长江口水动力场、浓度场数值模拟网格生成技术的研究

为很好地拟合研究区域长江河口的复杂边界及计算水域，本文在曲线坐标系下建立了贴体正交曲线网格生成的泊松方程变换，选择了适当的聚并函数以调节网格疏密程度。所生成网格的结果同时也与拉普拉斯方程变换的结果进行了比较，分析表明效果良好，可用于含有小岛的长江口多连通域的网格划分。     

2.5Ma以来黄土稳定同位素记录的植被及夏季风变化

洛川剖面2.5Ma以来有机碳同位素组成显示δ13 C值的变化范围为-18.7%～-23.5‰;剖面有机碳同位素变化可分为3个阶段,均与磁化率曲线对应且呈现一致的冰期-间冰期波动。表明研究区第四纪以来主要为C3植物为主的C3、C4混合草原植被类型;黄土序列有机碳同位素δ13 C值对应磁化率曲线在冰期—间冰期尺度上较好地记录了夏季风强度变化;与段家坡和渭南剖面有机碳结果对比显示,2.5Ma以来3个剖面在构造尺度上均出现了两次明显的转变。     

太湖水动力学三维数值试验研究─1.风生流和风涌增减水的三维数值模拟

本文建立了太湖风生流和风涌增减水的一个三维数值模型,该模型可对垂直方向进行多层次划分,且各计算网格点层数一样。模拟计算了１９９７年８月的１１号台风对太湖水位和湖流作用,用环湖六个水位站水位过程资料对模型计算出的水位进行了验证,并用太湖梅梁湖湾口的实测流速资料对模型计算出流场进行了校验。     

基于生物水文响应模型的刺激四大家鱼繁殖生态调度目标量化方法研究——以三峡水库为例

为了改善生态调度效果,提高生态调度实践成功率,采用医学领域适用性广、准确性高、直观性强的受试者工作特征曲线法(receiver operating characteristic, ROC),以三峡水库为例,提出了一套基于生物水文响应模型的刺激四大家鱼繁殖生态调度目标量化方法,包括涨水事件界定及生态水文指标选择、鱼类自然繁殖事件及有效繁殖响应界定、生物-水文响应模型构建与多指标判别优选等多个环节。运用三峡水库运行后2013—2019年(除2016年)6年47场次宜昌江段的涨水事件和24次四大家鱼有效繁殖响应的实际观测数据构建模型并量化三峡水库生态调度目标。结果表明:(1)依据初始流量Q₀、洪峰流量Q_peak、流量总增长量Q_sum和流量日增长率dQ这4个指标所建立的单指标生物-水文响应模型具有较好判别四大家鱼自然繁殖对水文条件是否响应的能力;(2)各评价指标Q₀、Q_peak、Q_sum、dQ的最佳阈值分别为14960 m³/s、19610 m³/s、4050 m³/s及1405 m³/(s·d);单指标模型性能排序为dQ＞Q_peak＞Q_sum＞Q₀;(3)依据dQ或Q_peak的指标组合方式建立的多指标生物-水文响应模型综合性能最佳。结果表明,ROC模型方法结果形式简单、预见性强,据此量化生态调度目标,可为其他流域、水库的鱼类繁殖响应判别和水库生态调度方案制定提供参考借鉴。     

Discovery of bacteriopheophytin-<Emphasis Type="Italic">a</Emphasis> in lacustrine deposits from Lake Zigetang on the central Tibetan Plateau and its paleoenvironmental significance

Lake Zigetang is located on the central Tibetan Plateau (TP) and represents a rare but typical meromictic lake in China. The lake’s stable meromixis sustains microflora communities, and changes in these communities are relatively independent of climate. Therefore, these communities can be used as paleoclimate proxies. In this paper, the stratification properties and their relationships with the microflora of Lake Zigetang were analyzed. We found that water depth and climate conditions were two important factors for maintaining meromixis in Lake Zigetang. Generally, stratification was enhanced during warm periods, while temperature differences between the mixolimnion and monimolimnion were decreased during cold periods. The presence of anoxygenic phototrophic bacteria (APB) was demonstrated by the discovery of bacteriopheophytin-a (Bph-a) in the sediments. This bacterial community is mainly concentrated at the bottom of the chemocline and the top of the monimolimnion, where it forms a thin APB layer. Moreover, total APB productivity is mainly affected by the light intensity penetrating to the APB layer, which exponentially increases as the thermocline becomes shallow. Therefore, high Bph-a values in the lake corresponded to a shallow thermocline and warm periods, low Bph-a values corresponded to cold periods, and zero changes indicated that the water was completely mixed and reflected an extreme cold climate or low lake level period. Thus, Bph-a can be used as a climate proxy to reconstruct the history of lake stratification and climate changes.     

Bayesian inference for the Errors-In-Variables model

We discuss the Bayesian inference based on the Errors-In-Variables (EIV) model. The proposed estimators are developed not only for the unknown parameters but also for the variance factor with or without prior information. The proposed Total Least-Squares (TLS) estimators of the unknown parameter are deemed as the quasi Least-Squares (LS) and quasi maximum a posterior (MAP) solution. In addition, the variance factor of the EIV model is proven to be always smaller than the variance factor of the traditional linear model. A numerical example demonstrates the performance of the proposed solutions.     

