计算几何算法在GIS图形分析中的应用

图形空间分析是地理信息系统的重要功能之一。根据地理信息系统应用领域的不同。所需的图形空间分析功能也不尽相同，但是，各种图形空间分析功能所涉及到的基本图形关系的判断确基本相同。文中介绍并改进了一些计算几何方法在ＧＩＳ常用图形分析中的应用。目的在于抛砖引玉，让更多的人开展这方面的研究。     

罕遇地震下多、高层支撑体系塑性极限的计算机分析

根据已建立的框架-斜撑结构的在水平地震作用下的破坏模式和极限承载力表达式，编制了计算程序。通过程序计算，可以得出结构在不同破坏模式下的承载力值。通过对承载力值进行分析，可以确定结构在水平地震作用下的最小荷载和最可能破坏模式。     

焉耆盆地三工河组储层流体包裹体形成期次分析

焉耆盆地三工河组流体包裹体具有丰度低、个体小的特征,并以液态烃相包裹体为主,主要分布在石英颗粒的溶孔或溶缝当中。结合盆地成岩作用和有机质演化历史分析,认为它们形成于侏罗纪晚期的以压溶和溶蚀作用为特征的晚成岩作用阶段。包裹体均一温度呈双峰型分布,具有 10 1~ 110℃和 12 1~ 130℃两个区间,结合焉耆盆地的埋藏史和盆地的热史,这两个温度区间分别对应于晚侏罗世和侏罗纪末期。包裹体组份特征分析也证实该地区存在两期包裹体,并且包裹体组分主要是在烃源岩低成熟阶段形成的。可以认为,焉耆盆地三工河组储层的流体包裹体主要是在晚侏罗世烃源岩的低成熟阶段和侏罗纪末期烃源岩的成熟阶段形成。     

Equivalent Permeability and Simulation of Two-Phase Flow in Heterogeneous Porous Media

The problem of calculating equivalent grid block permeability tensors for heterogeneous porous media is addressed. The homogenization method used involves solving Darcy's equation subject to linear boundary conditions with flux conservation in subregions of the reservoir and can be readily applied to unstructured grids. The resulting equivalent permeability tensor is stable as defined relative to G-convergence. It is proposed to use both conforming and mixed finite elements to solve the local problems and compute approximations from above and below of the equivalent permeability, respectively. Comparisons with results obtained using periodic, pressure and no-flux boundary conditions and the renormalization method are presented. A series of numerical examples demonstrates the effectiveness of the methodology for two-phase flow in heterogeneous reservoirs.     

极点对称模态分解下西安高温天气的趋势特征

基于1960-2016年西安均一化气象资料,采用极点对称模态分解法,对西安市的高温天气变化特征进行分析,探讨赤道东太平洋海温异常（El Ni?o）、西太平洋副热带高压变化（WPSH）,与西安极端高温变化的关系。结果表明：① 采用非均一化数据,会低估西安暖夜、夏季、热夜、热浪日数变化趋势,高估冬季供暖能耗下降幅度、夏季制冷能耗上升幅度,对暖昼、高温日数影响相对较小。② 在年代变化上,暖昼、热浪、高温日数和制冷度日等四个指标,反映西安白天高温变化特征,呈现一致的四阶段“下降—上升—下降—上升”的变化过程;表征夜间高温变化的暖夜和热夜日数,以1993年为节点,呈现两阶段“阶梯状”的上升趋势。③ 在影响因素上,赤道太平洋中西部海温异常与西安高温关系更为密切。当Ni?o 4区海温异常偏高时,西安暖昼、夏季、炎热天气制冷耗能明显增加,寒冷天气供暖能耗显著降低;同时,当WPSH强度越大,控制面积越大、西伸脊点偏西时,西安暖夜、夏季、热夜日数明显增加、寒冷天气供暖能耗明显下降。     

四川盆地威远气田碳酸盐岩中有机包裹体研究

本文通过对威远、资阳地区上震旦统碳酸盐岩储集层中有机包裹体的研究,提出有机包裹体多分布于储层孔洞缝中所充填的三期矿物中,研究区油气运移的主要通道是溶蚀孔洞和裂缝。并根据不同期次充填矿物中有机包裹体特征、均一温度及单个有机包裹体成分,追索了研究区油气热演化程度、油气运移期次、油气运移的深度和温度。研究结果表明,研究区存在三次主要的油气运移和聚集,其各自演化的程度及油气运移的深度和温度皆不同。     

Yield design of dry‐stone masonry retaining structures—Comparisons with analytical,numerical, and experimental data

Over the past few years, there has been a steady increase in the interest in dry‐stone walling not only to preserve existing constructions but also to build new ones. Yet, dry masonry's expansion is slowed down by the lack of scientific knowledge to assess its reliability. This study aims at contributing to the construction of this scientific frame using a simplified model based on yield design and homogenization, which can be directly exploited for engineering purposes. A new analytical expression of the ultimate load is thus established. Then, the validity of the method is assessed by comparisons with limit equilibrium analysis, distinct element method, and field trials. Finally, possible improvements of the model are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Simulation of airflow around rain gauges: Comparison of LES with RANS models

Wind is responsible for systematic errors that affect rain gauge measurements. The authors investigate the use of computational fluid dynamics (CFD) to calculate airflow around rain gauges by applying a high-resolution large eddy simulation (LES) model to determine the flow fields around a measuring system of two rain gauges. The simulated air flow field is characterized by the presence of massive separation which induces the formation and shedding of highly unsteady eddies in the detached shear layers and wakes. Parts of these detached structures occur over the orifice of the rain gauges and may substantially affect the dynamics of the raindrops in this critical region. Non-dissipative LES methods used with fine enough meshes can successfully predict these eddies and their associated fluctuations. The authors compare statistics from LES with steady-state Reynolds averaged Navier–Stokes (RANS) simulations using the k–ε and shear stress transport k–ω turbulence models. They find that both RANS and LES models predict similar mean velocity distributions around the rain gauges. However, they determine the distribution of the resolved turbulent kinetic energy (TKE) to be strongly dependent on the RANS model used. Neither RANS model predictions of TKE are close to those of LES. The authors conclude that the failure of RANS to predict TKE is an important limitation, as TKE is needed to scale the local velocity fluctuations in stochastic models used to calculate the motion of raindrops in the flow field.     

Taking into account general boundary conditions in upscaling absolute permeability

Upscaling methods that need to solve local problems subject to boundary conditions are addressed in this article. We define a new upscaling method based on optimization problems, which can take into account general boundary conditions applied to local problems. The determination of upscaled permeability leads to minimizing the difference of dissipated energies (or averaged velocity) at fine and large scale. Using optimal control techniques, we obtain an effective computing algorithm that allows us to recover, with classical boundary conditions, the well-known results. The uniqueness issue is tackled for the optimization problems introduced in our approach. We show that the method is stable with respect to G-convergence, a property that establishes a link with homogenization theory, and finally, 2D numerical experiments are presented.