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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
321

Determinação da taxa de desintegração de TC 99M e IN 111 em sistemas de coincidências / Disintegration rate of Tc -99m and In -111 radioactive solutions in coincidence systems

Brito, Andréia Barreto de 16 November 2011 (has links)
Este trabalho apresenta os métodos de padronização de 111In e 99mTc, em sistemas de coincidências 4πβ-γ. O 111In foi produzido em cíclotron pela reação 111Cd(p, n)111In; decai com uma meia vida de 2,8 dias pelo processo de captura eletrônica populando os níveis excitados do 111Cd, emitindo raios gama de 171 keV e 245 keV. O 99mTc decai com uma meia vida de 6,007 h por transição isomérica do decaimento radioativo do 99Mo . A padronização do 111In foi feita no sistema 4πβ-γ constituído de um detector proporcional em geometria 4π acoplado a dois cristais cintiladores de NaI(Tl) com eletrônica convencional. A radiação gama selecionada para medida em coincidência foi de (171 + 245) keV. A escolha da janela gama foi baseada na análise da previsão da curva de extrapolação obtida na simulação de Monte Carlo. A padronização do 99mTc foi feita num sistema 4πβ-γ usando um contador proporcional de janela fina acoplado a um cristal de cintilação NaI (Tl). A eficiência beta foi variada por discriminação eletrônica, usando sistema de coincidências por software (SCS). A padronização do 99mTc foi feita pela seleção de dois intervalos gama, um no pico de absorção total de 140 keV e outro no pico de absorção total dos raios X de 20 keV. O resultado da atividade experimental de duas soluções de 111In concorda com o resultado obtido pela simulação de Monte Carlo. As atividades experimentais do 99mTc para os dois intervalos gama selecionados estão de acordo dentro da incerteza experimental, indicando que a metodologia adotada é adequada. / The 111In and 99mTc standardization in a 4πβ-γ coincidence system is described. The 111In was produced by the reaction of 111Cd (p, n) 111In in the cyclotron. The 111In decays with a half life of 2.8 days by electron capture process, populating the excited levels of 111Cd, emitting two main gamma rays with energies of 171 keV and 245 keV. The 99mTc decay with a half life of 6.007 h for isomeric transition, from the radioactive decay of 99Mo . 111In standstand ardization was carried out in a 4πβ-γ system, consisted of a system, consisted of a system of a gas flow proportional counter with 4flow proportional counter with 4π geometry coupled to a pair of NaI(Tl) scintillation counter with conventional electronics. The gamma window was set comprising the (171 keV + 245 keV) total absorption energy peaks. The choice of the window was based on the analysis of the extrapolation curves prediction, obtained by Monte Carlo simulation. The 99mTc standardization has been accomplished by the 4πβ-γ coincidence method using a thin window proportional counter in a 4π geometry coupled to a single NaI(Tl) scintillation counter. The beta efficiency was varied by electronic discrimination using a software coincidence counting system (SCS). Two windows were selected for the gamma channel: one at 140 keV gamma ray and the other at 20 keV X ray total absorption peaks. The result of the experimental activity of 111In two solutions agree with the results obtained by Monte Carlo simulation. The experimental activities of 99mTc for the two gamma windows are in agreement within the experimental uncertainty, indicating that the adopted methodology is adequate.
322

Lei do preço único e seus desvios: existe algum padrão? / Law of one price deviations: is there any pattern?

Leal, Bruno Westin Prado Soares 16 December 2009 (has links)
O objetivo deste trabalho é identificar padrões nos desvios da Lei do Preço Único. Utilizando dados desagregados nacionais e internacionais do período 1998-2008, aplicaram-se duas metodologias distintas: i) análise de componentes principais; e ii) estimador group mean Fully Modified OLS para painel proposto por Pedroni (2000). A análise de componentes principais facilita a identificação de padrões na variação de uma quantidade grande de dados e, o estimador group mean FMOLS permite estimar a relação de longo prazo existente entre os preços de um mesmo produto, cotados na mesma moeda, praticados em mercados distintos. Os resultados obtidos indicam que o câmbio é o principal responsável pelos desvios da Lei do Preço Único. Ademais, os resultados sugerem a existência de uma relação fraca entre os preços de um mesmo bem, cotados em Reais, mas comercializados nos mercados brasileiro e americano. / The main goal of this essay is to identify patterns in deviation from the law of one price. Using disaggregated data from Brazil and USA for the period 1998-2008, we applied two different methodologies: i) principal component analysis and ii) panel group mean Fully Modified OLS estimator proposed by Pedroni (2000). The principal component analysis facilitates the identification of patterns in the variation of a large amount of data, while the group mean FMOLS estimates the long run relationship between prices of the same good, quoted in the same currency, charged in separated markets. The results indicate that the exchange rate is the main responsible for deviations from the law of one price. Moreover, the results suggest the existence of a weak relationship between the prices of the same good, quoted in Reais, but sold in the Brazilian and American markets.
323

