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应用界标分界法的电力系统动态仿真准确度评估 被引量:8
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作者 周成 贺仁睦 《中国电机工程学报》 EI CSCD 北大核心 2010年第7期42-47,共6页
动态仿真在电力系统分析方面已得到了广泛的应用,成为系统设计、运行不可缺少的工具;仿真的准确度直接决定了系统运行的安全性和经济性。针对现有仿真准确度评估方法的不足,综合了界标分界法与直接距离法,提出了基于形状相似度和数值相... 动态仿真在电力系统分析方面已得到了广泛的应用,成为系统设计、运行不可缺少的工具;仿真的准确度直接决定了系统运行的安全性和经济性。针对现有仿真准确度评估方法的不足,综合了界标分界法与直接距离法,提出了基于形状相似度和数值相似度2个指标的电力系统仿真准确度的评估方法。该方法克服了在噪声干扰情况下应用规范系数法求解形状相似度时评估结果失真的问题,其评估结果可为使用人员进行模型修正提供参考依据。结合2004年某地区大扰动试验的实测数据及使用不同负荷模型进行后验仿真的计算结果,进行了算例分析,验证了该评估方法的可行性。 展开更多
关键词 动态仿真 电力系统 界标分界 数值相似度 形状相似度
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基于现实世界研究中临床随访数据的两种动态预测建模方法的实证研究
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作者 杨锋 陈欣 +3 位作者 尤东方 黄丽红 魏朝晖 赵杨 《中国临床医学》 2021年第5期751-756,共6页
目的:针对现实世界研究(real-world study,RWS)中常见的具有纵向测量属性的动态观察指标,探讨界标法和联合建模法2种动态预测方法的应用价值。方法:基于358例某重症肺炎患者预后数据,分别采用界标法和联合建模法,基于R软件,对于第5天、... 目的:针对现实世界研究(real-world study,RWS)中常见的具有纵向测量属性的动态观察指标,探讨界标法和联合建模法2种动态预测方法的应用价值。方法:基于358例某重症肺炎患者预后数据,分别采用界标法和联合建模法,基于R软件,对于第5天、第10天、第15天尚处于观察期的某重症肺炎患者,预测其未来的死亡风险。结果:2种方法均能在各时间点预测个体未来发生结局事件的概率。第5天、第10天和第15天,利用界标法进行动态预测的AUC分别为81.64%、85.89%和82.15%;而联合建模法的AUC分别为81.11%、85.07%和72.09%。结论:在针对动态历史数据的现实世界研究中,可采用动态预测模型分析法,从而获得更为丰富的信息。 展开更多
关键词 纵向数据 动态预测 界标法 联合建模
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火炮动力后坐试验台建模及射击模拟准确度评估 被引量:3
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作者 杨玉良 秦俊奇 +2 位作者 狄长春 邓辉咏 张小嘎 《振动与冲击》 EI CSCD 北大核心 2014年第10期127-130,共4页
针对火炮动力后坐试验台模拟实弹射击准确度问题,基于ADAMS/ATV软件,以某型自行火炮为对象,建立火炮动力后坐试验台虚拟样机模型;在此基础上获得炮口强冲击条件下火炮后坐位移、速度及加速度仿真曲线;分别求解曲线间距相对误差,结合界... 针对火炮动力后坐试验台模拟实弹射击准确度问题,基于ADAMS/ATV软件,以某型自行火炮为对象,建立火炮动力后坐试验台虚拟样机模型;在此基础上获得炮口强冲击条件下火炮后坐位移、速度及加速度仿真曲线;分别求解曲线间距相对误差,结合界标分界法提出基于曲线形状相似度及数值相似度两指标的射击模拟准确度评估方法。通过计算获得试验台模拟准确度为0.8654。评估结果表明,该试验台能较准确模拟火炮实弹射击的后坐动态特性。 展开更多
关键词 火炮动力后坐 虚拟样机 数值相似度 界标分界 形状相似度
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Hybrid FEM-BEM for simulation of electromagnetic response
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作者 余海涛 《Journal of Southeast University(English Edition)》 EI CAS 2004年第3期303-308,共6页
A finite element method with boundary element method (FEM-BEM) is presented for computing electromagnetic induction. The features of an edge element method including the volume and surface edge element method are inve... A finite element method with boundary element method (FEM-BEM) is presented for computing electromagnetic induction. The features of an edge element method including the volume and surface edge element method are investigated in depth. Surface basis functions of edge elements to an arbitrary shape of target are derived according to the geometrical property of basis functions and applied to discretize the surface integral equation for 3-D general targets. The proposed model is presented to compute resonant frequencies and surface current of underground unexplored ordnance (UXO), and then the electromagnetic responses of single target with different frequencies and positions of sensor are simulated and results are validated by experiments. 展开更多
关键词 Boundary element method Electromagnetic field effects Finite element method GEOMETRY Integral equations Radial basis function networks
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A refinement of scaling laws in wall turbulence
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作者 张珂 《Journal of Chongqing University》 CAS 2009年第3期195-200,共6页
As a universal conclusion of turbulent scale, scaling laws are important to the research on statistic turbulence. We measured two-dimensional instantaneous velocity field in turbulent boundary layers of flat plate wit... As a universal conclusion of turbulent scale, scaling laws are important to the research on statistic turbulence. We measured two-dimensional instantaneous velocity field in turbulent boundary layers of flat plate with the momentum thickness Reynolds number Reθ=2 167. Scaling laws have different forms in different wall distance and scale. We proposed an expected scaling law and compared it with the She-Leveque (SL) scaling law based on the wavelet analysis and traditional statistical methods. Results show that the closer to the wall, the more the expected scaling law approached to the SL scaling law. 展开更多
关键词 turbulent boundary layer probability density function particle image velocimetry scaling laws
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б-sharpen immersed boundary method(б-SIBM)—New method for solving the horizontal pressure-gradient force(PGF) problem of б-coordinate 被引量:1
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作者 HEI PengFei ZHOU Gang +2 位作者 JIA DongDong YE YunTao LEI Kun 《Science China Earth Sciences》 SCIE EI CAS 2014年第7期1681-1691,共11页
Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method ... Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method called the "σ-sharpen immersed boundary method" (σ-SIBM) is put forward. In this method, the virtual flat bottom boundary is creatively introduced in regions with the steep boundary and is taken as the boundary of numerical domain. By this, OH/Ox of numerical domain changes to be a controllable value and the steep bottom problem is then transformed to the non-conforming boundary problem, which is, in turn, solved by the SIBM. The accuracy and efficiency of the σ-sharpen immersed boundary method (σ-SIBM) has been showed by both comparative theoretical analysis and classical numerical tests. First, it is shown that the σ-SIBM is more effective than the z-level method, in that σ-SIBM needs special treatment only in the steep section, but the z-level method needs the special treatment in each grid note. Second, it is superior to the p-method in that it is not restricted by the density distribution. This paper revisits the classical seamount numerical test used in numerous studies to prove the sigma errors of the pressure gradient force (PGFE) and their long-term effects on circulation. It can be seen that, as for the maximum erroneous velocity and kinetic energy, the value of σ-SIBM is much less than that of the z-level method and the traditional σ-method. 展开更多
关键词 sharpen immersed boundary method (SIBM) immersed boundary method (IBM) direct forcing method o-coordinate pressure gradient force (PGF)
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