Laser-induced breakdown spectroscopy(LIBS)has become a widely used atomic spectroscopic technique for rapid coal analysis.However,the vast amount of spectral information in LIBS contains signal uncertainty,which can a...Laser-induced breakdown spectroscopy(LIBS)has become a widely used atomic spectroscopic technique for rapid coal analysis.However,the vast amount of spectral information in LIBS contains signal uncertainty,which can affect its quantification performance.In this work,we propose a hybrid variable selection method to improve the performance of LIBS quantification.Important variables are first identified using Pearson's correlation coefficient,mutual information,least absolute shrinkage and selection operator(LASSO)and random forest,and then filtered and combined with empirical variables related to fingerprint elements of coal ash content.Subsequently,these variables are fed into a partial least squares regression(PLSR).Additionally,in some models,certain variables unrelated to ash content are removed manually to study the impact of variable deselection on model performance.The proposed hybrid strategy was tested on three LIBS datasets for quantitative analysis of coal ash content and compared with the corresponding data-driven baseline method.It is significantly better than the variable selection only method based on empirical knowledge and in most cases outperforms the baseline method.The results showed that on all three datasets the hybrid strategy for variable selection combining empirical knowledge and data-driven algorithms achieved the lowest root mean square error of prediction(RMSEP)values of 1.605,3.478 and 1.647,respectively,which were significantly lower than those obtained from multiple linear regression using only 12 empirical variables,which are 1.959,3.718 and 2.181,respectively.The LASSO-PLSR model with empirical support and 20 selected variables exhibited a significantly improved performance after variable deselection,with RMSEP values dropping from 1.635,3.962 and 1.647 to 1.483,3.086 and 1.567,respectively.Such results demonstrate that using empirical knowledge as a support for datadriven variable selection can be a viable approach to improve the accuracy and reliability of LIBS quantification.展开更多
Copper-based azide(Cu(N_(3))2 or CuN_(3),CA)chips synthesized by in-situ azide reaction and utilized in miniaturized explosive systems has become a hot research topic in recent years.However,the advantages of in-situ ...Copper-based azide(Cu(N_(3))2 or CuN_(3),CA)chips synthesized by in-situ azide reaction and utilized in miniaturized explosive systems has become a hot research topic in recent years.However,the advantages of in-situ synthesis method,including small size and low dosage,bring about difficulties in quantitative analysis and differences in ignition capabilities of CA chips.The aim of present work is to develop a simplified quantitative analysis method for accurate and safe analysis of components in CA chips to evaluate and investigate the corresponding ignition ability.In this work,Cu(N_(3))2 and CuN_(3)components in CA chips were separated through dissolution and distillation by utilizing the difference in solubility and corresponding content was obtained by measuring N_(3)-concentration through spectrophotometry.The spectrophotometry method was optimized by studying influencing factors and the recovery rate of different separation methods was studied,ensuring the accuracy and reproducibility of test results.The optimized method is linear in range from 1.0-25.0 mg/L,with a correlation coefficient R^(2)=0.9998,which meets the requirements of CA chips with a milligram-level content test.Compared with the existing ICP method,component analysis results of CA chips obtained by spectrophotometry are closer to real component content in samples and have satisfactory accuracy.Moreover,as its application in miniaturized explosive systems,the ignition ability of CA chips with different component contents for direct ink writing CL-20 and the corresponding mechanism was studied.This study provided a basis and idea for the design and performance evaluation of CA chips in miniaturized explosive systems.展开更多
The stable sub-angstrom resolution of the aberration-corrected scanning transmission electron microscope(ACSTEM)makes it an advanced and practical characterization technique for all materials.Owing to the prosperous a...The stable sub-angstrom resolution of the aberration-corrected scanning transmission electron microscope(ACSTEM)makes it an advanced and practical characterization technique for all materials.Owing to the prosperous advancement in computational technology,specialized software and programs have emerged as potent facilitators across the entirety of electron microscopy characterization process.Utilizing advanced image processing algorithms promotes the rectification of image distortions,concurrently elevating the overall image quality to superior standards.Extracting high-resolution,pixel-level discrete information and converting it into atomic-scale,followed by performing statistical calculations on the physical matters of interest through quantitative analysis,represent an effective strategy to maximize the value of electron microscope images.The efficacious utilization of quantitative analysis of electron microscope images has become a progressively prominent consideration for materials scientists and electron microscopy researchers.This article offers a concise overview of the pivotal procedures in quantitative analysis and summarizes the computational methodologies involved from three perspectives:contrast,lattice and strain,as well as atomic displacements and polarization.It further elaborates on practical applications of these methods in electronic functional materials,notably in piezoelectrics/ferroelectrics and thermoelectrics.It emphasizes the indispensable role of quantitative analysis in fundamental theoretical research,elucidating the structure–property correlations in high-performance systems,and guiding synthesis strategies.展开更多
This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to ach...This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to achieve synchronous,rapid,and accurate measurement of elements in a large number of samples,namely,SC-assisted CF-LIBS.Al alloy standard samples,divided into calibration and test samples,were applied to validate the proposed method.SC was built based on the characteristic line of Pb and Cr in the calibration sample,and the contents of Pb and Cr in the test sample were calculated with relative errors of 6%and 4%,respectively.SC built using Cr with multiple characteristic lines yielded better calculation results.The relative contents of ten elements in the test sample were calculated using CF-LIBS.Subsequently,the SC-assisted CF-LIBS was executed,with the majority of the calculation relative errors falling within the range of 2%-5%.Finally,the Al and Na contents of the Al alloy were predicted.The results demonstrate that it effectively enables the rapid and accurate quantitative analysis of multiple elements after a single-element SC analysis of the tested samples.Furthermore,this quantitative analysis method was successfully applied to soil and Astragalus samples,realizing an accurate calculation of the contents of multiple elements.Thus,it is important to advance the LIBS quantitative analysis and its related applications.展开更多
To obtain more stable spectral data for accurate quantitative analysis of multi-element,especially for the large-area in-situ elements detection of soils, we propose a method for a multielement quantitative analysis o...To obtain more stable spectral data for accurate quantitative analysis of multi-element,especially for the large-area in-situ elements detection of soils, we propose a method for a multielement quantitative analysis of soils using calibration-free laser-induced breakdown spectroscopy(CF-LIBS) based on data filtering. In this study, we analyze a standard soil sample doped with two heavy metal elements, Cu and Cd, with a specific focus on the line of Cu I324.75 nm for filtering the experimental data of multiple sample sets. Pre-and post-data filtering,the relative standard deviation for Cu decreased from 30% to 10%, The limits of detection(LOD)values for Cu and Cd decreased by 5% and 4%, respectively. Through CF-LIBS, a quantitative analysis was conducted to determine the relative content of elements in soils. Using Cu as a reference, the concentration of Cd was accurately calculated. The results show that post-data filtering, the average relative error of the Cd decreases from 11% to 5%, indicating the effectiveness of data filtering in improving the accuracy of quantitative analysis. Moreover, the content of Si, Fe and other elements can be accurately calculated using this method. To further correct the calculation, the results for Cd was used to provide a more precise calculation. This approach is of great importance for the large-area in-situ heavy metals and trace elements detection in soil, as well as for rapid and accurate quantitative analysis.展开更多
