A LIBS spectrum baseline correction method based on the non-parametric prior penalized least squares algorithm.

Laser-induced breakdown spectroscopy (LIBS) has become a popular element analysis technique because of its real-time multi-element detection and non-damage advantages. However, due to factors such as laser-substance interaction and the experimental environment, the measured LIBS spectrum signal contains a continuous background, severely influencing spectrum analysis. In this paper, we propose a LIBS spectrum baseline correction method based on the non-parametric prior penalized least squares (NPPPLS) algorithm. Compared with the traditional Penalized Least Squares (PLS) method, improvements have been made in two aspects. On the one hand, a new weight method with faster convergence is proposed. On the other hand, we combine the Adam algorithm and introduce the RMSE of the baseline correction result at the previous time to constrain the update of the balance parameter, which enables the balance parameter to be adjusted adaptively and no parameter prior is required. The simulation results show that the proposed NPPPLS algorithm can achieve excellent correction results, even with no parametric priors. In addition, the performance of the NPPPLS algorithm is not affected by the initial value of the balance parameter, and the stability and robustness are significantly improved. Finally, we conducted baseline correction of the experimental LIBS spectrum and performed univariate and multivariate analyses. The results show that the quantitative analysis accuracy is improved after baseline correction, and the correlation coefficient R2 of different elements obtained by the extreme learning machine method of multivariate analysis can reach 0.99, demonstrating a better quantitative analysis result. The simulation and experimental results verify the excellent performance of the proposed NPPPLS algorithm, which can be effectively used to improve the accuracy of quantitative analysis. In addition, this method is also expected to be used for baseline correction of the Raman spectrum, near-infrared spectrum and so on.

Quantitative determination of microbial materials activity based on infrared extinction properties.

Microbial bacteria play an irreplaceable role in natural and human production and life; thus, determining their activities is an important issue. This study proposed a method to quantitatively determine the activity of microbial materials through extinction property calculation using infrared spectroscopy. Complex refractive indices of different active biomaterials were calculated based on their infrared spectra, and their extinction properties were determined using the discrete dipole approximation method. Using partial least squares (PLS), support vector regression (SVR), and extreme learning machine (ELM) regression, quantitative determination models of microbial materials based on infrared extinction properties were established to predict their activity. The results demonstrated that the model of least angle regression (LAR) combined with PLS exhibited better potential for the determination of biomaterial activity. The coefficient of determination (R2) values acquired by the optimal model for the three biomaterials were 0.9699, 0.9744, and 0.9621, respectively. These findings suggested that a rapid and accurate quantitative determination of microbial activity can be achieved based on extinction property.

Overview of structure, function and integrated utilization of marine shell.

Marine shell resources have received great attention from researchers owing to their unique merits such as high hardness, good toughness, corrosion resistance, high adsorption, and bioactivity. Restricted by the level of comprehensive utilization technology, the utilization rate of shells is extremely low, resulting in serious waste and pollution. The research shows that the unique brick-mud structure of shells makes them have diverse and good functional characteristics, which guides them to have great utilization potential in different fields. Hence, this review highlights the constitutive relationship between microstructure-function-application of shells (e.g., gastropods, cephalopods, and amniotes), and the comprehensive applications and development ideas in the fields of biomedicine, adsorption enrichment, pHotocatalysis, marine carbon sink, and environmental deicer. It is worth mentioning that marine shells are currently well developed in three areas: bone repair, health care and medicinal value, and drug carrier, which together promote the progress of biomedical field. In addition, an in-depth summary of the application of marine shells in the adsorption and purification of various impurities such as crude oil, heavy metal ions and dyes at low-cost and high efficiency is presented. Finally, by integrating thoughts and approaches from different applications, we are committed to providing new pathways for the excavation and future high-value of shell resources, clarifying the existing development stages and bottlenecks, promoting the development of related technology industries, and achieving the synergistic win-win situation of economic and environmental benefits.

Analysis of factors influencing infrared extinction area of explosive smokescreen.

Objectives: Comparative studies of different smokescreen designs are essential to determine differences in extinction performance. This study aims to investigate the extinction performance of explosive smokescreen under different conditions, and to provide an evaluation method for the optimal design of its charge structure. Methods: The process of formation of the smokescreen with a cylindrical charge structure is described based on the smoothed particle hydrodynamics method. The blast radius and particle density distribution of the smokescreen were calculated for different charge structures and charge ratios through simulations. Lambert-Beer's law was combined to obtain the infrared extinction area. An analysis was then conducted to determine the influence of the number of baffles in the charge structure and charge ratio on the extinction performance of the smokescreen. Field tests were conducted to verify the simulation results. Results: Increasing the number of baffles in the projectile structure made the particle distribution of the smokescreen more uniform and resulted in a larger infrared extinction area. An increase in the explosive quantity, made the smokescreen more dispersed. However, too much of the explosives caused the smokescreen to be sparse, reducing the infrared extinction area.

Tunable broadband, wide-angle, and polarization-dependent perfect infrared absorber based on planar structure containing phase-change material.

A multilayer absorber composed of SiO2, Fe, Ge2Sb2Te5 (GST), and Al is designed, and the absorptive properties are theoretically investigated based on the Fresnel coefficients method in the wavelength range of 300-2500 nm by changing the thickness and crystallization rate of GST, the incident angle, and the polarization. The results show that the thin Fe layer plays a key role in obtaining an ultra-broadband perfect absorption. The absorption properties are polarization-dependent, and the perfect absorption can be nearly realized for a p-polarized wave at the incident angle smaller than 75° with the bandwidth larger than 316 nm at 90% of max absorption value. The absorptive peak of this absorber can be tuned with the crystallization rate of GST by temperature, and the peak wavelength moves from 1433 nm in the amorphous phase to 2051 nm in the crystalline phase. This structure can provide a feasible route to design the tunable broadband, wide-angle, and polarization-dependent perfect absorber without lithographic patterns in the infrared band.