北九州市立大学 学術リポジトリ(ルクソール)
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Study on the basic properties of carbon removal modified fly ash-based geopolymers for 3D printing
No full text北九州市立大学博士(工学)This PhD thesis focuses on developing eco-friendly, low-carbon 3D-printed geopolymer (3DPG) by utilizing solid waste fly ash. It investigates the optimal flotation pretreatment conditions and evaluates the feasibility of replacing kerosene with waste fried oil (WFO) as a collector. Comprehensive analyses of flotation performance, interaction mechanisms, and economic benefits of WFO were conducted. Modified fly ash was prepared through flotation, and its rheological behavior was systematically studied using particle packing, water film thickness, and calorimetric experiments. Preliminary printability verification tests confirmed material suitability. Furthermore, polypropylene fibers of different lengths and dosages were incorporated to examine their effects on fluidity, time-dependent rheology, printability, mechanical strength, and freeze–thaw resistance. The findings provide theoretical and technical guidance for reducing carbon emissions, advancing sustainable use of industrial by-products, and promoting the engineering application of 3DPG in green construction.doctoral thesi
Research on design strategies for thermal environment optimization in small-scale waterfront spaces
Get PDF北九州市立大学博士(工学)Currently, urban built environments are affected by both the greenhouse effect and the heat island effect, necessitating a focus on improving thermal environments in architectural and landscape design. However, architects and landscape designers primarily focus on the functionality and artistry of these spaces during the design process, with little consideration given to thermal environment optimization. Based on the diverse design of real-world waterside spaces, it conducts thermal environment simulations on waterside spaces of varying configurations. Using Envi-met software, dozens of scenarios were simulated to analyze the coupling effects of variables such as water bodies, buildings, vegetation, and ventilation. The research identifies thermal environment characteristics of waterside spaces and proposes universal design guidelines for optimizing thermal conditions. This work provides practical insights for improving thermal environments in waterside spaces and offers new design methodologies for future waterside space planning and construction.doctoral thesi
Study on stress-responsive optimization of spatial voronoi shell structures
Get PDF北九州市立大学博士(工学)This dissertation presents a multi-scale framework for stress-responsive optimization of spatial Voronoi shell structures in architecture, integrating topology optimization, genetic algorithms, and environmental risk assessment to enhance sustainability and performance. Motivated by the intersection of computational geometry, recycled materials, and additive manufacturing, the research addresses inefficiencies in traditional structural design by developing adaptive Voronoi tessellations that respond to stress fields while minimizing material use.The methodology encompasses macro-scale form-finding via SIMP topology optimization and Voronoi generation, meso-scale refinement through Lloyd relaxation and multi-objective genetic algorithms, and micro-scale validation using finite element analysis on 20 design variants. Environmental impacts are quantified through life-cycle assessment augmented by a Bayesian risk framework, accounting for innovation uncertainties in recycled PLA fabrication.Results demonstrate up to 40% material reduction with maintained structural integrity, superior stiffness-to-weight ratios, and reduced carbon footprints compared to conventional designs. This work advances computational architecture by reconciling performance optimization, digital fabrication feasibility, and environmental ethics, offering practical guidelines for sustainable built environments.doctoral thesi
Enhancing Disaster Risk Reduction Education: Course Design, Performance Evaluation, and Past Experience-Knowledge-Preparedness-Risk Perception Nexus
No full text北九州市立大学博士(学術)A significant increase in the frequency and intensity of disasters highlights the need to empower children and young people, as vulnerable groups, with the necessary knowledge and skills for self-protection. However, limited studies integrate climate change and disaster risk reduction content into the general education curriculum, particularly at the primary level. Comprehensive criteria that address knowledge and attitudes toward disaster-related behavior, especially at the primary level, and students’ disaster risk perception on school campuses in Vietnam are also lacking. Hue City is known as one of the most disaster-prone areas in Vietnam and a center of education. This study provides a general overview of DRR education in Vietnam by designing and evaluating a short course for primary schools and assessing risk perception at the university level. Based on the findings, solutions were proposed to enhance DRR education within Vietnam’s education system and in similar contexts in other countries.doctoral thesi
