A numerical approach for the solution of the scattering by an inhomogeneous H-plane discontinuity of arbitrary shape in a rectangular waveguide is described. The approach is a combination of the finite-element method and the analytical method. The validity of the method is confirmed by comparing numerical results for a waveguide-type dielectric filter, a right-angle corner bend, an inductive strip-planar circuit mounted in a waveguide, a T-junction and an inhomogeneous waveguide junction with the earlier theoretical and experimental results.

A nonperturbative method is presented for describing approximately the behavior of a self-oscillation of electric voltage in the Van der Pol equation over a wide range of the value of external parameter µ. To express an appreciably distorted wave form for the steady self-oscillation at µ1, a phase F of the voltage x, defined by x2A cos F (ωt), is approximated by a combination of several straight lines as a function of ωt from 0 to 2π with several numerical coefficients determined mainly from asymptotic behaviors of x for µ1 and µ1. It is shown that the resultant expression for x can describe well the numerical result over the wide range of µ. A bursting phenomenon induced by an oscillation of µ with a long period is also discussed on the basis of the present method, and the analytical results are in good agreement with the numerical ones.

This paper examines, from the viewpoint of network topology, the reliability of fiber optic networks for local area networks (LAN). The emphasis is on the comparison between the previously proposed simple transmission type (ST type) and the optical access type networks. The failure of an active device in a certain node station interrupts communication between other surviving node stations in the ST type fiber optic network, where fiber optic data highway is directly connected to optical active devices. In an optical access type network, optical signals in a data highway are dropped or inserted by optical passive devices and the failure of active devices does not disturb communication between other node stations. The availability expressions for the ST type and optical access type bus, loop, and star configurations are introduced to compare network reliability. Numerical calculation shows that an optical access type double loop configuration is more reliable, in comparison with other configuration discussed in this paper.

Some graph theoretic problems are considered and these problems are proved to be complete for nondeterministic log-space. These graph problems concern matching, connectivity, feedback node set, diameter, radius and so on. A consideration is also mode in connection with the Jones' open problem.

An extended state transition model and verification algorithm are proposed for specification and verification of protocols. The state transition model is an extention of Zafiropulo's two process protocol model to specify protocols designed for communication between more than two processes. A concept of Reduced Implementation Sequence (RIS)" is introduced to establish a protocol verification algorithm. By using RIS, potential movements of modeled systems are compactly described and the computation time necessary for verification becomes much shorter than that required for the method based on the traditional reachability analysis.

A newly devised beam-steerable antenna which is capable of steering its radiation beam without moving a main reflector is presented. This is the offset type spherical reflector antenna with two specific subreflectors. With the application of mathematical programming, a new technique to determine the shapes of the subreflectors is proposed in order to compoensate for the spherical aberration and the asymmetrical distortion of the aperture distribution, which deteriorates the electric characteristics. An experimental antenna has demonstrated its excellent performance and supported the adequacy and availability of the designing procedure. The results suggest the feasibility of the beam-steerable antenna for satellite communication use.

For full solid-state key telephone systems, high breakover voltage IC switches, which can connect to the central office lines directly and form a large scale matrix within a small volume, has been desired. Firstly, this paper compares several kinds of IC switches, which are suitable for formation of speech path matrix and shows that the photo-coupled PNPN crosspoint switch, connected in bridge format, is superier to the others because of low transmission loss, small matrix volume, reliability against lightning, self-latching speech path during power suspension and NTT technical requirements satisfaction. Secondly, the paper clarifies required electrical conditions for the PNPN element and the crosspoint circuit. They are breakover voltage above 300 V, dv/dt firing torelance above 160 V/0.1 µs, on-resistance within 9 Ω, less than 0.97 V forward voltage drop and restricting the reverse leak current which flows in the optically triggered PNPN element. Next, the IC switch structure is described, along with available technologies to satisfy the electrical requirements, such as canal isolation, highly efficient photo coupling structure and light shielding of anode junction. Actual IC switch characteristics satisfy all required values.

Expressions are derived for estimating the scattered and diffracted field in the presence of the polygonal cylinder using high frequency technique which is closely related with equivalent current or equivalent moment method proposed formerly. As the first step, we verified the method by applying it to various kinds of polygonal cylinders. The numerical results for radiation patterns are compared with those obtained by other methods when they are available. The agreement between them is fairly good and difference between them is not recognised in the figures except in a small part of region where observation point lies near a shadow boundary of the polygonal cylinder. The discrepancy is few decibels. Next we study a possibility of estimating the diffracted field of smooth convex cylinder by approximating it with corresponding polygonal cylinder. As an illustration we consider radiation of electric and magnetic line source in the presence of conducting circular cylinder since the exact solution of the problem is readily obtained. The approximation of smooth object with corresponding edged object is found to be useful from the standpoint of diffraction. The method is also applied to estimate the diffracted field by curved wedge and curved half plane.

The distance transformation of a digital picture (DT) is one of the most important techniques in image processing. In this paper, we propose a new variant called the max-type distance transformation for binary pictures (max-type DT). This transformation can be compared to the propagation of a wave, which propagates with a constant velocity to the pixels whose connectivity numbers are less than two. The connectivity number is calculated on the binary pattern obtained by regarding the pixels which the wave has not reached yet as 1-pixels and all the others as 0-pixels. The transformed value of a pixel is defined as the time when the wave reaches the pixel. After the transformation, the pixels on the core line of an input picture are given larger distance values increasing along the core line. Therefore, the max-type DT is effectively used in thinning and structure analysis of binary pictures. In the structure analysis using the max-type DT, both distance information and topological properties of binary pictures are used together. As an example, experimental results using hand-printed characters are shown. The max-type DT can also be applied to extract shape features by measuring the length of the core line such as the major axis of an ellipse.