In the spectral analysis of laser-induced breakdown spectroscopy,abundant characteristic spectral lines and severe interference information exist simultaneously in the original spectral data.Here,a feature selection m...In the spectral analysis of laser-induced breakdown spectroscopy,abundant characteristic spectral lines and severe interference information exist simultaneously in the original spectral data.Here,a feature selection method called recursive feature elimination based on ridge regression(Ridge-RFE)for the original spectral data is recommended to make full use of the valid information of spectra.In the Ridge-RFE method,the absolute value of the ridge regression coefficient was used as a criterion to screen spectral characteristic,the feature with the absolute value of minimum weight in the input subset features was removed by recursive feature elimination(RFE),and the selected features were used as inputs of the partial least squares regression(PLS)model.The Ridge-RFE method based PLS model was used to measure the Fe,Si,Mg,Cu,Zn and Mn for 51 aluminum alloy samples,and the results showed that the root mean square error of prediction decreased greatly compared to the PLS model with full spectrum as input.The overall results demonstrate that the Ridge-RFE method is more efficient to extract the redundant features,make PLS model for better quantitative analysis results and improve model generalization ability.展开更多
Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reactions.In this work,we present a laser-induced breakdown spectroscopy(LIBS)-based method to monitor the gas compositions fro...Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reactions.In this work,we present a laser-induced breakdown spectroscopy(LIBS)-based method to monitor the gas compositions from the exhaust system in the tokamak device.Helium(He),a main impurity in the exhaust gas,was mixed with hydrogen(H_(2))in different ratios through a self-designed gas distribution system,and sealed into a measurement chamber as a standard specimen.A 532 nm wavelength laser pulse with an output power of 100 mJ was used for plasma excitation.The time-resolved LIBS is used to study the time evolution characteristics of the signal strength,signal-to-background ratio(SBR),signal-to-noise ratio(SNR)and relative standard deviation(RSD)of the helium and hydrogen characteristic lines.The Boltzmann twoline method was employed to estimate the plasma temperature of laser-induced plasma(LIP).The Stark-broadened profile of He I 587.56 nm was exploited to measure the electron density.From these studies,an appropriate time was determined in which the low RSD%was consistent with the high signal-to-noise ratio.The He I 587.56 nm and Hαemission lines with good signalto-noise ratio were extracted from the spectrum and used in the external standard method and internal standard method for quantitative analysis.The test results for mixed gas showed that the average relative error of prediction was less than 11.15%,demonstrating the great potential of LIBS in detecting impurities in plasma exhaust gas.展开更多
An efficient and environment-friendly method for simultaneous determination of 13 typical derivatives of polycyclic aromatic hydrocarbon(PAH)in petroleum-polluted soil with nitro-,oxy-and alkylfunctional group was dev...An efficient and environment-friendly method for simultaneous determination of 13 typical derivatives of polycyclic aromatic hydrocarbon(PAH)in petroleum-polluted soil with nitro-,oxy-and alkylfunctional group was developed using supercritical fluid extraction(SFE)followed by ultra-high performance supercritical fluid chromatography(UHPSFC).Parameters of UHPSFC,including type of stationary phase and mobile phase modifiers,gradient elution process,backpressure,column temperature,and the flow rate of mobile phase,were systematically optimized,achieving a fast separation within4.2 min.Limits of detection(LOD)were 0.005-0.1μg mL^(-1)or 0.1-2.0 ng g^(-1),respectively,with a good repeatability(RSD<5.0%).Before UHPSFC-PDA analysis,the PAH-derivatives in soil samples were effectively enriched in 15.0 min using SFE with an online carbon nanotubes(CNTs)collection trap.The soil samples were analyzed by the proposed method and the results were verified by GC-MS.Thus,SFE equipped with an online CNTs trap followed by UHPSFC-PDA analysis,which only consumed about2.0 mL organic solvent for a whole run,has been demonstrated to be an efficient way for screening and quantitative analysis of trace-level PAH-derivatives in soil samples.展开更多
Abstract Heavy metals in water can be deposited on graphite flakes, which can be used as an enrichment method for laser-induced breakdown spectroscopy （LIBS） and is studied in this paper. The graphite samples were p...Abstract Heavy metals in water can be deposited on graphite flakes, which can be used as an enrichment method for laser-induced breakdown spectroscopy （LIBS） and is studied in this paper. The graphite samples were prepared with an automatic device, which was composed of a loading and unloading module, a quantitatively adding solution module, a rapid heating and drying module and a precise rotating module. The experimental results showed that the sample preparation methods had no significant effect on sample distribution and the LIBS signal accumulated in 20 pulses was stable and repeatable. With an increasing amount of the sample solution on the graphite flake, the peak intensity at Cu I 324.75 nm accorded with the exponential function with a correlation coefficient of 0.9963 and the background intensity remained unchanged. The limit of detection （LOD） was calculated through linear fitting of the peak intensity versus the concentration. The LOD decreased rapidly with an increasing amount of sample solution until the amount exceeded 20 mL and the correlation coefficient of exponential function fitting was 0.991. The LOD of Pb, Ni, Cd, Cr and Zn after evaporating different amounts of sample solution on the graphite flakes was measured and the variation tendency of their LOD with sample solution amounts was similar to the tendency for Cu. The experimental data and conclusions could provide a reference for automatic sample preparation and heavy metal in situ detection.展开更多
Broken gangue has been extensively used in rockfill dams,subgrade,embankment,foundation cushion and other engineering construction.The deformation characteristics of broken gangue under the bearing compression play a ...Broken gangue has been extensively used in rockfill dams,subgrade,embankment,foundation cushion and other engineering construction.The deformation characteristics of broken gangue under the bearing compression play a decisive role in the firmness,stability and safety of these structures(buildings),and the meso-fabric change of broken gangue under the bearing compression significantly affects its macro deformation.In this study,the transparent characterization and quantitative analysis of 3D fabric of broken gangue under the bearing compression were performed through CT scanning test,image processing and 3D reconstruction technology,and the influence mechanism of internal fabric of broken gangue on its macro deformation was revealed.The results show that:In the loading stage of 0–2 MPa,the sharp corners,thin edges on the blocks and the bar-shaped and blade-shaped blocks with poor regularity are broken first under the bearing compression;in the loading stage of 2–8 MPa,a large number of larger particles in the sample are crushed in the mode of fragmentation;in the loading stage of 8–10 MPa,the breakage degree of samples is relieved.The axial displacement of the block inside the sample occurs,as well as the lateral displacement of the block converging to the central axis of the sample.In the rapid deformation stage,the macro deformation of the broken gangue is mainly caused by the rearrangement and adjustment of the block structure and the breakage of the block;in the slow deformation stage,it is mainly caused by the breakage of the block;in the stable deformation stage,it is mainly caused by the optimization and adjustment of the bearing skeleton in the sample.展开更多
