研究者詳細 - 木本　和志

論文 - 木本　和志

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Ultrasonic measurement in variation of a degree of saturation in compacted bentonite 査読

Shun Kimura, Kazumi Kitayama, Kazushi Kimoto, Katsuyuki Kawamura, Hiroshige Kikura

Energy Procedia 131 428 - 435 2017年12月

担当区分：最終著者掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier BV

Bentonite, which is a kind of clay, is considered as a candidate for a buffer material in a geological repository of the high-level radioactive waste. Bentonite could provide long-term isolation of the radioactive waste because of its high adsorption capacity, low water permeability and good swelling property. In the context of long-term safety of disposal management, understanding groundwater behavior in bentonite buffer is one of the important issues, related to evaluating its long-term performance. In order to understand water behavior in compacted bentonite, the ultrasonic measurement was focused on. However, Ultrasonic wave propagation in compacted bentonite has not been understood well. Therefore, in this study, high spatial measurement system with Laser Doppler Vibrometer was developed in order to observe the ultrasonic wave propagation in compacted bentonite specimen. Ultrasonic wave propagation in compacted bentonite surface was measured. As a result, ultrasonic wave reflection was observed on the boundary between two different degrees of saturation. Thus, the capability of the developed system for investigation of the wave propagation in compacted bentonite is confirmed.

DOI： 10.1016/j.egypro.2017.09.417

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An elastodynamic computational time-reversal method for shape reconstruction of traction-free scatterers 査読

Kazushi Kimoto, Kazuyuki Nakahata, Takahiro Saitoh

Wave Motion 72 23 - 40 2017年7月

岩石材料中を透過する波動の位相特性査読

佐藤忠信, 木本和志

土木学会論文集A2（応用力学） 73 ( 2 ) I_73 - I_84 2017年

A finite difference method for elastic wave scattering by a planar crack with contacting faces 査読

Kazushi Kimoto, Yasuaki Ichikawa

Wave Motion 52 120 - 137 2015年1月

充填構造を考慮した不飽和砂の熱伝導率発現機構に関する研究査読

岩崎佳介, 木本和志

土木学会論文集A2（応用力学） 71 ( 2 ) I_595 - I_604 2015年

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人土木学会

本研究は，不飽和砂を気-液-固相の三相周期多孔質媒体としてモデル化してマクロ熱伝導率を求め，飽和度と固相粒子の充填構造の違いが不飽和砂の熱伝導性に与える影響を数値解析により調べたものである．ここでは，3種類の充填構造について，間隙部に設けた液相領域の位置と大きさを変化させて熱伝導解析を行うことで，マクロ熱伝導率を飽和度の関数として求めた．その結果，充填構造の違いは，熱伝導率の絶対値に与える影響が大きいこと，液相領域の間隙内位置と量は，飽和度と熱伝導率の関係を大きく変化させることが明らかとなった．また，本研究で提案したモデルにより，既往の研究で知られている，熱伝導率と飽和度の関係を表す代表的な3種類の曲線形が，数値解析により再現可能であることが示された．

DOI： 10.2208/jscejam.71.i_595

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A new theoretical mineral dissolution rate equation for physicochemical factors 査読

CHOI JUNGHAE, ICHIKAWA YASUAKI, KIMOTO KAZUSHI, Chae Byung-Gon

GEOCHEMICAL JOURNAL 49 ( 5 ) 549 - 557 2015年

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：GEOCHEMICAL SOCIETY OF JAPAN

The dissolution rate of minerals is affected by not only physical factors but also chemical factors, such as temperature, solid applied stress, pore water pressure and pH. In general, previous studies on mineral dissolution have dissociated these physical and chemical factors. In this paper, we propose a new dissolution rate equation for quartz dissolution that considers the physical and chemical effects of dissolution. Therefore, the reaction rate constant (k), which is the most important factor in the calculation of the reaction rate, was separated into three individual terms: temperature, solid applied stress and pore water pressure. Finally, the theoretical dissolution rate equation is proposed in this study; the equation contains all of the parameters that are related to the dissolution mechanism, such as temperature, solid applied stress at contact zone, pore pressure and pH conditions. To verify the proposed equation, it is compared with the experimental results, which were collected under various physical and chemical conditions; the equation is found to fit the experimental data well.

