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LEAST-SQUARES METHOD-BASED FEATURE FITTING AND EXTRACTION IN REVERSE ENGINEERING 被引量:3
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作者 Ke YinglinSun QingLu ZhenCollege of Mechanical andEnergy Engineering,Zhejiang University,Hangzhou 310027, China 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2003年第2期163-166,共4页
The main purpose of reverse engineering is to convert discrete data pointsinto piecewise smooth, continuous surface models. Before carrying out model reconstruction it issignificant to extract geometric features becau... The main purpose of reverse engineering is to convert discrete data pointsinto piecewise smooth, continuous surface models. Before carrying out model reconstruction it issignificant to extract geometric features because the quality of modeling greatly depends on therepresentation of features. Some fitting techniques of natural quadric surfaces with least-squaresmethod are described. And these techniques can be directly used to extract quadric surfaces featuresduring the process of segmentation for point cloud. 展开更多
关键词 reverse engineering feature extraction least-squares method segmentationand surface fitting
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Iterative circle fitting based on circular attracting factor
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作者 王恒升 张强 王福亮 《Journal of Central South University》 SCIE EI CAS 2013年第10期2663-2675,共13页
An intuitive method for circle fitting is proposed. Assuming an approximate circle(CA,n) for the fitting of some scattered points, it can be imagined that every point would apply a force to CA,n, which all together fo... An intuitive method for circle fitting is proposed. Assuming an approximate circle(CA,n) for the fitting of some scattered points, it can be imagined that every point would apply a force to CA,n, which all together form an overall effect that "draws" CA,n towards best fitting to the group of points. The basic element of the force is called circular attracting factor(CAF) which is defined as a real scalar in a radial direction of CA,n. An iterative algorithm based on this idea is proposed, and the convergence and accuracy are analyzed. The algorithm converges uniformly which is proved by the analysis of Lyapunov function, and the accuracy of the algorithm is in accord with that of geometric least squares of circle fitting. The algorithm is adopted to circle detection in grayscale images, in which the transferring to binary images is not required, and thus the algorithm is less sensitive to lightening and background noise. The main point for the adaption is the calculation of CAF which is extended in radial directions of CA,n for the whole image. All pixels would apply forces to CA,n, and the overall effect of forces would be equivalent to a force from the centroid of pixels to CA,n. The forces from would-be edge pixels would overweigh that from noisy pixels, so the following approximate circle would be of better fitting. To reduce the amount of calculation, pixels are only used in an annular area including the boundary of CA,n just in between for the calculation of CAF. Examples are given, showing the process of circle fitting of scattered points around a circle from an initial assuming circle, comparing the fitting results for scattered points from some related literature, applying the method proposed for circular edge detection in grayscale images with noise, and/or with only partial arc of a circle, and for circle detection in BGA inspection. 展开更多
