In this study, Al-Mg-Al trilaminated thin plates were fabricated by one-pass hot rolling to improve the processing capacity and bonding strength of magne- sium alloy plates. The effects of processing parameters were i...In this study, Al-Mg-Al trilaminated thin plates were fabricated by one-pass hot rolling to improve the processing capacity and bonding strength of magne- sium alloy plates. The effects of processing parameters were investigated. The results show that the optimal bonding strength is up to 20 MPa with a reduction ratio of 40 % and rolling temperature of 400 ℃, superior than that in other one-pass rolling studies with regard to thin lami- nated plates. In addition, a favorable property is achieved with the annealing temperature of 250-300 ℃ or annealing time of 1.5 h. When the annealing temperature exceeds 300 ℃ or annealing time exceeds 1.5 h, respectively, the bonding strength of Al/Mg/Al plate decreases. The scan- ning electron microscopy （SEM） and energy-dispersive spectroscopy （EDS） analyses suggest that the appearance of thin diffusion layers between Al and Mg interfaces is helpful to improve the bonding strength, while the presence of thick diffusion layer would reduce the bonding strength greatly.展开更多
For direct sequence spread spectrum （DSSS） receivers, the capability of rejecting narrow-band interference can be significantly improved by a process of frequency-domain interference suppression （FDIS）. The key is...For direct sequence spread spectrum （DSSS） receivers, the capability of rejecting narrow-band interference can be significantly improved by a process of frequency-domain interference suppression （FDIS）. The key issue of this process is how to determine a threshold to eliminate interference in the frequency domain, which has been extensively studied. However, these previous methods are tedious or very complex. A simple and ef- ficient algorithm based on medians is proposed. The elimination threshold is only related to the median by a scale factor, which can be obtained by the numerical analysis. Simulation results show that the algorithm provides excellent narrow-band interfer- ence suppression while only slightly degrading the signal-to-noise ratio （SNR）. A one-pass algorithm using logarithmic segmentation is further derived to estimate medians with low computational complexity. Finally, the FDIS is implemented in a field programmable gate array （FPGA） of Xilinx. Experiments are carried out by connecting the FDIS FPGA to a DSSS receiver, and the results show that the receiver has an effective countermeasure for a 60 dB interference-to-signal ratio （ISR）.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.51301118 and 51175363)the Specialized Research Fund for the Doctoral Program of Higher Education (No.20050112001)the Natural Science Foundation of Shanxi Province (No. 2006011051)
文摘In this study, Al-Mg-Al trilaminated thin plates were fabricated by one-pass hot rolling to improve the processing capacity and bonding strength of magne- sium alloy plates. The effects of processing parameters were investigated. The results show that the optimal bonding strength is up to 20 MPa with a reduction ratio of 40 % and rolling temperature of 400 ℃, superior than that in other one-pass rolling studies with regard to thin lami- nated plates. In addition, a favorable property is achieved with the annealing temperature of 250-300 ℃ or annealing time of 1.5 h. When the annealing temperature exceeds 300 ℃ or annealing time exceeds 1.5 h, respectively, the bonding strength of Al/Mg/Al plate decreases. The scan- ning electron microscopy （SEM） and energy-dispersive spectroscopy （EDS） analyses suggest that the appearance of thin diffusion layers between Al and Mg interfaces is helpful to improve the bonding strength, while the presence of thick diffusion layer would reduce the bonding strength greatly.
基金supported by the National Natural Science Foundation of China(60904090)
文摘For direct sequence spread spectrum （DSSS） receivers, the capability of rejecting narrow-band interference can be significantly improved by a process of frequency-domain interference suppression （FDIS）. The key issue of this process is how to determine a threshold to eliminate interference in the frequency domain, which has been extensively studied. However, these previous methods are tedious or very complex. A simple and ef- ficient algorithm based on medians is proposed. The elimination threshold is only related to the median by a scale factor, which can be obtained by the numerical analysis. Simulation results show that the algorithm provides excellent narrow-band interfer- ence suppression while only slightly degrading the signal-to-noise ratio （SNR）. A one-pass algorithm using logarithmic segmentation is further derived to estimate medians with low computational complexity. Finally, the FDIS is implemented in a field programmable gate array （FPGA） of Xilinx. Experiments are carried out by connecting the FDIS FPGA to a DSSS receiver, and the results show that the receiver has an effective countermeasure for a 60 dB interference-to-signal ratio （ISR）.