DOI： 10.2343/geochemj.2.0384

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Multi-species diffusion analysis in porous media under various dry density and temperature conditions: molecular dynamics simulation, homogenization analysis, and finite element method 査読

Jung Hae Choi, Katsuyuki Kawamura, Kazushi Kimoto, Yasuaki Ichikawa, Byung-Gon Chae

International Journal for Numerical and Analytical Methods in Geomechanics 38 ( 16 ) 1744 - 1760 2014年11月

含水した砂質土の熱応答特性に関する実験および数値解析査読

岩崎佳介, 木本和志, 市川康明

土木学会論文集 A2(応用力学) 70 ( 2 ) I_115 - I_124 2014年

担当区分：責任著者記述言語：日本語出版者・発行元：Japan Society of Civil Engineers

土壌は熱伝導率の大きく異なる三相から成るがそれらの構成比だけでなく形状によっても熱伝導率は変化する．本研究では砂質土の微視的な構造を三次元多孔質体モデルとして提案・作成し，熱伝導解析により熱伝導率の推定を行うとともに，豊浦砂を試料としてカラム供試体を作成し，室内実験と逆解析により試料の熱伝導率を推定することで，得られた熱伝導率と飽和度の関係から三次元モデルの妥当性を検討した．

DOI： 10.2208/jscejam.70.I_115

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リアルタイム波動伝搬シミュレータを援用した時間反転法による欠陥の映像化査読

中畑和之, 木本和志, 廣瀬壮一

非破壊検査 : journal of N.D.I 62 ( 9 ) 467 - 468 2013年9月

Quartz dissolution experiments at various pH, temperature and stress conditions: CLSM and ICP-AES investigations 査読

Jung Hae Choi, Kazushi Kimoto, Yasuaki Ichikawa

Environmental Earth Sciences 66 ( 8 ) 2431 - 2440 2012年8月

Reconstruction of Flaws in Heterogeneous Media Using Image-Based FIT and Time Reversal Approach 査読

NAKAHATA Kazuyuki, KIMOTO Kazushi

Journal of Solid Mechanics and Materials Engineering 6 ( 6 ) 771 - 781 2012年

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

Most commercial ultrasonic phased array systems implement B- and C-scan methods which use flight time and amplitude of flaw echoes. However, these methods are based on the fundamental ray-tracing theory in homogeneous media, and they are not directly applicable to heterogeneous media because of the complicated phenomenon of wave propagation. Time reversal techniques are adaptive methods that can be used in nondestructive evaluation to improve flaw detection in heterogeneous media. In this study, we propose a simulation-aided flaw imaging method based on the time reversal approach. Scattered waves from a flaw are recorded using an array transducer, and the time-reversed waves are re-emitted in the image-based FIT simulation. The re-emitted waves propagate through the heterogeneous media and focus on the flaw. The shape of the flaw can be visually estimated from the focal point of the ultrasonic wave in the simulation.

DOI： 10.1299/jmmp.6.771

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Real-time image-based FIT simulation using GPU computing and its application to nondestructive testing

Kazuyuki Nakahata, Kazushi Kimoto

ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers 4285 - 4297 2012年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

A signal prediction simulation tool for ultrasonic testing (UT) has been developed by combining the finite integration technique (FIT) with an image-based modeling approach. A realistic numerical model of a target can be made directly from digital images such as X-ray CT and three dimensional point cloud data. The image-based FIT for UT is accelerated using graphics processing units (GPUs) with Compute Unified Device Architecture (CUDA) Fortran. The methodology is described, and checked by numerical experiments using multiple GPU boards. The calculation speed can be dramatically improved compared to that obtained by running the same simulation on a conventional CPU. As an application of the image-based FIT, we propose a simulation-aided flaw reconstruction method for UT by means of the time reversal approach. Scattered waves from a flaw are recorded using an array transducer, and the time-reversed waves are re-emitted to numerical model in the FIT simulation. The re-emitted waves propagate through the heterogeneous media and focus on the flaw. The shape of the flaw can be visually estimated from the focal point of the ultrasonic wave in the simulation.

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斜角探傷用アレイ探触子を用いたFSAP方式による内部欠陥の超音波画像化査読

中畑和之, 竹内裕幸, 木本和志

日本機械学会論文集 A編 77 ( 779 ) 1112 - 1122 2011年

担当区分：最終著者掲載種別：研究論文（学術雑誌）出版者・発行元：The Japan Society of Mechanical Engineers

There is a phased array technique which makes use of flaw echoes, measured by every two-element combination as a pulser and a receiver, to synthesize high amplitude beams for any arbitrary angle and/or focal depth. Using this full waveform sampling and processing (FSAP) technique, we show a flaw reconstruction method for the angle beam phased array ultrasonic testing. In the case of the angle beam testing, it is necessary to estimate a beam path from a wedge to a specimen appropriately and to consider the mode conversion at the wedge-specimen interface. The main feature of our method is the use of processed wave data, called "scattering amplitude", which is extracted from each flaw echo. First, the basic principle of the reconstruction method is described and then some flaw reconstructions are demonstrated. The resolution of the flaw images and the accuracy of flaw sizing can be improved by means of the scattering amplitude.

