Naoshi Hirai

主任研究員(研究院准教授)

  • 604 Citations
  • 13 h-Index
1993 …2019
If you made any changes in Pure these will be visible here soon.

Research Output 1993 2019

  • 604 Citations
  • 13 h-Index
  • 63 Conference contribution
  • 27 Article
  • 1 Chapter
  • 1 Comment/debate
2019
Flame retardants
Nuclear power plants
Polyethylenes
Aging of materials
Permittivity

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

Antioxidants
Insulation
Infrared radiation
Low density polyethylenes
Infrared absorption

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

Silicone Elastomers
Dielectric spectroscopy
Silicones
Rubber
Degradation

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

Yang, Z., Hirai, N. & Ohki, Y., 2019 Apr 1, 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

Flame Retardants
Polyethylene
Flame retardants
Polyethylenes
Aging of materials

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

Low density polyethylenes
Polyethylene
Phenol
Antioxidants
Phenols

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

Nuclear power plants
Insulation
Accidents
Cables
Steam

Origins of Chemiluminescence in Polymeric Insulating Materials

Ohki, Y., Fujishima, D., Okamoto, M. & Hirai, N., 2019 Apr 1, 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

Chemiluminescence
Insulating materials
Polymers
Siloxanes
Epoxy Resins

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

Insulation
Cables
Degradation
Organic polymers
Electromagnetic waves
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

Siloxanes
Nuclear power plants
Accidents
Cables
Aging of materials

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

Insulating materials
Flame retardants
Radiation
Degradation
Dielectric properties

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

Silicone Elastomers
Dielectric spectroscopy
Silicones
Rubber
Degradation
1 Citation (Scopus)
Cables
Electric cables
Degradation
Fast Fourier transforms
Polymers

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

Polymers
Cables
Physical properties
Aging of materials
Radiation

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

Silicone Elastomers
Silicones
Rubber
Radiation
Absorption spectra
4 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

Terahertz spectroscopy
Insulating materials
antioxidants
Antioxidants
Absorption spectroscopy
1 Citation (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

Cables
Low density polyethylenes
Polymers
Coaxial cables
Electric network analyzers

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

Coaxial cables
Low density polyethylenes
Polymers
Fast Fourier transforms
Cables
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

Silicone Elastomers
Silicones
Propylene
Rubber
Ethylene

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

Insulation
Cables
Degradation
Organic polymers
Electromagnetic waves

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

Terahertz spectroscopy
Organic polymers
Absorption spectroscopy
crystallinity
Polyether ether ketones
2017
5 Citations (Scopus)
Polyether ether ketones
ketones
Gamma rays
Dielectric properties
dielectric properties
2 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

Flame Retardants
Silicone Elastomers
Elongation
Rubber
Polymers

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

Epoxy Resins
Epoxy resins
Dielectric properties
Fillers
Polymers

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

Magnesium Oxide
Epoxy Resins
Magnesia
Epoxy resins
Dielectric properties
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

Nuclear power plants
Insulation
Accidents
Cables
Containment vessels

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, Vol. 1. p. 61-64 4 p.

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

Antioxidants
Absorption spectra
Polymers
Polyethylene
Polyethylenes
2 Citations (Scopus)

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

Terahertz spectroscopy
Polyether ether ketones
Absorption spectroscopy
Infrared absorption
Absorption spectra
2016
4 Citations (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

Silicone Elastomers
Gamma rays
Silicones
Rubber
Aging of materials
3 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

Flame Retardants
Silicone Elastomers
Chemiluminescence
Flame retardants
Silicones

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

Coaxial cables
Cables
Low density polyethylenes
Degradation
Silicones
7 Citations (Scopus)
flame retardants
Scanning probe microscopy
dienes
Flame retardants
propylene
9 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

Spectroscopic analysis
Propylene
Ethylene
Permittivity
Copolymers
16 Citations (Scopus)
Cable cores
Insulation
Cables
Polyvinyl chlorides
Coaxial cables
Organic polymers
Photoluminescence
Fluorescence
Photons
Polyolefins
Propylene
Insulation
Ethylene
Copolymers
Oxidation
5 Citations (Scopus)

