Regarding recent concerns on the health effects of ELF (extremely low frequency) magnetic fields, compliance testing in accordance with guidelines in highly non-uniform magnetic field has been a critical issue. In these cases, when the measured maximum magnetic fields on the surface of the human body exceed the reference level, the basic restriction should be investigated in a different way. However, this requires numerical calculation of the induced current or electric field, which is not readily achievable. Therefore, a simplified method for investigation of the conformity with a guideline, particularly one applicable to practical situations, is strongly required. In this paper, a new simplified method that can be used to estimate the maximum induced current from magnetic field measurements in practical complex situations was proposed. This method is based on the reduction rate of the magnetic field within a spherical model. The relationship between the reduction rate of magnetic field and the rate of maximum induced current to that of uniform field exposure was approximated using a simple regression curve. The previously proposed method based on averaging of the magnetic field over a certain area was also investigated. The results obtained in the study have practical values for assessing compliance with guidelines.

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A method of circuit model synthesis for an arbitrary complex technical or biological system is described. The method is based on a rather general matrix-operator representation of a system. Conditions of sufficient model synthesis are formulated as a theorem and are then proved. The theorem is concerned with linear, nonlinear, nonstationary and discretization (multiply-valued) operators. The first three types of operators permit us to build an unbalanced circuit-type model on microelectronic element basement: ARC-linear, one-port nonlinear, and one-port stationary elements. It is shown that general nodal representation of a system circuit-type model can be obtained on the basis of initial description of the original system. This way is proposed to be the most convenient for complex system modeling. Some examples of method application and comparisons with well-known algorithms are given.

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Geoelectrical and geomagnetic fluctuations are the end product of several geophysical phenomena. In particular signals measured in seismically active areas can be attributed to stress and strain changes associated with earthquakes. The complexity of the phenomena requires the development of advanced signal discrimintion and statistical methods. In this paper, we analyzed the short-term variability of geoelectrical potential and geomagnetic fields measured at Kiyosumi, Uchiura, and Fudago stations located in the southern part of Boso Peninsula, which is one of the most seismically active areas in Japan. The directions of signal arrival have been investigated with the use of local mid-night geoelectrical potential data, when artificial noise is low. Reduction of intense signals with external origin has also been made with the use of the interstation transfer function method. These analyses have shown the capability to discriminate the signal sources. Especially, direction finding analysis of time series data has shown to be effective in source separation. To identify the waveform and the direction of arrival of signals is important for monitoring the ULF electromagnetic environment in seismic areas and for understanding the preparation process of crustal activity.

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The expressions of subaerial electric field excited by a unit electric current source in the ground, are derived using the method of image charges, and we have studied the attenuation and radiation directivity of the electric field from the current source. Lower frequency below ELF (extremely low frequency, less than 1kHz) is our interest. The main emphasis of this paper is the study on the condition and possibility for detecting seismogenic emissions for various orientations of the electric current source (from horizontal to vertical).

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We propose an improved direction-of-arrival estimation technique for ultra-wideband (UWB) electromagnetic waves, which allows for the effect of the antenna mutual coupling. This technique is comprised of a UWB interferometry, a Root-MUSIC, and a database. The effectiveness of our scheme is demonstrated through a numerical example.

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Electrostatic discharge (ESD) testing is prescribed in the IEC 61000-4-2, which is conducted by injecting the transient current through contact /air discharge of an ESD-gun. The current calibration in the IEC standard, however, is being made for the contact discharge because the current waveform injected through the air discharge is greatly affected by a gun approching speed. In this study, with two kinds of commercially available ESD-guns, we measured the transient current for the air discharge gun with arbitrary approaching speeds. As a result, we could confirmed that a similar specific relationship holds between the rise-time and current peak for each ESD-gun despite the poor reproducibility of the current waveform, which is also supported by other researcher's finding for the air discharge of a charged metal spheroid.

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Discharge currents through a hand-held metal piece from a charged human body were measured with respect to approaching speeds and charge voltages. A circuit approach for calculating the discharge current has also been shown. As a result, we have found that in case of 300 V charge voltage, the current waveform is not affected by the metal piece approaching speed, while in case of 800 V charge voltage, the fast approach gives the higher current peak. These current waveforms can be predicted from the time invariant spark resistance and the measured frequency characteristics of a human body impedance seen from a hand-held metal piece.

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Application of ICP in the development of mercury-less light sources have been investigated. Xenon has been used as a replacement for mercury as the environmental issues related to it necessitate the development of new type of light sources. RF energy at 13.56MHz was induced to the cylindrical tube with input power ranging from 1W up to 100W. By changing the xenon gas pressure, coil turns and phosphor coating conditions, differences in emission intensities (luminance), spectra and discharge states were observed. In order to obtain the ICP discharge, the lamp was operated first in capacitive mode and then in inductive mode. These modes are known as E-mode (capacitively or CCP) and H-mode (inductively or ICP) respectively. High luminance can only be obtained when operating the lamp in H-mode. The optical emission spectra of these two modes (E and H) were analysed carefully.

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