Faculty Profiles - KIWA Toshihiko

Papers - KIWA Toshihiko

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Evaluation of hardened and non- ardened regions using eddy current testing

Kenji Sakai, Takahiro Ito, Toshihiko Kiwa, Keiji Tsukada

Studies in Applied Electromagnetics and Mechanics 43 1 - 8 2018

Publishing type：Research paper (international conference proceedings)

© 2018 The authors and IOS Press. A steel plate having hardened and non-hardened regions in one plate is promising material in automobile field owing to its high performance. This steel plate has to be evaluated whether the non-hardened region was prepared properly at the desired position with desired hardness. However, the conventional evaluation method of hardness measurement is destructive testing and requires a long inspection time. Therefore, a reliable and fast nondestructive inspection method is required. In this study, the hardened and non-hardened regions were evaluated using an eddy current testing (ECT) to distinguish each region. The measured resistivity and permeability at each region were different and these differences were found to be caused by the crystal structure change of heat treatment. Therefore, the magnetic response between the hardened and nonhardened regions was different and this difference was correlated with the hardness of each region. These results indicate that the hardened and non-hardened regions can be distinguished using ECT.

DOI： 10.3233/978-1-61499-836-5-1

Development of in situ methods for battery using a THz chemical microscope

Kentaro Fujiwara, Yuki Akiwa, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

Optics InfoBase Conference Papers Part F113-CLEOPR 2018 2018

Immune assay using a micro-flow channels detected by a terahertz chemical microscopy

Tatsuki Kamiya, Masahiro Iida, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

Optics InfoBase Conference Papers Part F113-CLEOPR 2018 2018

Evaluation of penetration of cosmetic liquids using terahertz time of flight method

T. Kuroda, T. Morimoto, K. Sakai, T. Kiwa, K. Tsukada

2018 43RD INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ) 2018

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

The terahertz time-of-flight method was applied to evaluate the the penetration speed and the depth of the skin lotion into the skin. The result suggests that the terahertz time-of-flight method is one of useful option in this field.

Application of a HTS Coil with a Magnetic Sensor to Nondestructive Testing Using a Low-Frequency Magnetic Field Reviewed

Yasuaki Matsunaga, Ryota Isshiki, Yuta Nakamura, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

IEEE Transactions on Applied Superconductivity 27 ( 4 ) 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2016 IEEE. Detecting corrosion at an early stage on the backside of a thick steel plate using a magnetic field is difficult because of the high permeability of steel. Therefore, we used a low-frequency magnetic field to enable the penetration of magnetic flux deep into the steel plate. According to Faraday's law, to achieve a sufficiently intense signal at low frequencies, the number of turns of a normal conducting coil must be increased. However, a high-temperature superconducting (HTS) coil has a very low resistance; thus, the shielding current of a HTS coil can flow under magnetic fields with a wide-frequency range. Although HTS coils exhibit good shielding characteristics at low frequencies, their voltage signals are very weak. To solve this problem, a magnetic sensor was used to detect the shielding current of a HTS coil. The detection unit included the HTS coil, and the magnetic sensor was optimized; moreover, the possibility of operating the magnetic sensor at the liquid nitrogen temperature (77 K) was investigated. As a demonstration of nondestructive testing using the magnetic response of the HTS coil and magnetic sensor, we measured the change in the thickness of a steel plate in which corrosion was assumed to have occurred. Consequently, we obtained a good response even with a low-frequency magnetic field when using a HTS coil with a few turns. In the thickness measurements of steel plates, thicknesses ranging from 6 to 19 mm were obtained in the frequency range of 1-5 Hz.

DOI： 10.1109/TASC.2016.2631420

Detecting internal defects of a steel plate by using low-frequency magnetic flux leakage method Reviewed

Nannan Song, Yuta Haga, Tsuyoshi Goda, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

SAS 2017 - 2017 IEEE Sensors Applications Symposium, Proceedings MAG-16 ( 119-132.134 ) 2017.4

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

© 2017 IEEE. Steel is an important material in modern society. It is widely used in our lives, such as in buildings, bridges, and airplanes. We previously reported an analysis method for examining the internal defects of metal structures with eddy current testing (ECT) over a wide range of frequencies. However, internal defects in steel plates are difficult to detect using ECT. In this paper, we present a low-frequency magnetic flux leakage (MFL) method for the nondestructive evaluation of internal defects in steel structures, and an analysis and imaging method that uses the phase of a magnetic field to examine internal defects. By analyzing the phase change in the detected signal, the internal defects can be detected with no magnetic fluctuation. The phase map of the measured magnetic field exhibits good correlation with the simulation results. The two-dimensional magnetic phase map can be used to visualize the internal defects. This new method has been validated through both experiment and simulation.

