We succeeded in making water levitate in air, using not an extreme by strong magnet such as a Bitter - type hybrid magnet, but a compact superconducting magnet. The levitated water ball had a spherical shape and levitated stably for over a day. We named this phenomenon “magneto - Archimedes levitation,” because, to achieve it, we used gravitational and magnetic buoyancy forces in the presence of pressurized oxygen gas. In addition, our method enables paramagnetic substances to levitate in air, which has been considered to be impossible owing to the Maxwell relation, divB = 0. We also succeeded in making paramagnetic aqueous copper sulfate levitate in air. To the best of our knowledge, this is the first demonstration of stable levitation of paramagnetic substances in the atmosphere.

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This paper deals with the output characteristics of the rail wearing depth obtained by using reluctance rail sensor (RR sensor) for ordinary railway and Shinkansen (Japanese bullet train). The RR sensor consists of a U-shaped core (cut-core), two exciting coils, and two detecting coils, each wound with 250 turns of wire. The small-sized rail of 6 kg rail is selected as the model, it is clarified that dependency of the output voltage of the RR sensor on the lift-off, the rail displacement, and the rail wearing depth. The rail wearing depth and the lift-off is measured by using two RR sensors.

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The magnetic properties of electrical steel sheets at high frequency can be estimated from the skin effect. The permeability deteriorates, and the eddy current loss becomes smaller than the values calculated from those at low frequency, owing to the skin effect. However, hysteresis loss increases, and cannot be neglected even at high frequency, because the skin effect increases the flux density at the surface. Consequently, the ratio of hysteresis loss to eddy current loss becomes constant, and both losses have the same frequency dependences. At higher frequency, the skin effect becomes stronger, magnetic saturation at the surface increases, and the frequency dependences of losses become similar to those at low frequency.

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A new method for measuring the low-frequency impedance of energized single-phase powerlines is proposed, and measured data in the frequency range of 100 Hz-20 kHz are presented. To estimate the quantity of noise generated in commercial ac lines, we have to know the frequency characteristics of the line impedance. In the high-frequency range (20 kHz-30 MHz), experimental results have already been reported. However, it seems that data on the low-frequency range have not yet been reported. Because the audio-frequency range contains many harmonics of higher frequency than commercial ac, the data in this frequency range are indispensable for evaluating distortions. The proposed measurement circuit was constructed by using our original noise superimposer.

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A dental magnetic attachment is a unique denture retainer appli-cable to teeth in poor condition. Miniaturization of these attachments has made remarkable progress through improvement of the magnetic circuit since 1992, when they were developed in Japan. There are two kinds of magnetic circuit, called the capped type and the sandwiched type, whose relative merits are disputed. This study concluds the duspute by showing that the capped type is superior, with a height of less than 1.5 mm. In line with this conclusion, an advanced thin magnetic attachment with a capped magnetic circuit was successfully designed to have a diameter of 4.4 mm and a height of 1.3 mm with an attractive force of 8 N. It is well suited to molar teeth.

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This paper describes the construction and basic characteristics of a linear parametric motor with an open magnetic circuit by using I-shape core. The linear motor can be used by a single phase power source, and has overload protection characteristics. To increase the value of the thrust-to-mass ratio, we reduced the mass of a 4-legged linear parametric motor by eliminating a part of the magnetic circuit experimentally. To increase the thrust further, we investigated the design method of a 4-legged linear motor assembled by using I-shaped laminated cores.

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This paper describes the relations between the iron-core structure and the characteristics of a linear parametric motor with double driving surfaces. This linear motor has a number of advantages; it can be used by a single-phase (1 φ) power source, it is very easy to maintain, and it has a very simple shape, because it can be assembled by using an I-shaped core. This linear motor has two common magnetic circuits and two driving surfaces. The thrust of a double-surface driving-type linear motor was higher than that of a 4-legged linear motor.

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This paper describes a method for improving SRM's performance of the basis of simulations and experiments. Calculation methods can be used to simulate both the static and dynamic characteristics of the SRM. A method is presented for improving the performance by varying the timing of the lead excitation by simulation and experiments. The main results are as follows: (1) Leading the exciting timing is effective to improve the torque vs. speed characteristics; (2) The exciting timing has an optimum value, to get a maximum efficiency.

