In order to improve the performance of line spectrum detection,according to the feature that the underwater target radiated noise containing stable line spectrum,the differences of the phase difference between line sp...In order to improve the performance of line spectrum detection,according to the feature that the underwater target radiated noise containing stable line spectrum,the differences of the phase difference between line spectrum and background noise,a weighted line spectrum detection algorithm based on the phase variance is proposed in frequency domain.After phase difference alignment,the phase variance of line spectrum and the phase of background noise,respectively,are small and big in frequency domain,this method utilizes the weighted statistical algorithm to cumulate the frequency spectrum based on the phase variance,which can restrain the background noise disturbance,and enhance the signal to noise ratio（SNR）.The theory analysis and experimental results both verify that the proposed method can well enhance the energy of line spectrum,restrain the energy of background noise,and have better detection performance under lower SNR.展开更多
This paper investigates a new vortex wave imaging approach to improve the imaging quality of small metal targets of size less than 1.5 mm.Antennas with different spiral phase plates are designed to efficiently transmi...This paper investigates a new vortex wave imaging approach to improve the imaging quality of small metal targets of size less than 1.5 mm.Antennas with different spiral phase plates are designed to efficiently transmit vortex beams with orbital angular momentums(OAMs).By analyzing the OAM spectrum of the target,it was discovered that the predominant reflection contains a particular OAM mode that carries abundant azimuthal information.This can be explained by the OAM selectivity of the target and the guidance of the vortex transmitting beam.A simple reflection vortex imaging system was designed to capture the phase information.Measurement results show that the high image contrast reaches 14.9%,which is twice as high as that of the imaging without OAM.Both of simulations and experiments demonstrate that the vortex phase imaging approach proposed in this paper can effectively improve the imaging quality at 80 GHz.This approach is suitable for other millimeter wave imaging systems and is helpful to improve the resolution in anti-terrorism security checks.展开更多
研究了船舶螺旋桨噪声和轴系噪声的噪声包络调制检测(detection of envelope modulation on noise, DEMON)谱的轴频线谱相位特性,提出了一种新的船舶目标特征即船舶螺旋桨噪声与轴系噪声轴频线谱之间的相位差。通过对船舶辐射噪声中螺...研究了船舶螺旋桨噪声和轴系噪声的噪声包络调制检测(detection of envelope modulation on noise, DEMON)谱的轴频线谱相位特性,提出了一种新的船舶目标特征即船舶螺旋桨噪声与轴系噪声轴频线谱之间的相位差。通过对船舶辐射噪声中螺旋桨噪声和轴系噪声轴频线谱相位的分析,指出二者相位存在一个较稳定的相位差。通过建模和仿真验证了相位差提取的可行性,并据此提出一种船舶螺旋桨噪声与轴系噪声的轴频线谱相位差特征提取方法。利用文章提出的特征提取方法,对实验中获取的船舶辐射噪声数据进行相位差特征提取,研究了在不同航速和相同型号不同个体目标船舶两种条件下,相位差特征的稳定性和可分性。结果表明在一定的时间窗内,相位差特征在不同航速下具有较好的稳定性,在相同型号船舶间具有较好的可分性,可以为个体船舶目标识别提供参考。展开更多
Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase tr...Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase transformation for iron minerals was investigated by XRD and Mossbauer spectrum,and the characteristics of roasted product were analyzed by VSM and SEM-EDS.Results indicate that the magnetic concentrate is of 58.73% Fe with iron recovery of 83.96% at 650 °C.The hematite is rapidly transformed into magnetite during the roasting with transformation ratio of 92.75% at 650 °C.Roasting temperature has a significant influence on the phase transformation of hematite to magnetite.The transformation ratio increases with increased temperature.After roasting,the magnetic susceptibility is significantly improved,while iron ore microstructure is not altered significantly.展开更多
