京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22130号 / 農博第2376号 / 新制||農||1073(附属図書館) / 学位論文||R1||N5238(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 德地 直子, 教授 北島 薫, 准教授 舘野 隆之輔 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

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.

Tryckflammighet, ojämnheter på tryckta ytor är en icke önskvärd egenskap som länge bekymrat tryckeribranschen. Ojämnheterna har medfört en försämrad kvalité på kartongmaterial som visuellt får materialet att se fläckig och sämre ut. Egenskapen har visat sig vara mer tydlig på ytor som tryckts med färgen cyan, vanligt förekommande i metoderna flexotryck och offsettryck. Detta examensarbete har gjorts hos ett företag inom tryckeribranschen. Företaget har använt två metoder för bedömning av tryckflammighet på tryckta vätske- och förpackningskartong, en Parvis visuell bedömning och en instrumentell mätning med en skanner och programvaran STFI Mottling Expert. Programvaran har utvecklats med syftet att på ett identiskt sätt bedöma bland annat tryckflammighet på kartongmaterialytor så som den upplevs på den visuella bedömningen. Under en lång period har företaget använt instrumentet för att verifiera resultat som erhålls från den visuella metoden. Under de senaste åren har korrelationen mellan dessa metoder blivit sämre, till en punkt där företaget inte litar på instrumentet. Korrelationsanalys har därför utförts för att undersöka sambandet mellan dessa två metoder och orsaken till problemet. I samband med detta har företaget upptäckt en möjlighet, att undersöka topografiska egenskaper på otryckt material från samma produktionstillfälle och dess korrelation med tryckflammigheten. Topografiska värden har därför tagits fram via instrumentet L&W OptiTopo samt programvaran RISE OptiTopo Expert och korrelationsanalys utförts. Resultaten indikerar en fortfarande väldigt hög korrelation mellan de två metoder som används för bedömning av tryckflammighet, dock inom andra våglängder än den rekommenderad av programvaran och orsakerna till tidigare problem har lagts fram. Topografiska värden som ytråhet samt andelen kratrar under en viss tröskel har kunnat kopplas till tryckflammighetsvärdet och sambandet visats. / Print mottle, unevenness on printed surfaces is an undesirable property that has long worried the printing industry. The effect has led to a degraded quality in cartonboard which visually makes the material look stained and worse. The property has been shown to be more evident on surfaces printed with the color cyan, commonly in printing methods such as flexography and offset. This project degree has been conducted at a company in the printing industry. The company has used two methods for assessing print mottle on printed liquid- and packaging board, a Pairwise visual assessment and an instrumental measurement with a scanner and software STFI Mottling Expert. The software has been developed with the purpose of identifying among others print mottle on cartonboard surfaces in an identical way as the visual assessment. For a long period of time, the company has used the instrument to verify the results from the visual assessment. In recent years, the correlation between these methods has gotten worse, to a point where company does not trust the instrument. Correlation analysis has therefore been performed to investigate the relationship between these two methods and the cause of the problem. In connection with this, the company has discovered an opportunity, to investigate topographical properties on unprinted materials from the same production line and its correlation with print mottle. Topographical values have therefore been determined using the L&W OptiTopo instrument and RISE OptiTopo Expert software. The results indicate that there is still a very high correlation between the two methods used to assess print mottle, though within wavelengths other than the one recommended by the software and the causes of previous problems have been presented. Topographical values such as surface roughness and the proportion of craters under a certain threshold have been linked to the print mottle value and the correlation between them shown.

