渤海湾曹妃甸港区开发对水动力泥沙环境的影响

针对渤海湾曹妃甸海域波浪、潮流、泥沙及海床演变特点,应用波流共同作用下二维泥沙数学模型研究港区开发方案。2006年冬季和夏季大、小潮潮流泥沙验证表明,该海域潮位及15条同步垂线流速、流向、含沙量过程的计算值与实测值吻合良好,并进行了矿石码头港池前沿海域在潮流与波浪共同作用下悬沙引起的冲淤验证,计算的冲淤厚度及其分布趋势与实测值比较接近。在此基础上,研究了曹妃甸前岛后陆的港区围垦方案对水动力环境的影响问题,包括该工程引起的曹妃甸甸头以南深槽、老龙沟深槽及各港池的流速变化及底床的冲淤变形等。     

Strenulagus (Mammalia: Lagomorpha) from the Middle Eocene Irdin Manha Formation of the Erlian Basin, Nei Mongol, China

New material of Strenulagus solaris, a stem lagomorph, from the lower part of the Middle Eocene Irdin Manha Formation at the Irdin Manha and Huheboerhe localities, Erlian Basin, Nei Mongol, China includes remains of isolated cheek teeth, fragmentary upper incisors(d I2) and postcranial elements, reported from the species for the first time. The tarsal bones display advanced features, such as a wide calcaneofibular articulation surface and, along with an increase in hypsodonty, the new data document the early stage of lagomorph evolution in the Middle Eocene of the Erlian Basin. This finding is stratigraphically well constrained and probably predates that of the type material of S. solaris from the Khaychin Formation, Bugin-Tsav Basin, Mongolia.     

土水特征曲线的通用数学模型研究

土水特征曲线对于研究非饱和土的物理力学特性至关重要。根据土水特征曲线可以确定非饱和土的强度、体应变和渗透系数 ,甚至可以确定地下水面以上水份分布。由于土体物理力学特性的差异 ,导致描述其土水特征曲线的数学模型也各不相同。因此 ,建立土水特征曲线的通用数学表达式 ,显得尤为必要。本文对土水特征曲线数学模型进行了研究 ,依据这些模型的数学表达式形式 ,将其划分为 4种类型。分别由这 4种类型的数学模型推导出具有统一表达式形式的土水特征曲线通用数学模型 ,并运用陕北高原黄土土水特征曲线试验数据对通用数学模型进行了研究     

规则格网DEM局地坡面凸凹性精度分析

DEM地表形态精度分析理论与方法的建立,对DEM数据的生产和广泛应用具有重要意义。本文从局地坡面形态的凸凹性角度,剖析规则格网DEM格网点位置、格网分辨率对DEM局地坡面凸凹性的影响,以期进一步完善和发展DEM质量分析的理论与方法。论文首先阐述了DEM局地坡面凸凹性的基本概念,研究建立了规则格网DEM的局地坡面凸凹性量化分析方法,并以黄土丘陵5、10、15、25、……、155 m DEM为例,采用比较分析方法研究了局地坡面凸凹性随DEM格网点位置和格网分辨率的变化特征。研究表明:对于本研究中的1:5万DEM,10 m(跃变率≤0.3%)是其最佳的格网分辨率阈值,当DEM实际格网分辨率高于该阈值时,实际DEM与最佳格网分辨率DEM具有近乎相同的局地坡面凸凹性,主要在正地形与负地形的过渡区域会发生不同程度的坡面凸凹性变化;当DEM实际格网分辨率低于该阈值时,实际DEM的局地坡面凸凹性,会随着DEM格网点布设位置和DEM格网分辨率发生较大的不确定性变化。     

地球数字产品的空间数学基础

在分析当前地球数字产品空间数学基础局限性的基础上,将地图投影概念由传统的曲面到平面的变换扩展为曲面到曲面的变换,提出一套适合于大型GIS和地球数字产品的“地图投影”模型的实用模型,该模型的视图采用等距离切圆柱投影,度量空间是椭球面几何系统,符合计算机环境下GIS视图与度量空间分离的特性。鉴于全球多分辨率连续可视化,精密可视化量算,三维、多维地球数据统一,标准的空间定位框架和只有在统一的空间系统内全球资源、生态环境数据才能进行精确的地理分析等四个方面的需要,从地图投影进到本模型将是方向和技术趋势。     

Determination of the crop row orientations from Formosat-2 multi-temporal and panchromatic images

This paper presents a technique developed for the retrieval of the orientation of crop rows, over anthropic lands dedicated to agriculture in order to further improve estimate of crop production and soil erosion management. Five crop types are considered: wheat, barley, rapeseed, sunflower, corn and hemp. The study is part of the multi-sensor crop-monitoring experiment, conducted in 2010 throughout the agricultural season (MCM’10) over an area located in southwestern France, near Toulouse. The proposed methodology is based on the use of satellite images acquired by Formosat-2, at high spatial resolution in panchromatic and multispectral modes (with spatial resolution of 2 and 8 m, respectively). Orientations are derived and evaluated for each image and for each plot, using directional spatial filters (45° and 135°) and mathematical morphology algorithms. “Single-date” and “multi-temporal” approaches are considered. The single-date analyses confirm the good performances of the proposed method, but emphasize the limitation of the approach for estimating the crop row orientation over the whole landscape with only one date. The multi-date analyses allow (1) determining the most suitable agricultural period for the detection of the row orientations, and (2) extending the estimation to the entire footprint of the study area. For the winter crops (wheat, barley and rapeseed), best results are obtained with images acquired just after harvest, when surfaces are covered by stubbles or during the period of deep tillage (0.27 > R² > 0.99 and 7.15° > RMSE > 43.02°). For the summer crops (sunflower, corn and hemp), results are strongly crop and date dependents (0 > R² > 0.96, 10.22° > RMSE > 80°), with a well-marked impact of flowering, irrigation equipment and/or maximum crop development. Last, the extent of the method to the whole studied zone allows mapping 90% of the crop row orientations (more than 45,000 ha) with an error inferior to 40°, associated to a confidence index ranging from 1 to 5 for each agricultural plot.     