Fault location in a cable for a nuclear power plant by frequency domain reflectometry

Ohki, Y. & Hirai, N., 2016 Nov 28, CMD 2016 - International Conference on Condition Monitoring and Diagnosis. Institute of Electrical and Electronics Engineers Inc., p. 36-39 4 p. 7757782

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

Electric fault location
Nuclear power plants
Cables
Flame retardants
Radiation
Silicones
Rubber
Cables
Electric cables
Degradation
2 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

Propylene
Ethylene
Copolymers
Irradiation
Oxidation
2 Citations (Scopus)

Non-destructive diagnosis of degradation of silicone rubber by indenter modulus and scanning probe microscopy

Hanada, S., Odaka, D., Yang, L., Hirai, N. & Ohki, Y., 2016 Nov 28, CMD 2016 - International Conference on Condition Monitoring and Diagnosis. Institute of Electrical and Electronics Engineers Inc., p. 123-126 4 p. 7757791

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

Scanning probe microscopy
Silicones
Rubber
Thermal aging
Radiation
4 Citations (Scopus)

Space charge distributions in epoxy/MgO nanocomposites at various temperatures

Xie, Q., Cheng, Y. H., Hirai, N. & Ohki, Y., 2016 Dec 27, ICHVE 2016 - 2016 IEEE International Conference on High Voltage Engineering and Application. Institute of Electrical and Electronics Engineers Inc., 7800636

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

Charge distribution
Magnesia
Electric space charge
Nanocomposites
Epoxy resins

Terahertz spectroscopic diagnosis of degradation of ethylene-propylene-diene copolymer

Ohki, Y., Kozai, T., Komatsu, M. & Hirai, N., 2016 Aug 18, Proceedings of the 2016 IEEE International Conference on Dielectrics, ICD 2016. Institute of Electrical and Electronics Engineers Inc., Vol. 2. p. 646-649 4 p. 7547698

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

Flame Retardants
Terahertz spectroscopy
Propylene
Infrared spectroscopy
Ethylene
2015
4 Citations (Scopus)

Influence of cable structure on the fault location by frequency domain reflectometry

Ohki, Y. & Hirai, N., 2015 Dec 9, Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. Institute of Electrical and Electronics Engineers Inc., Vol. 2015-December. p. 274-277 4 p. 7352023

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

Electric fault location
Cables
Cable cores
Flame Retardants
Silicone Elastomers
2014
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

Chemiluminescence
Propylene
Ethylene
Copolymers
Low density polyethylenes
7 Citations (Scopus)

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

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

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

Cables
Electric cables
Flame Retardants
Telecommunication cables
Coaxial cables
2013
4 Citations (Scopus)

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, Proceedings of IEEE International Conference on Solid Dielectrics, ICSD. p. 117-120 4 p. 6619799

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

cables
communication cables
Cables
polyvinyl chloride
Telecommunication cables
4 Citations (Scopus)
Fourier transforms
Cables
Degradation
Insulation
Electric cables
18 Citations (Scopus)

Precise location of the excessive temperature points in polymer insulated cables

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

Research output: Contribution to journalArticle

Cables
Polymers
Telecommunication cables
Temperature
Coaxial cables
2012
4 Citations (Scopus)

Chemiluminescence as a clear diagnostic tool of polymer oxidation

Ohki, Y. & Hirai, N., 2012, Proceedings of the IEEE International Conference on Properties and Applications of Dielectric Materials. 6318953

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

Chemiluminescence
chemiluminescence
Polymers
Oxidation
oxidation
15 Citations (Scopus)

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

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

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

Cables
Spectroscopy
Degradation
Rubber
Flame retardants
10 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, Proceedings of 2012 IEEE International Conference on Condition Monitoring and Diagnosis, CMD 2012. p. 677-680 4 p. 6416236

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

Insulation
Cables
Spectroscopy
Degradation
Fast Fourier transforms