The presented thesis deals with the work On the Holy Places (De locis sanctis) compiled by the monk and abbot Adomnán of Iona (624-704). Adomnán's work provides evidence of the unknown Gallic pilgrim Arculf about his journey to the Holy Land. Furthermore, Adomnán's text represents a complex historical source about the character of the early medieval pilgrimage during the second half of the 7th Century. Moreover, On the Holy Places offers extensive description and topography of the holy places associated with Jesus Christ's life, passion, and resurrection, hence oscillates between itinerary and hagiography. From the perspective of literary history, Adomnán's narrative has a deep-rooted background within the tradition, nevertheless, provides a significant number of innovations beyond the traditional views. The thesis contextualised Adomnán's text within the 7th-Century Iro-Scottish literary production, i.e. introduces Adomnán's new concept of pilgrimage narrative. Moreover, the text presents the first translation of On the Holy Places from Latin into Czech along with extensive commentary. The historical-critical method of Classic and Medieval studies, together with synchronous and diachronic analysis, was used. The detailed commentary contextualised Adomnán's work within the archaeological excavations...

Internal waves are generated in stratified fluids, like the ocean, where density increases with depth. Tides are one of the major generation mechanisms of internal waves. As the tides move water back and forth over underwater topography, internal waves can be generated. The shape of the topography plays a major part in the properties of the generated internal wave and the type of wave and energy is known for multiple symmetric topographies, such as Gaussian or sinusoidal. In order to further understand the effects topographic shape plays, the effect of asymmetry on internal waves is investigated. First, two experimental methods are compared to evaluate which will capture the relevant information for comparing waves generated from oscillating asymmetric topographies. Two experimental methods are often used in internal wave research, Synthetic Schlieren (SS) and Particle Image Velocimetry (PIV). Both SS and PIV experimental methods are used to analyze a set of experiments in a variety of density profiles and with a variety of topographies. The results from these experiments are then compared both qualitatively and quantitatively to decide which method to use for further research. In the setup, the larger field of view of SS results in superior resolution in wavenumber analysis, when compared to PIV. In addition, SS is 25% faster to setup and significantly cheaper. These are the deciding factors leading to the selection of SS as the preferred experimental method for further tests regarding tidally generated internal waves from asymmetric topographies. Previous experimental and theoretical research on tidally generated internal waves has most often used symmetric topographies. However, due to the complex nature of real ocean topography, the effect of asymmetry can not be overlooked. A few studies have shown that asymmetry can have a significant effect on internal wave generation, but topographic asymmetry has not been studied in a systematic manner up to this point. This work presents a comparison of tidally generated internal waves from nine different asymmetric topographies, consisting of a steeper Gaussian curve on one side, and a wider Gaussian curve on the other. The wider curve has varying amplitude from 1 to 0.6 of the steeper curve's amplitude, and two oscillation frequencies are explored. First, kinetic energy density in tidally generated internal waves is compared qualitatively and quantitatively, in both physical and Fourier space. When compared to similar symmetric topographies, the asymmetric topographies varied distinctly in the amount of internal wave kinetic energy generated. In general, internal wave kinetic energy generated from asymmetric topographies is higher for waves generated at a lower frequency than at a higher frequency. Also, kinetic energy is higher in internal waves on the relatively steeper side of the topography. There is very little kinetic energy in the higher wavenumbers, with most of the internal waves being generated at the lower wavenumbers. The amplitude does not make an appreciable difference in the wavenumber at which the internal waves are generated. Thus, the differences quantified here are due solely to changing slope, showing a significant impact of a relatively slight asymmetry.

