abstract: The mechanical behavior of Pb-free solder alloys is important, since they must maintain mechanical integrity under thermomechanical fatigue, creep, and mechanical shock conditions. Mechanical shock, in particular, has become an increasing concern in the electronics industry, since electronic packages can be subjected to mechanical shock by mishandling during manufacture or by accidental dropping. In this study, the mechanical shock behavior of Sn and Sn-Ag-Cu alloys was systematically analyzed over the strain rate range 10-3 - 30 s-1 in bulk samples, and over 10-3 - 12 s-1 on the single solder joint level. More importantly, the influences of solder microstructure and intermetallic compounds (IMC) on mechanical shock resistance were quantified. A thorough microstructural characterization of Sn-rich alloys was conducted using synchrotron x-ray computed tomography. The three-dimensional morphology and distribution of contiguous phases and precipitates was analyzed. A multiscale approach was utilized to characterize Sn-rich phases on the microscale with x-ray tomography and focused ion beam tomography to characterize nanoscale precipitates. A high strain rate servohydraulic test system was developed in conjunction with a modified tensile specimen geometry and a high speed camera for quantifying deformation. The effect of microstructure and applied strain rate on the local strain and strain rate distributions were quantified using digital image correlation. Necking behavior was analyzed using a novel mirror fixture, and the triaxial stresses associated with necking were corrected using a self-consistent method to obtain the true stress-true strain constitutive behavior. Fracture mechanisms were quantified as a function of strain rate. Finally, the relationship between solder microstructure and intermetallic compound layer thickness with the mechanical shock resistance of Sn-3.8Ag-0.7Cu solder joints was characterized. It was found that at low strain rates the dynamic solder joint strength was controlled by the solder microstructure, while at high strain rates it was controlled by the IMC layer. The influences of solder microstructure and IMC layer thickness were then isolated using extended reflow or isothermal aging treatments. It was found that at large IMC layer thicknesses the trend described above does not hold true. The fracture mechanisms associated with the dynamic solder joint strength regimes were analyzed. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2012

La réduction continue des dimensions des transistors depuis les années 60 est à l’origine de l’explosion des usages de l’électronique. Toutefois, la réduction des dimensions à l’échelle nanométrique s’accompagne de nouvelles difficultés qui tendent à limiter les gains des transistors en termes de performances et de consommation.Afin de surmonter ces obstacles et maintenir cette dynamique, des canaux à base de nouveaux matériaux à forte mobilité et de nouvelles architectures de transistors sont désormais utilisées ou à l’étude. L’intérêt de films SiGe contraint en compression sur isolant (SGOI: SiGe-On-Insulator) ultra-minces est double : ils bénéficient de la forte mobilité des trous du SiGe contraint en compression ainsi que du meilleur contrôle électrostatique des structures dites « sur isolant ». Des films SGOI présentant une forte concentration en Ge et une importante contrainte peuvent être fabriqués par une technique industrielle appelée condensation. Cette technique repose sur deux processus simultanés : l’oxydation thermique et sélective du SiGe (seul le Si est oxydé) et l’inter-diffusion du SiGe entre l’oxyde thermique et l’oxyde enterré qui se comporte comme une barrière à la diffusion.L’utilisation de cette technique dans un environnement industriel nécessite de relever deux défis : maîtriser les mécanismes et la cinétique d’oxydation, et atteindre les plus fortes contraintes et qualités cristallines pour lesfilms SGOI.La cinétique de plusieurs procédés d’oxydation industriels et pertinents au regard des besoins technologiques actuels est étudiée à l’aide d’une nouvelle méthodologie d’analyse quantitative. Nous établissons une corrélationentre le coefficient de diffusion de l’espèce oxydante, qui détermine la cinétique d’oxydation, la concentration en Ge à l’interface d’oxydation, et la densité de l’oxyde mesurée par réflectivité de rayons X sur une ligne desynchrotron.Puis, nous avons fabriqué des films SGOI présentant des concentrations en Ge jusqu’à 80%. Nous discutons l’évolution de la contrainte de ces films en fonction des paramètres du procédé et des niveaux de contrainte. Enfin,nous mettons en évidence les effets du procédé de condensation sur la qualité cristalline du film SiGe aux interfaces avec les oxydes grâce à l’effet de canalisation d’une technique de rétrodiffusion d’ions à moyenne énergie (MEIS : Medium Energy Ion Scattering) / The tremendous spread of electronic devices and networks into our day-to-day life has been enabled by the constant downscaling of transistors since the 60’s. However, downsizing transistors has become increasingly difficult in the past few years and going to the nanometer scale brings new detrimental effects that have put power consumption and performances on quasi-plateaux for a