A method is described for approximately estimating the surface specific-absorption-rate (SAR) in an anatomically realistic model of the human head for microwave exposure using the external magnetic near-field. The finite-difference time-domain (FD-TD) technique is used to compute the electromagnetic fields in the head model for 750-MHz and 1.5-GHz far-field exposures with the 1991 ANSI specified safety level. The spatial pattern tracking between the one-gram averaged surface-SAR and external magnetic near-field is demonstrated on the horizontal cross sectional perimeter of the head model. The regression coefficients between them are also obtained on the fifty-five horizontal cross sectional perimeters, which could give an approximate value of the surface-SAR in an acutual head, if the external magnetic near-field would be measured. This is validated by the theoretical results in a semi-infinite homogeneous flat model for normal incidence microwave exposure.

A simple solution for the right-angle H-plane waveguide double bend is obtained in analytic series form. The simultaneous equations are solved to obtain the transmission and reflection coefficients in fast convergent series forms. The numerical computations are performed to show the behaviors of the transmission coefficient versus frequency.

The validity of numerical design scheme of CP-PASS (Circularly Polarized Printed Array antenna composed of Strips and Slots) is considered. The strip element of CP-PASS is composed of a strip dipole and a window which increases the frequency bandwidth of the strip element. With the window, however, analysis of the antenna becomes difficult if a simple analytical model is used. The previous design procedure requierd an experimental procedure. By using modern computers, the FDTD (finite-difference time-domain) method becomes powerful tool for the analysis of 3D-structured antennas. In this paper, numerical results of the FDTD analysis for CP-PASS is compared with results from experiments. The characteristics of the unit-radiator of CP-PASS are demonstrated numerically. This paper shows that CP-PASS can be designed numerically and a new path has opened in the study of CP-PASS.

In this paper, the influences of the cross-sectional deformation on the coplanar waveguide (CPW) characteristics for the use of Ti: LiNbO3optical modulator are presented based on quasi-static analysis. In particular, the influences of the changes in the thickness of Ti: LiNbO3 substrate and the cross-sectional shape of electrodes are studied in detail by using the finite element method proposed previously. As a result, it is found that the propagation characteristics of the dominant mode change significantly with the thickness of LiNbO3 substrate when it is less than 100 µm. It is also shown that an inverted trapezoidal deformation of the electrode cross section is promising because a wider electrode gap and thinner electrodes are available in the design of optical modulators.

A new simple formulation of absorbing boundary conditions with higher order approximation is proposed for the solution of Maxwell's equations with the finite-difference time-domain (FD-TD) method. Although this higher order approximation is based on the third order approximation of the one-way wave equations, we have succeeded in reducing it to an equation in a form quite similar to the second order appoximation. Numerical tests exhibit smaller reflection errors than the prevalent second order approximation.

A particle trajectory estimation method from far electromagnetic fields are discussed in this paper. Authors have already presented a trajectory estimation method for single particle system and good agreements between a source particle trajectory and an estimated one have been obtained. For this, this paper discusses twin particles system as an examples of multi-particles systems for simplicity. First of all, it is pointed out that far electromagnetic fields from the twin particles system show quite different aspect from the single particle system using an example, radiation patterns produced by two particles which carry out circular motion. This result tells us that any trajectory estimations for general multi-particles system are almost impossible. However, it is shown that when the distance between the particles is small, the estimation method for the single particle system can be applied to the twin particles system, and that twin particles effects appear as disturbance of estimated trajectory.

In this paper, the dispersion characteristics of magnetostatic surface waves (MSSW) in a nonlinear gyromagnetic medium are analytically investigated. Assuming the nonlinearity as the first order perturbation in permeability tensor of the gyromagnetic medium, the perturbation technique based on the multiple scale method is used to deduce the nonlinear dispersion relations for the MSSW. It is observed that for a given propagation constant of the MSSW the frequency decreases with microwave power. It is also observed that group velocity decreases, and as a consequence, delay time increases with power of the microwave. By evaluating the dependence of frequency on power and variation of group velocity on propagation constant within the accuracy of the perturbation theory, it is confirmed that the conditions for formation of bright soliton are not satisfied for the MSSW.

