A presente dissertação descreve o desenvolvimento e análise de um experimento concebido para avaliar a contribuição de materiais de fricção sobre vibrações induzidas na superfície de um disco de freio. O aparato proposto é equipado com um excitador modal (shaker), utilizado para promover e controlar o sinal de excitação que foi aplicado sobre os materiais de fricção avaliados. A resposta dessa excitação na superfície do disco de freio foi mensurada através de acelerômetros. Além da aplicação sobre o experimento proposto, foram avaliados o coeficiente de atrito e a distribuição de asperezas da superfície das oito amostras utilizadas. A característica modal do disco utilizado foi descrita através das suas frequências naturais, amortecimento e formas modais, parâmetros identificados através da aplicação de análise modal experimental. O experimento proposto foi utilizado para identificar as principais características de resposta do disco quando a excitação é realizada através do material de fricção. Essa condição também foi comparada com aquela em que a excitação foi aplicada diretamente no disco A métrica mais adequada para avaliação desse experimento foi identificada como o valor médio da magnitude da Função Resposta em Frequência (FRF), calculado através do estimador H3. O aparato proposto se mostrou capaz de identificar diferenças nas amostras avaliadas quanto à propensão dessas à produção de vibrações na superfície do disco. As amostras foram avaliadas no experimento proposto nas condições sem e com filme tribológico sobre a sua superfície, as quais correspondem ao estado das amostras antes e depois, respectivamente, do processo de caracterização do coeficiente de atrito destas, utilizando o tribômetro do LATRIB/UFRGS. Foi observado que as amostras com filme produziram maior vibração do que as amostras sem filme. Os resultados obtidos demonstraram uma forte correlação entre a propensão das amostras à produção de vibrações e a distribuição de asperezas da superfície das amostras. Esses resultados indicam que materiais de fricção com superfícies planas são capazes de transmitir mais vibração à superfície do disco do que aqueles com superfícies mais rugosas. / The present work describes the development and analysis of an experimental apparatus designed to evaluate the contribution of friction materials in vibrations induced on the surface of a brake disc. The proposed apparatus is equipped with a modal exciter (shaker), which was used to promote and control the excitation signal applied in the evaluated friction material. The response of this excitation in the disc surface was measured with accelerometers. The eight samples evaluated in this study was also characterized in terms of its friction coefficient and the asperity distribution of its surface. The modal characteristic of the disc was described in terms of its natural frequencies, damping and modal shapes, whose parameters were obtained by application of experimental modal analysis. The proposed apparatus was used to identify the main characteristics of the disc response when the excitation is applied throw the friction material. This case was also compared to the condition in which the disc was excited directly by the shaker. The most adequate metric to evaluate this experiment was selected as the mean value of the Frequency Response Function (FRF) spectrum, calculated by the H3 estimator The proposed apparatus showed being capable of identifying differences between the evaluated samples, regarding its propensity to produce vibrations on the disc surface. The samples were evaluated in with and without tribological film deposited on its surface. It was shown that the analyzed samples had the vibration increased with tribological film compared to the condition without the film. The obtained results demonstrated a strong correlation between the samples propensity to the production of vibration and the asperity distribution of the samples surfaces. These results indicate that friction materials with flat surfaces are capable to transmit more vibrations to the disc surface than those samples with rough asperity distribution.

