Body Mass Index, Perceived Health, and Happiness: Their Determinants and Structural Relationships

The structural relationships between body mass index, perceived health and happiness have been studied in a survey of 700 native Dutch citizens. We found an indirect effect of body mass index on happiness, via perceived health. Age had an inverted U-shaped relationship with body mass index, and both education and smoking had a negative effect on body mass index. Being married, doing paid work, owning a house, and doing sports had positive effects on perceived health, suggesting that living a regular life may lead to a better perceived health. Being married positively affected happiness. The other socio-demographic variables either had no effects on happiness or indirect effects via body mass index and perceived health.     

HETEROGENEITY AMONG SUSCEPTIBLES IN EPIDEMIC MODELS

When the infection rate associated with an epidemic appears to decline over time, one explanation is a constant level of infectiousness combined with heterogeneity among the susceptible population. In this paper we consider random effects models for such heterogeneity, particularly in discrete time. Maximum likelihood techniques are discussed as well as a more convenient approach based on martingale estimating equations. An application to data on a smallpox outbreak is considered.     

用一类辅助方程求五阶KdV方程的精确孤波解

本文给出了寻找适当的辅助方程的一种较一般化的方法,通过这种方法可以得到一系列的辅助方程,利用这些辅助方程又可以构造出非线性发展方程的许多精确孤波解.作为应用,本文给出了K dV方程守恒形式〔1〕,即五阶K dV方程的求解过程,并得到了此方程的六十八个孤波解.     

Variance Estimation in Spatial Regression Using a Non-parametric Semivariogram Based on Residuals

Abstract.  The empirical semivariogram of residuals from a regression model with stationary errors may be used to estimate the covariance structure of the underlying process. For prediction (kriging) the bias of the semivariogram estimate induced by using residuals instead of errors has only a minor effect because the bias is small for small lags. However, for estimating the variance of estimated regression coefficients and of predictions, the bias due to using residuals can be quite substantial. Thus we propose a method for reducing this bias. The adjusted empirical semivariogram is then isotonized and made conditionally negative-definite and used to estimate the variance of estimated regression coefficients in a general estimating equations setup. Simulation results for least squares and robust regression show that the proposed method works well in linear models with stationary correlated errors.     

基于一元三次方程求解的地心坐标至大地坐标的严密变换

基于一元三次方程的求解，给出了地心坐标向大地坐标转换的严密计算公式，并用算例说明了其正确性。本文提出的方法完全可以替代现有的以数值迭代计算为基础的转换方法。     

Characterization of certain incomplete block designs

It is shown that certain inequalities known for partially balanced incomplete block (PBIB) designs remain valid for general incomplete block designs. Some conditions for attaining their bounds are also given. Furthermore, the various types of PBIB designs are characterized by relating blocks of designs with association schemes. The approach here is based on the spectral expansion of NN' for the incidence matrix N of an incomplete block design.     

Optimal Weight Functions for Marginal Proportional Hazards Analysis of Clustered Failure Time Data

The choice of weights in estimating equations for multivariate survival data is considered. Specifically, we consider families of weight functions which are constant on fixed time intervals, including the special case of time-constant weights. For a fixed set of time intervals, the optimal weights are identified as the solution to a system of linear equations. The optimal weights are computed for several scenarios. It is found that for the scenarios examined, the gains in efficiency using the optimal weights are quite small relative to simpler approaches except under extreme dependence, and that a simple estimator of an exchangeable approximation to the weights also performs well.     

Externalizing Behavior Among Adopted Boys with Preadoptive Histories of Child Sexual Abuse

This study examined the severity of externalizing symptomology among adopted boys with preadoptive histories of child sexual abuse, physical abuse, neglect/abandonment, or no abuse. The study was based on data collected across a three-year period from parents who adopted children from Florida's child welfare system. The sample consisted of 1,136 adopted boys aged 6 to 18 years. In repeated cross-sectional multivariate analyses, the results revealed that adopted boys with preadoptive child sexual abuse were prone to significantly higher levels and clinically severe externalizing symptomotology as compared to adopted boys without such histories. The findings highlight the need for postadoption services and empirically validated interventions for families adopting boys with preadoptive child sexual abuse.     

（2＋1）维长短波方程整体吸引子的存在性

研究了无穷维动力系统中（2＋1）维长短波方程整体吸引子的存在性．运用Galekin方法构建了该系统的弱吸引子,并证明了所构建的弱吸引子是强吸引子．     

Robust Structural Equations for Designing and Monitoring Strategic International Facility Networks

Using predictive global sensitivity analysis, we develop a structural equations model to abstract from the details of a large‐scale mixed integer program (MIP) to capture essential design trade‐offs of global manufacturing and distribution networks. We provide a conceptual framework that describes a firm's network structure along three dimensions: market focus, plant focus, and network dispersion. Normalized dependent variables are specified that act as proxies for a company's placement into our conceptual network classification via the calculation of just a few key independent variables. We provide robust equation sets for eight cost structure clusters. Many different product types could be classified into one of these groups, which would allow managers to use the equations directly without needing to run the MIP for themselves. Our numerical tests suggest that the formulas representing the network structure drivers—economies of scale, complexity costs, transportation costs, and tariffs—may be sufficient for managers to design their strategic network structures, and perhaps more importantly, to monitor them over time to detect potential need for adjustment.