This paper summarizes the possibility of magnetic energy harvesting for zero-power sensor. Magnetic energy harvesting has the advantages of both wireless power transmission and energy harvesting technologies. From the view point of solar power harvesting technology using photovoltaics, the motivation of magnetic energy harvesting technology is explained. The global trend of energy harvesting from magnetic field on the power management system is summarized. Towards the contribution to IoT technologies, the possibilities of zero-power sensor using magnetic field are also discussed.

Recently developed fundamental mode orthogonal fluxgate (FM-OFG) offers high sensitivity sensing systems for magnetic signals with the amplitude ranging 1pT∼10µT. The mechanism of the FM-OFG is reviewed briefly and various sensors made based on it are presented. Magnetic field from human heart is measured with an array of 36 channels of FM-OFG magnetometers. Also shown are several applications using gradiometers built by extending a magnetometer design, including detection of lightening residue and of magnetic nanoparticle sample.

We have developed the active magnetic shielding system, which a reference-type MI element output is fed back to a sensor-head with a feedback coil, to reduce the environmental magnetic noise around the sensor-head. Output properties of MI elements could keep linearity by adjusting the DC magnetic field in the feedback coil to less than 1 µT. Furthermore, the noise at 60 Hz related to the power source line was reduced by 1/10 with this system. We have measured a variation of magnetic field with a stainless steel metal ball (SUS304, 0.3 mm diameter) movement by using a new MI gradiometer with this system, and the magnetic signal of 700 pT was detected clearly compared with a previous MI gradiometer. Consequently, we considered that this type MI gradiometer is an effective method of a very weak magnetic measurement in the environmental magnetic noise.

We propose a new simple method to directly apply dc current to the CoNbZr/Cu film of a sensor. A very sensitive thin film sensor was developed using a meandering coplanar line with biasing conductors fabricated from SrTiO film (0.75 µm thick), amorphous Co₈₅Nb₁₂Zr₃ film (1.0 mm × 2.45 mm, 1 µm thick) and Cu/Cr film (2 µm/0.1 µm). We discuss direct bias to CoNbZr film and Cu film under a CoNbZr film and compare it with an application of bias magnetic field. Good sensitivity (phase change over 100 degrees/Oe) was obtained by the proposed method.

We observed the repeatability of changes in the magnetic domains of three types of amorphous ribbons. These ribbons were cut at their edges and annealed to control their domain structures. The domain change of the cut samples had good repeatability. Moreover, jitter noise in the fluxgate-sensor output for the amorphous ribbon decreased. A decrease in the magnetization-reversal jitter could be achieved through magnetic domain-structure control of the sensor core, which could improve the sensitivity of the fluxgate.

Recently, magnetic field sensors such as hall sensor, magnetoresisitive sensor, fluxgate sensor and magnetoimpedance sensor advance their sensitivity and their miniaturization; this contributes to enhance of electromagnetic nondestructive testing and evaluation (NDT & E) techniques, eddy current testing (ECT) and magnetic flux leakage (MFL), for social foundations. This paper reviews the case studies in applications of higher sensitive and miniaturized magnetic field sensor for NDT & E techniques.

Hyperthermia is a cancer treatment, in which tumors are heated. We proposed hyperthermia treatment using heat dissipation from magnetic nanoparticles under an AC magnetic field applied by a pancake-type applicator. The excitation condition satisfies the reported guideline, defined by the influence that electromagnetic fields affect the human body. The applicator can form a sufficient AC magnetic field deep in the human body, which can excite the magnetic nanoparticles that have been injected into the tumor tissue, as long as the tumor diameter is greater than 10 mm. This will generate specific loss power of 37 kW/kg and heat the tumor tissue by 5 K, as required for hyperthermia treatment.

A TMR magnetic sensor array module with multi-channel synchronous detection ICs is proposed for detecting the extremely low leakage current in lithium-ion batteries. The sensor array consists of a multiple-element, highly sensitive, self-biased TMR magnetic sensor GIGS^® using an SmCo thin-film magnet. The 10ch demonstration module was successfully detected a low current of less than 3.6 mA in a laminated lithium-ion battery. The module noise in an RF shielded room was about 44 nT/√Hz at 100 Hz.

