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This thesis concerns the mathematical modelling of phase transformations with a special emphasis on martensitic phase transformations and their application to the modelling of steels. In Chapter 1, we develop a framework that determines the optimal transformation strain between any two Bravais lattices and use it to give a rigorous proof of a conjecture by E.C. Bain in 1924 on the optimality of the so-called Bain strain. In Chapter 2, we review the Ball-James model and related concepts. We present some simplification of existing results. In Chapter 3, we pose a conjecture for the explicit form of the quasiconvex hull of the three tetragonal wells, known as the three-well problem. We present a new approach to finding inner and outer bounds. In Chapter 4, we focus on highly compatible, so called self-accommodating, martensitic structures and present new results on their fine properties such as estimates on their minimum complexity and bounds on the relative proportion of each martensitic variant in them. In Chapter 5, we investigate the contrary situation when self-accommodating microstructures do not exist. We determine, whether in this situation, it is still energetically favourable to nucleate martensite within austenite. By constructing different types of inclusions, we find that the optimal shape of an inclusion is flat and thin which is in agreement with experimental observation. In Chapter 6, we introduce a mechanism that identifies transformation strains with orientation relationships. This mechanism allows us to develop a simpler, strain-based approach to phase transformation models in steels. One novelty of this approach is the derivation of an explicit dependence of the orientation relationships on the ratio of tetragonality of the product phase. In Chapter 7, we establish a correspondence between common phenomenological models for steels and the Ball-James model. This correspondence is then used to develop a new theory for the (5 5 7) lath transformation in low-carbon steels. Compared to existing theories, this new approach requires a significantly smaller number of input parameters. Furthermore, it predicts a microstructure morphology which differs from what is conventionally believed.

O desenvolvimento e aplicação de métodos analíticos na avaliação das concentrações de metais nas frações dissolvida e lábil na bacia do rio Piracicaba são de relevante importância para o estudo do comportamento químico-ambiental desses metais e para seu monitoramento, devido ao impacto das atividades antropogênicas nessa bacia. A técnica de difusão em filmes finos por gradiente de concentração (DGT, do inglês diffusive gradients in thin-films), é uma promissora ferramenta analítica de amostragem, pois permite pré-concentração, análise temporal, remoção de interferentes, avaliação lábil e amostragem in situ. A quantificação dos metais pelas técnicas de fluorescência de raios X dispersiva em energia por reflexão total (TXRF, total reflection X-ray fluorescence analysis) para amostras líquidas e da fluorescência de raios X dispersiva em energia (EDXRF, energy dispersive X-ray fluorescence) para amostras sólidas, mostram-se interessantes devido ao caráter multielementar, simultâneo e não destrutivo da análise. Neste trabalho avaliou-se a DGT para a determinação de Cr, Mn, Co, Ni, Cu, Zn e Pb em águas naturais, utilizando-se como agente ligante a membrana de celulose P 81 e como meio difusivo, o papel cromatográfico 3 MM. Calcularam-se os fatores de eluição e coeficientes de difusão para estes metais. Estudou-se o efeito da substância húmica, em diferentes concentrações, no desempenho da DGT para esses metais, e os resultados foram comparados e concordantes com as frações livre e a ligada à matéria orgânica, calculadas pelo programa Visual MINTEQ. Compararam-se o agente ligante e o meio difusivo à base de celulose, utilizados neste trabalho, com os à base de gel de poliacrilamida, empregando-se o complexante Chelex-100. Avaliou-se a homogeneidade da retenção dos analitos e do grupo ligante fosfato sobre a superfície do agente ligante. Nesses ensaios utilizaram-se soluções sintéticas contendo os analitos em pH 5,5 e força iônica 0,05 mol L-1 (ajustados com NaNO3). As determinações foram realizadas por TXRF e EDXRF. Avaliaram-se os acoplamentos DGT-SRTXRF e da DGT-EDXRF para a determinação da fração lábil de Cr, Mn, Co, Ni, Cu, Zn e Pb em amostras de água da bacia do rio Piracicaba, através de imersão em laboratório e in situ. Esses resultados foram comparados com as concentrações dissolvidas desses metais determinados pela técnica de fluorescência de raios X por reflexão total com excitação por luz síncrotron (SRTXRF, synchrotron radiation total reflection X-ray analysis). Os valores de concentrações de Mn, Cu e Zn nas frações dissolvida e lábil foram comparados com os valores máximos estabelecidos pela legislação brasileira Nas amostragens in situ, nos cinco pontos de coleta, as concentrações de Mn dissolvido e lábil foram maiores que a concentração total máxima permitida para esse elemento. Os elmentos Cr, Co, Ni e Pb, nas amostras coletadas, apresentaram-se abaixo do limite de detecção das técnicas SRTXRF (dissolvido), DGT-SRTXRF (lábil) e DGT-EDXRF (lábil). Os limites de detecção para o Cr, Mn, Co, Ni, Cu, Zn e Pb foram de 2,2 a 10 \'mü\'g L-1 na SRTXRF, de 0,21 a 3,6 \'mü\'g L-1 e de 7,2 a 24 \'mü\'g L-1 na DGT-SRTXRF e DGT-EDXRF, respectivamente / Analytical methods evaluation for metal dissolved and labile fractions determination in Piracicaba river basin is notable for metal-behavior studies in this environment as well as their monitoring due to anthropogenic activities. The diffusive gradients in thin films (DGT) is a promising sampling technique because of its pre-concentration, time-integrated, matrix interference removal, labile evaluation and in situ analytical features. The analytical techniques total reflection X-ray fluorescence (TXRF) for liquid samples and energy dispersive X-ray fluorescence (EDXRF) for solid samples analysis are advantageous due to simultaneous, multielemental and non-destructive characteristics. In this work, it was evaluated the DGT technique for Cr, Mn, Co, Ni, Cu, Zn and Pb determination in freshwater, using P 81 cellulose membrane as bind agent and 3 MM chromatographic paper as diffusive layer. Elution factors and diffusion coefficients were calculated for these metals. The humic acids effect on DGT performance was assessed and compared to free and humic acid bound metal fractions estimated by Visual MINTEQ software, in which agreement results were found. The paper-based DGT and gel-based one with Chelex-100 as bind agent were compared. The metal retention and phosphate group homogenization on P 81 membrane bind agent surface was studied. For these tests it was utilized a synthetic solution these metals containing with pH and ionic strength adjust to 5.5 and 0.05 mol L-1 (NaNO3), respectively. It was used the TXRF and EDXRF techniques for these metal quantifications. The DGT-SRTXRF and DGT-EDXRF were assessed in order to determine Cr, Mn, Co, Ni, Cu, Zn and Pb labile fractions in batch and in situ in Piracicaba river basin freshwater samples. These results were compared to their dissolved fractions by synchrotron radiation total reflection X-ray analysis, SRTXRF. The dissolved and labile Mn, Cu and Zn concentrations levels were compared to maximum allowed set by Brazilian legislation. The dissolved and labile Mn concentrations were higher than the maximum allowed in all five samples in situ sampling. Cr, Co, Ni, and Pb concentrations were lower than their limits of detection for dissolved fractions (SRTXRF) and labile ones (DGT-SRTXRF and DGT-EDXRF). The detection limits for Cr, Mn, Co, Ni, Cu, Zn and Pb were from 2.2 to 10 \'mü\'g L-1 for SRTXRF, from 0.21 to 3.6 \'mü\'g L-1 and from 7.2 to 24 \'mü\'g L-1 for DGT-SRTXRF and DGT-EDXRF, respectively

