京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第23437号 / エネ博第424号 / 新制||エネ||81(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 森井 孝, 教授 佐川 尚, 教授 片平 正人 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23709号 / 理博第4799号 / 新制||理||1687(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 田口 聡, 教授 松岡 彩子, 教授 榎本 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24074号 / 理博第4841号 / 新制||理||1692(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 寺西 利治, 教授 島川 祐一, 教授 倉田 博基 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Biochar, the solid product of thermal conversion of biomass with little or no available air, is acknowledged as a carbon dioxide removal technique and soil enhancer among other applications. Its potential soil enhancing properties consists of increased water and nutrient holding capacities, liming effects and sorption of pollutants. However, not all soils benefit equally from biochar amendments. The thesis aims to investigate the suitability of biochar applications to agricultural soils in Sweden and communicate the results visually with a biochar indication map, illustrating where biochar could serve the highest benefits as a soil improver. A literature review was carried out to analyse the soil enhancing opportunities of biochar applications, which determined that the criteria soil texture, nitrogen leaching, ground moisture, soil pH and soil organic matter (SOM) were suitable for the analysis in a Swedish context. Then, a multi-criteria analysis was conducted in ArcGIS, based on spatial data of these criteria. Each arable land block was assigned a biochar class, varying from high indication to no indication. Arable land was considered highly recommended for biochar applications if the soil texture was sandy and at least one of the soil criteria was beyond a limiting agronomic threshold. At the national level, high indication for biochar application occupied 24.2% (528 thousand ha) of the arable land in Sweden, while the remaining land had either medium indication (13%), low indication (3.5%) or no indication (59.3%). Despite spatial variations, all Swedish counties (with data coverage above 84%) had at least 2% of high indication arable land. In particular, 66.1% of Halland’s arable land showed high indication. In turn, Skåne had the largest area (148 thousand ha, 35.7%) with high indication for biochar applications. The corresponding biochar volume potential, at the national level, suggested that between 0.5 and 26.4 million tonnes biochar can be applied to arable land with high indication for biochar applications, given application rates between 1 and 50 tonnes/ha over a 20 year timeframe. This means that arable land in Sweden can accommodate for a future production of 500 000 tonnes per year, which was suggested as an upper limit in an inquiry from the Swedish government, if application rates remain below 20 tonnes/ha. The multi-criteria analysis performed includes several subjective choices and uncertain parameters (criteria combination, data accuracy, agronomic thresholds, and classification scheme). Therefore, the biochar indication maps cannot yet be used for farm- or field-level recommendations for biochar applications. Nonetheless, despite uncertainties, the national- and county- level indication maps may still provide interesting order of magnitude. More field experiments are needed in Sweden as well as a more detailed analysis. To be able to make more precise recommendations, the present analysis can be refined by connecting all criteria to physical agricultural mechanisms and to the properties of biochar, and by using spatial data with higher resolution or even field-level data. This said, models need to be validated with experimental data, which is to date, non- existent: controlled biochar field experiments are therefore needed in Sweden. / Biokol, en solid produkt från termisk omvandling av biomassa med begränsat syre tillgängligt, är identifierad som en möjlig teknik för att minska halten av koldioxid i atmosfären och som jordförbättrare bland andra applikationer. Dess potentiella jordförbättrande egenskaper består av vattenhållning, näringsbindning, balansering av pH-värdet och minskad biotillgänglighet av föroreningar. Däremot så drar inte alla jordar samma nytta av biokolapplikationer. Arbetet syftar till att undersöka lämpligheten av biokolapplikationer på jordbruksmark i Sverige och kommunicera resultaten visuellt med en indikationskarta. En litteraturstudie genomfördes för att analysera jordförbättringsmöjligheterna till följd av biokolsapplikationer. Det fastställdes att kriterierna jordtyp, kväveläckage, markfuktighet, pH och organiskt material var lämpliga för analys i svensk kontext. En multikriterieanalys utfördes i ArcGIS, baserat på rumsliga data för dessa kriterier. Vardera jordbruksblock tilldelades en biokolklass, som varierade mellan hög indikation och ingen indikation. Jordbruksmark ansågs högt rekommenderad för biokolapplikationer om jordtypen var av sandig