Orientadores: Edvaldo Sabadini, Marco-Aurelio De Paoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T06:55:08Z (GMT). No. of bitstreams: 1 Bacchi_RenatoVieira_M.pdf: 13069240 bytes, checksum: 33b4fb8f5e4184296681a0de7210799c (MD5) Previous issue date: 2011 / Resumo: Peças de polipropileno isotático, iPP, moldadas por injeção podem apresentar variação de propriedades em função dos parâmetros de injeção. Uma dessas propriedades é a propagação de ruptura, que foi estudada neste trabalho com o uso de imagens obtidas com câmera de alta velocidade ajustada para velocidades de captura entre 18.000 e 45.000 fotos por segundo. Os parâmetros modificados no processo de moldagem por injeção foram o tempo de resfriamento e a temperatura do molde. Foram formados seis grupos de corpos de prova (CP) a serem submetidos aos ensaios de tração. As imagens dos rompimentos nos ensaios de tração foram capturadas com a câmera de alta velocidade. Os CP dos grupos 1, 2 e 3 foram resfriados em molde a 22 °C durante 8, 25 e 55 s, respectivamente. Os CP dos grupos 4, 5 e 6 foram resfriados em molde a 80 °C por 8, 25 e 55 s, respectivamente. Foram observados três padrões de rompimento associados aos diferentes grupos. O primeiro padrão correspondente aos CP dos grupos 1 e 4, com tempos de ruptura entre 0,04 e 0,09 ms. O segundo padrão, apresentado pelos grupos 2 e 3, apresenta formação de pescoço e alto alongamento, porém sem tempo de ruptura definido. O terceiro padrão, observado nos grupos 5 e 6, apresenta ruptura com tempo de propagação médio de 1,5 ms e propagação elipsóide da fissura. Foram realizadas medidas de difração de raios-X e calorimetria diferencial exploratória, mas não foram observadas variações significativas dos graus de cristalinidade para os diferentes grupos. Foram obtidas micrografias por microscopia eletrônica de varredura para amostras dos seis grupos, que mostraram maior uniformidade na superfície de ruptura para os grupos 1 e 4. Para os grupos 2 e 3 foi observada presença de fibrilas. Para os grupos 5 e 6 foram observadas diferenças significativas entre as superfícies do centro do e das extremidades do CP. Para observar os efeitos do envelhecimento nos padrões de ruptura, foram armazenados alguns CP de cada um dos grupos durante 12 semanas. O enrijecimento do material tende a causar ruptura mais rápida em todos os grupos e os grupos 2 e 3 foram os mais afetados. Os resultados deste trabalho mostram que, não apenas as propriedades mecânicas do iPP são afetadas pelas variáveis na moldagem por injeção como também os mecanismos de rompimento variam consideravelmente, e estes são claramente observados com imagens em alta velocidade / Abstract: Injection-molded isotactic polypropylene, iPP, samples present different properties variation as a function of the injection parameters. One of these properties is the rupture propagation on the material, which was studied with the use a high-speed camera adjusted to capture from 18,000 to 45,000 frames per second. The injection molding parameters modified were: cooling time and temperature of the mold. Six groups of specimens were molded and submitted to tensile tests until failure. The rupture images were capture with the high-speed camera. The specimens of the groups 1, 2 and 3 were cooled in the mold at 22 °C during 8, 25 and 55 seconds, respectively. Groups 4, 5 and 6 were cooled in the mold at 80 °C during 8, 25 and 55 s, respectively. Three major rupture patterns associated with the groups were observed. The first pattern, presented by groups 1 and 4, consists in a rapid rupture, with time of propagation between 0.04 and 0.09 ms. A second pattern, observed in groups 2 and 3, presents necking and high elongation, but without a precise time for complete rupture. The third pattern, observed for groups 5 and 6, shows an ellipsoid crack propagation, with an average time for rupture of 1.5 ms. X-Ray diffraction and differential scanning calorimetry measurements were made, but no considerable differences in the degree of crystallinity among the groups was observed. Scanning electron microscopy images of the rupture surface of the specimens showed that there is considerable uniformity in groups 1 and 4. In groups 2 and 3 the appearance of fibrils was observed, whilst for groups 5 and 6 considerable differences between the skin and the core of the specimen was observed. Physical ageing effects on the rupture patterns were studied after the storage of few specimens during 12 weeks. Hardening of the material, due to physical ageing, affected all the groups, but it was most apparent in groups 2 and 3, which started to behave more like the other groups after this time. The result in this work showed that not only the mechanical properties of iPP are affected by the modification in the mold injection parameters, but also the rupture mechanisms can considerably vary. This is observed clearly in the high-speed images / Mestrado / Físico-Química / Mestre em Química

