Use of parity-based codes in computer systems can provide a cost-effective error detection and correction. Excellent parity-based main memory codes, such as odd-weight-column SEC-DED (Single bit Error Correcting Double bit Error Detecting) codes, can be used to arithmetic logic unit (ALU) by the technique proposed in this paper. They are more economical and better suited for a byte-sliced design of fault-tolerant computer systems than residue codes and triplication organization.

We carried out a research for the responses of Pb thin film microbridge Josephson device fabricated by electron lithography under microwave and millimeter wave radiations. The experimental results are reported in this paper.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

In order to develop a light and small sized fusion splice machine operating from a small battery, a new high frequency discharge method with high voltage trigger has been developed. The method uses a high voltage trigger at the beginning of discharge to reduce power consumption. It was found experimentally that the voltage of an A-C discharge depends vastly on the applied voltage waveform. To use a high voltage trigger method effectively, pertinent applied voltage conditions were found considering the ion movement. By adopting pertinent conditions, the power consumption for discharge reduces to 1/5 of that for the conventional discharge method. The new method is adopted for developing a fusion splice in optical fibers. The developed machine is 2.5 kg in weight including battery, and consumes 25 watts electric power. The average splice loss and splice tension strength are 0.03 dB and 480 g, respectively.

The class of languages generated by unary TOL systems with regular control is considered and investigated. It is shown that the equivalence problem for unary TOL systems with ultimately periodic regular control is decidable. The problems for other versions of unary TOL systems are discussed.

When realizing a high-quality land mobile radio transmission system, one of the most important and difficult problems is how to mitigate the multipath fading effect which degrades the signal transmission performance severely. Transmitter diversity without any feedback signal transmission link is the most effective technique, because mobile radio units can be simply implemented. This paper proposes a new transmitter diversity suitable for digital land mobile radio transmission systems using MSK with differential detection. More than two MSK signals carrying the same information are transmitted simultaneously from separate antennas, received combiningly by a single receiver antenna, and demodulated by the conventional differential detector. After describing the diversity principle, bit-error-rate (BER) performance improvement effect is theoretically analyzed and experimentally confirmed by the laboratory simulation tests.

A refractive-index profile formation mechanism in the VAD method for optical fiber preform fabrication was investigated and practical techniques for precisely controlling the preform index profile are proposed. The GeO2 dopant distribution in the preform is found to be mainly caused by the porous VAD preform surface temperature distribution and by the raw material vapors mixing effect. By applying the surface temperature effect, the index profile can be controlled in the wide profile parameter range of d1-10. Further, by utilizing the maxing effect, it is possible to adjust the profile parameter precisely around a desired value. Transmission characteristics for graded-index fibers obtained with the above control technique are also presented.

A new depth measurement method is described in this paper. This method uses the parallel planes of light each of which flickers in the time domain according to the binary code uniquely assigned to it. When the code length is n bits, we input n pictures projected on a certain object in which we locate and "identify" each slit image. Then the depth to the points on the slit images can be calculated by triangulation. The experimental results show that this method is faster and stronger for noise than the conventional methods. We aim to investigate the importance of knowledge about the task domain being used in signal level processing. Picture processing systems are usually task dependent, so the knowledge about the domain can be applied even in signal level processing. The knowledge is, we believe, more powerful to be used at earlier stage in picture processing than to be used at the latter one. A result about the transformation from knowledge to signal-to-noise ratio is shown as an example.

A time domain formulation for source sound isolation is presented using a new concept of matrix convolution, and is compared with the corresponding frequency domain formulation. Computer simulation suggests that this method is applicable to practical cases.

Frequency scaling method, employing the concept of path-averaged raindrop size distribution (D), is successfully applied to predicting the rain attenuation statistics. Experimentally determined Eq. (D)26,000-0.294 exp (-5.6-0.283D), (: a path-averaged, rainfall rate) is applicable to the prediction even in the frequency above 80 GHz where Laws and Parsons distribution falls into underestimation.