半参数模型在GPS季节性信号分离中的应用

根据噪声序列的Hurst指数特性,提出一种新的确定半参数模型平滑因子的方法--基于Hurst指数的二分搜索法,并将该方法应用于分离时变GPS季节性信号。通过对模拟数据及实测GPS坐标序列的分析,验证了该方法是一种有效的确定平滑因子的方法。将计算得到的平滑因子代入半参数模型,能够将GPS坐标序列中的季节性信号充分地分离出来。     

近岸带波浪传播过程中波性质的统计对比分析

通过对粤东后江湾近岸带垂岸方向上4个测站,同步观测到的波浪数据进行频域统计分析,初步探讨分析了波浪近岸传播过程中波浪统计性质的变化规律。结果表明:碎波带内波的频谱多峰特征显著,峰频两侧均存在着显著能量峰值,峰频能量发生转移;波浪经过破碎后,约束长波能量被释放出来;波浪向岸过程中谱宽度(ε)变大,同时谱尖度(Qp)减小,显著波陡(Ss)增大,峰值周期(Tp)增大,平均周期(Tm02)减小。     

一种引入Hurst指数的MEMS陀螺仪去噪模型

针对MEMS陀螺仪随机漂移产生的误差,提出一种引入Hurst指数的自适应噪声完备集成经验模态分解(CEEMDAN)与自适应卡尔曼滤波(AKF)相结合的去噪模型。首先,通过CEEMDAN对陀螺仪原始信号进行分解,得到一系列频率由高到低的本征模态函数(IMF)和一个残差余量;然后,提出Hurst指数模态筛选机制,将IMF分量划分为噪声IMF、混合IMF和信息IMF;最后,使用自适应卡尔曼滤波器对混合模态分量进行滤波并重构信号。结果表明,CEEMDAN较EMD和EEMD具有更高的分解精度;使用AKF处理混合模态,通过Hurst指数筛选机制重构信号的信噪比相较于排列熵和相关系数法分别提升约12%、36%;使用Hurst指数筛选机制,AKF处理混合模态后重构信号的RMSE较小波阈值滤波降低约23%。     

传感器波段设置对植被遥感参数反演的影响研究

植被是陆地生态系统的基本组成部分,遥感观测的植被冠层反射特性与植被参数之间的响应关系是植被遥感的基础,也是遥感传感器设计的关键.利用Sobol算法和PROSAIL模型,对叶绿素含量和叶面积指数等植被参数进行全局敏感性分析,研究植被参数在典型遥感波段(蓝、绿、红、红边和近红外)的响应敏感性,并对比了由传感器的中心波长和波...     

河北VP型宽频带垂直摆倾斜仪映震效能及时频特征分析

利用河北地区8套VP型宽频带垂直摆倾斜仪的连续观测资料,从映震特征及映震能力等方面讨论其映震效能,并对其时频响应特征进行分析。结果显示：1）河北地区宽频带垂直摆倾斜仪的映震能力与震级和震中距正相关,与震源深度负相关（崇礼台除外）;对于同一地震而言,各台站震中距的远近与仪器映震能力相关性不大。2）8套仪器均能记录到较为完整的远震地震波信息,从波形上能够清晰看到P波与S波的起始时刻。3）时频分析结果显示,仪器能够记录到较为完整的面波信号,但受采样率的限制,体波（P波和S波）信号记录不全,无法记录到0.5 Hz以上的信号。4）由于厂家修改了崇礼台仪器的高端截止频率参数,调整后仪器记录的高频成分增多,信噪比降低,对浅源地震的映震效能产生了与其他仪器相反的结论,对该仪器参数的修改结果需作进一步验证。     

基于粒子群算法的湖泊营养状态指数公式

提出了适用于16个富营养化指标的湖泊营养状态指数公式,并对指数公式中的参数采用粒子群算法进行优化,得到对16项指标都适用的营养状态指数公式.实例分析表明,优化后的湖泊营养状态指数公式计算简单、实用,具有客观性、可比性和通用性.因而,能够对湖泊富营养化进行较好的评价.     

