Interpolation using a generalized Green's function for a spherical surface spline in tension

A variety of methods exist for interpolating Cartesian or spherical surface data onto an equidistant lattice in a procedure known as gridding. Methods based on Green's functions are particularly simple to implement. In such methods, the Green's function for the gridding operator is determined and the resulting gridding solution is composed of the superposition of contributions from each data constraint, weighted by the Green's function evaluated for all output–input point separations. The Green's function method allows for considerable flexibility, such as complete freedom in specifying where the solution will be evaluated (it does not have to be on a lattice) and the ability to include both surface heights and surface gradients as data constraints. Green's function solutions for Cartesian data in 1-, 2- and 3-D spaces are well known, as is the dilogarithm solution for minimum curvature spline on a spherical surface. Here, the spherical surface case is extended to include tension and the new generalized Green's function is derived. It is shown that the new function reduces to the dilogarithm solution in the limit of zero tension. Properties of the new function are examined and the new gridding method is implemented in Matlab® and demonstrated on three geophysical data sets.     

顾及空间自相关的地理国情信息统计格网尺度选择——以植被覆盖信息统计为例

统计格网尺度的不同会带来统计结果的差异,如何选择统计格网是地理国情信息统计的重要工作。本文提出了一种顾及空间自相关的地理国情信息统计格网尺度选择方法。采用地理国情普查数据,在50 m、60 m、70 m、80 m、90 m、100 m、250 m、500 m和1000 m几个尺度下,以植被覆盖信息统计为例,利用面积占优法和中心点归属法两种方法分别进行格网化,得到了不同尺度的植被格网数据;计算植被覆盖面积统计误差,分析不同尺度下植被覆盖信息的空间自相关的变化特征,并利用Moran’s I系数差值进行尺度选择,得到了植被覆盖信息统计格网的适宜尺度。以龙沙区和清涧县作为研究区域,结果表明,在地理国情植被覆盖信息统计时,不同地区的格网统计适宜尺度是不一样的,植被覆盖度中低的龙沙区的适宜尺度为100 m,而植被覆盖度高的清涧县的适宜尺度为250 m。     

Uncertainty of rainfall-induced landslides considering spatial variability of parameters

A cross-correlation analysis is conducted to determine the impacts of the heterogeneity of hydraulic conductivity K_s, soil cohesion c′ and soil friction angle (tan φ′) on the uncertainty of slope stability in time and space during rainfall. We find the relative importance of tan φ′ and c′ depends on the effective stress. While the sensitivity of the stability to the variability of K_s is small, the large coefficient of variation of K_s may exacerbate the variability of pore-water pressure. Therefore, characterizing the heterogeneity of hydraulic properties and pore-water distribution in the field is critical to the stability analysis.     

Reliability bearing capacity analysis of footings on cohesive soil slopes using RFEM

Reliability analysis of bearing capacity of a strip footing at the crest of a simple slope with cohesive soil was carried out using the random finite element method (RFEM). Analyses showed that the coefficient of variation and the spatial correlation length of soil cohesion can have a large influence on footing bearing capacity, particularly for slopes with large height to footing width ratios. The paper demonstrates cases where a footing satisfies a deterministic design factor of safety of 3 but the probability of design failure is unacceptably high. Isotropic and anisotropic spatial variability of the soil strength was also considered.     

Research Advances of Coastal Ecological Carrying Capacity Evaluation Based on Sustainable Projects Plan

Coastal area is the region with the highest degree of economic and social development and the largest ecological stress in current China, where the proportions and the spatial patterns of developed coastal resource and environment are determined by projects planning. Ecological carrying capacity evaluation is the necessary prerequisite for sustainable utilization of natural resources and protecting ecological environment to ensure healthy and sustainable economic and social development to project planning. Based on the pressure types of projects planning on resources and environment, the concept and contents of coastal ecological carrying capacity were redefined for enhancing the practical value of ecological carrying capacity evaluation. The domestic and foreign research progress and advances related with coastal ecological carrying capacity evaluation were reviewed, which included habitat suitability evaluation, suitability assessment of construction land development, reclamation suitability evaluation and assessment of sea water environmental capacity. The conclusion noted that domestic research of coastal ecological carrying capacity needs to build a complete system of ecological carrying capacity evaluation methodology based on extensive reference to foreign research results, and quantitative evaluation and spatial visualization research related with coastal ecological carrying capacity should be carried out to provide strong support for ecological civilization process of economy and society in coustal areas.     

