Organised Motion in a Tall Spruce Canopy: Temporal Scales,Structure Spacing and Terrain Effects

This study investigates the organised motion near the canopy-atmosphere interface of a moderately dense spruce forest in heterogeneous, complex terrain. Wind direction is used to assess differences in topography and surface properties. Observations were obtained at several heights above and within the canopy using sonic anemometers and fast-response gas analysers over the course of several weeks. Analysed variables include the three-dimensional wind vector, the sonic temperature, and the concentration of carbon dioxide. Wavelet analysis was used to extract the organised motion from time series and to derive its temporal scales. Spectral Fourier analysis was deployed to compute power spectra and phase spectra. Profiles of temporal scales of ramp-like coherent structures in the vertical and longitudinal wind components showed a reversed variation with height and were of similar size within the canopy. Temporal scales of scalar fields were comparable to those of the longitudinal wind component suggesting that the lateral scalar transport dominates. The existence of a – 1 power law in the longitudinal power spectra was confirmed for a few cases only, with a majority showing a clear 5/3 decay. The variation of effective scales of organised motion in the longitudinal velocity and temperature were found to vary with atmospheric stability, suggesting that both Kelvin-Helmholtz instabilities and attached eddies dominate the flow with increasing convectional forcing. The canopy mixing-layer analogy was observed to be applicable for ramp-like coherent structures in the vertical wind component for selected wind directions only. Departures from the prediction of m = Λ _w L _s ⁻¹ = 8–10 (where Λ _w is the streamwise spacing of coherent structures in the vertical wind w and L _s is a canopy shear length scale) were caused by smaller shear length scales associated with large-scale changes in the terrain as well as the vertical structure of the canopy. The occurrence of linear gravity waves was related to a rise in local topography and can therefore be referred to as mountain-type gravity waves. Temporal scales of wave motion and ramp-like coherent structures were observed to be comparable.     

Analysis of turbulent exchange and coherent structures in the stable atmospheric boundary layer based on tower observations

Using data collected at the Spanish low troposphere research centre CIBA (Centro de Investigación de la Baja Atmósfera) and at the Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands, we analyzed the most significant features of different coherent structures occurring in the stable atmospheric boundary layer. In particular, we used both the Reynolds and wavelet methods to analyze a solitary wave, a gravity wave, a density current and a low-level jet. For each of these structures, we found that wavelet analysis had the capacity to distinguish the different scales involved in these events due to the different timing and heights of the thermal instabilities and downdrafts associated with the disturbances. In addition, the wavelet method highlights the different roles of turbulence and coherent structures in the transfer of heat, moisture and CO₂ in the nocturnal boundary layer.     

青藏高原东北部湖泊细菌群落结构特征季节性差异及驱动机制

微生物是湖泊生态系统重要的有机组分。了解不同时期青藏高原湖泊细菌群落特征、环境驱动因子及其群落构建过程的差异,对高原湖泊水生态管理具有重要的指导意义。分别于2020年6和12月采集青藏高原东北部5个湖泊水样,基于高通量测序技术、统计分析和模型分析,解析高原湖泊群在非冰封期和冰封期细菌群落结构、环境驱动因子和中性过程、确定性过程以及随机性过程在细菌群落构建过程的贡献。结果表明：（1）非冰封期湖泊细菌群落的Chao1丰度指数、Simpson和Shannon多样性指数低于冰封期,Spearman相关性分析结果表明非冰封期细菌群落的Chao1丰度指数和多样性指数与水温和海拔显著相关,而冰封期细菌群落的Chao1指数和多样性指数与总氮显著相关;（2）水体细菌群落的优势门均为变形菌门（Proteobacteria）,非冰封期细菌中拟杆菌门（Bacteroidetes）、放线菌门（Actinobacteria）和厚壁菌门（Firmicutes）的平均相对丰度明显高于冰封期。另外,主坐标分析和相似性分析结果表明非冰封期和冰封期的细菌群落组成差异极显著;（3）冗余分析结果表明不同时期湖泊群细菌群落结构的...     

复杂断层构造电磁波衰减系数层析成像模拟研究

传统矿井电磁波透视层析成像技术只考虑电磁波的传播距离而忽视传播的方向性,造成探测复杂构造时的层析成像分辨率较低。依据电磁波在煤岩介质中的传播规律推导出了与入射角有关的新振幅衰减常数。引用新振幅衰减常数并基于代数重建算法建立了层析成像数学模型,编制了程序软件。利用新振幅衰减常数层析成像算法分别对平行和交叉断层进行数值模拟。通过与传统衰减常数层析成像的效果进行对比,结果表明:改进后的新振幅衰减常数层析成像效果更好,对断层的位置、走向、延展长度等情况反映清晰准确;在介质背景衰减场不易确定的情况下,绝对衰减层析成像方式优于相对衰减层析成像方式;平行关系的断层构造分辨率要高于交叉关系的断层构造。通过在某采煤工作面的电磁波层析成像中成功圈定了一组隐伏的平行断层构造实例,说明采用新衰减常数的层析成像技术效果提高明显。     

Geology and field relations of the Wilsons Promontory batholith,Victoria: multiple,shallow-dipping,S-type,granitic sheets

