Shape memory alloy, which is a form of Fe-Mn-Cr-Si, was thermally treated in an argon and air atmosphere, and the magnetization and shape memory effect were then measured. In both cases the variables were the time and temperature of the heat treatment. As results obtained later results show, those factors had a significant influence on the magnetization and shape memory effect. The magnetization was measured by using a vibrating sample magnetometer, and the shape memory effect was determined by measuring the recovery angle of a bent wire made of the investigated alloy.

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We studied the possibility of creating electronic components using recycled powder prepared by grinding sludge of MnZn ferrite and commercially available clay for earthenware. The effects of the mixing ratios and heat treatment conditions on the magnetic properties and microstruetures of sintered samples were investigated. As the result, we found that it is possible to utilize the mixtures as composite materials for producing electromagnetic wave absorbers with better properties than those currently in use (R.L. ≥20 dB). The matching frequency and matching thickness were controlled 0.9 GHz to 5.5 GHz and 8 mm to 4 mm, respectively.

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In this study, the eddy current and the eddy current loss in the grains and the grain boundary of a toroidal core were simulated by using two fundamental Mn-Zn ferrite models, taking account of the microstructure by the spatial network method. The computation results show that an displacement current passes through the grain boundaries and forms the eddy current in the core, and that the eddy current loss in the grains increases in proportion to the forth power of the frequency. These calculated eddy current losses agree well with the experimental results, and express the rapid increase at high frequencies.

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Complex permeability spectra (μ*=μ'-iμ") of Mn-Zn ferrite composite materials were studied in the frequency range from 10 kHz to 10 GHz under magnetic fields up to 1 kOe. In sintered ferrite, μ' at low frequency decreases with increasing applied magnetic field, and the dispersion character changes from resonance type to relaxation type. This can be attributed to the decrease in the number of domain walls. The maximum of μ" in sintered ferrite and its composite materials shifts to higher frequencies with increasing magnetic field. The contribution of domain walls and spin rotational resonance to the permeability under a dc magnetic field was estimated by numerical fitting of a simple formula for sintered ferrites to the actual measurement data.

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Our previous report shows that Mn-Zn-Ti ferrite with Fe-poor composition (less than 50 mol% of Fe₂O₃) sintered in air exhibits a high resistivity and initial permeability at frequencies above 1 MHz. We examined Fe-poor ferrite sintered in N₂ like conventional Mn-Zn ferrite with Fe-rich composition in order to further improve the initial permeability. Sintering the Fe-poor ferrite in N₂ leads to a decrease in the phase of α-Fe₂O₃ in the surface layer of the ferrite, resulting in an improvement of the initial permeability at frequencies below 1 MHz. As a result, the novel ferrite exhibits a high initial permeability in a wide range of frequencies.

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A two-axis flux gate magnetic field sensor, with a multilayer structure composed of a Co-based amorphous magnetic ribbon and planar coils, was developed. Since the two planar spiral coils for ac excitation and flux detection were located on the same plane, it was easy to fabricate by the photo-lithography technique. The fabricated two-axis flux gate functioned as an earth magnetic field direction sensor.

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Thin-film orthogonal fluxgate magnetic sensors with dimensions of 4 mm × 1.2 mm were febricated by using micro-plating technology. Electro-plated 4-μm-thick NiFe films were utilized as the core material, and 100-turn Cu coils were wound around the magnetic core as sensing coils. The greatest magnetic sensitivity was obtained when weak magnetic anisotropy was induced with its easy axis in the transverse direction of the magnetic core. The low-field sensitivity also showed a strong dependence on the core width due to the shape magnetic anisotropy, and became maximum for a width of 100 μm. The optimized sensor elements were used to investigate the output characteristics with a negative feedback loop for the terrestrial magnetic flux, and a magnetic sensitivity of 16500 V/T was obtained. The output linearity to the external field was 1.4%, and showed an offset of 50mv.

