The worst month statistics of rain attenuation at 34.5 and 81.8 GHz along a terrestrial path of 1.3 km and rain rate were analyzed. The relation between the worst month percentage and the yearly percentage is independent of frequency. The results we obtained on the worst month statistics show a good agreement with Brussaard and Watson's semi-empirical model.

Wavelength-tunable 1.5 µm GaInAsP/InP bundle-integrated-guide distributed Bragg reflector (BIG-DBR) dynamic-single-mode lasers are presented. Tuning is due to free carrier plasma effect generated by the injected tuning current at the monolithically integrated tuning regions. Low threshold current CW operation of 28 mA was obtained in junction-up mounting. Wide-range continuous wavelength tuning more than 9 was demonstrated for the first time.

A new method for evaluating optical fiber strain in a bent cable is proposed. The method is applied to fiber strain measurement in an actual optical cable and is found to be effective.

A new method of high Q measurement in oscillating systems is proposed by using laser light wave. In order to prove the method simply, X-cut quartz was used as an oscillating element.

Fabrication of 1.5 µm GaInAsP/InP laser by OMVPE on p-type substrate is reported. Low threshold current density (1.2 kA/cm²) was obtained by reduction of growth time in order to prevent Zn diffusion from substrate. CW operations at room temperature were obtained in buried heterostructure (BH) devices fabricated by OMVPE-LPE hybrid growth method. No degradation was observed after 2000 hours' aging test.

A parasitic compensated switched-capacitor (SC) integrator using a fully differential structure is presented. The effect of the imperfect matching of the capacitors or of the parasitic capacitances appears only in the form of the variation in the integrator gain.

Several types of machines have been proposed to improve the performance of data base management systems, especially the relational one. Among them, a cellular logic type data base machine such as RAP is characterized by its simple structure. Whereas this type of machine outperforms the conventional DBMS software by orders of magnitude for the relatively light load operations such as selection and update, it exhibits poor performance for the heavy load operations such as join and projection. This is because it adopts the nested loop algorithm which is very inefficient. Join has been so far the major performance bottle neck. In this paper we propose a performance enhancement mechanism for the cellular logic data base machine. A novel relational algebra processing algorithm based on the dynamic clustering feature of hash is presented. By introducing the hashing hardware, join operation is much accelerated in comparison with the conventional cellular logic data base machine. Its execution time is evaluated by simulation experiments. It has also been a major problem to handle large relations which cannot fit into the cell memories, where frequent paging degrades the performance severaly. A bucket based staging scheme has been proposed, through which the enhanced architecture can perform the join of large relations efficiently.

An optimal control theoretic approach has played a key role in the development of a new assumed-mode approximation scheme for time-dependent partial differential equations. Under the new method, the approximation system of ordinary differential equations is generated as the solution to an optimal quadratic servo problem for the Gelerkin approximation system. The new scheme is shown to be convergent even when the Galerkin scheme is divergent. Furthermore, it does not require the basis functions to satisfy the boundary conditions. This feature would greatly alleviate the basis choice problem for complex dynamic systems defined on a multidimensional spatial domain. The new scheme of this paper could be an invaluable last resort in many cases where all the known approximation schemes have hailed.

The problem of the scattering by two parallel conducting rectangular cylinders has been rigorously analyzed by the Wiener-Hopf technique. The incident wave is an E-polarized plane wave. Since the field in the region between the two cylinders can be expressed in an expansion in terms of guided modal wave functions, the scattered field from cylinders in close proximity can be accurately calculated. The numerical results of the scattering pattern and the scattering cross section are graphically presented and compared with results found in the literature.

This paper presents a queueing network model for common memory access contention and access contention to common data that cannot be referenced by more than one processor in a multiprocessor-controlled switching system. The model takes into account the inter-dependence between these types of access contention, which is important for evaluating the performance of a single-bus multiprocessor system. Although this inter-dependence is incorporated into the queueing network model, an exact analysis is difficult. Therefore, an approximate analysis method is proposed based on decomposing the model into two submodels. Approximate analysis results are compared with simulation results and it is shown that the approximation method provides sufficient approximate values. This queuing network model is useful for estimating the call processing capacity of a multiprocessor-controlled switching system.

Among the most fundamental problems in the layout design of an integrated circuit is the following problem: Given a region bounded by n orthogonal line segments and a point q in its interior, find the region that is reachable from q along rectilinear paths with at most k bends which avoid obstructions, where k is some given constant. In this paper we present an efficient algorithm which determines such a region in O(kn) time for a rectilinear simple polygon without any hole in it.

This paper describes a newly developed fully automatic arc-fusion splice machine, by which all splice processes such as stripping, cutting, alignment, fusion, and reinforcement are carried out sequentially without human intervention. Fibers are aligned by using movable arms with 2 µm position accuracy controlled by microscopic image processing. Spliced portion is reinforced by a pair of plates with hot-melt adhesive. By using the new machine, an average splice loss of 0.07 dB and a median tensile strength of 2.6 GPa with reinforcement are obtained for graded-index multimode fibers.

A new practical method of predicting outage probability caused by multipath fading in the presence of thermal noise and interference has been presented for multi-level digital radio systems. First, the linear amplitude dispersion (LAD) method using the waveform factor was derived. Outage probability due to ISI can be easily predicted for any system and any paths using this method. The validity of the method was confirmed in field experiments. Synergistic effects of noise and interference on outage were also discussed. Closed form expressions to evaluate the synergistic effects have been derived and the results were compared with those predicted by the power sum method. Both sets of results agree well. Analysis proved that synergistic effects depend only on the difference between flat fading margin and dispersive fading margin, and are independent of modulation scheme or path characteristics. The method presented here can be applied in a unified way to various systems having different modulation scheme, symbol rate, spectrum shaping, etc.

A new linear spatially invariant filter is derived. It requires the 'rare information' about the observation noise, i.e., its Fourier transform magnitude. This filter is essentially of closed form but the recursive method can be also utilized to get the stable solution at the given spatial frequency points if necessary. The compensation method of degradation of the restored image due to the error of the estimated noise Fourier transform magnitude is also shown. And it is presented that the new filter is the deterministic version of a minimum mean square error (MMSE) filter under the same constraint condition. Finally experimental results are shown and compared to that of the other standard filters.