Researching | GPXYGPFX Volume 43 Issue 3,2023

ZHU Xiang, YUAN Chao-sheng, LIANG Yong-fu, WANG Zheng, LI Hai-ning, HUANGFU Zhan-biao, ZHOU Song, ZHOU Bo, DONG Xing-bang, CHENG Xue-rui, and YANG Kun

At present, ionic liquids’ high production and use costs are limiting their large-scale applications, so how to recycle them has attracted great attention. Crystallization processes are extremely important for developing new recycling technologies for ionic liquids, and cooling rates have important effects on the cryst At present, ionic liquids’ high production and use costs are limiting their large-scale applications, so how to recycle them has attracted great attention. Crystallization processes are extremely important for developing new recycling technologies for ionic liquids, and cooling rates have important effects on the crystallization processes. Based on these, in this paper, polarizing microscopy, small angle X-ray scattering and Raman spectroscopy were employed to research the phase transitions and the structural changes of 1-dodecyl-3-methylimidazolium tetrafluoroborate (［C12mim］［BF4］) from 60 to 0 ℃ at the cooling rates of 30 and 1 ℃·min-1, in order to reveal the effect of cooling rates on the crystallization process and product. POM results show that ［C12mim］［BF4］ experienced the phase transitions from the liquid state to liquid crystal state and then to crystal state Ⅰ during the rapid cooling process, and that ［C12mim］［BF4］ underwent the phase transitions from the liquid state to liquid crystal state and then to crystal state Ⅱ during the slow cooling process. The crystal state Ⅰ consisted of many “ball-like” crystals with large sizes, while the crystal state Ⅱ was composed of a lot of “needle-like” crystals with small sizes. In addition, SAXS results show that ［C12mim］［BF4］ has two crystal structures, including perpendicular and triclinic bilayer phases. Both were found simultaneously in the crystal state Ⅰ, but only the triclinic bilayer phase appeared in the crystal state Ⅱ. Therefore, crystal state Ⅰ is a mixed phase crystal, while crystal state Ⅱ is a single phase crystal. Furthermore, it can be concluded from the Raman results of ［C12mim］［BF4］ that the ［C12mim］+ in the perpendicular bilayer phase is the G conformation, and that the ［C12mim］+ in the triclinic bilayer phase is the A conformation. In conclusion, ［C12mim］［BF4］ underwent the phase transitions from the liquid state to liquid crystal state and then to crystal state Ⅰ at a rapid cooling process, and a mixed phase crystal composed of the perpendicular bilayer phase and the triclinic bilayer phase was obtained. However, ［C12mim］［BF4］ underwent the phase transitions from the liquid state to liquid crystal state and then to crystal state Ⅱ at a slow cooling, and a single phase crystal consisting of the triclinic bilayer phase was obtained. What is more, the mixed phase crystal includes the G conformation and the A conformation of ［C12mim］+, while the single phase crystal only contains the A conformation. So, the cooling rate has an important effect on the crystallization process and product of ［C12mim］［BF4］. These results provide important experimental data for enhancing the recovery technology of ［C12mim］［BF4］, and are also helpful in investigating the phase transition and structure change of similar ionic liquids..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 801 (2023)

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Fluorescence Spectroscopy for Studies on the Interaction Between Three Metalloporphyrins With Human Serum Albumin

REN Li-lei, PENG Yu-ling, WANG Shu-jun, ZHANG Cheng-gen, CHEN Yu, WANG Xin-tong, and MENG Xiao-ning

In recent years, porphyrins and metalloporphyrins have attracted much attention in photodynamic therapy and anticancer, and some have been approved for clinical use. Human serum albumin(HSA) can bind and transport some drug molecules. A detailed study of the binding mechanism of metalloporphyrins and HSA is of great si In recent years, porphyrins and metalloporphyrins have attracted much attention in photodynamic therapy and anticancer, and some have been approved for clinical use. Human serum albumin(HSA) can bind and transport some drug molecules. A detailed study of the binding mechanism of metalloporphyrins and HSA is of great significance in clarifying the action mechanism of porphyrin drugs. This study synthesised three kinds of novel free porphyrins modified with 6-chloronicotinic acid(4, 5, 6) and their Zn complex(4-Zn, 5-Zn, 6-Zn) and characterized by UV-Vis, IR, 1H NMR, elemental analysis, fluorescence spectra and theoretical calculations. The theoretical calculation results showed that the 6-chloronicotinate moieties in the three zinc porphyrins were far away from the porphyrin ring plane. The 4-Zn configuration was more stable than the 5-Zn and 6-Zn configurations with substituents. Under simulated physiological conditions, the bonding modes between three zinc porphyrins and HSA were studied by fluorescence spectra, and the results were calculated according to the Stern-Volmer equation, double-logarithmic equation and Van’t Hoff equation. The experimental results indicated: (1) Three zinc porphyrins could all quench the fluorescence of HSA and the values of Kq calculated by the Stern-Volmer equation were much larger than 2.0×1010 L·mol-1·s-1. Thus the quenching type was static quenching. (2) The binding constants were calculated by a double-logarithmic equation. Except for the 5-Zn at 318 K, other binding constants were all greater than 103 L·mol-1, and the binding sites were close to 1, indicating the formation of a 1∶1 complex. (3) According to the Van’t Hoff equation, the thermodynamic parameters ΔH, ΔS, ΔG were all less than 0, eg. those of 4-Zn were calculated to be ΔH=-123.9 kJ·mol-1, ΔS=-322.9 J·mol-1·K-1, ΔG=-27.7 kJ·mol-1 (298 K), indicating that the reaction process was spontaneous and the predominant forces between zinc porphyrins and HSA were vander waals force and hydrogen bond. The experimental data obtained in this experiment can provide useful information for studying the interaction mechanism between metalloporphyrins and biological small molecules..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 806 (2023)

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Research on Identification of Wood Species by Mid-Infrared Spectroscopy Based on CA-SDP-DenseNet

