SUPPORT VECTOR MACHINES; ELEMENTAL ANALYSIS; IRON-ORES; CLASSIFICATION; SPECTROMETRY; SAMPLES; PLASMA; INDUSTRY; ALLOYS; MODEL

The basicity of sintered ore, which is related to the melting point of the sinter, is vital to ore mining and blastfurnace smelting. Laser-induced breakdownspectroscopy (LIBS) with random forest regression (RFR) has been applied for measuring the basicity of sintered ore, which can be defined by the concentrations of oxides: CaO, SiO2, Al2O3 and MgO. In this work, thirty sintered ore samples are used, of which twenty samples are used for the calibration set to construct the random forest regression (RFR) calibration model for the above-mentioned oxides and ten samples are used for the test set. The characteristic lines of the main components in the sintered ore are identified using the National Institute of Standards and Technology (NIST) database. Two model parameters (the number of decision trees -ntree and the number of random variables - m(try)) of the RFR were optimized by out-of-bag (OOB) error estimation for improving the predictive accuracy of the RFR model. The RFR model was applied to sample measurements and the results were compared with partial least squares regression (PLSR) models. The RFR model has shown better predictive capabilities than the PLSR model. In order to verify the stability of the RFR model, fifty measurements were made and the relative standard deviation (RSD) of the data is between 0.27% and 0.59%. Therefore, LIBS combined with RFR could be a promising method for realtime online, rapid analysis in mining and mineral processing industries.

Laser-induced breakdown spectroscopy; LIBS; multivariate analysis; soft independent modeling of class analogy; SIMCA; partial least squares discriminant analysis; PLS-DA; edible salt;INDUCED BREAKDOWN SPECTROSCOPY; SEA SALTS; LIBS; IDENTIFICATION; COMPACT; ORIGIN

We report soft independent modeling of class analogy (SIMCA) analysis of laser-induced plasma emission spectra of edible salts from 12 different geographical origins for their classification model. The spectra were recorded by using a simple laser-induced breakdown spectroscopy (LIBS) device. Each class was modeled by principal component analysis (PCA) of the LIBS spectra. For the classification of a separate test data set, the SIMCA model showed 97% accuracy in classification. An additional insight could be obtained by comparing the SIMCA classification result with that of partial least squares discriminant analysis (PLS-DA). Different from SIMCA, the PLS-DA classification accuracy seems to be sensitive to addition of new sample classes to the whole data set. This indicates that the individual modeling approach (SIMCA) can be an alternative to global modeling (PLS-DA), particularly for the classification problems with a relatively large number of sample classes.

INDUCED PLASMA SPECTROSCOPY; ATOMIC EMISSION-SPECTROMETRY; VACUUM-ULTRAVIOLET; SULFUR; STEEL; NANOPARTICLES; CALIBRATION; SAMPLES; RATIOS; SYSTEM

This work introduces a new approach to perform LIBS elemental imaging in the vacuum ultraviolet (VUV) wavelength range by using an argon purged probe coupled to a compact spectrometer. In spite of several important elements for geological and industrial applications such as S, P, As, B, C, or Zn presenting strong lines in the VUV range, the need for using specific optics and working under oxygen-free conditions has limited the extension of LIBS systems available for such a range. Herein, we present an adaptation of our LIBS imaging instrumentation to access the VUV while operating under ambient conditions. The proposed detection system is based on an optical probe directly coupled to a Maya2000Pro compact spectrometer (Ocean Optics), all purged with argon. The technical design along with a detailed evaluation of the VUV probe is addressed. The possibility of using this VUV probe for LIBS imaging is also investigated by studying a Canadian mine core sample with special emphasis on the detection of sulfur. In addition to sulfur, more than 15 elements including P, As, C, Ca, Si, Mo, B, and Zn have also been detected. Elemental images covering sample surfaces in the range of cm(2) with a micrometric spatial resolution (10 mu m) are presented. A detection limit of 0.2 wt% for sulfur is demonstrated in a single shot configuration. These results open new perspectives for both conventional LIBS and LIBS-based imaging in various application fields.

