The probability distributions of sand particles' lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical ...The probability distributions of sand particles' lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry (PDA) in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the χ2-test for these probability distributions, that the probability density functions (pdf's) of the sand particles' lift-off and incident velocities as well as their vertical components are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions. These pdf's depend on not only the sand particle diameter but also the wind speed.展开更多
文件传输协议(File Transfer Protoco,FTP)速率提升优化涵盖了无线优化、传输优化及应用层参数优化等方面。传统的FTP优化主要基于无线优化和传输优化,往往未涉及用户应用层的优化。FTP在优化方法,以TCP/IP协议为基础,针对FTP业务信令...文件传输协议(File Transfer Protoco,FTP)速率提升优化涵盖了无线优化、传输优化及应用层参数优化等方面。传统的FTP优化主要基于无线优化和传输优化,往往未涉及用户应用层的优化。FTP在优化方法,以TCP/IP协议为基础,针对FTP业务信令流程特征及TCP/IP重要参数研究,结合3G无线接入网络信令特征,提出了具有指导意义的TCP/IP参数设置规范,对提高现网FTP下载速率及大流量业务应用(如手机流媒体等)具有一定的推广价值。展开更多
基金The project supported by the National Natural Science Foundation of China(10532040)the Hundred Talents Project.the Knowledge Innovation Project of Chinese Academy of Sciences(KZCX2-304).
文摘The probability distributions of sand particles' lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry (PDA) in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the χ2-test for these probability distributions, that the probability density functions (pdf's) of the sand particles' lift-off and incident velocities as well as their vertical components are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions. These pdf's depend on not only the sand particle diameter but also the wind speed.
文摘文件传输协议(File Transfer Protoco,FTP)速率提升优化涵盖了无线优化、传输优化及应用层参数优化等方面。传统的FTP优化主要基于无线优化和传输优化,往往未涉及用户应用层的优化。FTP在优化方法,以TCP/IP协议为基础,针对FTP业务信令流程特征及TCP/IP重要参数研究,结合3G无线接入网络信令特征,提出了具有指导意义的TCP/IP参数设置规范,对提高现网FTP下载速率及大流量业务应用(如手机流媒体等)具有一定的推广价值。