层理倾角对页岩三轴应力应变测试和纵横波速度的影响

针对页岩层理发育的特点,根据不同层理倾角条件下的三轴压缩实验和纵横波速度测试,获得层理倾角对页岩破坏形态、强度、弹性模量、泊松比和纵横波速的影响,明确轴向应力与纵横波速度变化关系,建立研究页岩储层的动、静态弹性模量与泊松比的相关因数,分析页岩的力学参数、纵横波速度的变异因数和各向异性因数。结果表明:页岩力学参数及纵横波速度受层理倾角线性变化,轴向应力与纵波速度正相关,动静态弹性模量和泊松比相关因数分别为1.39、1.18,力学参数的变异因数和各向异性因数均值较超声波速度大。该结果可以为页岩气测井解释、钻井设计和水力压裂改造提供基础参数。     

甘肃东部及相邻地区水位潮汐参数的观测结果

介绍了甘肃省东部及其相邻的西海固地区１９８４～１９９６年间６口深井的水位观测结果及其调和分析结果。分析了Ｍ２波潮汐参数的动态特征、气压对水位的影响和地核振荡对周日波潮汐参数的影响。     

伊犁地块构造及成矿区划刍议

伊犁地块可按昭苏-特克斯、婆罗科努南坡-尼勒克、婆罗科努北坡及博尔塔拉-伊林哈比尔尕等断裂,划分为三个构造单元,由南西向北东展布有:伊宁波疏带、婆罗科努波密带和温泉-赛里木波疏带,其构造演化过程是,温泉斯-赛里木、伊犁地块在元古代时期,镶嵌在塔里木地块的西北缘,后来,经历了寒武一中奥陶世早期边缘海盆演化.中奥陶世晚期,温泉-赛里木与伊犁地块裂陷.志留纪末,两地块镶嵌拼贴.晚古生代是断陷-拗陷活动时期.中石炭世是准噶尔地块西南缘伊林哈比尔尕波峰带与温泉-赛里木及婆罗科努构造带镶嵌的主要时期.研究区还划分出三个成矿区带.     

正压波和斜压波的三波共振与低频振荡

通过引进δ＝Ｈ＿１／Ｈ＿２参数，对两层模式中的正压波和斜压波（考虑了层结作用）的三波共振进行了研究，结果表明：δ叁数对三波共振条件有很大的影响；并进一步讨论了在一定初始振幅的条件下，δ参数和非线性强度对三波共振周期的影响；指出：在一定的初始振佰、δ参戮和非线性强度的条件下，大气中可以形成６０天以上的甚低频振荡及３０～６０天和准两周的低须振荡。     

A VOF-based numerical model for breaking waves in surf zone

This paper introduces a numerical model for studying the evolution of a periodic wave train, shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes (RANS) equations for a mean flow, and (he k-s equations for turbulence kinetic energy k and turbulence dissipation rate e. To track a free surface, the volume of fluid (VOF) function, satisfying the advection equation was introduced. In the numerical treatment, third-order upwind difference scheme was applied to the convection terms of the RANS equations in order to reduce the effect of numerical viscosity. The shoaling and breaking processes of a periodic wave train on gently sloping beaches were modeled. The computed wave heights of a sloping beach and the distribution of breaking wave pressure on a vertical wall were compared with laboratory data.     

Progressive modelling of the gravity-induced landslide using the local dynamic strength reduction method

The failure of slope is a progressive process, and the whole sliding surface is caused by the gradual softening of soil strength of the potential sliding surface. From this viewpoint, a local dynamic strength reduction method is proposed to capture the progressive failure of slope. This method can calculate the warning deformation of landslide in this study. Only strength parameters of the yielded zone of landslide will be reduced by using the method. Through continuous local reduction of the strength parameters of the yielded zone, the potential sliding surface developed gradually and evolved to breakthrough finally. The result shows that the proposed method can simulate the progressive failure of slope truly. The yielded zone and deformation of landslide obtained by the method are smaller than those of overall strength reduction method. The warning deformation of landslide can be obtained by using the local dynamic strength reduction method which is based on the softening characteristics of the sliding surface.     