A characterization of circuits and cut-sets of a 2-connected series-parallel graph is given using the representation tree. Cut-sets correspond to subtrees of the representation tree called P-subtree and circuits are characterized in the dual form.

Decomposition problems of boolean matrices are considered, and some interesting results are obtained. We decompose a given boolean matrix into a product of two boolean matrices. The decomposition operation is performed by means of transitivity of a matrix obtained from the given matrix. Decompositions of boolean matrices are important in many applications such as information retrieval, relational databases, large-scale systems, and so on. Boolean matrices represent relations, digraphs, and various binary systems. They are applied to many areas, so that decompositions of boolean matrices play an important role in the areas.

Optical experiments of collinear interaction between two optical guided waves and acoustic waves in multilayered directional couplers are firstly demonstrated. The device consists of ZnS/Ta2O5/Nb2O5 thin films on Y-cut LiNbO3 substrate. Surface acoustic waves of 750 mW at 28.6 MHz switched 90 percent of guided waves between the two waveguides. The bandwidth was 0.6 MHz, which agrees well with the theoretical result. The switching was found to be caused by the accumulation of slight deviation in the optical coupling periodic length along the interaction length. Fundamental optical experiments for this new-type acousto-optic multilayered film device assured the analytic results previously shown by the authors.

Cryptographic key sharing methods for multi-groups are proposed with threshold access schemes, and the methods are analyzed for safety and reliability, the measures of security. The threshold access scheme is extended from the members in a single group to members in multi-groups of equal or hierarchical status. In the horizontal scheme, agreement between a certain number of groups makes the secret key accessible. In the vertical scheme, agreement of a high level group or agreement between two groups at high and low level makes the secret key accessible. To realize these access schemes, mutually relative polynomials are proposed and the distributed keys are generated and synthesized by interpolation. The equipment and configuration to manage these methods are also explained. The system miss-access and inaccessibility rates of each scheme are formulated, and the characteristics of these schemes are evaluated by numerical examination. It is confirmed that sharing methods for multi-groups have greater safety than for single group.

A finite-element analysis is presented for predicting dispersion characteristics of acoustic waves propagating along the azimuthal direction in the cylindrically layered waveguides. The mathematical formulations are presented for both Rayleigh-type (or Lamb-type) waves and SH-type waves. The validity of the method is confirmed by comparing numerical results for Rayleigh waves and SH-type piezoelectric surface waves propagating along the convex cylindrical surface with those obtained analytically. We also demonstrate the application of this approach by analyzing the propagation problem of a waveguide composed of a cylindrical metal layer of finite thickness on the convex cylindrical surface.

Generation of line-drawing images in intelligent terminals seems to be an important theme in the area of computer graphics because of the recent architectures of computer systems. Required operations for the image generation should be local (or incremental), and each operation has to be carried out with limited amount of calculations and memories. The authors have reported the five-point method for this purpose. In this paper, the three-point method is newly investigated as a further study on this line. Traditional three-point methods cannot be applicable as their undulations" owing to the truncation of data points for local processing appear. Therefore, several types of estimations" are introduced in order to compensate the truncation; they are compared in view of derived results and required calculational steps, and one of the methods is recommended as the most useful local algorithm.

Preparation and properties of a new type a-Si:H solar cell based on an organic polymer film are described. Also are discussed the electrical and the optical properties of GD-CVD a-Si:H film used for the cell. The conversion efficiency of an polyimide/sputtered SUS/p-i-n a-Si:H/ITO cell with a size of 9 mm2 was 6.03% under the illumination of 92.5 mW/cm2 (AM-1). Cells on the polyimide film are stable even in high humidity over 150 days and allow flexible folding without any deterioration of the conversion efficiency. However, the conversion efficiency is always somewhat lower as compared with cells on SUS plate. Examining the correlation between the conversion efficiency and the surface morphology of a-Si:H layers, it was revealed that the higher roughness of sputtered SUS layer on polyimide film reduces the output current of the cell.

In a hearing aid, being small in size is one of the most important matters. An ear-hanging and an ear-plugging types of hearing aid are, therefore, comming to be preferred to those for wearing on. A new small sized receiver which is put in such the small hearing aid has been developed. In designing a small sized receiver, the following points are considered as of fundamental conceptions:(a) To be highly sensitive and to be low distortion.(b) To be stable even in any environment.(c) To be of simple construction and easy to manufacture.According to the above conceptions, a new construction of a small size receiver has been proposed. The feature of it consists in the point that the diaphragm including an armature is placed in the gap between the two poles and is directly driven by magnetic force. The target specification of the receiver expected to be 8.5φ6.5 mm in size, and 110 dB (0 dB210-4 µbar/mW, with 2 cc) in sensitivity. In order to make full study and easily on the magnetic and acoustic design of the receiver, the analogical rules have been applied to it, and a triple size model has also been manufactured for trial according those rules. As the result of manufacturing of the actual size receiver, it has satisfied the expected initial specifications with the property of high reliavility and mass productivity at the same time.

Two-dimensional acceptance angles of a proustite upconverter operating in several type I phase-match conditions are measured and compared with theoretical ones. They agree reasonably well with each other.

A label is given to each vertex of three views of a solid object. The relations among three dimentional vertices are obtained from a labeled tree. A face extracting algorithm by the tree searching method is reported with an example.

One of the bottlenecks for the efficient parallel processing is the communication overheads among resources. To solve this problem, we have been developing a high speed optical communication bus, which consists of laser diodes for signal emission, APDs for signal reception and a cylindrical mirror for broadcasting. The experimental system reported here operates at the clock frequency of 50 MHz.