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非補強レンガ積みの曲げ、せん断およびねじり挙動に対するポリプロピレンバンドの補強効果
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）毎年、ベトナムはいくつかの台風に見舞われる。既往の研究によれば、2000年から2017年までの間の国内災害関連被害の80％は台風に伴う強風によるものであり、その被害の7割は破壊する構造を有するセミパーマネント住宅である。
本研究は、ベトナムでのセミパーマネント住宅の強風被害を軽減することを目的とした。強風被害を受けやすい無補強レンガ積み壁を対象に、提案したポリプロピレン（PP）バンドを利用する補強方法の有効性について実験的に検討した。さらに、PPバンドによって補強されたレンガ積み壁の挙動についてさらなる示唆を得るために、実験結果から重要なパラメータを設定した有限要素モデルを用いて数値解析を行った。
実験的検討では、曲げ試験用9体、せん断試験用30体、ねじり試験用10体の合計49体の試験体を製作した。得られた知見は次のとおりである。曲げ試験では、PPバンド試験体の初期ひび割れ時および破壊時の荷重は、無PPバンド試験体に比べて大きかった。せん断試験では、圧縮応力度の大小にかかわらず、PPバンド試験体の最大荷重および初期剛性は無PPバンド試験体と顕著な差がなかった。ねじり試験では、PPバンド試験体の初期ひび割れ時の荷重と変形は無PPバンド試験体に比べて大きかった。これら3種の試験ともに、PPバンド試験体では初期に最大荷重を示した後に一度大きく荷重が低下し、その後は荷重が徐々に上昇し最終時まで変形能力が確保された。PPバンドを2枚の平鋼ワッシャーの間に挟み、レンガの側面に埋め込んだプラスチックプラグに鋼ネジで固定する、提案された固定方法によるPPバンド補強は、レンガとモルタルの界面での剥離を制限し、レンガ積みの耐風性能を向上させる。特に、PPバンド補強は曲げ挙動に有効である。
数値解析では、レンガと目地モルタルはインターフェース要素を介して接続されているとした有限要素解析を行った。PPバンドなしの解析モデルの結果は、実験でみられたレンガとモルタルの界面におけるひび割れの発生位置や進展状況を適切に評価した。また、PPバンドの補強効果を、提案された固定方法の力学的性状を基にモデル化することを試みた。このモデル化によるPPバンドありの解析モデルの結果は、実験結果にみられた一度大きく荷重低下した後の評価ができていないものの、初期の実験結果は比較的良く評価できた。Vietnam faces several typhoons every year. According to past research, 80% of domestic disaster-related damage from 2000 to 2017 was caused by strong winds associated with typhoons, and 70% of this damage was to semi-permanent houses with structures that could be destroyed.
This research aimed to reduce strong wind damage to semi-permanent houses in Vietnam. I experimentaliy investigated the effectiveness of a proposed reinforcement method using polypropylene (PP) bands for unreinforced brick masonry walls that were subject to damage from strong winds. In addition, to obtain further insights about the behavior of brick masonry walls rainforced by PP bands, numerical analysis was performed using finite element models with key parameters set from the experimental result.
In the experimental study, a total of 49 specimens were manufactured: 9 specimens for bending tests, 30 specimens for shear tests, and 10 specimens for torsional tests. The findings obtained are as follows: In the bending test, the initial cracking and fracture loads of the PP band specimen were larger than those of the non-PP band one. In the shear test, there was no significant difference in the maximum load and initial stiffness of the PP band specimen compared to the non-PP band one, regardless of the magnitude of compressive stress. In the torsional test, the load and deformation at the initial cracking of the PP band specimen were larger than those of the non-PP band one. In these three test types, the PP band specimen showed the maximum load at the beginning, then the load decreased significantly, and then the load gradually increased and the deformation capacity was maintained until the final stage. The PP band reinforcement using the proposed fixing method, in which the PP band is sandwiched between two flat steel washers and fixed with steel screws to a plastic plug embedded in the sides of the bricks, limits the delamination at the brick-mortar interface. This improves the wind resistance performance of the brickwork. In particular, PP band reinforcement is effective for bending behavior.
