The general trend in gear industry is an increased focus on gear transmission efficiency. This thesis focuses on the understanding of how different gear manufacturing methods – particularly the contribution of the running-in process – affect the surface characteristics and friction response, with the purpose of increasing gearbox efficiency. The thesis consists of a summary and five appended papers. The research hypothesis in paper A and paper B was that the dry elastic 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. The emphasis in paper B is the changes that occur during running-in and correlating these changes to design requirements. Paper C examines the influence of manganese phosphate coating and lubricants, with respect to friction and the risk of scuffing at the initial contact. Paper D examines the effect of running-in load on the friction response for different surfaces. In paper E, the question of whether the load during running-in influences the gear mesh efficiency is further expounded. The main conclusions of this thesis are that the running-in influences the gear mesh efficiency; a high running-in load enhances the gear mesh efficiency. The difference in mesh efficiency is in the range of one tenth of a per cent. Thus, the influence of running-in cannot be neglected because it is in the same order of magnitude as reported for other gear efficiency enhancements. Furthermore, the dry elastic contact area ratio presents a descriptive measure of how surface topography influences the contact, 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. Shaving was found to have the highest contact area ratio, and would therefore be the best choice if deviations from case hardening could be minimised. It was also confirmed that surfaces coated with manganese phosphate raise the limiting load for scuffing failure up to 13 times compared to the uncoated ground equivalent. / <p>QC 20141002</p>

Continental passive margins exhibit high elevation topography in many localities across the globe. The source and age of much of this topography remains a subject of great debate within the wider community, with numerous theories being presented, including significant post-rift uplift and isostatically preserved rift anks. Establishing the mechanisms that generate topography and the onshore evolution across passive margins is vital in understanding regional geological histories and their wider development. The passive margins of the NW Atlantic realm exhibit high elevation topography topped with low relief summits. The origin of this topography is debated, with both 3 km of uplift in the post-rift stage and the isostatic preservation of Cretaceous rift anks being suggested within the literature. The work of this thesis aims to resolve this debate by establishing the timing and source of uplift across the region and determining the onshore evolution prior to, during and after rifting with the application of apatite low temperature thermochronology. Contemporary analytical and modelling techniques are utilised to generate thermal histories from across both central West Greenland and SE Baffin Island, helping to de ne how the modern landscape has formed. Results from this work outline an onshore history dominated by uplift in the Cretaceous and exhumation throughout the Cenozoic. Basement samples from SW Greenland exhibit protracted cooling throughout the Mesozoic and Cenozoic, implying low rates of exhumation have been apparent throughout. Within the Nuussuaq Basin, centralWest Greenland, thermal histories display reheating i through the Late Cretaceous/Palaeogene and cooling to present, consistent with events outlined in the basin's stratigraphy and implying uplift of the topography is likely the result of extrusive volcanism and an isostatic response to the unroo ng of the lithosphere. Spatial trends in data and thermal histories across SE Ba n Island imply much of the landscape is shaped by rift ank uplift along its SE coastline, driving exhumation of the region throughout the Cenozoic. Collectively these results suggest the elevated topography of the NW Atlantic realm is the result of rift related uplift in the Cretaceous, magmatism and widespread exhumation throughout the Cenozoic, preserved by isostatic exure. This interpretation of the region's onshore history contributes greatly to our understanding of the NW Atlantic's geological evolution. The results highlight the role of extensional tectonism, exhumation and isostasy in shaping both margin's landscapes and helps to determine the principal characteristics of the wider extensional system and the evolution of the o shore domain. Moreover, these conclusions have a wider relevance to the evolution of passive margins across the North Atlantic, improving our understanding of how topography across other margins, such as of East Greenland, Norway and the UK, has formed.

