As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for...As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for high-accuracy radiometric interferometry can simultaneously deal with data transmission and spacecraft navigation.We demonstrate very long baseline interferometry(VLBI)tracking of the Chang’E-3 lander and rover to determine their relative lunar-surface position using downlink high data-rate signals.A new method based on the VLBI phase-referencing technique is proposed to obtain the differential phase delay,which is much more accurate than the differential group delay acquired by conventional VLBI approaches.The systemic errors among different signal channels have been well calibrated using the new method.The data from the Chang’E-3mission were then processed,and meter-level accuracy positions of the rover with respect to the lander have been obtained.This demonstration shows the feasibility of high-accuracy radiometric interferometry using high data-rate signals.The method proposed in this paper can also be applied to future deep-space navigation.展开更多
Due to having a large bandwidth to support Gbps-level data rate, terahertz communication attracts more and more attention in recent years. However, there are few medium access control （MAC） protocols for terahertz u...Due to having a large bandwidth to support Gbps-level data rate, terahertz communication attracts more and more attention in recent years. However, there are few medium access control （MAC） protocols for terahertz ultra-high data-rate wireless networks, which affects the research and application of terahertz communications. To address this problem and to achieve ultra-high data-rate wireless access with terahertz communication, a novel MAC protocol, called medium access control for terahertz communication （MAC-TC）, is proposed. Through designing a new channel access scheme, a new superframe structure, and related key parameters, MAC-TC can support a maximum data rate up to 10 Gbit/s even higher. Theoretical analysis and simulation results show that our proposed MAC protocol realizes the function of medium access control and attains a maximum data rate of 18.3 Gbit/s, which is 2 times higher than 5.78 Gbit/s, the theoretical maximum data rate of IEEE 802.15.3c standard.展开更多
目的 分析老年缺血性脑小血管病患者心率变异性参数与认知功能障碍的关系。方法 选择2020年12月至2022年12月西南医科大学附属医院神经内科收治的老年缺血性脑小血管病患者120例,依据蒙特利尔认知评估量表(Montreal cognitive assessmen...目的 分析老年缺血性脑小血管病患者心率变异性参数与认知功能障碍的关系。方法 选择2020年12月至2022年12月西南医科大学附属医院神经内科收治的老年缺血性脑小血管病患者120例,依据蒙特利尔认知评估量表(Montreal cognitive assessment, MoCA)评分分为认知障碍组(MoCA评分<26分)38例及认知正常组(MoCA评分≥26分)82例。所有患者进行动态心电图检查获取心率变异性参数,包括全部窦性心搏R-R间期标准差(standard deviation of the R-R interval, SDNN)、相差>50 ms的相邻R-R间期占R-R间期总数百分比(percentage of the number of pairs of adjacent R-R intervals differing by more than 50 ms, PNN50)、低频功率(power in low frequency range, LF)、高频功率(power in high frequency range, HF)。采用Spearman分析心率变异性参数与认知障碍的相关性,ROC曲线分析心率变异性参数对认知障碍的评估价值。结果 认知障碍组SDNN、PNN50、LF、HF明显低于认知正常组,差异有统计学意义(P<0.05,P<0.01)。Spearman相关性显示,SDNN、PNN50、LF、HF与老年缺血性脑小血管病患者认知障碍呈负相关(r=-0.185,r=-0.720,r=-0.278,r=-0.387,P<0.05)。ROC曲线分析显示,SDNN、PNN50、LF、HF联合评估老年缺血性脑小血管病患者认知障碍的曲线下面积为0.972(95%CI:0.949~0.996),敏感性为94.70%,特异性为89.00%,联合评估效能明显优于各指标单独评估(P<0.01)。结论 老年缺血性脑小血管病患者心率变异性参数与认知障碍密切相关,早期测定SDNN、PNN50、LF、HF等心率变异性参数可为认知障碍的评估提供参考价值。展开更多
基金supported by the Key Techniques Research Program of China’s Lunar Exploration(Grant No.TY3Q20100009)
文摘As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for high-accuracy radiometric interferometry can simultaneously deal with data transmission and spacecraft navigation.We demonstrate very long baseline interferometry(VLBI)tracking of the Chang’E-3 lander and rover to determine their relative lunar-surface position using downlink high data-rate signals.A new method based on the VLBI phase-referencing technique is proposed to obtain the differential phase delay,which is much more accurate than the differential group delay acquired by conventional VLBI approaches.The systemic errors among different signal channels have been well calibrated using the new method.The data from the Chang’E-3mission were then processed,and meter-level accuracy positions of the rover with respect to the lander have been obtained.This demonstration shows the feasibility of high-accuracy radiometric interferometry using high data-rate signals.The method proposed in this paper can also be applied to future deep-space navigation.