Laser-induced breakdown spectroscopy(LIBS)has been applied to many fields for the quantitative analysis of diverse materials.Improving the prediction accuracy of LIBS regression models is still of great significance f...Laser-induced breakdown spectroscopy(LIBS)has been applied to many fields for the quantitative analysis of diverse materials.Improving the prediction accuracy of LIBS regression models is still of great significance for the Mars exploration in the near future.In this study,we explored the quantitative analysis of LIBS for the one-dimensional Chem Cam(an instrument containing a LIBS spectrometer and a Remote Micro-Imager)spectral data whose spectra are produced by the Chem Cam team using LIBS under the Mars-like atmospheric conditions.We constructed a convolutional neural network(CNN)regression model with unified parameters for all oxides,which is efficient and concise.CNN that has the excellent capability of feature extraction can effectively overcome the chemical matrix effects that impede the prediction accuracy of regression models.Firstly,we explored the effects of four activation functions on the performance of the CNN model.The results show that the CNN model with the hyperbolic tangent(tanh)function outperforms the CNN models with the other activation functions(the rectified linear unit function,the linear function and the Sigmoid function).Secondly,we compared the performance among the CNN models using different optimization methods.The CNN model with the stochastic gradient descent optimization and the initial learning rate?=?0.0005 achieves satisfactory performance compared to the other CNN models.Finally,we compared the performance of the CNN model,the model based on support vector regression(SVR)and the model based on partial least square regression(PLSR).The results exhibit the CNN model is superior to the SVR model and the PLSR model for all oxides.Based on the above analysis,we conclude the CNN regression model can effectively improve the prediction accuracy of LIBS.展开更多
pH is one of the significant properties of soil,and is closely related to the decomposition of soil organic matter,anion-cation balance,growth of plants and many other soil processes.In the present work,laser-induced ...pH is one of the significant properties of soil,and is closely related to the decomposition of soil organic matter,anion-cation balance,growth of plants and many other soil processes.In the present work,laser-induced breakdown spectroscopy(LIBS) technique coupled with random forest(RF) was proposed to quantify the pH of soil.First,LIBS spectra of soil was collected,and some common elements in soil were identified based on the National Institute of Science and Technology database.Then,in order to obtain a better predictive result,the influence of different input variables(full spectrum,different spectral ranges,the intensity of characteristic bands and characteristic lines) on the predictive performance of RF calibration model was explored with the evaluation indicators of root mean square error(RMSE) and coefficient of determination(R2),the characteristic bands of four elements(AI,Ca,Mg and Si) were determined as the optimal input variables.Finally,the predictive performance of RF calibration model was compared with partial least squares calibration model with the optimal input variables and model parameters,and RF calibration model showed a better predictive performance,and the four evaluation indicators of R_p^2,RMSEP,mean absolute error and mean relative error were 0.9687,0.1285,0.1114 and 0.0136,respectively.It indicates that LIBS technique coupled with RF algorithm is an effective method for pH determination of soil.展开更多
Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperforma...Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.展开更多
Laser-induced breakdown spectroscopy(LIBS)is a capable technique for elementary analysis,while LIBS quantitation is still under development.In quantitation,precise laser focusing plays an important role because it ens...Laser-induced breakdown spectroscopy(LIBS)is a capable technique for elementary analysis,while LIBS quantitation is still under development.In quantitation,precise laser focusing plays an important role because it ensures the distance between the laser and samples.In the present work,we employed spectral intensity as a direct way to assist laser focusing in LIBS quantitation for copper alloys.It is found that both the air emission and the copper line could be used to determine the position of the sample surface by referencing the intensity maximum.Nevertheless,the fine quantitation was only realized at the position where the air emission(e.g.O(I)777.4 nm)reached intensity maximum,and also in this way,a repeatable quantitation was successfully achieved even after 120 days.The results suggested that the LIBS quantitation was highly dependent on the focusing position of the laser,and spectra-assisted focusing could be a simple way to find the identical condition for different samples’detection.In the future,this method might be applicable in field measurements for LIBS analysis of solids.展开更多
Contact force in a clearance joint affects the dynamic characteristics and leads to nonlinear response of the mechanism.It is necessary to assess the nonlinearity of contact force quantitatively.Therefore,a new method...Contact force in a clearance joint affects the dynamic characteristics and leads to nonlinear response of the mechanism.It is necessary to assess the nonlinearity of contact force quantitatively.Therefore,a new method named contact-force entropy weight is proposed in this paper.This method presents a comprehensive description of the judgment matrix in the X,Y,and Z directions.To assess the influence degrees of different clearances and angular velocities on the contact force,the method is applied to numerical calculation and simulation of a six-bar mechanism with a clearance joint to illustrate its application and investigate the influence degree of angular velocity and clearance on the contact force.By combining the simulation results and theoretical calculations,the influence degrees of different clearances and angular velocities on the contact-force entropy weight of the six-bar mechanism with a clearance joint are revealed.It is found that the angular velocity has a significant influence on the contact force entropy weight of the clearance joint,showing that the contact-force entropy weight is a feasible new method of assessing non-linearity of contact force quantitatively.The method gives a theoretical reference for quantitatively analyzing the nonlinear dynamics.展开更多
The concentrations of SiO,Al2O,KO,NaO,CaO,MgO,Fe2Oand TiO,and loss on ignition(L.O.I.) are the main inorganic components of geological samples.Concentrations of the eight oxides and L.O.I.are also the main indicators ...The concentrations of SiO,Al2O,KO,NaO,CaO,MgO,Fe2Oand TiO,and loss on ignition(L.O.I.) are the main inorganic components of geological samples.Concentrations of the eight oxides and L.O.I.are also the main indicators of concern in the production of building ceramics.Quantitative analysis of the eight oxides and L.O.I.was performed using fiber-laserbased laser-induced breakdown spectroscopy(LIBS).A combination of continuous background deduction,full width at half maximum(FWHM) intensity integral and spectral sum normalization was proposed for data processing.After the data processing combined the continuous background deduction,FWHM intensity integral and spectral sum normalization,the mean absolute errors(MAEs) of the calibration of L.O.I.,SiO,Al2O,KO,NaO,CaO,MgO,Fe2Oand TiOwas reduced from 2.03%,12.06%,4.84%,1.10%,0.69%,0.31%,0.11%,0.20%and 0.10% to 1.80%,9.48%,2.12%,0.36%,0.58%,0.11%,0.08%,0.19% and 0.05%,respectively.This multivariate method was further introduced and discussed to improve the analysis performance.The MAEs of L.O.I.,SiO,Al2O,KO and NaO were further reduced to1.12%,2.07%,1.38%,0.35% and 0.43%,respectively.The results show that the overall prediction error can meet the requirements for the production of building ceramics.The LIBS desktop analyzer has great potential in detection applications on geological samples.展开更多
