研究者詳細 - 紀和　利彦

Detection of Inner Corrosion of Steel Construction Using Magnetic Resistance Sensor and Magnetic Spectroscopy Analysis

Keiji Tsukada, Yuta Haga, Koji Morita, Nannan Song, Kenji Sakai, Toshihiko Kiwa, Weiying Cheng

IEEE Transactions on Magnetics 52 ( 7 ) 2016年7月

記述言語：英語出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2016 IEEE. The detection of the inner corrosion of steel construction, specifically backside corrosion of a steel plate, is highly demanded to maintain safety. Eddy-current testing (ECT) is widely used as a nondestructive testing and an evaluation method for detecting surface and subsurface flaws. However, the ECT is usually applied to non-ferromagnetic materials, but has difficulties when applied to ferromagnetic materials with high permeability, since the skin depth is smaller, and the signal-to-noise ratio (SNR) decreases due to magnetic flux fluctuation. In this paper, we developed a magnetic probe using an anisotropic magnetic resistance (AMR) sensor with the sensitivity of 1 nT/ Hz that can detect inner corrosion at extremely low frequency. We also developed an analysis method using magnetic spectroscopy to delete the magnetic flux fluctuation. To improve the SNR of the detected signal, a small cancellation coil around the AMR sensor canceled the applied magnetic field directly coupled to the sensor. The frequency of the applied magnetic field ranged from 1 Hz to 1 kHz. The sensor output at each frequency was lock-in detected. The weak ac magnetic field was applied to the initial permeability region of the magnetization curve. The obtained magnetic vector signal consisting of a real part and an imaginary part at each frequency was plotted as magnetic spectroscopy, and the magnetic component of the eddy current and the magnetic component of the magnetization of the steel were separated. By using the magnetic component of the eddy current, the thickness of an iron steel plate thinner than 16 mm could be measured. Moreover, the shape of the back-side corrosion was determined by scanning with the magnetic probe.

DOI： 10.1109/TMAG.2016.2530851

Hybrid Type HTS-SQUID Magnetometer with Vibrating and Rotating Sample

Keiji Tsukada, Koji Morita, Yasuaki Matsunaga, Mohd Mawardi Saari, Kenji Sakai, Toshihiko Kiwa

IEEE Transactions on Applied Superconductivity 26 ( 3 ) 2016年4月

記述言語：英語出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2016 IEEE. Highly sensitive measurement of the very weak magnetic characteristics of magnetic particles in solution or of a solution itself is required for applications, such as biomedical examinations. In this paper, higher sensitivity and additional performance with relaxation measurement and harmonic signal detection were achieved by an improvement of the driving mechanism and the high-resolution electric magnet, and optimization of the superconducting quantum interference device (SQUID) detection unit. A servomotor was used for sample vibration and rotation with precise control and high speed. For detection of the M-H characteristics, the sample was vibrated under the magnetic field in the electromagnet. For measuring the relaxation of the magnetization, the sample was rotated. A first-order differential pickup coil with a normal conducting wire connected to the input coil of a higherature superconductor-SQUID was used to detect the magnetic signal from the sample. High-resolution measurement of the magnetic moment on the order of 10-11 A m2 was achieved with this system configuration. An ac magnetic field with a dc bias could then be applied to the sample for detection of the harmonic signal. The magnetic relaxation signal from the sample was measured by another of the same type of differential detection coil equipped outside of the electric magnet by rotating, instead of vibrating, the sample. The magnetization curve for a low concentration of iron nanoparticles with a superparamagnetic character in the solution was successfully measured using the developed magnetometer, and the relaxation phenomenon was also characterized.

DOI： 10.1109/TASC.2016.2531632

Label-free detection of low-molecular-weight samples using a terahertz chemical microscope

Takuya Kuwana, Masahiro Ogawa, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

Applied Physics Express 9 ( 4 ) 2016年4月

記述言語：英語出版者・発行元：IOP PUBLISHING LTD

© 2016 The Japan Society of Applied Physics. A terahertz chemical microscope (TCM) has been proposed and developed to visualize the distribution of biomolecular interactions on a sensing plate without any labels. In this study, the concanavalin A (Con A)-D-(+)-mannose (mannose) interaction was detected using the TCM with mannose applied as the analyte and Con A immobilized on the sensing plate. To demonstrate this interaction, the amplitude of terahertz pulses as a function of Con A-mannose interaction time, as well as the Con A-mannose coupling concentration, was evaluated. The results suggest that coupling kinetics may be evaluated using a TCM.

DOI： 10.7567/APEX.9.042401

Compact AC/DC Susceptometer Using a High-Temperature Superconducting Quantum Interference Device

Ryuki Takagi, Mohd Mawardi Saari, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

Electronics and Communications in Japan 99 ( 3 ) 369 - 374 2016年3月

記述言語：英語出版者・発行元：WILEY-BLACKWELL

© 2016 Wiley Periodicals, Inc. We developed a compact susceptometer employing a high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) that can measure the M-H characteristics and the harmonic components induced in the ac magnetic field response from a sample. In the dc function for measuring M-H characteristics, the sample was vibrated in a dc magnetic field, and the secondary magnetic field generated from the sample was detected by a dc pickup coil. In the ac function for measuring harmonic components, the sample placed in an ac magnetic field, and the ac response was detected by an ac pickup coil. The pickup coil is connected in series with the input coil, which is inductively connected to the HTS-SQUID. A signal from the HTS-SQUID was transmitted to a lock-in amplifier and was analyzed as the intensity and phase of the measured magnetic field. In order to clarify the basic properties of the system, we measured the ac magnetic field response from a sample while varying the relative positions of the sample and the pickup coil, and the M-H characteristics while varying the dc bias magnetic field intensity. Furthermore, by analyzing the harmonic components of the ac/dc magnetic field response, the proposed system can measure magnetic field properties with high sensitivity and at high speed.

DOI： 10.1002/ecj.11779