Naoshi Hirai

上級研究員(研究院講師)

  • 758 Citations
  • 14 h-Index
1993 …2020

Research output per year

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Research Output

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Article
1 Citation (Scopus)
8 Citations (Scopus)
1 Citation (Scopus)
Open Access
2 Citations (Scopus)

Changes in mechanical and dielectric properties of silicone rubber induced by severe aging

Ito, S., Hirai, N. & Ohki, Y., 2020 Jun, In : IEEE Transactions on Dielectrics and Electrical Insulation. 27, 3, p. 722-730 9 p., 9099698.

Research output: Contribution to journalArticle

Chemical group in crosslinking byproducts responsible for charge trapping in polyethylene

Hirai, N., Minami, R., Tanaka, T., Ohki, Y., Okashita, M. & Maeno, T., 2003 Apr 1, In : IEEE Transactions on Dielectrics and Electrical Insulation. 10, 2, p. 320-330 11 p.

Research output: Contribution to journalArticle

41 Citations (Scopus)
Open Access

Degradation mechanisms of silicone rubber under different aging conditions

Kaneko, T., Ito, S., Minakawa, T., Hirai, N. & Ohki, Y., 2019 Oct 1, In : Polymer Degradation and Stability. 168, 108936.

Research output: Contribution to journalArticle

6 Citations (Scopus)
3 Citations (Scopus)
8 Citations (Scopus)

Dielectric properties of epoxy/clay nanocomposites -effects of curing agent and clay dispersion method

Tagami, N., Okada, M., Hirai, N., Ohki, Y., Tanaka, T., Imai, T., Harada, M. & Ochi, M., 2008 Feb 1, In : IEEE Transactions on Dielectrics and Electrical Insulation. 15, 1, p. 24-32 9 p.

Research output: Contribution to journalArticle

59 Citations (Scopus)

Dielectric spectroscopic analysis of degradation in ethylene-propylene-diene copolymer

Min, D., Li, S., Hirai, N. & Ohki, Y., 2016 Dec 1, In : IEEE Transactions on Dielectrics and Electrical Insulation. 23, 6, p. 3620-3630 11 p., 7823416.

Research output: Contribution to journalArticle

14 Citations (Scopus)

Effect of byproducts of dicumyl peroxide on space charge formation in low-density polyethylene

Hirai, N., Minami, R., Shibata, K., Ohki, Y., Okashita, M. & Maeno, T., 2001 Jan 1, In : Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Annual Report. p. 478-483 6 p.

Research output: Contribution to journalArticle

11 Citations (Scopus)

Effect of Glass Transition on Electrical Conduction Characteristics of Poly-L-lactic Acid

Maeno, Y., Yamaguchi, Y., Hirai, N., Ohki, Y., Tanaka, T., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2005 Jan 1, In : IEEJ Transactions on Fundamentals and Materials. 125, 3, p. 254-260 7 p.

Research output: Contribution to journalArticle

21 Citations (Scopus)

Effects of crosslinking byproducts on space charge formation in crosslinked polyethylene

Maeno, Y., Hirai, N., Ohki, Y., Tanaka, T., Okashita, M. & Maeno, T., 2005 Feb 1, In : IEEE Transactions on Dielectrics and Electrical Insulation. 12, 1, p. 90-97 8 p.

Research output: Contribution to journalArticle

63 Citations (Scopus)
24 Citations (Scopus)
39 Citations (Scopus)

Electronic transition process of fluorescence appearing in various organic polymers

Nishikawa, S., Tonoi, M., Yoshikawa, T., Hirai, N., Nakai, H. & Ohki, Y., 2016, In : IEEJ Transactions on Fundamentals and Materials. 136, 4, p. 205-211 7 p.

Research output: Contribution to journalArticle

Evaluation of degradation in polyimide by recovery voltage measurement

Yamaguchi, A., Wei, W., Hirai, N., Ohki, Y., Zaima, E. & Okabe, S., 2001 Jan 1, In : Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Annual Report. p. 216-220 5 p.

Research output: Contribution to journalArticle

2 Citations (Scopus)

Experimental investigation of the degradation mechanism of silicone rubber exposed to heat and gamma rays

Hanada, S., Miyamoto, M., Hirai, N., Yang, L. & Ohki, Y., 2017 Jun, In : High Voltage. 2, 2, p. 92-101 10 p.