关键词 circle detection circle fitting GRAYSCALE image ITERATIVE algorithm least squares fitting(lsf) CIRCULAR attracting factor(CAF) BGA inspection
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一种平面静电离子阱非正弦镜像电荷/电流信号的定量转换新算法
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作者 俞卓琦 王伟民 +4 位作者 王华 徐炳寅 吴焕铭 唐科奇 丁力 《质谱学报》 EI CAS CSCD 北大核心 2024年第3期332-342,I0001,共12页
傅里叶变换质谱(FTMS)的质量分辨率取决于镜像电荷/电流的采集时间。为了在较短的时间内获得较高的分辨率,除增加分析器场强外,还可以利用镜像电荷信号中的高次谐波。平面静电离子阱获得的镜像电荷信号具有非正弦波形,其中包含许多高次... 傅里叶变换质谱(FTMS)的质量分辨率取决于镜像电荷/电流的采集时间。为了在较短的时间内获得较高的分辨率,除增加分析器场强外,还可以利用镜像电荷信号中的高次谐波。平面静电离子阱获得的镜像电荷信号具有非正弦波形,其中包含许多高次谐波成分,增加了频谱分析的复杂程度,例如,难以辨认1个谱峰的谐波次数,以及当不同次的谐波发生重叠时出现定量困难。为了将多质荷比离子的镜像电荷信号转换成质谱,本文开发了一种新的定量算法,包含谱峰评分分类(SC)和最小二乘法拟合(LSF)。通过评分可以确定每个峰属于哪一次谐波,从而确定其对应的基频。打分算法列出所有候选离子的基频,并使用确定的基频构建所有基信号,然后用其对原频谱进行LSF,以确定每种质荷比离子的数量。使用48种不同质荷比离子的仿真镜像电荷信号对SCLSF算法进行测试。结果表明,该方法允许较宽的质量范围,即使在高噪声条件下,通过SC-LSF算法也能准确得到各种不同质荷比离子的数量。因为频谱中通常存在大量的空白频点,可以选择1个频点子集进行LSF,这相对于时域中的LSF,能够大大减少计算量,提高效率和准确度。此外,只有使用复数频谱数据进行LSF时才能获得良好的定量效果,而使用幅值数据则会对质荷比接近的离子定量造成较大的误差,这是因为质荷比接近的离子信号的低次谐波峰未能彻底分解,而复数的幅值不具有可加性,从而造成拟合的错误。 展开更多
关键词 镜像电荷 傅里叶变换质谱(FTMS) 定量算法 谱峰评分分类(SC) 最小二乘法拟合(lsf)
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The Convergence of Least-Squares Progressive Iterative Approximation for Singular Least-Squares Fitting System 被引量:13
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作者 LIN Hongwei CAO Qi ZHANG Xiaoting 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2018年第6期1618-1632,共15页
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
关键词 Data fitting GEOMETRIC modeling LSPIA SINGULAR least-squareS fitting system.
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A unified approach for least-squares surface fitting 被引量:7
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作者 ZHU Limin DING Han 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2004年第z1期72-78,共7页
This paper presents a novel approach for least-squares fitting of complex surface to measured 3D coordinate points by adjusting its location and/or shape. For a point expressed in the machine reference frame and a def... This paper presents a novel approach for least-squares fitting of complex surface to measured 3D coordinate points by adjusting its location and/or shape. For a point expressed in the machine reference frame and a deformable smooth surface represented in its own model frame, a signed point-to-surface distance function is defined, and its increment with respect to the differential motion and differential deformation of the surface is derived. On this basis, localization, surface reconstruction and geometric variation characterization are formulated as a unified nonlinear least-squares problem defined on the product space SE(3)×Km. By using Levenberg-Marquardt method, a sequential approximation surface fitting algorithm is developed. It has the advantages of implementational simplicity, computational efficiency and robustness. Applications confirm the validity of the proposed approach. 展开更多
关键词 surface fitting least-squares RIGID BODY motion deformation DISTANCE function optimization.
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基于PointCPP-LSF方法的航天筒段薄壁件滚弯成形质量分析 被引量:1
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作者 艾青波 张洁 +3 位作者 程辉 吕佑龙 左丽玲 胡蓝 《中国机械工程》 EI CAS CSCD 北大核心 2022年第8期977-985,共9页
为解决传统圆柱拟合方法对参数初值具有较高依赖性而导致无法满足航天筒段薄壁件滚弯成形质量检测精度及速度要求的问题,提出一种PointCPP-LSF方法,以实现航天筒段薄壁件滚弯成形质量分析。基于点云深度学习建立面向圆柱参数预测的点云... 为解决传统圆柱拟合方法对参数初值具有较高依赖性而导致无法满足航天筒段薄壁件滚弯成形质量检测精度及速度要求的问题,提出一种PointCPP-LSF方法,以实现航天筒段薄壁件滚弯成形质量分析。基于点云深度学习建立面向圆柱参数预测的点云网络(PointCPP)模型以获得可靠的圆柱参数初值,然后基于改进的最小二乘拟合(LSF)方法对圆柱参数进行迭代优化,并结合粗差点剔除机制,最终获取稳健的曲率半径计算结果。实验结果表明,所提方法能有效提高航天筒段薄壁件滚弯成形质量检测的准确度和速度。 展开更多
关键词 圆柱拟合 点云 深度学习 参数预测 最小二乘拟合
