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Journal Articles

Data-driven analyses of avalanche like turbulent transport phenomena

Asahi, Yuichi; Fujii, Keisuke*

Purazuma, Kaku Yugo Gakkai-Shi, 97(2), p.86 - 92, 2021/02

The 5D gyrokinetic simulation data has been analyzed with the data-driven analysis methods. By defining an entropy-like quantity with singular values, we have quantitatively evaluated the randomness of the plasma state. We found that the randomness of plasma increases after the avalanche like transport and then gradually decrease. Since the decrease of the randomness is expected to be relevant to the phase space structure formation, we have developed a method to extract the phase space structures from the time series of 5D data. The relationship between the avalanche-like transport and phase space structures is discussed based on the contribution of each principal component to the energy transport.

Journal Articles

Compressing the time series of five dimensional distribution function data from gyrokinetic simulation using principal component analysis

Asahi, Yuichi; Fujii, Keisuke*; Heim, D. M.*; Maeyama, Shinya*; Garbet, X.*; Grandgirard, V.*; Sarazin, Y.*; Dif-Pradalier, G.*; Idomura, Yasuhiro; Yagi, Masatoshi*

Physics of Plasmas, 28(1), p.012304_1 - 012304_21, 2021/01

AA2020-0790.pdf:7.13MB

 Times Cited Count:4 Percentile:44.85(Physics, Fluids & Plasmas)

This article demonstrates a data compression technique for the time series of five dimensional distribution function data based on Principal Component Analysis (PCA). Phase space bases and corresponding coefficients are constructed by PCA in order to reduce the data size and the dimensionality. It is shown that about 83% of the variance of the original five dimensional distribution can be expressed with 64 components. This leads to the compression of the degrees of freedom from $$1.3times 10^{12}$$ to $$1.4times 10^{9}$$. One of the important findings - resulting from the detailed analysis of the contribution of each principal component to the energy flux - deals with avalanche events, which are found to be mostly driven by coherent structures in the phase space, indicating the key role of resonant particles.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2018

Nakano, Masanao; Fujii, Tomoko; Nemoto, Masashi; Tobita, Keiji; Kono, Takahiko; Hosomi, Kenji; Nishimura, Shusaku; Matsubara, Natsumi; Maehara, Yushi; Narita, Ryosuke; et al.

JAEA-Review 2019-048, 165 Pages, 2020/03

JAEA-Review-2019-048.pdf:2.69MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2018 to March 2019. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co., Inc. (the trade name was changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016) in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and exceeded the normal range of fluctuation in the monitoring, were evaluated.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2017

Nakano, Masanao; Fujita, Hiroki; Mizutani, Tomoko; Nemoto, Masashi; Tobita, Keiji; Kono, Takahiko; Hosomi, Kenji; Hokama, Tomonori; Nishimura, Tomohiro; Matsubara, Natsumi; et al.

JAEA-Review 2018-025, 171 Pages, 2019/02

JAEA-Review-2018-025.pdf:3.81MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2016 to March 2017. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Electric Power Company Holdings, Inc. in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and were exceeded the normal range of fluctuation in the monitoring, were evaluated.

Journal Articles

High oxide-ion conductivity in Si-deficient La$$_{9.565}$$(Si$$_{5.826}$$[]$$_{0.174}$$)O$$_{26}$$ apatite without interstitial oxygens due to the overbonded channel oxygens

Fujii, Kotaro*; Yashima, Masatomo*; Hibino, Keisuke*; Shiraiwa, Masahiro*; Fukuda, Koichiro*; Nakayama, Susumu*; Ishizawa, Nobuo*; Hanashima, Takayasu*; Ohara, Takashi

Journal of Materials Chemistry A, 6(23), p.10835 - 10846, 2018/06

 Times Cited Count:24 Percentile:70.61(Chemistry, Physical)

JAEA Reports

Survey of radiation protection creiteria following the accident at the Fukushima Dai-ichi Nuclear Power Plant

Yamada, Katsunori; Fujii, Katsutoshi; Kanda, Hiroshi; Higashi, Daisuke; Kobayashi, Toshiaki; Nakagawa, Masahiro; Fukami, Tomoyo; Yoshida, Keisuke; Ueno, Yumi; Nakajima, Junya; et al.

