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.

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.

Diploma thesis deals with elastohydrodynamic lubrication of point contacts, which surfaces are influenced by topography and velocity vector of one rubbing surface is misaligned. Author summarizes knowledge of previously published research articles, which fundamentally enrich current state of knowledge. Diploma thesis contains experimental measurement results of the film thickness and the way of lubrication film formation in elliptical contact for different ellipticity parameters, kinds of rubbing surfaces and angles of the velocity vector. New findings have helped to better understand the behaviour of highly loaded lubricated contacts taking place in machine components and completed the current state of knowledge with results that can be used in next thorough study of this issue.

Silicon photonics is emerging as a potential field to achieve optical interconnects towards the realization of ultra high bandwidth. The indirect band-gap property of silicon still remains as a big challenge to incorporate silicon photonic active device, for example, silicon-based laser. In the Laboratory of Semiconductor Materials at KTH, a monolithic integration platform based on nano-epitaxial lateral overgrowth (nano-ELOG) technique has been proposed to integrate III-V semiconductor materials with silicon for light source application. The integration process involves uneven surface morphology at different stages. The surfaces of the indium phosphide seed layer on silicon used for ELOG, the mask deposited on it (the silicon/silicon dioxide waveguide) and the ELOG indium phosphide layer grown on it prior to laser growth are often rough. In this thesis work, we have optimized chemical mechanical polishing (CMP) technique in order to achieve an even surface. The same procedure is also necessary to reach the optimal thickness of different layers to enable effective coupling of light from the laser source into the waveguide. CMP of indium phosphide to obtain an average surface roughness of < 1 nm has been optimized by a two-step polishing using different slurries; it results in a step height of ca 3 nm. Similarly the surface of silicon/silicon dioxide “waveguide” has also been optimized with the roughness of ~ 0.5 nm. In the latter case, a step height of 40 nm is retained and this increase with respect to InP is identified to be mainly due to limitations of the polishing machine which is different from that used for indium phosphide. The reduction in step heights with polishing time is analyzed and compared with an existing theoretical model. Our results are in good qualitative agreement with the model. The optimized surface morphology obtained in this work was tested for its suitability for integration. For this evaluation, InP was grown by ELOG in a hydride vapour phase epitaxy reactor with and without CMP of the involved surfaces. The surface after CMP yields layers of better surface morphology with fewer defects as revealed by atomic force microscopy, surface profilometer and cathodoluminescence analysis. The results indicate that the CMP process is useful for monolithic integration for silicon photonics.

The general trend in gear industry, today, is an increased focus on gear transmission efficiency. Gear transmission efficiency losses arise from loaded and unloaded gear contacts, seals, lubricant and bearings. One way of minimising the losses is to lower the lubricant viscosity. This will reduce the speed dependent losses. However, the load dependent losses might increase. To avoid this, the ratio between lubricant film thickness and surface roughness must be maintained, which can be fulfilled by producing smoother gear surfaces. As a starting point for this realisation process, the present manufacturing processes, the design tools and the characteristics of the gear flank interface must be further investigated and developed. This must be achieved with an emphasis on economic production. This thesis focuses on our understanding of how different gear manufacturing methods —particularly the contribution of the running-in process—affect the surface characteristics, with the view of increasing gearbox efficiency. The thesis consists of a summary and three appended papers. Paper A and paper B discuss the relationship between design parameters and real gear wheel surfaces manufactured with different manufacturing methods. The research hypothesis was that the contact area ratio is a descriptive parameter for the contact condition. Paper A deals with the influence of manufacturing method on the initial contact conditions and also serves as a validation of the simulation program used. The emphasis in Paper B is the changes that occur during running-in, and to correlate these changes to design requirements. Paper C approaches the influences of manganese phosphate-coating and lubricants with respect to friction and the risk of scuffing at the initial contact. The main conclusions of this thesis are that the contact area ratio presents a descriptive measure of how surface topography influences the contact, seen at both a global (form deviation) and local (roughness) level. The surface topography caused by the manufacturing method has a significant influence on the contact area ratio. This is an important result, since neither national standards nor commercially available gear evaluation programs handle surface topography on the local scale. Shaving was found to have the highest contact area ratio, and should therefore be the best choice if deviations from case hardening could be minimised. It is also confirmed that gear-like surfaces coated with manganese phosphate have a low coefficient of friction, and raise the limiting load for scuffing failure enormously compared to the ground equivalent. / <p>QC 20100518</p> / KUGG / Sustainable gear transmission realization

Examination of peat samples collected from hummocks and hollows within a confined bog reveals that peat collected from different locations, designated by surface topography, vary in ash content, ash alkalinity, initial Kjeldahl nitrogen content, and fixed and total nitrogen after ammoniation with an ammonia-air mixture. The values of these properties have shown hummocks and hollows to be true entities having characteristic ranges of certain properties. The results have shown that, although peat is heterogenous with respect to certain properties, use can still be made of determined values if ranges of these values are recognized and utilized. Misinterpretations and meaninglessness of results are possible if this is not done. / Thesis / Master of Science (MSc)