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This paper deals with the characteristics of a voltage-detecting-type rail joint gap sensor using an air-coil. The sensor, designed for ordinary railways, is able to detect the flux change due to the eddy current between the sensor and the rail. The key points of this paper are as follows: (1) the principle of the measurement on the rail joint gap sensor, which is composed of two detecting coils under one exciting coil, (2) the dependence of the output voltage on the area of the detecting coils on the rail and the rail joint gap, (3) the distinction between normal and singular rail joint gaps.

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There are many requiremends for measuring torque, such as non-contact with the shaft, small size of the measurment device, and simple installation. Other requirements include no special processing in the shaft and cost-effectiveness. Therefore, we have proposed three magnetostrictive-type torque sensors for a steering shaft using an inverse magnetostrictive effect.
Generally, a magnetostrictive-type torque sensor for a low-carbon steel shaft has a large hysteresis to the torque and output fluctuation due to axis rotation (0-level fluctuation). In this sensor, we show that the hysteresis and the 0-level fluctuation on the output voltage can be drastically decreased.

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The figure of merit (FOM) of the magneto-impedance (MI) effect in amorphous wires is defined as (| ∂ Z / ∂ Hex| / Z₀) · f _cutoff. The magnitude of the FOM was found to be almost the same at two operating points on the MI characteristic curve in pulse-magnetized amorphous wires in the domain-wall-displacement-dominant range and the magnetization-rotation-dominant range. The magnitude of the FOM was increased in a twisted amorphous wire by increasing the efficiency of the magnetization rotation for the wire pulse current.
A frequency-modulation-(FM)-type wireless magnetic sensor with low power consumption was devised, utilizing the magnetization-rotation-dominant MI effect in a zero-magnetostrictive amorphous wire combined with two kinds of CMOS IC multivibrators. The wireless MI sensor has been successfully used as an automobile torque sensor.

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A new amplitude-modulation-type magnetic field sensor using a magnetic/dielectric hybrid transmission line is presented. The transmission characteristics of the transmission line are influenced by a permeability change due to application of on external magnetic field to the magnetic layer. This sensor uses the change in the input impedance of the transmission line. A big change in input impedance is provided when the transmission line is used as a stub that is short-circuited or opened with a trailing end.

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This paper discusses a microfabrication process for high-frequency carrier-type thin-film magnetic field sensors. We fabricated sensor elements by using the lift-off process and the ion milling process, and compared the shape of the sensor edge, the domain structure, and the characteristics of the impedance change in the sensor elements fabricated by the two processes. In the elements fabricated by the lift-off process, the sensor edge is more even than in those fabricated by the ion milling process. Moreover, when the width of the sensor element was 5 μm, its easy axis was induced in a transverse direction, and an impedance change of 14 Ω was achieved. We therefore chose the lift-off process for microfabrication of high-frequency carrier-type thin-film magnetic field sensors.

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A sensitive air-flow sensor element was constructed, using an arched CoSiB magnetostrictive amorphous wire connected to a straight hair-type amorphous wire. A sharp pulse current is applied through the arched wire to generate the stress-impedance (SI) effect with a strong skin effect. The resolution for air flow detection is about 0.16 m/s, which is almost the same as that of conventional heated resistance wire-type air-flow sensors. The amorphous wire air-flow sensor element is suitable for adding an air-flow-sensing ability to intelligent robots.

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Micro-strain sensors using the magnetostrictive properties of FeCeSiB films were investigated. To avoid the effects of the rigidity of the substrate on the stress sensitivity, a sensor was formed on thin polyimide ribbons (50 μm thick), which have superior heat resistance, wide elastic region, and excellent flexibility. By using the large difference in the coefficient of thermal expansion between FeCoSiB and polyimide, the residual stress in the magnetostrictive FeCoSiB patterned film was controlled. The sensor was formed under optimized conditions, and had an extremely high value of the figure of merit F = (ΔZ/Z)/Δε (change in film impedance Z per unit ε) of about 1500 at a carrier current frequency of 700 MHz. In addition, the point of stress representing the largest sensitivity of the sensor was controlled by controlling the field annealing conditions.

