基于RBF神经网络的GPS高程异常拟合

由GPS静态相对定位获取三维基线向量,通过GPS网平差可以获取高精度的、相对于WGS84椭球的GPS大地高,而在实际工程中应用的高程则为正常高,因此必须进行高程异常的拟合。结合水准测量的实测数据,分别采用RBF神经网络方法和多项式曲面拟合方法拟合某测区的GPS点的高程异常,计算各点的拟合残差,并对2种方法的精度进行比较分析,得到该地区解算正常高最适用的方法。     

机载激光雷达森林叶面积指数反演研究

叶面积指数(LAI)是分析冠层结构最常用的参数之一,它控制着植被的生物物理过程,如光合、呼吸、蒸腾、碳循环和降水截获等,因此快速、可靠和客观地评价LAI非常重要.本文发展了激光穿透指数(LPI)的简化计算方法,首次利用校正后的回波强度计算出LPI,以LPI为变量基于Beer-Lambert定律实现了甘肃大野口研究区森林LAI反演,并且与原始回波强度和回波数反演LAI的精度进行对比,结果发现通过距离和角度校正后的回波强度值能提高LAI反演精度.为了评价模型的可靠性和泛化性能,用留一法交叉验证程序(LOOCV)对最佳反演模型进行了验证,表明该模型没有过度拟合,具有很好的泛化能力.最后,用没有参加建模的16个实测LAI对预测值进行精度验证(R²=0.810,RMSE=0.198),发现校正后的回波强度反演山区森林LAI精度较高.本文还对激光雷达LAI反演结果与传统光学TM影像的反演结果进行了对比分析,结果表明机载激光雷达反演LAI精度(R²=0.825,RMSE=0.165)高于光学TM遥感数据(R²=0.605,RMSE=0.257),因此,可用激光雷达数据实现研究区的高精度LAI反演,为生态环境研究提供可靠的基础数据.     

城区GPS地籍三维控制网的数据处理和分析

对青岛市某区GPS地籍控制网进行了数据处理和精度分析,由已知CORS基准站的高程异常利用二次曲面模型拟合得到了四等控制网点的正常高,通过对拟合点高程精度进行检验分析,验证了控制网精度的可靠性。     

引入改进Snake模型的黄土地形沟沿线连接算法

提出了一种利用坡面汇流改进的Snake模型实现黄土地貌沟沿线栅格点自动连接的新方法.该方法基于高分辨率DEM数据,利用正负地形边界处坡度转折特征,识别沟沿线点,进而用坡面汇流方向场改进了Snake模型中的梯度矢量流场,指引分水线缓冲曲线向沟沿线点蠕移,达到有序连接沟沿线点从而实现正、负地形的自动分割的目的.对比实验结果表明,该方法所识别的黄土沟沿线较好地逼近真实的地形特征.     

渤海海域海洋平台抗震设防标准研究

This paper analyzes the seismicity and seismic risk distribution in the Bohai Sea. Based on the seismic design parameters of 46 platforms in the Bohai Sea, a statistic analysis is made on the ratios of the peak accelerations for different probability levels. In accordance with the two-stage design method, a scheme of two design seismic levels is proposed, and two fortification goals are established respectively for strength level earthquakes and ductility level earthquakes. Through analogy and comparison to the Chinese seismic code for buildings, it is proposed that the probability level for the strength and ductility level earthquakes takes return periods of 200a and 1000～2500a respectively, and we further expounded on its rationality. Finally, the fortification parameters in the sub-regions of Bohai Sea area are given in the light of seismic risk zonation and ground motion division. This article is a summary of experiences from many years of offshore platform seismic fortification work, and an exploratory study on the seismic fortification standards of offshore platforms in China, which may provide some references for the establishment of the standard.     

The characteristics of shear wave splitting in the source region of the April 20, 2013 Lushan earthquake

Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams, this paper preliminarily contains the polarization directions of fast shear wave and the time-delays of split shear waves at every station, and analyzes the crustal anisotropic characteristics in the source region. In the study area, the polarization directions at stations BAX, TQU, L132, L133, L134, and L135 are northeast, which is consistent with the strike of Dachuan–Shuangshi fault. There are two polarization directions at MDS and L131, which are northeast and southeast. The scatter of polarization directions suggests the complex stress field around these two stations where two faults intersect. For the normalized time-delays at every station, the range is 1.02–8.64 ms/km. The largest time-delay is from L134 which is closest to the mainshock, and the smallest one is from L133. The variations in time-delays show the decreasing at stations BAX, L134, and L135 because of the stress–relaxation after earthquake.     

射电阵列天线和接收机性能综合测试方法

首先回顾了在现场射电望远镜天线性能的Y系数测量方法,指出如略加改进并利用射电望远镜自身接收机作测试接收机,则即能测出天线性能,又能测出接收机性能,详尽描述了这种改进方法。测量方法是模拟接收机输入端分别连接到50Ω终端、噪声源及天线输出端,且天线分别指向冷空和太阳。由测量方法得出4个传输方程,进而导出模拟接收机系统噪声温度、天线噪声温度、模拟接收机增益及天线增益与测试数据紧密联系的表达式。以一个射电望远镜测试数据为依据,算出相应系统参数并与设计指标要求进行了比对。小结中列出这种方法的优点,同时也讨论了现场测量天线增益的方向图法。     

西昆仑阿勒塔什地区ASTER影像岩性划分方法研究

以西昆仑造山带西段阿勒塔什地区为例,在缺少地表各岩石单元样品的情况下,对ASTER VNIR-SWIR波段反射率数据进行处理,提取岩性信息。首先对VNIR-SWIR多波段反射率数据进行最佳指数因子(IOIF)运算,得出最佳波段组合Band7-Band4-Band3,从其假彩色合成图像上只能识别少量岩性单元;为了减少高相关性波段之间的信息冗余度、并对波段信息进行集成,后对ASTERVNIR-SWIR波段反射率数据采用主成分变换并进行彩色合成,该图像能详细划分研究区多种岩性单元,如元古宙岩层、志留纪岩层、二长花岗岩岩体和英云闪长岩岩体,以及微观地质信息,如侵入岩热接触变质带、小型岩株和岩性界线。对比已有少量地质资料,认为提取结果可靠,为野外地质制图工作能提供超前信息。     

松辽盆地南部协尔苏凹陷铀成矿控制因素与成矿模式探讨

通过对协尔苏凹陷地质特征的研究,认为协尔苏凹陷铀矿（化）为后生多期次叠加改造成因,其形成主要受铀源、构造、目的层沉积体系、层间氧化带发育程度和地下水动力变异等因素控制。在总结上述控制因素的基础上,初步建立了成矿模式。