LIU Si-qi, FENG Guo-hong, TANG Jie, and REN Jia-qi

Spectral analysis technology has a certain potential in wood species identification, and mid-infrared spectroscopy technology is also widely used in qualitative and quantitative analysis. This research focuses on the identification of wood species by mid-infrared spectroscopy. Based on a deep convolutional neural netwo Spectral analysis technology has a certain potential in wood species identification, and mid-infrared spectroscopy technology is also widely used in qualitative and quantitative analysis. This research focuses on the identification of wood species by mid-infrared spectroscopy. Based on a deep convolutional neural network, an algorithm that combines cluster analysis (CA), symmetrical lattice image analysis (SDP) and deep learning (DenseNet) is proposed to achieve a high recognition rate with few parameters. With the advantages of DenseNet, the accuracy of wood recognition in mid-infrared spectroscopy is improved. First, 250 sets of mid-infrared spectroscopy data, including guaiacum sanctum, dalbergiabariensis, pterocarpuserinaceus, pterocarpusmacarocarpus, and spiraea, are collected. Through eliminating outliers based on Euclidean distance, the feasibility analysis of the remaining 240 groups as data to be analyzed and classified. The optimal parameters of SDP conversion are determined through the SDP conversion analysis of the original spectral data. The characteristics of original spectral data are filtered out through CA. According to CA, different thresholds determine the characteristics of the three groups of dimensions and related discussions are carried out. The optimal dimensional feature is initially determined by comparing the three sets of feature data, including the intra-class similarity and the inter-class difference between the images after SDP conversion. The determined optimal dimensional feature data is input into the SDP-DenseNet model to obtain model recognition accuracy. Finally, the comparative analysis verifies the validity of the model. On the one hand, the original data and the feature data of the other two sets of contrast dimensions are input into the SDP-DenseNet model to compare recognition accuracy. On the other hand, the optimal dimensional feature data is input into the random forest for recognition to compare the accuracy of traditional machine recognition and SDP-DenseNet algorithm recognition. According to the results, the accuracy of the SDP-DenseNet model filtered by the CA feature is generally higher than that of the SDP-DenseNet model directly input to the original data. The optimal dimension of CA feature selection is 255 dimensions, with the highest recognition rate of 88.67%. In the control group, the recognition rate of 107 dimensions is 77.78%, and the recognition rate of 322 dimensions is 68.89%. In contrast, the SDP-DenseNet model recognition rate of the original data is only 57.78%. The recognition rate of the random forest model corresponding to the optimal dimensionality data screened by clustering features is relatively low, only 66.67%. Therefore, the CA-SDP-DenseNet model proposed in this study can effectively improve the accuracy of mid-infrared spectroscopy in identifying wood species..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 814 (2023)

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Quantitative Determination of Na and Fe in Sorghum by LIBS Combined With VDPSO-CMW Algorithm

WANG Hai-ping, ZHANG Peng-fei, XU Zhuo-pin, CHENG Wei-min, LI Xiao-hong, ZHAN Yue, WU Yue-jin, and WANG Qi

The content of metal elements in the root influences the growth of sorghum. Laser-Induced Breakdown Spectroscopy (LIBS) is an ideal technology for rapidly detecting metal elements in crops.In this paper, a quantitative analysis method of metal elements in sorghum roots was established based on laser-induced breakdown s The content of metal elements in the root influences the growth of sorghum. Laser-Induced Breakdown Spectroscopy (LIBS) is an ideal technology for rapidly detecting metal elements in crops.In this paper, a quantitative analysis method of metal elements in sorghum roots was established based on laser-induced breakdown spectroscopy and wavelength selection algorithm based on variable dimension particle swarm optimization-combined moving window (VDPSO-CMW). We collected 27 sorghum samples with different Na and Fe concentrations under sodium salt stress. For LIBS spectra of sorghum roots, the VDPSO-CMW algorithm was used to screen the characteristic bands related to Na and Fe, and PLS quantitative analysis model was constructed. After VDPSO-CMW algorithm optimization, the determination coefficient of cross validation (R2CV) of the PLS model for Na in sorghum root was 0.962, which was 6.5% higher than that before optimization. The root means square error of cross validation (RMSECV) was 1.261, which was 37.7% lower than thatbefore optimization; the determination coefficient of prediction (R2P) was 0.988, which was 16.8% greater than that before optimization. While the root means square error of prediction (RMSEP) was 1.063, which was 72.1% lower than that before optimization. After VDPSO-CMW algorithm optimization, the R2CV of the PLS model for Fe in sorghum root was 0.956, which was 7.4% higher than that before optimization; the RMSECV was 5.095, which was 37.1% lower than that before optimization; the R2P was 0.955, which was 4.3% higher than that before optimization; while the RMSEP was 6.438, which was 27.3% lower than that before optimization. The results show that the VDPSO-CMW wavelength selection algorithm can eliminate the LIBS bands affected by self-absorption, spectral line interference, and other factors and improve the accuracy of quantitative analysis. The combination of this algorithm and LIBS technology can not only realize the rapid and accurate determination of Na and Fe in sorghum roots but may also apply to the quantitative analysis of other samples and elements..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 823 (2023)

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Freshness Detection of Lamb Based on AW-OPS Hyperspectral Wavelength Selection Method

ZHAO Ting-ting, WANG Ke-jian, SI Yong-sheng, SHU Ying, HE Zhen-xue, WANG Chao, and ZHANG Zhi-sheng

Hyperspectral data contain not only critical information but also some interference information and invalid information, and using these data to build the model will reduce the reliability and accuracy of the relational model. Extracting feature wavelengths from full-band data is an effective way to improve the accurac Hyperspectral data contain not only critical information but also some interference information and invalid information, and using these data to build the model will reduce the reliability and accuracy of the relational model. Extracting feature wavelengths from full-band data is an effective way to improve the accuracy of prediction models. Ordered Predictive Selection (OPS) is a feature wavelength extraction algorithm that selects effective wavelength variables based on the information vector, and has shown good performance in feature wavelength variable screening. However, the model was built without removing the less important variables, resulting in too many invalid variables being involved in the model and reducing the model’s accuracy. The paper proposes an improved feature wavelength variable selection method based on an information vector and exponential decay function of ordered predictive selection method (AW-OPS) for lamb freshness detection, using lamb hyperspectral data as the research object. The algorithm calculates the information vector and ranks the wavelength variables by the relationship between the spectral data and the physicochemical value data. The exponential decay function (EDF) is used to remove some wavelength variables with relatively low absolute values of information vectors by multiple iterations. Finally, a multiple regression model was established by gradually adding wavelength points to the obtained effective wavelength variables, and the subset of wavelength variables with the lowest value of root mean square error (RMSECV) was selected as the characteristic wavelength variables. For the experiments, the partial least squares (PLS) relational models of lamb TVB-N were constructed by the OPS -and AW-OPS methods after selecting the characteristic wavelengths, respectively, and compared with the effects of FULL-PLS models. The results showed that the OPS algorithm took an average of 175.9 s to run the program, preferentially selected 370 characteristic wavelength variables, with an average OPS-PLS model correlation coefficient(RP)of 0.963 1 and an average root mean square error(RMSEP)of 0.727. while the improved ordered prediction selection method(AW-OPS)runs the program in an average time of 57.6 s, preferentially selects 275 characteristic wavelength variables, and the AW-OPS-PLS model RP improves to 0.973 1 on average, and RMSEP reduces to 0.572 8 on average. The number of full-spectrum wavelengths was 1 414 wavelength variables, and the average RP of its PLS model was 0.920 8, and the average RMSEP was 1.048 3. The AW-OPS-PLS model improved the test accuracy by 21.2% compared to the OPS-PLS model and 45% compared to the full-spectrum-PLS model, proving that the improved AW-OPS is an effective feature wavelength variable screening method that improves the accuracy of the OPS model and the efficiency of the program operation and reduces the complexity of the model..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 830 (2023)

