The fundamental theories of heat generation and transfer at the friction interface of a brake assume either matching or not matching surface temperatures by having a varying or uniform heat partition ratio respectively. In the research presented the behaviour of heat partition has been investigated in a fundamental study based on experimental measurements of temperature and the associated modelling and simulation of heat transfer in a brake friction pair. For a disc brake, an important parameter that was identified from the literature study is the interface tribo-layer (ITL), which has been modelled as an equivalent thermal resistance value based on its thickness and thermal conductivity. The interface real contact area was also an important parameter in this investigation, and it has been found to affect heat partitioning by adding its own thermal resistance. A 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model is presented, based on which a novel relationship which characterises the total thermal resistance (or conductance) at the friction interface has been characterised based on the ITL thermal properties, the contact area, and the contact pressure at the interface. Using the model the effect of friction material wear on the total thermal resistance (or conductance) at the friction interface was predicted and a comparison of the Archard and Arrhenius wear laws in predicting the wear of a resin bonded composite friction material operating against a cast iron mating surface is presented. A 3-dimensional (3D) model is also presented. This model has represented a small scale disc brake test rig which has been used in parallel with the simulation for validation in a drag braking scenario. Two simulation conditions with different pad surface states were investigated, the first having a nominally flat surface, and the second an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wear model was applied to significance of including wear on the total thermal resistance at the friction interface over a short brake application. A sensitivity analysis on the interface thermal conductance, the location of heat generation, and the magnitude of contact pressure has identified the importance of each factor in determining the total thermal resistance (or conductance) at the friction interface during any friction brake application. It is concluded that the heat partitioning is insensitive on the location of heat generation, and that the most sensitive parameter is the contact pressure.

The Pluto-Charon system has come into sharper focus following the flyby of New Horizons. We use N-body simulations to probe the unique dynamical history of this binary dwarf planet system. We follow the evolution of the debris disc that might have formed during the Charon-forming giant impact. First, we note that in situ formation of the four circumbinary moons is extremely difficult if Charon undergoes eccentric tidal evolution. We track collisions of disc debris with Charon, estimating that hundreds to hundreds of thousands of visible craters might arise from 0.3-5 km radius bodies. New Horizons data suggesting a dearth of these small craters may place constraints on the disc properties. While tidal heating will erase some of the cratering history, both tidal and radiogenic heating may also make it possible to differentiate disc debris craters from Kuiper belt object craters. We also track the debris ejected from the Pluto-Charon system into the Solar system; while most of this debris is ultimately lost from the Solar system, a few tens of 10-30 km radius bodies could survive as a Pluto-Charon collisional family. Most are plutinos in the 3: 2 resonance with Neptune, while a small number populate nearby resonances. We show that migration of the giant planets early in the Solar system's history would not destroy this collisional family. Finally, we suggest that identification of such a family would likely need to be based on composition as they show minimal clustering in relevant orbital parameters.

The automotive industry is constantly being challenged by customers and authorities to enhance the efficiency of the internal combustion engine (ICE) in order to achieve improved fuel consumption and reduced emissions. There are several interfaces within the design of an ICE that causes frictional losses, one of them is the valvetrain. An approach to reducing the friction in the valvetrain of modern engines is to implement cam-follower rollers, resulting in a rolling rather than sliding contact when interacting with the camshaft. The prominent type of wear in rolling contacts is surface fatigue, and specifically a phenomenon called micropitting. The company in collaboration with this project is Applied Nano Surfaces Sweden AB (ANS), located in Uppsala, Sweden. The company have specialized in surface treatment methods of mechanical components. ANS has developed a mechano-chemical treatment method called ANS Triboconditioning, which have shown beneficial friction and wear reducing properties when applied to metal surfaces. This thesis was conducted to investigate how the ANS Triboconditioning would affect the frictional behaviour compared to established surface treatment methods and the occurrence of micropitting in rolling contact configurations. Two types of test programs was implemented into a Wazau UTM 2000 Twin-Disc Tribometer. No clear trend could be established from the micropitting tests and therefore no conclusion regarding if ANS Triboconditioning affects the occurrence of micropitting damage in a positive or negative manner could be stated. The results from the friction test indicated an overall reduction in friction for the test specimens that had been treated with ANS Triboconditioning when compared to specimens that only had been treated with already established surface treatment methods. Summarized, additional tests and analyses are necessary in order to statistically confirm the observed results and determine their respective trends.

