In this paper, the research work on the early lightning spectrum is briefly reviewed, and then the latest progress of lightning spectrum research in the recent 20 years is reviewed in two stages. In the 1960s and early 1970s, although the lightning spectrum obtained by film cameras had many shortcomings, many important research results were achieved, which not only laid a solid foundation for the later research work of lightning spectrum but also pointed out the direction of development. Since 2001, the slit-less grating spectrograph assembled by ordinary digital camera has been used to study the lightning spectrum in China. Although an ordinary digital cameras solve the problem of film cameras, the shooting speed is slow (50 frames per second), and the nature of the lightning return stroke channel can only be studied in this time range. Nevertheless, these works once again promoted the development of lightning spectrum research, so the international gradually began to pay attention to lightning spectrum research. In 2011, Warner et al. recorded the spectrum of the cloud-ground lightning stepped leader with a slit-less spectrometer assembled with a high-speed camera, which improved the shooting speed to a certain extent (10 000 frames per second). Since 2012, the slit-less grating spectrograph integrated with a high-speed camera as a recording system has been used in China to capture the lightning spectrum, and a lot of research work has been carried out on the radiation spectrum at different stages of the lightning channel under the condition of higher temporal resolution, and several eye-catching research results have been achieved. They mainly include the spectral study of the stepped leader, dart leader and return stroke of the natural lightning, as well as the ball lightning and the lightning channel core. In 2017, Warner reported the spectra of artificially triggered lightning initiation, dart leader, return stroke, and continuous current at a wavelength range of 380~620 and 620~870 nm with a time resolution of about 1.5 microseconds, but the range was too small to capture the spectra of only one part of the lightning channel. Therefore, how to obtain spectral data with the higher spatial and temporal resolution is an urgent problem in lightning spectrum research.

Animal-derived food is one of the most essential parts of human nutrient ingestion. Veterinary drugs are vital for farming and are widely used for livestock breeding and disease prevention. However, excessive veterinary drug residue has severely impacted consumers’ health, which also hinders the development of animal-derived food. In such a concern, developing a rapid and effective detecting method is important to avoid adverse effects on consumers’ health. As a trace-level detection method, surface-enhanced Raman spectroscopy (SERS) demonstrates great potential in fulfilling the rapid, effective, and sensitive demands for veterinary drug residue in animal-derived food. This work reviewed the development of the SERS-based detection method for veterinary drug residue in animal-derived food, including meat (i.e., pork, chicken, duck, and fish), dairy products, and honey products. First, this review introduced the development of SERS technology in detecting the primary veterinary drug in meat products. The veterinary drug analysis includes several aspects, for example, tetracycline, sulfonamides, enrofloxacin, hormones in poultry products, β-agonists, chloramphenicol, and levamisole in pork, dye, sulfonamides, chloramphenicol in fish products. Second, the SERS-based detection of tetracycline, aminoglycosides, penicillin, and amide alcohols in dairy products is discussed. Third, this review briefly introduced the use of SERS for chloramphenicol and tetracycline detection in honey products. Finally, the conclusion and the perspectives of the SERS detection technology in animal-derived food are provided. The SERS demonstrates broad interest in the trace-level analysis of complicated chemical components in the food industry, especially suitable for prohibited and restricted chemical substances that may be hazardous to human health, making this technology highly perspective. However, opportunities exist with challenges. Breaking through the key technical bottlenecks, establishing rapid detection strategies for veterinary drug residue in animal-derived food, and developing on-site and real-time detection protocols will be significant in food safety supervision.

With the development of modern science and technology, higher requirements are put forward for radiation measurement of temperature, and multi-wavelength thermometry using wavelength closure to solve temperature has been widely used. However, it is difficult to determine the functional representation of the emissivity of the measured object to measure the real temperature. After introducing the concept of instrument measurement, the problem of determining object emissivity is transformed into a model of determining instrument emissivity. It is great progress in radiometric temperature measurement to construct the closed solution condition of real temperature using the wavelengths, which are the intersections of spectral distribution curves of emissivity of object and instrument. Based on this, a method of band integral is proposed to eliminate the influence of wavelength on temperature measurement caused by the binary function of object radiation, and the median wavelengths of the integral can replace the wavelengths of intersections. Combining with the “spectral color function”, the intersections of curves can be captured, and the measurement of real temperature is completed. It should be clear that the number of wavelengths required for temperature measurement is not the more, the better. By modifying the first and second radiation constants of Planck’s law, the generalized temperature measurement model is obtained, and the number of wavelengths required for measurement is limited to “3”, which can be used as the lower limit number of temperature measurement wavelengths required for the product of Planck’s law and emissivity series model. It is another breakthrough in radiation temperature measurement. The mathematical form on the definition level of object radiation represents the generalized model, and the connection between the generalized model and the emissivity of the linear instruments is realized. In the visible and near-infrared atmospheric window bands, the generalized model and instrument measurement equation is numerically fitted, and the adaptability of the definition and generalized model in the arbitrary band is verified. The experimental data of tungsten metal are simulated in the visible light bands. The results show that the generalized model can well restore the radiation data of tungsten by adjusting the limited undetermined parameters. The “spectral color function” design can realize the effective resolution of temperature measuring wavelengths. The relative temperature errors of tungsten are less than 0.15%, which proves that the temperature measurement method based on the intersection capture of the spectral distribution curve is an effective way to realize the real temperature radiometric measurement of objects.

The 2ν３ band R3 branch (6 046.95 cm-1) is the most commonly used band in near-infrared methane detection. The three spectral lines of the R3 branch are very close to each other, and the Lorentzian profile of a spectral line is usually used to describe its spectral shape to correct the second harmonic peak error caused by temperature and pressure. However, the error caused by the Lorentzian profile itself has not received enough attention. In this paper, the TDLAS system is simulated and analyzed as follows. The low-frequency sawtooth wave and the high-frequency sine wave are superimposed to modulate the laser. After the detection gas is absorbed, it is then demodulated by digital lock-in amplification and low-pass filtering, and finally, the second harmonic signal normalized by the first harmonic is obtained by the rotating coordinate system method. By comparing the influence of the Lorentzian profile approximation of a single spectral line and the Voigt profile of three spectral lines on the second harmonic, the second harmonic error caused by the Lorentzian profile approximation under the conditions of temperature and pressure changes is analyzed. The result indicates that: (1) When the pressure and temperature change, the peak error of the second harmonic of the Lorentzian profile is smaller than the average minimum value error; (2) The peak value error of the second harmonic caused by the Lorentzian profile approximation increases significantly with the decrease of pressure. When the temperature is 298 K, and the pressure is reduced to 0.2 atm, the peak value error of the second harmonic of methane gas brought by the Lorentzian profile approximation reaches 65.5%; (3) The second harmonic spectral shape is measured by parameters such as peak-to-valley ratio and harmonic width. When the temperature is 298 K, and the pressure is less than 0.8 atm, the peak-valley ratio error is more than 4.5%, and when the pressure is 1 atm, and the temperature is more than 380 K, the peak-to-valley rate error is more than 4.8%. Since the second harmonic spectral shape error is more sensitive to the peak-to-valley rate parameter, for methane gas at 6 046.95 cm-1, the Lorentzian profile is difficult to apply to the calibration-free algorithm; (4) The Lorentzian profile approximation error decreases as the modulation coefficient increases. When the temperature is 298 K and the pressure is 1 atm, the modulation current is greater than 2.2 mA (corresponding to the modulation factor of 1.33), the second harmonic peak error, peak-to-valley rate error and width error are all less than 3.5%. The proposed Lorentzian profile error analysis method has a certain reference significance for studying the methane detection error of TDLAS caused by profile approximation in the environment of temperature and pressure changes. It can also be extended to TDLAS detection of other gas multi-line bands.

Our research team recently found a natural diamond suspected to be a synthetic diamond during routine testing. The weight of the stone was 0.029 5 g (0.14 ct), the size of which was 3.32 mm×3.33 mm×2.08 mm, the color grade was H, the clarity grade was SI1, and there was abnormal extinction under the orthogonal polarizer. The sample had strong green-yellow fluorescence under short wave ultraviolet lamp, presented strong green-yellow phosphorescence, and the phosphorescence duration was more than 50 s. Fourier transform infrared spectrometer confirmed that the sample wasⅡa type, there was no obvious absorption peak between 1 400~400 cm-1, and there was an absorption peak caused by C—C lattice vibration between 1 970~2 500 cm-1. UV-VIS Spectrometer did not detect the 415 nm absorption peak, but 270 nm absorption peak could be observed. The above characteristics were suspected tobe an HPHT synthetic diamond. In order to confirm the sample formation, some spectral tests were carried out. The luminous image of the sample was tested by using Diamond-viewTM from De Beers. The testing showed that the luminous image of the sample was lizard skin and honeycomb. The constant temperature Photoluminescence spectrum of the sample found absorption peaks at 415, 428 and 450 nm under 405 nm excitation source. The peaks of 415, 428, 450 and 575 nm caused by nitrogen-vacancy Center (N-V)0 could be obtained, but 637nm absorption peak caused by nitrogen vacancy Center (N-V) was not found under the 365 nm excitation source. Ata low-temperature liquid nitrogen condition, the photoluminescence absorption peaks of 575 and 637 nm caused by nitrogen-vacancy centers (N-V)0 and (N-V)- could be determined by using 488 and 514 nm excitation sources, and the 575 nm peak intensity was much stronger than 637 nm peak intensity. The latest research results were summarized and compared: The 415 nm characteristic peak is an important characteristic of a natural colorless diamond. The diamond synthesized by CVD has a characteristic photoluminescence peak of 737 nm. HPHT synthetic diamond has characteristic photoluminescence peaks of 882 and 883 nm. The HPHT-treated diamond has 575 and 637 nm photoluminescence characteristic peaks, and the intensity of the 637 nm photoluminescence peak is much greater than that of 575 nm. By comparing the luminous image characteristics of natural, synthetic and treated diamonds tested by Diamond-viewTM, the luminous image of the test sample is consistent with the characteristics of natural diamonds. Based on the above results, it was finally confirmed that the sample was a natural Ⅱa-type diamond. The study of this sample showed that the identification of the diamonds needs to start from the standard gemological characteristics, and pay attention to the test of the infrared absorption spectrum and ultraviolet-visible spectrum, especially to the Diamond-viewTM fluorescence imaging and photoluminescence spectrum analysis. Only a comprehensive judgment through the above methods can obtain an accurate result.

In port transportation, the detection of sulfur content in vessel fuel has always been the focus of the maritime sector. However, the existing detection methods are tough to achieve remote monitoring effectively. This paper proposes a remote measuring method of CO2 and SO2 in vessel exhaust based on hyperspectral imaging technology. The Fourier transform interference hyperspectral imaging technology, and hyperspectral three-dimensional low-rank optimization technology is developed, which can effectively solve the low-concentration detection problems in open light path and complex environment. We perform the sulfur content detection tests for the fixed and random vessel day and night at Dongjiang Wharf of Tianjin Port. The Fourier transform interference hyperspectral imaging technology has been developed for remote exhaust detection under the complex open light paths. The hyperspectral data is preprocessed by hyperspectral imaging three-dimensional low-rank optimization technology. Finally, the accurate detection of sulfur content in vessel fuel has been analyzed accurately using partial least square (PLS) stoichiometry technology and a radiation transmission model according to the atmospheric radiation situation. The detection of fixed and random vessels filled with high sulfur fuel in day and night environments is accomplished. The detection distance is more than 1000 meters, and the single detection time is less than 3 s. The results are consistent with the data held by the maritime department, which verifies the feasibility of remote passive measurement of sulfur content in vessel fuel based on hyperspectral imaging technology.

