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Y. Fukada S. Hayakawa M. Ikeda I. Kasahara F. Makino Y. Tanaka 《Astrophysics and Space Science》1975,32(1):L1-L5
The energy spectrum of diffuse hard X-rays measured in the range 10–40 keV shows a rather sharp change of slope. The logarithmic derivative of the spectrum changes around 20–30 keV by the increment significantly greater than 0.5 within an interval smaller than 50 keV. 相似文献
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The imperative need to protect structures in mountainous areas against rockfall has led to the development of various protection methods. This study introduces a new type of rockfall protection fence made of posts, wire ropes, wire netting and energy absorbers. The performance of this rock fence was verified in both experiments and dynamic finite element analysis. In collision tests, a reinforced-concrete block rolled down a natural slope and struck the rock fence at the end of the slope. A specialized system of measuring instruments was employed to accurately measure the acceleration of the block without cable connection. In particular, the performance of two energy absorbers, which contribute also to preventing wire ropes from breaking, was investigated to determine the best energy absorber. In numerical simulation, a commercial finite element code having explicit dynamic capabilities was employed to create models of the two full-scale tests. To facilitate simulation, certain simplifying assumptions for mechanical data of each individual component of the rock fence and geometrical data of the model were adopted. Good agreement between numerical simulation and experimental data validated the numerical simulation. Furthermore, the results of numerical simulation helped highlight limitations of the testing method. The results of numerical simulation thus provide a deeper understanding of the structural behavior of individual components of the rock fence during rockfall impact. More importantly, numerical simulations can be used not only as supplements to or substitutes for full-scale tests but also in parametric study and design. 相似文献
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Y. Fukada S. Hayakawa I. Kasahara F. Makino I. Suzuki Y. Tanaka B. V. Sreekantan 《Solar physics》1975,42(2):441-444
A hard solar X-ray burst in the energy range 90–400 keV was observed at about 0528:30 UT on 13 April 1974. This event is peculiar in the sense that the X-ray flux is considerably high whereas the corresponding radio and optical flares are of moderate sizes, that the duration of the X-ray burst is very short, and that the X-ray peak is delayed by about 2.5 min relative to the first radio peak. 相似文献
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Y. Fukada S. Hayakawa I. Kasahara F. Makino Y. Tanaka H. Akiyama M. Matsuoka J. Nishimura M. Oda M. Nakagawa H. Sakurai V. S. Iyenger P. K. Kunte R. K. Manchanda B. V. Sreekantan 《Astrophysics and Space Science》1976,42(1):245-248
The size of the hard X-ray source in the Crab Nebula was observed with scintillation counters on board two balloons at a lunar occulatation on 24 January, 1975. The Gaussian width of the source is 34 (+17, –14) and the center thereof is offset from the pulsar by 6±4 at position angle 102°. The observed time profile can also be fitted to an alternative model of two line sources whose intensities are 48% at 11 and 25.5% at 7 on both sides of the pulsar.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
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