基于光谱混合分析的毛乌素沙地油蒿群落覆盖度提取

油蒿群落覆盖度是判断毛乌素沙地荒漠化程度严重与否的直接指标,其信息的准确获取有助于更为合理的荒漠化监测与评价。本研究以Landsat ETM 为数据源,深入探讨了光谱混合分析过程中影像预处理、端元选取、光谱混合模型选择及光谱混合分析结果分析等关键问题,给出了恰当的解决方案,进而进行了油蒿群落覆盖度的提取,并通过野外实测数据对提取结果进行了验证。验证结果表明:基于光谱混合分析技术提取的油蒿群落分量与实测油蒿群落覆盖度线性相关显著,相关系数为0.88,因而研究区的油蒿群落覆盖度可以通过油蒿群落分量的线性变换得到。因此,光谱混合分析是提取毛乌素沙地油蒿群落覆盖度的有效技术。     

北秦岭西峡骨头崖花岗岩锆石U-Pb定年、地球化学特征及地质意义

骨头崖花岗岩位于北秦岭构造带东部,西峡县北部,对其开展岩石成因研究有助于深入认识燕山期北秦岭豫西南段深部构造演化。岩体定年样品(GTY01)为中粒斑状黑云母二长花岗岩,30个锆石测点中有25个测点的U-Pb同位素测定值位于或者接近~(207)Pb/~(235)U–~(206)Pb/~(238)U一致线,23个测点的~(206)Pb/~(238)U年龄介于108.4±0.9Ma~114.3±1.0Ma之间,其加权平均年龄为111.7±0.6Ma(MSWD=1.4),代表了骨头崖花岗岩的形成时代。锆石稀土元素具有轻稀土亏损、重稀土富集、Ce正异常及负Eu异常的特征,形成温度介于626℃~769℃之间,岩体的锆石/熔体中重稀土元素特征表明,其形成过程中经历了岩浆混合作用。骨头崖花岗岩为富硅、碱和贫钙、镁的高钾钙碱性系列。岩体富集Rb、Th和亏损Nb、Ta、Ti。岩体的稀土配分模式具有右倾、轻稀土富集、重稀土亏损和负Eu异常的特征,(Eu值介于0.48~0.60之间,(La/Yb)_N范围为5.82~11.19,源区组成和部分熔融程度控制了骨头崖花岗岩的成分变异。骨头崖花岗岩形成于厚度为~40km的地壳内,其部分熔融源区为角闪岩相,部分熔融残余相主要为角闪石和斜长石。骨头崖花岗岩是岩石圈拆沉作用所触发的岩浆底侵作用的产物,从源区岩石部分熔融到最终上侵固结成岩耗时~15Ma,它是岩石圈拆沉作用滞后的岩浆响应。     

Interactions of uranium with bacteria and kaolinite clay

We assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8 × 10^− 6 M- and 4 × 10^− 4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH₃COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4 × 10^− 4 M U was analyzed by transmission electron microscope (TEM) equipped with EDS. The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH₃COOK, removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM–EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amount of uranium.     

大龙山岩体和城山岩体的铅同位素组成特征及其成因探讨

详细研究了大龙山岩体和城山岩体钾长石的铅同位素组成,并参考这些岩体的黑云母化学成分、锶同位素、稀土元素、岩石化学和地球物理资料,发现它们是多阶段侵入的复式岩体,与庐枞火山岩系有渊源关系,属燕山晚期岩浆活动的产物。它们的初始成岩物质来源于上地幔部分熔融,岩浆上升侵位过程中已不同程度地受到了上部地壳的混染。经计算,其中约有61.6％的铅来自上地幔,约有38.4％铅来自上地壳,该区陆壳的乎均年龄约26亿年,陆壳在演化过程中具有富铀的趋势。这些岩体与深大断裂和地幔隆起有成因上的密切联系。     