Using Ultraviolet-visible (UV-Vis) diffuse reflectance spectrum, Raman and Photoluminescence (PL) spectrum technology, the color properties of pearls with different sizes and different shades of golden saturation on the market are explored. The results show that yellow pearls can be initially divided into types Ⅰ and Ⅱ based on the UV-VIS reflection spectrum characteristics. The corresponding spectra of type Ⅰ pearls have absorption bands at (360±5) nm and weak absorption peaks or shoulders at (420±10) nm. These pearls are common in the current pearl market, pigments in their own structure caused the color of which. Other golden yellow pearls belong to Type Ⅱ except for type Ⅰ. The corresponding reflection spectral absorption band’s main peak is in the range of 330~430 nm. However, some type Ⅱ samples have no obvious absorption or only weak absorption shoulder at 280~600 nm. Raman spectroscopy was further used to detect the type Ⅱ pearl. The treated type Ⅱ yellow pearls displayed strong fluorescence peaks in the range of 150~1 000 cm-1 when the excitation intensity was low, and the intensity of the fluorescence peaks was significantly higher than the characteristic peak at about 1 086 cm-1 of aragonite. Meanwhile, the PL spectra of the treated type Ⅱ pearls also showed that fluorescence intensity increased significantly in the range of 500~600 nm. In addition, the above abnormal fluorescence and exotic characteristic peaks in the Raman and PL spectra of the type Ⅱ pearls can be used as evidence for treatment. The research provides theoretical and technical support for the coloring formation of golden pearls and the identification of imitation pearls. Meanwhile, it has important reference significance for Raman spectroscopy in detecting and identifying other kinds of precious jade, especially organic gems.

In view of the low efficiency and accuracy of the traditional spectral method for egg freshness testing, we propose and demonstrate the study of egg freshness by using the VIS-NIR spectroscopy testing method combined with XGBoost and other algorithms. In our experiments, eggs were under different storage conditions as samples were divided into the training set and testing set for model building and evaluation. The harmonic weighted average (F-measure) and Accuracy were used as the performance evaluation indexes of the classification model. A VIS-NIR spectroscopy system collected the reflection spectra of eggs. The obtained spectral data werethen preprocessed and used to build different models for egg freshness evaluation. Various classification algorithms,including random forest (RF), least square regression (PLS), support vector machine (SVM), Multi-layer Perceptual Model (MLP) and XGBoost algorithm, were used. The performance of each modelwas evaluated in detail. The analysis shows that better training results are obtained in the RF, SVM and XGBoost models with data preprocessed by Savitzky Golay first-derivative (SG-1st-Der) and the PLS and MLP models with data preprocessed by standard normal variables (SNV).The interval partial least squares (IPLS) method was used to select a working waveband for data dimension reduction for models with the raw spectral data preprocessed by SG-1st-Der combing with the RF, SVM and XGBoost algorithms and models with the raw spectral data preprocessed by SNV combining with PLS and MLP algorithms, respectively. Based on the verification using the test set, it can be seen that the IPLS-XGBoost classification model after SG-1st-Der pretreatment performs best.For the conditions of room temperature storage and cold storage, the F-measure reached 92.33% and 90% respectively, and the Accuracy reached 94.44% and 91.67% respectively. Moreover, the computing time of the model for the prediction of test set samples takes only 0.6 s. The results show that the visible-near infrared spectroscopy method combined with the IPLS-XGBoost classification algorithm can be applied in egg freshness evaluation. Compared with traditional methods, this method has advantages in model classification performance, evaluation accuracy and running speed.

Under the mutual influence of characteristic X-rays of the light elements and the measured elements, the measured X-rays’ fluorescence spectra will be seriously overlapped due to the restricted energy resolution of the instrument. This paper proposes a new method for analyzing EDXRF spectra by taking the chromatographic resolution Rs as an index to calculate the degree of spectral peak overlap and the overlapping peaks with Rs below 0.3 as the research object. First, this thesis introduces the peak sharpening method based on the fourth derivative in detail, and proposes the error wavelet transform. In addition, the new method was verified on simulated X-ray fluorescence spectroscopy. The simulation results show that when Rs=0.27, neither of the two methods can realize the analysis and identification of the overlapping spectral peaks; however, the processing by the 4-order peak sharpening method not only retains the peak position characteristics of the original signal, but also leads to increased Rs. Therefore, the resolution of the simulated overlapping peaks can be realized by adjusting the weight of the 4-order peak sharpening method to complete the initial sharpening of the overlapping peaks with low resolution, and then performing the error wavelet transform on the sharpened signal. Moreover, the combined new method (sharpening error wavelet transform) was proved to have a strong resolution ability for overlapping spectral peaks with very low resolution. Then, the superimposed Gaussian function was used to simulate the two sets of overlapping spectral peaks, which are the overlapping spectrum of the Kβ energy peak of Mn and the Kα energy peak of Fe (Rs=0.19) and the overlapping spectrum of the Kα energy peak of Al and its Kβ energy peak (Rs=0.11). The overlapping peaks were resolved by processing the spectral lines with the new method, and the result proved that the method is feasible for overlapping spectral peaks with extremely low resolution. Finally, the measured EDXRF spectrum was analyzed by sharpening the error wavelet, and comparative experiments were carried out by resolving three specific low resolution overlapping peaks. The results show that the method successfully resolves and identifies low-resolution overlapping peaks. This thesis aims to propose a practical and innovative method, and experiments show that the sharpening error wavelet transform is the cure, which can effectively decompose the overlapping spectral peaks with very low resolution.

The observation of solar scattering spectra was performed at Lhasa by Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which was used to retrieve the tropospheric vertical column densities (VCDtrop) of nitrogen dioxide (NO2) in order to investigate the variation characteristics of NO2 during the celebration period of the 70th anniversary of the peaceful liberation of Tibet. During the observation period (9 August 2021 to 31 August 2021), the averaged NO2 VCDtrop in the daytime was 4.46×1015 molec·cm-2, significantly higher than that on the celebration day of the 70th anniversary of the peaceful liberation of Tibet (2.85×1015 molec·cm-2). In addition, the daily averages of NO2 VCDtrop presented a good correlation with the results measured by the online surface observation, with a correlation coefficient of 0.58. During the observation experiment, the prevailing wind direction in Lhasa was westerly, and the east-west direction was the transport path of atmospheric NO2, which was consistent with the river valley topography of Lhasa city. The average diurnal variation of the hourly means of NO2 VCDtrop showed a “U” pattern, with higher values appearing in the morning and evening, and lower values occurring around 16:00. However, on the celebration day of the 70th anniversary of the peaceful liberation of Tibet, the diurnal variation of NO2 VCDtrop not only presented the peak values in the morning and evening but also at noon, which probably was related to the removal of road control measures after the activity and the emission of support vehicle. In conclusion, this study confirmed the good applicability of ground-based MAX-DOAS remote sensing in the typical city of Lhasa over the Tibetan Plateau. Meanwhile, it was also found that the level and variation of NO2 VCDtrop in Lhasa were mainly affected by urban traffic emissions. The atmospheric NO2 concentration in Lhasa was lower on the celebration day of the 70th anniversary of the peaceful liberation of Tibet.

As a disease with fast transmission speed and high frequency, cucumber powdery mildew will deal a serious blow to cucumber yield once it breaks out; therefore, it is of great significance for the identification and early prevention of cucumber powdery mildew. This study, used a portable spectrometer to collect the reflectance curves of near-infrared (NIR) spectral and the intensity curves of fluorescence spectral of cucumber leaves. LI-6400 photosynthetic meter was used to measure the photosynthetic rate of cucumber leaves, and we also collected the image information of cucumber leaves.Firstly, powdery mildew was classified by image segmentation. Secondly, the Pearson Correlation between net photosynthetic rate and spectrum was analyzed. Finally, Finally, a powdery mildew detection model was established using qualitative analysis and quantitative prediction methods combined with photosynthetic rate indexes of cucumber leaves. The results showed that the cucumber leaf region was segmented by binarization as the region of interest (ROI), and the powdery mildew spot area could be extracted effectively according to the color difference between RGB and L*a*b* color space. Pearson Correlation analyzed the correlation between the photosynthetic rate and the spectrum. Results showed that the photosynthetic rate and the spectrum were negatively correlated. The correlation weakened with the increasing reflectivity and spectral intensity, which indicated that it is feasible to predict the photosynthetic rate using bands with intense spectral correlations. After comparing the prediction accuracy, the qualitative model was finally analyzed by the Subspace Discriminant algorithm in Ensemble Learner, and the NIR spectrum model was stable, and the recognition accuracy was high. The PLSR model was used for quantitative analysis, and the MSC was used as a preprocessing method to effectively remove spectral interference information, of which theR2 obtained by the NIR spectrum model was high, and the RMSEP was smaller than the RMSEC. In addition, the predicted results of the NIR spectral model were more similar to the expected values, and the healthy samples were clearly distinguished from the ones with powdery mildew infection, indicating that the model is highly robust. The above results showed that the image recognition system and the photosynthetic rate detection model based on NIRspectroscopy could be used to identify cucumber powdery mildew and classification quickly and accurately, which provided a method and reference for the diagnosis of cucumber disease.

The mid-infrared (MIR) laser heterodyne spectroscopy with high sensitivity and high spectral resolution is a remote sensing technique for detecting atmospheric trace gas’s column concentration and vertical concentration profile by using a narrow linewidth laser as a local oscillator (LO) and amplifying the weak absorption signal. This paper proposes a new instrument structure based on the current laser heterodyne radiometer (LHR). A direct absorption spectrum system was introduced in the laser heterodyne system to realize the selection of working wavelength and frequency calibration. A compact IR blackbody source EMIRS200 was used as the broadband radiation source to replace sunlight and verify and analyze the laser heterodyne system. It provides a new method for the next system integration of LHR. A MIR-wide tuning LHR proof-of-concept (PoC) system was developed, and the basic parameters of the system were tested and analyzed. The system used an 8μm external cavity quantum cascade laser (EC-QCL) as the LO and an IR blackbody source, EMIRS200, as the radiation source. After testing and analyzing the basic parameters of the system, the signal-to-noise ratio (SNR) (~120) and heterodyne conversion efficiency (~0.006) of the system were measured. The stability time of EC-QCL measured was at least 133s using Allan variance analysis, so it is very suitable for laser heterodyne spectrum acquisition. The limit of detection (LoD) of the 1σ minimum volume fraction of the direct absorption spectrum system was 2.312×10-8, which can meet the requirements of highly sensitive detection of atmospheric CH4 and realize the selection of working wavelength and frequency calibration of the heterodyne system. Finally, the high-resolution heterodyne absorption spectrum of CH4 at 8 μm was obtained by using the established LHR PoC system and compared with the direct absorption spectra of CH4 at 8 μm. Finally, the spectral resolution parameters of the system were fitted, and the high spectral resolution of the LHR PoC system was verified, which can satisfy the high-resolution laser heterodyne spectrum measurement under the condition of narrow laser linewidth. Experimental results show that the direct absorption spectrum system can be used to select working wavelength and calibrate the frequency of the laser heterodyne system. The compact IR blackbody source EMIRS200 can be used to optimize the structure of LHR to realize the analysis and verification of the laser heterodyne system, which provides an experimental basis for further application in the measurement of multi-component gas spectrum in the actual atmosphere and expands the application of LHR in the field of high-precision remote sensing.

