A Weighted Composite Dose – Response Model For Human Salmonellosis

This article describes the development of a weighted composite dose – response model for human salmonellosis. Data from previously reported human challenge studies were categorized into two different groups representing low and moderately virulent/pathogenic Salmonella strains based on a disease end point. Because epidemiological data indicate that some Salmonella strains are particularly pathogenic, and in the absence of human feeding study data for such strains, Shigella dysenteriae was used as a proxy for highly virulent strains. Three single-hit dose – response models were applied to the human feeding study data and evaluated for best fit using maximum likelihood estimation: (1) the exponential (E-1pop), (2) the two-subpopulation exponential (E-2pop), and (3) the Beta-Poisson (BP). Based on the goodness-of-fit test, the E-1pop and BP were the best-fit models for low and moderately virulent/pathogenic Salmonella strains, and the E-2pop and BP models were better for highly virulent/pathogenic strains. Epistemic analysis was conducted by determining the degree of confidence associated with the selected models, which was found to be 50%/50% (E-1pop/BP) for low and moderately pathogenic Salmonella strains, and 9.8%/90.2% (E-2pop/BP) for highly virulent strains. The degree of confidence for each component model and variations in the proportion of strains within each virulence/pathogenicity category were incorporated into the overall composite model. This study describes the influence of variation in strain virulence and host susceptibility on the shape of the population dose – response relationship.     

B-spline estimation for partially linear varying coefficient composite quantile regression models

Abstract

In this article, a new composite quantile regression estimation (CQR) approach is proposed for partially linear varying coefficient models (PLVCM) under composite quantile loss function with B-spline approximations. The major advantage of the proposed procedures over the existing ones is easy to implement using existing software, and it requires no specification of the error distributions. Under the regularity conditions, the consistency and asymptotic normality of the estimators are also derived. Finally, a simulation study and a real data application are undertaken to assess the finite sample performance of the proposed estimation procedure.     

Alternate test statistics for a functional errors-in-variables model

Some test statistics for the structural coefficients of simultaneous equations model often referred to as the multivariate linear functional relationship model are proposed in this article. The following cases are considered: the covariance matrix of errors is either unknown, known up to a proportionality factor, or completely known. The exact and approximate distributions of the proposed test statistics, as well as those of some that are known, are also given.     

Estimation of the number of studies with positive trends when studies with negative trends are present

A two-point estimator is proposed for the proportion of studies with positive trends among a collection of studies, some of which may demonstrate negative trends. The proposed estimator is the y-intercept of the secant line joining the points (a, F?(a)) and (b, F?(b)), where F?(p) is the empirical distribution function of p-values from one-tailed tests for positive trend derived from the individual studies. Although this estimator is negatively biased for any choice of the points 0 ≤ a < b ≤ 1, the bias is less than that of the previously proposed one-point estimator defined by setting b = 1. The bias of the two-point estimator is smallest when a and b approach the inflection point of the true distribution function, E [F?(p)]. The utility of the two-point estimator is demonstrated by using it to estimate the number of male-mouse liver carcinogens among carcinogenicity studies conducted by the National Toxicology Program.     

钢-混凝土双面组合梁极限承载力计算方法研究

提出用简化计算方法、截面全过程分析和结构有限元分析等三种方法对双面组合连续梁极限抗弯承载力进行分析研究；以某一试验梁为例，对三种不同方法计算得到的承载力进行了比较分析，总结了各种方法的适用性，对双面组合梁的设计和研究有一定参考价值。     

均布荷载作用下双面组合梁的滑移效应分析

利用基本力学方法对钢．混凝土双面组合梁在均布荷载作用下的滑移效应进行分析，推导得到了负弯矩区上、下交界面滑移沿梁长方向的表达式，并通过算例比较了双面组合梁与传统单面连续组合梁的滑移特点。计算表明，与传统单面连续组合梁相比，钢-混凝土双面组合连续梁不仅在负弯矩区提高了截面承载力，也使截面刚度得到了提高。     

京津冀生态环境建设：现状、问题与应对

以一座钢管混凝土连续梁拱组合单线铁路桥为工程背景,采用先整体后局部的两步分析法,首先利用Midas/Civil软件建立全桥有限元模型,计算拱肋安装及后续施工阶段结构的受力状态,得到局部模型的力边界条件;然后利用ANSYS软件建立拱脚结点局部有限元模型,分析施工期间拱脚结点的局部应力分布规律和应力集中程度;最后将拱脚结点应力计算值与实测值进行比较。结果表明,拱肋与梁体间传力顺畅,拱脚混凝土基本处于受压状态;拱脚内侧与箱梁顶板交界处应力集中现象较明显;拱脚上部拱肋周围、拱脚前脚趾处及两拱脚之间箱梁顶板的局部区域出现较大的拉应力,建议在同类桥梁的设计中加强这些部位的构造措施和配筋。拱脚结点应力计算值与实测值比较接近,说明用实体有限元模型计算的局部应力是可靠的,可用于设计验算。     

殷墟墓葬中青铜生产工具组合的初步研究

自1928年殷墟开始科学考古以来,殷墟墓葬中出土了大量的青铜工具,这些青铜工具种类丰富,数量较多,是当时中国能够制造的最先进的工具。本文重点考察殷墟墓葬中出土的青铜工具的种类、数量及组合方面所具有的特点,揭示殷墟青铜工具组合是以木工工具为主的组合,并着重论述青铜工具在殷墟墓葬器物组合中所具有的特殊意义。     

基于单纤维压出实验分析硼纤维/环氧树脂复合材料的界面剪切强度

界面剪切强度是复合材料设计的重要指标,如何通过试验方法测定复合材料的界面性能是复合材料研究的一个重要领域。本文以硼纤维/环氧树脂叠层板(0/90)复合材料为载体,利用S-3400扫描电镜(SEM)与Gatan公司的拉伸台Microtest 2000组合,且在电镜上安装了自行设计制作的单纤维压头,测定界面的剪切强度。得知:在室温负荷作用下硼纤维呈阶梯式脱粘,当压出硼纤维长度为总压出长度约一半时,界面剪切强度达到最大值,并估算出界面的剪切模量,为进一步有限元法模拟研究复合材料的界面的力学行为提供依据。