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学科教学知识的结构化—叙事表征——内容表征—教学经验模型 被引量:14
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作者 张小菊 王祖浩 《外国教育研究》 CSSCI 北大核心 2014年第3期50-57,128,共9页
学科教学知识(PCK)是教师知识的核心成分,与教师的专业发展息息相关。学科教学知识的表征具有重要意义,但PCK具有情境性、缄默性,是隐性知识,难于表征,较少有研究涉猎PCK的表征研究。洛克伦的内容表征—教学经验模型影响较大,并在PCK的... 学科教学知识(PCK)是教师知识的核心成分,与教师的专业发展息息相关。学科教学知识的表征具有重要意义,但PCK具有情境性、缄默性,是隐性知识,难于表征,较少有研究涉猎PCK的表征研究。洛克伦的内容表征—教学经验模型影响较大,并在PCK的研究中得到广泛应用。 展开更多
关键词 学科教学知识 教学知识的表征 结构化表征 叙事表征
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基于聚类字典学习和稀疏表示的SAR图像抑斑方法 被引量:3
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作者 刘春辉 齐越 丁文锐 《系统工程与电子技术》 EI CSCD 北大核心 2017年第8期1709-1715,共7页
针对合成孔径雷达(synthetic aperture radar,SAR)图像相干斑抑制问题,提出一种基于聚类字典学习和稀疏表示的SAR图像抑斑方法。本方法以相干斑噪声的非对数加性模型为基础,通过改进相似度测度的K-means聚类和主成分分析方法进行字典学... 针对合成孔径雷达(synthetic aperture radar,SAR)图像相干斑抑制问题,提出一种基于聚类字典学习和稀疏表示的SAR图像抑斑方法。本方法以相干斑噪声的非对数加性模型为基础,通过改进相似度测度的K-means聚类和主成分分析方法进行字典学习,克服了相干斑噪声非高斯性带来的影响,形成具有结构性聚类的字典原子;在稀疏分解方面,通过引入方差稳定因子,建立了适用于抑制SAR相干斑噪声的稀疏表示模型,并通过交替迭代算法进行代价方程求解;同时算法还增加了点目标保护措施,避免了对图像点目标"过滤波"。通过卫星、无人机SAR图像的抑斑实验证明,相比经典的SAR图像抑斑方法,所提的方法在抑斑的视觉效果上和客观评价指标上都有较大的提升。 展开更多
关键词 合成孔径雷达 相干斑抑制 字典学习 稀疏表示 结构聚类
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Digital simulation of 3D turbulence wind field of Sutong Bridge based on measured wind spectra 被引量:2
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作者 Hao WANG Zhou-hong ZONG +3 位作者 Ai-qun LI Teng TONG Jie NIU Wen-ping DENG 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2012年第2期91-104,共14页
Time domain analysis is an essential implement to study the buffeting behavior of long-span bridges for it can consider the non-linear effect which is significant in long-span bridges. The prerequisite of time domain ... Time domain analysis is an essential implement to study the buffeting behavior of long-span bridges for it can consider the non-linear effect which is significant in long-span bridges. The prerequisite of time domain analysis is the accurate description of 3D turbulence winds. In this paper, some hypotheses for simplifying the 3D turbulence simulation of long-span cable-stayed bridges are conducted, considering the structural characteristics. The turbulence wind which is a 3D multivariate stochastic vector process is converted into four independent 1D univariate stochastic processes. Based on recorded wind data from structural health monitoring system (SHMS) of the Sutong Bridge, China, the measured spectra expressions are then presented using the nonlinear least-squares fitting method. Turbulence winds at the Sutong Bridge site are simulated based on the spectral representation method and the Fast Fourier transform (FFT) technique, and the relevant results derived from target spectra including measured spectra and recommended spectra are compared. The reliability and accuracy of the presented turbulence simulation method are validated through comparisons between simulated and target spectra (measured and recommended spectra). The obtained turbulence si-mulations can not only serve further analysis of the buffeting behavior of the Sutong Bridge, but references for structural anti-wind design in adjacent regions. 展开更多
关键词 骚乱模拟 光谱表示方法 Fourier 变换(快速傅里叶变换) 留下来电缆线的桥 结构的健康监视系统(SHMS ) 力量光谱密度
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