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As a result of developments in science technology, non-contact gears are needed for vibrationless, noiseless, and oilless operation. We have proposed non-contact hybrid-type magnetic gears, which consist of electromagnetic gear (on the driving side) and permanent magnetic gear(on the driven side).
This paper describes the meshing performance characteristics and mechanism of load-sharing in the contact zone. As a result, it was found that the following considerations must be taken account of in magnetic gear design.
(1) The meshing zone of magnetic gear consists of intersecting and main contact zones.
(2) The ratio of load-sharing between the intersecting and main contact zones is 3 : 7.
(3) The intersecting contact zone is effective for decreasing the thrust load, and the main contact zone is useful for increasing the load-carrying capacity.

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Fans are used to control the temperature rise of the central processing units of notebook PCs. They are generally located inside the body of the PC. The magnetic flux leakage sometimes affects the performance of other electric devices. It is said that, 3 dB noise difference is very significant when such a PC is used in a silent room at midnight. The main factor in the magnetic flux leakage and the noise is the performance of the fan. This paper deals with a method of reducing the magnetic flux leakage and the noise of the fan without changing the outer body design and the performance. The magnetic flux leakage and the noise characteristics of two types of fans are discussed. One is a resin impeller fan (resin motor), and the other is a metal (steel) impeller fan (metal motor).
The main findings are as follows:
(1) If the resin impeller is replaced by a metal one, the magnetic flux leakage of the metal motor is 49.5 % lower on the upper surface of case, and 50.8 % lower on the side than the magnetic flux leakage of the reisin motor.
(2) According to the experimental data, the noise of the metal motor is from 4 to 8 dB lower than that of the resin motor.

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Giant magnetostrictive materials (GMMs) have large magnetostriction, but suffer from the disadvantage that eddy currents can flow easily in then. The frequency characteristics up to high frequency of a small sectional area were measured and compared by the powder metallurgy method and the Bridgeman method. This paper describes the following findings: (1) the powder metallurgy method is more useful in a low magnetic field, (2) permeability decreases rapidly to more than 10 kHz in a section with an area of 1 mm², and (3) the displacement-magnetic field sensitivity decreases with the permeability, and has a resonance in the mechanical resonance frequency range.

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The condition for enlarging the product of the magnetic field and its gradient, B·dB/dz, of a ready-made small superconducting magnet was investigated by computer simulation. The calculation assumed the use of a superconducting magnet with 100-mm-diameter room-temperature bore and capable of producing a 10 T magnetic field at the center. The value of B·dB/dz seems to be amplified when an iron ring or inner coil is inserted into the bore of a small superconducting magnet. Indeed, when an iron ring with an inner diameter of 10 mm or a pair of inner coils with an inner diameter of 40 mm is inserted, the value of B·dB/dz increased sufficiently to satisfy the condition for water levitation. These results suggest the possibility of using an ordinary small superconducting magnet to levitate diamagnetic materials.

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Magnetic bearing systems of two different types for use in vertical-shaft and horizontal-shaft machines, respectively, employing permanent magnets have been designed and developed in our laboratory. The shape and configuration of the permanent magnets are very important for the satisfactory functioning of the bearings. The permanent magnet configuration, field distribution inside the permanent magnets, and their magnetic losses are studied in this paper and effects are discussed. Experimental results are also presented.

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Camcorders would be more compact, lighter, and lower-priced, if their drive motors were built into their lens barrels. This paper proposes a new direct-drive motor built into a lens barrel. A unique rolling mechanism for bearing a rotor was incorporated into the motor to reduce the friction torque and power consumption of the armature windings. Balls are arrayed between a helical raceway made on the inner surface of a lens barrel shell and the raceway groove of a ring magnet. Three-dimensional algebraic formulas for the air-gap magnetic flux densities are presented, taking account of the effect of the raceway on the magnetic flux densities. The angular air-gap magnetic flux density distributions at the winding centers are sinusoidal and repeated for all poles. The calculated values agree well with the measured values, and the formulas have been verified.

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The inspection of etching defects in an as-made printed circuit boards (PCBs) is an attractive application of eddy-current testing (ECT) technology, since ECT inspection has various advantages such as non-contact, low stress, conductive testing, and fast scanning. When the technique is applied to high-density PCBs, the difference from conventional approaches becomes more remarkable. This paper describes the relationship between the shape of the inductive sensor and the width of printed wiring. The evaluation of signal-to-noise ratio results obtained by experiment clarifies the limits of detection. To improve inspection for higher-density PCBs requires a finer ECT sensor, but it was confirmed the defects in the printed wiring with a width less than one third of the sensor pitch can be detected.

