This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction the...This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction theory which is the approximation of Mie scattering within the forward Fraunhofer diffraction lobe, and Rosin Rammler function is introduced to describe the particle size distribution in two phase flow in advance. Compared with the values by the sample weight method, the measurement results have a reasonable agreement. The present work has demonstrated that this method will be probably used to monitor the parameters of two phase flow.展开更多
Spectral relative dispersion of different hydrometeors is vital to accurately describe sedimentation.Here,the Weather Research and Forecasting model with spectral bin microphysics is used to simulate convective clouds...Spectral relative dispersion of different hydrometeors is vital to accurately describe sedimentation.Here,the Weather Research and Forecasting model with spectral bin microphysics is used to simulate convective clouds in Shouxian of Anhui province in China to study the spectral relative dispersion of different hydrometeors.Firstly,regardless of clean or polluted conditions,the relative dispersion of ice crystal spectra and its volume-mean diameter are negatively correlated,while the relative dispersion of other hydrometeor spectra is positively related to their respective volume-mean diameter.The correlations for cloud droplets and raindrops are affected by the process of collision-coalescence;the correlations for ice crystals,graupel particles,and snow particles could be affected by the deposition,riming,and aggregation processes,respectively.Secondly,relative dispersion parameterizations are developed based on a comprehensive consideration of the relationships between the relative dispersion and volume-mean diameter under both polluted and clean conditions.Finally,the relative dispersion parameterizations are applied to terminal velocity parameterizations.The results show that for cloud droplets,ice crystals,graupel particles,and snow particles,assuming the shape parameter in the Gamma distribution is equal to 0 underestimates the shape parameter and overestimates the relative dispersion;and for raindrops,assuming the shape parameter is equal to 0 is close to the relative dispersion parameterizations.The most appropriate constant shape parameters are recommended for different hydrometeors.The relative dispersion parameterizations developed here shed new light for further optimizing the terminal velocity parameterizations in models.展开更多
Two types of the dual mode-locked fiber lasers for asynchronous absolute distance measurement are investigated, The lasers are linear and ring cavity with repetition rate of 70 MHz and 100 MHz, respectively. The group...Two types of the dual mode-locked fiber lasers for asynchronous absolute distance measurement are investigated, The lasers are linear and ring cavity with repetition rate of 70 MHz and 100 MHz, respectively. The group velocity dispersion is not compensated in the first type of the lasers, while the others are fully done. The timing jitter with the Allan deviation below averaging time of 0.2 s during the distance measurement for around 1 m of both types of lasers were 2.5 ps with 600 nm and 1.6 ps with 200 nm. We concluded that the phase noise resulted from the intra-cavity dispersion is the main contribution for the uncertainty of the ranging in these two types of the lasers.展开更多
The extended Huygens-Fresnel principle and Goodman model was utilized for target surface to derive the mutual coherence function(MCF) of a Gaussian beam reflected from an arbitrary rough target in atmospheric turbulen...The extended Huygens-Fresnel principle and Goodman model was utilized for target surface to derive the mutual coherence function(MCF) of a Gaussian beam reflected from an arbitrary rough target in atmospheric turbulence. According to the MCF, expressions of the mean irradiance and average speckle size at the receiver were obtained. The analysis indicated that the mean intensity is closely related to the ratio of root mean square(rms) height to the lateral correlation length. In addition, the speckle size at the receiver is associated with turbulence strength, propagation distance and roughness of the target. The results can be reduced to the result of a Gaussian beam illuminating rough target and scattering from a target in free space.展开更多
文摘This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction theory which is the approximation of Mie scattering within the forward Fraunhofer diffraction lobe, and Rosin Rammler function is introduced to describe the particle size distribution in two phase flow in advance. Compared with the values by the sample weight method, the measurement results have a reasonable agreement. The present work has demonstrated that this method will be probably used to monitor the parameters of two phase flow.
基金supported by the National Natural Science Foundation of China[Grant Nos.41822504,41775131,42027804,42075073,41975181,and 41775136].
文摘Spectral relative dispersion of different hydrometeors is vital to accurately describe sedimentation.Here,the Weather Research and Forecasting model with spectral bin microphysics is used to simulate convective clouds in Shouxian of Anhui province in China to study the spectral relative dispersion of different hydrometeors.Firstly,regardless of clean or polluted conditions,the relative dispersion of ice crystal spectra and its volume-mean diameter are negatively correlated,while the relative dispersion of other hydrometeor spectra is positively related to their respective volume-mean diameter.The correlations for cloud droplets and raindrops are affected by the process of collision-coalescence;the correlations for ice crystals,graupel particles,and snow particles could be affected by the deposition,riming,and aggregation processes,respectively.Secondly,relative dispersion parameterizations are developed based on a comprehensive consideration of the relationships between the relative dispersion and volume-mean diameter under both polluted and clean conditions.Finally,the relative dispersion parameterizations are applied to terminal velocity parameterizations.The results show that for cloud droplets,ice crystals,graupel particles,and snow particles,assuming the shape parameter in the Gamma distribution is equal to 0 underestimates the shape parameter and overestimates the relative dispersion;and for raindrops,assuming the shape parameter is equal to 0 is close to the relative dispersion parameterizations.The most appropriate constant shape parameters are recommended for different hydrometeors.The relative dispersion parameterizations developed here shed new light for further optimizing the terminal velocity parameterizations in models.
文摘Two types of the dual mode-locked fiber lasers for asynchronous absolute distance measurement are investigated, The lasers are linear and ring cavity with repetition rate of 70 MHz and 100 MHz, respectively. The group velocity dispersion is not compensated in the first type of the lasers, while the others are fully done. The timing jitter with the Allan deviation below averaging time of 0.2 s during the distance measurement for around 1 m of both types of lasers were 2.5 ps with 600 nm and 1.6 ps with 200 nm. We concluded that the phase noise resulted from the intra-cavity dispersion is the main contribution for the uncertainty of the ranging in these two types of the lasers.
基金supported by the National Natural Science Foundation of China(Grant Nos.61172031,61271110 and 61102018)the New Scientific and Technological Star of Shaanxi Province Funded Project(Grant No.2011KJXX39)the Natural Science Foundation of Shaanxi Province education office,China(Grant No.12Jk0955)
文摘The extended Huygens-Fresnel principle and Goodman model was utilized for target surface to derive the mutual coherence function(MCF) of a Gaussian beam reflected from an arbitrary rough target in atmospheric turbulence. According to the MCF, expressions of the mean irradiance and average speckle size at the receiver were obtained. The analysis indicated that the mean intensity is closely related to the ratio of root mean square(rms) height to the lateral correlation length. In addition, the speckle size at the receiver is associated with turbulence strength, propagation distance and roughness of the target. The results can be reduced to the result of a Gaussian beam illuminating rough target and scattering from a target in free space.
