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您的检索式：作者名="Steven A.Cummer"
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| 1 | Automatic recognition of tweek atmospherics and plasma diagnostics in the lower ionosphere with the machine learning method显示文摘Tweek atmospherics are extremely low frequency and very low frequency pulse signals with frequency dispersion characteristics that originate from lightning discharges and that propagate in the Earth–ionosphere waveguide over long distances.In this study,we developed an automatic method to recognize tweek atmospherics and diagnose the lower ionosphere based on the machine learning method.The differences(automatic−manual)in each ionosphere parameter between the automatic method and the manual method were−0.07±2.73 km,0.03±0.92 cm^(−3),and 91±1,068 km for the ionospheric reflection height(h),equivalent electron densities at reflection heights(Ne),and propagation distance(d),respectively.Moreover,the automatic method is capable of recognizing higher harmonic tweek sferics.The evaluation results of the model suggest that the automatic method is a powerful tool for investigating the long-term variations in the lower ionosphere. | Mao Zhang GaoPeng Lu HaiLiang Huang ZhengWei Cheng YaZhou Chen Steven A.Cummer JiaYi Zheng JiuHou Lei | 2023 | Earth and Planetary Physics2023，7，3： | 0 |
| 2 | Achromatic metasurfaces by dispersion customization for ultra-broadband acoustic beam engineering显示文摘Metasurfaces,the ultra-thin media with extraordinary wavefront modulation ability,have shown great promise for many potential applications.However,most of the existing metasurfaces are limited by narrow-band and strong dispersive modulation,which complicates their real-world applications and,therefore require strict customized dispersion.To address this issue,we report a general methodology for generating ultra-broadband achromatic metasurfaces with prescribed ultra-broadband achromatic properties in a bottom-up inverse-design paradigm.We demonstrate three ultra-broadband functionalities,including acoustic beam deflection,focusing and levitation,with relative bandwidths of 93.3%,120%and 118.9%,respectively.In addition,we reveal a relationship between broadband achromatic functionality and element dispersion.All metasurface elements have anisotropic and asymmetric geometries with multiple scatterers and local cavities that synthetically support internal resonances,bi-anisotropy and multiple scattering for ultra-broadband customized dispersion.Our study opens new horizons for ultra-broadband highly efficient achromatic functional devices,with promising extension to optical and elastic metamaterials. | 董浩文 沈宸 赵胜东 邱维宝 郑海荣 张传增 Steven A.Cummer 汪越胜 方岱宁 成利 | 2022 | National Science Review2022，9，12： | 0 |
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