A compact plasmonic refractive index sensor with ultra-high sensitivity has been proposed based on a metal-dielectric-metal waveguide coupled with atilted semi-ring cavity. A semi-ring cavity with a tilted angle of 70° to the horizontal direction is introduced above the MDM wave guideso that the symmetry characteristics of the resonator have been broken and more resonance modes can be generated. The transmission spectrum of a baffle-contained MDM waveguide coupled with a tilted semi-ring with a radius of 185 nm has been calculated numerically through the finite element method. Three transmission peaks with asymmetric Fano line-shape appear at the wavelengths of 594, 868 and 1 734 nm, respectively. The magnetic field distributions at these three wavelengths demonstrate that the third, second and first order resonance modes occurred in the semi-ring cavity lead to the three peaks in the transmission spectrum, which FR3, FR2 and FR1, respectively denote. Based on the coupling interference effect between the first three order narrow resonant modes and wide band reflected propagation modes in the MDM waveguide generated by the metal baffle, the formation mechanisms of triple Fano resonances leading to the three asymmetric transmission peaks have been clarified in detail. Meanwhile, the dependence of peak wavelengths on the refractive index of the dielectric materials has been calculated numerically, and the sensitivity associated with FR3, FR2, and FR1 are thus obtained as 550, 840 and 1 724 nm·RIU-1, respectively. In addition, an approximate analytical formula of the sensing sensitivity has been derived from the resonant condition of the semi-ring cavity, which displayed the linear dependence of the refractive index sensing sensitivity on the cavity length L and the reciprocal of the resonant order m. Obviously, the calculated three sensitivity values of the semi-ring cavity approximately satisfy this relationship. Finally, a split-ring with a split angle of π/2 has been obtained by extending the arc length of the semi-ring cavity without altering the radius of curvature so that the cavity length L has been lengthened 1.5-fold by increasing the center angle from π to 3π/2. Numerical results demonstrated that the sensing sensitivity of the three Fano peaks is increased to 821, 1 250 and 2 517 nm·RIU-1, respectively, which are 1.5 times the original values achieved in the semi-ring cavity scheme. Numerical results further verify the effectiveness of the approximate analytical formula, which provides a theoretical guideline for the design of compact high-sensitivity refractive index sensor.

This paper studied the physicochemical properties and laser damage resistance of sol-gel thin films conditioned with CO2 laser. The results show that the surface roughness of the thin film after laser conditioning decreased from 14.08 to 9.76 nm, with a decrease of more than 30%. The thickness of the film decreases with the increase of the laser power. After laser conditioning of 20 W, the thickness of the film decreases by about 17%～28%. The mechanical properties, such as elasticity modulus and hardness, were improved after laser conditioning. The elasticity modulus increased from 1.5 to 6 GPa, and the hardness increased from 40 to 110 MPa. Results of Fourier transform infrared spectroscopy show that after laser conditioning, the main peak shifted from 1 125 to 1 120 cm-1, and the average bridge bond angle between silicon and oxygen atoms became small.The reason is that during the CO2 laser conditioning, the local temperature increase which accelerates the dehydration and condensation of Si—OH bond, and reduce the porosity and absorption. UV nanosecond laser was applied to the laser damage test of the film, and the results show that the laser damage area of the film after 12 W laser conditioning is smaller than the film without laser conditioning, and the laser damage threshold is increased from 4.8 to 7 J·cm-2, which increased by 46%; However, the laser damage threshold after 16 and 20 W laser conditioning did not changes significantly, that is due to the ablation deposition occurred on the film’s surface after high-power laser conditioning, which will affect the UV nanosecond laser damage threshold and can not effectively improve the laser damage resistance. The results of this study show that CO2 laser conditioning can effectively improve the mechanical properties, including elasticity modulus, hardness of sol-gel SiO2 films and the laser damage resistance. CO2 laser’s power has a great impact on the properties of the films. CO2 laser conditioning is an effective technical means to improve the UV nanosecond laser damage resistance of sol-gel SiO2 films.

The full state-resolved distribution of scattered CO2(0000) molecules from collisions with highly vibrationally excited Na2(ν″=30 and 45) is reported and investigated how internal energy content impacts the dynamics for collisional quenching of high energy molecules. Stimulated emission pumping was used to excite the Na2(ν″=30, J=11) and Na2(ν″=45, J=11). Under single-collision conditions, rotational levels of the vibrationally relaxed Na2(ν″-1) and Na2(ν″-2) are identified. Levels attributable to upward vibrational transfer could not be observed. The change in Na2 rotational energy was determined. Quantifying the simultaneous population change for low J states is accomplished by transient line profile measurements for individual states. The line width is a measure of the translational energy spread of the scattered molecules and the area under the line profile is a measure of the J-specific population. The nascent translational temperature Tpres (for presence) and Tdep (for depletion) are determined from the measured line widths Δνpres and Δνdep, respectively. The presence line widths Δνpres were obtained by fitting the double-Gaussian function to the transient line profile data at t=1 μs. The lab-frame translational temperature Tpres for the presence of scattered CO2 molecules and the relative (center-of-mass frame) translational temperatures Trel for Na2(ν″) /CO2 collisions were determined based on Δνpres measurements. Average translational energy gains for the presence of CO2(0000, J) following collisions with vibrationally excited Na2 are determined using 〈Erel〉=3/2k(Trel-Tcell). The comparison shows that the Na2 vibrational energy that goes into the translational energy of the CO2 strongly depends on the initial energy: the translational energy of the J-specific collision pruducts increases by 56% or more for a 35% increase in donor vibrational energy. The appearance rate constants for individual CO2 rotational states are determined. The total appearance rate constant for Na2(ν″=30) is kapp=(6.6±1.5)×10-10 cm3·molecule-1·s-1. This result is comparable to that for Na2(ν″=45), where the appearance rate constant is kapp=(5.9±1.3)×10-10 cm3·molecule-1·s-1. The results show that the Na2(ν″)/CO2 collision frequency is not particularly sensitive to the amount of Na2(ν″) vibrational energy. The full energy transfer distributions P(ΔE) for product energy gain confirm that the ΔE distributions broaden rapidly for relatively small increases in donor energy for Na2(ν″)/CO2 collisions. P(ΔE) curves for Na2(ν″=30) are shifted to lower ΔE values compared to Na2(ν″=45) data. The ΔE values in P(ΔE) include the change in CO2 rotational energy and the change in translational energy of Na2(ν″) and CO2 plus the change in rotational energy of Na2(ν″). Numerical integration of P(ΔE) over the full range of ΔE yields 〈ΔE〉trans=590 cm-1; in comparison, 〈ΔE〉trans=880 cm-1 for Na2(ν″=45).

Near-infrared spectroscopy is mainly the overtones and combination bands absorption spectra of organic molecules, which are generated by the overtones and combination bands of hydrogen-containing groups such as C—H, N—H, O—H, etc., which can obtain molecular structure, composition, state and other information. This technology is an important method for studying the vibration information of hydrogen-containing groups in organic matter and is often used for qualitative and quantitative analysis of biological substances such as food and crops. The research objects in the biochemical field also have hydrogen-containing groups. These hydrogen-containing groups have strong absorption frequency characteristics, are less affected by the internal and external environment of the molecule, and have more stable spectral characteristics in the near-infrared spectrum. This technology can be used to detect chemical warfare agents and hazardous chemicals. Sarin is a neurotoxic chemical agent. When studying its structure, chemical properties and spectral properties, in order to ensure safety, simulants are often used in the experiment to substitute for testing, but there is no fair near-infrared simulant for sarin. This paper uses density functional theory (DFT), based on the Gaussian program package, and uses B3LYP/def2-SVP to optimize the ground state structure of the sarin molecule, and calculates the fine structure of the sarin molecule and the fundamental frequency vibration mode of the molecule. The generalized second-order perturbation theory (GVPT2) is introduced to establish a theoretical model for simulating the near-infrared spectrum of biochemical poisons, obtaining the near-infrared vibration peaks and main vibration modes, and the near-infrared spectrum drawn from the vibrations of overtones and combination bands. Analyze the hydrogen-containing groups of sarin in the near-infrared region, use this method to identify its characteristic peaks, obtain three characteristic peaks of sarin molecules at 1 150, 1 362 and 1 500 nm and analyze their vibration modes. Among them, the position at 1 150 nm is produced by the contribution of multiple overtones and combination bands vibration. 1 362 nm is a wide absorption vibration region, mainly caused by the combination bands of atoms connected to C atoms in the molecule and other non-C, H atoms. The near-infrared vibration peak at 1 500 nm is mainly caused by the C8 Related vibration mode contribution. In this paper, the theoretical model of Sarin’s near-infrared spectroscopy is established through density functional theory, and the feasibility of the theoretical model is verified through experiments, which provides theoretical support for finding its near-infrared spectroscopy simulation agent.

In recent years, the problem of excessive heavy metals in pig fodder has been repeatedly banned, which has seriously endangered the health of people who eat pork and the environment’s safety. The dry ashing-Atomic Absorption Spectroscopy as the national standard text method faces problems such as being time-consuming, sample destruction, and environmental pollution caused by reagents. Laser-induced breakdown spectroscopy (LIBS) is known as the “future superstar” in chemical analysis for its fast, nearly non-destructive, and no need for complex sample preparation. Traditional LIBS technology has the disadvantages of weak characteristic spectrum intensity and low detection accuracy when applied to pig fodder safety and quality inspection. In response to this defect, it is proposed to combine LIBS technology with cavity-confinement and use the cavity-confinement method to improve the intensity of the analysis spectrum. In this way, the detection of lower concentration samples and the rapid green detection of Cu element content in pig fodder samples are realized. Take Cu Ⅰ 324.75 nm as the analysis line, under the optimized energy, it compares the influence of loading cylindrical cavity-confinement cavity with different heights and diameters under different delay times on the analysis line. Then it selects cavity-confinement cavity which has perfect overall enhancement effect of the analysis line to collect the LIBS spectrum of 7 groups of pig fodder samples with different concentrations. Then the sensitivity of the LIBS system was analyzed in combination with the reference concentrations of Cu elements in seven groups of pig feed samples obtained using national standard methods. The results show that loading the cavity-confinement cavity causes enhancement of the analyzed spectral lines’ intensity without significantly affect for the background spectrum. Under the maximum enhancement factor of the analysis spectral line intensity is 5.16, the diameter of the cavity-confinement cavity is 5.0 mm, and the height is 2.0 mm. The overall enhancement effect on the analysis spectrum is the best. Based on those mentioned above best experimental parameters, the pig fodder was quantitatively analyzed by the characteristic spectral peak intensity of Cu element at 324.75 nm. The results showed that the linear relationship between the concentration of Cu element in pig fodder samples and the intensity of the analysis spectrum under different concentrations after loading the space confinement cavity was significantly improved compared with the traditional LIBS. The univariate calibration model R2 was increased from 0.742 to 0.996, and the detection limit fell from 6.21 to 1.61 mg·kg-1 (the recommended content of Cu elemental diet in pigs in the Guidelines for Safe Use of Fodder Addition is 3~6 mg·kg-1), and the detection sensitivity is increased by 2.86 times. Studies have shown that the combination of space limitation and LIBS technology can greatly improve the detection accuracy and sensitivity of the system, and reduce the detection limit of the element to be measured below the national requirements. Moreover, it also provides support for the realizing rapid green detection of LIBS for samples with low Cu element content in pig fodder.

Piezofluorochromic organic materials are a class of smart materials with fluorescent change in response to external force stimuli, which have broad application prospects in pressure-sensitive devices, optical information storage and mechanosensory.Triphenylamine with a propeller structure can inhibit strong intermolecular interaction and close packing, which has attracted much attention in piezofluorochromism. A new compound 9,10-Bis［4-(N,N′-diphenylamino) phenyl］-2-methylanthracene (TPA-MA) with triphenylamine as branch and anthracene-2-methyl as core was prepared from 2-methylanthraquinone by zinc powder reduction, bromination with bromineand palladium catalyzed Suzuki coupling reaction, and characterized by 1H NMR, 13C NMR and MS. The solvatochromism effect and piezofluorochromic properties were studied by UV-Vis, photoluminescence (PL), X-ray diffraction (XRD) spectra, and density functional theory calculation. With the increase of solvent polarity, the absorption spectra of TPA-MA remain almost unchanged, but the PL peak is progressively red-shifted, accompanied by the decrease of PL intensity. The Lippert-Mataga plots and the density functional theory calculations reveal that the intramolecular charge transfer (ICT) characteristic of TPA-MA is responsible for the large solvatochromism effect. Meanwhile, TPA-MA has typical piezofluorochromic properties. In the solid state, the PL peak of TPA-MA is at 450 nm with strong blue fluorescence. Upon grinding, the PL peak is red-shifted to 466 nm, accompanied by a decrease in PL intensity.When the ground powder is exposed to dichloromethane vapor or heated to 150 ℃, it can return to the original blue fluorescence and has repeatability.XRD spectra show that the piezofluorochromic properties of TPA-MA are caused by the change of crystal packing arrangement. The experiments and reported literature indicate that introducing an anthracene 2-methyl group can further cause a molecular twist in the luminophore skeleton to inhibit the intermolecular interaction and make the crystal packing looser. When triggered by an external mechanical stimulus, the crystalline order is easily destroyed. Consequently,the molecular backbone is more planar under pressure, which enhances the ICT characteristics, resulting in the red-shift and quenching of TPA-MA emission.