JAEA-Review 2013-033, 51 Pages, 2013/12

JAEA-Review-2013-033.pdf:2.73MB

After the accident at Fukushima Dai-ichi Nuclear Power Plant, various numerical criteria relevant to radiation protection were defined. We surveyed these criteria through internet. As a result of survey, the following 13 items were identified: (1) criteria for taking stable iodine tablets, (2) criteria for the screening of surface contamination, (3) evacuation area, sheltering area, etc., (4) activity concentrations in food, drinking water, etc., (5) dose limit for radiation workers engaged in emergency work, (6) guideline levels of radioactive substances in bathing areas, (7) criteria for use of school buildings and schoolyards, (8) restriction on planting rice, (9) acceptable activity concentrations in feedstuff, (10) acceptable activity concentrations in compost, (11) criteria for export containers and ships, (12) criteria for contaminated waste, (13) standards for radiation workers engaged in decontamination work. In this report, the basis of and issues on these criteria are summarized.

JAEA Reports

Investigation on cause of malfunction of Wide Range Monitor (WRM) in High Temperature engineering Test Reactor (HTTR); Sample tests and destructive tests

Shinohara, Masanori; Motegi, Toshihiro; Saito, Kenji; Haga, Hiroyuki; Sasaki, Shinji; Katsuyama, Kozo; Takada, Kiyoshi*; Higashimura, Keisuke*; Fujii, Junichi*; Ukai, Takayuki*; et al.

JAEA-Technology 2012-032, 29 Pages, 2012/11

JAEA-Technology-2012-032.pdf:6.57MB

An event, in which one of WRMs were disabled to detect the neutron flux in the reactor core, occurred during the period of reactor shut down of HTTR in March, 2010. The actual life time of WRM was unexpectedly shorter than the past developed life time. Investigation of the cause of the outage of WRM toward the recovery of the life time up to the past developed life is one of the issues to develop the technology basis of HTGR. Then, two experimental investigations were carried out to reveal the cause of the malfunction by specifying the damaged part causing the event in the WRM. One is an experiment using a mock-up sample test which strength degradation on assembly accuracy and heat cycle to specify the damaged part in the WRM. The other is a destructive test in FMF to specify the damaged part in the WRM. This report summarized the results of the destructive test and the experimental investigation using the mock-up to reveal the cause of malfunction of WRM.

Journal Articles

Preparation of fullerenes by resistive heating vaporization method; Effect of carbon materials

Otsuki, Ryusei*; Nasu, Shoichi*; Fujimori, Ryosuke*; Anada, Kinji*; Ohashi, Kentaro*; Yamamoto, Ryoichi*; Fujii, Kimio; Okubo, Keisuke*

Funtai Oyobi Fummatsu Yakin, 51(8), p.622 - 625, 2004/08

Effects of carbon materials on weight yield of (C$$_{60}$$+C$$_{70}$$) and weight ratios of C$$_{60}$$ to (C$$_{60}$$+C$$_{70}$$) in soot were examined by the Joule resistive heating of four kinds of carbon materials at He gas pressures from 0.7$$times$$10$$^{4}$$$$sim$$8.0$$times$$10$$^{4}$$Pa for collector radii of 45, 50 and 55mm. The yields were in the range of 1 to 8% for graphite with hexagonal lattice, and better than those for glassy carbon. The most effective He gas pressure for the fullerene yield were in the range of 4.0$$sim$$5.3$$times$$10$$^{4}$$Pa. Any collector radii dependence of the yields was not observed. The weight ratios of C$$_{60}$$ to (C$$_{60}$$+C$$_{70}$$) were about 60 to 70%, and showed neither He gas pressure depenndennce nor collector radii depenndence four kinds of carbon materials.

Journal Articles

Preparation of fullerenes by arc discharge between graphite anode and tungsten cathode; Effects of gas species

Otsuki, Ryusei*; Nasu, Shoichi*; Ohashi, Kentaro*; Yamamoto, Ryoichi*; Fujii, Kimio; Okubo, Keisuke*

Funtai Oyobi Fummatsu Yakin, 51(8), p.626 - 629, 2004/08

The He, Ar and the Penning gas pressureeffects on the preparation yieldsof the fullerenes were investigated by means of the arc discharge method using graphite(PGX) anode buried in a tungsten rod and tungsten cathode for collector radii of 50mm. The maximum yield showed about 13-14 % at 67KPa in He gas. The yields in the mixtures of He and Ne gases (the Penning effect) were similar to those obtained in He gas. Weight ratios of C$$_{60}$$ to (C$$_{60}$$+C$$_{70}$$) were about 20% in Ar gas, while those in He and Penning gas were about 60%. Ultra sonic vibration was effective to separate C$$_{70}$$ from soot.

Journal Articles

Investigation of interaction between MeV-ions and first wall from neutron and $$gamma$$-ray measurements in JT-60U

Kondoh, Takashi; Kusama, Yoshinori; Kimura, Haruyuki; Saigusa, Mikio; Fujii, Tsuneyuki; Moriyama, Shinichi; Nemoto, Masahiro; Tobita, Kenji; Morioka, Atsuhiko; Nagashima, Keisuke; et al.

