Numerical Simulation of Waves Generated by Seafloor Movements

Waves generated by vertical seafloor movements are simulated by use of a fully nonlinear two-dimensional numerical wave tank. In the souree region, the seafloor lifts to a designated height by a generation function. The numerical tests show that the linear theory is only valid for estimating the wave behaviors induced by the seafloor movements with a small amplitude, and the fully nonlinear numerical model should be adopted in the simulation of the wave generation by the large amplitude seafloor movements. Without the background surface waves, many numerical tests on the stable maximum elevations η0^max are carried out by beth the linear theory and the fully nonlinear model. The results of two models are compared and analyzed. For the fully nonlinear model, the influences of the amplitudes and the horizontal lengths on η^max are stronger than that of the characteristic duration times. Furthermore, results reveal that there are significant differences be- tween the linear theory and the fully nonlinear model. When the influences of the background surface waves are considered, the corresponding numerical analyses reveal that with the fully nonlinear model the η0^max near-linearly varies with the wave amplitudes of the surface waves, and the η0^max has significant dependences on the wave lengths and the wave phases of the surface waves. In addition, the differences between the linear theory and the fully nonlinear model are still obvious, and these differences are significantly affected by the wave parameters of the background surface waves, such as the wave amplitude, the wave length and the wave phase.     

附加深度差和水平距离约束的深海控制点差分定位算法

针对现有方法确定海底控制点(应答器)三维坐标垂直解偏差大的问题,提出了附加控制点间深度差和水平距离约束的差分定位算法。首先研究了声速剖面的变化规律,并分析了声速剖面的不确定性对测距误差的影响。其次,根据测距误差的变化规律设计了相应的测线,并提出了适合这种走航策略的差分算法。仿真试验的结果显示,相比于传统方法(圆走航),控制点垂直解的偏差由30多个cm减小到了10 cm左右,表明本文提出的方法可以有效改善控制点定位垂直解偏差大的问题。     

Leaf to canopy upscaling approach affects the estimation of canopy traits

In remote sensing applications, leaf traits are often upscaled to canopy level using sunlit leaf samples collected from the upper canopy. The implicit assumption is that the top of canopy foliage material dominates canopy reflectance and the variability in leaf traits across the canopy is very small. However, the effect of different approaches of upscaling leaf traits to canopy level on model performance and estimation accuracy remains poorly understood. This is especially important in short or sparse canopies where foliage material from the lower canopy potentially contributes to the canopy reflectance. The principal aim of this study is to examine the effect of different approaches when upscaling leaf traits to canopy level on model performance and estimation accuracy using spectral measurements (in-situ canopy hyperspectral and simulated Sentinel-2 data) in short woody vegetation. To achieve this, we measured foliar nitrogen (N), leaf mass per area (LMA), foliar chlorophyll and carbon together with leaf area index (LAI) at three vertical canopy layers (lower, middle and upper) along the plant stem in a controlled laboratory environment. We then upscaled the leaf traits to canopy level by multiplying leaf traits by LAI based on different combinations of the three canopy layers. Concurrently, in-situ canopy reflectance was measured using an ASD FieldSpec-3 Pro FR spectrometer, and the canopy traits were related to in-situ spectral measurements using partial least square regression (PLSR). The PLSR models were cross-validated based on repeated k-fold, and the normalized root mean square errors (nRMSE_cv) obtained from each upscaling approach were compared using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test. Results of the study showed that leaf-to-canopy upscaling approaches that consider the contribution of leaf traits from the exposed upper canopy layer together with the shaded middle canopy layer yield significantly (p < 0.05) lower error (nRMSE_cv < 0.2 for canopy N, LMA and carbon) as well as high explained variance (R² > 0.71) for both in-situ hyperspectral and simulated Sentinel-2 data. The widely-used upscaling approach that considers only leaf traits from the upper illuminated canopy layer yielded a relatively high error (nRMSE_cv>0.2) and lower explained variance (R² < 0.71) for canopy N, LMA and carbon. In contrast, canopy chlorophyll upscaled based on leaf samples collected from the upper canopy and total canopy LAI exhibited a more accurate relationship with spectral measurements compared with other upscaling approaches. Results of this study demonstrate that leaf to canopy upscaling approaches have a profound effect on canopy traits estimation for both in-situ hyperspectral measurements and simulated Sentinel-2 data in short woody vegetation. These findings have implications for field sampling protocols of leaf traits measurement as well as upscaling leaf traits to canopy level especially in short and less foliated vegetation where leaves from the lower canopy contribute to the canopy reflectance.     

1∶5万区调中的基本层序调查

基本层序是一段地层沉积特征的客观表现 ,可根据实际观察到的单层叠覆规律和界面特征来划分 ,不受其成因或环境解释的影响 ,根据其控制因素可分为旋回性基本层序 (包括自旋回性基本层序和他旋回性基本层序 )和非旋回性基本层序。野外应注重其顶底界面的识别。其垂向叠覆具有规律性变化特点 ,在层序发展不同阶段 ,基本层序的叠覆规律亦相应变化。基本层序不具级别意义 ,其规模受所描述的地层所控制。米级旋回的研究范围仅限于他旋回性基本层序发育的地层 ,两者为两套地层单位系统 (岩石地层单位和旋回地层单位 )的基本单元 ,不能等同视之。     

