Reconfigurable intelligent surface(RIS)is a promising candidate technology of the upcoming Sixth Generation(6G)communication system for its ability to provide unprecedented spectral and energy efficiency increment thr...Reconfigurable intelligent surface(RIS)is a promising candidate technology of the upcoming Sixth Generation(6G)communication system for its ability to provide unprecedented spectral and energy efficiency increment through passive beamforming.However,it is challenging to obtain instantaneous channel state information(I-CSI)for RIS,which obliges us to use statistical channel state information(S-CSI)to achieve passive beamforming.In this paper,RIS-aided multiple-input single-output(MISO)multi-user downlink communication system with correlated channels is investigated.Then,we formulate the problem of joint beamforming design at the AP and RIS to maximize the sum ergodic spectral efficiency(ESE)of all users to improve the network capacity.Since it is too hard to compute sum ESE,an ESE approximation is adopted to reformulate the problem into a more tractable form.Then,we present two joint beamforming algorithms,namely the singular value decomposition-gradient descent(SVD-GD)algorithm and the fractional programming-gradient descent(FP-GD)algorithm.Simulation results show the effectiveness of our proposed algorithms and validate that 2-bits quantizer is enough for RIS phase shifts implementation.展开更多
为揭示中国西部地区旅游经济韧性的动态演变规律及其驱动机制,提升西部地区旅游业应对外部冲击的适应能力和恢复能力,从抵御力、恢复力、重构力和创新力等4个维度构建旅游经济韧性指标体系,以2011—2022年中国西部地区除西藏自治区外的1...为揭示中国西部地区旅游经济韧性的动态演变规律及其驱动机制,提升西部地区旅游业应对外部冲击的适应能力和恢复能力,从抵御力、恢复力、重构力和创新力等4个维度构建旅游经济韧性指标体系,以2011—2022年中国西部地区除西藏自治区外的11个省(自治区、直辖市)为研究对象,运用熵权TOPSIS法(Technique for Order Preference by Similarity to Ideal Solution,TOPSIS)、探索性空间数据分析和地理探测器模型,深入分析西部地区的旅游经济韧性水平和影响因素。研究结果表明:1) 2011—2022年,中国西部地区11个省(自治区、直辖市)的旅游经济韧性总体呈现持续上升态势,表现出较强的抗冲击和恢复能力。2)研究期内,西部地区的旅游经济韧性未呈现显著空间自相关,空间分异呈现“南热北冷”鲜明格局,南部区域长期处于旅游经济高韧性区和热点区,北部区域则持续处于旅游经济低韧性区和冷点区。3)西部地区的旅游经济韧性受到多重因素的综合影响,其中科技创新水平、旅游消费水平和政府支持力度是旅游经济韧性空间分异的关键影响因子,旅游产业结构合理化水平、旅游产业集聚水平和城市舒适度等因素虽对空间分异存在一定解释力,但相对较弱,且不同因子交互作用对旅游经济韧性的空间分异影响显著,驱动作用远超单一因子。研究成果为中国西部地区旅游产业转型及韧性提升提供了重要的理论依据与政策参考方向。展开更多
Soybean frogeye leaf spot(FLS) disease is a global disease affecting soybean yield, especially in the soybean growing area of Heilongjiang Province. In order to realize genomic selection breeding for FLS resistance of...Soybean frogeye leaf spot(FLS) disease is a global disease affecting soybean yield, especially in the soybean growing area of Heilongjiang Province. In order to realize genomic selection breeding for FLS resistance of soybean, least absolute shrinkage and selection operator(LASSO) regression and stepwise regression were combined, and a genomic selection model was established for 40 002 SNP markers covering soybean genome and relative lesion area of soybean FLS. As a result, 68 molecular markers controlling soybean FLS were detected accurately, and the phenotypic contribution rate of these markers reached 82.45%. In this study, a model was established, which could be used directly to evaluate the resistance of soybean FLS and to select excellent offspring. This research method could also provide ideas and methods for other plants to breeding in disease resistance.展开更多
基金partially supported by the National Key Research and Development Project under Grant 2020YFB1806805Science and Technology on Communication Networks Laboratorysupported by China Scholarship Council.
文摘Reconfigurable intelligent surface(RIS)is a promising candidate technology of the upcoming Sixth Generation(6G)communication system for its ability to provide unprecedented spectral and energy efficiency increment through passive beamforming.However,it is challenging to obtain instantaneous channel state information(I-CSI)for RIS,which obliges us to use statistical channel state information(S-CSI)to achieve passive beamforming.In this paper,RIS-aided multiple-input single-output(MISO)multi-user downlink communication system with correlated channels is investigated.Then,we formulate the problem of joint beamforming design at the AP and RIS to maximize the sum ergodic spectral efficiency(ESE)of all users to improve the network capacity.Since it is too hard to compute sum ESE,an ESE approximation is adopted to reformulate the problem into a more tractable form.Then,we present two joint beamforming algorithms,namely the singular value decomposition-gradient descent(SVD-GD)algorithm and the fractional programming-gradient descent(FP-GD)algorithm.Simulation results show the effectiveness of our proposed algorithms and validate that 2-bits quantizer is enough for RIS phase shifts implementation.
文摘为揭示中国西部地区旅游经济韧性的动态演变规律及其驱动机制,提升西部地区旅游业应对外部冲击的适应能力和恢复能力,从抵御力、恢复力、重构力和创新力等4个维度构建旅游经济韧性指标体系,以2011—2022年中国西部地区除西藏自治区外的11个省(自治区、直辖市)为研究对象,运用熵权TOPSIS法(Technique for Order Preference by Similarity to Ideal Solution,TOPSIS)、探索性空间数据分析和地理探测器模型,深入分析西部地区的旅游经济韧性水平和影响因素。研究结果表明:1) 2011—2022年,中国西部地区11个省(自治区、直辖市)的旅游经济韧性总体呈现持续上升态势,表现出较强的抗冲击和恢复能力。2)研究期内,西部地区的旅游经济韧性未呈现显著空间自相关,空间分异呈现“南热北冷”鲜明格局,南部区域长期处于旅游经济高韧性区和热点区,北部区域则持续处于旅游经济低韧性区和冷点区。3)西部地区的旅游经济韧性受到多重因素的综合影响,其中科技创新水平、旅游消费水平和政府支持力度是旅游经济韧性空间分异的关键影响因子,旅游产业结构合理化水平、旅游产业集聚水平和城市舒适度等因素虽对空间分异存在一定解释力,但相对较弱,且不同因子交互作用对旅游经济韧性的空间分异影响显著,驱动作用远超单一因子。研究成果为中国西部地区旅游产业转型及韧性提升提供了重要的理论依据与政策参考方向。
基金Supported by the National Key Research and Development Program of China(2021YFD1201103-01-05)。
文摘Soybean frogeye leaf spot(FLS) disease is a global disease affecting soybean yield, especially in the soybean growing area of Heilongjiang Province. In order to realize genomic selection breeding for FLS resistance of soybean, least absolute shrinkage and selection operator(LASSO) regression and stepwise regression were combined, and a genomic selection model was established for 40 002 SNP markers covering soybean genome and relative lesion area of soybean FLS. As a result, 68 molecular markers controlling soybean FLS were detected accurately, and the phenotypic contribution rate of these markers reached 82.45%. In this study, a model was established, which could be used directly to evaluate the resistance of soybean FLS and to select excellent offspring. This research method could also provide ideas and methods for other plants to breeding in disease resistance.
