PZ-90与WGS-84的坐标转换参数   总被引：1，自引：0，他引：1  

李建文  郝金明  张建军  李军正 《全球定位系统》2002,27(6):8-15,20

主要论述了GLONASS坐标系统PZ-90的定义及与GPS坐标系统WGS-84进行坐标转换的基本方法和数学模型。对现有转换参数的获取方法进行论述与评价，并对各种不同的转换参数进行了分析比较。  相似文献   

The scatter of time-delays in shear-wave splitting above small earthquakes   总被引：6，自引：0，他引：6  

Stuart Crampin  Sheila Peacock  Yuan Gao †  Sebastien Chastin 《Geophysical Journal International》2004,156(1):39-44

  相似文献   

Benthic community response to habitat variation: A case of study from a natural protected area,the Celestun coastal lagoon     

Daniel Pech  Pedro-Luis ArdissonNorma A. Hernández-Guevara 《Continental Shelf Research》2007

Little information currently exists on spatial and temporal benthic community variations in tropical coastal lagoons. Here, the benthic community response to habitat variation in the Celestun coastal lagoon, northwest Yucatan peninsula, was seasonally examined during the 1994–1995 climatic cycle into a grid of 12 sampling sites distributed along the salinity gradient of the lagoon. Habitat variation was assessed through physical factors associated both to the water column (e.g. salinity) and the bottom sediment (e.g. sand, silt and clay fractions). The benthic community response was assessed through species diversity measures and abundance. Under the influence of climatic seasonality, variations in habitat conditions followed by changes in the benthic community characteristics were expected. Results from two-way ANOVAs showed that for the period of study, Celestun lagoon was more heterogeneous along the spatial axis of variability than along the temporal one. Multiple regression analysis showed that salinity was spatially the main factor influencing the benthic community characteristics. Temporally, the sediment characteristics were observed to exert significant effects on the species diversity characteristics but not on abundance. Other variables assessed (dissolved oxygen, pH, temperature and water column transparency) exhibited no significant covariance with species diversity and abundance. Since generated from historical data, these results have the potential to be useful as a benchmark to the establishment of monitoring programs in the light of the increasing anthropogenic pressure on the natural resources of the lagoon and surrounding coastal area.  相似文献   

DEM数据源及分辨率对HEC-HMS水文模拟的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

高玉芳  陈耀登  蒋义芳  彭涛 《水科学进展》2015,26(5):624-630

DEM数据源及分辨率会影响流域特征参数的提取,进而影响水文模拟结果.将ASTER 30 m DEM、SRTM 90 m DEM及基于ASTER 30 m DEM的40 m、50 m、60 m、70 m、80 m、90 m重采样DEM作为HEC-geoHMS模型输入,提取流域特征,采用HEC-HMS模型,以西笤溪流域为研究区域,分析2011年6月和2011年8—9月的两场降雨径流过程中,DEM数据源和分辨率对水文模拟输出的影响.研究结果表明,两次径流模拟结果与实测数据拟合都较好,模型确定性系数都大于0.82,但是单峰的洪水模拟效果总体更好,基于SRTM 90 m的模型确定性系数比基于ASTER 30 m DEM、重采样90 m DEM的模型确定性系数都大.基于重采样DEM的模型确定性系数变化较大,而且与分辨率的变化呈非线性关系.在HEC-HMS的模拟中,基于ASTER 30 m DEM和基于SRTM 90 m DEM的模拟输出结果相对误差相差3%~5%,基于SRTM 90 m DEM和基于重采样90 m DEM的模拟输出结果相对误差相差2%~4%,基于重采样DEM的模拟输出结果相对误差相差最大达到了11%.  相似文献   

缢蛏（Sinonovacula constricta）GST和HSP90基因克隆及其在氨氮胁迫下的表达特征分析     

张欢  董迎辉  姚韩韩  俞凯佳  胡月亚  林志华 《海洋学报》2020,42(4):66-78

克隆获得缢蛏(Sinonovacula constricta)谷胱甘肽S-转移酶(Sc-GSTσ)和热休克蛋白90(Sc-HSP90)基因的cDNA全长,分析了它们的组织表达差异及其在氨氮胁迫下的表达特征。结果表明,Sc-GSTσ的全长cDNA为1 414 bp,含有639 bp的开放阅读框(Open Reading Frame,ORF),编码212个氨基酸,Sc-GSTσ氨基酸序列与其他物种的GST氨基酸序列同源性为31.88%～43.40%;而Sc-HSP90的全长cDNA为2 752 bp,ORF为2 181 bp,编码726个氨基酸,其氨基酸序列与其他物种HSP90的氨基酸序列同源性为76.77%～87.05%。荧光定量PCR分析发现,Sc-GSTσ和Sc-HSP90在缢蛏各组织中均有表达,两者均在肝胰腺中表达量最高。氨氮胁迫后,Sc-GSTσ和Sc-HSP90 mRNA在肝胰腺中表达均显著上调(p<0.05),表明氨氮胁迫引起机体的应激反应,2个基因可能参与机体解毒或防御过程。但胁迫后期表达量下降推测是机体的防御能力有限,不足以完全保护宿主免受应激诱导的细胞损伤。  相似文献   

Optimizing radiocarbon chronologies in peat profiles with examples from Xinjiang,China     

