京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20378号 / 工博第4315号 / 新制||工||1668(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 小山田 耕二, 教授 川上 養一, 教授 中村 裕一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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This master thesis work is aimed to investigate the possibilities of achieving more efficient industrial lighting. The study is divided in four parts: 1) Industrial lighting energy efficiency measures, 2) Added value of lighting, 3) Drivers and barriers for adopting lighting efficiency measures, and 4) Applications of AI in industrial lighting.The first part of the study explores various energy efficiency measures that could be applied in industrial lighting. The results show that using energy-efficient lighting fixtures, optimizing lighting controls, and adopting smart lighting solutions that integrate daylight in the illumination strategy and design are the most effective measures for reducing energy consumption and increasing efficiency.In the second part, the study examines the added values or non-energy benefitsof efficient industrial lighting. The findings indicate that apart from cost savings, efficient lighting leads to improvements on the quality of work environments, enhances workers health and safety conditions and improves environmental performance. Moreover, the study suggests that in many cases, the added values of lighting are not given the importance they should have and are not considered when an energy efficiency investment is planned to be done.The third part of the study identifies the drivers and barriers for adopting lighting efficiency measures in industrial settings. The study found that factors such as cost and energy savings, energy efficiency regulations are the main drivers for implementing efficient lighting solutions. However, barriers such as lack of awareness, perceived high initial costs, technology adoption and insufficient government incentives are the main obstacles to adoption.Finally, the study investigates the potential of artificial intelligence (AI) in industrial lighting. The results show that AI-based solutions, such as predictive maintenance and intelligent lighting control could significantly improve energy efficiency and reduce maintenance costs. Moreover, AI can bring the work environment to another level by the application of human centred and personalized lighting.Overall, this master thesis work provides valuable insights into achieving more efficient industrial lighting by highlighting effective energy efficiency measures, identifying the added value of efficient lighting, and examining the drivers and barriers to adoption. Moreover, the study sheds light on the potential of AI in industrial lighting and its potential benefits and future challenges.

Heavy metals, despite their essential roles as minerals in biological systems, pose a significant threat to human health and the environment due to their toxic properties. Even at low concentrations, heavy metals such as lead, mercury, arsenic, and cadmium can cause adverse effects on humans and animals. Consequently, stringent regulations have been established to limit heavy metal concentrations in water resources. However, existing laboratory-based analytical methods for heavy metal detection are time-consuming, expensive, and require skilled personnel. The current detection limit required by several health organizations around the globe is below 10 ppb for Lead, Mercury, Chromium, and Arsenic. The current state of the art which can accomplish low levels of detection is either expensive to operate or incapable of achieving the required trace level sensing. This thesis aims to address the need for a simple, cost-effective, and portable method for detecting heavy metals in water. The thesis begins by reviewing the current state-of-the-art heavy metal sensing methods, highlighting their limitations and the requirement for sample preconcentration. Various preconcentration techniques are discussed, emphasizing their performance parameters and advancements in trace-level detection. Furthermore, the thesis identifies the gaps in current technology, particularly in the context of developing a reliable and user-friendly method for testing heavy metal concentrations in drinking and surface waters. The primary objective of this thesis is to develop a preconcentration-based colorimetric method for detecting heavy metals in water. This method aims to overcome the limitations of existing techniques by offering high sensitivity and a limit of detection below regulatory ranges without the need for complex equipment or extensive sample preparation. The thesis contributes to the advancement of the state-of-the-art by providing a simplified, portable, and efficient solution for in-line detection of heavy metal contamination in water resources. This has been achieved through the design and deployment of sensor utilizing a novel architecture, measuring heavy metal ions down to the sub ppb level. we were able to detect ions such as copper and Lead at concentrations below 0.5 ppb with a limit of detection (LOD) of 0.14 ppb. Overall, this thesis combines knowledge from the fields of analytical chemistry, sensor technology, and environmental science to address the pressing need for a practical and accessible method for monitoring heavy metal concentrations in water. By achieving this goal, the research will contribute to safeguarding public health and promoting sustainable water resource management. / Thesis / Doctor of Philosophy (PhD) / Heavy metals can be found naturally and are needed in small amounts for our bodies to function properly. However, many heavy metals are toxic and can cause serious health problems even at very low concentrations. These metals can contaminate water sources through activities like mining and improper waste disposal. Currently, detecting heavy metals in water requires expensive equipment and skilled experts in a laboratory setting. This process is time-consuming and not easily portable for on-site testing. The existing methods also have limitations such as low sensitivity or the need for complex procedures. This thesis aims to improve the way we detect harmful heavy metals in water. The goal of this thesis is to develop a simpler and more sensitive method for detecting heavy metals in water. The focus is on using color-changing dyes that react to the presence of heavy metal ions. However, these dyes often have detection limits higher than what is considered safe, so the thesis also explores ways to concentrate the samples to improve sensitivity. By addressing these challenges, the thesis aims to contribute to the development of a reliable and easy-to-use method for testing heavy metal concentrations in drinking and surface waters, helping to protect public health and identify potential sources of contamination.

