Selective laser melting (SLM) of metallic powders is an additive manufacturing technique that is widely employed to produce 3D components, and is fast becoming an important method for manufacturing near-net shape and complex metallic parts. In this thesis, a comprehensive investigation on the effect of SLM on the mechanical and corrosion properties of the Al-12Si (AS), 316L stainless steel (SS), and 18(Ni)-300 grade managing steel (MS) is investigated, with particular emphasis on the developing (micro- as well as mesa-)structure -property correlations. Detailed microstructural characterization combined with quasi-static tensile, fracture toughness, fatigue crack growth, and unmatched fatigue tests were conducted. The effect of post-SLM heat treatment as well as the scanning strategy (linear vs. checker board hatch style) was examined and the results are compared with those of conventionally manufactured (CM) counterparts. The SLM alloys exhibit a mesostructured, in addition to the fine cellular structure along the boundaries. In a case of SLM-AS, the fine cellular structure imparts higher strength at the cost of ductility, while the mesostructured, which arises due to the laser track hatching, causes the crack path to be tortuous, and in turn leads to substantial increase in fracture toughness. This imparts significant anisotropy to the toughness while tensile properties are nearly-isotropic. The experimental results of SLM-SS also show that higher tensile strengths properties with a marked reduction ductility. In spite of these, the fracture toughness, which ranges between 63 and 87 MPa.m0.5, of the SLM-SS is good, which is a result of the mesostructured induced crack tortuousity.Both tensile and toughness properties of SLM-SS were found to be anisotropic in nature. Upon aging SLM-MS, nanoscale precipitation of intermetallic compounds occurs within the cells that, in turn, lead in marked improvements in tensile strengths properties, but substantial reductions in ductility and fracture toughness. Overall, the mechanical performance, except ductility, of the SLM-MS after aging is found to be similar to that of CM-MS. Importantly, the lack of ductility does not lead to a reduction in toughness. Although the SLM-MS alloy possesses a mesostructured, no significant anisotropy in the mechanical behaviour is observed. The unnoticed studies on SLM-AS, -SS, and -MS reveal that the tensile residual stresses, gas-pores, and unmelted powder particles, can degrade the unmatched highest fatigue properties considerably and hence need be eliminated for high fatigue strength. Room temperature, electrochemical corrosion resistances (CRs) of SLM-AS, -SS and -MS in 0.1M NaCl solution were also evaluated and compared with those CM counterparts. While SLM improves CRs of AS and SS, it degrades that of MS. The results are discussed in terms of microstructural refinement and porosity that are common in SLM alloys.

The diploma thesis deals with development of high resistant composite, which brings its properties closer to the melted basalt products. This fact will allow substitution of basalt elements in hostile chemical environment by newly developed material and completes its product line. High resistant composite also consists of secondary raw material in highest possible amount. Material that is being evolved carries high strength, abrasion resistance and is also resistable in hostile chemical environment.

Hot-melted asphalt (HMA) plants use sized gravels, asphalt and/or recycled asphalt as raw materials. In the plant, the materials are heated to certain preset temperatures and blended at fixed ratios at around 170oC to prepare the required HMA for road paving. In the asphalt-melting, hot-blending and dumping operations, fumes and particulates emit from the process equipments. The emitted gases contain various volatile organic compounds (VOCs) and poly aromatic hydrocarbons (PAHs) which are harmful to the health of the plant workers and nearby residents. Complaints from the residents also come with the fume and odorous emissions. In this study, an oxidation-reduction-in-series scrubbing process was tested to remove odorous compounds in waste gases emitted from HMA plants. Waste gas samples for test were collected from the vent hole of an oven which contains a heated sample of asphalt or recycled asphalt concrete. Sodium hypochlorite solution was used to scrub and oxidize the compounds and hydrogen peroxide to reduce the chlorine emitted from the oxidative scrubber. A gas chromatography with a mass spectrophotometric detector (GC-MSD) was used for the identification of the odorous species and their concentrations in the waste gases. Sensory tests were also used to determine the odor removal efficiency. GC-MSD examination results indicates that alkanes, arenes, alkenes, halides, esters, and carbonyl compounds were detected in the test gas. Scrubbing test results indicate that with oxidative solution of 50-60 mg/L residual chlorine at pH 7.0-7.5 and reductive solution of 35 mg/L hydrogen peroxide at pH >12, over 90% of the VOCs in the tested gas could be removed. Odor intensities could be reduced from 3,090 (expressed as dilutions to threshold) to 73. Pungent asphalt odor in the test gas was turned into slight sulfur smell after the scrubbing. For removing the odors from 500 Nm3/min of the flue gas vented from a HMA plant, an analysis indicates the required total cost for chemicals (sodium hypochlorite solution, hydrogen peroxide and sodium hydroxide) added to the scrubbers was around 2,800 NT$/day (US$ 95/day) for a daily operation time of 10 hours. The cost is far lower than that by the traditional thermal incineration one (25,000 NT$/day or US$ 850/day) or by the regenerative thermal oxidation (RTO) one (14,300 NT$/day or US$ 485/day). This study has successfully developed an economical and effective chemical scrubbing technology for the removal of odorous compounds in gases emitted from HMA plants.

