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サンゴ石を用いた歴史的組積造建築物の構造保全に関する研究：ザンジバル・ストーンタウンの事例
Get PDFAncient civilizations imprinted their legacy on Zanzibar Stone Town by constructing revered stone masonry buildings, which
were experiencing rapid deterioration due to severe environmental impacts. With financial limitations and a lack of proper
conservation strategies and preservation plans, 22.9 % of the historic structures are in deteriorated and poor condition and on the
point of collapse. This research aims to investigate field exploration and sample procurement for physical, mechanical, and chemical
testing in conjunction with the on-field implementation through ambient Vibration Testing(AVT) and numerical prediction of
historical stone masonry buildings in Zanzibar Stone Town to analyse the material and dynamic characteristics of the buildings.
The findings of this study will contribute to future modifications and improvements in restoration guidelines for Zanzibar Stone
Town.
The results indicate considerable water absorption, varying porosity, and specific gravities, highlighting marine
environmental factors'significant water retention and susceptibility. The uniaxial compressive strength (CS) for coral stone, mortar,
and wood falls under 7.64 MP a to 15. 15 MP a, 0.56 to 0.99 MP a, and 52.91 to 69.32 MP a reveals the heterogenous characteristics
across the samples. The flexural strength of coral stone and wood was investigated to be 2.02 MPa to 3.44 and 72.17 MPa to 98.64
MPa, indicating a high risk of susceptibility to breakage and fracture. Meanwhile, the average range of ultra pulse velocity (UPV)
yields 1668 to 2070 mis, revealing the range of void in the building materials. In addition, the chemical invetigation includes X·ray
diffraction(XRD) andXでay Fluorescence(XRF), indicating the higher content of CaO in coral stone and mortar with predominant
mineral aragonite indicates the fragile nature of rapid chemical attacks.
Meanwhile, The Ambient vibration test(AVT) reveals structural dynamic properties in terms of peak resonance frequencies
(fr(avg)}, mode shape, and damping ratio, in conjunction with the development of correlation with the geometric parameters of the
building. The result reveals that fr(avg) ranges between 2.8 to 5.3 Hz for various investigated structures, non-uniform deformed
mode shapes, and damping ratio ranges between 2.36 to 4.45 at various orientation axes of the understudy buildings. However, the
relationship of natural frequencies indicates a higher association with the geometrical parameters of the building, yielding a
correlation coefficient (R2) between 0.85 and 0.99. Moreover, the numerical prediction via eigenvalue analysis (EVA) yields a
considerable association with investigated data quantified by Root Mean Square Error( RMSE), mean absolute error (M紐;) ranged
between 0.29 to 0.3, while Nash-Sutcliffe efficiency (NSE) and R2 between 0.81 to 0.99 respectively.
Therefore, based on the findings, future conservation efforts in Zanzibar Stone Town are recommended to prioritize moisture
control strategies, such as applying water-repellent coatings and improved drainage systems, to reduce the high water absorption
observed in coral stone and mortar. Additionally, selective structural reinforcement should be implemented, particularly in areas
with low compressive and flexural strength, using techniques like retrofitting and fiber·reinforced polymers (FRP). Protective
coatings and regular chemical composition monitoring should be introduced to combat chemical degradation. Integrating long-term
structural health monitoring (SHM) systems is also essential for tracking dynamic changes and preventing potential structural
failures. Finally, future restoration guidelines should incorporate geometric analysis and numerical simulations to optimize
intervention strategies and prioritize structures at the highest risk of collapse.博士（工学）琉球大学University of the Ryukyu
ハイブリッド再生可能エネルギーシステムの最適な運用と管理
Get PDFRecently, energy has become the driving force behind growth and development across all sectors of the economy. Rapid population growth has led to a sharp increase in energy consumption. Countries have increasingly turned to renewable energy sources for their effectiveness in producing energy and reducing pollution. However, the intermittent and unpredictable nature of RESs, poses several challenges. Advanced EMSs, supported by AI, offer solutions by balancing supply and demand in realtime. These systems ensure efficient, sustainable energy management and promote consumer selfsufficiency. This thesis deals with the feasibility of power flow management for a hybrid RESs and its impact on reducing energy losses and increasing the reliability of the microgrid. The integration of multi-RESs leads to techno-economic challenges such as power quality, voltage stability, and