基于Geodatabase的长江(江苏段)岸线资源数据库建设

文章首先介绍了Geodatabase空间数据模型,并基于Geodatabase数据模型运用面向对象的方法设计、建设了长江(江苏段)岸线资源数据库.     

固壁附近水平圆柱在波浪水流共存场中的流动显示及水动力特征

固壁附近的水平的圆柱体在波浪、波流作用下的受力情况与其周围的流场状态密切相关。为探讨圆柱形成的机理，应当对流场的涡结构有充分的认识，受力过程与记演化过程的同步分析万为重要。本文通过实验研究并对比数值分析的结果，对波浪、波流场中圆柱体受力与流场状态的关系做一初步讨论。     

Estimation of internal nutrient release in large shallow Lake Taihu,China

Based on field investigation of wave, sediment suspension and the changes in nutrient concentration of the water column in Lake Taihu, China, we proposed two release models to quantify nutrient release under static and dynamic conditions, respectively. Under static conditions, nutrient release from sediments to the overlying water mainly depends on chemical diffusion induced by concentration gradient, in which the nutrient release is controlled by the temperature, dissolved oxygen concentration in the sediment-water interface, oxidation-reduction potential and the concentration difference between porewater and overlying water. Under dynamic condition (or disturbed condition), both dissolved and particulate nutrients in sediments are released into the water column because of wind-induced sediment suspension. The amount of nutrient release under dynamic conditions is larger than that under the static condition. The release of dissolved nutrients, however, does not increase because the wind induced turbulence made oxidation of metallic elements such as Fe (ferric iron), Mn which are capable of precipitating soluble reactive phosphate (SRP). Under dynamic conditions, therefore, the release of total phosphorus (TP) increases dramatically but the release of SRP is close to those under static conditions. In sediments of Lake Taihu, high Fe content leads to a high ratio of Fe to P contents in sediments (Fe:P ratio). Under dynamic conditions, therefore, nutrient release is controlled by the intensity of disturbance, sediment consolidation and nutrient content in sediments. As for dissolved nutrients, especially SRP, the release is also controlled by the intensity of dynamic re-oxidation, Fe content in sediments and nutrient concentration gradient between porewater and overlying water. Based on these two release modes, the release flux in Lake Taihu has been estimated. In the static condition (i.e. laboratory experimental condition), total release of NH₄ ⁺-N for whole lake is ca. 10,000 ton/a, and PO₄ ³⁻-P is ca. 900 ton/a. In the dynamic condition, nutrient release following sediment suspension was estimated according to three different intensities of wind forcing which were defined as “calm” (wind speed is less than 2 m/s), “gentle” (wind speed is greater than 2 m/s and less than 6 m/s) and “gust” (wind speed is greater than 6 m/s). The release rate in the condition of “calm” was estimated in terms of the nutrient release in the laboratory experimental static condition; whereas the release rate in conditions of “gentle” and “gust” was estimated in terms of measurement during sediment resuspension conducted in flume experiments. With the observation of wind velocity and frequency in 2001, each type of wind forcing took the frequency of 12%, 82% and 6% for “calm”, “gentle” and “gust”, respectively. The yearly release of nitrogen was 81,000 ton and phosphorus was 21,000 ton, which is about 2–6 folds of annual external loading, respectively.

     

利用陆基高光谱遥感捕捉太湖蓝藻水华日内快速变化过程

受蓝藻自身垂直迁移和频繁风浪扰动影响,太湖蓝藻水华漂浮混合和迁移堆积等变化迅速,在传统的湖面定位和断面监测中总感觉蓝藻水华有些"来无影、去无踪",限制了对其形成过程、驱动机制和防控治理的深入认识.卫星遥感可以实现蓝藻水华空间分布同步观测,但由于观测频次的限制很难捕捉蓝藻水华快速动态变化过程.本文利用与杭州海康威视数字技术股份有限公司联合自主研发的陆基（地基、岸基或者平台、船舶、桩基等能固定安装的均可）高光谱多参数水质遥感监测仪,架设于中国科学院太湖湖泊生态系统研究站（简称太湖站）水上观测场,通过对叶绿素a浓度及其他关键水质参数秒-分钟级的连续观测,有效捕捉了一天内蓝藻水华短期突然和快速变化过程.研究结果显示,在微风和小风条件下蓝藻容易在表层水体漂浮,盛行西北风驱动湖面开敞水域蓝藻水华快速漂浮集聚到太湖站岸边,短短半小时内表层水体叶绿素a浓度可以由10 μg/L快速攀升到100 μg/L以上,一天内会出现多个叶绿素a峰值,清晰展示了蓝藻快速日内动态变化过程.受蓝藻快速日内变化影响,透明度、总氮、总磷和高锰酸盐指数等水质参数也呈现出快速日内变化,叶绿素a浓度与透明度存在极显著负相关,与总氮、总磷和高锰酸盐指数存在极显著正相关,叶绿素a能解释总氮、总磷80%以上的变化,说明蓝藻短期内的漂浮和集聚深刻影响到湖泊水质.     