Made available in DSpace on 2017-05-12T14:42:44Z (GMT). No. of bitstreams: 1 Cleverson_Holocheski.pdf: 3361676 bytes, checksum: 7e3dfcfe4af0abe5639e043c72615586 (MD5) Previous issue date: 2011-08-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Whereas erosion is a process that detracts from the soil, reducing its productivity or even making impossible the food production in it, it is worth emphasizing the importance of studies on this topic, especially with explanations and solutions to problems found in areas that are degraded by erosive processes. The installation and evolution of this process depends on a number of factors, all of them related to the pedological cover and the shapes of slopes, such as those linked to the hydrology of the hillside. With emphasis on this type of erosion phenomenon, this work takes as its main objective to recognize the factors correlated with onset and progression of tunnels, particularly those concerning the characteristics of soils and landforms in a hillside of Rio das Pombas, in the city of Guarapuava, South Center of the Paraná State. To this end, the research was developed from a comprehensive pedological system approach, identifying and individualizing the units of soil through surveys, and also monitoring the rainfall and hydrological flows in order to observe the dynamics of subsurface water in that slope. The methodology used in the study was divided into four phases with the first phase was consisted basically of bibliographic content to be worked, then the second part of the research was carried out on field work, and in this phase samples for laboratory analysis were collected; the piezometers for monitoring of subsurface flows were installed and it was also installed the weather station to the collections related to rainfall. In the third phase, the work was focused on laboratory and office, where were then carried out the sizing analysis and also the preparation of cartographic material combined with the tabulation of data for the construction of graphs. The fourth and final phase was the analysis of integrated data, from which, through the analysis the results were achieved. In the case studied, the results indicated that the main factors of installation and maintenance of erosion of those tunnels were that related to the physical properties of pedologic cover, such as the particle size, the shape of the slope and mainly the hydrological conditions. Regarding the evolution of the erosion on that slope, it can be said that the tunnels in the future may finally become a crater, damaging the use of the area. / Considerando que a erosão é um processo que deprecia o solo diminuindo a sua produtividade ou até mesmo impossibilitando a sua produção de alimentos, cabe ressaltar, a importância de estudos sobre essa temática, principalmente, com explicações e soluções para os problemas encontrados em áreas degradadas por processos erosivos. A instalação e evolução da erosão em túneis depende de uma série de fatores, tanto aqueles relativos à cobertura pedológica e as formas das vertentes, como aqueles vinculados à hidrologia da encosta. Com destaque para esse tipo de fenômeno erosivo, o presente trabalho, adota como objetivo principal reconhecer os fatores correlacionados a instalação e evolução de túneis, particularmente, aqueles relativos às características dos solos e das formas de relevo, em uma encosta do Rio das Pombas, Município de Guarapuava, Centro Sul do Estado do Paraná. Para tanto, a pesquisa desenvolveu-se a partir de uma abordagem detalhada do sistema pedológico, identificando e individualizando as unidades de solo através de sondagens e também, monitorando as precipitações e os fluxos hidrológicos, a fim de, observar à dinâmica subsuperficial da água na referida encosta. A metodologia utilizada na pesquisa dividiu-se em quatro fases, sendo que a primeira fase consistiu basicamente no levantamento bibliográfico do conteúdo a ser trabalhado, em seguida na segunda parte da pesquisa realizou-se os trabalhos de campo, sendo que nessa fase foram coletadas as amostras para análises em laboratório; instalados os piezômetros para o monitoramento dos fluxos subsuperficiais e também instalada a estação meteorológica, para as coletas referentes às precipitações. Na terceira fase os trabalhos concentraram-se em laboratório e em gabinete, onde então foram realizadas as análises granulométricas e também a confecção do material cartográfico juntamente com a tabulação dos dados para confecção dos gráficos. Na quarta e última fase ocorreu à análise integrada dos dados, de onde então através dessa análise chegou-se aos resultados da pesquisa. No caso estudado, os resultados apontam que os principais fatores de instalação e manutenção de erosão dos túneis foram àqueles referentes às propriedades físicas da cobertura pedológica, tais como, a composição granulométrica, a forma da encosta e principalmente as condições hidrológicas. No que diz respeito à evolução do processo erosivo na referida encosta, pode-se afirmar que os túneis futuramente poderão chegar a se tornar uma voçoroca, prejudicando utilização da área.

No description available.

Cell-semiconductor hybrid systems are a potential centerpiece in the scenery of biotechnological applications. The selection and study of promising crystalline semiconductor materials for bio-sensing applications is at the basis of the development of such hybrid systems. In this work we introduce crystalline SiC as an extremely appealing material for bio-applications. For the first time we report biocompatibility studies of different SiC polytypes whose results document the biocompatibility of this material and its capability of directly interfacing cells without the need of surface functionalization. Since the successful implementation of biosensors requires a good understanding and versatile control of the semiconductor surface properties, the chemistry, crystallography and electronic status of different SiC surfaces are extensively studied while their surface morphologies are thoroughly controlled via hydrogen etching. Also, investigations of the effect of cell surface charge on the electronic status of SiC surfaces are attempted adopting a contactless surface potential monitoring technique. The results obtained from these contactless measurements lead to the development of theoretical models well-suited for the description of cell-semiconductor hybrid systems electronic interactions.

