小波二叉分解在信号压缩处理中的应用

讨论了小波在信号压缩中由于正交离散小波变换缺乏平移不变性,会对信号压缩的性能造成不利的影响.为了解决这一问题,在讨论正交离散小波变换时对每个变换尺度上均对偶采样和奇采样的结果进行保留,从而衍生出了二叉树结构,按相应准则可以确定最优分解路线并由此可重构原信号,最后给出的仿真结果证实了该变换方式较标准正交离散小波变换在取得较高压缩能力的同时,具有更高的信噪比.     

2008年冬季西太平洋表层海水浮游藻类分布特征——分子有机地球化学研究

通过对西太平洋海区表层海水颗粒物的过滤收集,利用有机地球化学方法,提取了与浮游植物相关的脂类分子,如菜子甾醇、甲藻甾醇、直链烯酮、长链二醇,分别对应于硅藻、甲藻、颗石藻、黄绿藻,分析探讨了以浮游植物生物标志物为基础的海洋生物群落和生物量的变化特征及其影响因素。研究结果表明,利用脂类标志物方法所得生物量与海洋叶绿素分布有较好的对应关系,是一种有效的重建海洋浮游植物生产力与群落结构的方法。该区域浮游植物生物分布呈明显的区域特征,长江河口陆架区域最高,其次为新几内亚群岛东部沿岸区和菲律宾群岛沿岸,而远洋区域最低。造成该结果的主要因素是河流、洋流以及区域地貌、沉积物再悬浮。硅藻由于其对营养物质的竞争优势,丰度普遍较高,其次为甲藻,而颗石藻、黄绿藻含量较低。该研究成果不仅可用于现代海洋生态结构变化的检测,更将为利用脂类分子进行古海洋群落结构的真实重建提供重要的科学依据。     

格尔木流体观测井数字资料映震效能分析

介绍了格尔木流体观测井及数字化仪器的基本情况,对数字化观测资料进行了初步分析,并分析了格尔木周边3次6级以上地震前的异常特征,结果显示:同一方法提取的异常在不同地震前差别较大,且异常可能与区域构造相关。对于该观测井不同测项,震前的异常差异也较大。     

基于GIS的无参数地图投影转换技术研究

基于GIS理论和技术平台,通过模拟—试验—再模拟—再试验,较好地解决了无参数地图投影转换这一难题,这将为地学、生物学等相关领域提供可贵的基础地理底图资料。尤其在教学地图中,它可以向学生展示全球地貌形态和景观格局,并可以利用它编制各种专题教学地图,便于学生学习各种地理知识,理解、分析复杂的地理现象。     

Satellite Measurements of the Madden–Julian Oscillation in Wintertime Stratospheric Ozone over the Tibetan Plateau and East Asia

We investigate the Madden–Julian Oscillation(MJO) signal in wintertime stratospheric ozone over the Tibetan Plateau and East Asia using the harmonized dataset of satellite ozone profiles. Two different MJO indices — the all-season Real-Time multivariate MJO index(RMM) and outgoing longwave radiation-based MJO index(OMI) — are used to compare the MJOrelated ozone anomalies. The results show that there are pronounced eastward-propagating MJO-related stratospheric ozone anomalies(mainly within 20–200 h Pa) over the subtropics. The negative stratospheric ozone anomalies are over the Tibetan Plateau and East Asia in MJO phases 4–7, when MJO-related tropical deep convective anomalies move from the equatorial Indian Ocean towards the western Pacific Ocean. Compared with the results based on RMM, the MJO-related stratospheric column ozone anomalies based on OMI are stronger and one phase ahead. Further analysis suggests that different sampling errors, observation principles and retrieval algorithms may be responsible for the discrepancies among different satellite measurements. The MJO-related stratospheric ozone anomalies can be attributed to the MJO-related circulation anomalies,i.e., the uplifted tropopause and the northward shifted westerly jet in the upper troposphere. Compared to the result based on RMM, the upper tropospheric westerly jet may play a less important role in generating the stratospheric column ozone anomalies based on OMI. Our study indicates that the circulation-based MJO index(RMM) can better characterize the MJOrelated anomalies in tropopause pressure and thus the MJO influence on atmospheric trace gases in the upper troposphere and lower stratosphere, especially over subtropical East Asia.     

