Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the el...Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the electromagnetic waves from the active transmission for additional information transfer(i.e.,passive transmission).In this paper,a hybrid RIS-based modulation,termed hybrid phase and code modulation(HPCM),is proposed to improve the reliability of RIS-assisted symbiotic radio.In RIS-HPCM,the RIS simultaneously performs direct sequence spread spectrum and passive beamforming on incident signals.Moreover,both the spreading code and phase offset are exploited to carry the RIS’s own information.A low-complexity detector is designed,in which the receiver first detects the spreading codes and then demodulates the constellation symbols.We analyze the bit error rate(BER)performance of RIS-HPCM over Rician fading channels.BER upper bounds and approximate BER expressions are derived in closed-form for maximum-likelihood and low-complexity detectors,respectively.Simulation results in terms of BER verify the analysis and show the superiority of RIS-HPCM over the existing RIS-based modulation.展开更多
我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境...我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境监测,并对广州市白云区帽峰山开展对比测试,采用一种干扰阈值判断方法对电磁环境监测数据进行了分析。分析结果显示,位于清远市阳山县杜步镇附近的洼地射频干扰(radio frequency interference,RFI)数量少且强度弱,该洼地远离城市中心,经济活动少,周围群山环抱,具有良好的电磁隔离性,适合大口径单天线和阵列射电望远镜的建设。本文的数据分析结果可为大口径射电望远镜的选址提供依据。展开更多
随着空间卫星的广泛使用,射电天文望远镜受到高仰角的干扰越来越多,进一步确定整个天空中卫星干扰源的频率、位置和分布,是有效规划天文观测的重要手段。本文介绍了一种基于时频差对高仰角卫星干扰源定位的方法,即基于时频差信息,将干...随着空间卫星的广泛使用,射电天文望远镜受到高仰角的干扰越来越多,进一步确定整个天空中卫星干扰源的频率、位置和分布,是有效规划天文观测的重要手段。本文介绍了一种基于时频差对高仰角卫星干扰源定位的方法,即基于时频差信息,将干扰源定位解构为时频差联合估计与定位的问题。首先建立用于时频差联合估计的地面接收信号模型,基于四阶最大似然进行到达时间差(time difference of arrival,TDOA)与到达频率差(frequency difference of arrival,FDOA)的联合估计;然后建立干扰源定位模型,根据两步加权最小二乘算法对干扰源进行定位。经过仿真验证,实现了对高仰角快速运动干扰源的定位与轨迹估计,对于300 km高度干扰源的定位误差最小可达到78 m。利用基于联合时频差分析的卫星干扰源定位算法进行射电天文台址无线电环境测量可提升射电望远镜的科学产出,并保障其平稳运行。展开更多
Pufferfish is prone to deterioration due to abundant nutrients and high moisture content.Drying technology can extend the shelf life and enhance the flavor quality of aquatic products.The study investigated the effect...Pufferfish is prone to deterioration due to abundant nutrients and high moisture content.Drying technology can extend the shelf life and enhance the flavor quality of aquatic products.The study investigated the effect of hot air drying(HAD),microwave vacuum drying(MVD)and hot air assisted radio frequency drying(HARFD)on the taste and volatile profiles of Takifugu obscurus.Different drying methods had significant influence on the color,rehydration,5’-nucleotides,free amino acids and volatile components(P<0.05).The results showed that HAD and HARFD could promote the flavor of T.obscurus by producing higher equivalent umami concentration(EUC)values,which were about two times of MVD group,and more pronounced pleasant odor according to sensory analysis.HAD is more appropriate for industrial application than HARFD and MVD considering the economic benefits.This study could provide a reference for the industrial application of drying T.obscurus.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 62201228 and Grant 62001190in part by the Science and Technology Major Project of Tibetan Autonomous Region of China under Grant No.XZ202201ZD0006G02.
文摘Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the electromagnetic waves from the active transmission for additional information transfer(i.e.,passive transmission).In this paper,a hybrid RIS-based modulation,termed hybrid phase and code modulation(HPCM),is proposed to improve the reliability of RIS-assisted symbiotic radio.In RIS-HPCM,the RIS simultaneously performs direct sequence spread spectrum and passive beamforming on incident signals.Moreover,both the spreading code and phase offset are exploited to carry the RIS’s own information.A low-complexity detector is designed,in which the receiver first detects the spreading codes and then demodulates the constellation symbols.We analyze the bit error rate(BER)performance of RIS-HPCM over Rician fading channels.BER upper bounds and approximate BER expressions are derived in closed-form for maximum-likelihood and low-complexity detectors,respectively.Simulation results in terms of BER verify the analysis and show the superiority of RIS-HPCM over the existing RIS-based modulation.
文摘我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境监测,并对广州市白云区帽峰山开展对比测试,采用一种干扰阈值判断方法对电磁环境监测数据进行了分析。分析结果显示,位于清远市阳山县杜步镇附近的洼地射频干扰(radio frequency interference,RFI)数量少且强度弱,该洼地远离城市中心,经济活动少,周围群山环抱,具有良好的电磁隔离性,适合大口径单天线和阵列射电望远镜的建设。本文的数据分析结果可为大口径射电望远镜的选址提供依据。
文摘随着空间卫星的广泛使用,射电天文望远镜受到高仰角的干扰越来越多,进一步确定整个天空中卫星干扰源的频率、位置和分布,是有效规划天文观测的重要手段。本文介绍了一种基于时频差对高仰角卫星干扰源定位的方法,即基于时频差信息,将干扰源定位解构为时频差联合估计与定位的问题。首先建立用于时频差联合估计的地面接收信号模型,基于四阶最大似然进行到达时间差(time difference of arrival,TDOA)与到达频率差(frequency difference of arrival,FDOA)的联合估计;然后建立干扰源定位模型,根据两步加权最小二乘算法对干扰源进行定位。经过仿真验证,实现了对高仰角快速运动干扰源的定位与轨迹估计,对于300 km高度干扰源的定位误差最小可达到78 m。利用基于联合时频差分析的卫星干扰源定位算法进行射电天文台址无线电环境测量可提升射电望远镜的科学产出,并保障其平稳运行。
基金supported by The National Natural Science Foundation of China (32001824, 31972198, 31901813, 31901816, 32001827)Startup Fund for Youngman Research at SJTU (SFYR at SJTU)
文摘Pufferfish is prone to deterioration due to abundant nutrients and high moisture content.Drying technology can extend the shelf life and enhance the flavor quality of aquatic products.The study investigated the effect of hot air drying(HAD),microwave vacuum drying(MVD)and hot air assisted radio frequency drying(HARFD)on the taste and volatile profiles of Takifugu obscurus.Different drying methods had significant influence on the color,rehydration,5’-nucleotides,free amino acids and volatile components(P<0.05).The results showed that HAD and HARFD could promote the flavor of T.obscurus by producing higher equivalent umami concentration(EUC)values,which were about two times of MVD group,and more pronounced pleasant odor according to sensory analysis.HAD is more appropriate for industrial application than HARFD and MVD considering the economic benefits.This study could provide a reference for the industrial application of drying T.obscurus.
