基于局地相似理论的蒸发波导计算方案及敏感性试验

蒸发波导是海洋环境中最常出现的异常大气折射结构,具有很高的利用价值.利用局地相似理论代替 Monin-Obukhov 相似理论来确定近地层温度、湿度垂直分布廓线,并借助热带海洋全球大气-海气耦合响应试验(TOGA COARE) 中提出的总体通量算法,对 Local 模式和 New 的推导过程和算法设计进行了详细的阐述和说明.通过比较不同模式的计算结果和敏感性试验发现,在较强逆温和低风速(强稳定层结) 条件下,除 P-J 模式外,基于 Monin-Obukhov 相似理论的蒸发波导模式计算的高度值均出现异常突变;而基于局地相似理论的 Local 模式能够有效抑制这种异常突变的现象,且与加入人为修正的 P-J 模式结果比较接近.New 模式集 Babin 模式与 Local 模式的优点于一身,应该说是目前理论上最为完善的模式.     

三维轴对称驻点流系统的一些研究(英文)

为了研究Navier-Stokes方程相关的三维轴对称驻点流系统的解,给出了一个积分方程系统,扩展了它的用途.并通过研究该积分方程系统的性质,在更广的范围内,利用这个系统的解,得出了与Navier-Stokes方程相关的三维轴对称驻点流系统的相似解.同时还改进了一个相似解的不存在性结果.     

油气混输系统的实验研究与实验模拟准则

描述了油气混输系统的实验研究,特别是多相流的流态、增压、计量系统的实验研究,并用动力相似理论分析了油气混输两相管流实验模拟所需满足的相似参数,提出了各种简化条件下的相似规律,讨论了用水和空气的两相流动来模拟原油和天然气的两相流动的可靠性和提高实验精度的手段和方法。     

Quantitative relations between spatial similarity degree and map scale change of individual linear objects in multi-scale map spaces

Quantitative relations between spatial similarity degree and map scale change in multi-scale map spaces play important roles in map generalization and construction of spatial data infrastructure. Nevertheless, no achievements have been made regarding this issue. To fill the gap, this paper firstly proposes a model for calculating spatial similarity degrees between an individual linear object at one scale and its generalized counterpart at the other scale. Then psychological experiments are designed to validate the new model, taking four different individual linear objects at five different scales as test samples. The experiments have shown that spatial similarity degrees calculated by the new model can be accepted by a majority of the subjects. After this, it constructs a formula that can calculate spatial similarity degree using map scale change (and vice versa) for individual linear objects in multi-scale map spaces by the curve fitting method using the point data from the psychological experiments. Both the formula and the model can calculate quantitative relations between spatial similarity degree and map scale change of individual linear objects in multi-scale map spaces, which facilitates automation of map generalization algorithms for linear features.     

基于相似预报法的宁夏雷电潜势预报业务系统

以宁夏雷暴、闪电观测资料和ECMWF、T213数值预报产品为基础,采用VB、VC语言和MS SQL Server数据库等编程技术,研制开发了基于相似预报法的宁夏雷电潜势预报业务系统。系统在客观形势相似和影响系统判别的基础上进行物理量相似离度分析,可提供0～168h环流形势和物理量相似预报结果,并以相似离度最小的前10(20)个最佳相似个例中的一个作为预报蓝本,以人机交互的方式完成0～12h雷电潜势预报的制作与分发,增强了雷电潜势预报的客观化和自动化;实现了历史雷电数据的查询、统计、输出、保存、添加入库及闪电信息的统计显示等功能,成为宁夏雷电潜势预报制作发布的主要工作平台。     

基于CiteSpace的近三十年中国泥石流灾害风险研究综合分析

本文以吉林省永吉县为研究区,结合历史资料与现场实际情况,研究了基于地理信息相似度的负样本采样策略在泥石流易发性评价中的应用,并探索了不同取值范围下选取的负样本对最终易发性评价结果的影响。本次研究选取了高程、坡度、坡向、平面曲率、剖面曲率、年平均降水量、归一化植被指数、地形湿度指数、断层密度、道路密度、水系密度、人口密度、土地利用类型、岩土体类型等14个因子,依离散型与连续型两种分类采用不同方法计算单因子相似度,综合获得全区地理信息相似度后按其不同阈值进行负样本采样,并以支持向量机模型为基础模型,采用受试者工作特征曲线、正样本准确率和预报效率曲线3种评价方法进行了评价。结果显示：当负样本的地理信息相似度值逐渐增大时,模型精度和正样本准确率逐步降低,预报效率先增后降,易发程度由高估向低估变化;在地理信息相似度取值范围0~0.5内选取的负样本兼顾了模型准确性与土地利用价值,并具有最高的预测效率,是一种优秀的负样本取样策略。本次研究结果与实际较为相近,基于地理信息相似度的负样本采样策略有效提升了负样本质量,提高了预测效率,合理平衡了易发区划分与土地利用的矛盾,可为研究区防灾政策的制订、区域防灾的土地规划提供依据,也为区域泥石流易发性评价提供了一种新的思路。     

基于理想分形规则扩展的地图曲线模拟方法研究

针对地图目标中许多线状要素具有典型统计分形特征的性质,探讨了在理想分形规则基础上通过增加随机因子,从而根据分维数反过来模拟构建地图曲线的方法.     

两种地图点群综合算法的比较

通过搭建实验程序,分别对基于非加权Voronoi图和加权Voronoi图的点群自动综合算法进行验证,详细对比和分析两种算法计算结果对点群的统计信息、拓扑信息、度量信息和专题信息的传递情况,计算部分结果的相似度,从而得出加权Voronoi图点群综合算法更优的结论。     

Modelling time varying scouring at bed sills

In this paper a modelling approach is presented to predict local scour under time varying flow conditions. The approach is validated using experimental data of unsteady scour at bed sills. The model is based on a number of hypotheses concerning the characteristics of the flow hydrograph, the temporal evolution of the scour and the geometry of the scour hole. A key assumption is that, at any time, the scour depth evolves at the same rate as in an equivalent steady flow. The assumption is supported by existing evidence of geometrical affinity and similarity of scour holes formed under different steady hydraulic conditions. Experimental data are presented that show the scour hole development downstream of bed sills due to flood hydrographs follow a predictable pattern. Numerical simulations are performed with the same input parameters used in the experimental tests but with no post‐simulation calibration. Comparison between the experimental and model results indicates good correspondence, especially in the rising limb of the flow hydrograph. This suggests that the underlying assumptions used in the modelling approach are appropriate. In principle, the approach is general and can be applied to a wide range of environments (e.g. bed sills, step‐pool systems) in which scouring at rapid bed elevation changes caused by time varying flows occurs, provided appropriate scaling information is available, and the scour response to steady flow conditions can be estimated. Copyright © 2011 John Wiley & Sons, Ltd.