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Rapid ATR-FTIR Principal Component Analysis of Commercial Milk

FENG Yu, and ZHANG Yun-hong

The determination of the main components of milk is an important criterion for evaluating the quality of milk. Relevant national departments have formulated a series of relatively detailed specifications to ensure the quality and safety of milkand other dairy products. However,thetraditional detection methods are often The determination of the main components of milk is an important criterion for evaluating the quality of milk. Relevant national departments have formulated a series of relatively detailed specifications to ensure the quality and safety of milkand other dairy products. However,thetraditional detection methods are often complex, time-consuming and labor-intensive. Some even cause environmental pollution, making it difficult to meet the rapid detection needs of contemporary dairy production and consumption. In this study, the portable attenuated total reflectionFourier transform infrared spectroscopy (ATR-FTIR) technique was combined with relative humidity (RH) control system to establish a method to measure the infrared spectra of different kinds of milk under the condition of continuous decline of RH. This method provides a new way for non-destructive testing, classification and quality analysis of milk products. The main contents include:(1)Selecting five types of milk of YiLi brand (pure milk, Zhennong milk, skimmed pure milk, high-calcium low-fat milk, and Shuhua milk) as research objects. Whose infrared spectra in the process of evaporation and concentration were collected under continuous decline of RH, and the peak position attribution and qualitative analysis of main nutritional components were carried out. It only takes a few microliters of milk samples for us to obtain the spectral information of the main components, such as water, carbohydrates, fats, and proteins, during the sample concentration process in a short time and achievea relatively comprehensive characterization of the chemical components of milk; (2) Using NWUSA software to build the model and process the infrared spectral data, choosing 4 000～400 cm-1 band as the variables to perform PCA and evaluating the identification ability of the model for different types of milk, it shows that the data of PCA process are well aggregated in the same group. The coordinate axes in different groups are far apart, indicating that the model selection is both reliable and representative. A total of 75 milk samples were used in the experiment, in which the production date and place were random factors, and the type and brand of milk were fixed factors. The results show that the proposed method has the advantages of simple operation, sensitive response, high spectral quality and non-destructive measurement, which is suitable for in-situ, rapid and non-destructive identification and analysis of milk and other dairy products..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 838 (2023)

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Rapid Determination of Oxytetracycline Hydrochloride Illegally Added in Cattle Premix by ATR-FTIR

XU Wei-xin, XIA Jing-jing, WEI Yun, CHEN Yue-yao, MAO Xin-ran, MIN Shun-geng, and XIONG Yan-mei

A rapid quantification of oxytetracycline hydrochloride in cattle premix using Attenuated total reflection-Fourier-transform infrared spectroscopy (ATR-FTIR) combined with partial least squares (PLS) was performed. Rapid quantification of the prohibited component of oxytetracycline hydrochloride in cattle premix was ca

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 842 (2023)

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Influence of Thermal Modification on Poplar Strength Class by Fourier Infrared Spectroscopy Analysis

YUE Kong, LU Dong, and SONG Xue-song

The study was performed to evaluate the effects of thermal modification on the mechanical properties, optimize the modification temperature based on strength class, and provide a basis for the rational application of thermally modified wood in buildings. In this study, a total of 560 poplar wood specimens were tested t The study was performed to evaluate the effects of thermal modification on the mechanical properties, optimize the modification temperature based on strength class, and provide a basis for the rational application of thermally modified wood in buildings. In this study, a total of 560 poplar wood specimens were tested to determine the effects of thermal modification between 160 and 210 ℃ on mechanical properties, such as bending strength (fm), parallel-to-grain tensile strength along the grain (ft, 0), perpendicular-to-grain tangential (ft, T, 90) and radial tensile strength (ft, R, 90), parallel-to-grain compressive strength (fc, 0), parallel-to-grain tangential (fv, T) and radial shear strength (fv, R), and modulus of elasticity (E0). The Fourier transform infrared spectroscopy was used to analyze the changes in chemical components of thermally modified wood at different temperature levels. The optimization temperature of thermal modification based on strength class was put forward. The results showed that the hemicellulose within wood had the lowest heat resistance under high-temperature condition and was first degraded by thermal exposure followed by acceleration at ≥190 ℃. The thermal resistance of cellulose was relatively higher, which was slightly degraded at the higher temperature, and mainly occurred in the amorphous region, increasing the orderly arrangement of microfibril. It was shown that thermal modification had an obvious adverse effects on fm, ft, 0, ft, 90 and fv of poplar wood. At room temperature, fm, ft, 0, ft, T, 90, ft, R, 90, fv, T　and fv, R were determined as 67.0, 86.2, 5.8, 8.9, 7.7 and 6.7 MPa, respectively. At lower temperatures, the chemical components of wood degraded slightly, and the mechanical properties of thermally modified poplar wood specimens decreased slowly. These parameters decreased to 53.5, 78.9, 4.0, 4.8, 6.0 and 5.4 MPa at 180 ℃, respectively. When the temperature was ≥190 ℃, severe pyrolysis occurred to the main chemical components, resulting in the rapid reduction of mechanical properties. At 210 ℃, these parameters represented 44.5%, 56.1%, 43.1%, 29.2%, 34.5% and 26.7% of the values at normal temperature, respectively. fc, 0 and E0 of thermally modified poplar wood increased as the temperature increased from 160 to 180 ℃, then decreased in the temperature range between 190 and 210 ℃. fc, 0 and E0 were 41.4 and 8 568 MPa at 20 ℃, respectively. In the temperature range between 160 and 180 ℃, the crystallization of cellulose increased, leading to the increase of the two parameters. At temperature of 180 ℃, fc, 0 and E0 were 30.7% and 12.8% higher than those at room temperature, respectively. The pyrolysis of cellulose increased with the temperature, resulting in the two values decreasing continuously until they achieved 45.0 and 8 104 MPa at 210 ℃, respectively. The untreated poplar wood cannot be used as a structural material, because E0 does not meet the requirements of the minimum strength class D18 according to European standard BS EN 338. The E0 of the modified wood specimen between 160 and 170 ℃ was higher than that of the untreated, but it was still lower than that specified by the minimum strength grade D18. After that, E0 increased with increasing temperature, and the modified poplar wood reached strength class D18 at 180 ℃. At temperatures between 190 and 200 ℃, the E0 of thermally modified wood specimens was higher than the corresponding value of strength class D18, but they still cannot be used as loading-bearing materials due to the excessive reduction of fv, R. The study can provide a basis for the rational application of thermal modification technology and low-quality fast-growing wood in engineering structures..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 848 (2023)

