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Mizutani H.,Salesian Polytechnic Tokyo | Ishikawa R.,University of Electro - Communications | Honjo K.,University of Electro - Communications
European Microwave Week 2016: "Microwaves Everywhere", EuMW 2016 - Conference Proceedings; 46th European Microwave Conference, EuMC 2016 | Year: 2016

This paper describes the demonstrated GaN SPST MMIC switches based on HPF/LPF switching concept for high power applications. The developed MMIC switches indicate high isolation of more than 80-dB with insertion loss of better than 2-dB below 2.4 GHz. The effective chip size is 1.15 × 1.58 mm2. The measured P1dB of insertion loss is 31.2-dBm. The isolation varies with respect to the input power from about 80-dB at small signal operation to about 40-dB for large signal input. The possible cause is the change of average FET off capacitance. This MMIC switches with HPF/LPF switching concept promises to provide new switch products having high power handling capability with low cost. © 2016 EuMA.


Ota M.,Chiba University | Kurihara K.,Chiba University | Arimoto H.,Chiba University | Shida K.,Chiba University | Inage T.,Salesian Polytechnic Tokyo
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

The Background Oriented Schlieren (BOS) technique is one of the novel measurement techniques and its application range is very wide. The principle of BOS is similar to that of the conventional schlieren technique, it exploits the bending of light ray caused by a refractive-index change corresponding to the density change in the medium. The BOS technique allows the quantitative measurement of density with very simple experimental setup and proper image analysis. Only a background and a digital camera are required for the experiment, so that even the real scale experiments can be realized. In recent years, the development of the high-speed camera is remarkable and so many high-speed phenomena can now be captured. To realize the precise measurement with BOS technique using high-speed camera, higher resolution (larger number of pixels) is desirable. In this paper, with a technical support from Nobby Tech Ltd., a 4K high-speed camera (4096 × 2160 pixels) is applied to the BOS measurement of the lateral jet/cross flow interaction filed in the supersonic wind tunnel test as a trial of the quantitative density measurement with higher resolution. The measurement system consists of a 4K high-speed camera and a pulsed laser for background illumination. A telecentric optical system is also employed to improve the spatial resolution of the measurement. The measurement results of BOS technique up to 1000 fps with higher resolution are discussed. © 2017 SPIE.


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.


Goto H.,Hosei University | Shimakawa Y.,Salesian Polytechnic Tokyo
International Journal of Geographical Information Science | Year: 2016

A storage-efficient contour generation method, focusing on planar contours, is developed. Given cartographic elevations on a rectangular lattice, a continuous bivariate function, z = f(x, y), is determined by interpolating the elevation values. Then, we focus on a contour determined by z = constant. The contour curve is partitioned into multiple sections, each of which is exactly or approximately round. Three curvature types are introduced to evaluate the roundness of each section. The area and perimeter of the contour are computed by one-dimensional line integration using Green’s theorem. If the contour is open, it is divided into two curves starting from the same initial point, with the control points advancing in opposite directions. Two types of numerical experiments are performed to validate the effectiveness of the proposed method. One experiment uses an analytically defined elevation function and investigates the number of control points and computation time for a resulting computation error. The second experiment uses actual digital elevation model data of an isolated island in Japan and compares the proposed method with existing ones. Because the algorithm does not require lattice subdivision and the number of control points is drastically reduced, the proposed method is storage efficient. © 2015 Taylor & Francis.


Goto H.,Hosei University | Shimakawa Y.,Salesian Polytechnic Tokyo
Geo-Spatial Information Science | Year: 2016

A storage-efficient reconstruction framework for cartographic planar contours is developed. With a smaller number of control points, we aim to calculate the area and perimeter as well as to reconstruct a smooth curve. The input data forms an oriented contour, each control point of which consists of three values: the Cartesian coordinates (x, y) and tangent angle θ. Two types of interpolation methods are developed, one of which is based on an arc spline while the other one is on a cubic Hermite spline. The arc spline-based method reconstructs a G1 continuous curve, with which the exact area and perimeter can be calculated. The benefit of using the Hermite spline-based method is that it can achieve G2 continuity on most control points and can obtain the exact area, whereas the resulting perimeter is approximate. In a numerical experiment for analytically defined curves, more accurate computation of the area and perimeter was achieved with a smaller number of control points. In another experiment using a digital elevation model data, the reconstructed contours were smoother than those by a conventional method. © 2016 Wuhan University. Published by Informa UK Limited, trading as Taylor & Francis Group


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.