Improving energy efficient lighting is a necessary step in reducing energy consumption.Lighting currently consumes 17% of all U.S. residential and commercial electricity, but a report from the U.S. Office of Energy Efficiency and Renewable Energy projects that switching to LED lighting over the next 20 years will save 46% of electricity used in lighting.GaN LEDs are used for their efficient conversion of electricity to light, but improving GaN efficiency requires optically engineering the chip to extract more light.Total internal reflection limits GaN LED performance since light must approach the chip surface within 23.6° of normal to escape into air.This thesis systematically studies the effect of index of refraction, material thickness, and nano-grating period on light extraction efficiency.An ITO layer is added to the LED surface to increase the critical angle of light, and standing wave analysis is used to optimize material thicknesses.When these results are combined with the best grating period, light output improves by 254% over the unmodified LED.

Vertical farming has been proposed as a solution for providing food security for an increasing, urbanized human population. Light-emitting diode (LED) technology has become increasingly affordable and efficient, making it an ideal choice as artificial lighting for indoor farms. Still largely undiscovered parameters are the optimal plant varieties and types of production systems for plant growth, profit, and human nutrition. Aquaponics may be able to provide sustainable animal protein for vertical farms, increasing their ability to provide more substantial nutrition to consumers. This research aimed to better understand vertical farming as a food production system, and to determine if aquaponics can be an appropriate and applicable fit for it. The experiment was a randomized, factorial design with three independent variables: (1) LED photoperiod interval (2) LED-plant distance, and (3) nutrient solution, as well as several dependent variables to assess both plant yield and quality. A 4-tiered shelving unit was constructed for nutrient film technique (NFT) plant production, and treatments were assigned to each row: (1) LED experiment: Row A, 12/12hr reduced photoperiod with adjustable LEDs 4in. above plant surface; Row B, 2/1hr altered photoperiod interval relative to the control; Row C (control), 16/8hr “standard” photoperiod. (2) Nutrient experiment: Row C, aquaponic nutrient solution; Row H, hydroponic nutrient solution. Rows C and H had matched photoperiod and light intensity. Kale from Row A had significantly lower fresh and dry plant yield relative to the control, Row C (p<0.05). Hydroponic romaine, Row H, had significantly higher plant yield relative to aquaponics, Row C (p<0.05). Butterhead yields were not significantly different in any treatments (p>0.05). Future research may implement a larger sample size of only one plant variety, harvest plants earlier, limit light intensity variation, effectively “balance” the aquaponics system, and have more measures of plant “quality.”

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Wide bandgap semiconductor visible light-emitting diodes (LED) development has spawned the prestigious Nobel Prize in Physics in 2014. Building upon this success, the scope of research has expanded to ultrawide bandgap semiconductors, which possess immense potential in the realm of deep ultraviolet (DUV) photonics. These materials have gained attention for their applicability in various areas, including public sterilization, solar-blind DUV communication, and real-time monitoring. Leveraging on the unique ultrawide tunable bandgap property, highly crystalline capability, and robust behavior, group III-Oxide and III-Nitride semiconductors were employed for sensitive DUV photodetector (PD) and efficient DUV emission, respectively. The primary research are as follows: • III-Oxide heteroepitaxial growth optimization: The influences of substrate temperature, laser energy, and oxygen pressure for the Ga2O3 growth are systematically investigated. Furthermore, the doping capability, multi-phase availability, and bandgap tunability are demonstrated. • Flexible Ga2O3 film growth and electronic devices: Flexible Mica substrate is employed to epitaxially grow κ-phase Ga2O3 thin film. The fabricated flexible PD has an Iphoton/Idark ratio of over 107 under DUV luminescence. The fatigue test performed with 1-3 cm bending radii and 10,000 bending cycles exhibits the robust flexibility of the demonstrated DUV PD. • Transferable Ga2O3 membrane for vertical electronics: Mica as a Ga2O3 growth platform enables the large-scale transfer of ultra-thin Ga2O3 membrane from mica to arbitrary tape due to the weak interfacial bond energy. A vertical and self-powered PD is demonstrated with a responsivity of 17 mA/W under DUV illumination and 0 V bias. • Interfacial mismatch engineering for freestanding Ga2O3 membrane: Looking beyond the hetero-mismatch and engineering the interfacial thermal strain between Si-doped Ga2O3 and AlN could result in the exfoliation of freestanding ultrathin Ga2O3 membrane, allowing vertical device configuration and preferable thermal management. The exfoliation mechanism has been clarified and vertical DUV PD with high on/off ratio is demonstrated. • Efficient III-Nitride LEDs: Buried polarization-induced tunneling junction is employed to suppress electron overflow and simultaneously enhance hole injection. Furthermore, monolithic integration of DUV and visible LEDs is proposed and demonstrated by deliberately cascading DUV and visible active regions, which could replace the current integration technique in the sterilization system.

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