With the discovery of the double neutron star (DNS) merger event GW170817 by LIGO, DNS systems have become one of the important candidates for gravitational wave (GW) observation. There are 19 DNS systems that have been discovered, and PSR J1906+0746 is the youngest DNS system with the age of about 0.1 Myrs. We simulate its orbital decay over its entire life by the GW radiation from the initial stage to the coalescence. For the DNS PSR J1906+0746, we obtain its initial orbital period of 3.99 hrs (3.98 hrs at present) with the nearly circular orbit, and the merger age of 3.18 × 108 yr. At the last minute of coalescence, corresponding to the orbital radius change from 335 to 30 km, we present the GW frequency to be 30 and 1122 Hz, respectively. As a comparison, with the GW frequency from 45 to 450 Hz, the orbital radii of the source GW170817 correspond to 163 and 57 km, respectively.
Recent laboratory and field experiments have confirmed that sand does indeed exhibit time-dependent behaviour. Based on these
findings, it was considered necessary to revisit some of the published experimental results on the static liquefaction phenomenon
of loose anisotropic Hostun RF sand. Time-dependency might have had a significant influence on the observed undrained response
of anisotropic consolidated sand specimens. Specific triaxial tests have been performed and a qualitative analysis is presented
in this paper. It is shown that, despite the differences on the anisotropic consolidation path employed, different specimens
show qualitatively identical undrained responses if creep periods are performed at identical test stages or if the anisotropic
consolidation takes place very slowly. With time, the undrained stiffness and strength are considerably improved and this
may explain why the static liquefaction phenomenon is not as common in practice as could be predicted based on an instability
line concept. Whereas the original instability line concept was developed independently of time-dependency, in field situations,
the liquefaction resistance of the sand can increase with time. 相似文献
Active faults that rupture the earth's surface leave an imprint on the topography that is recognized using a combination of geomorphic and geologic metrics including triangular facets, the shape of mountain fronts, the drainage network, and incised river valleys with inset terraces. We document the presence of a network of active, high-angle extensional faults, collectively embedded in the actively shortening mountain front of the Northern Apennines, that possess unique geomorphic expressions. We measure the strain rate for these structures and find that they have a constant throw-to-length ratio. We demonstrate the necessary and sufficient conditions for triangular facet development in the footwalls of these faults and argue that rock-type exerts the strongest control. The slip rates of these faults range from 0.1 to 0.3 mm/yr, which is similar to the average rate of river incision and mountain front unroofing determined by corollary studies. The faults are a near-surface manifestation of deeper crustal processes that are actively uplifting rocks and growing topography at a rate commensurate with surface processes that are eroding the mountain front to base level. 相似文献