Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have ...Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have been investigated by employing DV - Xa method, in which different cluster models were adopted to calculate electron structure.It is proved that some regulations must be taken into ac- count in order to carry out alloy design calculation successfully,which are described in this paper in detail.展开更多
相比传统高压直流输电HVDC(high voltage direct arrent),基于电压源换流器的高压直流输电VSC-HVDC(voltage source converter based HVDC)具有较多独特优势,是智能电网发展具有代表性的关键技术之一。首先,基于VSC-HVDC稳态模型的标幺...相比传统高压直流输电HVDC(high voltage direct arrent),基于电压源换流器的高压直流输电VSC-HVDC(voltage source converter based HVDC)具有较多独特优势,是智能电网发展具有代表性的关键技术之一。首先,基于VSC-HVDC稳态模型的标幺制处理分析了VSC-HVDC的稳态方程,并给出了适用于求解含VSC-HVDC的交直流系统潮流的统一法迭代形式;进而,通过计算预估值和校正值2个步骤,利用具有2.414阶次收敛速率的改进牛顿-拉夫逊法修正交直流系统的雅可比矩阵,以节省程序迭代过程中的数据存储空间,加快程序执行调用的速度,从而提高雅可比矩阵的计算速率。最后,基于修改后的IEEE标准算例,从交直流潮流结果、控制方式、算法效率等方面的对比分析,验证了该方法求解含VSC-HVDC的交直流系统潮流的有效性和正确性。展开更多
为解决交直流混联系统暂态响应难以快速精确求解的问题,文中基于动态相量法基本原理,对电网换相换流器型高压直流输电(line commutated converter high voltage direct current,LCC-HVDC)全系统进行详细的建模推导。首先建立含锁相环的...为解决交直流混联系统暂态响应难以快速精确求解的问题,文中基于动态相量法基本原理,对电网换相换流器型高压直流输电(line commutated converter high voltage direct current,LCC-HVDC)全系统进行详细的建模推导。首先建立含锁相环的换流器动态相量模型,通过将锁相环输出与改进开关函数相结合,准确还原换流器的工作过程,提高计算的速度和精度。随后,通过对直流线路和控制系统的精确建模,实现了系统的闭环计算。同时,针对逆变侧易出现的换相失败情况,提出复合判据和开关函数修正法对其进行快速判断和处理,拓展模型的适用性。将所建模型应用于CIGRE Benchmark标准直流系统,多故障类型下的仿真结果进一步证明了其相较于传统动态相量模型的优势。展开更多
Voidage is important in determining the hydrodynamic behavior of a fluidized bed and estimating the drag force,Exact calculation methods are limited,especially in terms of determining the intersection bf a particle an...Voidage is important in determining the hydrodynamic behavior of a fluidized bed and estimating the drag force,Exact calculation methods are limited,especially in terms of determining the intersection bf a particle and cell,This paper presents a method of directly calculating voidage.First,a judgment criterion of particle-cell overlap,which relies on the relationship of the distance from the particle to a cell face,edge,or vertex,is proposed.Eight cases of the overlap volume of a particle and cell are then ascribed to a unified formula in the framework of the cuboid cell,This formula relies on the volume of two kinds of segments named the hemispherical segment and quarter-spherical segment.The presented method is validated by calculating the voidage of simple cubic packing.Moreover,a three-dimensional fluidized bed with large particles is simulated and the results of numerical simulation are compared against experimental and simulation results reported in the literature.All numerical results are in good agreement with corresponding experimental data,and demonstrate the accuracy and reliability of the presented method in the three-dimensional simulation of fluidized beds.展开更多
文摘Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have been investigated by employing DV - Xa method, in which different cluster models were adopted to calculate electron structure.It is proved that some regulations must be taken into ac- count in order to carry out alloy design calculation successfully,which are described in this paper in detail.
文摘相比传统高压直流输电HVDC(high voltage direct arrent),基于电压源换流器的高压直流输电VSC-HVDC(voltage source converter based HVDC)具有较多独特优势,是智能电网发展具有代表性的关键技术之一。首先,基于VSC-HVDC稳态模型的标幺制处理分析了VSC-HVDC的稳态方程,并给出了适用于求解含VSC-HVDC的交直流系统潮流的统一法迭代形式;进而,通过计算预估值和校正值2个步骤,利用具有2.414阶次收敛速率的改进牛顿-拉夫逊法修正交直流系统的雅可比矩阵,以节省程序迭代过程中的数据存储空间,加快程序执行调用的速度,从而提高雅可比矩阵的计算速率。最后,基于修改后的IEEE标准算例,从交直流潮流结果、控制方式、算法效率等方面的对比分析,验证了该方法求解含VSC-HVDC的交直流系统潮流的有效性和正确性。
文摘为解决交直流混联系统暂态响应难以快速精确求解的问题,文中基于动态相量法基本原理,对电网换相换流器型高压直流输电(line commutated converter high voltage direct current,LCC-HVDC)全系统进行详细的建模推导。首先建立含锁相环的换流器动态相量模型,通过将锁相环输出与改进开关函数相结合,准确还原换流器的工作过程,提高计算的速度和精度。随后,通过对直流线路和控制系统的精确建模,实现了系统的闭环计算。同时,针对逆变侧易出现的换相失败情况,提出复合判据和开关函数修正法对其进行快速判断和处理,拓展模型的适用性。将所建模型应用于CIGRE Benchmark标准直流系统,多故障类型下的仿真结果进一步证明了其相较于传统动态相量模型的优势。
文摘Voidage is important in determining the hydrodynamic behavior of a fluidized bed and estimating the drag force,Exact calculation methods are limited,especially in terms of determining the intersection bf a particle and cell,This paper presents a method of directly calculating voidage.First,a judgment criterion of particle-cell overlap,which relies on the relationship of the distance from the particle to a cell face,edge,or vertex,is proposed.Eight cases of the overlap volume of a particle and cell are then ascribed to a unified formula in the framework of the cuboid cell,This formula relies on the volume of two kinds of segments named the hemispherical segment and quarter-spherical segment.The presented method is validated by calculating the voidage of simple cubic packing.Moreover,a three-dimensional fluidized bed with large particles is simulated and the results of numerical simulation are compared against experimental and simulation results reported in the literature.All numerical results are in good agreement with corresponding experimental data,and demonstrate the accuracy and reliability of the presented method in the three-dimensional simulation of fluidized beds.