Analysis on velocity distribution and displacement along the profile of a slope using both empirical and analytical methods

Assessing the slope deformation is significant for landslide prediction. Many researchers have studied the slope displacement based on field data from the inclinometer in combination with complicated numerical analysis. They found that there was a shear zone above the slip surface, and they usually focused on the distribution of velocity and displacement within the shear zone. In this paper, two simple methods are proposed to analyze the distribution of displacement and velocity along the whole profile of a slope from the slip surface to the slope surface during slow movement. In the empirical method, the slope soil above the shear zone is assumed as a rigid body. Dual or triple piecewise fitting functions are empirically proposed for the distribution of velocity along the profile of a slope. In the analytical method, the slope soil is not assumed as a rigid body but as a deformable material. Continuous functions of the velocity and displacement along the profile of a slope are directly obtained by solving the Newton's equation of motion associated with the Bingham model. Using the two proposed methods respectively, the displacement and velocity along the slope profiles of three slopes are determined. A reasonable agreement between the measured data and the calculated results of the two proposed methods has been reached. In comparison with the empirical method, the analytical method would be more beneficial for slope deformation analysis in slope engineering, because the parameters are material constants in the analytical solution independent of time t, and the nonlinear viscosity of the soil can be considered.     

Elimination of the impact of vessels on ocean wave height inversion with X-band wave monitoring radar

Directional wave spectra and integrated wave parameters can be derived from X-band radar sea surface images.A vessel on the sea surface has a significant influence on wave parameter inversions that can be seen as intensive backscatter speckles in X-band wave monitoring radar sea surface images.A novel algorithm to eliminate the interference of vessels in ocean wave height inversions from X-band wave monitoring radar is proposed.This algorithm is based on the characteristics of the interference.The principal components(PCs) of a sea surface image sequence are extracted using empirical orthogonal function(EOF)analysis.The standard deviation of the PCs is then used to identify vessel interference within the image sequence.To mitigate the interference,a suppression method based on a frequency domain geometric model is applied.The algorithm framework has been applied to OSMAR-X,a wave monitoring system developed by Wuhan University,based on nautical X-band radar.Several sea surface images captured on vessels by OSMAR-X are processed using the method proposed in this paper.Inversion schemes are validated by comparisons with data from in situ wave buoys.The root-mean-square error between the significant wave heights(SWH) retrieved from original interference radar images and those measured by the buoy is reduced by 0.25 m.The determinations of surface gravity wave parameters,in particular SWH,confirm the applicability of the proposed method.     

南京市高温热浪时空分布研究

在全球气候变暖的背景下,城市夏季高温热浪已经成为城市最严重的气象灾害之一,给城市居民健康和经济发展带来了巨大的影响。以2013年8月7日-13日的南京高温热浪灾害事件为例,基于Landsat 8 OLI 卫星遥感数据、MODIS卫星遥感数据和气象站点数据,在MODIS地表温度降尺度基础上,估算近地表气温,进而结合空气相对湿度的空间插值数据计算南京地区100 m分辨率的炎热指数和高温热浪指数,分析其时空分布特征。结果表明：在这次高温热浪演变过程中,南京炎热指数呈现先升高后降低的变化趋势,8月11日炎热指数最高,平均达到86.99,12日降到最低值,平均值为85.05;高温热浪强度主要集中于轻度热浪与中度热浪,随着时间的推移,其范围也呈现先扩大后减小的趋势;在空间分布上,南京北部及中心城区的炎热指数较高,主要表现为中度热浪,而南部地区及中心城区周边郊区较低,主要为轻度热浪,山体和水域炎热指数则最低,多为无热浪。     

Soil nutrients in relation to vertical roots distribution in the riparian zone of Three Gorges Reservoir,China