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DMPFIT: A Tool for Atomic-Scale Metrology via Nonlinear Least-Squares Fitting of Peaks in Atomic-Resolution TEM Images
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作者 Hongchu Du 《Nanomanufacturing and Metrology》 EI 2022年第2期101-111,共11页
Despite the wide availability and usage of Gatan’s DigitalMicrograph software in the electron microscopy community for image recording and analysis, nonlinear least-squares fitting in DigitalMicrograph is less straig... Despite the wide availability and usage of Gatan’s DigitalMicrograph software in the electron microscopy community for image recording and analysis, nonlinear least-squares fitting in DigitalMicrograph is less straightforward. This work presents a ready-to-use tool, the DMPFIT software package, written in DigitalMicrograph script and C++ language, for nonlinear least-squares fitting of the intensity distribution of atomic columns in atomic-resolution transmission electron microscopy (TEM) images with a general two-dimensional (2D) Gaussian model. Applications of the DMPFIT software are demonstrated both in atomic-resolution conventional coherent TEM (CTEM) images recorded by the negative spherical aberration imaging technique and in high angle annular dark field (HAADF) scanning TEM (STEM) images. The implemented peak-finding algorithm based on the periodicity of 2D lattices enables reliable and convenient atomic-scale metrology as well as intuitive presentation of the resolved atomic structures. 展开更多
关键词 Quantitative TEM Nonlinear least-squares fitting Image quantification Image analysis Atomic-scale metrology
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红外甲烷传感器检测中的算法研究 被引量:9
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作者 梁永直 李卯东 +1 位作者 夏路易 王正 《仪表技术与传感器》 CSCD 北大核心 2012年第11期149-150,165,共3页
针对在红外甲烷气体检测中处理数据精度不高的问题,通过对最小二乘法曲线拟合进行分析,阐述了在红外甲烷检测中使用最小二乘法拟合所存在的问题,提出了一种改进的分段最小二乘法。并根据试验中测试的数据对两种拟合方法进行了分析及对... 针对在红外甲烷气体检测中处理数据精度不高的问题,通过对最小二乘法曲线拟合进行分析,阐述了在红外甲烷检测中使用最小二乘法拟合所存在的问题,提出了一种改进的分段最小二乘法。并根据试验中测试的数据对两种拟合方法进行了分析及对比研究。试验证明:分段最小二乘法可有效提高气体检测的测量精度。 展开更多
关键词 红外甲烷检测 最小二乘法 分段最小二乘曲线拟合 红外传感器
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基于最小二乘拟合和特征基函数法的目标宽带RCS快速计算 被引量:3
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作者 王仲根 王宵 +2 位作者 李敏 吴文凤 涂冰花 《安徽师范大学学报(自然科学版)》 CAS 2017年第1期38-42,共5页
提出一种快速分析目标宽带雷达散射截面的方法,该方法将最小二乘拟合与特征基函数法相结合,通过计算选定的若干频率点的表面电流便可快速求解出整个频带内的表面电流.具体过程为利用特征基函数法求解选定频率点目标表面电流,进而利用最... 提出一种快速分析目标宽带雷达散射截面的方法,该方法将最小二乘拟合与特征基函数法相结合,通过计算选定的若干频率点的表面电流便可快速求解出整个频带内的表面电流.具体过程为利用特征基函数法求解选定频率点目标表面电流,进而利用最小二乘拟合实现表面电流和雷达散射截面的快速计算.数值计算结果表明:在不影响精度的前提下,该方法可大大提高计算效率、减少内存需求. 展开更多
关键词 最小二乘拟合 特征基函数法 雷达散射截面 矩量法
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台阶法测量CCD成像系统MTF的原理及方法
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作者 王云秀 王婉丽 《光电子技术》 CAS 2002年第3期171-174,共4页
简要叙述了用台阶法测量高能闪光照相系统调制传递函数(MTF)的原理及方法,并针对具体的闪光图像对数据进行了处理。这些对于实验的布局以及对成像系统性能的定性分析都有很重要的实用价值。
关键词 台阶法 CCD成像系统 MTF 线扩展函数 点扩展函数 调制传递函数
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继电保护装置恒定失效率估算方法 被引量:23
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作者 薛安成 王睿琛 +3 位作者 刘蔚 庄博 王宁 黄少锋 《电力系统自动化》 EI CSCD 北大核心 2012年第4期6-10,共5页
继电保护装置恒定失效率的估算,是继电保护装置可靠性评估的基础。文中分析了根据现场数据估算恒定失效率时存在的数据问题,讨论了适合现场数据的恒定失效率估算方法,即极大似然估计和最小二乘曲线拟合方法。特别地,推导了考虑数据检修... 继电保护装置恒定失效率的估算,是继电保护装置可靠性评估的基础。文中分析了根据现场数据估算恒定失效率时存在的数据问题,讨论了适合现场数据的恒定失效率估算方法,即极大似然估计和最小二乘曲线拟合方法。特别地,推导了考虑数据检修、截尾特性的基于极大似然估计的继电保护装置恒定失效率计算方法和最小二乘拟合方法。最后,基于某区域电网220kV及以上线路保护装置2006年和2007年实际运行数据,结合不同数据类型与对应的失效率估算方法估算该电网保护装置整体失效率。对比结果表明:计算恒定失效率时,需要着重考虑数据截尾影响。进一步,结合不同估算方法的特点,讨论了具有较高适应性的估算方法。 展开更多
关键词 继电保护装置 失效率 截尾数据 极大似然估计 最小二乘拟合