few years. To overcome these limitations, high mobility channels based on new materials and new transistor architectures are being introduced. Ultrathin compressivelystrained SiGe-On-Insulator (SGOI) films benefit from the advantages of both the higher hole mobility of compressively strained SiGe as well as of the better electrostatic control of On-Insulator structures. The condensation techniqueis a CMOS-compatible technique that allows fabrication of such films with possibly high Ge content and high strain levels. The technique is based on Si-selective thermal oxidation of SiGe and concurrent SiGe diffusion between the thermal oxide and the buried oxide layer that acts as a diffusion barrier.Two main challenges still need to be taken up for an efficient and optimized use of the condensation technique in an industrial environment: oxidation mechanisms and kinetics must be well controlled, and strain and crystal quality of the SGOI film must be as high as possible.Firstly, this work bridges the gap between previous studies by covering various oxidation processes relevant to today’s technological needs with a new and quantitative analysis methodology of oxidation kinetics. A correlation is established between the diffusivity of the oxidizing species that governs oxidation kinetics, the Ge concentration at the oxidation interface, and the oxide density measured by X-Ray Reflectivity on a synchrotron beamline.Secondly, SGOI films with Ge concentrations up to 80% were fabricated by the condensation technique. The evolution of strain of SGOI films is discussed as a function of process parameters and strain energy levels. How the condensation technique alters the crystal quality, both at interfaces with oxides and in the bulk of the SiGe crystal, is evaluated by the Medium Energy Ion Scattering (MEIS) technique by using the channeling effect.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14163号 / 工博第2997号 / 新制||工||1445(附属図書館) / 26469 / UT51-2008-N480 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 落合 庄治郎, 教授 河合 潤, 准教授 奥田 浩司 / 学位規則第4条第1項該当

Ceramics have been widely used for personnel and vehicle armour because of their desirable properties such as high hardness and low density. However the brittle nature associated with the ceramic materials, i.e. low toughness, reduces their ability to withstand multiple ballistic hits. The present work is focused on ceramic armour materials made from alumina and zirconia toughened alumina (ZTA). The effects of grain size and zirconia phase transformation toughening on the mechanical and high strain rate properties in both materials were investigated in detail. Alumina, 10%, 15% and 20% nano ZTA with 1.5 mol% yttria stabiliser were produced with various grain sizes. The processing of the materials started from suspension preparation, spray freeze drying of the suspension and die pressing to produce homogeneous green bodies with densities above 54%. Then, the green bodies were sintered using conventional single stage and/or two stage sintering to produce the samples with full density and a range of grain sizes (0.5 to 1.5 µm alumina grains and 60 to 300 nm zirconia grains). The effects of the processing conditions on the microstructures were studied and the optimum processing route for each sample was determined. The mechanical properties of the alumina and ZTA samples were investigated, including Vickers hardness, indentation toughness, 4-point bend strength and wear resistance. The results showed that, with an increasing amount of zirconia addition, evident increases of the toughness, strength and wear resistance properties were observed, whilst the hardness reduced slightly correspondingly. The effect of density and grain sizes on the hardness and toughness were studied as well: larger alumina grain size led to a higher hardness and negligible change in toughness, whilst the zirconia grain coarsening enhanced the phase transformation toughening effect and the samples displayed a higher toughness. In addition to the investigation of the mechanical properties, the alumina and nano ZTA samples were subjected to high strain rate testing, including split Hopkinson pressure bar (SHPB) (8-16 m/s) and gas gun impact testing (100-150 m/s). The high strain rate performances were compared in terms of their fracture behaviours, fragmentation process and fragment size distribution. Raman spectroscopy was used to measure the amount of zirconia phase transformation in ZTA samples after the high strain rate testing. The residual stress and dislocation density in alumina grains after testing were quantitatively measured using Cr3+ fluorescence spectroscopy. The results indicated that zirconia phase transformation can reduce the residual stress and dislocation densities in the ZTA samples, resulting in less damage, lower plastic deformation and less crack propagation. In addition, a nano zirconia material with 1.5 mol% yttria stabiliser (1.5YSZ) was subjected to a gas gun impact test with a very high impact speed (142 m/s); a deep projectile penetration was observed, due to the low hardness of the pure zirconia, whilst the sample stayed intact. The result further confirmed that the zirconia phase transformation toughening effect can improve the sample's high strain rate performance.

