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293 results on '"Tachibana, Takeshi"'

1. Negativity and its capacity in JT gravity

Author

Okuyama, Kazumi and Tachibana, Takeshi

Subjects
High Energy Physics - Theory
Abstract

We study the refined R\'{e}nyi negativity in the matrix model of Jackiw-Teitelboim (JT) gravity. We first consider the JT gravity with dynamical branes, which serves as a toy model of the evaporating black hole. By including the backreaction of branes, we find that the refined R\'{e}nyi negativity monotonically decreases at late time of the evaporation. Next we define a novel quantity, which we call ``capacity of negativity,'' as a derivative of the refined R\'{e}nyi negativity with respect to the replica number. We find that the capacity of negativity has two peaks as a function of time, which comes from the exchange of dominance of the different types of replica wormholes., Comment: 23 pages

Published
2023

14. Preparation of ammonium nitrate/ammonium perchlorate-based solid propellant for combustion control by N2O supply

Author

Nakasako, Tomoyasu, Higashi, Eiko, Matsunaga, Hiroki, Tachibana, Takeshi, and Kato, Katsumi

Subjects
Incombustible AN/AP-based propellant, control of combustion, N2O supply
Abstract

N2O供給により燃焼をON/OFF制御できる非自律燃焼性(非自燃性)固体推進薬の調製を試み，その燃焼性を調査した．本研究では，スプレードライにより防湿処理を施した硝酸アンモニウム(AN)と過塩素酸アンモニウム(AP)を酸化剤とし，末端水酸基ポリブタジエン(HTPB)をバインダとした固体推進薬を調製した．HTPBを23.5 wt%とし，酸化剤中のAN/AP比を40/60，50/50，60/40 とした推進薬についてN2雰囲気0.3-6.0 MPa で燃焼試験を行ったところ，AN/AP=40/60 はすべての圧力範囲で燃焼が完結したが，50/50 および60/40 では0.5-0.7 MPa 以下で着火しなかった．これら2 種類の推進薬は，N2O供給下，0.3 MPa での燃焼試験では燃焼が持続し，N2O供給を止めると燃焼が停止したため，本実験で調製したAN/AP 系推進薬はN2O供給により燃焼をON/OFF制御できる可能性が示唆された．, In this study, in an attempt to prepare propellants capable of on/off control of combustion by oxidizing gas supply, we prepared incombustible propellants in a N2 atmosphere composed of moisture-proof ammonium nitrate (AN) prepared by spray drying and ammonium perchlorate (AP) as oxidizers and hydroxyl-terminated polybutadiene (HTPB) as a fuel, and investigated their combustibility by N2O supply. The burning tests performed under a N2 atmosphere for the propellants having different AN/AP mass ratios (AN/AP = 40/60, 50/50, and 60/40) with 23.5 wt% HTPB revealed that the AN/AP=50/50 and 60/40 samples did not ignite under pressures less than 0.5-0.7 MPa, whereas the AN/AP=40/60 sample burned under the entire tested pressure range (0.3-6.0 MPa). Moreover, it was confirmed that the AN/AP=50/50 and 60/40 samples stably burned under N2O supply at 0.3 MPa. However, when the N2O supply was stopped, their combustion was interrupted with a little time delay, suggesting that combustion of the prepared propellants can be controlled by regulating the N2O supply., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1830031008, レポート番号: JAXA-RR-18-006

Published
2019

26. X-ray diffraction pole figure measurements of diamond films grown on platinum (111)

Author

Tachibana, Takeshi, Yokota, Yoshihiro, Kobashi, Koji, and Shintani, Yoshihiro

Subjects
Diamond films -- Research, Scanning electron microscopes -- Usage, X-rays -- Diffraction, Physics
Abstract

Scanning electron microscopy and x-ray diffraction pole figure measurements are used to examine diamond films grown on bulk single crystal platinum substrates. Experiment results reveal that the increase in film thickness results to a corresponding increase in x-ray diffraction measurements and the coalescence between neighboring diamond surfaces. However, film thickness does not affect azimuthal alignment.

Published
1997

28. R&D of diamond films in the Frontier Carbon Technology Project and related topics

Author

Kobashi, Koji, Nishibayashi, Yoshiki, Yokota, Yoshihiro, Ando, Yutaka, Tachibana, Takeshi, Kawakami, Nobuyuki, Hayashi, Kazushi, Inoue, Kenichi, Meguro, Kiichi, Imai, Hiroshi, Furuta, Hiroshi, Hirao, Takashi, Oura, Kenjiro, Gotoh, Yasuhito, Nakahara, Hironori, Tsuji, Hiroshi, Ishikawa, Junzo, Koeck, Franz A., Nemanich, Robert J., Sakai, Tadashi, Sakuma, Naoshi, and Yoshida, Hiroaki

Published
2003
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42. Crystal and magnetic structures and their temperature dependence of Co2Z-type hexaferrite (Ba,Sr)3Co2Fe24O41 by high-temperature neutron diffraction.

