In Situ Underwater Laser-Induced Breakdown Spectroscopy Analysis for Trace Cr(VI) in Aqueous Solution Supported by Electrosorption Enrichment and a Gas-Assisted Localized Liquid Discharge Apparatus.

Traditional laser-induced breakdown spectroscopy (LIBS) always fails to directly detect target in aqueous solution due to rapid quenching of emitted light and adsorption of pulse energy by surrounding water. A method is proposed for the in situ underwater LIBS analysis of Cr(VI) in aqueous solution freed from the common problems mentioned above by combining a gas-assisted localized liquid discharge apparatus with electrosorption for the first time. In this approach, the introduction of the gas-assisted localized liquid discharge apparatus provides an instantaneous gaseous environment for underwater LIBS measurement (that is, the transfer of sampling matrix is not needed from aqueous solution to dry state). The preconcentration of Cr(VI) is achieved by electrosorption with a positive potential applied around adsorbents, which can promote the adsorption of Cr(VI) and inhibit that of the coexisting cations leading to a good anti-interference. Amino groups functionalized chitosan-modified graphene oxide (CS-GO) is utilized for Cr(VI) enrichment, which can be protonated to form NH3+ in acidic condition promoting the adsorption toward Cr(VI) by electrostatic attraction. The highest detection sensitivity of 5.15 counts µg-1 L toward Cr(VI) is found for the optimized electrosorption potential (EES = 1.5 V) and electrosorption time (tES = 600 s) without interference from coexisting metal ions. A corresponding limit of detection (LOD) of 12.3 µg L-1 (3σ method) is achieved, which is amazingly improved by 2 or even 3 orders of magnitude compared to the previous reports of LIBS.

Study on Three-Dimensional Fluorescence Spectral Characteristics of Heterocyclic Pesticides in Different Environmental Conditions.

The impact analysis of different environments on the fluorescence emission spectrum of pesticides is critical in detecting the concentration of pesticides. In this paper, three kinds of pesticides, carbendazim, carbaryl and fuberidazole, were selected as the research objects. Under different environment, such as different pH values and the presence of different common anion or cation, three-dimensional fluorescence spectral emission (EEM) characteristic of pesticides were analyzed. The experimental results showed that the primary fluorescence peaks for three kinds of pesticides were at λex/λem=280/300, 310/340 and 280/335 nm (respectively); Carbendazim and fuberidazole had a secondary peak at 245/305 nm (PeakB) and 250/340 nm (PeakB). We can come to the conclusion that with the change of pH value, the characteristic of fluorescence emission of carbendazim and fuberidazole is similar. We can find that the fluorescence intensities of carbendazim and fuberidazole were enhanced with the declining of the solution acidity or alkalinity and the fluorescence intensity of carbaryl had not changed with the declining of the solution acidity, but it increased with the declining of the solution alkalinity; the fluorescence emission spectra of the three kinds of pesticides had good fluorescence characteristics with the scope of the pH varying from 6.16 to 7.4. Twelve common ions in water (CO2-3，SO2-4，NO-3，Cl-，HPO2-4，HCO-3，Mg2+，Zn2+，NH+4，Na+，Ca2+，K+) had no significant effect on fluorescence emission characteristics of carbendazim and fuberidazole. The fluorescence intensities were seriously influenced by Fe3+ and Cu2+. The results showed that the pesticides fluorescence intensities were decreased with the ion concentration increasing. It was necessary to consider the quenching effects on pesticides of Fe3+ and Cu2+for the analytic results. The obtained results provided the basic research for improving the accuracy of the heterocyclic pesticides measurement in water.

[Comparative Study on Laser Induced Breakdown Spectroscopy Based on Single Pulse and Re-Heating Orthogonal Dual Pulse].

