漏磁效应对永磁饱和型故障限流器(permanent-magnet-biased saturation based fault current limiter,PMFCL)的动态特性具有重要影响。针对一种直线式PMFCL的磁拓扑,以铁心磁通的工作零点作为分界阐明了其2个阶段的限流机理,指出铁心磁...漏磁效应对永磁饱和型故障限流器(permanent-magnet-biased saturation based fault current limiter,PMFCL)的动态特性具有重要影响。针对一种直线式PMFCL的磁拓扑,以铁心磁通的工作零点作为分界阐明了其2个阶段的限流机理,指出铁心磁通自过零反向后将发生畸变,永磁体不再参与限流过程。基于磁场分割原理实现2类等效磁路模型中总漏磁导和漏磁系数的计算,针对拟圆环截面磁通管的漏磁导,提出基于曲线拟合而改变积分变量的求解方法。在Matlab/Simulink环境下建立了考虑漏磁效应的PMFCL仿真模型,分别与小电流和大电流工况的实验结果进行对比,验证了建模方法的有效性。展开更多
Data fitting is an extensively employed modeling tool in geometric design. With the advent of the big data era, the data sets to be fitted are made larger and larger, leading to more and more least-squares fitting sys...Data fitting is an extensively employed modeling tool in geometric design. With the advent of the big data era, the data sets to be fitted are made larger and larger, leading to more and more least-squares fitting systems with singular coefficient matrices. LSPIA (least-squares progressive iterative approximation) is an efficient iterative method for the least-squares fitting. However, the convergence of LSPIA for the singular least-squares fitting systems remains as an open problem. In this paper, the authors showed that LSPIA for the singular least-squares fitting systems is convergent. Moreover, in a special case, LSPIA converges to the Moore-Penrose (M-P) pseudo-inverse solution to the least- squares fitting result of the data set. This property makes LSPIA, an iterative method with clear geometric meanings, robust in geometric modeling applications. In addition, the authors discussed some implementation detail of LSPIA, and presented an example to validate the convergence of LSPIA for the singular least-squares fitting systems.展开更多
Due to the complex nature of multi-source geological data, it is difficult to rebuild every geological structure through a single 3D modeling method. The multi-source data interpretation method put forward in this ana...Due to the complex nature of multi-source geological data, it is difficult to rebuild every geological structure through a single 3D modeling method. The multi-source data interpretation method put forward in this analysis is based on a database-driven pattern and focuses on the discrete and irregular features of geological data. The geological data from a variety of sources covering a range of accuracy, resolution, quantity and quality are classified and integrated according to their reliability and consistency for 3D modeling. The new interpolation-approximation fitting construction algorithm of geological surfaces with the non-uniform rational B-spline(NURBS) technique is then presented. The NURBS technique can retain the balance among the requirements for accuracy, surface continuity and data storage of geological structures. Finally, four alternative 3D modeling approaches are demonstrated with reference to some examples, which are selected according to the data quantity and accuracy specification. The proposed approaches offer flexible modeling patterns for different practical engineering demands.展开更多
以EDEM软件的Hertz-Mindlin with bonding (HMB)接触模型为基础,对岩石离散元模型构建方法进行了研究。首先,确保HMB岩石模型的黏结键全部为弱键,即黏结键抗拉强度小于其法向极限应力,然后通过仿真试验,分别建立了岩石模型的弹性模量E...以EDEM软件的Hertz-Mindlin with bonding (HMB)接触模型为基础,对岩石离散元模型构建方法进行了研究。首先,确保HMB岩石模型的黏结键全部为弱键,即黏结键抗拉强度小于其法向极限应力,然后通过仿真试验,分别建立了岩石模型的弹性模量E、泊松比μ和抗拉强度σt与颗粒和黏结键参数之间的3个回归关系式。根据上述3个回归关系式,构建了用HMB模型拟合真实岩石E、μ、σt的数学模型。对HMB岩石模型的抗压强度σc,当黏结键的极限应力比(法向极限应力σmax/切向极限应力τmax)δτσ在1~2范围内时,σc受到σmax、τmax以及二者比值δστ的共同影响,特别是δστ在1.5附近时,单轴压缩仿真试验的破坏形式与试验结果吻合的较好,且δστ一定时,σc与σmax呈线性关系。综合上述成果,提出了一种拟合真实岩石试样的弹性模量E、泊松比μ、抗拉强度σt、抗压强度σc以及岩石试样破坏形式的HMB岩石模型构建方法,并给出了详细拟合步骤。最后通过实例验证了按照此方法构建的砂岩和花岗岩模型既能够拟合岩石的静态力学特性,也可用于分析岩石的动态力学特性。展开更多
