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Ohya H.,Chiba University | Tsuchiya F.,Tohoku University | Nakata H.,Chiba University | Shiokawa K.,Nagoya University | And 3 more authors.
Journal of Geophysical Research: Space Physics | Year: 2012

We report multipoint observations of daytime tweek atmospherics during the solar eclipse of 22 July 2009. Sixteen and sixty-three tweek atmospherics were observed at Moshiri and Kagoshima, Japan, where the magnitudes of the solar eclipse were 0.458 and 0.966, respectively. This was the first observation of tweek atmospherics during a low-magnitude eclipse (0.458). The average and standard deviation of the reflection height were 94.9 13.7km at Moshiri and 87.2 12.9km at Kagoshima. The reflection height at Moshiri was almost the same as that for normal nighttime conditions in July (96.7 12.6km) in spite of the low magnitude of the eclipse. The reflection height at Kagoshima seems be divided into two parts: propagation across the total solar eclipse path and propagation in the partial solar eclipse path. During the eclipse, we also observed the phase variation in the LF transmitter signals. The average change in the phase delay of the LF signals was 109 for the paths that crossed the eclipse path and 27 for the paths that did not cross the eclipse path. Assuming a normal daytime height for LF waves of 65km, a ray tracing analysis indicates that the variations in phase correspond to a height increase of 5-6km for the paths across the eclipse and 1-2km for partial eclipse paths. The wide range of estimated tweek reflection heights at Kagoshima also suggests a difference in electron density in the lower ionosphere between total and partial solar eclipses. © 2012. American Geophysical Union. All Rights Reserved. Source

Miyata T.,Salesian Polytechnic Tokyo | Okamoto K.,SHINKO DENSHI CO. | Aikawa N.,Tokyo University of Science
IEEJ Transactions on Electronics, Information and Systems | Year: 2015

Automatically dynamic measurement systems to measure object weights are used in logistics and food industry, etc. The systems are composed of belt conveyor and road cell, and is called checkweigher. Checkweighers have a problem that noises of error factor change according to speed of belt conveyor and installation surrounding. As a result, variable filters are better suited for checkweighers to reduce the noises after installation. In this paper, we propose a design method of quasi-equiripple variable linear-phase FIR (Finite Impulse Response) filters using iterative weighted least squares method in the frequency domain. The proposed variable filter has some piecewise high attenuations in the stopband, and can change multi-factor in the stopband characteristics and some notch frequencies using variable parameters. In the proposed variable filter, filter coefficients are approximated by polynomial using polynomial coefficients and variable parameters. The number of the polynomial coefficients increases when variable parameters are the plural number or polynomial orders are high. Therefore, we also propose a reduction method of the polynomial coefficients. The usefulness of the proposed design method is verified through the examples. © 2015 The Institute of Electrical Engineers of Japan. Source

Kakimoto Y.,Nagaoka University of Technology | Takahashi H.,Nagaoka University of Technology | Shimakawa Y.,Salesian Polytechnic Tokyo
Journal of Japan Industrial Management Association | Year: 2016

In this paper, the effect of constraints is shown in the case of solving a constraint satisfaction problem (CSP) using linear programming (LP). A timetabling problem (TP) is formulated as example CSP. Then, the authors try to solve the problem using a simplex method in order to get the exact solution by selectively varying the constraints. Using the results obtained, how constraints affect the solutions obtained are examined. The computation time and simplex pivot count are observed, excepting the constraints that do not affect the feasible TP solutions. Certain kinds of constraints are shown to make the problem difficult. As the result, it is found that constraints, such as giving two successive classes and limiting the number of times giving the same classes in a day, is a major factor for making the problem complicated. In addition, a method for importing ambiguous constraints is proposed. Source

Yamashita K.-I.,Salesian Polytechnic Tokyo | Nishikata S.,Tokyo Denki University
ICEMS 2012 - Proceedings: 15th International Conference on Electrical Machines and Systems | Year: 2012

A DC transmission system including wind turbine generating systems has been proposed and its steady-state characteristics have been analyzed for a tested system. In this paper, in order to obtain more general results, the steady-state characteristics of the proposed system under average-constant conditions are analyzed. Furthermore, the effects of the system parameters such as duplex reactor inductances and synchronous machine short-circuit ratio on the characteristics of the system are revealed. It is shown that when the short-circuit ratio of the synchronous compensator at the receiving-end circuit is large, the kVA capacity of the synchronous compensator can be reduced. Finally, appropriate system parameters are discussed in detail. © 2012 IEEJ Industry Appl Soc. Source

Usha N.,Alagappa University | Sivakumar R.,Alagappa University | Sanjeeviraja C.,Alagappa Chettiar College of Engineering And Technology | Kuroki Y.,Salesian Polytechnic Tokyo
Journal of Alloys and Compounds | Year: 2015

In this work, the effect of substrate temperature on the structural, optical, vibrational and electrochromic properties of radio frequency (rf) magnetron sputter deposited mixed Nb2O5:MoO3 (90:10) thin films have been studied. X-ray diffraction analysis revealed that all the deposited films belong to amorphous nature. The x-ray photoelectron spectroscopic study confirms the compositional purity and the presence of five-valent niobium (Nb5+) and six-valent molybdenum (Mo6+) in the deposited film. The average optical transmittance of the films varied between 88 and 92%. The refractive index and extinction coefficient of films are found to decrease with increasing substrate temperature. Photoluminescence spectra exhibit three characteristic emission peaks and confirm the better optical quality of the deposited film. The longitudinal and transverse optic modes of Nb-O stretching vibrations were observed from the micro-Raman study. The cyclic voltammograms of Li+ and H+ ions clearly show all the films are having better reversibility and reproducibility in their electrochemical analysis. The maximum coloration efficiency of 51.94 cm2/C was obtained for the mixed Nb2O5:MoO3 (90:10) film. © 2015 Elsevier B.V. All rights reserved. Source

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