一种古构造恢复方法探讨--以乌马营构造为例

古构造恢复是探索多旋回盆地油气藏改造、重组的有效手段之一。古构造恢复的基本原理是“回剥”,即通过“退变形”而获得不同地质演化阶段某构造层的埋藏起伏变化。回剥可以视为剔除上覆地层,并将不同时期古水准面恢复到原位的过程。利用层序充填特点和古水平面重塑研究古构造的新方法。在三维地震覆盖区,标示古水平面的层序特点在较高精度成像的地震数据体中是可以识别的,利用三维地震解释技术,可以精确恢复针对圈闭或局部构造单元的变形史和变形基础。在黄骅坳陷乌马营地区进行了实例应用研究,研究表明：利用该方法可精确恢复三维空间内、不同时期潜山高点迁移的变化规律;古构造恢复的结论与WS1井气藏特点的吻合,为潜山天然气藏的评价和目标勘探提供了决定性依据。     

基于演化过程的互层斜坡深层倾倒稳定性评价

互层倾倒是一类典型的深层倾倒模式,为准确评价其稳定性,开展互层倾倒的工程地质特性及稳定性评价研究。以雅砻江上游发育的深层倾倒体为典型实例,利用基于演化过程的研究方法,在构建倾倒体工程地质模型的基础上,从变形过程和演化阶段上定量评价斜坡整体稳定性。研究表明:互层倾倒是由块体倾覆和板梁弯曲形成的复合倾倒模式,即:硬岩发生块状-弯曲倾倒,而软岩发生弯曲倾倒;空间上,一个发育完备的倾倒体可划分为:滑动区(A区)、强倾倒区(B区)、弱倾倒区(C区)以及原岩区(D区)。基于实测数据提出的斜坡倾倒定量描述体系,可以作为岩体倾倒变形识别和变形程度分级的基本依据;时间上,互层倾倒演化过程主要经历4个演化阶段:卸荷回弹陡倾拉裂面阶段,初始变形阶段,板梁根部折断、剪切面贯通阶段以及破坏阶段,并最终转化为蠕滑-拉裂模式形成滑坡。该滑动面受强变形岩体中倾向坡外结构面控制,而并非沿最大弯折带发育;滑动区(A区)的出现意味着斜坡最终破坏的发生,对应于演化的第三阶段,为斜坡的极限平衡状态,稳定性系数介于1.0~1.05之间。基于演化过程的评价方法,能有效解决互层倾倒稳定性评价问题。     

“生产-生活-生态”空间识别与优化研究进展

“生产-生活-生态”(简称“三生”)空间识别与优化研究是在识别现状空间结构、格局及问题的基础上,对未来空间进行优化布局,实现空间的均衡、可持续性发展,是一种更具综合性的国土空间分区方式,已成为当前学术前沿和国土空间规划亟需解决的实践问题。论文通过文献调研法、对比法和归纳法,系统梳理了“三生”空间概念内涵、识别与优化研究现状。目前,“三生”空间识别研究取得了阶段性成果,但“三生”空间形成的内在机理与概念探讨不足,“三生”空间的定量识别方法与技术体系研究有待完善,“三生”空间动态演化及驱动机制、空间冲突诊断和问题分析较为薄弱,“三生”空间优化理论和技术体系尚处于初级阶段。未来,应形成“三生”空间识别与优化“质”“量”观,借鉴国际空间规划已有的研究成果,以“‘三生’空间形成机理与概念界定、定量识别、演化机制挖掘、冲突诊断与问题分析、优化调控与模拟”为主线,系统构建“三生”空间识别与优化的理论与技术体系;同时,重视具有水平方向和垂直方向特征的山区“三生”空间识别与优化研究。     

Spatio-temporal modeling of PM2.5 concentrations with missing data problem: a case study in Beijing,China

ABSTRACT

One of the major challenges in conducting epidemiological studies of air pollution and health is the difficulty of estimating the degree of exposure accurately. Fine particulate matter (PM_2.5) concentrations vary in space and time, which are difficult to estimate in rural, suburban and smaller urban areas due to the sparsity of the ground monitoring network. Satellite retrieved aerosol optical depth (AOD) has been increasingly used as a proxy of ground PM_2.5 observations, although it suffers from non-trivial missing data problems. To address these issues, we developed a multi-stage statistical model in which daily PM_2.5 concentrations can be obtained with complete spatial coverage. The model consists of three stages – an inverse probability weighting scheme to correct non-random missing patterns of AOD values, a spatio-temporal linear mixed effect model to account for the spatially and temporally varying PM_2.5-AOD relationships, and a gap-filling model based on the integrated nested Laplace approximation-stochastic partial differential equations (INLA-SPDE). Good model performance was achieved from out-of-sample validation as shown in R² of 0.93 and root mean square error of 9.64 μg/m³. The results indicated that the multi-stage PM_2.5 prediction model proposed in the present study yielded highly accurate predictions, while gaining computational efficiency from the INLA-SPDE.