正交频分复用(orthogonal frequency division multi-plexing,OFDM)技术在低压电力线高速通信研究和应用领域获得了广泛重视。传统的OFDM系统通过对每个符号添加大于信道响应长度的循环前缀(cyclic-prefix,CP)来消除符号间干扰,使传输...正交频分复用(orthogonal frequency division multi-plexing,OFDM)技术在低压电力线高速通信研究和应用领域获得了广泛重视。传统的OFDM系统通过对每个符号添加大于信道响应长度的循环前缀(cyclic-prefix,CP)来消除符号间干扰,使传输效率降低。提出一种低压电力线信息符号无循环前缀的OFDM通信系统的信道估计与迭代均衡策略,该策略采用m序列作为训练序列,利用其特殊的自相关特性,在系统接收端获得信道的时域响应,进而对无循环前缀的OFDM信息符号进行迭代均衡,以消除符号间干扰。仿真实验表明,该策略可提高传输效率、增强系统的抗噪性能、获得比传统OFDM系统更低的信道估计均方误差和误码率,且具有较低的计算复杂度。展开更多
The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obt...The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obtained andused in a simulation model of CRTS III prefabricated slab track to study the interlayer damage.The results show that 1)the digital image correlation(DIC)technique can accurately capture the strain field changes on the interface of compositespecimens under splitting and shear loading;2)when the temperature gradient is−40℃/m−60℃/m,the interfacedamage of the slab track is minimal and presents different patterns of expansion under positive and negative temperaturegradients,each corresponding to damage of the cohesive element dominated by shear stress and normal tensile stress,respectively;3)the reduction of the elastic modulus at the concrete base after freeze-thaw inhibits interface damage andleads to a higher starting temperature gradient load,but cracking can occur on the concrete base after 150 freeze-thaws.For this reason,in the light of damage control of both the interface and concrete base,the elastic modulus of the concretebase is 54%or over that without freeze-thaw cycles.展开更多
通信传输一方面需要足够的传输容量,能完成数据传输的任务;另一方面又要考虑通信安全,保证敏感信息不会被截获。针对通信传输过程中波形相关特征容易被利用的问题,分析了标准正交频分复用(orthogonal frequency division multiplexing,O...通信传输一方面需要足够的传输容量,能完成数据传输的任务;另一方面又要考虑通信安全,保证敏感信息不会被截获。针对通信传输过程中波形相关特征容易被利用的问题,分析了标准正交频分复用(orthogonal frequency division multiplexing,OFDM)波形存在的缺陷,提出一种抗侦收的下行传输波形设计方法。该方法采用两层级联生成的混沌序列作为训练序列,传输波形中不使用循环前缀(cyclic prefix,CP),并且在接收端使用干扰迭代消除的方法抵消干扰。对信号波形仿真分析,结果表明无循环前缀的方法误码率接近有循环前缀的OFDM无线通信系统,并且新构造的波形无法使用基于相关运算的方法进行参数估计。展开更多
文摘正交频分复用(orthogonal frequency division multi-plexing,OFDM)技术在低压电力线高速通信研究和应用领域获得了广泛重视。传统的OFDM系统通过对每个符号添加大于信道响应长度的循环前缀(cyclic-prefix,CP)来消除符号间干扰,使传输效率降低。提出一种低压电力线信息符号无循环前缀的OFDM通信系统的信道估计与迭代均衡策略,该策略采用m序列作为训练序列,利用其特殊的自相关特性,在系统接收端获得信道的时域响应,进而对无循环前缀的OFDM信息符号进行迭代均衡,以消除符号间干扰。仿真实验表明,该策略可提高传输效率、增强系统的抗噪性能、获得比传统OFDM系统更低的信道估计均方误差和误码率,且具有较低的计算复杂度。
基金Project(52425213)supported by the National Science Fund for Distinguished Young Scholars of ChinaProjects(52278461,52308467)supported by the National Natural Science Foundation of China+1 种基金Projects(2021YFF0502100,2021YFB2600900)supported by the National Key R&D Program of ChinaProject(2022JDTD0015)supported by the Sichuan Province Youth Science and Technology Innovation Team,China。
文摘The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obtained andused in a simulation model of CRTS III prefabricated slab track to study the interlayer damage.The results show that 1)the digital image correlation(DIC)technique can accurately capture the strain field changes on the interface of compositespecimens under splitting and shear loading;2)when the temperature gradient is−40℃/m−60℃/m,the interfacedamage of the slab track is minimal and presents different patterns of expansion under positive and negative temperaturegradients,each corresponding to damage of the cohesive element dominated by shear stress and normal tensile stress,respectively;3)the reduction of the elastic modulus at the concrete base after freeze-thaw inhibits interface damage andleads to a higher starting temperature gradient load,but cracking can occur on the concrete base after 150 freeze-thaws.For this reason,in the light of damage control of both the interface and concrete base,the elastic modulus of the concretebase is 54%or over that without freeze-thaw cycles.
文摘通信传输一方面需要足够的传输容量,能完成数据传输的任务;另一方面又要考虑通信安全,保证敏感信息不会被截获。针对通信传输过程中波形相关特征容易被利用的问题,分析了标准正交频分复用(orthogonal frequency division multiplexing,OFDM)波形存在的缺陷,提出一种抗侦收的下行传输波形设计方法。该方法采用两层级联生成的混沌序列作为训练序列,传输波形中不使用循环前缀(cyclic prefix,CP),并且在接收端使用干扰迭代消除的方法抵消干扰。对信号波形仿真分析,结果表明无循环前缀的方法误码率接近有循环前缀的OFDM无线通信系统,并且新构造的波形无法使用基于相关运算的方法进行参数估计。