In order to improve the detection sensitivity and spectral characteristic of laser-induced breakdown spectroscopy (LIBS), re-heating orthogonal dual-pulse configuration is adopted to analyze Fe, Pb, Ca and Mg contained in the sample and soil sample contained different concentrations of heavy mental Cr. Variation relationship between spectral intensity, signal-to-background(SBR) of four characteristic spectral lines FeⅠ：404.581 nm，PbⅠ：405.78 nm，CaⅠ：422.67 nm and MgⅠ：518.361 nm and time interval of two laser pulses is discussed, the best time interval of two laser pulses is obtained 1.0 µs. In the condition of single pulse and dual-pulse, the enhancement factor of spectral intensity of four characteristic spectral lines FeⅠ：404.581 nm，PbⅠ：405.78 nm，CaⅠ：422.67 nm and MgⅠ：518.361 nm is respectively 2.23，2.31，2.42 and 2.10; The time evolution characteristic of spectral intensity of characteristic spectral lines FeⅠ：404.581 nm and CaⅠ：422.67 nm is considered, and also the variation relationship between spectral acquisition delay time and SBR of four characteristic spectral lines, dual-pulse can prolong decay time of spectral intensity and improve the SBR of characteristic spectral lines; time evolution characteristic of plasma temperature and electron density is compared in the condition of single pulse and dual-pulse, maximum elevation of plasma temperature is found to be 730 K, and the maximum increase of electron density is 1.8×1016 cm-3. The limits of detection of heavy mental Cr are obtained 38 and 20 µg·g-1 respectively in condition of single and double pulse, limit of detection of Cr is reduced approximately 2 times by the condition of re-heating orthogonal dual pulse. Results above indicate that re-heating orthogonal dual-pulse can improve detection sensibility and spectral characteristic of LIBS technique, which provides an effective method for decreasing the limit of detection of elements.

[Rapid Soil Classification with Laser Induced Breakdown Spectroscopy].

Soil classification is an important research content in soil science field. It is the basis of soil survey and resource evaluation which is important to agricultural production. There are many soil classification standards all over the world. China has two kinds of classifications including soil genetic classification and soil system classification. There are great differences between different types of soil elements, so it is feasible for soil classification to use laser induced breakdown spectroscopy. Laser induced breakdown spectroscopy (LIBS) is a new element analysis technology which uses a laser pulse with high energy density to ablate samples. LIBS has been used in many fields including environmental protection and industrial production control. It can directly reflect the difference of element content in different soils. The experimental setup including an Nd: YAG laser, a spectrometer, a computer and a rotating platform. In the experiment 7 kinds of soil (red soil, brick red soil, lateritic red soil, paddy soil, cinnamon, alluvial soil and alpine meadow soil) including 25 samples were used. All soil samples were grinded and sieved before the experiment. Under the same experimental condition, the temperatures of the plasma created by the laser pulses on the surface of the different soil samples have great differences. The lateritic red soil had the highest temperature, and the alpine meadow soil had the lowest. But it was not enough to form the basis for classification. Therefore six constant elements including Si, Fe, Al, Mg, Ca and Ti were selected and their spectral line intensity were treated as classification index. Principal component analysis (PCA) was used to simplify the classification process. The PCA method could simplify the 6 indexes to few independent indexes which could also reflect the spectral information of the 6 elements. The original spectral data was processed by Matlab. The process consisted of spectral background removal, characteristic spectrum identify and extraction. The classification results showed a three--dimensional figure. Except alpine meadow soil which varied in element concentrations 6 kinds of soils achieved good classification. The brick red soil and lateritic red soil varied in PC1, but their PC2s and PC3s were the same. The two kinds of soil overlapped with each other and they couldn't be separated. Back-propagation artificial network was also used to achieve soil classification. The classification results were the same with the PCA. Some brick red soil and lateritic red soil samples were identified inaccurately. When the PC1, 2, 3 were used as the input of the BP-neural network, the classification had much better accuracy because less input improved the performance of the BP-neural network. Only one alpine meadow soil sample was identified to cinnamon soil. When the plasma temperature was also taken into account, all the soil samples could be distinguished. The results showed that LIBS could be used to classify soils based on their element content differences. The PCA, soil plasma temperature and BP-neural network were useful tools to achieve soil classification. The LIBS provides a useful tool for general detailed soil survey and rational utilization of soil.