In order to maintain the pipeline better and remove the dirt more effectively, it was necessary to analyze the contents of elements in dirt. Mg in soil outside of the pipe and the dirt inside of the pipe was quantitat...In order to maintain the pipeline better and remove the dirt more effectively, it was necessary to analyze the contents of elements in dirt. Mg in soil outside of the pipe and the dirt inside of the pipe was quantitatively analyzed and compared by using the laser-induced breakdown spectroscopy （LIBS）. Firstly, Mg was quantitatively analyzed on the basis of Mg I 285.213 nm by calibration curve for integrated intensity and peak intensity of the spectrum before and after subtracting noise, respectively. Then calibration curves on the basis of Mg II 279.553 nm and Mg II 280.270 nm were analyzed. The results indicated that it is better to use integrated intensity after subtracting noise of the spectrum line with high relative intensity to make the calibration curve.展开更多
Access to any development is a connection between the buildings and urban roadways. The impact of access on urban roads varies with location of the access. This paper studies the impact of access to large buildings on...Access to any development is a connection between the buildings and urban roadways. The impact of access on urban roads varies with location of the access. This paper studies the impact of access to large buildings on the surrounding road network by exploring traffic conflicts based on the configuration of the access. The concept of conflict intensity is introduced in this study as a new evaluation indicator to evaluate the traffic conflict triggered by the presence of access. The results show that the greater the speed,the greater the conflict intensity of access. Meanwhile,a similar situation exists when other variables （e.g.,conflict angle or the number of conflicts） change. The larger the conflict intensity,the more dangerous the access. Results from this study can help developers and traffic engineers choose suitable locations of access and organize the traffic in a logical manner.展开更多
The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical,thermal,and mechanical fields in applications.Characterizing and quantifying the multi-field coup...The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical,thermal,and mechanical fields in applications.Characterizing and quantifying the multi-field coupling behaviors requires interdisciplinary efforts.Here,we design experiments under mechanical constraints and introduce an in-situ analytical framework to clarify the complex interaction mechanisms and coupling degrees among multi-physics fields.The proposed analytical framework integrates the parameterization of equivalent models,in-situ mechanical analysis,and quantitative assessment of coupling behavior.The results indicate that the significant impact of pressure on impedance at low temperatures results from the diffusion-controlled step,enhancing kinetics when external pressure,like 180 to 240 k Pa at 10℃,is applied.The diversity in control steps for the electrochemical reaction accounts for the varying impact of pressure on battery performance across different temperatures.The thermal expansion rate suggests that the swelling force varies by less than 1.60%per unit of elevated temperature during the lithiation process.By introducing a composite metric,we quantify the coupling correlation and intensity between characteristic parameters and physical fields,uncovering the highest coupling degree in electrochemical-thermal fields.These results underscore the potential of analytical approaches in revealing the mechanisms of interaction among multi-fields,with the goal of enhancing battery performance and advancing battery management.展开更多
Optimization and simplification of optical systems represent a milestone in advancing the development of handheld and portable laser-induced breakdown spectroscopy(LIBS)systems towards smaller,more integrated forms.Th...Optimization and simplification of optical systems represent a milestone in advancing the development of handheld and portable laser-induced breakdown spectroscopy(LIBS)systems towards smaller,more integrated forms.This research,for the first time,conducted a comprehensive optimization design and comparative analysis of three compact LIBS system optical paths:the paraxial optical path(OP),the off-axis OP,and the reflective OP.The differences in spectral intensity and stability among these paths were revealed,providing a scientific basis for selecting the optimal OP for LIBS systems.The research found that the paraxial OP excels in spectral performance and quantitative analysis accuracy,making it the preferred choice for compact LIBS systems.Specifically,the paraxial OP significantly enhances spectral intensity,achieving a 6 times improvement over the off-axis OP and an even more remarkable 150 times increase compared to the reflective OP,greatly enhancing detection sensitivity.Additionally,the relative standard deviation,spectral stability index,maintains a consistently low level,ranging from 10.9%to 13.4%,significantly outperforming the other two OPs and ensuring the reliability of analytical results.In the field of quantitative analysis,the paraxial OP also demonstrates higher accuracy,precision,and sensitivity,comparing to other OPs.The quantitative analysis models for Si,Cu,and Ti elements exhibit excellent fitting,providing users with high-quality quantitative analysis results that are of great significance for applications in material science,environmental monitoring,industrial inspection,and other fields.In summary,this study not only confirms the enormous application potential of the paraxial OP in compact LIBS systems but also provides valuable practical experience and theoretical support for the miniaturization and integration of LIBS systems.Looking ahead,with continuous technological advancements,the design of the paraxial OP is expected to further propel the widespread adoption of LIBS technology in portable,on-site detection applications.展开更多
基金financial supports from National Natural Science Foundation of China(No.62205172)Huaneng Group Science and Technology Research Project(No.HNKJ22-H105)Tsinghua University Initiative Scientific Research Program and the International Joint Mission on Climate Change and Carbon Neutrality。
文摘Laser-induced breakdown spectroscopy(LIBS)has become a widely used atomic spectroscopic technique for rapid coal analysis.However,the vast amount of spectral information in LIBS contains signal uncertainty,which can affect its quantification performance.In this work,we propose a hybrid variable selection method to improve the performance of LIBS quantification.Important variables are first identified using Pearson's correlation coefficient,mutual information,least absolute shrinkage and selection operator(LASSO)and random forest,and then filtered and combined with empirical variables related to fingerprint elements of coal ash content.Subsequently,these variables are fed into a partial least squares regression(PLSR).Additionally,in some models,certain variables unrelated to ash content are removed manually to study the impact of variable deselection on model performance.The proposed hybrid strategy was tested on three LIBS datasets for quantitative analysis of coal ash content and compared with the corresponding data-driven baseline method.It is significantly better than the variable selection only method based on empirical knowledge and in most cases outperforms the baseline method.The results showed that on all three datasets the hybrid strategy for variable selection combining empirical knowledge and data-driven algorithms achieved the lowest root mean square error of prediction(RMSEP)values of 1.605,3.478 and 1.647,respectively,which were significantly lower than those obtained from multiple linear regression using only 12 empirical variables,which are 1.959,3.718 and 2.181,respectively.The LASSO-PLSR model with empirical support and 20 selected variables exhibited a significantly improved performance after variable deselection,with RMSEP values dropping from 1.635,3.962 and 1.647 to 1.483,3.086 and 1.567,respectively.Such results demonstrate that using empirical knowledge as a support for datadriven variable selection can be a viable approach to improve the accuracy and reliability of LIBS quantification.