Renminbi Undervaluation and the U.S.-China Bilateral Trade Balance

Choi, Hyun-ji January 2007 (has links)
Thesis advisor: Robert G. Murphy / This paper examines the impact of the fixed exchange rate policy and the undervaluation of the Chinese currency (Renminbi) on the U.S.-China bilateral trade balance. Due to China's fixed exchange rate policy during the last decade, many have suspected that the Renminbi has been undervalued, and that this undervaluation has contributed to the expansion of the U.S. trade deficit. Based on previous studies, the first part of this paper explores Chinese economic policy and the possible consequences of the fixed exchange rate and the undervaluation of the Renminbi. The second part of the paper examines the following through empirical analysis: (1) the misalignment of the Renminbi through the behavioral equilibrium exchange rate (BEER) approach, (2) the relationship between the real exchange rate of the Renminbi and the U.S.-China bilateral trade balance and (3) the relationship between the undervaluation and the US bilateral trade deficit with China. The results indicate that the undervaluation of the Renminbi is neither substantial nor permanent. Moreover, the devalued Renminbi does not significantly increase China's trade surplus with the United States. The U.S. bilateral trade deficit with China is not permanently adversely affected by Renminbi undervaluation. / Thesis (BA) — Boston College, 2007. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: International Studies. / Discipline: College Honors Program.
324

Does lower exchange rate volatility influence economic growth? : A study about the relationship between exchange rate volatility and economic growth.

Olofsson, Martin January 2019 (has links)
Introduction – The introduction gives background to exchange rate volatility and the negative effects on economic growth that emerges when the exchange rate volatility is high.  Exchange rate volatility can affect economic growth in different ways such as establishing trade barriers or investment uncertainty. Previous studies have become quite outdated and the studies that have focused around the EMU have only compared smaller economies, hence this paper investigates the topic for developed economies and with new up-to-date data. The paper also examines two different types of exchange rate volatility, effective nominal exchange rate volatility and nominal exchange rate volatility to test if the choice of exchange rate volatility has an impact on the results. The sample for the paper contains the 36 OECD countries and the time period is 2000-2016.   Purpose – The purpose of this study is to explore how exchange rate volatility affects growth for the OECD countries. The paper also looks at what the effect of adopting the Euro as a primary currency has been for the countries in the OECD sample when looking at the exchange rate volatility and economic growth. Method – This study is conducted with a quantitative methodology, investigating a sample of 36 countries over 17 time periods from 2000-2016. The effect from exchange rate volatility on growth is analyzed through a content analysis and four panel-data regressions. This study also introduces a causality test to see if the exchange rate affects the economic growth or if economic growth affects the exchange rate volatility. Conclusion – The paper finds that both measures of exchange rate volatility have a negative effect on economic growth. There is also evidence that adopting the Euro as your currency for the time period has been negative for economic growth. Regarding the causality between exchange rate volatility and economic growth the paper finds evidence for a bidirectional causality, meaning that exchange rate volatility affects economic growth and economic growth affects exchange rate volatility.
325

Whisker growth in electro-plated tin on copper. / 電鍍錫在銅質底材上晶鬚生長的硏究 / Whisker growth in electro-plated tin on copper. / Dian du xi zai tong zhi di cai shang jing xu sheng chang de yan jiu