microgrid efficiency. To overcome these challenges, this thesis focuses on implementing a highly efficient hybrid energy system through two basic stages. The first stage involves the implementation of a hardware prototype for a real-time EMS. This system is designed to automatically determine the optimal power source for supplying the load. It undergoes thorough experimental validation to ensure its effectiveness. The appropriate microcontroller is selected to effectively manage the power flow, depending on the response speed of the microcontroller. The proposed smart EMS is implemented using the FPGA board, chosen for its high response speed. The second phase employs AI to enhance energy flow by developing a coordinated operation strategy for optimizing the operation and management of isolated microgrids. A multi-objective optimization problem is formulated to guarantee both sustainable reliability and economic efficiency in microgrid operations. This study aims to verify the feasibility of integrating hybrid backup systems within the microgrid that incorporates V2G technology. The proposed strategy is verified through a real case study in a remote area of Egypt. Several operating configurations for the hybrid backup system are studied. The proposed SEMS achieves effective integration between the resilient microcontroller, chosen for its rapid response speed and its capability to perform multiple operations simultaneously, and the optimization techniques to enhance the power quality. A significant aspect of the study focuses on optimizing power generation from PV using hybrid TFWO-ANFIS and GTO-ANFIS methods to enhance energy capture efficiency by combining ANFIS with MH algorithms. This thesis introduces an adaptive AI-based HEMS to mitigate the discomfort of customers and reduce operational costs. The proposed HEMS aims to optimize the performance of the microgrid and obtain an optimal operating plan for home microgrids by integrating power limitations using a developed coordinated strategy. Overall, this thesis introduces an adaptive AI-based EMS and HEMS that optimizes microgrid performance, ensuring cost savings, reliability, and enhanced customer comfort.博士（工学）琉球大学University of the Ryukyu
魚卵専者イイジマウミヘビの採餌生態の研究
Get PDFSea snakes are a major component of predator communities on Indo-Pacific coral reefs. Among the hydrophiine species, Emydocephalus ijimae is specialized to prey solely on fish eggs that are laid on the substrate of coral reefs. Fish eggs are very unusual among snake diets because of their very small sizes, and therefore the snakes must consume a huge number of eggs and feed at high frequencies. In this study I investigated foraging habits of E. ijimae and discusses possible foraging strategy of this fish egg specialist.
Despite biological interest, it is undetermined what kinds of fish species are involved in this unique predator-prey system. One obstacle of dietary studies on E. ijimae resides in difficulty of species identification of fish eggs. However, recent development of DNA barcoding technique allows us to do it. As a preliminary study for identification of stomach contents of E. ijimae using DNA barcoding, sequence variation in a part of the mitochondrial 12S ribosomal RNA (12S) gene among damselfish species, that are the major diets of E. ijimae, was examined. Adding many new sequences to the DNA database, I confirmed that 96.0% of the 150 species examined were identified exactly at the species level. Also, I examined natural marking of E. ijimae to establish a basis for individual identification, it was critical for study on dietary variation among individuals. I examined band pattern on the tail surfaces in a total of 593 snakes I captured, and showed that these natural markings are unique and ontogenetically stable and can be used reliably for individual identification if the pattern of both sides of the tails are incorporated.
I conducted an intensive stomach contents analysis for E. ijimae in Zamamijima Island, and fish eggs of at least 30 species and 14 genera in 5 families were detected as their diets. Snake predation peaked in June, with 3.38 clutches per stomach on average, and dropped to 0.04 clutches per stomach in December–January. Pomacentridae (22 species) comprised 93.4 % of the total predated clutches, followed by 4.05 % of Plesiopidae (2 species), 1.94 % of Gobiidae (4 species), 0.49 % of Tripterygiidae (1 species) and 0.16 % of Blenniidae (1 species). The predation frequencies for prey species were generally correlated with the relative abundances in the habitat, suggesting that E. ijimae preys on fish eggs largely in proportion to their availability. Nonetheless, predation frequencies for several pomacentrid species deviated significantly from their abundances in the community, suggesting a certain degree of prey selectivity by E. ijimae.