基金the financial support provided by the National Natural Science Foundation of China(Grant No.11872013).
文摘Copper-based azide(Cu(N_(3))2 or CuN_(3),CA)chips synthesized by in-situ azide reaction and utilized in miniaturized explosive systems has become a hot research topic in recent years.However,the advantages of in-situ synthesis method,including small size and low dosage,bring about difficulties in quantitative analysis and differences in ignition capabilities of CA chips.The aim of present work is to develop a simplified quantitative analysis method for accurate and safe analysis of components in CA chips to evaluate and investigate the corresponding ignition ability.In this work,Cu(N_(3))2 and CuN_(3)components in CA chips were separated through dissolution and distillation by utilizing the difference in solubility and corresponding content was obtained by measuring N_(3)-concentration through spectrophotometry.The spectrophotometry method was optimized by studying influencing factors and the recovery rate of different separation methods was studied,ensuring the accuracy and reproducibility of test results.The optimized method is linear in range from 1.0-25.0 mg/L,with a correlation coefficient R^(2)=0.9998,which meets the requirements of CA chips with a milligram-level content test.Compared with the existing ICP method,component analysis results of CA chips obtained by spectrophotometry are closer to real component content in samples and have satisfactory accuracy.Moreover,as its application in miniaturized explosive systems,the ignition ability of CA chips with different component contents for direct ink writing CL-20 and the corresponding mechanism was studied.This study provided a basis and idea for the design and performance evaluation of CA chips in miniaturized explosive systems.
基金Project supported by the financial support from the National Key R&D Program of China(Grant No.2021YFB3201100)the National Natural Science Foundation of China(Grant No.52172128)the Top Young Talents Programme of Xi’an Jiaotong University.
文摘The stable sub-angstrom resolution of the aberration-corrected scanning transmission electron microscope(ACSTEM)makes it an advanced and practical characterization technique for all materials.Owing to the prosperous advancement in computational technology,specialized software and programs have emerged as potent facilitators across the entirety of electron microscopy characterization process.Utilizing advanced image processing algorithms promotes the rectification of image distortions,concurrently elevating the overall image quality to superior standards.Extracting high-resolution,pixel-level discrete information and converting it into atomic-scale,followed by performing statistical calculations on the physical matters of interest through quantitative analysis,represent an effective strategy to maximize the value of electron microscope images.The efficacious utilization of quantitative analysis of electron microscope images has become a progressively prominent consideration for materials scientists and electron microscopy researchers.This article offers a concise overview of the pivotal procedures in quantitative analysis and summarizes the computational methodologies involved from three perspectives:contrast,lattice and strain,as well as atomic displacements and polarization.It further elaborates on practical applications of these methods in electronic functional materials,notably in piezoelectrics/ferroelectrics and thermoelectrics.It emphasizes the indispensable role of quantitative analysis in fundamental theoretical research,elucidating the structure–property correlations in high-performance systems,and guiding synthesis strategies.
基金supported by the Major Science and TechnologyTechnol-ogy Projects in Gansu Province(No.22ZD6FA021-5)Industrial Support Project of Gansu Province(Nos.2023CYZC-19 and 2021CYZC-22)+1 种基金Science and Technol-ogy Project of Gansu Province(Nos.23YFFA0074,22JR5RA137,and 22JR5RA151)Central Leading Local Science and Technology Development Fund Projects(No.23ZYQA293).
文摘This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to achieve synchronous,rapid,and accurate measurement of elements in a large number of samples,namely,SC-assisted CF-LIBS.Al alloy standard samples,divided into calibration and test samples,were applied to validate the proposed method.SC was built based on the characteristic line of Pb and Cr in the calibration sample,and the contents of Pb and Cr in the test sample were calculated with relative errors of 6%and 4%,respectively.SC built using Cr with multiple characteristic lines yielded better calculation results.The relative contents of ten elements in the test sample were calculated using CF-LIBS.Subsequently,the SC-assisted CF-LIBS was executed,with the majority of the calculation relative errors falling within the range of 2%-5%.Finally,the Al and Na contents of the Al alloy were predicted.The results demonstrate that it effectively enables the rapid and accurate quantitative analysis of multiple elements after a single-element SC analysis of the tested samples.Furthermore,this quantitative analysis method was successfully applied to soil and Astragalus samples,realizing an accurate calculation of the contents of multiple elements.Thus,it is important to advance the LIBS quantitative analysis and its related applications.
基金supported by the Major Science and Technology Project of Gansu Province(No.22ZD6FA021-5)the Industrial Support Project of Gansu Province(Nos.2023CYZC-19 and 2021CYZC-22)the Science and Technology Project of Gansu Province(Nos.23YFFA0074,22JR5RA137 and 22JR5RA151).