Gold sprinkled paper is a traditional processing paper with a long history and good decorative effect in China. It is widely used in writing, painting, and binding. The application of gold-sprinkled paper has a long history, during which it spread to Korean Peninsula, Japan with great popularity. Gold sprinkled paper is processed by various processing techniques, which fully shows the unique paper decoration technology and artistic aesthetics in ancient China. There are still many kinds of cultural relics made by gold sprinkled paper, but few relevant researches on scientific and technological analysis exist. Using the optical microscope, scanning electron microscope, energy dispersive spectrometer and infrared spectrometer, this paper analyzes the structure and composition of a gold sprinkled paper sample from the Qing Dynasty, and at the same time, the “sprinkled gold” material and technology of traditional gold sprinkled paper were discussed. It shows that the sample’s “sprinkled gold” area is foil. Besides, the metallic luster wasdetected by optical microscope and electron microscope. The results illustrate that Al, S, K, Cu, Ag and Au show obvious gradient distribution, which is consistent with the shape and contour of “sprinkled gold” particles. Further analysis shows that the main color pigment Au, Ag and Cu is half-life impurities. What’s more, Mg, Al, Si, S, K, Ca and other elements should mainly come from fillers, such as common talc (Mg3［Si4O10］(OH)2), calcium carbonate (CaCO3), etc. Infrared spectrum analysis shows that the characteristic absorption peaks of 1 105 and 662 cm-1 of “sprinkled gold” material are consistent with the O—S—O bond stretching and bending vibration peaks of SO2-4, 1 106 and 662 cm-1, and the characteristic absorption peaks of 1 641 cm-1 and 3 277～3 337 cm-1 are consistent with the characteristic absorption peaks of gelatin. Combined with Al, S and K in the above results, it suggests that there is alum water in sprinkled gold material. That is, the adhesive is made of gelatin Alum (KAl(SO4)2·12H2O) plays the role of connecting material in “sprinkled gold” material. It is inferred from this research that the “sprinkled gold” of the sample is mainly colored by gold foil, using gum alum water as an adhesive and adding fillers such as talc and calcium carbonate. The research on the materials and technology of “sprinkled gold” of traditional gold sprinkled paper lays a foundation for the inheritance and development of traditional gold sprinkled paper, as well as the protection, restoration, reproduction and identification of cultural relics and works of art of gold sprinkled paper.

Porcelain green paper is a famous processing paper in ancient China, and the relic made of porcelain green paper is often museum treasure. There are few records and researches on porcelain green paper, and there is a lack of systematic knowledge of its composition and production technology, making it difficult to carry out scientific protection and restoration of relics made by porcelain green paper. In order to further deepen the understanding of ancient porcelain green paper, three-dimensional video microscopy, Raman spectrometer, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and fiber analysis were employed to analyse the raw materials and manufacture process of one early Ming dynasty porcelain green paper sample. The result indicated that the dye on the sample matched the Raman peak position of indigo, and in the range of 1 570~1 701 cm-1, the stretching vibration of the CC bond, CO bond and N—H bond conjugate system is the characteristic absorption peak of indigo dye molecules. The sample’s strong Raman peak at 1 570 cm-1 is consistent with the Raman spectral characteristics of indigo, so it can be identified as indigo, which is also consistent with a long history of planting bluegrass and extracting indigo as a dye in China. The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis indicated that the main elements of paper such as S, Ca, Al, Si, and Mg should come from filler or coating. The paper has been filled and coated in order to improve the paper opacity, permeability, and gloss, but also ruled out the possibility that the sample blue dye is azurite, lapis lazuli or natural ultramarine blue. There are transverse nodules on the fiber wall, a colloidal membrane on the outer fiber wall, a small amount of calcium oxalate crystal in the fiber, and more yellow amorphous wax on the fiber. These characteristics are similar to that of tapa and mulberry bark fibers. Therefore, the base paper of porcelain green paper should belong to the bark paper, the strength of the bark paper fiber is relatively strong, so it is not easy to hydrolyze in the dyeing process. Therefore, the production process of the porcelain green paper is as follows: indigo dye is dyed on one side of the bark paper filled and coated, then superimposed up and down. This study can deepen the understanding of the materials and technology of Ming porcelain green paper making and provide a basis for the research, protection, restoration and reproduction of porcelain green paper relics.

Loquat is a freshwater fruit at the turn of spring and summer, it has a sour taste and can be eaten directly or made into candied fruit or wine, and it has the effect of resolving phlegm, relieving cough, harmonizing the stomach and lowering gas. The texture of loquat is soft and juicy, so it is prone to be bruised during picking, storage and transportation, resulting in economic losses. Therefore, detecting bruised loquats with high precision and rapid classification is essential. Meanwhile, we have used different methods to treat loquats with different bruising levels to reduce economic losses. The ones with light bruises can make loquat juice and paste. The ones with moderate bruises can be removed from damage region to make canned loquats for preservation. The ones with heavy bruises can be disposed of directly to save storage costs. At present, the bruise level of loquats is mainly discriminated by the operator’s naked eye. It is affected by personal habits, light intensity and subjective psychological factors, which will cause misclassification. In this paper, we propose a method based on hyperspectral imaging technology spectral combined with color features to classify loquat bruise level with high precision, rapidity and non-destructiveness. Firstly, we used a free-fall collision device to prepare light, moderate and heavy bruised loquat samples and used a hyperspectral imaging system to collect data. Secondly, we select the average spectrum of 100 pixels in the region of interest as the sample spectrum and preprocess the spectrum with MSC, which is used as the spectral feature for the subsequent model. Finally, we combined spectral features with color features and used RF, PLS-DA, ELM, and LS-SVM to build loquat bruising level models based on spectral features, RGB color features combined with spectral features, HSI color features combined with spectral features, and mixed color features combined with spectral features, respectively. Among all the above models, the loquat bruise level model based on mixed color features combined with spectral features has the best prediction effect. The overall recognition accuracy of the models using RF, PLS-DA, ELM and LS-SVM algorithms is 91.11%, 86.67%, 95.56%, and 100%, respectively. The RBF-LS-SVM bruising loquat model has the highest accuracy. The results show that the model based on single spectral features has the lowest accuracy, the model combined with RGB or HSI color features has higher accuracy, and the model based on spectral features combined with mixed color features has the highest accuracy. This study provides a certain theoretical reference and experimental basis for fruit bruising level discrimination.

Soluble solids content (SSC) is the key indicator to evaluate the quality of watermelon pulp. In order to meet the needs of different groups of people and improve market competitiveness, an online detection model of watermelon SSC is established, which can realize the online grading of watermelon quality according to its SSC. In this paper, the 160 Jingmei2K watermelons are used as the research object, and the visible near-infrared full transmission spectrum data of the two postures of watermelons are collected using the online detection equipment independently developed by our laboratory. The partial least squares regression (PLSR) prediction model is established with the SSC of different parts of the watermelon to explore the best posture and part of online detection of watermelon SSC.Firstly, the SSC measurements of different parts of watermelon were defined as Pedicel Sugar, Central Sugar, Melon Navel Sugar and Average Sugar, and the two postures detected online were defined as T1 posture and T2 posture, respectively.Secondly, comparing the SSC of different parts of watermelon, the evaluation standard of watermelon SSC was discussed. Then, the spectral data with low transmission intensity and high frequency containing much noise and useless information were removed. Finally, the spectrum with a wavelength range (671~1 116 nm) was selected for analysis. The Savitzky-Golay smoothing (SGS) algorithm is combined with multiplicative scatter correction (MSC), unit vector normalization (UVN) and standard normal variate transformation (SNV) to preprocess the spectral data under two postures. Then the prediction model is established for the SSC of different parts of watermelon. By comparing the prediction results of different models, it is found that the combination of SGS and MSC has the best preprocessing effect for T1 posture spectral data, while The spectral data of T2 posturehas better performance using SGS combined with UVN preprocessing methods. The prediction effect of the T1 pose is better than that of the T2 posture spectral data. The prediction results of Pedicel Sugar and Average Sugar are better than that of Melon Navel Sugar, and Central Sugar is the worst. Finally, competitive adaptive reweighted sampling (CARS) was used to optimize the prediction models of Pedicel Sugar and Average Sugar. 81 and 106 wavelength points were selected to establish the prediction model of Pedicel Sugar and Average Sugar, respectively. The correlation coefficients of the prediction sets of the two models are 0.881 0 and 0.875 8, and the root mean square errors are 0.866 7% and 0.758 9%, respectively, simplifying the model and improving the prediction accuracy.The results showed that different postures and SSC prediction of different parts of a watermelon affected the results of online detection and quality evaluation. The model should be selected and optimized according to the actual needs of users. This paper, proposes an evaluation index for the online watermelon SCC detection, which provides a technical basis for further development of watermelon SSC online detection equipment.

In order to explore the role of red and blue light in the coloring process of tomato fruit, the micro tomato was planted with rock wool in an artificial light plant factory and irradiated with different lighting modes such as pure red light, combined red and blue light and alternating red/blue light. The reflection spectrum and hue index of tomato fruits at different development stages were analyzed to study the effects of red and blue irradiation modes on the spectral characteristics and coloring of tomato fruit. The results showed that: (1) The alternating irradiation mode of R6h/RB2h (pure red light/combined red and blue light, 6 h/2 h) was the most beneficial to the accumulation of the red pigments (e. g. β-carotene and lycopene) and the decomposition of chlorophyll, finally led to the earlier color conversion of tomato fruit; The effects of R (pure red light) was second only to R6h/RB2h; In contrast, the mixed irradiation mode of RB (combined red and blue light) was not conducive to the accumulation of red pigments and fruit coloring process of tomato fruit. (2) There are both synergistic enhancement effects and signal crosstalk weakening effects between red and blue light in promoting tomato fruit coloring. The alternated irradiation of R and RB may maximize the positive effects of single red light and mixed red and blue light in tomato fruit coloring. (3) The dynamics of pigment content reflected by spectral parameters such as Red/Green, MCARI, |PRI| of tomato fruit in the color conversion period displayed consistent with the color of tomato fruit reflected by Hue value, the reflection spectral characteristics of tomato fruit in this period were highly unified with peel coloring. The reflection spectrum of tomato fruit in the color conversion period can better reflect the degree and process of tomato fruit coloring.