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

>Magister Scientiae - MSc / The research was driven by a need to increase the knowledge base concerning wetland ecological responses, as well as to identify and evaluate the factors driving the functioning of the Franschhoek Trust Wetland. An ecohydrological study was undertaken in which vegetation cover, depth to groundwater, water and soil chemistry were monitored at 14 sites along three transects for a 12 month period. The parameters used include temperature, pH, electrical conductivity (EC), sodium, potassium, magnesium, calcium, iron, chloride, bicarbonate, sulphate, total nitrogen, ammonia, nitrate, nitrite and phosphorus. T-tests and Principal Component Analysis (PCA) were used to analyze trends and to express the relationship between abiotic factors and vegetation. Results reflect the strong influence of hydrology, microtopography and nutrient availability in structuring vegetation composition in the wetland. The wetland has been classified as a palustrine valley bottom with channel wetland, which is predominantly groundwater-fed (phreatrotropic), but receives surface water inputs as well. Small scale gradients of microtopography allow for differences in flooding frequency and duration resulting in hydrologically distinct sites which differ chemically. Three zones were distinguished in the wetland. Hollows or low sites were characterized by intermittent flooding and drying and higher nutrient concentrations in soil and groundwater. High sites which were rarely or never flooded exhibited higher groundwater temperature and ammonia as well as iron in soils and groundwater. The inundated sites remained flooded throughout the year and were characterized by high nitrate and nitrite in soil as well as high EC, magnesium, bicarbonate, sulphate and phosphorus in groundwater. The limited availability of nitrogen in the wetland favoured plant types Typha capensis, Paspalum urvillei and Juncus .kraussii which are able to either fix nitrogen or store nitrogen during more favorable conditions. The main chemical concentration changes take place between summer and winter. The Principal Component Analyses suggest that sodium, chloride, potassium, ammonia and phosphorus are the dominant ions determining the chemistry of groundwater. Increased abstraction from the table mountain aquifer to supplement human demand may put the wetland at risk of degradation. Intensified agriculture and other land use in the area are likely to increase pollution loads into the wetland causing shifts in nutrient availability and vegetation composition. Continued and long term monitoring is essential to ensure effective management of the wetland and is highly recommended. Closer partnerships between wetland managers and scientists as well as community awareness and involvement through a volunteer monitoring programme should be encouraged

It is accepted worldwide that the best final solution for spent nuclear fuel is to bury it in deep geological repositories. Despite the physical and chemical barriers that are supposed to isolate the nuclear waste for at least 100.000 years, some uncertainty factors may cause underground water to get in contact with the nuclear waste. Due to radioactivity and oxidation under air, dissolution experiments using UO2 pellets are difficult and frequently lead to incoherent results. Therefore, to enable a detailed study of the influence of microstructure and surface properties on the stability of spent nuclear fuel over time, it is necessary to produce analogues that closely resemble nuclear fuel in terms of crystallography and microstructure. At the same time, in-depth understanding of dissolution phenomena is crucial to geological processes such as dissolution precipitation creep and solvent mediated phase transformations. My thesis is based in two manuscripts. Paper I reports the microstructures obtained after sintering CaF2 powders at temperatures up to 1240°C. Pellets with microstructure, density and pore structure similar to that of UO2 spent nuclear fuel pellets were obtained in the temperature range between 900°C and 1000°C. Paper II reports how differences of surface chemistry and crystal symmetry, characteristics of each surface orientation, affect the topography of CaF2 pellets described in paper I during dissolution. I propose that every orientation of the fluorite structure can be decomposed in the three reference surfaces {100}, {110} and {111}. The {111} is the most stable surface with a dissolution rate of the top surface of 1,13x10-9 mol.m-2.s-1, and {112} the less stable surface with a dissolution rate 34 times faster that {111}. Surfaces that expose both Ca and F atoms in the same plan dissolve faster, possibly because the calcium is more susceptible to be solvated. The faster dissolving surfaces are replaced by the more stable {111} and {100} surfaces which causes the development of roughness on the top surface and stabilizes the surface on high energy sites; i.e. pores or grain boundaries. The main consequences of these observations are i) the increase of the total surface area; ii) the decrease of the overall surface energy. I present a dissolution model for surfaces of crystal with different surface energies. The main conclusions are: a) dissolution rates calculated from surface area are over estimated to the real dissolution rate; b) dissolution rates are faster at the beginning of dissolution and tend to diminish with time until a minimum value is reached.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23479号 / 工博第4891号 / 新制||工||1764(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 立川 康人, 准教授 市川 温, 教授 角 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM