With the increasing prevalence of high-temperature erasable pens, there are growing concerns regarding information security under thermal exposure and the potential risks of document falsification. To address this issue, this work proposes a novel approach using laser-induced breakdown spectroscopy (LIBS) to identify thermally erased text. By analyzing the spectral differences between blank paper and ink, the characteristic spectral line Li I 670.79 nm in the ink was identified, and the spatial distribution of spectral line intensity was used to recover the text. The peak signal-to-noise ratio was utilized for quantitative evaluation of text restoration efficacy. Experimental results demonstrate that this method effectively detects long-term stored samples with micro damage and excellent reproducibility. Samples stored for different durations (1-13 days) were tested, along with three replicate experiments for each sample. The results show that this method effectively restores information from long-term stored samples, with micro damage to the materials and excellent repeatability. This study proposes a novel method for recovering information from high-temperature erasable ink. Although the preliminary results were obtained under specific paper-ink combination conditions, they provide an innovative approach for document authentication and demonstrate the feasibility of LIBS technology.

A method for restoring fadable ink writings using laser-induced breakdown spectroscopy (LIBS) combined with machine learning was proposed. This research employed dimensionality reduction and clustering analysis to process LIBS data, significantly improving analytical efficiency and accuracy. Unlike traditional chemical detection methods, this approach minimizes chemical damage to samples while ensuring operator safety. Compared to physical restoration techniques, it achieves higher accuracy and lower operational costs. Experimental results demonstrated stable recognition performance in complex environments. For samples stored over extended periods, the method successfully restored handwriting. Repeated detection tests confirmed preserved clarity. The proposed method was validated through analysis of various ink samples, including those from the high-temperature fadable pen and sodium chloride (NaCl) solution, showcasing its effectiveness across different ink types. This work highlights a novel technique for recognizing fadable ink writings, with micro damage to samples and providing reliable analysis for samples stored over extended periods. This method avoids damage to samples from chemical reagents, is non-irritating to the human body, and is cost-effective. The technique can effectively restore fadable ink traces in important documents, including commercial contracts and legal evidence, providing an efficient solution for forensic document authentication, and offers a novel approach to information decryption in the field of encryption.

Six cold medications with similar compositions were identified using t-SNE and BPNN combined with laser-induced breakdown spectroscopy.

In this study, we investigated the additive patterns observed in near-infrared (NIR) diffuse reflectance spectra within the context of food and pharmaceutical product formulation. Employing the Kubelka–Munk theory, we examined the linear correlation between spectra and concentration in polymer materials and tobacco powder samples. Our findings confirm the principle of spectral additivity in diffuse reflectance spectra, demonstrating a linear relationship when the sample scattering coefficient remains constant. Moreover, our results validate the feasibility of substituting actual mixed spectra with NIR additive spectra in tobacco leaf systems. This approach can potentially enhance formulation design, thereby improving efficiency and accuracy while expanding the scope and combination of formulation materials. Furthermore, this study offers a rapid, information-rich, and environmentally friendly alternative to traditional methods, with significant implications for the future of product formulation.

In this work, laser-induced breakdown spectroscopy（LIBS） was applied for the detection of Pb in Tieguanyin tea and ash. Firstly, the Tieguanyin tea and ash containing Pb were prepared, and the difference of intensities of Pb I spectral lines before and after the ashing treatment was studied. It was found that the intensities of Pb I lines increased by 30 times and the standard deviation of background signal decreased by 41% after the ashing treatment. Therefore, the enrichment of Pb element by ashing treatment was used to detect Pb in tea with high sensitivity. Then, the calibration curve of Pb was established using spectral lines without self-absorption, and the determination coefficient（R~2） for the linear fitting of calibration curve was 0.979 9. Finally, it was found that the limit of detection of Pb was 233.8 ppb. Compared with the results of other works which detect Pb directly, the enrichment of Pb by ashing treatment improved the detection sensitivity of Pb by about 200 times. In addition, this method can be applied to the high sensitivity detection of other heavy metals, such as Cr, Cd, Hg, etc in plants, Chinese herbal medicine, flour, rice, coal and other solid materials.

Tea ash is the inorganic residue of tea after a series of chemical and physical reactions under high temperature environment. The compositions of tea and ash are very different. In addition, the compositions of ash are closely related to the quality of tea. In this work, the compositions of Tieguanyin tea and ash were analyzed by laser-induced breakdown spectroscopy (LIBS), and the differences of elements in tea and ash were analyzed qualitatively. Tea contains the main elements, such as Ca, Na, Mg, and K, trace elements Fe, Cu, Zn, Mn and Sr, and other metallic elements Al, Li and Ba. Comparing the atomic and ionic lines in LIBS spectra of tea and ash, it was found that the spectral line intensities of metallic elements, i.e. Ca, Al, Mn, Mg, K, Na, Li, in the ash were significantly enhanced. In addition, there were CN, C 2 and CaO molecular lines in the LIBS spectra of tea, but only CaO free radical was detected in the LIBS spectra of ash. The reason of the differences between the molecular lines of LIBS spectra of tea and ash was analyzed. This work is to determine the material compositions of tea and ash, which provides a basic foundation for the quality judgment of tea and a new idea for the enrichment detection of metallic elements.