Housing shortage is sweeping over Nordic countries, where college/university students has involved in this housing crisis. More innovative housing solutions are appealed to buffer housing shortage and supply affordable housing for students. The existence of module housing and container housing in a number of Nordic municipalities has come into being a new housing term: temporary housing. At the same time, students’ housing expenditure has influence on their financial strain, and students’ housing location affects student involvement on campus. The design of temporary housing aims to cope with housing shortage. This study intends to figure out an ideal temporary housing with a great rent in order to alleviate students’ financial strain, a good location so as to enhance the level of student involvement, and a satisfactory housing type for purpose of meeting students’ housing preference. To understand students’ view of temporary housing, Cockerham’s theory of health and lifestyle is applied to develop “living condition” in student group. A self-administered questionnaire in quantitative research is conducted, and with a case study element as well. The survey groups centers on college/university students so that this study is following a down-up perspective. Finally, based on students’ feelings and opinion, an ideal temporary housing is depicted as a new product in student housing. This ideal temporary housing is discussed in relation to variables, such as an acceptable rent, good housing location and pleasant housing type.

The aim of this thesis was to compare the indicators of egg production of hens which are bred for production of consumable eggs i.e. Hy-Line Brown and Hy-Line White in selected farms. Selected parameters of egg production were evaluated during 12-months-laying cycle. In the selected farm during the monitored period was achieved the intensity of laying 86,8 %, laying at the initial state 26.5 eggs, number of eggs included in first quality class 96.4%, mortality of egg layer 1.06%, consumption of compound feed per 1 egg 130.0 g and consumption of compound feed per 1 feeding day 110.8 g. Hy-Line Brown showed higher intensity of laying (88,0 %, respectively 85,2 %), laying at the initial state 26.7 eggs, respectively 26.1 eggs, lower consumption of compound feed 128.7 g, respectively 133.2 g. Hy-Line White showed a statistically significant higher proportion of eggs included in the first quality (97.3%, respectively 85.4%), statistically significant lower mortality (0.49% and 1.51%) and statistically significantly lower consumption mixtures per 1 egg (100.7, respectively 114.9 g).

The aim of this thesis is to analyse the physical strain of a PE teacher at the second stage of the primary education during the PE lessons and within the everyday school life. In the theoretical part of the thesis key concepts pedagogy, pedeutology and a brief history of teaching are explained. Furthermore, the profession of a teacher, their duties, personality traits, role and teaching styles are described, as well as the job-analysis of a PE teacher. The most important part is the description and analysis of the physical strain, stress, noise and workload of a PE teacher and the influence of the physical strain on their heart rate. In the practical part of the thesis we deal with eight days of surveying in which we describe in detail the PE lessons. Afterwards we collect the data obtained by using a sport tester within these 30 PE lessons and its parts and we can find out what the energy output of the PE teacher is. From the data obtained according to general physiology we can put the demandingness of the profession of a PE teacher into the corresponding category of work load.