DOI： 10.1109/SAS.2017.7894069

Novel terahertz measurements systems born in Okayama

Toshihiko Kiwa

Journal of the Institute of Electronics, Information and Communication Engineers 99 ( 10 ) 975 - 979 2016.10

Simultaneously detection two types of ions using THz chemical microscopy Reviewed

Kosuke Akimune, Yuki Okawa, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

2015 11th Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2015 3 2016.1

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

© 2015 IEEE. THz chemical microscopy has been proposed and developed to detect ions in water solutions. In this work, the change in the amplitude of THz radiation was measured when ion solutions was dropped on detection plate.

DOI： 10.1109/CLEOPR.2015.7376395

A terahertz technology for label-free immune assay Reviewed

Toshihiko Kiwa, Masahiro Ogawa, Kousuke Akimune, Hiroyuki Nino, Kenji Sakai, Keiji Tsukada

2015 11th Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2015 3 2016.1

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

© 2015 IEEE. This paper reviews recent works of label-free immune assay using terahertz technologies, which includes a terahertz chemical microscopy. Experimental results of label-free detection of lectin-suger chain reactions were also presented.

DOI： 10.1109/CLEOPR.2015.7376392

pH Measurements Of nano-liter Solutions Using THz Technology Reviewed

Y. Zhou, K. Akimune, K. Hamada, K. Sakai, T. Kiwa, K. Tsukada

SENSORS AND ELECTRONIC INSTRUMENTATION ADVANCES (SEIA) 60 - 61 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：INT FREQUENCY SENSOR ASSOC-IFSA

A terahertz chemical microscopy (TCM) has been proposed and developed to visualize the electric potential changes of water solution on the semiconductor-based plate named 'sensing plate'. The TCM detects the change in the amplitude of THz waves from the sensing plate, which can be related to the electric potential of the water solutions on the sensing plate. Since the top surface of the sensing plate was made from the SiO2, the electric potential at the surface of the sensing plate could be change by changing the pH values of the solutions on the sensing plate. In order to detect the small amount of water solutions, micro-wells made of UV curable resin were patterned on the surface of the sensing plate with diameters range between 50 mu m to 500 mu m. Thus the solution of 16-nL were measured, which indicated that the pH measurements of nano-litter solutions could be possible using TCM.

Terahertz-Time-of-Flight Method for Evaluating Cosmetic Samples Penetrating into Skin Samples Reviewed

T. Arisawa, T. Morimoto, K. Sakai, T. Kiwa, K. Tsukada

SENSORS AND ELECTRONIC INSTRUMENTATION ADVANCES (SEIA) 117 - 119 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：INT FREQUENCY SENSOR ASSOC-IFSA

A terahertz(THz)-time-of-flight(TOF) method was carried out for in-vitro measurements of the penetration depth of cosmetic liquid into skin samples. In our group, a sensing plate, which can generate terahertz pulses, has been developed. By irradiating the back side of the sensing plate using a femto-second laser pulses, the THz pulses with the pulse width of approximately 1 ps were radiated into a free space. When the artificial skin samples were put on the sensing plate, the generated THz pulses travel in the skin samples and are reflected at the boundary between the regions where the cosmetic liquid exists and does not exist. Since traveling time of the THz pulses are generally proportional to the traveling path, the distance between the boundary and the sensing plate can be estimated by evaluating the traveling time of the THz pulses. Here, as demonstration of the developed method, the penetration of liquid into the artificial dermis made from collagen were evaluated.