A dor lombar acomete a humanidade desde tempos remotos, tendo seus primeiros relatos descritos no \"Papiro de Edwin Smith\" (1500 a.C.). Acredita-se que durante a vida até 90% da população terá pelo menos um episódio de dor lombar, sendo tal patologia uma das principais causas de afastamento do trabalho, acarretando em vultosos prejuízos financeiros anuais. Cinco a 10% dos pacientes que possuem lombalgia também apresentam dor irradiada para o membro inferior (ciatalgia) e esta última, 85% das vezes é secundária à hérnia de disco lombar (HDL), cuja prevalência anual na população geral é estimada em 2.2%. O objetivo deste estudo foi avaliar a eficácia da aplicação do laser diodo de 980 nm intradiscal no tratamento da ciatalgia em pacientes portadores de hérnias lombares contidas em comparação com o grupo controle. Vinte e cinco pacientes (30 discos intervertebrais) com HDL e dor neuropática de distribuição metamérica foram randomizados, 12 no grupo controle e treze no grupo laser. No grupo controle foi feita injeção de dexametasona, clonidina e lidocaína intradiscais e no grupo laser aplicada média de 900 J de energia intradiscal, além das mesmas medicações. Os grupos foram avaliados nos tempos antes, imediatamente após, um mês, dois, três, seis e 12 meses decorridos do procedimento quanto aos parâmetros: dor, pela Escala Numérico Visual (ENV), uso de medicações para o controle desse sintoma e efeitos colaterais. Os resultados demonstraram queda nas médias das ENVs e necessidade de medicações para controle da dor em ambos os grupos logo após o tratamento (p<0,05), que perdurou no grupo laser onde houve média de redução de 80,73% nas ENVs, e de 75,51% na necessidade de medicação em um ano de seguimento (p<0,05). Já no grupo controle, as ENVs e as necessidades de analgésicos voltaram a ser semelhantes aos valores anteriores ao tratamento a partir do segundo mês de avaliação (p>0,05). Foi verificada predominância da doença no sexo masculino (68%), com faixa etária média de 44 anos, e baixa incidência de efeitos colaterais semelhantemente a dados anteriormente relatados. O laser diodo de 980 nm é eficaz na redução da ciatalgia secundária à herniação discal contida e superior à injeção intradiscal de clonidina, dexametasona e lidocaína, no que se refere à duração da redução das ENVs e da necessidade de medicações analgésicas. / Lumbar pain affects mankind from earliest times having its first descriptions in the \"Edwin Smith Papyrus\" (1500 BC). It is believed that during life up to 90% of the population will have at least one episode of low back pain, being such pathology one of the main causes of work withdrawal with huge annual financial losses. Five to 10% of patients with low back pain also have lower-limb pain (sciatica), and the latter, 85% of the time, is secondary to lumbar disc herniation (LDH), whose annual prevalence in the general population is estimated at 2.2%. The objective of this study was to evaluate the efficacy of intradiscal diode laser 980 nm wavelength in comparison with a control group on sciatica treatment in patients with contained lumbar disc herniations. A total of 25 patients (30 intervertebral discs) with LDH and neuropathic pain of metameric distribution were randomized, 12 patients in the control group and 13 patients in the laser group. In the control group, intradiscal injection of dexamethasone, clonidine and lidocaine was performed and in the laser group an average of 900 J of intradiscal energy was delivered, in addition to the same medications. The groups were evaluated at the time before, immediately after, 1, 2, 3, 6, and 12 months after the procedure for the parameters: pain measured by Visual Numerical Scale (VNS), medication use to control this symptom and side effects. The results showed a decrease in VNS and the need for pain control medications in both groups after treatment (p<0.05) that lasted in the laser group which demonstrated an average in VNSs reduction of 80,73% and in pain analgesic needs of 75,51% after 1 year (p<0,05). In the control group, VNSs and analgesic needs were again similar to pre-treatment values from the second month of evaluation (p>0.05). The predominance of the disease was found in males (68%), with a mean age of 44 years and a low incidence of side effects similar to the data reported before. The 980 nm diode laser is effective in reducing sciatica due to contained LDH and superior to intradiscal injection of clonidine, dexamethasone and lidocaine for the duration of the reduction of VNS and need for analgesic medications.

