基于混沌时间序列的Volterra自适应滤波极移预报方法

针对极移复杂的时变特性, 根据混沌相空间坐标延迟重构理论, 提出一种基于Volterra自适应滤波的极移预报方法. 首先, 利用最小二乘拟合算法分离极移序列中的线性趋势项、钱德勒项和周年项, 获得线性极移、钱德勒极移和周年极移的外推值; 其次, 通过C-C关联积分法对最小二乘拟合残差序列进行相空间重构, 并利用小数据量法计算残差序列的最大Lyapunov指数验证其混沌特性, 在此基础上, 构建Volterra自适应滤波器对残差序列进行预测; 最后, 将线性极移、钱德勒极移和周年极移的外推值以及最小二乘拟合残差的预测值相加获得极移最终预报值. 利用国际地球自转服务局(International Earth Rotation and Reference Systems Service, IERS)提供的极移数据进行1--60d跨度预报, 并将预报结果分别与国际地球定向参数预报比较竞赛(Earth Orientation Parameters Prediction Comparison Campaign, EOP PCC)结果和IERS A公报发布的极移预报产品进行对比, 结果表明: 对于1--30d的短期预报, 该方法的预报精度与EOP PCC最优预报方法相当, 当预报跨度超过30d时, 该方法的预报精度低于EOP PCC最优预报方法, 优于参与EOP PCC的其他方法; 与IERS A公报相比, 该方法的短期预报效果较好, 当预报跨度增加时预报精度低于IERS A公报. 预报结果表明该方法更适合于极移短期预报.     

Sentinel-2密集时间序列数据和Google Earth Engine的潮间带湿地快速自动分类

潮间带湿地是滨海湿地的重要组成部分,具有维持生物多样性、促进碳汇等重要生态功能.及时、准确地掌握潮间带湿地现状是实现潮间带湿地可持续管理目标的基础.先前的潮间带湿地分类研究依赖于训练样本、人工设定阈值或后处理等,本研究基于GEE (Google Earth Engine)平台开发一种自动、快速、高精度的潮间带湿地分类方...     

藏东南帕隆藏布现今河流地貌特征及其晚第四纪演化

河流沉积与地貌对构造与气候的变化极为敏感,可记录区域构造活动、气候变化和环境演变等多方面的丰富信息。由于独特的构造背景与气候条件,帕隆藏布不仅成为雅鲁藏布水系水量最大的支流,而且其流域在藏东南地区占有重要的地位。帕隆藏布流域内地表过程活跃且河流地貌演化过程快速,是揭示青藏高原东南部构造地貌演化的重要载体。通过对该河流地貌的形态学和沉积学分析发现,帕隆藏布河流形态具有明显的线状特征,其干流近似直线展布,而主要支流呈羽状分布,两者多呈直角交汇,表明河流形态明显受到嘉黎断裂带的构造形迹控制。进一步利用光释光和14C定年方法,对帕隆藏布的晚第四纪河流地貌演化,尤其是干流和东久河支流的晚第四纪河流阶地进行研究后发现,末次冰期以来的气候变化导致帕隆藏布的晚第四纪河流地貌呈现出典型的分段式特征,根据海拔高度主要可划分为3段：1）海拔2 600 m以下的河谷地貌呈V形峡谷,河谷比降大,阶地沉积年龄均在9.0～2.0 kaBP间,沉积属性以河流相和坡积相为主,表明是全新世以来气候变暖条件下形成的;2）海拔2 600～3 300 m的中游段河谷呈冰蚀围谷盆地、U形槽谷等,河谷比降小,河岸谷坡坡度小,主谷两岸冰碛垄发育,存留了古冰缘地貌遗迹,阶地沉积属性以古湖相、冰水相及河流相为主,测年结果在29.8～10.9 kaBP和50.9～39.8 kaBP间,显示其曾经为末次冰期和冰消期冰缘湖泊体系,后被现今的帕隆藏布所贯通;3）海拔3 300 m以上河流地貌为典型的冰川U形槽谷,谷底平坦,发育现代冰湖,仅发育Ⅰ级阶地并上面覆有冰碛物堆积体,有末次冰期的冰缘地貌遗迹,但主要受周围海洋性冰川作用,呈现现代冰缘地貌特征。整体上看,帕隆藏布的现今河流地貌上、下游两端年轻,主要形成于全新世期间;中游的河流地貌出现较早,残留了末次冰期和冰消期的冰缘地貌特征,并保留了广泛的古冰湖相沉积物。因此,帕隆藏布现今的河流形态主要出现在末次冰期以来。     