Bacillus anthracis is a highly pathogenic microorganism. Anthrax is an infectious disease caused by Bacillus anthracis, classified as Class B of our country’s statutory reporting infectious diseases. Therefore, the establishment of simple operation, rapid and sensitive detection methods for Bacillus anthracis is vital for preventing and contralling the spread of anthrax and maintaining public health security. This study innovatively proposed to synthesize soy protein gold nanoclusters (SPI-AuNCs) with strong red fluorescence emission by microwave heating using the green material soy protein as a protective agent and reducing agent.TEM, XPS, FTIR, FL, and UV-Vis characterizations were used to verify successful synthesis of SPI-AuNCs. SPI-AuNCs are spherical, which the particle size is in the range of 1.8～3.2 nm, an average diameter of 2.65 nm, and no surface plasma resonance absorption from 500 to 550 nm. The maximum excitation wavelength of SPI-AuNCs is 370 nm, and the maximum emission wavelength appears at 680 nm. The surface functional groups of SPI-AuNCs mainly include —NH, —COOH, —OH, —SH, and the element composition includes C, N, O, S, Au elements. The fluorescence of SPI-AuNCs could be quenched by the coordination between Cu2+ and surface groups of SPI-AuNCs, while DPA has a stronger chelation effect with Cu2+, which could compete for Cu2+ from the surface of SPI-AuNCs and restore the fluorescence of SPI-AuNCs. Accordingly, a new method for DPA detection based on the fluorescent “off-on” strategy was established. Under the optimal experimental conditions, the fluorescence recovery efficiency (ΔF/F1) performs a good linear relationship with DPA concentration in the range of 1.15~70.0 μmol·L-1. The linear regression equation is ΔF/F1=0.011c+0.131 with high correlation coefficient (r=0.991), and the detection limit is 0.34 μmol·L-1. In addition, the spiking experiments of the DPA in lake water and milk samples were performed. The spiked recoveries were 97.3%~103.6%, indicating that this method has great application potential in DPA detection for environmental and food samples, and can provide methodological guidance for environmental monitoring and food safety.

With the wide spread of new psychoactive substances (NPS) nationwide, it is an urgent need for the drug law-enforcing departments and relevant technicians to conduct an in-field rapid qualitative analysis of suspected NPS samples. Synthetic cathinones are cathinone derivatives and are the second-largest category of NPS. This study used a portable Raman spectrometer to analyze the Raman spectra of 70 synthetic cathinone reference substances.The Raman spectrum characteristics of synthetic cathinones were systematically summarized, which will help to identify the unknown synthetic cathinones. All analyzed synthetic cathinones showed strong bands at (1 597±19) and (1 676±16) cm-1, which was caused by the stretching vibration of the aromaticCC and CO bonds, and can be used to distinguish synthetic cathinones from other types of NPS. The benzene ring mono-substituted, and 1,3-disubstituted synthetic cathinones showed the most intense bands at 992~1 000 cm-1, caused by the in-plane deformation vibration of C—H on the benzene ring. 3,4-Methylenedioxy substituted synthetic cathinones showed strong bands at (712±9), (809±5), (1 250±16), (1 355±9), (1 444±12), (1 597±19), and (1 676±16) cm-1; meanwhile, shoulder-bands were observed around (1 597±19) cm-1. The overall discriminant ability of Raman for various regioisomers and structural analogues was also investigated. Raman spectra of 70 kinds of cathinones were compared one by one. Raman was generally distinguishable for most synthetic cathinones, especially for regioisomers substituted by the methyl, halogen and methoxy groups on the benzene ring. It is one of the significant advantages of Raman compared with GC-MS and LC-MS. Raman spectra of some structural analogues with different alkyl substitutions were highly similar but could also be distinguished by characteristic peaks. Raman was also used to analyze seized samples, and the results showed that when there was no fluorescence interference in the sample, the Raman database search result was consistent with that of GC-MS, which proved the high method reliability and applicability. The portable Raman spectrometer has the advantages of simple operation, fast and non-contact sample measurement, and can be used for the fast in-field preliminary qualitative screening of NPS.

Potassium is one of the major elements in seawater. Research on the structure of potassium sulfate aqueous solution is helpful in explaining the microscopic mechanism of its solubility, thereby providing theoretical guidance for the separation and purification of potassium salt in seawater. In this paper, the microstructure of K2SO4 aqueous solution with different mass fraction was studied using an X-ray diffractometer refitted in the laboratory, Shanghai Synchrotron Radiation Facility device and Raman spectroscopy. The F(Q) obtained from the processing of the X-ray scattering data shows that the double peak near Q=2.5 -1 gradually becomes two peaks of equal intensity, which is associated with the hydrogen bonded network in the liquids. As the mass fraction increases, the peak position near Q=5.0 -1 moves to the right of the coordinate axis. It can be seen from G(r) that the peak at 2.8  tends to broaden with the increase of the mass fractions, which is mainly affected by the O—O interaction. In the Raman spectrum, the intensity of the shoulder peak near 3 200 cm-1 gradually decreases with the increase of solute content, and the overall peak shape becomes narrower in the range of 2 800～3 800 cm-1. The results of deconvolution fitting of Raman spectra show that adding K2SO4 destroys the tetrahedral hydrogen bond configuration of water and slightly promotes the formation of proton-donor hydrogen bonds. The analysis results from X-ray scattering and Raman spectroscopy indicated that the addition of K2SO4 destroyed the original tetrahedral network structure of water molecules.

Iron cultural relics are an important cultural heritage of humanity and are of great significance for studying the development and progress of human society. Conservators protect such cultural relics as much as possible to provide valuable physical materials for historical and cultural research. The characteristics of iron with high activity and easy corrosion make iron cultural relics one of the difficulties in conserving metal cultural relics. There are many studies on the protection and restoration of iron cultural relics and the qualitative analysis of iron rust products, while there are relatively few studies on the quantitative characterization of iron rust products. Furthermore, the complexity of corrosion products also increases the difficulty of quantitative analysis. In order to understand the composition of iron cultural relics rust products and evaluate their stability, it is necessary to establish a method for quantitative analysis of the rust products of iron cultural relics. In this study, five rust products (α-Fe2O3, Fe3O4, α-FeOOH, β-FeOOH, γ-FeOOH) were used to simulate samples (three groups of binary mixture systems and a set of quaternary mixture systems) of iron artifacts. Infrared spectroscopy combined with the Classical Least Squares (CLS), Principal Components Regression (PCR) and Partial Least Squares (PLS) in TQ Analyst software was used to construct quantitative analysis models of four groups of mixtures, respectively. The results show that PCR and PLS are more suitable for establishing quantitative models of rust products of iron cultural relics among the three quantitative analysis models. Moreover, the root mean squared error of calibration (RMSEC) and root mean squared error of prediction (RMSEP) are small, and the correlation coefficient is close to 1. The quantitative models have good predictability and stability. The research results provide a basis for the quantitative analysis of the rust products of iron cultural relics and then the evaluation of the chemical stability of iron cultural relics.

The Qulong Site, located in Ngari Prefecture of Tibet Autonomous Region, is a relic of human activities with a long duration and rich types of remains. The ornaments studied in this paper were excavated from tomb No.2(M2) of Sailaqinbopu Locus, the Qulong Site, dating back to about 2700~2400 years ago. Due to the processing and grinding during production and the weathering and erosion suffered by long-term underground burial, it is impossible to judge the raw materials of the eight ornaments only from their appearance. Therefore, ultra-depth of field microscopic analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction experimental analysis (XRD), thermal analysis (TGA-DSC), X-ray fluorescence spectrometry (XRF), Scanning electron microscopy (SEM) and porous material density, porosity, water absorption test were used not only to determine the chemical composition and raw material source of ornaments, but also to scientifically and comprehensively analyze its microscopic morphology, shape and structure characteristics and preservation condition. The results show that the raw materials of eight ornaments come from the pearl layer of different freshwater shellfish shells, and the main components are aragonite calcium carbonate, with a small amount of organic matter and trace elements such as Fe, Ba, Cr, Cu; there are grinding marks on the surface of the ornaments, and the drilling method is drilling from both sides, and holes of thicker ornaments are drilled with a bit; the overall weathering is serious, luster is no longer and all have a certain degree of crisp powder, porosity and water absorption rate of the open holes are higher than the modern shell, and the main reason for these diseases is the loose and disorderly shell pearl layer aragonite plates caused by loss of organic matter. On the one hand, the above research conclusions provide important information on the material selection, shape and production technology of ornaments in the Xiangxiong period in western Tibet, and reflect the situation and aesthetic connotation of shellfish use in society at that time. On the other hand, they also provide valuable reference materials for the subsequent protection and restoration of such unearthed cultural relics.

As a kind of disastrous weather with great harmfulness, sandstorm event significantly impacts the ecological environment in Northwest China. This study, it is to explore the spatial-temporal evolution of a typical dust event in northwest China in 2016 based on ground-measured particulate matter data, MODIS data, OMI sensor data and CALIPSO LiDAR data. Firstly, the characteristics and pollution situation of typical urban air pollution sources in Northwest China were determined based on PM2.5/PM10 index. Then, the spatial distribution characteristics of dust levels in atmospheric aerosols were analyzed using MODIS image MCD19-A2 AOD data, OMAEROe data product OMAEROe data product AAI data and CALIPSO-Level1 data. Finally, the backward trajectory of dust flow was simulated by the HYSPLIT model to determine the dust transport path in Northwest China. The results showed that the PM10 index of Xining, Lanzhou and Yinchuan was more than 200 μg·m-3 from April 30th to May 1th, 2016, and their PM2.5/PM10 value was less than 0.6, which was at a low level, indicating that the content of inhalable particulate matter in the air increases due to the influence of natural pollution sources. It could be inferred that this was the influence of the sandstorm event. Aerosol showed obvious horizontal variation during the sandstorm event. The sandstorm originated from the Southern Xinjiang Basin and continuously affected southern and central Xinjiang from May 1th to May 4th. In addition, Qinghai, Gansu, Ningxia and some parts of Shaanxi were also affected. According to its spatial variation, the Taklimakan Desert was the center of the formation of aerosol pollution in this sandstorm event. The sandstorm event mainly affected the southern basin and central Xinjiang, and the northern part of Qinghai Province. It could be seen from the simulation results of the air flow track that the sandstorm event from April 30th to May 1th, 2016, mainly affected Xinjiang and some areas of Qinghai through the westward path. What is more, the sandstorm material might have come from Southern Xinjiang basin and the Gurbangut Desert in the inner Junggar Basin of northern Xinjiang and Kazakhstan outside China. These results would provide an important scientific basis for suppressing the process of dust generation and protecting the sustainable development of an ecological environment in Northwest China.

In astronomy, stars whose brightness changes with time are called variable stars. It is of great significance to study the distance of galaxies, the evolution of stars and the properties of stars in different stages. At present, the identification of variable stars mainly depends on observing their brightness changes for a long time and analyzing the spectrum of stars. This work requires astronomers to invest much time, so it is not easy to carry out large-scale classification. A data fusion method of photometric image and one-dimensional spectrum is proposed to classify variable stars. Experiments are carried out on identifying eclipsing variable stars, pulsar variable stars and standard stars. The Sloan Digital Sky Survey project includes photometric images and spectral data. For spectral data, this paper selects the flow value in the wavelength range of 380.0~680.0 nm. The photometric image comprises five data bands: u, g, r, i and z. The corresponding center wavelengths are 355.1, 468.6, 616.6, 748.0 and 893.2 nm respectively. The photometric value is generally distributed between 0 and 200. For the image part, this paper uses the data of five bands for classification, and locates the position of the target star in the photometric image through the star catalogue. In order to facilitate network training, photometric and spectral data are standardized. The method of combining photometric image and spectral data for classification proposed in this paper uses four indicators: accuracy, recall, F1 value and average accuracy. The experimental results after data fusion are better than those using spectral or photometric data alone. For the classification tasks of eclipsing binaries, pulsars and standard stars, the accuracy rates are 91.1%, 92.8% and 98.2% respectively. Experiments show that the combination of image data and photometric data is an effective method for star classification, which provides a new idea and method for star classification in the future.

