Laser-induced breakdown spectroscopy has been used to measure the organic oxygen content in pulverized anthracite coal under atmospheric conditions. Special spectral processing including the optimal O(I) emission-line selection by comparing the spectral correlation coefficients with the N(I) line, internal normalization with the N(I) line, and temperature correction are proposed and employed to satisfy the multi-line analysis method and yield the most accurate quantitative results. The calibration method for determining the organic oxygen content of coal is presented, with an accuracy of 1.15-1.37% and an average relative error of 19.39% being evaluated through an experiment performed on six anthracite coal samples. The relative measurement error distribution has also been studied.

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A 2-D multibeam antenna based on the dimension gradient metasurface is proposed in this paper. The metasurface is composed of four subunits formed by square patches with the dimension gradient in a 5 Â 5 pattern. When the dimension gradient of subunits is adjusted, the beam direction in the azimuth plane can be switched in a larger range. Furthermore, by introducing L-shaped slots in the ground plane and two stubs on the feeding lines, the peak gain, sidelobe level and isolation of the antenna can be improved. Meanwhile, the antenna maintains a low profile of 0.06 λ 0 . The measured results show that the impedance bandwidth of the antenna is 16.5% (5.5-6.49 GHz). Four beams are generated and pointed at (φ 0 , θ 0 ) = (70 , 23 ), (160 , 24 ), (250 , 21 ), and (340 , 24 ). The peak gains of the beams reach 8.54 dBi.