We aim to provide a comprehensive overview of the progress in research and development of the reconfigurable intelligent surface(RIS)over the last 2-3 years in this paper,especially when the RIS is used as relays in n...We aim to provide a comprehensive overview of the progress in research and development of the reconfigurable intelligent surface(RIS)over the last 2-3 years in this paper,especially when the RIS is used as relays in next-generation mobile networks.Major areas of re-search in academia are outlined,including fundamental performance,channel estimation,joint optimization with antenna precoding at base stations,propagation channel modeling and meta-material devices of RIS elements.Development in industry is surveyed from the aspects of performance potentials and issues,realistic joint optimization algorithms,control mechanisms,field trials and related activities in standardiza-tion development organizations(SDOs).Our views on how to carry out the engineering-aspect study on RIS for 6G systems are also presented,which cover the realistic performance,the comparison with other topological improvements,approaches for channel modeling,factors for de-signing control mechanisms and the timeline for RIS standardization.展开更多
Absorption of acoustic nanowave in specific frequency region is important for the design of acoustic filter. This paper puts forward a meta material model made up of fluid-conveying carbon nanotubes （CNT）, which can...Absorption of acoustic nanowave in specific frequency region is important for the design of acoustic filter. This paper puts forward a meta material model made up of fluid-conveying carbon nanotubes （CNT）, which can absorb acoustic nanowave in a given frequency range by adjusting the lengths and fluid velocities of themselves. Absorption coefficients are calculated out through the combination of the finite element method with the theoretical model, which are 0.4-0.55 relating to different fluid velocities for the crossing-distributed model. Comparisons are made between the crossed model and the aligned one, which prove that the CNT forest with crossed distribution is more effective in acoustic wave absorption.展开更多
The frequency range that surface plasmon polariton(SPP) mode exists is mainly limited by the metal material.With high permittivity dielectrics above metal surface, the SPP mode at high frequency has extremely large lo...The frequency range that surface plasmon polariton(SPP) mode exists is mainly limited by the metal material.With high permittivity dielectrics above metal surface, the SPP mode at high frequency has extremely large loss or can be cutoff, which limits the potential applications of SPP in the field of optical interconnection, active SPP devices and so on.To extend the frequency range of SPP mode, the surface mode guided by metal/dielectric multilayers meta-material has been studied based on the theory of electromagnetic field. It is demonstrated that surface mode not only could be supported by the meta-material but also extends the frequency to where conventional metal SPP cannot exist. Meanwhile, the characteristics of this surface mode, such as dispersion relation, frequency range, propagation loss and skin depth in metamaterial and dielectrics, are also studied. It is indicated that, by varying the structure parameters, the meta-material guided SPP mode presents its advantages and flexibility over traditional metal one.展开更多
基金Supported by the National Natural Science Foundation of China(61331005,61801509,61671467)Research Found of Department of Basic Sciences at Air Force Engineering University(JK2019207)
文摘We aim to provide a comprehensive overview of the progress in research and development of the reconfigurable intelligent surface(RIS)over the last 2-3 years in this paper,especially when the RIS is used as relays in next-generation mobile networks.Major areas of re-search in academia are outlined,including fundamental performance,channel estimation,joint optimization with antenna precoding at base stations,propagation channel modeling and meta-material devices of RIS elements.Development in industry is surveyed from the aspects of performance potentials and issues,realistic joint optimization algorithms,control mechanisms,field trials and related activities in standardiza-tion development organizations(SDOs).Our views on how to carry out the engineering-aspect study on RIS for 6G systems are also presented,which cover the realistic performance,the comparison with other topological improvements,approaches for channel modeling,factors for de-signing control mechanisms and the timeline for RIS standardization.
基金Project supported by the Basic Scientific Research of National Defense(No.B2720133015)the Basic Research Fund of Northwestern Polytechnical University(No.3102014JCQ01045)
文摘Absorption of acoustic nanowave in specific frequency region is important for the design of acoustic filter. This paper puts forward a meta material model made up of fluid-conveying carbon nanotubes （CNT）, which can absorb acoustic nanowave in a given frequency range by adjusting the lengths and fluid velocities of themselves. Absorption coefficients are calculated out through the combination of the finite element method with the theoretical model, which are 0.4-0.55 relating to different fluid velocities for the crossing-distributed model. Comparisons are made between the crossed model and the aligned one, which prove that the CNT forest with crossed distribution is more effective in acoustic wave absorption.
基金supported by the National Basic Research Programs of China(973 Program)under Contracts No.2013CBA01704the National Natural Science Foundation of China(NSFC-61575104)
文摘The frequency range that surface plasmon polariton(SPP) mode exists is mainly limited by the metal material.With high permittivity dielectrics above metal surface, the SPP mode at high frequency has extremely large loss or can be cutoff, which limits the potential applications of SPP in the field of optical interconnection, active SPP devices and so on.To extend the frequency range of SPP mode, the surface mode guided by metal/dielectric multilayers meta-material has been studied based on the theory of electromagnetic field. It is demonstrated that surface mode not only could be supported by the meta-material but also extends the frequency to where conventional metal SPP cannot exist. Meanwhile, the characteristics of this surface mode, such as dispersion relation, frequency range, propagation loss and skin depth in metamaterial and dielectrics, are also studied. It is indicated that, by varying the structure parameters, the meta-material guided SPP mode presents its advantages and flexibility over traditional metal one.
