Simulation of interactions among multiple debris flows

Adjacent debris flows may interact in many ways: two or more concurrent debris flows may merge; one debris flow can run out over an existing debris flow fan. Such interactions may cause debris flow properties to change in the mixing process as well as more severe adverse effects than those caused by a single debris flow. This paper aims to investigate the interactions among channelized debris flows originated from adjacent catchments. Both concurrent and successive debris flows are considered. If several debris flows originate from different locations concurrently and merge, the volumetric sediment concentration (i.e., the ratio of the volume of solid material to the total volume of debris flow), C _v, is a good index to capture the mixing process of these debris flows. The change in C _v reflects where mixing occurs and the mixing degree. The debris flow properties (e.g., yield stress and dynamic viscosity) evolve in the mixing process and can be captured by the change in C _v. The debris flow with a larger volume dominates the mixing process, and the properties of the mixed debris flow are more similar to those of the larger debris flow. The inundated areas and runout distances of successive debris flows are smaller than those of concurrent debris flows of the same total volume due to the smaller scales of the individual events and blockage by the earlier debris flows. However, the deposit depth in the interacting part of the debris flow fans of successive debris flows can be much larger than that of concurrent debris flows, leading to more destructive cascading hazards (e.g., the formation of debris barrier lakes). The sequence of successive debris flows not only significantly influences the runout characteristics of the debris flows but also substantially affects the cascading hazards.     

川中磨溪—高石梯地区下寒武统龙王庙组层序格架内滩体的发育演化特征及对储层的控制

川中磨溪—高石梯地区龙王庙组可划分为两个三级层序。通过大量岩心、薄片以及测井资料综合分析,磨溪—高石梯地区龙王庙期整体属于局限台地沉积,可划分为台内滩、滩间洼地以及潟湖亚相。以台内滩颗粒含量、沉积构造以及单层滩体沉积厚度为基础,结合测井响应特征分析,将台内滩划分为滩核、滩翼以及白云岩坪等微相,并建立了台内滩的3种典型沉积序列:滩翼—滩核—白云岩坪、潟湖—滩间洼地—台内滩,以及滩间洼地—台内滩。层序格架内台内滩的纵横向发育特征表明:SQ_2时期较SQ_1时期更为发育,滩体单层厚度和总厚度均较大,层序界面附近的滩核—白云岩坪沉积序列上部为最有利的储层发育相带。     

尼日尔Termit盆地上白垩统Madama组地震相识别与沉积相演化分析

以层序地层学及沉积学理论为指导,综合运用测井、录井以及地震资料,将尼日尔Termit盆地上白垩统Madama组划分为一个三级层序(MS),并进一步识别出低位体系域、海侵体系域以及高位体系域。在等时层序地层格架内,识别出前积反射地震相、河道充填反射地震相、平行-亚平行反射地震相以及杂乱反射地震相等四种类型,并识别出辫状河三角洲的沉积相类型。认为层序MS的低位体系域主要发育辫状河三角洲前缘亚相,高位体系域则主要发育辫状河三角洲平原亚相。Madama组整体表现为一个海退的沉积演化过程。     

Dye adsorption on electrochemical exfoliated graphene oxide nanosheets: pH influence,kinetics and equilibrium in aqueous solution

Graphene oxide nanosheets were synthesized by electrochemical exfoliation. X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectrometry and Fourier transform infrared spectrometry were used to characterize crystal structure, particle size, thickness and function groups of the nanosheets. The nanosheets were examined for adsorption of methyl orange, an anionic dye, in aqueous solution at different pHs and temperatures. The maximum adsorption capacity of methyl orange on graphene oxide nanosheets obtained from the Langmuir isotherm was 138.69 mg/g at pH 2.0, which is larger than that of other carbonaceous adsorbents. The large adsorption affinity of graphene oxide nanosheets to methyl orange might be due to the presence of hydrogen bonding and π–π interaction between methyl orange and graphene oxide nanosheets. Adsorption kinetics followed a pseudo-second-order kinetic model, and the isotherm adsorption results were fitted with Langmuir isotherm model in a monolayer adsorption manner. The thermodynamic studies indicated that the adsorption reaction was a spontaneous physisorption process.     

Wavefield analysis of crosswell seismic data

Despite the numerous advantages of crosswell seismic data over surface seismic data, crosswell seismic geophysics is still underutilized and underdeveloped. The factors limiting the full utilization of crosswell data include the lack of standardized methods for processing and imaging the data. This is because crosswell data is not completely understood. To improve the understanding of crosswell data, we performed acoustic and elastic modeling of a west Texas carbonate oilfield data using finite difference methods and crosswell geometry. To account for the different wave modes in the field data, we decomposed the full data into its constituent wave modes. Results of the forward modeling show that elastic synthetic data is a better representation of crosswell field data than the popular acoustic synthetic data. Wavefield decomposition gave insight into the time-space kinematics behavior of the different wave modes that constitute the full data. Overall, the study improved our understanding of crosswell field data. The learning from this study has been utilized to perform data-driven reflection enhancement processing where the discerned characteristic of different seismic arrival is utilize to suppress unwanted and enhanced the desired wave modes. The processing reduced the complex data to only up-going P-P reflections that can be imaged to reveal the subtle geological structures of the oilfield.     