L’objectif de cette thèse est de proposer de nouvelles solutions matériaux moins sensibles à la fissuration par fatigue thermique induite en frottement, première cause de remplacement des disques de frein de véhicule « poids lourd ». Les performances en freinage doivent être équivalentes à celles obtenues avec le couple de matériaux actuels : disque de frein en fonte à graphite lamellaire- garniture en matériau de friction composite à matrice semi-métallique. L’étude repose sur une approche multidisciplinaire des phénomènes et des couplages induits en freinage. Elle comporte quatre parties : la première partie expose les principaux enjeux industriels et scientifiques du freinage des véhicules « poids lourds » ; la seconde développe une approche modèle-expérience originale pour caractériser les sollicitations de freinage conduisant à la dégradation de disques de frein échelle 1 en fonte à graphite lamellaire ; enfin les nouvelles solutions matériaux considérées sont évaluées suivant une étude tribologique (troisième partie) et en cyclage thermique (quatrième partie), développée en laboratoire / This PhD thesis was carried out with the aim of developing new materials for truck brake discs, so as to increase disc lifespans. Premature failure is the major problem encountered in the operation. Braking performances of new materials should be equivalent to those obtained with the current material couple: lamellar grey cast iron brake disc and commercial semi-metallic brake lining material. To do this, the study is divided in four parts: Firstly, major industrial and scientific aspects in braking are identified in literature and with investigations on truck brake discs used on road. Next, a coupled numerical-experimental approach enable us to characterize thermomechanical loadings induced by braking and leading to damage mechanisms of the lamellar grey cast iron disc. Finally, two aspects of new materials solutions are investigated in laboratory: tribological behaviour and thermal cycling behaviour

Cette thèse vise à développer une démarche de dimensionnement à la fatigue thermomécanique de disques de freins automobiles en fonte à graphite lamellaire. La première étape est la proposition d'une loi de comportement cyclique permettant de représenter les phénomènes non-linéaires ainsi que la forte dissymétrie de comportement entre traction et compression observés sur la fonte GL. Le modèle s'appuie sur l'introduction d'un tenseur d'endommagement d'ordre 2 induit par le chargement. A partir de l'analyse des mécanismes d'endommagement, on propose ensuite un critère de fatigue fondé sur la densité d'énergie dissipée par cycle, permettant de prédire l'amorçage de fissures dans les zones critiques. On s'intéresse enfin à l'étude de la formation d'un réseau de faïençage observé sur les pistes des disques de frein. / This thesis aims at developing an approach for thermomechanical fatigue design of automotive brake discs made of flake graphite (grey) cast-iron. The first step of this work consists of modeling the nonlinear cyclic behavior and tension/compression strong dissymmetry of grey cast iron. The proposed model is based on the introduction of a second-order induced damage tensor. From the analysis of the damage mechanisms, a fatigue criterion based on the dissipated energy per cycle, allowing crack initiation in the critical areas to be defined, is proposed. Finally, the formation of crack networks on braking discs is studied.