CaO and CN molecular lines were applied to detection of lead chrome green in Tieguanyin tea combined with principal component analysis and laser-induced breakdown spectroscopy.

Assuming the intracavity photon number densities and initial population-inversion density are Gaussian distributions, the rate equations of the actively Q-switched dual-wavelength Raman laser based on one Raman mode are deduced. Under the condition that the wavelength separation of the two Raman lasers is very small, these space-dependent rate equations are normalized and solved numerically. A set of universal theoretical curves describing the operations of the dual-wavelength Raman laser is obtained. The influence of the composite normalization variables on the performances of the dual-wavelength Raman laser is analyzed. The normalization theory is verified with experimental data. The experimental results are consistent with the numerical ones, which proves that the proposed rate equations are correct and feasible.

In view of the current situation of high energy consumption and unsatisfactory energy-saving effect of existing large commercial office buildings, green operation management is applied to the operation and management process of existing large commercial office buildings. By constructing an evolutionary game model between owners and property management enterprises under market mechanism and government incentive, this paper explores the acceptance degree of owners and property management enterprises to green operation management under different circumstances, as well as their strategic choices and changing trends. Finally, the paper proposes that the government should actively play a leading role and encourage the development of green operation management.

Ultra-short pulse (picosecond) anti-Stokes laser can be obtained by using Raman frequency converter in a crystal medium by the coherent anti-Stokes Raman scattering effect. The crystalline Raman frequency converter based on the pump-probe method can realize the collinear interaction of coherent anti-Stokes Raman scattering, thus effectively improving the conversion efficiency of the anti-Stokes light. Theoretical simulation is an important means to study laser operation. Coupled wave equation is widely used to study the characteristics of Raman laser and anti-Stokes laser. Although the coupling wave theory of anti-Stokes Raman frequency shifter reported previously can reflect the operation law of the frequency shifter, the optimization of the frequency shifter and the influence of the frequency shifter parameters on the output characteristics of anti-Stokes laser have not been reported so far. In this paper, the picosecond anti-Stokes Raman frequency converter based on the pump-probe method is studied theoretically. Considering the generation of the first Stokes light in the probe channel and the second Stokes light in the pump channel, the coupled wave equation of the collinear picosecond anti-Stokes Raman frequency converter is established under the plane wave approximation. Without loss of generality, four dimensionless comprehensive parameters are introduced to normalize the equations. A set of universal theoretical curves describing the operation of the Raman frequency converter is obtained. The numerical solutions of the equations show that the performance of the Raman frequency converter mainly depends on three parameters: the normalized phase mismatch parameter ΔK, the normalized Raman gain coefficient G, and the energy ratio of the probe light to the fundamental light rprobe. The reasonable values of normalized variables are determined when the high efficiency anti-Stokes conversion is realized. Experimental data are used to verify the correctness of the theoretical model. The theoretical value of the anti-Stokes conversion efficiency is basically consistent with the literature data. The normalized coupled wave theory proposed in this paper is helpful in understanding the operation law of the picosecond anti-Stokes Raman frequency shifter, and has guiding significance for the design of the frequency converter.

In this study, based on the wave equation and material equation of a solid Raman medium and neglecting the transient effect of stimulated Raman scattering, the coupled wave equations of the interaction of the first anti Stokes beams, the pump, and first to third Stokes beams in extra-cavity pumped anti-Stokes lasers arc obtained using the plane wave approximation. Normalized parameters arc introduced to normalize the equations. The effects of the normalized Raman gain coefficient, normalized pump pulse width, and normalized wave mismatch on the performances of extra-cavity pumped anti-Stokes lasers arc analyzed by numerically solving the normalized coupled wave equations. The experimental data arc substituted into the coupled wave equations. The theoretical estimations of the anti-Stokes optical conversion efficiencies arc consistent with the reported data, which validate the correctness of the theoretical model. By analyzing the theoretical calculation results, methods to improve the conversion efficiency of extra-cavity pumped anti-Stokes lasers and associated methods of lasers design arc proposed.

The space-dependent rate equations of intracavity coherent anti-Stokes Raman lasers are deduced by adding the term describing the coherent anti-Stokes scattering effect to the rate equations of the intracavity Raman laser. The intracavity photon densities of the fundamental and first Stokes lights and the initial population-inversion density are assumed to be Gaussian spatial distributions. The rate equations are normalized and solved numerically, and a group of general curves is generated. The influence of normalized parameters on the pulse parameters of the output anti-Stokes laser is investigated. The normalized rate-equation theory and numerical results will be of help in the design of high-performance intracavity coherent anti-Stokes Raman lasers.