Tyres are used in everyday life for a variety of practical and recreational tasks. Frictional behaviour of tyres on any surface is important for vehicle safety and control; this behaviour becomes more important when that surface is snow. The interaction of rubber and a snow surface is complex and a deeper understanding of both is needed in order to help develop better tyres. Outdoor full scale tyre test results were compared to results from indoor laboratory tests using a linear tribometer and a surface of compacted artificial snow; these were in excellent correlation allowing a systematic and comprehensive study of rubber friction on snow to be conducted in the laboratory. Rubber samples of varied rubber compositions and geometries were used to gain an understanding of friction on snow. Samples with varying glass transition temperature (Tg), dynamic rigidity (G*) and Payne effect (dependence of the dynamic moduli on the amplitude of the applied strain) were investigated along with samples with and without sipes. The rubber friction coefficient (μ) was measured as a function of velocity and temperature. The siped samples exhibited a higher μ than those without sipes. FE simulations, rubber friction tests for varying contact pressures and steel blade force tests were performed to evaluate contributions from ‘surface’ friction and ploughing separately. The increased μ was attributed to the ploughing force from the front edges of the ‘subblocks’ created by the sipes. Although it is well known in the industry that siped tyres grip well, this is the first time it has been explained how sipes grip effectively through a combination of ploughing and rubber snow interaction. A comprehensive study of varying rubber properties (Tg, G* and Payne effect) was conducted to better understand their impact on snow friction. The findings were evaluated using the WLF shift factor to account for the running frequency of the rubber from the snow surface roughness. G* was found to be the dominant parameter for rubber μ when considering running frequency. Increased μ values were exhibited by rubbers with a lower G*. The decreased G* makes the rubber more compliant, thus increasing the contact area between the rubber and the snow, in turn increasing μ. A better knowledge of the surface roughness of snow will aid the understanding of the interaction between rubber and snow for tyres. A method was developed to characterise the artificial snow surface utilising sectioning and imaging of chemically stabilised snow samples. From images of the snow surface before friction testing the average indentor size can be found, this is used to analyse the running frequency of the rubber. Qualitatively comparing the surfaces before and after rubber friction testing shows a decrease in surface profile aggressivity after a test; this is attributed to melting of the snow from frictional heating and snow grain fracture. Friction tests were conducted to directly compare rubber friction on snow and ice using round edged samples. Again it was found that the rubber with the decreased G* exhibited higher friction; this was seen on both snow and ice confirming G* as the dominant rubber property for both surfaces, regardless of the surface roughness change. It was found that at low temperatures ice had a higher μ than snow, while at high temperatures snow exhibited a higher μ than ice. It is hypothesised that this intriguing switch is due to the surface roughness change leading to differing contact areas both with and without melt water. This switch is not seen when a simple heat transfer model is used, confirming the effect as a surface roughness change. The use of a modified Hertz model shows that indentation is the dominant mechanism at low velocities on snow. It is hypothesised that at high velocities melt water dominates on both snow and ice while adhesion may have a more significant role on ice at low velocities. These findings provide knowledge that can be used in the design of tyres for snow and ice in the future.

by Dong, Mei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 83-90). / Abstracts in English and Chinese. / INTRODUCTION --- p.1 / Chapter 1.1 --- Bump Height Inspection --- p.1 / Chapter 1.2 --- Our Height Inspection System --- p.2 / Chapter 1.3 --- Thesis Outline --- p.3 / BACKGROUND --- p.5 / Chapter 2.1 --- Wafer Bumps --- p.5 / Chapter 2.2 --- Common Defects of Wafer Bumps --- p.7 / Chapter 2.3 --- Traditional Methods for Bump Inspection --- p.11 / BIPLANAR DISPARITY METHOD --- p.22 / Chapter 3.1 --- Problem Nature --- p.22 / Chapter 3.2 --- System Overview --- p.25 / Chapter 3.3 --- Biplanar Disparity Matrix D --- p.30 / Chapter 3.4 --- Planar Homography --- p.36 / Chapter 3.4.1 --- Planar Homography --- p.36 / Chapter 3.4.2 --- Homography Estimation --- p.39 / Chapter 3.5 --- Harris Corner Detector --- p.45 / Chapter 3.6 --- Experiments --- p.47 / Chapter 3.6.1 --- Synthetic Experiments --- p.47 / Chapter 3.6.2 --- Real image experiment --- p.52 / Chapter 3.7 --- Conclusion and problems --- p.61 / PARAPLANAR DISPARITY METHOD --- p.62 / Chapter 4.1 --- The Parallel Constraint --- p.63 / Chapter 4.2 --- Homography estimation --- p.66 / Chapter 4.3. --- Experiment: --- p.69 / Chapter 4.3.1 --- Synthetic Experiment: --- p.69 / Chapter 4.3.2 --- Real Image Experiment: --- p.74 / CONCLUSION AND FUTURE WORK --- p.80 / Chapter 5.1 --- Summary of the contributions --- p.80 / Chapter 5.2 --- Future Work --- p.81 / Publication related to this work: --- p.83 / BIBLIOGRAPHY --- p.83