Author

Takada, Yukio, Nakagawa, Takashi, Tokunaga, Masatoshi, Fukuta, Yasunari, Tanaka, Takayoshi, Yamamoto, Takao A., Tachibana, Takeshi, Kawano, Shinji, Ishii, Yoshinobu, and Igawa, Naoki

Subjects
FERRITES, COBALT, ELECTROMAGNETIC noise, NEUTRON diffraction, RIETVELD refinement
Abstract

We have prepared nonoriented and magnetically oriented specimens of Co2Z-type Ba ferrite Ba3Co2Fe24O41 (Ba3Z) and those with Sr2+ substitution for Ba2+, i.e., Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5Z) and Sr3Co2Fe24O41 (Sr3Z) with the conventional solid-state reaction method. Permeability measurements of nonoriented specimens have shown that this substitution improves the frequency characteristic of permeability, though the permeability in Sr3Z significantly decreases. X-ray diffraction (XRD) and magnetization measurements of magnetically oriented specimens have shown that the magnetic moments of iron and cobalt ions in Ba3Z and Ba1.5Sr1.5Z lie in the c plane, but that those in Sr3Z deviate from the c plane. We have studied the substitution effect of Sr2+ for Ba2+ on the crystal structures and the effective sizes and directions of magnetic moments and their temperature dependences with high-temperature neutron diffraction technique. This substitution induces the change in the distribution of cobalt ions and moment directions of magnetic ions. Magnetic moments in Ba3Z and Ba1.5Sr1.5Z turn to the c axis when temperature rises from 523 to 573 K. However, the moments in Sr3Z turn to the c axis at the lower temperature of 50 K. These results were consistent with the present measurements on permeability, XRD, and magnetization. The change in moment direction caused by temperature rise must be attributed to the disappearance of effective moments of cobalt ions in these temperature regions. [ABSTRACT FROM AUTHOR]

Published
2006
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44. 燃料過多推進薬への酸化剤供給による燃焼制御特性

Author

Kakami, Akira and Tachibana, Takeshi

Abstract

平成27年度宇宙輸送シンポジウム（2016年1月14日-15日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県, Space Transportation Symposium FY2015 (January 14-15, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000050030, レポート番号: STCP-2015-031

Published
2016

45. Crystal and magnetic structures and their temperature dependence of [Co.sub.2]Z-type hexaferrite [(Ba, Sr).sub.3][Co.sub.2][Fe.sub.24][O.sub.41] by high-temperature neutron diffraction

Author

Takada, Yukio, Nakagawa, Takashi, Tokunaga, Masatoshi, Fukuta, Yasunari, Tanaka, Takayoshi, Yamamoto, Takao A., Tachibana, Takeshi, Kawano, Shinji, Ishii, Yoshinobu, and Igawa, Naoki

Subjects
Cobalt -- Magnetic properties, Cobalt -- Thermal properties, Cobalt -- Structure, Barium -- Magnetic properties, Barium -- Thermal properties, Barium -- Structure, Iron -- Magnetic properties, Iron -- Thermal properties, Iron -- Structure, Physics
Abstract

The nonoriented and magnetically oriented specimens of [Co.sub.2]Z-type Ba ferrite [Ba.sub.3][Co.sub.2][Fe.sub.24][O.sub.41] ([Ba.sub.3]Z) and those with [Sr.sup.2+] substitution for [Ba.sup.2+] are prepared with the conventional solid-state reaction method. The change in the moment direction caused by temperature rise is attributed to the disappearance of effective moments of cobalt ions in the temperature regions of 523 to 573 K.

Published
2006

46. Development of injector for liquid PPT using DME as a propellant

Author

Fukunaga, Masato, Kakami, Akira, and Tachibana, Takeshi

Abstract

平成20年度宇宙輸送シンポジウム(2009年1月19日-20日, 宇宙航空研究開発機構宇宙科学研究本部), 形態: カラー図版あり, 資料番号: AA0064292100

Published
2009

47. 固体点火薬を推進剤に用いた同軸型PPT

Author

Okabe, Shuhei, Kakami, Akira, Nakano, Masakatsu, and Tachibana, Takeshi

Abstract

平成19年度宇宙輸送シンポジウム（2008年1月28日-29日. 宇宙航空研究開発機構宇宙科学研究本部）, 相模原市, 神奈川県, Space Transportation Symposium FY2007 (January 28-29, 2008. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000004118

Published
2008

48. 固体推進薬のレーザによる支援燃焼

Author

Takai, Tsutomu, Kakami, Akira, and Tachibana, Takeshi

Abstract

平成19年度宇宙輸送シンポジウム（2008年1月28日-29日. 宇宙航空研究開発機構宇宙科学研究本部）, 相模原市, 神奈川県, Space Transportation Symposium FY2007 (January 28-29, 2008. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000004039

Published
2008

49. レーザを用いた固体推進薬の燃焼制御

Author

Hiyamizu, Ryoma, Takai, Tsutomu, Kakami, Akira, and Tachibana, Takeshi

Abstract

平成18年度宇宙輸送シンポジウム（2007年1月18日-19日. 宇宙航空研究開発機構宇宙科学研究本部）, 相模原市, 神奈川県, Space Transportation Symposium FY2006 (January 18-19, 2007. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000005002

Published
2007

50. アーク放電と亜酸化窒素による非自燃性固体推進薬の燃焼制御

Author

Shimoda, Masayuki, Kakami, Akira, and Tachibana, Takeshi

Abstract

平成26年度宇宙輸送シンポジウム（2015年1月15日-16日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県, Space Transportation Symposium FY2014 (January 15-16, 2015. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000036034, レポート番号: STCP-2014-034

Published
2015

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