Application to Non-destructive Evaluation of Gas Barrier Films Using a High-speed Terahertz Time-domain Spectroscopy Reviewed

Masaya Inamo, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

2016 PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS) 3921 - 3921 2016

Development of Terahertz Chemical Microscope for Detecting Small Molecules Reviewed

Takuya Kuwana, Yuki Hanaoka, Toshihiko Kiwa, Kenji Sakai, Keiji Tsukada

2016 PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS) 3927 - 3927 2016

Combinatorial Sensing of Catalytic Materials Using Terahertz Chemical Microscope Reviewed

Yuji Hino, Yuki Kawakami, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

SENSORS AND ELECTRONIC INSTRUMENTATION ADVANCES (SEIA) 104 - 106 2016

Language：English Publishing type：Research paper (international conference proceedings) Publisher：INT FREQUENCY SENSOR ASSOC-IFSA

Terahertz chemical microscope (TCM) has been developed to visualize the electrical and/ or chemical potential on the 'sensing plate' as the distribution of the amplitude of THz pulses radiated from the sensing plate. In this study, the combinatorial search of membrane materials using TCM was proposed and evaluation of catalytic reactions of Pt thin film was demonstrated. Pt thin films with the thickness of 4 nm, 7 nm, 10 nm and 15 nm were fabricated on the same sensing plate. Each Pt thin film on the sensing plate was exposed to the dry air (80 % nitrogen gas and 20 % oxygen gas) and hydrogen gas (1 %) and air every three minutes, independently. The amplitudes shifts of radiated THz pulses could be related to the thickness of Pt thin films on the sensing plate. This result suggests that TCM is one of useful option for the combinatorial sensing of catalytic materials.

Automatic Scanning System for Back-Side Defect of Steel Structure Using Magnetic Flux Leakage Method Reviewed

Kenji Sakai, Koji Morita, Yuta Haga, Toshihiko Kiwa, Katsumi Inoue, Keiji Tsukada

IEEE Transactions on Magnetics 51 ( 11 ) 2015.11

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 1965-2012 IEEE. An automatic nondestructive evaluation system using the magnetic-flux-leakage method was developed for detecting the back-side defects of large structures in order to realize fast detection in a wide measurement area. A magnetic field was applied to an object using a ferrite yoke with an induction coil, and the leaked magnetic flux from the object was detected by a magnetoresistive sensor. This measurement probe was fixed on an automatic scanning system. The developed automatic scanning system detected magnetic signal changes corresponding to the back-side defects of the steel plates. To demonstrate the effectiveness of the developed system, we measured the steel plate of a cargo crane, which was corroded on the back side. We found that the detected magnetic signal changed markedly in the area with corrosion, whereas only a slight magnetic signal change was detected in the area without corrosion. Therefore, the developed system is useful for detecting the back-side defects in a wide area, and can be used for screening tests.

DOI： 10.1109/TMAG.2015.2453211

Development of a planar type ion sensor for urine testing Reviewed

K. Sakai, T. Yamamoto, R. Sugai, T. Kiwa, K. Tsukada

Sensor Letters 13 ( 8 ) 706 - 710 2015.8

Language：English Publishing type：Research paper (international conference proceedings) Publisher：American Scientific Publishers

Copyright © 2015 American Scientific Publishers All rights reserved. A new planar-type ion sensor with an Ag/AgCl electrode without a standard solution and liquid junction was proposed for urine testing. The proposed sensor integrates a reference electrode onto a single chip, and thus, it is possible to manufacture a compact planar-type ion sensor. The potential change of the developed sensor is proportional to the Na+ and K+ concentration. Although the Ag/AgCl electrode without a standard solution and liquid junction reacted to Cl-, AC impedance analysis was used to compensate the effect of Cl-on the potential change. Therefore, the proposed planar-type ion sensor can be used for routine urine testing because the proposed sensor is low cost, disposable, and also has a simple structure.

