为了提高区间振荡动态特性中振型信息的有效获取速度,提出了一种利用相关分析的快速估计区间振荡振型的新方法。它首先通过一个由先验知识设计并在线校正的低通或带通滤波器,从电力系统广域测量系统(wide area measurement system,WAMS...为了提高区间振荡动态特性中振型信息的有效获取速度,提出了一种利用相关分析的快速估计区间振荡振型的新方法。它首先通过一个由先验知识设计并在线校正的低通或带通滤波器,从电力系统广域测量系统(wide area measurement system,WAMS)采集的各联络线有功功率信号中提取以弱阻尼模式为主导的分量信号,然后对该信号进行时域相关性分析,借助自相关和互相关系数确定该模式下各区间功率偏差的归一化幅值和相对相位,进而获得其功率偏差振型,并结合离线计算、在线修正的模态表确认等效转速偏差振型和对应模式。通过对一对弱阻尼的平稳信号和一对非指数时变幅值的反相非平稳信号进行分析,表明了相关分析法的适用性。案例分析在一个4区域9节点系统和一个华东电网规划系统中展开,结果表明了该方法的快速性、有效性以及潜在的实用性。展开更多
A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-sp...A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-splines free-form deformation(FFD).The affine transformation performed a rough registration targeting the mismatch between the CT and MR images.The B-splines FFD transformation performed a finer registration by correcting local motion deformation.In the registration algorithm,the normalized mutual information(NMI) was used as similarity measure,and the limited memory Broyden-Fletcher- Goldfarb-Shannon(L-BFGS) optimization method was applied for optimization process.The algorithm was applied to the fully automated registration of liver CT and MR images in three subjects.The results demonstrate that the proposed method not only significantly improves the registration accuracy but also reduces the running time,which is effective and efficient for nonrigid registration.展开更多
文摘为了提高区间振荡动态特性中振型信息的有效获取速度,提出了一种利用相关分析的快速估计区间振荡振型的新方法。它首先通过一个由先验知识设计并在线校正的低通或带通滤波器,从电力系统广域测量系统(wide area measurement system,WAMS)采集的各联络线有功功率信号中提取以弱阻尼模式为主导的分量信号,然后对该信号进行时域相关性分析,借助自相关和互相关系数确定该模式下各区间功率偏差的归一化幅值和相对相位,进而获得其功率偏差振型,并结合离线计算、在线修正的模态表确认等效转速偏差振型和对应模式。通过对一对弱阻尼的平稳信号和一对非指数时变幅值的反相非平稳信号进行分析,表明了相关分析法的适用性。案例分析在一个4区域9节点系统和一个华东电网规划系统中展开,结果表明了该方法的快速性、有效性以及潜在的实用性。
基金Project(61240010)supported by the National Natural Science Foundation of ChinaProject(20070007070)supported by Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-splines free-form deformation(FFD).The affine transformation performed a rough registration targeting the mismatch between the CT and MR images.The B-splines FFD transformation performed a finer registration by correcting local motion deformation.In the registration algorithm,the normalized mutual information(NMI) was used as similarity measure,and the limited memory Broyden-Fletcher- Goldfarb-Shannon(L-BFGS) optimization method was applied for optimization process.The algorithm was applied to the fully automated registration of liver CT and MR images in three subjects.The results demonstrate that the proposed method not only significantly improves the registration accuracy but also reduces the running time,which is effective and efficient for nonrigid registration.