Effects of rainfall on thermal stratification and dissolved oxygen in a deep drinking water reservoir

Thermal stratification is crucial for water quality and ecological processes in deep lakes and reservoirs and can be substantially affected by meteorological and hydrological processes in the catchment. However, how thermal stratification responds to rainfalls of different intensities and changing hydrological processes has not been documented very well. Here, high frequency water column profiles at three stations in a large subtropical deep reservoir (Lake Qiandaohu, China) in 2017 were used to elucidate the impacts of rainfall on lake physical process and chemical environment. The impact of rainfalls on the thermal stratification and dissolved oxygen in riverine zone was more impressive than that in transitional and lacustrine zones. The effect on thermal stratification by rainfall was largely affected by the magnitude of rainfall. Moderate and heavy rainfall events could reduce the thermal stability of water column, deepen the mixing layer depth, and shape the thermocline, resulting from decrease of surface water temperature and increased inflows. While rainstorms could totally break up thermoclines in the riverine zone by high volume inflow flushing. In addition, we found that the hypoxia and anoxia initial depths increased during rainfall events in this reservoir, which were well related to the changes of mixing layer depths. This research highlights that quantifying the effects of rainfalls on thermal stratification and dissolved oxygen will be beneficial for optimizing reservoir management.     

川东北长兴组—飞仙关组古原油成藏的孔隙度门限

近年来,在四川盆地二叠系、三叠系海相碳酸盐岩层系中发现了如普光、龙岗、元坝等多个大中型、高孔高渗气田,且天然气主要为古油藏原油裂解气.在油源充足的条件下,孔隙度成为了控制古原油成藏的关键因素,讨论古原油充注的孔隙度门限,尤其对于致密碳酸盐岩储层是否发生古原油的聚集具有指导意义.川东北地区长兴组-飞仙关组礁滩相储层发现了大量的固体沥青,岩石薄片镜下观察到这些固体沥青主要分布于亮晶鲕粒灰岩的粒间孔隙中、结晶白云岩的晶间孔中以及残余鲕粒白云岩的铸模孔中,极少发现沥青充填之后的胶结物.本研究定量统计了沥青含量与现今面孔隙度来恢复视古孔隙度,分别讨论现今面孔隙度、视古孔隙度与沥青含量的关系,确定了视古孔隙度门限,最后经过压实作用校正得到了古原油成藏的孔隙度门限.研究结果揭示,沥青含量与现今面孔隙度无线性关系.而与视古孔隙度有着较明显的正相关关系,当视古孔隙度大于一定值时,沥青含量显著增加;川东北长兴组-飞仙关组碳酸盐岩储层古原油成藏的孔隙度门限值为6.4％～7.4％(平均6.8％).     

Sentinel-2与Landsat 8数据组合下的多特征冬小麦面积提取

遥感卫星的波段设置、信噪比及传感器观测角度等因素都会影响作物提取精度。为充分挖掘与发挥Sentinel-2卫星多光谱成像仪(MSI)与Landsat 8陆地成像仪(OLI)在冬小麦信息提取方面的优势,本文以商河县为研究区,基于两数据源的光谱特征、纹理特征、植被指数特征组合数据,利用随机森林(RF)与支持向量机(SVM)对冬小麦进行提取。结果表明:基于单一影像的最优Kappa系数与最优OA分别为0.89和95.13%,基于组合数据源的最优Kappa系数为0.92,最优OA为95.28%,两数据源组合的精度优于单一数据源提取精度;数据组合效果与分类器的性能有关,RF的Kappa系数相对于SVM分别提升0.04、0.20和0.11,OA分别提升2.41%、11.31%和6%,RF对冬小麦提取精度优于SVM。本文研究结果对于构建中高分辨率影像组合的典型农作物分类提取体系具有重要意义。     

实景三维多源数据场景融合北大核心CSCD

在城市级实景三维建设中,对多来源、多尺度实景三维数据进行场景融合,能够进一步完善实景三维场景细节表达,提高城市级实景三维场景的完整性,满足实景三维场景局部更新机制要求。本文针对海量、异构、多尺度实景三维融合技术方法开展了相关研究,探索并改进了多源实景三维数据的空间精度匹配与数据接边的方法,结合实景三维数据成果的标准化、轻量化处理方法,提升了实景三维场景调度显示效率,进一步扩大了实景三维融合成果的应用领域。     

利用自适应最小二乘配置的GPS水准与重力似大地水准面的拟合

针对GPS水准与重力似大地水准面之差中存在系统误差的问题,使用最小二乘配置估计信号大小,来提高似大地水准面的拟合精度.对于最小二乘配置的噪声与信号的协方差之间的关系不合理,采用自适应因子纠正两者之间的关系,并首次将自适应最小二乘配置算法应用于似大地水准面精化.最后使用我国东部面积将近2万km2的城市A的数据进行验证,计算结果表明,最小二乘配置及自适应最小二乘配置在一定程度上能够提高拟合效果,使似大地水准面更接近于真实值,实现了国内较大城市面积的1.0 cm检核精度的区域似大地水准面成果.     

基于粒子群优化算法的多因子自适应滤波

在抗差多因子自适应滤波的基础上,提出基于粒子群优化智能算法进一步搜索自适应因子的优化值,提高自适应因子的可靠性.在基于状态不符值构造的自适应因子的基础上,构造适应性函数,采用粒子群优化算法搜索更有效的自适应多因子.利用动态导航数据进行验证,结果表明,基于粒子群优化的多因子自适应滤波能更有效地控制异常影响,提高动态导航精度.