小波气候突变的检测--应用范围及应注意的问题

气候突变及其检测是气候变化研究的一个重要方面。气候突变的表现多种多样,目前也有许多检测气候突变的方法,但这些方法能否准确地检测出气候突变现象,他们的适用范围如何,是一个值得注意的问题。研究表明,尽管小波分析方法在检测序列突变方面具有严格的数学意义,但因为其检测到的是序列的均值突变,因此,在应用于气候突变的检测方面应该特别注意,数学上的严格并不等同于气候意义上的严格。因为某些情况下有些突变点并没有一定的气候意义。     

Outlier detection algorithms and their performance in GOCE gravity field processing

The satellite missions CHAMP, GRACE, and GOCE mark the beginning of a new era in gravity field determination and modeling. They provide unique models of the global stationary gravity field and its variation in time. Due to inevitable measurement errors, sophisticated pre-processing steps have to be applied before further use of the satellite measurements. In the framework of the GOCE mission, this includes outlier detection, absolute calibration and validation of the SGG (satellite gravity gradiometry) measurements, and removal of temporal effects. In general, outliers are defined as observations that appear to be inconsistent with the remainder of the data set. One goal is to evaluate the effect of additive, innovative and bulk outliers on the estimates of the spherical harmonic coefficients. It can be shown that even a small number of undetected outliers (<0.2 of all data points) can have an adverse effect on the coefficient estimates. Consequently, concepts for the identification and removal of outliers have to be developed. Novel outlier detection algorithms are derived and statistical methods are presented that may be used for this purpose. The methods aim at high outlier identification rates as well as small failure rates. A combined algorithm, based on wavelets and a statistical method, shows best performance with an identification rate of about 99%. To further reduce the influence of undetected outliers, an outlier detection algorithm is implemented inside the gravity field solver (the Quick-Look Gravity Field Analysis tool was used). This results in spherical harmonic coefficient estimates that are of similar quality to those obtained without outliers in the input data.     

Particle size dependent response of aerosol counters

During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions.The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the specific instrument was found. An enhanced detection efficiency for ultrafine hygroscopic sodium chloride aerosols was observed with water operated systems, an analogous trend was found for n-butanol operated systems with nonhygroscopic silver and tungsten oxide particles.     

金属腐蚀探测

本阐述了金属腐蚀的危害性和金属管道腐蚀探测的迫切性，并介绍了几种具有探测腐蚀功能的物探方法。     

Applicability of a Backprojection Algorithm to Reconstruct Images of Subsurface Horizontal Planes for Laboratory Experiments in Electrical Resistance Tomography

This paper describes the use of a backprojection algorithm to reconstruct subsurface images of the electrical resistivity in horizontal planes parallel to the surface. The algorithm can be applied to detect buried objects such as tanks or pipes and possible leakages from them. Two imaging strategies are compared: juxtaposition of vertical planes, and 3D reconstruction from the sensitivity matrix corresponding to the entire volume whose surface is explored. The electrode arrays used for voltage measurement are the dipole–dipole array and a modified Schlumberger array. A personal computer controls current injection, electrode switching, and voltage detection. The system injects 1 kHz, 20 V peak-to-peak square waveforms, thus avoiding electrode polarization effects. Experimental laboratory measurements show that the algorithm detects localized objects such as an insulating sphere and a conductive cylinder immersed in water. Furthermore, covering half of the cylinder by a rubber sleeve to simulate a nonconductive leak, yields a distinct image for the leak. The backprojection algorithm does not need any regularization parameter and it is very fast in inverting the sensitivity matrix because it approximates the inverse matrix by its transposed. The dipole–dipole array usually yields a lower overall pixel error than the modified Schlumberger array but both allow the detection of simulated underground leaks.     

基于ROSE2.0的普洱地区CINRAD/CC雷达冰雹探测算法评估及参数本地化

为提高冰雹探测算法（Hail Detection Algorithm,HDA）产品的可用性,针对2015—2020年普洱地区监测到的22次冰雹个例,利用新一代雷达业务应用软件ROSE2.0对相关雷达基数据进行回放及产品分析,以命中率、虚警率、临界成功指数为指标对HDA算法在普洱地区的识别效果进行评估并给出本地化参数配置方案。结果表明:HDA算法在普洱地区命中率接近100%,但虚警现象非常普遍,使用强冰雹概率（Probability of Severe Hail,POSH）的预警效果优于任意大小冰雹概率（Probability of Hail,POH）,且冰雹尺寸越大POSH虚警的概率越低。进一步使用模拟测评法对POSH算法的适配参数进行分析,发现正确输入降雹日当天的0 ℃层和-20 ℃层高度能有效减少POSH的虚警率及提高临界成功指数;同时使算法预测的最大冰雹直径普遍偏大的情况得到控制,其中,中小冰雹直径偏离百分比减小76.07%,改善效果显著高于大冰雹。此外,增大反射率因子及POSH阈值能有效控制虚警,但也导致漏报次数快速增加,当阈值太大时命中率明显降低,为了保证较高的命中率和临界成功指数,选择Z=50 dBz或POSH=70%为阈值能明显改善HDA算法的识别效果。     

载荷试验检测复合桩基承载力的影响因素

针对桩基检测中水泥土桩复合地基检测承载力实测值与设计值差别很大,从工程地质条件、地基处理情况、检测方法出发,通过实例分析了复合地基承载力取值的影响因素。分析表明:桩设计参数取值偏低、地基土的力学性能未充分利用、设计的安全储备偏大是影响承载力取值的主要因素,检测时桩间土含水量的变化也有一定程度的影响。     

GPS RTK校准检测试验场建设的研究

叙述了GPSRTK接收机校准检测试验场建设的方法,介绍了GPSRTK接收机校准检测的步骤,提出了GPSRTK校准检测的项目和结果判定方法,为未来的GPSRTK国家检定规程的出台做了有益地探索。     

浅水湖泊水生植被遥感监测研究进展

在浅水湖泊中,水生植物具有净化水质、抑制藻类、提供鱼类食物和栖息环境等生态功能,同时,其过度扩张也会加速湖泊淤浅和沼泽化、引起湖泊二次污染等环境负效应.实时动态地掌握湖泊水生植被类群和种群的空间分布及其面积、生物量等指标信息,对湖泊生态修复和评估、水生植被恢复和管理等具有重要现实意义.遥感技术的大面积、实时、动态等特点...     

改进Faster R-CNN的遥感图像多尺度飞机目标检测

为了提高遥感图像中多尺度飞机目标的检测精度,本文提出一种基于改进Faster R-CNN的遥感图像飞机目标检测方法。该方法借助多层级融合结构,将深层次的语义特征与浅层次的细节特征相结合,生成多种尺度的既具有精确的位置信息又具有深层次的语义特征的特征图;再借助Faster R-CNN的多尺度RPN (Region Proposal Network)机制,通过对RPN中候选区域尺度的修正,从而提高遥感图像中多尺度飞机目标的定位精度;最后利用Faster R-CNN的分类回归网络,得到飞机目标检测结果。在高分辨率遥感图像中进行了实验,对3种特征提取网络ZF、VGG-16以及ResNet-50进行改进,改进后的精度分别提高了11.34%、9.87%以及1.66%,并且生成的检测框更加贴合飞机目标。实验结果表明,本文方法适用于遥感图像多尺度飞机目标检测,在提高目标定位精度的同时降低了目标漏检现象。