研究者詳細 - 藤森　和博

論文 - 藤森　和博

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Optimal Design Method of RF-DC Conversion Circuits for Various Input and Load Conditions Required for Rectenna Site Design 招待査読

Kazuhiro Fujimori, Kensuke Kobayashi

2022 16th European Conference on Antennas and Propagation (EuCAP) 2022年3月

Impedance relationship of operating diode and planar circuit in high-efficiently operated RF-DC conversion circuit 査読

Kensuke Kobayashi, Kazuhiro Fujimori

IEICE Communications Express 10 ( 9 ) 660 - 664 2021年9月

Improvement of transmission efficiency by using annular array metamaterial for magnetic coupling wireless power transmission system 査読

Liwei Jia, Kazuhiro Fujimori

IEICE Communications Express 10 ( 9 ) 673 - 676 2021年9月

Elucidation of Impedance Conditions in High-Efficiency Operation RF-DC Conversion Circuits 査読

Kensuke Kobayashi, Kazuhiro Fujimori

2020 International Symposium on Antennas and Propagation 2021年1月

Designing Microwave Circuits Using Genetic Algorithms Accelerated by Convolutional Neural Networks 査読

Takuma Akada, Kazuhiro Fujimori

50th European Microwave Conference 290 - 293 2021年1月

A study on an online acceleration of automatic design of RF-DC conversion circuit using neural networks 査読

Takuma Akada, Kazuhiro Fujimori

2020 International Symposium on Antennas and Propagation 2021年1月

Improvement of Transmission Efficiency by using Annular Array Metamaterial for Magnetic Coupling Wireless Power Transmission System 査読

2020 International Symposium on Antennas and Propagation 2021年1月

Proposal of time domain near-field measurement system for 5G antenna system 査読

Yusuke Maruyama, Kazuhiro Fujimori, Hiroyuki Arai, Toshiyasu Tanaka

2020 International Symposium on Antennas and Propagation 2021年1月

One-Minute Joule Annealing Enhances the Thermoelectric Properties of Carbon Nanotube Yarns via the Formation of Graphene at the Interface 査読

Masaki Hada, Taisuke Hasegawa, Hirotaka Inoue, Makito Takagi, Kazuki Omoto, Daiki Chujo, Shogo Iemoto, Taihei Kuroda, Taiga Morimoto, Takuma Hayashi, Toru Iijima, Tomoharu Tokunaga, Naoshi Ikeda, Kazuhiro Fujimori, Chihiro Itoh, Takeshi Nishikawa, Yoshifumi Yamashita, Toshihiko Kiwa, Shin-ya Koshihara, Satoshi Maeda, Yasuhiko Hayashi

ACS Applied Energy Materials 2 ( 10 ) 7700 - 7708 2019年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Chemical Society (ACS)

Interfaces in nanocarbon materials are highly important, as they determine the properties of carbon-based devices. In terms of carrier and thermal transport properties, the interfacial features are often more important than the intrinsic characteristics. Herein, we describe how 1 min Joule annealing of carbon nanotube (CNT) yarns can convert the interfacial amorphous carbon into graphene fragments. After 1 min Joule annealing, we have obtained multiwalled CNT yarns with extremely high Seebeck coefficients (±100 μV/K) and high thermoelectric power factor (400 and 1000 μW/mK2) at room temperature, both with or without polyethylenimine doping. Theoretical simulations and experimental measurements helped to determine the optimal annealing conditions in terms of a rapid transformation of the interfacial amorphous carbon between the bundled CNTs in the yarn into graphene fragments at â¼2000 K. The present approach represents significant progress in energy materials science, as it provides a guiding principle for the design of interfaces in nanocarbon materials with potential applications in energy-harvesting systems.

