Satomi HATANO Yutaka KATSUYAMA Kazuo HOGARI Toshinao KOKUBUN
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.
Seiho URATSUKA Toshio IHARA Katumi KITAMURA Takeshi MANABE Yuji IMAI Yoji FURUHAMA
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.
Keisuke EBISUTANI Milton CONTRERAS
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.
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.
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.
Yasuyuki MIYAMOTO Chiaki WATANABE Masashi NAGASHIMA Kazuhito FURUYA Yasuharu SUEMATSU Yuichi TOHMORI Shigehisa ARAI
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.
Yuichi TOHMORI Kazuhiro KOMORI Shigehisa ARAI Yasuharu SUEMATSU Hiromi OOHASHI
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.
Masaru KITSUREGAWA Mikio TAKAGI
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.
Let L{0, α, β, 1} and endow it with a lattice structure (, +,
Hiroshi KONDO Hiroyasu SAKAMOTO
A new spatially variant smoothing filter is derived for image enhancement. The main object of this filter is to improve the output image of a linear spatially invariant image restoration filter such as Wiener filter. In this filter the processing for flat fields of image gray levels is quite different from that of edge portions of the image. As a new trial we apply one-dimensional smoothing to the edge portions. This is because it would be important that the edge line of an image is linked smoothly for our visual perception. For flat fields we divide these into three categories, 'full flat field', 'ordinary flat field', and 'less flat field'. In each field the unknown parameter of the new smoothing filter is determined optimally. The resulting smoothed image is more preferable for human eye.
Takao NAGATOMO Yoshikazu TAODA Shinichi HIRANO Osamu OMOTO
The doping characteristics of a-Si:H films prepared by rf planar magnetron reactive sputtering (MRS) are described. The room-temperature conductivity reaches ca. 1Ω-1 cm-1 at 1000 vppm in the both cases of phosphorus doping and boron doping. MRS a-Si:H films have the doping characteristics similar to GD a-Si:H films. However the maximum conductivity is large compared to GD a-Si:H films, and especially for the boron doping one is large two or three orders of magnitude. The room-temperature conductivity of MRS a-Si:H films depends strongly on the target voltage and the deposition pressure for impurity doping. And also the temperature dependence of conductivity of phosphorus- and boron-doped MRS a-Si:H films are described as a function of dopant concentration. The electronic properties and the densities of gap states of the undoped MRS a-Si:H films are discussed as parameters of hydrogen contents and the ratio of SiH bonds to SiH2 bonds.
Wave scattering from moving planar and non-planar surfaces is considered. Both deterministic and non-deterministic motion are considered. The reformulated current method is introduced and used to find the scattered field components from these moving surfaces. Comparison between this method and other methods is made.
A simpler and more straightforward proof is given for the recently-proved theorem such that real-time one-way cellular automata languages are closed under reversal.
Shinji SHINNAKA Takashi SUZUKI
This paper presents a method for designing discrete-time adaptive pole placer to unknown-order plants with disturbance. Since pole placement is inherently free from the problems on existence of nonminimum phase zeros and uncertainty of dead-time of plant, the method can be applied to nonminimum phase, unknown-dead-time, unknown-order plants with disturbance. It takes indirect approach and is characterized by new algorithms for estimating plant parameters from input, output and determing controller parameters based on the estimates, which are intended to be shown in detail.
Kazuhiro KOMORI Yuichi TOHMORI Shigehisa ARAI Yasuharu SUEMATSU
A dynamic-single-mode bundle-integrated-guide distributed-bragg-reflector (BIG-DBR-DSM) laser with short active region was experimentally demonstrated for low threshold current and high sub-mode suppression. CW threshold current of 22 mA was obtained for the case of active region length of 50 µm. Sub-modes were suppressed more than 35 dB.
Hiroaki YAMAMOTO Masahiro ASADA Yasuharu SUEMATSU
A new intersectional switch of small size using total internal reflection generated by an electric-field-induced refractive-index-variation in the multiquantum well (MQW) structure is proposed. The intersectional angle is expected theoretically to be more than 10 for the applied field of 32.8 V/µm in GaInAsP/InP MQW waveguide. This switch is expected to be of small size with high speed response, and is integrable monolithically together with integrated lasers.
Makoto SHIMIZU Hiroki ITOH Yasuji OHMORI
The hydroxyl loss increase characteristics for antimony oxide-doped silica fibers were investigated to ensure long-term reliability. The loss increase was measured for non-irradiated and γ-irradiated fibers with hydrogen molecule diffusion and heat treatments. The loss increase characteristics for these experiments were similar to those for germanium oxide-doped silica fibers.
This letter analyzes the performance of a virtual-token passing scheme, fair BRAM, for local area networks. A Markovian model of the system is developed and analyzed by the equilibrium point analysis. The throughput and average message delay characteristics are shown.
The reconstruction of the modulating signal from the zero crossings has been treated extensively in the literature. However, the analysis on the zero crossings is only an approximation based on the average pulse counts. The relating reconstruction methods or zero-crossing discriminations, are also elaborate and costly. It is the purpose of this letter to analyze the zero crossings of an FM signal exactly in the frequency domain. From this analysis, a very simple method is proposed to demodulate an FM signal.