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In this paper we propose to use a dynamic neural networks as multi-frequency models of eddy current sensor. Two models are proposed: a forward model, which could be utilized as a fast solver in an inversion iterative algorithm, and an inverse model, which enable us to directly obtain an unknown flaw profile directly from the sensor output signal.

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A simple over-current detection method based on the magnetic saturation of an outer-magnetic-core-type planar inductor is proposed. The planar inductor has two planar windings: an inner planar coil connected to the main electrical circuit, and an outer planar search coil on the top surface of the outer magnetic core. The electromotive force across the outer search coil increases only when the magnetic shielding by the outer magnetic core is degraded because of magnetic saturation owing to the large ac current flowing in the inner coil, and the mutual coupling between the inner and outer coils is increased.

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We developed a new type of wave power generation system. In this system, water valves without mechanical operation are combined with air chambers. The main advantage of this system is that there are few failures in the rectifying water valves, since there are no moving parts. A test plant was installed on the south breakwater at Haramachi thermal power station, and testing for practical use has been carried out at the Haramachi site since 1996. In the testing, we measure the wave height, the pressure in the air chambers, the pressure in the water valve chambers, the pressure in the turbine room, the electric output, and so on. We have obtained over 200 series of data between 1996 and 2000. This paper presents a summary of the characteristics of the power generation system in view of the results obtained thus far.

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We previously proposed a three-phase variable inductor for control equipment in an electric power system. The three-phase variable inductor is constructed with three orthogonal cores that have wedge gaps for reduction of harmonics. When the three-phase variable inductor is connected to a power line in parallel, a simple, reliable var compensator will be realized.
In order to reduce the 3rd harmonic of the output currents of the three-phase variable inductor, the secondary windings of the orthogonal cores are connected in a delta configuration. On the other hand, when the three-phase variable inductor is connected to the line in series, the variable inductor can control a power flow in a power system. However, the secondary windings cannot be connected in a delta configuration. In this paper, we present one method of reducing the 3rd harmonic by using the third windings of the orthogonal cores.

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By using an orthogonal-core-type variable inductor and capacitor, we will realize a simple, reliable, and high-quality voltage regulator. However, the nonlinear magnetization characteristic of the orthogonal core causes harmonics in the output current. To reduce the harmonic current of the orthogonal-core-type variable inductor, we previously proposed an orthogonal core with wedge gaps. A trial three-phase 100-kVA variable inductor demonstrates that the variable inductor can be put to practical use in a 6.6-kV ac distribution system. For wide application, it is necessary to examine the optimum size of the wedge gap and to establish a design method for the orthogonal core. In this paper, we present a method for quantitative analysis of the orthogonal core with wedge gaps, and examine the characteristics of the variable inductor for various dimensions of the wedge gap.

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A contactless power station (CLPS) with cone-type coils is proposed for use in the sea. The cone-type coils are used in order to keep the efficiency high by means of dislocation. It was confirmed that the power transmission characteristics in the sea agreed well with those in the air. The mutual inductance and self-inductance were calculated by using Neumann’s formula, which involves by the diameters of the coils, the number of turns and the coil gap. It was confirmed that the calculated values agreed well with the experimental values. The relation between the coupling factor and the ratio of the coil diameter and the coil gap was discovered, and the coil was designed for the optimum load.

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A transcutaneous energy transmission system transmits electrical energy by utilizing magnetic coupling through the skin for an implanted device or stimulator, such as an artificial heart. The problem is that the heat of the coil burns the skin. The efficiency can be improved by connecting the capacitor in series or in parallel for the load in the internal. We examined the relation between the air gap and the capacitor parameters.

