Ultra-broadband and polarization-independent planar absorber based on multilayered graphene

We propose an ultra-broadband and polarization independent planar absorber comprising multilayered graphene. The bandwidth of the proposed absorber is extended by increasing the number of layers of graphene, and it is polarization independent due to its symmetrical unit structure. The full wave simulation results show that an absorber with three graphenebased layers can efficiently harvest an electromagnetic wave with random polarization from 17.9 GHz to 188.7 GHz（i.e.,covering frequency regimes from K to D bands and relative bandwidth of - 165%）. The physical absorption mechanism of ultra-broadband absorption has been elaborated upon using the destructive interference method and multiple resonances approach in a multilayered medium. The proposed absorber can be used in many applications such as medical treatment,electromagnetic compatibility, and stealth technique.

保护地方畜禽品种资源 促进畜牧业可持续发展

保护地方畜禽品种资源刻不容缓,事关人类的生存、畜牧业的可持续发展和农民收入的增加。保护工作是政府行为,开发利用需要全社会的支持。目前首要的是提高认识、增加投入、加强研究。中长期要建立种质评价、动态监测、信息网络、资源保护、开发利用体系,达到品种资源的永续利用。