We experimentally demonstrate that perfect electromagnetic absorption can be realized in the one-atom thick graphene. Employing coherent illumination in the waveguide system, the absorbance of the unpatterned graphene monolayer is observed to be greater than 94% over the microwave X-band, 7–13 GHz, and to achieve a full absorption, >99% in experiment, at ∼8.3 GHz. In addition, the absorption characteristic manifests equivalently a wide range of incident angle. The experimental results agree very well with the theoretical calculations. Our work accomplishes the broadband, wide-angle, high-performance absorption in the thinnest material with simple configuration.

According to the theory, an ultrathin conductive film can achromatically dissipate electromagnetic waves with frequency ranging from radio to terahertz. A moderate absorption effect, which gives rise to a maximal absorbance of 50%, can be found if an impedance matching condition is satisfied. We have experimentally demonstrated the frequency-irrelevant, maximal absorption by employing a conductive nanofilm and launching terahertz waves at Brewster angle when the sheet (square) resistance of the film meets the impedance matching condition. In the entire terahertz spectral range covered by our experiments, the frequency-independent optical properties were consistent with the theoretical calculations.

In order to use lithium battery as energy storage device in DC operating power supply system, and optimize the performances of lithium ion battery such as efficiency, etc., an on-line charging and discharging control scheme for lithium ion battery in DC operating power supply is proposed. Firstly, the internal equivalent state of lithium ion battery is estimated by the output voltage and current of lithium ion battery. Secondly, the expected charging and discharging state and current value of lithium ion battery is determined by the internal equivalent state of lithium ion battery. Finally, the output voltage of AC/DC converter is adjusted according to the internal equivalent state of lithium ion battery and the expected charging and discharging state and current value. The actual charging and discharging current of lithium ion battery is forced to tend to the expected current value, so as to optimize the performances of lithium ion battery. Theoretical analysis and case study show that the scheme is feasible.

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