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61.
Stress wave attenuation across fractured rock masses is a great concern of underground structure safety. When the wave amplitude is large, fractures experience nonlinear deformation during the wave propagation. This paper presents a study on normal transmission of P‐wave across parallel fractures with nonlinear deformational behaviour (static Barton–Bandis model). The results show that the magnitude of transmission coefficient is a function of incident wave amplitude, nondimensional fracture spacing and number of fractures. Two important indices of nondimensional fracture spacing are identified, and they divide the area of nondimensional fracture spacing into three parts (individual fracture area, transition area and small spacing area). In the different areas, the magnitude of transmission coefficient has different trends with nondimensional fracture spacing and number of fractures. In addition, the study reveals that under some circumstances, the magnitude of transmission coefficient increases with increasing number of fractures, and is larger than 1. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
62.
Zhan-Le Du Hua-Ning Wang Xiang-Tao He National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2006,6(4):489-494
The maximum amplitudes of solar activity cycles are found to be well anti-correlated (r = -0.72) with the newly defined solar cycle lengths three cycles before (at lag -3) in 13-month running mean sunspot numbers during the past 190 years. This result could be used for predicting the maximum sunspot numbers. The amplitudes of Cycles 24 and 25 are estimated to be 149.5±27.6 and 144.3±27.6, respectively. 相似文献
63.
Nikos Prantzos 《Astrophysics and Space Science》2003,284(2):675-684
We develop a detailed model of the Milky Way (a `prototypical' disk galaxy) and extend it to other disks with the help of
some simple scaling relations, obtained in the framework of Cold Dark Matter models. This phenomenological (`hybrid') approach
to the study of disk galaxy evolution allows us to reproduce successfully a large number of observed properties of disk galaxies
in the local Universe and up to redshift z ∼ 1. The important conclusion is that, on average, massive disks have formed the bulk of their stars earlier than their lower
mass counterparts: the `star formation hierarchy' has been apparently opposite to the `dark matter assembly' hierarchy. It
is not yet clear whether `feedback' (as used in semi-analytical models of galaxy evolution) can explain that discrepancy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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