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Least-Squares Seismic Inversion with Stochastic Conjugate Gradient Method 被引量:2
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作者 Wei Huang Hua-Wei Zhou 《Journal of Earth Science》 SCIE CAS CSCD 2015年第4期463-470,共8页
With the development of computational power, there has been an increased focus on data-fitting related seismic inversion techniques for high fidelity seismic velocity model and image, such as full-waveform inversion a... With the development of computational power, there has been an increased focus on data-fitting related seismic inversion techniques for high fidelity seismic velocity model and image, such as full-waveform inversion and least squares migration. However, though more advanced than conventional methods, these data fitting methods can be very expensive in terms of computational cost. Recently, various techniques to optimize these data-fitting seismic inversion problems have been implemented to cater for the industrial need for much improved efficiency. In this study, we propose a general stochastic conjugate gradient method for these data-fitting related inverse problems. We first prescribe the basic theory of our method and then give synthetic examples. Our numerical experiments illustrate the potential of this method for large-size seismic inversion application. 展开更多
关键词 least-squares seismic inversion stochastic conjugate gradient method data fitting Kirchhoff migration.
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Baseline correction for digital strong-motion records by using the pre-event portion 被引量:1
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作者 Li Heng Yao Yunsheng +2 位作者 Zheng Shuiming Cai Yongjian Lei Dongning 《Geodesy and Geodynamics》 2011年第1期43-46,共4页
Baseline offset in digital strong-motion acceleration record and initial velocity can produce unrealistic results for ground velocity and displacement derived from the acceleration by integration. A new method is prop... Baseline offset in digital strong-motion acceleration record and initial velocity can produce unrealistic results for ground velocity and displacement derived from the acceleration by integration. A new method is proposed for the baseline correction and initial velocity calculation. It is based on linear least-squares fitting of the pre-event portion of velocity derived from the uncorrected acceleration data. Compared with the conventional method,which is based on removing the mean values of the pre-event portions of the acceleration and velocity traces,this method has clearer physical meaning and better stability. 展开更多
关键词 baseline offset CORRECTION acceleration records initial velocity least-square fitting
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Isogeometric Least-Squares Collocation Method with Consistency and Convergence Analysis
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作者 LIN Hongwei XIONG Yunyang +2 位作者 WANG Xiao HU Qianqian REN Jingwen 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2020年第5期1656-1693,共38页
This paper presents the isogeometric least-squares collocatio method,which determines the numerical solution by making the approximate differential operator fit the real differential operator in a least-squares sense.... This paper presents the isogeometric least-squares collocatio method,which determines the numerical solution by making the approximate differential operator fit the real differential operator in a least-squares sense.The number of collocation points employed in IGA-L can be larger than that of the unknowns.Theoretical analysis and numerical examples presented in this paper show the superiority of IGA-L over state-of-the-art collocation methods.First,a small increase in the number of collocation points in IGA-L leads to a large improvement in the accuracy of its numerical solution.Second,IGA-L method is more flexible and more stable,because the number of collocation points in IGA-L is variable.Third,IGA-L is convergent in some cases of singular parameterization.Moreover,the consistency and convergence analysis are also developed in this paper. 展开更多