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We propose a desk-type for a contactless power station (CLPS) using spiral formed coils. In this system, in order to supply electrical power efficiently to equipment on the desk, the primary coils are arranged to cover the desk. It is required that the loss of the transmission electrical power should be small, irrespective of where the equipment on the secondary side is located. However, in the configuration where one primary is used for one secondary coil, the transmission loss in the valley of the primary coils increase. A configuration using several primary coils for each secondary coil was therefore proposed and examined. As a result, we confirmed the effectiveness of using several primary coils.

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This paper describes the development of a magnetic-flux-control-type transformer (MFC transformer).
An on-load tap changing transformer and step voltage regulator is used as a conventional voltage-controller for distribution lines. But the response time for controlling the voltage is not satisfactory, and the voltage control is performed in discrete steps. An MFC transformer can control the output voltage and reactive power at high speed, and continuously, and its copper and iron composition gives it high endurance and reliability.
In this paper, we report on the basic structure of an MFC transformer, the control characteristics of a trial single-phase 30-kVA MFC transformer, and the outline of a three-phase 350-kVA prototype.

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In a previous paper, we proposed a 3-phase variable inductor, which has a sinusoidal output current and good controllability. We developed a var compensator for a 6.6 kV ac distribution system using the 3-phase variable inductor, which is composed of three orthogonalcores that have wedge gaps for reducing the harmonics in the output current. To reduce the eddy current loss, the orthogonalcore needs a proper insulation film between the primary and the secondary core. When an apparatus is scaled up,

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A planar parametric transformer has several desirable features, including voltage regulation, overload protection, and noise rejection. We examined various transformers of different sizes and movement frequencies. The characteristics of the transformers had been previously analyzed by the harmonic balance method. In order to examine the influence of the leak magnetic flux on the characteristics of a transformer, we examined the relation of the winding position and the characteristics. As a result, it became clear that the movement point of a transformer can be varied by changing the winding position.

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Recently, the fault current limiters (FCLs) have become a hot topic in relation to the reliable operation of power supply. Authors reported the characteristics of an FCL using a permanent magnet and a C-type core. In this paper, the characteristics of a FCL using the an E-type core are investigated by the use of numerical analysis, taking account of the eddy current effect. Numerical analysis was performed on the core dimension ratios of the FCL.
The results, clearly showed that the characteristics were strongly influenced by the dimension ratios of the core. The experimental results show a reasonable agreement with the analytical results.

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A magnetic infrared sensor (MIS) is a device that converts radiated infrared rays into magnetic change by means of its energy. Photoelectrical sensors using photoconductive, photovoltaic, photoemissive and pyroelectric effects have hitherto been used as an infrared sensor. The MIS system constructed with a 1.0-μm-thickness ferrimagnetic Film (FMF) prepared by RF sputtering and a magnetoresistance element. When infrared rays are directed onto the FMF, it receives energy and the device’s temperature rises, causing magnetic change. After this minute change is read out by a magnetoresistance element, it is converted into voltage. This paper describes the structure of the MIS and its application to the measurements of human action patterns for a telecare system without a monitor camera that protects the privacy of old people living alone.

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A crossed-anisotropy amorphous-film (CoFeB) MI element was deposited on a glass substrate by dc sputtering with two layers each 4.5 μm thick, applying a dc field of 270 Oe in a designed anisotropy direction. The MI element showed an asymmetrical MI effect when magnetized with a dc-biased ac current without any bias magnetic field. When the domain of the MI element was observed with a Kerr effect microscope, it was confirmed that the domain structure of the MI element became close to a single domain structure when a dc current was applied. The crossed-anisotropy film MI element induces spiral magnetic anisotropy when a dc current is applied.