January 2001 (has links)
by Chan To = 電鍍錫在銅質底材上晶鬚生長的硏究 / 陳濤. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Chan To = Dian du xi zai tong zhi di cai shang jing xu sheng chang de yan jiu / Chen Tao. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Content --- p.v / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Lead-free movement and the problem of whisker --- p.1-1 / Chapter 1.2 --- Properties of tin and tin-copper intermetallics --- p.1-2 / Chapter ´Ø --- Tin --- p.1-2 / Chapter ´Ø --- Tin-copper intermetallics --- p.1-2 / Chapter 1.3 --- Literature Review of Whisker --- p.1-4 / Chapter 1.3.1 --- Feature of the whisker --- p.1-4 / Chapter 1.3.2 --- Conditions prone to whisker growth --- p.1-8 / Chapter 1.3.3 --- Growth mechanism of the whisker --- p.1-10 / Chapter 1.3.4 --- Methods to prevent or remove whisker --- p.1-11 / Chapter 1.4 --- Motivation & Aims of Studies --- p.1-12 / Chapter Chapter 2 --- EXPERIMENTAL & INSTRUMENTATION / Chapter 2.1 --- Sample Preparation --- p.2-1 / Chapter ´Ø --- Electroplating process --- p.2-1 / Chapter 2.2 --- Instrumentation --- p.2-6 / Chapter 2.2.1 --- Scanning Auger Microscope (SAM) analysis --- p.2-6 / Chapter ´Ø --- Experimental conditions --- p.2-9 / Chapter ´Ø --- Sample preparation for Auger analysis --- p.2-10 / Chapter ´Ø --- Depth profile analysis --- p.2-11 / Chapter ´Ø --- Mapping --- p.2-11 / Chapter ´Ø --- Line scan --- p.2-12 / Chapter 2.2.2 --- X-ray diffractometer (XRD) --- p.2-12 / Chapter 2.2.3 --- Scanning Electron Microscope (SEM) --- p.2-13 / Chapter Chapter 3 --- INFLUENCE OF CATHODIC/ANODIC ELECTROCHEMICAL CLEANING ON THE WHISKER GROWTH / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- Theory --- p.3-2 / Chapter ´Ø --- Reactions occurring at the anode/cathode --- p.3-3 / Chapter 3.3 --- Sample description --- p.3-5 / Chapter 3.4 --- Results and discussion --- p.3-5 / Chapter ´Ø --- Surface morphology before electroplating --- p.3-5 / Chapter ´Ø --- Whisker observation --- p.3-7 / Chapter 3.5 --- Summary --- p.3-18 / Chapter Chapter 4 --- INFLUENCE OF COPPER CONCENTRATION IN THE PLATING BATH ON COPPER DIFFUSION AND WHISKER FORMATION / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- Theory and Literature Review --- p.4-2 / Chapter ´Ø --- Diffusion kinetic --- p.4-2 / Chapter ´Ø --- Influence of solute atoms --- p.4-5 / Chapter 4.3 --- Sample description --- p.4-6 / Chapter 4.4 --- Results and discussion --- p.4-6 / Chapter ´Ø --- SEM observations --- p.4-6 / Chapter ´Ø --- Cross-sectional analysis --- p.4-8 / Chapter ´Ø --- Surface and depth profile analysis --- p.4-15 / Chapter ´Ø --- XRD analysis --- p.4-21 / Chapter 4.5 --- Summary --- p.4_24 / Chapter Chapter 5 --- ANNEALING EFFECT ON THE WHISKER GROWTH / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Theory and Literature Review --- p.5-2 / Chapter 5.3 --- Sample description --- p.5-3 / Chapter 5.4 --- Results and discussion --- p.5-4 / Chapter ´Ø --- SEM whisker observation --- p.5-4 / Chapter ´Ø --- Cross-sectional Auger analysis --- p.5-4 / Chapter ´Ø --- Surface and depth profile analysis --- p.5-16 / Chapter 5.5 --- Summary --- p.5-27 / Chapter Chapter 6 --- FORMATION MECHANISM OF THE STRIATION ON WHISKER / Chapter 6.1 --- Introduction --- p.6-1 / Chapter 6.2 --- Results and discussion --- p.6-2 / Chapter ´Ø --- Texture of the striation --- p.6-2 / Chapter ´Ø --- Time evolution in the surface morphology --- p.6-6 / Chapter ´Ø --- Stage of whisker growth --- p.6-6 / Chapter 6.3 --- Summary --- p.6-12 / Chapter Chapter 7 --- CONCLUSIONS & FUTURE STUDIES / Chapter 7.1 --- Conclusions --- p.7-1 / Chapter 7.2 --- Future studies --- p.7-3 / Reference
326

The assessment of the behaviour of the basis of hibor futures.