Dopamine appears to play a critical role in regulating spatial working memory (SWM) in non-human primates, and SWM deficits are observed in patients with Parkinson�s disease and schizophrenia. Unfortunately, the current experimental literature in humans is marred by inconsistent behavioural findings, and there is a void in neuroimaging studies examining dopaminergic manipulation of SWM-related brain activity. The present thesis used a combination of behavioural neurocognitive testing and brain imaging to further examine dopaminergic manipulation of SWM in healthy humans, using two pharmacological challenges: 1) acute tyrosine depletion (TPD) (to acutely deplete tonic dopamine), and 2) D1/D2 receptor activation using the dopamine receptor agonist pergolide (to stimulate dopamine neurotransmission) under conditions of TPD. The effects of TPD on behavioural performance were examined using three SWM tasks: 1) a delayed-recognition task previously impaired by TPD (Experiment 1) and 2) two delayed-response tasks designed to vary only in response requirements (Experiment 2). The findings demonstrated an apparent failure of TPD to impair performance on any of the tasks. Further, the effects of TPD on SWM-related brain activity during a SWM n-back task were examined using regional Cerebral Blood Flow (rCBF) measured by H2 150 Positron Emission Tomography (Experiment 2), and Steady State Visually Evoked Potentials (SSVEP) measured by Steady State Probe Topography (Experiment 4). TPD failed to produce discernable effects on either neural networks (task-related rCBF) or temporal electrophysiological activity (SSVEP) associated with the SWM n-back task. In contrast, D1/D2 receptor stimulation under dopamine depleted conditions impaired performance on both a SWM delayed-response task (Experiment 1) and SWM n-back task (Experiment 2), and resulted in task-related increases in fronto-temporal SSVEP latency (suggestive of increased inhibition) and decreases in parieto-occipital SSVEP amplitude (suggestive of increased activation) during the early delay period of the SWM n-back task (Experiment 4). These changes are consistent with the undisputed role of frontal and parietal regions in n-back task performance, and with previous evidence of dopaminergic modulation of these regions in animals and humans. In summary, TPD did not modulate SWM behavioural performance on four different SWM tasks with differing task demands, and failed to produce measurable changes to either SWM-related neural networks (task-related rCBF) or cortical electrophysiological activity (SSVEP) associated with the SWM n-back task. The implication of these findings, when taken together with previous studies, is that the degree of dopaminergic depletion achieved with TPD may be insufficient to consistently and robustly modulate SWM networks in healthy humans, questioning the utility of TPD as a probe of dopaminergic function. In addition, these findings demonstrate the complexity of stimulating D1/D2 receptors under dopamine depleted conditions, and highlight the critical importance of baseline dopamine levels in influencing the effects of acute dopamine challenge on SWM performance.

This research is an investigation into the phrase 'landscape as infrastructure' and questions the influence of this notion in the design of new housing developments along the Maribyrnong River, Melbourne. The phrase lends itself to a systems based agenda because the word 'infrastructure' implies that it performs some kind of function. It is through this functioning that we can understand the way landscape acts as a stage for activities to occur, not just background to the object. The main question within the research is how landscape can precede housing development and set the parameters for its location, density, and relationship to the river. This is tested through four overriding themes which summarise the key ideas and methodologies for designing with landscape as infrastructure. The themes 'Catalyst', 'Time', 'Cause and Effect' and 'Experience' are tested on four different sites along the Maribyrnong River responding to different site conditions and the influence of geology and topography. The four sites have been named to reflect the primary function they perform within the overall strategy. To establish a framework for this discourse the research has been filtered through seven principals, originally developed by Stan Allen as a series of propositions for infrastructure. These principals question issues of force, process, typology, scale, invisible form, structure, function and change and visible form and set up a mechanism enabling me to challenge the notion of landscape as infrastructure. If the landscape is infrastructure then Allen's principals will also apply for the design of housing developments. This Appropriate Visual Record (AVR) is a selection of research material and design solutions developed over the last three years as part of the Research Masters Degree at RMIT.

