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Activity of International Research and Education for the Center for Rare Earths Research (Muroran Materia)
Get PDFapplication/pdfThe Center for Rare Earths Research (Muroran Materia) was established in 2012 at Muroran Institute of Technology. The purpose of this research center is to develop environmentally friendly materials that make effective use of rare earths, to make effective use of unused energy, and to conduct research from a multifaceted perspective on urgent issues related to materials and recycling technology. The center's activities include not only research, but also science enlightenment activities such as science schools, lectures by domestic and foreign researchers, international workshop, and educational programs at graduate school (environmental friendly materials engineering education program). In this article, we report on the international education and research activities of this center.特集departmental bulletin pape
水和反応モデルに基づく膨張コンクリートの力学的性質及び中性化深さの予測に関する研究
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdfコンクリート用膨張材（EX）は、コンクリートの乾燥収縮によるひび割れを低減するために広く用いられているが、膨張材とセメントの水和反応に基づいて膨張コンクリートの力学的性質及び耐久性の予測に関する研究は少ないのが現状である。そこで本研究では、膨張材を混和したコンクリートの初期材齢からの水和反応をモデル化するとともに，その水和反応モデルに基づいて膨張コンクリートの圧縮強度、中性化深さ及び膨張ひずみを予測する手法を確立することを目的としている。さらに、膨張コンクリートにおける圧縮強度、耐凍害性及び中性化抵抗性に及ぼす拘束条件の影響を実験的に把握している。本研究で提案した膨張材の水和反応モデルは、セメントの鉱物組成（C3S、C2S、C3A、C4AF）をパラメータとして用い、膨張材とセメントの水和率、水和発熱量、ゲルスペース比、ケイ酸カルシウム水和物（CSH）、水酸化ナトリウム（CH）、エトリンガイトの生成量及び空隙率を予測することが可能である。水和反応モデルから算出されたゲルスペース比から膨張コンクリートの圧縮強度を予測する関係式を示した。また、水和反応モデルからCH及びCSHの生成量を算出し，大気中のCO2のコンクリートへの拡散とCH及びCSHとCO2との反応を考慮して膨張コンクリートの中性化深さを予測するための数学モデルを提案した。さらに、水和反応モデルからエトリンガイトの生成量を予測し、乾燥収縮の影響と拘束の影響を組み合わせて係数化することで、膨張コンクリートの体積変化と膨張ひずみを予測する考え方を示した。また、提案した水和反応モデル及び各種予測結果を検証するために、水和発熱、膨張ひずみ、圧縮強度、空隙量、凍結融解抵抗性及び中性化抵抗性に関する実験を行っており、予測結果と実験結果が比較的良く一致することを確認している。圧縮強度の予測において，予測精度を向上させるための補正係数を見出した。さらに、拘束条件での膨張コンクリートの膨張ひずみを予測するための拘束程度に関わる係数を設定することで推定精度が向上することを示した。本研究の結果として，膨張材の水和反応モデルから膨張コンクリートの水和率、力学的性質及び中性化深さを予測可能であり、効果的かつ有用であることを示した。Although expansive additives have been widely used to efficiently reduce shrinkage cracking in concrete, little research has been undertaken to model the hydration reaction of cement and expansive additive blends and to predict the properties and durability of expansive concrete. In this study, a numerical model to simulate the hydration reaction of cement paste containing expansive additive at an early age is proposed and then the compressive strength, carbonation depth and expansion strain of expansive concrete is predicted based on the hydration reaction model. Additionally, the influence of restrained condition on the mechanical properties and durability such as frost resistance and carbonation resistance are also investigated in this research. Using the proposed model, this study predicted the hydration degree, rate of heat evolution, gel/space ratio, amount of calcium silicate hydroxide (CSH), calcium hydroxide (CH), ettringite of hardening cement-expansive additive paste, and porosity of expansive concrete. For the experimental investigation, rate of heat evolution test, under-water weighing test, length change ratio test, expansion strain test, compressive strength test, mercury intrusion porosimetry test, freezing-thawing test and accelerated carbonation test were performed to verify the proposed model and predicting equation. From the relationship between the gel/space ration and compressive strength, an equation was deduced for prediction of the development of compressive strength of expansive concrete. Considering the diffusion of CO2 in a gaseous phase into concrete pore and the reaction of CO2 with CH and CSH, a mathematic model was proposed to predict the carbonation depth of expansive concrete. A hypothesis was described to predict the expansion strain through a model the volumetric change of expansive concrete calculated by combining the formation of ettringite, influence coefficient of shrinkage and restraint degree coefficient. For verification of model and predicting equation, the results indicated good agreement of the calculated data with the measured data. Furthermore, this work also found that the model parameters (in hydration reaction model) can be represented as a function of the mineral composition of the cement. A coefficient was deduced to find the satisfactory value for predicted results (in predicting compressive strength). A restraint degree coefficient was found to build an equation for predicting the expansion strain of expansive concrete under restrained condition. The results demonstrate that the proposed model and equation are effective and useful in predicting the hydration, mechanical properties and carbonation depth of expansive concrete.doctoral thesi