Individual-level dietary analyses revealed that the putative prey preference across the population actually resulted from individual variations. Some individuals consumed certain prey species but some others consumed other prey species, suggesting niche partitioning for diet among individuals within the population of E. ijimae. However, two-year continuous investigation of individuals’ stomach contents revealed that individual preferences were not fixed, but changed temporally. These results suggest that their diets may be determined by learning rather than genetic basis.
In this study, the unique feeding systems of E.ijimae were revealed, and the effect of individual learning on dietary variation within populations was discussed. In addition, the role of these sea snakes as predators on coral reefs was comprehensively considered.博士（理学）琉球大学University of the Ryukyu
1H-MRS を用いた非定型髄膜腫、再発髄膜腫の代謝産物比較
No full textOBJECTIVE: Meningiomas are predominantly benign, but some cases exhibit recurrent growth after surgery and undergo malignant transformation to WHO grade 2 or grade 3. Despite progress in genetic analyses, advancements in metabolomic analysis remain less established. Herein, the authors investigated metabolic activity differences between WHO grade 1 meningiomas and WHO grade 2 or 3 meningiomas by noninvasively using proton magnetic resonance spectroscopy (1H-MRS), aiming to preoperatively estimate malignancy. They also reviewed the literature to elucidate this aspect of meningioma research.
METHODS: At Ryukyu University Hospital, the authors focused on 93 patients diagnosed with meningioma between 2011 and 2021. The inclusion criteria encompassed prior surgery, pathological diagnoses of meningioma, and preoperative 1H-MRS. Group I included 71 patients with WHO grade 1 meningioma and group II included 22 patients, comprising 19 and 3 with WHO grade 2 and 3 meningioma, respectively. The authors retrospectively conducted a comparative analysis of patient backgrounds and tumor metabolites.
RESULTS: Group I and II did not differ significantly in terms of patient demographic characteristics (age and sex). Group II demonstrated a significantly lower extent of tumor resection (p < 0.01), higher MIB-1 labeling index (LI) (p < 0.05), higher incidence of prior irradiation (p < 0.001), and increased rate of tumor recurrence (p = 0.005) compared to group I. According to 1H-MRS, all metabolites, except lactate, displayed significantly higher median creatine (Cr) ratios in group II than group I: glutamine/Cr was 8.46, glutamate/Cr was 9.49, lipid/Cr was 11.36, and choline/Cr was 2.77. According to the receiver operating characteristic (ROC) analysis, glutamine had the largest area under the curve of 0.765 among 10 metabolites, and the cutoff value for distinguishing between group I and II was 5.76.
CONCLUSIONS: In cases pathologically graded as WHO grade 2 or 3 meningiomas, metabolic products such as glutamine, glutamate, lipids, and choline increased significantly. These changes were correlated with elevation of the MIB-1 LI. In group II, the mean MIB-1 LI was 8.58, significantly higher than in group I, suggesting a strong association with pathological malignancy. Therefore, 1H-MRS may help to noninvasively predict tumor metabolic activity and tumor recurrence. Furthermore, the authors concluded from the ROC analysis that glutamine may be a potential indicator of future growth of meningioma and benefits of early surgery.博士（医学）琉球大学University of the Ryukyu
ミヤコカナヘビの生活史に生息密度が及ぼす影響に関する研究
