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Miaodao Islands, lying across the Bohai Gulf between Jiaodong Peninsula and Liaodong Peninsula.are also called Changshan Islands. They consist of eighteen big and small islands, aligned in NNEdirection. The largest of them is the South Changshan Island, which lies at the southernmost end. Thedistance between South Changshan Island and Penglai County is 7 km, and Miaodao Islands have anarea of 12.75 km~2. Because of the fall of the sea level, Miaodao Islands formed a land bridge linkingJiaodong Peninsula and Liaodong Peninsula during the Quaternary period, thus playing an importantrole in the development of mankind and exchange of culture (Fig. 1). Miaodao Islands have been in a structural uplift for a long time, and their outlines are controlledby structural lines in NE, NNE, NW and EW directions. Most of the islands are composed of quartzite of Sinian Age. The coast of each island is bordered with cliffs. The quartzite gravels, fine in textureand multicoloured, on the beach are well rounded. The height 相似文献
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In this paper, the morphology, sedimentary structure, bioherm--building mollusk assem-blages and their growing and piling-up models of modern oyster bioherms in the estuariesof the Zimaigou and Xiaoqing Rivers are described and expounded, the environmentalconditions for the development of oyster bioherms, such as the dynamical geomorphicbackground, water depth, hydrodynamic factors and ecological conditions in the estuaries,are analyzed, the relationship of the successively seaward migrating of oyster biohermswith average annual sea-level changes and the erosion--accretion processes in the estuariesare probed and explained, and the geological significance of oyster bioherms in the studyof Quaternary marine environmental evolution is presented. 相似文献
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We experimentally report on the evolution from singly-dressed to doubly-dressed four-wave mixing (FWM) process by controlling the powers of the probe, the pump and the dressing fields respectively. The differences in the enhancement and the suppression of FWM signal between the two-level and cascade three-level atomic systems are observed and explained by the multi-dressed effect theoretically. Both the x direction and the y direction spatial splittings of the degenerate-FWM (DWFM) beams are obtained. We also investigate the switch between the enhancement and the suppression of the DWFM signals and between its spatial splittings in x direction and y direction. The spatial splittings in x direction and y direction can be controlled by the relative position and the intensity of the involved laser beams. Such a study can be useful for optimizing the efficiency of the FWM process and providing potential applications in spatial signal processing. 相似文献
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