Study on Detection Sensitivity of Heavy Metal in Water Based on LIBS Combined with Electrode Enrichment Method.

In order to improve the detection sensitivity of laser-induced breakdown spectroscopy (LIBS) and lower the limit of the detection of elements, LIBS combined with Aluminum electrode enrichment method is adopted to analyze heavy metals such as Pb,Cdand Ni in the water. The relationship between the characteristic spectral intensity and the key parameters-voltage of electrode method is discussed, the spectral intensity increases first and then decreases with the increase of voltage. The spectral intensity reaches the maximum value when the enrichment voltage is 1.2 V while the optimal enrichment voltage value is 1.2 V. The stability of characteristic spectral lines of heavy metals is studied, and the relative standard deviation(RSD) of spectral intensity of Pb, Cd and Ni is 5.98％，4.25 ％ and 5.27％ respectively, the result shows that the spectral line obtained by this method has high stability. A series of samples in the range of 0~0.13 mg·L-1 are prepared and quantitatively analyzed, the limit of detection of Pb, Cd and Ni is obtained 1.2，3.1 and 1.7 ppb respectively. The above result shows that LIBS combined with aluminum electrode enrichment method can effectively improve the stability of characteristic spectral lines and lower the limit of detection of Pb,Cd and Ni. This research also provides a method to further improve detection sensitivity of LIBS and analysis ability of heavy metal in the water.

[Rapid Quantitative Detection of Bacterial in Water Based on Multi-Wavelength Scattering Spectra].

The structures of bacterial cells are analyzed in this paper. The scattering components of individual cell were divided into two parts including external structure and internal structure. The interpretation model of bacteria about scattering light is established. The model is used to analyze the scattering light of Escherichia coli in the region of 400~900 nm. The average size of external structure and the internal structure can be obtained, and the ratio of the two parts is also obtained. According to the relationship of the optical density of single cell and the overall measurement, the concentration of bacterial can be obtained quickly. The maximum difference in all the concentrations of the bacteria repeated measurements is 1.83%; compared with the plate culture method, the measurement results were in the same order of magnitude, with relative error of 3.43%. The scattering light of Escherichia coli and Klebsiella pneumoniae are analyzed in different growth stages, the curves of the concentration and the size of the two species bacteria over time are obtained. The results can provide a quick way for the study of bacterial growth and technical support for rapid detection of bacteria in the water.

[Laser Induced Time-Resolved Fluorescence Spectroscopy Characteristics of Fluoranthene in Ethanol with Eanosecond Laser of 355 nm].

Polycyclic Aromatic Hydrocarbons (PAHs) have been widely investigated in environmental field, for most of them are mutagenic (carcinogenic, teratogenic, mutagenic). The influence of delay time and gate width on the time-resolved fluorescence spectroscopy of fluoranthene in ethanol was studied in this paper. Furthermore, laser induced time-resolved fluorescence spectroscopy of fluoranthene with different concentration were also researched. According to the results, fluorescence kinetics decay curves and fluorescence lifetime of fluoranthene matched. The research results showed that there was closely relationship between the fluorescence spectrum of fluoranthene and the delay time and gate width of detector. When the delay time was fixed, the fluorescence intensity of fluoranthene grew increased as the gate width increased. When the gate width was fixed, the fluorescence intensity of fluoranthene increased first and then decreased with the delay time increases. The process of the attenuation of fluorescence intensity of fluoranthene with time delay conformed to the exponential decay process. The stepwise dilution of fluoranthene ethanol solution was also studied. With increasing dilution, the fitting of fluoranthene fluorescence lifetime increased. The results of this paper can provide a technical basis for the detection of PAHs in the environment, due to the different characteristics of the fluorescent substance having fluorescence lifetime.