No full textTakydromus toyamai, a grass lizard endemic to the Miyako Islands of the Ryukyu Archipelago, has been rapidly declining in recent years and is regarded as one of the most endangered reptiles in Japan. This species has been quite common in the grassy zones in various environments including fa1mlands and around human villages. Recently, only a few individuals were found at most places, and high-density populations were very limited. Population density is one factor that may influence population dynamics, and low density can decrease individual fitness and drive to extinction. To understand the maintenance mechanisms of high-density populations, I aimed to explore the effect of population density on life history of T. toyamai. In Chapter 1, I conducted a 5.5-year capture-mark-recapture survey to examine the detailed basic life history of this species in high-density populations, and clarified that the prolonged breeding season and rapid growth to maturity allowed some individuals that hatched in early spring to produce a second generation in their first year. Nearly half of breeding adults are involved in this lifecycle with two generations per year. In Chapter 2, I investigated the spatial distribution pattern within high-density populations and the factors affecting them. Takydromus toyamai often exhibited a significantly aggregated distribution within their habitat, and this aggregation cannot be explained by coincident with vegetation heterogeneity. Analyses for aggregated members revealed that the aggregations are transient and umelated to mating behaviors. These results suggest that the aggregated distribution is likely driven by some intrinsic factors other than sexual behavior, and that the aggregated lizards gain some benefits from the aggregations. Therefore, I examined the effects of population density on life history parameters related to reproduction and survival in Chapter 3. The results showed that the proportion of gravid females and juvenile growth rate were greater in high-density areas than in low-density areas, and a life cycle with two generations within a single year is not achieved in the non highdensity area. Overall, this study revealed that population density strongly influences the high-density population stability of this species, and it, in tum, may be one of the factors responsible for the rapid decline in T. toyamai. In the future conservation measures on T. toyamai, it is essential to consider not only the removal of factors that directly cause reduction of population number, but also the density-dependent effects on the population maintenance.博士（理学）琉球大学University of the Ryukyu
ヤイトハタにおける月周性リズム発振に関する分子生物学的研究
Get PDFSome fish species inhabiting tropical and subtropical waters utilize lunar periodicity for their reproductive and migratory events. They may possess the ability to perceive cues from the moon and convert them into internal signals. Among the core clock gene components (period: PER, circadian locomotor output cycles kaput: CLOCK, aryl hydrocarbon receptor nuclear translocator like 1: BMALI, and cryptochrome: CRY), CRY are hypothesized to be involved in driving this rhythmic entrainment. Reports indicate that the expression of Cry genes show moon-dependent fluctuations in several species. For instance, the mRNA expression of Cry2 in the stony coral Acropora millepora is higher during the full moon night than during the new moon. In the brain of the goldlined spinefoot Siganus guttatus, the mRNA expressions of Cry] and Cry3 increase during the first quarter