We formulate an improved lower bound on the maximum number of prime implicants of n-variable Boolean functions. It is given as n!/(n/3!(n1)/3!(n2)/3!)(n, 0, (n1)/32)(n, O, (n2)/32), where (n, 0, r) is evaluated by the following recursive procedure: (n, 0, r)0 for r0, (n, 0, 0)1 and (n, 0, r)n!/(r/2!(nr)!(r1)/2!)(n, 0, (r1)/2 2) for 1rn. The total logarithm computing time cost and the total uniform computing time cost of this lower bound by a random access machine are O (n (log2n)2) and O (n), respectively. The ratio of this new lower bound to the old lower bound is bounded by 1c (1/2)n/3, where c is a constant independent of n.

Variation of power distribution caused by splices is calculated as a function of numbers of splice points and misalignment. The calculated power distribution is verified by experiment. Calculation shows that mode conversion caused by splice makes power distribution approach to steady-state. The numbers of splice points required to make power distribution stationary are calculated as a function of misalignment. Pulse broadenning in the fiber transmission line is calculated for the case that fibers are mode conversion free. Pulse broadenning rate becomes proportional to the square root of transmission distance after optical pulse passes many splice points. These calculated results show that mode conversion caused by splice has similar tendency as that caused by longitudinal inhomogeneity of waveguide.

The statistical model for urban radio propagation has been proposed to describe the characteristic of radio pulse propagation in urban area. A modified Poisson process was used to model the clustering phenomena of the pulse arrival time sequence. In this paper, the model analysis is extended for more flexibility in data fitting, and generalized using a Markov chain to get a clear view of the statistical model. Some numerical results are shown for different values of the clustering parameter (Δ). Referring to the numerical results, the effect of Δ and the another clustering parameter (K) on the pulse number distribution is discussed. Next, the relation between the empirical pulse occupancy rate and the underlying occupancy rate of the model is derived for Δ1 using a Markov chain. By this extension and generalization, the statistical model of the pulse arrival times will be applied to a wide range of the clustering phenomena.

We consider an adaptive PCM system, in which the input samples are expanded or compressed by a constant factor c or 1/c each time before quantization. Assuming a stationary Gaussian input with a rational power spectral density, we derive an integral equation for the joint distribution of the input and the state of the system. Its solution provides us with a feasible way to numerical computation. The mean-squared error are computed for the Gauss-Markov input in terms of the constant c, the sampling interval T, bound parameters for the scaler and the number of quantization levels. The numerical results show good performance in comparison with regular PCM.

First, it is shown that pole sensitivity with variation of gain-bandwidth product is dominant in an RC active circuit realized by an internal phase-compensated operational amplifier. Second, a method is described, by which a single amplifier 2nd-order RC active circuit with prescribed pole sensitivity with variation of gain-bandwidth product can be realized.

The bandwidth of the single-mode fiber is derived for both the amplitude-modulation and the heterodyne-detection (AM) system and the intensity-modulation and the intensity-detection (IM) system, in case that the spectral width of the light source is much less than the modulation bandwidth. In the wavelength-division-multiplexing system, the bandwidth per carrier wave is given as a function of the wavelength, and also at the zero-dispersion wavelength. In case of IM system, the frequency dispersion of the fiber causes the harmonic distortion of the signal and reduces the bandwidth to about a third of that in case of AM system.

This paper gives an experimental result on the measurement of the maximum coupling coefficient and the coupling length between the active waveguide and the passive output waveguide in GaAs/AlGaAs integrated twin-guide (ITG) injection lasers prepared by LPE. Very high coupling efficiency between the active and the passive waveguides was experimentally confirmed. The maximum coupling coefficient and the coupling length were measured to be about 90% and 250 µm, respectively. These values were in agreement with theory. At properly chosen parameters, the threshold current density on an ITG-type" laser was as low as 3 kA/cm2 at room temperature.

Several reports have been published on the quantitative analysis of kink formation mechanism in the output vs. current relation in stripe geometry injection lasers. The results, however, contradict with each other in basic points. In seeking for a better quantitative understanding of the transverse mode instabilities manifested by the kink formation, this paper examines basic aspects of the spatial hole-burning induced mode deformation, which is believed to cause the instabilities. Properties of the eigen functions and eigen values corresponding to the light propagation in a complex dielectric waveguide with a spatial gain and/or loss variation are examined, and an efficient approximation scheme is proposed for computing modal gain. This scheme is applied to a numerical model which approximates gain and refractive index profiles with spatially burned holes in a stripe geometry injection laser. It is found that the mode deformation induced by the hole-burning substantially affects the modal gain, and that the extent of the influence depends strongly on the refractive index contribution to the waveguiding.

Aliasing effect of a sampled signal can be reduced by estimating the signal from the samples and then updating the estimate by an iterative technique. This idea can be implemented easily by a multiplier and a feedback loop.

Two-dimensional diffracted fields from semiinfinite conducting plane with a circular cylinder of various types at its apex are studied for the purpose of suppressing the backward radiations from the reflector antennas. The basic policy for the suppression of the diffracted fields was already obtained by the authors. It concludes that the electrically and magnetically conducting cylinders are most effective in suppressing the diffraction for the E and H wave incidence, respectively. From the practical point of view, the main difficulty in this policy is how to realize the magnetically conducting cylinder which suppresses the H wave diffraction. In this paper, a corrugated cylinder is adopted for the purpose of the suppression of the H wave diffraction. The characteristics of this cylinder are analyzed by the mode-matching techniques and it is indicated that the corrugated cylinder fairly suppresses the diffracted fields, not only for the H wave but also for the E wave incidence, to almost the optimal level. Additionally, the wideband frequency characteristics are introduced. All these theoretical results are confirmed by the equivalent two-dimensional experiments. At the end of this paper, the applicability of the corrugated cylinder to the suppression of the three-dimensional diffracted fields is suggested experimentally.