[Study of the Impact of Sample Thickness on Thin Film Method X-Ray Fluorescence Spectrum Measurement].

The mixed samples of nylon film enrichment of Cr, Pb and Cd three elements and glass fiber membrane filter were as the research object. With the method of superposition of membrane filter, the XRF spectra were measured under different thin film samples thicknesses. According the changes of characteristic XRF of Cr, Pb and Cd elements in the mixed sample and Ca, As and Sr elements in glass fiber membranes, the effects of sample thickness on thin film method XRF spectrum measurement were studied. The study results showed that the effects of thin film sample thickness on the fluorescent properties of elements with characteristic spectral lines in different energy ranges were different. The energy of characteristic spectral lines was greater, the loss of element characteristic X-ray fluorescence when it passed through membrane and reached detector was less. But matrix effect caused by thin film sample thickness increase was stronger with the energy of characteristic spectral lines greater. The background fluorescent intensity in corresponding characteristic spectral line location was greater. So the impact of matrix effect caused by sample thickness increase on thin film method XRF spectrum measurement sensitivity was greater. For elements with low energy characteristic spectral lines (energy≤7 keV), the way of increasing thin film sample thickness in order to increase the mass-thickness concentration of component measured, can not effectively improve the sensitivity of thin film method XRF spectrum measurement. And thin film samples thickness within 0.96 mm is conductive to the measurement and analysis of XRF spectrum. For element with higher energy characteristic spectra lines(energy＞7 keV), the sensitivity of XRF spectrum measurement can be appropriately increased by the way of increase thin film sample thickness in order to increase the mass-thickness concentration of component measured. And thin film samples thickness within 0.96～2.24 mm is more conductive to the measurement and analysis of XRF spectrum. The study provides an important theoretical basis for thin sample preparation and enrichment technology of thin film method X-ray fluorescence spectrum analysis the atmosphere and water heavy metal.

[Effect of Methanol-Water Mixture on Three-Dimensional Fluorescence Spectra of Carbaryl].

Extensive use of pesticides has a significant impact on the environment. Carbaryl, whose residues stay in the surface water, is one of the most widely used broad spectrum insecticides in agriculture. It is important to understand carbaryl spectral characteristics and detection methods. The characteristic of excitation-emission three-dimensional spectra of carbaryl is studied. By changing the concentration of methanol in methanol-water binary solvent, the impact of methanol-water mixture on three-dimensional fluorescence spectra of carbaryl is discussed. The results show that the characteristic excitation-emission spectra of carbaryl is single peak, the range of the excitation wavelength and emission wavelength are: 244~304 and 300~350 nm respectively, the maximum excitation/emission peak located at 280 and 335 nm. With increasing the content of methanol in methanol-water binary solvent mixture, there is no obviously spectra shift of three dimensional fluorescence spectra of carbaryl. However, the intensity of fluorescence is nonlinear dependent on the content of methanol, mainly due to the specific properties of binary mixed solvent.

[Quantitative Analysis of Cr in Soil with Laser Induced Breakdown Spectroscopy Combined With Multivariate Calibration].

Laser-induced breakdown spectroscopy (LIBS) was used to calibrate the concentration of Cr in soils combined with Support Vector Machine. The Nd:YAG pulse laser with the wavelength of 1 064 nm was used as the excitation source. The grating spectrometer and the charge couple device were used as spectral separation device and the spectral detection device. The multiple linear regression and support vector machine were adopted to make quantitative analysis on Cr in soils respectively. The result indicate that the multiple linear regression can get more accurate informination of the spectral lines: the correlation coefficient is increased from 0.689 to 0.980 compared with conventional quantitative method. Thereofre, the the accuracy of quantitative analysis is increased. The slope about calibration curve with support vector machine of test set is nearly about 1 and the correlation coefficient is 0.998, the relative errors for the test set all are lower than 2.57%, the quantitative analysis results about support vector machine are better than the results combined with the conventional quantitative method and the multiple linear regression. The support vector machine can correct the matrix effect and improve the accuracy of prediction on the concentration of Cr in soil.

