A robust object-based shadow detection method for cloud-free high resolution satellite images over urban areas and water bodies

Unwanted contrast in high resolution satellite images such as shadow areas directly affects the result of further processing in urban remote sensing images. Detecting and finding the precise position of shadows is critical in different remote sensing processing chains such as change detection, image classification and digital elevation model generation from stereo images. The spectral similarity between shadow areas, water bodies, and some dark asphalt roads makes the development of robust shadow detection algorithms challenging. In addition, most of the existing methods work on pixel-level and neglect the contextual information contained in neighboring pixels. In this paper, a new object-based shadow detection framework is introduced. In the proposed method a pixel-level shadow mask is built by extending established thresholding methods with a new C₄ index which enables to solve the ambiguity of shadow and water bodies. Then the pixel-based results are further processed in an object-based majority analysis to detect the final shadow objects. Four different high resolution satellite images are used to validate this new approach. The result shows the superiority of the proposed method over some state-of-the-art shadow detection method with an average of 96% in F-measure.     

FET振荡器注入锁相伏特拉级数分析

应用伏特拉级数法分析了电容耦合ＦＥＴ振荡系统在外加信号下的注入锁定现象，推导出输出信号和注入锁定带宽表达式。与一般非线性系统分析方法相比，伏特拉级数法在建立好系统模型后只需进行代数运算，从而避开了求解非线性，非齐次高阶微分方程的复杂过程。     

弹道交班自适应算法研究

为实现复合制导不同制导弹道的平滑过渡,用二阶吻合法设计了一不同制导律间的指令交接导引段。建立了自适应弹道交接导引算法的模型。理论分析和仿真结果表明,该算法具较好的弹道过载平滑能力,有一定的应用价值。     

现场动平衡技术在生产中的应用

利用美国恩泰克公司提供的DP1500数据采集仪及现场动平衡软件,以实例说明了现场动平衡技术在锅炉引风机、排粉风机、电动机、机泵等转动设备不平衡故障排除中的应用,介绍了不平衡故障的识别方法,揭示出该技术在生产中的实用性、先进性和经济性.     

液相色谱仪故障分析与处理

简述了液相色谱仪工作原理，对常见故障进行了分析，并给出了处理方法。     

Phase coherence of MHD waves in the solar wind

Large amplitude MHD waves are commonly found in the solar wind. Nonlinear interactions between the MHD waves are likely to produce finite correlation among the wave phases. For discussions of various transport processes of energetic particles, it is fundamentally important to determine whether the wave phases are randomly distributed (as assumed in quasi-linear theories) or they have a finite coherence. Using a method based on a surrogate data technique and a fractal analysis, we analyzed Geotail magnetic field data (provided by S. Kokubun and T. Nagai through DARTS at the Institute of Space and Astronautical Science) to evaluate the phase coherence among the MHD waves in the earth's foreshock region. The correlation of wave phases does exist, indicating that the nonlinear interactions between the waves is in progress. This revised version was published online in August 2006 with corrections to the Cover Date.     

费率受制于位相半马氏过程的风险模型

对带马氏链的线性和非线性系统，经过众多学者近20多年的努力，已取得一系列重要成果。然而，由于马氏链状态逗留时间服从负指数分布，使得这些成果在应用中有很大的局限性。本文首先探讨了位相半马氏过程的性质，然后以位相半马氏过程代替马氏过程，研究风险模型的相关问题，取得了与马氏链相同的研究成果，从而说明了位相半马氏过程在克服由马氏过程带来的局限性中的作用。     

镀膜光纤声光相位调制器频率响应特性的研究

本文对光纤声光相位调制器（OF—AOPM）的频率特性进行研究。分析了OF—AOPM的调相原理，研究结果表明：在调制频率远离氧化锌压电薄膜的半波谐振频率的时候，光相位的调制不仅依靠径向应力。同时还依靠轴向应力。通过同时考虑径向和轴向应力的变化，得出了OF—AOPM在整个频率域范围内的响应特性。     

分集接收机鉴相算法研究与设计

从介绍分集接收机的基本工作原理入手,着重论述分集接收机中差模环的两种鉴相算法,并给出两种算法在使用FPGA实现时的资源占用情况,最后介绍了两种算法在实际工程中的应用。     

动态测量系统的逆系统设计

为了从测量信号中恢复出原始的物理信息 ,需要设计动态测量系统的逆系统 ,以使整个系统的传递函数为 1。但对于非最小相位测量系统 ,简单的逆变换会引起系统不稳定 ,零相位误差算法的引入有效地解决了这个问题。文中以温度测量为例 ,对其进行反演 ,仿真表明结果真实可靠 ,方法具有一定的实用价值