moon and decrease during the full moon. In the brain of the honeycomb grouper Epinephelus merra, Cry2 increase around the new moon. These findings suggest that several clock genes may serve as entrainers or drivers of lunar periodicity. The Malabar grouper, Epinephelus malabaricus, is widely distributed in the Indo-Pacific Ocean and holds significant commercial value in aquaculture. This species exhibits lunar-synchronized spawning with a peak around the new moon, making it a valuable model for studying lunar periodicity. The aim of this study was to investigate the molecular mechanisms underlying lunar periodicity in the Malabar grouper. First, the key factors constituting the circadian clock, such as Bmal, Clock, Period and Cry, were partially cloned in this species. Focusing on Cry genes, these Cry genes (mgCryl. mgCry2 and mgCry3) were examined for their tissue distribution and daily variation. Subsequently, lunar variations in mgCry mRNA abundance in the brain were investigated. Real-time quantitative PCR analysis revealed daily variations in the mRNA abundance of mgCryl and mgCry2 in the diencephalon and telencephalon. Weekly changes in mgCry2, but not mgCryl, were found to be moon-dependent, with higher levels around the new moon, particularly when fish were reared under natural moonlight. Rearing fish under moonlight-blocked conditions resulted in increased mgCry gene expression in the pituitary during the night of the full moon, while no significant changes were observed in the diencephalon and telencephalon. In situ hybridization showed that mgCry2 mRNA was expresses in the lower part of the pituitary. From these results, mgCry genes in the brain of the Malabar grouper exhibits moon dependency, with changes according to the duration of darkness at night. It can be concluded that weekly changes in Cry genes in the brain play a role in entraining moon-dependent events in the Malabar grouper.博士（理学）琉球大学University of the Ryukyu
ホウ素同位体による地下水汚染の定量的評価とLA-(MC)-ICP-MSを用いたテクトニクスとマグマプロセスの地球化学的研究
Get PDFBased on the geochemical characteristics of boron, this study aimed to quantitatively assess groundwater contamination in islands of the low-island type of the Ryukyu Arc (southern part of Okinawa Island, Yoron Island, Tarama Island, and Kuroshima Island). On these islands, where Ryukyu limestone forms the aquifer, terrestrial human activities have affected groundwater quality. In these islands, the boron concentration and its isotopic composition in groundwater have positive and negative correlations with nitrate-nitrogen concentration in groundwater, indicating effectiveness of boron as a tracer. With boron data for possible contamination sources, I performed quantitative evaluation of contamination based on the mixing calculation between typical end-members. In addition, I developed the symplified separation method of boron in groundwater with low boron concentration. Three commercially available certified reference materials (CRM; riverwater and tap wataer) have been analyzed for the first time; δ11B values of CRM 7202-c, 0301-2, 7201-a are -8.81 ± 0.08‰, 14.33 ± 0.24‰, and 17.86 ± 0.07‰, respectively. These values are expected to be milestones in groundwater boron isotope studies, since there are very few reference materials in terms of validation of analytical method. The laser ablation (LA)-ICP-MS and LA-Multi-collecter (MC)-ICP-MS methods are analytical systems that can analyze trace elements (content and isotope ratios) in small areas on the surface of geoenvironmental solid samples