Chapter 8.4.1 --- Somatically Significant Dose (SSD) --- p.162 / Chapter 8.4.2 --- Results --- p.163 / Chapter 8.5 --- LEUKAEMIC RISK --- p.166 / Chapter 8.5.1 --- Leukaemically Significant Dose (LSD) --- p.166 / Chapter 8.5.2 --- Results --- p.167 / Chapter 8.6 --- GENETIC RISK --- p.170 / Chapter 8.6.1 --- Genetically Significant Dose (GSD) --- p.170 / Chapter 8.6.2 --- Results --- p.171 / Chapter 8.7 --- DISCUSSION --- p.174 / Chapter CHAPTER 9. --- DISCUSSION --- p.199 / Chapter 9.1 --- MEAN ESDs PER PROJECTION --- p.199 / Chapter 9.2 --- A COMPARISON OF MEAN ESDs BETWEEN LOCAL CENTRES --- p.200 / Chapter 9.3 --- A COMPARISON OF MEAN ESDs BETWEEN COUNTRIES --- p.202 / Chapter 9.4 --- EFFECTIVE DOSE PER EXAMINATION --- p.203 / Chapter 9.5 --- NEED FOR LOCAL ANTHROPOMORPHIC PHANTOM --- p.204 / Chapter 9.6 --- ORGAN DOSES WITH HIGH CANCER INDUCTION --- p.205 / Chapter 9.7 --- A DISTRIBUTION OF COLLECTIVE DOSES --- p.206 / Chapter 9.8 --- "A DISTRIBUTION OF SSD, LSD AND GSD" --- p.209 / Chapter 9.9 --- OVERALL RISK ESTIMATION --- p.212 / Chapter 9.10 --- POPULATION ORGAN DOSES --- p.213 / Chapter 9.11 --- SUMMARY --- p.214 / Chapter CHAPTER 10. --- CONCLUSION --- p.217 / REFERENCES --- p.R 1 - 12 / APPENDICES / Chapter A. --- RADIATION QUANTITIES USED IN PATIENT DOSIMETRY --- p.A 1 - 12 / Chapter B. --- QUALITY ASSURANCE --- p.B 1 - 14 / Chapter C. --- DOSE REDUCTION --- p.C 1 - 11 / Chapter D. --- REJECT ANALYSIS --- p.D 1 - 15 / Chapter E. --- PUBLISHED WORK IN DOSE MEASUREMENT --- p.E 1 - 18 / Chapter F. --- THERMOLUMINESCENT DOSIMETRY --- p.F 1 - 27 / Chapter G. --- A STUDY ON ANTHROPOMORPHIC PHANTOM --- p.G 1 - 4

Os avanços na microeletrônica contribuíram para a redução de tamanho do nó tecnológico, diminuindo a tensão de limiar e aumentando a freqüência de operação dos sistemas. Embora tenha resultado em ganhos positivos relacionados ao desempenho e ao consumo de energia dos circuitos VLSI, a miniaturização também tem um impacto negativo em termos de confiabilidade dos projetos. À medida que a tecnologia diminui, os circuitos estão se tornando mais suscetíveis a inúmeros efeitos devido à redução da robustez ao ruído externo, bem como ao aumento do grau de incerteza relacionado às muitas fontes de variabilidade. As técnicas de tolerancia a falhas geralmente são usadas para melhorar a robustez das aplicações de segurança crítica. No entanto, as implicações da redução da tecnologia interferem na eficácia de tais abordagem em fornecer a cobertura de falhas desejada. Por esse motivo, este trabalho avaliou a robustez aos efeitos de radiação de diferentes circuitos projetados na tecnologia FinFET sob efeitos de variabilidade. Para determinar as melhores opções de projeto para implementar técnicas de tolerancia a falhas, como os esquemas de Redundância de módulo triplo (TMR) e/ou duplicação com comparação (DWC), o conjunto de circuitos analisados é composto por dez diferentes topologias de porta lógica OR-exclusivo (XOR) e dois circuitos votadores maioritários (MJV). Para investigar o efeito da configuração do gate dos dispositivos FinFET, os circuitos XOR são analisados usando a configuração de double-gate (DG FinFET) e tri-gate (TG FinFET). A variabilidade ambiental, como variabilidade de temperatura e tensão, são avaliadas no conjunto de circuitos analisados. Além disso, o efeito da variabilidade de processo Work-Function Fluctuation (WFF) também é avaliado. A fim de fornecer um estudo mais preciso, o projeto do leiaute dos circuitos MJV usando 7nm FinFET PDK é avaliado pela ferramenta preditiva MUSCA SEP3 para estimar o Soft-Error Rate (SER) dos circuitos considerando as características do leiaute e as camadas de Back-End-Of-Line (BEOL) e Front-End-Of-Line (FEOL) de um nó tecnológico avançado. / Advances in microelectronics have contributed to the size reduction of the technological node, lowering the threshold voltage and increasing the operating frequency of the systems. Although it has positive outcomes related to the performance and power consumption of VLSI circuits, it does also have a strong negative impact in terms of the reliability of designs. As technology scales down, the circuits are becoming more susceptible to numerous effects due to the reduction of robustness to external noise as well as the increase of uncertainty degree related to the many sources of variability. Faulttolerant techniques are usually used to improve the robustness of safety critical applications. However, the implications of the scaling of technology have interfered against the effectiveness of fault-tolerant approaches to provide the fault coverage. For this reason, this work has evaluated the radiation robustness of different circuits designed in FinFET technology under variability effects. In order to determine the best design options to implement fault-tolerant techniques such as the Triple-Module Redundancy (TMR) and/or Duplication with Comparison (DWC) schemes, the set of analyzed circuits is composed of ten different exclusive-OR (XOR) logic gate topologies and two majority voter (MJV) circuits. To investigate the effect of gate configuration of FinFET devices, the XOR circuits is analyzed using double-gate configuration (DG FinFET) and tri-gate configuration (TG FinFET). Environmental Variability such as Temperature and Voltage Variability are evaluated in the set of analyzed circuits. Additionally, the process-related variability effect Work-Function Fluctuation (WFF) is also evaluated. In order to provide a more precise study, the layout design of the MJV circuits using a 7nm FinFET PDK is evaluated by the predictive MUSCA SEP3 tool to estimate the Soft-Error Rate (SER) of the circuits considering the layout contrainsts and Back-End-Of-Line (BEOL) and Front-End-Of-Line (FEOL) layers of an advanced technology node.

