Local influence in ridge semiparametric models

ABSTRACT

Ridge penalized least-squares estimators has been suggested as an alternative to the minimum penalized sum of squares estimates in the presence of collinearity among the explanatory variables in semiparametric regression models (SPRMs). This paper studies the local influence of minor perturbations on the ridge estimates in the SPRM. The diagnostics under the perturbation of ridge penalized sum of squares, response variable, explanatory variables and ridge parameter are considered. Some local influence diagnostics are given. A Monte Carlo simulation study and a real example are used to illustrate the proposed perturbations.     

考虑徐变影响的双面组合连续箱梁应力分析

研究钢 混凝土双面组合连续箱梁的徐变问题。根据混凝土徐变后的双面组合连续箱梁的截面应力自相平衡,内力仍为零这一条件,通过平衡方程得到负弯矩区截面的曲率,进而得到截面的应力计算公式;通过算例分析双面组合连续箱梁的应力重分布情况。     

Polynomial Spline Estimation for a Generalized Additive Coefficient Model

Abstract.  We study a semiparametric generalized additive coefficient model (GACM), in which linear predictors in the conventional generalized linear models are generalized to unknown functions depending on certain covariates, and approximate the non-parametric functions by using polynomial spline. The asymptotic expansion with optimal rates of convergence for the estimators of the non-parametric part is established. Semiparametric generalized likelihood ratio test is also proposed to check if a non-parametric coefficient can be simplified as a parametric one. A conditional bootstrap version is suggested to approximate the distribution of the test under the null hypothesis. Extensive Monte Carlo simulation studies are conducted to examine the finite sample performance of the proposed methods. We further apply the proposed model and methods to a data set from a human visceral Leishmaniasis study conducted in Brazil from 1994 to 1997. Numerical results outperform the traditional generalized linear model and the proposed GACM is preferable.     

On Variance Components in Semiparametric Mixed Models for Longitudinal Data

Abstract. First, to test the existence of random effects in semiparametric mixed models (SMMs) under only moment conditions on random effects and errors, we propose a very simple and easily implemented non‐parametric test based on a difference between two estimators of the error variance. One test is consistent only under the null and the other can be so under both the null and alternatives. Instead of erroneously solving the non‐standard two‐sided testing problem, as in most papers in the literature, we solve it correctly and prove that the asymptotic distribution of our test statistic is standard normal. This avoids Monte Carlo approximations to obtain p ‐values, as is needed for many existing methods, and the test can detect local alternatives approaching the null at rates up to root n. Second, as the higher moments of the error are necessarily estimated because the standardizing constant involves these quantities, we propose a general method to conveniently estimate any moments of the error. Finally, a simulation study and a real data analysis are conducted to investigate the properties of our procedures.     

基于三点分段的一类三角样条曲线的扩展

基于文献[5]中三点分段的一次和二次三角基函数的扩展,首先给出了带参数的二次和三次三角调配函数,当λi=0时,二次和三次三角基函数分别退化为文献[5]中的一次和二次三角基函数,然后建立了一种带局部调节参数λi的分段三角样条曲线。通过调整参数λi,能够使得当参数λi越大时,分段三角样条曲线越逼近控制多边形。对于曲线的连续性也做了相关的讨论,二次最高可达G2连续,三次最高可达G4连续。最后给出了两个数值例子,分别利用文中给出的二次和三次调配函数构造了达到G1连续和G3连续的两条曲线。     

Acting your age? Sports science and the ageing body

The medicalisation of aging and old age constructs ageing as first and foremost a biomedical event and as a process of inevitable decline. In sports science and sports medicine the functional decrements normally associated with ageing are being addressed. There is evidence reported in the scientific literature suggesting that certain exercise interventions can ‘reduc[e] or prevent[…] functional declines linked to secondary aging’ [Goggin, N.L., and Morrow, J.R. Jr. (2001). "Physical Activity Behaviors of Older Adults." Journal of Aging and Physical Activity 9, 58–66.].However a sociological critique is necessary. Whilst sports science seeks to position itself as a key player in the fight against ageing, it also opens the potential for the reconstruction of the ageing body as fit. However the evidence that exercise can fundamentally reshape older bodies is equivocal. A new frame is proposed which divorces exercise from anti-ageing purposes and uses the science of exercise to enable older people to recover a sense of physical competence as a creative pursuit in its own right.     

语用预设在新闻发言人应答话语中的功能探析——以外交部新闻发布会话语为例

针对高速铁路32 m双线箱梁养护过程中传统温度监控系统的传感器布线繁琐、 线缆影响其他设备操作等问题,提出了基于ZigBee的混凝土箱梁温度监测系统方案。该系统以主从式模式工作, 采用ZigBee无线网络技术,实现了对箱梁温度的无线测量。系统结构简单,施工便利, 安全可靠,电池使用寿命长,保证了箱梁养护过程的质量。     

四十里峪大桥无落地支架现浇箱梁施工技术

结合张石高速公路四十里峪大桥无落地支架现浇箱梁施工,利用墩柱抱箍和施工完的盖梁作为支点拼装贝雷梁作为支架进行现浇箱梁施工,取得了成功。重点介绍了现浇箱梁施工过程中的关键技术和控制要点,为同类施工提供参考。     

Estimation of smooth regression functions in monotone response models

We consider the estimation of smooth regression functions in a class of conditionally parametric co-variate-response models. Independent and identically distributed observations are available from the distribution of (Z,X)$(Z,X)$, where Z is a real-valued co-variate with some unknown distribution, and the response X conditional on Z   is distributed according to the density p(·,ψ(Z))$p(·,\psi (Z))$, where p(·,θ)$p(·,\theta )$ is a one-parameter exponential family. The function ψ$\psi$ is a smooth monotone function. Under this formulation, the regression function E(X|Z)$E(X|Z)$ is monotone in the co-variate Z   (and can be expressed as a one–one function of ψ$\psi$); hence the term “monotone response model”. Using a penalized least squares approach that incorporates both monotonicity and smoothness, we develop a scheme for producing smooth monotone estimates of the regression function and also the function ψ$\psi$ across this entire class of models. Point-wise asymptotic normality of this estimator is established, with the rate of convergence depending on the smoothing parameter. This enables construction of Wald-type (point-wise) as well as pivotal confidence sets for ψ$\psi$ and also the regression function. The methodology is extended to the general heteroscedastic model, and its asymptotic properties are discussed.     

斜交变截面连续箱梁桥的有限单元法

从薄壁箱梁单元出发,采用带刚臂的偏心结点,导出一种能考虑斜桥弯扭特性结点偏心的薄壁箱梁单元刚度矩阵．通过一有机玻璃三跨双室斜支承模型试验分析,并与粱格分析方法结果对比,表明该方法是有效的．