Effects of experimental parameters on elemental analysis of coal by laser-induced breakdown spectroscopy

The purpose of this work is to improve the precision of the elemental analysis of coal using laser-induced breakdown spectroscopy (LIBS). The LIBS technique has the ability to allow simultaneous elemental analysis and on-line determination, so it could be used in the elemental analysis of coal. Organic components such as C, H, O, N and inorganic components such as Ca, Mg, Fe, Al, Si, Ti, Na, and K of coal have been identified. The precision of the LIBS technique depends strongly on the experimental conditions, and the choice of experimental parameters should be aimed at optimizing the repeatability of the measurements. The dependences of the relative standard deviation (RSD) of the LIBS measurements on the experimental parameters including the sample preparation parameters, lens-to-sample distance, sample operation mode, and ambient gas have been investigated. The results indicate that the precision of LIBS measurements for the coal sample can be improved by using the optimum experimental parameters

Influence of coal characteristics on laser-induced plasmas

peer reviewedEight kinds of typical coal samples were chosen for studying the influence of coal characteristics on laser—induced plasmas．Element analysis and industry analysis were carried out for every sample．Experimental study on the interaction between laser and different coal samples was completed，and factors affecting laser plasma were analyzed，such as coal moisture and coal dust．The experiment result indicates that the coal samples with different coalification degrees have different plasma time—resolved spectral characteristics，all of them tend to rise at the beginning of plasma formation (< 1us)，then with the decay of plasmas emission．they tend to decrease in about 1us，while secondary ionization occurs in highly coalificated coals after 2 us．The plasma temperature differs from one kind to another，the higher the coalification degree is，the higher the plasma temperature will be

Matrix Effect on Laser Induced Breakdown Spectroscopy of Fine Coal

peer reviewedThe feasibility of laser—induced breakdown spectroscopy as a diagnostic tool for elementary analysis was documented widely,as well as the matrix effect of target material was proved to be remarkable impact on the spectral analysis． The influence of physical characteristics of fine coal，including particle size and area density，on the emission spectrum was surveyed，such as spectral intensity,standard deviation of characteristic spectrum and the detection threshold．An intense laser radiation with a wavelength of 1064 nm was used to ablate fine coal to form plasma plume，and the emission spectrum emitted as the plasma cooling of was analyzed by high—resolution echelle grating spectrometer coupled to intensified CCD camera．The results suggest that moderate particle size and material density are more advantageous to quantitative analysis of coal by laser—induced breakdown spectroscopy than the smallest or biggest size，which can be interpretable by heat—transfer mechanism in target after a shot of laser pulse

Precise Measurements of Branching Fractions for Ds+D_s^+ Meson Decays to Two Pseudoscalar Mesons

We measure the branching fractions for seven $D_{s}^{+}$ two-body decays to pseudo-scalar mesons, by analyzing data collected at $\sqrt{s}=4.178\sim4.226$ GeV with the BESIII detector at the BEPCII collider. The branching fractions are determined to be $\mathcal{B}(D_s^+\to K^+\eta^{\prime})=(2.68\pm0.17\pm0.17\pm0.08)\times10^{-3}$, $\mathcal{B}(D_s^+\to\eta^{\prime}\pi^+)=(37.8\pm0.4\pm2.1\pm1.2)\times10^{-3}$, $\mathcal{B}(D_s^+\to K^+\eta)=(1.62\pm0.10\pm0.03\pm0.05)\times10^{-3}$, $\mathcal{B}(D_s^+\to\eta\pi^+)=(17.41\pm0.18\pm0.27\pm0.54)\times10^{-3}$, $\mathcal{B}(D_s^+\to K^+K_S^0)=(15.02\pm0.10\pm0.27\pm0.47)\times10^{-3}$, $\mathcal{B}(D_s^+\to K_S^0\pi^+)=(1.109\pm0.034\pm0.023\pm0.035)\times10^{-3}$, $\mathcal{B}(D_s^+\to K^+\pi^0)=(0.748\pm0.049\pm0.018\pm0.023)\times10^{-3}$, where the first uncertainties are statistical, the second are systematic, and the third are from external input branching fraction of the normalization mode $D_s^+\to K^+K^-\pi^+$. Precision of our measurements is significantly improved compared with that of the current world average values

Whole-genome sequencing of <em>Oryza brachyantha</em> reveals mechanisms underlying <em>Oryza</em> genome evolution

The wild species of the genus Oryza contain a largely untapped reservoir of agronomically important genes for rice improvement. Here we report the 261-Mb de novo assembled genome sequence of Oryza brachyantha. Low activity of long-terminal repeat retrotransposons and massive internal deletions of ancient long-terminal repeat elements lead to the compact genome of Oryza brachyantha. We model 32,038 protein-coding genes in the Oryza brachyantha genome, of which only 70% are located in collinear positions in comparison with the rice genome. Analysing breakpoints of non-collinear genes suggests that double-strand break repair through non-homologous end joining has an important role in gene movement and erosion of collinearity in the Oryza genomes. Transition of euchromatin to heterochromatin in the rice genome is accompanied by segmental and tandem duplications, further expanded by transposable element insertions. The high-quality reference genome sequence of Oryza brachyantha provides an important resource for functional and evolutionary studies in the genus Oryza

Effects of coal sampling density on the elemental analysis by using laser-induced breakdown spectroscopy

peer reviewedThree representative coals from different mines were sampled for analysis. In order to investigate t he effect s of density of samples on t he coal analysis by laser-induced breakdown spectroscopy, the powder samples and pellet samples which pressed with different pressures were selected for the experiment . The spectra of 200～850 nm of powder and pellet coal samples were obtained , and the emission lines of component s such as C , H , O , N , Al , Fe , Ca , Mg , Si , Ti , Na and K were recorded. Emission lines of C , Al , Ca , Mg , Si and Ti element s were chosen for analysis of calibration curve method and internal standardization met hod because of their high intensity and little interference. The results showed that the density of the samples has more effect s on the calibration curve met hod than the internal standardization met hod

Study on Real-time Evaluation of Slagging Propensities of Coals Based on Laser-induced Breakdown Spectroscopy

peer reviewedA method of real-time evaluation of slagging propensities of coals based on element quantitative technique by laser-induced breakdown spectroscopy Was introduced ．An experiment apparatus Was set up according to the principle of analysis technique，an d in which six typical coals samples were analyzed．Four ones were used to construct calibration curves of the analyzed elements as a reference diagram determining the relation between element concentration an d spectral intensity， afterwards，analyzed silicon element an d aluminum element in other sampleswere surveyed with the reference diagram ．Ratios of silicon dioxide to aluminum trioxide were computed subsequently according to chemical calculation to evaluate the slagging propensities of coals．Comparing the evaluation with the computed result based on ash composition analyzed with conventional measure，the two match well．After all，some improvement program s to optimize the measurement mechanism were discussed

Enrichment of lanthanides in aragonite

Using the constant addition technique, the coprecipitation of lanthanum, gadolinium, and lutetium with aragonite in seawater was experimentally investigated at 25 degrees C. Their concentrations in aragonite overgrowths were determined by inductive coupled plasma mass spectrometer. All these lanthanides were strongly enriched in aragonite overgrowths. The amount of lanthanum, gadolinium, and lutetium incorporated into aragonite accounted for 57%-99%, 50%-89%, and 40%-91% of their initial total amount, respectively. With the increase of aragonite precipitation rate, more lanthanides were incorporated into aragonite while their relative fraction in aragonite overgrowths decreased consistently. It indicated that the coprecipitation of lanthanides with aragonite was controlled by the kinetics of aragonite precipitation