文摘To obtain more stable spectral data for accurate quantitative analysis of multi-element,especially for the large-area in-situ elements detection of soils, we propose a method for a multielement quantitative analysis of soils using calibration-free laser-induced breakdown spectroscopy(CF-LIBS) based on data filtering. In this study, we analyze a standard soil sample doped with two heavy metal elements, Cu and Cd, with a specific focus on the line of Cu I324.75 nm for filtering the experimental data of multiple sample sets. Pre-and post-data filtering,the relative standard deviation for Cu decreased from 30% to 10%, The limits of detection(LOD)values for Cu and Cd decreased by 5% and 4%, respectively. Through CF-LIBS, a quantitative analysis was conducted to determine the relative content of elements in soils. Using Cu as a reference, the concentration of Cd was accurately calculated. The results show that post-data filtering, the average relative error of the Cd decreases from 11% to 5%, indicating the effectiveness of data filtering in improving the accuracy of quantitative analysis. Moreover, the content of Si, Fe and other elements can be accurately calculated using this method. To further correct the calculation, the results for Cd was used to provide a more precise calculation. This approach is of great importance for the large-area in-situ heavy metals and trace elements detection in soil, as well as for rapid and accurate quantitative analysis.
基金supported by National Key Research and Development Program of China(No.2016YFF0102502)the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-JSC037)the Youth Innovation Promotion Association,CAS,Liao Ning Revitalization Talents Program(No.XLYC1807110)。
文摘In the spectral analysis of laser-induced breakdown spectroscopy,abundant characteristic spectral lines and severe interference information exist simultaneously in the original spectral data.Here,a feature selection method called recursive feature elimination based on ridge regression(Ridge-RFE)for the original spectral data is recommended to make full use of the valid information of spectra.In the Ridge-RFE method,the absolute value of the ridge regression coefficient was used as a criterion to screen spectral characteristic,the feature with the absolute value of minimum weight in the input subset features was removed by recursive feature elimination(RFE),and the selected features were used as inputs of the partial least squares regression(PLS)model.The Ridge-RFE method based PLS model was used to measure the Fe,Si,Mg,Cu,Zn and Mn for 51 aluminum alloy samples,and the results showed that the root mean square error of prediction decreased greatly compared to the PLS model with full spectrum as input.The overall results demonstrate that the Ridge-RFE method is more efficient to extract the redundant features,make PLS model for better quantitative analysis results and improve model generalization ability.
基金supported by the National Key R&D Program of China(Nos.2017YFE0301506 and 2017YFE0301306)。
文摘Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reactions.In this work,we present a laser-induced breakdown spectroscopy(LIBS)-based method to monitor the gas compositions from the exhaust system in the tokamak device.Helium(He),a main impurity in the exhaust gas,was mixed with hydrogen(H_(2))in different ratios through a self-designed gas distribution system,and sealed into a measurement chamber as a standard specimen.A 532 nm wavelength laser pulse with an output power of 100 mJ was used for plasma excitation.The time-resolved LIBS is used to study the time evolution characteristics of the signal strength,signal-to-background ratio(SBR),signal-to-noise ratio(SNR)and relative standard deviation(RSD)of the helium and hydrogen characteristic lines.The Boltzmann twoline method was employed to estimate the plasma temperature of laser-induced plasma(LIP).The Stark-broadened profile of He I 587.56 nm was exploited to measure the electron density.From these studies,an appropriate time was determined in which the low RSD%was consistent with the high signal-to-noise ratio.The He I 587.56 nm and Hαemission lines with good signalto-noise ratio were extracted from the spectrum and used in the external standard method and internal standard method for quantitative analysis.The test results for mixed gas showed that the average relative error of prediction was less than 11.15%,demonstrating the great potential of LIBS in detecting impurities in plasma exhaust gas.
基金financially supported by the National Natural Science Foundation of China(No.21874153)Science Foundation of China University of Petroleum,Beijing(No.2462017BJB09)PetroChina Innovation Foundation(No.2016D-5007-0402)。
文摘An efficient and environment-friendly method for simultaneous determination of 13 typical derivatives of polycyclic aromatic hydrocarbon(PAH)in petroleum-polluted soil with nitro-,oxy-and alkylfunctional group was developed using supercritical fluid extraction(SFE)followed by ultra-high performance supercritical fluid chromatography(UHPSFC).Parameters of UHPSFC,including type of stationary phase and mobile phase modifiers,gradient elution process,backpressure,column temperature,and the flow rate of mobile phase,were systematically optimized,achieving a fast separation within4.2 min.Limits of detection(LOD)were 0.005-0.1μg mL^(-1)or 0.1-2.0 ng g^(-1),respectively,with a good repeatability(RSD<5.0%).Before UHPSFC-PDA analysis,the PAH-derivatives in soil samples were effectively enriched in 15.0 min using SFE with an online carbon nanotubes(CNTs)collection trap.The soil samples were analyzed by the proposed method and the results were verified by GC-MS.Thus,SFE equipped with an online CNTs trap followed by UHPSFC-PDA analysis,which only consumed about2.0 mL organic solvent for a whole run,has been demonstrated to be an efficient way for screening and quantitative analysis of trace-level PAH-derivatives in soil samples.
基金supported by National Natural Science Foundation of China(No.60908018)National High Technology Research and Development Program of China(No.2013AA065502)Anhui Province Outstanding Youth Science Fund of China(No.1108085J19)
文摘Abstract Heavy metals in water can be deposited on graphite flakes, which can be used as an enrichment method for laser-induced breakdown spectroscopy （LIBS） and is studied in this paper. The graphite samples were prepared with an automatic device, which was composed of a loading and unloading module, a quantitatively adding solution module, a rapid heating and drying module and a precise rotating module. The experimental results showed that the sample preparation methods had no significant effect on sample distribution and the LIBS signal accumulated in 20 pulses was stable and repeatable. With an increasing amount of the sample solution on the graphite flake, the peak intensity at Cu I 324.75 nm accorded with the exponential function with a correlation coefficient of 0.9963 and the background intensity remained unchanged. The limit of detection （LOD） was calculated through linear fitting of the peak intensity versus the concentration. The LOD decreased rapidly with an increasing amount of sample solution until the amount exceeded 20 mL and the correlation coefficient of exponential function fitting was 0.991. The LOD of Pb, Ni, Cd, Cr and Zn after evaporating different amounts of sample solution on the graphite flakes was measured and the variation tendency of their LOD with sample solution amounts was similar to the tendency for Cu. The experimental data and conclusions could provide a reference for automatic sample preparation and heavy metal in situ detection.
