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131.
天津Z2线轨道交通工程地处滨海软土地区。基于《软土地区岩土工程勘察规程》中简化的分层总和法,采用一维土层非线性地震响应分析程序EERA替代Seed经验公式计算土层的动应力,同时采用修正的软土残余应变势简化计算公式,开展了天津Z2线全部98个钻孔的软土震陷计算。结果表明,地表震陷主要源自较浅土层,地表深度20 m以下的震陷可不考虑;隧道由地下线过渡到高架线的上升段震陷较大,应考虑采取防控措施;场地震陷主要由淤泥质土层产生,占地表震陷的70%~80%以上。研究对于类似工程具有一定参考价值。 相似文献
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Julia Wohlers-Z?llner Antje Biermann Anja Engel Petra D?rge Aleksandra M. Lewandowska Markus von Scheibner Ulf Riebesell 《Marine Biology》2012,159(11):2503-2518
A comparative analysis of data, obtained during four indoor-mesocosm experiments with natural spring plankton communities from the Baltic Sea, was conducted to investigate whether biogeochemical cycling is affected by an increase in water temperature of up to 6?°C above present-day conditions. In all experiments, warming stimulated in particular heterotrophic bacterial processes and had an accelerating effect on the temporal development of phytoplankton blooms. This was also mirrored in the build-up and partitioning of organic matter between particulate and dissolved phases. Thus, warming increased both the magnitude and rate of dissolved organic carbon (DOC) build-up, whereas the accumulation of particulate organic carbon (POC) and phosphorus (POP) decreased with rising temperature. In concert, the observed temperature-mediated changes in biogeochemical components suggest strong shifts in the functioning of marine pelagic food webs and the ocean’s biological carbon pump, hence providing potential feedback mechanisms to Earth’s climate system. 相似文献
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Direct and indirect fossil records of megachilid bees from the Paleogene of Central Europe (Hymenoptera: Megachilidae) 总被引:1,自引:0,他引:1
Aside from pollen and nectar, bees of the subfamily Megachilinae are closely associated with plants as a source of materials
for nest construction. Megachilines use resins, masticated leaves, trichomes and other plant materials sometimes along with
mud to construct nests in cavities or in soil. Among these, the leafcutter bees (Megachile s.l.) are the most famous for their behaviour to line their brood cells with discs cut from various plants. We report on
fossil records of one body fossil of a new non-leafcutting megachiline and of 12 leafcuttings from three European sites—Eckfeld
and Messel, both in Germany (Eocene), and Menat, France (Paleocene). The excisions include the currently earliest record of
probable Megachile activity and suggest the presence of such bees in the Paleocene European fauna. Comparison with extant leafcuttings permits
the interpretation of a minimal number of species that produced these excisions. The wide range of size for the leafcuttings
indirectly might suggest at least two species of Megachile for the fauna of Messel in addition to the other megachiline bee described here. The presence of several cuttings on most
leaves from Eckfeld implies that the preferential foraging behaviour of extant Megachile arose early in megachiline evolution. These results demonstrate that combined investigation of body and trace fossils complement
each other in understanding past biodiversity, the latter permitting the detection of taxa not otherwise directly sampled
and inferences on behavioural evolution. 相似文献
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