Spectral index methodology has been widely used in Leaf Area Index(LAI) retrieval at different spatial scales. There are differences in the spectral response of different remote sensors and thus spectral scale effect ...Spectral index methodology has been widely used in Leaf Area Index(LAI) retrieval at different spatial scales. There are differences in the spectral response of different remote sensors and thus spectral scale effect generated during the use of spectral indices to retrieve LAI. In this study, PROSPECT, leaf optical properties model and Scattering by Arbitrarily Inclined Layers(SAIL) model, were used to simulate canopy spectral reflectance with a bandwidth of 5 nm and a Gaussian spectral response function was employed to simulate the spectral data at six bandwidths ranging from 10 to 35 nm. Additionally, for bandwidths from 5 to 35 nm, the correlation between the spectral index and LAI, and the sensitivities of the spectral index to changes in LAI and bandwidth were analyzed. Finally, the reflectance data at six bandwidths ranging from 40 to 65 nm were used to verify the spectral scale effect generated during the use of the spectral index to retrieve LAI. Results indicate that Vegetation Index of the Universal Pattern Decomposition(VIUPD) had the highest accuracy during LAI retrieval. Followed by Normalized Difference Vegetation Index(NDVI), Modified Simple Ratio Indices(MSRI) and Triangle Vegetation Index(TVI), although the coefficient of determination R^2 was higher than 0.96, the retrieved LAI values were less than the actual value and thus lacked validity. Other spectral indices were significantly affected by the spectral scale effect with poor retrieval results. In this study, VIUPD, which exhibited a relatively good correlation and sensitivity to LAI, was less affected by the spectral scale effect and had a relatively good retrieval capability. This conclusion supports a purported feature independent of the sensor of this model and also confirms the great potential of VIUPD for retrieval of physicochemical parameters of vegetation using multi-source remote sensing data.展开更多
In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ET...In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ETAS model parameters are then inversed by the POWELL method. The results show that phase 1 and 2, in which there is no water injection, have moderate-to-low ratio of background earthquakes （40 % - 50 % ）, and aftershocks are relatively less for a single earthquake sequence. In phase 3, where there is water injection, the aftershocks triggered by foreshocks dominate （ 93. 1% ）, and background earthquakes amount only to 6. 9 %, less than those of phase 1 and 2. The results conflict with the existing cognition. To resolve this problem, we propose that the occurrence ratio of background earthquakes in unit time, that is, the p value in ETAS model is used as an indicator of water injection triggered earthquakes. Compared to the first two phases, phase 3 has the largest u value, which illustrates that the water injection has an obvious triggering effect on earthquakes of this region.展开更多
Studied in this paper is a(2+1)-dimensional coupled nonlinear Schr?dinger system with variable coefficients,which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifie...Studied in this paper is a(2+1)-dimensional coupled nonlinear Schr?dinger system with variable coefficients,which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifier with the polarization effects. According to the similarity transformation, we derive the type-Ⅰ and type-Ⅱ rogue-wave solutions. We graphically present two types of the rouge wave and discuss the influence of the diffraction parameter on the rogue waves.When the diffraction parameters are exponentially-growing-periodic, exponential, linear and quadratic parameters, we obtain the periodic rogue wave and composite rogue waves respectively.展开更多
基金National Natural Science Foundation of China(No.41401002)Jilin Province Science Foundation for Youths(No.20160520077JH)
文摘Spectral index methodology has been widely used in Leaf Area Index(LAI) retrieval at different spatial scales. There are differences in the spectral response of different remote sensors and thus spectral scale effect generated during the use of spectral indices to retrieve LAI. In this study, PROSPECT, leaf optical properties model and Scattering by Arbitrarily Inclined Layers(SAIL) model, were used to simulate canopy spectral reflectance with a bandwidth of 5 nm and a Gaussian spectral response function was employed to simulate the spectral data at six bandwidths ranging from 10 to 35 nm. Additionally, for bandwidths from 5 to 35 nm, the correlation between the spectral index and LAI, and the sensitivities of the spectral index to changes in LAI and bandwidth were analyzed. Finally, the reflectance data at six bandwidths ranging from 40 to 65 nm were used to verify the spectral scale effect generated during the use of the spectral index to retrieve LAI. Results indicate that Vegetation Index of the Universal Pattern Decomposition(VIUPD) had the highest accuracy during LAI retrieval. Followed by Normalized Difference Vegetation Index(NDVI), Modified Simple Ratio Indices(MSRI) and Triangle Vegetation Index(TVI), although the coefficient of determination R^2 was higher than 0.96, the retrieved LAI values were less than the actual value and thus lacked validity. Other spectral indices were significantly affected by the spectral scale effect with poor retrieval results. In this study, VIUPD, which exhibited a relatively good correlation and sensitivity to LAI, was less affected by the spectral scale effect and had a relatively good retrieval capability. This conclusion supports a purported feature independent of the sensor of this model and also confirms the great potential of VIUPD for retrieval of physicochemical parameters of vegetation using multi-source remote sensing data.
基金supported by "Study on Strong Earthquake Risk in Southern Region of Longmenshan Fault,Huayingshan Fault and Border Area of Sichuan and Yunnan Provinces",Department of Earthquake Monitoring and Prediction,China Earthquake Administration
文摘In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ETAS model parameters are then inversed by the POWELL method. The results show that phase 1 and 2, in which there is no water injection, have moderate-to-low ratio of background earthquakes （40 % - 50 % ）, and aftershocks are relatively less for a single earthquake sequence. In phase 3, where there is water injection, the aftershocks triggered by foreshocks dominate （ 93. 1% ）, and background earthquakes amount only to 6. 9 %, less than those of phase 1 and 2. The results conflict with the existing cognition. To resolve this problem, we propose that the occurrence ratio of background earthquakes in unit time, that is, the p value in ETAS model is used as an indicator of water injection triggered earthquakes. Compared to the first two phases, phase 3 has the largest u value, which illustrates that the water injection has an obvious triggering effect on earthquakes of this region.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11772017,11272023,and 11471050the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),China(IPOC:2017ZZ05)the Fundamental Research Funds for the Central Universities of China under Grant No.2011BUPTYB02
文摘Studied in this paper is a(2+1)-dimensional coupled nonlinear Schr?dinger system with variable coefficients,which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifier with the polarization effects. According to the similarity transformation, we derive the type-Ⅰ and type-Ⅱ rogue-wave solutions. We graphically present two types of the rouge wave and discuss the influence of the diffraction parameter on the rogue waves.When the diffraction parameters are exponentially-growing-periodic, exponential, linear and quadratic parameters, we obtain the periodic rogue wave and composite rogue waves respectively.
