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231.
Radium-226 (226Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First
Chinese National Arctic Research Expedition. The results showed that 226Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m3 with an average of 0.76 Bq/m3 in the Arctic Ocean, and from 0.25 to 1.26 Bq/m3 with an average of 0.71 Bq/m3 in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating that
the study area may be partly influenced by sea ice meltwater. In the Bering Sea, 226Ra in the surface water decreased northward, probably as a result of the exchange between the 226Ra-deficient sea ice meltwater and the 226Ra-rich Pacific water. In the Arctic Ocean, 226Ra in the surface water increased northward and eastward. This spatial distribution of 226Ra reflected the variation of the 226Ra-enriched river component in the water mass of the Arctic Ocean. The vertical profiles of 226Ra in the Canadian Basin showed a concentration maximum at 200 m, which could be attributed to the inputs of the Pacific water
or/and the bottom shelf water with high 226Ra concentration. This conclusion was consistent with the results from 2H, 18O tracers. 相似文献
232.
Using data obtained with the 20-cm H full-disk telescope at Big Bear Solar Observatory and Fexii 195 Å EIT on SOHO, we analyze a sudden disappearance event of a quiescent filament in detail. The filament was located along the common boundary of the active regions NOAA 9672 (S19 E13) and NOAA 9673 (N03 E18). The filament disappeared during a time interval between 17:59 UT and 19:47 UT on 22 October 2001 immediately after the onset of a major flare, which occurred in the active region NOAA 9672. At about 23:23 UT of the same day, the filament began to reappear in H and, after about 15 hours, the filament recovered to its steady state with its size being slightly smaller than that before its disappearance. This filament disappearance event belongs to the thermal type of sudden filament disappearances, which is caused by an input of additional heat. The heating mechanism that leads to sudden thermal disappearances of quiescent filaments is still not well understood. This simple event, due to the explicit cause and effect relationship between the flare and the disappearance of the filament, shows us that the flare triggered some kind of heating mechanism which continued several hours. The heat may come from the flare via heat conduction from its ribbon or from the excitation of dissipating Alfvén waves. However, from the data analysis, we conclude that the flare triggered an in-situ heating, which is likely caused by magnetic reconnection. 相似文献
233.
黄浦江水质指标与反射光谱特征的关系分析 总被引:16,自引:0,他引:16
利用地物光谱测量技术及同步配套的常规水质采样分析实验,对上海市黄浦江全河段水体进行调查研究。共选取31个典型站位进行了光谱测量和同步水质取样,每个测点分析了9个水质指标,包括TP,TN,CODMn,CODCr,NH3-N,BOD5,DO,悬浮物浓度和浊度。各水质参数之间存在较大的相关性,以总氮(TN)和悬浮物浓度两个水质指标为例,分析了这两个水质指标与单波段归一化反射率、反射率的一阶微分、不同波段之间反射率的比值以及反射率取对数等之间的相关关系,给出了以上两个水质指标的单波段归一化反射率、一阶微分反射率识别的特征波段,以及两个波段比值的最佳波段组合。建立了常规水质参数与水体光谱反射率之间的关系模型,为利用遥感技术监测水环境提供了基础。 相似文献
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237.
Weifeng SONG Lihua CHEN Xiuping LIU 《国际泥沙研究》2006,21(3):230-237
1 INTRODUCTION China is rich in mountains. The mountainous area occupies 69% of the total land of the country. Thus, landslides frequently occur in the mountain areas of China. Landslides originating in subsurface soils are typical, and constitute approxi… 相似文献
238.
Xie Xin Xu Xisheng Zou Haibo Jiang Shaoyong Zhang Ming Qiu Jiansheng 《中国科学D辑(英文版)》2006,49(8):796-815
Magmatism in SE China was dormant during 204–180 Ma, but was reactivated in 180–170 Ma (early J2), and then became more and more intensive towards the end of early Cretaceous. The small-scale early J2 magmatism is the incipience to long-term and large-scale magmatism in this region. A near east-west (EW) trend volcanic belt
was distributed across south Hunan, south Jiangxi and southwest Fujian was formed during early J2 time. Along this belt from the inland toward the coast, the lithology of basalts changes from alkali into tholeiite, and
the amount of erupted volcanic rocks and the proportions of rhyolites coexisting with the basalts increase. On the basis of
geochemical characteristics of these basalts, we infer that the melting degree of source rocks and the extent of fractional
crystallization and crustal contamination all increased whereas the depth of mantle source decreased from the inland to the
coast, which led to the variations of geological characteristics of the volcanic belt. In early J2, the western spreading Pacific plate began to subduct underneath SE China continental block, reactivating near EW trend deep
fault that was originally formed during the Indosinian event. The stress of the western spreading Pacific plate and the extent
of asthenosphere upwelling increased from the inland to the coast, which is consistent with the generation and evolution of
early J2 basalts. 相似文献
239.
Summary A new method of four-dimensional data assimilation based on Singular Value Decomposition (SVD) is proposed. In it, a set of
atmospheric states is obtained by integrating a numerical weather prediction model and simulated observations are taken and
calculated from the model variables. Then the SVD technique is used to create the base vectors from this coupled data set.
Finally, the analysis is obtained by projecting actual observation data into a space spanned by the base vectors. Using this
approach, the four-dimensional data assimilation becomes a simple linear inverse problem the linearization of the nonlinear
forward model is avoided, and the developments of the adjoint and background error covariance matrix are no longer needed.
Since the SVD technique is used here, the method is simply called 4DSVD. 相似文献
240.
本文根据夏热冬暖地区的气候特点,针对目前建筑节能设计存在的薄弱环节,分析了建筑围护结构的构造措施及其热工性能,提出在节能设计中应注意的问题。 相似文献