Goto H.,Hosei University | Ishige T.,Hosei University | Shimakawa Y.,Salesian Polytechnic Tokyo
IEEE International Conference on Industrial Engineering and Engineering Management | Year: 2016

Using low resolution digital elevation model (DEM) data, reconstruction of cartographic contours is focused on. With a small number of control points, we aim to draw a smooth curve as well as to compute the area and perimeter of a closed contour accurately. The input data forms an oriented contour, each control point of which consists of three values: x, y, and tangent angle. An interpolation method based on arc spline is developed. The method can reproduce G1 continuous curves,in which the exact area and perimeter can be calculated. In a numerical experiment for analytically defined curves, accurate computation of the area and perimeter was achieved with a smaller number of control points. In another experiment using a DEM data, the reconstructed contours were smoother than those by a conventional method. © 2015 IEEE.


Yamashita K.-I.,Salesian Polytechnic Tokyo | Kameda Y.,Salesian Polytechnic Tokyo | Nishikata S.,Tokyo Denki University
2015 18th International Conference on Electrical Machines and Systems, ICEMS 2015 | Year: 2015

A high-voltage direct current (HVDC) transmission system including wind turbine generating systems has been proposed. In the system, the thyristor converter and inverter are used in the same way as in traditional HVDC transmission systems. Hence, the system is suitable for large-scale wind farms and it has high reliability. However, the traditional HVDC transmission systems cause a large number of harmonics in the sending-end grid current and the receiving-end grid current. In this paper, a novel harmonics elimination method using a three-winding transformer with negative leakage inductance for the HVDC transmission systems is proposed. The theory of the proposed method is discussed and the simulation model of the proposed system is developed first. The proposed method is confirmed to be effective when a resistance load is connected to the output terminal of the system. It is shown that the proposed method is useful to eliminate harmonic distortions generated at the inverter. Also, to obtain an accurate simulated result, the simulation model is modified to take in the effects of the excitation circuit of the transformer and its magnetic hysteresis loop. Finally, current waveforms and voltage waveforms of the transformer when receiving-end grid is connected to the output terminal of the system are discussed. © 2015 IEEE.


Majima H.,Tokyo University of Science | Majima H.,Salesian Polytechnic Tokyo | Suzuki A.,Tokyo University of Science
Foundations of Physics | Year: 2015

A general relation between entropy and an evolutionary superoperator is derived based on the theory of the real-time formulation. The formulation establishing the relation relies only on the framework of quantum statistical mechanics and the standard definition of the von Neumann entropy. Applying the theory of the imaginary-time formulation, a similar relation is obtained for the entropy change due to the change in reservoir temperatures. To show the usefulness of these formulas, we derived the expression for the entropy production induced by some dissipation in an open quantum system as the exemplary model system. © 2015, Springer Science+Business Media New York.


Yamashita K.-I.,Salesian Polytechnic Tokyo | Nishikata S.,Tokyo Denki University
2013 International Conference on Electrical Machines and Systems, ICEMS 2013 | Year: 2013

A DC transmission system including wind turbine generating systems has been proposed and its steady-state performances have been revealed. The proposed system can be used as an offshore wind farm. In this system, each voltage on the DC transmission line should be controlled properly for utilizing wind power to the maximum. In this paper, the control systems are developed first, and their dynamic performances are discussed. It is shown that the dynamic responses of the system become oscillatory. These oscillations can be diminished by applying current minor loops to the control system. Furthermore, two types of the maximum power tracking control systems for the wind turbine generating systems are compared. It is clarified that the turbine torque control is appropriate for the proposed wind turbine generating systems. Finally, a method of improving the maximum power tracking control system is suggested and its dynamic responses are analyzed. © 2013 IEEE.

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