An adaptive image denosing technique was proposed to achieve the tradeoff between details retain and noises removal. In order to achieve this objective, the contourlet transform was introduced and a new threshold meth...An adaptive image denosing technique was proposed to achieve the tradeoff between details retain and noises removal. In order to achieve this objective, the contourlet transform was introduced and a new threshold method, namely CWinShrink, is presented. It shrinks the contourlet coefficients with adaptive shrinkage factors. The shrinkage factors were calculated with reference to the sum of squares of the contourlet coefficients within the neighborhood window. This approach achieves enhanced results for images those are corrupted with additive Gaussian noise. In numerical comparisons with various methods, for a set of noisy images （the PSNR range fi＇om 10.86dB to 26.91dB） , the presented method outperforms VisuShrink and Wiener filter in terms of the PSNR. Experiments also show that this method not only keeps the details of image but also yields denoised images with better visual quality.展开更多
Simulation results of the WDM6 scheme and the Thompson scheme,both of which are commonly-used double-moment bulkmicrophysics schemes,are compared within theWeather Research and Forecasting model.The purpose of the com...Simulation results of the WDM6 scheme and the Thompson scheme,both of which are commonly-used double-moment bulkmicrophysics schemes,are compared within theWeather Research and Forecasting model.The purpose of the comparison is to study the difference in the aspects of the warm-rain hydrometeor number concentrations,the droplet size distributions,and the budgets of the rain mixing ratio and number concentration.It is found that the WDM6 scheme overestimates the ratio and the amount of large precipitation,and underestimates those of small precipitation,compared to the Thompson scheme.The cloud number concentration(CNC)predicted in the WDM6 scheme is one to three orders ofmagnitude smaller than that of the Thompson scheme,which is set to the specific valueof CNC.The cloud droplet spectra of the WDM6 scheme are broader.The WDM6 scheme produces a larger rain number concentration and smaller mass mean diameter of raindrops under the influence of both warm and cold rain processes—specifically,autoconversion and melting of snow and graupel.The WDM6 scheme produces a larger autoconversion rate and smaller total melting rate of snow and graupel than the Thompson scheme in the rain mixing ratio budget.The sign of the difference in the rain-cloud collection varieswith region,and the rain-cloud collection process together with evaporation of rain have a major influence on the sign of the surface precipitation difference between the two schemes.展开更多
Let {vij}, i, j = 1, 2, …, be i.i.d, random variables with Ev11 = 0, Ev11^2 = 1 and a1 = （ai1,…, aiM） be random vectors with {aij} being i.i.d, random variables. Define XN =（x1,…, xk） and SN =XNXN^T,where xi=ai...Let {vij}, i, j = 1, 2, …, be i.i.d, random variables with Ev11 = 0, Ev11^2 = 1 and a1 = （ai1,…, aiM） be random vectors with {aij} being i.i.d, random variables. Define XN =（x1,…, xk） and SN =XNXN^T,where xi=ai×si and si=1/√N（v1i,…, vN,i）^T. The spectral distribution of SN is proven to converge, with probability one, to a nonrandom distribution function under mild conditions.展开更多
Distribution of monsoon forests is important for the research of carbon and water cycles in the tropical regions. In this paper, a simple approach is proposed to map monsoon forests using the Normalized Difference Veg...Distribution of monsoon forests is important for the research of carbon and water cycles in the tropical regions. In this paper, a simple approach is proposed to map monsoon forests using the Normalized Difference Vegetation lndex （NDVI） derived from the Moderate Resolution Imaging Spectroradiometer （MODIS） data. Owing to the high contrast of greenness between wet season and dry season, the monsoon forest can be easily discriminated from other forests by combining the maximum and minimum annual NDVI. The MODIS-based monsoon forest maps （MODMF） from 2000 to 2009 are derived and evaluated using the ground-truth dataset. The MODMF achieves an average producer accuracy of 80.0% and the Kappa statistic of 0.719. The variability of MODMF among different years is compared with that calculated from MODIS land cover products （MCD 12Q 1）. The results show that the coefficient of variation of total monsoon forest area in MODMF is 7.3%, which is far lower than that in MCD12Q1 with 24.3%. Moreover, the pixels in MODMv which can be identified for 7 to 9 times between 200l and 2009 account for 53.1%, while only 7.9% ofMCD12QI pixels have this frequency. Additionally, the monsoon forest areas estimated in MODMF, Global Land Cover 2000 （GLC2000）, MCDI2Q1 and University of Maryland （UMD） products are compared with the statistical dataset at national level, which reveals that MODMv has the highest R^2 of 0.95 and the lowest RMSE of 14 014 km^2. This algorithm is simple but reliable for mapping the monsoon forests without complex classification techniques.展开更多
