Middle and Late Devonian microbial carbonates,reefs and mounds in Guilin,South China and their sequence stratigraphic,paleoenvironmental and paleoclimatic significance   总被引：2，自引：0，他引：2  

Pedoja Kevin 《中国科学D辑(英文版)》2005,48(11):1900-1912

The importance of calcimicrobes and microbialite in carbonate platform and reefal environments has been stressed in recent literature. Burne and Moore[1] introduced the term microbialite to describe the clotted, laminated and undifferentiated fabrics formed by mi-crobial communities. Microbialites are organosedi-mentary deposits that have accreted as a result of ben-thic (prokaryotic or eukaryotic) communities, trapping and binding detrital sediment[1]. Microbial organisms and microbialite are…  相似文献   

Carbonate biomineralization induced by soil bacterium Bacillus megaterium     

Bin Lian  Jun Chen  H. Henry Teng 《Geochimica et cosmochimica acta》2006,70(22):5522-5535

Biogenic carbonates spawned from microbial activities are common occurrences in soils. Here, we investigate the carbonate biomineralization mediated by the bacterium Bacillus megaterium, a dominant strain separated from a loess profile in China. Upon completing bacterial cultivation, the ensuring products are centrifuged, and the resultant supernatant and the concentrated bacterial sludge as well as the un-separated culture are added separately into a Ca-CO₃ containing solution for crystallization experiments. Results of XRD and SEM analysis indicate that calcite is the dominant mineral phase formed when the bacteria are present. When the supernatant alone is used, however, a significant portion of vaterite is also precipitated. Experimental results further reveal that the bacteria have a strong tendency to colonize the center area of the calcite {1 0  4} faces. Observed crystal morphology suggests that the bacterial colony may promote the growth normal to each individual {1 0  4} face of calcite when the cell concentration is high, but may retard it or even cause dissolution of the immediate substrate surfaces when the concentration is low. SEM images taken at earlier stages of the crystallization experiments demonstrate the nucleation of calcite on the bacterial cell walls but do not show obvious morphological changes on the nanometer- to submicron-sized nuclei. δ¹³C measurements unveil that the crystals grown in the presence of bacteria are further enriched in the heavy carbon isotope, implying that the bacterial metabolism may not be the carbon sources for the mineralization. Based upon these findings, we propose a mechanism for the B. megaterium mediated calcite mineralization and conclude that the whole process involves epi- and inter-cellular growth in the local microenvironments whose conditions may be controlled by cell sequestration and proton pumping during bacterial respiration.  相似文献   

基于时间序列法的北京市需水量预报(英文)   总被引：2，自引：0，他引：2  

翟远征  王金生  滕彦国  左锐 《地理学报(英文版)》2012,22(5):919-932

It is essential to establish the water resources exploitation and utilization planning,which is mainly based on recognizing and forecasting the water consumed structure rationally and scientifically.During the past 30 years(1980-2009),mean annual precipitation and total water resource of Beijing have decreased by 6.89% and 31.37% compared with those perennial values,respectively,while total water consumption during the same period reached pinnacle historically.Accordingly,it is of great significance for the harmony between socio-economic development and environmental development.Based on analyzing total water consumption,agricultural,industrial,domestic and environmental water consumption,and evolution of water consumed structure,further driving forces of evolution of total water consumption and water consumed structure are revealed systematically.Prediction and discussion are achieved for evolution of total water consumption,water consumed structure,and supply-demand situation of water resource in the near future of Beijing using Time Series Forecasting Method.The purpose of the endeavor of this paper is to provide scientific basis for the harmonious development between socio-economy and water resources,for the establishment of rational strategic planning of water resources,and for the social sustainable development of Beijing with scientific bases.  相似文献   

引入纹理特征的SSVM算法在极化SAR影像分类中的应用     

刘利敏  余洁  燕琴  刘振宇  朱腾 《测绘通报》2012,(8):7-10

在极化SAR影像极化特征的基础上,引入影像的纹理信息,利用带核函数的SSVM算法对极化SAR影像进行分类研究。该方法首先利用精致LEE滤波器对极化SAR影像进行去噪处理;然后采用小波变换对去噪后的总功率影像Span进行纹理特征提取;最后将纹理信息和极化信息结合,并采用SSVM方法对极化SAR影像进行分类。利用NASA/JPL AIRSAR获取的L波段SanFrancisco海湾和荷兰中部Flevoland地区的影像对该方法进行验证,结果表明,SSVM算法可有效地用于极化SAR影像分类,且分类精度和分类效率都优于SVM算法。同时纹理信息的引入使SSVM算法的分类精度得到了进一步提高。  相似文献   

