A nonlinear modified Laplacian operator for ridgeline extraction in a picture is proposed. The operator shows better performance in enhancing the ridgeline and suppressing noise compared with the conventional Laplacian operator.

Self-healing breakdowns of anodic Y2O3 films with the thickness of 500 to 2000 have been measured. The measurements reveal that the breakdown is a single-hole type and that the breakdown field, which is closely correlated to the anodizing field, is independent of the Y2O3 thickness. An ionic motion is considered to the effective in initiating the breakdown which forms a conducting channel through the Y2O3 film. The energy of the breakdown spot formation is calculated assuming the thermochemical evaporation process of the substances. It agrees well with the discharged energy of the specimen capacitor at the breakdown.

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.

A technique is presented for the automated calculation and the imaging of the electric field around a moving animal. This technique is based on the numerical analysis of an electric field using the finite difference method. Its usefulness in practice is demonstrated by applying it to a free-moving mouse. The mouse is photographed in a 35 mm monochromatic film, and it is transformed in a digital image using a flying spot scanner (FSS). This image is used as a boundary condition for the numerical calculation of the electric field. The distributions of both equipotential lines and electric lines of force are plotted on an X-Y plotter. The intensity distribution of the electric field is presented in the luminance on a CRT display of the FSS and recorded on a film. The surface electric field of the animal body is calculated by extrapolation along the electric line of force and presented in vector patterns. It is shown quantatively that the electric field on the animal body (e.g. nose, back, ears) changes considerably as the animal changes its posture. This method is widely applicable to the objects with any shapes including a human.

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 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.

A technique was developed to reduce ECG data efficiently within a controlled accuracy. The sampled and digitized data of the original waveform of an ECG is transformed in three major processes. They are the calculation of a beat-to-beat variation, a polygonal approximation and the calculation of the difference between consecutive node points. Then, an adaptive coding technique is applied to minimize redundancies in the data. It was demonstrated that the ECG waveform sampled in 200 Hz, 10 bit/sample, 5 µV/digit could be reduced with the bit reduction ratio of about 10% and within the reconstruction error of about 2.5%. A polygonal approximation method, called MSAPA, was newly developed as a modification of the well known method, SAPA. It was shown that the MSAPA gave better reduction efficiency and smaller reconstruction error than the SAPA, when it was applied to the beat-to-beat variation waveform. The importance of the low-pass filtering as a preprocessing for the polygonal approximation was confirmed in concrete examples. The efficiency of the proposed technique was compared with the cased in which the polygonal approximation was not used. Through these analyses, it was found that the redundancy elimination of the coding technique worked effectively in the proposed technique.

Fourier reconstruction has orginally been one of the methods for three-dimensional structure reconstruction in medical applications such as the computed tomography (CT). The technique is found to be applicable to designing circularly symmetric FIR digital filters. The algorithm is simple, straightforward and practical. The approach basically consists of designing a one-dimensional (1-D) FIR prototype, rotating its frequency response in the two-dimensional (2-D) frequency plane, inverse Fourier transforming and then windowing the result. An unlimited number of profections at different orientations of the obtained impulse response are essentially identical with the 1-D FIR prototype. The even size 2-D FIR filters can also be designed. The impulse response has eightfold (octagonal) symmetry. The frequency response is shown to have nearly circular symmetry that is evaluated with rms and maximum absolute errors.