With the implementation of more and more large-scale spectral surveys, many star spectral data are generated, which is of great significance to the study of star evolution theory, but also brings great challenges to the traditional spectral classification and processing. In the LAMOST DR7 (v2.0 version) spectral data set released in 2021, the total spectrum of stars has reached the order of millions, but the number of O-type is only 129, and the data set is seriously unbalanced. Traditional machine learning classification methods cannot achieve good results for such a large amount of data and a serious imbalance of data sets. Therefore, they are mostly used to classify the spectra of adjacent stars of two types, partial types or subclasses. An automatic star spectrum classification method based on semi-supervised mode of one dimensional convolutional neural network (CNN) and one dimensional generative adversarial network (GAN) is used to solve this problem. Firstly, each spectrum is tailored and denoised, and the wavelength range of the spectrum is 370.00~867.16 nm. Then, uniform sampling and normalization are carried out to generate 1×3 700 data set samples, which are sent to one-dimensional CNN for training. In order to avoid overfitting and improve model’s prediction ability for unknown data, dropout is applied between the full connection layer and the pooling layer. This one-dimensional CNN network is used to classify six kinds of spectra except for O-type, and the average classification accuracy is 98.08%. This experiment uses one-dimensional GAN network to solve the problem that the number of O-type is seriously small. The input of GAN is a noise signal whose size is 1×900.Through the fully connected three-layer convolution operation in the generator, the output size is 1×3 700. The separate alternating iterative training of the generator and discriminator finally outputs the required number of O-type star samples to expand the data set. Compared with oversampling, using data sets expanded by GAN to classify the star spectra can improve the classification accuracy of O-type stars from 72.92% to 97.92%, and the accuracy of the classifier can reach 96.28%. The experimental results show that the automatic star spectra classification method using this semi-supervised mode can realize the rapid and accurate classification of seven types of star spectra and can also be used to mine the unclassified spectra marked as “unknown”.

We conduct observation and research on ground solar radiation using the international standard RAMSES spectrometers and CMP11 global solar radiometers for 8 cities (Ngari, Shigaze, Lhasa, Nyingchi, Chengdu, Wuhan, Hangzhou, Shanghai) along the 30°N latitude region of China during 2019 and 2020. Observation results show that along the 30 °N region in China, Tibet’s overall solar spectrum intensities are not only much higher than that of low altitude inland cities, but also the spectral curves are smoother and less absorbed than that at low altitude in terms of morphological characteristics. During the observation period, the maximum monochromatic solar spectral intensity on the ground in Tibet reached 2 018.48 mW·(m2·nm)-1 (Ngari, Jun.21, 2020), and the maximum monochromatic solar spectral intensity in other mainland cities at the same latitude is only 756.22 mW·(m2·nm)-1(Chengdu, Nov. 3, 2019); The ultraviolet spectra (280-400nm) contained in the ground solar spectra of Tibet is about 1.5 times higher than that of the low altitude in the mainland. The strong ultraviolet has a corresponding impact on the ecology and human health in Tibet; It is found that during the observation, the ground solar spectral intensity of Lhasa is about 1.5～1.7 times than that of Chengdu; The ground solar spectral intensity of Ngari is about 0.2 times higher than that of Shanghai. The observation results provide field solar spectral data for the utilization of solar energy resources and ecological environment research in the 30°N latitude region; We conduct observational studies synchronously to the solar spectrum of the solar eclipse during the summer solstice in 2020. It is found that the radiation energy loss in Lhasa and Ngari during the solar eclipse is more than 95%. The effects of atmospheric factors such as clouds and aerosols on the solar spectrum and total solar radiation are analyzed. The work shows that the global solar radiation value in Ngari and other places in Tibet frequently exceeds the solar constant during the summers.

It is difficult to accurately determine the spatial distribution of tidal flats in intertidal zones due to periodic tidal inundation. Therefore, it is urgent to use remotely-sensed technology to detect the spectral variation characteristics of tidal flats, construct a tidal flat extraction index, and then provide methods and basic data support for flat tidal interpretation. Based on multi-temporal Sentinel-2 images, this research analyzed the spectral reflectance differences of different land cover types in the high- and low-tide images and then determined the bands that can reflect flat tidal characteristics. Finally, a tidal flat recognition index was proposed by mathematical combination. The proposed tidal flat index is studied: (1) the proposed tidal flat recognition index was applied to three study areas with different tidal flat types, and the tidal flat recognition index’s separability and applicability to different tidal flat types are studied. The results showed that the proposed tidal flat recognition index showed a good performance on tidal flat separability compared with other land cover types and is applicable to different types of sandy and muddy tidal flats; (2) the applicability of the tidal flat recognition index to different classification methods (including minimum distance method, maximum likelihood method and support vector machine) is studied. The results showed that the overall accuracy is greater than 93%, and the kappa coefficient is greater than 0.85 for distinguishing tidal flats. The tidal flat recognition index is universal to different classification methods and can effectively improve the accuracy of distinguishing tidal flats; (3) the suitability of the tidal flat recognition index to different remotely-sensed data sources is studied. Compared the Sentinel-2 images with OHS images, the results showed that the tidal flats are distinguished, and the tidal flat recognition index proposed is applicable to different data sources, achieving a higher classification accuracy. This study improves the accuracy of distinguishing tidal flats using remote sensing data, enriches the theory of flat tidal interpretation, and provides theoretical guidance and significance for the scientific management and protection of the coastal.

Indian Longdan stone was introduced into China as a carving stone because of its similar colors and materials to Qingtian Longdan stone. However, the spectral, mineral compositional, and structural characteristics of Indian Longdan stone are still unclear. In this paper, the gemmological characteristics, color genesis and spectral characteristics of a representative sample were studied by polarizing microscopy, X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM), Electron Probe Micro Analyzer (EPMA) and Fourier Infrared Spectrometer (FTIR). Indian Longdan stone is characterized by “white meat and red heart”. The polarizing microscope shows that the illite is a cryptocrystalline lepidoblastic texture. Obvious red-brown spotted materials are aggregating in the “red heart” area, presenting as dense to loose from the central red area to the edge yellow-green area, consistent with the color change. XRD results show that the light yellow-green “white meat” and “red heart” diffraction patterns are the same, showing three strong diffraction peaks at 10.00, 4.99 and 3.33 . Clear peaks can be observed at 2.86, 2.99, 3.20, 3.49 and 3.73  and no other mineral phasecan be detected, indicating that the sample is pure 2M1 type illite. The full width at half maximum of XRD at 10.00  peak is 0.092°Δ two theta, indicating that the order and crystallinity of illite are well. EPMA further confirms that the Indian Longdan stone is mainly illite, with an average cation content of 0.824 p. u. f. and a structural iron content of 0.05%～0.08%. SEM backscattering composition images show that the red-brown patchy material has obvious bright contrast but generally shows similar morphology of illite. The energy spectrum analyses show that the average content of iron in this area is 0.48% wt, which is one order of magnitude higher than the content of structural iron in illite, indicating that the red-brown patchy iron-bearing material may be the chromogenic material of Indian Longdan stone. SEM observation reveals KCl crystals with cubic morphology, indicating that the illite may be directly crystallized in K-rich fluid. The results of FTIR show that the samples have an OH stretching vibration peak at 3 630 cm-1 and an Al—O vibration peak in tetrahedron at 830 cm-1. The absorption peak at 756 cm-1 is related to the substitution of Al in tetrahedral coordination instead of Si, which is characteristic of Si—O—Al vibration in the tetrahedron. The absorption peaks of OH stretching vibration near 3 625 cm-1 and at 825 and 750 cm-1 double fingerprints are the characteristic infrared absorption peaks of illite minerals, which confirms that the main mineral of Indian Longdan stone is illite. The study of Indian Longdan stone enriches the understanding of the gemmological and spectral characteristics of carved stone material, and the infrared spectral characteristics can be used as the identification basis for rapid, nondestructive testing of carved stone samples.

In this paper, the carbon-14 dating was used, and 9 batches of Os Draconis samples correspond to the fossil age range: 3 batches of samples are between 18000 and 37000 years, and 6 batches of samples are 43500 years before. XRD and EPMA were used to determine the phase composition and elemental morphology of 9 batches of authentic Os Draconis. The main component of the Os Draconis was calcium hydroxyphosphate and some samples were hydroxyphosphate Symbiosis of calcium and calcium carbonate; the micro-phase is mainly hydroxyapatite, while calcium carbonate is mostly in the form of calcite-type calcium carbonate, and a small part is in the form of dolomite. The ARF, ICP-AES, ICP-MS, and AES were used to determine the element content of the samples. The results showed that the Ga/P ratio in the Os Draconis was greater than 2. The trace elements of the 9 batches of Os Draconis had approximately the same Distribution pattern: Sc, V, Cr, Co, Ni, Cu are all depleted relative to the original mantle, Ba, Sr, As are abnormally enriched, and element U is highly enriched; the distribution of rare earth elements in 9 batches of Os Draconis is also It has roughly the same distribution pattern, showing LREE enrichment type, with Ce negative anomaly, Eu partial positive anomaly, partial negative anomaly, LREE positive anomaly; 6 batches of Os Draconis before 43500 years, the total amount of rare earth elements is significantly higher The three batches of samples between 18000 and 37000 years are presumed to be related to their burial diagenetic environment on the one hand, and to the older the age, the higher the concentration of some elements.

Rock color reflects the geological environment and mineral and element composition of its formation. And it is one of the important basis and indicators for vertical stratigraphic correlation and lateral environmental evolution. Rock color mainly relies on visual identification and subjective description or uses color charts for comparative interpretation. These methods are greatly affected by individual differences and the environment, lack quantitative calculation methods, and cannot meet the needs of accurate color identification in batches. Therefore, it is of great significance for the research and application of geological work to quickly realize the objective identification and numerical quantification of color. This research is based on the principle of colorimetry, using spectral analysis technology combined with the quantitative recognition software of rock color compiled by Python computer language. It can perform numerical quantification and automatic batch conversion of rock color. The method improves color judgment accuracy and recognition efficiency. The comparison of 《Munsell Rock Book》shows that the calculation results of the CIE RGB color system are highly consistent with the color card. In the calculation results of the Munsell system, the consistency of hue value (<3 NBS units) reached 86.7%, the consistency of lightness value and purity value reached 92.2% and 82.2%, and the correlation was 98.83% and 87.50%. Their errors all belong to the small chromatic aberration range. Compared with the calculation results of the Munsell system, the CIE RGB calculation results of the 31 rock samples are more consistent and accurate with the color of the samples. The reasons for the errors are complex and diverse, related to the conversion error between color systems , human subjective comparison and interpretation, and closely related to the particularity of rock samples and the environment and other factors. This study provides a feasible method for the quantitative characterization of rock color. This research has good application value.

With the delay of rice maturity in rice-wheat rotation areas in the middle and lower reaches of the Yangtze River, the delay of the sowing date of winter wheat has become the main obstacle affecting the yield, so it is necessary to screen better resistant varieties in late sowing wheat. This study was designed to monitor the relative chlorophyll content of canopy leaves during the early winter wheat growth for late-sowing winter wheat variety screening. In order to explore the feasibility of monitoring chlorophyll content in winter wheat, this study used five single-band spectral reflectance and 15 vegetation indices obtained by UAV as the independent variables. Through recursive feature elimination (RFE) feature variables screening, redundant variables were removed. A remote sensing inversion model of winter wheat’s relative chlorophyll content (SPAD) was established using the BP neural network regression algorithm. Based on the measured leaf SPAD values of winter wheat in the experimental site of Guangling District, Yangzhou city, Jiangsu Province, during 2020—2021, the correlation between remote sensing variables and SPAD values in the two growth stages was analyzed combined with multi-spectral UAV images obtained simultaneously. In addition, feature variables were screened based on the ranking of feature importance among remote sensing variables, and the selected variables were used as the input of the model to construct and screen out the best inversion model for each growth period. Using Ridge regression (Ridge) and Gradient Boosting Decision Tree (GBD) algorithms as a comparison, and R2 and RMSE as model evaluation indexes, the three models’ self-learning ability and generalization ability were analyzed on the validation set. The results showed that the BP neural network model based on optimal spectral information screening showed the strongest regression prediction ability in the two growth periods. R2 and RMSE were 0.806 and 1.861 in the overwintering stage and 0.827 and 0.507 in the jointing stage, respectively. In this paper, the variable selection of UAV multi-spectral data was carried out, and the BP neural network of optimization model constructed had high estimation accuracy. It showed that the effect of early monitoring of winter wheat was better in the elongation stage than in the overwintering stage. It is valuable to use UAV multi-spectrum to estimate the SPAD value of late-sowing winter wheat for variety resistance screening.