O aumento de demanda por combustíveis menos poluentes e de fontes renováveis faz com que o Etanol se destaque como uma alternativa as fontes convencionais de energia. O crescente aumento no consumo deste produto, para os próximos anos, exigirá meios de transporte e estocagem eficientes e seguros, desde os diversos produtores até os terminais de distribuição. O transporte por dutos é, sem dúvida, a forma mais econômica de transporte deste produto, porém, há evidências de que esses dutos de transporte e fundo de tanques de armazenamento de etanol poderiam ser susceptíveis ao fenômeno de corrosão sob tensão. Este fenômeno pode ser avaliado, por exemplo, por ensaios de baixa taxa de deformação (BTD) com corpos de prova com ou sem entalhe. Este trabalho tem por objetivo avaliar a influência da severidade do entalhe em corpos de prova ensaiados a baixa taxa de deformação no meio etanol combustível simulado (PRCI SFGE). Foram preparados quatro tipos de corpos de prova de aço API X70: sem entalhe, com entalhe da norma NACE TM 0111, com entalhe “intermediário” (severidade 18,9% menor que o da norma) e com entalhe “menos severo” (redução de 37,2% na severidade do entalhe, segundo concentração de tensões, quando comparado com o da norma). Os resultados mostram que os quatro tipos de corpos de prova apresentaram susceptibilidade ao meio (etanol PRCI SFGE). Nos corpos de prova sem entalhe esta susceptibilidade foi evidenciada somente nas imagens fractográficas. Já nos CPs com entalhe, mesmo com redução de concentrações de tensões no entalhe, observou-se resultados bem semelhantes, ficando evidenciada a susceptibilidade ao meio tanto nas imagens fractográficas (fratura frágil), quanto pela diminuição da ductilidade. / The increasing demand for cleaner fuels and renewable sources makes the ethanol rise as an alternative to conventional energy sources. The increasing consumption rate of this product, predicted for the upcoming years, will require safer and more efficient methods for transportation and storage through the entire transport cycle. Pipelines are the most economical way to transport it. However, there is evidence that pipeline transportation and the bottom of the storage tanks for ethanol might be susceptible to the stress corrosion cracking phenomenon. This phenomenon can be assessed by slow strain rate tests (SSRT) using smooth or notched specimen. This work aims to evaluate the influence of notch severity in specimens submitted to SSRT technique in simulated fuelgrade ethanol (PRCI SFGE). Four types of specimens of steel API X70 were prepared: unnotched, notched according to standard NACE TM 0111, notched with “intermediate” severity (severity 18.9% lower than the standard) and “less severe” notched (reduction of 37.2% on severity of the notched when compared with the standard). The results show that both sample types presented susceptibility in the solution (ethanol PRCI SFGE). For the unnotched specimens this susceptibility was observed only in fractographic images. In the notched specimens, despite the reduction of stress concentrations in the notch, the results were very similar. In this case the susceptibility can be observed in fractographic images (brittle fracture) as well as by decrease in the ductility.

Objetivo: investigar a associação entre estresse no trabalho e a autopercepção de saúde bucal. Método: Os dados analisados foram obtidos por meio de questionário de autopreenchimento de 3253 funcionários técnicos administrativos da Universidade Estadual do Rio de Janeiro um Estudo do Pró-Saúde. O estresse no trabalho foi medido através de um questionário elaborado por Karasek 1970 e reduzido por Theorell 1988. O instrumento é composto pelas seguintes dimensões: alta exigência no trabalho (alta demanda e baixo controle), baixa exigência (baixa demanda e alto controle), trabalho ativo (altos níveis de demanda e controle) e passivo (baixos níveis de demanda e controle). Autopercepção de saúde bucal foi obtida pela pergunta: “De um modo geral, como você considera o seu estado de saúde bucal (dentes e gengiva)?”, com opções de resposta variando entre, “muito bom” e “muito ruim”. Para a análise dos dados utilizou-se regressão logística ordinal, posteriormente ajustada para três blocos de variáveis: 1) saúde bucal (perda de dentes e dor de dentes nas duas últimas semanas) e uso e utilização serviço de saúde (frequência de visita ao dentista) 2) sociodemográficas (idade, sexo, escolaridade e renda) e 3) comportamentais em saúde (fumo e autopercepção de saúde geral). Resultados: Trabalhadores expostos à alta exigência e pouco controle no trabalho (OR=1,67; IC95%: 1,38-2,03) e ao trabalho passivo (OR=1,31; IC95%: 1,12-1,54), tiveram maiores chances de perceber pior saúde bucal, quando comparados àqueles expostos a baixa exigência no trabalho, não se