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Remove Background Peak of Substrate From SERS Signals of Hair Based on Gaussian Mixture Model

LI Wei, HE Yao, LIN Dong-yue, DONG Rong-lu, and YANG Liang-bao

In the analysis of trace substances in hair by Surface-Enhanced Raman Spectroscopy (SERS), the characteristic peaks of hair are coupled with the background peaks of the substrate. In the case of coupling, the background peaks are mistakenly identified as the characteristic peak of hair, resulting in the identification In the analysis of trace substances in hair by Surface-Enhanced Raman Spectroscopy (SERS), the characteristic peaks of hair are coupled with the background peaks of the substrate. In the case of coupling, the background peaks are mistakenly identified as the characteristic peak of hair, resulting in the identification error of the analyte to be tested. In addition, the strong background peak has a masking interference on the weak characteristic peak in hair. Therefore, the background peak deduction is an important way to solve the above problems. However, the conventional peak deduction method always leads to serious distortion of the surrounding peaks. In this paper, a Gaussian mixture model is proposed. The model not only characterizes the SERS signal but also makes each characteristic peak independent of the other, and does not interfere with the adjacent peaks in the process of peak deduction, which realizes the deduction of interference peaks and ensures the micro distortion of adjacent peaks. The core problem of the Gaussian mixture model is the solution of model parameters. In this paper, wavelet transform and conjugate gradient methods are proposed to solve the model’s initial parameter problem and optimal solution problem. The wavelet transforms fully extracts the subtle feature information of the signal by mapping the detailed information of the amplified SERS signal and takes the feature information as the initial parameter of the model. The conjugate gradient method is an iterative optimization method, and the model parameters are iteratively optimized. The final convergence result is the optimal solution of the model parameters. In summary, the two methods can accurately establish the Gaussian mixture model, and the single Gaussian function is the characteristic peak of the SERS signal, and the peak shape of the two methods is consistent. The deduction of background peak should include the extraction of effective data, model establishment, and peak deduction. The effective data extraction is to detect the blank and sampled substrate in the same position, thus obtaining a set of SERS signals. The model was established to characterize the SERS signal of the sampled substrate by the Gaussian mixture model, which multiple Gaussian functions can express. Finally, the SERS signal of the sampled substrate was identified by the characteristic peaks of the blank substrate, and the characteristic peaks with similar peak shapes and the same peak position can be deducted. The results show that when the variance ratio is the smallest, the peak position, peak width, and peak intensity of the Gaussian mixture model are the same as those of the hair SERS signal. At this time, the Gaussian mixture model can accurately characterize the information of SERS signal of hair. In seven groups of hair peak deduction experiments, of the hair SERS signal background peak deduction rate reached 50%~100%, while the hair characteristic peak wasalso effectively extracted. The model was used to identify tramadol in the rapid analysis of real hair samples..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 854 (2023)

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Quantitative Analysis of Polycyclic Aromatic Hydrocarbons by Raman Spectroscopy Based on ML-PCA-BP Model

YIN Xiong-yi, SHI Yuan-bo, WANG Sheng-jun, JIAO Xian-he, and KONG Xian-ming

Pyrene, a kind of polycyclic aromatic hydrocarbons (PAHs), widely exists in the natural environment. It has strong lipophilicity and carcinogenic effect on the human body. Therefore, the rapid analysis of pyrene content in edible oil has far-reaching significance for quality control. The quantitative analysis of polycy Pyrene, a kind of polycyclic aromatic hydrocarbons (PAHs), widely exists in the natural environment. It has strong lipophilicity and carcinogenic effect on the human body. Therefore, the rapid analysis of pyrene content in edible oil has far-reaching significance for quality control. The quantitative analysis of polycyclic aromatic hydrocarbons using Raman spectroscopy and artificial intelligence algorithm is a current research hotspot. One milliliter of edible oil is mixed with pyrene liquid with different fixed concentrations to make samples, and then a thin-layer chromatography plate and gold particles are made. The experiment is carried out by combining thin-layer chromatography, and surface-enhanced Raman scattering (SERS) spectrum to obtain the spectral data. The adaptive iterative weighted penalty least square algorithm is selected for preprocessing, Then the Multi parameter-Principal Component Analysis- Back Propagation Neural Network model was used for quantitative analysis. Firstly, two characteristic peaks are selected in the preprocessed spectrum for peak fitting, and the parameters such as height, half-width, height and area of characteristic peaks are obtained. Normalized the Raman data of the two characteristic peaks and the parameters obtained by fitting, and then use the principal component analysis to obtain the key parameters. The obtained key parameters are input into the BP neural network based on L2 regularization as the input layer to output the predicted concentration. The experimental results show that the R2 determination coefficient of the test set is 0.58 and the root mean square error (RMSEC) is 1.85; The linear regression is used to fit the law between the characteristic peak area and pyrene concentration. The final predicted pyrene concentration has an R2 determination coefficient of 0.26, and a root mean square error (RMSEC) of 2.28; For the pyrene concentration predicted by the Multi parameter-Principal Component Analysis-Back Propagation Neural Network model, the R2 determination coefficient of the test set is 0.99, and the root mean square error (RMSEC) is 0.31. The multi-parameter principal component analysis-back propagation neural network model has higher measurement accuracy and less error. The model is aimed at the nonlinear and high-dimensional relationship between spectral data information and sample concentration. The prediction accuracy and modeling efficiency are higher than similar comparison algorithms. The model fits the characteristic peak to obtain the key variables and takes the Raman displacement of the variable and the characteristic peak as the characteristic vector, so the characteristic vector is sufficient. The model uses PCA to extract the nonlinear characteristics of the Raman spectrum and adopts the advantages of strong generalization based on L2 regularization BP neural network to prevent overfitting, so that it can predict the concentration of naphthalene more accurately and quickly..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 861 (2023)