文摘漏磁效应对永磁饱和型故障限流器(permanent-magnet-biased saturation based fault current limiter,PMFCL)的动态特性具有重要影响。针对一种直线式PMFCL的磁拓扑,以铁心磁通的工作零点作为分界阐明了其2个阶段的限流机理,指出铁心磁通自过零反向后将发生畸变,永磁体不再参与限流过程。基于磁场分割原理实现2类等效磁路模型中总漏磁导和漏磁系数的计算,针对拟圆环截面磁通管的漏磁导,提出基于曲线拟合而改变积分变量的求解方法。在Matlab/Simulink环境下建立了考虑漏磁效应的PMFCL仿真模型,分别与小电流和大电流工况的实验结果进行对比,验证了建模方法的有效性。
基金supported by the Natural Science Foundation of China under Grant No.61379072
文摘Data fitting is an extensively employed modeling tool in geometric design. With the advent of the big data era, the data sets to be fitted are made larger and larger, leading to more and more least-squares fitting systems with singular coefficient matrices. LSPIA (least-squares progressive iterative approximation) is an efficient iterative method for the least-squares fitting. However, the convergence of LSPIA for the singular least-squares fitting systems remains as an open problem. In this paper, the authors showed that LSPIA for the singular least-squares fitting systems is convergent. Moreover, in a special case, LSPIA converges to the Moore-Penrose (M-P) pseudo-inverse solution to the least- squares fitting result of the data set. This property makes LSPIA, an iterative method with clear geometric meanings, robust in geometric modeling applications. In addition, the authors discussed some implementation detail of LSPIA, and presented an example to validate the convergence of LSPIA for the singular least-squares fitting systems.
基金Supported by the National Natural Science Foundation of China(No.51379006 and No.51009106)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-12-0404)the National Basic Research Program of China("973"Program,No.2013CB035903)
文摘Due to the complex nature of multi-source geological data, it is difficult to rebuild every geological structure through a single 3D modeling method. The multi-source data interpretation method put forward in this analysis is based on a database-driven pattern and focuses on the discrete and irregular features of geological data. The geological data from a variety of sources covering a range of accuracy, resolution, quantity and quality are classified and integrated according to their reliability and consistency for 3D modeling. The new interpolation-approximation fitting construction algorithm of geological surfaces with the non-uniform rational B-spline(NURBS) technique is then presented. The NURBS technique can retain the balance among the requirements for accuracy, surface continuity and data storage of geological structures. Finally, four alternative 3D modeling approaches are demonstrated with reference to some examples, which are selected according to the data quantity and accuracy specification. The proposed approaches offer flexible modeling patterns for different practical engineering demands.
文摘以EDEM软件的Hertz-Mindlin with bonding (HMB)接触模型为基础,对岩石离散元模型构建方法进行了研究。首先,确保HMB岩石模型的黏结键全部为弱键,即黏结键抗拉强度小于其法向极限应力,然后通过仿真试验,分别建立了岩石模型的弹性模量E、泊松比μ和抗拉强度σt与颗粒和黏结键参数之间的3个回归关系式。根据上述3个回归关系式,构建了用HMB模型拟合真实岩石E、μ、σt的数学模型。对HMB岩石模型的抗压强度σc,当黏结键的极限应力比(法向极限应力σmax/切向极限应力τmax)δτσ在1~2范围内时,σc受到σmax、τmax以及二者比值δστ的共同影响,特别是δστ在1.5附近时,单轴压缩仿真试验的破坏形式与试验结果吻合的较好,且δστ一定时,σc与σmax呈线性关系。综合上述成果,提出了一种拟合真实岩石试样的弹性模量E、泊松比μ、抗拉强度σt、抗压强度σc以及岩石试样破坏形式的HMB岩石模型构建方法,并给出了详细拟合步骤。最后通过实例验证了按照此方法构建的砂岩和花岗岩模型既能够拟合岩石的静态力学特性,也可用于分析岩石的动态力学特性。