GPU加速的改进PAM聚类算法研究与应用

空间聚类是空间数据挖掘的重要方法,而K-Medoids是一种常用的空间聚类算法。K-Medoids聚类算法存在初始点选择问题,而且计算复杂。为了提高算法的有效性和时间效率,本文结合模拟退火算法思想,改进了传统的K-Medoids算法PAM,提出一种基于GPU计算的并行模拟退火PAM算法。类比矩阵乘法运算,定义了一种新的矩阵计算方法,可以有效减少数据在GPU全局内存和共享内存之间的传输,提高了算法在GPU中的执行效率。利用模拟退火算法搜索聚类中心点,保证了聚类结果的全局最优性。基于不同的数据集,将串行和并行模拟退火PAM算法以及已有的遗传PAM算法进行比较,结果表明并行模拟退火PAM算法聚类结果正确,且时间效率高。最后,应用本文改进算法对贵州省安监系统的安全监管隐患数据进行聚类分析,发现了隐患聚集中心,相关结果对政府的决策具有一定的实际应用价值。     

Planners to the rescue: Spatial planning facilitating the development of offshore wind energy

The development of offshore wind energy has started to take place surprisingly quickly, especially in North European waters. This has taken the wind energy industry out of the territory of planning systems that usually govern the siting of wind farms on land, and into the world of departmental, sectoral regulation of marine activities. Although this has favoured the expansion of offshore wind energy in some respects, evidence suggests that the practice and principles of spatial planning can make an important contribution to the proper consideration of proposals for offshore wind arrays. This is especially so when a strategic planning process is put in place for marine areas, in which offshore wind is treated as part of the overall configuration of marine interests, so that adjustments can be made in the interests of wind energy. The current process of marine planning in the Netherlands is described as an illustration of this.     

Effects of sampling effort on the estimation of spatial gradients in a tropical reservoir impacted by an oil refinery

We investigated the effects of increase in sampling effort (30-1043 sampling points) on the accuracy of assessment of the spatial patterns of surface-water quality in a eutrophic tropical reservoir. The investigation was carried out during the dry season, when previous investigations showed that the spatial heterogeneity is more stable. A multi-parameter Yellow Springs Instruments probe coupled to a TechGeo D-GPS was used. This system is equipped to measure and store in a continuous recording mode, several physical and chemical parameters linked to geographical coordinates obtained with a precision of less than 1 m. We used different geostatistical approaches to determine the optimal number of sampling points required to reflect the real spatial patterns of water quality in the system. This approach was tested in a small tropical reservoir (Ibirité) that receives effluents from an oil refinery (the state-owned REGAP oil refinery, PETROBRAS) located near the city of Belo Horizonte. The study showed not only that the spatial patterns of water quality are significantly affected by sampling effort but also it was demonstrated that the establishment of an adequate sampling program is a critical point for the precise identification of source points of pollution. The results of this investigation enabled us to demonstrate the potential uses and limits of this method for rapid assessment of the water quality of lakes and reservoirs that receive external inputs of water contaminants or nutrients.     

滇西南地震活动特征分析

对滇西南1970年以来所有M≥4.6级地震前的空间活动图像进行研究,用地震频度作为参数描述地震前区域的地震活动增强与平静现象,用空区、条带描述地震的孕震过程,得到以下认识:①地震频度增加是滇西南地区5级以上地震前的共性特征;②滇西南地区M≥4.6级地震前出现空区的比例随着地震震级的增加而有所增加,4.6~4.9级地震前只有60%的地震出现空区,5.0~5.9级地震前有90.9%的地震出现空区,而6.0级以上地震前全部出现空区;③空区平均持续时间也随着震级的加大而增加,空区平均持续时间为13.58个月,最短为3个月,最长为37个月;④主震位置(27/33)多发生在空区边缘(含长轴端12次、短轴端8次)。震前出现条带的规律则不明显。