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Evaluation of Long-Term Stability for Non-Standard Method and Application in Trace Element Analysis of Pure Nickel by Glow Discharge Mass Spectrometry

YANG Guo-wu, HOU Yan-xia, SUN Xiao-fei, JIA Yun-hai, and LI Xiao-jia

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 867 (2023)

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Identification and Influence of Color Components in Red Lime From the Roof of Yangxin Hall in the Palace Museum

ZHANG Dian, WANG Hui, CHEN Yin-wei, and WANG Ju-lin

Natural mineral red clay was used as the color agent in red lime of traditional palace buildings. However, due to red clay mining being restricted, iron oxide red synthesized in the industrial method was commonly used to replace red clay in the restoration of ancient buildings, which caused poor water resistance, crack Natural mineral red clay was used as the color agent in red lime of traditional palace buildings. However, due to red clay mining being restricted, iron oxide red synthesized in the industrial method was commonly used to replace red clay in the restoration of ancient buildings, which caused poor water resistance, cracking, peeling, and other that phenomena happened in red lime. In order to explore the cause of this phenomenon, in this study, red Jia-long lime samples were collected from the roofs of three halls (Zheng hall, Xiwei Hall and Hou hall) of Yangxin Hall in the Forbidden city and determined the main phase composition of the samples by X-ray diffraction (XRD). The results show that the main components of the samples are calcite, iron oxide and quartz, in addition to a small amount of albite and halloysite. Since the quite difference in chromaticity of the samples from each hall, it combined powder microscopic morphology and mapping test, comparing the shape and color of the microscopic particles and the element distribution of the sample section to determine the main color components of the red lime sample. The results show that the powder micromorphology of the samples in Zheng Hall and Hou Hall is uniform and full of dark red particles, accompanied by black or brown-yellow mineral particles, and the distribution of Fe in the samples is not uniform and is inconsistent with the distribution of Al and Si elements. However, the powder morphology of the Xiwei Hall sample shows light color particles accompanied by other mineral components. The distribution of Fe elements in the sample is uniform, consistent with the distribution of Al and Si elements. It is concluded that the raw materials and coloring materials used in red lime samples from Zheng Hall and Hou Hall are lime, red clay and iron oxide red. The raw materials and coloring materials used in red lime samples from the Xiwei Hall are lime and red clay. It is the first time that the identification method between red clay and iron oxide red has been proposed. Scanning electron microscopy (SEM) was used to explore the effect of color components on the micro-morphology of the sample, and it was shown that the structure of the sample containing only red clay was continuous and compact, and the two phases were poorly combined after adding iron oxide red, and there were pores. In order to further explore the influence of red clay and iron oxide red on the performance of samples, the simulated samples with red clay and iron oxide red were prepared respectively. It can be seen that the use of iron oxide red instead of red clay to make Jia-long lime has poor physical and mechanical properties compared to the Jia-long lime made with red clay..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 877 (2023)

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Study on the Fluorescence Spectral Characteristics of Waxing Jadeite

LI Hao-dong, LI Ju-zi, CHEN Yan-lin, and HUANG Yu-jing

Jadeite is one of the most common jades in the current market, and the processing means to cover up the tiny defects on the surface of jadeite and improve its luster by waxing is commonly accepted by consumers. The waxing of A jadeite, B and B+C jadeite and B and B+C jadeite will fluoresce under a UV lamp after waxing,Jadeite is one of the most common jades in the current market, and the processing means to cover up the tiny defects on the surface of jadeite and improve its luster by waxing is commonly accepted by consumers. The waxing of A jadeite, B and B+C jadeite and B and B+C jadeite will fluoresce under a UV lamp after waxing, and how to identify these jadeites quickly and effectively is a problem that needs to be solved now. The common A, B, B+C jadeite and two kinds of optimized waxes in the current market were collected, and the optimized waxes were used to wax this jadeite, and the samples before and after waxing were systematically compared and studied by using a UV fluorescent lamp, and infrared spectrometer and fluorescence spectrometer. The results showed that the A jadeite did not fluoresce under UV fluorescent light, the B and B+C jadeite had weak-medium fluorescence, and all the jadeites emitted similar fluorescence after waxing. Infrared spectroscopy direct transmission method showed that the absorption peaks of 3 064, 3 032, 3 003 cm-1 were generated by the stretching vibration of the functional group ν(C—H) on the aromatic ring of the aromatic compounds in the functional group area of B and B+C jadeite; the high-quality waxes were generated by the stretching vibration of the functional group ν(—CH2—) of the alkane compounds absorption peaks at 2 915, 2 846 cm-1 and possibly 1 681 cm-1 due to the stretching vibration of the functional group ν(CO),respectively. In contrast, only absorption peaks from methyl and methylene groups were detected in Chuan wax. The fluorescence spectra showed no fluorescence response for A jadeite and fluorescence response for B and B+C jadeite. The high similarity of the profiles of some B+C jadeite and B jadeite indicates that the filling emits the fluorescence, and the ions in the dyes cause the fluorescence peaks to be shifted and the fluorescence intensity to change. According to the B+C, jadeite fluorescence peak position can be divided into three categories, excitation wavelengths were 350, 358, 370 nm, and emission wavelengths were 370, 420, 414/434 nm. Two optimized wax fluorescence peak is different, and the quality of wax fluorescence intensity is higher than Chuan wax. After waxing, the fluorescence peak of A jadeite will appear. The fluorescence intensity is related to the concentration of wax on the surface of jadeite, B and B+C jadeite will also appear after waxing, the fluorescence peak of optimized wax, but because the concentration of optimized wax is low, the strongest fluorescence peak is issued by the filling of jadeite and compared to the wax before, the fluorescence peak has redshift. Fluorescence spectroscopy can be used as a fast and non-destructive detection means to distinguish A, B and B+C jadeite before and after waxing, and the A jadeite and B or B+C jadeite after waxing can also be effectively distinguished, perfecting the basis on which fluorescence spectroscopy can be widely used in the jadeite market..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 883 (2023)

