STUDY ON THE MRF-BASED METHOD FOR DAMAGED BUILDINGS EXTRACTION FROM THE SINGLE-PHASE SEISMIC IMAGE

Earthquake events are one of the most extraordinarily serious natural calamities, which not only cause heavy casualties and economic losses, but also various secondary disasters. Such events are devastating, and have far-reaching influences. As the main disaster bearing body in earthquake, buildings are often seriously damaged, thus it can be used as an important reference for earthquake damage assessment. Identifying damaged buildings from post-earthquake images quickly and accurately is of real importance, which has guidance meaning to rescue and emergency response. At present, the assessment of earthquake damage is mainly through artificial field investigation, which is time-consuming and cannot meet the urgent requirements of rapid emergency response. Markov Random Field(MRF)combines the neighborhood system of pixels with the prior distribution model to effectively describe the dependence between spatial pixels and pixels, so as to obtain more accurate segmentation results. The support vector machine(SVM)model is a simple and clear mathematical model which has a solid theoretical basis; in addition, it also has unique advantages in solving small sample, nonlinear and high-dimensional pattern recognition problems. Thus, in this paper, a Markov random field-based method for damaged buildings extraction from the single-phase seismic image is proposed. The framework of the proposed method has three components. Firstly, Markov Random Field was used to segment the image; then, the spectral and texture features of the post-earthquake damaged building area are extracted. After that, Support Vector Machine was used to extract the damaged buildings according to the extracted features. In order to evaluate the proposed method, 5 areas in ADS40 earthquake remote sensing image were selected as experimental data, this image covers parts of Wenchuan City, Sichuan Province, where an earthquake had struck in 2008. And in order to verify the applicability of this method to different resolution images, an experimental area was selected from different resolution images obtained by the same equipment. The experimental results show that the proposed method has good performance and could effectively identify the damaged buildings after the earthquake. The average overall accuracy of the selected experimental areas is 93.02%. Compared with the result extracted by the widely used eCognition software, the proposed method is simpler in operation and can improve the extraction accuracy and running time significantly. Therefore, it has significant meaning for both emergency rescue work and accurate disaster information providing after earthquake.     

Crustal structure study based on principal component analysis of receiver functions

The receiver function(RF) technique is an effective method for studying crustal structure. For a single station, the average 1-D crustal structure is usually derived by stacking the radial RFs from all back-azimuths, whereas structural variations(such as dipping discontinuities or anisotropy) can be constrained through analysis of waveform dependence on the backazimuth of both the radial and tangential RFs. However, it is often difficult to directly extract information about structural variations from the waveform of RF, due to the common presence of noise in real data. In this study, we proposed a new method to derive structural variation information for individual stations by applying principal component analysis(PCA) to RFs sorted by back-azimuth. In this method(termed as RF-PCA), a set of principal components(PCs), which are uncorrelated with each other and reflect different characteristics of the RF data, were extracted and utilized separately to reconstruct new RFs. Synthetic tests show that the first PC of the radial RFs contains the average structural information of the crust beneath the corresponding station, and the second PC of the radial RFs and the first PC of the tangential RFs both reflect the variations of the crustal structure. Our synthetic modeling results indicate that the new RF-PCA method is valid for a variety of synthetic models with intra-crustal dipping discontinuities and/or anisotropy. We applied this method to the real data from a broadband temporary seismic station(s233) in the central part of the Sichuan Basin. The results suggest that the RF data can be best explained by the presence of two nearly parallel dipping discontinuities within the crust. Combining with previous logging data, seismic exploration and deep sounding observations, we interpret the shallow dipping discontinuity as the top boundary of the Precambrian crystalline basement of the Sichuan Basin and the deep one corresponding to the Conrad interface between the upper and lower crust, consistent with the geological feature of the study area. In this work, both synthetic tests and real data application results demonstrate the effectiveness of the RF-PCA method for studying crustal structures.     

