Smartcombination of manifold carbonaceous materials with admirable functionalities(like full of pores/functional groups,high specific surface area) is still a mainstream/preferential way to address knotty issues of po...Smartcombination of manifold carbonaceous materials with admirable functionalities(like full of pores/functional groups,high specific surface area) is still a mainstream/preferential way to address knotty issues of polysulfides dissolution/shuttling and poor electrical conductivity for S-based cathodes.However,extensive use of conductive carbon fillers in cell designs/technology would induce electrolytic overconsumption and thereby shelve high-energy-density promise of Li-S cells.To cut down carbon usage,we propose the incorporation of multi-functionalized NiFe2O4 quantum dots(QDs) as affordable additive substitutes.The total carbon content can be greatly curtailed from 26%(in traditional S/C cathodes) to a low/commercial mass ratio(~5%).Particularly,note that NiFe2O4 QDs additives own superb chemisorption interactions with soluble Li2Sn molecules and proper catalytic features facilitating polysulfide phase conversions and can also strengthen charge-transfer capability/redox kinetics of overall cathode systems.Benefiting from these intrinsic properties,such hybrid cathodes demonstrate prominent rate behaviors(decent capacity retention with ~526 mAh g^-1 even at 5 A g^-1) and stable cyclic performance in LiNO3-free electrolytes(only ~0.08% capacity decay per cycle in 500 cycles at 0.2 A g^-1).This work may arouse tremendous research interest in seeking other alternative QDs and offer an economical/more applicable methodology to construct low-carbon-content electrodes for practical usage.展开更多
Anechoic chambers are used for indoor antenna measurements. The common method of constructing an anechoic chamber is to cover all inside walls by the electromagnetic absorbers. In this paper, a fully metallic spherica...Anechoic chambers are used for indoor antenna measurements. The common method of constructing an anechoic chamber is to cover all inside walls by the electromagnetic absorbers. In this paper, a fully metallic spherical chamber structure is presented in which the propagation of the electromagnetic waves inside the chamber is controlled and they are guided to an absorber. In the proposed method, an appropriate quiet zone is obtained, and unlike ordinary anechoic chambers, the absorber usage amount is reduced greatly. The performance of the chamber is evaluated by simulation. The results show that the proposed method could provide a useful technique for the indoor antenna measurements.展开更多
基金financial supports from National Natural Science Foundation of China (51802269 and 21773138)Chongqing Natural Science Foundation (cstc2018jcyjAX0624)+1 种基金Fundamental Research Funds for the Central Universities (XDJK2019AA002)Venture & Innovation Support Program for Chongqing overseas returnees (cx2018027)。
文摘Smartcombination of manifold carbonaceous materials with admirable functionalities(like full of pores/functional groups,high specific surface area) is still a mainstream/preferential way to address knotty issues of polysulfides dissolution/shuttling and poor electrical conductivity for S-based cathodes.However,extensive use of conductive carbon fillers in cell designs/technology would induce electrolytic overconsumption and thereby shelve high-energy-density promise of Li-S cells.To cut down carbon usage,we propose the incorporation of multi-functionalized NiFe2O4 quantum dots(QDs) as affordable additive substitutes.The total carbon content can be greatly curtailed from 26%(in traditional S/C cathodes) to a low/commercial mass ratio(~5%).Particularly,note that NiFe2O4 QDs additives own superb chemisorption interactions with soluble Li2Sn molecules and proper catalytic features facilitating polysulfide phase conversions and can also strengthen charge-transfer capability/redox kinetics of overall cathode systems.Benefiting from these intrinsic properties,such hybrid cathodes demonstrate prominent rate behaviors(decent capacity retention with ~526 mAh g^-1 even at 5 A g^-1) and stable cyclic performance in LiNO3-free electrolytes(only ~0.08% capacity decay per cycle in 500 cycles at 0.2 A g^-1).This work may arouse tremendous research interest in seeking other alternative QDs and offer an economical/more applicable methodology to construct low-carbon-content electrodes for practical usage.
文摘Anechoic chambers are used for indoor antenna measurements. The common method of constructing an anechoic chamber is to cover all inside walls by the electromagnetic absorbers. In this paper, a fully metallic spherical chamber structure is presented in which the propagation of the electromagnetic waves inside the chamber is controlled and they are guided to an absorber. In the proposed method, an appropriate quiet zone is obtained, and unlike ordinary anechoic chambers, the absorber usage amount is reduced greatly. The performance of the chamber is evaluated by simulation. The results show that the proposed method could provide a useful technique for the indoor antenna measurements.
