A new framework for studying the relationship of aurora and plasma sheet dynamics     

《Journal of Atmospheric and Solar》2002,64(2):115-124

Auroras have been extensively studied using images obtained by space-borne experiments. We use global UVI images obtained from Polar and simultaneous plasma data obtained by the 3D instrument on Wind from the near-earth plasma sheet to study the dynamics of auroras with different size and intensity. Unstable phase space ion distributions are detected in the plasma sheet under diverse geomagnetic and solar wind IMF conditions (positive and negative B_z) and at all phases of a substorm. These results indicate that plasma instability processes with different disturbance levels operate in the plasma sheet and produce a continuum of auroral size and intensity. The criteria for triggering an instability are dependent on the local properties of the plasma distributions. These observations suggest a new framework to integrate previous and current results and a new way to examine the causal relationships of auroral and plasma sheet dynamics.  相似文献   

基于球面的电子全站仪测高大气竖直折射角严密计算方法研究     

姜晨光  王辉  方丽娟  郭海琳  彭建国 《现代测绘》2009,32(2)

大气竖直折射是影响竖直角观测精度的关键因素之一.大气竖直折射的计算一直是困扰测绘界的难题.为了更加合理地计算大气竖直折射,提出了基于球面的电子全站仪测高大气竖直折射计算方法,给出了基于球面的电子全站仪测高严格计算公式.  相似文献   

荧光标记微卫星分析人工饲养中华绒螯蟹的遗传多样性   总被引：5，自引：1，他引：5  

朱泽远  王亚菊  施用晖  乐国伟 《中国海洋大学学报(自然科学版)》2007,37(4):591-596

分析中华绒螯蟹的遗传多样性，采集来自无锡、苏州和上海人工养殖样品102个，运用毛细管电泳检测荧光标记（FAM或HEX）的10个中华绒螯蟹微卫星DNA位点。在所有的3个群体中，单一位点等位基因数从15～42个，平均值为22．9；多态信息含量（PIC）和有效等位基因数（E）分别高达0．826和7．699。结果表明10个位点均为高度多态位点，中华绒螯蟹人工养殖群体具有较高的遗传多样性。欧氏遗传距离、遗传相似性和群体各亚群体内固定系数（Fst）平均值分别为0．439，0．825和0．099，结果显示不同的人工养殖群体之间也存在较大的遗传多样性。除上海群体在同步突变模式（SMM）下，近期不会有瓶颈（P=0．35）；所有群体在SMM和无限等位基因模式（IAM）下均有显著或极显著的瓶颈（P〈0．01或0．05），结果说明科学的品种保护计划的迫切性。本研究首次选择遗传标记微卫星DNA评估中华绒螯蟹的遗传多样性，并采用高精度的毛细管电泳检测技术，将对中华绒螯蟹的品种保护和合理利国提倡科学依据。  相似文献   

多元系统耦合多新息随机梯度类辨识方法     

丁锋  汪菲菲 《南京气象学院学报》2014,6(1):1-16

针对多元线性回归系统,利用耦合辨识概念和多新息辨识理论,讨论了多元随机梯度算法、多元多新息随机梯度算法,以及变递推间隔多元多新息梯度算法,进一步分解多元系统为一些子系统,给出了耦合子系统随机梯度算法、耦合随机梯度算法、耦合子系统多新息随机梯度算法、耦合多新息随机梯度算法,并将这些方法推广到多元伪线性滑动平均系统和多元伪线性自回归滑动平均系统.文中给出了几个典型耦合随机梯度算法、耦合多新息随机梯度算法的计算步骤和示意图.  相似文献   

规范状态空间系统辨识方法     

丁锋  马兴云 《南京气象学院学报》2014,6(6):481-504

因为状态空间模型既包含了未知状态,又包含了未知参数,且二者是非线性乘积关系,使得辨识问题变得复杂.针对这一问题,详细研究了规范状态空间系统的状态与参数联合估计方法.采用交互估计理论,即采用递推方法或迭代方法实现系统状态与参数的交互估计.基本思路是在计算参数估计时,辨识算法信息向量中的未知状态用其估计值代替,然后利用获得的参数估计,设计基于参数估计的状态观测器或基于参数估计的Kalman滤波算法估计系统的状态,二者形成一个交互计算过程(递阶计算过程).沿着这条思路,分别从递推方案和迭代方案,研究和提出了基于状态观测器和基于Kalman滤波状态估计的随机梯度辨识算法、递推最小二乘辨识算法、多新息随机梯度辨识算法、多新息最小二乘辨识算法,以及模型分解的辨识算法,并给出了几个典型算法的计算步骤、流程图和计算量.  相似文献   

Determining dynamic parameters of different-scale ionospheric irregularities over northern Siberia     