High-temperature erosive wear characteristics and bonding requirements of hard carbides cast-in insertion multi-component white cast iron
No full textapplication/pdfThis research investigated wear resistance characteristics of hard carbide cast-in insertion cast iron by hightemperature erosive test. Moreover, good bonding conditions between cast iron and hard carbide alloy were examined by using casting simulation CAE. Two types of multi-component white cast iron with Cr, Mo, W, V, and Nb for base metal, tungsten carbide (WC) and titanium carbide (TiC) for insert were prepared. High-temperature erosion tests were conducted using alumina ball (average diameter: 1.16 mm, hardness: 1140 HV) with impact angle of 30, 60, and 90 deg. at 873 K. The air velocity of 100 m/s (particle velocity about 30 m/s). The total particle loading was 8 kg. The mass of the test specimen was measured before and after each test to evaluate the erosive wear property by erosion rate which is volumetric removal divided by the total feed of impact particles. As a result of erosion tests, WC cast-in insertion multi-component white cast iron showed good wear resistance characteristics compared with TiC one. TiC cast-in insertion multi-component white cast iron increased wear amounts due to cracking on insert surfaces that occurred by heat shock when pouring. Temperature history of interfacial molten cast iron and insert on solidification process were acquired by using solidification analysis to compere condition of molten steel and insert at the bonding interface. To longer liquid phase contact time is the thicker diffusion and reaction layer of each cast-in insertion sample. Both diffusion and reaction layers were created in the bonding interface of WC cast-in insertion sample. On the other hand, only diffusion layer was created in TiC cast-in insertion sample. These differences in bondability are due to diffusion coefficient of insert elements and gibbs standard free energy of carbides.journal articl
Amplitude and rotational speed control of variable length pendulum by periodic input
Get PDFapplication/pdfIn this paper, a control law to stabilize the amplitude or rotational speed of a variable length pendulum to a desired value by periodically changing the position of the center of gravity is proposed. First, the motion of the pendulum oscillating around a lower equilibrium point is analyzed using the averaging method, and a first-order differential equation for the amplitude of the pendulum is derived. Subsequently, using the derived equation of motion, a control law is designed to control the amplitude of the pendulum to the desired value. Similarly, the motion of a pendulum rotating continuously around the rotation axis is analyzed, the first-order differential equation for the angular velocity of the pendulum is derived, and then a control law of the rotational speed is designed. The derived nonlinear feedback control law consists of the amplitude, angle, and angular velocity of the pendulum in the case of amplitude control, and in the case of rotational speed control, the rotational velocity and angular acceleration of the pendulum. Finally, by using the proposed control method, it is shown that the amplitude and rotational speed of the pendulum can be controlled to the desired values.journal articl
Optimal design of NRD guide devices using 2D full-vectorial finite element method
Get PDFapplication/pdfIn this paper, we propose an optimal design approach based on a concept of mosaic-like structure for achieving high performance NRD devices. In order to improve design efficiency, we employ the recently proposed two-dimensional full vectorial finite element method (2D-FVFEM) which can accurately model 3D structure of NRD as a numerical simulation method. As an optimization method, we employ either direct binary search (DES) algorithm or genetic algorithm (GA) depending on design problems. In order to show the usefulness of our approach, design examples of crossing and T-branch waveguides are considered and high transmission efficiency greater than 99.9% for crossing waveguide and 49.8%: 49.8% for T-branch waveguide is achieved. The numerical results by 2D-FVFEM are verified by 3D-FVFEM.journal articl