Research output: Contribution to journalArticle

Open Access
20 Citations (Scopus)
6 Citations (Scopus)

Identification and quantification of phenol-type antioxidants in low-density polyethylene by broadband far-infrared spectroscopy

Ogishima, T., Kuroda, C., Hirai, N. & Ohki, Y., 2019 Jul 1, In : Polymer Testing. 76, p. 10-18 9 p.

Research output: Contribution to journalArticle

2 Citations (Scopus)

Identification of antioxidants in polymeric insulating materials by terahertz absorption spectroscopy

Kozai, T., Kaneko, T., Hirai, N. & Ohki, Y., 2018 Jan 1, In : Polymer Degradation and Stability. 147, p. 284-290 7 p.

Research output: Contribution to journalArticle

7 Citations (Scopus)

Insulation performance of safety-related cables for nuclear power plants under simulated severe accident conditions

Minakawa, T., Ikeda, M., Hirai, N. & Ohki, Y., 2019 Jan 1, In : IEEJ Transactions on Fundamentals and Materials. 139, 2, p. 54-59 6 p.

Research output: Contribution to journalArticle

Location attempt of a degraded portion in a long polymer-insulated cable

Ohki, Y. & Hirai, N., 2018 Dec 1, In : IEEE Transactions on Dielectrics and Electrical Insulation. 25, 6, p. 2461-2466 6 p., 8561354.

Research output: Contribution to journalArticle

3 Citations (Scopus)
1 Citation (Scopus)
5 Citations (Scopus)
7 Citations (Scopus)

Modeling of oxidation process and property changes of ethylene-propylene-diene copolymer

Min, D., Li, S., Hirai, N. & Ohki, Y., 2016 Feb 1, In : IEEE Transactions on Dielectrics and Electrical Insulation. 23, 1, p. 537-546 10 p., 7422602.

Research output: Contribution to journalArticle

3 Citations (Scopus)

Numerical evaluation of complex permittivity of silicone rubber based on Jonscher's law

Yang, Z., Ito, S., Hirai, N. & Ohki, Y., 2020 May 1, In : IEEJ Transactions on Electrical and Electronic Engineering. 15, 5, p. 658-662 5 p.

Research output: Contribution to journalArticle

Partial discharge degradation of several biodegradable polymers

Fuse, N., Fujita, S., Hirai, N., Tanaka, T., Kozako, M., Kohtoh, M., Okabe, S. & Ohki, Y., 2007, In : IEEJ Transactions on Fundamentals and Materials. 127, 8, p. 459-466+5

Research output: Contribution to journalArticle

12 Citations (Scopus)

Partial discharge degradation of several biodegradable polymers

Fuse, N., Fujita, S., Hirai, N., Tanaka, T., Kozako, M., Kohtoh, M., Okabe, S. & Ohki, Y., 2009 Jul 30, In : Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi). 168, 2, p. 1-10 10 p.

Research output: Contribution to journalArticle

2 Citations (Scopus)

Possible cause of chemiluminescence in silicone rubber

Ohki, Y. & Hirai, N., 2020 Apr 1, In : Japanese journal of applied physics. 59, 4, 041005.

Research output: Contribution to journalArticle

Precise location of the excessive temperature points in polymer insulated cables

Ohki, Y., Yamada, T. & Hirai, N., 2013 Dec, In : IEEE Transactions on Dielectrics and Electrical Insulation. 20, 6, p. 2099-2106 8 p., 6678858.

Research output: Contribution to journalArticle

26 Citations (Scopus)

Status Quo and Trends of Insulation Monitoring and Diagnosis Methods for Electric Power Apparatus in Japan

Hirai, N., Ohki, Y., Tanaka, T. & Shindo, T., 2004, In : IEEJ Transactions on Power and Energy. 124, 3, p. 496-503 8 p.

Research output: Contribution to journalArticle

2 Citations (Scopus)

Terahertz absorption spectra of several polymer nanocomposites indicating polymer-filler interactions

Mori, K., Seki, T., Hirai, N. & Ohki, Y., 2019 Oct 1, In : AIP Advances. 9, 10, 105109.

Research output: Contribution to journalArticle

Open Access
1 Citation (Scopus)