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181.
We conducted acoustical surveys with a horizontal beam transducer to detect fish and with a vertical beam transducer to detect depth and macrophytes in two typical shallow lakes along the middle and lower reaches of the Changjiang(Yangtze) River in November 2013. Both lakes are subject to active fish management with annual stocking and removal of large fish. The purpose of the study was to compare hydroacoustic horizontal beam estimates with fish landings. The preliminary results show that the fish distribution patterns dif fered in the two lakes and were af fected by water depth and macrophyte coverage. The hydroacoustically estimated fish biomass matched the commercial catch very well in Niushan Lake, but it was two times higher in Kuilei Lake. However, acoustic estimates included all fish, whereas the catch included only fish 45 cm(smaller ones were released). We were unable to determine the proper regression between acoustic target strength and fish length for the dominant fish species in the two lakes. 相似文献
182.
The factors required for estimation of the accuracy of the confidence region construction in the problem of asteroid orbit determination are considered. Blunders and large systematic errors occurring in asteroid observations increase the sizes of confidence regions and cause their noticeable shift in the space of determined parameters. We present the factors that, in addition to analysis of discrepancies (O–C), provide an opportunity to estimate the efficiency of screening observations containing gross systematic errors. The developed factors have been tested for efficiency using simulated observations. The observations have been simulated by parameters set by us and assumed true. It is shown how the sizes of systematic errors and the number of observations with these errors influence the results of screening. All calculations have been performed within the Keplerian model of asteroid motion. 相似文献
183.
Ye. V. Zhuleva 《Oceanology》2010,50(1):107-112
The volumes of formed volcanoes are an important indicator of the formation intensity of the ocean floor volcanogenic morphostructure
under different geodynamic conditions. The distribution of the volumes of volcanoes that formed within the oceanic lithosphere
of different geological ages is considered to analyze the spatial and time dynamics of the scopes of the seamount formation.
The greatest volumes of effused rocks concentrate in volcanoes of different heights on the different-age segments of the lithosphere.
The total volumes of volcanogenic substance growing with increasing age and thickness of the lithosphere is caused by the
increasing range of the heights of the formed volcanoes and the growing number of big seamounts. Despite that the volcanic
seamounts formed within the mid-oceanic ridges, on the divergent boundaries of the lithospheric plates and in the transform
faults most often, half of the volcanogenic material was emitted to the earth’s surface during the spreading of the intraplate
volcanism. A leading part in the formation of the volcanogenic morphostructure of the ocean floor belongs to the formation
of big seamounts with heights of 4–6 km and volumes from 1500 to 5100 km3, respectively, in the provinces with ages from 60 to 90 mln years. 相似文献
184.
将两光子晶体单模波导平行、邻近放置构成一个光子晶体波导耦合结构.根据耦合和解耦合理论,设计了一种新型的高效异质结构四波长波分复用器.应用时域有限差分法模拟了该器件的效率,并通过改变一排介质柱的折射率,实现了较高的透射率.进一步发现在入射口处添加三对介质柱,可以有效地降低系统的反射,实现了四个波长的高效传输,四个波长的透射率均超过了90%.该器件不仅具有较高的透射率,而且其尺寸仅为36 μm×17 μm,在未来的光子集成回路中具有潜在的应用价值. 相似文献
185.
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187.
全国重要矿产总量预测方法 总被引:11,自引:0,他引:11
全国重要矿产资源评价涉及25种重要矿产的近百种矿床类型,需要在1∶20万尺度水平圈定成矿预测远景区,并科学估算各远景区资源量,为国家矿产资源战略勘查和战略部署提供技术支撑。为了保证预测成果在同一层面上进行全国汇总,制定了全国一致的、标准的技术要求和方法。通过对中国以往一轮、二轮区划预测方法、全国矿产资源总量预测方法及国外最新预测方法的分析和总结,结合近年来预测理论的新发展,确定了全国重要矿产总量预测的理论基础是成矿系列理论、现代成矿动力学理论和综合信息矿产预测理论,采用的预测思路是矿床模型综合地质信息预测方法。文章陈述了总量预测的方法流程和预测技术要求,有关方法思路可供资源评价人员参考。 相似文献
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189.
“人类世”以来,南海海域因周边或域外大国等地缘行为体的介入,使地缘环境变得错综复杂,中国海洋权益不断遭受限制、挤压和挑战。文章从自然和社会基因子系统的地理环境、地缘关系和地缘结构出发,以地名为逻辑起点划分古代-遗传形地名DNA、近代-变异形地名DNA和现代-复合形地名DNA三种类型,构建南海诸岛海域地名国别地缘环境分析框架。结果表明:1)南海诸岛海域地名是在自然基因子系统和社会基因子系统交互耦合作用下形成的。2)因果关联作用下,南海诸岛海域地名遵从“主人―他人―主人”的历史演变规律,导致地名基因在转录和表达上呈现遗传、变异和复合的过程;建构作用下,周边或域外大国以非法手段构建多边争夺南海海洋资源和海洋权益的新型地缘关系。3)南海诸岛海域地名基因在转录与表达上是空间与物质显性基因和理念与历史演变隐性基因的交互耦合过程。 相似文献
190.
SHI Jinghua LIU Fei CHEN Honghan LI Ye 《《地质学报》英文版》2007,81(5):827-832
Tetrachloroethene (PCE) is biodegraded by reductive dechlorination with co-metabolism substrates under anaerobic conditions. By inoculating sludge from an anaerobic pool, a biodegradation test of PCE is conducted in the anaerobic condition. In the test, several substrates including methanol, ethanol, formate, acetate, lactate and glucose, are conducive to the conversion from PCE to TCE and 1,1-DCE. The results show the microbe can be cultivated well under the anaerobic circumstances of mixture of sewage (sludge) and soil with the index of COD after eleven days. Degradation of PCE accords with one order reaction kinetics equation. The sequence of the reaction rate constant is Kacetate 〉Kglucose 〉 Klactate 〉 Kethanol 〉 Kformate 〉 Kmethanol, and acetate is an outstanding co-metabolism substratum whose reaction rate constant is 0.6632d^-1. 相似文献