基金supported by the National Natural Science Foundation of China(Nos.52104103,52022107,52174128)the Natural Science Foundation of Jiangsu Province(Nos.BK20210499,BK20190031)。
文摘Broken gangue has been extensively used in rockfill dams,subgrade,embankment,foundation cushion and other engineering construction.The deformation characteristics of broken gangue under the bearing compression play a decisive role in the firmness,stability and safety of these structures(buildings),and the meso-fabric change of broken gangue under the bearing compression significantly affects its macro deformation.In this study,the transparent characterization and quantitative analysis of 3D fabric of broken gangue under the bearing compression were performed through CT scanning test,image processing and 3D reconstruction technology,and the influence mechanism of internal fabric of broken gangue on its macro deformation was revealed.The results show that:In the loading stage of 0–2 MPa,the sharp corners,thin edges on the blocks and the bar-shaped and blade-shaped blocks with poor regularity are broken first under the bearing compression;in the loading stage of 2–8 MPa,a large number of larger particles in the sample are crushed in the mode of fragmentation;in the loading stage of 8–10 MPa,the breakage degree of samples is relieved.The axial displacement of the block inside the sample occurs,as well as the lateral displacement of the block converging to the central axis of the sample.In the rapid deformation stage,the macro deformation of the broken gangue is mainly caused by the rearrangement and adjustment of the block structure and the breakage of the block;in the slow deformation stage,it is mainly caused by the breakage of the block;in the stable deformation stage,it is mainly caused by the optimization and adjustment of the bearing skeleton in the sample.
基金supported by the Pre-research project on Civil Aerospace Technologies(No.D020102)funded by China National Space Administration(CNSA)the funding from National Natural Science Foundation of China(Nos.U1931211,41573056)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2019MD008)the Major Research Project of Shandong Province(No.GG201809130208)。
文摘Laser-induced breakdown spectroscopy(LIBS)has been applied to many fields for the quantitative analysis of diverse materials.Improving the prediction accuracy of LIBS regression models is still of great significance for the Mars exploration in the near future.In this study,we explored the quantitative analysis of LIBS for the one-dimensional Chem Cam(an instrument containing a LIBS spectrometer and a Remote Micro-Imager)spectral data whose spectra are produced by the Chem Cam team using LIBS under the Mars-like atmospheric conditions.We constructed a convolutional neural network(CNN)regression model with unified parameters for all oxides,which is efficient and concise.CNN that has the excellent capability of feature extraction can effectively overcome the chemical matrix effects that impede the prediction accuracy of regression models.Firstly,we explored the effects of four activation functions on the performance of the CNN model.The results show that the CNN model with the hyperbolic tangent(tanh)function outperforms the CNN models with the other activation functions(the rectified linear unit function,the linear function and the Sigmoid function).Secondly,we compared the performance among the CNN models using different optimization methods.The CNN model with the stochastic gradient descent optimization and the initial learning rate?=?0.0005 achieves satisfactory performance compared to the other CNN models.Finally,we compared the performance of the CNN model,the model based on support vector regression(SVR)and the model based on partial least square regression(PLSR).The results exhibit the CNN model is superior to the SVR model and the PLSR model for all oxides.Based on the above analysis,we conclude the CNN regression model can effectively improve the prediction accuracy of LIBS.
基金support of National Natural Science Foundation of China(Nos.21873076,21675123,21605123,21375105)Natural Science Basic Research Plan in Shaanxi Province of China(No.2018JQ2013)Scientific Research Plan Projects of Shaanxi Education Department(No.17JK0780)。
文摘pH is one of the significant properties of soil,and is closely related to the decomposition of soil organic matter,anion-cation balance,growth of plants and many other soil processes.In the present work,laser-induced breakdown spectroscopy(LIBS) technique coupled with random forest(RF) was proposed to quantify the pH of soil.First,LIBS spectra of soil was collected,and some common elements in soil were identified based on the National Institute of Science and Technology database.Then,in order to obtain a better predictive result,the influence of different input variables(full spectrum,different spectral ranges,the intensity of characteristic bands and characteristic lines) on the predictive performance of RF calibration model was explored with the evaluation indicators of root mean square error(RMSE) and coefficient of determination(R2),the characteristic bands of four elements(AI,Ca,Mg and Si) were determined as the optimal input variables.Finally,the predictive performance of RF calibration model was compared with partial least squares calibration model with the optimal input variables and model parameters,and RF calibration model showed a better predictive performance,and the four evaluation indicators of R_p^2,RMSEP,mean absolute error and mean relative error were 0.9687,0.1285,0.1114 and 0.0136,respectively.It indicates that LIBS technique coupled with RF algorithm is an effective method for pH determination of soil.
基金supported by Beijing Natural Science Foundation(JQ20004)National Key Research and Development Program(2016YFA0202500)Scientific and Technological Key Project of Shanxi Province(20191102003).
文摘Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.
基金financially supported by the Provincial Key Research and Development Program of Shandong,China(No.2019GHZ010)the Natural Science Foundation of Shandong Province(No.ZR2020MF123)+1 种基金National Natural Science Foundation of China(Nos.61975190 and12174359)the Fundamental Research Funds for the Central Universities(No.202161002)。
文摘Laser-induced breakdown spectroscopy(LIBS)is a capable technique for elementary analysis,while LIBS quantitation is still under development.In quantitation,precise laser focusing plays an important role because it ensures the distance between the laser and samples.In the present work,we employed spectral intensity as a direct way to assist laser focusing in LIBS quantitation for copper alloys.It is found that both the air emission and the copper line could be used to determine the position of the sample surface by referencing the intensity maximum.Nevertheless,the fine quantitation was only realized at the position where the air emission(e.g.O(I)777.4 nm)reached intensity maximum,and also in this way,a repeatable quantitation was successfully achieved even after 120 days.The results suggested that the LIBS quantitation was highly dependent on the focusing position of the laser,and spectra-assisted focusing could be a simple way to find the identical condition for different samples’detection.In the future,this method might be applicable in field measurements for LIBS analysis of solids.
基金Project supported by the National Natural Science Foundation of China(Grant No.51875531)。
文摘Contact force in a clearance joint affects the dynamic characteristics and leads to nonlinear response of the mechanism.It is necessary to assess the nonlinearity of contact force quantitatively.Therefore,a new method named contact-force entropy weight is proposed in this paper.This method presents a comprehensive description of the judgment matrix in the X,Y,and Z directions.To assess the influence degrees of different clearances and angular velocities on the contact force,the method is applied to numerical calculation and simulation of a six-bar mechanism with a clearance joint to illustrate its application and investigate the influence degree of angular velocity and clearance on the contact force.By combining the simulation results and theoretical calculations,the influence degrees of different clearances and angular velocities on the contact-force entropy weight of the six-bar mechanism with a clearance joint are revealed.It is found that the angular velocity has a significant influence on the contact force entropy weight of the clearance joint,showing that the contact-force entropy weight is a feasible new method of assessing non-linearity of contact force quantitatively.The method gives a theoretical reference for quantitatively analyzing the nonlinear dynamics.