The body of work in this dissertation focuses on the properties of an environmental thin film system, including the roughness and composition of the surface. The deposition of particles, such as airborne soil and plant pollen, from the atmosphere creates a thin film known as “environmental film” or “urban film” that covers virtually all of Earth’s solid surfaces. Environmental films have been shown to accumulate a variety of chemicals, including toxic pollutants. To investigate the means by which environmental films uptake chemicals, model films are made in the lab and real films are collected outside. Model films serve to mimic the properties of native films and allow for a simple analysis of a complex system. Native films serve to provide real field samples to analyze. The properties of model and native films are characterized using reflected light to determine what the film is made of and microscopes capable of imaging small particles. The results of the model film study indicate a model capable of reproducing the surface roughness and other properties of native films. This study serves as a platform with the goal of making model films that better mimic native films. The results of the native film study indicate successful imaging using microscopes capable of revealing the structure and chemical composition of the films. This imaging adds an important contribution to the field that has not previously been performed.

This dissertation presents an investigation of the effects of a stochastic component of sediment transport in sandy rivers in an attempt to gain information about the transport system and its implications for the evolution of Earth's surface topography. First, a method for characterizing the geometries of bed forms is introduced and compared to previously proposed methods. This new method is then implemented on a field dataset as well as laboratory dataset and the results are compared to those obtained by traditional methods. Second, a method for characterizing the dynamic evolution of the bed geometries is demonstrated. It produces a velocity scale, the mean migration rate of the bed topography, and a deformation scale, the evolutionary departures of the bed topography from pure migration. These scales are calculated for the field and laboratory data and are compared. The flux of bed sediment is then shown to depend on the stochastic component of bed evolution. The fluxes for each dataset are calculated, they are related to the environmental conditions causing the transport of sediment, and suggestions are made for the design of field campaigns that attempt to measure sediment transport by repeated surveys of bed topography. Finally, the implications of stochasticity for sediment transport are investigated. A null hypothesis is formulated for topographic change by a stochastic process. Then the effects of measurement and field collection methods on the null hypothesis are evaluated. The most important prediction is non-trivial behaviors in measurable rates of surface change at short timescales. This prediction is then evaluated with field data from a growing sandy channel network whose behaviors can be determined at timescales of decades to centuries (dendrochronology), tens of thousands of years (cosmogenic radiochemistry), and hundreds of thousands to millions of years (age of channel system and sediments through which it cuts). These three investigations create a coherent account of the expressions and implications of variability in the transport of sediment, and therefore the evolution of topography, in sandy river systems that can then be generalized to changes across Earth's surface. / text

Many industrial processes involve powders in some form when making products, and the behavior of the powders processed is impacted by the adhesion of the individual particles which comprise it. This adhesion behavior, in turn, is critically influenced by the complementarity between the topography of a surface and the shape and roughness of the particles that adhere to that surface. Problems such as poor flowability, dust hazards, and equipment wear arise due to uncontrolled particle adhesion and can lead to production challenges. Computational models have been developed to predict the behavior of highly idealized powders (i.e., powders comprised of simple geometries such as spheres) under various processes but are limited in their ability to model and optimize the manufacturing and handling of powders comprised of many complex particles. This work focuses on further developing an experimental and modeling framework, called the Enhanced Centrifuge Method (ECM), that maps particle-scale and surface properties onto experimentally-validated ‘effective’ adhesion distributions that describe the adhesion between particles in powders. These distributions represent an engineering approach that allows powders comprised of particles of complex shape and roughness, which are challenging to model, to be described as if they were perfect, smooth spheres, which are comparatively simple to model. The complexity associated with the shape and size distributions of the individual particles is captured by the ‘effective’ adhesion parameters. These ‘effective’ adhesion parameter distributions provide a quantitative guide as to how the specific particle properties are interacting with the surface topography which directly impacts the overall powder adhesion. The initial framework of the ECM is constructed around characterizing the van der Waals adhesion of silica and polystyrene powders. The impact of the surface topography and the particle properties of each of the powders is captured in ‘effective’ Hamaker constant distributions. These distributions provide a quantitative guide for specifically how the particles interact with the surface topography based on the respective scales of the particle and surface features. The ECM framework is further adapted here to investigate the effects of topographical changes of stainless steel due to polishing on the adhesion properties of three different pharmaceutical powders to the stainless steel. In this adaptation of the ECM framework, the force of adhesion was described by modifying the Johnson, Kendall, and Roberts (JKR) model describing elastic-like particle contact to a flat plate. Within the modified JKR adhesion description, the work of adhesion is tuned to be an ‘effective’ work of adhesion parameter. These size-dependent ‘effective’ work of adhesion distributions provide a quantifiable measure of the change in the powder and surface adhesion that reflects the size, shape, and topographical features on the powder and surface with which the powder interacts. To investigate environmental effects on the adhesion properties, the ECM framework is also extended to characterize the effect humidity has on altering surface and particle interactions of the three pharmaceutical powders to stainless steel. In addition to the work with the pharmaceutical powders, the investigation of the effect of humidity on the powder’s adhesion includes a study of the influence of water on the interactions between silica particles and a silica substrate. In all cases, the ‘effective’ adhesion force distributions developed through the ECM provide the ability to quickly determine quantitatively how environmental and process conditions alter particle and surface properties, and overall powder behavior.