This thesis deals with the differential response of healthy and cancerous cells to surface topography at the nanoscale and the microscale. Using a statistical method we developed we studied the interactions of cells with grooves of nanoscale depth. We demonstrate that healthy cells have a greater ability to align with deeper grooves, whereas cancerous cells are more sensitive to shallow grooves. Analysis reveals that the nucleus follows the alignment of the cell body more closely in cancerous cells, and that the nucleus of cancerous cells is more sensitive to shallow grooves.On microscale pillars we demonstrate for the first time that osteosarcoma cells deform to adopt the surface topography and that the deformation extends to the interior of the cell and in particular to the nucleus. We show that healthy cells only deform during the initial stages of adhesion and that immortalized cells show intermediate deformation between the healthy and cancerous cells. When the spacing between the pillars is reduced, differences in the deformation of different cancerous cell lines are detected. Deformation was also found to be related to the malignancy in keratinocytes, and related to the expression of Cdx2 in adenocarcinoma. The mechanism of deformation is tentatively attributed to the cytoskeleton and attempts to identify the main actors of deformation were performed using confocal microscopy and cytoskeleton inhibitors. Live cell imaging experiments reveal that the deformed cells are very mobile on the surfaces, loss of deformation is necessary for mitosis to occur and deformation after mitosis is more rapid than initial deformation upon adhesion to surfaces.

The East African Plateau provides a spectacular example of geodynamic plateau uplift, active continental rifting, and associated climatic forcing. It is an integral part of the East African Rift System and has an average elevation of approximately 1,000 m. Its location coincides with a negative Bouguer gravity anomaly with a semi-circular shape, closely related to a mantle plume, which influences the Cenozoic crustal development since its impingement in Eocene-Oligocene time. The uplift of the East African Plateau, preceding volcanism, and rifting formed an important orographic barrier and tectonically controlled environment, which is profoundly influenced by climate driven processes. Its location within the equatorial realm supports recently proposed hypotheses, that topographic changes in this region must be considered as the dominant forcing factor influencing atmospheric circulation patterns and rainfall distribution. The uplift of this region has therefore often been associated with fundamental climatic and environmental changes in East Africa and adjacent regions. While the far-reaching influence of the plateau uplift is widely accepted, the timing and the magnitude of the uplift are ambiguous and are still subject to ongoing discussion. This dilemma stems from the lack of datable, geomorphically meaningful reference horizons that could record surface uplift. In order to quantify the amount of plateau uplift and to find evidence for the existence of significant relief along the East African Plateau prior to rifting, I analyzed and modeled one of the longest terrestrial lava flows; the 300-km-long Yatta phonolite flow in Kenya. This lava flow is 13.5 Ma old and originated in the region that now corresponds to the eastern rift shoulders. The phonolitic flow utilized an old riverbed that once drained the eastern flank of the plateau. Due to differential erosion this lava flow now forms a positive relief above the parallel-flowing Athi River, which is mimicking the course of the paleo-river. My approach is a lava-flow modeling, based on an improved composition and temperature dependent method to parameterize the flow of an arbitrary lava in a rectangular-shaped channel. The essential growth pattern is described by a one-dimensional model, in which Newtonian rheological flow advance is governed by the development of viscosity and/or velocity in the internal parts of the lava-flow front. Comparing assessments of different magma compositions reveal that length-dominated, channelized lava flows are characterized by high effusion rates, rapid emplacement under approximately isothermal conditions, and laminar flow. By integrating the Yatta lava flow dimensions and the covered paleo-topography (slope angle) into the model, I was able to determine the pre-rift topography of the East African Plateau. The modeling results yield a pre-rift slope of at least 0.2°, suggesting that the lava flow must have originated at a