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排序方式: 共有156条查询结果,搜索用时 31 毫秒
41.
Ozone Vertical Profile Characteristics over Qinghai Plateau Measured by Electrochemical Concentration Cell Ozonesondes 总被引:7,自引:0,他引:7
OzoneVerticalProfileCharacteristicsoverQinghaiPlateauMeasuredbyElectrochemicalConcentrationCelOzonesondes①LiuQijun(刘奇俊),Zheng... 相似文献
42.
Yang Xiaoqian Wen Xin Zhou Chengxu Zhu Xiaojuan Meng Ran Luo Qijun Yan Xiaojun 《中国海洋湖沼学报》2018,36(5):1697-1706
Journal of Oceanology and Limnology - Typical harmful micro-algal species constantly occurred in high density in marine aquaculture ponds in Xiangshan and Sanmen Bay, Zhejiang Province. Fates of... 相似文献
43.
44.
网络地图评价指标体系及其应用 总被引:1,自引:0,他引:1
随着因特网技术的迅速发展和普及,网络地图越来越受到大众用户的青睐。结合网络地图的功能和特点,通过分析影响网络地图性能的主要要素之间的层次关系,构建了包括数据、服务功能、搜索性能和操作四个方面的网络地图评价体系及其评价方法,从定量和定性的角度比较分析了MAPbar、MAPabc、百度地图、51地图、Google Map、微软的Windows Live search、搜狗、爱问、雅虎中国等中文网络地图的性能,讨论了中文网络地图存在的主要问题,比如地物命名规范化、自然语言查询、专业化程度、地图数据覆盖度和用户认可程度等方面。该研究可以为网络地图开发人员和用户提供参考,对推广和普及网络地图,具有一定的理科学义和实践价值。 相似文献
45.
一种公交换乘优化算法设计 总被引:4,自引:1,他引:3
目前,在智能交通系统应用中,公交查询亟待解决其算法效率和换乘两大问题。对此,本文首先在分析乘客出行因素和公交网络特性的基础上,提出了关键站点的公交网络通达矩阵,分析了直达矩阵的计算原理;其次,阐述了城市道路网络最短路径算法,引入直达矩阵和公交网络通达矩阵,设计了一种公交换乘优化算法。该算法的基本原理:利用公交网络通达矩阵来确定哪些临时标记节点是潜在的永久标记结点,并始终优先考虑直达节点作为最短路径上的节点,从而实现对经典最短路径算法--Dijkstra算法的改进;最后,通过一个案例对该算法进行验证。实验表明,该算法不仅能够获得优于Dijkstra算法的性能,而且换乘次数更加合理。该算法能够适用于一般公交网络,对于换乘代价较高的公交网络更有优势。 相似文献
46.
The interaction between groundwater and surface water in northern Shaanxi is quite complicated and frequent under the influence of regional hydrogeological condition and human intervention. These performances bring serious challenges to regional water resources assessment and utilization. The river baseflow process at Gaojiabu Station in windy desert region, Gaoshiya and Caoping Station in loess region were taken as research objects, and their variation trends and change points in the river baseflow series were analyzed in this paper. In addition, to explore the cause of the baseflow change, this research compared their correlations with precipitations in the same area respectively from two aspects of flow variation and multi timescale characteristics. The results show that: ①groundwater recharges for river flow in windy desert region significantly exceed those in loess region; ②baseflows of all the rivers in the study area reducing significantly are mainly determined by human intervention such as the extensive pumping of groundwater; ③periodic changes of baseflow in each station response closely to precipitation change on meso-scale and small-scales; ④precipitation-runoff relationships in windy desert regions are much more complicated and unstable than loess region, which is mainly because of its more significant impact from groundwater storage and the lateral recharge change. Under the changing environment, the water cycle in windy desert regions would be in complexity and variability. Therefore, it is recommended that, groundwater changes need to be considered in regional water resources assessment. 相似文献
47.
68 groups of type III bursts recorded with the dynamic spectrograph (from1 to 2 GHz) at the Beijing Astronomical Observatory
are statistically analyzed in this present article, with the frequency drift, duration, bandwidth and polarization of each
of these events being analyzed in detail. These observational features are different from those of metric, decimetric and
microwave high frequency type III bursts, showing that there possibly exist transition phenomena in the microwave low frequency
band and the microwave type III bursts at low frequencies are possibly produced by the harmonic plasma radiation caused by
nonthermal electronic beams and by the electron gyro-maser radiation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
48.
Ji Huirong Fu Qijun Liu Yuying Cheng Congling Chen Zhijun Yan Yihua Zheng Leping Ning Zongjun Tan Chengmin Lao Debang Li Shuke Gao Jiyong Wang Zhiqiang Yu Minhong 《Solar physics》2003,213(2):359-366
The properties, structure and performance of a Solar Radio Spectrometer working at 5.2–7.6 GHz developed by National Astronomical Observatories/Beijing and Hebei Semiconductor Research Institute are described. The spectrometer has a spectral resolution of 20 MHz and a temporal resolution of 5 ms, with an instantaneous detectable range from 2% to 10 times flux of the quiet Sun. It can measure both left and right circular polarizations with an accuracy of 10% of polarization degree. Some results of preliminary observations are presented. 相似文献
49.
G. P. Chernov R. A. Sych Yihua Yan Qijun Fu Chengming Tan Guangli Huang De-Yu Wang Hongao Wu 《Solar physics》2006,237(2):397-418
We present results of the first simultaneous observations of zebra patterns (ZPs) with super-fine spiky structure in the microwave range made at two observatories ~1000 km apart (Beijing and Nanjing, China). The fine structure was recorded by a spectra polarimeter in the 5.2 – 7.6 and 2.8 – 3.6 GHz ranges at the Huairou station and by the spectrometer in the 4.5 – 7.5 GHz range at the Purple Mountain Observatory. Simultaneously, the locations of radio sources were observed by the Siberian Solar Radio Telescope (SSRT) at 5.7 GHz. For a general analysis of the April 10, 2001 event, the Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) data and Transition Region and Coronal Explorer (TRACE) images in EUV 171 Å line were used. The circular polarization degree was very weak for the burst background radio emission and moderate to strong for the fine structure. The polarization sign in all the cases probably corresponds to the extraordinary wave mode. Estimations of the magnetic field values in the whistler model for fine structure agree well with the extrapolated values from magnetic maps. Given the possibility of wave transformation in the perpendicular magnetic field and the spiky structure of the ZP, the whistler wave model appears to be the most appropriate explanation for the zebra stripe phenomenon. 相似文献
50.
临沧花岗岩岩体(简称临沧岩体)是滇西澜沧江地区南段出露面积最大的复式岩基,也是特提斯构造域的重要组成单元,其岩石类型主要为黑云母二长花岗岩。锆石样品得出的定年结果为225.1±6.1 Ma,表明这些花岗岩类侵位于晚三叠世。临沧花岗岩的K2O/Na2O值大于1,铝饱和指数A/CNK=1.05~1.95属高钾钙碱性过铝-强过铝质S型花岗岩。岩石总体上富集轻稀土元素((La/Yb)N=6.06~21.01),亏损重稀土元素,并显示出明显的负Eu异常(δEu=0.20~0.38)。岩石地球化学特征指示,临沧花岗岩应为昌宁-孟连古特提斯封闭过程的产物原岩为中下地壳贫粘土的变质砂岩和变质泥岩,其Pearce构造判别图解中的同碰撞属性是对古特提斯封闭及保山-思茅地块碰撞的响应。 相似文献