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123 results on '"Fujii, Kohei"'

6. Enantioselective Construction of Tetrahydroindole Skeletons by Rh‐Catalyzed [2+2+2] Cycloaddition of Homopropargyl Enamides with Alkynes.

Author

Yamashiro, Kairi, Fujii, Kohei, Sato, Yu, Masutomi, Koji, Shimotsukue, Ryota, Nagashima, Yuki, and Tanaka, Ken

Abstract

We have developed the Rh‐catalyzed enantioselective [2+2+2] cycloaddition of homopropargyl enamides (tosylamide‐tethered 1,6‐enynes) with alkynes to construct tetrahydroindole skeletons found in natural alkaloids and pharmaceuticals. This cycloaddition proceeds at room temperature in high yields and regio‐ and enantioselectivity with a broad substrate scope. The preparative scale reaction followed by substituent conversion on the nitrogen atom and the diastereoselective [4+2] cycloaddition with singlet O2 affords hexahydroindole‐diols bearing three stereogenic centers and variable substituents on the nitrogen. Mechanistic studies have revealed that the substituents of the enynes change the ratio of intramolecular and intermolecular rhodacycle formation when using terminal alkynes, varying the ee values of the cycloadducts. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Chronic hyperadiponectinemia induced by transgenic overexpression increases plasma exosomes without significantly improving glucose and lipid metabolism

Author

Kawada, Keitaro, primary, Kita, Shunbun, additional, Fukuda, Shiro, additional, Fukuoka, Keita, additional, Okita, Tomonori, additional, Kawada-Horitani, Emi, additional, Iioka, Masahito, additional, Sakaue, Taka-aki, additional, Kawachi, Yusuke, additional, Fujii, Kohei, additional, Kimura, Yu, additional, Otabe, Shuichi, additional, Fujishima, Yuya, additional, Nishizawa, Hitoshi, additional, Maeda, Norikazu, additional, and Shimomura, Iichiro, additional

Published
2023
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10. A Study on the Actual Conditions of Renewable Energy Use in the Japanese Prefectures based on the Second Nationwide Survey

Author

FUJII, Kohei and YAMASHITA, Hidetoshi

Abstract

Three years has passed since the first nationwide questionnaire survey of prefectures on renewable energy policy in Japan was completed. Since then, the situations with which prefectures are faced have been changed drastically. In order to find out how prefectures react to such changes, and how are new trends in renewable energy policy emerging, the second survey was conducted from October 2020 through March 2021 jointly by the Hitotsubashi University Natural Resource-based Economies Project, The Asahi Shimbun Company, Hosei University, Nagoya University, and Institute for Sustainable Energy Policies. There were responses from 47 prefectures, for a response rate of 100%. In this paper, we present the first aggregate analysis of replies to the questionnaire and issues that are expected from the results.

Published
2021

11. A Study on the Actual Conditions of Renewable Energy Use in the Japanese Municipalities based on the Three Nationwide Surveys

Author

YAMASHITA, Hidetoshi and FUJII, Kohei

Abstract

Three national surveys have been carried out jointly by the Hitotsubashi University Natural Resource-based Economies Project, The Asahi Shimbun Company, and so on up to now, in 2014, 2017 and 2020. Previously, the aggregated results of each survey have been compared to discuss the changes in the situation faced by municipalities. This paper, on the other hand, uses the integrated data from the three surveys to reconfirm the changes in the responses of municipalities and the challenges they face in promoting renewable energy, taking into account the changes in the responses of individual municipalities. As a result, we obtained more realistic insights into what we could not have known or had the wrong impression of by simply following the trends of the grand totals of the previous rounds.

Published
2021

12. A Study on the Actual Conditions of Renewable Energy Use in the Japanese Municipalities based on the Third Nationwide Survey

Author

FUJII, Kohei and YAMASHITA, Hidetoshi

Abstract

Three years has passed since the second nationwide questionnaire survey of municipalities on renewable energy policy in Japan was completed. Since then, the situations with which municipalities are faced have been changed drastically. In order to find out how municipalities react to such changes, and how are new trends in renewable energy policy emerging, the third survey was conducted from October 2020 through March 2021 jointly by the Hitotsubashi University NaturalResource-based Economies Project, The Asahi Shimbun Company, Hosei University, Nagoya University, and Institute for Sustainable Energy Policies. There were responses from 1289 municipalities, for a response rate of 74.0%. In this paper, we present the first aggregate analysis of replies to the questionnaire and issues that are expected from the results.

Published
2021

16. Strength improvement of poly(vinyl alcohol) (PVA) reinforced by Halloysite nanotube (HNT) treated with sulfuric acid

Author

Nakagaito, Antonio Norio, Fujii, Kohei, Takagi, Hitoshi, and Dong, Yu

Subjects
integumentary system, technology, industry, and agriculture, etching, acid, clay, halloysite, poly(vinyl alcohol)
Abstract

Halloysite nanotube (HNT) is a natural clay mineral with a hollow and tubular structure, which can be a potential reinforcement for biodegradable polymers such as poly(vinyl alcohol) (PVA). This study investigates the improvement of interfacial adhesion between HNT and PVA by means of controlled acid etching on HNT surfaces. Such an improvement is attributed to a porous structure with rough HNT surfaces in that acid favors the dissolution of AlO6. The strength of PVA/HNT nanocomposites increased up to 10% when HNT were subjected to 1 h acid treatment. However, the reinforcement effect could have been more pronounced if HNT aspect ratio were maintained during the composite fabrication process.