with high resolution and accuracy. In this paper, this analytical system is applied to dating and estimation of magmatic processes conditions. Using LA-MC-ICP-MS, Sr isotope stratigraphic dating of bivalve fossils in sandstone dredged from sea knoll under a cliff at a water depth of ~1,000 m, the north off Kume Island, was carried out. The age of ~2 Ma was obtained, and this age and lithology were compared to the Aka Formation on Kume Island. The result suggests that the main formation (rifting) of the Okinawa Trough occurred after 2 Ma. Using LA-ICP-MS, trace element contents of apatite and zircon in the mafic-ultramafic Malayer Plutonic complex (ca. 170 Ma) in western Iran were determined. The results indicate that the magma became reducing conditions during magma differentiation in a hydrous basaltic magma reservoir.博士（理学）琉球大学University of the Ryukyu
真空成形を志向した熱可塑性樹脂の大変形粘弾性解析に関する研究
Get PDF熱可塑性樹脂の成形方法の一つである真空成形は,ブロー成形,射出成形など他のプロセスと比較して,低圧,金型コストが低く,成形品の大型化が可能であり,例えば航空・宇宙製品に適用されている.この手法は、材料を加熱軟化させて形状を成形するが、時間がかかり、材料の粘弾性が最終的な品質に影響を与える.従って,適切な条件選定には試行錯誤が伴う.本論文では,熱可塑性樹脂を用いた成形方法の一つである真空成形法を志向した成形シミュレーション技術構築を目的としており,本プロセスの特徴であるガラス転移点温度(T砂近傍かつ大変形下における熱可塑性樹脂の力学的特性を予測するための材料構成則の検討およびFEM解析の実施を行った.第1章では,本研究の背最と目的について述べる.第2章では,微小変形粘弾性解析の基礎理論について概説する.第3章では,真空成形適用を目的とした熱可塑性樹脂の特性評価に焦点を当て,具体的にはポリメタリクリル酸エステル(PMMA)の動的粘弾性を温度や周波数分散を通じて評価し,材料の熱粘弾性特性とガラス転移点(Tg)を明らかにする.さらに,393.15Kのガラス転移点温度域および約50％の大変形ひずみ域での長時間(25X103s)応カーひずみ挙動を解析するため,クリープおよび応力緩和の実験を行った結果をまとめる.第4章では,PMMAのクリープ特性を考慮した解析を目的とし,材料がゴム状態であること,そしてその動的特性が線形粘弾性論による演算の拡張により表現可能であるとの仮定を置いたこの前提の下,緩和時間が変形量に依存しないMaxwellモデルおよび等方性超弾性の一形態であるNeo-Hookeanモデルを力学モデルとして採用した.さらに,時間一温度換算則として,W.L.F.式の使用を選択した.粘弾性モデル及び解析手法の妥当性を評価するため,DMAによる実験データから材料定数を同定し,これを基にしたクリープ試験の予測結果と実際の試験データを比較検証した.その結果,提案手法は試験結果を適切に再現あるいは予測する能力を有しており,本手法の有効性が確認された.前章で述べたモデルは,クリープ解析における予測結果で良好な成果を示したものの,多数のMaxwellモデルの導入が必要であり,それに伴い決定すべき材料定数が増加するという課題があった.これにより,材料の動特性や物理的背景の理解が困難となっていた.これを解決するために,第5章では非整数階微分型の熱粘弾性モデルの開発を行った新たに提案されるこのモデルは,単一の超弾性バネと2つの非整数階微分要素から構成され,温度依存性をも考慮に入れている.このモデルを用いた幾何学的クリープ解析の実施と,クリープおよび応力緩和試験結果との比較検討を通じて,様々な試験条件下でのデータを適切に再現または予測することが可能であることを確認した.最後に6章で本研究を総括する．博士（工学）琉球大学University of the Ryukyu
分散型再生可能エネルギーと多様な負荷を有する不平衡配電系統の最適な運用と計画
Get PDF脱炭素社会へ向けた再生可能エネルギーの大量導入によって、配電系統における電圧不平衡の発生が懸念される。許容範囲を超える電圧不平衡は三相機器の不調や損失増加を招く恐れがあるため、適切に補償される必要がある。しかし、配電電圧制御に関する多数の先行研究において、電圧不平衡補償を考慮した研究は例が少ない。本研究では、以下に述べる研究項目に従って研究を遂行し、上述の課題に対処した。第一に、電圧不平衡評価指標の適切な選出について検討した。電圧不平衡評価指標は機関や組織に応じて多数の定義が存在し、これによって電圧不平衡の評価に混乱が生じている。このため、各評価指標が逆相電圧および零相電圧どの程度検出できるかを検証した。第二に、配電系統の線路上に設置される自動電圧調整器(SVR : Step Voltage Regulator)を用いた電圧不平衡補償について検討した。従来三相一括で電圧を制御するSVR の三相個別制御(3φSVR) を導入し、制御動作を最適化することで電圧不平衡補償への対応を可能とした。最適化手法として、離散変数の取り扱いに適したタブー探索法を用いた。電圧不平衡の低減、電圧逸脱・配電損失・制御動作回数などの複数の運用目標の改善、配電用変電所の負荷時タップ切り替え変圧器との協調動作を達成した。第三に、不平衡配電系統における3φSVR の多目的最滴配置について検討した。設置台数と制御効果は、トレードオフの関係となることが予想されるため、最適配置問題は設置台数および制御効果を目的関数とした多目的最適化問題として定式化した。多目的最適化手法として、0-1 変数に適したNSGA-II を適用し、設置台数毎の制御効果および最適な配置を明らかにした。第四に、不平衡配電系統の運用最滴化における目的削減について検討した。運用最適化においては四つ以上の目的関数が存在し求解が困難となるため、目的関数間のトレードオフの関係を明らかにし、目的関数の次元を削減することを試みた。主成分分析を用いることで、目的関数間の相関関係を明らかにした。全ての目的関数が相反関係にあるが、制約などの条件次第で目的関数が削減できる可能性が示された。第五に、3φSVR とスマートインバータの協調制御について検討した。3φSVR とスマートインバータ間で制御負荷を分担することにより、電圧制御に係る有効電力抑制量を削減することを目的とした。粒子群最適化により3φSVR のタップとスマートインバータの有効・無効電力出力を最適化することで、適正電圧を維持しつつ有効電力抑制量を80％程度削減することができた。第六に、モデル予測制御(MPC : Model Predictive Control)を適用した不平衡配電系統の運用について検討した。太陽光発電や負荷の予測情報に基づいて各機器の制御を効率化することを目的とした。MPC の適用により、予測に応じた適切な制御が可能となった。第七に、EV 導入が配電系統の電圧不平衡に及ぼす影響を調査した。EV の増加に伴い配電系統の電圧不平衡は悪化するが、3φSVR などによる最適電圧制御によってその影響を軽減できることを示した。博士（工学）琉球大学University of the Ryukyu