基于PSP观测的行星际Ⅲ型射电爆发的研究进展

与太阳射电爆发相比,通常认为频率较低的行星际射电爆发产生于远离低日冕的行星际空间.地球电离层的截止导致地基设备无法对其进行观测.美国国家航空航天局(National Aeronautics and Space Administration, NASA)发射的帕克太阳探测器(Parker Solar Probe, PSP)是迄今为止距离太阳最近的空间探测器.其搭载的射电频谱仪能够对10 k Hz–19.17 MHz频段范围内的射电辐射进行观测. PSP能够靠近甚至可能穿越行星际III型射电爆发的辐射源区,因此使用PSP对行星际射电爆发进行观测具有前所未有的优势.简要介绍了目前为止使用PSP的射电观测数据对行星际III型射电爆发的多方面研究,包括爆发的发生率、偏振、散射、截止频率、可能的辐射机制和相关的辐射源区等方面的研究进展,并讨论了其未来的研究前景.     

基于加权水平精度因子的伪卫星基站选择方法

提出一种以加权水平精度因子为依据的基站选择方法,该方法根据基站和用户的相对位置给予每个基站不同的权值,降低测量误差较大的基站被选中参与定位的可能性。通过对伪距测量误差数学模型的分析,推导伪卫星定位系统加权矩阵,并设计了基于基站对WHDOP贡献的基站选择方法。仿真结果表明,该方法能更加高效、准确地实现伪卫星基站的选择,降低接收机的计算量,提高系统的定位精度。     

高精度室内地图辅助VLC与PDR融合定位

针对传统室内定位方式存在的忽略地图精度对于整体定位精度的支撑性作用、需要额外的辅助设施和附加模块以协助定位系统实现目标点定位、定位信标的保密性差、定位信号源与辅助基站等具有较强的信号辐射等问题,本研究引入高精度室内地图辅助,提出了一种VLC与PDR融合的室内定位算法。首先,本研究摒弃了传统人工勾绘方式,在室内扫描机器人turtlrbot平台上（装载有二维激光扫描雷达）,利用Gmapping二维栅格地图构建算法,生成高精度室内地图。在此基础上,采用扩展卡尔曼滤波算法结合高精度地图信息实现VLC与PDR融合定位。该融合定位算法较好地结合了VLC定位与PDR定位各自的技术优势,实现了VLC定位结合高精度地图信息对PDR定位自适应动态纠偏,对于进一步实现新型低成本、无信号辐射、保密性强、附加模块少的高精度室内定位提供了较好的理论与技术支撑。实验结果表明：在高精度室内扫描地图构建过程中,其测距分辨率<0.5 mm,VLC与PDR融合定位算法的整体定位精度为1.33 m,平均定位响应时间为0.58 s。     

主题模型与SVM组合的小尺度街区用地分类方法

城市用地分类作为城市规划重要的基础和依据,对城市资源配置、建设发展等具有重要意义。现有研究对用地分类都聚焦于“稀路网、大街区”的大尺度区域,随着城市发展,大尺度区域的规划模式造成了城市交通效率低下、土地低效率开发等问题,而小尺度的城市街区建设规划为解决上述问题提供了一种新的思路。为了充分挖掘现有交通大数据的潜在价值,更以高效地服务小尺度街区规划,本文将主题模型与支持向量机（SVM）相组合,提出一种面向小尺度街区的用地分类方法。本文以上海市黄浦区人民广场附近为研究区域,依据精细路网对研究区域划分,通过对一周（7天）出租车GPS数据处理,结合区域兴趣点（POI）数据,基于隐含狄利克雷分布（LDA）模型和SVM模型进行用地分类。在人工解译的分类图的基础上对本文方法进行精度评价,并基于百度地图地理数据进行结果验证。研究表明本文方法基于现有的交通大数据,实现了对小尺度街区用地分类,方法分类精度较高,在一定程度上可以节约人力物力,以便更好地服务于小尺度城市规划。     

