M. Nakamura’s research while affiliated with Yamagata University and other places

This paper describes the application of remote temperature sensors made of an amorphous magnetic ribbon and a low Curie temperature ferrite tube to the measurement of temperature in an arbitrary range. By combining an amorphous magnetic ribbon and a ferrite tube with a Curie temperature of 40 °C, a resonant frequency change rate of 6.3%/°C was realized in the 35 to 40 °C temperature range. Similarly, by combining an amorphous magnetic ribbon and a ferrite tube with a Curie temperature of 47 °C, a resonant frequency change rate of 4.9%/°C was achieved in the 41 to 47 °C temperature range. These values are ∼100 times larger than that of the previously reported remote temperature sensor made only of an amorphous ribbon. Therefore, this confirms that a highly sensitive remote temperature sensor can be realized in an arbitrary temperature range. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper describes a remote hydrogen sensor based on the mechanical resonance of a Pd-coated magnetic ribbon. The resonant frequency of the magnetic ribbon increases by 1.3% as the H2 partial pressure is increased from 40 Pa to 8×104 Pa. We demonstrate that this sensor can monitor a wide range of H2 partial pressures wirelessly.

The paper describes the use of magnetoelastic ribbon in a remote temperature sensor. Magnetoelastic ribbon was placed in an ac magnetic field generated by an external coil. The vibration of the ribbon was monitored with a pickup coil and reached its maximum value at the mechanical resonant frequency, in accordance with the magnetostriction effect. We monitored the temperature by measuring the output voltage of a pickup coil at frequencies near the resonance. The maximum change in output voltage was 0.57%°C-1, in the temperature range from 20°C to 80°C. This finding indicates the potential of the ribbon for use in a sensitive and compact remote temperature sensor.

This paper describes the use of magnetoelastic ribbon as a remote viscosity and density sensor. Magnetoelastic ribbon was placed in an AC magnetic field generated by an external coil. The vibration of the ribbon could be monitored with a pickup coil and it reached its maximum value at the mechanical resonant frequency based on the magnetostriction effect. We confirmed that the mechanical resonant frequency of the ribbon was proportional to the square root of the product of the viscosity and density of the surrounding liquids. Moreover, we demonstrated that we could measure the viscosity of the liquid when it was very high by dipping only the edge of the ribbon in the liquid. These results suggest that this configuration is a promising candidate for use as a remote viscosity and/or density sensor.

The paper describes the application of Fe-based nanocrystalline alloy ribbon to a common-mode noise filter and a shielded cable in the 10 MHz-1 GHz frequency range. A 0.01-mm-thick Fe-based nanocrystalline alloy ribbon exhibited high permeability and high impedance characteristics. The resistance of a 5.5-mm-diameter roll of Fe-nanocrystalline ribbon (12.5 mm wide and 6 cm long) increased from 1.0 Ω at 1 MHz to 5.1 Ω at 700 MHz. We confirmed that this filter exhibited the same noise attenuation as a conventional filter (ferrite core) but with 1/20th its volume. Moreover, the noise emission from a twisted pair cable is greatly reduced without any increase in the cable volume by employing the nanocrystalline ribbon as a shielding material.