Three classes of Boolean functions with four-valued Walsh spectra are presented and their Walsh spectrum distributions are determined. They are derived from Bent functions of the MaioranaMc Farland and Dillon PS ap ty...Three classes of Boolean functions with four-valued Walsh spectra are presented and their Walsh spectrum distributions are determined. They are derived from Bent functions of the MaioranaMc Farland and Dillon PS ap types and of the monomial form Tr1^2m（λx^r（2^m-1）） by complementing the values of the Bent functions at two points.展开更多
Ionospheric peak value of F2 layer （NmF2） is an important parameter in the ionosphere, which has important applications in short-wave communication, ionospheric modeling and so on. In this paper, the empirical ortho...Ionospheric peak value of F2 layer （NmF2） is an important parameter in the ionosphere, which has important applications in short-wave communication, ionospheric modeling and so on. In this paper, the empirical orthogonal function （EOF） decompo- sition method is used to analyze the NmFz obtained from the occultation data. Daily spatial distribution of NmF2 at the same time is relatively even. Variance of first modal is much larger than the other modals. A local wavelet power spectrum （LWPS） method is applied to analysis the cycle of Flo.7 index and time coefficient of first modal. The result shows that they have simi- lar cycle distribution, indicating that Flo.7 index is the main factor affecting variation of NmF〉 A function is established be- tween the tine coefficient of first modal and F10.7 index, average F10.7 index value of early 81 days fp by least squares method. The results show that contribution coefficient offp is negative which indicates that fp has an inert effect existing in the iono- sphere. Contribution coefficient of F10.7 is positive, which is consistent with the fact that it has an anomaly in winter/spring seasons. In summary, it is feasible to establish a mid-latitude empirical NmF2 model in northern hemisphere based on occulta- tion data and EOF decomposition method.展开更多
The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, obs...The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, observations have revealed that the use of such methods is not applicable for all actual cases. In this study, formulas were derived based on cloud microphysics and the properties of gamma function to solve the average cloud droplet radius and the cloud droplet spectral shape parameter. The gamma distribution shape parameter, relative dispersion, and cloud droplet spectral distribution can be derived through solving the droplet spectral shape parameter equation using the average droplet radius, volume radius, and their ratio, thereby deriving an analytic solution. We further examined the equation for the droplet spectral shape parameter using the observational droplet spectral data, and results revealed the feasibility of the method. In addition, when the method was applied to the two-parameter cloud microphysical scheme of the Weather Research and Forecast(WRF) model to further examine its feasibility, the modeling results showed that it improved precipitation simulation performance, thereby indicating that it can be utilized in two-parameter cloud microphysical schemes.展开更多
In this work, predictions of the spectral energy distribution from populations of single and binary stars are incorporated into a galactic chemical and color evolution model to explore the significance of the effects ...In this work, predictions of the spectral energy distribution from populations of single and binary stars are incorporated into a galactic chemical and color evolution model to explore the significance of the effects of the binary interactions on the color evolution of M33. We first constructed a model without binary interactions, and the model is able to reproduce most of the available observational constraints on the distribution of stellar parameters. We then run simulations with the same set of model parameters but with binary interactions considered. By comparing the results for the populations with and without binary interactions, we find that the inclusion of binary interactions makes the surface brightness greater (~0.1 mag arcsec 2) in FUV-band but smaller (~0.7 mag arcsec 2) in K-band, while it results in the FUV K color bluer (~0.8 mag). To reproduce the observations, a model that considers the binary interactions should make more gas fall onto the disk in the early time of the galaxy evolution, or increase the total stellar mass, or both.展开更多
基金Sponsored by Key Lab of Optoelectronic Technology &System,Department of Education, China(Grant No.200373 -1 -2).