DOI： 10.1299/kikaia.77.1112

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Flaw shape reconstruction using topological gradient for 2d scalar wave equation 査読

K. Kimoto, S. Hirose

REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION, VOL 27A AND 27B 975 672 - 679 2008年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AMER INST PHYSICS

This study is concerned with a non-linear inverse scattering technique called Time-Domain Topological Gradient (TDTG) for 2D wave equation. The TDTG is a recently developed shape optimization technique for elastodynamic problems with several potential advantages. The method, however, hasn't been used in the context of array ultrasonic imaging. In this study, performance of the TDTG is investigated numerically and experimentally by solving two example problems. The first is a numerical example in which a vertical slit in a plate is reconstructed from simulated data. The second one is a reconstruction from experimental data. Ultrasonic signals from a side-drilled hole in a steel block specimen are measured by an array transducer. The profile of the hole is reconstructed from those ultrasonic signals in the second problem. The results show that the TDTG can effectively use the phase focused beam fields, and very accurate in reconstructing not only a flat object but also a round one.

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動弾性有限積分法を用いた波動伝搬解析のためのイメージベースモデリング査読

中畑和之, 木本和志, 廣瀬壮一

計算数理工学論文集 7 ( 2 ) No. 17-080317 2008年

A Large Scale Simulation of Ultrasonic Wave Propagation in Concrete Using Parallelized EFIT 査読

NAKAHATA Kazuyuki, TOKUNAGA Jyunichi, KIMOTO Kazushi, HIROSE Sohichi

Journal of Solid Mechanics and Materials Engineering 2 ( 11 ) 1462 - 1469 2008年

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

A time domain simulation tool for the ultrasonic propagation in concrete is developed using the elastodynamic finite integration technique (EFIT) and the image-based modeling. The EFIT is a grid-based time domain differential technique and easily treats the different boundary conditions in the inhomogeneous material such as concrete. Here, the geometry of concrete is determined by a scanned image of concrete and the processed color bitmap image is fed into the EFIT. Although the ultrasonic wave simulation in such a complex material requires much time to calculate, we here execute the EFIT by a parallel computing technique using a shared memory computer system. In this study, formulations of the EFIT and treatment of the different boundary conditions are briefly described and examples of shear horizontal wave propagations in reinforced concrete are demonstrated. The methodology and performance of parallelization for the EFIT are also discussed.

DOI： 10.1299/jmmp.2.1462

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A large scale analysis for ultrasonic wave propagation using parallelized FDTD method 査読

K. Nakahata, J. Tokunaga, K. Kimoto, S. Hirose

REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION, VOL 27A AND 27B 975 107 - + 2008年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AMER INST PHYSICS

A finite difference time domain method (FDTD) is based on a grid-based time domain differential technique, in which wave equations are solved in a leapfrog manner. It is required to discretize a whole target domain into computational grids with an adequate size. Therefore computational burden increases if the computational domain is much larger than the wave length. To solve such a large-scale problem in high speed, we apply a parallel computing technique to the FDTD. OpeuMP is an interface to execute program codes in parallel using a shared memory system of computers. As an example of large-scale analysis, SH wave propagations in concrete material are demonstrated in this study.

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Image-based sizing of surface-breaking cracks by SH-wave array ultrasonic testng 査読

KIMOTO K, UENO S, HIROSE S

Ultrasonics 45 ( 1-4 ) 152 - 164 2006年12月

SH波超音波リニアアレイ探触子の時間領域モデリング査読

木本和志, 廣瀬壮一

土木学会応用力学論文集 9 115 - 121 2006年

A 3D linearized inverse scattering method for scatterers in a two layered medium 査読

Kazushi Kimoto, Sohichi Hirose

Structural Engineering/Earthquake Engineering 22 ( 2 ) 201S - 207S 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

This paper presents a 3D linearized inverse scattering method for shape reconstruction of obstacles in a two layered medium. The problem here is to estimate the shape of an obstacle embedded in the bottom layer, using scattered waves observed at points in the top layer. Wave sources are assumed to be acoustic monopoles settled in the top layer. For this situation, two inversion formulas based on the Born and the Kirchhoff approximations are proposed with the help of the Green's function for the layered medium. In numerical examples, the two inversion formulae are tested for reconstruction of spherical and spheroidal rigid scatterers from simulated wave data. It is shown that an illuminated side of the scatterers is well reconstructed by the proposed methods.

DOI： 10.2208/jsceseee.22.201s

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論文 - 木本 和志

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論文 - 木本　和志