SHORT COMMUNICATION CHEMOMETRIC ASPECTS OF AN ENVIRONMENTAL STUDY

The application of several chemometric topics in connection with an environmental study is described.Atwo-way ANOVA is used to show the irregularity of the distribution of heavy metals in the rural soilsaround a lead smelter.Multivariate statistical methods are also applied to show significant correlationsbetween metals and the wind direction.Principal components analysis and Varimax rotation seem toconfirm the validity of the conclusions.     

瑞雷波法在建筑高边坡勘察中的应用

结合一项边坡工程实例,将瑞雷波技术应用到人工填方建筑高边坡勘察工程中,探测出边坡区基岩面埋深、风化层厚度及坡面起伏形态等,并在“重点坡段”关键位置布置钻孔,对原始坡面埋深进行了校核。结果表明,探察结果与钻探结果具有很好一致性,充分展现了瑞雷波勘探技术在建筑高边坡勘察中的可行性和有效性。     

地震活动性热红外异常提取方法研究

热红外遥感以其大视野、高精度和短周期等诸多优势以及对某些强震红外异常的良好反映,成为监测断裂活动性及地震短临前兆的很有前途的观测技术。热红外异常与地震关系的研究也受到国内外地震学者的广泛关注。但由于地表热红外辐射受云层、地形地貌、地物类型和气象等诸多非震因素的影响,因此,如何从复杂的红外遥感数据中提取出与地震活动有关的热异常一直是这项研究中的瓶颈问题。在对若干震例和地震活动区的热红外影像进行长期分析研究的基础上,对这一问题进行了探讨,同时提出了一些实用化的异常识别与提取方法,并对其可行性进行了分析。认为地震红外异常是地表亮温的相对变化,判别地震异常时,至少需利用两年以上的卫星资料,从不同的时空尺度上加以综合对比分析,仅靠震前震后一定时段的卫星资料不足以排除所有非震因素的影响。     

Influence of reservoir geometry and conditions on the seismic response of arch dams

An analysis of the influence that reservoir levels and bottom sediment properties (especially on the degree of saturation) have on the dynamic response of arch dams is carried out. For this purpose, a Boundary Element Model developed by the authors that allows the direct dynamic study of problems that incorporate scalar (dammed up water), viscoelastic (dam and soil site) and poroelastic media (bottom sediments in the reservoir) is used. All of the regions are discretized using boundary elements, later formulating equations of compatibility and equilibrium that allow their interaction to be rigorously established. The seismic excitation consists in plane longitudinal waves (P waves) and shear waves (S waves) impinging the dam site with an angle of vertical incidence. The analysis is carried out in the frequency domain, and the time response is obtained, for synthesized artificial accelerograms defined in terms of the elastic response spectrum taken from Eurocode 8, using a FFT algorithm. The variables used to characterize the response are: Amplitude of the complex-valued frequency-response function, acceleration response spectra and the integral of velocity of points located at the structure. These variables clearly indicate the importance that the factors analyzed have on the dynamic response.     

南沙海域地震资料处理技术发展历程

南沙海域是我局多年来的勘探重点区域，投入多道地震工作量达8万多公里。我局地震资料的处理技术也随着时代的发展而进步，从最早的简单处理到目前的多方法、多手段、多系统的较复杂处理，经历了多次处理设备的更新换代和处理技术人员的更替，处理质量和处理水平、处理能力与时俱进。     

嵌埋星团质量分层的数值模拟研究

目前,对大质量恒星形成的初始条件不很清楚,特别是大质量恒星是否形成于星团中心仍有争议.有人从时标上考虑,认为嵌埋星团的质量分层现象意味着大质量恒星只能在星团中心诞生.利用Monte Carlo方法对嵌埋星团的动力学演化进行了数值模拟,并与观测进行了比较.假设初始时刻大质量恒星随机分布,一定比例的嵌埋星团因为大质量恒星的随机运动,在演化的某个时刻会呈现暂态质量分层,其中一部分相当明显.这说明,大质量恒星在中心形成并非嵌埋星团质量分层现象的唯一解释.此外,气体的动力学摩擦能有效地减小动力学质量分层的时标,从而增大暂态质量分层的概率.     

