基于形态重构的图像去噪方法研究

应用数学形态学中的形态重构滤波,对噪声图像进行了处理,在去除噪声的同时,也保持了边缘及细节信息。     

宁夏鸳鸯湖电厂空冷气象条件分析

通过在宁夏鸳鸯湖电厂建立气温、风向、风速60 m梯度及地面观测站,与邻近的灵武市气象站展开为期一年的同步观测,获得实地观测资料。利用两地同步气象观测资料进行对比分析,揭示出电厂所在地气候特点。同时结合灵武市气象站1971~2000年观测资料,采用相关性分析方法,订正得到电厂地面历年气象要素特征值。结果表明,电厂风向和风速特征明显有别于邻近的灵武市气象站。分析结果主要用于该地火电厂空冷系统的安装与安全运行。     

工作状态下梁及桥梁模态与损伤识别的新方法

工作状态下桥梁结构的模态参数识别是桥梁损伤识别的重要环节,考虑桥梁检测的实用性,桥梁检测一般应建立在环境激励的基础上,已有的环境激励下模态参数识别的方法对模态频率的识别的精度较高,而对位移模态的识别则误差较大。提出了一种利用移动质量块在不同位置时对桥梁的模态频率进行多次测量,用各次测得的频率值确定位移模态的新方法,使得位移模态识别的精度接近频率识别的精度,建立了该方法的初步模型,推导了频率与位移模态关系的理论公式,并通过数值模拟对该方法的有效性进行了说明。     

高密度空间采样地震数据特点分析

中国陆相沉积盆地的地质结构复杂,储层岩性的多变,需要有高精度的勘探方法。高密度空间采样是提高地震勘探精度的一项新技术。本文简要说明了点激发和点接收技术,分析高密度空间采样的野外工作方法,介绍了Gijs j．o．Vermeer提出的对称采样原理,从波场连续性的角度探讨了高密度空间采样技术。重点分析高密度空间采样数据的特点, 即:高密集的初至波有利于近地表结构的调查,可提高静校正的精度;小偏移距、小点距接收增加了浅层的有效覆盖次数,提高浅层反射的成像精度; 对规则噪声可实现无假频采样,室内的噪声分析和噪声压制的精度随着提高;高密度采集使波场连续性增强,使得各种数学变换的精度提高,有利于不同波场的分离。最后指出高密度空间采样地震勘探技术的难点在于室内数据处理,针对海量数据的分析和处理方法还需要进行深入细致的研究工作。     

Scaling and correlation of atmospheric acid deposition evolutions

Detrended fluctuation analysis (DFA) and power spectrum density are applied to verify the presence of temporal scaling behavior and long-range persistence (LRP) of weekly hydrogen ion deposition (WHD), NO₃^- and SO₄^2- deposition series in National Atmospheric Deposition Program, USA, for the period 1978–2001. The results show a common scaling behavior for all sites analyzed. Two distinct scaling regions are identified by DFA1, one corresponding to 1 month to 1 year and the other to 1 year to 5 years. The WHD series obey power-law in two temporal regimes respectively with mean DFA1 scaling exponents α ₁≈0.68 and α ₂≈0.45, implying the presence of LRP in the acid deposition series and there is a tendency for a large deposition event to be followed by another large event, and vice versa. For DFA2–DFA4, however, the annual crossover, which divides the temporal scale into two regimes, disappears gradually with the order q of DFAq increasing, and the two scaling regimes turn to share the same scaling exponent close to α ₁. The result indicates that the scaling behavior exits in the two regimes with the same scaling exponent α ₁, and LRP prevails during the examined 1-month to 5-years scale. NO₃^- and SO₄^2- deposition evolve the same way as WHD does, implying the pollutants involving in acid deposition may share some prominent mechanism controlling their evolutions. We ascribe the long-range power-law scaling of acid deposition evolutions to the self-organized critical behavior of atmosphere under pollution stress and it should be considered in the trend prediction of acid deposition as an important factor.     