O recente avanço da indústria de semicondutores tem possibilitado a integração de componentes complexos e arquiteturas de sistemas dentro de um único chip de silício. Atualmente, FPGAs do estado da arte incluem, não apenas a matriz de lógica programável, mas também outros blocos de hardware, como processadores de propósito geral, blocos de processamento dedicado, interfaces para vários periféricos, estruturas de barramento internas ao chip, e blocos analógicos. Estes novos dispositivos são comumente chamados de Sistemasem-Chip Totalmente Programáveis (APSoCs). Uma das maiores preocupações acerca dos efeitos da radiação em APSoCs é o fato de que erros induzidos pela radiação podem ter diferente probabilidade e criticalidade em seus blocos de hardware heterogêneos, em ambos os níveis de dispositivo e projeto. Por esta razão, este trabalho realiza uma investigação profunda acerca dos efeitos da radiação em APSoCs e da correlação entre a sensibilidade de recursos de hardware e software na performance geral do sistema. Diversos experimentos estáticos e dinâmicos inéditos foram realizados nos blocos de hardware de um APSoC a fim de melhor entender as relações entre confiabilidade e performance de cada parte separadamente. Os resultados mostram que há um comprometimento a ser analisado entre o desempenho e a área de choque de um projeto durante o desenvolvimento de um sistema em um APSoC. Desse modo, é fundamental levar em consideração cada opção de projeto disponível e todos os parâmetros do sistema envolvidos, como o tempo de execução e a carga de trabalho, e não apenas a sua seção de choque. Exemplificativamente, os resultados mostram que é possível aumentar o desempenho de um sistema em até 5.000 vezes com um pequeno aumento na sua seção de choque de até 8 vezes, aumentando assim a confiabilidade operacional do sistema. Este trabalho também propõe um fluxo de análise de confiabilidade baseado em injeções de falhas para estimar a tendência de confiabilidade de projetos somente de hardware, de software, ou de hardware e software. O fluxo objetiva acelerar a procura pelo esquema de projeto com a melhor relação entre performance e confiabilidade dentre as opções possíveis. A metodologia leva em consideração quatro grupos de parâmetros, os quais são: recursos e performance; erros e bits críticos; medidas de radiação, tais como seções de choque estáticas e dinâmicas; e, carga de trabalho média entre falhas. Os resultados obtidos mostram que o fluxo proposto é um método apropriado para estimar tendências de confiabilidade de projeto de sistemas em APSoCs antes de experimentos com radiação. / The recent advance of the semiconductor industry has allowed the integration of complex components and systems’ architectures into a single silicon die. Nowadays, state-ofthe-art FPGAs include not only the programmable logic fabric but also hard-core parts, such as hard-core general-purpose processors, dedicated processing blocks, interfaces to various peripherals, on-chip bus structures, and analog blocks. These new devices are commonly called of All Programmable System-on-Chip (APSoC) devices. One of the major concerns about radiation effects on APSoCs is that radiation-induced errors may have different probability and criticality in their heterogeneous hardware parts at both device and design levels. For this reason, this work performs a deep investigation about the radiation effects on APSoCs and the correlation between hardware and software resources sensitivity in the overall system performance. Several static and dynamic experiments were performed on different hardware parts of an APSoC to better understand the trade-offs between reliability and performance of each part separately. Results show that there is a trade-off between design cross section and performance to be analyzed when developing a system on an APSoC. Therefore, today it is mandatory to take into account each design option available and all the parameters of the system involved, such as the execution time and the workload of the system, and not only its cross section. As an example, results show that it is possible to increase the performance of a system up to 5,000 times by changing its architecture with a small impact in cross section (increase up to 8 times), significantly increasing the operational reliability of the system. This work also proposes a reliability analysis flow based on fault injection for estimating the reliability trend of hardware-only designs, software-only designs, and hardware and software co-designs. It aims to accelerate the search for the design scheme with the best trade-off between performance and reliability among the possible ones. The methodology takes into account four groups of parameters, which are the following: area resources and performance; the number of output errors and critical bits; radiation measurements, such as static and dynamic cross sections; and, Mean Workload Between Failures. The obtained results show that the proposed flow is a suitable method for estimating the reliability trend of system designs on APSoCs before radiation experiments.

