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

1 Citation (Scopus)

Aging mechanism of silicone rubber by heat and gamma-rays

Ohki, Y., Hanada, S., Miyamoto, M., Hirai, N. & Yang, L., 2016 Dec 15, 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2016. Institute of Electrical and Electronics Engineers Inc., Vol. 2016-December. p. 869-872 4 p. 7785487

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Citations (Scopus)
8 Citations (Scopus)
1 Citation (Scopus)

Aging State Analysis of Safety-related Cables for Nuclear Power Plants Exposed to Simulated Accident Conditions

Minakawa, T., Ikeda, M., Hirai, N. & Ohki, Y., 2018 Nov 26, 2018 IEEE CEIDP Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2018. Institute of Electrical and Electronics Engineers Inc., Vol. 2018-October. p. 602-605 4 p. 8544872

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Broadband Far-infrared Spectroscopic Identification and Quantification of Antioxidants in Polymeric Insulation

Ogishima, T., Kozai, T., Hirai, N. & Ohki, Y., 2019 Feb 13, ICHVE 2018 - 2018 IEEE International Conference on High Voltage Engineering and Application. Institute of Electrical and Electronics Engineers Inc., 8641948. (ICHVE 2018 - 2018 IEEE International Conference on High Voltage Engineering and Application).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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., 2002 Jan 1, In : Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Annual Report. p. 626-630 5 p.

Research output: Contribution to journalConference article

2 Citations (Scopus)

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)

Chemiluminescence as a clear diagnostic tool of polymer oxidation

Ohki, Y. & Hirai, N., 2012 Nov 26, ICPADM 2012 - 2012 IEEE 10th International Conference on the Properties and Applications of Dielectric Materials, Technical Papers. 6318953. (Proceedings of the IEEE International Conference on Properties and Applications of Dielectric Materials).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)

Chemiluminescence characteristics of FR-EPDM and SiR aged by concurrently-given heat and radiation

Ikeno, R., Hirai, N. & Ohki, Y., 2016 Dec 15, 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2016. Institute of Electrical and Electronics Engineers Inc., Vol. 2016-December. p. 853-856 4 p. 7785443

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)

Chemiluminescence due to oxidation of ethylene propylene diene copolymers

Ohki, Y. & Hirai, N., 2014 Dec 22, 2014 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2014. Institute of Electrical and Electronics Engineers Inc., p. 425-428 4 p. 6995786

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)

Comparison of broadband impedance spectroscopy and time domain reflectometry for locating cable degradation

Hirai, N., Yamada, T. & Ohki, Y., 2012 Dec 1, Proceedings of 2012 IEEE International Conference on Condition Monitoring and Diagnosis, CMD 2012. p. 229-232 4 p. 6416417. (Proceedings of 2012 IEEE International Conference on Condition Monitoring and Diagnosis, CMD 2012).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

18 Citations (Scopus)

Comparison of location abilities of degradation in a polymer-insulated cable between frequency domain reflectometry and line resonance analysis

Ohki, Y. & Hirai, N., 2016 Dec 27, ICHVE 2016 - 2016 IEEE International Conference on High Voltage Engineering and Application. Institute of Electrical and Electronics Engineers Inc., 7800602

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)
Open Access

Correlation between indenter modulus and elongation-at-break observed for four electrical insulating polymers

Hirai, N. & Ohki, Y., 2017 Dec 4, Proceedings of 2017 International Symposium on Electrical Insulating Materials, ISEIM 2017. Institute of Electrical Engineers of Japan, Vol. 2. p. 753-756 4 p.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)

Degradation behavior and mechanisms of several polymeric insulating materials exposed to heat and radiation

Yang, L., Ohki, Y., Hirai, N. & Li, S., 2018 Feb 2, 2017 3rd International Conference on Condition Assessment Techniques in Electrical Systems, CATCON 2017 - Proceedings. Institute of Electrical and Electronics Engineers Inc., Vol. 2018-January. p. 98-103 6 p.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Degradation in Dielectric Behavior of Soft Epoxy Resin by Concurrent Aging with Heat and Radiation

Ishii, H., Yamaguchi, H., Mori, K., Hirai, N. & Ohki, Y., 2019 Oct, 2019 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2019 - Proceedings. Institute of Electrical and Electronics Engineers Inc., p. 18-21 4 p. 9010557. (Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP; vol. 2019-October).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Degradation in Mechanical and Dielectric Properties of Silicone Rubber under Severe Aging Conditions

Hirai, N., Kaneko, T., Ito, S., Minakawa, T. & Ohki, Y., 2019 Oct, 2019 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2019 - Proceedings. Institute of Electrical and Electronics Engineers Inc., p. 126-129 4 p. 9009713. (Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP; vol. 2019-October).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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)

Degradation of silicone rubber analyzed by instrumental analyses and dielectric spectroscopy

Ohki, Y., Hirai, N., Min, D., Yang, L. & Li, S., 2018 Jan 1, Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors. Springer International Publishing, p. 107-116 10 p. (Minerals, Metals and Materials Series; vol. Part F11).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Degradation of silicone rubber analyzed by instrumental analyses and dielectric spectroscopy

Ohki, Y., Hirai, N., Min, D., Yang, L. & Li, S., 2019 Jan 1, Minerals, Metals and Materials Series. Springer International Publishing, p. 1323-1332 10 p. (Minerals, Metals and Materials Series).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)
3 Citations (Scopus)

Diagnosis of cable aging by broadband impedance spectroscopy

Ohki, Y., Yamada, T. & Hirai, N., 2011 Dec 1, In : Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. p. 24-27 4 p., 6232587.

