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

1993

Measurement of hole mobility in dielectric liquids

Hirai, N., Arii, K., Kikuchi, H., Masoaka, T. & Nitanada, H., 1993 Dec 1, Proceedings of the 11th International Conference on Conduction and. Publ by IEEE, p. 101-105 5 p. (Proceedings of the 11th International Conference on Conduction and).

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

1996
1998
1 Citation (Scopus)
1999

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)
2000
27 Citations (Scopus)
2001

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)

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 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)

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)

On the mechanism of recovery voltage in a dielectric solid proposal of a simple equation

Yamaguchi, A., Hirai, N. & Ohki, Y., 2001 Dec 1, p. 67-70. 4 p.

Research output: Contribution to conferencePaper

Photoluminescence in polymeric insulating materials (low density polyethylene and polypropylene) induced by ultraviolet photons

Ito, T., Toyoda, T., Hirai, N. & Ohki, Y., 2001 Jan 1, p. 319-323. 5 p.

Research output: Contribution to conferencePaper

1 Citation (Scopus)
2002

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)
6 Citations (Scopus)

Interpretation of the relation between residual charge and water trees in XLPE cables

Hirai, N., Ohki, Y., Takeda, T. & Okamoto, T., 2002 Dec 1, p. 1094-1099. 6 p.

Research output: Contribution to conferencePaper

4 Citations (Scopus)
2003

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)

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)

Roles of cumyl alcohol and crosslinked structure in homo-charge trapping in crosslinked polyethylene

Hirai, N., Maeno, Y., Tanaka, T., Ohki, Y., Okashita, M. & Maeno, T., 2003 Nov 21, In : Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Annual Report. p. 213-216 4 p.

Research output: Contribution to journalConference article

11 Citations (Scopus)

Surface Change of Polyamide Nanocomposite Caused by Partial Discharges

Kozako, M., Fuse, N., Shibata, K., Hirai, N., Ohki, Y., Okamoto, T. & Tanaka, T., 2003 Nov 21, In : Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Annual Report. p. 75-78 4 p.

Research output: Contribution to journalConference article

43 Citations (Scopus)
2004

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)

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)

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)
2005

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 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)

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 ultraviolet photon irradiation on the space charge accumulation properties of several biodegradable polymers

Yamaguchi, Y., Hirai, N., Tanaka, T., Ohki, Y., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2005 Oct 7, p. 421-424. 4 p.

Research output: Contribution to conferencePaper

4 Citations (Scopus)

Effects of water temperature on degradation of several biodegradable polymers immersed in water

Hirai, N., Tanaka, T., Ohki, Y., Tajitsu, Y., Kohtoh, M. & Okabe, S., 2005 Oct 7, p. 771-774. 4 p.

Research output: Contribution to conferencePaper

6 Citations (Scopus)
2006

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)
2007

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)
39 Citations (Scopus)

Electrical conduction properties of several biodegradable polymers

Hirai, N., Ishikawa, H. & Ohki, Y., 2007 Dec 1, In : Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. p. 592-595 4 p., 4451542.

Research output: Contribution to journalConference article

19 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., 2007, In : IEEJ Transactions on Fundamentals and Materials. 127, 8, p. 459-466+5

Research output: Contribution to journalArticle

12 Citations (Scopus)
2008

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)

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)

Need for condition monitoring and diagnosis of electric wires and cables used in nuclear power plants

Ohki, Y., Hirai, N. & Yamamoto, T., 2008 Jan 1, Proceedings of 2008 International Conference on Condition Monitoring and Diagnosis, CMD 2008. IEEE Computer Society, p. 1207-1211 5 p. 4580505. (Proceedings of 2008 International Conference on Condition Monitoring and Diagnosis, CMD 2008).

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

4 Citations (Scopus)
2009

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)
2010

Endurance of polymeric insulating materials in nuclear power plants and needs for condition monitoring of electric cables

Ohki, Y., Hirai, N., Yamamoto, T., Seguchi, T., Kudoh, H. & Okamoto, T., 2010 Dec 1.

Research output: Contribution to conferencePaper

9 Citations (Scopus)

Experimental research on the feasibility of biodegradable polymeric insulating materials

Ohki, Y., Hirai, N., Kaneko, S. & Okabe, S., 2010 Dec 1.

Research output: Contribution to conferencePaper

2011

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)
2012

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)

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)

Improvement in sensitivity of broadband impedance spectroscopy for locating degradation in cable insulation by ascending the measurement frequency

Yamada, T., Hirai, N. & Ohki, Y., 2012 Dec 1, Proceedings of 2012 IEEE International Conference on Condition Monitoring and Diagnosis, CMD 2012. p. 677-680 4 p. 6416236. (Proceedings of 2012 IEEE International Conference on Condition Monitoring and Diagnosis, CMD 2012).

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

13 Citations (Scopus)

Improvement of inspection and maintenance procedures of polymeric cable insulation used in nuclear power plants in Japan

Ohki, Y., Hirai, N., Yamamoto, T., Minakawa, T. & Okamoto, T., 2012 Dec 1.

Research output: Contribution to conferencePaper

5 Citations (Scopus)
2013

Highly sensitive location method of an abnormal temperature point in a cable by frequency domain reflectometry

Ohki, Y., Hirai, N., Yamada, T. & Kumagai, S., 2013 Dec 1, ICSD 2013 - Proceedings of the 2013 IEEE International Conference on Solid Dielectrics. p. 117-120 4 p. 6619799. (Proceedings of IEEE International Conference on Solid Dielectrics, ICSD).

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

5 Citations (Scopus)
7 Citations (Scopus)

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)
2014

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)

Highly sensitive detection of distorted points in a cable by frequency domain reflectometry

Hirai, N. & Ohki, Y., 2014 Jan 1, Proceedings of 2014 International Symposium on Electrical Insulating Materials, ISEIM 2014. Institute of Electrical Engineers of Japan, p. 144-147 4 p. 6870741. (Proceedings of the International Symposium on Electrical Insulating Materials).

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

10 Citations (Scopus)