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Institution

Chiba Institute of Technology

EducationNarashino, Japan
About: Chiba Institute of Technology is a education organization based out in Narashino, Japan. It is known for research contribution in the topics: RNA & Coercivity. The organization has 2663 authors who have published 4999 publications receiving 56870 citations. The organization is also known as: Chiba kōgyō daigaku & Kōa Institute of Technology.
Topics: RNA, Coercivity, Magnet, Mobile robot, Robot


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Journal ArticleDOI
05 Mar 2010-Science
TL;DR: Records of the global stratigraphy across this boundary are synthesized to assess the proposed causes of the Cretaceous-Paleogene boundary and conclude that the Chicxulub impact triggered the mass extinction.
Abstract: The Cretaceous-Paleogene boundary similar to 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.

1,135 citations

Journal ArticleDOI
TL;DR: The requirements for the exploration mission in the Fukushima Daiichi Nuclear Power Plants are presented, the implementation is discussed, and the results of the mission are reported.
Abstract: On March 11, 2011, a massive earthquake (magnitude 9.0) and accompanying tsunami hit the Tohoku region of eastern Japan. Since then, the Fukushima Daiichi Nuclear Power Plants have been facing a crisis due to the loss of all power that resulted from the meltdown accidents. Three buildings housing nuclear reactors were seriously damaged from hydrogen explosions, and, in one building, the nuclear reactions became out of control. It was too dangerous for humans to enter the buildings to inspect the damage because radioactive materials were also being released. In response to this crisis, it was decided that mobile rescue robots would be used to carry out surveillance missions. The mobile rescue robots needed could not be delivered to the Tokyo Electric Power Company (TEPCO) until various technical issues were resolved. Those issues involved hardware reliability, communication functions, and the ability of the robots' electronic components to withstand radiation. Additional sensors and functionality that would enable the robots to respond effectively to the crisis were also needed. Available robots were therefore retrofitted for the disaster reponse missions. First, the radiation tolerance of the electronic componenets was checked by means of gamma ray irradiation tests, which were conducted using the facilities of the Japan Atomic Energy Agency (JAEA). The commercial electronic devices used in the original robot systems operated long enough (more than 100 h at a 10% safety margin) in the assumed environment (100 mGy/h). Next, the usability of wireless communication in the target environment was assessed. Such tests were not possible in the target environment itself, so they were performed at the Hamaoka Daiichi Nuclear Power Plants, which are similar to the target environment. As previously predicted, the test results indicated that robust wireless communication would not be possible in the reactor buildings. It was therefore determined that a wired communication device would need to be installed. After TEPCO's official urgent mission proposal was received, the team mounted additional devices to facilitate the installation of a water gauge in the basement of the reactor buildings to determine flooding levels. While these preparations were taking place, prospective robot operators from TEPCO trained in a laboratory environment. Finally, one of the robots was delivered to the Fukushima Daiichi Nuclear Power Plants on June 20, 2011, where it performed a number of important missions inside the buildings. In this paper, the requirements for the exploration mission in the Fukushima Daiichi Nuclear Power Plants are presented, the implementation is discussed, and the results of the mission are reported. © 2013 Wiley Periodicals, Inc. (Webpage: http://www.astro.mech.tohoku.ac.jp/)

513 citations

Journal ArticleDOI
Sei-ichiro Watanabe1, Sei-ichiro Watanabe2, Masatoshi Hirabayashi3, Naru Hirata4, Na. Hirata5, Rina Noguchi2, Yuri Shimaki2, H. Ikeda, Eri Tatsumi6, Makoto Yoshikawa7, Makoto Yoshikawa2, Shota Kikuchi2, Hikaru Yabuta8, Tomoki Nakamura9, Shogo Tachibana2, Shogo Tachibana6, Yoshiaki Ishihara2, Tomokatsu Morota1, Kohei Kitazato4, Naoya Sakatani2, Koji Matsumoto7, Koji Wada10, Hiroki Senshu10, C. Honda4, Tatsuhiro Michikami11, Hiroshi Takeuchi2, Hiroshi Takeuchi7, Toru Kouyama12, R. Honda13, Shingo Kameda14, Tetsuharu Fuse15, Hideaki Miyamoto6, Goro Komatsu10, S. Sugita6, Tatsuaki Okada6, Tatsuaki Okada2, Noriyuki Namiki7, Masahiko Arakawa5, Masateru Ishiguro16, Masanao Abe7, Masanao Abe2, Robert Gaskell17, Eric Palmer17, Olivier S. Barnouin18, Patrick Michel19, A. S. French20, Jay W. McMahon20, Daniel J. Scheeres20, Paul A. Abell, Yukio Yamamoto7, Yukio Yamamoto2, Satoshi Tanaka2, Satoshi Tanaka7, Kei Shirai2, Moe Matsuoka2, Manabu Yamada10, Y. Yokota2, Y. Yokota13, H. Suzuki21, Kosuke Yoshioka6, Yuichiro Cho6, Naoki Nishikawa5, T. Sugiyama4, Hideaki Kikuchi6, Ryodo Hemmi6, Tomohiro Yamaguchi2, Naoko Ogawa2, Go Ono, Yuya Mimasu2, Kent Yoshikawa, T. Takahashi2, Yuto Takei2, Atsushi Fujii2, Chikako Hirose, Takahiro Iwata2, Takahiro Iwata7, Masahiro Hayakawa2, Satoshi Hosoda2, Osamu Mori2, Hirotaka Sawada2, Takanobu Shimada2, Stefania Soldini2, Hajime Yano2, Hajime Yano7, Ryudo Tsukizaki2, M. Ozaki7, M. Ozaki2, Yuichi Iijima2, K. Ogawa5, Masaki Fujimoto2, T. M. Ho22, Aurelie Moussi23, Ralf Jaumann, J. P. Bibring, Christian Krause, Fuyuto Terui2, Takanao Saiki2, Satoru Nakazawa2, Yoshiyuki Tsuda7, Yoshiyuki Tsuda2 
19 Mar 2019-Science
TL;DR: The Hayabusa2 spacecraft measured the mass, size, shape, density, and spin rate of asteroid Ryugu, showing that it is a porous rubble pile, and observations of Ryugu's shape, mass, and geomorphology suggest that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation.
Abstract: The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu’s shape, mass, and geomorphology. Ryugu has an oblate “spinning top” shape, with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 grams per cubic centimeter, indicates a high-porosity (>50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu’s shape may have been produced from having once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identified a suitable sample collection site on the equatorial ridge.

