No / A method for measuring the evaporation kinetics of pure solvents and solutions containing Cd3P2 quantum dots (QDs) in SiO/SiO2 rolled-up microtube (RUT) resonators is reported. The QDs serve as wavelength-tunable fluorescent sources for the RUT resonator. The first-order kinetic constant (295 K) of the evaporation of toluene embedded in a RUT (D = 9.10 μm) is evaluated (0.055 min−1). / Doctoral Program Education of China. Grant Number: 20110111120008; Alexander von Humboldt Foundation

The relative merits of methods of determining the density of dislocations are reviewed. In particular, consideration has been given to the evidence available tending to indicate a loss of dislocations from foils of deformed metal during thinning processes preparatory to viewing in the electron microscope. By measurement of the electrical resistivity ratio, 293˚K./77˚K., during thinning, annealed specimens of super-purity aluminum foil were shown to obey Fuch’s theory for thin films, but cold-rolled specimens could not be fitted to the theory. This discrepancy has been attributed to the loss of dislocations from the cold-rolled material, and the results are shown to be consistent with a “loss-fringe” model of dislocation loss from the surface. / Thesis / Master of Science (MSc)

Variation is inevitable in any process, so it has to be dealt with effectively and economically. Reducing variation can be achieved in assembly lines strategically and dynamically. Implementing both the strategic and dynamic variation reduction techniques is expected to lead to further reduction in the number of failed final assemblies. The dissertation is divided into three major parts. In the first part, we propose to reduce variation for assemblies by developing efficient inspection plans based on (1) historical data for existing products, or simulated data for newly developed products; (2) Monte Carlo simulation; and (3) optimization search techniques. The cost function to be minimized is the total of inspection, rework, scrap and failure costs. The novelty of the proposed approach is three-fold. First, the use of CAD data to develop inspection plans for newly launched products is new, and has not been introduced in the literature before. Second, frequency of inspection is considered as the main decision variable, instead of considering whether or not to inspect a quality characteristic of a subassembly. Third, we use a realistic reaction plan (rework-scrap-keep) that mimics reality in the sense that not all out-of-tolerance items should be scrapped or reworked. At a certain stage, real-time inspection data for a batch of subassemblies could be available. In the second part of this dissertation, we propose utilizing this data in near real-time to dynamically reduce variation by assigning the inspected subassembly parts together. In proposing mathematical models, we found that they are hard to solve using traditional optimization techniques. Therefore, we propose using heuristics.Finally, we propose exploring opportunities to reduce the aforementioned cost function by integrating the inspection planning model with the Dynamic Throughput Maximization (DTM) model. This hybrid model adds one decision variable in the inspection planning; which is whether to implement DTM (assemble the inspected subassemblies selectively) or to assemble the inspected items arbitrarily. We expect this hybrid implementation to substantially reduce the failure cost when assembling the final assemblies for some cases. To demonstrate this, we solve a numerical example that supports our findings. / Ph. D.

Lithium ion batteries (LIBs) have attracted considerable interest due to their wide range of applications, such as portable electronics, electric vehicles (EVs) and aerospace applications. Particularly, the emergence of a variety of nanostructured materials has driven the development of LIBs towards the next generation, which is featured with high specific energy and large power density. Herein, rolled-up nanotechnology is introduced for the design of strain-released materials as anodes of LIBs. Upon this approach, self-rolled nanostructures can be elegantly combined with different functional materials and form a tubular shape by relaxing the intrinsic strain, thus allowing for enhanced tolerance towards stress cracking. In addition, the hollow tube center efficiently facilitates electrolyte mass flow and accommodates volume variation during cycling. In this context, such structures are promising candidates for electrode materials of LIBs to potentially address their intrinsic issues. This work focuses on the development of superior structures of Si and SnO2 for LIBs based on the rolled-up nanotech. Specifically, Si is the most promising substitute for graphite anodes due to its abundance and high theoretical gravimetric capacity. Combined with the C material, a Si/C self-wound nanomembrane structure is firstly realized. Benefiting from a strain-released tubular shape, the bilayer self-rolled structures exhibit an enhanced electrochemical behavior over commercial Si microparticles. Remarkably, this behavior is further improved by introducing a double-sided carbon coating to form a C/Si/C self-rolled structure. With SnO2 as active material, an intriguing sandwich-stacked structure is studied. Furthermore, this novel structure, with a minimized strain energy due to strain release, exposes more active sites for the electrochemical reactions, and also provides additional channels for fast ion diffusion and electron transport. The electrochemical characterization and morphology evolution reveal the excellent cycling performance and stability of such structures.