关键词 Collocation method consistency and convergence least-squares fitting isogeometric analysis NURBS
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Study on the Shear Effect on Dye Patches Diffused in Wall-Bounded Shear Flow
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作者 Qianqian Shao Takahiro Tsukahara Yasuo Kawaguchi 《Open Journal of Fluid Dynamics》 2016年第4期438-452,共15页
This paper focuses on the high intensity filaments (dye patches) embedded in dye plumes in a wall-bounded shear flow, to investigate the shear effect on the dye patch distribution. Motivated by the widely concerned in... This paper focuses on the high intensity filaments (dye patches) embedded in dye plumes in a wall-bounded shear flow, to investigate the shear effect on the dye patch distribution. Motivated by the widely concerned inverse estimation of the source location, we try extracting useful information to know the source location from down-stream dye patches. Accordingly, we changed the dye injection location at different distances from the wall and made observations at different downstream (diffusion) distances from the source. The orientation angle and roundness of dye patches were concerned to examine the shear effect and dye patch characteristics. To capture the dye plume images, a planar laser induced fluorescence (PLIF) technique was used. The orientation and roundness of each dye patch were calculated by least-square fitting. The statistics of both the orientation angle and the roundness were compared with those in homogeneous turbulent cases to reveal the shear effect. Different from uniformly-orientated dye patches in the homogeneous flow, larger occurrence probabilities with positive orientation angles of dye patches are observed in wall-bounded shear flow, in particular, when the injection location is near the wall. As with information extraction for the inverse estimation of source location, it is found that the orientation distribution of dye patches is independent of the diffusion distance, but related with the injection location from the wall. While for the homogeneous flow cases, a strong dependence on the diffusion distance is observed in the orientation distribution profiles. As for the roundness, similar aspects are found regarding the dependencies on the injection location in shear flow and on diffusion distance in homogeneous flow. 展开更多
关键词 Dye Patch Image Processing Inverse Problem least-square fitting Passive Scalar Shear Flow Source Estimation Point-Source Diffusion Wall Turbulence
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一种可用于调制传递函数计算的新型线扩展函数拟合模型 被引量:12
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作者 李铁成 冯华君 +1 位作者 徐之海 李晓彤 《光学学报》 EI CAS CSCD 北大核心 2010年第12期3454-3459,共6页
调制传递函数(MTF)被广泛用于定性和定量地描述一个光学成像系统成像本领。事实上有多种不同的方法可以获取成像系统的MTF。提出了一种新型线扩展函数(LSF)拟合模型用于计算MTF。函数模型中的各个参数可以使用非线性最小二乘法来确定。... 调制传递函数(MTF)被广泛用于定性和定量地描述一个光学成像系统成像本领。事实上有多种不同的方法可以获取成像系统的MTF。提出了一种新型线扩展函数(LSF)拟合模型用于计算MTF。函数模型中的各个参数可以使用非线性最小二乘法来确定。与以前提出的函数模型相比,不论在何种噪声条件下,该函数模型的MTF计算结果总与参考值最为接近。使用该函数模型计算退化图像的MTF,并将其应用于降质图像的复原,实验结果证明了计算值的可靠性和用于图像复原时的有效性。 展开更多
关键词 图像处理 调制传递函数(MTF) 线扩展函数(lsf) 非线性最小二乘拟合 图像复原