D.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

Increasingly higher and higher conveyor speeds are driven in industrial manufacturing. This goes along with a significant rise of the sound pressure level in the production lines. The main cause of this is the articulated and multi-articulated construction of standard plastic-slide-chains in conveyor systems. This condition could be significantly improved by the use of a nonarticulated attraction in the form of a transport toothed belt. In addition, the conveying speeds could be significantly increased. Modifications to the belt teeth provide fastening possibilities for plastic support plates. / Zunehmend werden immer höhere Fördergeschwindigkeiten in industriellen Anlagen gefahren. Dies geht einher mit einer signifikanten Erhöhung des Schalldruckpegels der Anlagen. Die Hauptursache dafür liegt im gliederartigen sowie mehrgelenkigen Aufbau von Standard-Kunststoffgleitketten in Förderanlagen. Dieser Zustand konnte durch die Verwendung eines gliederlosen Zugmittels in Form eines Transportzahnriemens deutlich verbessert sowie die Transportgeschwindigkeiten signifikant erhöht werden. Durch Modifikationen an den Riemen-zähnen werden Befestigungsmöglichkeiten für Kunststofftragplatten geschaffen.

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The present work investigates the structure of supersonic turbulent deflagration typically observed as precursors to the onset of detonation. These high-speed flames are obtained after detonation interaction with cylindrical obstacles. Two mixtures having the same propensity for local hot spot generation were used, namely stoichiometric hydrogen-oxygen and methane-oxygen. It was shown that the methane mixture sustained turbulent fast flames, while the hydrogen mixture did not. Three visualization techniques, Schlieren, shadowgraph, and direct chemi-luminescence were implemented to record the evolution of the structure following the detonation interaction with the obstacle. Detailed high-speed visualizations of the nearly two-dimensional flow fields permitted the identification of the key mechanism involved. It was found that the shock reflections in methane permitted strong forward jets behind periodically formed Mach shocks on the front of the deflagration. These hot spots in the re-circulation zones of the jets provided local enhancement of the reactivity through mixing, supporting the formation of new generations of new hot spots. The hot spot formation was identified as the prominent difference between the different mixtures. These reactive pockets further sustained the shock reflection processes. As the methane-oxygen fast flame propagates along the channel, the wave front was observed to organize into fewer modes and eventually led to a reflection capable of the transition to detonation. In the hydrogen mixtures, at similar thermo-chemical parameters, self-sustained fast flames were not observed. Following detonation interaction in the hydrogen mixture, reactive reflections were observed. As the wave propagated downstream after a limited number of reactive reflections, the wave developed a planar wave front and decayed as the reaction zone trailed with an ever-increasing distance. It is postulated that the absence of the forward jets did not allow such fast flames to establish. This jetting slip line instability in methane shock reflections was recently found to be correlated with the low value of the isentropic exponent and its control of Mach shock jetting described by Mach & Radulescu. The lack of the forward jetting of the slip line in the hydrogen mixture with the higher value of the isentropic exponent is in agreement with the Mach & Radulescu.