402 citations

Journal ArticleDOI
TL;DR: In this article, a porosity model based on N-body simulations of aggregate collisions is applied to study the porosity change upon collision for a wide range of impact energies. But the authors neglect collisional fragmentation and instead focus on dust evolution outside the snow line, where the fragmentation has been suggested to be less significant than inside the snowline because of the high sticking efficiency of icy particles.
Abstract: Rapid orbital drift of macroscopic dust particles is one of the major obstacles to planetesimal formation in protoplanetary disks. We re-examine this problem by considering the porosity evolution of dust aggregates. We apply a porosity model based on recent N-body simulations of aggregate collisions, which allows us to study the porosity change upon collision for a wide range of impact energies. As a first step, we neglect collisional fragmentation and instead focus on dust evolution outside the snow line, where the fragmentation has been suggested to be less significant than inside the snow line because of the high sticking efficiency of icy particles. We show that dust particles can evolve into highly porous aggregates (with internal densities of much less than 0.1 g cm–3) even if collisional compression is taken into account. We also show that the high porosity triggers significant acceleration in collisional growth. This acceleration is a natural consequence of the particles' aerodynamical properties at low Knudsen numbers, i.e., at particle radii larger than the mean free path of the gas molecules. Thanks to this rapid growth, the highly porous aggregates are found to overcome the radial drift barrier at orbital radii less than 10 AU (assuming the minimum-mass solar nebula model). This suggests that, if collisional fragmentation is truly insignificant, formation of icy planetesimals is possible via direct collisional growth of submicron-sized icy particles.

397 citations

Journal ArticleDOI
TL;DR: In this article, the authors carried out more than 4000 runs of three-dimensional numerical simulations of collisions between icy equal-mass clusters formed under ballistic particle-cluster aggregation (BPCA), including offset collisions with various values of the impact parameter.
Abstract: Collisions between dust aggregates are the key to understand the formation of planetesimals because the collision inevitably takes place in protoplanetary disks. To clarify whether or not dust aggregates can grow through their mutual collisions at relatively high velocities, we carry out more than 4000 runs of three-dimensional numerical simulations of collisions between icy equal-mass clusters formed under ballistic particle-cluster aggregation (BPCA) as well as those of ballistic cluster-cluster aggregation, including offset collisions with various values of the impact parameter. Since our BPCA clusters have a fractal dimension of 3 and a relatively compact structure, their results enable us to determine the criteria for growth and disruption of compressed aggregates at their collisions in protoplanetary disks. The results show that ice dust aggregates are able to grow at collisions with velocities up to 50 m s–1, in spite of their initial structures and impact parameters. We also find that the mass of ejecta relative to the total mass of colliding aggregates decreases with increasing the size of the aggregates. These results demonstrate the feasibility of growth and survival for dust aggregates through their mutual collisions with relatively high velocities in protoplanetary disks.

370 citations


Authors

Showing all 2681 results

NameH-indexPapersCitations
Shigeyuki Yokoyama107111349711
Hiroyuki Shimada8888130180
Naoki Yamamoto7449222987
Kazuhito Tsukagoshi6240913609
Kunitada Shimotohno5516112006
Sahin Kaya Ozdemir5426715042
Hiroshi Kimura5430811407
Takahiro Hiroi472567107
Ryuji Tada451956524
Takashi Kumasaka4216612036
Ichiro Hirao412445811
Harald Krüger391624830
Goro Komatsu382155089
Kin-ichiro Miura382207730
Keiji Nagatani372205274
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202311
202225
2021243
2020281
2019296
2018295