karaktär och minst ett av kriterierna översteg ett begränsande tröskelvärde. På nationell nivå ockuperade hög indikation för biokolapplikationer 24.2% (528 tusen hektar) av Sveriges jordbruksmark, medan den återstående marken hade antingen måttlig indikation (13%), låg indikation (3.5%) eller ingen indikation (59.3%). Trots rumsliga variationer, hade samtliga svenska län (med datatillgänglighet över 84%) minst 2% åkermark med hög indikation. I synnerhet, 66.1% av Hallands åkermark visade hög indikation. Vidare, Skåne hade den största arealen (148 tusen hektar, 35.7%) med hög indikation för biokolapplikationer. Den motsvarande potentialen för biokol, på nationell nivå, antyder att mellan 0.5 och 26.4 miljoner ton biokol kan appliceras på jordbruksmark med hög indikation för biokolapplikationer, givet appliceringsgrader mellan 1 och 50 ton/hektar över en 20-årsperiod. Detta innebär att svensk jordbruksmark kan rymma en framtida produktion på 500 000 ton per år, förslaget av en statlig utredning, ifall appliceringsgraden förblir under 20 ton/ha. Den utförda multikriterieanalysen inkluderar flertalet subjektiva val och osäkerheter (kriteriakombination, datans noggranhet, tröskelvärden, och klassificeringsmetod). Därmed kan indikationskartorna för biokol ännu inte användas för rekommendationer på jordbruksblocknivå. Resultaten kan emellertid, trots osäkerheter, antyda intressanta storleksordningar på nationell- och länsnivå. Fler svenska fältexperiment samt en mer detaljerad analys behövs. För att kunna ge mer exakta rekommendationer, kan den nuvarande analysen utvecklas genom att koppla samtliga kriterier till fysiska jordbruksmekanismer och biokolsegenskaper och genom att tillämpa rumsliga data av högre upplösning eller till och med fältnivådata. Modeller måste valideras med experimentella data, som hittills är obefintlig: kontrollerade fältförsök med biokol behövs därmed i Sverige.

<p>Social learning, defined as learning from other individuals, has been well studied in vertebrates and social insect species. In order to promote further understanding of the evolution of social learning, I tested a non-social insect for social learning and socially influenced behaviour. The desert locust (Schistocerca gregaria) is a gregarious insect which has the opportunity for social learning and can benefit from such ability. Locusts showed rapid individual learning, preferring a diet they have experienced over another of equal nutritional quality. Adult locusts also showed socially influenced behaviour, preferring to eat and lay eggs in the vicinity of other locusts over doing so alone. Fifth instar locusts did not show the same socially influenced behaviours. Neither adult nor nymphs showed social learning after interacting with previously fed models or after observing models feed through a screen. These results provide evidence for socially influenced behaviour in locusts and for a difference in social behaviour between nymphs and adults. Further research utilizing locusts as a model system may help us gain a better understanding of the evolution of social learning.</p> / Master of Science (MS)

The effect of using high voltage DC and AC on the heat transfer process during the melting of a Phase Change Material (PCM) in a rectangular enclosure was studied experimentally and numerically. The experiments were conducted for two configurations: (a) a horizontal rectangular enclosure in which the initial melting process is governed by heat conduction, (b) a vertical rectangular enclosure in which the initial melting process is governed by heat convection. The level of heat transfer enhancement was quantified by using a novel experimental facility for the horizontal configuration. The experimental methodology was verified first against non-EHD melting cases and then was further expanded to include the EHD effects. The experiments showed that EHD forces can be used to enhance a conduction dominated melting up to a maximum of 8.6-fold locally and that the level of enhancement is directly related to the magnitude of the applied voltage. It was found that the main mechanism of enhancement in these cases can be attributed to the electrophoretic forces and that the role of the dielectrophoretic forces is minimal under the applied voltages. In the vertical configuration, the effect of the magnitude of the applied voltage, the applied voltage wave-form, the gravitational Rayleigh number, Stefan number and the aspect ratio of the enclosure on the heat transfer enhancement were investigated experimentally. A novel shadowgraph experimental measurement system was developed and verified against the analytical correlations of natural convection in rectangular enclosures and the non-EHD melting performance was verified against the bench mark experiments of Ho (1984). The shadowgraph system was used to measure the local heat transfer coefficient across the heat source wall (the heat exchanger surface). The local heat transfer measurements along with the melting temporal