minimum elevation of 1,400 m. Hence, high topography in the region of the present-day Kenya Rift must have existed by at least 13.5 Ma. This inferred mid-Miocene uplift coincides with the two-step expansion of grasslands, as well as important radiation and speciation events in tropical Africa. Accordingly, the combination of my results regarding the Yatta lava flow emplacement history, its location, and its morphologic character, validates it as a suitable “paleo-tiltmeter” and has thus to be considered as an important topographic and volcanic feature for the topographic evolution in East Africa. / Das Ostafrikanische Plateau ist ein eindrucksvolles Beispiel für aktive, kontinentale Grabenbildung, aber auch für geodynamische Hochebenenbildung mit weitreichendem klimatischen Einfluss auf die gesamte Region. Als integraler Bestandteil des Ostafrikanischen Grabensystems beläuft sich die mittlere Höhe des Plateaus auf durchschnittlich 1000 m ü.NN. Seine Lage korreliert gut mit der Präsenz einer halbkreisförmigen negativen Bouguer-Schwereanomalie, die an den Aufstieg eines Manteldiapirs im Untergrund gekoppelt ist. Dieser prägte die känozoische Krustenentwicklung seit seinem Aufstieg im Eozän-Oligozän. Die Hebungsgeschichte und topographische Entwicklung des Hochlandes steht seither in enger Beziehung zum einsetzenden Vulkanismus, der Bildung erster Abschiebungssysteme und führte schließlich zur Entwicklung des heutigen Vollgrabensystems. Neueste Hypothesen lassen den Schluss zu, dass topographische Veränderungen als dominierende Einflussgrößen atmosphärischer Zirkulationsmuster sowie der regionalen Niederschlagsverbreitung anzusehen sind. Zusätzlich werden diese Prozesse durch die äquatoriale Lage des Ostafrikanischen Plateaus verstärkt und die Hebung dieser Region oft mit wichtigen Klima- und Umweltveränderungen in Ostafrika und angrenzende Gebiete in Verbindung gebracht. Während der weitreichende klimatische Einfluss des Hochlandes größtenteils akzeptiert ist, sind Zeitpunkt und Ausmaß seiner Heraushebung nicht eindeutig bestimmt und daher noch immer Grundlage bestehender Diskussionen. Diese Zwangslage hat ihre Ursache im Fehlen aussagekräftiger und datierbarer Referenzhorizonte. Um den Hebungsbetrag zu quantifizieren und Beweise signifikanten Reliefs vor der Entwicklung des Grabensystems entlang des Ostafrikanischen Hochlandes zu erbringen, analysierte und modellierte ich einen der längsten terrestrischen Lavaströme. Dieser vor 13,5 Ma abgelagerte Yatta-Lavastrom hat mit 300 km Länge seinen Ursprung in der Region der heutigen östlichen Grabenschulter des zentralen Kenia-Rifts. Die phonolitische Lava ergoss sich entlang eines Flussbettes, das einst die östliche Flanke des Hochlandes entwässerte. Aufgrund unterschiedlicher Erosionspotentiale bildet der Lavastrom gegenwärtig ein positives Relief und befindet sich oberhalb des Athi Flusses, der parallel zum Paläofluß, und somit versetzt zu seinen früheren Verlauf, strömt. Mein Ansatz der Lavastrom-Modellierung basiert auf einer Methode, die das Fließverhalten einer beliebigen Lava in Abhängigkeit von Temperatur und Magmenzusammensetzung in einem rechtwinkligen Kanal berechnet. Die wesentlichen Wachstumsmuster des Lavastroms sind durch ein eindimensionales Modell beschrieben, wobei Newtonsches Fließverhalten im Innern hinter der Lavastromfront von der zeitlichen Entwicklung der Viskosität und/oder der Fließgeschwindigkeit bestimmt wird. Vergleiche meiner Resultate mit verschiedenen Magmenzusammensetzungen zeigen, dass sich lange, kanalisierte Lavaströme mit hohen Ergussraten und schneller Platznahme bilden können. Dies geschieht unter annähernd isothermalen Bedingungen und erfordert laminares Fließen. Die Integration der Yatta- Lavastrom-Dimensionen und der bedeckten Paläotopographie (Neigungswinkel) in das Modell, erlaubte es mir die Topographie des Ostafrikanischen Hochlandes vor der Grabenbildung zu modellieren. Das Ergebnis der Modellierung ergibt einen Neigungswinkel von mindestens 0,2° und impliziert, dass der Lavastrom seinen Ursprung in einer Höhe von mindestens 1400 m ü.NN gehabt haben muss. Somit existierte bereits vor 13,5 Ma hohe Topographie in der heutigen Region des zentralen Kenia-Rifts. Diese abgeleitete regionale Hebungsgeschichte im mittleren Miozän korreliert mit der zweistufigen Ausbreitung der Graslandschaften, sowie dem Aufkommen neuer Arten im tropischen Afrika. Die Kombination aus Fließverhalten, Entstehungsort und morphologischer Eigenschaften macht den Yatta-Lavastrom zu einem “Paläoneigungsmesser” und wichtigen vulkanischen Untersuchungsobjekt für die topographische Entwicklung in Ostafrika.