地震引起地球自转速率变化的分析

由地震引起地球内部质量重新分布将影响地球惯量矩的变化，从而引起地球自转速率的变化，即日长的变化。一般说，大地震产生大的附加位移场。它对地球自转特性有较强的影响。本文采用Ｈａｒｖａｒｄ目录中１９７７－１９９４年间的地震有关参数，和根据地震激发地球自转的变化理论及Ｄａｈｌｅｎ和Ｌａｍ－ｂｅｃｋ推出有关公式计算了地震引起地球轴向惯量矩的变化。结果表明：由单个地震引起的日长变化要比观测值小几个量级，它的累积效应表现出长期的变化即日长减小，就是地震活动加速地球自转。地震使地球自转能量随时间稳定地增加。并表明，虽地震活动影响日长，但它不是十年尺度变化的主要原因，它可能是地球自转非潮汐加速机制之一     

基于Google Earth Engine的红树林年际变化监测研究

遥感技术已广泛应用于红树林资源调查与动态监测中,但仍然存在遥感数据获取困难、数据预处理工作量大、监测时间长而周期过大等问题,影响了学者对红树林演变过程的精细刻画与理解。本文基于Google Earth Engine（GEE）云遥感数据处理平台,选取Landsat系列卫星数据,生成长时间序列年际极少云影像集（云量少于5%）,利用3个红外波段反射率（NIR、SWIR1、SWIR2）和3个特征指数（NDVI、NDWI、NDMI）建立阈值规则集,实现对实验区越南玉显县红树林、红树林-虾塘、不透水面-裸地、水体4种目标地物的专家知识决策树分类和土地覆盖的制图,并基于分类结果监测该区域1993-2017年的红树林年际动态变化。结果表明：GEE平台可满足多云多雨地区红树林的长时间序列年际变化监测需求;本文阈值分类方法可以有效提取红树林及红树林-虾塘,实验区有86%年份的影像分类精度达到80%以上;年际变化监测可精细刻画实验区红树林面积先增后减再增的变化过程,也能准确反映红树林与红树林-虾塘养殖系统面积之间的负相关关系。红树林年际动态监测结果可以降低红树林演变分析的不确定性,并能更精细地量化红树林与其他土地覆盖类型的转化过程,从而评估经济发展、政策等因素对红树林演变的影响。     

Fe–Mg partitioning between ringwoodite and magnesiowüstite and the effect of pressure, temperature and oxygen fugacity

 The partitioning of Mg and Fe between magnesiowüstite and ringwoodite solid solutions has been measured between 15 and 23 GPa and 1200–1600 ^∘C using both Fe and Re capsule materials to vary the oxidation conditions. The partitioning results show a clear dependence on the capsule material used due to the variation in Fe³⁺ concentrations as a consequence of the different oxidation environments. Using results from experiments performed in Fe capsules, where metallic Fe was also added to the starting materials, the difference in the interaction parameters for the two solid solutions (W _FeMg ^mw−W _FeMg ^ring) is calculated to be 8.5±1 kJ mol⁻¹. Similar experiments performed in Re metal capsules result in a value for W _FeMg ^mw−W _FeMg ^ring that is apparently 4 kJ higher, if all Fe is assumed to be FeO. Electron energy-loss near-edge structure (ELNES) spectroscopic analyses, however, show Fe³⁺ concentrations to be approximately three times higher in magnesiowüstite produced in Re capsules than in Fe capsules and that Fe³⁺ partitions preferentially into magnesiowüstite, with K _{D Fe3+} ^ring/mw estimated between 0.1 and 0.6. Using an existing activity composition model for magnesiowüstite, a least–squares fit to the partitioning data collected in Fe capsules results in a value for the ringwoodite interaction parameter (W _FeMg ^ring) of 3.5±1 kJ mol⁻¹. The equivalent regular interaction parameter for magnesiowüstite (W _FeMg ^mw) is 12.1±1.8 kJ mol. These determinations take into account the Fe³⁺ concentrations that occur in both phases in the presence of metallic Fe. The free energy change in J mol⁻¹ for the Fe exchange reaction can be described, over the range of experimental conditions, by 912 + 4.15 (T−298)+18.9P with T in K, P in kbar. The estimated volume change for this reaction is smaller than that predicted using current compilations of equation of state data and is much closer to the volume change at ambient conditions. These results are therefore a useful test of high pressure and temperature equation of state data. Using thermodynamic data consistent with this study the reaction of ringwoodite to form magnesiowüstite and stishovite is calculated from the data collected using Fe capsules. Comparison of these results with previous studies shows that the presence of Fe³⁺ in phases produced in multianvil experiments using Re capsules can have a marked effect on apparent phase relations and determined thermodynamic properties. Received: 13 September 2000 / Accepted: 25 March 2001     