January 1999 (has links)
by Low Fung Seong Jenny, Yau Yin. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 53). / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.iv / ACKNOWLEDGMENTS --- p.v / Chapter / Chapter I. --- INTRODUCTION --- p.1 / Chapter II. --- THE HONG KONG MONETARY SYSTEM --- p.3 / Linked Exchange Rate System --- p.3 / Monetary Base --- p.3 / Capital Inflow and Outflow --- p.4 / Interest Rate and the Link --- p.5 / The Interbank Market --- p.9 / Chapter III. --- INTRODUCTION TO HIBOR FUTURES --- p.11 / Background of the HIBOR Futures --- p.12 / Features of Three-Month HIBOR Futures Contract --- p.14 / Futures Quotations and Futures Prices --- p.16 / Delivery and Determination of Final Settlement Prices --- p.17 / Functions of HIBOR Futures Contract --- p.17 / Short Hedge --- p.18 / Long Hedge --- p.20 / Speculation --- p.22 / Chapter IV. --- TEST OF COST OF CARRY RELATIONSHIP FOR HIBOR FUTURES --- p.24 / Cost of carry Relationship --- p.24 / Forward and Futures Prices --- p.27 / Cash Prices versus Futures Prices --- p.27 / Testing the Cost of Carry on Three-month HIBOR Futures Contracts --- p.30 / Collection of Data --- p.30 / Methodology --- p.30 / Findings --- p.31 / Analysis of Findings --- p.35 / Chapter V. --- CONCLUSION --- p.37 / ENDNOTES --- p.38 / APPENDICES --- p.40 / BIBLIOGRAPHY --- p.53
327

Measuring speech motor skills in phonologically disordered pre-school children and their normally developing peers

Cohen, Wendy Melissa Myers January 1999 (has links)
Previous research has demonstrated that normally developing children are expected to have adult like control of their speech production skills by 10 years of age, as evidenced by increases in speed of production and decreases in performance variability. (e. g. Kent and Fortier 1980). There is also some evidence to suggest that phonologically disordered children may have poorer speech motor skills than their normally developing peers (e. g. Henry 1990, Edwards 1992, Waters 1992, Towne 1994). There are numerous techniques that can be used to measure a number of different aspects of speech motor control. However, there are methodological difficulties in devising appropriate protocols for the collection and analysis of speed of speech production as used as an index of speech motor skill in young children. Some of the techniques that have had clinical application include measurement of rate in connected speech production and measurement of diadochokinetic (DDK) repetition rate. This investigation compared normally developing and phonologically disordered preschool children on various indirect measures of speech motor skills, in imitated and spontaneous connected speech and in DDK tasks. The investigation also focused on refining the techniques of data collection and analysis appropriate to young children. While the results vary with regard to the statistical significance of the differences between the two groups of children on articulation rates and DDK rates, analysis of the error patterns in single word, spontaneous connected speech, imitated connected speech and DDK productions identified a sub group of phonologically disordered children who may present with an underlying speech motor deficit as the basis of their phonological disability. The results of the investigation are considered in terms of their implication for the speech motor skills of the two groups of children, techniques for measuring various aspects of speech motor skill and the clinical identification of phonologically disordered children who have an underlying speech motor deficit.
328

