Propagation modeling of ocean-scattered low-elevation GPS signals for maritime tropospheric duct inversion

The maritime tropospheric duct is a low-altitude anomalous refractivity structure over the ocean surface,and it can significantly affect the performance of many shore-based/shipboard radar and communication systems.We propose the idea that maritime tropospheric ducts can be retrieved from ocean forward-scattered low-elevation global positioning system(GPS) signals.Retrieval is accomplished by matching the measured power patterns of the signals to those predicted by the forward propagation model as a function of the modified refractivity profile.On the basis of a parabolic equation method and bistatic radar equation,we develop such a forward model for computing the trapped propagation characteristics of an ocean forward-scattered GPS signal within a tropospheric duct.A new GPS scattering initial field is defined for this model to start the propagation modeling.A preliminary test on the performance of this model is conducted using measured data obtained from a 2009-experiment in the South China Sea.Results demonstrate that this model can predict GPS propagation characteristics within maritime tropospheric ducts and serve as a forward model for duct inversion.     

准静态蒸发Kerr黑洞的量子热效应

该文采用新的广义乌龟坐标变换后,在事件视界附近直接求解Klein-Gordon方程,得到以(t,r)坐标描述的轴对称Kerr黑洞的视界位置、辐射温度.计算结果表明,考虑蒸发后Kerr黑洞的视界面是一个随时间变化的椭球面,Hawking辐射温度不仅随时间变化,而且与方位角有关.进一步分析表明Hawking辐射温度是时间坐标尺度下的补偿效应.     

基于雷达海杂波的区域性非均匀蒸发波导反演方法

由于不同海域上空气象条件的不同, 海上蒸发波导在大尺度海面上空发生时通常是区域性非均匀的, 这一特性使得该环境中的电波传播特性相对于水平均匀的蒸发波导环境情况而明显不同, 因此, 进行区域性非均匀的蒸发波导探测反演对正确预测电波传播特性及提高雷达系统的工作性能具有重要的意义. 考虑到实际应用中蒸发波导信息获取手段的多样性, 将中尺度数值气象模式MM5预报的区域性蒸发波导修正折射率剖面作为先验信息, 提出了一种含该先验信息的区域性非均匀蒸发波导的雷达海杂波后验概率估计模型. 该模型使用主分量分析法对蒸发波导的水平非均匀性进行参数化建模, 然后通过贝叶斯理论将修正折射率剖面参数的先验概率分布、后验概率分布和似然函数联系起来, 利用雷达海杂波实现蒸发波导剖面参数的最大后验概率估计反演. 通过我国东海海域的实际区域性非均匀蒸发波导反演测试, 表明该模型能够以更高的精度实现区域性非均匀蒸发波导的反演.     

生长曲线模型参数估计的几个相对效率

对于生长曲线模型该文在１中定义了的三种相对效率,即：其中,Ｂ＝（Ａ’∑~（－１）Ａ）~（－１）Ａ’∑’~（－１）ＹＶ~（－１）~Ｃ’（ＣＶ~（－１）Ｃ’）~（－１）,Ｂ＝（Ａ’∑~（－１）Ａ）~（－１）Ａ’∑~（－１）ＹＣ’（ＣＣ’）＼＋－１,μ＝ＡＢＣ,μ·＝ＡＢ·Ｃ．在２,３,４中分别给出了它们的上界,并给予了证明．