The master thesis discusses the principles, design and realization of the original device for measuring of the electromagnetic radiation scattering in the structure of solar cells. It follows the results of a previous project "Analýza optických vlastností solárných článku" (ev.n.FT-TA3/142) and as well as knowledge gained from Ing. Vladimir Grundling’s master thesis, which has been done under this project. The subject of this thesis was to make a device for measuring of the electromagnetic radiation scattering in the visible spectrum. The aim of this work is an innovation of the previous device, so that the electromagnetic radiation scattering in the near infrared spectrum can be studied. This makes the possibility to qualify the influence of the rear surface of an active part of solar cell on electromagnetic radiation scattering, i.e., on the conversion efficiency of solar energy into electric. For this reasons it was necessary to modify the device, so that we can change the radiation source and detector because of the transparency of silicon wafers for the near infrared area. The work is supported by the project „Barevné solární články s vysokou účinností pro architektonické aplikace“ (FRTI1/168) in cooperation with Solartec s.r.o.

Previous studies of cooling igneous plutons did not consider the possible influence of sloping surface topography. Topographically-driven fluids in high relief terrain, however, are thought to interact with deep buoyancy-driven fluids to produce large lateral-flow systems up to 5 km long and 20 km long in silicic and andesitic volcanic terrain, respectively. In this study, a quantitative investigation of the interaction of topographically-driven and buoyancy-driven fluid flow is conducted through the use of a finite element numerical model to simulate the fluid flow and thermal regimes associated with a cooling igneous pluton in the presence of significant topographic relief. The system considered in this study is that of a pluton with dimensions 2 km by 3 km and an initial temperature of 980 °C centered beneath a mountain having relief of 1 km over a horizontal distance of 3 km. Simulation results indicate that the topographic component of flow interacts with buoyancy to produce two separate flow systems, a shallow topographically-driven flow system and a deeper convecting system. The resulting hydrothermal system evolves in a more complicated fashion than in flat topography cases. In addition, the existence of the shallow topographically-driven flow system partially masks the presence of the heat source by preventing fluids having the chemical signature of the deeper, hotter environment from reaching the surface. Cooling rate of the pluton is also increased and boiling is inhibited. These effects, however, are primarily a result of the pluton being injected into a cooler host rock. The host rock is cooler in the sloping topography case due to advective cooling prior to pluton injection. Model results also indicate that temperature beneath the mountain and the position of the zone of mixing remain relatively constant for almost 50,000 years. The stability of the temperature conditions and the position of the zone of mixing may increase the likelihood for the deposition of epithermal ore bodies in this region.