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This study reports the performance of a high-frequency carrier-type thin-film magnetic field sensor that uses impedance change at high frequencies. To obtain high resolution, we reduced environmental electromagnetic noise and used high resolution instruments. A voltage change ratio (similar to the MR ratio) of 26.7% was achieved when ac carrier frequency was 400MHz. The resolution of the sensor was dc 2 × 10^-4 Oe and ac 8 × 10^-5 Oe, respectively.

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A non-uniform bridge connection of a high-frequency carrier-type thin-film magnetic field sensor was examined, using CoNbZr magnetic legs and Cu conductive legs in order to avoid cross-talk of the magnetic flux in adjacent legs of the bridge. A linearity of 0.70% was obtained with an external magnetic field of -4 to +4 Oe when feedback was provided with a feedback coil. The gain of the sensor was as high as 7.5 V/Oe when the gain of the differential amplifier of the feedback circuitry was 100.

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We prepared magneto-impedance (MI) elements of Cu wires electrolessly-deposited with Fe-Ni-P and Fe-Ni-B film layers, and investigated the dependence of their MI effect on the frequency (f) and the film thickness (t). A maximum MI sensitivity of about 100 %/Oe was obtained for the MI element of an 11.3 wt.% Fe-Ni-P film with t = 5 μm at f = 10 MHz. High MI sensitivity was obtained with an increase in the film thickness of the element, owing to the larger maximum MI ratio (η_max) and the smaller anisotropy field (H_k).

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A planar integrated magnetic component (PIM) with a transformer and an inductor is effective for switching the power supply. We analyzed the iron loss of the PIM by using the finite element method to calculate the magnetic flux distribution taking account of the magnetic interaction between the transformer and the inductor. As a result, we obtained a more exact value for the iron loss of the PIM, which was lower than that of similar, simply combined components.

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We investigated the use of planar-type inductors containing Co based soft magnetic films, which have highly electrical resistivity, as magnetic cores. Inductors were fabricated by using an RF magnetron sputtering method and a lift-off technique. Realizing smaller magnetostriction composition in a magnetic core is a major factor in obtaining a high quality factor (Q) in a inductor. Multilayering a zero magnetostrictive Co-based film with SiO₂ film is an effective means of obtaining soft magnetic films at low substrate temperatures. A composite multilayered film consisting of thin and thick SiO₂ films proved to be an excellent soft magnetic film with very low eddy current loss and loss due to a resonance. The highest values of Q and the inductance of the inductor, which were obtained by using a composite multilayered film subjected to rotational field annealing, were 25.5 and 26 nH at 180 MHz, respectively.

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The film material for 1 GHz-drive inductors used in mobile communication handsets needs a resistivity as high as 500μΩcm and resonance frequency higher than 2 GHz in order to avoid loss generation at 1 GHz. Fe-Al-O film is a possible candidate for the inductors, but it has a trade-off correlation between the resistivity and resonance frequency. Fe₆₁Al₁₃O₂₆ is a suitable composition for this purpose. To induce stabilized uniaxial anisotropy, Fe-Al-O films were micro-patterned into small rectangles by using photolithography and ion milling . The anisotropy field was increased from 2800 A/m to 6400 A/m, which enhanced the resonance frequency from 1.8 GHz to 2.7 GHz.

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We fabricated thin-film inductors for integration with semiconductor devices. Ni-Fe magnetic thin films made by rf magnetron sputtering were used for the inductors. We determined the sputtering conditions for obtaining a magnetic thin film. The inductor has a spiral coil sandwiched between upper and lower magnetic thin films. Aluminum was used as the spiral coil, and polyimide was used as an insulator. And also, we presented the integration of the thin-film inductors with semiconductor devices. As a result, the fabrication of the magnetic devices did not affect the properties of the semiconductor devices.