The 1200 km², Early Devonian (395 Ma) Wilsons Promontory batholith is a post-tectonic, high-level, composite body of S-type granites exposed on Wilsons Promontory and its offshore islands. Four plutons and six members are mapped and described. The rocks commonly contain magmatic garnet and cordierite, in addition to biotite, and biotite–quartz pseudomorphs after orthopyroxene. Planar fabrics abound in the batholith, which is characterised by emplacement of shallow-dipping granitic sheets, on a variety of scales. Particle size and density separation occurred during magma flow, and produced a wide variety of structures including layering, pipes and whorls rich in mafic minerals, K-feldspar phenocryst alignments and a notable swarm of enclaves. Local filter pressing may have played a role in the production of accumulations of K-feldspar crystals and the formation of late, tourmaline-bearing leucogranites and quartz veins. Batholith zonation and the distribution of component plutons are inferred to have been formed through sequential intrusion of separate magma batches rather than in situ differentiation. Overall, the batholith appears to consist of saucer-shaped plutons, and it is tilted gently to the east.     

2009年姚安6.0级地震震害特征分析

介绍了姚安6.0级地震震区的土木结构、砖木结构、砖混结构和框架结构房屋、生命线系统的概况及震害特征。分析了各种破坏产生的机理,提出了震区在恢复重建与规划发展时的建议、各类建(构)筑物加强抗震的措施。     

新疆塔里木库车冲断带东段更新世变形特征及其与西段的对比

库车新生代前陆褶皱冲断带经历了两期重大的挤压变形事件:中新世晚期-上新世早期近东西向的逆冲活动及伴生的近北西向左行剪切变换带在全区有统一的变形样式; 更新世变形使库车冲断带分为东、西两段。西段(西秋里塔格)山脉高耸,背斜及其核部冲断层延绵长逾百千米,仅见一条近北西向的左行剪切断层; 东段发育一组近南北向的右行剪切断层,把东秋里塔格山脉切成若干段,东秋背斜的北翼断层、南翼断层和核部断层在每一段内都有自己的特点。更新世变形还造成冲断带东、西两段的地貌和水系有明显不同。作为油气藏盖层的膏盐层在其东、西两段有不同的层位和厚度,东段膏盐层的层位高且相对较薄,早期形成的油气藏经更新世变形改造后的保存情况逊于西段,据此讨论了东段油气勘探中应注意的问题。     

银川断陷盆地地壳结构与构造的地震学证据

通过跨银川断陷盆地,完成了一条长68.9 km的高分辨深地震反射探测剖面,首次获得了银川盆地地壳精细结构、地堑型断陷盆地深部断裂系（黄河断裂、银川断裂、贺兰山东麓断裂）特征及深浅构造关系.结果表明：银川断陷盆地上地壳为双程走时8 s（深度约20 km）反射面以上的区域,上地壳上部地层层位丰富,地层分段连续性较好,上地壳下部地层分层特征不明显,地质构造简单;下地壳(8～13 s)反射能量较弱,反射同相轴不明显;下地壳下部壳幔过渡带（13 s附近）由一组能量较强、持续时间较长（1.5 s）的反射波组组成,厚度约4.5 km.芦花台断裂、银川断裂分别于12～12.5 km、18～19 km深处交汇于贺兰山东麓断裂,贺兰山东麓断裂于28～29 km深处交汇于黄河断裂,黄河断裂为错断Moho面的深大断裂,银川地堑为以黄河断裂为主,其他断裂为辅组合而成的负花状构造.根据贺兰山东麓断裂和银川断裂的相互关系,认为贺兰山东麓断裂对1739年平罗—银川8级地震起主要控制作用.     

塔里木盆地东河砂岩沉积和储层特征及综合分析

东河砂岩是一套覆盖广泛的海侵初期的沉积产物,但不是一个等时沉积体,相当于晚泥盆世晚期至早石炭世早期沉积,具体沉积时间各地有差异。东河砂岩具有海侵初期填平补齐的特征,其沉积相决定于海侵的速度、沉积物的供给和海侵前的古地貌。塔北地区受塔北古隆起的阻挡,海水在古隆起周围滞留时间较长,又有较粗粒的物源供给,其沉积产物主要是滨岸海滩沉积;塔中地区由于地形复杂,沉积类型也比较复杂,底部砾岩段为河流相沉积,而块状砂岩段和砂砾岩段为河口湾和滨岸海滩沉积,不同段在成分、分选性和粒级上有较大的差异;塔里木盆地其他低平地区主要是海侵期快速的滨岸和陆架沉积。受沉积因素影响,东河砂岩有效储层的分布具有地域性,除沉积因素外,低的地温梯度和短期的深埋藏也是优质储层发育的重要控制因素。     

基于承压板试验的岩体蠕变参数反演统一解析公式法

由于岩体性状的复杂性和多样性,现场试验是进行岩石力学研究的重要手段。以往的现场承压板试验,由于试验条件的限制,试验荷载的设定将使岩体蠕变呈衰减蠕变形态,却难以反映岩体的等速蠕变和加速蠕变。坝基软弱岩体的力学特性是影响大坝及地下结构长期稳定性的重要因素。通过对坝基软弱岩体现场承压板试验曲线中表现出的衰减蠕变和等速蠕变两阶段特性,辨识了蠕变模型。并推导了刚、柔性承压板深部岩体的黏弹性一般解,给出了Maxwell模型、广义Kelvin模型、Burgers模型的黏弹性位移的统一表达式。结合试验数据,以理论解析反演法得到相关的蠕变参数,为以后的坝基长期稳定性计算奠定基础。