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167 results on '"Sasaki, Masafumi"'

5. Reliability analysis for a two-echelon repair system considering lateral resupply, return policy and transportation times

Author

Yanagi, Shigeru and Sasaki, Masafumi

Subjects
Reliability (Engineering) -- Analysis, Repairing -- Research
Abstract

This paper considers a 2-echelon repair system. This system consists of identical items, one central depot and several bases where the items are operated. When an item fails in a base, the failed item is replaced with a spare item, if available, and is sent to the depot for repair. The purpose of this paper is to build models for evaluating the effectiveness of return policy and lateral resupply on reliability improvement of the items. Key words: 2-echelon repair system, lateral resupply, return policy, transportation time

Published
1994

6. Evaluation of MEA Durability Test Protocols

Author

HASHIMASA, Yoshiyuki, MATSUDA, Yoshiyuki, IMAMURA, Daichi, AKAI, Motoaki, and SASAKI, Masafumi

Subjects
Fuel Cell, Test Protocol, PEFC / MEA, Durability
Abstract

The membrane electrode assembly (MEA) durability test protocols proposed by FCCJ, USFCC and DOE were compared in their deterioration behavior of performances and materials. These MEA durability tests for polymer electrolyte fuel cells were performed using JARI's standard single cell. In the carbon support corrosion test protocols, carbon decomposition (oxidation), collapsing of the porous structure of the carbon support, and agglomeration and dropout of the platinum (Pt) catalyst were observed. A proper fast evaluation can be done by the FCCJ protocol because of the highest applied voltage. In the Pt catalyst stability test protocols, both Pt particle growth and also carbon oxidation were observed in the Pt/C catalyst used in this study. It was found that the carbon oxidation rate was the lowest in the DOE protocol. In the membrane durability test protocols, decomposed fluorine F- and thinning of membrane were observed. Tests results suggest that the FCCJ protocol (using air, without pressure difference between anode and cathode) was the best at early stage evaluation.

Published
2011

7. Study of Circulation Control Wing aerodynamics design

Author

Sasaki, Masafumi

Subjects
2次元モデル, validation, 超臨界翼, 空力設計, lift drag ratio, 空力係数, angle of attack, 揚抗比, high-lift device, 計算流体力学, computational fluid dynamics, trailing edge flap, two dimensional model, 風洞試験, aerodynamic design, supercritical wing, 実証, 後縁フラップ, aerodynamic coefficient, 高揚力装置, 迎角, 航空機設計, wind tunnel test, aircraft design
Abstract

In this study, the aerodynamic performance of CCW (Circulation Control Wings) is investigated by two-dimensional (2D) CFD (Computational Fluid Dynamics) and the results are verified by 2D Wind-Tunnel-Test. It is found that CCW can achieve very higher lift and various lift-drag ratios at constant angle of attack (0 deg) in comparison with a conventional high-lift-device., 資料番号: AA0063897006, レポート番号: JAXA-SP-07-019

Published
2008

10. 環北極陸域システムの変動と気候への影響：観測の現状と今後の展開

Author

Park, Hontaek, Sugimoto, Atsuko, Uchida, Masaki, Matsuura, Yojiro, Ohta, Takeshi, Hiyama, Tetsuya, Ishikawa, Mamoru, Sasaki, Masafumi, Osawa, Akira, Suzuki, Rikie, Yamazaki, Takeshi, Saito, Kazuyuki, Hontaek, Park, and Ise, Takeshi

Abstract

第4回極域科学シンポジウム横断セッション：[IA] 「急変する北極気候システム及びその全球的な影響の総合的解明」―GRENE北極気候変動研究事業研究成果報告2013―11月12日（火） 国立極地研究所 ２階大会議室

Published
2013

13. Air-lake exchange of methane during the open water season in Syowa Oasis, East Antarctica

Author

SASAKI, Masafumi, ENDOH, Noboru, IMURA, Satoshi, KUDOH, Sakae, YAMANOUCHI, Takashi, MORIMOTO, Shinji, HASHIDA, Gen, SASAKI, Masafumi, ENDOH, Noboru, IMURA, Satoshi, KUDOH, Sakae, YAMANOUCHI, Takashi, MORIMOTO, Shinji, and HASHIDA, Gen

Abstract

Dissolved methane concentrations (DM) in 17 lakes were measured as a part of the operations of the 45th Japanese Antarctic Research Expedition in ice-free rocky areas along the eastern coast of Lutzow-Holm Bay (Syowa Oasis) in East Antarctica in the summer of 2003~2004. DM at the surfaces of 14 lakes ranged from the atmospheric equilibrium concentration (about 4 nmol L?1 for fresh water) to 385 nmol L?1. Relatively low DM of less than 50 nmol L?1 were observed at about 60% of the lakes. Many of the lakes (area fraction of 85%) were supersaturated and are thus sources of methane to the atmosphere. The exchange coefficient was calculated using wind speed data at Syowa Station. Area fraction frequency distributions with 4 surface DM ranges were applied to all lakes at Syowa Oasis (110 lakes: total lake area of 9 km2). Extrapolation to the whole Syowa Oasis gives an estimate of total emission of about 1 t-CH4 yr?1. This is the first estimation of methane flux from the surfaces of thawed lakes to the atmosphere in Antarctica. Since methane efflux of about 2 t-CH4 yr?1 from frozen bubbles in lake ice was estimated in our previous study, a total amount of 3 t-CH4 yr?1 would be released to the atmosphere from the lakes during the ice melting season (December ~ January) at Syowa Oasis.

Published
2010

14. Methane efflux from bubbles suspended in ice-covered lakes in Syowa Oasis, East Antarctica

Author

Sasaki, Masafumi, Imura, Satoshi, Kudoh, Sakae, Yamanouchi, Takashi, Morimoto, Shinji, Hashida, Gen, Sasaki, Masafumi, Imura, Satoshi, Kudoh, Sakae, Yamanouchi, Takashi, Morimoto, Shinji, and Hashida, Gen

Abstract

This is the first estimation of methane efflux from bubbles in lake ice in Antarctica. Bubbles suspended in shallow ice in 20 lakes were observed as part of the operations of the 45th Japanese Antarctic Research Expedition in ice-free rocky areas along the eastern coast of Lutzow-Holm Bay (Syowa Oasis) in East Antarctica in 2004. Anomalous methane concentrations in bubbles suspended in lake ice and anomalous dissolved methane concentrations in lake water were frequently found. Methane concentrations in bubbles varied of five orders of magnitude, from 1.9 ppmv to 18% v/v. A procedure that makes estimations of methane flux from ice-bubbles possible has been developed, based on a relationship between bubble-density distribution, brightness observed by digital photographs and methane concentration in bubbles. Such a procedure applied to Lake Oyako Ike in the Skarvsnes area, where the maximum methane concentration was observed, suggests that total bubble volume is about 0.6% of ice volume and the mass of methane in bubbles in the lake is about 74 kg. Almost all gases in bubbles are released to the atmosphere in the early ice melt season (a period of a few weeks in December and January). By applying area fraction frequency distributions to methane concentration ranges for 20 lakes surveyed, extrapolation to the whole Syowa Oasis, including 110 lakes, would give a provisional estimate of total emission of about 2 tons-CH4/yr.

Published
2009

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