Laser-induced breakdown spectroscopy; Deep Sea; Double pulse; Cavitation bubble; High pressure;BULK AQUEOUS-SOLUTIONS; ELEMENTAL ANALYSIS; SINGLE-PULSE; SHOCK-WAVES; LIQUIDS; LIBS; EXCITATION; INTENSITY; ABLATION; INSIGHTS

There is a growing interest in the development of sensors use in exploration of the deep ocean. Techniques for the chemical analysis of submerged solids are of special interest, as they show promise for subsea mining applications where a rapid sorting of materials found in the sea bottom would improve efficiency. Laser-Induced Breakdown Spectroscopy (LIBS) has demonstrated potential for this application thanks to its unique capability of providing the atomic composition of submerged solids. Here we present a study on the parameters that affect the spectral response of metallic targets in an oceanic pressure environment. Following laser excitation of the solid, the plasma persistence and the cavitation bubble size are considerably reduced as the hydrostatic pressure increases. These effects are of particular concern in dual pulse excitation as reported here, where a careful choice of the interpulse timing is required. Shadowgraphic images of the plasma demonstrate that cavitation bubbles are formed early after the plasma onset and that the effect of hydrostatic pressure is negligible during the early stage of plasma expansion. Contrarily to what is observed at atmospheric pressure, emission spectra observed at high pressures are characterized by self-absorbed atomic lines on continuum radiation resulting from strong radiative recombination in the electron-rich confined environment. This effect is much less evident with ionic lines due to the much higher energy of the levels involved and ionization energy of ions, as well as to the lower extent of absorption effects occurring in the inner part of the plasma, where ionized species are more abundant. As a result of the smaller shorter-lived cavitation bubble, the LIBS intensity enhancement resulting from dual pulse excitation is reduced when the applied pressure increases. (C) 2017 Elsevier B.V. All rights reserved.

Laser induced breakdown spectroscopy (LIBS); Laser wavelength; Plasma time evolution; Plasma shielding effect; Coal;INDUCED BREAKDOWN SPECTROSCOPY; ELEMENTAL ANALYSIS; DEPENDENCE; PARAMETERS

In face of the complicated and changeable coal in Chinese power stations, the on-line measurement of coal elemental composition is extremely significant in terms of enhancing the safety and efficiency of boilers as well as lowering the waste emission during operation. In this work, laser induced breakdownspectroscopy (LIBS) was applied to coal quality measurement. Laser wavelength was changed as 355, 532 and 1 064 nm to investigate the influence on coal LIBS features, including plasma time evolution and the spectral lines intensity-time characteristics of different elements. Energy threshold for shielding effect was also tested to verify how it varies with laser wavelengths. Additionally, coal LIBS spectrum was analyzed under different laser wavelengths. It has been proven by experiments that higher intensity of coal LIBS spectrum and energy threshold can be easily achieved when using laser of 532 nm, making it a fantastic energy source for coal LIBS tests. Results of these experiments serve to guide the industrial application of LIBS technology in the field of coal quality measurement.

Laser-induced breakdown spectroscopy; miniature laser; nickel ore;QUANTITATIVE-ANALYSIS; INDUCED PLASMA; LIBS; DISCRIMINATION; CONFIGURATION; STEEL; SOIL; CU

A newly designed and developed bench-top instrument is reported for laser-induced breakdown spectroscopy offering compact size and relatively low cost. A miniature laser was designed in the laboratory with a small volume and a light weight. The spectrometer was controlled using laboratory-written software. The instrument is suitable for the direct and rapid analysis of solid samples after simple pretreatment. Good stability and accuracy were achieved for quantitative analysis. The performance of the instrument was evaluated by qualitative and quantitative analyses of nickel ore for Mn, Al, Fe, Cr, Zn, Mg, Si, and Ca. The quantitative analysis showed linear calibration graphs and small relative standard deviations. The results show that the new instrument is suitable for elemental analysis.