不同海水营养盐现场连续观测系统的比较研究

海水营养盐自动观测技术是海洋观测技术的核心之一, 也是世界各国海洋观测技术发展的重点。本文概述了海水营养盐自动观测技术在海洋环境监测中的研究进展, 并基于航次的现场实践, 比较了海水营养盐自动观测设备的应用情况, 归纳了不同设备的优缺点。基于紫外光谱法的硝酸盐传感器(in-situ ultraviolet spectroscopy, ISUS)具有不需化学试剂、响应速度快、适合连续长期观测、耐压深度深的优点, 可广泛应用于海水和淡水环境的走航观测、现场剖面观测和浮标定点观测; 其缺点是测定参数少、灵敏度低。基于湿化学法的营养盐剖面自动分析仪(Autonomous Profiling Nutreint Analyzer, APNA)与连续流动在线分析仪(型号为QuAAtro)具有测定精度和准确度高、多营养盐参数同步测定的优点, 可用于浅水剖面和短时间连续观测, 但存在操作复杂、工作时间短、试剂用量大的缺点, 不适合长期时间序列或深水观测; APNA能进行原位观测, QuAAtro基于船载, 需要加载样品采集过滤系统。本研究基于以上实践与经验, 进一步探讨了现有海水营养盐自动观测技术目前所面临的技术瓶颈及未来发展趋势, 旨在为海洋现场自动监测仪器的选用提供参考。     

空沟对冲击荷载隔离的现场试验与数值模拟

在场地开挖了一条空沟,以落锤式弯沉仪（falling weight deflectometer,简写为FWD）的荷载模拟冲击荷载,通过FWD自带的传感器测得空沟后一定范围内的竖向位移。通过室内试验,获取试验场地的岩土参数,采用非线性动力有限元软件ABAQUS建立二维模型（将远处单元定义为无限单元来模拟吸收边界,从而避免振动波的来回反射）。以空沟中心线的现场测试数据为依据,校核有限元模型。通过分析不同工况模拟的竖向位移,研究得出空沟-荷载间距、沟深、沟宽等对隔振效果的影响。结果表明,(1) 空沟-荷载间距越小,隔振效果越好,但实际隔振工程中,为避免振动对空沟侧壁的稳定性的影响,空沟与振源不宜太近,因此可以不计空沟-荷载间距对隔振效果的影响;(2) 就提高隔振效果而言,增大沟深比增大沟宽更有效,而相同的隔振效果,窄-深沟的挖方量远小于宽-浅沟;(3) 在对冲击荷载进行隔振设计时,对于一般的民用和工业建筑,综合隔振效果、开挖和支护费用等因素,采用宽度为0.5～1.0 m,深度为2.0～2.5 m的空沟较为合理,与某工程实例进行比对,验证结论的合理性。     

墨西哥湾含水合物和油气渗漏区海底表层沉积物中有机质饱和烃组成分布特征研究

报道了采自墨西哥湾富含水合物和油气渗漏区6个海底表层沉积物样品中有机质的丰度、组成和分布特征.研究发现,所分析的6个沉积物样品中有机质的丰度和组成变化很大,其中S-1、S-7和S-9样品中饱和烃的组成分布主要反映了现代海洋沉积有机质及其受细菌微生物改造作用的特征,而S-8、S-10和S-11样品中饱和烃组成以特征的石油污染成因的不可分辨的混合物(UCM)为主,相关甾萜类参数也表明沉积物受到原油渗漏或泄露污染;另一方面,S-8和S-11样品中正构烷烃不同程度的缺失表明有机质遭受了较为强烈的的生物降解作用.仅在S-1沉积物中鉴定出了与甲烷古细菌厌氧氧化有关的特征标志物--2,6,10,15,19-五甲基二十烯烃系列化合物(PMI△)并且具有极负的碳同位素组成,这表明S-1样品所在海底可能有天然气水合物的产出.     

岩浆脉动结晶的实例:山东伟德山岩体

伟德山花岗岩体位于胶东半岛的东部。燕山运动晚期,地下深处形成的岩浆由于重力不稳性和构造减压而发生上升,并侵入于地壳上层,结晶成岩。早期结晶的是熔点较高,暗色矿物较多的组分,因对流及扩散作用发生分异,形成边缘岩带;由于脉动作用,岩浆冲破早先结晶的岩石,岩浆体一方面上升,一方面扩大体积,并继续结晶,从而形成过渡岩带;进而又一次岩浆脉动,形成中心岩带。由于这种脉动作用,形成成分、结构、构造都呈近同心分带的伟德山岩体。     

毛乌素沙地东南部边缘不同地质成因类型土地沙漠化粒度特征及其地质意义

首次对毛乌素沙地东南部边缘沙漠—黄土地带的土地沙漠化进行系统的地质学分类,提出了沙地内部就地起沙型沙漠化、河流谷地就地起沙型沙漠化、风化残积就地起沙型沙漠化和风沙侵入型沙漠化等四种土地沙漠化类型。通过深入分析不同地质成因类型土地沙漠化的粒度特征,探讨了不同地质作用对土地沙漠化的贡献及其对土地沙漠化防治方面的重要意义。研究表明,研究区的土地沙漠化以就地起沙型为主,河流的水力搬运是沙漠化物质搬运的主要途径,风力作用则是对河流湖泊沉积物的进一步分选和再沉积。最后,提出了不同类型的土地沙漠化防治对策建议。     

我国中新生代盆地砂岩型铀矿研究现状及发展方向的探讨

砂岩型铀矿是我国具有工业意义的铀矿床类型之一 ,是核工业目前主要勘查类型。本文在扼要概述砂岩型铀矿成矿地质条件的基础上 ,对当前研究现状 ,尤其是地浸砂岩型铀矿的研究现状及地浸地质条件进行了评述。从多方面探讨了该类型铀矿床的发展方向及值得重视的基础地质研究及研究方法手段等。