[Backscattering spectrum analysis of nonspheroid soot particle].

In the process of measuring soot concentration and grain diameter, the backscattering spectrum of soot particle model was calculated to ascertain and analyze main effective factor of backscattering intensity. In the present paper, ellipsoid, column and generalized Chebyshev, three nonspheroid models, were selected according to micrograph of practical soot particle, which aims to simulate practical soot particle with equivalent diameter of about 1 microm. T-matrix method was used to calculate backscattering spectrum of the three nonspheriod models, and the main effective factor curves of intensity were obtained, too. Both numerical computer simulations and experimental results illustrate that nonspheroid particle backscattering intensity is stronger than that of spheroid particle in the visible/infrared spectrum band, especially for generalized Chebyshev model, whose backscattering intensity can be even 3.5 times higher than that of forward scattering. Meanwhile, the absorbency non-spheroid particle (complex refractive index m = 1.57 - 0.56i) backscattering intensity is stronger than that of non-absorbency nonspheriod particle (complex refractive index m = 1.57 - 0.001i). Furthermore, with the increase in particle equivalent radius, the light source wavelength also needs to be increase to obtain more light intensity information. The backscattering light spectrum information provides a reasonable basis for selecting light source and measure angle.

[Complex refractive index measurement of fly ash particles using suspension spectral transmission method].

Spectral complex refractive index of fly ash particles is an important parameter in the processing of scattering properties calculation. On the basis of theory about inversion of complex refraction index using transimission method, a novel method was proposed, in which fly ash particles were dispersed in the water to compose turbid liquid, and spectral transmissivity of turbid liquid was measured using visible spectrophotometer. Particles size distribution was measured using laser particles sizing. So complex refraction index of fly ash particles was inverted simply. The result indicated that no signifcant absorption appeared in the visible wavelength range for fly ash particles, but transmittance decreased with wavelength increasing. The inversion results from the proposed method agreed with KBr sampling method. The proposed method is simpler, and has fewer constraints, meanwhile the inverion wavelength will be expanded if using infrared spectrophotometer.

[Analysis of visible extinction spectrum of particle system and selection of optimal wavelength].

In the total light scattering particle sizing technique, the extinction spectrum of particle system contains some information about the particle size and refractive index. The visible extinction spectra of the common monomodal and biomodal R-R particle size distribution were computed, and the variation in the visible extinction spectrum with the particle size and refractive index was analyzed. The corresponding wavelengths were selected as the measurement wavelengths at which the second order differential extinction spectrum was discontinuous. Furthermore, the minimum and the maximum wavelengths in the visible region were also selected as the measurement wavelengths. The genetic algorithm was used as the inversion method under the dependent model The computer simulation and experiments illustrate that it is feasible to make an analysis of the extinction spectrum and use this selection method of the optimal wavelength in the total light scattering particle sizing. The rough contour of the particle size distribution can be determined after the analysis of visible extinction spectrum, so the search range of the particle size parameter is reduced in the optimal algorithm, and then a more accurate inversion result can be obtained using the selection method. The inversion results of monomodal and biomodal distribution are all still satisfactory when 1% stochastic noise is put in the transmission extinction measurement values.

[Study of inversion and classification of particle size distribution under dependent model algorithm].

For the total light scattering particle sizing technique, an inversion and classification method was proposed with the dependent model algorithm. The measured particle system was inversed simultaneously by different particle distribution functions whose mathematic model was known in advance, and then classified according to the inversion errors. The simulation experiments illustrated that it is feasible to use the inversion errors to determine the particle size distribution. The particle size distribution function was obtained accurately at only three wavelengths in the visible light range with the genetic algorithm, and the inversion results were steady and reliable, which decreased the number of multi wavelengths to the greatest extent and increased the selectivity of light source. The single peak distribution inversion error was less than 5% and the bimodal distribution inversion error was less than 10% when 5% stochastic noise was put in the transmission extinction measurement values at two wavelengths. The running time of this method was less than 2 s. The method has advantages of simplicity, rapidity, and suitability for on-line particle size measurement.

[Research on the measurement of flue-dust concentration in Vis, IR spectral region].

In the measurement of flue-dust concentration based on the transmission method, the dependent model algorithm was used to invert the flue-dust concentration in the visible, infrared and visible-infrared spectral regions respectively. By the analysis and comparison of the accuracy, linearity and sensitivity of the inversion flue-dust concentration, the optimal spectral region was determined. Meanwhile, the influence of the water droplet with different size distribution and volume concentration was simulated, and a method was proposed which has advantages of simplicity, rapidity, and suitability for on line measurement. Simulation experiments illustrate that the flue-dust concentration can be inverted very well in the visible-infrared spectral region, and it is feasible to use the ratio of the constrained light extinction method to overcome the influence of water droplet. The inverse results all remain satisfactory when 2% stochastic noise is added to the value of the light extinction.

[Multi-spectral thermometry based on GA-BP algorithm].

Considering some defects of back-propagation neural network (BP), a new algorithm combining genetic algorithm (GA) with BP was described. The application of GA-BP to the data processing of multi-spectral thermometry was proposed. The simulation experiments, based on GA-BP algorithm and BP neural network respectively, show that the recognition precision of trained emissivity samples is +/-5 K and +/-10 K respectively, and that of untrained emissivity samples is +/-10 K and +/-20 K respectively. No matter GA-BP algorithm or BP neural network is used, in general, the recognition precision of trained emissivity samples is higher than that of untrained emissivity samples. The recognition precision of true temperature is lower near the edge of sample sets. The GA-BP algorithm was more efficient than the BP neural network in the true temperature measurement.