[1] [1] YANG D Q,YAN C W,ZHANG J,et al.Chloride threshold value and initial corrosion time of steel bars in concrete exposed to saline soil environments[J].Construction and Building Materials,2020,267(3):120979.

[3] [3] WANG Z, YUAN T B, HOU Z Y, et al. Laser-induced breakdown spectroscopy in China[J].Frontiers of Physics,2014,9(4):419-438.

[4] [4] ZHAO Y,XU X,SUN M,et al.He.Deep learning associated with laser-induced breakdown spectroscopy (LIBS) for the prediction of lead in soil[J].Applied Spectroscopy,2019,73(5):565-573.

[7] [7] MISRA A K,ACOSTA-MAEDA T E,PORTER J N,et al.EXPRESS:a two-component approach for long range remote Raman and laser-induced breakdown (LIBS) spectroscopy using low laser pulse energy[J].Applied Spectroscopy,2018,73(3):000370281881214.

[8] [8] LI X W,YANG Z F,WU J,et al.Spatial confinement in laser-induced breakdown spectroscopy[J].Journal of Phvsics D Applied Physics,2017,50(1):015203.

[9] [9] ZHANG D, CHEN A M, WANG X, et al.Influence of the distance between target surface and focal point on the expansion dynamics of a laser-induced silicon plasma with spatial confinement[J].Spectrochimica Acta Part B Atomic Spectroscopy,2018,143(4):71-77.

[10] [10] GAO X,LIU L,SONG C,et al.The role of spatial confinement on nanosecond YAG laser-induced Cu plasma[J].Journal of Physics D Applied Physics,2015,48(17):175205.

[11] [11] CHEN J Z,BAI J N,SONG G J,et al.Enhancement effects of flat-mirror reflection on plasma radiation[J].Applied Optics,2013,52(25):6295-6299.

[13] [13] STAVROPOULOS P,PALAGAS C,ANGELOPOULOS G N,et al.Calibration Measurements in laser-induced breakdown spectroscopy using nanosecond and picosecond lasers[J].Spectrochimica Acta Part B Atomic Spectroscopy,2004,59(12):1885-1892.

[14] [14] PRAHER B,PALLESCHI V,VISKUP R,et al.Calibration free laser-induced breakdown spectroscopy of oxide materials[J].Spectrochimica Acta Part B Atomic Spectroscopy,2010,65(8):671-679.