Foram avaliados 58 cães portadores de discopatia nos segmentos torácico, toracolombar, lombar ou lombosacro da coluna vertebral pelos exames radiográficos simples, contrastado (mielografia) e pela tomografia computadorizada (TC). Os animais com padrão de raça definido foram os mais acometidos (88%), sendo a raça Dachshund com maior representatividade (48%). A faixa etária mais acometida foi entre 4-7 anos de idade (48%). O exame radiográfico simples detectou aspectos radiográficos compatíveis com extrusão em 29 observações. A mielografia diagnosticou 98 protrusões, 43 extrusões e 10 hérnias de disco, além de fornecer informações relativas ao grau de comprometimento medular. A TC diagnosticou 84 observações de protrusões, 48 extrusões e 2 hérnias de disco. Os espaços mais comprometidos pela extrusão diagnosticados pelos métodos empregados foram T12-13, T13-L1 e T11-12. A TC esclareceu as dúvidas sugeridas pela mielografia, embora também apresentou limitações quando a compressão medular não apresentou a presença de material hiperatenuante. Nos casos com interrupção da coluna de contraste a TC foi capaz de detectar a extrusão devido à presença de material hiperatenuante em canal medular. Os métodos de diagnóstico por imagem empregados foram complementares e forneceram informações importantes para o prognóstico desses animais. / Disc disease in thoracic, thoracolumbar, lumbar or lumbosacral spine hás been evaluated in 58 dogs by survey radiography, mielography and computed tomography. The disc disease infrequently occurs in mixed-breed dogs; Dachshunds werw at higher risk for disc disease than other breeds (48%. Most dogs are between 4-7 years of age (48%). The survey radiography showed 29 observations of extrusions. The mielography showed 98 protrusions, 43 extrusions and 10 disc herniated. The CT showed 84 protrusions, 48 extrusions and 2 disc herniated. The affected disc spaces by extrusion seen in this study were T12-13, T13-L1 and T11-12. The mielography releasedsomo doubts, that have been resolved by CT; howeverthe CT showed doubts when there wasn´t soft-tissue mineralization in vertebral canal. When thre was a complete blockage of contraste because of contrast material the CT diagnoses the disc lesion because the presence of soft tissue mineralization vertebral canal. The methods of imaging diagnosis used complete each other and provided important information used to assess prognosis of the affected animals.

Lors de cette thèse, je me suis servis du modèle de la Galaxie de Besançon (BGM), modèle développé dans ce laboratoire depuis plusieurs années.Ce modèle, fortement utilisé par la communauté internationale (papier de référence Robin, Reylé et al, 2003, cité plus de 1250 fois), a été choisi comme modèle de référence dans la préparation de la mission spatiale de l’ESA Gaia.Ce modèle est un outil puissant pour étudier notre Galaxie car il permet de simuler statistiquement son contenu en étoiles. Ce contenu dépendant d'hypothèses émies sur la forme et l'histoire de la Voie Lactée.Ici, je me concentre sur une population de la Voie Lactée particulière, le disque épais (un ensemble d'étoiles vieilles qui représente environ 30% des étoiles de notre Voie Lactée).A l'aide du BGM, il est possible d’essayer de mieux comprendre sa forme et son histoire. La méthode utilisée pendant cette thèse est la comparaison d'observations avec les simulations du BGM et d'un ajustement des propriétés du disque épais à l'aide d’une méthode basée sur le principe des chaînes de Markov - Monte Carlo (MCMC). / During my Phd thesis, I have used the Besançon Galaxy's Model (BGM) developed in my laboratory for many years.This model is widely use by astrophysicist around the world (the reference article is Robin, Reylé et al, 2003 and is cited more than 1250 times) and have been chose to be the reference model to prepare ESA's space mission Gaia.The BGM allow us to study our Galaxy by simulating statistically her stellar content. This stellar content is depending of hypothesis for the shape and history of the Milky Way.Here, I focus on the Milky Way's thick disc (old stars representing about 30 % of the total stellar content of the Milky Way).Thanks to the BGM, we can try to understand the shape and history of the thick disc. During this thesis, I've compared observation and simulations made by the BGM and adjusted the thick disc properties by using a Markov chain of Monte Carlo (MCMC).