Vegetation covers can do well in carbon sequestration and water retention. In this paper, we used artificial runoff and artificial rainfall equipment to simulate rainfall (storm: 50 mm·h-1) on a 6° slope with or without vegetation planting. In this case, combined with the 3DEEM-PARAFAC method, the source and component structure of runoff liquid (Dissolved Organic Matter, DOM) at different slope locations are analyzed to determine the relationship between DOM and the carbon and water sequestration effect of the soil. The results showed that: ① Compared with bare ground, the reduction of sediment concentration and (Dissolved Organic Carbon, DOC) of the vegetated surface is consistent: overland runoff>through runoff>subsurface runoff. Besides, the rank of the reduction of soil erosion is through runoff>subsurface runoff>overland runoff. Compared with bare ground, the rank of runoff reduction of the vegetated surface is: subsurface runoff>through runoff>overland runoff. ②According to the analysis of the fluorescence index, the results of FI and BIX characterization are the same. The source of DOM is influenced by the metabolism of the endogenous material: overland flow>through runoff>subsurface runoff. Compared with the humus source of bare land, the humus source of the vegetated surface changed from endogenous material to the combination of endogenous material and allothigene. The HIX index under vegetation covers is higher than that of bare land, and the degree of humification of runoff fluid is overland flow>through runoff>subsurface runoff. ③By parallel factor analysis, different runoff fluid DOM included four fluorescence components: humic acid-like ( C1: Ex/Em=260/455 nm), UV fulvic acid-like (C2: Ex/Em=240/395 nm), tryptophan-like (C3: Ex/Em=230~275/335 nm, 230~275nm/400 nm) and tyrosine-like (C4: Ex/Em=215/395 nm). ④The analysis of fluorescence intensity and Fmax values of different treatments showed that the Fmax values of the treatment with vegetation cover were all greater than those of the bare land. The Fmax values of C1, C2 and C4 components showed the same trend: above-ground runoff>soil flow> underground runoff. The Fmax values of C3 components showed the trend: above-ground runoffin-soil flow>subsurface runoff. ⑤ Runoff, erosion, and sediment concentration are positively correlated, while C1 and C4 components are significantly negatively correlated with runoff and erosion. Based on this, according to DOM fluorescence spectrum characteristics of slope rainfall-runoff, vegetation coverage can change organic matter components in soil, which provides the theoretical basis for the healthy development of soil ecosystems in the eroded environment. Moreover,it also indicates that the stability and content of humic acid and protein-like substances play an important role in soil consolidation and water retention.

In view of the weld quality problems caused by unstable wire feeding in laser welding of ER316L stainless steels, this paper proposes an on-line monitoring method based on plasma emission spectrum diagnosis and builds a weld quality prediction model, which is of great significance to realize the adaptive control of welding process and intelligent laser welding. In order to further study the interaction mechanism between laser and welding material in laser welding, experiments of laser welding and laser wire filling welding were carried out. The laser-induced plasma’s spectral information was collected synchronously and compared with the arc spectrum of TIG welding process. The results showed that the spectrum during laser welding consisted of continuous spectrum and Fe Ⅰ 636.44 nm and Cr Ⅰ 427.48 nm line spectrum. During laser wire filling welding, the radiation intensity increased significantly, and many Cr Ⅰ lines were generated. The arc spectrum contained a large number of Ar Ⅰ and Ar Ⅱ lines and a small number of Fe Ⅰ lines. According to Boltzmann plotting and Stark broadening methods, the plasma electron temperature and electron density during laser wire filling welding were calculated. They were 5 024.9 K and 2.375×1016 cm-3, respectively, satisfying the local thermodynamic equilibrium state. The intrinsic relationship between laser welding quality and spectral features was explored on this basis. The results showed that the spectral line intensity and electron temperature strongly correlated with the weld quality. When the forming was good, the intensity of the CrⅠ spectral line was higher than that of the FeⅠ spectral line, and the electron temperature fluctuated steadily in a small range. The intensity of the CrⅠ line was lower than that of the FeⅠ line, and the electron temperature changed sharply when the bias defect occurred. Using the CrⅠ 529.83 nm spectral line intensity, FeⅠ 636.44 nm spectral line intensity and electron temperature as inputs, the weld quality classification model of a single hidden layer neural network was established to identify two states of well-formed and defects. The average accuracy of 10 tests was 88%. The t-distribution t-stochastic neighbor embedding was used to reduce the dimension of spectral data, and the three-dimensional embedding vectors were taken as the input features. The same neural network structure was used for weld quality pattern recognition, with an average accuracy of 97%. The results showed that the features obtained by dimensionality reduction of spectral data contained the information of line spectrum and continuous spectrum, characterizing the weld quality more accurately than the line spectrum selected by a human.

Multi-spectral radiation temperature measurement measures multiple spectral radiation intensity information of a certain point of the object to be measured and obtain the true temperature through the Planck formula inversion. However, the unknown spectral emissivity is the biggest obstacle to the inversion process of multi-spectral radiation temperature measurement. At present, a set of emissivity models (emissivity-wavelength or emissivity-temperature models) are often used in advance. If the assumption model matches the actual situation, the inversion result can meet the requirements. If the assumption model does not match the actual situation, the reverse result of the performance is a very error. Whether it can realize the direct inversion of true temperature and spectral emissivity without any hypothetical model of spectral emissivity has always been a hot and difficult point in the theoretical research of multi-spectral radiation temperature measurement. For this reason, a generalized inverse matrix-coordinate rotation algorithm is proposed to transform the inversion problem of multi-spectral radiation temperature measurement into a constrained optimization problem. Since the generalized inverse method needs to constrain the emissivity range, and the coordinate rotation method needs to set a proper initial emissivity value, considering the respective advantages and disadvantages of the two algorithms, the two algorithms can be combined. The minimum norm solution obtained by the generalized inverse method is used as the initial point of the iterative search in the constrained optimization algorithm, which further improves the adaptability of the algorithm to the emissivity of different materials. In order to verify whether the algorithm can find a special solution that meets the thermophysical parameters (emissivity) and true temperature of the target under test without considering the assumed relationship between emissivity and wavelength, six types of targets with a representative emissivity change trend are selected Material is simulated experiment. The simulation results of six different spectral emissivity models show that the new algorithm does not require any prior knowledge about emissivity, and the inversion results of different emissivity models perform well. In the case of a true temperature of 1 800 K, the absolute error and relative errors are less than 5.0%. Compared with the gradient projection method, the calculation efficiency is increased by 202 times on average. It shows that the algorithm has the advantages of not considering any prior knowledge of spectral emission rate, fast inversion speed and being suitable for various emission models. It further improves the theory of multi-spectral radiation temperature measurement and has good application prospects in high-temperature measurement.

Ultra precision micro nano devices are the core devices in the manufacturing field. With the rapid development of ultra-precision machining technology, the corresponding micro nano detection technology is required to be higher and higher. Micro nano measurement technology is an important means to ensure the accuracy and stability of ultra-precision machining technology and is the premise for further development. The surface profile detection methods for micro/nanodevices can be divided into optical and non-optical types according to whether optical principles are used. Non-optical detection usually adopts point scanning and contact detection, which is inefficient and easy to damages the surface morphology of the device to be tested. Optical detection methods are mostly surface scanning, and non-contact measurement, which will not scratch the device to be tested, and the detection efficiency is high. In optical detection, white light interferometry has been widely concerned by researchers at home and abroad because of its short coherence length, which can achieve high-precision measurement of three-dimensional morphology of micro-nano devices. In white light interference detection technology, the signal demodulation algorithm is very important to the entire detection system. Traditional white light interference signal demodulation algorithm only uses part of the information of the interference signal, which has low demodulation accuracy. However, high-precision phase shift demodulation algorithm depends on the accuracy of rough positioning, which cannot directly achieve the high-precision three-dimensional shape recovery. In order to solve the above problems, this paper proposes a signal demodulation algorithm based on the correlation. This algorithm calculates the correlation through a three-level sliding window and uses all the white light interference signal information. Without rough positioning, it can directly determine the three-dimensional surface topography information of the object to be measured. In order to verify the performance of the algorithm, this paper has carried out simulation and experimental verification. The simulation results show that the method is feasible and can accurately restore the 3D structure morphology to be measured. The setting of a three-stage sliding window can effectively improve the calculation efficiency. At the same time, the white light interference vertical scanning experimental system is built, and the grating structure and microlens structure are measured. The experimental results are compared with the traditional gravity center and phase shift methods. The experimental results show that this method can accurately restore the three-dimensional topography of different objects, and its accuracy and robustness are better than the improved barycenter method, which is close to the phase-shifting method. The grating height recovery results show that the error between this and phase-shifting methods is less than 0.5 nm. The simulation and experimental results show that the white light interference signal demodulation method based on the correlation proposed in this paper is feasible. It can achieve high-precision recovery of the three-dimensional surface topography of the object to be measured without rough positioning and has the characteristics of high precision and high robustness.

The coal resources in China are mainly concentrated in the arid and rain-less northern areas. Open-pit mining and transportation can easily cause the diffusion and pollution of coal dust. After the dust diffuses, some of them settle and cover the surrounding vegetation under gravity, leading to the common phenomenon of dust falling on vegetation. When remote sensing is used to monitor vegetation growth and health status, the dust fall effect will affect the spectral purity of vegetation so that the signal obtained by remote sensing is the mixed spectral signal of vegetation and dust fall, which seriously affects the quantitative remote sensing accuracy of vegetation. In order to study the dust retention effect of coal dust in vegetation remote sensing, the experiment of spectral measurement for dusty leaf was carried out, and the change of spectrum and vegetation index was studied. On this basis, sentinel-2A remote sensing images with red-edge bands were used to compare vegetation indices in the coal dust affected area and control area in Huolinhe open-pit mining area, the Inner Mongolia Autonomous Region, respectively, to verify the experimental results of ground spectral measurement.In this experiment, vegetation leaves were selected from a coal mining area in Shenyang. The coal dust was evenly sprayed on the leaf surface with a level difference of 2 g·m-2 to simulate the effect of dust retention on the actual leaf surface. Spad-502 chlorophyll meter was used to measure the spectrum of dust retention on the leaf surface, and the spectrum and vegetation index variation rules were explored.Since the red edge band was used for the vegetation index in this experiment, sentinel-2A remote sensing images were selected. Huolinhe Open-pit mine in NeiMengGu province and its surrounding areas were selected as the verification area. The coal-dust-affected area, and the control area were selected for vegetation index comparison to verify the experimental results of ground spectral measurement. The results show that, with the increase of dust retention (0～36 g·m-2), coal dust on the surface of the leaves will gradually reduce the overall reflectance of the leaves, and the change amplitude of the reflectance at the peak of the leaf spectrum (560, 720, 860, 1 680, 2 220 nm) is significantly higher than that at the trough (445, 681, 1 940 nm).With the increase in dust retention, NDVI (normalized difference vegetation index), SR705 (simple ratio), and ND705 (normalized difference index) decreased significantly. However, MTCI (the medium resolution imaging spectrometer terrestrial chlorophyll index), mSR705(modified simple ratio) and mND705 (modified normalized difference index) are unchanged, showing the characteristics of coal dust resistance. The reflectivity at 445 and 681 nm in these indices play an important role. By using Sentinel-2A remote sensing image in Huolinhe open pit coal mine area and comparing the coal dust affected area with the control area, MTCI, mSR705, and mND705 indices show the characteristics of coal dust resistance, verifying the results of ground experiments. The study would lay a foundation for vegetation remote sensing in the area of coal dust pollution and ensure the accuracy of vegetation remote sensing inversion.