Small livestock is an important resource for rural human populations in dry climates. How strongly will climate change affect the capacity of the rangeland? We used hierarchical modelling to scale quantitatively the growth of shrubs and annual plants, the main food of sheep and goats, to the landscape extent in the eastern Mediterranean region. Without grazing, productivity increased in a sigmoid way with mean annual precipitation. Grazing reduced productivity more strongly the drier the landscape. At a point just under the stocking capacity of the vegetation, productivity declined precipitously with more intense grazing due to a lack of seed production of annuals. We repeated simulations with precipitation patterns projected by two contrasting IPCC scenarios. Compared to results based on historic patterns, productivity and stocking capacity did not differ in most cases. Thus, grazing intensity remains the stronger impact on landscape productivity in this dry region even in the future. / Kleinvieh ist eine wichtige Lebensgrundlage für die Landbevölkerung in trockenen Regionen. Wie stark wird sich der Klimawandel auf die Tragfähigkeit der Weideflächen auswirken? Wir benutzten hierarchische Modellierung, um das Wachstum von Sträuchern und einjährigen Kräutern, das wichtigste Futter für Ziegen und Schafe, quantitativ auf die Fläche von Landschaften in der östlichen Mittelmeerregion zu dimensionieren. Die Produktivität ohne Beweidung stieg sigmoidal mit dem mittleren Jahresniederschlag. Je trockener die Landschaft, desto stärker verminderte Beweidung die Produktion. An einem Punkt knapp unter der Tragfähigkeit der Vegetation, sank die Produktion stark mit zunehmender Beweidung, weil die Samenproduktion der Kräuter zu gering war. Wir wiederholten die Simulationen mit Niederschlagsverteilungsmustern gemäß zweier gegensätzlicher IPCC-Szenarien. Zukünftige Produktivität und Tragfähigkeit unterschieden sich in den meisten Fällen nicht von Ergebnissen auf Grund von historischer Niederschlagsverteilung. Allerdings war die zukünftige Produktivität in trockenen Habitaten der semiariden und trocken-mediterranen Regionen niedriger. Somit hat auch in Zukunft die Besatzdichte die größere Auswirkung auf die Produktivität dieser trockenen Landschaft als das Klima. "This abstract is provided by the authors, and is for convenience of the users only. The author certifies that the translation faithfully represents the official version in the language of the journal, which is the published Abstract of record and is the only Abstract to be used for reference and citation."

The correct tribological design will have a considerable effect on a gear’s service life and efficiency. The purpose of this thesis is to clarify the impact of variation in the gear tooth flank tribological system on the gear contact load capacity – to increase the understanding of how surface topography and lubricant interact. In this thesis the variation in surface topography inherent in the manufacturing method has been shown, by experimental work and computer simulations, to be an important factor for the contact condition in the early life of gears. Surface analysis revealed that the formation and composition of surface boundary layers depends strongly on the chemical composition of the lubricant, but also on pre-existing surface boundary layers. Additionally, surface boundary layers play a major role in frictional behaviour, wear and in allowing the lubricant to react properly with the surfaces. Paper A presents the current ISO 6336 calculation of surface durability. A robust design approach was used to investigate the extent to which the current standard for calculation of surface durability allows for manufacturing variations and the choice of lubricant. Paper B investigates the extent to which a logarithmical profile modification can increase gear contact pressure robustness compared to traditional lead profiles for gears. Paper C compares different gear manufacturing methods and their as-manufactured (fresh unworn) surface topographies, using measured surface topographies as input to a contact simulation program. Paper D examines surface boundary layer formation and the corresponding wear in relation to different anti-wear additives in an environmentally adapted base oil. Papers E and F make use of specimens with surface topographies imitating two gear manufacturing methods (grinding and superfinishing) to be used in a twin-disc and barrel-on-disc machine respectively. The contacts are analysed by friction measurements and simulations combined with methods for surface analysis. / <p>QC 20120925</p>