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A wireless temperature sensing system for isolated local areas such as those in an organism was investigated. The sensor does not need an internal power supply, and is composed only of a ferrite rod (1x1x10 mm) with low Curie temperature, a chip capacitor, and a wound coil. It was therefore possible to reduce the volume of the sensor to less than that of a medicine capsule, and the sensor is designed as an LC series circuit. As the inductance of the coil changes with the temperature, the resonance frequency is varied. The temperature around the sensor can be measured by measuring the resonance frequency. The sensor was driven and signals from the sensor were received by using the loop coil with electromagnetic induction.
It was found that a temperature signal can be detected at a distance of 300 mm.

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We are investigating a large-scale displacement sensor using a magnetostrictive wire with torsional and longitudinal elastic waves.
Until now, many differential transformer and potentiometers have been used as displacement sensors in the industrial field. The displacement sensor described in this paper, however, measures displacement by using magnetostrictive wire. The advantage of this sensor is its non-contact, high-precision displacement measurement.
We examined the generation and detection of torsional and longitudinal elastic waves. This paper describes the result of measuring how much the magnetostriction and elastic wave detection property of magnetostrictive wire are affected by heat treatment and demagnetization. It is shown that the treatment and demagnetization methods have different effects on longitudinal elastic waves and torsional waves.

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Incremental permeability measurement was performed for two types of structural steels along with the magnetization of their hysteresis minor-loop. The obtained incremental permeability change curve has two sharp peaks, and the width between the two peaks is crrelated with the coactivity. Hence the existence of good correlation was verified. On the basis of this result, nondestructive measurement experiments were carried out with planar coils to evaluate changes in the material properties of ferromagnetic structural steel plates. Changes in output voltages from planar coils with different test plates were correlated with their mechanical and magnetic properties. The correlation is so good that the measurement method adopted in this work could be used for nondestructive evaluation of material degradation in ferromagnetic structural steels.

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A method is proposed for detecting cracks non-destructively by measuring the magnetic field around a distribution line. Experimental and calculated results for the magnetic flux density around the distribution line are reported, and the characteristics of the magnetic field distribution around the line are considered. A parameter ΔLm that varies with the existence of cracks is introduced, and an algorithm using ΔLm for detecting the cracks is presented. The probability of the non-destructive detection is confirmed and the characteristics of ΔLm with respect to the noise and error of sensors are considered.

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The magnetic properties of thin films with reduced lateral dimension are significantly different from those of materials in the bulk state, and have provided a wealth of scientific interest and potential technological applications. It is therefore very important to study magnetism in microstructures or small magnetic domains, and one of the most powerful tools for investigating such magnetism is the photoelectron emission microscope with synchrotron radiation as its light source (SR-PEEM).
We report in this paper our set-up of a new SR-PEEM system, and present the preliminary results.

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A new versatile room temperature scanning Hall probe microscope system (RT-SHPM) was developed and used for the magnetic imaging of longitudinal magnetic recording media, low coercivity perpendicularly anisotropic iron garnet epitaxial layers, and demagnetized strontium ferrite permanent magnets placed in externally applied magnetic fields. The RT-SHPM incorporates an ultra-high sensitive sub-micron GaAs Hall probe (active area of ∼ 0.8x0.8 μm²; room temperature Hall coefficient of 0.3Ω/G; field sensitivity of 0.04 G/√Hz) with an integrated scanning tunnelling microscope tip for vertically positioning the probe in very close proximity to sample surfaces. The Hall probe is not magnetized by magnetic fields hence enabling the real time (∼1 frame/sec) measurments in external magnetic fields. Results described include the observation of otherwise sharp magnetic transitions in written floppy disks to coalesce into small islands under external fields greater than 1300 Oe and the transformation of magnetic bubble lattices into striped-maze patterns in Bi-substituted iron garnet epilayers in cycled external fields.

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In this paper, a new eddy current probe using a meander coil is presented for pipes including weld zones. Simulations clarified distributions of the eddy current in a tube with a weld zone, and revealed that a probe with long meander coil can generate a more uniform eddy current than a short meander coil. Experiments were carried out with a figure-of-eight detection coil, and demonstrated that the probe can detect OD 30% defects which is located near weld zone and its length is 15 mm.