A magneto-optical head lens actuator was developed for use at a high information bit rate and high density recording. A high bit rate at the outer diameter of a 300 mm disk (velocity = 27.3 m/s) was attained by mounting an aspherical plastic lens and optimizing the shape of lens holder for achieving higher spurious frequency over 30 kHz, utilizing the finite element method (FEM). Another approach was focused on reducing gain peak at the natural frequnecy by adopting "multi-wire" and a silicone "gel box" damping system for stabilizing the pull-in characteristic for focusing and tracking. By the actuator realization, a high density recording of 0.34 µm/bit and high information bit rate 80 Mbps (1, 7 code modulation) recording were attained.

A new positioning method for higher track density hard disk using embossed-servo-mark magnetic disks is proposed. An embossed-servo-mark medium with grooved-guard-band data tracks for 208 TPMM was developed using molded plastic substrate. The marks were magnetized so that conventional magnetic head can reproduce position signals. Simple analogy from optical disk track following to magnetic disk track following was taken and examined. A DSP controlled feed-forward servo was introduced to resolve the inherent eccentricity caused by mounting preformed tracks onto an independent spindle axis. The prototype drives with a form factor of 2.5 inches were designed introducing the disks, the servo scheme and the newly developed orthogonal MR head. As a result, an areal density of 650 kbits/mm2 (about 420 Mbits/in2) recording was successfully demonstrated on the media using 2.5-inch form factor prototype drives.

This paper presents the history of Flash memories and the basic concept of their functions and also reviews a variety of Flash EEPROM's so far. As Flash memories have two influential features, non-volatility and low cost per bit, they are expected to become a driving force after DRAM's to support the semiconductor industry for the next thirty years, replacing hard and floppy disks which have a large market.

A multi-channel high temperature superconducting interference device (high Tc SQUID) system with high magnetic field resolution has been developed. Step edge junctions were employed as weakly coupled Josephson junctions for the SQUID. These junctions worked well and their I-V curves fit the resistively shunted junction (RSJ) model. The SQUID design was investigated to improve magnetic field resolution. The size of the SQUID's center hole was investigated, and we found the optimized size of the hole to be about 25 µm. Meissner effect of superconductor was used in order to concentrate magnetic fluxes. A large washer SQUID and a flux concentrating plate was developed to concentrate magnetic flux to the SQUID center hole. The magnetic field resolution became 370 fT/Hz at 10 Hz and 220 fT/Hz at 10 kHz. This field resolution was enough to detect biomagnetic signals such as magnetocardiac signals. The SQUID was mounted on a special chip carrier and was sealed with epoxy resin for protection from humidity. We have designed and developed a 4-channel and a 16-channel high Tc SQUID system. We used them in a magnetically shielded room to measure magnetic signals of the human heart. We obtained clear multi-channel magnetocardiac signals, which showed clear so called QRS and T wave peaks. A clear isofield contour map of magnetocardiac signals was also obtained. These data indicated that high Tc SQUID is feasible for these biomagnetic applications.

To study the biological effects of the ion-current commonly found under ultra-high voltage DC transmission lines, a technique was developed to evaluate the human exposure to the ion-current field. This technique is based on numerical analysis using the boundary element method. The difficulty of handling the space charge in the calculation was overcome by assuming a lumped source ion-current. This technique is applicable to a three-dimensionally complex object such as a human body. In comparison with theoretical values, the accuracy of this technique was evaluated to be satisfactory for our purposes. It was then applied to a human body in an ion-current field. The distribution of the electric field along the body surface was obtained. The general characteristics of the field distribution were essentially the same as in those without space charges. However, it was found that the strength of the field concentration was significantly enhanced by the space charges. Further, the field exposure when a human body was charged by an ion-current was evaluated. As the charged voltage increases, the position of the field concentration moves from a human's head toward his legs. But the shock of micro spark increases. This technique provides a useful tool for the study of biological effects and safety standards of ion-current fields.

