Osamu Ishii’s research while affiliated with Yamagata University and other places

This paper describes a wireless humidity sensor that employs the mechanical resonance frequency, fr, change in a magnetic ribbon coated with poly(3,4‐ethylenedioxythiophene) doped with poly(4‐styrenesulfonate) (PEDOT/PSS). PEDOT/PSS expands or contracts by several percentage when it absorbs or desorbs water vapor, and so the curvature, 1/R, of the ribbon varies in response to changes in relative humidity, RH. It is also proved that fr is proportional to 1/R. Consequently, RH can be detected by monitoring the fr using a pickup coil placed away from the ribbon; fr changes from 68 kHz at RH = 87% to 148 kHz at RH = 0%. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

抄録 A position sensing system of nasogastric tube using a wireless magnetic ribbon type marker has been developed. A Qualityfactor of the marker is 121 which is 13 times higher than conventional LC resonated marker. Position accuracy within 6.4mm was obtained when the marker inside a commercial nasogastic tube was parallel translation to 100mm. The marker inside the tube was roughly tracked in esophagus and in trachea of human model.

Polycrystalline Gd1−xCaxBaSrCu3O7−δ samples (0 ≤ x ≤ 0.1) were prepared via solid-state reaction. The superconducting critical temperature Tc and lattice parameter decrease with doping content. Temperature dependence of the specific heat of all samples was measured with the thermal relaxation technique using a Physical Property Measurement System from about 2 K to 150 K. The calculated Debye temperature ΘD at 10 K is found to be inversely proportional to Tc. Subsequently, the electron–phonon coupling constant was estimated based on standard BCS theory (λBCS) in the weak coupling limit and two-dimensional Van Hove scenario (λVH). The calculated values of λVH in this study (around 0.04) are close to the experimental data as reported by other researchers on Bi-based and YBCO samples. Hence, the two-dimensional Van Hove scenario seems to be a viable candidate for the mechanism of superconductivity if electron–phonon coupling plays a role in superconductivity of these materials.

IntroductionExperimentalResults and DiscussionConclusion

This paper describes a new bimorph-type actuator composed of a shape-memory-alloy coated magnetic ribbon. A high magnetostrictive amorphous ribbon (Metglas 2605SC, 37 mm×6 mm×0.025 mm) coated with a 1.0 mum thick sputter-deposited Ti48.5Ni33.5Cu18 film exhibited a repeatable shape memory effect in the temperature range from 10 °C to 70 °C reverse martensitic transformation upon heating bent the ribbon and martensitic transformation upon cooling flattened it. Simultaneous application of AC and DC magnetic fields excited the longitudinal mechanical vibration which can be monitored wirelessly with a pickup coil. The resonance frequency was proportional to the displacement of the ribbon within an accuracy of 0.76 %. Consequently, it is confirmed that a TiNiCu-coated magnetic ribbon actuator with high positioning resolution can be realized by monitoring its resonance frequency and feeding back it to the heating and/or cooling power control algorithms.

This paper describes a new type of actuator composed of a shape-memory-alloy coated magnetic ribbon that detects any deformation of the shape memory alloy. The ribbons reversibly deform by heating or cooling in the temperature region from 10°C to 80°C. The deformation causes a change in the mechanical resonant frequency, which can be detected wirelessly with a pick-up coil. The deformation of the ribbons is confirmed to be proportional to the mechanical resonant frequency with an accuracy of ±0.58%. A heat-driven actuator with a high positioning resolution will be realized by monitoring the resonant frequency and feeding back it to the heating power.

To reduce the error of a magnetic rotation angle sensor, we investigated the effect of sensor element configuration on the output signal of the sensor by using numerical calculations. The sensor elements were made of spin-valve films with a large shape-induced anisotropy. The magnetization of elements was calculated by minimizing the magnetic energy in a framework of the Stoner-Wohlfarth model. The sensor response was calculated as a function of the relative angle between the spin-valve elements. The error of signals was minimized when the relative angle was 99.5°. It is clear that this configuration is robust against the variation of shape-induced anisotropy.

Gd1−xCaxBaSrCu3O7−δ samples (0 ⩽ x ⩽ 0.1) were prepared via solid-state reaction. Four-point probes method was used for resistance versus temperature measurements. Results show decrease in Tc by increasing x content. This variation is assumed to be irrelevant to the different phases or impurity effects since X-ray patterns show all samples are tetragonal single-phase. Ca doping decreases the oxygen content and lattice parameters of the samples. It is suggested that Ca prevents the dislocation of oxygen, and then disrupts the hole concentration of the system and antiferromagnetic correlation at CuO2 planes. Subsequently, destroys the superconductivity of the samples.