Landslide susceptibility mapping based on Support Vector Machine: A case study on natural slopes of Hong Kong, China

The Support Vector Machine (SVM) is an increasingly popular learning procedure based on statistical learning theory, and involves a training phase in which the model is trained by a training dataset of associated input and target output values. The trained model is then used to evaluate a separate set of testing data. There are two main ideas underlying the SVM for discriminant-type problems. The first is an optimum linear separating hyperplane that separates the data patterns. The second is the use of kernel functions to convert the original non-linear data patterns into the format that is linearly separable in a high-dimensional feature space. In this paper, an overview of the SVM, both one-class and two-class SVM methods, is first presented followed by its use in landslide susceptibility mapping. A study area was selected from the natural terrain of Hong Kong, and slope angle, slope aspect, elevation, profile curvature of slope, lithology, vegetation cover and topographic wetness index (TWI) were used as environmental parameters which influence the occurrence of landslides. One-class and two-class SVM models were trained and then used to map landslide susceptibility respectively. The resulting susceptibility maps obtained by the methods were compared to that obtained by the logistic regression (LR) method. It is concluded that two-class SVM possesses better prediction efficiency than logistic regression and one-class SVM. However, one-class SVM, which only requires failed cases, has an advantage over the other two methods as only “failed” case information is usually available in landslide susceptibility mapping.     

煤岩强度离散性及三轴压缩试验研究

简述了煤的强度离散性原因。采用超声脉冲穿透法测量煤样波速并进行岩石力学试验,回归分析得出了煤岩试件声速与其力学参数之间的关系式,为尽可能避免因煤样离散性而带来的盲目试验提供了一条技术途径。采用MTS815岩石伺服试验系统进行了煤样三轴压缩试验。结果表明,与花岗岩等高强度岩石不同,由于煤的孔隙裂隙发育在围压作用下孔隙裂隙被压密闭合,煤的弹性模量随围压增大而增大,但并非线性关系;煤的轴向破坏应力及残余强度均随围压增大而增大。研究结论对于在破碎煤体中掘进的巷道的锚固机理研究有重要指导意义。     

共线不连通断层标本变形过程中群体微破裂事件的时空演化

设计了共线不连通断层物理模型,在概念上可模拟与地震孕育相关的障碍体或强固区。开展了中等尺度辉长岩标本的双轴破裂实验,对4600余次微破裂事件进行了精确定位,据此对共线不连通断层标本变形过程中群体微破裂事件时空演化的统计特征进行初步研究。由于强闭锁作用,变形过程中在98％的峰值强度,以前围绕不连通区域显示一系列在时间上依次递进、空间上逐步收缩、长轴方向随之改变的“空区”演化图像。在峰值强度后的弱化阶段,较大的声发射事件在被动盘明显丛集,而主动盘则小AE事件呈弥散性分布,与弹性变形阶段相比。弱化阶段AE主体活动区域从主动盘迁移至被动盘,并且AE较大事件次数明显增多、应变能释放急剧增加,声发射率在不连通区域破裂前的瞬间达到最高值。b值在不连通区域破裂失稳前显示“趋势性降低—快速回升”这一典型变化过程。对比研究还表明,破裂型失稳较粘滑型失稳具有更为明显、丰富的微破裂前兆。     

A Statistical Approach to Geological Mapping

A geological map is the representation, on a two-dimensional plane, of the disposition of three-dimensional rock bodies exposed on the earth's surface. The problem of mapping is essentially that of dividing an area into homogeneous subregions on the basis of the exposed rock types. Automatic Bayesian methods of model selection using default Bayes factors have been employed to solve the problem of choosing a set of boundaries between homogeneous subregions, assuming no complication excepting low-angle tilting affected rock bodies. The method is tested on two data sets. A sampling scheme for optimum allocation of observation points is also presented.     

固体传压高温高压实验中岩样环境温度场实验分析

固体传压高温高压实验中,岩样环境温度是重要参数。本文用有限元法进行了理论估算,并用热电偶实测了岩样区的温度场分布。给出了场的特征分析。     

热解——动力学法测定岩石和化探样品中痕量碘

以五氧化二钒和三氧化二铋为熔剂,研究了分离富集痕量碘的最佳条性,以及影响催化反应速度的因素。用改变温度和时间的方法提高测定方法的灵敏度和扩大碘的测定范围。本方法具有灵敏度高、选择性好、操作简便、快速和经济的特点,最低检出限为0.033ppm碘,标准偏差为4.45％。     

支持向量机中遗传模糊C-均值的样本预选取方法

提出了在支持向量机(support vector machine,SVM)方法中采用遗传模糊C均值(FCM)进行样本预选取的方法,旨在保留最优分类超平面附近的样本点,去除远处样本点,使训练样本集减小,消除冗余,从而减小所需内存。并以航空影像中的居民地为例进行分析,结果表明,按比例减少样本集后的分割结果与用原样本集的基本一样。     

遥感图像分类精度的点、群样本检验与评估

遥感专题分类结果在使用前,必须进行客观可靠的精度验证和分析,以保持遥感分类结果的可靠性.本文利用不同分辨率遥感数据获取的同一地区土地利用/覆盖信息,进行了简单随机抽样、系统抽样和分层抽样三种不同抽样组织方式下的点样本和群样本检验分析,评估了不同抽样方式下的点样本和群样本检验效果.研究结果表明：（1）抽样方式对遥感分类精度评价结果的影响是客观存在的,不同抽样方式下的点样本和群样本检验结果都存在一定的随机性,但同一种抽样方式下,点样本检验精度评估结果的波动幅度小于群样本检验,稳定性比群样本检验要好;（2）不同抽样方式下的多次点样本和群样本检验的平均精度检验结果基本上都能够反映分类图像的精度特征,其中,点样本检验中,分层随机抽样点样本检验效果较好;群样本检验中,系统抽样群样本检验和分层随机抽样群样本检验的效果优于简单随机抽样群样本检验.     

少量树木年轮样品的X射线荧光光谱分析

采用活体采样技术，对少量树木年轮样品的制备和测定方法进行了研究。使用X射线荧光光谱和透空测量方式，对树木年轮中Cl、Si、Na、Al、Mg、P、S、Ca、K、Ti、Mn、Fe、Zn、Cu、Pb、Rb、Sr、Ba等18种元素进行了分析测定，结果与其他方法相符，部分元素的精密度（RSD，n=10）为0．2％～15％。该法效果比较好，同时保证了少量树木年轮样品无损失、无化学组成变化．为后续的等离子体原子发射光谱和质谱联测创造了条件。     

取气用真空螺旋钻机具

为研究地质环境对气候演变的影响,研制了一种轻型取气用真空螺旋钻机,介绍了其主要技术参数,以及配套钻具的结构特点和取气原理。