In the numerical analysis, a finite element analysis was performed assuming that the bricks and joint mortar were connected through the interface element. The results of the analytical model without the PP band approximately evaluated the location and progress of cracks at the brick-mortar interface observed in the experiment. I also attempted to model the reinforcing effect of the PP band based on the mechanical properties of the proposed fixing method. Although the results of the analytical model with the PP band based on this modeling cannot evaluate the experimental behavior after the load decreased significantly, the initial experimental results could be evaluated relatively well.doctoral thesi
Guided Mode Analysis of NRD Guide Using Efficient FEM With Impedance Boundary Conditions for THz Applications
Get PDFNumerical modeling of very thin structures, specifically in the THz region, required extremely fine discretization, which increased both the complexity and the computing cost. Impedance boundary conditions are a promising method for the accurate modeling of waveguides without any discretization due to their high level of accuracy, ease of implementation, and low computation cost. In this paper, we developed a finite element method with impedance boundary conditions for modeling NRD guides, taking into account conduction loss, which is not ignorable in the THz domain. In order to show the effectiveness of the proposed technique, we performed a guided mode analysis of the NRD guide for both hybrid LSM01 and parasitic LSE01 modes. Excellent accuracy and very low computational cost are confirmed by comparing the results obtained by the proposed technique with conventional 3D-FEM. In addition, we also proposed the modified structure of the NRD guide, which greatly reduces the loss compared to the conventional one. The proposed technique and structure may have a potential for various high-performance NRD guide devices for 6G integrated circuit applications and beyond.journal articl
大型鋳鋼品におけるポロシティと疲労強度との相関
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）プレス部材，圧延機用ロールスタンドなど数 100 トンを超える鋳鋼品は大型鋳鋼品と言われる．これらは，使用環境が過酷であることから高い靭性と繰り返し荷重に長時間耐えうることができる高い疲労限度を有し，溶接性に優れ高強度であることが求められる．しかし，鋳鋼品では不可避的に鋳造欠陥（ポロシティ）や割れが発生する．本研究では，鋳鋼品における鋳造欠陥と疲労強度との相関について解明し，鋳造方案立案や疲労限度を推定することを目的とした．
鋳鋼品において凝固解析技術を駆使し，鋳造欠陥（ポロシティや割れ）を精度よく予測することは，健全な鋳物を製造するため，欠かすことができない技術である．本論文では凝固解析における各種材料物性値を検討し，連続測温により得られた冷却曲線より最適な物性値を設定することができた．また，疲労限度を顕著に低下させる凝固割れを予測する技術も必要不可欠である．本実験結果より鋳鋼における割れ発生メカニズムを解明し，割れ感受性指標と割れとの相関を得た．得られた結果から凝固解析に反映することで複雑形状品でも凝固割れを予測することが可能となった．
また，極値統計法，X 線 CT 装置を活用した疲労限度予測について検討した．NiCrMo鋼に発生するポロシティが疲労限度に与える影響について√を用いて調査し，疲労限度予測式を推定することができた．そして，欠陥評価に産業用 X 線 CT システム及びマイクロ X 線 CT システムを使用し，一般的な大型鋳鋼品に用いられる SCW480 鋼において鋳鋼品内部に発生する欠陥と疲労限度の関係を調査した．その結果より応力勾配を考慮した予測式を導出し，X 線 CT を用い試験材内部の欠陥面積，中立線からの距離を測定することで疲労限度予測式を導出した．また、組織が異なる各種供試材においても疲労限度予測式から算出した値は誤差 10％以内で疲労限度を予測可能であることを確認した．
大型鋳鋼品において凝固解析によるポロシティ予測と疲労限度予測式を導出したことから実機品におけるポロシティ予測と疲労限予測を実施した．凝固解析及び疲労限度予測を実施し，製品品質を評価した．凝固解析では健全度予測を満足する鋳造方案を立案し可能な限り健全な鋳鋼品を製造する．凝固割れ解析を実施し，最大応力部に割れが発生しないよう製造する．応力解析を実施することで疲労限度を予測する．以上の手法，手順により製造することが健全な鋳鋼品を製造する上で最重要であることが分かった．今後，本製造方法を適用し製造すべきである．Steel castings that weigh more than several hundred tons, such as press components and roll stands for rolling mills, are called large castings. Because of the harsh operating environment, these products must have high toughness, a high fatigue limit that can withstand repeated loading for a long period of time, and high strength with excellent weldability. However, cast steel products inevitably suffer from casting defects (porosity) and cracking. The purpose of this study is to elucidate the correlation between casting defects and fatigue strength of cast steel products and to estimate the casting method and fatigue limit.
The accurate prediction of casting defects using solidification analysis technology is an indispensable technique for the production of sound castings. In this paper, various material properties in solidification analysis are investigated, and the optimum property values are determined from cooling curves obtained by continuous temperature measurement. It is also essential to have a technique to predict solidification cracking, which significantly reduces the fatigue limit. From the experimental results, the mechanism of cracking in cast steel was clarified, and a correlation between cracking susceptibility indices and cracking was obtained. The obtained results can be reflected in solidification analysis to predict solidification cracking even in complex-shaped products.