A simple theoretical model for surface acoustic wave (SAW) ΔV/V waveguides on anisotropic crystals is presented. Applying the theory to the waveguides on Y-cut LiNbO3, the dispersion relations are calculated. Experimental results of the velocity dispersion were shown to be in a reasonable agreement with the theory. Although the observation of the SAW field revealed a small discrepancy from the theoretically predicted profile outside the waveguide, it can be concluded that the present model gives a very good approximate method to the study of ΔV/V waveguides on anisotropic substrates.

This paper proposes a new approach to the problem of efficient digital coding of the NTSC composite color TV signal. First, a new method, named Comb-Filter Integration method", of deriving a prediction function effective for the NTSC composite signal is introduced. This method is based on the technique of integrating a simple comb-filtering operation into an arbitrary linear prediction function tailored for monochrome TV signals, and thus coverting it to a prediction function effective for the NTSC signal. Practical examples of such composite prediction functions are shown. Then, 32 Mb/s and 44 Mb/s DPCM systems, using one of these prediction functions, are described along with their simulated performances. The results show that these systems are promising for the high-quality transmission of the NTSC signal.

The effect of the intraband electronic relaxation on the relaxation oscillation of the light output from the injection laser modulated directly is examined theoretically. Assuming the k-selection rule, carriers are devided into two parts; that is, carriers which contribute to the laser gain directly, and the rest. The intraband electronic relaxation is taken into account as the coupling of the two parts of the carriers in rate equations. As the result of the small signal analysis of rate equations, the height of the resonance-like" peak in the frequency response of the direct modulation depends on the electronic relaxation time remarkably in the range from 10-13 to 10-12 s. The intraband electronic relaxation possibly concerns with the suppression of the relaxation oscillation of the light output from the GaAs injection lasers.

Atmospheric propagation affects the optimization problem of an optical terrestrial communication link. The optimum system parameters are computed for a CO2 heterodyne communication link for different atmospheric visibilities.

This paper proposes a heuristic algorithm for constructing a new school timetable by revising partially the school timetable already constructed for the previous year. This algorithm is considered as an extension of the algorithm proposed in the author's previous paper which aims at constructing a new school timetable. It is noted that the assignments in the present algorithm begin with an almost filled school timetable, while the assignments in the previous algorithm begin with an almost empty school timetable. Numerical examples show that the computation time of the present algorithm is considerably shorter than that of the previous algorithm when a timetable for the previous year is available.

Results obtained from a study on junction properties of n-CdS/p-InP heterodiodes which were prepared as solar cells by the close-spaced technique are described. The junction properties were examined by means of injection electroluminescence. It has been shown that these diodes have very low interface state density at least in deep levels even for an as-grown sample from the fact that only an electroluminescence due to the band-to-band transitions was observed at room temperature. At liquid nitrogen temperature, however, luminescence spectra originated from both band-to-band and free-to-bound transitions were observed. The energy difference between the two spectral peaks was found to be 67 meV, which corresponds to the activation energy of typical acceptors in InP. The internal electroluminescent quantum efficiency was 12.8% at 77 K.

A design method for transmission apparatus lightning surge protection has not yet been clarified, because study on lightning surge inducing mechanism has been neglected. This paper analyzes the lightning surges induced on overhead lines by the return strokes, when ground conductivity is finite. The lightning surges induced on overhead lines are calculated by considering the vertical electric field and horizontal electric field created by the return stroke. Calculated values agree well with measured values. Lightning surgre dependency on the distance between strike point and cable, on cable length, on ground conductivity, on cable terminal earth resistance and on cable height above ground are clarified. The probability distribution for peak values, front time and time to half values of the lightning surge waves are obtained both theoretically and experimentally. As a result, data on a standard lightning surge wave form, which is expressed by peak value, front time and time to half value, may be obtained from the relation between the blown fuse rate and the lightning surge occurrence rate.

Analytic expressions for evaluating minimum propagation delay time tpd are derived, using a model which is effective for analysis of the device with a merged structure. Calculated results are in good agreement with experimental ones. Junction modifying coefficient k is newly introduced for the theory. k affects tpd through a variable function of current gains, and a deviation from the Klaassen's theory is pointed out. Role of the pnp transistor on the performance of the I2L gate is emphasized.

On a HeNe laser oscillating simultaneously at 0.63 and 3.39 µm, the effects of an axial and a transverse magnetic fields on the output as a function of a cavity detuning are investigated theoretically and experimentally. The experiment is carried out using the laser tube with Brewster windows and the resonant mirrors for 0.63 µm. The outputs are mainly characterized by 3.39 µm mode despite of low Q resonator at 3.39 µm. The output power versus cavity detuning at 0.63 µm presents the inverse pattern to the one at 3.39 µm. In the axial magnetic field, large Faraday rotation arises at 3.39 µm and it saturates in the vicinity of 60 Gauss. In the transverse magnetic field, σ modes of two wave-lengths occur when the windows have maximum transmission for σ polarization. For fields higher than about 60 Gauss, the σ mode of 3.39 µm is quenched and π mode appears because of the strong coupling of σ-π transition and its effect is enhanced by the competition between two wavelengths. The output powers versus cavity detuning agree well with our theoretical result which is analyzed by the semiclassical treatment of two transitions with a common upper level in a Zeeman laser. Furthermore the optical modulation on 3.39 µm line is also proposed by means of the competition effect.

A transversal equalizer composed of a surface-acoustic-wave tapped delay line and PIN diode control circuits is described. In the amplitude frequency response, the change, which can be expressed in terms of a cosinusoid, can be obtained by controlling the amplitude of the echo signals.