Laser-induced breakdown spectroscopy（LIBS） combined with K-means algorithm was employed to automatically differentiate industrial polymers under atmospheric conditions.The unsupervised learning algorithm K-means wer...Laser-induced breakdown spectroscopy（LIBS） combined with K-means algorithm was employed to automatically differentiate industrial polymers under atmospheric conditions.The unsupervised learning algorithm K-means were utilized for the clustering of LIBS dataset measured from twenty kinds of industrial polymers.To prevent the interference from metallic elements,three atomic emission lines（C I 247.86 nm,H I 656.3 nm,and O I 777.3 nm） and one molecular line C–N（0,0） 388.3 nm were used.The cluster analysis results were obtained through an iterative process.The Davies–Bouldin index was employed to determine the initial number of clusters.The average relative standard deviation values of characteristic spectral lines were used as the iterative criterion.With the proposed approach,the classification accuracy for twenty kinds of industrial polymers achieved 99.6%.The results demonstrated that this approach has great potential for industrial polymers recycling by LIBS.展开更多
We developed a systematic experimental method to demonstrate that damage threshold fluence(DTF) for fused silica changes with the number of femtosecond laser(800 nm, 65 ± 5 fs, 10 Hz and 600 Hz) pulses. Based on ...We developed a systematic experimental method to demonstrate that damage threshold fluence(DTF) for fused silica changes with the number of femtosecond laser(800 nm, 65 ± 5 fs, 10 Hz and 600 Hz) pulses. Based on the experimental data, we were able to develop a model which indicates that the change in DTF varies with the number of shots logarithmically up to a critical value. Above this value, DTF approaches an asymptotic value. Both DTF for a single shot and the asymptotic value as well as the critical value where this happens, are extrinsic parameters dependent on the configuration(repetition rate, pressure and geometry near or at the surface). These measurements indicate that the power of this dependence is an intrinsic parameter independent of the configuration.展开更多
A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdow...A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.展开更多
基金supported by National Natural Science Foundation of China (Nos.61575073 and 51429501)
文摘Laser-induced breakdown spectroscopy（LIBS） combined with K-means algorithm was employed to automatically differentiate industrial polymers under atmospheric conditions.The unsupervised learning algorithm K-means were utilized for the clustering of LIBS dataset measured from twenty kinds of industrial polymers.To prevent the interference from metallic elements,three atomic emission lines（C I 247.86 nm,H I 656.3 nm,and O I 777.3 nm） and one molecular line C–N（0,0） 388.3 nm were used.The cluster analysis results were obtained through an iterative process.The Davies–Bouldin index was employed to determine the initial number of clusters.The average relative standard deviation values of characteristic spectral lines were used as the iterative criterion.With the proposed approach,the classification accuracy for twenty kinds of industrial polymers achieved 99.6%.The results demonstrated that this approach has great potential for industrial polymers recycling by LIBS.
基金supported by the U.S.Department of Energy under Contracts DE-AC02-76SF00515(SLAC)Israel Science Foundation
文摘We developed a systematic experimental method to demonstrate that damage threshold fluence(DTF) for fused silica changes with the number of femtosecond laser(800 nm, 65 ± 5 fs, 10 Hz and 600 Hz) pulses. Based on the experimental data, we were able to develop a model which indicates that the change in DTF varies with the number of shots logarithmically up to a critical value. Above this value, DTF approaches an asymptotic value. Both DTF for a single shot and the asymptotic value as well as the critical value where this happens, are extrinsic parameters dependent on the configuration(repetition rate, pressure and geometry near or at the surface). These measurements indicate that the power of this dependence is an intrinsic parameter independent of the configuration.
文摘A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.