Since the impoundment of the Three Gorges Reservoir (TGR), the riparian zone has been subjected to numerous environmental changes. This study was conducted to recognize the distribution of grass roots and its impacts on soil nutrients in the water level fluctuation zone of TGR. Roots of four predominant herbaceous plants in the study area, specifically, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, and their corresponding relation with soil nutrient contents were investigated. Root surface area density was determined with WinRHIZO, and the relationships of root distribution with soil depths and soil nutrient contents were studied. The results indicates that most roots are distributed in the top soil layer of 0–10 cm. Estimated root surface area density for the selected grass species ranges from 0.16 to 13.44 cm2/cm3, and decreases exponentially with an increase in soil depth. Soil organic matter and total nitrogen contents are significantly lower on bare control area than the corresponding values on the grasslands. Total nutrient contents on grasslands of C. dactylon and H. compressa are higher than those of other grass areas. Root length density and root surface area density are significantly correlated with soil organic matter and total nitrogen content for the four grasslands. The present results suggests that plant roots have significant effects on the distribution of soil nutrients in soil profiles in the riparian zone along the TGR. Nevertheless, additional investigations are needed to reveal the specific interactions between plant roots distribution, soil nutrients and water level fluctuations.     

2013年芦山7.0级地震前重力固体潮参数时空变化研究

以2013年芦山7.0级地震为例,探讨重力固体潮参数的时空分布特征与地震孕育的关系。收集分析芦山震区附近17个台站震前2 a的连续重力观测数据,采用VAV调和分析方法分析计算日波和半日波潮汐参数,主要研究半日波M 2波潮汐因子随时间变化的趋势及空间分布情况。结果表明,芦山地震前M 2波潮汐因子趋势变化空间分布大体呈现上升与下降趋势的四象限分布,芦山地震处于四象限中心部位,可能是由震前存在的“闭锁剪力”引起的区域介质变形或密度扰动所致。     

Distribution of the nonlinear random ocean wave period

Because of the intrinsic difficulty in determining distributions for wave periods, previous studies on wave period distribution models have not taken nonlinearity into account and have not performed well in terms of describing and statistically analyzing the probability density distribution of ocean waves. In this study, a statistical model of random waves is developed using Stokes wave theory of water wave dynamics. In addition, a new nonlinear probability distribution function for the wave period is presented with the parameters of spectral density width and nonlinear wave steepness, which is more reasonable as a physical mechanism. The magnitude of wave steepness determines the intensity of the nonlinear effect, while the spectral width only changes the energy distribution. The wave steepness is found to be an important parameter in terms of not only dynamics but also statistics. The value of wave steepness reflects the degree that the wave period distribution skews from the Cauchy distribution, and it also describes the variation in the distribution function, which resembles that of the wave surface elevation distribution and wave height distribution. We found that the distribution curves skew leftward and upward as the wave steepness increases. The wave period observations for the SZFII-1 buoy, made off the coast of Weihai (37°27.6′ N, 122°15.1′ E), China, are used to verify the new distribution. The coefficient of the correlation between the new distribution and the buoy data at different spectral widths (ν=0.3−0.5) is within the range of 0.968 6 to 0.991 7. In addition, the Longuet-Higgins (1975) and Sun (1988) distributions and the new distribution presented in this work are compared. The validations and comparisons indicate that the new nonlinear probability density distribution fits the buoy measurements better than the Longuet-Higgins and Sun distributions do. We believe that adoption of the new wave period distribution would improve traditional statistical wave theory.     

Probability Analysis of the Wave-Slamming Pressure Values of the Horizontal Deck with Elastic Support

This paper presents the probability distribution of the slamming pressure from an experimental study of regular wave slamming on an elastically supported horizontal deck. The time series of the slamming pressure during the wave impact were first obtained through statistical analyses on experimental data. The exceeding probability distribution of the maximum slamming pressure peak and distribution parameters were analyzed, and the results show that the exceeding probability distribution of the maximum slamming pressure peak accords with the three-parameter Weibull distribution. Furthermore, the range and relationships of the distribution parameters were studied. The sum of the location parameter D and the scale parameter L was approximately equal to 1.0, and the exceeding probability was more than 36.79% when the random peak was equal to the sample average during the wave impact. The variation of the distribution parameters and slamming pressure under different model conditions were comprehensively presented, and the parameter values of the Weibull distribution of wave-slamming pressure peaks were different due to different test models. The parameter values were found to decrease due to the increased stiffness of the elastic support. The damage criterion of the structure model caused by the wave impact was initially discussed, and the structure model was destroyed when the average slamming time was greater than a certain value during the duration of the wave impact. The conclusions of the experimental study were then described.