Journal of Nuclear Materials, 241-243, p.564 - 568, 1997/02

 Times Cited Count:12 Percentile:67.96(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Present status of JT-60 ICRF heating experiment

Kimura, Haruyuki; Fujii, Tsuneyuki; Saigusa, Mikio; Hamamatsu, Kiyotaka; Kusama, Yoshinori; Tobita, Kenji; Nemoto, Masahiro; Nagashima, Keisuke; *; Moriyama, Shinichi; et al.

JAERI-M 88-123, 24 Pages, 1988/07

JAERI-M-88-123.pdf:0.82MB

no abstracts in English

Oral presentation

Development of the technology basis for holistic waste management taking into consideration whole fuel cycle system, 4; Study on issues and approaches for developing an advanced performance assessment technique

Maekawa, Keisuke; Makino, Hitoshi; Umeki, Hiroyuki; Hioki, Kazumasa; Kaneko, Yu*; Takase, Hiroyasu*; Fujii, Naoki*

no journal, , 

no abstracts in English

Oral presentation

Compressing the time series of five dimensional distribution function data from gyrokinetic simulation using Principal component analysis

Asahi, Yuichi; Fujii, Keisuke*; Dennis, H.*; Maeyama, Shinya*; Idomura, Yasuhiro

no journal, , 

Phase space structures are extracted from the time series of five dimensional distribution function data computed by the flux-driven full-fgyrokinetic code GT5D. Principal component analysis (PCA) is applied to reduce the dimensionality and the size of the data. Phase space bases and the corresponding spatial coefficients (poloidal cross section) are constructed by PCA. It is shown that 83% of the variance of the original five-dimensional distribution can be expressed with 64 principal components, i.e., the compression $$10^{12}$$ of the degrees of freedom from 10 to $$3times 10^9$$. The relationship between avalanche-like transport phenomena and phase space structure is discussed based on the contribution of each principal component to the heat transport.

Oral presentation

Phase-Space Pattern Extraction from 5D gyrokinetic simulation data

Asahi, Yuichi; Fujii, Keisuke*; Maeyama, Shinya*; Idomura, Yasuhiro

no journal, , 

We propose to use a dimensionality reduction technique, namely principal component analysis (PCA) to extract patterns from the series of 5D gyrokinetic plasma simulation data. It is shown that 83% of the variance of the original 6D (5D phase space + 1D time) data can be expressed with 64 principal components. Through the detailed analysis of the contribution of each principal component to the energy flux, we demonstrate that the avalanche like energy transport is driven by coherent mode structures in the phase space, indicating the key role of resonant particles.

Oral presentation

Developing data driven analysis methods for extreme scale numerical simulations

Asahi, Yuichi; Maeyama, Shinya*; Bigot, J.*; Garbet, X.*; Grandgirard, V.*; Fujii, Keisuke*; Shimokawabe, Takashi*; Watanabe, Tomohiko*; Idomura, Yasuhiro; Onodera, Naoyuki; et al.

no journal, , 

We have established an in-situ data analysis method for large scale fluid simulation data and developed deep learning based surrogate models to predict fluid simulation results. Firstly, we have developed an in-situ data processing approach, which loosely couples the MPI application and python scripts. It has been shown that this approach is simple and efficient which offers the speedup of 2.7 compared to post hoc data processing. Secondly, we have developed a deep learning model for predicting multiresolution steady flow fields. The deep learning model can give reasonably accurate predictions of simulation results with orders of magnitude faster compared to simulations.

Oral presentation

Targeting exa-scale systems; Performance portability and scalable data analysis

Asahi, Yuichi; Maeyama, Shinya*; Bigot, J.*; Garbet, X.*; Grandgirard, V.*; Obrejan, K.*; Padioleau, T.*; Fujii, Keisuke*; Shimokawabe, Takashi*; Watanabe, Tomohiko*; et al.

no journal, , 

We will demonstrate the performance portable implementation of a kinetic plasma code over CPUs, Nvidia and AMD GPUs. We will also discuss the performance portability of the code with C++ parallel algorithm. Deep learning based surrogate models for fluid simulations will also be demonstrated.

Oral presentation

Targeting exa-scale systems; Performance portability and scalable data analysis

Asahi, Yuichi; Maeyama, Shinya*; Bigot, J.*; Garbet, X.*; Grandgirard, V.*; Obrejan, K.*; Padioleau, T.*; Fujii, Keisuke*; Shimokawabe, Takashi*; Watanabe, Tomohiko*; et al.

no journal, , 

We will demonstrate the performance portable implementation of a kinetic plasma code over CPUs, Nvidia and AMD GPUs. We will also discuss the performance portability of the code with C++ parallel algorithm. Deep learning based surrogate models for fluid simulations will also be demonstrated.

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