耐衝撃挙動を考慮した落石防護柵支柱の根入れ深さ決定法に関する基礎的研究
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdf本研究では，無筋コンクリート製落石防護擁壁天端に設置されている防護柵支柱の根入れ深さに関する耐衝撃性を考慮した合理的な設計手法を確立することを目的に，無筋コンクリート躯体（以後，躯体）中に支柱を貫通させた場合や根入れ深さを有限長とする場合の試験体を作製し，静荷重及び重錘落下衝撃荷重載荷実験を実施した。測定項目は，載荷荷重，載荷点変位，支柱各点の軸方向ひずみに関する時刻歴波形および躯体のひび割れ分布である。本論文の構成は，以下の通りである。第１章では，本研究の背景および現行設計法の考え方，研究の目的について述べている。第２章では，本研究で用いた実験装置および計測器の概要について述べている。第３章では，支柱を躯体中に貫通させた場合の曲げが卓越する載荷状態に着目し，静荷重および衝撃荷重載荷実験について述べている。実験結果より，静荷重載荷時には基部近傍に塑性ヒンジが形成され，降伏荷重程度に漸近することを明らかにしている。衝撃荷重載荷時には，最大荷重は全塑性荷重程度であることや，コンクリート基部前面（以後，基部）のひび割れ分布は支柱の上下フランジ端部から上下45°方向にひび割れが進展すること，現行設計法による根入れ深さは，実験結果に比較して安全側の結果を与えること等を明らかにしている。第４章では，曲げとせん断が連成する場合に関する実験について述べている。実験結果より，平均衝撃力は全塑性荷重程度であることや，入力エネルギーが大きい場合には支柱下部のコンクリートがブロック化して剥落する傾向を示すこと等を明らかにしている。第５章では，第３章，第４章で得られた実験結果を基に，最大変位及び残留変位と入力エネルギー関係について論じ，載荷点位置に拘わらず最大変位と残留変位は入力エネルギーに対して線形な分布性状を示すことを明らかにしている。 第６章では，根入れを有限長にした場合における，第４章と同様の実験について述べている。実験結果から，根入れが確保されている場合には基部近傍に塑性ヒンジが形成されること，根入れが確保されていない場合には静荷重載荷時には押抜きせん断破壊に至ること，衝撃荷重載荷時には支柱下部コンクリートがブロック化して剥落する傾向を示すこと，現行設計法に基づく根入れ深さは実験結果に対して安全側の評価を与えること等を明らかにしている。第７章では，総括として本研究で得られた結果をまとめると共に，今後の課題と展望について述べている。Rockfall protection walls and fences were constructed along the roadsides with steep cliff to ensure the safety of people’s lives and transportation networks. Generally, the walls were made of plain concrete and the base of steel posts of the fences were embedded into the top of the walls. Normally, the anchoring depth of the posts has been designed following the specification which is constituted with not considering the dynamic effect due to the rocks impacting but considering only static loads. It may be important to investigate an applicability of the design method to the impact loading. In order to establish a rational design method, static and drop-weight impact loading tests of small sized H-section post models supported by anchoring one end into the plain concrete block were conducted, in which the anchoring depth and input impact energy were varied. In these experiments, the time histories of impact force, deflection at the loading point, and the axial strain distribution along the depth of the post were measured and crack patterns of the concrete block after experiments were inspected. The results obtained from this study are as follows: (1) the plastic hinge was formed in the post near the base of the concrete block under not only static but also impact loading; (2) in the case of that the anchoring depth was sufficient, the maximum and residual deflection at the loading point may linearly increase corresponding to an increment of the input impact energy; (3) even if the anchoring depth was insufficient, the concrete cover underneath of the post may be exfoliated; (4) the anchoring depth obtained from the impact load testing tends to be decreased comparing with that from static one; and (5) the required anchoring depth obtained following the current design specifications approximately corresponds to that obtained from the experimental results.doctoral thesi
高天端人工リーフの安定性に関する実験的検討
Get PDF高天端人工リーフの安定性は，被覆ブロック構造で松田らなど一部の既往研究が存在するものの，消波ブロック構造での研究事例はほとんどない．本検討は，断面二次元固定床実験を実施し，検討事例が少ない高天端人工リーフの被災形態を分析，堤体安定性の検討を行った．その結果，1)捨石マウンドの沖側法肩部分での被災に伴い，ブロックの安定性が損なわれる危険性があること，2)高天端人工リーフは，戻り流れにより被災する場合が多く，必要ブロック質量はハドソン式で算定した値よりも大きくなること，3)高天端人工リーフにおいて，乱積では有脚軸型ブロックより放射型ブロックの方が安定性が高い可能性があること，4)本実験と既往研究から，人工リーフの安定性が最も危険となる条件が，潮位と天端高が一致する場合であることが示唆された．There are few research cases of stability of high-top artificial reef although there are some previous studies in the case of coated blocks. In the case of high top artificial reef whose crown height is as high as the design high tide level, wave power caused by the impact of waves and flow caused by wave breaking and return flow on the dyke are thought to affect the stability of the dyke. Therefore, it is unclear whether stability can be evaluated by a desk study such as Hudson's formula because of complicated wave/flow field compared to general breakwaters and artificial reefs.