Deformation twinning in Magnesium alloys both facilitates slip and forms sites for failure. Currently, basic studies of twinning in Mg are facilitated by electron backscatter diffraction (EBSD) which is able to extract a myriad of information relating to crystalline microstructures. Although much information is available via EBSD, various problems relating to deformation twinning have not been solved. This dissertation provides new insights into deformation twinning in Mg alloys, with particular focus on AZ31. These insights were gained through the development of new EBSD and related machine learning tools that extract more information beyond what is currently accessed.The first tool relating to characterization of deformed and twinned materials focuses on surface topography crack detection. The intensity map across EBSD images contains vital information that can be used to detect evolution of surface roughness and crack formation, which typically occurs at twin boundaries. The method of topography recovery resulted in reconstruction errors as low as 2% over a 500 μm length. The method was then applied to a 3 μm x 3 μm area of twinned Tantalum which experienced topographic alterations. The topography of Ta correlated with other measured changes in the microstructure. Additionally, EBSD images were used to identify the presence of cracks in Nickel microstructures. Several cracks were identified on the Ni specimen, demonstrating that cracks as thin as 34 nm could be measured.A further EBSD based tool developed for this study was used to identify thin compression twins in Mg; these are often missed in a traditional EBSD scan due to their size relative to the electron probe. This tool takes advantage of crystallographic relationships that exist between parent and twinned grains; common planes that exist in both grains lead to bands of consistent intensity as a scan crosses a twin. Hence, twin boundaries in a microstructure can be recognized, even when they are associated with thin twins. Proof of concept was performed on known twins in Inconel 600, Tantalum, and Magnesium AZ31. This method was then used to search for undetected twins in a Mg AZ31 structure, revealing nearly double the number of twins compared with those initially measured by standard procedures.To uncover the driving forces behind deformation twinning in Mg, a machine learning framework was developed to leverage all of the data available from EBSD and use that to create a physics based models of twin nucleation and growth. The resultant models for nucleation and growth were measured to be up to 86.5% and 96.1% accurate respectively. Each model revealed a unique combination of crystallographic attributes that affected twinning in the AZ31.

Zirconia has been established as a promising material for dental implants. Various surface treatment methods have been utilized to promote better osseointegration and improve the success rate of dental implants. However, a better understanding of the influences of topographic characteristics on cell attachment, proliferation, and differentiation is needed. Different surface topographic zirconia specimens, As sintered, Mild rough, Moderate rough, and Rough zirconia groups were fabricated with sandblasting method in various distances and stages. The surface texture, microstructure, and wettability were inspected with the optical profiler, SEM, and contact angle measurement respectfully. Human primary osteoblast cells were cultured on the four groups of zirconia with different surface modifications in 24 well plates and on plates without test material as control. Crystal violet and triton X-100 solution were used to evaluate cell attachment efficiency at 9 hours and proliferation rate at 7, 14, and 21 days after seeding. ALP activity was measured with fluorometric assay. The expression of osteocalcin was measured with an ELISA kit. Alizarin red staining was conducted to evaluate the mineralization. The cell morphologies were inspected under SEM after cell fixation and critical point drying process. The data were analyzed with one-way ANOVA for experiment on each time interval and two-way ANOVA for all time points. Tukey post hoc test was used for pairwise comparison. P value < 0.05 was considered statistically significant. Topographic parameters and contact angle measured in As sintered, Mild rough, Moderate rough, and Rough surface groups were as follow: Sa = 0.23, 0.50, 2.13, 5 µm, Sal = 49.88, 21.20, 30.42, 49.87 µm, Sdq = 64.64, 248.60, 511, 734.66 µm/mm, Sk = 0.7, 1.54, 4.19,16 µm, Spk = 0.31, 0.64, 1.47, 5.13 µm, Svk = 0.35, 0.71, 5.96, 6.18 µm respectively, and contact angle = 64.6°, 55.2°, 43.5°, 38.6° respectively. The result showed that Rough zirconia group induced the highest cell attachment efficiency at 9 hours (p<.001). As sintered zirconia group promoted significant cell proliferation rate at 21 days (p<.001) while Rough zirconia group drastically down-regulated cell proliferation (p<0.001). The most elevated levels of ALP, osteocalcin, and mineralization expressions at 21 days were found in the Moderate rough group with significant differences (p<.001, p<.001, p<.001 accordingly) Within the limitations of this in vitro study, it can be concluded 1) the modified microroughened zirconia surfaces of Sa 5 µm would promote human osteoblast attachment but down-regulate cell proliferation, 2) the As sintered zirconia surface would stimulate cell proliferation, and 3) the microroughened surfaces of Sa 2 µm would up-regulate osteoblast differentiation. These findings could be incorporated into designing and fabricating the dental implant surfaces for optimal osseointegration.