Lead zirconate titantate (PZT) is an electroceramic material with many important technological applications in sensing and computer memory. Some of these applications require the PZT based devices to operate in radiation fields where they will be exposed to a high flux of energetic, heavy and light, charged and uncharged particles. The risk to any device exposed to ionizing radiation is the accumulation of displacement and ionization damage. Significant damage accumulation over time can lead to property drifts and, in some cases, failure of the device to perform properly. The goal of the undertaking recounted in this dissertation was to study changes in the ferroelectric properties of PZT exposed to the neutron field of a research nuclear reactor and to help develop an understanding for the type of radiation induced defects that play a dominant role in the degradation process. Thin film PZT capacitors were prepared using a wet chemical technique. The capacitors were then irradiated in a 1 MW TRIGA research nuclear reactor at the University of Texas at Austin up to a maximum 1 MeV equivalent neutron flux of 5.2 x 10¹⁵ cm⁻². Following irradiation, electronic characterization of polarization-electric field hysteresis loops, first order reversal curves, and small-signal permittivity were performed to ascertain tendencies between irradiation dose and ferroelectric properties. The measurements indicate a drop in remanent polarization, a loss of domain wall mobility, shifts in local switching fields and the formation of dipolar defects. These effects are all attributed to the introduction of defects into the material through displacement damage cascades. Numerical models of the damage cascades were performed to determine the displacement concentration. Comparison of those values and the primary recoil spectrum with typical survival rates found in the literature suggest that both free point defects as well as defect clusters are produced in comparable if not larger concentrations. It is proposed that defect clusters play a more significant role in ferroelectric property change than previously believed. / text

The effects of neutron displacement damage on materials are sensitive to neutron energy spectra. In controlled neutron damage experiments, a well characterized neutron flux spectrum is critical in determining the equivalent dose for displacement damage. Two techniques were used to characterize the neutron flux spectra in the University of Texas at Austin TRIGA research nuclear reactor. The first technique uses a standard method of measuring the reaction rates of two identical metal foils, one of which was irradiated in a Cd cover, the other of which was irradiated bare. Assuming an analytic form of the neutron spectrum the reaction rates were used to determine an approximate spectrum. The second technique uses the reaction rates measured from a set of activated metal foils along with two spectral unfolding techniques to approximate and then refine the neutron spectrum. A Matlab code was developed which fits radiative capture reaction rates to an approximate spectrum using a least squares approach. The result was used as an initial guess in a second Matlab code which refines the epithermal and fast energy ranges of the spectrum using reaction rates from threshold reactions. Errors in the reaction rates calculated from the resulting spectrum to the measured reaction rates were used to assess the accuracy of the final neutron spectrum. / text

No description available.

Radiation-induced changes in microstructures often lead to significant changes in mechanical properties of alloys used in the construction of nuclear reactors. It is desirable to test small specimens to make efficient use of the small volumes available in test and commercial reactor cores and also because small specimens are less affected by the sometimes steep flux gradients experienced in reactor cores and the sometimes large temperature gradients developed in the specimens from gamma heating. (Continues...).

No description available.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 4 uppsatser.

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