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A Study of the Mechanism of Binding Between Quercetin and CAV-1 Based on Molecular Simulation, Bio-Layer Interferometry and

HOU Qian-yi, DONG Zhuang-zhuang, YUAN Hong-xia, and LI Qing-shan

Caveolin-1 (CAV-1) plays a key role in developing cardiovascular diseases such as atherosclerosis. The interaction between quercetin and CAV-1 was studied by multispectral, homology modeling, molecular docking simulation and bio-layer interferometry (BLI) in the simulated physiological environment and different tempera Caveolin-1 (CAV-1) plays a key role in developing cardiovascular diseases such as atherosclerosis. The interaction between quercetin and CAV-1 was studied by multispectral, homology modeling, molecular docking simulation and bio-layer interferometry (BLI) in the simulated physiological environment and different temperatures. The fluorescence quenching data showed that the Kq value (the quenching rate constant) were all much larger than 2.0×1010 L·mol-1·s-1, and the fluorescence quenching constant (KSV) decreased with the increase of temperature, which proves that the quenching process of the interaction between quercetin and CAV-1 is static quenching. Furthermore, the thermodynamic parameters, enthalpy change ΔH＜0, entropy change ΔS＜0 and ΔG＜0 indicated that the bonding process is spontaneous and enthalpy driven, indicating that the main types of interaction are van der Waals force and hydrogen bonding. Through the synchronous fluorescence and three-dimensional fluorescence spectrums analysis of the interaction between quercetin and CAV-1, it was found that the fluorescence intensity of CAV-1 was progressively decreased upon the addition of quercetin, indicating that quercetin interacted with CAV-1. Further analysis showed that quercetin caused the redshift of the maximum emission wavelength of the aromatic amino acid residues in CAV-1, enhanced the polarity of the microenvironment around the CAV-1, enhanced its hydrophilicity, indicating that the addition of quercetin changed the protein conformation of CAV-1. The UV-Vis absorption spectrum showed that a ground-state complex was formed between CAV-1 and quercetin, which further confirmed the static quenching mechanism between CAV-1 and quercetin. The X-ray crystal structure template of CAV-1 was constructed using homology modeling. The molecular docking simulation results showed that the binding force of quercetin and CAV-1 was -7.372 kcal·mol-1. The docking results showed that quercetin could bind to the active pocket composed of amino acids such as Glu20, ASP70, VAL16 and ARG19. There were the van der Waals forces between quercetin and residues GLN21, VAL16 and ARG19 of CAV-1, and hydrogen bonds between quercetin and GLU20 and ASP70. Various forces affected the micro-environmental changes of CAV-1 and led to its fluorescence quenching, which is a key factor involved in the formation of the complex. Finally, the binding of quercetin and CAV-1 was quantitatively studied by the BLI technique. The results showed that quercetin had a good binding activity with CAV-1 with an equilibrium constant (KD) value of 2.50×10-5 mol·L-1. The response signal value increased with quercetin concentration, evidencing the specific binding between CAV-1 and quercetin. This research was helpful in understanding the mechanism of interaction between quercetin and CAV-1 and provide references for research on the therapeutic targets of quercetin in atherosclerosis..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 890 (2023)

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Comparative Study on Mineralogical Identification and Spectral Characteristics of Halloysitum Album, a Commercial Mineral Medicine

ZHANG Li-qian, LIU Yang-jie, LIN Bing-lan, and DUAN Jun

Halloysitum Album is one of the most commonly used mineral drugs. It is often found fake or mixed in the market, which is related to the unclear identification of mineralogy. The purpose of this paper is to observe the characters and identify them by mineralogy. The mineralogical and spectral characteristics of Halloys Halloysitum Album is one of the most commonly used mineral drugs. It is often found fake or mixed in the market, which is related to the unclear identification of mineralogy. The purpose of this paper is to observe the characters and identify them by mineralogy. The mineralogical and spectral characteristics of Halloysitum Albumfrom different places on the market were compared using scanning electron microscopy (SEM), X-ray diffraction (XRD), semi-quantitative trace element spectroscopy, differential thermal analysisand infrared spectroscopy(IR). The results are as follows: (1) Halloysitum Album is white, with earthy luster, small hardness, water-absorbing and sticky tongue, and slightly earthy and fishy. The main minerals are kaolinite, illite and quartz. The main impurity minerals are feldspar, calcite and limonite. (2) The SEM results showed that all white stone lipids had grid-like fiber structure, and the main components were O, Si and Al. (3) The results of XRD showed that the main diffraction lines of the samples are 7.44(3), 3.53(4), the main composition is kaolinite, the diffraction lines are 10.45(5), 4.51(3) and illite, and the quartz diffraction lines are 5.04(3), 4.51(3), 3.06(10), secondary diffraction lines show the presence of and small amounts of feldspar, calcite and limonite. (4) The micronutrient spectrum Quantitative analysis showed that Ca, Mg, K, Na and Cr were the main components in the white stone lipids. (5) The differential thermal analysis (DTA) showed an obvious heat absorption effect of kaolinite and illite. (6) The results ofIR showed that the high frequency bands of 3 700～3 000 cm-1 have sharp and strong absorption peaks near 3 440.98, 3 621.18 and 3 620.45 cm-1, respectively. All the samples can be divided into 1 200～1 000, 950～900 and 800～600 cm-1 bands. The bands of the three samples are the same, and the main mineral composition is kaolinite. To sum up, the quality of commercially available Halloysitum Album can be judged effectively using properties, mineralogy, SEM, IR, XRD and differential thermal analysis..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 897 (2023)

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VIS-NIR Hyperspectral Prediction of Soil Organic Matter Based on Stacking Generalization Model

ZHANG Xiu-quan, LI Zhi-wei, ZHENG De-cong, SONG Hai-yan, and WANG Guo-liang

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 903 (2023)

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Spectral Analysis of Liquefaction Residue From Corn Stalk Polyhydric Alcohols Liquefaction at Ambient Pressure

ZHANG Yan, WANG Hui-le, LIU Zhong, ZHAO Hui-fang, YU Ying-ying, LI Jing, and TONG Xin

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 911 (2023)

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Research on Forest Fire Monitoring Based on Multi-Source Satellite Remote Sensing Images