Aspects of fitness and physical activity patterns in Edinburgh school children

Blackwood, Susan Kim January 1997 (has links)
There is growing concern that many children in Britain do not take sufficient exercise to benefit cardiovascular health. This is supported by extensive evidence advocating the importance of regular physical activity for lifelong health and well-being, and is of particular relevance in Scotland given it's notorious record of adult coronary heart disease death. This study examined aspects of fitness and physical activity in groups of Edinburgh school children, aged between 13 and 14 years. A three stage investigation was adopted: Phase One: A repeated measures, same subject design was used to examine the reliability and validity of selected measures (20m shuttle run test, peak oxygen uptake (V02 Peak), and anthropometric measures). Thirty three children (15 boys, 18 girls) performed each test on 3 separate days. Anthropometric measures showed strong reliability (r > 0.94, n=33) whilst reliability for the treadmill test ofV02 peak and shuttle run performance was lower (r=0.89 and r=0.79 respectively). Multiple regression analysis yielded a new equation for predicting V02 peak for children. This age specific prediction equation incorporated shuttle run performance in conjunction with skinfold thickness measures (Boys, R2=0.64 SEE=3.46; Girls, R2=0.79, SEE=2.81). Repeat testing was also recommended. Phase Two: An evaluation of methods of heart rate data analysis to assess physical activity in children. Twenty eight children (14 boys, 14 girls) wore continuous heart rate monitors (polar Electro PE4000, Finland) over a period of 7 days (Monday to Sunday), mean duration 737 (+/-55) mins/day. A detailed 7 day self report activity diary was also completed. Variability of heart rate measures was high (R=0.10-0.30), and it was noted that using data for just 4 days or less resulted in considerable underestimation of total weekly activity levels (44-100% error). If activity levels are to be compared against current recommendations, researchers must endeavour to achieve weekly rather than daily estimates of activity. Evaluation of methods of heart rate data analysis showed good correlation between heart rate activity indices and reported seven day activity. For boys strongest correlation was achieved using the number of 5 minute periods with HR > 139 b.min"l and the number of 5 minute periods with HR > 50% heart rate reserve (r=0.80, n=14). Total activity time was similar for both males and females but girls engaged in fewer sustained bouts of activity (>5 minutes) and a better correlate with activity in females was achieved using the total number of elevated heart rates (total HR > 50% heart rate reserve, r=0.64, n=14). Phase Three: A cross sectional survey was conducted to investigate standards of aerobic fitness and patterns of physical activity in groups of Edinburgh school children. Height, weight, skinfold thickness, shuttle run performance and physical activity (assessed by heart rate monitoring and activity diary) were recorded in a sample of 91 children (44 Boys, 47 Girls). Overall, males performed significantly better on the shuttle run test (t=5.4, df=88, p < 0.05), had higher predicted peak oxygen uptake (t=5.6, df=87, p < 0.05), and engaged in more bouts of moderate to vigorous activity than females. Seventy percent of boys and 50% of girls fulfilled current physical activity guidelines. Most activities were school based (131 mins per week as compared to 85 mins per week of out of school activities). Activity tended to be sporadic with active days interspersed with inactive days (mean 3.2 +/·1.6 days per week). After school activities specifically targeting young girls should be promoted.
329