Fusarium verticillioides è l’agente responsabile della Fusariosi della Spiga del mais, contamina la granella con fumonisine, micotossine responsabili di diverse patologie umane e animali. Per la resistenza alla fusariosi e all’accumulo di fumonisine esiste variabilità tra genotipi diversi ma non sono ancora disponibili ibridi immuni. L’obiettivo di questo lavoro è stato quello di individuare marcatori associati alla resistenza a F. verticillioides. Mediante un bioassay è stato testato un association panel per la resistenza a F. verticillioides. Al fine di identificare i marcatori di resistenza sono stati applicati un approccio GWAS e uno per geni candidati. L’analisi GWAS è stata eseguita con 227K SNPs restituendo 206 marcatori significativi. Da un lavoro di RNASequencing sono stati individuati i geni coinvolti nella risposta a F. verticillioides mentre i geni R sono stati recuperati della letteratura scientifica. Genotipi resistenti (CO433 e CO441) e suscettibili (CO354 e CO389) sono stati scelti per individuare polimorfismi nei geni candidati da associare ai fenotipi rilevati mediante il bioassay. Quattro marcatori sono risultati significativi. Infine, la correlazione tra l’incidenza della fusariosi rilevata in campo e mediante bioassay è stata analizzata in una popolazione di 172 RIL derivanti da CO441 x CO354, tuttavia, non è stata individuata alcuna corrispondenza. / Fusarium verticillioides is the causal agent of Fusarium ear rot (FER) in maize and contaminates grains with fumonisin, a family of mycotoxins involved in several human and animal diseases. Quantitative genetic variation exists for resistance to FER and fumonisin contamination among genotypes, however, resistant maize hybrids are currently not available. The aim of this work was the identification of genetic markers associated to resistance against F. verticillioides. A bioassay was used to screen inbred lines of the maize association population for FER resistance, GWAS and candidate gene approaches were applied to identify markers. GWAS was performed using a 227K SNP matrix and resulting in 206 significant markers. Genes involved in F. verticillioides response in developing maize kernels were retrieved from a previous RNASequencing study while maize R genes were retrieved from scientific literature. Resistant (CO433 and CO441) and susceptible genotypes (CO389 and CO354) were selected to amplify and sequence candidate genes. Polymorphisms detected were used to find association with phenotypes scored using the bioassay. Four significant markers were found. Finally, the correlation between FER phenotypes scored in field experiments and bioassay phenotypes was investigated. A population of 172 RILs (CO441 x CO354), was tested. No correlation was found.

Master of Science / Department of Animal Sciences and Industry / James S. Drouillard / A trial was conducted replacing portions of steam-flaked corn with either dry-rolled corn or dried distiller’s grains with solubles to evaluate effects on performance, carcass characteristics, carcass composition, meat color stability, and meat sensory attributes. Seven hundred crossbred yearling heifers (302 ± 65 kg initial BW) were used in a randomized complete block experiment with a 2 x 2 factorial arrangement of treatments. All diets contained steam-flaked corn (SFC), and factors consisted of the levels of dry-rolled corn (DRC; 0 or 25%) and dried corn distiller’s grains with solubles (DDGS; 0 or 25%). Results revealed no interactions between DRC and DDGS in terms of effects on feedlot performance, and only minor interactive effects were observed for carcass characteristics and meat quality attributes. Feedlot performance and carcass characteristics were not affected by the addition of DRC or DDGS (P > 0.05). Carcass composition and meat quality attributes were measured to determine if fat content of carcasses was altered by feeding DDGS. Diet had no significant effects, as carcasses from the four treatments contained similar amounts of separable portions of muscle, adipose, and bone; and similar percentages of protein, moisture, and ether extract. Compositions of both adipose and muscle tissue were evaluated to assess differences in fatty acid profile. Minimal effects were noted on the fatty acid profiles of the muscle and adipose tissue from cattle fed DDGS or DRC. Feeding cattle DDGS decreased alpha tocopherol (vitamin E) content of meat (P < 0.05). Meat quality attributes were largely unaffected by addition of DRC or DDGS to the diet, as retail color display life, lipid oxidation, sensory attributes, and heterocyclic amine concentrations were not different among treatments. Overall, DRC or DDGS can replace portions of SFC without negatively altering feedlot performance, carcass characteristics, meat composition, or meat quality attributes.