Relief-rejuvenation and topographic length scales in a fluvial drainage basin, Napf area, Central Switzerland

This paper explores how, and to what extent, a phase of relief-rejuvenation modifies the mode of surface erosion in an approximately 63 km² drainage basin located at the northern border of the Swiss Alps (Luzern area). In the study area, the retreat of the Alpine glaciers at the end of the Last Glacial Maximum (LGM) caused base level to lower by approximately 80 m. The fluvial system adapted to the lowered base level by headward erosion. This is indicated by knickzones in the longitudinal stream profiles and by the continuous upstream narrowing of the width of the valley floor towards these knickzones. In the headwaters above these knickzones, processes are still to a significant extent controlled by the higher base level of the LGM. There, frequent exposure of bedrock in channels and especially on hillslopes implies that sediment flux is to a large extent limited by weathering rates. In the knickzones, however, exposure of bedrock in channels implies that sediment flux is supply-limited, and that erosion rates are controlled by stream power.The morphometric analysis reveals the existence of length scales in the topography that result from distinct geomorphic processes. Along the tributaries where the upstream sizes of the drainage basins exceed 100,000–200,000 m², the mode of sediment transport and erosion changes from predominantly hillslope processes (i.e., landsliding, creep of regolith, rock avalanches and to some extent debris flows) to processes in channels (fluvial processes and debris flows). This length scale reflects the minimum size of the contributing area for channelized processes to take over in the geomorphic development (i.e., threshold size of drainage basin). This threshold size depends on the ratio between production rates of sediment on hillslopes, and export rates of sediment by processes in channels. Consequently, in the headwaters, erosion rates and sediment flux, and hence landscape evolution rates, are to a large extent limited by weathering processes. In contrast, in the lower portion of the drainage basin that adjusts to the lowered base-level, rates of channelized erosion and relief formation are controlled mainly by stream power. Hence, this paper shows that base-level lowering, headward erosion and establishment of knickzones separate drainage basins in two segments with different controls on rates of surface erosion, sediment flux and relief formation.     

构造应力场三维数值模拟的有限单元法

目前构造应力场的研究主要是基于平面的二维分析,随着油气成藏过程三维模拟的发展,应力场的三维数值模拟显得越来越重要.从三维空间角度出发,分析了应力场的有限元模拟与求解的整个过程.基于不规则六面体单元的角点网格数据模型,对有限元求解法进行了分析与研究并提出计算方法.基于不规则角点网格数据模型的三维构造应力场有限元计算方法是本文的创新点.最后用上述方法对东营凹陷的牛庄-王家岗区域三维应力场进行了实际模拟计算,计算结果相比于其他数据模型更符合实际情况.      

The active layer in gravel-bed rivers: An empirical appraisal

The vertical position of the streambed–water boundary fluctuates during the course of sediment transport episodes, due to particle entrainment/deposition and bedform migration, amongst other hydraulic and bedload mechanisms. These vertical oscillations define a topmost stratum of the streambed (i.e. the ‘active layer or active depth’), which usually represents the main source of particles entrained during long and high-magnitude bedload transport episodes. The vertical extent of this layer is hence a capital parameter for the quantification of bedload volumes and a major driver of stream ecology in gravel-bed rivers. However, knowledge on how the active depth scales to flow strength and the nature of the different controls on the relation between the flow strength and the active depth is still scarce. In this paper we present a meta-analysis over active depth data coming from ~130 transport episodes extracted from a series of published field studies. We also incorporate our own field data for the rivers Ebro and Muga (unpublished), both in the Iberian Peninsula. We explore the database searching for the influence of flow strength, grain size, streambed mobility and channel morphology on the vertical extent of the active layer. A multivariate statistical analysis (stepwise multiple regression) confirms that the set of selected variables explains a significant amount of variance in the compiled variables. The analysis shows a positive scaling between active depth and flow strength. We have also identified some links between the active depth and particle travel distances. However, these relations are also largely modulated by other fluvial drivers, such as the grain size of the bed surface and the dominant channel macro-bedforms, with remarkable differences between plane-bed, step-pool and riffle-pool channels. © 2020 John Wiley & Sons, Ltd.     

两种土壤温度算法的对比分析

为了定量理解黄土高原土壤的物理特性和过程, 为进一步提高陆面模式对该地区地表能量平衡模拟能力奠定基础, 本文利用2005年黄土高原陆面过程试验中7月22～26日期间裸土地表观测站土壤温度观测资料, 采用热传导（结合数学拟合法)、热传导－对流两种方法分别计算了该地区土壤热扩散率。本文还利用热传导－对流方法计算0.05～0.1 m浅薄土壤层的热扩散率垂直梯度与水通量密度之和, 其值介于0.80×10-6～2.43×10-6m/s之间。在此基础之上, 以0.05 m深度的土壤层为上边界, 分别利用上述两种方法模拟0.10 m深度的土壤层温度, 结果表明: 由于忽略土壤的垂直不均匀性和水分的垂直运动而只考虑热传导过程, 热传导方法不仅高估了土壤温度振幅, 而且高估了位相的延迟。而热传导－对流方法对温度振幅和位相的模拟值与实际观测值吻合较好, 白天 (北京时间08:00～20:00) 的温度模拟值相对测量值的平均误差、 标准差和归一化标准差分别为0.19 K、0.18 K和0.08%。