Hiroo Tarao

Intercomparison of induced fields in Japanese male model for ELF magnetic field exposures: effect of different computational methods and codes

The present study provides an intercomparison of the induced quantities in a human model for uniform magnetic field exposures at extremely low frequency. A total of six research groups have cooperated in this joint intercomparison study. The computational conditions and numeric human phantom including the conductivity of tissue were set identically to focus on the uncertainty in computed fields. Differences in the maximal and 99th percentile value of the in situ electric field were less than 30 and 10 % except for the results of one group. Differences in the current density averaged over 1 cm(2) of the central nerve tissue are 10 % or less except for the results of one group. This comparison suggests that the computational uncertainty of the in situ electric field/current density due to different methods and coding is smaller than that caused by different human phantoms and the conductivitys of tissue, which was reported in a previous study.

Simple estimation of induced electric fields in nervous system tissues for human exposure to non-uniform electric fields at power frequency

Most results regarding induced current in the human body related to electric field dosimetry have been calculated under uniform field conditions. We have found in previous work that a contact current is a more suitable way to evaluate induced electric fields, even in the case of exposure to non-uniform fields. If the relationship between induced currents and external non-uniform fields can be understood, induced electric fields in nervous system tissues may be able to be estimated from measurements of ambient non-uniform fields. In the present paper, we numerically calculated the induced electric fields and currents in a human model by considering non-uniform fields based on distortion by a cubic conductor under an unperturbed electric field of 1 kV m(-1) at 60 Hz. We investigated the relationship between a non-uniform external electric field with no human present and the induced current through the neck, and the relationship between the current through the neck and the induced electric fields in nervous system tissues such as the brain, heart, and spinal cord. The results showed that the current through the neck can be formulated by means of an external electric field at the central position of the human head, and the distance between the conductor and the human model. As expected, there is a strong correlation between the current through the neck and the induced electric fields in the nervous system tissues. The combination of these relationships indicates that induced electric fields in these tissues can be estimated solely by measurements of the external field at a point and the distance from the conductor.

Comparison of the extremely low-frequency electric field meters at 400 kV and 220 kV substations

The objective of the paper is to present the measurement examples of the meters and compare the differences in real situations at 400 kV and 220 kV substations. We used two meters: the Narda EFA-300 LF Field Analyzer and Maschek ESM-100 H/E Field Meter. Both meters were used to measure the electric field strength from the same spot at 17 different sites. The Maschek produced slightly higher readings while measuring the electric field strengths although the explanation could be the difference in distance to the ground from the actual probing elements of both meters due to user error.

Measurements of leakage magnetic fields from induction heating range using different sized pans

Recently, induction heating (IH) ranges, which heats using Joule heat based on eddy currents in a pan, have been increasing not only for household use but commercial use. Some of users have concerns about the possible health effects of magnetic fields from induction heating ranges. In this study, we quantitatively measured leakage magnetic fields from an IH range as a survey range. Especially, we investigated the effect of the size of a pan. The magnitudes of the measured magnetic field at the edge were 5-40 μT, depending on the size of the pan used. Furthermore, the magnitudes were inversely proportional to the cubic of the distance from the edge of the range, which indicated that leakage magnetic fields from IH range can be expressed as a magnetic dipole moment. The magnetic fields increased when the size of the pan was smaller, since much magnetic fields may leak from the operating coils.

Effect of membrane on current distribution in biological sphere tissue with a membrane placed in uniform and eddy current fields

Some experimental reports suggest the significant role of tissue membrane on the ELF magnetically induced current distribution, which is rarely implemented in a numerical procedure of induced current estimation. The paper presents an analytical examination of those results by demonstrating how the thickness and conductivity of the tissue membrane affects the current profiles near a simple biological tissue model exposed either to ELF uniform current or to ELF nonuniform current.