Performance optimization of radiant floor heating system integrated with encased phase change materials
Get PDF北九州市立大学博士(工学)Phase change materials (PCM) provide an innovative approach to enhancing radiant floor heating systems (RFHS), with encased PCM systems offering improved energy efficiency and design flexibility. Integrating PCM within tubes and hot water pipes addresses key challenges, including thermal efficiency, response speed, temperature control, costs, and energy usage. This study focuses on optimizing the thermal performance of encased PCM systems for practical applications. It reviews PCM applications, thermal properties, encapsulation techniques, system design, operation strategies, and performance evaluation, supported by mathematical modeling, CFD simulations, and experimental validation. Key analyses include the advantages of encased PCM systems, adjustments to hot water pipe positioning, optimizing PCM encasement shapes, and introducing double-layer PCM structures to enhance heat storage and release efficiency. The paper concludes with insights into technical and economic challenges and outlines future directions for sustainable RFHS development.doctoral thesi
Geographical Distribution and Characteristics of Sports Organizations for Children: Implications for the Sustainable Development of Communities
Get PDF本研究は、北九州市における子ども向けスポーツ団体の地理的分布と運営形態を明らかにし、地域社会の持続可能な発展に対する示唆を提供することを目的とした。605団体の公開情報を基に、スポーツの種類、対象年齢、運営形態、プログラム形式、および施設利用状況を分析し、活動場所の分布パターンを地図化した。departmental bulletin pape
A questionnaire survey on urban agricultural activities among residents of the shrinking city, Kitakyushu, Japan
Get PDF北九州市では、1980年代以降、一貫して人口減少と高齢化が進み、縮減に因む沢山の課題を抱えている。海外の縮減都市では、空き家や空閑地などを農的に利用し、居住環境の改善、コミュニティ再生、高齢者の居場所作りなど、地域の課題を解決した事例もある。北九州市でも地域課題の解決に都市農業の有効活用を考察すべきであるが、関連研究は少ない。本研究では、北九州市民を対象にアンケート調査を実施し、市民の都市農業活動に関する現状やニーズを明らかにし、都市農業活動を振興させるための考察を行う。departmental bulletin pape
Simulation study of heat transfer performance of underground energy pile under the optimization of new fins
Get PDF北九州市立大学博士(工学)The article takes the energy stack at a field test site in Nanjing as an example and uses the solid heat transfer module of COMSOL Multiphysics to create a two-dimensional numerical model of the energy stack. By comparing experimental data, the correctness of the COMSOL multiphysics model has been confirmed. A new type of energy pile fin has been designed to improve the heat transfer of the pile. The impact of a new type of fin on the heat transfer efficiency of the energy stack was evaluated, and the temperature changes of the soil around the stack before and after fin installation were checked by comparing parameters such as pipeline configuration, buried pipe depth, and concrete thermal conductivity. Then, three new types of metal fins were compared to improve the heat transfer performance of energy stacks.doctoral thesi
Novel Partial Nitritation Process with External Selector Treating Low-strengthen Wastewater
Get PDF北九州市立大学博士(工学)This study used a laboratory-scale activated sludge system with an external selector to inhibit nitrite-oxidizing microorganisms (NOO) to achieve partial nitrification (PN). The external selector receives concentrated microorganisms from the aeration tank, which are exposed to toxic compounds to partially destroy NOO before returning to the aeration tank.The experiment operated for 400 days, using the mixture of nitrite and ammonia (about 1,000 mg-N L−1 each) accelerated the microbial decay of both NOO and AOO in the external selector. In addition, the IWA-ASM1 model was used in this study to determine the kinetic parameters of NOO and AOO. From the kinetic analysis, the preferable operational range to attain 57%-partial nitritation was estimated.DNA analysis showed that Nitrosomonas was the most prevalent AOO and Nitrospira was the most dominant NOO. The DNA-based fractions for AOO and NOO were reasonably correlated to the model-based ones. A linear relationship between the kinetic model-based biomass fraction and the DNA-based one was found for each microbial species. These linearities were supposed to enable us to estimate the nitrifier concentrations of the activated sludge systems by using the DNA analytical method.doctoral thesi