北斗卫星导航系统精密定轨技术研究现状   总被引：2，自引：0，他引：2  

郝金明  刘伟平  杨力  李建文  吕志伟 《测绘科学技术学报》2015,(3):221-225,230

北斗系统开通运行以来,无论是系统建设还是精密定轨技术均获得了长足发展。文中简要介绍了北斗系统目前的建设情况,总结梳理了北斗卫星精密定轨技术发展现状。在此基础上,分析论述了北斗系统精密定轨中亟待解决的主要问题。  相似文献   

多媒体数字视频监控技术的现状和应用发展   总被引：2，自引：0，他引：2  

吴鹏 《大地测量与地球动力学》2009,29(Z1):155-158

介绍数字化视频监控技术的应用前景，探讨其下一代产品的发展趋势。包括:1)视频压缩算法——决定产品主要特性的技术；2)网络技术——面向未来多用途的视频多媒体设备以及大规模数字视频多媒体网络系统的构成基础；3）智能化技术——数字视频系统根据应用领域的不同可以提供各种智能化的功能。  相似文献   

中国珊瑚礁资源状况及其药用研究调查 Ⅲ.民间药用与药物研究状况   总被引：1，自引：0，他引：1  

邵长伦  傅秀梅  王长云  韩磊  刘新  方玉春  李国强  曾晓起  刘光兴  管华诗 《中国海洋大学学报(自然科学版)》2009,39(4)

对中国珊瑚药用状况和研究现状进行了调查.结果表明,中国有造礁石珊瑚、柳珊瑚、软珊瑚等珊瑚物种 490 种,民间药用的仅有22种.目前,已经对100种南海软珊瑚和柳珊瑚进行了化学成分的研究.其中,软珊瑚以豆荚软珊瑚Lobophytum,肉芝软珊瑚Sarcophyton,短指软珊瑚Sinularia,柔荑软珊瑚Nephthea和异花软珊瑚Xenia等属研究较多,柳珊瑚以小月柳珊瑚Menella,竹节柳珊瑚Isis和灯芯柳珊瑚Junceella等属研究较多.主要化合物结构类型包括二萜、甾体、倍半萜,含氮化合物等,其中部分化合物显示较强的抗肿瘤、抗菌、抗氧化、防生物附着等多种生物活性,具有潜在的药物开发应用价值.  相似文献   

Estimate of Global Sea-Air CO2 Flux with Sea-State-Dependent Parameterization     

HU Wei  GUAN Changlong 《中国海洋大学学报(英文版)》2008,7(3)

Although the annual global sea-air CO2 flux has been estimated extensively with various wind-dependent-k parameteri- zations, uncertainty still exists in the estimates. The sea-state-dependent-k parameterization is expected to improve the uncertainty existing in these estimates. In the present study, the annual global sea-air CO2 flux is estimated with the sea-state-dependent-k parameterization proposed by Woolf (2005), using NOAA/NCEP reanalysis wind speed and hindcast wave data from 1998 to 2006, and a new estimate, -2.18 Gt C year-1, is obtained, which is comparable with previous estimates with biochemical methods. It is in- teresting to note that the averaged value of previous estimates with various wind-dependent-k parameterizations is almost identical to that of previous estimates with biochemical methods by various authors, and that the new estimate is quite consistent with these av- eraged estimates.  相似文献   

Assessing the ecological status of the North-western Adriatic Sea within the European Water Framework Directive: a comparison of Bentix, AMBI and M-AMBI methods     

Roberto Simonini  Valentina Grandi  Gloria Massamba-N'Siala  Mirko Iotti  Giuseppe Montanari  & Daniela Prevedelli 《Marine Ecology》2009,30(2):241-254