O processamento é uma das principais características da radiografia digital. Diante da frequência da discopatia em cães, a importância do exame radiográfico na investigação inicial desta doença e na orientação de outros exames de imagem (tomografia computadorizada, mielotomografia e imagem por ressonância magnética), buscou-se avaliar a efetiva contribuição das ferramentas de processamento da imagem no diagnóstico das hérnias de disco. Para tanto, foram avaliados 80 forames intervertebrais através da radiologia computadorizada pelos filtros padrão, invertido e realce de borda e a combinação entre esses (padrão e invertido, padrão e realce de borda e realce de borda e invertido) para pesquisa da opacificação do forame intervertebral associada às hérnias de disco em cães. A análise radiográfica foi realizada por dois avaliadores às cegas com tempo de experiência superior a 10 anos em radiodiagnóstico. Foram calculadas as medidas de sensibilidade, especificidade, valores preditivos positivos e negativos, acurácia e razão de verossimilhanças para os respectivos filtros e a combinação destes pelos dois avaliadores. A tomografia computadorizada foi tomada como padrão ouro da detecção de opacificação do forame intervertebral. O coeficiente de kappa e seu respectivo intervalo de 95% de confiança foram utilizados para analisar a concordância dos resultados. Os valores de sensibilidade obtidos pelos avaliadores foram de 58,7% na detecção das opacificações pelo filtro padrão, 52,2% pelo filtro invertido e 50% de sensibilidade no estudo realizado pelo filtro realce de borda. Na combinação entre os filtros padrão e invertido e realce de borda e invertido os valores foram os mesmos com 43,5%, sendo que a sensibilidade do filtro padrão associado com o filtro realce de borda foi de 50%. A acurácia alcançada na detecção das opacificações do forame intervertebral pelos filtros individualmente foi de 78,8% para o filtro padrão, 75% para o filtro invertido e 75,6% para o filtro realce de borda, não apresentando diferenças significativas quando a combinação entre os filtros foi realizada, obtendo-se 76,9% nas associações entre os filtros padrão e invertido e padrão e realce de borda e 75,6% através dos filtros realce de borda e invertido. O processamento da imagem digital pode aumentar a acurácia na detecção das opacificações do forame, no entanto os filtros podem somente realçar uma alteração existente e não aumentar a capacidade de detecção da lesão pelo exame radiográfico simples sendo necessária para tal, a associação de exames de imagem mais sensíveis (mielografia/tomografia computadorizada/ imagem por ressonância magnética). A preferência pessoal na utilização dos filtros também foi comprovada. / Processing is a major feature of digital radiography. Given the frequency of disc disease in dogs, the importance of radiographic examination in the initial investigation of this disease and the guidance of other imaging studies (computed tomography, myelography and magnetic resonance imaging), it was evaluate the effective contribution of the processing tools image in the diagnosis of herniated discs. For this, eigthy intervertebral foramina through were evaluated computed radiography by standart filters, reverse and edge enhancement and the combination of these (standard and inverted pattern, standard and edge enhancement and edge enhancement and inverted) in the investigation of opacification of the intervertebral foramen associated with hernia disc in dogs. Radiographic analysis was performed by two raters blind to time of more than 10 years experience in diagnostic radiology. It was calculated measures of sensitivity, specificity, positive and negative predictive values, accuracy and likelihood ratio for the respective filters and the combination of the two evaluators. Therefore, the CT scan was taken as the gold standard of detection opacification of the intervertebral foramen. The kappa coefficient and its corresponding interval of 95% confidence intervals were used to analyze the correlation of the results. The sensitivity values obtained by the evaluators were 58.7% in detecting the opacities of the standard filter, the filter inverted 52.2% and 50% sensitivity in the study by edge enhancement filter. In combination between standard and inverted filters and edge enhancement and inverted values were the same with 43.5%, and the sensitivity of the filter pattern associated with the filter edge enhancement was 50%. The accuracy achieved in the detection of opacities of the intervertebral foramen by the filters individually was 78.8% for the standard filter, 75% to inverted filter and 75.6% for edge enhancement filter, showing no significant differences when the combination between the filters was performed. yielding 76.9% associations between the filters standard and inverted pattern, and pattern and edge enhancement and 75.6% through the filter edge enhancement and inverted. The digital image processing can increase the accuracy in the detection of opacities foramen, however filters can only highlight a change and not increase the existing capacity of lesion detection by simple radiographic examination is necessary association of more sensitive imaging ( myelography / CT / MRI). Personal preference through the use of filters was also confirmed.