[Outlier Detection of Time Series Three-Dimensional Fluorescence Spectroscopy].

The qualitative and quantitative analysis are often interfered by the outliers in time series three-dimensional fluorescence spectroscopy. In this work, an efficient outlier detection method is proposed by taking advantage of the characteristics in time dimension and the spectral dimension. Firstly, the wavelength points that are mostly the outliers are extracted by the variance in time dimension. Secondly, by the analysis of the existence styles of outliers and similarity score of any two samples, the cumulative similarity is introduced in spectral dimension. At last, fluorescence intensity at each wavelength of all samples is modified by the correction matrix in time dimension and the outlier detection is completed according the to cumulative similarity scores. The application of the correction matrix in time dimension not only improves the validity of the method but also reduces the computation by the choice of characteristics region in correction matrix. Numerical experiments show that the outliers can still be detected by the 50 percent of all points in spectral dimension.

[Quantitative Analysis of Heavy Metals in Water with LIBS Based on Signal-to-Background Ratio].

There are many influence factors in the precision and accuracy of the quantitative analysis with LIBS technology. According to approximately the same characteristics trend of background spectrum and characteristic spectrum along with the change of temperature through in-depth analysis, signal-to-background ratio (S/B) measurement and regression analysis could compensate the spectral line intensity changes caused by system parameters such as laser power, spectral efficiency of receiving. Because the measurement dates were limited and nonlinear, we used support vector machine (SVM) for regression algorithm. The experimental results showed that the method could improve the stability and the accuracy of quantitative analysis of LIBS, and the relative standard deviation and average relative error of test set respectively were 4.7% and 9.5%. Data fitting method based on signal-to-background ratio(S/B) is Less susceptible to matrix elements and background spectrum etc, and provides data processing reference for real-time online LIBS quantitative analysis technology.

[Photosynthetic Parameters Inversion Algorithm Study Based on Chlorophyll Fluorescence Induction Kinetics Curve].

The fast chlorophyll fluorescence induction curve contains rich information of photosynthesis. It can reflect various information of vegetation, such as, the survival status, the pathological condition and the physiology trends under the stress state. Through the acquisition of algae fluorescence and induced optical signal, the fast phase of chlorophyll fluorescence kinetics curve was fitted. Based on least square fitting method, we introduced adaptive minimum error approaching method for fast multivariate nonlinear regression fitting toward chlorophyll fluorescence kinetics curve. We realized Fo (fixedfluorescent), Fm (maximum fluorescence yield), σPSII (PSII functional absorption cross section) details parameters inversion and the photosynthetic parameters inversion of Chlorella pyrenoidosa. And we also studied physiological variation of Chlorella pyrenoidosa under the stress of Cu(2+).

[Study of Rapid Species Identification of Bacteria in Water].

Multi-wavelength ultraviolet visible (UV-Vis) transmission spectra of bacteria combined the forward scattering and absorption properties of microbes, contains substantial information on size, shape, and the other chemical, physiological character of bacterial cells, has the bacterial species specificity, which can be applied to rapid species identification of bacterial microbes. Four different kinds of bacteria including Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Klebsiella pneumonia which were commonly existed in water were researched in this paper. Their multi-wavelength UV-Vis transmission spectra were measured and analyzed. The rapid identification method and model of bacteria were built which were based on support vector machine (SVM) and multi-wavelength UV-Vis transmission spectra of the bacteria. Using the internal cross validation based on grid search method of the training set for obtaining the best penalty factor C and the kernel parameter g, which the model needed. Established the bacteria fast identification model according to the optimal parameters and one-against-one classification method included in LibSVM. Using different experimental bacteria strains of transmission spectra as a test set of classification accuracy verification of the model, the analysis results showed that the bacterial rapid identification model built in this paper can identification the four kinds bacterial which chosen in this paper as the accuracy was 100%, and the model also can identified different subspecies of E. coli test set as the accuracy was 100%, proved the model had a good stability in identification bacterial species. In this paper, the research results of this study not only can provide a method for rapid identification and early warning of bacterial microbial in drinking water sources, but also can be used as the microbes identified in biomedical a simple, rapid and accurate means.