Effects of periodic saturation on K0 for a sandstone-mudstone particle mixture

Abstract

Sandstone-mudstone particle mixture (SMPM) is one of the main materials, which has been widely used for filling in and around reservoirs for water conservation projects. During the periodic rising and falling of the water level, the fill material for the embankments, dam, and other waterfront features will also undergo drainage-saturation cycles. The deformation and coefficient of lateral pressure at rest K₀ may be affected by periodic saturation. In this study, a device is modified for testing the K₀ for gravel-soil under periodic saturation. In order to investigate the effects of periodic saturation on K₀, a series of experiments were performed for SMPM under different vertical stress and saturation cycling. K₀^N values of SMPM containing 20% mudstone particles under periodic saturation were obtained. The results shows that the K₀^N initially increased, but eventually reached a stable value with the increasing number of periodic saturation cycles. The magnitude of the coefficient increment was also found to be related to the stress condition. K₀^N is a logarithmic function of the saturation cycling time. By calculating K₀^N with the proposed empirical formula, the deformation and stress distribution of the SMPM filler in waterfront engineering works can be calculated with greater precision.     

The derivation of an Arctic sea ice normal through temporal mixture analysis of satellite imagery

The use of temporal mixture analysis (TMA) for creating a long-term baseline, or environmental “normal” is described. TMA is a promising analysis method derived from the hyperspectral image processing technique of spectral mixture analysis (SMA). TMA is algebraically identical to SMA, except that it is applied to temporal spectra rather than to electromagnetic spectra. TMA has particular potential to extract climate signals from long image sequences.     

Effects of periodic saturation on stress–strain relationship of a sandstone mixture

While a crushed sandstone particle mixture, usually used as an engineering fill, is filled along bank of or in a large reservoir, it is subjected to periodic saturation induced by filling-drawdown cycles of reservoir water. The periodic saturation may induce post-construction settlement, and reduce stability of the filled body. In order to evaluate the effects of periodic saturation on stress–strain relationship of the mixture, several triaxial tests are carried out. According to experimental data, the periodic saturation may induce an increment of axial strain (Δε; <0.226%), a decrement of crest of deviator stress (Δ(σ₁?σ₃)_f; <0.192?MPa) and a decrement of angle of shearing resistance (Δφ; <3.70°). With increment of the number of periodic saturation cycles, the variations of the three parameters may be fitted by logarithmic curves. And with increase in the stress level for periodic saturation, the variations of the three parameters may be fitted by straight lines. Three fitting equations to predict the three parameters’ values, and an equation to calculate the settlement induced by the periodic saturation of a large-area filled foundation, are suggested.     

Discriminating lava flows of different age within Nyamuragira’s volcanic field using spectral mixture analysis

In this study, linear spectral mixture analysis (LSMA) is used to characterize the spectral heterogeneity of lava flows from Nyamuragira volcano, Democratic Republic of Congo, where vegetation and lava are the two main land covers. In order to estimate fractions of vegetation and lava through satellite remote sensing, we made use of 30 m resolution Landsat Enhanced Thematic Mapper Plus (ETM+) and Advanced Land Imager (ALI) imagery. 2 m Pleiades data was used for validation. From the results, we conclude that (1) LSMA is capable of characterizing volcanic fields and discriminating between different types of lava surfaces; (2) three lava endmembers can be identified as lava of old, intermediate and young age, corresponding to different stages in lichen growth and chemical weathering; (3) a strong relationship is observed between vegetation fraction and lava age, where vegetation at Nyamuragira starts to significantly colonize lava flows ∼15 years after eruption and occupies over 50% of the lava surfaces ∼40 years after eruption. Our study demonstrates the capability of spectral unmixing to characterize lava surfaces and vegetation colonization over time, which is particularly useful for poorly known volcanoes or those not accessible for physical or political reasons.     

土石混合料的结构分类

探讨了振动三参数：离心力、激振频率和名义振幅对土石混合料振动压实效果的影响,提出了两种对比工艺。并根据土石混合料在同一振动工艺下的压实特性,指出土石混合料具有三种结构类型,以最大干密度为判据,含石量为指标进行了结构分类,给出了分类区间。     

顾及时变非高斯噪声的高斯和滤波及其导航应用

高斯和滤波可利用高斯混合模型精化非高斯嗓声随机模型来提高估计精度,但导航测量环境的动态性和复杂性使非高斯噪声具有时变性特征,若GMM不随之调整会导致滤波解算失真.针对该问题,本文提出一种基于位移参数自适应估计的高斯和滤波算法.首先分析GMM位移参数对非高斯噪声拟合精度的影响,然后利用位移参数自适应技术修正GMM,进而改...