We propose a multistage DeBruijn graph, a generalization of the DeBruijn graph, for dense symmetric interconnection networks in multicomputer systems. The proposed graph is symmetric and contains remarkably large number of vertices than other known symmetric graphs such as the Boolean n-cube and the star graph for given degree and diameter.

A programmable variable delay-line IC is designed and fabricated for a very-high-speed time-division switching system. The IC has 16-steps 200 ps delay step and multi-Gbit/s operation speed. The IC can be applied to a new pipelining data transmission system having Gbit/s speed. Maximum data transmission speed based on this IC is also calculated.

This letter investigates a criterion of fingerprint image quality. To establish the criterion is very important for developing the more excellent image enhancement technique. As the criterion, this letter proposes a method based on the conception of autocorrelation. From experimental results, it can be shown that the method is basically available for estimating the fingerprint image quality.

Spline functions attract attention as useful approximate functions which are smooth and apt not to vibrate. But the approximation by them is not characterized with any physical meanings such as the harmonic frequency for the Fourier series. The present paper aims to analyze characteristics of the spline approximation in the aspect of comparison with those of the Fourier series approximation. The results are summarized as follows. (1) Characteristics of the spline approximation change from those of the staircase approximation toward those of the Fourier series approximation according to the increase of the order of the spline function. This means that the spline approximation can adjust its characteristics to a signal given to be approximated if we choose an appropriate order. (2) The approximation power of a spline function is not constant on the time axis while that of a Fourier series is constant. A spline function has the spans with higher approximation power and those with lower power in turn on the time axis. This means that better approximation can be obtained by putting the spans with higher approximation power at the spans where good approximation is desired such as at peaks of a given signal. The above findings contribute to better use of spline functions in approximating signals.

A new class of codes defined as Separable Code has been considered to be successfully applied to a new error-control scheme called Type- Hyprid ARQ, which is based on the concept that some of the parity-check digits of the codes are sent to the receiver only when they are requested for error correction. Sevaral separable codes suitable to random error channels have been constructed and analyzed. In this paper, a new class of separable codes suitable to the burst error channels is constructed by modifying the Fire codes. Performance analysis of the codes based on the generalized Gilbert channel is given, showing that the proposed codes are superior to the Fire codes. Also, a new method of constructing a class of separable codes suitable to random error channels by puncturing linear block codes is given. It is shown that these codes are easier to implement than the known separable code.

Frequency synthesizers are widely used in the radio communication systems and as the signal generators. Usually, the frequency synthesizers are built as a PLL, and the requirements for both switching speed and frequency step size are in conflict. In this paper, a new digital frequency synthesizer using a phase accumulator is proposed, and a new phase frequency detector is described. The frequency of the phase accumulator is used as a reference generator and its frequency can be changed with a fine resolution at a high frequency, which offers a rapid frequency switching. Since the phase accumulator generates binary data, a new phase estimation technique is used and is extended to have an ability to detect the frequency error. Due to a high reference frequency which offers a high loop gain and the better characteristics of the phase-frequency detector, the speed of the frequency switching is improved. The properties of the proposed frequency synthesizer is investigated by experiments and theoretical analysis and is compared with the conventional PLL frequency synthesizer, resulting in that the proposed system has faster frequency switching speed and better signal purity than those of the conventional PLL frequency synthesizer.

The characteristics of an echelette grating are analyzed by the region dividing method which divides the free-space region above the grating into some subregions which overlap one another. The field in each subregion is expressed by the method of separation of variables; the coefficients of the modal functions in each subregion are determined by using the orthogonality of these functions. Hence, this method eliminates many of the unknown coefficients analytically, and gives sufficiently exact characteristics without regard to the shape of the echelette grating. One of the subregions above the grating is a sector. This paper shows the method of separation of variables applied to the sectorial region; a new expansion for an arbitrary function by orthogonal functions composed of the cylindrical functions is derived. The properties of the cylindrical function used in this expansion and a new method of numerical calculation of the function are given.

A low-loss and high-crosstalk-attenuation two-channel optical multi/demultiplexer for single-mode fiber systems is fabricated. This device is composed of new waveguides compatible with optical fibers (WCF) and interference filters. The waveguides are fabricated by the same method as used for optical fibers. The device has a low insertion loss of less than 2.3 dB, and high far-end and near-end crosstalk attenuations of over 54 dB and 68 dB. Coupling loss between the device and single-mode fibers is measured at less than 0.12 dB. Polarization dependence is not observed in the device.