[The study of selecting sample detecting position and lead plate inner material in thin film method X-ray fluorescence measurement].

(1) In this paper type 316 stainless steel metal plate as the research object, the selection of sample detecting position was studied when thin film method X-ray fluorescence measurement was conducted. The study showed that the optimal location for the sample detection was sample distance X-ray tube and detector baseline 1cm with the baseline into a 16°angle. (2) Heavy metal pollutants of Pb, Cd and Cr in industrial ambient air as the main analysis object, when thin film method X-ray fluorescence conducted with lead plate protection, X-rays will penetrate the membrane and continuely stimulate the protective lead plate. Therefore there is lead spectral line interference in the filter membrane background spectrum, which will affect the detection of lead element in real samples. Studies show that when a layer of isolating material was applied between the thin sample and the protective lead plate, the interference of lead line can effectively be avoided. (3) Several rigid insulating material of type 316 stainless steel, brass, aluminum, red copper and PTEE as lead inner material were selected and studied. The study results showed that compared with X-ray fluorescence spectra of other lead inner materials, the X-ray fluorescence spectrum of red copper contained the least element spectral lines. There were not Cr, Cd and Pb spectrum peaks in the X-ray fluorescence spectrum of red copper. And the target timber scattering spectrum intensity in the high energy part was weaker compared to other X-ray fluorescence spectrum. The above analysis shows that red copper has the minimal disturbance to the actual measurement of heavy metals Cr, Cd and Pb. At the same time, red copper as lead inner materials can effectively avoid the interference of lead spectrum line in lead plate. So red copper is the best lead plate inner materials in thin film method X-ray fluorescence spectroscopy measurement. This study provides an important theoretical basis for the assembling and setting'up air and water weight metal X-ray fluorescence spectrometer.

[The research on separating and extracting overlapping spectral feature lines in LIBS using damped least squares method].

In recent years, the technology of laser induced breakdown spectroscopy has been developed rapidly. As one kind of new material composition detection technology, laser induced breakdown spectroscopy can simultaneously detect multi elements fast and simply without any complex sample preparation and realize field, in-situ material composition detection of the sample to be tested. This kind of technology is very promising in many fields. It is very important to separate, fit and extract spectral feature lines in laser induced breakdown spectroscopy, which is the cornerstone of spectral feature recognition and subsequent elements concentrations inversion research. In order to realize effective separation, fitting and extraction of spectral feature lines in laser induced breakdown spectroscopy, the original parameters for spectral lines fitting before iteration were analyzed and determined. The spectral feature line of' chromium (Cr I : 427.480 nm) in fly ash gathered from a coal-fired power station, which was overlapped with another line(FeI: 427.176 nm), was separated from the other one and extracted by using damped least squares method. Based on Gauss-Newton iteration, damped least squares method adds damping factor to step and adjust step length dynamically according to the feedback information after each iteration, in order to prevent the iteration from diverging and make sure that the iteration could converge fast. Damped least squares method helps to obtain better results of separating, fitting and extracting spectral feature lines and give more accurate intensity values of these spectral feature lines: The spectral feature lines of chromium in samples which contain different concentrations of chromium were separated and extracted. And then, the intensity values of corresponding spectral lines were given by using damped least squares method and least squares method separately. The calibration curves were plotted, which showed the relationship between spectral line intensity values and chromium concentrations in different samples. And then their respective linear correlations were compared. The experimental results showed that the linear correlation of the intensity values of spectral feature lines and the concentrations of chromium in different samples, which was obtained by damped least squares method, was better than that one obtained by least squares method. And therefore, damped least squares method was stable, reliable and suitable for separating, fitting and extracting spectral feature lines in laser induced breakdown spectroscopy.