Research output: Contribution to journalConference article

19 Citations (Scopus)
8 Citations (Scopus)

Dielectric properties of biodegradable polylactic acid and starch ester

Hirai, N., Maeno, Y., Tamura, H., Kaneko, D., Tanaka, T., Ohki, Y., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2004 Jan 1, Proceedings of the 2004 IEEE International Conference on Solid Dielectrics ICSD 2004. Institute of Electrical and Electronics Engineers Inc., p. 87-90 4 p. 1P-12. (Proceedings of the 2004 IEEE International Conference on Solid Dielectrics ICSD 2004; vol. 1).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

14 Citations (Scopus)

Dielectric properties of biodegradable polymers

Ohki, Y. & Hirai, N., 2006 Dec 1, 2006 Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. p. 668-671 4 p. 4105521. (Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

9 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)

Dipolar polarization and depolarization currents in biodegradable polymers

Maeno, Y., Kino, H., Omori, S., Hirai, N., Tanaka, T., Ohki, Y., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2005 Oct 10, p. 417-420. 4 p.

Research output: Contribution to conferencePaper

4 Citations (Scopus)

Effect of blending on the dielectric breakdown of polyethylene

Ono, H., Hirai, N. & Ohki, Y., 2001 Dec 1, p. 574-577. 4 p.

Research output: Contribution to conferencePaper

1 Citation (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 contaminant in breakdown time lag of uniform electric field using impulse breakdown in mineral oil

Hirai, N., Akumu, A. O. & Arii, K., 1999 Dec 1, p. 207-210. 4 p.

Research output: Contribution to conferencePaper

1 Citation (Scopus)

Effect of crosslinking on space charge formation in crosslinked polyethylene

Hirai, N., Maeno, Y., Tanaka, T., Ohki, Y., Okashita, M. & Maeno, T., 2003 Oct 20, p. 917-920. 4 p.

Research output: Contribution to conferencePaper

11 Citations (Scopus)

Effect of glass transition on conduction current in biodegradable poly-L-lactic acid

Maeno, Y., Yamaguchi, Y., Hirai, N., Tanaka, T., Ohki, Y., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2004 Dec 1, In : Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. p. 49-52 4 p.

Research output: Contribution to journalConference article

8 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 addition of MgO fillers with various sizes and co-addition of nano-sized SiO2 fillers on the dielectric properties of epoxy resin

Yanashima, R., Hirai, N. & Ohki, Y., 2017 Dec 4, Proceedings of 2017 International Symposium on Electrical Insulating Materials, ISEIM 2017. Institute of Electrical Engineers of Japan, Vol. 2. p. 650-653 4 p.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)

Effects of blending various biodegradable polymer plasticizers on the conduction current and AC breakdown strength in starch ester

Nemoto, Y., Kato, F., Hirai, N., Ohki, Y., Kaneko, S. & Okabe, S., 2008 Dec 31, p. 542-545. 4 p.

Research output: Contribution to conferencePaper

5 Citations (Scopus)
27 Citations (Scopus)

Effects of byproducts of dicumyl peroxide on space charge formation in polyethylene

Hirai, N., Minami, R., Ohki, Y., Okashita, M. & Maeno, T., 2001 Jan 1, p. 450-455. 6 p.

Research output: Contribution to conferencePaper

15 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)

Effects of curing and filler dispersion methods on dielectric properties of epoxy nanocomposites

Tagami, N., Okada, M., Hirai, N., Tanaka, T., Ohki, Y., Imai, T., Harada, M. & Ochi, M., 2007 Dec 1, In : Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. p. 232-235 4 p., 4451465.

Research output: Contribution to journalConference article

7 Citations (Scopus)

Effects of glass transition on the dielectric breakdown and electrical conduction in several biodegradable polymers

Matsushita, M., Maeno, Y., Kino, H., Fujita, S., Hirai, N., Tanaka, T., Ohki, Y., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2005, p. 413-416. 4 p.

Research output: Contribution to conferencePaper

12 Citations (Scopus)

Effects of Heat and Radiation Aging and Burning on the Surface Physical Properties of Polymer-Insulated Cables

Ito, S., Hirai, N., Minakawa, T., Kuroda, C. & Ohki, Y., 2018 Nov 26, 2018 IEEE CEIDP Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2018. Institute of Electrical and Electronics Engineers Inc., Vol. 2018-October. p. 374-377 4 p. 8544768

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Effects of Heat and Radiation on the Terahertz Absorption in Silicone Rubber

Kaneko, T., Hirai, N. & Ohki, Y., 2018 Sep 19, 2018 IEEE 2nd International Conference on Dielectrics, ICD 2018. Institute of Electrical and Electronics Engineers Inc., p. 223DUMMY 8470044

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Effects of liquid chemicals on space charge evolution in low-density polyethylene

Minami, R., Hirai, N., Ohki, Y., Okashita, M. & Maeno, T., 2001 Dec 1, p. 87-90. 4 p.

Research output: Contribution to conferencePaper

7 Citations (Scopus)
24 Citations (Scopus)