profiles were used to explain and visualize the coupling between the Electrohydrodynamics (EHD) forces and the gravitational forces. It was found that the EHD forces could still enhance the melting process even for an initially convection dominated melting process. The mechanism of enhancement was found to be a bifurcation of the initial convection cell into multiple electro-convective cells between the rows of the electrodes. The shadowgraph system was used to assess the interaction between the electrical and the gravitational forces through the visualization of these cells and quantifying their size. The EHD heat transfer enhancement factor was found to increase by the increase of the applied voltage, reaching a 1.7 fold enhancement at the lower gravitational Rayleigh number tested and 1.45 fold for the highest gravitational Rayleigh and Stefan number. The effect of the polarity of the applied voltage was tested for the different cases and it was found that there was no significant difference between the positive and the negative polarities when the magnitude of the applied voltage was below 4 kV. At higher voltages- 6kV- the negative polarities showed better level of enhancement when compared to the positive applied voltage. It was again found that the main mechanism of enhancement is attributed to charge injection from the high voltage electrodes. A scaling analysis was conducted based on the previous conclusions and the dominant mechanism of enhancement to describe the problem in non-dimensional form. An electrical Rayleigh number was introduced and its magnitude was correlated to the magnitude of the injected current. The melt volume fraction was then represented against the non-dimensional parameter (n+1)(H/W)Fo.Ste.RaE^0.25 and the melt fraction temporal profiles for the different voltages collapsed well against this parameter. Finally, a numerical analysis was conducted on the role of the dielectrophoretic forces during the melting of Octadecane and when they would become of significant importance. The results of the numerical model supported the experimental findings and suggested that a minimum of 15 kV is needed in order to realize the effect of the dielectrophoretic forces. The numerical model was used to understand the interaction between the gravitational and the dielectrophoretic forces at different ranges of both gravitational Rayleigh number and electrical Rayleigh number. The model was complemented with scaling analysis to determine the governing scales of the problem and the dielectrophoretic Rayleigh number was deduced from the study. / Thesis / Doctor of Philosophy (PhD)

Image and video enhancement, a classical problem of signal processing, has remained a very active research topic for past decades. This technical subject will not become obsolete even as the sensitivity and quality of modern image sensors steadily improve. No matter what level of sophistication cameras reach, there will always be more extreme and complex lighting conditions, in which the acquired images are improperly exposed and thus need to be enhanced. The central theme of enhancement is to algorithmically compensate for sensor limitations under ill lighting and make illegible details conspicuous, while maintaining a degree of naturalness. In retrospect, all existing contrast enhancement methods focus on heightening of spatial details in the luminance channel to fulfil the goal, with no or little consideration of the colour fidelity of the processed images; as a result they can introduce highly noticeable distortions in chrominance. This long-time much overlooked problem is addressed and systematically investigated by the thesis. We then propose a novel optimization-based enhancement algorithm, generating optimal tone mapping that not only makes maximal gain of contrast but also constrains tone and chrominance distortion, achieving superior output perceptual quality against severe underexposure and/or overexposure. Besides, we present a novel solution to restore images captured under more challenging backlit scenes, by combining the above enhancement method and feature-driven, machine learning based segmentation. We demonstrate the superior performance of the proposed method in terms of segmentation accuracy and restoration results over state-of-the-art methods. We also shed light on a common yet largely untreated video restoration problem called Yin-Yang Phasing (YYP), featured by involuntary, intense fluctuation in intensity and chrominance of an object as the video plays. We propose a novel video restoration technique to suppress YYP artifacts while retaining temporal consistency of objects appearance via inter-frame, spatially-adaptive optimal tone mapping. Experimental results are encouraging, pointing to an effective and practical solution to the problem. / Thesis / Doctor of Philosophy (PhD)