基金supported by National Natural Science Foundation of China(No.62173321)the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-JSC037)+2 种基金the Science and Technology Service Network Initiative Program,CAS(No.KFJ-STS-QYZD-2021-19-002)the Liaoning Provincial Natural Science Foundation(No.2021-BS-022)the Youth Innovation Promotion Association,CAS。
文摘The concentrations of SiO,Al2O,KO,NaO,CaO,MgO,Fe2Oand TiO,and loss on ignition(L.O.I.) are the main inorganic components of geological samples.Concentrations of the eight oxides and L.O.I.are also the main indicators of concern in the production of building ceramics.Quantitative analysis of the eight oxides and L.O.I.was performed using fiber-laserbased laser-induced breakdown spectroscopy(LIBS).A combination of continuous background deduction,full width at half maximum(FWHM) intensity integral and spectral sum normalization was proposed for data processing.After the data processing combined the continuous background deduction,FWHM intensity integral and spectral sum normalization,the mean absolute errors(MAEs) of the calibration of L.O.I.,SiO,Al2O,KO,NaO,CaO,MgO,Fe2Oand TiOwas reduced from 2.03%,12.06%,4.84%,1.10%,0.69%,0.31%,0.11%,0.20%and 0.10% to 1.80%,9.48%,2.12%,0.36%,0.58%,0.11%,0.08%,0.19% and 0.05%,respectively.This multivariate method was further introduced and discussed to improve the analysis performance.The MAEs of L.O.I.,SiO,Al2O,KO and NaO were further reduced to1.12%,2.07%,1.38%,0.35% and 0.43%,respectively.The results show that the overall prediction error can meet the requirements for the production of building ceramics.The LIBS desktop analyzer has great potential in detection applications on geological samples.
基金supported partly by the Natural Science Foundation of Hubei Province,China(No.2012FFB00105)partly by the Science Research Program of Education Department of Hubei Province,China(No.B2013288)
文摘In order to maintain the pipeline better and remove the dirt more effectively, it was necessary to analyze the contents of elements in dirt. Mg in soil outside of the pipe and the dirt inside of the pipe was quantitatively analyzed and compared by using the laser-induced breakdown spectroscopy （LIBS）. Firstly, Mg was quantitatively analyzed on the basis of Mg I 285.213 nm by calibration curve for integrated intensity and peak intensity of the spectrum before and after subtracting noise, respectively. Then calibration curves on the basis of Mg II 279.553 nm and Mg II 280.270 nm were analyzed. The results indicated that it is better to use integrated intensity after subtracting noise of the spectrum line with high relative intensity to make the calibration curve.
基金The Specialized Research Fund for Key Laboratory of Transportation Engineering of Beijing University of Technology (No.JTP-2009-12)
文摘Access to any development is a connection between the buildings and urban roadways. The impact of access on urban roads varies with location of the access. This paper studies the impact of access to large buildings on the surrounding road network by exploring traffic conflicts based on the configuration of the access. The concept of conflict intensity is introduced in this study as a new evaluation indicator to evaluate the traffic conflict triggered by the presence of access. The results show that the greater the speed,the greater the conflict intensity of access. Meanwhile,a similar situation exists when other variables （e.g.,conflict angle or the number of conflicts） change. The larger the conflict intensity,the more dangerous the access. Results from this study can help developers and traffic engineers choose suitable locations of access and organize the traffic in a logical manner.
基金supported by the National Science Fund for Excellent Youth Scholars of China(52222708)the National Natural Science Foundation of China(51977007)。
文摘The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical,thermal,and mechanical fields in applications.Characterizing and quantifying the multi-field coupling behaviors requires interdisciplinary efforts.Here,we design experiments under mechanical constraints and introduce an in-situ analytical framework to clarify the complex interaction mechanisms and coupling degrees among multi-physics fields.The proposed analytical framework integrates the parameterization of equivalent models,in-situ mechanical analysis,and quantitative assessment of coupling behavior.The results indicate that the significant impact of pressure on impedance at low temperatures results from the diffusion-controlled step,enhancing kinetics when external pressure,like 180 to 240 k Pa at 10℃,is applied.The diversity in control steps for the electrochemical reaction accounts for the varying impact of pressure on battery performance across different temperatures.The thermal expansion rate suggests that the swelling force varies by less than 1.60%per unit of elevated temperature during the lithiation process.By introducing a composite metric,we quantify the coupling correlation and intensity between characteristic parameters and physical fields,uncovering the highest coupling degree in electrochemical-thermal fields.These results underscore the potential of analytical approaches in revealing the mechanisms of interaction among multi-fields,with the goal of enhancing battery performance and advancing battery management.
基金financially supported by National Natural Science Foundation of China (Nos.62305392 and 62305123)Independent Research and Development Project of Naval Engineering University (No.2023504050)the Nursery Plan Project of Navel University of Engineering (2022)。
文摘Optimization and simplification of optical systems represent a milestone in advancing the development of handheld and portable laser-induced breakdown spectroscopy(LIBS)systems towards smaller,more integrated forms.This research,for the first time,conducted a comprehensive optimization design and comparative analysis of three compact LIBS system optical paths:the paraxial optical path(OP),the off-axis OP,and the reflective OP.The differences in spectral intensity and stability among these paths were revealed,providing a scientific basis for selecting the optimal OP for LIBS systems.The research found that the paraxial OP excels in spectral performance and quantitative analysis accuracy,making it the preferred choice for compact LIBS systems.Specifically,the paraxial OP significantly enhances spectral intensity,achieving a 6 times improvement over the off-axis OP and an even more remarkable 150 times increase compared to the reflective OP,greatly enhancing detection sensitivity.Additionally,the relative standard deviation,spectral stability index,maintains a consistently low level,ranging from 10.9%to 13.4%,significantly outperforming the other two OPs and ensuring the reliability of analytical results.In the field of quantitative analysis,the paraxial OP also demonstrates higher accuracy,precision,and sensitivity,comparing to other OPs.The quantitative analysis models for Si,Cu,and Ti elements exhibit excellent fitting,providing users with high-quality quantitative analysis results that are of great significance for applications in material science,environmental monitoring,industrial inspection,and other fields.In summary,this study not only confirms the enormous application potential of the paraxial OP in compact LIBS systems but also provides valuable practical experience and theoretical support for the miniaturization and integration of LIBS systems.Looking ahead,with continuous technological advancements,the design of the paraxial OP is expected to further propel the widespread adoption of LIBS technology in portable,on-site detection applications.