Many studies have been done in cognitive radios to maximize the network efficiency. There is always a trade-off between sensing and transmission time which has been addressed fully in the literature. There is also som...Many studies have been done in cognitive radios to maximize the network efficiency. There is always a trade-off between sensing and transmission time which has been addressed fully in the literature. There is also some missed idle times during the waiting phase when secondary user finds the channel busy. Therefore, the longer the transmission time is, the higher the successfully delivered bits would be and the higher the missed idle times in the waiting stage would be expected. In this work, we formulate these missed idle times to addressed this trade-off. Furthermore, interference due to PU re-occupancy is modelled in successful transmitted time and in collision probability. Moreover, we derive secondary user's packet delay distribution using phase type model at which retransmission due to collision results from both sensing error and PU re-occupancy is considered. Thanks to derived delay distribution, any statistical moments of delay could be found as a closed form mathematical expression. These moments can be used as constraints for applications with delay sensitive packets. Numerical results are given to clarify the network metrics. Finally, the optimized values for sensing and transmission time are computed using genetic algorithm in order to maximize access efficiency.展开更多
无人机协同目标感知技术是有人机无人机混合运行的重要安全保障.针对复杂空域环境下的感知可靠性问题,分析大中型无人机的复杂融合空域运行场景,并确定无人机协同目标感知的精准性、高实时性、抗干扰性和低载荷性等需求,提出一种四单元...无人机协同目标感知技术是有人机无人机混合运行的重要安全保障.针对复杂空域环境下的感知可靠性问题,分析大中型无人机的复杂融合空域运行场景,并确定无人机协同目标感知的精准性、高实时性、抗干扰性和低载荷性等需求,提出一种四单元阵列天线和数字化射频体制的无人机协同目标感知系统架构;同时,结合空管雷达信号特性和天线体制,设计方位感知算法,通过修正协方差矩阵、信号子空间加权和噪声子空间加权等方法,设计基于多信号分类(multiple signal classification,MUSIC)的空间谱估计算法,并提出基于子空间分解的幅相误差在线估计算法;最后,开展算法仿真试验和实际空域环境飞行试验.研究结果表明:相比传统MUSIC算法,优化算法的方位感知高分辨性能提升23.3%,并改善了无人机协同目标方位感知的高实时性、抗干扰性和低载荷性.展开更多
基金supported by the National Natural Science Foundation of China(61372180)the Young Talent Frontier Project of Institute of Acoustics of Chinese Academy of Sciences(Y454341261)
文摘In order to improve the performance of line spectrum detection,according to the feature that the underwater target radiated noise containing stable line spectrum,the differences of the phase difference between line spectrum and background noise,a weighted line spectrum detection algorithm based on the phase variance is proposed in frequency domain.After phase difference alignment,the phase variance of line spectrum and the phase of background noise,respectively,are small and big in frequency domain,this method utilizes the weighted statistical algorithm to cumulate the frequency spectrum based on the phase variance,which can restrain the background noise disturbance,and enhance the signal to noise ratio（SNR）.The theory analysis and experimental results both verify that the proposed method can well enhance the energy of line spectrum,restrain the energy of background noise,and have better detection performance under lower SNR.
基金Science,Technology and Innovation Project of Xiongan New Area (Grant No.2022XAGG0181)LiaoNing Revitalization Talents Program (Grant No.XLYC2007074)+1 种基金Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program (Grant No.RC220523)Natural Science Foundation of Liaoning Province of China (Grant Nos.2022-YGJC-03 and 2022-MS-034)to provide fund for conducting experiments。
文摘This paper investigates a new vortex wave imaging approach to improve the imaging quality of small metal targets of size less than 1.5 mm.Antennas with different spiral phase plates are designed to efficiently transmit vortex beams with orbital angular momentums(OAMs).By analyzing the OAM spectrum of the target,it was discovered that the predominant reflection contains a particular OAM mode that carries abundant azimuthal information.This can be explained by the OAM selectivity of the target and the guidance of the vortex transmitting beam.A simple reflection vortex imaging system was designed to capture the phase information.Measurement results show that the high image contrast reaches 14.9%,which is twice as high as that of the imaging without OAM.Both of simulations and experiments demonstrate that the vortex phase imaging approach proposed in this paper can effectively improve the imaging quality at 80 GHz.This approach is suitable for other millimeter wave imaging systems and is helpful to improve the resolution in anti-terrorism security checks.
