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51.
海洋平台复杂节点阴极保护电位分布的有限元法计算 总被引:1,自引:0,他引:1
了解阴极保护电位分布是合理设计阴极保护工程的必要条件和评价阴极保护效果的重要依据。本文应用有限元素法(FEM)计算海洋平台复杂节点表面的阴极保护电位分布。在实验室通过边界条件试验建立数学模型,计算海水中被保护的I,Y,K型复杂节点电位分布情况。计算结果与测量结果吻合得很好,说明FEM能够应用于海洋平台复杂节点阴极保护电位分布的计算,所获得的边界条件合理。 相似文献
52.
利用2006年南极威德尔海冬季科学考察期间由机载激光高度计测得的海冰上表面形态数据,以拖曳分割理论为基础研究了冰脊形拖曳力及其对冰-气总拖曳力的贡献以及中性条件下对应10 m高度处风速的冰-气拖曳系数Cdn(10)。结果显示,在密集冰区,冰脊形拖曳力及其对总拖曳力的贡献随冰脊强度(脊高/脊距)的增大呈递增趋势,而随粗糙长度的增大而减小,对应于威德尔海冬季典型冰脊强度和粗糙长度,占总拖曳力的35%,说明了冰脊形拖曳力在冰-气界面动量交换中的重要作用。Cdn(10)随冰脊强度的增大而增大,但冰脊强度较小时,Cdn(10)随粗糙长度增大而增大;而对较大的冰脊强度,Cdn(10)则随粗糙长度增大而减小。 相似文献
53.
54.
太湖、洞庭湖野生青虾肌肉中有机氯农药的气相色谱-质谱法测定 总被引:4,自引:0,他引:4
使用气相色谱质谱技术测定了青虾肌肉组织中的8种有机氯农药.包括六氯苯、氯丹、滴滴涕(ΣDDTs)、艾氏剂、狄氏剂、异狄氏剂、七氯和灭蚁灵,对太湖和洞庭湖15个点位29组野士青虾样品的测定结果显示,青虾肌肉组织内残留的有机氯农药主要是六氯苯和滴滴涕,六氯苯含量为nd-13.2μg/kg(湿重),滴滴涕含量为0.790-5.82μg/kg(湿重),洞庭湖青虾肌肉中有机氯农药的含量略高于太湖青虾,两湖青虾肌肉残留有机氯农药在枯水期时的含量多数大于丰水期时的含量. 相似文献
55.
微囊藻群体总RNA提取方法的比较 总被引:1,自引:0,他引:1
微囊藻群体富含多糖类物质是影响微囊藻RNA提取的关键因素.为了获得高质量的微囊藻群体总RNA,对比分析4种针对多糖含量较高的方法——方法 1 PGTX-bead法、方法 2 CTAB-bead法、方法 3 Fast RNAPro Blue Kit和方法 4RNeasy Mini Kit对微囊藻群体总RNA的提取效果.采用琼脂糖凝胶电泳检测微囊藻群体RNA的完整性,Nanodrop ND1000分光光度计检测RNA纯度及浓度,并采用q PCR检测DNA污染情况.结果表明,4种方法都能从微囊藻群体中提取获得RNA,并在去除DNA后都可以进行RT-PCR等后续实验.方法 1 PGTX-bead提取的RNA产量最高,纯度好,DNA污染小,成本低,适合从微囊藻群体中大量提取RNA;方法 2 CTAB-bead提取的RNA样品产量也较高,但DNA污染严重,适合需要同时提取DNA和RNA的样本;方法 3 Fast RNAPro Blue Kit和方法 4 RNeasy Mini Kit提取的RNA产量都较低,但方法 4操作简单,耗时短,所检测目的基因的相对表达量较高,更适合从少量的微囊藻群体中提取总RNA. 相似文献
56.
57.
C. S. Yao 《Theoretical and Applied Climatology》1997,57(1-2):111-118
Summary In this paper, a new method of cluster analysis incorporating a statistical test, was proposed in order to decide whether to accept or reject the assumption of a numerical classification of climate according to a
2 test. On the basis of normality of errors, the
2 test has been derived from the variance of the Euclidean distance or from that of the reduced distance.This new method of cluster analysis consists of uniform clustering and central clustering. The former is adapted to a more detailed numerical classification of climate, while the latter is appropriate for the large-scale numerical classification of climate. Examples of calculation and application of this new method of cluster analysis are presented in order to illustrate calculations undertaken in the processes of climate classification. 相似文献
58.