基金supported by the National Natural Science Foundation of China (60972068)the Program for Changjiang Scholars and Innovative Research Team in University (IRT1299)+2 种基金the project of Chongqing Municipal Education Commission (Kjzh11206)the Natural Science Foundation of Chongqing (cstc2012jjA40051)the open project of Emergency Communication Laboratory of Chongqing (201201)
文摘Due to having a large bandwidth to support Gbps-level data rate, terahertz communication attracts more and more attention in recent years. However, there are few medium access control （MAC） protocols for terahertz ultra-high data-rate wireless networks, which affects the research and application of terahertz communications. To address this problem and to achieve ultra-high data-rate wireless access with terahertz communication, a novel MAC protocol, called medium access control for terahertz communication （MAC-TC）, is proposed. Through designing a new channel access scheme, a new superframe structure, and related key parameters, MAC-TC can support a maximum data rate up to 10 Gbit/s even higher. Theoretical analysis and simulation results show that our proposed MAC protocol realizes the function of medium access control and attains a maximum data rate of 18.3 Gbit/s, which is 2 times higher than 5.78 Gbit/s, the theoretical maximum data rate of IEEE 802.15.3c standard.
文摘目的 分析老年缺血性脑小血管病患者心率变异性参数与认知功能障碍的关系。方法 选择2020年12月至2022年12月西南医科大学附属医院神经内科收治的老年缺血性脑小血管病患者120例,依据蒙特利尔认知评估量表(Montreal cognitive assessment, MoCA)评分分为认知障碍组(MoCA评分<26分)38例及认知正常组(MoCA评分≥26分)82例。所有患者进行动态心电图检查获取心率变异性参数,包括全部窦性心搏R-R间期标准差(standard deviation of the R-R interval, SDNN)、相差>50 ms的相邻R-R间期占R-R间期总数百分比(percentage of the number of pairs of adjacent R-R intervals differing by more than 50 ms, PNN50)、低频功率(power in low frequency range, LF)、高频功率(power in high frequency range, HF)。采用Spearman分析心率变异性参数与认知障碍的相关性,ROC曲线分析心率变异性参数对认知障碍的评估价值。结果 认知障碍组SDNN、PNN50、LF、HF明显低于认知正常组,差异有统计学意义(P<0.05,P<0.01)。Spearman相关性显示,SDNN、PNN50、LF、HF与老年缺血性脑小血管病患者认知障碍呈负相关(r=-0.185,r=-0.720,r=-0.278,r=-0.387,P<0.05)。ROC曲线分析显示,SDNN、PNN50、LF、HF联合评估老年缺血性脑小血管病患者认知障碍的曲线下面积为0.972(95%CI:0.949~0.996),敏感性为94.70%,特异性为89.00%,联合评估效能明显优于各指标单独评估(P<0.01)。结论 老年缺血性脑小血管病患者心率变异性参数与认知障碍密切相关,早期测定SDNN、PNN50、LF、HF等心率变异性参数可为认知障碍的评估提供参考价值。
