成灌高铁运行对成都地磁台观测数据干扰测试

成都地磁台距成灌高铁运行线路垂直距离约1.5 km,使用数字化磁通门磁力仪GM4,在轨道沿线不同距离处进行野外测试。测试结果表明,轨道交通的运行对周围地磁观测环境产生干扰,干扰距离约6 km,干扰主要来自轨道泄露电流及输电线路产生的磁场。     

The influence of tectonic subsidence on volcaniclastic sedimentation: The Cretaceous upper Daeri Member,Wido Island,Korea

The Daeri Member, a Cretaceous volcanic–sedimentary succession, can be divided into lower, middle, and upper parts based on vertical changes in its lithologic characters. The lower Daeri Member is composed of siliciclastic deposits formed in a semi‐arid floodplain environment, which is overlain by the middle Daeri Member consisting mainly of andesite lava flow. After the emplacement of the andesite, activities of intrabasinal normal faults created accommodation on hanging wall blocks together with the development of intrabasinal topographic relief. The upper Daeri Member occurs only in hanging wall blocks and is composed of rhyolitic volcaniclastic sediments formed during an explosive volcanic eruption. Following the eruption, owing to semi‐arid climatic conditions and the destruction of vegetation, the eruptive materials were easily remobilized and deposited by episodic sediment gravity flows, resulting in deposition of the resedimented volcaniclastic deposits with sheet‐like geometry. Away from the intrabasinal normal faults, the resedimented volcaniclastic deposits show a decrease in grain size together with changes in inferred depositional processes from debris flows to hyperconcentrated flows and supercritical sheetfloods. This suggests that the resedimented volcaniclastic deposits were stacked on alluvial fan environments induced by intrabasinal topographic relief associated with normal fault activities. In addition, episodic movement of the faults gave rise to periodic fluctuation of the accommodation and an increase in gradient of the alluvial fan surface, resulting in the development of coarsening‐upward trends in the resedimented volcaniclastic deposits. The development of the alluvial fan and the coarsening‐upward trends indicate that dynamic tectonic subsidence and concomitant changes in the intrabasinal physiographic relief influenced the depositional processes and sizes of the transported volcaniclastic sediments of the upper Daeri Member. Thus, it is necessary to carefully observe tectonic signatures in volcaniclastic successions, particularly the syneruptive lithofacies, in order to reconstruct the tectonic and volcanic histories of receiving basins.     

基于全局弱式无单元法直流电阻率正演模拟

全局弱式无单元法是在有限单元法基础上发展起来的一种数值模拟方法,它采用局部支持域内的节点信息来构造形函数实现局部精确逼近,摆脱了单元,仅依赖于节点信息,具有预处理简单、模拟精度高、灵活性强的特点,适用于复杂地电条件下直流电阻率正演模拟.本文采用RPIM构造直流电阻率全局弱式无单元法形函数,利用RPIM形函数推导了直流电阻率全局弱式无单元法方程.然后,编制了直流电阻率全局弱式无单元法正演模拟Fortran程序,利用该程序对典型的地电模型进行了正演模拟,并将正演结果与基于线性插值的FEM正演结果及解析解进行对比,结果表明采用RPIM形函数的全局弱式无单元法用于直流电阻率正演模拟的正确性及有效性,且在同等条件下,全局弱式无单元法模拟精度高于矩形剖分的FEM,更有利于指导电法勘探的数据解译;利用该程序对复杂地电模型进行了正演模拟,结果表明全局弱式无单元法对复杂地电模型模拟效果良好,适应性强,灵活性高,可任意加密节点提高模拟精度.     

Consumption,growth and survival of the endemic stream shredder Limnephilus atlanticus (Trichoptera,Limnephilidae) fed with distinct leaf species