Puerariae Thomsonii Radix is a medicinal and edible plant with an extremely high medicinal and edible value containing puerarin, starch, cellulose, vitamins, etc. Extensive research has shown that the content of chemical components in Puerariae Thomsonii Radix is closely related to the growth period. However, much of the research up to now has been descriptive. The main disadvantage of traditional techniques is that the operation cycle is long, and the destructiveness is large, which cannot be tested on a large scale. The development of hyperspectral imaging (HIS) has provided new insights for the rapid non-destructive identification of Puerariae Thomsonii’ s age.In order to avoid the quality problems caused by the insufficient growth years of Pueraria, hyperspectral imaging technology combined with machine learning was used in this experiment to identify the years of Pueraria accurately. However, in fact, one major drawback of this approach is that there is a great deal of redundant information in hyperspectral image data. What is more, the huge amount of data and highly correlated between characteristic bands directly increases the difficulty of sample identification. Principal Component Analysis (PCA) has been taken to extract features from the data to avoid an impact on subsequent classification effects. Based on the full band and PCA dimensionality reduction data to achieve accurate identification of different years of age, there are four classification models currently being adopted in research, including support vector machines (SVM), logistic regression (LR), multi-layer perceptron (MLP) and random forest (Random Forest, RF).When using full-band data modeling, the accuracy of four different classification models under different lenses is 78.09%, 77.03%, 81.43%, 72.09% and 93.11%, 93.79%, 94.23%, 89.77% respectively. The MLP model achieved the best effect under both SN0605VNIR(VNIR) and N3124SWIR(SWIR) lenses. When using PCA dimensionality reduction data modeling, the test set accuracy of four different classification models under two lenses is 96.12%, 87.53%, 95.02%, 93.41% and 99.26%, 97.09%, 99.16%, 97.91% respectively, in which SVM has achieved the optimal prediction accuracy under both VNIR and SWIR lenses. In summary, these results show that the method of PCA can effectively improve the model’s prediction accuracy. In addition, in order to explore the influence of principal component content on prediction accuracy, the authors analyzed the model parameters further, and the experimental results showed that under the VNIR lens, the principal components of the four models accounted for 65%, 75%, 80% and 45% when the accuracy of the test set reached the highest. Under the SWIR lens, when the accuracy of the test set of the four models reached the highest, the proportion of principal components was 20%, 60%, 35% and 30%, respectively. Among them, the PCA-SVM performed the best comprehensive effect, and high prediction accuracy (99.28%) was achieved with 20% principal components. Therefore, the findings of hyperspectral imaging technology combined with machine learning will be of interest to realisingrapid, non-destructive and high-precision identification of the age of Puerariae Thomsonii Radix.

Soil moisture determines a region’s ecological carrying capacity and soil physical and chemical properties to a certain extent. It is significant to obtain soil moisture content accurately and quickly for ecological environment monitoring and soil degradation restoration. Hyperspectral remote sensing is widely used in soil parameter inversion, but the research on hyperspectral characteristics and parameter inversion of alpine meadow soil needs further study. Consequently, to develop a hyperspectral inversion model of soil moisture content in alpine meadows applicable to fragile alpine ecosystems, 102 soil samples were collected from Henan County in the Yellow River source area. Multiple linear stepwise regression (MLSR), partial least squares regression (PLSR) and back propagation neural network (BPNN) methods were used to model the soil moisture content with the original spectrum and its mathematically transformed characteristic bands, and the inversion accuracy was verified by the coefficient of determination (R2), root mean square error (RMSE) and the residual ratio of prediction (RPD). The major findings are as follows: (1) In the visible-near infrared band, the spectral reflectance of soil samples has water absorption interval near 710, 780 and 950 nm, and the absorption intensity is different. The reflectance tends to decrease rapidly and increase slowly with increasing soil moisture content. (2) SPA algorithm was used to select the spectrum’s characteristic bands after S-G smoothing, four transformations as independent variables and water content as dependent variables. Then MLSR and PLSR were used to establish the inversion model. The PLSR model corresponding to the first-order differential (FD) and first-order logarithmic differential (FDL) transformations can achieve a rough inversion of soil moisture in alpine meadows, and the PLSR model corresponding to the FD transformation is accurate. (3) In the BPNN inversion models, except for the model corresponding to continue to remove (CR), theR2 of other models is greater than 0.9, and RMSE is between 0.048 and 0.074. In all the models, the BPNN model corresponding to FD, FDL and LG transform is highly accurate, with R2 and RPD greater than 0.8 and 2.5 respectively. The BPNN model corresponding to the LG transform has the highest accuracy, with R2, RMSE and RPD up to 0.967, 0.038 and 5.039, respectively. Therefore, the BPNN model can achieve relatively accurate hyperspectral inversion of soil moisture content of alpine meadow in the source region of the Yellow River, which can provide the technical basis and data support for ecological environment monitoring and soil restoration in this region and even other alpine regions.

The mechanical properties of paper are mainly characterized by tensile strength. According to GB/T 12914—2008, this indicator is usually tested with a tensile machine. However, this method requires a large sample size and many samples, which is unsuitable for precious paper cultural relics. In this work, Thermomechanical Analyzer (TMA) is used for mechanical testing of paper cultural relics for the first time to establish a new evaluation method by taking advantage of its precise and nondestructive feature. The environmental changes in the Qianlong Garden of the Palace Museum were monitored, and the aging conditions were designed based on the monitoring results. UV, dry-heat, and humid-heat accelerated aging experiments were carried out on the handmade bamboo paper, which is usually used to restore Pengbihushi in the Palace Museum. TMA, SEM and FTIR were used to test the changes in tensile strength, micro-morphology, and chemical structure of bamboo paper samples before and after aging to analyze the aging characteristics of bamboo paper. The results show that TMA can effectively measure the mechanical strength of bamboo paper with low strength after aging. The tensile strength of bamboo paper after humid-heat aging was the highest (up 1.01%), followed by dry-heat aging (down 15.11%), and after UV aging the lowest (down 63.85%). Correspondingly, it was observed by SEM that there was no obvious change in the fiber structure of the humid-heat and dry-heat aging samples, but the fiber structure of the UV aging samples showed obvious fracture and damage. Infrared spectroscopy analysis also showed that the UV aging sample had the lowest absorption peak in the cellulose fingerprint region, indicating that the cellulose degradation was the most serious. The three test results can confirm each other. In addition, the size of the sample required by TMA is only at the millimeter level (10~20 mm in length, about 1 mm in width), which is much smaller than that of a conventional tensile machine. Moreover, the TMA test only requires about 7 samples to achieve good repeatability and accuracy. TMA has good applicability to low strength paper, so it is expected to explore further the possibility of applying TMA to precious ancient paper with extremely low strength.

High sulfate content in cement carries risks of volume expansion in late hydration. Nano-TiO2 and nano-SiO2 were used to modify semi-dry flue gas desulfurization ash, which contains a high rate of CaSO3·0.5H2O, and nano-modified semi-dry flue gas desulfurization ash was used to prepare nano-solid waste high sulfur cement, to solve the problem of poor durability caused by high CaSO3·0.5H2O content in the matrix. The ratio of each component in nano-solid waste high sulfur cement was determined according to the stability, water requirement of normal consistency, setting time and compressive strength of nano-solid waste high sulfur cement. LPSA was used to analyze the particle size distribution of raw materials. The water contact angle measurement was used to analyze the wettability of hardened slurry, the XRD was used to analyze the mineral composition of raw material and hardened slurry, the FTIR was used to analyze the change of microstructure of raw material and hardened slurry, the SEM was used to analyze the micromorphology of raw material and hardened slurry. The results show that the particle size distribution range of semi-dry flue gas desulfurization ash is 0.31~127.38 μm, which is wider and finer than that of cement particles, and so can optimize the grading range of cement. The semi-dry flue gas desulfurization ash could delay the setting of cement hydration, prolong the setting time, and reduce the compressive strength, especially with a large amount. Adding nano SiO2 and nano TiO2 can reduce the water requirement of normal consistency of cement matrix and improve its compressive strength. The synergistic modification of 3% nano TiO2 and 2% nano SiO2 can effectively stabilize CaSO3·0.5H2O in semi-dry flue gas desulfurization ash, further stimulating the potential activity of semi-dry flue gas desulfurization ash and improve the mechanical properties of cement hardened slurry. The 28-day compressive strength of modified nano-solid waste high sulfur cement is 64.72 MPa, 83% higher than that of unmodified high sulfur cement and even 16% higher than that of pure cement. The wetting edge angle increases to hydrophobic change, which is conducive to improving durability. XRD analysis results show that the content of AFM-like mineralsin hydration products is shallow, which reduces the risk of expansion. FTIR analysis showed that the stretching vibration peak of —OH contained in Ca(OH)2 in the hydration system was enhanced, further improving the hardened slurry’s chemical erosion resistance. SEM analysis shows that the hydration product has uniform texture and fewer microstructure defects. Nano-TiO2 and nano-SiO2 co-modified semi-dry flue gas desulfurization ash can stabilize sulfate and sulfite and are used to prepare high-performance nano solid waste high sulfur cement is beneficial to carbon reduction, energy conservation and environmental protection.

To explore the impact of the new crown epidemic prevention and control measures on NO2 pollution in Urumqi, and to promote air pollution control more effectively. In this study, based on the combination of OMI (Ozone Monitoring Instrument) satellite remote sensing hyperspectral technology and ground monitoring data, the NO2 dry deposition flux was estimated. To study the NO2 diffusion trajectory and potential sources in Urumqi City during epidemic prevention and control in 2019—2021. Using night light data, the Baidu map heat map tool, and AutoNavi map POI (Point Of Interface) functional area, the source of NO2 pollution in Urumqi was further analyzed and discussed. The research shows that: (1) The overall performance of NO2 concentration in Urumqi City is: Xincheng District>Shayibak District>Tianshan District>Shuimogou District>Midong District, the comparison between 2020 (epidemic outbreak period) and 2019 (pre-epidemic period) during the same period. It is found that the NO2 concentration in each urban area has decreased significantly, among which the Shaybak District has the largest decrease of 47.63%. The comparison between 2021 (post-epidemic era) and 2020 (epidemic outbreak period) shows that the NO2 concentration in each urban area has gradually recovered. The Ibarque district saw the largest increase, at 60.09%. The urban thermal conditions are as follows: Tianshan District>Shayibak District>Shuimogou District>Xincheng District>Midong District. The urban thermal conditions and NO2 concentration changes are roughly the same, and the urban population agglomeration in Midong District is the lowest, so the urban thermal value and NO2 concentration are both the lowest. (2) The long tributaries are transported in the long-distance northwest direction. The farthest distance is from Kazakhstan, and the airflow accounts for the largest proportion, reaching 80.32%. The short tributaries mainly come from and around Urumqi, and the air flow accounts for 19.69%. NO2 is a short-lived gas, so the short-distance transportation of air flow has a greater impact on NO2 in Urumqi. The probabilities of the potential source regions passed by various types of airflow are relatively consistent in the spatial distribution. The potential source contributions simulated by the PSCF analysis method have great credibility. (3) Analyze the atmospheric system as a gray system, and divide it into: standard coal consumption>secondary industry>total industrial output value>industrial electricity consumption>population density>car ownership>tertiary industry>primary industry. Under static and stable weather conditions, the dry deposition flux was estimated based on OMI satellite remote sensing data. This method can compensate for the shortage of ground monitoring and provide evidence for the estimation of dry deposition flux.

9-fluororenoneis a typical oxygenated PAH, the derivatives of PAHs containing carbonyl functional groups. Oxygenated PAHs can be formed by direct photolysis or oxidation of parent PAHs