Stratified spectral mixture analysis of medium resolution imagery for impervious surface mapping

Linear spectral mixture analysis (LSMA) is widely employed in impervious surface estimation, especially for estimating impervious surface abundance in medium spatial resolution images. However, it suffers from a difficulty in endmember selection due to within-class spectral variability and the variation in the number and the type of endmember classes contained from pixel to pixel, which may lead to over or under estimation of impervious surface. Stratification is considered as a promising process to address the problem. This paper presents a stratified spectral mixture analysis in spectral domain (Sp_SSMA) for impervious surface mapping. It categorizes the entire data into three groups based on the Combinational Build-up Index (CBI), the intensity component in the color space and the Normalized Difference Vegetation Index (NDVI) values. A suitable endmember model is developed for each group to accommodate the spectral variation from group to group. The unmixing into the associated subset (or full set) of endmembers in each group can make the unmixing adaptive to the types of endmember classes that each pixel actually contains. Results indicate that the Sp_SSMA method achieves a better performance than full-set-endmember SMA and prior-knowledge-based spectral mixture analysis (PKSMA) in terms of R, RMSE and SE.     

从中国目视资料分析1998年狮子座流星雨

本文分析了１９９８ 年狮子座流星雨的一部分中国目视资料。资料启示：１９９８ 年狮子座流星雨来自两股不同组成的流星体颗粒的不均匀混合流。按照这种观点进行了以这些目视资料为基础的计算,从而解释了目视观测与雷达观测所得结果之间的矛盾。     

Influence of cohesion on California bearing ratio of clay-gravel mixtures

An understanding of the behavior of cohesive sediment is required to solve various engineering problems such as scour around bridge elements, mitigation of soil erosion, pavement design, river bed degradation,stable channel design. Pavement foundation designers principally use the California bearing ratio(CBR)to describe the subgrade and subbase materials and their strength. Several laboratory experiments were done to study the variation in the CBR of cohesive mixtures comprised of clay-gravel m...     

苏北盐城凹陷天然气与凝析油的成因机制

盐城凹陷天然气中甲烷含量高,碳同位素具有正分布系列,主体具有高成熟腐泥型气特征,伴随产出的凝析油则体现出与本区湖相原油和海相原油既相似又相区别的特征。不同组分间存在成熟度差异,轻质组分反映高成熟,中等组分体现出未熟低熟,重质组分表现出成熟特征。母源分析对比表明天然气与凝析油主要源自古生界海相腐泥型源岩,混有泰州组少许贡献,造成组分差异和成熟度变化的重要原因是大量气体注入配以长期发育断裂引起的运移分馏和不同成熟度油气混合所致。     

基于像素工厂处理不同影像数据源制作DOM的研究

简要介绍了像素工厂影像处理系统,通过卫星影像、ADS80影像、DMC框幅式影像3种数据源的处理,分析3种数据源处理过程中生产DOM(数字正射影像)各个环节的流程,以及在处理过程中与Arc GIS和Terrasolid等软件的配合使用。     

Bivariate Gaussian mixture–based equivalent linearization method for stochastic seismic analysis of nonlinear structures

To address challenges in stochastic seismic analysis of nonlinear structures, this paper further develops a recently proposed Gaussian mixture–based equivalent linearization method (GM‐ELM). The GM‐ELM uses a Gaussian mixture distribution model to approximate the probabilistic distribution of a nonlinear system response. Using properties of the Gaussian mixture model, GM‐ELM can decompose the non‐Gaussian response of a nonlinear system into multiple Gaussian responses of linear single–degree of freedom oscillators. With the set of the equivalent linear systems identified by GM‐ELM, response statistics as crossing rate and first‐passage probability can be computed conveniently using theories of linear random vibration analysis. However, the original version of GM‐ELM may lead to an inaccurate estimate because of the heuristic parameters of the linear system introduced to supplement insufficient information. To overcome this limitation and define unique equivalent linear systems, this paper proposes a further developed version of GM‐ELM, which uses a mixture of bivariate Gaussian densities instead of univariate models. Moreover, to facilitate the use of elastic response spectra for estimating the mean peak responses of a nonlinear structure, a new response spectrum combination rule is proposed for GM‐ELM. Two numerical examples of hysteretic structural systems are presented in this paper to illustrate the application of the bivariate GM‐ELM to nonlinear stochastic seismic analysis. The analysis results obtained by the bivariate GM‐ELM are compared with those obtained by the univariate GM‐ELM, the conventional equivalent linearization method, the tail equivalent linearization method, and Monte Carlo simulation. The supporting source code and data are available for download at https://github.com/yisangri/GitHub‐bGM‐ELM‐code.git     

黏土水泥浆材特性的试验研究

黏土水泥浆材是采空区处治的优选注浆材料,但目前关于优化浆材配比的研究较少。针对毕威高速公路水塘隧道出口段采空区处治工程,提出采用黏土水泥浆液进行注浆处理,并进行室内试验研究,得到了不同配比浆液的凝结时间、结石率、结石密度、结石体抗压强度、渗透系数及冲蚀率等性能指标。试验结果表明,固相比较低的浆液凝结时间较短,抗压强度较高,渗透系数较大;随原浆比重增加,浆液的凝结时间缩短,强度提高且渗透系数降低;偏铝酸钠可有效缩短浆液的凝结时间;最终确定了黏土水泥浆材的配比和原浆比重。本次研究可为高速公路下伏采空区的注浆治理提供设计依据。     

像平面坐标到经纬度坐标的转换

坐标转换是所有的遥感、GIS、航测等软件都必须具备的一个基本功能,在功能实现中会遇到大规模的矩阵运算问题,而灵活运用IDL编程工具中的结构数组运算能大大地简化计算步骤,加快图像处理的速度。本文运用IDL设计了坐标转行算法,对于一幅row(行)、col(列)的图像,在已知该幅图像其中一个像元点在图像中的像元位置和经纬度坐标的情况下,利用该算法能够实现整幅图像中所有点的经纬度坐标的计算,并验证了其正确性。     

孔隙液体的可压缩性对非饱和孔隙介质弹塑性分析的影响

首先在多相孔隙介质的混合物理论框架内探讨了如何利用固-液两相孔隙介质模型描述介质的非饱和问题。其次,讨论了一个实用的描述孔隙液体可压缩性的方法,并建立了小变形条件下固-液两相孔隙介质的弹塑性本构方程。最后,采用俞茂宏统一强度理论,针对一个具体的结构例子,分析了孔隙液体的可压缩性对结构弹塑性分析的影响。     

浅谈QuickBird-2卫星影像在PixelFactory中的空三方法

像素工厂可以快速、高效地生产卫片正射影像,而空三加密又是正射影像生产过程中的重要步骤。本文以QuickBird-2卫星影像为例,结合实际生产,探讨了大区域卫星影像在PixelFactory软件中的空三方法及注意事项。