《Quaternary Geochronology》2023

Reliable chronological frameworks are crucial to paleoenvironmental studies, and high precision ¹⁴C dating is the foundation, but many factors, such as dating materials, surficial deposition (influenced by nuclear bomb), and the ¹⁴C age plateau, will affect the reliability of the ¹⁴C ages and chronology frameworks. In this paper, we present 87 ¹⁴C dates of different peat fractions from three peat sites in Xinjiang, China. Plant macrofossils, rootlets, the fine fraction of <90 μm, the mid-size fraction of 90–250 μm and the coarse fraction of >250 μm from selected peat samples were measured to investigate the alternative suitable fraction for dating except for plant macrofossils. We discovered that the 90–250 μm component of peat can provide alternative and reliable results in case of plant macrofossils are not available. Additionally, more dating samples from surficial peat deposition were collected, and accurate surface chronological control points were produced by comparing ¹⁴C results of plant macrofossils with atmospheric ¹⁴C bomb data. Furthermore, multiple data sets with wiggle matching were used along the radiocarbon age plateau to minimize calibrated errors when dates on the ¹⁴C age plateau were shown. Finally, radiocarbon chronology frameworks in peat profiles were optimized. In conclusion, we not only focus on the reliable dating materials, but also highlight that the importance of surficial deposition (after 1950AD) and the anomalous ¹⁴C dates when establishing the dating framework in peat profiles. Furthermore, we propose that the obtaining chronological control points of surficial peat is an important part of the establishing and improving of peat chronological framework in future research.  相似文献   

新疆天文台26米望远镜L波段接收机线-圆偏振的转换     

陈勇  孙正文  闫浩  李健  李大磊  李笑飞  刘烽 《天文研究与技术》2019,(3):262-267

新疆天文台南山基地26 m射电望远镜L波段接收机使用线偏振馈源接收电磁波信号用于脉冲星观测。分子谱线观测和VLBI国际联测需要圆偏振信号,因此希望接收机能够观测圆偏振信号。论述了将线偏振电磁波转换为圆偏振电磁波的方案,研究了90 °电桥在偏振转换中的作用,介绍了偏振转换的调试方法。在圆偏振模块中使用90 °电桥完成线偏振信号到圆偏振信号的转换,两路圆偏振信号的隔离度达到使用要求,满足圆偏振观测的需求。这种线偏振信号到圆偏振信号的转换方式不影响接收机的系统温度。  相似文献   

添加剂对放射性废物处置场中U及~(90)Sr的分配系数研究     

于静  吴勇  孙晋玉 《矿物岩石》2009,29(2)

通过滞留实验评价放射性废物处置场盖层不同基础物料与添加剂对放射性U与^90Sr的屏障效果,以确定不同基础物料及添加荆配合条件下U与^90Sr的分配系数Ka。滞留实验成果表明天然深褐色含腐殖质含角砾砂质亚粘土对U与^90Sr的Kd分别为1838．13和36．16,为良好的基础物料,添加Na2S和Na2CO3后可增大对^90Sr的滞留,添加碳质砂岩粉可增加对U的滞留。在还原条件下,洪积物及泥石流堆积物以及残积成因含角砾粉砂土基础物料在添加Na2S后,^90Sr的Kd为3069．30～3494．28;添加Na2CO3后,^90Sr的Kd为81．22～22203．6。洪积物及泥石流堆积物的泥、砂和砾石混合物、变质碳质粉砂岩风化物、残积成因砂质亚粘土和坡积物砂质亚粘土等4类基础物料添加FeS2、腐殖土后对U和^90Sr的滞留效果总体较差;净水剂、磷灰岩和粉煤灰3类添加剂对U和Sr的屏障效果以负面影响为主,不宜用作屏障添加剂。实验结果表明U与Sr的迁移-固定性能相反,在放射性元素迁移途径上宜分别建造U,Sr屏障,且优先处置U放射性元素。  相似文献   

河流相砂体识别预测及古气候响应: 以渤中坳陷石南地区明下段为例          下载免费PDF全文

李东伟  龚承林  王军  李一超  李虹  戈道瑶 《古地理学报》2022,24(4):742-758

河流相砂体的识别预测及其发育演化对古气候变化的响应是当前河流相沉积研究的热点。基于地震沉积学方法,采用三步走的河流相砂体识别预测方法(井震结合建格架→90°相位调整标岩性→切片属性辨砂体),在渤海湾盆地渤中坳陷石臼坨凸起南部(石南)新近系明化镇组下段(简称“明下段”)识别出了顺直和蜿蜒河道砂、河道—堤坝复合体、点砂坝、河口坝、牛轭湖和决口扇6种河流相砂体。依据明下段泥岩颜色,结合藻类种属记录和孢粉记录分析,认为石南地区明下段沉积早期到中期经历了干湿交替→湿润主导的湿润化气候演变; 而明下段沉积中期到晚期经历了湿润主导→干旱主导的干旱化气候演变。润湿化气候演变使得明下段沉积中期河流相砂体宽度和单层厚度减小、弯曲度增大,且带状孤立河道砂体更发育; 而干旱化气候演变使得明下段沉积晚期流相砂体宽度和单层厚度增大、弯曲度减小,且带状河道—溢岸复合带和河口坝砂更发育。研究成果可为其他断陷盆地河流相砂体识别、预测提供参考,对指导构造活动相对较弱的湖盆萎缩期油气勘探实践具有一定的实践价值。  相似文献   

基于ObjectARX的天津90坐标系图幅号算法及实现     

周海平  杨秋莲  张耕 《测绘与空间地理信息》2014,(11)

天津90图幅号算法入手,建立了一个基于ObjectArx2004的二次开发程序。通过加载ARX文件到Auto-CAD环境,能够实时、准确地计算出给定范围的图幅号。为此,对实际作业中的点、线、面和图幅号对象进行抽象,设计了新的基于面的图幅号算法,实现了AutoCAD环境下方便获取天津90图幅号。  相似文献