Downstream suspended sediment dynamics of reservoir sediment flushing

Tarekegn, Tesfaye Haimanot January 2016 (has links)
Reservoir sediment flushing is increasingly considered beneficial to reduce sedimentation of reservoirs and maintain sediment supply downstream of impounded rivers. Nevertheless, flushing of the accumulated sediments downstream of the dam also bears numerous negative impacts. In this study, first the most important downstream impacts of fine sediment releases of flushing were identified based on previously published research of twenty case studies in eleven countries. The results showed that the long-term as well as short term biological and physical impacts decreased with distance from the dam. The temporal scale of impacts on macro-invertebrates could span from few weeks or a month to several months while the effect on fish could last for a number of years. The impacts on downstream vegetation dynamics is driven by many years of flushing activities. The study also enabled proposing generic management strategies aimed to reduce the impacts. Second, fine sediment transport in coarse immobile bed, which is a common phenomenon downstream of dams during flushing releases, dam removal and also in many mountain and canyon rivers, was investigated. Particularly, the dynamics of the downstream erosion and transport of fine sediments released during sediment flushing was investigated based on a series of flume experiments that were carried out in immobile gravel bed and using a one-dimensional (1-D) suspended sediment transport model developed in the present study. In the framework of the flume experiment, firstly gravel bed roughness, porosity and roughness density were exclusively extracted from gravel surface elevation data in which developing a spatial filter to overcome elevation errors was carried out. Secondly a new technique to acquire fine sediment erosion in immobile coarse bed in running water condition was developed. The method proved to be the back bone of all fine sediment erosion experiments conducted in the present study and could be used for similar studies. This study presents a first work of direct measurement of erosion rate and characterizing its spatial heterogeneity in gravel bed. The experimental data of erosion rate of fine sediments showed that it varied spatially with high erosion rate on the stoss side of gravels and less on the lee side conforming to sweeps and ejections characteristics in coherent flow structure of gravel bed flows. Erosion rate was significantly affected by increase in roughness of immobile gravel bed with high erosion rate noticed when sand level was reduced although the effect on stream-wise velocity was not significant. The vertical profile of erosion rate was found to decrease linearly and showed an exponential decay in time in the gravel matrix. Third, a new non-equilibrium erosion rate relation is proposed. Drag force profile in the interfacial sublayer of clean gravel bed was found to be scaled well with roughness density and allowed predicting the effective shear stress distribution available for fine sediment entrainment with an empirical equation. vi The new relation is a modified version of the pick-up rate function of van Rijn (1984b) in which the predicted shear stress in the roughness layer was implemented. The most important finding was that if the shear stress distribution in the interfacial sublayer is predicted, a relation for sand bed condition can be applied to predict fine sediment erosion rate in immobile gravel bed. This approach is conceptually superior to previous approaches where erosion rate in sand bed condition was scaled empirically for various fine sediment bed level within the interfacial sublayer. Finally, the effect of the interaction between hydrodynamic and sediment wave dynamics of sediment flushing on spatial pattern of sediment deposition was investigated. The 1-D model was developed to include major processes observed in sediment flushing: sediment wave celerity correction, variable bed roughness, bed exchange in immobile bed, hindered settling velocity and rough bed porosity. The proposed erosion rate relation showed encouraging results when implemented in the 1-D model. The wave celerity factor did not show significant effect on the spatial lag in immobile bed condition although was significant in sand bed condition. Variable bed roughness modified both the flow field and sediment deposition in which larger length of sediment deposit was noted. The immobile bed porosity allowed modelling clogged depth of fine sediments. The model was also found to be very valuable to investigate flushing scenarios that reduce significant deposition through the analysis of the dependence of deposition on peak-to-base flow and intermittence of releases. The highest peak-to-base flows produced the longest and thickest region of deposition while those with the lowest ratio produced the shortest and thinnest. A single flushing release followed by clear water release reduced area or length of sediment deposition more than intermittent flushing followed by inter- and post-flushing clear water releases. In the latter case, the peak of concentration reduced but remained higher for longer duration than the former, which suggests that a large quantity of clear water release has to be available. Overall, the present research represents a step forward in understanding relevant processes involved in the downstream transport of fine sediments released during sediment flushing and the associated impacts that can help the development of better management strategies and predictive tools.
330

Modelling helium embrittlement in iron based metals under DEMO conditions

Menzies, Luke January 2018 (has links)
Steel components within fusion reactors will be subject to high transmutation rates due to high energy neutrons. In iron based alloys such as steels, high amounts of helium accumulate through transmutation. This leads to helium embrittlement through helium accumulating on the grain boundaries of metal. Worst case scenario predictions were made for DEMO, estimating that for a grain size of 5 micro-meters, embrittlement could happen within 2 years of the blanket region of DEMO. This thesis elaborates on previous worst case scenario calculations by including inter-granular tapping mechanisms, within rate theory simulations. A rate theory code was developed for the purpose of this work, tailored towards a fusion environment. Calculations were performed using rate theory that predicted the timescales in which helium embrittlement occurred within a conceptual DEMO design in the first wall region and the blanket region. The calculations used several parameter sets, where preliminary simulations were performed using the parameter sets, that were compared with cluster density data determined using Transmission Electron Microscopy (TEM) and Positron Annihilation Spectroscopy (PAS). The simulations showed that the helium embrittlement time was heavily influenced by the chosen dislocation density, parameter set and grain size. The simulations conducted to represent the blanket region, showed an increase as high as 94% from the 2 years that has previously been predicted under certain scenarios. However results also showed that assuming a certain parameter set with a low dislocation density, showed no significant increase in embrittlement time. This was not a concern since it was concluded that advanced steel concepts would be expected to have a small average grain size, that would dramatically increase the embrittlement time. The work in this thesis also focused on defect interaction with dislocations. A model was constructed that made use of elasticity theory and VASP calculations that produced the interaction energy map for various defects with an edge dislocation. The interaction energy map for helium interstitials with an edge dislocation was compared with molecular dynamics (MD) simulations produced for this work. The model and simulations showed good agreement. Temperature effects were then included in the model that allowed the concentration around a dislocation to be temperature dependent. These temperature dependent interaction energy maps were then implemented into the advection-diffusion equation, that were solved numerically to explore the capture efficiencies and bias towards certain defects within iron. These values were then used within the rate theory simulations to produce temperature effects on the dislocation sink strengths for vacancies, SIA and helium interstitials.

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