Bacterial biofilms are communities of micro-organisms encased a self-produced extracellular matrix. While they form readily in a nature, biofilm formation in man-made systems have economic and health consequences. Prior research demonstrated that topographical features comprised of uniform, micro-meter sized particles hindered the biofilm formation of Pseudomonas aeruginosa (P. aeruginosa), an opportunistic human pathogen. The goal of the present work is to 1) further develop a potential anti-biofilm coating by improving its robustness and 2) study the mechanism(s) by which surface topography hinders biofilm formation. The robustness of a topographical coating comprised of an array of silica particles is improved by the introduction of silica bridges through a sol-gel reaction. To study the mechanism(s), specifically, we hypothesized that the motion, or surface motility, of P. aeruginosa is hindered by the presence of micro-meter scale obstacles via physical obstruction. To test this, we analyzed the behavior of single P. aeruginosa cells at micron-scale spatial resolutions using time-lapse fluorescence microscopy, image analysis, and particle tracking techniques. We fabricated various types of micron-scale topography with curvature (particle arrays) and recti-linear features (vertical steps) and varied the critical dimension within the range of 0.5 – 10 µm which spans the dimensions of a typical P. aeruginosa cell. We found that there was a threshold feature size of 1-2 µm at which bacterial surface motility is drastically impacted. On positively curved topography (particle arrays), we found that the frequent obstacles reduced the average speed of a bacterium from 6.2  0.3 µm per 5 min on a flat surface to 2.1  0.3 µm per 5 min on an array of 2 µm particles. Furthermore, we observed that bacteria often move in-between particles, suggesting that bacteria have difficulty climbing over tall obstacles. To further investigate P. aeruginosa's ability to cope with topography, we examined the effect of recti-linear features (vertical steps) on surface motility. We found that step heights > 0.9 µm drastically reduced the probability of crossing and that the average speed when approaching the step is reduced by a factor of 2. Interestingly, we find that bacteria have a slight preference to traverse down which is against the direction of gravity in our system. In summary, these results offer insights into how a surface motile bacterium copes with a topographical surface. Our data indicate that the topography of a surface can impede the surface motility of bacterium and thus, may be an important mechanism by which topography prevents biofilm formation. / Doctor of Philosophy / Bacteria and other micro-organisms can grow on surfaces such as medical devices and cause infections. Other examples of where bacteria can grow are on drains and pipes causing clogging, and on the hulls of ships, thus increasing drag. The goal of the current work is to investigate material coatings that resist the attachment and growth of bacteria on surfaces. We demonstrate that changing the roughness of the surface can reduce the number of bacteria found on the surface. More specifically, we have made surfaces covered with spheres that are approximately the same size as a bacterium, about 1 micrometer (10x smaller than the diameter of hair). We find that the spheres act as physical obstacles that block bacteria from moving on a surface. These results suggest that changing the micro-scale geometry of a surface may reduce the rate of infections on medical devices or hinder the growth of bacteria in other systems