This paper deals with the backscatter coefficients known as sigma0 at Ku band and C band based on the GDR-M (Merged Geophysical Data Record) of TOPEX/Poseidon (T/P) through Jan.1993 to Dec.2004 over land surface of Ch...This paper deals with the backscatter coefficients known as sigma0 at Ku band and C band based on the GDR-M (Merged Geophysical Data Record) of TOPEX/Poseidon (T/P) through Jan.1993 to Dec.2004 over land surface of China.After smoothing and interpolating the backscatter coefficients for both bands, we achieve the 5′×5′ grid data and the time series of backscatter coefficients in 12 years.The spatial distribution of sigma0 over typical areas (wetland, desert, mountainous area, agriculture base, etc.) of Chinese territory is analyzed and discussed.The fast Fourier transformation (FFT) is used to detect the cycles of seasonal variations of sigma0 time series and gives that the annual period is the major cycle.Meanwhile a semiannual period is also found in some places.We use the least squares method on both periods and find that the amplitude of annual period is obviously greater than that of semi-annual period.The relationship among the anomalousness of time series, variations of environment and climate change, and the serious natural calamity (flood, drought) is also discussed.Data of topography slope extracted from SRTM are used to do correlation analysis with the backscatter coefficients in parts of China to quantify the impact of slope on backscatter coefficients in Ku and C bands, and the results show that they all have a negative correlation but the magnitudes are different in different places with different coverages.Such as the area of Liaoning and Jilin has the maximum correlation -0.56, the Taklimakan Desert has the minimum correlation -0.11, and the other places commonly have correlations in (-0.3, -0.5).展开更多
Complexity measures for sequences, such as the linear complexity and the k-error linear complexity, play an important role in stream ciphers. This contribution studies the distribution of 1-error linear complexity of ...Complexity measures for sequences, such as the linear complexity and the k-error linear complexity, play an important role in stream ciphers. This contribution studies the distribution of 1-error linear complexity of binary sequences with arbitrary prime period. For any odd prime N, the authors present all possible values of 1-error linear complexity of N-periodic binary sequences, and derive the exact formulas to count the number of N-periodic binary sequences with any given 1-error linear complexity.展开更多
基金supported by National Natural Science Founda-tion of China(Grant Nos.40974004 and 40774009)International Sci&Tech Cooperation Program of China(Grant No.2009DFB00130)+1 种基金Key Laboratory of Mapping from Space of NASMG,China(Grant No.K201103)the R&I Team Supporting Program and Graduate Sci.&Tech Innovation Fund of SDUST,China(Grant No.YCB110010)
文摘This paper deals with the backscatter coefficients known as sigma0 at Ku band and C band based on the GDR-M (Merged Geophysical Data Record) of TOPEX/Poseidon (T/P) through Jan.1993 to Dec.2004 over land surface of China.After smoothing and interpolating the backscatter coefficients for both bands, we achieve the 5′×5′ grid data and the time series of backscatter coefficients in 12 years.The spatial distribution of sigma0 over typical areas (wetland, desert, mountainous area, agriculture base, etc.) of Chinese territory is analyzed and discussed.The fast Fourier transformation (FFT) is used to detect the cycles of seasonal variations of sigma0 time series and gives that the annual period is the major cycle.Meanwhile a semiannual period is also found in some places.We use the least squares method on both periods and find that the amplitude of annual period is obviously greater than that of semi-annual period.The relationship among the anomalousness of time series, variations of environment and climate change, and the serious natural calamity (flood, drought) is also discussed.Data of topography slope extracted from SRTM are used to do correlation analysis with the backscatter coefficients in parts of China to quantify the impact of slope on backscatter coefficients in Ku and C bands, and the results show that they all have a negative correlation but the magnitudes are different in different places with different coverages.Such as the area of Liaoning and Jilin has the maximum correlation -0.56, the Taklimakan Desert has the minimum correlation -0.11, and the other places commonly have correlations in (-0.3, -0.5).
基金supported by the National Natural Science Foundation of China under Grant Nos.61070178, 61100200,and 60833008
文摘Complexity measures for sequences, such as the linear complexity and the k-error linear complexity, play an important role in stream ciphers. This contribution studies the distribution of 1-error linear complexity of binary sequences with arbitrary prime period. For any odd prime N, the authors present all possible values of 1-error linear complexity of N-periodic binary sequences, and derive the exact formulas to count the number of N-periodic binary sequences with any given 1-error linear complexity.