DOI： 10.1021/acsaem.9b01736

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Design of the RF-DC Conversion Circuit by GA Adopting Mutation Based on Fourier Coefficients on Unit Structures 査読

Kento Nakagawa, Kazuhiro Fujimori

Progress In Electromagnetics Research Symposium 2018年8月

The prototypes of X-band active integrated antenna array for a satellite on-board tracking system 査読

Shigeo Kawasaki, Ray Katoh, Tamotsu Suda, Yuki Nakano, Kazuhiro Fujimori, Jun Matsumoto, Hideki Kato, Osamu Mori, Junichiro Kawaguchi

2018 IEEE Radio and Wireless Symposium (RWS) 91 - 93 2018年1月

Selective electroless plating of 3D-printed plastic structures for three-dimensional microwave metamaterials 査読

Atsushi Ishikawa, Taiki Kato, Nobuyuki Takeyasu, Kazuhiro Fujimori, Kenji Tsuruta

Applied Physics Letters 111 ( 18 ) 183102 - 183102 2017年10月

アルカリ金属を用いた交流磁界の光学検出―市販の磁界テスタとの比較と永久磁石を用いたプローブ化の検討― 査読

田上周路, 篠原優, 豊田啓孝, 藤森和博, 深野秀樹

電子情報通信学会論文誌 J100-B ( 3 ) 158 - 165 2017年3月

記述言語：日本語出版者・発行元：電子情報通信学会

電磁波による情報通信や電力伝送などの普及により，正確な電磁環境計測の需要が高まっている．我々は，アルカリ金属蒸気の電子スピン偏極を利用した光学式磁界センサの電磁環境計測を目指している．本センサは，コイルを用いた従来のセンサと比較して高い感度や空間分解能を有しており，金属ケーブルなどを用いないため，正確な計測が期待できる．センサの高感度動作には，測定対象周波数に応じた静磁界の印加が必要であり，従来の研究では測定部よりも大きなコイルを用いて空間的に均一な磁界を印加していた．本研究では，20 kHzの交流磁界に対して市販の磁界テスタを用いた感度較正を行い，構築したセンサの線形な出力特性と0.4 nTのノイズレベルを確認した．次に，センサ部分の非金属化と小型化を目的として，静磁界の印加に小型の永久磁石を用いて交流磁界検出を行った．永久磁石を用いて静磁界を印加させることで，理想的な場合と比較すると，信号強度は約81％となり，感度帯域は約126％となった．この原因について，印加される静磁界強度の空間的な不均一によると考察した．

DOI： 10.14923/transcomj.2016PEP0010

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Terahertz acoustic wave on piezoelectric semiconductor film via large-scale molecular dynamics simulation 査読

Hikata Ryo, Tsuruta Kenji, Ishikawa Atsushi, Fujimori Kazuhiro

Jpn. J. Appl. Phys. 54 ( 7S1 ) 07HB07 - 07HB07 2015年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Institute of Physics

By atomistic simulation, we investigate an acoustic wave at THz frequencies in nanoscale thin films of aluminum–nitride piezoelectric material. A mode analysis reveals that the thickness longitudinal mode along the [0001] direction exists stably at the atomic level. To control the acoustic wave, we introduce a phononic crystal (PC) structure in the films. We determine the band-gap frequency in the phonon dispersion of the PC structure and confirm via molecular dynamics simulation that the acoustic wave within the band-gap frequency can be confined by a waveguide structure with a PC. The possibility of designing and controlling a THz acoustic wave in a nanoscale thin film with a PC is thereby demonstrated.

DOI： 10.7567/jjap.54.07hb07

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その他リンク： http://stacks.iop.org/1347-4065/54/i=7S1/a=07HB07?key=crossref.8f2a84b57934c8e893b2c43c68be3386

Ferroelectric Domain Contribution to the Tunability of Ba0.8Sr0.2TiO3Ceramics 査読

Takashi Teranishi, Tsuyoshi Sogabe, Hidetaka Hayashi, Akira Kishimoto, Kazuhiro Fujimori

Japanese Journal of Applied Physics 52 ( 9S1 ) 09KF06 - 09KF06 2013年9月

Design and development of highly eﬃcient transducer for ultrasonic wireless power transmission system 査読