Analysis on the noises from continuously monitoring GPS sites

In this paper,we analyze the time series of site coordinates of 27 continuously monitoring GPS sites covered bythe Crustal Movement Observation Network of China over the whole country.The data are obtained in the periodfrom the beginning of the observation to the November of 2005.On the basis of data processing,we analyze thepower spectrum density of coordinate component noise at each site and calculate the spectral indexes manifestingthe noise property of each component.The spectral indexes indicate that for most sites,the noise of time series ofeach coordinate component can be addressed by the model of white noise flicker noise;and for a small amountof sites,it can be described by the model of white noise flicker noise random walk noise.We also quantita-tively estimate each noise component in the model by using the criterion of maximum likelihood estimation.Theresult shows that the white noise in the time series of GPS site coordinates does not constitute the main part ofnoise.Therefore,the error estimation of site movement parameters is usually too small,or too optimistic if weconsider the white noise only.Correspondingly,if this factor is not fully considered in explaining these movementparameters,it might mislead the readers.     

利用背景噪声进行地震成像的新方法

利用背景地震噪声提取格林函数，即通过一对台站记录的地震噪声进行互相关计算，来近似台站间的格林函数，并进一步通过地震成像获取地下结构的认识，成为最近跨学科研究的热点问题之一.本文首先叙述了其发展背景及过程，然后分别从四个角度，简要介绍了目前对其物理原理的解释.如果该方法能得到进一步的发展，将不再依赖于天然地震以及人工地震，而仅仅利用地震台站记录的地震噪声便可获取高分辨率的地下成像.该方法将会大大促进地震学的发展.     

On the link between GPS pseudorange noise and day-boundary discontinuities in geodetic time transfer solutions

When neglecting calibration issues, the accuracy of GPS-based time and frequency transfer using a combined analysis of code and carrier phase measurements highly depends on the noise of the GPS codes. In particular, the pseudorange noise is responsible for day-boundary discontinuities which can reach more than 1 ns in the time transfer results obtained from geodetic analysis. These discontinuities are caused by the fact that the data are analyzed in daily data batches where the absolute clock offset is determined by the mean code value during the daily data batch. This pseudorange noise is not a white noise, in particular due to multipath and variations of instrumental delays. In this paper, the pseudorange noise behavior is characterized in order to improve the understanding of the origin of the large day-boundary discontinuities in the geodetic time transfer results. In a first step, the effect of short-term noise and multipath is estimated, and shown to be responsible for only a maximum of 150 ps (picoseconds) of the day-boundary jumps, with only one exception at NRC1 where the correction provides a jump reduction of 300 ps. In a second step, a combination of time transfer results obtained with pseudoranges only and geodetic time transfer results is used to characterize the long-term evolution of pseudorange errors. It demonstrates that the day-boundary jumps, especially those of large amplitude, can be explained by an instrumental effect imposing a common behavior on all the satellite pseudoranges. Using known influences as temperature variations at ALGO or cable damages at HOB2, it is shown that the approach developed in this study can be used to look for the origin of the day-boundary discontinuities in other stations.     

长垣县城区冬季噪声监测与评价

借助HS6288系列噪声分析仪,对河南省长垣县城区噪声进行了实地监测。依据国家城市区域环境噪声标准,并结合综合污染指数法和模糊综合评价法对监测结果进行分析评价。结果表明,长垣县城区总体噪声水平为4级(中污染),声环境已出现恶化。在分析长垣县城区噪声污染及其分布的同时,结合实地调查,提出了一些针对小城镇噪声污染防治的对策。     

基于多分辨分析的滤波算法在SAR图像斑点噪声消除中的应用

合成孔径雷达 (SAR)图像一般都存在相干噪声 ,对地物信息的提取及 SAR图像应用的干扰非常严重 ,对此许多人提出了不少处理方法 ,并分析对比了多种滤波算法 ,认为改良 K -均值自适应滤波效果最佳。本文中分析了改良 K -均值自适应滤波法的数学基础的局限性 ,并采用了一种基于多分辨分析的滤波算法 ,该算法通过将噪声 (或较小的结构特征 )与较大的结构特征相分离 ,然后滤出噪声 (或较小的结构特征 ) ,从而达到消除斑点噪声的目的。实验结果证明 ,基于多分辨分析的滤波算法在消除 SAR图像的斑点噪声方面优于改良 K -均值自适应滤波法。