This practical-theoretic diploma thesis deals with a glass artist and a schoolmaster Stanislav Libenský. He taught students in every grade of glass education however the subject matter of this thesis is his work in tertiary education at Academy of Arts, Architecture & Design in Prague according to the historical context. The practical part of the thesis comprises a melted and cut glass sculpture called Kontakty (Touches) which is realized according to findings in theoretical part of the thesis.

The effect of reducing the fat content of low-moisture part-skim Mozzarella cheese from 19% to less than 5% on melted cheese properties, i.e., apparent viscosity, cheese melt, and cook color, was investigated. Functional properties of melt and stretch and cook color were evaluated at d 1, 7, 14, and 28. A rapid microwave oven method underestimated the moisture content of the low fat cheeses by approximately 10%. Low fat cheese did not melt as well as did the low-moisture part-skim Mozzarella cheese although the moisture content of the low fat cheese (moisture content ranged from 62.5% to 63.6%) was greater than the moisture content of the part-skim control (52.1 %). Storage for 28 d only marginally increased the meltability of low fat cheese. Lower fat content increased cook color. The amount of intact a αs-CN decreased by at least 48% in all cheeses as a result of proteolysis during 28 d of storage. The relative proportion of bound, entrapped, and expressible water was determined for a reduced-fat (8% fat) and control (19% fat) Mozzarella cheese on d 1, 7, 14, and 21 of refrigerated storage. Changes in the state of water were related to changes in cheese microstructure of a commercial Mozzarella cheese and to changes in cheese meltability of the control cheese. The amount of expressible water was proportional to fat content. Throughout storage, fat/serum channels became smaller and the protein matrix expanded into the areas between fat globules. The meltability of both cheeses increased during storage. Both cheeses contained 0.71g bound water/ g protein. Expressible water decreased in both cheeses until by d 21 no water was expressible. Entrapped moisture increased from approximately 10% to 60% for the control cheese and from approximately 33% to 50% for the reduced-fat cheese. An objective test was developed for measuring stretch, a characteristic of melted cheese. Three nonfat and four low-moisture part-skim cheeses were evaluated using the new test and the results compared with conventional test methods. Two new melted cheese parameters were defined: melt strength, the maximum load (g) obtained during the test, and stretch quality, the average load (g) as the cheese fibers stretched and elongated. Melt strength correlated with apparent viscosity. Stretch quality was determined for selected nonfat and low-moisture part-skim cheeses. A three-pronged probe was used to pull cheese vertically from a melted cheese pool. Use of this elongation stretch test, along with more traditional melted cheese tests, provides more complete information about the functional properties of Mozzarella cheese.

Made available in DSpace on 2016-12-08T17:19:29Z (GMT). No. of bitstreams: 1 Elementos pre-textuais.pdf: 67551 bytes, checksum: e2f4918c24aa245b8e48c363968398b9 (MD5) Previous issue date: 2006-10-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / It is well known that the element copper, even with an impurity level less than 0,3% modifies substancially the susceptibility to intergranular corrosion in alloys of commercial denomination 356 (nominal composition Al7Si0,3Mg). This paper aims to evaluate the influence of variations in the content of the element copper and the effect of thermal treatment of solubilization on the tendency to intergranular corrosion in samples of alloys of commercial denomination 356 and the Al-Cu system alloys melted in permanent moulds. The alloys were produced using an induction electric oven and involving contents of the element copper as impurity as well as alloy element. Samples were evaluated in fusion and heat treatment conditions utilizing six hours of heating in temperatures of approximately 540 ± 10ºC, and then a fast cooling in water so that the solid solution obtained be maintained in room temperature. The resistance to corrosion was evaluated by the decrease of mass after the samples were subjected to intergranular corrosion tests carried out according to the ASTM G110-92 norm. The results obtained indicate a strong influence of the element copper on the increase of the tendency to corrosion in the investigated alloys, and alterations in this behavior in the comparisons between the fusion and the solubilized conditions. / Trabalhos anteriores mostraram que o elemento cobre, mesmo num teor de impureza (menos de 0,3%Cu), altera substancialmente a suscetibilidade à corrosão intergranular nas ligas de denominação comercial 356 (composição nominal Al7Si0,3Mg). Este trabalho tem por objetivo avaliar a influência de variações nos teores do elemento cobre e o efeito do tratamento térmico de solubilização sobre a tendência à corrosão intergranular em amostras das ligas de denominação comercial 356 e das ligas do sistema Al-Cu fundidas em moldes permanentes. As ligas foram fabricadas usando forno elétrico à indução e envolvendo teores do elemento cobre tanto como impureza quanto como elemento de liga. Foram avaliadas amostras na condição bruta de fusão e solubilizadas utilizando seis horas de aquecimento, após a passagem deste período numa temperatura aproximada de 540 ± 10ºC, um resfriamento rápido em água foi feito para manter na temperatura ambiente, a solução sólida obtida à alta temperatura. A resistência à corrosão foi avaliada através da perda em massa após as amostras terem sido submetidas a ensaios de corrosão intergranular realizados de acordo com a norma ASTM G110-92. Os resultados obtidos indicam uma forte influência do elemento cobre sobre o aumento da tendência à corrosão nas ligas investigadas, e alterações nesse comportamento nas comparações entre as condições brutas de fusão e solubilizadas.