用地磁脉动日食效应探讨甚低纬Pc3-4地磁脉动源

在3次日食期间,利用甚低纬区和从低纬到甚低纬过渡区地面站进行的地磁脉动观测资料,分析了Pc3-4地磁脉动的南北分量（H）和东西分量（D）在H-D平面内矢端图主轴方向的变化．结果表明,当观测点纬度低于日全食带纬度时,H-D矢端图主轴有90°相移现象;当观测点纬度高于日全食带纬度时,则无这种现象．由此我们推测,甚低纬区和从低纬到甚低纬过渡区Pc3-4地磁脉动可能主要是过滤机制产生的．     

电磁波法探测地下异常体的数值模型和实验模型

本文研究均匀有耗媒质全空间及半空间中三维异常体散射的数值模型和实验模型。用矩量法解体积分方程,导出自小块积分的简单准确的计算公式,说明非自小块积分以及索末菲积分的简化计算方法。给出两个利用金属镜象板的水池测试装置,说明与测试方法有关的若干主要问题。计算结果与测量结果基本吻合。     

Land cover mapping at Alkali Flat and Lake Lucero,White Sands,New Mexico,USA using multi-temporal and multi-spectral remote sensing data

The goal of this research is to map land cover patterns and to detect changes that occurred at Alkali Flat and Lake Lucero, White Sands using multispectral Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Land Imager (ALI), and hyperspectral Hyperion and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data. The other objectives of this study were: (1) to evaluate the information dimensionality limits of Landsat 7 ETM+, ASTER, ALI, Hyperion, and AVIRIS data with respect to signal-to-noise and spectral resolution, (2) to determine the spatial distribution and fractional abundances of land cover endmembers, and (3) to check ground correspondence with satellite data. A better understanding of the spatial and spectral resolution of these sensors, optimum spectral bands and their information contents, appropriate image processing methods, spectral signatures of land cover classes, and atmospheric effects are needed to our ability to detect and map minerals from space. Image spectra were validated using samples collected from various localities across Alkali Flat and Lake Lucero. These samples were measured in the laboratory using VNIR–SWIR (0.4–2.5 μm) spectra and X-ray Diffraction (XRD) method. Dry gypsum deposits, wet gypsum deposits, standing water, green vegetation, and clastic alluvial sediments dominated by mixtures of ferric iron (ferricrete) and calcite were identified in the study area using Minimum Noise Fraction (MNF), Pixel Purity Index (PPI), and n-D Visualization. The results of MNF confirm that AVIRIS and Hyperion data have higher information dimensionality thresholds exceeding the number of available bands of Landsat 7 ETM+, ASTER, and ALI data. ASTER and ALI data can be a reasonable alternative to AVIRIS and Hyperion data for the purpose of monitoring land cover, hydrology and sedimentation in the basin. The spectral unmixing analysis and dimensionality eigen analysis between the various datasets helped to uncover the most optimum spatial–spectral–temporal and radiometric-resolution sensor characteristics for remote sensing based on monitoring of seasonal land cover, surface water, groundwater, and alluvial sediment input changes within the basin. The results demonstrated good agreement between ground truth data and XRD analysis of samples, and the results of Matched Filtering (MF) mapping method.     

The influence of petrophysical properties on the salt weathering of porous building rocks

The influence of pore structure, water transport properties and rock strength on salt weathering is evaluated by means of a thorough rock characterisation and a statistical analysis. The pore structure was described in terms of its porosity, pore size distribution (quantified by mean pore radius) and specific surface area, density and water transport was characterised by means of water permeability (saturated flow) and capillary imbibition (unsaturated flow); whilst the rock strength test was carried out using uniaxial compressive strength, compressional and shear wave velocities, dynamic elastic constants and waveform energy and attenuation were obtained from the digital analysis of the transmitted signal. A principal component analysis and a stepwise multiple regression model was carried out in order to examine the direct relationships between salt weathering and petrophysical properties. From the principal component analysis, two main components were obtained and assigned a petrophysical meaning. The first component is mostly linked to mechanical properties, porosity and density whereas the second component is associated with the water transport and pore structure. Salt weathering, quantified by the percentage of weight loss after salt crystallisation, was included in both principal components, showing its dependence on their petrophysical properties. The stepwise multiple regression analysis found that rock strength has a predominant statistical weight in the prediction of salt weathering, with a minor contribution of water transport and pore structure parameters.