Oceanic freshwater communities tend to be species poor but rich in endemism due to their physical isolation. The ecology of endemic freshwater species is, however, poorly known. This study assessed allometric relationships, feeding preferences, growth and survival of larvae of the endemic stream insect Limnephilus atlanticus (Trichoptera, Limnephilidae) exposed to four leaf species differing in their physical and chemical characteristics (Ilex perado, Morella faya, Alnus glutinosa and Clethra arborea), in laboratory trials. All regression models used to estimate L. atlanticus dry mass from body and case dimensions and wet mass were significant, but wet mass and body length were the best predictors. Limnephilus atlanticus consumed all the four leaf species offered, but when given a choice, shredders significantly preferred A. glutinosa over the other three leaf species. Relative larval growth rate was significantly higher when L. atlanticus fed on A. glutinosa and I. perado leaves in comparison with the other leaf species. Survival of 95% was found when individuals fed on A. glutinosa leaves while it decreased to 75% when they fed on the other leaf species. Our results suggest that L. atlanticus can be an active shredder and that it exhibits the same basic patterns of food exploitation as its continental counterparts. The lack of an effect of shredders on litter decomposition in Azorean streams revealed by previous studies may thus be due to low densities or to a preference for food resources other than the low quality native litter species.     

立柱直径比对四立柱平台涡激运动性能影响的数值研究

与单立柱平台(Spar)类似,四立柱平台在洋流作用下也容易发生涡激运动,对锚泊和立管系统的疲劳寿命产生不利影响。一种非对称半潜式平台具有两种不同尺寸的立柱,立柱直径比对非对称平台涡激运动性能的影响尚需深入研究。采用计算流体力学(CFD)方法,对直径比分别为1.0、1.5和2.0的立柱组合在两种不同角度水流作用下的运动响应进行了二维数值模拟,分析发现:立柱直径比不为1时四立柱平台也具有明显的涡激运动,其横荡运动具有显著的锁定现象;在广义折合速度定义下,与相同直径的四立柱平台相比,立柱直径比不为1时其横荡运动锁定区间变宽且滞后,横荡响应幅值的峰值具有明显差异;在所研究的直径比范围内,大直径立柱在上游时涡激运动响应比其在下游时更显著,且这种差异随着直径比变大而变大。     

基于M-BEMT2.0研究串列海流发电机的水动力性能

海流发电机(MCT)是开发海洋可再生能源的重要装置。在预测海流发电机水动力性能方面,修正叶素动量理论(M-BEMT)方法被验证是一种简单有效的方法。为了进一步提高M-BEMT方法的适用性和准确性,基于M-BEMT方法开发M-BEMT2.0方法包括时均法(TA-BEMT2.0)和瞬态积分法(TI-BEMT2.0),新方法考虑了来流的轴向非均匀性和周向非均匀性。首先使用文献的试验结果验证均匀来流时新方法的适用性。然后使用计算流体力学(CFD)计算结果验证非均匀来流时新方法的适用性。最后结合新方法和CFD方法深入研究两个串列排布海流发电机(MCTA)的水动力性能。基于M-BEMT2.0研究发现,均匀来流时计算结果与试验结果基本吻合,非均匀来流时新方法的计算结果优于M-BEMT的计算结果。对于MCTA,当第一个MCT的叶尖速度比越大,第二个MCT功率比和推力比恢复到90%的距离越短。     

正二十面体六边形全球离散格网编码运算

全球离散格网系统是指把地球表面按照一定规则离散分割成多分辨率层次结构的格网单元,广泛应用于海量多源空间数据的组织、管理和分析中。六边形全球离散格网具有优良的几何特性,非常适合于空间数据的处理,如何进一步提高六边形全球离散格网编码运算的效率仍是当前研究的重点。本文采用正二十面体施耐德投影四孔径六边形全球离散格网模型,基于六边形三轴坐标与编码的二进制数的对应关系构建四孔六边形的基础编码结构,将二十面体划分为32个基础六边形,并将之分为3种基础六边形剖分瓦片,在每个六边形剖分瓦片采用基础编码结构进行编码,建立了四孔六边形全球离散格网编码,同时设计了并实现了四孔六边形编码与六边形三轴坐标之间的快速转换,基于此构建了一种高效的四孔六边形全球离散格网编码运算方案,包括编码的算数运算、空间拓扑运算和邻域检索运算及跨面运算。与现有的六边形全球离散格网编码运算方案相比,本文的方案进一步提高了编码算数运算、空间拓扑运算和邻域检索运算的效率,编码加法运算是HLQT的2～3倍,邻域检索运算分别是HLQT的3～5倍和H3的2～3倍,且受格网编码层次的影响较小,编码的跨面邻域检索运算时间略高于面内的运算,可以为全...