In this study, two-dimensional hydraulic model experiment was conducted to analyze the damaged pat- terns of the high-top artificial reef, which have very few cases of study, and to examine the stability of the dyke stability. The results shows that (1)there is a risk that the stability of the block could be impaired due to the damage on the offshore shoulder of the rubble mound, although the focus is on the required block mass in the desk study of stability of offshore wave-dissipating facilities, (2)although the damage patterns of the high-top artificial reef was damaged by both pushing and pulling waves, it was often damaged by the pulling waves, and necessary mass of the block was larger than the required mass calculated by Hudson's formula, (3)in case of installing high-top artificial reef by random stacking of blocks, radial type blocks may be more stable than legged shaft type blocks, (4) considering this experiment and previous studies, the most dangerous condition for the stability of artificial reef is when the crown height and the tide level are equivalent.journal articl
電気抵抗の計測による舗装層間の水分検知技術の適用性に関する検討
Get PDF舗装ひび割れ部や縁石・地覆前面の舗装端部などから浸入した雨水や融雪水は，舗装層間などの空隙を通じて舗装体内に広がり，層間剥離やポットホール発生の要因となっている．さらに，凍結融解作用が加わると，このような舗装損傷が加速する．このため，舗装内への水分の浸入を抑制する適切な止水技術や補修方法が求められている．本研究では，舗装層間に浸入した水分を直接検知する技術の開発を目的として，電気抵抗の計測による水分検知技術の適用性について室内および屋外において検討した．その結果，舗装層間に銅箔を用いた電極を埋設し，電気抵抗を計測することにより，層間の水分検知が可能であることが明らかになったことから，本研究で提案する技術は，止水技術等の性能評価に利用できる可能性が示唆された．Rainwater and snowmelt water enter from cracks in the pavement and from the edges of pavement. These waters spread between the layers of pavement. And it causes delamination and potholes. Furthermore, the addition of freeze-thaw action to these accelerates pavement damage. Therefore, a technology that appropriately suppresses the ingress of water is required. The purpose of this research is to develop a technology to detect the moisture between layers of pavement. This technology is necessary to evaluate the performance of the technology that suppresses the ingress of water. In this study, the applicability of technology to detect moisture by measuring electrical resistance is discussed. Electrical resistance was measured using copper foil electrodes. Based on the various test results, it was found that the developed technology can be detected the moisture infiltrated between the layers of pavement.journal articl
On the Intonation Patterns of Danish Interrogatives
Get PDFapplication/pdfThis paper will inquire into the patterns of sentence-final melodies found in several interrogatives in Danish. A large number of studies have been made on Danish interrogative intonation, but their academic attention has only been paid to interrogatives with simple and complete syntactic construction. In contrast to those previous studies, this paper will shed a light on interrogatives with syntactically incomplete and exceptional structures, such as echo-questions and tag questions. The author conducted several field researches with one native speaker and elicited many phonetic data of various types of interrogative sentences through read-aloud tasks. Through careful consideration of the elicited data, the following important facts are revealed: a) the words appearing in a sentence-final position always determine the sentence-final melodies; it is not crucial whether an interrogative is wh- or Yes/No-question, and it is also irrelevant whether an interrogative has a complete and regular sentence structure or not. b) tonal patterns of the final words appear as terminal melodies of interrogative sentences. i) contrary to what the previous studies have claimed, interrogatives will have a rising tone when a sentence-final word is oxytonal and lacks stød. ii) otherwise, a sentence-final melody will be either a globally high and level tone or a falling tone when it especially has stød. Almost no textbooks and grammars of Danish devote any pages to interrogative intonation. In this sense, the present study will be quite significant in both linguistic/academic and pedagogical respects.学術論文departmental bulletin pape
Effect of Carbon Content on Three-body Abrasive Wear Characteristics of 28Cr-3Ni Cast Alloys
Get PDFapplication/pdfAbrasive wear resistance of white cast iron can be improved by adding transition metals due to carbide formation and matrix stabilization. However, it must also be affected by carbon content which has received little attention from researchers. Therefore, this study would investigate the influence of (1.4 and 2.8 wt.%) C on three body abrasive wear characteristics of 28Cr-3Ni cast alloys. High Cr-based multi-component white cast irons (Hi-Cr MWCIs) were used as comparison materials to estimate the life-service of each material. The abrasion test was performed using a rubber wheel abrasion machine test with two different sizes of silica sands (1100HV1). As results, the microstructure consists of martensite (the main matrix) and M7C3 carbide. Additionally, M2C carbide was also precipitated on the microstructure of Hi-Cr MWCIs. Meanwhile, Ni or Co was embedded in the matrix area of materials microstructure. In the case of 28Cr-3Ni, the higher amount of C has a higher carbide volume fraction and hardness leading to be better abrasive wear resistance at high loads. However, the reverse trend occurred at low loads with different sizes of abrasive particles. By comparing to Hi-Cr MWCIs, its abrasive wear resistance is lower owing to the fewer carbide types. In the case of Hi-Cr MWCIs, the higher Cr addition significantly consumes C content during the solidification process resulting to lower hardness and wear resistance. Therefore, it can be concluded that the three abrasive wear performance of materials is strongly influenced by C content, applied load, and abrasive particle size.journal articl