DOI： 10.1166/sl.2015.3475

Effect of diamagnetic contribution of water on harmonics distribution in a dilute solution of iron oxide nanoparticles measured using high-T<inf>c</inf> SQUID magnetometer Reviewed

Mohd Mawardi Saari, Yuya Tsukamoto, Toki Kusaka, Yuichi Ishihara, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

Journal of Magnetism and Magnetic Materials 394 260 - 265 2015.7

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

© 2015 Elsevier B.V. All rights reserved. The magnetization curve of iron oxide nanoparticles in low-concentration solutions was investigated by a highly sensitive high-Tc superconducting quantum interference device (SQUID) magnetometer. The diamagnetic contribution of water that was used as the carrier liquid was observed in the measured magnetization curves in the high magnetic field region over 100 mT. The effect of the diamagnetic contribution of water on the generation of harmonics during the application of AC and DC magnetic fields was simulated on the basis of measured magnetization curves. Although the diamagnetic effect depends on concentration, a linear relation was observed between the detected harmonics and concentration in the simulated and measured results. The simulation results suggested that improvement could be expected in harmonics generation because of the diamagnetic effect when the iron concentration was lower than 72 μg/ml. The use of second harmonics with an appropriate bias of the DC magnetic field could be utilized for realization of a fast and highly sensitive detection of magnetic nanoparticles in a low-concentration solution.

DOI： 10.1016/j.jmmm.2015.06.090

Ion transportation of electrolytes in a flow channel mapped by an HTS SQUID scanning system Reviewed

Toshihiko Kiwa, Kohei Tanaka, Shohei Kasuya, Kenji Sakai, Keiji Tsukada

IEEE Transactions on Applied Superconductivity 25 ( 3 ) 2015.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2014 IEEE. In this paper, we propose and develop a device for visualizing the magnetic field produced by ion transportation in electrolyte cells. Using 0.5 mM potassium ferricyanide (K3[Fe(CN)6]) dissolved in 0.5 M sodium sulfate (Na2SO4) as the electrolyte, the magnetic distribution was obtained using high-TC SQUID scanning performed by a planar gradiometer located above the electrolyte cell across the surface. The difference in the ion transportation path in the electrolyte cells is discussed with regard to flow channels fabricated in the electrolyte cells.

DOI： 10.1109/TASC.2014.2382656

Moisture content evaluation using improved high-tc squid-based rotating-sample magnetometer Reviewed

Kenji Sakai, Naohiro Okamoto, Yuuta Watanabe, Mohd Mawardi Saari, Toshihiko Kiwa, Keiji Tsukada

IEEE Transactions on Applied Superconductivity 25 ( 3 ) 2015.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2002-2011 IEEE. Moisture content evaluated by magnetic signal change measured by rotating-sample magnetometer using higherature superconductor superconducting quantum interference device (HTS-SQUID) was investigated. To realize highly sensitive measurement of moisture content, an improvement in signal-to-noise (S/N) ratio of the previously developed magnetometer was examined. To increase the S/N ratio, the sample case with short width along the sample's movement direction was employed. By reducing the sample case width, the obtained magnetic signal intensity increased, and the frequency component of magnetic signal shifted toward high frequencies, leading to the low magnetic field noise range measurements. Using the improved magnetometer, the moisture content of silica gel was measured, and the magnetic signal intensity increased as the amount of water in the silica gel increased. Therefore, we propose a high-sensitivity, noncontact, and nondestructive method for moisture content evaluation using rotating-sample magnetometer.

DOI： 10.1109/TASC.2014.2363353

Optimization of an AC/DC High- T<inf>c</inf> SQUID magnetometer detection unit for evaluation of magnetic nanoparticles in solution Reviewed

Mohd Mawardi Saari, Yuichi Ishihara, Yuya Tsukamoto, Toki Kusaka, Koji Morita, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

IEEE Transactions on Applied Superconductivity 25 ( 3 ) 2015.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2002-2011 IEEE. We have optimized the detection unit of a previously developed AC/DC magnetometer that employs a high critical temperature superconducting quantum interference device (high- Tc SQUID). Optimization involves improvement of the usable dynamic range of the high- Tc SQUID system during excitation with an AC magnetic field using a tuned compensation coil and an increase in the DC magnetic field resolution using a secondary excitation coil. The compensation coil technique had resulted in a single and compact detection coil using one SQUID for both AC and DC magnetization measurement functions with improved sensitivity in AC measurements. The sensitivity of the improved system is demonstrated by measuring the magnetization curve and harmonics distribution of low-concentration iron oxide nanoparticles solutions. Highly sensitive evaluation of magnetic nanoparticles in solutions can be expected with the developed system.

DOI： 10.1109/TASC.2014.2363633

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