An Evaluation of Risk Estimation Procedures for Mixtures of Carcinogens

The estimation of health risks from exposure to a mixture of chemical carcinogens is generally based on the combination of information from several available single compound studies. The current practice of directly summing the upper bound risk estimates of individual carcinogenic components as an upper bound on the total risk of a mixture is known to be generally too conservative. Gaylor and Chen (1996, Risk Analysis) proposed a simple procedure to compute an upper bound on the total risk using only the upper confidence limits and central risk estimates of individual carcinogens. The Gaylor-Chen procedure was derived based on an underlying assumption of the normality for the distributions of individual risk estimates. In this paper we evaluated the Gaylor-Chen approach in terms of the coverage probability. The performance of the Gaylor-Chen approach in terms the coverages of the upper confidence limits on the true risks of individual carcinogens. In general, if the coverage probabilities for the individual carcinogens are all approximately equal to the nominal level, then the Gaylor-Chen approach should perform well. However, the Gaylor-Chen approach can be conservative or anti-conservative if some or all individual upper confidence limit estimates are conservative or anti-conservative.     

基于正交试验法研究乳化炸药螺杆泵螺杆加工三要素

针对主轴转速、进给速度、背吃刀量切削三要素不同值影响螺杆表面粗糙度规律,剖析传统的依靠人工经验选择三要素存在人为缺陷及遗传算法优化选择三要素需大而全的数据库难以实现的现状,探讨一种科学简单、易于实现的正交试验法应用于筛选三要素的优化组合,通过设计3因素3水平试验并对数据进行数理统计分析计算,得出三要素中背吃刀量对螺杆表面质量影响最显著,主轴转速对其影响非显著的结论,研究出的三要素最优值组合能确保螺杆加工表面质量、提高工效,对实际生产具有一定的指导意义。     

数控轴向柱塞变量泵开发及静特性实验研究

本文讨论数控轴向柱塞变量泵开发及静态调节特性。文中给出该泵的流量与调节参数之关系。通过实验分析，验证了关系式的正确性。发现影响变量调节速度的一些因素，提出了提高调节速度的一些措施。     

一种高效率低电压3倍负压电荷泵的设计

根据正压电荷泵的理论推导出负压电荷泵的基本单元,得出了低电压供电的2倍负压泵和为提高其效率而采取的一些优化方法。最后在2倍负压泵的基础上给出一个1.5V工作电压高性能3倍负压泵的设计实例。该3倍负压泵的设计经流片证明是成功的,并且已经应用于量产产品中。     

Fuzzy综合评判及其应用

借助于Fuzzy综合评判的基本理论 ,建立了单级与多级Fuzzy综合评判的算法模型 ,并给出实际例子说明该算法模型的有效性与实用性     

多级离心压缩机级间静止部件气动特性与旋涡结构的数值研究

通过CFD技术对某型多级离心压缩机内的流动进行了数值模拟,重点研究了多级离心压缩机级间装置如回流器、两类弯道内气动特点及其旋涡结构的特征,旨在揭示气流经弯道与回流器后气动参数的变化规律.结果表明,不同位置的弯道对流动的影响是截然不同的.由于这些静止部件对流体的扰动,使次级动叶的进口来流工况点偏离设计值,易于造成整机气动性能的下降.因此,多级压缩机的动叶设计应对来流的不均匀性加以充分考虑.     

Model Uncertainty and Risk Estimation for Experimental Studies of Quantal Responses

Experimental animal studies often serve as the basis for predicting risk of adverse responses in humans exposed to occupational hazards. A statistical model is applied to exposure-response data and this fitted model may be used to obtain estimates of the exposure associated with a specified level of adverse response. Unfortunately, a number of different statistical models are candidates for fitting the data and may result in wide ranging estimates of risk. Bayesian model averaging (BMA) offers a strategy for addressing uncertainty in the selection of statistical models when generating risk estimates. This strategy is illustrated with two examples: applying the multistage model to cancer responses and a second example where different quantal models are fit to kidney lesion data. BMA provides excess risk estimates or benchmark dose estimates that reflects model uncertainty.     

从弗莱的象征机制审视《红色手推车》

弗莱将全部文学作为象征系统来考察,强调的是文学作品的两个方面:"可以被孤立考察的结构单位"和"有所指称".前一方面视文学作品为独立自主的个体创造,后一方面则体现出使所有独立作品彼此联系在一起的约定俗成的传统.他还以象征分层次,其象征体系的五个阶段体现了从外向内、从离心机制向向心机制逐步演化的过程.解读文学作品时,引入此种象征机制,既符合文学艺术的规律性,又具有可操作性.本文运用弗莱的这种象征机制,将威廉·卡洛斯·威廉斯的<红色手推车>置于同时期、同地域的诗歌体系中,加以深入研究,以剥笋式的逐层深入、层层剖析的阐释,从文学作品的载体--语言入手,对<红色手推车>一诗形、义、音各个方面的独特艺术形式进行评析、论证,从而了解威廉斯是如何对文化传统进行继承、变革与创新的,并由此确认威廉斯对二十世纪美国诗歌改革的巨大贡献.     

中日传统家族中“向心力”与“离心力”差异形成的社会原因及其影响试析

同属东亚儒学文化圈的中国与日本 ,在不同的历史背景和地理环境中 ,其家族的内涵呈现出不同的发展趋势 ,对两国人民的思想观念和行为方式产生了截然不同的影响。这种迥然异趣的心理模式 ,又对中日两国社会产生了深远的影响     

离心泵性能实验教学改革初探

离心泵性能实验是化工原理实验教学的重要内容,结合离心泵性能实验的教学实践,就实验内容的选择,实验理论课的讲解、电化教学手段的采用、实验成绩的考核办法、实验指导方式的改革以及对实验教学过程中的流量Q的处理和数据处理的改进等方面进行了探索。