“…The calculated value of R-square was equal to ~0.98, which indicates the good approximation of the regression line to the real data. Compared with the linear responsivity of R > 0.99 for other gases [29] , [35] , the strong adsorption of HF contributed to the slight decrease. Fig.…”
Section: Resultsmentioning
confidence: 73%
“…In addition, compared to the photodetector used in the TDLAS technology, the commercial standard QTF has the advantages of smaller, cheaper, narrower in resonance band and not limited by the detection wavelength. Therefore, LITES based gas sensing technique is widely used in various gas detection [32] , [33] , [34] , [35] .…”
“…The calculated value of R-square was equal to ~0.98, which indicates the good approximation of the regression line to the real data. Compared with the linear responsivity of R > 0.99 for other gases [29] , [35] , the strong adsorption of HF contributed to the slight decrease. Fig.…”
Section: Resultsmentioning
confidence: 73%
“…In addition, compared to the photodetector used in the TDLAS technology, the commercial standard QTF has the advantages of smaller, cheaper, narrower in resonance band and not limited by the detection wavelength. Therefore, LITES based gas sensing technique is widely used in various gas detection [32] , [33] , [34] , [35] .…”
“…Meanwhile, the chemical method cannot be used for real-time analysis of water quality. Compared to chemical method, optical method based on the material characteristic spectrum has been drew much attention in recent years for its rapid detection and pollution-free characteristics [4][5][6][7][8][9][10].…”
In this invited paper, a novel water chemical oxygen demand (COD) detection method based on laser spectroscopy is proposed, and the COD value is obtained according to the intensity ratio of laser Fluorescence-Raman signal produced by laser incident into water. Based on the laser Fluorescence-Raman ratio (LFRR) method, we design a portable water quality measurement system. In which, a 405 nm semiconductor laser is used as the light source. The laser is coupled into the delivering port of Y-type fiber and then transmitted into water. The generated Mie scattered light, water Raman light and corresponding fluorescence are received and transmitted into spectrometer through the detecting port of Y-type fiber, and the COD value can be obtained by analyzing the LFRR of water spectra. The mixed solution of sodium humate and glucose is used as the COD standard solution to calibrate the designed system. The experiment results show that the optimal volume ratio of the two solutions is 1:29. When the COD of standard solutions is in the 1–12 mg/L concentration range, a good linear relationship can be found between the COD value and LFRR value with a correlation coefficient of 0.974. In addition, the COD of natural water samples are measured with LFRR method, the results of which are consistent with COD values obtained by rapid digestion spectrophotometry. Meanwhile, experimental results prove that the COD detection method proposed in this paper has the advantages of high sensitivity, high precision, high detection speed and simplicity, which can be widely used in various water areas for real-time COD monitoring.
“…A non-contract in situ testing technique that will not destroy the combustion flow field is urgently needed, and it can obtain more different combustion parameters at the same time. Spectral analysis technology can perfectly satisfy all the aforementioned requirements, and it can also reproduce the flow field information on the combustion process as real as possible [3][4][5][6][7][8][9].…”
Computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS) has been widely used in the diagnosis of the combustion flow field. Several optimized CT reconstruction algorithms such as iteration methods, transformation methods, and nonlinear least squares were applied. Considering the industrial application background, the performances of algebraic iteration reconstruction with the simultaneous algebra reconstruction technique (SART), Tikhonov regularization, and least squares with the polynomial fitting method were discussed in this study. For the mentioned algorithm, identical simulated reconstruction parameters that contained 32-path laser structures, assumed temperature distribution, and absorption databases were adopted to evaluate the reconstruction performance including accuracy, efficiency, and measurement of environment applicability. In this study, different CT reconstruction algorithms were also used to calculate the temperature distribution of the Bunsen burner flame. The different reconstruction results were compared with thermocouple detection data. With the theoretically simulated and experimental analysis, the least squares with the polynomial fitting technique has advantages in reconstruction accuracy, calculation efficiency, and laser path applicability for the measurement condition. It will be helpful in enhancing CT-TDLAS technique development.
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