The diagenetic geochemistry and contamination assessment of iron,cadmium, and lead in the sediments from the Shuangtaizi estuary,China

Sediment and pore water samples have been collected from the coastal tidal flat in the Shuangtaizi estuary, China, in order to investigate the geochemical behavior of iron, cadmium, and lead during diagenesis and to assess the degree of contamination. The calculated enrichment factors and geoaccumulation indices for separate elements show that anthropogenic activities have had no significant influence on the distribution of Fe and Pb in the study area, whereas the distribution of Cd has been closely influenced in this way. The high percentage of exchangeable Cd (average of 56.34%) suggests that Cd represents a potential hazard to benthic organisms in the estuary. The calculated diffusive fluxes of metals show that the most mobilized metal is Fe (9.22 mg m^?2 a^?1), followed by Cd (0.54 mg m^?2 a^?1) and Pb (0.42 mg m^?2 a^?1). Low Fe²⁺ contents in surface pore water, alongside high chromium-reducible sulfur contents, and low acid-volatile sulfur, and elemental sulfur contents at 0–25 cm depth in sediments show that Fe²⁺ is formed by the reduction of Fe oxides and is transformed first to a solid phase of iron monosulfides (FeS) and eventually to pyrite (FeS₂). The release of adsorbed Pb due to reductive dissolution of Fe/Mn oxides during early diagenesis could be a source of Pb²⁺ in pore water. From the relatively low total organic carbon contents measured in sediments (0.46–1.28%, with an average of 0.94%) and the vertical variation of Cd²⁺ in pore water, sulfide or Fe/Mn oxides (instead of organic matter) are presumed to exert a significant influence on carrying or releasing Cd by the sediments.     

中国天山积雪对气候变化响应的多通径分析

基于天山山区1961-2013年60个气象站点实测气温、降水、相对湿度、日照时数和积雪深度等气候资料,结合时间序列分析、空间分析以及通径分析等方法,全面精确地获取了天山山区气候变化特征以及气候变化对积雪的通径影响。结果表明：天山山区气候变化显著,主要表现为整体增暖、局部变湿与黯化;气候变暖导致天山山区固态降水（降雪）保证率明显降低,尤其是低海拔区域。各气象要素对积雪不仅存在直接的单因素影响而且各气象要素之间还存在间接的相互交叉、相互联结的多因素影响。单因素影响通径分别为气温、降水和日照时数对积雪深度的3条直接影响通径;多因素影响通径分别为气温、降水和日照时数通过相互之间的内在关系对积雪深度产生的6条间接影响通径。最终结果表明气温是积雪变化的主要影响因素,其影响效应远远大于降水和日照时数的影响。     

汾河源区生态系统服务价值的时空变化

运用GIS和遥感技术分析了汾河源区宁武县1990、2000、2010年的土地利用/覆被时空变化特征,并参照中国不同陆地生态系统单位面积服务价值,分析了该区域生态系统服务价值的时空变化。结果表明:1990-2010年,研究区生态系统服务价值共损失0.34×10⁸元,且损失量和损失幅度呈增加趋势;研究区东北到西南方向上的大片低海拔区域生态系统服务价值减幅较大,主要与该区域频繁的人类活动有关,而高海拔山区减幅较小或略有增加。气候暖干化、过度放牧和建设用地增加引起的草地和水域减少是导致研究区生态系统服务价值减少的主要原因。     

毛乌素沙地西南缘灌丛沙丘沉积物的粒度和元素特征

对毛乌素沙地白刺(Nitraria tangutorum)灌丛沙丘沉积物粒度和元素特征进行了采样分析.结果表明:灌丛沙丘沉积物来源单一,几乎全部由丘间地物质组成,其粒度和元素特征与丘间地物质极其相似;相对而言,灌丛沙丘沉积物比丘间地物质含有更多粗颗粒物,主要因丘间地可做跃移运动的中沙和细沙更易被灌丛阻挡而堆积;灌丛沙丘沉积物中大部分元素含量比丘间地物质低,主要因这些元素易被淋溶迁移到丘间地富集;灌丛沙丘发育以来,虽然其沉积环境存在波动,但相对稳定,未发生过显著变化.     

荒漠草原不同植被盖度区面积对降水的响应

降水波动是气候变化的主要指标之一,其在半干旱荒漠草原区植被变化中起着主要的驱动作用。在考虑到年降水量与生长期降水量的前提下,本文通过地面植被盖度反射光谱模型构建和基于3S技术的区域植被盖度分布格局反演,分析了荒漠草原不同植被盖度分布面积对降水的响应。结果表明:在荒漠草原区,不同植被盖度的区域面积和年降水量、生长期降水量呈波动变化。年降水量和生长期降水量与不同植被盖度区域面积可以拟合成线性、幂函数、指数和对数函数曲线关系。植被盖度小于10%的区域面积随着降水量的增加而下降,植被盖度大于10%区域面积随着降水量的增加而增加,盖度10%是低盖度与高盖度间相互转化阈值。当植被盖度为<2%、2%～6%、10%～15%、15%～20%、20%～25%时,拟合的曲线关系能较好地表达不同植被盖度区域面积随降水量变化的趋势(p< 0.01)。荒漠草原不同植被盖度区域面积的波动变化主要与多根葱、阿尔泰狗娃花、松叶猪尾菜和小画眉草等草本植物生长响应降水变化密切相关。