Quantitative analysis of cement raw materials based on nanoparticle-enhanced laser-induced breakdown spectroscopy.

The nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) technique has attracted much attention because of its significant spectral enhancement as well as the reduction of spectral noise. More NELIBS studies have focused on the effect of nanoparticles on spectral intensity and the optimization of experiments. NELIBS has not been studied for the detection of cement raw material components and the repeatability of quantitative analysis. In this paper, the effect of NELIBS on the spectral quality as well as the repeatability of the quantitative analysis of cement raw materials is investigated. The effects of different AuNP sizes and volumes on LIBS brought about by pre-ablation were compared and modeled for quantitative analysis. The results showed that the signal-to-noise ratio (SNR) of NELIBS spectra after pre-ablation was improved from 2.72 to 7.81, and the relative standard deviations (RSDs) of CaO, SiO2, Al2O3, and Fe2O3 in cement raw materials were reduced by 47%, 30%, 31%, and 33%, respectively. In summary, this paper provides a comprehensive discussion and comparison of AuNPs versus LIBS for quantitative analysis of cement raw material components, and also provides a new solution for quantitative analysis of cement raw materials.

LIBS combined with SG-SPXY spectral data pre-processing for cement raw meal composition analysis.

Rapid testing of cement raw meal plays a crucial role in the cement production process, so there is an urgent need for a fast and accurate testing method. In this paper, a method based on the Savitzky-Golay (SG) smoothing and sample set partitioning based on joint x-y distance (SPXY) spectral data pre-processing is proposed to improve the accuracy of the laser-induced breakdown spectroscopy (LIBS) technique for quantitative analysis of cement raw meal components. Firstly, the spectral data is denoised by SG smoothing, which effectively reduces the noise and baseline variations in the spectra. Then, the denoised data is divided into sample sets by combining the SPXY sample division method, which improves the efficiency of data analysis. Finally, the delineated data set is modeled for quantitative analysis by a back-propagation (BP) neural network. Compared to the modeling effect of the four oxide contents of CaO, S i O 2, A l 2 O 3, and F e 2 O 3 in the Hold-Out method, the correlation coefficient (R) was improved by 26%, 10%, 17%, and 4%, respectively. The root mean square error (RMSE) was reduced by 47%, 33%, 43%, and 21%, respectively. The mean absolute percentage error (MAPE) was reduced by 63%, 60%, 36%, and 51%, respectively. The results show that there is a significant improvement in the model effect, which can effectively improve the accuracy of quantitative analysis of cement raw meal composition by LIBS. This is of great significance for the real-time detection of cement raw meal composition analysis.

Enhancing optical delay using cross-Kerr nonlinearity in Rydberg atoms.

A scheme to enhance the optical delay in Rydberg atoms is proposed. In the linear case, the optical delay in a four-level system can be significantly enhanced compared to that of the three-level system. However, the width of the transparent window will decrease with an increase in the optical delay. In the nonlinear case, the nonlinear dispersion becomes steep around the transparency window. The enhanced cross-Kerr nonlinearity mainly contributes to the effective dispersion, which dramatically increases the optical delay. The simulation result shows that the optical delay of the system could be enhanced tens of times; moreover, the wide transparency window remains. So the delay-bandwidth product could be significantly improved due to nonlinear dispersion. We further examine Gaussian pulse propagation in the Rydberg atoms.

Proposal of Rydberg atomic receiver for amplitude-modulated microwave signals with active Raman gain.

An efficient scheme for a microwave (MW) receiver is proposed based on the active Raman gain (ARG) in Rydberg atoms. The 87Rb atoms are excited to the Rydberg state (53D5/2), and the gain spectrum has a single gain peak. The MW field is resonant with the Rydberg transition (53D5/2→54P3/2), resulting in a split in the gain spectrum. The frequency splitting of two peaks depends linearly on the MW field strength. The distortion and attenuation of the probe field are reduced, due to the system's operating in the stimulated Raman emission mode. Simulation results show that the fidelity of MW communication based on the Rydberg atomic ARG scheme is improved by at least 10 times compared to that based on an electromagnetically induced transparency scheme, and the system seems more robust to amplitude modulation signals with different modulation depths.

THz white light cavity with nonlinear dispersion in graphene.

A white light cavity (WLC) scheme is proposed to achieve broadband response in the terahertz (THz) region by enhanced nonlinear dispersion in a magnetized graphene system. In the weak probe field limit, the cavity linewidth is narrowed due to electromagnetically induced transparency, and then it becomes nearly as broad as the empty-cavity linewidth under the condition of Autler-Towns splitting. It is interesting to find that the cavity linewidth can be further broadened by enhanced nonlinear dispersion. The simulation result shows that the response range of the cavity is from 6.273 THz to 6.308 THz under the given condition, which is nearly 11 times larger than the empty-cavity linewidth. Furthermore, the improvement in cavity transmission and the response of WLC at different frequencies are investigated.

[4 + 2]-Cycloaddition and 1,4-Addition of ortho-Quinone Methides by a Chiral Crotyl Silane.

Anhydrous FeCl3 in the presence of 2,6-lutidine promotes the substrate-controlled enantioselective [4 + 2]-cycloaddition and crotylation reaction between an enantioenriched ( S, E)-crotyl silane and in situ generated ortho-quinone methides ( oQMs). The reaction produces both the chiral chroman and crotylation products in a ratio reflective of the electronic nature of the parent oQM with overall combined yields up to 96%. A ring-opening and elimination sequence was subsequently developed to provide direct access to the crotylation products, containing two contiguous tertiary carbon stereocenters, in good yields and enantioselectivities.