文摘研究了船舶螺旋桨噪声和轴系噪声的噪声包络调制检测(detection of envelope modulation on noise, DEMON)谱的轴频线谱相位特性,提出了一种新的船舶目标特征即船舶螺旋桨噪声与轴系噪声轴频线谱之间的相位差。通过对船舶辐射噪声中螺旋桨噪声和轴系噪声轴频线谱相位的分析,指出二者相位存在一个较稳定的相位差。通过建模和仿真验证了相位差提取的可行性,并据此提出一种船舶螺旋桨噪声与轴系噪声的轴频线谱相位差特征提取方法。利用文章提出的特征提取方法,对实验中获取的船舶辐射噪声数据进行相位差特征提取,研究了在不同航速和相同型号不同个体目标船舶两种条件下,相位差特征的稳定性和可分性。结果表明在一定的时间窗内,相位差特征在不同航速下具有较好的稳定性,在相同型号船舶间具有较好的可分性,可以为个体船舶目标识别提供参考。
基金Project([2011]01-69-07)supported by the China Geological Survey Project
文摘Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase transformation for iron minerals was investigated by XRD and Mossbauer spectrum,and the characteristics of roasted product were analyzed by VSM and SEM-EDS.Results indicate that the magnetic concentrate is of 58.73% Fe with iron recovery of 83.96% at 650 °C.The hematite is rapidly transformed into magnetite during the roasting with transformation ratio of 92.75% at 650 °C.Roasting temperature has a significant influence on the phase transformation of hematite to magnetite.The transformation ratio increases with increased temperature.After roasting,the magnetic susceptibility is significantly improved,while iron ore microstructure is not altered significantly.
基金supported by Islamic Azad University,Boroujerd Branch,Iran
文摘Many studies have been done in cognitive radios to maximize the network efficiency. There is always a trade-off between sensing and transmission time which has been addressed fully in the literature. There is also some missed idle times during the waiting phase when secondary user finds the channel busy. Therefore, the longer the transmission time is, the higher the successfully delivered bits would be and the higher the missed idle times in the waiting stage would be expected. In this work, we formulate these missed idle times to addressed this trade-off. Furthermore, interference due to PU re-occupancy is modelled in successful transmitted time and in collision probability. Moreover, we derive secondary user's packet delay distribution using phase type model at which retransmission due to collision results from both sensing error and PU re-occupancy is considered. Thanks to derived delay distribution, any statistical moments of delay could be found as a closed form mathematical expression. These moments can be used as constraints for applications with delay sensitive packets. Numerical results are given to clarify the network metrics. Finally, the optimized values for sensing and transmission time are computed using genetic algorithm in order to maximize access efficiency.
文摘无人机协同目标感知技术是有人机无人机混合运行的重要安全保障.针对复杂空域环境下的感知可靠性问题,分析大中型无人机的复杂融合空域运行场景,并确定无人机协同目标感知的精准性、高实时性、抗干扰性和低载荷性等需求,提出一种四单元阵列天线和数字化射频体制的无人机协同目标感知系统架构;同时,结合空管雷达信号特性和天线体制,设计方位感知算法,通过修正协方差矩阵、信号子空间加权和噪声子空间加权等方法,设计基于多信号分类(multiple signal classification,MUSIC)的空间谱估计算法,并提出基于子空间分解的幅相误差在线估计算法;最后,开展算法仿真试验和实际空域环境飞行试验.研究结果表明:相比传统MUSIC算法,优化算法的方位感知高分辨性能提升23.3%,并改善了无人机协同目标方位感知的高实时性、抗干扰性和低载荷性.