La modification de la structure des matériaux par Détente Instantanée Contrôlée (DIC), implique nécessairement un processus d’autovaporisation instantanée en conditions thermodynamiques extrêmes de surchauffe du liquide. Les divers processus DIC de modification de la structure par expansion contrôlée, d’extraction et de refroidissement instantané sont d’un intérêt particulier. Les conditions opératoires et les caractéristiques spécifiques du produit interagissent mutuellement pour aboutir au meilleur résultat, principalement en termes de texture. Les modifications des caractéristiques structurelles généralement traduites par des taux d’expansion du produit, dépendent donc des conditions opératoires et des propriétés thermiques et rhéologiques de la matière. De nombreuses études initiales ont montré l’intérêt de déterminer l’évolution des divers processus à travers un suivi et un enregistrement instantané des images, des températures et de la pression à l’échelle de 1000 unités par seconde ; il a ainsi été indispensable de mettre en opération une caméra ultra rapide à 1000 images / s, des capteurs de température et de pression à temps de réponse de l’ordre du ms, placés dans le réacteur et au sein du produit. Une analyse fondamentale a prouvé l’importance de la thermodynamique, du transfert et de la problématique d’expansion pendant le traitement. L’analyse des expériences est réalisée par la détermination des taux d’expansion, surfacique et volumique, de la durée du processus d’expansion proprement dite, de l’analyse des caractéristiques micro-structurelles par MEB, mais principalement par la détermination de la température de transition vitreuse, de la différence de température minimale et d’ébullition, et du taux d’échange de chaleur. Plusieurs produits ont été étudiés (fromage, tofu, pomme, pomme de terre, carotte et banane). Des essais préliminaires adéquats ont permis d’identifier les domaines de variation des paramètres opératoires et d’adopter la méthode des plans d’expériences rota tables à cinq niveaux pour quantifier les diverses réponses nécessaires. / The structural modification of materials by the process of instant controlled pressure drop (DIC), is mainly based on the instant autovaporization process in very far from thermodynamic equilibrium conditions. The structure modification process and the volume evolution strictly depend on DIC operational parameters and the product characteristics mutually interacting to achieve the objective in terms of texture.The change in the structural characteristics of the product is generally revealed through the expansion rates of the product ; it depends on the operating conditions. This study will use a snapshot taken by a high speed video camera 1000 fps, coupled with 1 ms response temperature and pressure sensors, placed in the treatment vessel and inside the product. A fundamental analysis has proved the importance of thermodynamics, the transfer and the specific problematic of expansion during treatment. Study was carried out by determining the3D expansion ratio, the 2D surface expansion ratio, and the volumetric expansion ratio, as well as the durations of expansion just after pressure drops, the analysis of SEM micro-structural characteristics, the different glass transition temperatures Tg, the differences between lowest product and reactor temperatures and boiling temperature, and the heat exchange rate. Various products were considered (cheese, tofu, apple, potato, carrot and banana). The preliminary tests with each have led us to identify the relevant operating parameter ranges. Different fundamental conclusions and industrial application could be thus defined.

This master's thesis describes the current state of passenger rail transport and the most important long-distance projects in Europe in the 20th century. It also deals with current changes in the European rail market and its further development. The aim of this master's thesis is to analyze the state of long-distance rail passenger transport in the Czech Republic and abroad, a general view on the high speed rail, which is described in terms of its development, technology, benefits and costs and the analysis of the competitiveness of high speed rail compared to air transport from a user's perspective. This thesis also solves possible relations between high speed rail and other means of transport and whether high speed rail could be competitive in the Praha -- Brno line.

