对舰船辐射噪声中线谱成分的检测,是被动声纳对目标定位识别中的关键技术。应用自适应线谱增强器(Adaptive Line Enhancer,ALE),可以有效从宽带背景噪声中提取出舰船辐射噪声的线谱成分。基于最小均方误差(Least-Mean-Square,LMS)的ALE...对舰船辐射噪声中线谱成分的检测,是被动声纳对目标定位识别中的关键技术。应用自适应线谱增强器(Adaptive Line Enhancer,ALE),可以有效从宽带背景噪声中提取出舰船辐射噪声的线谱成分。基于最小均方误差(Least-Mean-Square,LMS)的ALE收敛速度慢,提出应用基于快速横向滤波(Fast Transversal Filter,FTF)的ALE对舰船辐射噪声的非线谱成分进行抑制。仿真结果显示,FTF算法自适应线谱增强器收敛速度快,输出精度较高,有利于对舰船辐射噪声线谱成分的提取。展开更多
Freeze-thaw processes significantly modulate hydraulic and thermal char- acteristics of soil. The changes in the frost and thaw fronts （FTFs） affect the water and energy cycles between the land surface and the atmos...Freeze-thaw processes significantly modulate hydraulic and thermal char- acteristics of soil. The changes in the frost and thaw fronts （FTFs） affect the water and energy cycles between the land surface and the atmosphere. Thus, the frozen soil com- prising permafrost and seasonally frozen soil has important effects on the land surface hydrology in cold regions. In this study, a two-directional freeze and thaw algorithm is incorporated into a thermal diffusion equation for simulating FTFs. A local adaptive variable-grid method is used to discretize the model. Sensitivity tests demonstrate that the method is stable and FTFs can be tracked continuously. The FTFs and soil tempera- ture at the Qinghai-Tibet Plateau D66 site are simulated hourly from September 1, 1997 to September 22, 1998. The results show that the incorporated model performs much better in the soil temperature simulation than the original thermal diffusion equation, showing potential applications of the method in land-surface process modeling.展开更多
文摘对舰船辐射噪声中线谱成分的检测,是被动声纳对目标定位识别中的关键技术。应用自适应线谱增强器(Adaptive Line Enhancer,ALE),可以有效从宽带背景噪声中提取出舰船辐射噪声的线谱成分。基于最小均方误差(Least-Mean-Square,LMS)的ALE收敛速度慢,提出应用基于快速横向滤波(Fast Transversal Filter,FTF)的ALE对舰船辐射噪声的非线谱成分进行抑制。仿真结果显示,FTF算法自适应线谱增强器收敛速度快,输出精度较高,有利于对舰船辐射噪声线谱成分的提取。
基金Project supported by the National Natural Science Foundation of China(Nos.41575096 and91125016)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA05110102)
文摘Freeze-thaw processes significantly modulate hydraulic and thermal char- acteristics of soil. The changes in the frost and thaw fronts （FTFs） affect the water and energy cycles between the land surface and the atmosphere. Thus, the frozen soil com- prising permafrost and seasonally frozen soil has important effects on the land surface hydrology in cold regions. In this study, a two-directional freeze and thaw algorithm is incorporated into a thermal diffusion equation for simulating FTFs. A local adaptive variable-grid method is used to discretize the model. Sensitivity tests demonstrate that the method is stable and FTFs can be tracked continuously. The FTFs and soil tempera- ture at the Qinghai-Tibet Plateau D66 site are simulated hourly from September 1, 1997 to September 22, 1998. The results show that the incorporated model performs much better in the soil temperature simulation than the original thermal diffusion equation, showing potential applications of the method in land-surface process modeling.