Heat transfer technologies based on boiling refer to applications like heat pumps, waste heat recovery systems, power plants and electronic components cooling. The widespread use of boiling as the heat transfer mode is due to high heat transfer coefficients associated with the phase change from liquid to vapor. Boiling heat transfer coefficients can be further enhanced by modifying the texture or chemical composition of the interface at which boiling occurs. The objective of this research is to fabricate textured surfaces with electrical discharge machining (EDM) and investigate the enhancement in pool boiling heat transfer, concerning machining and surface characterization parameters. It is complemented by a qualitative analysis of bubble dynamics with high-speed imaging, to provide insights into the differences in boiling performance associated with the changes in surface topography. Sink electrical discharge machined surfaces demonstrated ten times higher heat transfer coefficient compared to a polished surface during these studies. / Thesis / Master of Applied Science (MASc)

Chronic pain is a frequent and debilitating comorbidity of SCI (Ravenscroft et al., 2000). Although exercise is an effective strategy for managing pain in other chronic pain populations (e.g., Ettinger et al., 1997), exercise training has not been previously examined in the SCI population. In a RCT of 34 sedentary men and women with traumatic SCI, the effects of exercise on perceived pain and physical and psychological well-being were examined. Additionally, the efficacy of exercise as a pain management strategy was assessed. Exercisers performed aerobic and resistance training twice weekly over 9-months. Controls maintained their usual level of activity. Measures of pain (Ware & Sherbourne, 1992), physical well-being (Reboussin et al., 2000), stress (Cohen et al., 1992), depression (Radlof, 1977) and subjective well-being (Cantril 1965; Patrick et al., 1988) were administered at baseline and at the 3, 6 and 9 months points of the intervention. A series of ANCOV As adjusted for baseline scores revealed a significant group main effect for the measures of pain, stress, depression and subjective well-being which reflected improvement in all of these domains for the exercisers (i.e., decreased pain, stress and depression and increased subjective well-being) and decrement in all of these domains for the controls (ps<.05). Hierarchical linear regression analyses (cf. Baron & Kenny, 1986) revealed that change in physical well-being partially mediated change in pain, change in pain mediated change in stress and subjective well-being and change in stress mediated change in depression. These findings suggest that variables mediating exercise-induced change should be targeted to maximize the effectiveness of exercise as a pain management strategy for individuals with SCI. The therapeutic and theoretical implications of these findings are discussed. / Thesis / Master of Science (MS)

Vehicle crashes remain the leading cause of accidental death and injuries in the United States, claiming tens of thousands of lives and injuring millions of people each year. Many of these crashes occur during nighttime, where a variety of modifiers affect the risk of a crash, primarily through the reduction of object visibility. Furthermore, many of these modifiers also affect the nighttime mobility of older drivers, who avoid driving during the nighttime. Thus, a two-fold need exists for new technologies that enhance night visibility. Two separate studies were completed as part of this research. Study 1 served as a baseline by evaluating visual performance during nighttime driving under clear weather conditions. Visual performance was evaluated in terms of the detection and recognition distances obtained when different vision enhancement systems were used at the Smart Road testing facility. Study 2, also using detection and recognition distances, compared the visual performance of drivers during low visibility conditions (i.e., due to rain) to the risk perception of driving during nighttime under low visibility conditions. These comparisons were made as a function of various vision enhancement systems. The age of the driver and the characteristics of the object presented (e.g., contrast, motion) were variables of interest in both studies. The pivotal contribution of this investigation is the generation of a model describing the relationships between driver characteristics, risk perception, and visual performance in nighttime driving in the context of a variety of standard and prototype vision enhancement systems. Improvement of mobility, especially for older individuals, can be achieved through better understanding of the factors that increase risk perception, identification of systems that improve detection and recognition distances, and consideration of drivers' opinions on possible solutions that improve nighttime driving safety. In addition, this research effort empirically described the night vision enhancement capabilities of 12 different vision enhancement systems during clear and adverse weather environments. / Ph. D.