La détermination des propriétés en fatigue à grand nombre de cycles des aciers laminés destinés à l'industrie automobile est un processus coûteux en temps et en quantité de matière : 25 éprouvettes et presque un mois d'essais sont nécessaires à l'obtention d'une courbe de fatigue standard. Dans l'objectif de réduire ces temps de caractérisation, une méthode rapide, basée sur l'auto-échauffement de la matière sous sollicitation cyclique est mise en place sur un très grand nombre de nuances. Les mesures d'auto-échauffement mettent en évidence la présence de deux régimes dissipatifs distincts, un pour les plus faibles amplitudes de chargement cyclique et un pour les plus hautes. Un modèle probabiliste à deux échelles est ensuite développé, dont le but est de prévoir le comportement en fatigue à grand nombre de cycles à partir des mesures d'auto-échauffement. Il est composé d'une matrice au comportement élasto-plastique et d'une population d'inclusions possédant un second comportement élasto-plastique dont le seuil d'activation est aléatoire. Les deux régimes d'auto-échauffement peuvent ainsi être décrits fidèlement. En utilisant l'hypothèse du maillon le plus faible et un critère énergétique, une prévision du comportement en fatigue est réalisée. Trois jours seulement sont alors requis pour obtenir une courbe de fatigue complète. La pertinence de l'approche est validée en comparant avec des courbes de fatigue standards. Puis, des observations par microscopie optique, par microscopie à force atomique et par EBSD sont entreprises sur un acier micro-allié. L'objectif est double : en premier lieu, mieux comprendre les phénomènes qui se produisent sous sollicitation cyclique conduisant à l'obtention des deux régimes d'auto-échauffement ; en second lieu, justifier la pertinence des ingrédients introduits dans la modélisation. Dans une seconde grande partie, il est question de l'influence d'une pré-déformation plastique sur l'évolution des propriétés en fatigue. En effet, les composants automobiles obtenus à partir de tôles en acier laminé subissent diverses opérations de mise en forme, conduisant à déformer plastiquement la matière. Ces modifications de l'état de la matière engendrent des évolutions des propriétés en fatigue qui ne sont cependant pas prises en compte dans le dimensionnement actuel des pièces (non déterminées par la méthode standard car trop coûteux en temps). La rapidité de la méthode développée autorise à caractériser ces évolutions. A partir des modifications des propriétés à l'auto-échauffement après divers modes de pré-déformation plastique (traction, traction plane, cisaillement) et en étudiant diverses directions de sollicitation, il est possible de prévoir l'évolution des propriétés en fatigue associée pour de larges gammes de pré-déformations. La qualité des prévisions est validée en comparant avec des courbes de fatigue standards. / The determination of high cycle fatigue properties of high strength steel sheets for automotive industry is time and specimens consuming : 25 specimens and almost one month are required to obtain a traditional fatigue SN curve. In order to reduce the time dedicated to the fatigue characterization, a fast method, based on the self-heating of steels under cyclic loading is developed and applied to a wide range of grades. Self-heating measurements show the presence of two distinct dissipative regimes, a firstone for the low amplitudes of cyclic loading and a secondary one for the highest. A two scales probabilistic model is then developed in order to establish a dialogue between self-heating measurements and the fatigue properties. It is composed by a matrix having an elasto-plastic behaviorand a population of inclusions having a second elasto-plastic behavior with a random activation threshold. Both self-heating regimes can be perfectly described. By using the weakest link theory and an energetic criterion, a prediction of fatigue properties is made. Only three days are required to obtain acomplete fatigue curve. The pertinence of the approach is validated by a comparison with standard fatigue curves. Then, observations with optical microscopy, atomic force microscopy and EBSD are made on a high strength low alloyed steel grade. This study has two objectives: a better understanding of phenomenon occurring during cyclic loading leading to the two self-heating regimes; a justification of the ingredients introduced into the model. In a second important section, it deals with the influence of aplastic pre-strain on the fatigue properties evolution. Indeed, automotive components obtained from high strength steel sheets are subjected to primary forming operations, inducing plastic strain. These modifications lead to fatigue properties evolutions that are nevertheless not taken into account intraditional fatigue design of components (not determined with the standard method because ofprohibitive time). The speed of the proposed approach authorizes to characterize these evolutions. From the modifications of the self-heating properties after different modes of plastic pre-strain (tension, planetension, shearing) and by studying different directions of loading, it is possible to predict the fatigue properties evolutions for a wide range of plastic strain. The quality of the predictions is validated by acomparison with standard fatigue curves.

Os aços elétricos apresentam uma enorme relevância para o mundo moderno, pois estão presentes na maioria das máquinas e aparelhos que funcionam a partir de energia elétrica. Existem duas classes de aços elétricos: Os aços elétricos de grão orientado (GO) e os aços elétricos de grão-não-orientado (GNO). Aços elétricos GNO são utilizados em motores elétricos. O rendimento energético dessas máquinas depende da permeabilidade e das perdas magnéticas. Durante a laminação a frio as propriedades magnéticas dos aços se modificam em conseqüência de mudanças estruturais e de textura que acompanham a deformação plástica. A evolução da textura e da microestrutura de deformação do aço elétrico de grão não orientado com 1,25% Si é descrita para graus de deformação entre 10 e 90%. A principal técnica de caracterização empregada foi à difração de elétrons retroespalhados (EBSD), acoplado ao microscópio eletrônico de varredura, que se mostrou bastante eficaz na caracterização da textura e da microestrutura de deformação, mesmo para altas taxas de deformação por laminação a frio. Uma mesma área selecionada também foi analisada, grão a grão, pela técnica de EBSD com vários graus de deformação. A distribuição de deformação na microestrutura em função do nível de deformação foi analisada qualitativamente. Regiões dos contornos de grãos apresentam altos níveis de deformação devido a suas altas densidades de discordâncias. Os grãos não rotacionam uniformemente quando submetidos à deformação. Subestruturas de deformação caracterizadas pela heterogeneidade de cores dentro dos grãos mostram a fragmentação do grão como resultado da operação de diferentes sistemas de deslizamento. Avaliou-se que possíveis efeitos da vizinhança não foram significativos e que orientação inicial do grão pode ser determinante na escolha da trajetória de rotação durante a deformação. / Electric steels are used in most of the machine and equipment using electrical energy. There are two classes of electric steels: Oriented grain electric steel (GO) and non-oriented electric steels (GNO). GNO electric steels are utilized in electrical motors. The energetic yield of these machines depends on magnetic permeability of the steels. This is a consequence of structural and textural changes which results from plastic deformation during manufacturing. Deformation texture and microstructure evolution for Fe-1,25% Si non oriented grain electric steel is presented for deformation levels between 10 and 90%. The main characterization technique utilized was Electron Backscattering Diffraction (EBSD) in a Scanning Electron Microscopy (SEM) which was very efficient in the characterization of deformation microstructure and texture, even for high deformation levels in cold rolling. A selected area was also analyzed, observing individual grains, by EBSD technique with different deformation levels. Grain boundaries show high deformation level due to these high deformation densities. Grains do not rotate uniformly when deformed. Deformation substructures characterized as different colors inside the grains show grain fragmentation due to the activation of different slip system. Possible neighborhood effects were evaluated, but they seemed to be not significant and the initial grain orientation was the main ground for the choice of the rotation trajectory during deformation.

