Naoshi Hirai

上級研究員(研究院講師)

  • 777 Citations
  • 15 h-Index
1993 …2020

Research output per year

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Research Output

2020

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

Open Access
1 Citation (Scopus)
1 Citation (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

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

2019
1 Citation (Scopus)
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
3 Citations (Scopus)

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

7 Citations (Scopus)

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)

Evaluation of Aging Status of Flame-retardant Cross-linked Polyethylene by Measuring Indenter Modulus

Yang, Z., Hirai, N. & Ohki, Y., 2019 Apr, ICEMPE 2019 - 2nd International Conference on Electrical Materials and Power Equipment, Proceedings. Institute of Electrical and Electronics Engineers Inc., p. 57-60 4 p. 8727348. (ICEMPE 2019 - 2nd International Conference on Electrical Materials and Power Equipment, Proceedings).

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

1 Citation (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)

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

1 Citation (Scopus)

Origins of Chemiluminescence in Polymeric Insulating Materials

Ohki, Y., Fujishima, D., Okamoto, M. & Hirai, N., 2019 Apr, ICEMPE 2019 - 2nd International Conference on Electrical Materials and Power Equipment, Proceedings. Institute of Electrical and Electronics Engineers Inc., p. 12-16 5 p. 8727389. (ICEMPE 2019 - 2nd International Conference on Electrical Materials and Power Equipment, Proceedings).

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

1 Citation (Scopus)

Relation between the Glass Transition and Dielectric Properties in Bisphenol A and F Epoxy Resins

Mori, K., Hirai, N., Ohki, Y., Otake, Y., Umemoto, T. & Muto, H., 2019 Oct, 2019 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2019 - Proceedings. Institute of Electrical and Electronics Engineers Inc., p. 426-429 4 p. 9010555. (Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP; vol. 2019-October).

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

Spatial resolution of a cable fault location attempt by frequency domain reflectometry

Ohki, Y. & Hirai, N., 2019, p. 845-851. 7 p.

Research output: Contribution to conferencePaper

Successful detection of insulation degradation in cables by frequency domain reflectometry

Ohki, Y. & Hirai, N., 2019 Jan 1, Minerals, Metals and Materials Series. Springer International Publishing, p. 1293-1301 9 p. (Minerals, Metals and Materials Series).

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

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
2018

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)

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 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

3 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)

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)

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)

Location Attempt of Multiple Heated Spots in a Polymer-insulated Coaxial Cable by Frequency Domain Reflectometry

Hirai, N. & Ohki, Y., 2018 Nov 14, 2018 Condition Monitoring and Diagnosis, CMD 2018 - Proceedings. Abu-Siada, A. (ed.). Institute of Electrical and Electronics Engineers Inc., 8535734

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

2 Citations (Scopus)

Similarity in degradation behavior by heat and irradiation between ethylene-propylene-diene rubber and silicone rubber

Ohki, Y., Kotani, H., Fujishima, D. & Hirai, N., 2018 Jan 12, CEIDP 2017 - IEEE Conference on Electrical Insulation and Dielectric Phenomenon. Institute of Electrical and Electronics Engineers Inc., Vol. 2017-October. p. 157-160 4 p.

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

2 Citations (Scopus)

Successful detection of insulation degradation in cables by frequency domain reflectometry

Ohki, Y. & Hirai, N., 2018 Jan 1, Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors. Springer International Publishing, p. 77-85 9 p. (Minerals, Metals and Materials Series; vol. Part F11).

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

2 Citations (Scopus)

Terahertz time-domain spectroscopic analyses on crystallinity of several organic polymers

Ohki, Y., Azeyanagi, C., Kaneko, T. & Hirai, N., 2018 Jun 29, ICPADM 2018 - 12th International Conference on the Properties and Applications of Dielectric Materials. Institute of Electrical and Electronics Engineers Inc., Vol. 2018-May. p. 86-89 4 p.

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

2017
10 Citations (Scopus)

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

5 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)

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
21 Citations (Scopus)

Improved high-temperature dielectric property of epoxy resin composites with nano- and micro-sized magnesia fillers

Xie, Q., Ohki, Y., Hirai, N. & Cheng, Y. H., 2017 May 31, 2017 IEEE International Workshop on Integrated Power Packaging, IWIPP 2017. Institute of Electrical and Electronics Engineers Inc., 7936745

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

1 Citation (Scopus)

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

Minakawa, T., Ikeda, M., 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. 716-719 4 p.

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

1 Citation (Scopus)

Terahertz absorption spectra of antioxidants in insulating polymers

Kozai, T., Kaneko, T., Hirai, N. & Ohki, Y., 2017 Oct 27, Proceedings of 2017 International Symposium on Electrical Insulating Materials, ISEIM 2017. Institute of Electrical Engineers of Japan, p. 61-64 4 p. (Proceedings of the International Symposium on Electrical Insulating Materials; vol. 1).

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

Terahertz absorption spectroscopy of poly(ether ether ketone)

Kaneko, T., 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. 539-542 4 p.

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

3 Citations (Scopus)
2016

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

7 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)

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)
8 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

16 Citations (Scopus)
24 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