A mode-matching method in the sense of least squares are proposed for analyzing grating coupler having a periodic groove structure of finite extent which is formed on the surface of the core region of the thin-film waveguide. The grating couplers are analyzed for the plane wave incidence when the Bragg condition is satisfied. The discussion is developed about the grating couplers formed on the asymmetric and symmetric waveguides. The approximate scattered fields of each region of the grating coupler are described by the superpositions of the plane waves with band-limited spectra, respectively. These approximate wave functions are determined by the minimization of the mean-square boundary residual. This method results in the simultaneous Fredholm type integral equations of the second kind for these spectra. Results of analyses based on the first order approximate solutions are presented. A comparison between our results and those of Green's function approach for grating couplers having rectangular, triangular and sinusoidal grooves of different depth is presented.

The propagation properties of the TE0 mode in an optically nonlinear tapered waveguide are examined and discussed. It is assumed that the nonlinear core has the Kerr-like refractive index of self-focusing type. The size of the tapered waveguide is so chosen that for a small input power, the guided light is cut off on the way to the taper end, and so the transmitted power becomes nearly zero. If the input power exceeds a threshold, the increment of the core index makes the nonlinear guide break away from the cut-off state, and the output power abruptly goes up at the threshold. Hence, the guide can be used as an all-optical threshold device which has a strong point that the very abrupt increase of the output at the threshold can easily be obtained for its length. Some applications of the tapered guide to pulse compression, optical AND gates, and optical differential amplification are also shown. The above abrupt increase gives the differential amplifier with very high gain.

Static characteristics between self-lubricating composite materials, of which resistivities were lowered by modifying the conventional material compositions, and copper, molybdenum, and carbon, which were selected as the mating materials, were examined. As the results, it was found that the contact resistances were lowered as much as by 1/10, and was ascertained that the formations of films due to Joule's heat were lessened through the verification of the Fritting phenomena. It was further found, however, that contact resistances were increased along with the increases of the resistivities of the mating materials in the order of copper, molybdenum, and carbon to indicate the reduction of the modification effects of the properties of the composite materials.

Petri net based satisfiability testing for non-clausal propositional calculus is presented. Every formula in propositional calculus is hierarchically represented by an acyclic free-choice Petri net called logic Petri net. Then a logic Petri net is combined with two way alternating modules, whose number depends upon the number of atoms used in the formula. It is shown that the satisfiability of a formula with non-clausal form can be tested by obtaining reachable firing set of the complete logic Petri net corresponding to the formula under the maximum firing rule.

The queueing system with multiple servers of possibly different rates under a threshold-type scheduling is analyzed. We first derive the general expressions for state probabilities and the average queueing delay in which the conventional M/M/n queueing system is also included as the special case of zero-threshold policy. Next, the numerical calculation is carried out for the queueing system with 3 servers under a threshold-type scheduling to consider the impact of the multiple thresholds on the average queueing delay of the system. It is found that the average queueing delay of the queueing system with multiple servers of different rates can be reduced under a threshold-type scheduling by selecting the threshold values appropriately. The threshold-type scheduling is more effective as the difference of the service rates becomes larger.

The present paper deals with the scattering of a H-polarized Gaussian beam from a conducting cylinder with an irregular surface by using the perturbation technique. The correlation function and the variance of the far-zone scattered field are derived under the first-order perturbation and several numerical examples are shown.

A down sampling technique was applied to signal processing for optical fiber gyroscopes. It lowered the higher speed requirement for the sampling system and numerical operations. Utilizing the technique, a digital signal processing circuit extracted rotational information from the gyroscope signal.

Recently, dielectric material with a large relative dielectric constant (εr100) has received much attention as a substrate suitable for microwave integrated circuits. In this letter, an analysis on transmission-line-characteristics of a new type broadside-coupled strip transmission-line is presented which consists of two center strips placed respectively on the upper- and lower-side surface of a rectangular dielectric substrate with a large relative dielectric constant and two ground electrodes placed respectively on the other surfaces of the rectangular substrate. Analytical expressions for characteristic impedances of this transmission-line are given through a conformal mapping technique. The graphs of characteristic impedances and the coupling factor as a function of various waveguide-parameters are also given to facilitate the design works. Using this new strip-line, microwave miniature multi-stage broadside-coupled filters are easy to realize.

A simplified two-dimensional model that includes only an electron current equation is shown to be successfully applied to the calculation of current-voltage characteristics of GaAs MESFET's with a p-beffer layer or with the semi-insulating substrate including hole traps.