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This paper introduces an innovative image processing technique for the inspection of Printed Circuit Board (PCB) by an Eddy-Current Testing (ECT) probe. The visualization of an inspected model is obtained from a phase of an output signal measured by an lock-in amplifier. Although the lock-in amplifier delivers also information about an amplitude of the output signal, the visualization process can be performed without the amplitude. Information about size of a defect can be extracted from the shape of phase characteristic. Introduction of the phase into image processing allows farther combination of the amplitude with the phase and developing a confirmation process, where information about defects obtained from the amplitude characteristic can be confirmed by information obtained from the phase characteristic.

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Conventional non-destructive testing methods cannot necessarily estimate the amount of fatigue damage. If this can be estimated, the service life of a structure can be extended and accidents can be prevented. We measured the magnetic flux density caused by residual magnetization in order to estimate the amount of fatigue damage to austenitic stainless steel plates (SUS304), using a fluxgate sensor. Our experiments showed that the residual magnetization is clearly dependent on an increase in the plane bending stress and the number of stress cycles. This paper discusses the evaluation of plane bending fatigue in austenitic stainless steel plates using residual magnetization.

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A variety of techniques have been provided to obtain quantitative measurement of the surface magnetic properties of materials with high spatial resolution Scanning magnetoresistance microscopy (SMRM) is a scanning probe technique in which a magnetoresistive (MR) sensor is used as a magnetic probe. It allows direct imaging of the magnetic flux in the sample. In previous work on SMRM, no feed-back system has been used to control the sample-sensor distance. Therefore, it was impossible to obtain topographic information on the sample. We made a cantilever with a MR sensor by means of photolithography, electron beam lithography, and micromachining. By using the feedback system of atomic force microscope, simultaneous measurement of the magnetic field and surface topography was realized.

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Modern electronic devices always contain printed circuit boards (PCBs) with multiple layers. If the currents in the PCBs can be visualized without disassembling the electronic devices, the testing and inspection of the devices can be carried out extremely efficiently.
This paper proposes a methodology for estimating the current distribution in multi-layered PCBs. The estimation of the current distributions in a PCB from locally measured magnetic fields can always be reduced to solution of an ill-posed inverse problem. This paper reveals that the conventional least squares method give a reasonable solution of our inverse problem. Thus, we succeeded in realizing a highly reliable non-destructive testing methodology for electronic devices.

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A method for structural design of thin-film spiral inductors was studied, using FEM electromagnetic field simulation. By analyzing the direction of the eddy current, we found that specific divisions of magnetic layers effectively reduced the electric power loss in magnetic layers. A 3 mm x 13 mm thin-film inductor for which L = 0.9 μH Q = 14.5 and I_bias = 0.55 A at 5 MHz was developed, based on an analysis of the electromagnetic field simulation. With this structure, a thin-film inductor of Q = 20 was achieved by increasing the coil thickness.

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Thin-film inductors with micro-patterned CoNbZr films for use as the impedance-matching elements in 1-GHz-drive mobile communication handsets were demonstrated. Intrinsic easy axis orientation at an angle of 45 degrees and micro-patterning enable the entire area of the magnetic film on the spiral to be used, because hard-axis excitation is possible in any part of the film. When a bidirectional film with a line and space of 10 μm/1 μm, the rf inductor exhibited an inductance of L = 8.2nH. This increase in inductance is twice as large than that in the same type of inductor using a uniaxial magnetic film.

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The stray capacitance of a ferromagnetic RF integrated inductor is discussed on the basis of both experiments and equivalent circuit analysis. The test inductor occupied an area of 380 x 380 μm², and has an inductance of 7.5nH at 1 GHz. The coil-magnetic film capacitance was most significant, reducing the LC resonance frequency from 6 GHz to 5 GHz. This became lower with increasing the distance between the coil and magnetic film, while the inductance was almost constant.

