为了更快地实现主动降噪,设计了噪音多项式拟合模型,提出了改进的变步长滤波最小均方算法(Improved Filtered-x Least Mean Square,IFxLMS)。该算法在统计噪音信号的同时,对噪音信号进行拟合与预测,随后结合误差信号与预测信号对步长进...为了更快地实现主动降噪,设计了噪音多项式拟合模型,提出了改进的变步长滤波最小均方算法(Improved Filtered-x Least Mean Square,IFxLMS)。该算法在统计噪音信号的同时,对噪音信号进行拟合与预测,随后结合误差信号与预测信号对步长进行调节,达到快速调节的目的。为了验证该算法的性能,将该算法与传统变步长滤波最小均方算法对比试验,仿真结果显示,在相同噪音条件下,新算法将噪音信号降到10 dB、20 dB、30 dB、35 dB等信噪比时,所需的迭代次数减少了4次~60次不等,在同时新算法的鲁棒性也优于普通的滤波变步长最小均方算法。展开更多
Vegetation restoration is the primary task of ecological reconstruction and rocky desertification control in Karst areas. With vegetation net primary productivity and coverage as two key indicators, a vegetation ecolo...Vegetation restoration is the primary task of ecological reconstruction and rocky desertification control in Karst areas. With vegetation net primary productivity and coverage as two key indicators, a vegetation ecological quality evaluation model was built based on meteorological and remote sensing data. Spatiotemporal variation of vegetation ecological quality index and its response to climate change in rocky desertification areas in Southwest China during 2000-2020 were also analyzed by using the difference method and linear trend method. The results showed that:(1) Vegetation ecological quality in rocky desertification areas in Southwest China showed a fluctuating upward trend during 2000-2020. In 2020, the vegetation ecological quality index reached 69.7, which was 19.9% and 9.3% higher than the averaged values for 2000 and 2000-2019, respectively, ranking the fourth highest since 2000.(2) Vegetation ecological quality of the rocky desertification areas in Yunnan, Guangxi and Guizhou provinces have been improved by 89.2%, 99.2% and 98.5%, respectively, from 2000 to 2020, with their vegetation ecological quality index values increasing by 0.5-0.75 per year in southeast Yunnan, most areas in Guizhou and northwest Guangxi.(3) Precipitation was an important meteorological factor affecting the vegetation ecological quality in rocky desertification areas. The vegetation ecological quality index in the northwest and central Yunnan rocky desertification areas has been rising slowly, but with localized declines at a yearly rate of nearly 0.25 caused by climatic warming and drying.展开更多
文摘为了更快地实现主动降噪,设计了噪音多项式拟合模型,提出了改进的变步长滤波最小均方算法(Improved Filtered-x Least Mean Square,IFxLMS)。该算法在统计噪音信号的同时,对噪音信号进行拟合与预测,随后结合误差信号与预测信号对步长进行调节,达到快速调节的目的。为了验证该算法的性能,将该算法与传统变步长滤波最小均方算法对比试验,仿真结果显示,在相同噪音条件下,新算法将噪音信号降到10 dB、20 dB、30 dB、35 dB等信噪比时,所需的迭代次数减少了4次~60次不等,在同时新算法的鲁棒性也优于普通的滤波变步长最小均方算法。
基金The National Natural Science Foundation of China (31700421)。
文摘Vegetation restoration is the primary task of ecological reconstruction and rocky desertification control in Karst areas. With vegetation net primary productivity and coverage as two key indicators, a vegetation ecological quality evaluation model was built based on meteorological and remote sensing data. Spatiotemporal variation of vegetation ecological quality index and its response to climate change in rocky desertification areas in Southwest China during 2000-2020 were also analyzed by using the difference method and linear trend method. The results showed that:(1) Vegetation ecological quality in rocky desertification areas in Southwest China showed a fluctuating upward trend during 2000-2020. In 2020, the vegetation ecological quality index reached 69.7, which was 19.9% and 9.3% higher than the averaged values for 2000 and 2000-2019, respectively, ranking the fourth highest since 2000.(2) Vegetation ecological quality of the rocky desertification areas in Yunnan, Guangxi and Guizhou provinces have been improved by 89.2%, 99.2% and 98.5%, respectively, from 2000 to 2020, with their vegetation ecological quality index values increasing by 0.5-0.75 per year in southeast Yunnan, most areas in Guizhou and northwest Guangxi.(3) Precipitation was an important meteorological factor affecting the vegetation ecological quality in rocky desertification areas. The vegetation ecological quality index in the northwest and central Yunnan rocky desertification areas has been rising slowly, but with localized declines at a yearly rate of nearly 0.25 caused by climatic warming and drying.