一种基于神经网络的确知信号检测技术

建立在统计信号处理理论基础上的相关检测器和匹配滤波器取得了广泛的应用,但两种模型都是建立在对实际通信信道线性化近似基础上的,在适应信道的非线性变化方面有所不足.利用神经网络自适应、非线性和高速并行运算的特点,在此提出了一种结构简单有效的神经网络接收机,并可推广到其他确知信号.     

空间碎片地基雷达探测综述

分析了空间碎片地基雷达探测的必要性和现实意义,介绍了国外有代表性的地基雷达工作概况,在此基础上,给出了描述空间碎片的轨道参量和物理参量,并对空间碎片地基雷达探测所需的关键技术进行了探讨。     

气候序列不连续点的小波分析和混合聚类分析

不论是单纯的小波分析还是单纯的非参数分析法都有其局限性.当样本量很大时,Fisher算法的计算量也是很大的,而且它不具有谱系结构,因此,为了保证谱系结构以及较快的计算速度,作者以小波变换和聚类分析相结合的方法来研究各类不连续点,给出了相应的算法和实验分析,并且实验结果给出了各类不连续点位置的比较精确的估计.     

Wave propagation in a seven-story reinforced concrete building: II. Observed wavenumbers

This paper presents estimates of wavenumbers of propagating waves in a seven-story reinforced concrete building in Van Nuys, California, using recorded response to four earthquakes. The phase velocities inferred from these wavenumbers are consistent from one earthquake to another. They are also consistent, inside the building, with independent estimates of the shear wave velocities in the building (e.g. using ambient vibration tests), and along the base, with phase velocities of Love waves typical for San Fernando Valley.     

Determining the spatial scale of variation in soil radon concentration

Increasing concern about possible links between emissions of radon and certain types of malignant disease has led to local and regional surveys to measure radon concentrations in the soil and in dwellings. The spatial scale at which radon varies is largely unknown, and so efficient sampling schemes and methods of mapping cannot be selected. To determine the spatial scale of radon variation in the English Midlands we measured radon in the soil using solid-state nuclear track detection in three areas of different geological complexity. In two of them we used an unbalanced multistage sampling scheme with seven stages of nesting: the Hereford survey covered distances from 10 m to 7.5 km, and the Buxton survey distances from 1 m to 3.75 km. The results from the nested surveys suggested that geology exerts a strong control on the variation. Finally radon was measured every 20 m along a 2-km long transect which crossed several lithologies close to Nottingham. The soil radon values changed in an erratic way along the transect. The sample variogram of radon has a substantial nugget variance, suggesting that much of the variation occurred for distances less than the sampling interval. The structure at the longer scale seems to be controlled by the underlying geology. These results have implications for designing further surveys and for selecting a method of mapping. Stratification based on lithology might be the only feasible solution to sampling, estimating and mapping radon concentrations over large areas. Where the locally erratic component of variation is large, estimation by kriging, for example, would confer little additional benefit compared with that by classification.     

桩的垂直静载试验极限承载力判定方法综述

桩的垂直静载试验极限承载力（或极限荷载）的确定是试验数据处理的关键。本文汇集编录了极限承载力的各种判定方法，但需指出的是：在具体应用判定试桩的极限承载力时，应以现行规范规定的方法为准，必要时可用其它方法进行校验。     

新一代双偏振天气雷达(CINRAD/SAD)精细化探测技术

新一代双偏振天气雷达在暴雨、台风等灾害性天气监测和预警中发挥了重要的作用。随着气象现代化发展以及预报时效性、精细化度的要求不断提高,S波段新一代双偏振天气雷达已不能充分满足发展过程迅速的中小尺度天气系统的研究、预警。气象雷达的时空分辨率对探测强对流过程中小尺度结构有重要作用,提高天气雷达时空分辨率是精细化探测技术的关键,本文着重从新一代天气雷达的时空分辨率、体扫方式等方面,通过对天气雷达脉冲重复频率、信号处理方法及扫描方式等进行改进,提高新一代双偏振天气雷达对中小尺度气旋和龙卷风等灾害性天气的探测能力,以获取快速变化的天气过程精细化特征,获得更新更快、分辨率更高的观测资料。     

FORSAT: a 3D forest monitoring system for cover mapping and volumetric 3D change detection

ABSTRACT

A 3D forest monitoring system, called FORSAT (a satellite very high resolution image processing platform for forest assessment), was developed for the extraction of 3D geometric forest information from very high resolution (VHR) satellite imagery and the automatic 3D change detection. FORSAT is composed of two complementary tasks: (1) the geometric and radiometric processing of satellite optical imagery and digital surface model (DSM) reconstruction by using a precise and robust image matching approach specially designed for VHR satellite imagery, (2) 3D surface comparison for change detection. It allows the users to import DSMs, align them using an advanced 3D surface matching approach and calculate the 3D differences and volume changes (together with precision values) between epochs. FORSAT is a single source and flexible forest information solution, allowing expert and non-expert remote sensing users to monitor forests in three and four (time) dimensions. The geometric resolution and thematic content of VHR optical imagery are sufficient for many forest information needs such as deforestation, clear-cut and fire severity mapping. The capacity and benefits of FORSAT, as a forest information system contributing to the sustainable forest management, have been tested and validated in case studies located in Austria, Switzerland and Spain.     

DETERMINATION OF A MULTIVARIATE DETECTION LIMIT AND LOCAL CHEMICAL RANK BY DESIGNING A NON-PARAMETRIC TEST FROM THE ZERO-COMPONENT REGIONS

In this paper we redefine the term detection limit to embrace the inherent multivariate nature of samples,instrumental measurements and chemometrics resolution procedures. The so-called zero-componentregions, i.e. parts with no chemical components eluting, are used as repeated analytical blanks to estimatea statistical multivariate detection limit for determining the number of chemical species in local regionsof a single two-way chromatogram or a collection of synchronized one-way chromatograms. For two-waychromatography the detection limit is determined from the distribution of the first eigenvalues obtainedfrom all possible combinations of spectra in the zero-component regions. The number of spectra in eachcalculation should correspond to the number included in the later examination of the local retention timeregions. For one-way chromatography on a collection of samples with similar chemical components atvarying concentrations the same procedure is used, with the samples taking the role of the spectra intwo-way chromatography. The detection limit can be chosen at various confidence levels depending onwhether false positive or negative detection of minor components is most critical. The results obtainedfrom the zero-eigenvalue distribution are more robust than those obtained by a previously developedF-test.     

The role of the chemical environment in frictional deformation: Stress corrosion cracking and comminution

The roles of chemically assisted crack and fracture propagation and chemically assisted comminution in frictional deformation are evaluated in this study. Double cantilever beam (DCB) crack propagation data are presented which show that the role of pH in chemically assisted fracture, and to a lesser extent the role of ionic concentration are important in stress corrosion cracking. Data on very slow crack growth and the stress corrosion limit are also presented. These data suggest that stress corrosion cracking may play an important role in compound earthquakes and in asperity breakdown in faults. The comminution literature is also reviewed in order to assess the role of chemically assisted comminution in frictional deformation. It appears that chemically assisted comminution may be important at low and high ionic strength because it may reduce the effective viscosity and the shear strength of fault gouge. At intermediate ionic concentration the role of pH, as an agent which enhances crack and fracture propagation, appears to be more important in reducing the coefficient of sliding friction.