Michal Zitek: The internal debates about the future direction of the KSČ(M) from 1989 to 1993 The aim of this thesis is to offer a comprehensive look at the debates that took place within the Communist Party and aimed to transform into a modern left- wing party. Work will familiarize you with some debates and opinion- platforms that arose in these discussions.

No description available.

Microstructure and micro-mechanical characterization of as-built and heat-treated samples of Hastelloy X produced by laser powder bed fusion (LPBF) process has been carried out in this study. As-built LPBF blocks were solution heat-treated at 1177°C and 1220°C followed by fast cooling. The microstructure of as-built and heat-treated samples were studied by light optical microscopy, scanning electron microscopy, and electron backscatter diffraction. Instrumented indentation micro Vickers testing was performed to obtain microhardness and elastic modulus of asbuilt and heat-treated samples. Microtensile samples from as-built and heat-treated blocks were prepared and polished for mechanical characterization. Microtensile testing inside the scanning electron microscope was performed to evaluate the mechanical properties and to get information about the microstructural changes during plastic deformation. Microstructure characterization revealed disrupted epitaxial grain growth for the as-built samples whereas the two heated-treated Hastelloy X samples exhibited equiaxed grains with varying twin fractions. As-built Hastelloy X samples exhibited higher mean hardness than heat-treated samples. The yield strength of as-built samples reveals higher values as compared to conventional wrought Hastelloy X samples, whereas lower yield strength and higher elongation were observed for heat-treated samples as compared to as-built samples. Higher elongation and lower yield strength values were observed for the samples solution heat-treated at 1220°C compared to the solution heat-treated at 1177°C. Microstructural evaluation at different plastic strains during in-situ microtensile testing reveals a clear difference in dislocation density for as-built and heat-treated samples.