observando associação com aqueles expostos ao trabalho ativo (OR=1,05; IC95%: 0,90-1,23). Entretanto, no modelo de regressão múltipla estas estimativas reduziram em magnitude e perderam significância estatística, a saber: alta exigência (OR=1,19; IC95%: 0,95-1,49), trabalho passivo (OR=1,09; IC95%: 0,91-1,31). Conclusão: Funcionários expostos a alta exigência no trabalho apresentaram pior saúde bucal autorreferida (modelo bruto e ajustado para os três blocos de variáveis) que parece ser parcialmente explicada pelas comportamentais em saúde, presença de problemas de saúde bucal (dor e perda dentária) e uso de serviços odontológicos com uma frequência maior do que uma vez ao ano. / Objective: To investigate the association between occupational stress and oral health self-perception. Method: Data obtained through a self-completion questionnaire with 3253 administrative technicians from a university in Rio de Janeiro, in the Pro-Health Study, were analyzed. Occupational stress was measured through a questionnaire prepared by Karasek, 1970, and reduced by Theorell, 1988. Oral health self-perception was obtained through the question: “In general, how do you consider your oral health state (teeth and gums)?”, with answer options ranging from “very good” to “very bad”. For data analysis, ordinal logistic regression was used, subsequently adjusted to three blocks of variables: 1) oral health (loss of teeth and toothache in the past two weeks) and use of the health service (frequency at which the dentist is attended); 2) socio-demographic (age, sex, schooling, and income); and 3) health-related behavior (smoking and general health self-perception). Results: Workers exposed to high strain and little control at work (OR=1.67; 95%CI: 1.38-2.03) and to passive work (OR=1.31; 95%CI: 1.12-1.54) had greater chances of perceiving worse oral health, when compared with those exposed to high-strain work, and no association was observed with those exposed to active work (OR=1.05; 95%CI: 0.90-1.23). However, in the multiple regression model, these estimates declined in magnitude and lost statistical significance, namely: high strain (OR=1.19; 95%CI: 0.95-1.49), passive work (OR=1.09; 95%CI: 0.91-1.31). Conclusion: Workers exposed to high-strain work presented worse self-reported oral health (raw model and adjusted to the three blocks of variables), which seems to be partially explained by health-related behavior, presence of oral health problems (toothache and dental loss), and use of dental services at greater frequency than once a year.

Caffeine consistently enhances endurance performance in temperate environmental conditions, while far less research has examined its ergogenic and physiological effects during prolonged exercise in the heat. Despite the performance benefit of an acute caffeine doses being less pronounced in regular caffeine users versus those not habituated to the drug, few studies have examined the influence of a prolonged period of controlled caffeine intake on endurance performance. The endogenous trace amine octopamine is purported to possess stimulant-like properties and influence fat metabolism, although no study has examined these effects in humans. The aim of this thesis was to further characterise the performance and physiological effects of caffeine during prolonged exercise, while elucidating a potential ergogenic role for octopamine. The first two studies investigated the ergogenic and thermoregulatory effects of low to moderate caffeine doses during prolonged cycle exercise in the heat. Chapter 4 demonstrated that 3 mg kg-1 caffeine, administered either as a single or split-dose (2 x 1.5 mg kg-1) before exercise, improved endurance performance without influencing thermoregulation during prolonged exercise at a fixed work-rate. Dividing the caffeine bolus appeared to confer an additional performance benefit, suggesting repeated low dose may potentiate the efficiency of the same total caffeine dose under these conditions. Chapter 5 demonstrated that a 6 mg kg-1 caffeine dose improved endurance cycle performance without differentially influencing thermoregulation than placebo. The level of habituation to caffeine influences the ergogenic effect of an acute dose, yet previous studies have employed sub-chronic supplementation protocols. Chapter 6 investigated the effect of a twenty-eight day supplementation period on endurance cycle performance. Habituation to caffeine attenuated the ergogenic effect of an acute caffeine dose, without any change in circulating caffeine, substrate oxidation or hormonal concentrations. In chapter 7 the performance and metabolic effects of octopamine was investigated. Octopamine supplementation did not influence performance, hormonal concentrations or substrate oxidation, likely due to low serum concentrations of the drug.