[Analysis of lead in unknown samples based on the standard addition method using laser induced breakdown spectroscopy].

The standard addition method with laser induced breakdown spectroscopy was used to analyze an unknown sample taken from a lead battery factory. the matrix influence on the results was effectively avoided when the external or internal standard method was used, and the pretreatment of samples was simple and quick. The Nd ' YAG pulse laser with wavelength 1 064 nm was used as the excitation source. The echelle spectroscopy with high resolution and wide spectral range was used as the spectral separation device, and the intensified charge coupled device (ICCD) as the spectral detection device in the experiment. The characteristic line at 405. 78 nrn was chosen as the analysis line to measure Pb concentration. Fe I : 404. 58 line was chosen as the internal standard. Pre-experiment was carried out to confirm the appropriate condition. Under the laser energy of 128. 5 mJ, the delay time of 2. 5 tps, and the gate width of 3 ps, it was determined that with the addition of Pb to the sample in the range of 0 and 25 000 mg . kg-1, there wasn't self-absorption. There was a good linear relationship between the intensity of the spectral line of 405. 78 nm and the addition of Pb. The appropriate concentration of Pb added into the sample for analysis was determined by this series of samples. On this basis, four samples were prepared with three parallel samples for each sample in order to verify the repeatability and reliability of the method, i. e. 5 000, 10 000, 15 000, 20 000 mg . kg-1 Pb was added into the original sample. The results were compared with the result of ICP-MS. The twelve samples' relative errors were between -24. 6% and 17. 6%. The average result was 43 069 mg . kg-1 with the relative error -2. 44%.

[Determination of chemical rank of three-dimensional fluorescence spectra using mathematical morphology method].

The present paper firstly denoises the signal with morphological method, selecting sine-shaped structure element, using the morphological difference in waveform between the three-dimensional fluorescence and noise signal, then singular value decomposition is applied to the denoised data, and finally the chemical rank is determinated jointing eigenvalues and eigenvectors form singular value decomposition. This paper principally discusses the theory basis of morphological filtering method, firstly simulated data is analysed by morphological filtering method to confirm the necessity and effectiveness of proposed method, then the feasibility and practicability of the proposed method is verified by the determination of components number of phenols mixture three-dimensional fluorescence spectra compared with traditional Monte Carlo method. The experiments demonstrate that the proposed method is able to estimate the chemical rank correctly.

[Analysis of three-dimensional fluorescence overlapping spectra using nonnegative matrix factorization].

The present paper primarily tests and verifies the effect of NMF in blind source separation of three-dimensional simulative fluorescence spectra, and then four different computational algorithms (multiplicative iterative; alternating least square; second order method; projected gradient algorithm) were used in three practical phenolic compounds (cresol, phenol, thymol) overlapping fluorescence spectra to find out which nonnegatively constrained algorithms is the most efficient for fluorescence spectra unmixing. The experiments demonstrate that four ways have the normalized residuals below 0.06%, and alternating least square (ALS) is the best at both convergence behavior and robustness.

[Research on parameter optimization of LIBS used for multi-element measurements in water].

The one of the advantages about Laser Induced Breakdown Spectroscopy (LIBS) is multielement detection at the same time. In order to obtain the optimum signal in the multi-element measurements of water with LIBS, the present paper firstly models the numerical relationship between the signal-to-background ratio of characteristic spectral lines and the delay time and gate width time with BP neural network, using DM design experiment data as the checking sample to ensure the generalization ability of the BP neural network model. Based on the above model, genetic algorithm is used to optimize measurement parameters and the fitness function phi is defined. When the optimum delay time and gate width time is (15.5 micros, 21.5 micros), the minimum value of psi is 0.102 4. The optimization results of genetic algorithm are further confirmed with experimental results. So the method of parameters optimization overall improves S/B of multi-element measurements in water with LBS, and provides the reference for parameter optimization of other experiments.