标准TCP把A d hoc网络中的移动丢包错误解释为拥塞丢包,从而不必要地启动拥塞控制,降低了TCP性能.目前绝大多数的方法都是利用中间节点的反馈信息来改善A d hoc网络中TCP性能.但当在同一条路由上同时发生多处链路中断时,现有方法在路由...标准TCP把A d hoc网络中的移动丢包错误解释为拥塞丢包,从而不必要地启动拥塞控制,降低了TCP性能.目前绝大多数的方法都是利用中间节点的反馈信息来改善A d hoc网络中TCP性能.但当在同一条路由上同时发生多处链路中断时,现有方法在路由重建后不能从正确的状态开始恢复TCP传输,使得TCP在刚恢复传输时就启动‘快速重传/快速恢复’.本文提出的TCP-FSR方法能够很好地解决这个问题,分析和试验证明此方法是有效的.展开更多
The application scope of the forward scatter radar(FSR)based on the Global Navigation Satellite System(GNSS)can be expanded by improving the detection capability.Firstly,the forward-scatter signal model when the targe...The application scope of the forward scatter radar(FSR)based on the Global Navigation Satellite System(GNSS)can be expanded by improving the detection capability.Firstly,the forward-scatter signal model when the target crosses the baseline is constructed.Then,the detection method of the for-ward-scatter signal based on the Rényi entropy of time-fre-quency distribution is proposed and the detection performance with different time-frequency distributions is compared.Simula-tion results show that the method based on the smooth pseudo Wigner-Ville distribution(SPWVD)can achieve the best perfor-mance.Next,combined with the geometry of FSR,the influence on detection performance of the relative distance between the target and the baseline is analyzed.Finally,the proposed method is validated by the anechoic chamber measurements and the results show that the detection ability has a 10 dB improvement compared with the common constant false alarm rate(CFAR)detection.展开更多
基于美国NCEP(National Centers for Environmental Prediction)的CFSR(Climate Forecast System Reanalysis)近20a(1991-2010)10m风场再分析数据(0.3°×0.3°,1h/次,简称CFSR风场),对我国近海风能资源分布特征进行了统计...基于美国NCEP(National Centers for Environmental Prediction)的CFSR(Climate Forecast System Reanalysis)近20a(1991-2010)10m风场再分析数据(0.3°×0.3°,1h/次,简称CFSR风场),对我国近海风能资源分布特征进行了统计分析与评估。利用天津渤海A平台观测站(118°25′E,38°27′N)逐时观测风速数据对CFSR风速数据进行了检验,发现均方根误差和平均偏差仅为均较小(分别为2.28m/s与0.16m/s)。基于此CFSR风场,本文章进一步统计并给出了我国陆地年平均风功率密度分布,结果与第三次风能普查(1971-2000年)及相关文献结果 (1991-2010年)相当一致。依据国家风电场风能资源评估方法,由CFSR风场推算了我国近海20a平均的70m高度风能资源分布。结果显示,年平均风功率密度均达到了200 W/m2以上,大于6m/s的风速累积小时数为4 000h以上;其中台湾海峡和东海南部海区风能最为丰富,黄海中部、渤海中部和辽东湾海区风能次之。参照海上风场选址要求,28°N以北的近岸海域由于水深较浅,30m/s以上风速发生频次极低,比较适合建立海上风电场。展开更多
文摘标准TCP把A d hoc网络中的移动丢包错误解释为拥塞丢包,从而不必要地启动拥塞控制,降低了TCP性能.目前绝大多数的方法都是利用中间节点的反馈信息来改善A d hoc网络中TCP性能.但当在同一条路由上同时发生多处链路中断时,现有方法在路由重建后不能从正确的状态开始恢复TCP传输,使得TCP在刚恢复传输时就启动‘快速重传/快速恢复’.本文提出的TCP-FSR方法能够很好地解决这个问题,分析和试验证明此方法是有效的.
基金This work was supported by the National Natural Science Foundation of China(62071475,61890541,62171447).
文摘The application scope of the forward scatter radar(FSR)based on the Global Navigation Satellite System(GNSS)can be expanded by improving the detection capability.Firstly,the forward-scatter signal model when the target crosses the baseline is constructed.Then,the detection method of the for-ward-scatter signal based on the Rényi entropy of time-fre-quency distribution is proposed and the detection performance with different time-frequency distributions is compared.Simula-tion results show that the method based on the smooth pseudo Wigner-Ville distribution(SPWVD)can achieve the best perfor-mance.Next,combined with the geometry of FSR,the influence on detection performance of the relative distance between the target and the baseline is analyzed.Finally,the proposed method is validated by the anechoic chamber measurements and the results show that the detection ability has a 10 dB improvement compared with the common constant false alarm rate(CFAR)detection.