《Journal of Atmospheric and Solar》2000,62(2):133-140

In 1995–1996, observations were carried out at Norilsk (geomagnetic latitude and longitude 64.2°N and 160.4°E) to determine dynamic parameters of irregularities in the high-latitude ionosphere. The short-baseline spaced-receiver method that has been implemented at the ionospheric facility of the Norilsk Integrated Magnetic–Ionospheric Station, provides a means of simultaneously measuring parameters of small-scale irregularities (spatial scale of 3–5 km) by the Similar-Fading Method (SFM), as well as of medium-scale irregularities (time scale of 10–30 min, spatial scale of hundreds of kilometres) by the Statistical Angle-of-arrival and Doppler Method (SADM). About 20 h of the observational data for the F2-layer under quiet geomagnetic conditions (K_p < 3), 20 h under disturbed conditions (K_p ≥ 3) and about 15 h for the sporadic E-layer (K_p ≈ 3) were processed. It has been found that the propagation directions and velocities of different-scale irregularities do not coincide. Small-scale irregularities of the F2-layer travel predominantly eastward or westward. The velocity of the F2-layer irregularities is about 100 m/s, and under disturbed conditions it is up to 200–250 m/s. Small-scale irregularities of the sporadic E-layer travel mostly in the northward direction. It is confirmed that the E_s-layer is characterised by high velocities of the irregularities (as high as 1000 m/s). Medium-scale irregularities with periods in the range of 10–30 min travel mostly in a southward direction with velocities of 20–40 m/s.  相似文献   

辅助模型辨识方法(4):基本思想与梯度辨识     

丁锋 《南京气象学院学报》2016,8(4):289-309

辅助模型辨识思想是针对系统存在一些不可测变量的辨识问题提出的,它是研究含有未知变量的线性系统、非线性系统辨识的重要手段.本文阐述了辅助模型辨识思想,针对白噪声干扰的输入非线性有限脉冲响应系统,研究辅助模型梯度辨识方法、辅助模型多新息梯度辨识方法、变递推间隔辅助模型多新息梯度辨识方法,以及派生的变递推间隔辅助模型梯度辨识方法、等递推间隔辅助模型梯度辨识方法和等递推间隔辅助模型多新息梯度辨识方法.  相似文献   

特征筛选方法在高分辨率遥感影像建筑物提取中的应用     

刘润  张绍良  贾蓉 《测绘通报》2018,(2):126-130

城市建筑物信息的自动提取是城市遥感的关键技术之一,由于阴影、下垫面等多因素干扰,建筑物信息提取精度往往不稳定。本文以Pleiades卫星影像为数据源,通过改进Relief F特征筛选方法,探讨建筑物信息提取精度提高的可行性。首先构建高分辨率遥感影像建筑物基础特征空间,然后利用改进型Relief F算法分析特征对象的权重并筛选出最优特征,最后用监督分类、无特征筛选分类和基于改进型Relief F特征筛选等3种方法分别提取研究区建筑物信息,并结合实地调查数据进行精度验证。结果表明,基于改进型Relief F特征筛选的分类方法提取精度能够达到91.34%,较其他两种方法提取精度分别提高了34.31%和5.62%,且运算速度快,自动识别效率高。  相似文献   

Shaking table model test on Shanghai World Financial Center Tower     

Xilin Lu  Yun Zou  Wensheng Lu  Bin Zhao 《地震工程与结构动力学》2007,36(4):439-457

The height of 101‐storey Shanghai World Financial Center Tower is 492m above ground making it possible the tallest building in the world when completed. Three parallel structural systems including mega‐frame structure, reinforced concrete and braced steel services core and outrigger trusses, are combined to resist vertical and lateral loads. The building could be classified as a vertically irregular structure due to a number of stiffened and transfer stories in the building. Complexities related to structural system layout are mainly exhibited in the design of services core, mega‐diagonals and outrigger trusses. According to Chinese Code, the height 190 m of the building clearly exceeds the stipulated maximum height of for a composite frame/reinforced concrete core building. The aspect ratio of height to width also exceeds the stipulated limit of 7 for seismic design intensity 7. A 1/50 scaled model is made and tested on shaking table under a series of one and two‐dimensional base excitations with gradually increasing acceleration amplitudes. This paper presents the dynamic characteristics, the seismic responses and the failure mechanism of the structure. The test results demonstrate that the structural system is a good solution to withstand earthquakes. The inter‐storey drift and the overall behaviour meet the requirements of Chinese Design Code. Furthermore, weak positions under seldom‐occurred earthquakes of seismic design intensity 8 are found based on the visible damages on the testing model, and some corresponding suggestions are proposed for the engineering design of the structure under extremely strong earthquake. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

海水仔稚鱼微粒饲料微观形态和水中稳定性的比较研究     

谢中国  王芙蓉  刘海英  祝爱侠  牛化欣  过世东 《中国海洋大学学报(自然科学版)》2013,(3):55-61

采用不同的方法制备海水仔稚鱼微粒饲料,并对其微观形态和水中稳定性进行分析比较。锐孔凝固浴法制备的微胶囊饲料粒径较大,表面粗糙、凹陷,有许多裂缝;流化床方法制备的微胶囊饲料形状不规则,表面有一层光滑一致的包衣膜,氮保留率为52.2%;挤出滚圆-流化床方法制备的微胶囊饲料为近似的球形,结构较为致密,表面为一层均匀一致的包衣膜,氮保留率为43.9%;喷雾干燥法制备的微胶囊饲料为近似的球形,表面有皱褶和凹陷,氮保留率为36.0%;挤出-破碎法制备的微黏饲料形状不规则,结构较致密,氮保留率为23.6%;筛分法制备的微黏饲料形态不规则,原料杂乱的黏合在一起,氮保留率为15.2%。结果显示,流化床方法和挤出滚圆-流化床法更适合制备海水仔稚鱼微胶囊饲料。  相似文献