On the Estimation of Nonlinear Mixed-Effects Models and Latent Curve Models for Longitudinal Data

Nonlinear models are effective tools for the analysis of longitudinal data. These models provide a flexible means for describing data that follow complex forms of change. Exponential and logistic functions that include a parameter to represent an asymptote, for instance, are useful for describing responses that tend to level off with time. There are forms of nonlinear latent curve models and nonlinear mixed-effects model that are equivalent, and so given the same set of data, growth function, distributional assumptions, and method of estimation, the 2 models yield equivalent results. There are also forms that are strikingly different and can yield different interpretations for a given set of data. This article discusses cases in which nonlinear mixed-effects models and nonlinear latent curve models are equivalent and those in which they are different and clarifies the estimation needs of the different models. Examples based on empirical data help to illustrate these points.     

The Impact of Sample Size and Other Factors When Estimating Multilevel Logistic Models

The design of research studies utilizing binary multilevel models must necessarily incorporate knowledge of multiple factors, including estimation method, variance component size, or number of predictors, in addition to sample sizes. This Monte Carlo study examined the performance of random effect binary outcome multilevel models under varying methods of estimation, level-1 and level-2 sample size, outcome prevalence, variance component sizes, and number of predictors using SAS software. Mean estimates of statistical power were influenced primarily by sample sizes at both levels. In addition, confidence interval coverage and width and the likelihood of nonpositive definite random effect covariance matrices were impacted by variance component size and estimation method. The interactions of these and other factors with various model performance outcomes are explored.     

The Misspecification of the Covariance Structures in Multilevel Models for Single-Case Data: A Monte Carlo Simulation Study

The impact of misspecifying covariance matrices at the second and third levels of the three-level model is evaluated. Results indicate that ignoring existing covariance has no effect on the treatment effect estimate. In addition, the between-case variance estimates are unbiased when covariance is either modeled or ignored. If the research interest lies in the between-study variance estimate, including at least 30 studies is warranted. Modeling covariance does not result in less biased between-study variance estimates as the between-study covariance estimate is biased. When the research interest lies in the between-case covariance, the model including covariance results in unbiased between-case variance estimates. The three-level model appears to be less appropriate for estimating between-study variance if fewer than 30 studies are included.     

非线性相位FIR滤波器设计方案研究

介绍了一种非线性相位滤波器的设计方法,它建立在线性相位滤波器设计方法的基础上,用这种方法可以设计性能优越的特定相位的滤波器。     

一类固定设计方差函数模型的小波估计

考虑非参数方差模型Yi=σ(xi)εi,i=1,2,…,n,其中xi是固定设计点列,{εi}是严平稳α-混合序列.该文利用小波方法构造了方差函数σ2(x)的估计量,在设定的假设条件下,讨论了其小波估计的有偏性、方差和相合性.     

Strategies for Efficient Experimental Design in Studies Probing 2-1-1 Mediation

Abstract

When well-implemented, mediation analyses play a critical role in probing theories of action because their results help lay the ground work for the critical development of a treatment and the iterative advancement of theories that are foundational to a discipline. Despite strong interest in designs that incorporate mediation, few studies have developed effective and efficient strategies to plan experiments examining multilevel mediation. We probe several design strategies for cluster-randomized designs and derive sampling plans that maximize power under cost constraints. The results suggest that among the more durable design strategies for mediation is covariance adjustment on variables predictive of the outcome and optimal sample allocation. The statistical power and optimal sample allocation results are implemented in the R package PowerUpR.     

一类非线性时滞积分不等式中未知函数的估计

通过对一类具有弱奇异核的非线性时滞积分不等式进行讨论,给出了这一类不等式中未知函数的估计,并且利用构造辅助函数的方法,运用换元、放大、求导、积分等分析技巧证明了主要的结果.     

面向成本的设计中成本估算方法的研究

设计阶段决定了产品成本的60%-70%。日益加剧的市场竞争促使人们愈来愈重视对设计阶段的产品成本估算方法的研究。本文论述了近几十年来国内外在这一领域的发展概况及趋势,从并行设计的角度提出面向成本的设计(design for cost, DFC)的思想,在分析DFC中全生命周期成本的构成及其估算方法的基础上,建立基于CAD/CAPP模型的成本估算框架体系,在产品设计阶段不但考虑产品的技术性能,还考虑产品的经济性能,实现参数化成本估算,从而实现了考虑成本的优化设计,使得设计出的产品更加适应市场的需求,有助于提高企业在市场上的竞争力。     

随机右截断下半线性模型中估计的相合性

考虑一个随机右截断下的线性模型，在王启华＾「１」研究的参数β的核型估计β＾ｎ一致性的基础上，继续并且改进了王启华＾「１」的有关工作。     

随机变系数线性结构关系EV模型参数估计的强相合性

证明了随机变系数线性结构关系EV模型中参数估计的强相合性.     