川北旺苍苍王峡龙潭子河壶穴形态及成因初探

河成壶穴是山区河床基岩上常见的微地貌类型,记录了区域地貌演化过程、水流与河床边界相互作用的关键信息。基于此,本文以川北旺苍苍王峡龙潭子河110处河成壶穴为研究对象,详细测量其形态特征并进行统计分析。结果表明：非串珠状壶穴大小、深度及形态在河床纵剖面上的分布没有明显的规律性,而串珠状壶穴具有一定的规律性;壶穴集中分布在下寒武统阎王碥组硅质砾岩中,其中发育的石英砂岩夹层对壶穴的形成和演化起到了关键性作用,双层天生桥壶穴则是典型的代表;区内发育NE、E—W向平面共轭X型构造节理和S—N向构造节理,三角形、菱形、不规则形壶穴多受两组或 3 组节理控制,其中S—N向构造节理还控制了壶穴的长轴走向和河谷走向;构造节理对壶穴口形态的演化影响显著,而对壶穴垂直剖面形态的影响不显著。本研究将丰富和完善河成壶穴地貌的数据资料,为米仓山地区河流地貌和构造演化提供科学依据。     

Biomolecular Preservation of Miocene Fossil Liquidambar from Tiantai, China and Clarkia, USA: Implications for Palaeoenvironmental Study

Biomolecular characteristics of fossil Liquidambar from the Miocene Shengxian Formation, Tiantai, Zhejiang province in eastern China and Miocene Clarkia sediment, Idaho, U.S.A., are obtained by means of Pyrolysis-Gas chromatography-Mass spectrometry analysis (Py-GC-MS). Their modern equivalent (Liquidambar formosana) collected from Nanjing, eastern China, is also analyzed for comparison. The total ion chromatograms (TIC) of modern L. formosana leaves shows abundant pyrolysates of lignin, polysaccharide, aliphatic acid, and amino acid. However, only one polysaccharide molecule, i.e., levoglucosan, is retained in fossil Liquidambar leaves from the two Miocene sites with the Tiantai specimen possessing higher intensity. As expected, some lignin pyrolysates including benzene, phenol, guaiacol, vinylphenol and their derivatives, are detected in Miocene Tiantai L. miosinica. However, the lignin components with large molecular weight other than benzene and phenol compounds, are absent in Miocene Clarkia L. pachyphyllum. Abundant pristene and homologous series of n-alk-1-ene/n-alkane pairs with a long retention time are shown in pyrograms of both Tiantai and Clarkia fossils. Based upon our Py-GC-MS data, the molecular preservation in these Liquidambar leaf samples can be ranked as the following (from high to low quality respectively): modern sample >Tiantai sample >Clarkia sample. Vinyl phenol, an important compound, is present in modern and Tiantai Liquidambar leaves, while absent in Clarkia sample, implying that vinyl phenol may be sourced from lignin for Liquidambar leaves. Our data support the hypothesis of in situ polymerization for the origin of long-chain homologous series of n-alk-1-ene/n-alkane pairs as leaf alteration products. Our data have implications of the impact of leaf degradation toward biases for palaeoenvironmental reconstruction using stable carbon isotope of fossil plants, and suggest the importance of evaluating molecular preservation of fossil leaf tissues prior to the application of carbon isotope compositions of fossil leaves.     

基于弹性系数法的径流对气候变化与人类活动响应研究

基于永定河流域内1957~2010年降雨、蒸发和径流数据,采用Mann-Kendall趋势检验法结合距平序列变化情况分析蒸发能力、降雨和径流的变化趋势;运用Mann-Kendall突变检验法、Hurst系数法分析流域径流序列的突变年及对应的突变程度;在此基础上以径流突变年为界划分基准期和变化期,采用弹性系数法定量分析气候变化和人类活动对径流的影响,并简要分析其原因。结果表明:流域蒸发能力呈现上升趋势,降雨和径流呈现递减趋势;径流序列突变点发生在1984年,突变程度属中度变异;永定河流域由气候变化引起的径流变化率为28%,而由于人类活动引起的径流变化率为72%,可见人类活动是影响永定河流域径流变化的主要驱动因素。     

2018年5月6日称多5.3级地震序列重定位及发震构造分析

采用双差定位法对2018年5月6日称多5.3级地震及其余震序列进行重新定位,至2018年7月15日共获取129个地震的重新定位结果。结果显示,称多5.3级地震序列主要呈NWW或NNW向分布,其中长轴沿NWW向展布,长约11 km,震源深度主要分布在6-12 km范围内,优势分布为8-11 km。此次地震的震源机制解为走滑型,最佳波形拟合深度为10.1 km。结合精定位、震源机制等综合分析,认为主破裂面走向呈NNW向,发震构造应为巴颜喀拉山主峰断裂。     

A visualization approach for discovering colocation patterns

Colocation mining is one of the major spatial data mining tasks. When discovering colocation patterns, spatial statistics or data mining approaches are commonly used. Colocation mining results are typically presented in a textual form and do not provide any spatial information; thus, the results lack an intuitive approach to obtain cognition of colocation rules. Here, we propose a visualization approach to discover colocation patterns for two independent point distributions and generate visual results. This approach makes use of the ability of human color perception. For two geographic features, our approach first generates density surfaces of the input features and then visualizes the density surfaces using a red or green light with different intensities. Then, based on the law of additive color mixing, our approach mixes the colors of the two density surfaces to generate a colocation rule map. The visualization approach can also provide local details of colocation and be used for local colocation analysis. Users can detect colocation patterns and their distribution from the colocation rule maps. We use both synthetic data and real data to test the performance of our approach.