This paper considers a two-counter tandem queuing system attended by a moving server with walking time. The first queue capacity is infinite, but the second queue capacity is equal to a finite number, N. A walking time, with a general distribution is required whenever the server moves from one counter to the other. The server continues servicing at the first counter until N services have been effected without interruption, or until the first queue becomes empty, whichever comes first. After completing the services at the first counter, the server moves to the second counter, and it serves all of the calls in the second queue before coming back to the first counter. The arrival process is assumed to be Poission and the service processes are independent renewal processes. Under steady-state conditions, it tbtains a Laplace-Stieltjes transform for the total sojourn time a call stays in the system, until the completion of sequential services at the two counters. It also acquires the first moment of the server's cycle time, the server's occupancy and the walking time percentage.

This paper considers an optimal preventive maintenance problem of a 2-unit standby system. The system consists of two identical Markovian degradation units. A control limit rule is shown to be an optimal policy which maximizes the system availability by using semi-Markovian decision process. The system availability under the rule is obtained and the optimal control limit state is determined.

This paper attempts a complete analysis of circulator in reference to "circuit-invariance" in order to arrive at an invariant of and a canonical representation for circulator. Furthermore, a suitable figure of merit of circulator can be initially derive by means of this invariant, and a compensating circuit for circulator is discussed in as thorough a manner as possible.

Low-loss dispersion-free single-mode fibers near 1.5 µm were fabricated by controlling their waveguide dispersion. The deviation of the zero-dispersion wavelength from the calculated one was within 0.02 µm, and the minimum loss of the fiber was 0.46 dB/km at 1.56 µm. The pulse broadening in the 20 km long fiber was measured to be 1.3 ps/km/nm at 1.50 µm. These results confirmed that it is beneficial to use the dispersion-free single-mode fibers for high capacity and long distance transmission media.

In the digital satellite communications, the Unique Word (UW) having a unique code pattern is often used for frame synchronization. Reliable detection of the UW is very important to achieve stable frame synchronization. This paper proposes a UW detection method capable of providing lower UW error rates even in the low carrier-to-noise ratio. The UW error rate (UWER) performance of the proposed method, as well as of the conventional method, has been examined for the case where hard-decision or soft-decision is applied to the UW bits which are transmitted in the form of binary phase-shift keying and coherently demodulated. In this paper, the UW detection processes are described for both the proposed and the conventional methods, and computed or simulated results of the UWERs are presented on the assumption of a typical UW pattern. Comparison is made on the UWER performance between the proposed method and conventional method as well as indication of the optimum soft-decision characteristics. As a conclusion, it is shown that the proposed method incorporated with soft-decision can provide excellent UW detection performance.

Filtering properties of multilayered optical tunable couplers and appropriate material composition are theoretically studied. In the structure of ZnS/Ta₂O₅/Nb₂O₅ films on a LiNbO₃ substrate, narrow bandpass filter of the width 5 can be realized by using acoustic power of several tens mW.

A schematic method of determining the functional form of a given three-valued majority function from its weights and thresholds is presented.

Ionospheric scintillation at 4 GHz was observed on the earth-space path in Kuwait. From the spectral analysis of this data, the phenomenon of gradual change of the power spectrum, keeping the form of power-law, was found in strong scintillations.

Mode power distribution of a 1 km long parabolic-index optical fiber is measured by two methods; the far-field pattern method and the pulse method. These results are in good agreement with each other and the validity of the far-field pattern method to the parabolic-index fiber is confirmed.

The information of closed curves obtained from figures is one of important features for describing them. Concerned with such kinds of studies, the feature extraction of a single closed curve has been reported in many papers. In this paper, a method of converting a collection of open-curves into that of the closed curves is proposed by supposing a smooth slope around the region including the curves with levels. As an example, contour lines of mountainous map are processed for obtaining closed contour lines.

Lower mode excitation was confirmed for the coupling of semiconductor lasers into multimode fibers with tapered hemispherical ends, by measuring modal power distribution. Judging from the measured power distribution, 2 dB lower transmission loss can be expected for tapered hemispherical end coupling than for flat-end fiber coupling.