The influence of porosity generated in NiCrMo steel on fatigue limit was investigated using extreme value statistical method and X-ray CT system, and the fatigue limit prediction equation was estimated. In addition, the relationship between the fatigue limit and the defects inside the castings of SCW480 steel, which is generally used for large castings, was investigated by using an industrial X-ray CT system and a micro X-ray CT system for defect evaluation. From the results, a prediction equation considering the stress gradient was derived, and the fatigue limit prediction equation was derived by measuring the defect area and the distance from the neutral line inside the specimen using the X-ray CT system. It was confirmed that the fatigue limit could be predicted within an error of 10% for various specimens with different microstructures.
Porosity and fatigue limit prediction equations were derived for large cast steel products by solidification analysis. The product quality was evaluated by solidification analysis and fatigue limit prediction. In the solidification analysis, a casting plan that satisfies the soundness prediction is developed to
produce as sound a cast steel product as possible. Solidification cracking analysis is conducted to ensure that cracking does not occur in the area of maximum stress. To predict the fatigue limit by conducting stress analysis. It was found that the above methods and procedures are the most important for producing sound cast steel products. This manufacturing method should be applied in the future.doctoral thesi
Sharp Interface Limit for a Quasi-linear Large Deviation Rate Function
Get PDFWe discuss the sharp interface limit, leading to a mean curvature flow energy, for the rate function of the large deviation principle of a Glauber+Kawasaki process with speed change. We provide an explicit formula of the limiting functional given by the mobility and the transport coefficient.journal articl
Usage of Polynesian words for “water”
Get PDF多くのポリネシア諸語においては、「淡水」と「海水」の区別が語彙的に明確な形でなされているか、或いは、淡水と海水の明確に区別せず一般的に水を表す語を用いる言語でも、別途専ら「海水」を表す語が存在するという事例が多くみられた。これには淡水と海水の区別の重要性が反映しているものと考えられる。水以外の様々な水状の液体については、概して、甘いものは淡水又は水（一般）の下位区分として、塩気のあるものは海水の下位区分として分類される傾向がみられた。また、薬及び身体から出される液体については淡水又は水（一般）の下位区分として分類される傾向がみられた。journal articl
Memoirs of the Muroran Institute of Technology No. 73
Get PDFapplication/pdf個々の収録アイテムdepartmental bulletin pape
A Study Using Thematic Maps for Vocabulary Acquisition in Japanese and Colombian University English Classes
Get PDFThis paper examines the effectiveness of using thematic maps as a tool for teaching in CLIL and EFL
contexts by focusing on how they improve vocabulary acquisition and retention among undergraduate
university students in Japan and Colombia. The data collected from pretest and posttest vocabulary test
scores indicate that using thematic maps can progress students' vocabulary acquisition and retention.
The study shows that thematic maps can assist in teaching new vocabulary and improving student’s
knowledge of English speaking countries, as they provide a visual representation of words in context
and encourage students to analyze, interpret and explain real-world information. This paper also
provides insights for educators in CLIL/EFL classrooms via classroom procedure descriptions of map
usage and thus its utility can be replicated.departmental bulletin pape
Reversal Structure in the New Testament ‘Epistle to the Ephesians’: Verification Based on Murai’s Chiastic Structure
Get PDF本稿では、新約聖書の「エペソ人への手紙」の分析を、裏返し構造の特徴と照合する観点からおこなった。裏返し構造は、異郷訪問譚における構造上の「共通の約束」であるとされてきた一方で、聖書テキストにおいては、異郷訪問譚の形式ではないにもかかわらず、当該構造がみとめられる事例があることが報告されている。本稿の目的は、聖書テキストに裏返し構造がみいだされることの蓋然性を検証するところにある。本稿の知見によれば、「エペソ人への手紙」は裏返し構造により構成されている。journal articl
Improvement of Channel Capacity of MIMO Communication Using Yagi-Uda Planar Antennas with a Propagation Path through a PVC Pipe Wall
Get PDFThis study investigates the improvement of the channel ca-
pacity of 5-GHz-band multiple-input multiple-output (MIMO) communica-
tion using microwave-guided modes propagating along a polyvinyl chloride
(PVC) pipe wall for a buried pipe inspection robot. We design a planar
Yagi–Uda antenna to reduce transmission losses in communication with
PVC pipe walls as propagation paths. Coupling efficiency between the an-
tenna and a PVC pipe is improved by attaching a PVC adapter with the same
curvature as the PVC pipe’s inner wall to the Yagi–Uda antenna to eliminate
any gap between the antenna and the inner wall of the PVC pipe. The use
of a planar Yagi–Uda antenna with a PVC adaptor decreases the transmis-
sion loss of a 5-GHz-band microwave signal propagating along a 1-m-lomg
straight PVC pipe wall by 7 dB compared to a dipole antenna. The channel
capacity of a 2 × 2 MIMO system using planar Yagi–Uda antennas is more
than twice that of the system using dipole antennas.journal articl