Published
2019

19. A Study on the Actual Conditions of Renewable Energy Use in the Japanese Municipalities based on the Second Nationwide Survey

Author

YAMASHITA, Hidetoshi, FUJII, Kohei, and YAMASHITA, Noriaki

Abstract

Three years has passed since the first nationwide questionnaire survey of municipalities on renewable energy policy in Japan was completed. Since then, the situations with which municipalities are faced have been changed drastically. In order to find out how municipalities react to such changes, and how are new trends in renewable energy policy emerging, the second survey was conducted from May through July 2017 jointly by the Hitotsubashi University Natural Resource-based Economies Project, Hosei University Sustainability Study Society, The Asahi Shimbun Company, and Institute for Sustainable Energy Policies. There were responses from 1385 municipalities, for a response rate of 79.4% and 47 prefectures. In this paper, we present the first aggregate analysis of replies to the questionnaire and issues that are expected from the results.

Published
2018

28. A Study on the Actual Conditions of Renewable Energy Use in the Japanese Municipalities

Author

FUJII, Kohei and YAMASHITA, Hidetoshi

Abstract

Based on the current situation that is not fully captured the actual conditions of renewable energy use in the Japanese municipalities, the purpose of this study is to find out how renewables are being used in localities, the challenges faced and the role that national government should play by the questionnaire survey. This survey was conducted from May through July 2014 jointly by the Hitotsubashi University Natural Resource-based Economies Project and The Asahi Shimbun Company. There were responses from 1372 municipalities, for a response rate of 78.8%. In this paper, we present the first aggregate analysis of replies to the questionnaire and issues that are expected from the results.

Published
2015

29. Six-port self-calibration based on active loads synthesis

Author

Yakabe, Toshiyuki, Ghannouchi, Fadhel M., Eid, Eid E., Fujii, Kohei, and Yabe, Hatsuo

Subjects
Microwave measurements -- Analysis, Business, Computers, Electronics, Electronics and electrical industries
Abstract

An automatic method for self. calibrating six-port reflectometers is reported in this paper. It is based on the use of an active impedance synthesis system. This self-calibration method allows a completely autonomous operation, reduces measurement errors caused by the frequent connecting and disconnecting of calibration standards, and is suitable for low and high frequencies, where sliding shorts are difficult to manufacture. In addition, it simplifies operation of six-port reflectometers to nonspecialized users. The experimented impedance synthesis presented relies on an in-phase and quadrature vector modulator, and the entire system is computer controlled. Index Terms--Microwave measurement, self-calibration, six-port.

Published
2002

30. Accurate modeling for drain breakdown current of GaAs MESFET's

Author

Fujii, Kohei, Hara, Yasuhiko, Yakabe, Toshiyuki, and Yabe, Hatsuo

Subjects
Breakdown (Electricity) -- Research, Electric currents -- Research, Field-effect transistors -- Research, Metal oxide semiconductor field effect transistors -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

Extensive measurements of a drain breakdown current as a function of device bias are reported in this paper. To represent the measured drain breakdown currents accurately, a new modeling function and an equivalent circuit controlled by two voltages are proposed. This model, when integrated into a large-signal analysis program, improves the accuracy of the simulation. Index Terms - Breakdown, large signal, MESFET, nonlinear model.

Published
1999

40. A Large-Signal Switching MESFET Model for Intermodulation Distortion Analysis

Author

Fujii, Kohei, Hara, Yasuhiko, Yakabe, Toshiyuki, and Yabe, Hatsuo

Subjects
Electronics -- Research, Harmonic functions -- Analysis, Nonlinear networks -- Analysis, Nonlinear theories -- Analysis, Electric distortion -- Analysis, Business, Computers, Electronics, Electronics and electrical industries
Abstract

This paper describes an improved large-signal model for predicting an intermodulation distortion (IMD) power characteristic of MESFET's in switching applications. The model is capable of modeling the voltage-dependent drain current and its derivatives, including gate-source and gate-drain capacitors. The drain current and its derivatives are described by a function of a voltage-dependent drain conductance. The model parameters are extracted from a measured drain conductance versus gate voltage characteristic of an MESFET. This paper also presents a new fully symmetric equivalent circuit for switching MESFET's. The IMD power characteristics calculated with the use of the proposed method are compared with experimental data taken from a monolithic-microwave integrated-circuit single-pole double-throw switch. Good agreements over the large gate voltages and input power levels are observed. Index Terms--Harmonic distortion, MESFET's, nonlinear model, nonlinearities.

Published
2000

45. A Novel Low Cost Enhancement Mode Power Amplifier MMIC in SMT Package for 7 to 18 GHz Applications

Author

Fujii, Kohei, Morkner, Henrik, and Brown, Edward

Subjects
ING-INF/01 Elettronica
Abstract

This paper describes a novel power amplifier based on Enhancement mode PHEMT (E-PEHMT) suitable for low cost 7-18 GHz applications. The designed power amplifier exhibits 20 dB of small signal gain, 30dBm P-1dB output power at 17 GHz. A 50 Ω output match and single 5V supply requirement simplify the application. These MMIC is fabricated in Agilent’s advanced E-PHEMT 0.25u gate process and packaged in a 5x5mm surface mount laminate package for ease in assembly. This is the only known or published E-PHEMT MMIC power amplifier to work at these frequencies for SMT applications.

Published
2004

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