基于典型应用场景的北斗导航效能评估方法

针对北斗典型应用场景下缺乏有效的导航效能评估手段问题,在场景建模的基础上提出用户终端的导航效能评估方法。首先分析北斗卫星导航可能存在的典型挑战性环境,提出典型应用场景构建要素,并根据构建要素构建了山地应用场景;然后提出以卫星可见性、导航精度为指标的导航效能评估方法;最后通过选取数字高程数据等建立具体场景,对其中的导航用户进行了效能分析。结果表明,该场景可以反映真实的导航情景,在此背景下提出的效能评估方法具有实用价值。     

基于出租车用户出行的功能区识别

出租车数据作为城市大数据重要来源,其上车行为和下车行为直接反映城市人群出行行为特征,帮助城市规划者发现城市人群出行规律和城市功能结构。但是出租车数据隐含多维度信息,一维或者二维模型不足以表达和挖掘其蕴含的多维信息,因此本文选择可以承载多维数据的张量模型对出租车OD（上车/下车）数据进行时空模式挖掘。本文将北京六环区域划分为500 m×500 m格网,采用北京市2012年11月1-16日的出租车OD数据,分别构建O点和D点张量,利用张量分解模型从日尺度、时段尺度揭示出租车用户出行时间模式,同时获取不同时段对应的出租车用户出行空间模式,并推测空间模式包含的语义属性。本文结合城市兴趣点（Point of Interest, POI）数据,提高空间模式语义属性推测的准确性,识别出租车用户出行功能区。结果表明：出租车用户出行时间符合工作日和休息日的早高峰、日间、晚高峰以及夜间模式;对应8种时间模式,出租车用户出行包含8种空间模式,每一种空间模式都是对应时间模式下的上下车热点区域,因此空间模式的变化表明城市人群在不同的时间点,到达不同的场所,进行不同的活动,间接表达空间功能的动态变化;区域的功能不是单一静态的,而是随着时间在不断地变化,是不同时段功能的组合。本文揭示出租车OD数据中隐含的出租车用户出行模式和空间功能动态变化,对利用人类行为时空模式研究区域空间功能结构具有科学参考价值。     

济南市农地流转市场发育程度评价研究

农地流转中市场发育情况的研究可以较好地判断未来农地利用可能发生的风险,以济南市农地流转中的市场发育程度评价指标为例,研究农地流转市场的发育程度,以采取切实可行的措施完善农地流转制度。运用特尔菲法确定市场发育程度评价指标体系,并对指标数据进行无量纲处理,用熵值法计算指标权重,利用线性加权法计算市场发育综合评价值,采用正态分布"3σ"方法确定市场发育程度阈值。在统计年限内,济南市2009年、2010年土地流转市场处于过冷区间,2011年偏冷,2012年、2013年正常,2014年、2015年过热,说明农地流转市场发育较快,但滞后于流转量的变化。所选取的评价指体系能够较好的反映济南市农地流转市场发育情况,市场发育程度阈值计算比较科学合理。在当前农地流转市场的培育阶段,当流转量开始下降的时候,需要采取措施以防止流转量的继续下滑,以避免对农地流转市场的发展产生不利影响,进而影响农业经济的发展。     

基于熵权TOPSIS模型的海洋资源环境承载力评价研究——以湛江市为例

为了解和把握湛江市海洋资源环境承载力水平与演变趋势,通过建立包括海洋经济发展、海洋资源承载和海洋环境承载3个系统下具体33个指标的海洋资源环境承载力评价体系,采用熵权TOPSIS模型对湛江市2007-2016年这10年内海洋资源环境承载力水平及3个子系统水平进行动态评价。研究结果表明:湛江市海洋资源环境承载力水平在2007-2016年间处于波动起伏的状态,总体水平较高,但仍存在下行的风险。其中,湛江市海洋经济发展水平逐年上升;海洋资源承载水平整体较高,且与海洋资源环境承载力变化趋势较为吻合;海洋环境承载力水平整体呈现较为平稳的趋势。湛江市在制定海洋发展战略规划的同时,应在创新海洋经济发展的基础上,重点向海洋资源保护和海洋生态环境修复倾斜。