Recrystallisation is an important topic in the metal industry since the process may drastically alter the properties of the materials subjected to it. By controlling the recrystallisation process, the material properties can be adjusted as desired, which could lead to stronger materials and hence lighter constructions, decreasing our material consumption. This is currently regulated using softening curves complied from tensile tests, a method which does not show the degree of recrystallisation of a metal. This thesis work therefore explores the possibility to characterise the recrystallisation process using in situ X-ray diffraction, XRD, during heating.The method proposed is using in situ heat treatments of aluminium samples combined with XRD measurements. The results show that it is possible to follow the recrystallisation process of rolled aluminium alloy AA3003 by using in situ XRD during heating, a discovery that could facilitate development and understanding of new materials. Nevertheless, further investigations of the subject is required before the method will be profitable. / Rekristallisation är ett viktigt ämne inom metallindustrin, detta eftersom materialegenskaper drastiskt kan förändras under rekristallisationsprocessen. Genom att kontrollera rekristallisationsprocessen kan materialegenskaper skräddarsys efter applikation. Även starkare material kan tillverkas och därav kan lättare strukturer konstrueras och på så vis minskar även materialåtgången. Idag regleras rekristallisation med hjälp av mjukningskurvor sammanställda genom dragprov, en metod som inte kan visa rekristallisationsgraden av en metall. Detta examensarbete utforskar möjligheten att karaktärisera rekristallisationsprocessen genom att använda in situ röntgendiffraktion, XRD, under värmningsprocessen.Den framtagna metoden inkluderar in situ värmebehandlingar av aluminiumprover i kombination med XRD-mätningar. De erhållna resultaten från experimenten visar på att det är fullt möjligt att följa rekristallisationsprocessen av aluminiumlegering AA3003 med in situ XRD, en upptäckt som kan komma att underlätta vid utveckling och förståelse av legeringar och nya material. Dock krävs fortsatta studier i ämnet innan metoden kan anses vara lönsam.

Os aços elétricos apresentam uma enorme relevância para o mundo moderno, pois estão presentes na maioria das máquinas e aparelhos que funcionam a partir de energia elétrica. Existem duas classes de aços elétricos: Os aços elétricos de grão orientado (GO) e os aços elétricos de grão-não-orientado (GNO). Aços elétricos GNO são utilizados em motores elétricos. O rendimento energético dessas máquinas depende da permeabilidade e das perdas magnéticas. Durante a laminação a frio as propriedades magnéticas dos aços se modificam em conseqüência de mudanças estruturais e de textura que acompanham a deformação plástica. A evolução da textura e da microestrutura de deformação do aço elétrico de grão não orientado com 1,25% Si é descrita para graus de deformação entre 10 e 90%. A principal técnica de caracterização empregada foi à difração de elétrons retroespalhados (EBSD), acoplado ao microscópio eletrônico de varredura, que se mostrou bastante eficaz na caracterização da textura e da microestrutura de deformação, mesmo para altas taxas de deformação por laminação a frio. Uma mesma área selecionada também foi analisada, grão a grão, pela técnica de EBSD com vários graus de deformação. A distribuição de deformação na microestrutura em função do nível de deformação foi analisada qualitativamente. Regiões dos contornos de grãos apresentam altos níveis de deformação devido a suas altas densidades de discordâncias. Os grãos não rotacionam uniformemente quando submetidos à deformação. Subestruturas de deformação caracterizadas pela heterogeneidade de cores dentro dos grãos mostram a fragmentação do grão como resultado da operação de diferentes sistemas de deslizamento. Avaliou-se que possíveis efeitos da vizinhança não foram significativos e que orientação inicial do grão pode ser determinante na escolha da trajetória de rotação durante a deformação. / Electric steels are used in most of the machine and equipment using electrical energy. There are two classes of electric steels: Oriented grain electric steel (GO) and non-oriented electric steels (GNO). GNO electric steels are utilized in electrical motors. The energetic yield of these machines depends on magnetic permeability of the steels. This is a consequence of structural and textural changes which results from plastic deformation during manufacturing. Deformation texture and microstructure evolution for Fe-1,25% Si non oriented grain electric steel is presented for deformation levels between 10 and 90%. The main characterization technique utilized was Electron Backscattering Diffraction (EBSD) in a Scanning Electron Microscopy (SEM) which was very efficient in the characterization of deformation microstructure and texture, even for high deformation levels in cold rolling. A selected area was also analyzed, observing individual grains, by EBSD technique with different deformation levels. Grain boundaries show high deformation level due to these high deformation densities. Grains do not rotate uniformly when deformed. Deformation substructures characterized as different colors inside the grains show grain fragmentation due to the activation of different slip system. Possible neighborhood effects were evaluated, but they seemed to be not significant and the initial grain orientation was the main ground for the choice of the rotation trajectory during deformation.