After the end of the NASA space shuttle programme, there has been resurgence of interest in developing a single stage-to-orbit spacecraft. The key technology to realize this dream is the airbreathing scramjet engine. The scramjet concept has been around for decades, but much work is still needed in order to eliminate the remaining obstacles to develop a practical working prototype of the engine. Many such obstacles are related to the inlet which functions as the main compression unit for the engine. Typically, a high speed inlet is designed to function properly in a single flight condition. Such an inlet would experience adverse flow conditions related to various shock-shock interactions, viscous effects, shock-boundary layer interactions, and many other flow phenomena at off-design conditions. The traditional mechanism to mitigate the adverse flow conditions is by varying the inlet geometry at off-design conditions. There are still gaps in understanding the behaviour of inlets at off-design conditions and the effectiveness of variable geometry as inlet flow control. This is partly due to complex flow diagnostics setup, which limits the type, quantity and quality of information that can be extracted from the inlet flow. The first objective of this thesis was to develop a global inlet measurement system that can provide an abundance of information on inlet flow. The pressure sensitive paint method was employed together with other methods to provide comprehensive understanding on inlet flow characteristics. Calculation of Mach number at the isolator exit using the isolator sidewall pressure map was successfully demonstrated. The measurement of Mach number at the isolator exit has allowed for performance of the inlet to be calculated without the need for intrusive flow diagnostics tools used by previous researchers. The global measurement system was then employed to investigate the characteristics of the scramjet inlet operating at various off-design conditions. Complex shock structures were observed at the inlet cowl entrance as the angle-of-attack was increased. The relationship of flow quality and inlet performance was examined and discussed. General improvements on the inlet performance were obtained if the size of separation on the compression ramp was reduced. The inlet was also observed to perform poorly when compression shocks impinged on the inner cowl surface. Cowl deflections were demonstrated to be effective in controlling the internal flow of the inlet and improving its performance. An exploratory study on the role of micro-vortex generators to control boundary layer separation on scramjet inlets has been included as well. Strategies for optimizing an inlet at off-design conditions were analysed, and it was found that any variable geometry combination must maintain high throat-to-freestream Mach number ratio in order to preserve high inlet performance.

This Master Thesis focuses on rail transport in Japan. It describes the evolution of Japanese railroads from the beginning until present day, when is Japan the leading country in personal rail transportation. Further, there are described major railway operators and high-speed railway network Shinkansen. Later it explains modern system Maglev, which is momentarily built in Japan. The analysis focuses on financial indicators and specific traits of Japanese railroads. In the end the author compares Shinkansen against other means of transport on two major routes of different length. He asks question how introduction of new forms of rail transportation can change the Japan.

While conventional turbines have been extensively researched and tested, Tesla and boundary layer type turbines have not. In order to construct a dynamometer, thermodynamic flow apparatus and future turbines, we modeled the Tesla turbine using theoretical calculations and preliminary experiments. Thus a series of experiments were run to determine stall torque and maximum run speed for a known pressure range. This data was then applied to modeling formulas to estimate stall torque over an extended range of variables. The data were then used to design an appropriate dynamometer and airflow experiment. The model data also served to estimate various specifications and power output of the future turbine. An Obi Laser SSTG‐001 Tesla turbine was used in the experiments described. Experimental stall torque measurements were conducted in two stages. Shaft speed measurements were taken with an optical laser tachometer and Tesla turbine stall torque was measured using a spring force gauge. Two methods were chosen to model Tesla turbine stall torque: 1) flow over flat plate and 2) free vortex with a sink. A functional dynamometer and thermodynamic apparatus were constructed once the model was confirmed to be within the experimental uncertainty. Results of the experiments show that the experimental turbine at 65 PSI has a speed of approximately 27,000 RPM and a measured stall torque of 0.1279 N‐m. 65 PSI is an important data point because that data set is the cut‐off from laminar to turbulent flow. Thus at 65 PSI, a rejection of the null hypothesis for research question one with respect to the flow over flat plate method can be seen from the data, while the vortex model results in a failure to reject the null hypothesis. In conclusion, the experimental turbine was seen to have a laminar and a turbulent flow regime at different air pressures, rather than the assumed laminar flow regime. As a result of this model work, a new Tesla turbine of different dimensions was designed to adjust for flaws in the experimental turbine. The theoretical stall torque models were then applied to the new Tesla turbine design. Results of the models show that the vortex model sets the upper bound for theoretical stall torque for the new and the flat plate flow model sets the lower bound.