小刺豆荚软珊瑚化学成分研究

对采自南海南沙群岛永暑礁水域的小刺豆荚软珊瑚Lobophytummicrospiculatum的化学成分进行了研究,分离出7个化合物。其中化合物1为新的神经酰胺,命名为小刺酰胺。化合物3为22－表－孕马烷甾醇,首次从软珊瑚中分离到。     

象山港潮波响应和变形研究 Ⅱ.象山港潮波数值研究

通过象山港水域的潮波运动数值模拟,分析了象山港M4分潮的生成和增长机制．结果说明,潮波传播中的非线性底摩擦效应是M4分潮生成和增长的主要控制因子,M4分潮在湾内的共振现象也起着重要的放大作用二平流效应在绝大部分区域中抑制了M4分潮的发展,只有在佛渡水道中一些岛屿周围极小区域内对M4分潮有增强作用．潮滩在湾内对M4分潮的影响极其微弱．     

陕西周户地区“秦岭群”的解体

根据区内传统秦岭群包含不同原岩建造、不同变质岩石组合以及变形变质、副矿物和微量元素特征的差异，将其解作为丹凤岩群、深成侵入体、浅成一超浅成侵入体、片麻岩套等5个部分，首次区分出两类不同性质的混合岩，确认了秦岭群在该区的存在。     

PRB反应介质火山渣净化石油类污染地下水特性

以石油类污染地下水为研究对象、火山渣为天然活性可渗透反应格栅(PRB)反应介质,进行净化总石油烃(TPH)的性能和作用机理的研究。颗粒分级实验表明:粒径为0.25～2.00 mm的火山渣,对TPH及特征污染物苯、萘、菲、十八烷的去除效果均为80%以上。吸附动力学和等温吸附模型研究结果表明:吸附过程遵循准二级动力学模型,等温吸附模型符合Langmuir等温吸附方程,理论上最大吸附量为1.7mg/g。联合场发射扫描电子显微镜、傅里叶变换近红外光谱仪、X射线衍射仪、X射线荧光光谱分析仪进行作用机理分析。研究结果表明:火山渣的蜂窝状孔隙和突起有利于物理吸附作用,火山渣赋存硅盐促进了化学吸附作用,水体中烃类有机化合物和火山渣在微观尺度上的有效碰撞对火山渣中的[SiO4]4-四面体结构产生微扰,同时烃类有机官能团与[Si-O]、[Si-H]键间发生了分子间键合作用。     

气候变暖背景下青藏高原山地灾害及其风险分析

基于青藏高原1930-2010年山地灾害实例,分析了气候变暖对青藏高原山地灾害的影响。结果表明：在气候变暖背景下,冰湖溃决灾害增多,冰川泥石流趋于活跃,特大灾害出现频繁,灾害链生特征明显,表现出时间和空间上的延拓性,巨灾发生概率增大;在藏东南地区表现出雨热同期的气候特征,构成了利于冰川类泥石流形成的条件;波密县城位于两条泥石流危险区的建筑物占地面积由1988年0.014 km²扩展到2012年1.004 km²,人口与经济密集区与灾害高风险区重叠,加之气候变化导致的灾害危险性增加,青藏高原灾害风险显著增大。上述结果提供了气候变化对青藏高原山地灾害影响的证据,初步阐述了其影响特征,有助于山地减灾和进一步认识气候变化对山地灾害的影响机理。     

An Analytical Method for Groundwater Inflow into a Drained Circular Tunnel

Groundwater inflow estimation is essential for the design and construction of tunnel and the assessment of the environmental impacts. Analytical solutions used in current engineering practice do not adequately account for the effect of the excavation‐induced drawdown, which leads to significant change in pore water pressure distribution and reductions of the water level beyond tunnel. Based on the numerical analysis results, this article proposes semianalytical method to predict the height of lowered water level and groundwater tunnel inflow. The tunnel problem is conceptualized as two‐dimensional flow in a plane perpendicular to the tunnel axis. The analytical formula, considering the effect of the excavation‐induced drawdown, provides a better prediction of the tunnel inflow compared to the existing analytical formulas, even for the cases with inclined groundwater level.     

地球磁场对太阳风的加载响应与地震

地磁预报地震的方法越来越多,本文应用加卸载响应比方法,分析山西地区2009—2016年观测的加卸载响应比与山西地区4.0级地震之间的对应关系,初步给出适用于山西地区震例特征的磁异常判别指标。     

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.     

A new multipath mitigation method based on adaptive thresholding wavelet denoising and double reference shift strategy

Multipath disturbance is one of the major error sources in high-accuracy positioning for global navigation satellite system (GNSS). Although various methods based on software and hardware strategies have been developed to mitigate this error, they are still limited by different kinds of factors and the effect is not ideal. After analyzing the existing methods, a new single-difference sidereal filtering method, based on adaptive thresholding wavelet denoising and double reference shift strategy (ATDR), is proposed to mitigate multipath effects for static short-baseline GNSS applications. The key idea of the proposed method is the use of both the adaptive thresholding wavelet denoising to extract an accurate multipath correction model from the reference Day and the double reference shift strategy to mitigate multipath for subsequent Day 2 more accurately and efficiently. By applying the introduced adaptive thresholding method, the average improvement rate of the RMS values of the single-difference residuals can reach about 15.82% compared with the constant thresholding method. Moreover, after applying the proposed ATDR method, the 3D positioning precision is improved by about 37.73% for the single epoch mode with 30 s data sampling rate and about 31.22% for the continuous mode with 1 s high sampling rate compared with the original results. Even compared with the constant thresholding single orbital reference (CTSR) method, the improvement percentage is about 33.94% in single epoch mode and about 25.40% in continuous mode for 3D positioning precision, respectively. In conclusion, the results of the two experiments indicate that the proposed ATDR method performs much better than the CTSR method in mitigating multipath for different sampling rates and different processing modes in the measurement domain for GNSS static short-baseline postprocessing applications.