The magnetoresistance measurements of NiCu micro-wires with various widths fabricated on a LiNbO₃ substrate were performed. An external magnetic field dependence of the magnetoresistances indicated that stripe domain structure can be also formed in the NiCu micro-wires. The competition of shape anisotropy and magnetic anisotropy induced by magnetoelastic effect enables us to control domain structure and magnetization reversal characteristics.

The authors have observed E-field waveforms of lightning discharges and estimated duration of negative downward stepped leader by measuring time interval between onsets of preliminary breakdown pulses and the following first return stroke. 334 examples obtained in Sagamihara city on six days of summer in 2015 are subject to an analysis. Mean and median durations of negative downward stepped leader measured by our observations were 29.7 ms and 22.0 ms, respectively. We found out that there were correlations between duration of negative downward stepped leader and peak current of the following first return stroke estimated by the JLDN. The duration of negative downward stepped leader became short when absolute value of estimated peak current of first return stroke became large. The time interval of the leader pulse in the E-field waveform did not depend on the current amplitude of the following first stroke, therefore, the above-mentioned result might be due to the increase of the step length of the leader with the increase of the current amplitude of the following first return stroke.

Techniques for concrete diagnosis are needed in construction industry because degradation could occur unseen in concrete. Microwave tomography is one of hopeful techniques for concrete diagnosis. Because usually a target of concrete diagnosis cannot be separated from the concrete structure and taken into a radio wave darkroom for measuring, the time of observing wave scattering has to be limited to eliminate the influence of obstacles outside the computational domain in getting tomography. As a result, a part of the concrete target in the computational domain is un-reconstructable. However, in a concrete diagnosis, the reconstructable zone cannot be recognized in advance, because the velocity of wave propagating through the concrete body is unknown. It is one of the key problems of microwave tomography in concrete diagnosis. This paper proposes a “Successive Estimation Technique” to solve the problem. Successive estimation technique is an iteration method to reconstruct the target part by part, by using “time-divided” information of scattering waves. It is suitable for microwave tomography in concrete diagnosis because the reconstructable and un-reconstructable zones can be distinguished automatically, and good reconstructed images are obtained efficiently, even in a noise contamination case.

This paper describes the frequency dependence of the partial discharge characteristics in a needle-plane electrode system under sine wave applied voltage 50 Hz to 10000 Hz. We measured the pulse occurrence frequency, the maximum discharge magnitude, the φ-n distribution, the pulse mean φ-q distribution, and skewness of the φ-q distribution. We used the needle-plain electrodes with tip radius 30µm and 300µm at sine wave applied voltage of 1.25 kVp and 2 kVp. We found that the frequency dependences of these partial discharge characteristics are small.

Effect of electrical stimulation on yield of Pholiota microspora in log cultivation was investigated experimentally. The pulsed voltage was generated by two types of high-voltage pulsed power generator, based on Cockcroft-Walton circuit and Marx generator in order to evaluate an influence of the applied voltage pulse width. The input energy was controlled by number of the pulsed voltage applying. The pulsed voltage was applied to the cultivation log before harvest of first flush. The fruit body yield was evaluated by total weight harvested during two harvest seasons. The experimental results showed that the fruit body yield increased to be 1.5-3.0 times higher by applying pulse voltage. The fruit body yield in the second season also increased by pulse voltage applying at former harvest season. This result indicates that the pulse high-voltage stimulation affect the yield at not only same harvest season but also next harvest season. The yield increment is mainly determined by input energy into cultivation log.

This paper describes an effect of transient electromagnetic fields on the growth of plants. In our experiment, several transient electromagnetic fields were applied to seeds and seedlings of radish and turnip. The pulse application cycles were set to 3 times / 1day, 6 times / 2days and 9 times / 3days. As a result, we found that samples, which had been applied 6 times / 2days, became greater than other conditions by around 10∼62%.

The activated carbon particles made of Kastanien nuts were applied to the EDLC electrodes by using an alkaline activation method. The capacitance and internal resistance of the assembled EDLC cell were measured with 34% KOH water Electrolyte. The density of capacitance of Kastanien nut cells was approximately 30F/cm³ (4.1Wh/L) in the EDLC cell. The density of capacitance of Kastanien nut cells achieved 1.8 times one of charcoal cells. The surface area per unit weight of activated Kastanien nut particles is also more than 2 times as wide as charcoal. It shows that the density of capacitance of EDLC cells is strongly dependent on the base material of activated carbon.