YIN Jun-yue, HE Rui-rui, ZHAO Feng-jun, and YE Jiang-xia

At present, remote sensing forest fire monitoring mainly focuses on the accuracy of fire point detection by polar-orbiting satellites. At the same time, there is less research on remote sensing monitoring and identification of fire points, smoke characteristics and other comprehensive fire information based on multi-so At present, remote sensing forest fire monitoring mainly focuses on the accuracy of fire point detection by polar-orbiting satellites. At the same time, there is less research on remote sensing monitoring and identification of fire points, smoke characteristics and other comprehensive fire information based on multi-source remote sensing images. The forest fire of May 9, 2020, in Anning City, Yunnan Province, was studied based on the Gaofen-6 wide-field (GF-6 WFV) data and the FY-3D polar-orbiting meteorological satellite medium-resolution spectrometer (FY-3D MERSI) data for smoke, burned areas extraction and fire point identification. Firstly, Based on GF-6 WFV data, six spectral feature indices were selected to identify fire smoke and fire trails by maximum likelihood, support vector machine, and random forest classification methods, and evaluated for accuracy. Then, Based on the 1 km mid-infrared channel data of FY-3D MERSI, the potential fire point identification algorithm is improved, and the basic principles of FY-3C VIRR and MODIS fire point detection are combined with dynamic threshold and context detection method to identify fire points. Then the identification results are optimized by combining the far-infrared channel with 250 m resolution. Finally, the information on smoke, fire points and fire trails extracted from the two kinds of data were combined to explore and analyze the monitoring capability of GF-6 WFV and FY-3D MERSI for forest fires. The results show that the smoke and burned areas can be effectively identified by five feature indices and eight bands of GF-6 WVF data, and the random forest classification is the most effective among the three classification methods, with an overall classification accuracy and Kappa coefficient of 97.20% and 0.955. The improved fire point recognition algorithm for FY-3D MERSI data can effectively improve the recognition accuracy of fire points. Combining the mid-infrared -and far-infrared channels to detect fires can improve the fire detection accuracy from kilometer to 100 meter level. The combined GF-6 and FY-3D MERSI data can effectively extract smoke, burned areas and fire point information from the fire site, and the use of multi-source data can carry out forest fire monitoring and early warning in multiple directions, which is of great significance to improve the capacity of satellite remote sensing forest fire monitoring..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 917 (2023)

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Decomposition Products Detection of Sulfur Hexafluoride Based on Frequency Comb Spectroscopy

LIU Ting-ting, SHEN Xu-ling, REN Xin-yi, WEN Zhao-yang, YAN Ming, and ZENG He-ping

With the rapid development of power systems towards high voltage, large capacity and application sininformation technology, the efficient operation and maintenance of power equipment is of great significance to ensure the safe operation of power systems and steady economic growth. Detecting sulfur hexafluoride gas deco With the rapid development of power systems towards high voltage, large capacity and application sininformation technology, the efficient operation and maintenance of power equipment is of great significance to ensure the safe operation of power systems and steady economic growth. Detecting sulfur hexafluoride gas decomposition products is an effective method for leak detection and fault diagnosis in electrical insulation equipment. Dual-comb spectroscopy, derived from optical frequency combs, has the advantages of high resolution, high precision, wide spectrum and high speed, and is expected to provide a reliable method for quantitative analysis of characteristic gases in leakage troubleshooting of power equipment. In this paper, a dual-comb spectroscopy detection equipment was built by using two integrated erbium-doped fiber optical combs. With precise frequency control and fine temperature control, the frequency fluctuation of the repetition rate was decreased from 18.37 Hz to 607.72 μHz and the stability of the comb teeth was improved to 10-12. The long-term stability and integration enabled the combs strong immunity to environmental disturbance and the combs maintained high coherence within more than 2 hours in outdoor operation as the repetition rate and the carrier envelope phase offset signals of the combs kept phase-locked. In terms of spectral detection, the mixture of CO and CO2 was measured with the help of an ultra-sensitive multi-pass cell and as a result, the absorption peaks of CO and CO2 within the 1 540～1 590 nm band were simultaneously measured with 1 pm spectral resolution on the ms time scale. Taking the characteristic absorption peaks of CO at 1 585.47, 1 581.946 nm, and CO2 at 1 580.5, 1 579.575 nm, for example, the molecular densities of CO and CO2 could be easily derived from Lorentzian fitting, and the uncertainties were reduced to 0.32% and 0.24%, respectively, using multi-peaks fitting, which were nearly one order of magnitude lower than that of single-peak measurement (2%). Our research promotes the application of dual-comb spectroscopy and the related system in non-contact real-time detection of characteristic gases in power equipment. Compared with the traditional contact detection technology, which has the shortcomings of single gas detection, long integration time, and difficulty in long-term online real-time monitoring, the dual-comb spectroscopy is advantaged in simultaneously multi-peaks detection of diverse gases in ms order of time, which can shorten detection time and improve the accuracy. In a word, dual-comb spectroscopy provides an effective method for timely troubleshooting and fault diagnosis for leak detection in power equipment..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 927 (2023)

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Characteristics of the Plasma Plume and Micro-Impulse Generated by Irradiating the Aluminum Target With a Nanosecond Laser Pulse at Oblique Incidence

YU Cheng-hao, YE Ji-fei, ZHOU Wei-jing, CHANG Hao, and GUO Wei

To study the impulse coupling mechanism of a pulsed laser ablation aluminum target, the direct measurement of its macroscopic impulse coupling characteristics is one of the means. However, laser ablation involves many physical processes. Therefore, analysing the impulse formation mechanism only by studying its macrosco To study the impulse coupling mechanism of a pulsed laser ablation aluminum target, the direct measurement of its macroscopic impulse coupling characteristics is one of the means. However, laser ablation involves many physical processes. Therefore, analysing the impulse formation mechanism only by studying its macroscopic mechanical properties is difficult. Plasma plume ejection formed by pulsed laser ablation is an important process to induce the mechanical effect. Hence, based on studying the macroscopic mechanical properties, this paper deeply analyzes the impulse coupling mechanism of pulsed laser ablation by measuring the plasma plume and emission spectrum characteristics. In this paper, a single pulse laser with a wavelength of 1 064 nm is used to ablate aluminum targets. By constructing a fast photogrammetry system and optical emission spectroscopy measurement system, the plasma plume image, the plasma spectral image, and the plasma emission spectrum generated by laser oblique incident ablation of the aluminum target were obtained. Based on optical emission spectroscopy of the plasma plume, the Boltzmann plotting method and Stark broadening method were used to study the variation of plasma temperature and electron number density with the laser fluence at different incidence angles of a pulsed laser, respectively. Moreover, a torsion pendulum system was built to study the trend of the impulse coupling coefficient with the laser fluence along the direction of laser incident at various incident angles. The study follows the research ideas from the plume microscale evolution process to impulse macro mechanical properties analysis. The experimental results show that the luminescence intensity of the plasma plume strengthens with the laser fluence, accompanied by the rise of plume ionization degree. Moreover, the plasma temperature and electron number density increase rapidly, resulting in the impulse coupling coefficient heightening rapidly. When the laser fluence is greater than 15 J·cm-2, the plasma temperature and the electron number density are gradually saturated due to the plasma shielding effect. The change of plasma temperature and electron number density results in the decrease of impulse coupling coefficient with increased laser fluence. In addition, the plasma temperature and the electron number density decrease with the increase of incident angle, which reduces the impulse coupling coefficient. The results show that the coupling mechanism of the ablation impulse can be well analyzed using fast photography and optical emission spectroscopy. The results can provide a reference for optimising key parameters for space applications such as laser space debris removal, space micro-thruster and despinning non-cooperative targets in space..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 933 (2023)