分组数据下指数分布参数的Bayes估计

当数据为分组型时，本文给出了当寿命分布为指数分布时参数的Bayes估计及平均寿命的Bayes置信下限，并对三种估计下限进行了模拟比较。     

高职物流实验室建设方案的设计

随着现代物流业的迅速发展和高职院校物流专业的不断扩展,如何培养适应市场需求的高技能物流人才,如何建设与高职院校物流专业人才培养目标相一致的物流实验室,已成为国内许多高职院校的热门话题。文章在对物流实验室的现状进行剖析的基础上,提出了物流实验室建设的思路,设计了高职物流实验室的建设方案。     

A Comparison of Diagonal Weighted Least Squares Robust Estimation Techniques for Ordinal Data

This study compared diagonal weighted least squares robust estimation techniques available in 2 popular statistical programs: diagonal weighted least squares (DWLS; LISREL version 8.80) and weighted least squares–mean (WLSM) and weighted least squares—mean and variance adjusted (WLSMV; Mplus version 6.11). A 20-item confirmatory factor analysis was estimated using item-level ordered categorical data. Three different nonnormality conditions were applied to 2- to 7-category data with sample sizes of 200, 400, and 800. Convergence problems were seen with nonnormal data when DWLS was used with few categories. Both DWLS and WLSMV produced accurate parameter estimates; however, bias in standard errors of parameter estimates was extreme for select conditions when nonnormal data were present. The robust estimators generally reported acceptable model–data fit, unless few categories were used with nonnormal data at smaller sample sizes; WLSMV yielded better fit than WLSM for most indices.     

一类非线性动力系统的设计与电路实现

提出了一类非线性动力系统——分数阶多翅膀混沌系统的理论设计和电路实现方法。基于一个分数阶线性系统,通过设计一个非线性状态反馈控制器,能产生不同分数阶的多翅膀混沌吸引子。以分数阶6-,8-,10-翅膀混沌系统的产生为例,进行了改进型模块化电路设计,并给出了实验结果,证实了所设计方法的有效性和可行性。     

Comparison of Inverse Wishart and Separation-Strategy Priors for Bayesian Estimation of Covariance Parameter Matrix in Growth Curve Analysis

Growth curve modeling provides a general framework for analyzing longitudinal data from social, behavioral, and educational sciences. Bayesian methods have been used to estimate growth curve models, in which priors need to be specified for unknown parameters. For the covariance parameter matrix, the inverse Wishart prior is most commonly used due to its proper and conjugate properties. However, many researchers have pointed out that the inverse Wishart prior might not work as expected. The purpose of this study is to investigate the influence of the inverse Wishart prior and compare it with a class of separation-strategy priors on the parameter estimates of growth curve models. In this article, we illustrate the use of different types of priors with 2 real data analyses, and then conduct simulation studies to evaluate and compare these priors in estimating both linear and nonlinear growth curve models. For the linear model, the simulation study shows that both the inverse Wishart and the separation-strategy priors work well for the fixed effects parameters. For the Level 1 residual variance estimate, the separation-strategy prior performs better than the inverse Wishart prior. For the covariance matrix, the results are mixed. Overall, the inverse Wishart prior is suggested if the population correlation coefficient and at least 1 of the 2 marginal variances are large. Otherwise, the separation-strategy prior is preferred. For the nonlinear growth curve model, the separation-strategy priors work better than the inverse Wishart prior.     

管壳式换热器优化设计模型研究

以年总费用为目标函数,建立管壳式换热器优化设计的数学模型.分别推导建立单级无相变和有相变传热过程的设计模型;在单级模型基础上,结合简单序贯换热器的模拟计算方法,建立多级换热器系统的优化设计模型.这些模型联立非线性的变量关系,符合工程实际,适用面广.     

一类四阶微分方程第二广义谱的估计

考虑一类四阶微分方程第二广义谱的估计,利用方程谱理论、分部积分、Rayleigh定理和Cauchy-Schwarz不等式等估计方法,获得了用第一个谱来估计第二个谱的上界不等式,且其估计系数与所论区间的几何度量无关。     

大学生社交焦虑的团体认知行为干预方案设计

探讨了认知行为疗法对社交焦虑的干预,并根据美国心理学家Stefan G.Hofmann提出的社交焦虑的认知行为治疗模型,采用演讲暴露、心理教育、认知重建以及现实暴露等认知行为的干预技术,设计出符合我国大学生的社交焦虑的团体干预方案。该团体治疗方案共八次,以切实可行的不断增加难度的演讲暴露为主要暴露方式。实践证明,对于大学生社交焦虑的症状改善具有显著效果,易于推广。     

新型云计算数据中心网络结构设计

随着云计算和大数据应用的飞速发展,对传统的数据中心网络提出了新的挑战。本文设计一种新型的以服务器为中心的层次递归云计算数据中心网络结构GCube,该网络可以采用通用服务器和普通商用交换机进行构建,具有极高的性价比、优秀的性能和可扩展性。     

Design and Development of a Multimedia Educational Tool for Interactive Visualization and Three-Dimensional Perception of Vibrational Spectra Data of Molecules

In this paper the design and development of 3DNormalModes, an educational tool for interactive visualization and three dimensional perception of vibrational spectra data of molecules is presented. The details of the architecture of the tool and its functionality are described. Means of application in chemical education at university level are discussed. A pilot study summarizes the strengths, the educational value and the possible extensions of the system.