Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser （FEL）. In previous literature, it was demonstrated that...Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser （FEL）. In previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands. Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron- beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.展开更多
The average lamellar spacing and interface undercooling in steady-state irregular eutectic growth were estimated based on the Jackson and Hunt’s analysis by relaxing the isothermal interface assumption.At low growth ...The average lamellar spacing and interface undercooling in steady-state irregular eutectic growth were estimated based on the Jackson and Hunt’s analysis by relaxing the isothermal interface assumption.At low growth rates,the average lamellar spacing and average interface undercooling are dependent only on the characteristic thermo-physical properties of a binary eutectic system. For a general Al-Si eutectic,it is found that the eutectic characteristic length based on the present non-isothermal analysis is consistent with that obtained from isothermal analysis;however,the average interface undercooling is remarkably different between them,and such discrepancy in average interface undercooling increases with increasing of growth rate.The measured interface undercooling obtained from literature is reasonably interpreted by present non-isothermal analysis.展开更多
利用三维激光扫描仪获取的空间数据,进行三维实景构建研究。首先对扫描仪获取的数据按照基于格网的方法进行压缩,然后对压缩后的数据建立三角网数字地面模型,最后将原始空间数据按照一定的拓扑结构映射到二维球面(α,θ面)并在α,θ面...利用三维激光扫描仪获取的空间数据,进行三维实景构建研究。首先对扫描仪获取的数据按照基于格网的方法进行压缩,然后对压缩后的数据建立三角网数字地面模型,最后将原始空间数据按照一定的拓扑结构映射到二维球面(α,θ面)并在α,θ面等角划分形成二维矩阵,以落在矩阵各栅格内的点云强度均值作为该处像素值以图像形式显示,再同实际影像比较,选出同名点,根据摄影测量后方交会原理计算得到影像的内外方位元素,由得到的内外方位元素计算出相应的纹理坐标,完成纹理映射过程。文中以Trimble地面三维激光扫描仪为例以地物作为采集对象,用Visual Studio 6.0作为开发平台进行三维实景构建。展开更多
基金Project supported by the Science Foundation of Department of Education of Sichuan Province,China (Grant No.12233454)the Youth Foundation of Department of Education of Sichuan Province,China (Grant No.10ZB080)the Xihua University Foundation,China (Grant No.Z0913306)
文摘Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser （FEL）. In previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands. Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron- beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.
基金Projects(50201012,50471065)supported by the National Natural Science Foundation of China
文摘The average lamellar spacing and interface undercooling in steady-state irregular eutectic growth were estimated based on the Jackson and Hunt’s analysis by relaxing the isothermal interface assumption.At low growth rates,the average lamellar spacing and average interface undercooling are dependent only on the characteristic thermo-physical properties of a binary eutectic system. For a general Al-Si eutectic,it is found that the eutectic characteristic length based on the present non-isothermal analysis is consistent with that obtained from isothermal analysis;however,the average interface undercooling is remarkably different between them,and such discrepancy in average interface undercooling increases with increasing of growth rate.The measured interface undercooling obtained from literature is reasonably interpreted by present non-isothermal analysis.
文摘利用三维激光扫描仪获取的空间数据,进行三维实景构建研究。首先对扫描仪获取的数据按照基于格网的方法进行压缩,然后对压缩后的数据建立三角网数字地面模型,最后将原始空间数据按照一定的拓扑结构映射到二维球面(α,θ面)并在α,θ面等角划分形成二维矩阵,以落在矩阵各栅格内的点云强度均值作为该处像素值以图像形式显示,再同实际影像比较,选出同名点,根据摄影测量后方交会原理计算得到影像的内外方位元素,由得到的内外方位元素计算出相应的纹理坐标,完成纹理映射过程。文中以Trimble地面三维激光扫描仪为例以地物作为采集对象,用Visual Studio 6.0作为开发平台进行三维实景构建。