The growth and morphology of fibroblasts cultured on a physically and chemically modified surface was investigated. The need to understand cellular relationships with surface topography and chemistry is essential in the fields of biomedical engineering and biotechnology. It is well documented that mammalian cell behavior senses and responds to the surrounding micro- and nano- scale environment, but the research defining the chemistry, surface architecture, and material properties for control of this behavior is still in its infancy. The cell response to a substrate is complex, involving membrane proteins, extracellular matrix (ECM), cytoskeletal rearrangement, and changes in gene expression. Conventional cell culture is carried out on two-dimensional (2-D) cell culture platforms, such as polystyrene (PS) or glass, and forces cell behavior to adapt and adhere to an unnatural, planar environment. The biological behavior of these cells is used as a starting point for drug screening, implant design, and metabolic processes, but this is a misrepresentation of cells in their native environment. This discrepancy may be hampering biological research or initiating experimental efforts that are invalid. This body of work seeks to address these issues and contains established protocols for inexpensive, pseudo three-dimensional (3-D) culture scaffolds. The research described offers a multi-disciplinary approach for fabrication of biomaterials to achieve user defined or in vivo cell behavior using human fibroblasts. To provide insight into the design of alternative cell culture templates we have analyzed cell-surface interactions and characterized the surface properties. The substrates fabricated utilized micro-roughened surface topography with 2 – 6 µm wide features and surface chemistry as a method for controlling cell behavior. Surface roughness was templated onto polydimethylsiloxane (PDMS) and PS. The fabricated polymer surfaces have been characterized by atomic force microscopy (AFM), contact angle goniometry, fluorescence microscopy, and infrared (IR) spectroscopy. Initial studies of the textured surface yielded a super-hydrophobic surface with a 154° contact angle and high surface adhesion that was investigated using surface free energy calculations. This was followed by modification of the micro-roughness with self-assembled monolayers (SAMs), proteins, or thin films of polymer for use as a culture platform for cells. Cell behavior on the modified polymers was compared and analyzed against unmodified surfaces and tissue culture PS dishes. Cell morphology on rough PDMS surface was altered by the surface topography decreasing the average cell area to 1760 µm2 compared to an average cell area of 3410 µm2 on smooth PDMS. Gene expression changes were also noted with a 2.3 fold increase in the matrix metalloproteinase, MMP14, in cells on the rough surface compared to cells cultured on Petri dishes. Surface roughness was also combined with other surface modification methods for cell culture, including cell alignment and cell sheet engineering. 50 µm wide lines of fibronectin (FN) patterned on the rough PDMS induced cell directionality while still maintaining a pseudo 3-D culture system creating the first cell culture surface of its kind. The micro-roughness was also templated onto PS and chemically modified with a thermo-responsive polymer. This novel surface produced confluent cell sheets that detached from the surface when cooled below 32°C. Cell sheets cultured on the modified PS surfaces had an increase in FN fibril formation stimulated by the surface roughness when compared to cell sheets detached from a smooth, control surface. The minor alterations to surface topology were proven to be effective in modifying cell biochemical response compared to cells cultured on flat substrates. Differences in surface topography and chemistry stimulated changes in cell adhesion, cytoskeletal arrangement, ECM composition, and gene expression. These cell properties were used as markers for comparison to native cell systems and other reports of 3 D culture scaffolds. The mechanism of altering cell response is discussed in each chapter with respect to the specific type of surface used and compared to cell response and behavior on planar culture systems. New fabrication procedures are described that include the incorporation of other surface modification techniques such as SAMs, surface patterning, and thermo-responsive polymer grafting with surface roughness for original cell culture platforms to mimic an in vivo environment. The research presented here demonstrates that micro- and nano- changes to surface topography have large impacts on the cell-surface relationship which have important implications for research and medical applications involving adherent cells.