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This paper describes the chaotic behavior of Barkhausen noise. We previously revealed that Barkhausen noises under a rotational magnetic field were different from those under an alternating magnetic field, and showed that the heat fatigue level of Inconel-600 steel plates could be detected by using the proposed Barkhausen noises. In this paper, we examine the latter chaotic behavior in order to apply it to the estimation of the fatigue level of metallic structures.

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A repulsive type magnetic bearing system uses the repulsive forces between the stator and rotor permanent magnets without any radial control. This type of magnetic bearing system is superior to other magnetic bearings because of the low cost of displacement sensors due to the single-axis control and the reduced number of the peripheral devices such as electromagnets and control circuits. This paper discusses methods of adjusting the repulsive force and stiffness in the direction of levitation by using magnetic materials and changing the arrangement of stator permanent magnets in order to develop a smaller size magnetic bearing.

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We previously developed E&S modeling. It is desirable to improve the precision of this modeling in order to achieve a large increase in the efficiency of electrical machinery. We first define E&S modeling, taking account of the fifth harmonic wave element, and then compare it with the conventional method.

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A micro-strip line is an exponent of a distributed parameter circuit. Micro-strip lines are the main components of microwave circuits, and are used in the high frequency range. Magnetic micro-strip lines are constructed by adding magnetic film to micro-strip lines. The characteristics of a stripline depend on its construction and size. The magnetic film contained in it greatly affects the characteristics. This paper describes the characteristics of magnetic micro-strip line. Magnetic micro-strip lines can make miniaturization possible. Some applications, such as in band pass filters, can be expected in view of the unique magnetic characteristics of the strip lines.

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The magnetoresistance (MR) effect is a phenomenon whereby application of a magnetic field changes the electrical resistance of a ferromagnetic material. Magnetic thin-film devices using the MR effect, such as magnetic field sensors, have been widely studied in recent years, and rapid progress is being made in this field. MR films will therefore be used in functional thin-film devices such as mutipliers and modulators. In this paper, we introduce a new MR thin-film device with a modulation function, and report on the principle of the device’s modulation function and on the results of computer simulation.

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A new method is presented by which line spectrum noise can be cancelled, using the beat phenomenon. A reference magnetic field is superposed on the magnetic noise field in order to obtain a beat waveform, from which the phase and the amplitude of the magnetic noise can be identified. We applied the method to an open-structure, vertical cylindrical magnetic shield employing magnetic shaking, and evaluated the effect of canceling a line spectrum.

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In this study, MCGs in seven male rats were measured using a 12- channel high-resolution dc-SQUID gradiometer before and after performing coronary artery occlusion. The source imaging was estimated by minimum norm estimation (MNE). Changes in the current source distribution before and after coronary artery occlusion were clarified. As a result, in the ST segment, the current distribution significantly increased in the ischemic area. In the T wave, the direction of the current distribution clearly shifted to the left. The increased area of the estimated current distribution in the ST segment corresponded to the ischemic area. In conclusion, the large gradient potential of the left anterior region generated by the ischemic action potential produced increased currents. Our system will promote and facilitate future in vivo studies on myocardial ischemia.

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In this paper, the sphere of magnetophosphene in the visual field and the flickering frequency of the magnetophosphene are investigated. Magnetophosphene, a flickering light sensation perceived when a human head or visual system is exposed to an ELF magnetic field with sufficient intensity, is considered to be a sensation caused by activity of the stimulated retina. As the intensity of the magnetic field is increased, the sphere of the magnetophosphene spreads gradually over the visual field. The flickering frequency goes up and down when the frequency of the magnetic field is increased and decreased. We discuss these results with respect to not only the estimated current density induced in the retina by a magnetic field but also the threshold of the current density that is required to cause retinal cell activity in a magnetically stimulated human eye. The magnetophosphene is considered to be perceived in the local visual field corresponding to the retinal sphere of activity.

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