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Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance. The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments: assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction. From the comparison of the friction coefficients, a fully liquefaction state was detected for the fine particle mixture. When the mixing ratio and particle size of the fine sediment were different, some other cases were considered to be in a partially liquefied transition state. These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes, but also by the flow conditions.

2013-05-24 08:30:58
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1 0 0 0 OA 本学教員寄贈著書紹介

出版者: 筑波大学図書館課
雑誌: つくばね : 筑波大学図書館報 (ISSN:13497707)
巻号頁・発行日: vol.30, no.1, 2004-12-22

2013-05-24 08:30:52
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http://hdl.handle.net/2241/119183

1 0 0 0 OA Ask Us としょかんミニガイド自動貸出装置の使い方

出版者: 筑波大学図書館課
雑誌: つくばね : 筑波大学図書館報 (ISSN:13497707)
巻号頁・発行日: vol.30, no.1, 2004-12-22

2013-05-24 08:30:47
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http://hdl.handle.net/2241/119182

1 0 0 0 OA 附属図書館特別展「オリエントの歴史と文化-古代学の形成と展開-」実施報告

出版者: 筑波大学図書館課
雑誌: つくばね : 筑波大学図書館報 (ISSN:13497707)
巻号頁・発行日: vol.30, no.1, 2004-12-22

2013-05-24 08:30:41
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http://hdl.handle.net/2241/119180

1 0 0 0 OA Xenoturbella bocki exhibits direct development with similarities to Acoelomorpha

著者: Nakano Hiroaki Lundin Kennet Bourlat Sarah J. Telford Maximilian J. Funch Peter Nyengaard Jens R. Obst Matthias Thorndyke Michael C.
出版者: Nature Publishing Group
雑誌: Nature Communications (ISSN:20411723)
巻号頁・発行日: vol.4, pp.1537, 2013-02
被引用文献数: 31 2

Xenoturbella bocki, a marine animal with a simple body plan, has recently been suggested to be sister group to the Acoelomorpha, together forming the new phylum Xenacoelomorpha. The phylogenetic position of the phylum is still under debate, either as an early branching bilaterian or as a sister group to the Ambulacraria (hemichordates and echinoderms) within the deuterostomes. Although development has been described for several species of Acoelomorpha, little is known about the life cycle of Xenoturbella. Here we report the embryonic stages of Xenoturbella, and show that it is a direct developer without a feeding larval stage. This mode of development is similar to that of the acoelomorphs, supporting the newly proposed phylum Xenacoelomorpha and suggesting that the last common ancestor of the phylum might have been a direct developer.

2013-05-24 08:30:25
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1 0 0 0 OA Note: Near-field imaging of thermal radiation at low temperatures by passive millimeter-wave microscopy

著者: Nozokido T. Ishino M. Kudo H. Bae J.
出版者: American Institute of Physics
雑誌: Review of scientific instruments (ISSN:00346748)
巻号頁・発行日: vol.84, no.3, pp.036103, 2013-03
被引用文献数: 7

Imaging of thermal radiation with a spatial resolution below the diffraction limit is demonstrated with a passive millimeter-wave microscope. This technique utilizes a sensitive radiometric receiver in combination with a scanning near-field microscope. Experiments were performed at 50 GHz (λ = 6 mm) with sample temperatures ranging from room temperature down to 160 K, and the performance was shown to be superior to that achieved with passive imaging systems in the infrared region. The images are affected by non-uniformities in the transmission of thermal radiation from the sample to the receiver via the near-field probe and the reflection of thermal radiation back to the receiver from the probe. The effects of these non-uniformities were successfully removed using a sample image acquired by active measurements using a vector network analyzer.

2013-05-24 08:30:19
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1 0 0 0 OA Direct imaging of hot spots in Bi2Sr2CaCu2O8+δ mesa terahertz sources

著者: Benseman T. M. Koshelev A. E. Kwok W.-K. Welp U. Vlasko-Vlasov V. K. Kadowaki K. Minami H. Watanabe C.
出版者: American Institute of Physics
雑誌: Journal of applied physics (ISSN:00218979)
巻号頁・発行日: vol.113, no.13, pp.133902, 2013-04
被引用文献数: 55

Stacks of intrinsic Josephson junctions (IJJs) made from high-temperature superconductors such as Bi2Sr2CaCu2O8+δ (Bi-2212) (BSCCO) are a promising source of coherent continuous-wave terahertz radiation. It is thought that at electrical bias conditions under which THz-emission occurs, hot spots may form due to resistive self-heating, and that these spots may be highly beneficial for the generation of high levels of THz power. Here, we perform an imaging study of the temperature distribution at the surface of BSCCO stacks utilizing the temperature-dependent 612 nm fluorescence line of Eu3+ in a europium chelate. The images directly reveal a highly non-uniform temperature distribution in which the temperature in the middle of the stack can exceed the superconducting transition temperature by tens of Kelvin under biasing conditions typical for THz-emission.