Wavelet filter analysis of splitting and coupling of seismic normal modes below 1.5 mHz with superconducting gravimeter records after the December 26, 2004 Sumatra earthquake

New generation superconducting gravimeters (SGs), which have been demonstrated to be better than the best seismometers STS-1 at frequencies below 1 mHz, can be accepted as the quietest vertical seismometers for observation of long-period earth free oscillations. Wavelet filtering with narrow band-pass frequency response as shown in this paper is very helpful in removing at- mospheric pressure effects from on gravity records in long-period seismic mode frequency bands. The processing of high quality SG records after the great Sumatra earthquake (Dec. 26, 2004) with wavelet filtering leads to clear observations of all coupled toroidal modes below 1.5 mHz except these for 0T5, 0T7 and 1T1; moreover 1T2 and 1T3 are, for the first time, unambiguously revealed in the vertical components of the free oscillations. The three well-resolved splitting singlets of overtones 2S1 are observed from a single SG record for the first time.     

基于电磁感应仪的表聚型土壤盐渍剖面特征解译研究

针对目前黄河三角洲地区存在的土壤盐渍化问题,以该地区分布最广泛的表聚型盐分剖面类型为研究对象,运用磁感大地电导率仪EM38,建立了磁感式表观电导率和土壤盐分之间的(多元)回归模型,在分析土壤盐分剖面分布特征的基础上提出了指数衰减模型,并运用该模型对盐分剖面进行了参数拟合和验证。结果表明:磁感式表观电导率EMh和EMv呈极显著的线性相关,土壤盐分在垂直方向上的变异主要表现在表层0~25cm的深度范围内。统计分析和Friedman检验结果表明,回归模型和指数衰减模型均具有较好的拟合结果和预测效果,二者的预测精度差异也不显著,表明本文提出的指数衰减模型不仅能降低待估参数的数量、提高土壤盐分剖面磁感式解译的实用性,同时还具有较高的预测精度。该研究结果为利用电磁感应仪快速、精确地进行土壤盐分预测以及盐分剖面解译提供了一定的理论参考和实践依据。     

MT时间序列的FIR数字滤波分析

大地电磁测深法(MT)野外观测得到的原始资料是包含多种频谱的时间序列,这种时间序列中常包含不需要的信息和50 Hz及其谐波的干扰。结合FIR数字滤波技术与MT时间序列的特征,提出了一种基于FIR数字滤波技术的MT时间序列去噪方法,讨论了FIR数字滤波器的原理和实现,分析了理论数据通过FIR数字滤波的带通和陷波处理,探讨了对实测时间序列的带通和陷波所取得的效果。     

矿物材料应用于香烟过滤嘴降害的研究现状与展望

总结了近几十年来包括活性炭、沸石、蒙脱石、海泡石、麦饭石、凹凸棒石、氧化铝、氢氧化钠、明矾、纳米材料等矿物材料作为卷烟滤嘴添加剂以去除烟气中有毒有害物质的研究和实验应用及效果。实验结果和市场调查表明,活性炭是减少卷烟危害最快、香烟市场应用增长最快的过滤嘴添加剂。从降低卷烟有害成分的比例和成本等综合因素来看,铝硅酸盐类滤嘴和多材料复合滤嘴亦有很好的应用前景和市场需求,应积极进行研制。     

JMD型滤池双层滤料的净水试验及比较

大量的试验数据表明石英砂和陶粒组成的双层滤料，其净水处理性能明显好于石英砂和无烟煤双层滤料以及单层石英砂滤料，特别是出水浊度、微絮凝作用，反冲洗周期、藻类的去除、絮凝剂的使用量等指标上具有明显优势，陶粒做为一种新的水处理滤料，正被应用于净水和污水处理。     

陆相沉积的天文地层研究方法简介——以井下地层为例

通过对我国大陆三十余口井的测井资料研究成果,归纳出对陆相地层进行天文地层研究的方法。介绍了所用的新的天文周期理论值、测井资料的选取及预处理方法,重点说明谱分析的数据点数的选定、不同参数(自然伽玛、自然电位和岩屑)的测井资料谱分析结果的对比,以实例说明如何选定主要优势旋回和AR值,以及FIR数字滤波器的基本性质和数字滤波结果,小波分析的特点和通过小波图进行调频的方法,并介绍了地层单位的延续时间计算和年龄确定方法。     

三次谐波对配电系统的危害及抑制措施

为了更好地降低或消除供电系统中的三次谐波，保障供电系统的安全运行，针对三次谐波对供配电系统的影响越来越严重的现状，以国家气象信息中心供配电系统为研究对象，采用理论分析与实际测量相结合的方法，对三次谐波的危害及抑制措施进行了研究。指出了三次谐波产生的原因，分析了三次谐波引起的5种主要危害，并以此为依据，提出了降低或消除三次谐波的6种不同方法。通过对降低或消除三次谐波不同方法进行分析、对比，结合实践的检验，通过在配电系统接近负荷的位置安装D-Yn接法隔离变压器，可以最有效地抑制三次谐波产生的各种危害，明显改善供电系统的供电质量和配电系统及设备的安全运行，是行之有效的三次谐波抑制措施。     

基于中值滤波和小波变换的天气雷达回波图像处理

本文提出了一种中值滤波和小波变换相结合的天气雷达回波图像处理方法,分别从目标回波的视觉角度和统计量的客观角度对处理后图像进行了分析。实验结果表明,本文算法实现了去除回波图像中高斯和脉冲混合噪声的目的,有效的保留了回波图像边缘细节,视觉效果好,层次感较为丰富,处理效果明显优于传统图像处理方法,为自动识别回波种类的研究提供了良好的基础。     

Integrated Navigation System and Experiment of a Low-Cost and Low-Accuracy SINS/GPS

When SINS (strap-down inertial navigation system) is combined with GPS, the observability of the course angle is weak. Although the course angle error is improved to some extent through Kalman filtering, the course angle still assumes a divergent trend. This trend is aggravated further when using low-cost and low-accuracy SINS. In order to restrain this trend, a method that uses AHRS to substitute for SINS course angle information is put forward aimed at the hardware component characteristic of the low-cost and low-accuracy SINS including AHRS (attitude and heading reference system) and IMU (inertial measurement unit). Real static and dynamic experiments show that the method can restrain the divergent trend of the navigation system angle effectively, and the positioning accuracy is high.     

A method to improve the alignment performance for GPS-IMU System

Zero velocity and zero east component of rotation rate relative to local geographic frame have been traditionally applied as measurements for fine alignment of a GPS-IMU system. The performance of the fine alignment, however, will be affected by several types of inertial sensor errors, which could cause part of the Kalman filter states to be unobservable. To overcome this problem, a new method that utilizes the total outputs of the gyro triad and the accelerometer triad as part of the measurements has been proposed by the authors. The initial results have confirmed the effectiveness of the method. In this paper, the observability for both traditional and new alignment methods will be first reviewed. The results from computer simulations will then be presented to compare the traditional and the new alignment methods for the purpose of evaluating the performance of the proposed new method. Data acquired from real inertial sensors will also be applied to assess the traditional and new alignment methods by analyzing their innovation sequences from the Klaman filter. Based on a paper presented at the 18th International Technical Meeting of the Satellite Division of the Institute of Navigation, Long Beach, California, September 2005.