Stochastic characteristics of the Benue River streamflow process are examined under conditions of data austerity. The streamflow process is investigated for trend, non-stationarity and seasonality for a time period of...Stochastic characteristics of the Benue River streamflow process are examined under conditions of data austerity. The streamflow process is investigated for trend, non-stationarity and seasonality for a time period of 26 years. Results of trend analyses with Mann-Kendall test show that there is no trend in the annual mean discharges. Monthly flow series examined with seasonal Kendall test indicate the presence of positive change in the trend for some months, especially the months of August, January, and February. For the stationarity test, daily and monthly flow series appear to be stationary whereas at 1%, 5%, and 10% significant levels, the stationarity alternative hypothesis is rejected for the annual flow series. Though monthly flow appears to be stationary going by this test, because of high seasonality, it could be said to exhibit periodic stationarity based on the seasonality analysis. The following conclusions are drawn： （1） There is seasonality in both the mean and variance with unimodal distribution. （2） Days with high mean also have high variance. （3） Skewness coefficients for the months within the dry season period are greater than those of the wet season period, and seasonal autocorrelations for streamflow during dry season are generally larger than those of the wet season. Precisely, they are significantly different for most of the months. （4） The autocorrelation functions estimated ＂over time＂ are greater in the absolute value for data that have not been deseasonalised but were initially normalised by logarithmic transformation only, while autocorrelation functions for i = 1, 2 365 estimated ＂over realisations＂ have their coefficients significantly different from other coefficients.展开更多
High speed and large capacity belt conveyor is the main development trend. In the design, calculated and used of belt conveyor must be considered the high speed, large capacity, dynamic load. This paper starts from th...High speed and large capacity belt conveyor is the main development trend. In the design, calculated and used of belt conveyor must be considered the high speed, large capacity, dynamic load. This paper starts from the analysis of conveyor belt transverse vibration. Through calculate transverse vibration natural frequency of conveyor belt, and analyze the lateral stability of belt conveyor.展开更多
Band gap, which can be tuned by changing the size of quantum dots (QDs) based on the quantum confinement effect, plays a fundamental role in electrical and optical properties of QDs. However, the tuning of the band ga...Band gap, which can be tuned by changing the size of quantum dots (QDs) based on the quantum confinement effect, plays a fundamental role in electrical and optical properties of QDs. However, the tuning of the band gap by changing the size results in a series of intrinsic problems, such as the instability of the extremely small QDs, negative combination with biomolecules because of the large size of QDs, etc. Recently, several new methods have been developed to further study and improve the tuning of the band gap. In this paper, we summarized the recent progress in the fields of tuning the band gap of QDs, including alloyed QDs, core-shell QDs and doped QDs. The review has also prospected the development trend of tuning the band gap as well as their applications.展开更多
基金Supported by the Post Graduate Research Fund from Federal Government of Nigeria under the BEA Scholarship Program （No.CSC2005566002）
文摘Stochastic characteristics of the Benue River streamflow process are examined under conditions of data austerity. The streamflow process is investigated for trend, non-stationarity and seasonality for a time period of 26 years. Results of trend analyses with Mann-Kendall test show that there is no trend in the annual mean discharges. Monthly flow series examined with seasonal Kendall test indicate the presence of positive change in the trend for some months, especially the months of August, January, and February. For the stationarity test, daily and monthly flow series appear to be stationary whereas at 1%, 5%, and 10% significant levels, the stationarity alternative hypothesis is rejected for the annual flow series. Though monthly flow appears to be stationary going by this test, because of high seasonality, it could be said to exhibit periodic stationarity based on the seasonality analysis. The following conclusions are drawn： （1） There is seasonality in both the mean and variance with unimodal distribution. （2） Days with high mean also have high variance. （3） Skewness coefficients for the months within the dry season period are greater than those of the wet season period, and seasonal autocorrelations for streamflow during dry season are generally larger than those of the wet season. Precisely, they are significantly different for most of the months. （4） The autocorrelation functions estimated ＂over time＂ are greater in the absolute value for data that have not been deseasonalised but were initially normalised by logarithmic transformation only, while autocorrelation functions for i = 1, 2 365 estimated ＂over realisations＂ have their coefficients significantly different from other coefficients.
文摘High speed and large capacity belt conveyor is the main development trend. In the design, calculated and used of belt conveyor must be considered the high speed, large capacity, dynamic load. This paper starts from the analysis of conveyor belt transverse vibration. Through calculate transverse vibration natural frequency of conveyor belt, and analyze the lateral stability of belt conveyor.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51073115, 51003072, 51173127, 51011140072)the National Basic Research Program of China ("973" Program) (Grant No. 2010CB934700)the Natural Science Foundation of Tianjin City (Grant No. 10JCZDJC22400)
文摘Band gap, which can be tuned by changing the size of quantum dots (QDs) based on the quantum confinement effect, plays a fundamental role in electrical and optical properties of QDs. However, the tuning of the band gap by changing the size results in a series of intrinsic problems, such as the instability of the extremely small QDs, negative combination with biomolecules because of the large size of QDs, etc. Recently, several new methods have been developed to further study and improve the tuning of the band gap. In this paper, we summarized the recent progress in the fields of tuning the band gap of QDs, including alloyed QDs, core-shell QDs and doped QDs. The review has also prospected the development trend of tuning the band gap as well as their applications.