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This paper describes the characteristics of sandwich-type thin transformers with a fine-grain Mn-Zn ferrite core and three kinds of arrangements of planar windings. Thin transformer with primary and secondary conductors positioned alternately have excellent load characteristics. The results of the flux distribution analyses in the transformers with three kinds of winding structures show that the above mentioned transformer with primary and secondary conductors positioned alternately has good flux coupling between primary and secondary windings even when load current is flowing.

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We microfabricated magnetic thin-film inductors for use as rf front-end receiver impedance matchers in 1-GHz-drive mobile communication handsets. This is the first practical application of soft magnetic films in the 1-GHz range. Fe-Al-O high-resistivity thin films were used for the inductors. The purpose of this paper is to demonstrate a method of reducing the loss of magnetic thin films. Thin Cr films were used as underlayers for the Fe-Al-O films in order to solve the problem. We slit the magnetic thin films in order to reduce eddy current losses. The resistance of the inductor decreased by 40% at 1 GHz. A quality factor of Q = 7.4 was achieved by using a Cr underlayer and slits at 1 GHz.

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This paper describes a low-pass filter with a distributed constant circuit, which has electrically grounded top and bottom metallic magnetic layers, dielectric layers, and inner conductor lines. A trial large-scale device was used as an output noise filter in a 5 MHz switching boost micro dc-dc converter. With the new low-pass filter, the output spike noise was strongly suppressed.

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The fundamental swimming properties of spiral-type magnetic micro-machines were investigated in detail by constructing four micro-machines with different structures. These micro-machines are able to swim in various liquids with kinematic viscosities ranging from 1.37 to 1000 mm²/s. This result suggests that the micro-machines have potential medical uses. In particular, they can swim against the stream in a liquid whose the velocity is comparable to the that of venous blood.

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This paper presents a study of the linear compensation of nonlinear hysteric piezoelectric actuators in which highly magnetostrictive film patterns was used as a strain sensor. The elements have a hybrid structure, in which thin soft glass substrates with highly magnetostrictive amorphous FeCoSiB film were bonded onto a PZT piezoelectric substrates. The magnetostrictive film as a strain sensor detects the deflection of the actuator, and a voltage signal from the magnetostrictive strain sensor related to a deflection of the actuator is used for linear control of the actuator.

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The swimming properties of magnetic micro-machines with spiral structures were analyzed theoretically by employing the two-dimensional finite volume method. Good agreement between the experimental and theoretical results was obtained. It was demonstrated that the swimming properties of machines depend strongly on the operational environment, including the state of the flow field and machine structure. Thus, there exists an optimum machine structure corresponding to the operation environment, which can be determined from the present analytical results.

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Cellular phones are widely used these days, and there is a strong need for a thin model. Most cellular phones contain a vibrator that notifies the user of informing calls. For this purpose, a small rotary vibration motor is used. To make a thin cellular phone, it may be possible to use a linear oscillatory actuator (LOA) as the vibrator. This paper describes (1) considerations regarding the magnetic circuit and thrust of the LOA, (2) considerations regarding the use of the transfer function in the design method of the LOA, and (3) its trial fabrication of an LOA, measurement of vibration acceleration, and comparison of the LOA with rotary vibration motors.

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Permanent-magnet-type linear synchronous motors (LSMs) have high-velocity and high-accuracy positioning characteristics, and are therefore widely used as factory automation hardware. The authors have previously considered their static characteristics; this paper deals with the results of analysis of their kinetic characteristics.
The main findings are as follows:
(1) Measurement of the kinetic characteristics of a PM-type LSM showed a rated current of 3.8 A and a rated thrust of 176 N.
(2) The efficiency characteristics of the LSM were obtained in the velocity range from 1.1 to 1.5 m/s. For a velocity of 1.5 m/s, the maximum efficiency was 59.6 %.
(3) The eddy current loss and hysteresis loss were separated from the iron loss. For a frequency of 20 Hz (v = 1.6 m/s), the percentage of eddy current loss in the iron loss was 66 %.

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This paper presents a hard-magnetic-material-type rotary device whose axis of rotation is parallel to the direction of the exciting magnetic field. Cylindrical permanent magnets and some silicon steel sheets were used to obtain the radial components of the field strength. Because the principle of movement is similar to that of synchronous motors, the starting torque was still small and the moving direction was also unstable. To solve these problems, the permanent magnets distributed on the rotor surface were inclined to the fixed rotation direction. In addition, triangular silicon steel sheets were used instead of the previous rectangular ones. Measurement results show that the improved device has a starting torque in the fixed direction of motion.