Introdução: A dor lombar crônica pode ser definida como dor ou desconforto persistente por mais de 12 semanas nos níveis lombar e sacral da coluna vertebral. Cerca de 5% dos pacientes apresentam comprometimento de raiz nervosa, e uma razão comum é a herniação discal. Os músculos multífido lombar (ML) e transverso do abdome (TrA) são preferencialmente acometidos frente a episódios de dor lombar. Contudo, há escassa literatura que tenha avaliado a fadiga do ML e a capacidade de ativação do TrA em indivíduos com e sem hérnia de disco lombar. Objetivo: Avaliar a fadiga do músculo multífido lombar e a capacidade de ativação do transverso do abdome em indivíduos com hérnia de disco e dor lombar crônica, e controle. Métodos: Participaram do estudo 60 indivíduos com idade entre 20 a 50 anos, divididos em dois grupos: Hérnia Lombar (GHL) com dor há mais de três meses (n=30) e Grupo Controle (GC) sem dor (n=30). A fadiga do multífido lombar foi avaliada com a eletromiografia de superfície durante a realização do teste de esforço de Sorensen e a capacidade de ativação do TrA pela Unidade de Biofeedback Pressórico (UBP). A dor foi avaliada com a escala visual analógica - EVA e questionário McGill de Dor, a incapacidade funcional pelo Índice de incapacidade de Oswestry e o relato de esforço percebido pela escala de Borg. O nível de significância adotado foi de 5%. Na análise dos dados de frequência mediana quanto menor o valor maior a fadiga. Resultados: Houve aumento da fadiga nos dois grupos, porém mais intensa no GHL (p=0,0001) proporcionando a instalação da fadiga em menor tempo (163 s). Na capacidade de ativação do TrA, o GHL apresentou ativação insuficiente (-0,9 mmHg) e GC próximo a valores ideais ( -3,9 mmHg). Na escala de Borg, houve diferença entre os grupos para o esforço inicial (p=0,0002), contudo não foi observado diferença para o esforço final (p=0,0611). O GHL apresentou dor moderada (6,4 cm) quando avaliada pela EVA e pelo Questionário McGill de dor nas categorias sensorial (19,2) afetiva (8,6) e total (36,3) e incapacidade funcional mínima. Conclusão: Os indivíduos com hérnia de disco e dor lombar crônica apresentam maior fadiga do músculo multífido lombar e ativação do transverso do abdome insuficiente quando comparados aos controles. / Introduction: Chronic low back pain can be defined as pain or discomfort lasting more than 12 weeks in the lumbar and sacral levels of the spine. About 5% of patients have nerve root impairment, and the more common etiology is the disc herniation. The lumbar multifidus (LM) and transversus abdominis (TrA) muscles are often affected in low back pain. However, the literature on the fatigue assessment of ML and the ability of TRA activation in individuals with and without lumbar disc herniation is scarce. Objective: To evaluate the lumbar multifidus muscle fatigue and transversus abdominis activation in individuals with disc herniation and chronic low back pain, and control. Methods: The study included 60 subjects aged 20 to 50 years, divided into two groups: lumbar herniated group (GLH) with pain for more than three months (n = 30) and control group (CG) without pain (n = 30). The fatigue of the lumbar multifidus was measured with surface electromyography during the Sorensen test and ability of activation of TRA with Unit Biofeedback pressure (PBU). Pain was assessed by visual analog scale - VAS and McGill pain questionnaire, functional disability by Oswestry Disability Index, and the reporting of perceived exertion with Borg scale. The significance level was established in 5%. Results: We found increased fatigue in both groups however more intense in GLH (p=0.0001) providing the onset of fatigue in less time (163 s). The ability to activate the TrA, the GLH showed insufficient activation (-0.9 mmHg) and CG near the ideal values (-3.9 mmHg). In Borg scale, difference was observed between groups for the initial effort (p = 0.0002), however no difference was observed for the final effort (p = 0.061). The GLH had moderate pain (6.4 cm) when assessed by the VAS and the McGill Pain Questionnaire in sensory (19.2), affective (8.6) and total (36.3) categories and minimal functional disability. Conclusion: Individuals with disc herniation and chronic low back pain have higher fatigue of lumbar multifidus and insufficient transversus abdominis muscle activation when compared to controls.