文摘An adaptive image denosing technique was proposed to achieve the tradeoff between details retain and noises removal. In order to achieve this objective, the contourlet transform was introduced and a new threshold method, namely CWinShrink, is presented. It shrinks the contourlet coefficients with adaptive shrinkage factors. The shrinkage factors were calculated with reference to the sum of squares of the contourlet coefficients within the neighborhood window. This approach achieves enhanced results for images those are corrupted with additive Gaussian noise. In numerical comparisons with various methods, for a set of noisy images （the PSNR range fi＇om 10.86dB to 26.91dB） , the presented method outperforms VisuShrink and Wiener filter in terms of the PSNR. Experiments also show that this method not only keeps the details of image but also yields denoised images with better visual quality.
基金sponsored by the National Natural Science Foundation of China [grant number 41530427]
文摘Simulation results of the WDM6 scheme and the Thompson scheme,both of which are commonly-used double-moment bulkmicrophysics schemes,are compared within theWeather Research and Forecasting model.The purpose of the comparison is to study the difference in the aspects of the warm-rain hydrometeor number concentrations,the droplet size distributions,and the budgets of the rain mixing ratio and number concentration.It is found that the WDM6 scheme overestimates the ratio and the amount of large precipitation,and underestimates those of small precipitation,compared to the Thompson scheme.The cloud number concentration(CNC)predicted in the WDM6 scheme is one to three orders ofmagnitude smaller than that of the Thompson scheme,which is set to the specific valueof CNC.The cloud droplet spectra of the WDM6 scheme are broader.The WDM6 scheme produces a larger rain number concentration and smaller mass mean diameter of raindrops under the influence of both warm and cold rain processes—specifically,autoconversion and melting of snow and graupel.The WDM6 scheme produces a larger autoconversion rate and smaller total melting rate of snow and graupel than the Thompson scheme in the rain mixing ratio budget.The sign of the difference in the rain-cloud collection varieswith region,and the rain-cloud collection process together with evaporation of rain have a major influence on the sign of the surface precipitation difference between the two schemes.
文摘Let {vij}, i, j = 1, 2, …, be i.i.d, random variables with Ev11 = 0, Ev11^2 = 1 and a1 = （ai1,…, aiM） be random vectors with {aij} being i.i.d, random variables. Define XN =（x1,…, xk） and SN =XNXN^T,where xi=ai×si and si=1/√N（v1i,…, vN,i）^T. The spectral distribution of SN is proven to converge, with probability one, to a nonrandom distribution function under mild conditions.
基金National Natural Science Foundation of China(No.41171285)Research and Development Special Fund for Public Welfare Industry(Meteorology)of China(No.GYHY201106014)
文摘Distribution of monsoon forests is important for the research of carbon and water cycles in the tropical regions. In this paper, a simple approach is proposed to map monsoon forests using the Normalized Difference Vegetation lndex （NDVI） derived from the Moderate Resolution Imaging Spectroradiometer （MODIS） data. Owing to the high contrast of greenness between wet season and dry season, the monsoon forest can be easily discriminated from other forests by combining the maximum and minimum annual NDVI. The MODIS-based monsoon forest maps （MODMF） from 2000 to 2009 are derived and evaluated using the ground-truth dataset. The MODMF achieves an average producer accuracy of 80.0% and the Kappa statistic of 0.719. The variability of MODMF among different years is compared with that calculated from MODIS land cover products （MCD 12Q 1）. The results show that the coefficient of variation of total monsoon forest area in MODMF is 7.3%, which is far lower than that in MCD12Q1 with 24.3%. Moreover, the pixels in MODMv which can be identified for 7 to 9 times between 200l and 2009 account for 53.1%, while only 7.9% ofMCD12QI pixels have this frequency. Additionally, the monsoon forest areas estimated in MODMF, Global Land Cover 2000 （GLC2000）, MCDI2Q1 and University of Maryland （UMD） products are compared with the statistical dataset at national level, which reveals that MODMv has the highest R^2 of 0.95 and the lowest RMSE of 14 014 km^2. This algorithm is simple but reliable for mapping the monsoon forests without complex classification techniques.
