太赫兹通信是未来6G中业界关注的重要场景之一。太赫兹频段可以支持超大带宽和超高速率的无线通信,目前3GPP协议中的正交频分复用(Orthogonal Frequency Division Multiplex, OFDM)技术使用支持的最大子载波间隔和最大快速傅里叶逆变换(...太赫兹通信是未来6G中业界关注的重要场景之一。太赫兹频段可以支持超大带宽和超高速率的无线通信,目前3GPP协议中的正交频分复用(Orthogonal Frequency Division Multiplex, OFDM)技术使用支持的最大子载波间隔和最大快速傅里叶逆变换(Inverse Fast Fourier Transform, IFFT)点数不足以满足太赫兹场景超大带宽的需求。提出了一种新的波形方案:广义滤波器组-正交频分复用(Generalized Filter Bank Orthogonal Frequency Division Multiplexing, GFB-OFDM)波形,可以将原有的大点数IFFT分解成两级小点数的IFFT,以支持更大的传输带宽。GFB-OFDM还可以灵活地支持不同子载波间隔、不同数据类型的联合处理,以实现不同业务类型的传输。GFB-OFDM在接收端仍然可以采用传统的循环前缀正交频分复用(Cyclic Prefix Orthogonal Frequency Division Multiplexing, CP-OFDM)接收方法,仿真结果表明GFB-OFDM的综合性能优于CP-OFDM。展开更多
为探究成渝地区双城经济圈NPP时空变化及与气候的关系,基于MOD17A3产品NPP数据,采用一元线性回归模型模拟2001—2020年植被NPP演变趋势,分析植被NPP变化特征,结合ANUSPLIN插值的气象数据,采用相关性分析法定量分析气候变化对研究区植被...为探究成渝地区双城经济圈NPP时空变化及与气候的关系,基于MOD17A3产品NPP数据,采用一元线性回归模型模拟2001—2020年植被NPP演变趋势,分析植被NPP变化特征,结合ANUSPLIN插值的气象数据,采用相关性分析法定量分析气候变化对研究区植被NPP变化的影响。研究表明:(1)研究区内植被NPP整体呈现缓慢增长的趋势,增长率为7.53 g C·m^(-2)·a^(-1),同时植被NPP均值分布呈现四周高中间低的空间格局。(2)研究区内气候因子对植被NPP变化的影响存在空间异质性,在眉山市、乐山市、雅安市以及重庆市黔江区、彭水县部分地区气温与植被NPP负相关关系明显,其呈正相关关系的区域广泛分布在成渝城市群的中部和东部;降水与植被NPP呈正相关关系的区域面积占比达到92.46%。(3)研究区主要受非气候因子影响,面积占比高达86.87%,说明人类活动对植被NPP变化的影响愈来愈烈,研究人为影响应是成渝城市群生态修复的重点。展开更多
Tin(IV)oxide(Sn_(3)O_(4))is layered tin and exhibits mixed valence states.It has emerged as a highly promising visible-light pho-tocatalyst,attracting considerable attention.This comprehensive review is aimed at provi...Tin(IV)oxide(Sn_(3)O_(4))is layered tin and exhibits mixed valence states.It has emerged as a highly promising visible-light pho-tocatalyst,attracting considerable attention.This comprehensive review is aimed at providing a detailed overview of the latest advance-ments in research,applications,advantages,and challenges associated with Sn_(3)O_(4)photocatalytic nanomaterials.The fundamental con-cepts and principles of Sn_(3)O_(4)are introduced.Sn_(3)O_(4)possesses a unique crystal structure and optoelectronic properties that allow it to ab-sorb visible light efficiently and generate photoexcited charge carriers that drive photocatalytic reactions.Subsequently,strategies for the control and improved performance of Sn_(3)O_(4)photocatalytic nanomaterials are discussed.Morphology control,ion doping,and hetero-structure construction are widely employed in the optimization of the photocatalytic performance of Sn_(3)O_(4)materials.The effective imple-mentation of these strategies improves the photocatalytic activity and stability of Sn_(3)O_(4)nanomaterials.Furthermore,the review explores the diverse applications of Sn_(3)O_(4)photocatalytic nanomaterials in various fields,such as photocatalytic degradation,photocatalytic hydro-gen production,photocatalytic reduction of carbon dioxide,solar cells,photocatalytic sterilization,and optoelectronic sensors.The discus-sion focuses on the potential of Sn_(3)O_(4)-based nanomaterials in these applications,highlighting their unique attributes and functionalities.Finally,the review provides an outlook on the future development directions in the field and offers guidance for the exploration and de-velopment of novel and efficient Sn_(3)O_(4)-based nanomaterials.Through the identification of emerging research areas and potential avenues for improvement,this review aims to stimulate further advancements in Sn_(3)O_(4)-based photocatalysis and facilitate the translation of this promising technology into practical applications.展开更多
Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB ...Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations.展开更多
文摘太赫兹通信是未来6G中业界关注的重要场景之一。太赫兹频段可以支持超大带宽和超高速率的无线通信,目前3GPP协议中的正交频分复用(Orthogonal Frequency Division Multiplex, OFDM)技术使用支持的最大子载波间隔和最大快速傅里叶逆变换(Inverse Fast Fourier Transform, IFFT)点数不足以满足太赫兹场景超大带宽的需求。提出了一种新的波形方案:广义滤波器组-正交频分复用(Generalized Filter Bank Orthogonal Frequency Division Multiplexing, GFB-OFDM)波形,可以将原有的大点数IFFT分解成两级小点数的IFFT,以支持更大的传输带宽。GFB-OFDM还可以灵活地支持不同子载波间隔、不同数据类型的联合处理,以实现不同业务类型的传输。GFB-OFDM在接收端仍然可以采用传统的循环前缀正交频分复用(Cyclic Prefix Orthogonal Frequency Division Multiplexing, CP-OFDM)接收方法,仿真结果表明GFB-OFDM的综合性能优于CP-OFDM。