A mono-sectional optical isolator consists of two mode selectors and one mode converter whose magnetization is uniform and tilts in the plane transverse to the light propagation direction by an elevation angle θ from the film plane. Nonreciprocal mode conversion properties of the converter which is the gyrotropic waveguide magnetized in an arbitrary direction have been theoretically investigated by using hybrid modes, and isolation properties of the mono-sectional optical isolator have been derived. The unidirectional mode conversion can be achieved in one mode converter because the mode conversions through the first and second order magnetooptic factors, and f₄₄M², add up and cancel each other in the backward and forward directions, respectively, when the film thickness is near the cut-off. The propagation length for the unidirectional mode conversion becomes small with the increase of and θ depends on f₄₄M²/. When the refractive index and the optical birefringence are 2.18 and 1.2810³, 4.18510³, f₄₄M²0.2 for the Bi:YIG guide layer and the refractive index of the substrate is n₂2.165, the isolation ratio of 30dB can be achieved at θ82 for the length of 5.0mm and the guide layer thickness of 1.64µm. Under this condition, the single mode operation which is essential to the optical isolator can be guaranteed.

This paper describes the wide-band linear phase surface acoustic wave (SAW) filters composed of slanted finger transducers. To calculate the characteristics of slanted finger transducers, the transducers were divided to multiple channels. In each channel, amplitude and phase performance for the slanted fingers are approximated as that of normal fingers, and admittance matrix of each channel is calculated by applying Smith's equivalent circuit, after that, all the channels are connected in parallel one another. Two filters with 13% and 50% fractional bandwidths were designed using a finger pair weighting technique. Considering the features of the filters composed of the slanted finger transducers, that their pass-band characteristics can be controlled by changing the conditions of propagation path, filters having notches in the pass-band were studied. Fixed and variable notch filters with 50% fractional bandwidth were designed, and characteristics were verified by experiments.

A reversible cellular automaton (CA) is a backward deterministic" CA, i.e., every configuration of it has at most one predecessor. Toffoli showed that a two-dimensional reversible cellular automaton is computation universal. He posed an open problem whether a one-dimensional reversible CA is computation universal. In this paper, we solve this problem affirmatively. This result is proved by using the previous result of Morita et al. that a 1-tape reversible Turing machine is computation universal. We give a construction method of a reversible CA which simulates a given 1-tape reversible Turing machine. To do this, we introduce a one-dimensional partitioned cellular automaton" (1-PCA). 1-PCA has the property that the local reversibility (i.e., injectivity of a local function) is equivalent to the global reversibility, and thus it facilitates to design a reversible CA.

This paper describes an easy method of generating cloud images by using density contour lines. First, the operator inputs the density contour lines. Features of the contour lines are then extracted. Next, the form is reconstructed on the assumption that it is a homogeneous corpuscle layer of could. Finally, a cloud image is generated, using the reconstructed form and a light attenuation model. The burden on the operator is much lighter than in conventional methods, which use mathematical functions to define objects. Furthermore, the reconstructed shapes can be represented either as mountains or clouds, an important advantage for making a database of computer animation backgrounds. This is an extension of our previously reported method of reconstructing three-dimensional mountainous shapes.

Conventional retrieval methods of image database (IDB) systems are utilizing non-image information, or alphanumerical data, as keywords. These methods are suitable for document database systems, but not for IDB systems because the contents of image cannot be expressed by only such keywords. In this paper, a new image retrieval method using the layout structure" is proposed. This method can realize image retrieval based on the contents of image. Because, the layout structure means structural information such as object location and spatial relation and it corresponds to composition" of the image. This information, called region feature description (RED), is obtained in the input process of original images. In the retrieval process, we use some specified files which are created form RFD on the basis of each structural feature. Thus, interactive image retrieval based on structural information, that is composition", can be performed. Since India ink paintings are adopted as target images in this paper, it is difficult to extract and describe structural feature of object regions as they are. The structural information is described as geometrical feature by approximating them to simple polygons. As a result, composition" of the target image is obtained. This paper describes the description scheme and the extraction procedure of the structural information. And some experimental results are also presented to confirm the effectiveness of this method.