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Cross Comparison Between Landsat New Land Surface Temperature Product and the Corresponding MODIS Product

LI Chun-qiang, GAO Yong-gang, and XU Han-qiu

Landsat Collection 2 Level-2 Surface Temperature (LC2L2ST) was formally released in December 2020 by the U.S. Geological Survey (USGS). However, there are few reports on this new land surface temperature (LST) product. As this product will be the only LST data provided by the USGS starting in 2022, it is necessary to e Landsat Collection 2 Level-2 Surface Temperature (LC2L2ST) was formally released in December 2020 by the U.S. Geological Survey (USGS). However, there are few reports on this new land surface temperature (LST) product. As this product will be the only LST data provided by the USGS starting in 2022, it is necessary to evaluate the product timely. Among various satellite LST products, the quality of the MODIS LST product is well recognized, and widely used. Therefore, this paper, for the first time, performed a cross-comparison between the new Landsat LST product and the MODIS LST product to examine the quality of the new product. Different regions in China (Fuzhou, Taihu, Yinchuan and Dunhuang) were selected as the test areas, and 20 pairs of LC2L2ST and MODIS LST synchronous images were used for the comparison. The images cover different land types, such as vegetation, water, town and deserts across different seasons. A total of 560 homogeneous regions of interest (ROI) were selected from the images of the test areas. The regression analysis was carried out to examine the fit of the ROIs and the quantitative relationship between the two LST products. The conversion model between them was also developed. The results showed that the new LC2L2ST product is highly correlated with the MODIS LST product. Each of the four test areas can achieve a coefficient of determination (R2) greater than 0.98. Integrating the 560 samples from the four test areas also obtain an R2 close to 0.98. Nevertheless, differences between the two products have also been founded. The LC2L2ST is 0.90℃ averagely higher than the MODIS LST (RMSE = 2.29 ℃). However, LC2L2ST can be slightly lower than MODIS LST in late fall and winter seasons but significantly higher than extremely hot summer seasons with a bias close to 7 ℃. The analysis revealed that the differences were related to spatial resolution, sensor viewing angles, land cover types and seasons. In general, the new LC2L2ST product strongly correlates with the MODIS LST, but significant differences were also observed in the summer months. Therefore, the new Landsat LST product must be further tested with in-situ measured LST data. Due to the differences in this paper, the two LST data products need to be converted when they must be collaboratively used. This study developed the conversion equation between the two LSTs based on the 560 ROIs. The verification found that the differences between the two data after conversion were greatly reduced. It is conducive to the cooperative use of the two LST data and providing continuous remote sensing data for long-term LST monitoring..

Spectroscopy and Spectral Analysis

Publication Date: Jan. 01, 1900
Vol. 43, Issue 3, 940 (2023)

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Comparative Study on Hyperspectral Inversion Models of Water Quality Parameters

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Water is a basic need for life and health. Human production and life are inseparable from water. Excessive nitrogen and phosphorus in the water body lead to excess nutrients, resulting in eutrophication of the water body, and then the deterioration of water quality has a wide-ranging impact. The application of hyperspe Water is a basic need for life and health. Human production and life are inseparable from water. Excessive nitrogen and phosphorus in the water body lead to excess nutrients, resulting in eutrophication of the water body, and then the deterioration of water quality has a wide-ranging impact. The application of hyperspectral remote sensing in the inland water quality monitoring field is becoming more and more extensive. Based on this research, to reduce the influence of outdoor water body-specific factors, this study builds an experimental laboratory system by simulating external conditions in the laboratory. According to national emission standards, this study prepares 40 sodium phosphate standard solutions with different concentration gradients in the concentration range of 0～2.5 mg·L-1 and 40 different concentration gradient ammonium chloride standard solutions in the concentration range of 0～20 mg·L-1. After obtaining hyperspectral images of all standard solutions, The spectral responses of water quality parameters total phosphorus and total nitrogen were analyzed. This study finds the sensitive bands corresponding to total phosphorus and total nitrogen at around 420, 720 nm and around 410 nm. Building a hyperspectral water quality inversion dataset using Principal Component Analysis (PCA). By preprocessing hyperspectral image radiometric calibration, Savitzky-Golay filtering (SG filtering), and using the BP artificial neural network method to construct a laboratory hyperspectral water quality inversion model. The coefficient of determination of the constructed laboratory hyperspectral total phosphorus inversion model is 0.980 2, and the determination coefficient of the laboratory hyperspectral total nitrogen inversion model is 0.860 2. Taking an indoor river in Yixing, Jiangsu as the research object. The model is applied to the outdoor hyperspectral image data obtained by the outdoor UAV equipped with the hyperspectral imaging system. The inversion accuracies of the mean concentrations of total phosphorus and total nitrogen are 95.00% and 93.52%, respectively. The outdoor hyperspectral water quality inversion model constructed by using the traditional method to directly draw water from the observation points of the river to be tested the average values of total phosphorus and total nitrogen concentrations obtained at the same five points with an inversion accuracy of 86.87% and 86.48%. This study compares the inversion results of the two groups. It is found that the inversion accuracy of 90% of the spectral inversion results obtained by the laboratory hyperspectral water quality inversion model constructed in this study is slightly higher than that of the outdoor water quality inversion model. It is confirmed that this study can effectively predict the content of total phosphorus and total nitrogen in the river to be measured, and can also provide certain technical support for the hyperspectral remote sensing inversion of total phosphorus and total nitrogen in the water..

Spectroscopy and Spectral Analysis