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扫频激励下的DPOAE的局部加权最小二乘估计算法
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作者 韩晓丽 傅新星 +1 位作者 崔杰 肖灵 《生物医学工程学杂志》 EI CAS CSCD 北大核心 2013年第6期1153-1158,1170,共7页
畸变产物耳声发射(DPOAE)信号可以用于听力损失的诊断,具有重要的临床应用价值。但是,大频率范围内进行DPOAE测量时,需要耗费大量的时间。采用扫频信号作为诱发信号,为记录大频率范围内的DPOAE测量数据提供了一种快速而有效的手段。本... 畸变产物耳声发射(DPOAE)信号可以用于听力损失的诊断,具有重要的临床应用价值。但是,大频率范围内进行DPOAE测量时,需要耗费大量的时间。采用扫频信号作为诱发信号,为记录大频率范围内的DPOAE测量数据提供了一种快速而有效的手段。本文在已有的最小二乘拟合(LSF)算法的基础上,给出一种估计扫频激励下的DPOAE信号的局部加权最小二乘估计(LWLSE)算法,从扫频激励下的DPOAE记录信号中提取方差根音2f1-f2频率处的DPOAE信号。仿真结果表明,该方法相对于常用的LSF方法,对DPOAE信号和初始刺激信号的估计更准确,并且估计结果具有更小的估计方差,有利于提取更加准确的DPOAE精细结构。 展开更多
关键词 畸变产物耳声发射 最小二乘拟合 加权最小二乘估计 精细结构
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Statistical distribution based detector response function of a Si(PIN) detector for K_α and K_β X-ray 被引量:3
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作者 李哲 庹先国 +3 位作者 杨剑波 刘明哲 成毅 王磊 《Chinese Physics C》 SCIE CAS CSCD 2013年第1期144-148,共5页
A semi-empirical detector response function (DRF) model of Si (PIN) detector is proposed to fit element Kα and Kβ X-ray spectra, which is based on statistical distribution analytic (SDA) method. The model for ... A semi-empirical detector response function (DRF) model of Si (PIN) detector is proposed to fit element Kα and Kβ X-ray spectra, which is based on statistical distribution analytic (SDA) method. The model for each single peak contains a step function, a Gaussian function and an exponential tail function. Parameters in the model are obtained by weighted nonlinear least-squares fitting method. In the application, six kinds of elements' characteristic X-ray spectra are obtained by Si (PIN) detector, and fitted out by the established DRF model. Reduced chi-square values are at the interval of 1.11-1.25. Other applications of the method are also discussed. 展开更多
关键词 detector response function Si (PIN) detector statistical distribution analytic method weighted nonlinear least-squares fitting
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MODELING STRATEGIES FOR CONTROLLING H1N1 OUTBREAKS IN CHINA
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作者 JIN ZHANG YANNI XIAO 《International Journal of Biomathematics》 2012年第4期63-81,共19页
There has been a global attack of A/H1N1 virus in 2009, which widely affected the world's normal stability and economic development. Since the emergence of the first diagnosed A/H1N1 influenza infected person in 11 M... There has been a global attack of A/H1N1 virus in 2009, which widely affected the world's normal stability and economic development. Since the emergence of the first diagnosed A/H1N1 influenza infected person in 11 May 2009 in China, very strict policy including quarantine and isolation measures were widely implemented to control the spread of this disease before the vaccine appeared. We propose a compartmental model that mimics the infection process of A/H1N1 under control strategies taken in China's Mainland. Apart from theoretical analysis, using the statistic data of Shaanxi Province, we estimated the unknown epidemiological parameters of this disease in Shaanxi via least-squares fitting method. The estimated control reproductive number of H1N1 for its first peak was Rc1 = 2.555 (95% CI: 2.362 2.748) and that for the second peak was Rc2 = 1.886 (95% CI: 1.765-2.001). Our findings in this paper suggest that neither quarantine nor isolation measures could be relaxed, and the implementation of these interventions can reduce the pandemic outbreak of A/H1N1 pandemic significantly. 展开更多
关键词 A/HIN1 influenza QUARANTINE ISOLATION least-squares fitting.
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