基于ANSYS的行李车改造成发电车的车架设计与分析

现代设计方法的发展和使用,使铁路车辆设计变得越来越快速高效。在行李车改造为发电车过程中,首先根据车架结构对车厢进行布局设计,其次运用有限元分析软件ANSYS对改造后的车辆车架系统从强度和刚度方面进行计算和分析。然后根据分析结果,使用APDL语言对车架薄弱环节和不合理结构进行改进。最后,对改造后车架进行模态分析和谐响应分析,确定有害频率和振型,并采取有效减振措施。从研究结果看,改造后的车辆车架能达到安全使用的设计目的。     

Improved randomized response in additive scrambling models

Randomized response models deal with stigmatizing variables appearing in health surveys. Additive and subtractive scrambling in split sample and double response yield unbiased mean and sensitivity estimators of high precision. The split sample method is protective of privacy. The double response method is as protective only conditionally. To achieve the maximum efficiency, the scrambling variables must be similar to each other and the probability of obtaining a true response must be as large as possible. The randomized response procedures yield more efficient estimates of the average total number of classes missed by university students.     

项目制研究的现状与新路径

项目制作为一种新的国家治理体制,在中国经济与社会发展中发挥着日益深广的影响力。文献考察发现,国内研究围绕五个主要议题展开,研究成果较集中于近六年内;国外研究也有一定基础。既有研究尚存在两方面突出问题：一是研究视角有缺失,偏重宏观层面和政府视角而忽视了基层村庄社会的回应;二是研究议题失均衡,对项目制负面效应发生机理和防范机制研究还很薄弱。“村庄回应”是项目制研究值得重视的一条新路径,以此路径切入,可探寻“项目进村”的实践逻辑与问题成因,是有利于找到优化基层治理格局、提升项目制实践成效并防范“项目进村”负面效应的有效方法。     

苏轼的"枯淡"论研究——兼论"东坡和陶诗"的文化史意义

苏轼对"平淡"风格的认识,主要体现在他对陶渊明诗歌"枯淡"美的批评上。"枯淡"风格的形成是一个"绚烂之极归于平淡"的过程,体现在陶渊明的诗歌中就是"质而实绮,癯而实腴"、"外枯而中膏,似淡而实美"的美学效果。从"枯淡"风格出发,苏轼发现了柳宗元、韦应物诗风与陶渊明"同源",并作出了"柳在韦上"的判断。苏轼还创作了大量的"和陶诗",这在中国古代文化史上具有重要的认识价值。     

我国出口信用保险与出口贸易动态关系研究--来自沿海经济圈省际面板数据的经验证据

利用沿海经济圈省际面板数据作为样本,使用面板向量自回归模型研究了出口信用保险与出口贸易的动态关系。研究发现：出口信用保险在短期内能促进出口贸易,长期内不具有持续效应;出口贸易提高出口信用保险需求水平的能力有限。两者呈现出非对等关系,出现这一现象的主要原因是保险费率垄断。     

Zero-inflated models for adjusting varying exposures: a cautionary note on the pitfalls of using offset

Zero-inflated count data are frequently encountered in public health and epidemiology research. Two-parts model is often used to model the excessive zeros, which are a mixture of two components: a point mass at zero and a count distribution, such as a Poisson distribution. When the rate of events per unit exposure is of interest, offset is commonly used to account for the varying extent of exposure, which is essentially a predictor whose regression coefficient is fixed at one. Such an assumption of exposure effect is, however, quite restrictive for many practical problems. Further, for zero-inflated models, offset is often only included in the count component of the model. However, the probability of excessive zero component could also be affected by the amount of ‘exposure’. We, therefore, proposed incorporating the varying exposure as a covariate rather than an offset term in both the probability of excessive zeros and conditional counts components of the zero-inflated model. A real example is used to illustrate the usage of the proposed methods, and simulation studies are conducted to assess the performance of the proposed methods for a broad variety of situations.     

过程写作法在英语专业低年级的运用

过程写作法近年来盛行海外，已经成为西方写作教学主流。它将写作视为交互循环的心理认知过程和语言交际过程，重视写作的具体过程及其交际性，被证明对于提高学习者写作能力效果显著。本文系统地研究了过程写作法产生的背景、理论基础及其在写作教学中的实际应用。     

QMRA for Drinking Water: 2. The Effect of Pathogen Clustering in Single‐Hit Dose‐Response Models

Spatial and/or temporal clustering of pathogens will invalidate the commonly used assumption of Poisson‐distributed pathogen counts (doses) in quantitative microbial risk assessment. In this work, the theoretically predicted effect of spatial clustering in conventional “single‐hit” dose‐response models is investigated by employing the stuttering Poisson distribution, a very general family of count distributions that naturally models pathogen clustering and contains the Poisson and negative binomial distributions as special cases. The analysis is facilitated by formulating the dose‐response models in terms of probability generating functions. It is shown formally that the theoretical single‐hit risk obtained with a stuttering Poisson distribution is lower than that obtained with a Poisson distribution, assuming identical mean doses. A similar result holds for mixed Poisson distributions. Numerical examples indicate that the theoretical single‐hit risk is fairly insensitive to moderate clustering, though the effect tends to be more pronounced for low mean doses. Furthermore, using Jensen's inequality, an upper bound on risk is derived that tends to better approximate the exact theoretical single‐hit risk for highly overdispersed dose distributions. The bound holds with any dose distribution (characterized by its mean and zero inflation index) and any conditional dose‐response model that is concave in the dose variable. Its application is exemplified with published data from Norovirus feeding trials, for which some of the administered doses were prepared from an inoculum of aggregated viruses. The potential implications of clustering for dose‐response assessment as well as practical risk characterization are discussed.     

Benchmark Dose Analysis via Nonparametric Regression Modeling

Estimation of benchmark doses (BMDs) in quantitative risk assessment traditionally is based upon parametric dose‐response modeling. It is a well‐known concern, however, that if the chosen parametric model is uncertain and/or misspecified, inaccurate and possibly unsafe low‐dose inferences can result. We describe a nonparametric approach for estimating BMDs with quantal‐response data based on an isotonic regression method, and also study use of corresponding, nonparametric, bootstrap‐based confidence limits for the BMD. We explore the confidence limits’ small‐sample properties via a simulation study, and illustrate the calculations with an example from cancer risk assessment. It is seen that this nonparametric approach can provide a useful alternative for BMD estimation when faced with the problem of parametric model uncertainty.     

Keeping Surveys Valid,Reliable, and Useful: A Tutorial

This tutorial focuses on how to produce reliable and generalizable data from random‐digit‐dialing (RDD) landline and cell phone surveys. The article notes that RDD response rates have declined and explores the impact of this pronounced decline. The tutorial addresses order, response mode, and many other biases, sample size, cooperation and response rates, weighting, and hybrid designs‐all using examples from risk analysis to illustrate the key points. The article ends with a brief review of the advantages and disadvantages of major Internet and paper surveys tools, and how these can be molded and sometimes combined in repeated, longitudinal, and other designs to answer questions about risk preferences and perceptions.