基于ASTER遥感影像的西昆仑岩性信息提取方法研究   总被引：1，自引：0，他引：1  

余健  张志  李闵佳  陈腾  何文熹 《国土资源遥感》2012,(1):22-27

基于西昆仑西段布伦口地区各岩性段内岩石样品的矿物组成及其光谱特征分析,提取代表各岩性单元的岩性端元波谱曲线;对研究区内ASTER可见光(VNIR)和短波红外(SWIR)数据进行匹配滤波处理,成功提取了研究区内9种重要的岩性单元(包括古元古界布仑阔勒群的黑云石英岩、黑云斜长片麻岩、黑云石英片岩和黑云角闪斜长片麻岩,志留系温泉沟群的绿泥石绢云母板岩、黑色千枚岩和绢云母石英片岩,以及石英闪长岩和英云闪长岩)。经已知地质资料和野外查证资料分析证明,用上述方法提取岩性信息的结果可靠,能为岩性填图及矿床勘查工作提供参考。  相似文献   

高铁无砟轨道基准点平面测量方法     

范亚军  黄腾  刘岭  李东升 《测绘工程》2012,21(1):58-62

介绍一种在狭长测量条件下基于边角后方交会自由设站的测量方法,阐述方法的原理,并结合石武高铁CRTSⅡ型板式无砟轨道基准点平面测量的具体实例应用,分析该测量方法的精度,证明该方法在狭长呈带状、要求越来越高的测量环境中应用的可行性和可靠性,对其他大型精密工程测量具有参考价值。  相似文献   

南京长江第四大桥索夹的定位测量     

李支彬  黄腾  康建松  刘岭 《测绘工程》2012,21(5):53-55

以南京长江第四大桥索夹放样为例,介绍该桥索夹位置计算和测量放样的基本方法和流程。分析影响悬索桥索夹放样精度的因素,并加以修正或消除,用以提高索夹放样精度。实践证明本桥索夹放样方法简单、可靠,满足设计要求。  相似文献   

北斗RDSS用户机测试系统指标监测校准方案设计     

唐斌  柳奇  张益青  舒展  李腾 《全球定位系统》2012,37(1):13-16

北斗卫星无线电测定业务(RDSS)用户机是我国北斗卫星导航试验系统的应用终端,测试系统可为用户机研制和使用提供可靠保障。鉴于RDSS体制的特殊性,测试系统的重要性能指标包括:用户机入站信号测量指标、用户机时延测量指标、以及用户机测试系统出站信号。为确保测试系统测试标准的统一,需要对测试系统的这些指标进行监测和校准。通过对普通用户机提出技术改进设计,为测试系统校准提供可行性方案,实现测试系统指标向标准测试仪器的溯源。  相似文献   

基于云团特征的短时临近强降水预报技术     

胡波  杜惠良  滕卫平  石蓉蓉 《气象》2009,35(9):104-111

通过分析2005-2008年影响浙江的梅汛期强降水云团特征,将云团分为偏北型、居中型和偏南型,研究这三种类型云团云顶亮温与地面1小时强降水极值和10mm/h以上降水覆盖面积关系,结果表明偏南型和偏北型云团有较多相似特征,而居中型云团较其他两种云团则有较多相反特征.通过分析1小时强降水相对于云团中心移动路径的落区,指出梅汛期云顶1小时变温和亮温梯度与地面1小时强降水落区无明显配对模型.随后利用天气形势场资料,分析强降水云团与环境要素场的关系,指出云顶亮温的宏观特征与中高层的垂直速度、水汽通量密切相关,最后尝试建立三种类型强降水云团成熟阶段云顶亮温和地面降水人工神经网络预报方程,给预报员提供参考.  相似文献   

南支气流对高原低涡移出高原影响的数值试验   总被引：2，自引：0，他引：2  

郁淑华  肖玉华  高文良  滕家谟 《四川气象》2009,(3):1-7

本文在对2000年以来移出青藏高原后活动时间长的高原低涡活动过程,进行对流层中层南支气流对高原低涡移出高原的影响的观测事实分析基础上,通过对2001年6月1～5日索县低涡移出高原活动的数值模拟和试验分析,得出了在高原低涡以南的南支气流减弱或者是没有南风或者是没有南风脉动的影响,会使低涡移出高原的速度减慢,移出高原12小时后减弱消失。低涡以南的南支气流起到了向低涡区输送水汽通量、正涡度平流的作用,提供利于低涡活动持续的条件。从而丰富了高原低涡东移的认识,为高原低涡洪涝暴雨的预报提供了科学依据。  相似文献