In this paper we looked for the most suitable method for benthic ecological quality status (EcoQS) assessment of the North-western Adriatic Sea. Taking into account the historical and present information, we inter-compared our expectations in terms of EcoQS, with the Bentix, AMBI and M-AMBI classification metrics results, and investigated the sensitivity of these indices to the spatial, seasonal and inter-annual variability of benthic communities. The sampling sites were located at increasing distances with respect to the Po River mouth, along an (inverse) gradient of eutrophication. Moreover, a 2-year monthly monitoring plan (October 2004–September 2006) was carried out at the CEBEB site, located in a central position with respect to the investigated area. The results highlighted that the three indices differed in the sensitivity to spatial and temporal variability of the benthic communities. The strong seasonal and inter-annual changes in the benthic communities had a significant effect on the Bentix, whereas no relevant modifications were observed on the EcoQS assignation obtained using the M-AMBI and AMBI methods. The environmental quality ratios (EQR) values and EcoQS classification obtained by the Bentix and AMBI did not match expectations, as they were not inversely correlated with the site distances with respect to the Po mouth, whereas the M-AMBI clearly discriminated the most and the least eutrophicated sites. It thus appears that the M-AMBI could be considered to be the most valuable method for the ecological-status assessment of the North-western Adriatic Sea benthic ecosystem.  相似文献   

SHIFTS IN THE WHOLESALE TRADE STATUS OF U.S. METROPOLITAN AREAS*     

J. Dennis Lord 《The Professional geographer》1984,36(1):51-63

Considerable instability exists among large U.S. metropolitan areas in their status as wholesale trade centers. Differences in wholesale trade growth rates, changes in national shares, and shifts in rank position reflect not only population growth patterns, but also structural changes in the national economy. In the latter instance, the wholesale product mix of SMSAs is an important factor in explaining their differential fortunes within the wholesaling hierarchy.  相似文献   

中国城市生活空间及社区可持续发展研究现状与趋势   总被引：10，自引：1，他引：10  

孙峰华  王兴中 《地理科学进展》2002,21(5):491-499

本文首先回顾了西方发达国家研究城市生活空间和社区可持续发展的历史 ,指出中国对该论题的研究仅处于起步阶段。中国研究城市生活空间和社区可持续发展的现状主要包括以下 7个方面 :1城市生活空间要素研究 ;2城市生活空间结构及其基本理论研究 ;3城市生活空间质量评价与实践探索 ;4城市生活空间规划的理论研究与实践探索 ;5城市生活空间适居性研究 ;6城市生活空间发展变化的研究 ;7城市生活空间与社区可持续发展研究。其趋势主要表现在以下 6个方面 :1城市生活空间与自然的和谐 ;2城市生活空间结构要素的协调发展和社区系统要素的整合 ;3城市生活空间整合和社区融合 ;4城市生活情境空间和社区情境空间的总体艺术布局 ;5绿色城市生活空间和绿色社区设计 ;6城市生活信息空间和智能环境社区。总之 ,创建绿色城市生活空间和绿色社区 ,促进城市社区的可持续发展 ,是 2 1世纪诸多相关学科共同研究的主题。为了今后更好地开展城市生活空间和社区可持续发展研究 ,本文提出了研究中应该注意的若干问题。  相似文献   

灌注桩抽芯钻进工况的自动识别     

鄢泰宁  姚爱国 《地质与勘探》1996,32(3):49-54

对钻孔灌注桩进行抽芯检验时，可能因钻头切断钢筋而使桩基承载力下降甚至整根桩报废，本文提出的方法可对钻头遇到钢筋的孔内工况进行自动识别，声光报警，并给出遇钢筋的深度，以防切断钢筋，文中还介绍了判断钢筋笼歪斜情况的简易方法。  相似文献   

勘查地球化学的现状与未来展望   总被引：28，自引：2，他引：28  

谢学锦 《地质论评》1996,42(4):346-356

勘查地球化学在过去50年发展迅速,并取得巨大成功。从它近年的发展及在中国北京与澳大利亚Townsville召开的第16届及第17届国际地球化学勘查学术讨论会上所表现的创新与非传统性看来,勘查地球化学正在从经验式阶段向革新技术与加强理论研究的新阶段过渡。其主要标志是由于国际地球化学填图研究的进展及各种宽阔地球化学模式的认识,地球化学勘查将逐步成为能左右矿产勘查部署的战略性方法,各种新技术的出现使隐伏区找矿特别是找巨型矿床正在取得重大突破。高质量的地球化学图还将使今后的环境研究更具全球眼光,中国的工作是这些方  相似文献   

IMMIGRATION, GEOGRAPHIC DISTRIBUTION AND SOCIAL ECONOMIC STATUS OF AMERICAN CHINESE     

Zhang Zhenyu Henan Institute of Geography  Zhengzhou  P.R.ChinaWang Jue The University of Kansas  Lawrence  USA 《地理学报(英文版)》1997,(1)

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