Seiji Hayano

A formulation of the inverse problems in magnetostatic fields and its application to a source position searching of the human eye fields

In order to exploit an inverse problem solver in the magnetostatic fields, a new formulation of the inverse problems is proposed in this paper. As a result, it is shown that all of the inverse problems in magnetostatic fields can be reduced to find the position and magnitude of field source. By combining this new formulation, the finite‐element method, and the artificial intelligence technique, we work out a general purpose inverse problem solver in the magnetostatic fields. Intensive tests of this solver suggest that the ability of this solver is depending greatly on the available data base. This solver is now applied to find a source position of the human eye fields. As a result, a plausible source position of the human eye fields can be estimated.

Alumite disc using anordic oxidation

Perpendicular magnetic alumite discs were obtained using an anodic oxidation method.The additional new pore widening process was effective to control the coercive force. The electro-deposited fine iron needles were single crystals and the growth direction was [110]. The recording characteristics of 3.5 and 5.25 inch rigid discs were evaluated. A recording density D 50 of 50 KBPI was attained for the disc with a media thickness 1.5 µm. The environmental test under an atmosphere of of 40 °C 90 % R. H. over 1000 hr affirmed the stability of the alumite disc with 250A SiO 2 overcoat.

A new type high frequency transformer

In order to realize small power supplies, the authors propose a type of coreless high-frequency transformer. This transformer is composed of simple twisted coils and its operating principle is based on the skin effect of current carrying conductors. Approximate analysis based on the symmetrical current distributions in each of the coil axes has been applied to this transformer. As a result, it has been clarified that the simple analytical model can be used to estimate the rough performance of the transformer. Analytical and experimental studies suggest that twisted coils have versatile possibilities as a high-frequency transformer. >

A perpendicular magnetic recording medium by alumite

Abstract Magnetic properties of electrodeposited alumite media for perpendicular recording were investigated. By means of the pore widening process enabled to realize the coercive force less than 1000 Oe. Mossbauer spectra suggested that the direction of magnetization of the processed alumite was almost perpendicular to the surface.

A magnetization model for computational magnetodynamics

In order to calculate the magnetodynamic fields exactly, it is essential to work out a magnetization model. We have previously proposed a Chua‐type magnetization model based on magnetic domain theory. This Chua‐type model is now applied to typical ferromagnetic materials, such as iron, ferrite, and amorphous magnetic material. As a result, it is revealed that the typical magnetization characteristics of representative ferromagnetic materials can be satisfactory reproduced by our Chua‐type model.

Finite element solution of unbounded magnetic field problem containing ferromagnetic materials

The strategic dual image method for obtaining the finite-element solution of unbounded magnetic field problems can be applied to any complex magnetic field distributions with unbounded boundary. However, a difficulty in generalizing the method to magnetic field problems involving ferromagnetic materials has been pointed out. It is shown that this difficulty can be removed by utilizing the B= mu 0(H+M) formulation instead of B= mu H, where B, H, M, mu /sub 0/, and mu are, respectively, the flux density, field intensity, magnetization, permeability of air, and permeability of the ferromagnetic material. The resulting method can be used to obtain the finite-element solution of unbounded saturable magnetic field problems. >

A neural behavior estimation by the generalized correlative analysis

The authors propose an approach to magnetoencephalogram (MEG) analysis. The problem of obtaining the current signal flow in the brain reduces to the inverse problem, the governing equation of which is written in an integral form. The authors propose a generalized correlative analysis method based on the Cauchy-Schwarz relation to solve the system equation derived from the governing equation. As a result, they have succeeded in estimating current signal flows in the human brain. A comparison between the conventional single dipole model and generalized corrective analyses has demonstrated that the proposed method is far superior to the conventional one. >

Crack identification in metallic materials

A novel formulation for the crack identification problem is proposed. In this formulation, cracks are regarded as the equivalent field or potential sources due to the discontinuity of conductivity at the crack positions. This means that crack identification problems are reduced to the inverse problems of searching for equivalent sources. The system equation of the inverse problems, derived by discretizing the integral equation, is successfully solved by the sampled pattern matching method. As a consequence, fairly good results are obtained even in the case of plural defect problems. >

Defect recognition in conductive materials by local magnetic‐field measurement

Among the various nondestructive testing methods, the electric potential method requires relatively simple device and measurement. However, because of the high electrical contact resistance, sometimes it is difficult to measure the correct local electric potentials by direct contact. In order to overcome this difficulty, method is proposed which involves substituting the local magnetic field for electric potential measurements. The comparison with the conventional electric potential method demonstrates the usefulness this method, especially for materials with low resistivity.

Application of a Chua type model to the loss and skin effect calculations

Previously, we have proposed a specific Chua type model, and shown that our model is closely related with the Preisach and Rayleigh models. In the present paper, a simple linearized Chua type model is proposed for the loss and skin effect calculations. As a result, it is found that the hysteresis makes the skin depth deeper.