Experimental study on weathering of seafloor volcanic glass by bacteria (Pseudomonas fluorescens) – Implications for the contribution of bacteria to the water–rock reaction at the Mid-Oceanic Ridge setting

The biologically mediated weathering of the ocean crust has received increasing attention in recent decades, but the rates and the possible mechanism of elemental release during microbe–basalt interactions occurring below the seafloor have not been studied in detail. In this study, we established an experimental weathering study of seafloor natural basaltic glass comparing the effect of microbial activity (Pseudomonas fluorescens) in P-rich and P-poor media with parallel controls containing either nonviable cells or organic acid. The changes in the chemical parameters, including pH, bacterial densities, and ion concentrations (Ca, Mg, Si, Mn, Al, Fe, and P) in the solution, were examined during the different batch experiments. The results showed that the pH decreased from 7.0 to 3.5 and the bacterial density increased from 10⁵ to 10⁸ cells/ml during the first 120 h, and the cell numbers remained constant at 10⁸ cells/ml and the pH increased from 3.5 to 6 between 120 h and 864 h in the P-bearing reactors containing bacteria. In contrast, during all the experimental time, the pH remained close to neutral condition in the abiotic control systems and the dissolution rates increased markedly with a decrease in pH and became minimal at near-neutral pH in P-bearing reactors containing bacteria, where Ca, Si, and Mg release rates were 2- to 4-fold higher than those obtained in chemical systems and biotic P-limited systems. Furthermore, the surfaces of the natural volcanic glass from the biotic systems were colonized by bacteria. Simultaneously, the etch pits were observed by Scanning Electron Microscope, which further indicate that the bacteria may promote the mineral dissolution for energy gain. Some elements (e.g., Fe, Mn, and Al) releasing from natural volcanic glass are likely an important source of the elemental budget in the ocean, and thus the element release and its possible mechanism conducted in this experimental study have potential implications on the biogeochemical cycling process in the Mid-Oceanic Ridge setting.     

Google Earth支持下校园真实感三维建模方法及应用

以Google Earth为平台,结合SketchUp的建筑物真实感三维建模功能,以西南交通大学校园为例建立校园真实感三维模型,并对其应用进行分析。该方法实现地形数据与建筑物三维模型的精确叠加,解决建模过程中的数据获取和融合问题,为虚拟环境的构建提供具有参考价值的解决方案。     

气压变化及其对地壳形变和深井水位的影响

根据北京塔院地区1984和1985年的微气压计记录采用频谱分析和调和分析两种方法得出了大气潮谱的详细结构;用负荷勒甫数代替潮汐勒甫数,仿照固体潮的有关公式,导出了大气潮引起的地壳应变和地倾斜公式;使用北京塔院井的水位观测资料结合当地的气压资料,分析了气压变化对深井水位的影响.理论计算和实测资料的分析结果基本相符,特别是两种结果都得出S₂大气潮引起的体膨胀约为S₂固体潮体膨胀的20％.     

若尔盖县弯曲河流精细提取研究

利用Google Earth Engine遥感大数据云平台,以若尔盖县的弯曲河流为研究对象,以空间分辨率为10 m的Sentinel-2多光谱卫星遥感影像为数据源,选用归一化差分水体指数(NDWI)、改进型归一化差分水体指数(MNDWI)和自动水体提取指数(AWEI)相组合的方式,建立支持向量机模型,进行弯曲河流信息的提取;利用归一化差分水体指数、改进型归一化差分水体指数和自动水体提取指数,提取出弯曲河流信息,并与支持向量机模型提取的结果进行了比较。研究结果表明,利用归一化差分水体指数提取的弯曲河流的整体性和连续性最优;利用改进型归一化差分水体指数提取的地势复杂区域细小河流的精度较高;利用支持向量机模型提取的弯曲河流更为准确,并消除了山体和植物阴影对弯曲河流提取的影响;与利用3种指数提取的结果相比,支持向量机模型提取的弯曲河流的总体精度和用户精度都相对最高。