Phase change recording with an optically switched laser (OSL) head is realised for the first time. This head consists of a 1.3µm wavelength laser diode monolithically integrated with a photodetector (LD-PD) and a flying slider. The lensless OSL head has a minimum power of 18 mW (1 MHz) for writing information on a 1200 rpm, 130 mm diameter, SbTe based alloy disk. The bit shape and crystalized level are uniform and the readout signals are of high quality.

A parallel FFT (Fast Fourier Transform) is actually executed on a clustered multiprocessor system with 32 processors to study real performance of three communication schemes, common memory, linear array and ring array. The speed-up of parallel FFT to a serial computer really depends on the number of data to be transformed and the number of processors. It is also proved that the performance really depends on the communication scheme of multiprocessor system.

This letter illustrates the characteristics and causes of the noise voltage induced in adjacent circuit having resistive terminations at the break of silver contacts with inductive load.

A distributed power supply system with highly efficient characteristics has been developed to replace conventional centralized power systems in telecommunications offices. In this system as in conventional centralized power systems, a stand-by energy system composed of batteries and engine-generator sets is used as a back-up system for the commericial power lines. However, the distributed power system, except for the engine-generator set, is installed in the telecommunications room. Thus, the floor load limitation is an important design factor. This paper describes a stand-by energy system design that considers floor load conditions and is based on reliability analyses. These analyses show that the distributed power system should be designed as follows: (1) Using a fully duplicated engine-generator set. (2) With battery reserve time reduced to one sixth that of conventional centralized power systems. (3) With transfer switch unavailability designed to be less than one half of the existence switch unavailability.

An all digital 256 QAM modulator including the carrier signal of nearly 10 MHz, was constructed. In order to achieve, the very high-speed operation of nearly 100 MHz is required. In this experiment, the very high-speed digital devices such as digital multiplier with delay time of 4.3 ns was employed. Excellent modulation performance was achieved with no adjustment. Roll-off spectal shaping filter using a new BTF circuits was constructed. The excellent transmission performance was obtained and the transmission capacity of nearly 20 Mbit/s was achieved. The results provide prospects for an all digital LSI-based high-speed 256 QAM modem for high-capacity Digital Microwave Radio.

Osaka Gas has been investigating artificial intelligence for 6 years, focusing especially on research into ICAI. We have developed a simulation based GTS (Generic Training System) in cooperation with Vanderbilt University, in Tennessee USA. This system is one of the few practical ICAI systems used for real fields, and the coursewares can be developed without any programming skill. Topics covered in this paper include the system architecture, system modules and main features. As an example, a model-based intelligent tutoring system for power distribution training systems (PDTS) is also provided. The system is in use at several places in Osaka Gas.

In this paper, we propose two parallel M/M/1 queueing systems with dynamic routing under a threshold-type scheduling. Arriving customer is sent to the buffer of the faster server as far as the difference of two queues does not exceed a threshold value, but it should be sent to the buffer of the slower server if and only if the difference of two queues exceeds a threshold value. It is shown that as the difference of the two service rates becomes large, the two parallel M/M/1 queueing systems with dynamic routing under the threshold-type scheduling can reduce the mean queueing time of costomers in the system compared to the conventional nonthreshold-type one. It is also found that as the asymmetry in the two service rates increases, the optimum threshold value which minimizes the mean queueing time should be large to reduce the number of queueing customer in the buffer of the slower server. On the other hand, as the traffic intensity becomes large, the optimum threshold value tends to be small in order to increase the total service rate.

The waveform moments are used for analyzing the various types of signal waves. The ordinary moments can't properly express the characteristics of the given signal sequence, because they are calculated with simple summation formulas of the original signal values and the positive and negative values may cancel each other. So we define the power moments which utilize the square of signal in order to prevent the above defect. Moreover, the cross moments which evaluate the product of signals are derived as more generalized definitions. The cross moments can evaluate not only the characteristics of signal power but also the relations between two signals. Further, we extend the cross moments to the blockwise cross moments and the multicross moments, and then derive the corresponding expressions in frequency domain. Finally, we illustrate the usefulness of the cross moments with some application examples.

A new recognition method for partially occluded two dimensional objects is described in the present paper. Several vectors named PSVs, Partial Shape Vectors, are proposed as local features of an object and used for recognition. Two dimensional objects similar to a given model are extracted by this method. PSVs denote turning angles at an arbitrary point of the contour line of an object. In the recognition process, PSVs of each picture point in the given image are obtained and compared with PSVs of feature points which were set on the model. From coordinate values of the candidates for the feature points, objects similar to the model are extracted.

This letter is concerned with application of a spectral domain method combined with the generalized sampling theorem to electromagnetic problems. Discretizations are performed by selecting unequally-spaced sampling points coincident with the zeros of an entire function of exponetial type. Numerical examples are also given for the scattering by a plane metallic grating, and it is demonstrated that the numerical results show a good convergence.