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.

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.

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.

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.

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.

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.

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.

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.