This project explores how to use band-pass filtering with a variety of filters to filter both two and three dimensional surface data. The software developed collects and makes available these filtering methods to support a larger project. It is used to automate the filtering procedure. This paper goes through the work-flow of the program, explaining how each filter was implemented. Then it demonstrates how the filters work by applying them to surface data used to test correlation between friction and roughness [Berglund and Rosen, 2009]. It also provides some explanations of the mathematical development of the filtering procedures as obtained from literature.

O estudo avaliou, in vitro, as variáveis relacionadas à alteração de cor e à rugosidade superficial das resinas compostas micro-híbridas: Charisma (Heraeus-Kulzer), Filtek Z-250 (3M - Espe), Herculite XRV (Kerr), Opallis (FGM), TPH Spectrum (Dentsply) e W3D (Wilcos), antes e após o envelhecimento artificial acelerado, tendo como fatores de variação duas fontes de luz, lâmpada halógena e LED, com densidades de potência de 300 mW/cm2 ou 600 mW/cm2. Foram confeccionados 240 corpos-de-prova distribuídos em grupos de 10 unidades para cada condição de estudo totalizando 24 grupos constituídos por 4 protocolos de fotoativação para cada marca de resina composta. Estes corpos-de-prova foram armazenados em água deionizada, ao abrigo de luz e a temperatura de 37oC por 1 semana quando então receberam polimento superficial com discos Diamondpro (FGM). Sequencialmente, os mesmos foram submetidos às análises iniciais de rugosidade superficial (rugosímetro Hommle Tester T1000 basic) e de cor (Espectrofotômetro EasyShade). Decorridas 24 horas, os espécimes foram submetidos ao Sistema de Envelhecimento Acelerado para materiais não metálicos C-UV por 384 horas quando então foram novamente realizadas as leituras de rugosidade e cor. Os valores de rugosidade superficial e alteração de cor das resinas compostas, após o processo de envelhecimento acelerado, demonstraram alterações significativas, sendo os valores de E muito superiores ao considerado clinicamente aceitável (E3,3). De forma geral, o efeito exercido pelos protocolos de fotoativação não permitiu distinguir a influência direta das irradiâncias das fontes de luz no comportamento das diferentes resinas compostas, observando-se uma correlação positiva média entre rugosidade superficial e a alteração de cor. / This study aimed to evaluate changes in color and surface roughness, before and after artificial accelerated aging of six micro hybrids composites resins (comparable to Vita shade A2) cured by quartz tungsten halogen (H) or a light emitting diode (L) polymerization unit with 300 mW/cm2 or 600 mW/cm2. Forty disc specimens (7 x 2 mm) were prepared for each composite (Charisma®, Filtek Z-250®, Herculite XRV®, Opallis®, TPH Spectrum®, W3D®), being 10 specimens for each condition (Q 300/600 mW/cm2 or L 300/600 mW/cm2). After cured, each specimen was evaluated by color (Easy Shade® spectrophotometer) according to CIE L*a*b* color scale and by surface roughness (Hommelwerke GmbH ) Ra values before and after submitting to artificial accelerated aging (4 h UV-B/4 h condensing vapor) for 384 hours total. The surface roughness and color change values of composite resins, after the process of accelerated aging, showed significant changes. Also, the values of E after accelerated aging were much higher than the values considered clinically acceptable (E 3.3). In general, the protocols curing effects showed varied influence over different composite resins and a positive correlation between average change in surface roughness and color change after accelerated aging process.

O efeito das superfícies cerâmicas no desgaste do esmalte antagonista foi estudado in vitro. Foram avaliados os desgastes produzidos pelas porcelanas glazeadas e polidas. Para tal finalidade utilizaram-se cinco cerâmicas: IPS Empress 2 (Ivoclar),IPS Empress (Ivoclar), Duceram Plus (Degussa), Duceram LFC (Degussa) e Symbio (Degussa). Oito conjuntos dente e cerâmica foram testados para cada situação, com carga padronizada e imersos em água a 37 0 C. As medidas do desgaste do esmalte e cerâmica foram avaliadas após 150000 e 300000 ciclos. Os resultados revelaram que o desgaste final do esmalte do dente antagonista foi significantemente menor quando as cerâmicas foram polidas. A quantidade do desgaste do esmalte antagonista foi maior nos primeiros 150000 ciclos. A cerâmica IPS Empress provocou um desgaste significativamente maior do esmalte do dente antagonista quando comparada com as outras cerâmicas testadas (p<0,01). As rugosidades iniciais das superfícies cerâmicas foram diferentes entre si, sendo que diminuíram após o polimento, exceto para a cerâmica IPS Empress. Não houve correlação entre a rugosidade superficial inicial das cerâmicas com o desgaste gerado no esmalte dos dentes antagonistas. / The effect of glazed and polish dental ceramic on the wear of human enamel was studied in vitro. Five ceramics: IPS Empress 2 (Ivoclar), IPS Empress (Ivoclar),Duceram Plus (Degussa), Duceram LFC (Degussa) and Symbio (Degussa), were tested in water at 37 0 C, under standard load. The amount of wear enamel and specimens was determined after 150000 and 300000 cycles. The results showed that the polished ceramics produce less amount of enamel wear. The amount of enamel wear opposite to IPS Empress ceramic was significant higher (p<0,001). The enamel wear rate increased on the first 150000 cycles. Differences between roughnesses were found in all ceramics, the roughness decreased when the ceramics were polished except for IPS Empress ceramic. No correlation on the roughness and enamel wear were found.