CRISPR/Cas9 induced DNA breaks can be precisely repaired by cellular homology-directed repair (HDR) pathways using exogenously provided template DNA (donor). However, the full potential of precision editing is hindered in many model systems by low cutting efficiencies, low HDR efficiencies and, cytotoxicity related to Cas9 and donor DNA. In this thesis, I address these challenges and present methods that we developed to increase HDR efficiencies in multiple model organisms. In Caenorhabditis elegans, we show that by reducing toxicity high editing efficiencies can be achieved with single stranded oligonucleotide (ssODN) donors. We demonstrate that melting dsDNA donors dramatically improves the knock-in efficiencies of longer (1kb) edits. In addition, we describe 5′-terminal modifications to the donor molecules that further increase the frequency of precision editing. With our methodology a single optimally injected animal can yield more than 100 Green Fluorescent Protein (GFP) positive progeny, dramatically enhancing efficiency of genome editing. Next, we demonstrate the generality of 5′ modified donors by extending our studies to human cell cultures and mice zygotes. In mammalian models, 2′OMe-RNA modifications consistently increase HDR efficiencies by several fold over unmodified donors. Furthermore, end-modified donors exhibited a striking reduction in end-joining reactions including reduced concatemer formation and reduced direct ligation into the host genome. Our study demonstrates that HDR can be improved without inhibiting competing end-joining pathways and provides a platform to identify new chemical modifications that could further increase the potency and efficacy of precision genome editing.

The objective of this diploma thesis is to describe nowadays almost forgotten events in France during the Second World War, when the historical statues and monuments from the Third Republic in France are irretrievably destroyed because of melting non-ferrous metals used for arms-production in Nazi Germany. The key goal of the thesis is to mention some of the main decisions that led to the destruction of certain works and on the basis of that analysis consider to what extent the occupier contributed to their loss and to what extent their removal was inevitable. Within historical context, the first chapter introduces the period and ideas of the Third Republic until the arrival of the Vichy régime with its new ideals. The second chapter mentions expansion of sculpture of the Third Republic and statuomania. The development of the campaign for collection of non-ferrous metals and its actors are discussed in the third chapter. Afterwards this work presents specific decisions about the destruction of statues, based on religious, political and aesthetic subtext. In the fifth chapter in practical part, the thesis tries to analyze these decisions and to determine the cause of the elimination of statues based on the decisions. The last part focuses on the different generals reactions to destruction of the...