Comparison of surface variables from ERA and NCEP reanalysis with station data over eastern China 总被引:1,自引:1,他引:1
Zhaofei Liu Zongxue Xu Zhijun Yao Heqing Huang 《Theoretical and Applied Climatology》2012,107(3-4):611-621
This study compared precipitation, mean air temperature (MAT) and mean sea level pressure (MSLP) from two widely used reanalysis datasets (ERA-40 and NCEP) with those from observed stations across eastern China. The evaluation was based on a comparison of both temporal and spatial variability and included several assessment criteria such as the mean values, normalized root mean square error, Mann–Kendall test, empirical orthogonal functions (EOFs) and probability density functions. The results showed that both the ERA-40 and NCEP datasets could capture temporal and spatial variability of the observed precipitation, MAT and MSLP over eastern China. The results showed that the two reanalysis datasets performed better for MAT and MSLP than for precipitation. Overall, the two reanalysis datasets revealed reasonable agreement with observations according to the evaluation. ERA-40 was better at capturing the temporal and spatial distributions for these three variables than NCEP, especially for MAT and MSLP. NCEP tended to overestimate the annual precipitation for both mean and extreme values, while ERA-40 tended to underestimate it, particularly for extreme values. The two reanalysis datasets performed better in the east and northeast regions of the study area than in other regions for capturing the temporal variability of MAT and MSLP. ERA-40 was poor at capturing the temporal variability of precipitation in northeastern China. According to the trend analysis, the two reanalysis datasets showed lower trends for MAT and precipitation and higher trends for MSLP. Both ERA-40 and NCEP had larger explained variances for the first two EOFs than the observed precipitation. This implies that both reanalysis datasets tend to simulate a more uniform spatial distribution for precipitation in the study area. 相似文献
59.
姚展予 《中国气象科学研究院年报》2003,(1):24-26
国家重点科技攻关项目“人工增雨技术研究及示范’’经过两年的攻关,在人工增雨综合探测、云水资源评估、催化作业、数值模拟、效果检验技术和外场示范试验等方面取得了一系列成果和应用效益,基本形成了一套人工增雨综合技术。2003年12月13日顺利通过科技部组织的专家验收。课题研究成果通过在示范区的检验、试用和完善,显示出具有业务应用和推广前景。课题主要成果为: 相似文献
60.
On the basis of new paleontological data,the sequence and distributions of the Middle Devonian-Tournaisian rocks on Hainan Island have been sorted out for the first time.The Devonian rocks include the Middle Devonian Jinbo Formation and the Upper Devonian Changjiang Formation,which are distributed in northwestern Hainan Island.The Jinbo Formation is represented by631 m of littoral facies deposits,and was intruded by the Yanshanian granite in the base.The presence of chitinozoans Eisenackitina caster,Funsochitina pilosa,and Lagenochitina amottensis indicates the Givetian in age.The Changjiang Formation is made up of 140 m of neritic facies rocks,and contains the Famennian conodonts Palmatolepis gracilis sigmoidalis,Polygnathus germanus,and corals Cystophrentis kalaohoensis.The Devonian-Tournaisian transition beds,the lower part of the Jishi Formation,are composed of 61–129 m sandstone and siltstone,with gastropods Euomphalus spp.and brachiopods,and marked by conglomerate with the underlying Devonian rocks.The middle-upper part of the Tournaisian Jishi Formation consists of 100–251 m clastic and carbonate rocks,containing abundant corals Pseudoularinia irregularis,conodonts Siphonodella isosticha,trilobites Weberiphillipsia linguiformis,and brachiopods.On the basis of the occurrence of Xinanosprifer flabellum and Homotoma sp.,the Nanhao Formation in southern Hainan Island is now regarded as the Lower Silurian,instead of the previously designated Lower Carboniferous.It is confirmed that no Carboniferous rocks occurred in the area south to the Gancheng-Wanning Fault. 相似文献