The filling and exhausting processes in a pneumatic system are involved with many factors, and numerical solutions of many partial differential equations are always adapted in the study of those processes, which have ...The filling and exhausting processes in a pneumatic system are involved with many factors, and numerical solutions of many partial differential equations are always adapted in the study of those processes, which have been proved to be troublesome and less intuitive. Analytical solutions based on loss-less tube model and average friction tube model are found respectively by using fluid net theory, and they fit the experimental results well. The research work shows that： Fluid net theory can be used to solve the analytical solution of filling and exhausting processes of pneumatic system, and the result of loss-less tube model is close to that of average friction model, so loss-less tube model is recommended since it is simpler, and the difference between filling time and exhausting time is determined by initial and final pressures, the volume of container and the section area of tube, and has nothing to do with the length of the tube.展开更多
传统的正交频分复用(Orthogonal frequency division multiplexing,OFDM)信号压缩算法由于低的压缩比和低的信号量化误差比(Signal to quantization-error ratio,SQR)造成较高的误码率,无法满足OFDM系统的需求。为了实现高的压缩比和低...传统的正交频分复用(Orthogonal frequency division multiplexing,OFDM)信号压缩算法由于低的压缩比和低的信号量化误差比(Signal to quantization-error ratio,SQR)造成较高的误码率,无法满足OFDM系统的需求。为了实现高的压缩比和低的误码率,提出了一种联合削峰尾插(Clipping with tail plug,CTP)技术、几何级数压扩(Geometric series companding,GSC)技术及部分采样点校正(Partial sample calibration,PSC)技术的准无损压缩算法。计算机仿真结果表明,对于4096-正交幅度调制(Quadrature amplitude modulation,QAM)的OFDM信号,压缩比最高可达1.86∶1,误码率低于10-7,量化误差对应的平均SQR高达70dB,因而能够很好地满足光纤到分配点+千兆数字用户线路(Fiber to the distribution point+GCga digital subscriber line,FTTdp+GDSL)系统的需求。展开更多
基金This project is supported by National Natural Science Foundation of China(No.50575209).
文摘The filling and exhausting processes in a pneumatic system are involved with many factors, and numerical solutions of many partial differential equations are always adapted in the study of those processes, which have been proved to be troublesome and less intuitive. Analytical solutions based on loss-less tube model and average friction tube model are found respectively by using fluid net theory, and they fit the experimental results well. The research work shows that： Fluid net theory can be used to solve the analytical solution of filling and exhausting processes of pneumatic system, and the result of loss-less tube model is close to that of average friction model, so loss-less tube model is recommended since it is simpler, and the difference between filling time and exhausting time is determined by initial and final pressures, the volume of container and the section area of tube, and has nothing to do with the length of the tube.
文摘传统的正交频分复用(Orthogonal frequency division multiplexing,OFDM)信号压缩算法由于低的压缩比和低的信号量化误差比(Signal to quantization-error ratio,SQR)造成较高的误码率,无法满足OFDM系统的需求。为了实现高的压缩比和低的误码率,提出了一种联合削峰尾插(Clipping with tail plug,CTP)技术、几何级数压扩(Geometric series companding,GSC)技术及部分采样点校正(Partial sample calibration,PSC)技术的准无损压缩算法。计算机仿真结果表明,对于4096-正交幅度调制(Quadrature amplitude modulation,QAM)的OFDM信号,压缩比最高可达1.86∶1,误码率低于10-7,量化误差对应的平均SQR高达70dB,因而能够很好地满足光纤到分配点+千兆数字用户线路(Fiber to the distribution point+GCga digital subscriber line,FTTdp+GDSL)系统的需求。