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The electrical and mechanical time constants of a moving-magnet-type linear dc motor (LDM) are required to have small values so as to realize a high-speed response LDM. This paper describes the relationship between the time constant and slot width of a moving-magnet-type LDM. The following results were obtained:
(1) The measured electrical and mechanical time constants were 10.5 ms and 1.6 ms, respectively. The calculated values of the electrical time constant obtained by the permeance method and the FEM were 13.4 ms and 10.2 ms, respectively. The calculated values of the mechanical time constant obtained by the permeance method and the FEM were 1.4 ms and 1.5 ms, respectively.
(2) When the slot width was changed from 3 mm to 8 mm, the electrical time constant decreased by 30.9% and the mechanical time constant became increased by 6.9 %. Changing the slot width improved the response time by 5 ms.

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This paper presents a method for calculating the hysteresis loss in a linear dc motor (LDM). The main findings are as follows: (1) under dc bias magnetization, the hysteresis loss of the toroidal pure-iron core increases; (2) under the influence of the dc bias magnetization, the approximate relationship between the hysteresis loss and the maximum magnetic flux density changes from an exponential function to a polynomial one; and (3) the hysteresis loss of the LDM can be calculated from the measured values of the hysteresis loss of the toroidal pure-iron core under dc bias magnetization, and the error of the calculated results is 20.7%.

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In recent years, linear dc motors (LDMs) have gained wide popularity in the fields of office and factory automation. As a result,they need higher performance (e.g. high-speed, high-accuracy positioning). This paper deals with the effects of using a short-circuit ring in an LDM to achieve high-speed positioning, as follows: (1) expression of the transient performance of the coil current, (2) effective method of designing the short-circuit ring, and (3) effects of the short-circuit ring on the positioning characteristics.

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The X-Y LIM features a construction in which two kinds of windings (one in the X direction and the other in the Y direction) are wrapped respectively around two horizontal axes, X and Y. Its construction makes it difficult to compare the measured values of the flux density. Under such circumstances, it becomes necessary to conduct analysis based on the three-dimensional finite element method for suitable planning of X-Y LIM.
In this paper propose a suitable planning method based on a three-dimensional model of one pole, whereby fundamental equations used in analysis are derived to extract one pole of X-Y LIM. To obtain guidelines for the future, the paper examines (1) the adequacy of the analysis method, (2) the flux density with respect to the tooth width and slot width of the primary iron core, (3) the flux density with respect to the air gap, and (4) the relation between the primary current and the thrust.

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The constitution of the two-stage solenoid-type electromagnetic launcher (EML), the specifications of the projectiles and solenoid coils, and a method of improving the launching velocity by eliminating the eddy current are introduced. The influence of the projectiles with and without a slit on the launching velocity is discussed on the basis of experiments. The results are as follows: (1) For a carbon steel (S45C) projectile, the effect of a slit is very obvious. The maximum launching velocity of a projectile with a slit is 51.4 m/s, 8% higher than one without a slit. (2) For a permendur projectile, the effect of a slit is slight. The launching velocity with and without a slit is respectively 54.3 m/s, and 53.5 m/s, because the resistivity of permendur is 4 times than that of S45C.

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A wave soldering system has been used for more than 50 years in the process of circuit board assembly, but the needs for maintenance-free operations, high solderability, and downsizing of the solder capacity have still not been met. To meet these requirements, the authors made practical use of a wave soldering system in which a direct thrust is applied to the molten solder by means of a linear electromagnetic pump, thus realizing maintenance-free system, a 1/10 to 1/20 reduction of the defect rate, and a 57% reduction of the solder capacity.

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One of the features of linear motors is that they can be driven directly with linear motion. This paper proposes a meal assistance apparatus which can be easily operated by hospital patients. This apparatus uses the scoop operation to the patients in order to assist the operation. This is driven by a direct-current surface motor (DSM). In this paper, we focus on three aspects of the DSM: (1) a 21-mm thin DSM was manufactured experimentally; (2) magnetic characteristics and magnetic circuit were calculated by the FEM, and it was designed in the most suitable way; and (3) the maximum static thrusts of the DSM in the x-direction and y-direction were 19.5 N and 50.3 N, respectively.

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