基金supported by the National Key Basic Research Program of China under Grant No.2013CB834203the National Natural Science Foundation of China under Grant No.61472417+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No.XDA06010702the State Key Laboratory of Information Security,Chinese Academy of Sciences
文摘Three classes of Boolean functions with four-valued Walsh spectra are presented and their Walsh spectrum distributions are determined. They are derived from Bent functions of the MaioranaMc Farland and Dillon PS ap types and of the monomial form Tr1^2m（λx^r（2^m-1）） by complementing the values of the Bent functions at two points.
基金supported by the National Natural Science Foundation of China(Grant No.40505005)the Specialized Research Fund for State Key Laboratories(Grant No.Y22612A33S)
文摘Ionospheric peak value of F2 layer （NmF2） is an important parameter in the ionosphere, which has important applications in short-wave communication, ionospheric modeling and so on. In this paper, the empirical orthogonal function （EOF） decompo- sition method is used to analyze the NmFz obtained from the occultation data. Daily spatial distribution of NmF2 at the same time is relatively even. Variance of first modal is much larger than the other modals. A local wavelet power spectrum （LWPS） method is applied to analysis the cycle of Flo.7 index and time coefficient of first modal. The result shows that they have simi- lar cycle distribution, indicating that Flo.7 index is the main factor affecting variation of NmF〉 A function is established be- tween the tine coefficient of first modal and F10.7 index, average F10.7 index value of early 81 days fp by least squares method. The results show that contribution coefficient offp is negative which indicates that fp has an inert effect existing in the iono- sphere. Contribution coefficient of F10.7 is positive, which is consistent with the fact that it has an anomaly in winter/spring seasons. In summary, it is feasible to establish a mid-latitude empirical NmF2 model in northern hemisphere based on occulta- tion data and EOF decomposition method.
基金supported by National Basic Research Program of China(Grant No.2011CB403406)
文摘The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, observations have revealed that the use of such methods is not applicable for all actual cases. In this study, formulas were derived based on cloud microphysics and the properties of gamma function to solve the average cloud droplet radius and the cloud droplet spectral shape parameter. The gamma distribution shape parameter, relative dispersion, and cloud droplet spectral distribution can be derived through solving the droplet spectral shape parameter equation using the average droplet radius, volume radius, and their ratio, thereby deriving an analytic solution. We further examined the equation for the droplet spectral shape parameter using the observational droplet spectral data, and results revealed the feasibility of the method. In addition, when the method was applied to the two-parameter cloud microphysical scheme of the Weather Research and Forecast(WRF) model to further examine its feasibility, the modeling results showed that it improved precipitation simulation performance, thereby indicating that it can be utilized in two-parameter cloud microphysical schemes.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11033008 and 10821061)the Chinese Academy of Sciences (Grant No. KJCX2-YW-T24)
文摘In this work, predictions of the spectral energy distribution from populations of single and binary stars are incorporated into a galactic chemical and color evolution model to explore the significance of the effects of the binary interactions on the color evolution of M33. We first constructed a model without binary interactions, and the model is able to reproduce most of the available observational constraints on the distribution of stellar parameters. We then run simulations with the same set of model parameters but with binary interactions considered. By comparing the results for the populations with and without binary interactions, we find that the inclusion of binary interactions makes the surface brightness greater (~0.1 mag arcsec 2) in FUV-band but smaller (~0.7 mag arcsec 2) in K-band, while it results in the FUV K color bluer (~0.8 mag). To reproduce the observations, a model that considers the binary interactions should make more gas fall onto the disk in the early time of the galaxy evolution, or increase the total stellar mass, or both.