Qin, Jie. / "November 2010." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 162-173). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

O desgaste de anéis de pistão e cilindro foi modelado através de um programa computacional que calcula as pressões hidrodinâmicas e de contato rugoso agindo nas superficies deslizantes de contato. Os valores previstos de desgaste são comparados com um ensaio em dinamometro de um motor diesel. / The wear of piston rings and cylinder liner was modelled through a computer code that calculates the hydrodynamic and roughness contact pressures acting in the contact surfaces. The predicted wear is compared with a 750 hours dynamometer test of a medium duty diesel engine

O presente trabalho aborda a modelagem unidimensional do regime misto de lubrificação para problemas caracterizados por condições genéricas de carga, velocidade e geometria. Tal modelagem foi desenvolvida a partir de modelos clássicos, tais como a equação de Reynolds relacionada com os fenômenos hidrodinâmicos, e as formulações de Greenwood & Williamson e Greenwood & Tripp utilizadas na descrição do contato de asperezas entre superfícies rugosas. A cavitação do fluido lubrificante foi considerada através dos modelos tradicionais de half-Sommerfeld e Swift-Steiber (Reynolds). Com relação à reologia do lubrificante, as possíveis variações de viscosidade devidas ao próprio campo de pressões hidrodinâmicas e às altas taxas de cisalhamento do fluido (\"shear-thinning\") foram também contempladas na modelagem proposta. Adicionalmente, quatro filtros não convencionais de rugosidade foram propostos e implementados com o objetivo de eliminar as distorções verificadas na definição do plano (ou linha) médio(a) de referência em topografias caracterizadas pela presença de vales profundos, tais como as obtidas após a aplicação da técnica de texturização a laser (LST). A definição adequada desse plano (ou linha) médio(a) de referência é imprescindível para a correta determinação dos parâmetros necessários para a utilização dos modelos de contato de Greenwood a partir das metodologias consideradas neste trabalho. Toda a modelagem unidimensional foi implementada em um programa computacional denominado VTL (\"Virtual Tribology Laboratory\"), cujo código fonte está disponível para qualquer usuário interessado em realizar simulações envolvendo sistemas lubrificados caracterizados por perfis com geometrias genéricas. A validação da modelagem unidimensional proposta foi verificada utilizando os resultados experimentais de um teste de atrito com movimento alternado (\"reciprocating test\") publicado na literatura. Como resultado, a correlação experimental dos resultados calculados com o programa VTL foi excelente. O programa VTL foi também utilizado para verificar a possibilidade da redução de atrito em sistemas lubrificados envolvendo superfícies planas texturizadas, como as obtidas utilizando a técnica de texturização a laser (LST). Devido à limitação unidimensional da modelagem proposta, as fileiras ortogonais de 7 micro-cavidades foram aproximadas como sendo ranhuras (\"grooves\") de dimensões fixas. Para tais situações, apesar da limitação comentada acima, a modelagem unidimensional proposta pode ser utilizada para analisar qualitativamente o mecanismo de micro-mancais responsável pela geração de pressão hidrodinâmica entre superfícies paralelas caracterizadas por esse tipo de micro-texturas. / This dissertation focuses on one dimensional modelling of the mixed lubrication regime for problems with general conditions of load, velocity and geometry. Such modelling was based on classical models, such as the Reynolds equation related to the hydrodynamic phenomena, and the Greenwood & Williamson and Greenwood & Tripp formulations for the description of the asperity contact between rough surfaces. Cavitation of the lubricant was considered adopting the well-known half-Sommerfeld and Swift-Steiber (Reynolds) models. As for the lubricant rheology, the viscosity-pressure dependence and viscosity-shear-thinning effects were considered. Furthermore, four non-conventional roughness filters were conceived and implemented in order to eliminate the distortions observed on the definition of the reference mean plane (or line) of topographies (or profiles) with deep valleys, such as those obtained with the laser surface texturing (LST) technique. The proper definition of the reference plane (or line) is indispensable for the calculation of the Greenwood\'s contact parameters according to the methodologies used in this work. The complete one dimensional modelling proposed was implemented as a computational program named Virtual Tribology Laboratory (VTL), an open source code available for any user interested in performing simulations of lubricated systems with generic profiles. In order to validate the one dimensional model, experimental results of a frictional reciprocating test published in the literature were considered for comparison. The correlations between the experimental and simulated results calculated with VTL were excellent. Simulations using the VTL program were also performed in order to evaluate the friction reduction potentialities of textured surfaces (LST). Due to the one dimensional model limitations, grooves were considered instead of micro-cavities (dimples). In such scenery, regardless the above mentioned limitations, the one dimensional modelling proposed yielded good qualitative descriptions of the micro-bearing mechanism that generates hydrodynamic load carrying capacity between parallel textured surfaces.

