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.

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.

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 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 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.

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.

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.

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 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.

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.

It is well know that charges stored in condenser decay exponentially in time through resistor in CR-circuit. But in some types of condensers the exponential decay at initial stage breakes down, and the speed of discharge slows down. There the decay has long time tail characteristic to fractal time random walk.

Mesh-connected computers (MCC's for short) are an important class of physically realizable parallel processors, since many scientific problems can be naturally mapped on them and because their regular structures and simple nearest-neighbour interconnections are particularly suitable for VLSI implementations. In former days iterative arrays and cellular automata were studied and recently special attention has been paid to the study of systolic arrays as a model of parallel computation on VLSI implemented MCC's. These abstract computational models constitute a family of MCC's. In this paper we study the effects of broadcasting bus systems augmented with a mesh-connected computer. First we develop a direct proof technique for the elimination of broadcasting buses. Then, as an application of the technique, we will show that a rich variety of broadcasting bus systems on one- and two-dimensional arrays can be eliminated without any loss of time efficiency. No-time-loss elimination of broadcasting buses on one-dimensional arrays has been shown by a different technique by Ibarra et al., but without our technique, it would be more difficult, but not impossible, to get the same results that we presented newly in this paper.

This paper presents a method for analyzing a Markov process of the generalized loss system which includes the , /M1, M2/S, the , /, /S and the , /M1, /S loss systems. The generalized loss system is a loss system with multi-class of batch arrival customers. In the system, a customer requires more than one server at the same time. The analyzing method makes use of the existence of a product form solution for a Markov process. This paper also presents a theorem for the , /M1, M2/S (PBAS) loss system. The theorem asserts that the steady-state probability of the total customers of the , /M1, M2/S (PBAS) loss system can be derived as that of the M x/M/S (PBAS) loss system with the same traffic intensity and batch size distribution. For the , /M1, M2/S (WBAS) loss system, two approximation analysis methods that assume the product form solution and use the theorem of the PBAS type system are propesed to obtain the blocking probability. The analysis for the generalized loss system and approximation analysis for the , , M2/S (WBAS) loss system are applied to the design and dimensioning of resource sharing systems in ISDN.

The accumulation of the thermal noise can be considered to be one of the most important parameters for the effective design of a multirelay transmission system. A theoretical model for prediction of the distribution of this parameter has recently been proposed. The method has assumed the log-normal form for the unconditional point rainfall rate distribution. In the present work an extension of the previous method is proposed, to include the case of the gamma distribution which is more applicable to Japan and other regions with similar climatic conditions. Numerical results are compared with experimental data taken from a 20 GHz multirelay system located in Japan.

Sampling theorem for all bandlimited distributions which converges in the sense of distributions is presented. An inter-extrapolation formula with the most general sampling points on the negative time axis is provided and especially for equally-spaced sampling points an explicit formula is given, where it is proved that the Newton interpolating polynomial through the finite number of sample values converges with the Mittag-Leffler summation. These formulas are both proved to be convergent in the topology of distribution, hence a consistent theory is accomplished within the scope of distributions. As many linear operations on signals such as differentiation are continuous with respect to the distribution topology, the given formulas exhibit great facility when applied to signal analysis.

In optical coherent communications with homodyne detection system, it is one of the most essential problems to synchronize the phase of local oscillator with that of received signal on the receiver. In general, the phase-locking performance is limited by frequency fluctuation and quantum noise of light source. So far some optical phase-locked loops have been proposed in order to optimize phase-locking performance. Their main purpose is to minimize phase error variance of systems with frequency fluctuation and quantum noise transformed into the electric region. To improve the phase-locking performance under the same situations, this paper proposes a new optical phase-locked loop with received quantum state controller, called a Squeezed-PLL, which can reduce the impact of quantum noise in the optical region. This system can eliminate the effect of the vacuum noise due to the beam splitting. Finally, the general signal to noise ratio of data-branch is shown, and phase-locking performance of the Squeezed-PLL is verified by computer simulation.

An AR model is one of linear stochastic equations, which is characterized by the eigenvalues and eigenvectors. Since the poles in the AR model correspond to the eigenvalues in linear equations, the weights of poles in the AR model correspond to the eigenvectors in linear equations. The AR type model has essentially two types poles; system poles and virtual poles corresponding to system zeros. These poles can be distinguished by observing the weight of each pole in the partial fraction expansion of the AR model transfer function. The rules for separation of AR poles are: (a) If the weight of an AR pole is constant for AR model order change, the AR pole is a system pole. (b) If the weight of that is inversely proportional to the AR model order, the AR pole is one of virtual poles.

With popularity of radio communication, voice scrambling has received increased attention for communication privacy. It has been known that pre-emphasis at the transmit side and de-emphasis at the receive side improves the received signal to noise power ratio (SNR) both for scrambled and nonscrambled signals. In this paper, optimum pre- and de-emphasis are theoretically investigated for FM and PM transmission including frequency-domain scrambling for voice security. Using a linear system model, the optimum frequency-characteristics for pre- and de-emphasis filter are given as a function of a voice signal spectrum, demodulator output noise spectrum, and the scrambling method. Comparisons of the maximum attainable SNR are made for various case including plain voice (non scrambling) and secured voice scrambled by spectrum inversion, reverberation and FFT spectrum transformation, assuming simple voice and noise spectra.

This paper proposes a new evaluation method for ARQ schemes. The decoded bit error rate versus Eb/N0 and the bandwidth expansion ratio are adopted as criteria to measure performance capability. The method makes it possible to compare the performance capabilities of various error control schemes on the same basis. Since this method clarifies the Eb/N0 and the bandwidth required for obtaining the desired BER, it gives some useful indication on deciding which scheme to use in a particular application. FEC, ARQ, Type- hybrid ARQ, and Type- hybrid ARQ, each of which uses a binary BCH code with a common code length, are taken up as examples for analysis. The numerical results show that well designed hybrid ARQ schemes can considerably reduce Eb/N0, at a cost of a small bandwidth increase. Based on the foregoing analysis, this paper also proposes a constant-rate ARQ scheme with finite buffers. This scheme offers a constant throughput rate and a constant delay time as a conventional FEC scheme. It requires less Eb/N0 than an FEC scheme. The numerical results are presented for some examples. The results on the fixed bandwidth expansion ratio show that the proposed scheme with a binary BCH code requires less Eb/N0 than an FEC scheme using a convolutional code and soft decision Viterbi decoding. The decoder of the proposed scheme is much simpler than a Viterbi decoder. This proposed rate-constant ARQ scheme is suitable for application to those systems in which a feedback channel is available and a constant throughput rate and a constant delay time are required.

This paper discusses branch metric computation in the main decoder placed in an SST (Scarce State Transition) Viterbi decoder. The basic assumptions that all the message sequences are equally likely and that the channel is memoryless do not hold for the main decoder in an SST Viterbi decoder, when an inverse encoder or a pseudo-inverse encoder is used as a pre-decoder. Therefore, in contrast to a conventional method, an MAP (Maximum A Posteriori probability) estimation method itself, which is the starting point of the maximum likelihood decoding, has been applied to branch metric computation. Then, it has been clarified that the conventional branch metric computed in a usual SST Viterbi decoder happens to be equal to the branch metric derived using the MAP estimation method only for systematic codes. For general non-systematic codes, in particular, it has been found that it is impossible to decompose a path metric into such branch metrics that follow the original code trellis structure, because the branch metric derived at time k is also dependent on future state transitions.