The high energy lasers are emerging as an innovative material processing tool to effectively fabricate complex shapes on the hard and brittle structural ceramics, which previously had been near impossible to be machined effectively using various conventional machining techniques. In addition, the in-situ measurement of the thermo-physical properties in the severe laser machining conditions (high temperature, short time duration, and small interaction volume) is an extremely difficult task. As a consequence, it is extremely challenging to investigate the evolution of surface topography through experimental analyses. To address this issue, an integrated experimental and computational (multistep and multiphysics based finite-element modeling) approach was employed to understand the influence of laser processing parameters to effectively control the various thermo-physical effects (recoil pressure, Marangoni convection, and surface tension) during transient physical processes (melting, vaporization) for controlled surface topography (surface finish). The results indicated that the material lost due to evaporation causes an increase in crater depth of machined cavity, whereas liquid expulsion created by the recoil pressure increases the material pileup height around the lip of machined cavity, the major attributes of surface topography (roughness). Also, it was found that the surface roughness increased with increase in laser energy density and pulse rate (from 10 to 50Hz), and with the decrease in distance between two pulses (from 0.6 to 0.1mm) or the increase in lateral and transverse overlap (0, 17, 33, 50, 67, and 83%). The results of the computational model are also validated by experimental observations with reasonably close agreement.

No description available.

No description available.

Among the central constituents of the innate immune system are macrophages, which are known for phagocytosis or ‘eating’ foreign particles or pathogens. Macrophages express several cell-surface proteins including transmembrane and membrane-anchored receptors, which play a vital role in their response to pathogenic stimuli. The plasma membrane is a highly fluid and dynamic environment, which facilitates the diffusion of lipids and proteins within the plane of the membrane. This study aims to measure the lateral diffusion of two types of plasma membrane receptors on macrophages, toll-like receptor II (TLR2) and cluster of differentiation 14 (CD14), to answer three main research questions: 1) Which type of fluorescence-based microscopy techniques is best suited for measuring the lateral diffusion of TLR2 and CD14 on macrophage plasma membrane? 2) Does culturing macrophages on different surface topographies impact the diffusion of TLR2 in the plasma membrane and its pro-inflammatory response, along with morphological changes? 3) Does aging alter the lateral diffusion of TLR2 in the plasma membrane of macrophages? To date, a variety of fluorescence-based methods have been developed to study the dynamics of cell membrane constituents. These techniques are based on either ensemble or single particle measurements. We have used single particle tracking methods to track the mobility of fluorescently labeled membrane receptors on murine bone marrow-derived macrophages. Total internal reflection fluorescence microscopy (TIRF) was used to visualize and capture the dynamics in live cells. Using a custom routine algorithm we detected, localized, and tracked the particles to calculate their diffusion coefficient, extracted from the mean-squared displacement as the most common measure of diffusion. We also measured the diffusion coefficient using an ensemble-based technique known as Raster Image Correlation Spectroscopy (RICS) with a confocal laser-scanning microscope. The use of confocal eliminates the out-of-focus signal and enables measurements that are confined to a narrow plane in the cell. Also, the ability of RICS to separate the slow and immobile fractions of particles makes it possible to detect heterogeneities in diffusion. To our knowledge, this is the first study that has utilized both SPT and RICS to directly compare receptors’ diffusion in different membrane sections. Moreover, this is the first study that has examined the diffusion of receptors on macrophages adhered to different surface topographies, and the first that has investigated the receptors’ diffusion in young and old macrophages. / Thesis / Doctor of Philosophy (PhD) / The immune system is highly dependent on a specialized subset of white blood cells known as macrophages that are capable of clearing damaged and dead cells as well as a wide range of invading micro-organisms. Specific receptor proteins present on the membrane of macrophages are involved in the recognition of particles and subsequent signaling to recruit other immune cells or to promote healing and wound repair. To date, a variety of fluorescence-based microscopy methods have been used to study the dynamics of cell membrane components. The mobility of several membrane receptors in macrophages has been studied using microscopy techniques, which have provided valuable insights into their function. However, there is still insufficient information about the behavior of two key receptors (TLR2 and CD14) that participate in signaling in response to bacterial products. This thesis aims to answer three major questions with regard to receptor mobility (i.e., diffusion) within macrophage membrane: 1) Which type of fluorescence-based microscopy technique is more suitable for measuring the mobility of TLR2 and CD14 receptors on macrophage membranes? 2) What is the impact of different surface topographies on TLR2 diffusion in adhered macrophages, as well as cell shape, and the ability of macrophages to internalize particles? 3) Does aging alter TLR2 mobility in the membrane of macrophages? The following chapters provide detailed answers to these questions. In brief, we have demonstrated that TLR2 and CD14 diffusion measurements in adhered macrophages highly depend on the membrane section chosen. In addition, our results show that micro- and nanostructured surface topographies alter the shape of adhered macrophages and yield higher bacteria internalization, while the diffusion of TLR2 is not changed. When comparing macrophages derived from young and old mice, we find similar diffusion rate of TLR2 in macrophages of the two age groups.