Naoshi Hirai

主任研究員(研究院准教授)

  • 595 Citations
  • 13 h-Index
1993 …2019
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Research Output 1993 2019

  • 595 Citations
  • 13 h-Index
  • 61 Conference contribution
  • 26 Article
  • 1 Chapter
  • 1 Comment/debate
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Article
2019

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
2018
1 Citation (Scopus)
Cables
Electric cables
Degradation
Fast Fourier transforms
Polymers
3 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
2017
4 Citations (Scopus)
Polyether ether ketones
ketones
Gamma rays
Dielectric properties
dielectric properties
2016
7 Citations (Scopus)
flame retardants
Scanning probe microscopy
dienes
Flame retardants
propylene
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

Spectroscopic analysis
Propylene
Ethylene
Permittivity
Copolymers
16 Citations (Scopus)
Cable cores
Insulation
Cables
Polyvinyl chlorides
Coaxial cables
Organic polymers
Photoluminescence
Fluorescence
Photons
Polyolefins
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
2013
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
3 Citations (Scopus)
Fourier transforms
Cables
Degradation
Insulation
Electric cables
2009
2 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

Biodegradable polymers
Partial discharges
Low density polyethylenes
Degradation
Lactic acid
2008
58 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, In : IEEE Transactions on Dielectrics and Electrical Insulation. 15, 1, p. 24-32 9 p.

Research output: Contribution to journalArticle

Dielectric properties
Curing
Amines
Nanocomposites
Clay
2007
38 Citations (Scopus)
Biodegradable polymers
Lactic acid
Polycaprolactone
Polyethylene terephthalates
Low density polyethylenes
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., 2007, In : IEEJ Transactions on Fundamentals and Materials. 127, 8

Research output: Contribution to journalArticle

Biodegradable polymers
Partial discharges
Low density polyethylenes
Degradation
Lactic acid
2005
21 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, In : IEEJ Transactions on Fundamentals and Materials. 125, 3, p. 254-260 7 p.

Research output: Contribution to journalArticle

Lactic acid
Glass transition
Depolarization
Short circuit currents
Fourier transform infrared spectroscopy
51 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, In : IEEE Transactions on Dielectrics and Electrical Insulation. 12, 1, p. 90-97 8 p.

Research output: Contribution to journalArticle

Electric space charge
Crosslinking
Byproducts
Polyethylenes
Low density polyethylenes
2004
2 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

Insulation
Monitoring
Fiber optics
Personnel
Costs
2003
35 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, In : IEEE Transactions on Dielectrics and Electrical Insulation. 10, 2, p. 320-330 11 p.

Research output: Contribution to journalArticle

Charge trapping
Electric space charge
Crosslinking
Byproducts
Polyethylenes
2002
5 Citations (Scopus)
Linear low density polyethylenes
Dielectric properties
Low density polyethylenes
Electric breakdown
Crosslinking
1998
1 Citation (Scopus)
mineral oils
Mineral oils
impulses
time lag
breakdown
1996
Dielectric liquids
Electric charge
Charge distribution
electric charge
elastic waves