Wavelet-based deconvolution of ultrasonic signals in nondestructive evaluation

INTRODUCTION Deconvolution of ultrasonic signals is defined as the solution of the inverse problem of convolving an input signal, known as the system function h(n), with a medium reflectivity function x(n) and can be rep- resented by y(n)=h(n)*x(n) η(n), (1) where y(n) is the measured signal, * denotes the convolution operation and η(n) is the additive noise. Recovering x(n) from the observation y(n) leads to improving the appearance and the axial resolution of the RF-signals by removin…     

从专业素质教育谈推拿学课程考试改革

推拿学是运动医学领域内的一门操作性极强的实践性课程,也是国家教委指定的体育专业学生的一门必修课程。借鉴和参照竞技体育裁判规则和评价尺度,结合专业学科的实际情况,制定出具有较好科学性、客观性、标准性及可操作性的推拿手法操作技能的考核与评定方法。以推拿技能操作考核为主笔试为辅,客观、公正地评价考生的推拿技能,以考促教,加强学生专业素质和实际动手能力的培养。     

规范化:教育科学研究的学术观

目前 ,对教育学的学科地位问题仍然有不小的怀疑和争论 ,原因固然是多方面的 ,但很大程度上是与教育学的学术声誉不好、专业化程度不高密切相关的。即长久以来教育学没有形成自己健全的学术规范 ,研究的规范化程度与社会科学中其它学科相比有较大距离 ,如何构建教育学的学术规范 ,本文进行了有益的探讨。     

德语中外来词的演变与规范

现代德语含有大量的外来词,这是日耳曼文化与欧洲其他文化相碰撞的结果。从历史进程来看,对德语影响较大的语种依次为：古希腊语、拉丁语、法语和英语。外来词在丰富了德语表达方式的同时,也对德语语言的纯洁性构成了一定的威胁。为此,德国人不断对德语中的外来词加以规范。其规范的主要原则有：一、需要的原则;二、意义明确的原则;三、文字标准化原则。     

高校自科学报参考文献著录中存在的问题

列举了高校自科学报参考文献著录中存在的常见问题，分析了产生问题的原因，指出编者熟练掌握参考文献著录格式是解决问题的关键。     

A Regularized GLS for Structural Equation Modeling

Ill conditioning of covariance and weight matrices used in structural equation modeling (SEM) is a possible source of inadequate performance of SEM statistics in nonasymptotic samples. A maximum a posteriori (MAP) covariance matrix is proposed for weight matrix regularization in normal theory generalized least squares (GLS) estimation. Maximum likelihood (ML), GLS, and regularized GLS test statistics (RGLS and rGLS) are studied by simulation in a 15-variable, 3-factor model with 15 levels of sample size varying from 60 to 100,000. A key result showed that in terms of nominal rejection rates, RGLS outperformed ML at all sample sizes below 500, and GLS at most sample sizes below 500. In larger samples, their performance was equivalent. The second regularization methodology (rGLS) performed well asymptotically, but poorly in small samples. Regularization in SEM deserves further study.     

自适应阈值收缩算子的稀疏正则化图像重建算法

针对图像重建中采用稀疏正则化算法时,阈值收缩算子的阈值参数难以选取的问题,提出一种采用自适应阈值收缩算子的稀疏正则化算法。该算法收缩算子的阈值参数在迭代求解过程中根据解的稀疏度进行更新;同时在该算子中引入权重系数,研究阈值算子的衰减特性对图像重建质量的影响;并将该算法应用于电学层析成像的仿真和实验图像重建。结果表明：与传统的稀疏正则化算法相比,使用具有衰减特性的阈值收缩算子的稀疏正则化算法重建图像的性能指标有所提高。当被测物场的内含物分布较为简单时,采用较大的权重系数;当被测物场的内含物分布相对复杂时,使用较小的权重系数,有利于提高重建图像的质量。     

Exploratory Mediation Analysis via Regularization

Exploratory mediation analysis refers to a class of methods used to identify a set of potential mediators of a process of interest. Despite its exploratory nature, conventional approaches are rooted in confirmatory traditions, and as such have limitations in exploratory contexts. We propose a two-stage approach called exploratory mediation analysis via regularization (XMed) to better address these concerns. We demonstrate that this approach is able to correctly identify mediators more often than conventional approaches and that its estimates are unbiased. Finally, this approach is illustrated through an empirical example examining the relationship between college acceptance and enrollment.     

一类与时间有关的非线性椭圆抛物型方程解的存在性

本文讨论了在更为一般的L^p空间上,利用Yosida逼近和凸函数的标准正则化将问题两次离散化,进而求出变形后方程的解,最后对其解进行一致性估计和取极限,就证明了原问题的解,这种解更具有一般性。     

求解半正定病态积分方程的多尺度快速Lavrentiev迭代算法

基于多尺度投影方法,构造了求解半正定病态积分方程的截断快速Lavrentiev迭代算法,并给出了新的后验参数选择办法.与传统全投影方法相比,减少了内积计算个数,保持了最优收敛率.最后,算例验证了算法的有效性.