The biological effects of power frequency electric and magnetic fields have been a source of concern for the past many years, especially since 1979 when an epidemiological study report suggested a positive relationship between childhood cancer and exposure to power frequency electromagnetic fields from residential overhead power lines. The extensive studies of dosimetry and biological effects have since been carried out. It is believed that power frequency electromagnetic fields does induce biological effects (no serious threat to human health). The clear explanations for the possible interaction mechanisms remain to be identified. The problem with the study on dosimetry has been lack of theory that applies to the physical interaction of power frequency electric and magnetic fields with humans. At present, it seems to be widely accepted that the density of induced currents in the human body can be used as the decisive parameter in evaluating human exposure to these fields. In order to predict the distribution of induced current density inside a human body exposed to electric fields, magnetic fields, or electric and magnetic fields that coexist, the precise measurements of electromagnetic environments are necessary. According to necessity, the fields have to be characterized in terms of strength, orientation and phase angle. This paper presents: (1) Measurements of power frequency electromagnetic environments in 187kV substation yard and in the vicinity of the ground under 187 kV line using laboratory-made instruments; (2) Development of magnetic field exposure monitor; and (3) Review of state of the art of theoretical dosimetry for electric fields, magnetic fields and combined electric and magnetic fields, and evaluation method of human exposure for the future research.

For the study of the biological effects of ELF (Extremely Low Frequency) electric fields, the perception mechanism of ELF electric fields was analyzed. When a human body is exposed to an electric field, the hair on the body surface moves due to the electric force exerted on the hair. In theoretical analysis, it was shown that the force is approximately proportional to the dielectric constant of hair and the spatial gradient of the square of the electric field at the hair. The dielectric constant of hair was measured with different temperatures and humidities of the surrounding air. A technique was developed to estimate the electric force exerted on a hair during the field exposure. After experiments with model hair, the technique was applied to a body hair of a living human being. It was found that the force increased with field strength and relative humidity. The variations of the force agreed well with those expected from the theoretical analysis and the measurement of hair dielectric constants. These results explain the cause of the reported variation in the threshold of biological effects of an electric field. The results will help to establish a practical safety standard for the held exposure.

The studies on the biological effects of ELF electric fields conducted in Japan are reviewed. Among international studies, they are characterized as the studies from the viewpoint of bioengineering. In early studies, the safety standard of high voltage transmission lines was determined by a distinct biological effect, i.e., the sensation of the spark discharge caused by electrostatic induction. In numerical analysis, the field coupling to both animal and human bodies became well understood. Some new measurement techniques were developed which enabled us to evaluate the field exposure on a human body. A system was developed to realize the chronic exposure of an electric field on mice and cats. An optical telemetry technique was developed to measure the physiological response of an animal when it was exposed to an electric field. An ion-current shuttle box was developed to investigate the behavioral change of a rat when it was exposed to an ion-current as well as an electric field. In animal experiments, a mechanism of sensing the field was investigated. The cause of the seasonal change of field sensitivity was found. In cases of chronic exposure, suppression of growth was suspected. In shuttle box studies, an avoidance behavior from an ion-current was quantified. To find whether there are any adverse or beneficial effects of the field exposure on human beings, further study is required to clarify the mechanisms of the biological effects.

This paper surveys the researches on biological and electeromagnetic environments in RF (radio frequency) and microwave regions in Japan. Publicized research reports on biological objectives, evaluation of exposure rate, electromagnetic environments and guideline for the protection from radio wave nuisances are briefly introduced. Some researches on the evaluation of the exposure rate caused by the near field effect of portable radio transceiver are reviewed. Radio frequency exposer protection guidelines in Japan are also described.

An analysis of the circuit for dead angle compensation in the dc-to-dc converter controlled by a magnetic amplifier is presented. This circuit suppresses the dead angle so that the core loss may be reduced without spoiling the current surge suppression characteristics of the magnetic amplifier. The analysis is given by modeling the magnetization characteristics of the core containing the saturation inductance and the reverse recovery of the diode. As a result, the control characteristics of the converter with the compensation circuit are expressed analytically and a limit of compensation is derived theoretically.

An exact analysis for magnetostatic surface wave excitation by a single microstrip is presented. Conventional approaches for such an excitation problem do not explain experimental results in a reasonable manner. The theory proposed here explains radiation resistances obtained by experiments, owing to having considered the edge conditions and an expansion form of excitation current on the microstrip properly.

The exact characteristic equation for the hybrid modes in Goubau line is given. By solving the equation numerically we find the hybrid modes Lnm, defined in this paper. We also examine the propagation and attenuation constants of the hybrid modes. As a result the hybrid K12 mode has the extremely low attenuation at the specific frequency similar to the hybrid K11 mode. The electric field distributions of K11 and L11 modes are plotted.

For analyzing the transient electromagnetic fields caused by electrostatic discharge (ESD), a new ESD model is presented here. Numerical calculation is also given to explain the distinctive phenomenon being well-recognized in the ESD event.