Yuki Hori, Kazuhiro Fujimori, Kenji Tsuruta, Shigeji Nogi

Electrical Engineering in Japan 184 ( 3 ) 27 - 35 2013年5月

担当区分：責任著者出版者・発行元：Wiley

<jats:title>Abstract</jats:title><jats:p>In this paper, a transducer that is suitable for the ultrasonic wireless power transmission system is discussed. The transducer is designed based on Mason's equivalent circuit theory, basically. The transducer was developed using design parameters optimized by multiphysics analysis. As a result, it is conﬁrmed that the transmission eﬃciency is drastically improved to more than 50%. This result suggests that wireless power transmission by acoustic wave is feasible. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(3): 27–35, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22406</jats:p>

DOI： 10.1002/eej.22406

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その他リンク： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-25600132/

超音波無線電力伝送のための高効率なトランスデューサの設計と開発査読

堀祐貴, 藤森和博, 鶴田健二, 野木茂次

電気学会論文誌. C, 電子・情報・システム部門誌 = The transactions of the Institute of Electrical Engineers of Japan. C, A publication of Electronics, Information and Systems Society 132 ( 3 ) 337 - 343 2012年

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：The Institute of Electrical Engineers of Japan

In this paper, the transducer that is suitable for the ultrasonic wireless power transmission system is discussed. The transducer is designed based on the Mason's equivalent circuit theory, basically. Design parameters of the transducer are optimized for by using the multi physics analysis and developed. As results, it is confirmed that the transmission efficiency is drastically improved to more than 50%. This result suggests that the WPT by acoustic wave is practicable.

DOI： 10.1541/ieejeiss.132.337

Characteristics of RF-DC conversion circuit for wireless power transmission using the low resistance GaN schottky barrier diode 査読

Kazuhiro Fujimori, Teruhiko Wagi, Kenji Tsuruta, Shigeji Nogi, Yuichiro Ozawa, Minoru Furukawa, Teruo Fujiwara

International Symposium on Antennas and Propagation 190 - 193 2012年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

RF-DC conversion circuit is one of the most important components in the wireless power transmission technologies. For realizing highly efficient wireless power transmission, it is necessary to design the RF-DC conversion circuit with high conversion efficiency, and the designing method of the circuit is actively investigating. In this paper, we manufacture the GaN schottky barrier diode for a high frequency rectification, and discuss characteristics of the GaN circuit by comparing to the Si circuit. As a result, optimal electrical parameters of the diode are demonstrated for obtaining higher conversion efficiency in the RF-DC conversion circuit. © 2012 IEICE.

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Frequency characteristic of transmission efficiency depended on matching condition of transducer in ultrasonic wireless power transmission system 査読

Kazuhiro Fujimori, Shota Tominaga, Koichiro Tanda, Kenji Tsuruta, Shigeji Nogi

International Symposium on Antennas and Propagation 166 - 169 2012年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The ultrasonic wireless power transmission technology is researching as the one option of wireless power transmission technologies, because the loss of the electromagnetic wave becomes larger around a human body area or under juicy environments. For highly efficient power transmission, it is necessary to investigate the transducer as the transmitter and the receiver. In this paper, the frequency characteristic of transmission efficiency depended on matching condition of developed transducer is investigated. As results, the transmission efficiency is made wideband to select optimal matching condition at each frequency. Especially, maximum transmission efficiency is 75.1% at designed frequency 1.20MHz. © 2012 IEICE.

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The Design of mW-Class Compact Size Rectenna using Sharp Directional Antenna 査読

Yasuo Hiramatsu, Tsunayuki Yamamoto, Kazuhiro Fujimori, Minoru Sanagi, Shigeji Nogi

2009 EUROPEAN MICROWAVE CONFERENCE, VOLS 1-3 EuMC Poster01-48 1243 - 1246 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

This paper proposes the compact size rectenna using the open ended diamond antenna which is radiation pattern of sharp. This antenna which is fabricated at the planer has same dimension as the patch antenna. In addition,this antenna's half beamwidth is more narrow than the patch antenna. To realize the compact size rectenna,the dimension of the rectification circuit is smaller than the antenna. So the rectification circuit is constructed of the chip device has the 59.5% of conversion efficiency and the dimension of this circuit has 10mm x 10mm at 5.8GHz. The rectenna array which is composed of 2 elements is fabricated, and confirm operating. As a result the output voltage is 117mV at 0.6m, and 69mV at 1.0m.

DOI： 10.1109/EUMC.2009.5295939

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