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71.
通过对大直径硬岩钻进中常用钻进方法优缺点的分析,结合对聚能爆破原理和影响因素的探讨,提出在大直径硬岩钻进中采用聚能爆破和普通钻进方法相结合的复合钻进工艺,指出了聚能爆破在大直径硬岩钻进中具有广阔的应用前景 相似文献
72.
This paper systematically studies the statistical diagnosis and hypothesis testing for the semiparametric linear regression model according to the theories and methods of the statistical diagnosis and hypothesis testing for parametric regression model. Several diagnostic measures and the methods for gross error testing are derived. Especially, the global and local influence analysis of the gross error on the parameter X and the nonparameter s are discussed in detail; at the same time, the paper proves that the data point deletion model is equivalent to the mean shift model for the semiparametric regression model. Finally, with one simulative computing example, some helpful conclusions are drawn. 相似文献
73.
本文简述了沙柳河南区有色金属矿床的基本特征。通过对成矿热液及成矿物质的来源与性质的研究,认为该矿床的成因类型为火山沉积—接触交代改造叠加型,进而探讨了该矿床的成矿模式。 相似文献
74.
Ectomycorrhizal fungi,a group of widcspread symbiotic fungi with plant,obtain carbon source from trees and improve plant mineral nutrient uptake with their widespread hyphal network.Ectomycorrhizal fun... 相似文献
75.
Based on the sequence data of the nuclear ribosomal DNA internal transcribed spacer (ITS) 1, 5.8 S, and ITS 2, the molecular
phylogeny was analyzed on Ulvaceae species collected from Qingdao coasts in summer of 2007, including 15 attached Ulva and Enteromorpha samples from 10 locations and 10 free-floating Enteromorpha samples from seven locations. The result supported the monophyly of all free-floating Enteromorpha samples, implying the unialgal composition of the free-floating Enteromorpha, and the attached Ulvaceae species from Qingdao coasts were grouped into other five clades, suggesting that they were not
the biogeographic origin of the free-floating Enteromorpha in that season.
Supported by NSFC (40506030); the Innovative Key Project of the Chinese Academy of Sciences (KZCX2-YW-209); Science & Technology
Project of Qingdao City (06-2-2-12-JCH) 相似文献
76.
Filamentous Bangia, which are distributed extensively throughout the world, have simple and similar morphological characteristics. Scientists can classify these organisms using molecular markers in combination with morphology. We successfully sequenced the complete nuclear ribosomal DNA, approximately 13 kb in length, from a marine Bangia population. We further analyzed the small subunit ribosomal DNA gene (nrSSU) and the internal transcribed spacer (ITS) sequence regions along with nine other marine, and two freshwater Bangia samples from China. Pairwise distances of the nrSSU and 5.8S ribosomal DNA gene sequences show the marine samples grouping together with low divergences (00.003; 0–0.006, respectively) from each other, but high divergences (0.123–0.126; 0.198, respectively) from freshwater samples. An exception is the marine sample collected from Weihai, which shows high divergence from both other marine samples (0.063–0.065; 0.129, respectively) and the freshwater samples (0.097; 0.120, respectively). A maximum likelihood phylogenetic tree based on a combined SSU-ITS dataset with maximum likelihood method shows the samples divided into three clades, with the two marine sample clades containing Bangia spp. from North America, Europe, Asia, and Australia; and one freshwater clade, containing Bangia atropurpurea from North America and China. 相似文献
77.
Inter-tidal(subtidal) transport processes in coastal sea depend on the residual motion, turbulent dispersion and relevant sources/sinks. In Feng et al.(2008), an updated Lagrangian inter-tidal transport equation, as well as new concept of Lagrangian in- ter-tidal concentration(LIC), has been proposed for a general nonlinear shallow water system. In the present study, the LIC is nu- merically applied for the first time to passive tracers in idealized settings and salinity in the Bohai Sea, China. Circulation and tracer motion in the three idealized model seas with different topography or coastline, termed as ‘flat-bottom', ‘stairs' and ‘cape' case, re- spectively, are simulated. The dependence of the LIC on initial tidal phase suggests that the nonlinearities in the stairs and cape cases are stronger than that in the flat-bottom case. Therefore, the ‘flat-bottom' case still meets the convectively weakly nonlinear condi- tion. For the Bohai Sea, the simulation results show that most parts of it still meet the weakly nonlinear condition. However, the de- pendence of the LIS(Lagrangian inter-tidal salinity) on initial tidal phase is significant around the southern headland of the Liaodong Peninsula and near the mouth of the Yellow River. The nonlinearity in the former region is mainly related to the complicated coast- lines, and that in the latter region is due to the presence of the estuarine salinity front. 相似文献
78.
在第一代DZW-Ⅰ重力仪基础上,采用新的机电一体的数字智能化设计,研制出改进的DZW-Ⅱ型重力仪。介绍了DZW-Ⅱ型重力仪的基本原理,对仪器使用过程中出现的问题进行分析,改进和优化仪器设计,进一步提高了仪器的可靠性和稳定性。 相似文献
79.
ENVIRONMENTAL CHANGE AND ITS IMPACTS ON HUMAN SETTLF, MENT IN THE CHANGJIANG RIVER DELTA IN NEOLITHIC AGE 总被引:1,自引:0,他引:1
ZHANGQiang LIUChun-ling ZHUCheng JIANGTong 《中国地理科学(英文版)》2004,14(3):239-244
Dating data, altitude of Neolithic sites, climatic changes from sedimentary records and previous research results were collected and analyzed to detect possible connections between climatic changes and human activities in the Changjiang River Delta in the Neolithic Age. The results indicated that hydrological changes greatly impacted the human activities in the study region. Low-lying geomorphology made the floods and sea level changes become the important factors affecting human activities, especially the altitude change of human settlements. People usually moved to higher places during the periods characterized by high sea level and frequent floods to escape the negative influences from water body expansion, which resulted in cultural hiatus in certain profiles. However, some higher-altitude settlements were not the results of climatic changes but the results of social factors, such as religious ceremony and social status. Therefore, further research will be necessary for the degree and types of impacts of climatic changes on human activities in the study area at that time. 相似文献
80.
生物对其生活环境中的不同元素和同位素存在不同程度的选择性吸收、利用和富集。其影响因子分为内因和外因两大类。具体选择机制可以从生物的形态构造直至分子水平上加以解释。当环境中元素、同位素含量发生变化时,生物因其对各元素生态幅和耐受限度的差异而并不完全对环境中化学因子的变化产生一致性的响应。生物对其耐受限度较小的元素保持较高的属内有效性和特异性选择;而对于生态幅较宽的元素,生物属内的特异性选择弱化,生态幅可能与它属生物发生部分重叠。部分生物壳体第二层与其围岩碳、氧同位素比值及其变化趋势保持着较好的一致性。上述认识不同程度地在Rhynchospirifer属和Stringocephalus属为代表的腕足动物及其围岩的研究中得到验证。 相似文献