Orientador: Guilherme de Siqueira Ferreira Anzaloni Saavedra / Coorientadora: Anelyse Arata / Banca: Dolores Ribeiro Ricci Lazar / Banca: João Paulo Barros Machado / Banca: Renata Marques de Melo Marinho / Banca: Estevão Tomomitsu Kimpara / Resumo: Neste estudo avaliou-se por caracterização mecânica e microestrutural, a degradação em meio bucal e in vitro da cerâmica Y-TZP sinterizada por energia de micro-ondas em comparação ao método convencional. Foram confeccionados noventa e seis discos por CAD-CAM (ISO 6872), sinterizados de modo convencional (C) 1530°C/120 minutos e por energia de micro-ondas (M) 1450°C/15 minutos. E submetidos à degradação hidrotérmica em reator pressurizado (E) (1,5h/150°C/3 bar) e à degradação in situ (B) (240 horas em meio bucal), formando-se 8 grupos (n = 12): M, C, ME, CE, MB, CB, MEB e CEB. Foram realizadas análises de contração volumétrica, difração de raios-X (DRX), rugosidade superficial (Ra e Rz), ângulo de contato, microscopia eletrônica de varredura (MEV), quantificação do biofilme por UFC/mL e análise de resistência mecânica por flexão biaxial. Os resultados obtidos foram analisados estatisticamente por t-Student, Anova dois e três fatores, e teste de Tukey (5%). Por DRX observou-se transformação de fase tetragonal para monoclínica (t-m) nos grupos envelhecidos, exceto para o grupo MB. Não foram observadas diferenças significantes na contração volumétrica (p=0,274), na rugosidade Ra (p=0,137) e Rz (p=0,187), assim como nos valores de ângulo de contato entre os métodos de sinterização (p=0,669). Por MEV observou-se a presença de formação de biofilme inicial e na contagem de Unidades Formadoras de Colônias (UFC/mL) foi maior quando os espécimes foram previamente envelhecidos in vitro (... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this study ir was evaluated the effect of in situ low temperature degradation of yttrium oxide stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics sintered by microwave energy in comparison to the conventional method. Ninety-six discs milled by CAD/CAM (ISO 6872) were divided in: conventionally sintered (C) at 1530 ° C / 120 minutes and microwave energy (M) 1450°C / 15 minutes. Specimens were submitted to hydrothermal degradation in a pressurized reactor (E) (1.5h / 150°C / 3 bar) and in situ degradation (B) (240 hours in the buccal medium), forming eight groups (n=12): M, C, ME, CE, MB, CB, MEB and CEB. Specimens were evaluated through analysis of volumetric contraction, X-ray diffraction (XRD), surface roughness (Ra and Rz), contact angle, scanning electron microscopy (SEM), biofilm quantification by CFU / mL and biaxial flexural strength. Results were statistically analyzed through t-Student, two, three-way Anova and Tukey tests (5%). By XRD, tetragonal to monoclinic phase transformation (t-m) was observed in the aged groups, except for the MB group. No significant differences were observed in the volumetric contraction (p = 0.274), Ra roughness (p = 0.137) and Rz (p = 0.187), as well as contact angle values between sintering methods (p = 0.669). SEM images showed that the initial biofilm formation was observed after 8 hours in situ, an increase of CFU / mL occurred when the specimens were previously aged in vitro (p = 0.001). Regarding biaxial flexural strength... (Complete abstract click electronic access below) / Doutor