At low doses, relevant to nuclear incidents and accidental releases of radioactivity, the detriment of radiation extends beyond direct effects. This thesis investigates genomic instability, a subclass of non-targeted effects where damage and lethality is transmitted vertically and expressed in the progeny of cells many generations after initial radiation exposure. Through a series of experiments using clonogenic assay of human and fish cell culture, studies described in this thesis describe lethal mutations, hyper radiosensitivity and increased radioresistance – processes involving repair mechanisms that dictate survival in cells exposed to low doses. Further study investigates the difference in the relative biological effect of alpha particle radiation compared to what is expected at high doses. Results demonstrate increased radioresistance in a human cell line while also revealing increased lethality in a fish cell line confirming the need for consideration of dose-dependence as well as variance in behaviors of different cell lines and species. It is hoped the conclusions of this thesis will inspire the creation of protocols with greater attention to the indirect consequences of exposure to radiation at doses relevant to nuclear incidents and accidents. / Thesis / Master of Science (MSc)

Abstract in English, Tswana and Northern Sotho / The study aimed to explore teachers’ mathematical knowledge in respect of teaching the concept of fractions to Grade 6 learners. To that end a qualitative study was done, using a case study design. Data were collected through the observation of, and interviews with, three teachers at three schools in the Capricorn South district. Rooted in the theory of constructivism, the study was supplemented by the conceptual framework of mathematical knowledge for teaching (MKT) (Ball et al., 2008) and Shulman’s (1986) notion of pedagogical knowledge for teaching (PCK). The key finding of this investigation revealed that, of the three teachers, two did not develop the concept of fractions for their learners, but merely followed the traditional method of teaching the concept by encouraging their learners to memorise rules without understanding. Only one teacher emphasised an understanding of mathematical concepts. The main observation which the researcher made, was that teachers require a great deal of knowledge and expertise, in carrying out the work of teaching subject matter related to fractions. / Maikaelelo a thutopatlisiso e ne e le go tlhotlhomisa kitso ya dipalo ya barutabana malebana le go ruta barutwana ba Mophato wa 6 mogopolo wa dikarolwana. Go fitlhelela seo, go dirilwe thutopatlisiso e e lebelelang mabaka, go dirisiwa thadiso ya thutopatlisiso ya dikgetsi. Go kokoantswe data ka go ela tlhoko le go nna le dipotsolotso le barutabana ba le bararo kwa dikolong tsa kgaolo ya Capricorn Borwa. Thutopatlisiso eno e e theilweng mo tioring ya kago ya kitso e ne e tshegeditswe ke letlhomeso la sediriswa sa tokololo sa kitso ya dipalo ya go ruta (MKT) (Ball et al. 2008) le mogopolo wa ga Shulman (1986) wa kitso e e kgethegileng ya go ruta (PCK). Phitlhelelo ya botlhokwa ya patlisiso eno e senotse gore mo barutabaneng ba le bararo, ba le babedi ga ba a tlhamela barutwana ba bona mogopolo wa dikarolwana, mme ba latetse fela mokgwa wa tlwaelo wa go ruta mogopolo ka go rotloetsa barutwana go tshwarelela melawana kwa ntle ga go tlhaloganya. Ke morutabana a le mongwe fela yo o gateletseng go tlhaloganngwa ga megopolo ya dipalo. Temogo e kgolo e e dirilweng ke mmatlisisi ke gore barutabana ba tlhoka kitso le boitseanape jo bogolo go tsweletsa tiro ya go ruta dithuto tse di amanang le dikarolwana. / Dinyakišišo di ikemišeditše go utolla tsebo ya dipalo ya baithuti mabapi le go ruta kgopolo ya dipalophatlo go baithuti ba Kreiti ya 6. Ka lebaka la se go dirilwe dinyakišišo tša boleng, go šomišwa tlhamo ya dinyakišišo tša seemo. Tshedimošo e kgobokeditšwe ka go lekodišiša, le go dira dipoledišano le, barutiši ba bararo ka dikolong tše tharo ka seleteng sa Borwa bja Capricorn. Ka ge di theilwe go teori ya gore baithuti ba itlhamela tsebo, dinyakišišo di tlaleleditšwe ke tlhako ya boikgopolelo ya tsebo ya dipalo go ruteng (MKT) (Ball le ba bangwe, 2008) le kgopolo ya Shulman (1986) ya tsebo ya diteng tša thuto (PCK). Kutollo ye bohlokwa ya dinyakišišo tše e utollotše gore, go barutiši ba bararo, ba babedi ga se ba ba le kgopolo ya dipalophatlo go baithuti ba bona, eupša fela ba no latela mokgwa wa setlwaedi wa go ruta kgopolo ye ya dipalophatlo ka go hlohleletša baithuti ba bona go tsenya melawana ye ka hlogong ka ntle le go e kwešiša. Ke fela morutiši o tee yo a gateletšego gore go swanetše go ba le kwešišo ya dikgopolo tša dipalo. Temogo e tee yeo monyakišiši a bilego le yona, ebile gore barutiši ba hloka tsebo ye kgolo le botsebi, go phethagatša mošomo wa go ruta diteng tša thuto tšeo di amanago le dipalophatlo. / Mathematics Education / M. Ed. (Mathematics Education)