文摘为探究成渝地区双城经济圈NPP时空变化及与气候的关系,基于MOD17A3产品NPP数据,采用一元线性回归模型模拟2001—2020年植被NPP演变趋势,分析植被NPP变化特征,结合ANUSPLIN插值的气象数据,采用相关性分析法定量分析气候变化对研究区植被NPP变化的影响。研究表明:(1)研究区内植被NPP整体呈现缓慢增长的趋势,增长率为7.53 g C·m^(-2)·a^(-1),同时植被NPP均值分布呈现四周高中间低的空间格局。(2)研究区内气候因子对植被NPP变化的影响存在空间异质性,在眉山市、乐山市、雅安市以及重庆市黔江区、彭水县部分地区气温与植被NPP负相关关系明显,其呈正相关关系的区域广泛分布在成渝城市群的中部和东部;降水与植被NPP呈正相关关系的区域面积占比达到92.46%。(3)研究区主要受非气候因子影响,面积占比高达86.87%,说明人类活动对植被NPP变化的影响愈来愈烈,研究人为影响应是成渝城市群生态修复的重点。
基金the National Natural Science Foundation of China(No.52272212)the Natural Science Foundation of Shandong Province(Nos.ZR2022JQ20 and ZR2023MB126)+2 种基金the Taishan Scholar Project of Shandong Province(No.tsqn202211168)the Key Laboratory of Optic-electric Sensing and Analytical Chemistry for Life Science,MOE(No.M2022-7)the STIEI scientific research funding project(No.GCC2023036).
文摘Tin(IV)oxide(Sn_(3)O_(4))is layered tin and exhibits mixed valence states.It has emerged as a highly promising visible-light pho-tocatalyst,attracting considerable attention.This comprehensive review is aimed at providing a detailed overview of the latest advance-ments in research,applications,advantages,and challenges associated with Sn_(3)O_(4)photocatalytic nanomaterials.The fundamental con-cepts and principles of Sn_(3)O_(4)are introduced.Sn_(3)O_(4)possesses a unique crystal structure and optoelectronic properties that allow it to ab-sorb visible light efficiently and generate photoexcited charge carriers that drive photocatalytic reactions.Subsequently,strategies for the control and improved performance of Sn_(3)O_(4)photocatalytic nanomaterials are discussed.Morphology control,ion doping,and hetero-structure construction are widely employed in the optimization of the photocatalytic performance of Sn_(3)O_(4)materials.The effective imple-mentation of these strategies improves the photocatalytic activity and stability of Sn_(3)O_(4)nanomaterials.Furthermore,the review explores the diverse applications of Sn_(3)O_(4)photocatalytic nanomaterials in various fields,such as photocatalytic degradation,photocatalytic hydro-gen production,photocatalytic reduction of carbon dioxide,solar cells,photocatalytic sterilization,and optoelectronic sensors.The discus-sion focuses on the potential of Sn_(3)O_(4)-based nanomaterials in these applications,highlighting their unique attributes and functionalities.Finally,the review provides an outlook on the future development directions in the field and offers guidance for the exploration and de-velopment of novel and efficient Sn_(3)O_(4)-based nanomaterials.Through the identification of emerging research areas and potential avenues for improvement,this review aims to stimulate further advancements in Sn_(3)O_(4)-based photocatalysis and facilitate the translation of this promising technology into practical applications.
基金We acknowledge the funding support from the National Natural Science Foundation of China Youth Fund(Grant No.52004019)the National Natural Science Foundation of China(Grant No.41825018)China Postdoctoral Science Foundation(Grant No.2023M733481).
文摘Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations.
文摘玻璃生产线退火窑辊道系统轴承运行状态显著影响玻璃品质和生产效率,实时监测各轴承运行状态对确保退火窑系统的平稳运行具有重要意义,提出结合Inception模块和长短期神经网络(Long Short-term Memory,LSTM)的迁移诊断方法,对退火窑辊道系统中的辊道轴承和通轴轴承运行状态进行监测、诊断。首先,使用集合经验模态分解(Ensemble Empirical Mode Decomposition,EEMD)对轴承信号进行分解和重构降噪,并利用直方均衡化增强重构信号小波时频图的聚集性。然后,针对样本充足的辊道轴承,建立Inception-LSTM网络,提取多尺度特征并学习其中的时间依赖关系,实现状态诊断。再次,针对转速不同且样本量少的通轴轴承,以辊道轴承信号为源域,以通轴轴承信号为目标域,以Inception-LSTM网络为基础,使用多核最大均值差异(Multi-kernel Maximum Mean Discrepancies,MKMMD)减小分布差异,实现故障样本不平衡条件下的跨转速域不变特征提取和迁移诊断。最后,利用实验数据和实测数据验证本算法的有效性,结果表明,该方法能有效诊断出退火窑辊道系统轴承故障,且具有较高的准确率。