La formulation de nouvelles nuances d’aciers présentant des caractéristiques mécaniques équivalentes pour des épaisseurs moindres et la plus-value associée à la possibilité d'assembler deux nuances différentes, nécessitent le développement et la maîtrise des procédés d’assemblage. Grâce à sa haute précision et à sa flexibilité, le procédé de soudage par laser est devenu une des principales techniques pour le raboutage des flans d'aciers de nature différente. La prédiction de la composition chimique locale de la zone fondue formée entre deux aciers en fonction des paramètres de soudage est de grande importance, puisque la dilution et la distribution des éléments d'alliage conditionnent la résistance mécanique finale du cordon. La présente étude a pour objectif la conception et la validation d’un modèle numérique multi-physiques décrivant la formation du mélange dans le cordon de soudure entre des aciers de nature différente, obtenu par fusion laser. Pour une meilleure compréhension du mélange issu de la diffusion et de la convection dans le bain liquide formé lors d'un soudage laser débouchant, une simulation 3D à l'aide du code de calcul commercial Comsol Multiphysics®, couplant les transferts thermiques, l’écoulement du métal liquide, et la diffusion des espèces, a été réalisée afin de prédire la géométrie du bain liquide et d'obtenir des informations sur la distribution des éléments chimiques à l'intérieur du cordon. Afin de réduire le temps de calcul, le modèle a été développé avec les hypothèses simplificatrices suivantes : le capillaire de vapeur a une géométrie fixe et l’ensemble des équations est résolu sous forme pseudo-stationnaire. Un modèle d’écoulement turbulent est utilisé pour le calcul du champ de vitesse. La loi de Fick est introduite pour modéliser le transport des espèces dans le bain liquide. Dans un premier temps et afin de valider les hypothèses sur les phénomènes de convection, une série d’essais de soudage avec des inserts de nickel pur, utilisés comme traceur chimique, a été réalisée pour cartographier post-mortem la distribution du nickel dans le cordon de soudure. Les résultats de la simulation numérique ont été trouvés en bon accord avec les résultats expérimentaux. Par la suite, le modèle a été appliqué au cas du soudage entre un acier Dual Phase et un acier TWIP riche en manganèse et enfin adapté à l'étude du mélange des revêtements dans le bain de métal liquide formé durant le soudage laser. / The design of new steel grades offering equivalent mechanical performances for lower thicknesses and the added value with the possibility to join two different steel grades, require development and control of joining processes. Thanks to high precision and good flexibility, the laser welding became one of the most used processes for joining of dissimilar welded blanks. The prediction of local chemical composition in the weld formed between dissimilar steels in function of the welding parameters is essential because the dilution rate and the distribution of alloying elements in the melted zone determine the final tensile strength of the weld. The goal of the present study is to create and to validate a multiphysical numerical model studying the mixing of dissimilar steels in laser weld pool. For a better understanding of materials mixing based on convection-diffusion process in the melted pool in case of full penetrated laser welding, a 3D simulation developed within COMSOL Multiphysics®, including heat transfer, fluid flow and transport of species has been performed to provide the weld geometry and quantitative mapping of elements distributions in the melted zone. In order to reduce computation time, the model has been developed basing on the following hypothesis: a steady keyhole approximation and solved in quasi-stationary form. Turbulent flow model was used to calculate velocity field. Fick law for diluted species was integrated to simulate the transport of alloying elements in the weld pool. In parallel, to validate the model, a number of experiments using pure Ni foils as tracers have been performed to obtain mapping post-mortem of Ni distribution in the melted zone. The results of simulations have been found in good agreement with experimental data. Afterwards the model was applied to laser welding between Dual Phase steel (DP) and high Mn steel (TWIP) and finally it was adapted to the study of coating dissolution in laser weld pool.

The recent discovery of the 31-km-wide Hiawatha impact crater has raised unanswered questions about its age, impactor and highly unusual organic carbon component. Previous research suggests a fractionated iron meteorite impactor, a probable maximum 3–2.4 Ma impact age and a possible Younger Dryas impact age. The first objective in this study has been to investigate a possible link between the Cape York meteorites and the Hiawatha impact crater by comparing the chromium isotopic signature in chromite from a Cape York meteorite with the chromium isotopic signature in potential chromite from the Hiawatha impactor. The second objective has been to investigate a possible Hiawatha signature in the Younger Dryas deposits from Baffin Bay. The third objective has been to study the organic carbon component in impactites derived from the Hiawatha impact crater. Heavy mineral grains were separated from glaciofluvial sediment which contains Hiawatha impactite grains. Not a single chromite grain was found and the possible link to the Cape York meteorites could not be tested. The petrographic examination of Younger Dryas marine deposits resulted in absence of impact-related Hiawatha grains. A petrological investigation revealed that organic carbon was likely found in five of six variably shocked impactites derived from the Hiawatha impact crater. The character of the organic carbon varies between the samples and also within individual samples. Vitrinite reflectance measurements of the organic carbon in two impactites yielded low reflectance values compared to charcoalification experiments of wood. Organic particles with different reflectance in the same sample suggest that the particles had different impact histories prior to settling and becoming a rock. Diagnostic conifer cellular texture was found in at least one of the samples. The character of the organic particles in the impactites supports the suggestion in a previous study that the sources of the Hiawatha organic carbon component are unmetamorphosed surficial deposits containing dead conifer tree trunks and fine-grained layered clay and organic matter.  In this study it is concluded that the apparent absence of chromite in the examined glaciofluvial sediment sample corroborates the significance of previous research which suggests that the Hiawatha impactor was an iron meteorite. The apparent absence of impact related grains in the Younger Dryas deposits suggests that although a Younger Dryas age for the Hiawatha impact crater is less likely now, the possibility remains open. The organic carbon with diagnostic conifer cellular texture in the Hiawatha impactites corroborates the conclusion in a previous study that the Hiawatha impact-related organic carbon component stems from local, thermally degraded conifer trees with a probable age of ca. 3–2.4 Ma. It is also concluded that the relatively low reflectance values of the organic carbon in the Hiawatha impactites seem to be related to the short duration of the high-temperature excursion during the hypervelocity impact event.