重载铁路圆柱形桥墩横向振动试验研究

随着我国既有铁路扩能运输的实施,运营列车的轴重以及载运量逐步增加给圆柱形桥墩带来了越来越严重影响,如墩顶横向振幅过大、冲击振动加剧等,严重影响了铁路桥梁的安全运营。以朔黄铁路圆柱形桥墩为研究对象,理论结合试验分析其加固前后在列车荷载增大的情况下桥墩的横向动力特性,研究不同运营列车作用下桥墩横向振动的规律,评价分析该圆柱形桥墩加固效果,为重载铁路圆柱形桥墩的加固研究和维护管理提供科学依据。     

我国学士学位制度发展三十年述评

经过三十年的发展,我国已经形成了比较完整的学士学位授予体系与国家、省级和学位授予单位三级学位管理体制;学士学位制度基本满足了高等教育办学类型多样化的需求,社会对毕业生学位的重视程度也不断提升,学士学位授予工作的国际合作也日益加强。今后学士学位授予工作还应当适当调整学士学位授予标准;进一步明确学士学位授予程序;优化学士学位授予体制;完善学士学位制度的监管体系。     

直齿圆锥齿轮弧齿厚的计算

本文介绍利用球面渐开线方程计算圆锥齿轮背锥齿形弧齿厚的方法,并通过实例指出利用当量圆柱齿轮计算弧齿厚的理论误差。     

A four-moment approach and other practical solutions to the behrens-f1sher problem

Fixed sample size approximately similar tests for the Behrens-Fisher problem are studied and compared with various other tests suggested in current sttistical methodelogy texts. Several fourmoment approxiamtely similar tests are developed and offered as alternatives. These tests are shown to be good practical solutions which are easily implemented in practice.     

从统计学史解析“自由度”概念

自由度是统计学中一个十分重要而又长期没有被圆满解释的概念。对此,从统计学史角度,对皮尔逊、费歇尔有关自由度问题争论原始文献细致考察,彻底澄清了自由度概念的内涵及与其相关的统计思想,弥补了Fienberg、Stigler与陈希孺已有解释的缺陷。研究表明：皮尔逊关于卡方检验中无论总体分布已知还是其来自于样本推断统计量都具有同一分布的错误判断,导致卡方检验的准确性出现偏差,这种偏差虽被同时代少数几个统计学家察觉但他们却无法解释其根源。费歇尔提出自由度概念并结合n维几何、假设检验与最大似然方法的论证不仅修正了皮尔逊的错误,也完善了从样本统计量估计总体参数的数理逻辑。     

Statistical Inference Enables Bad Science; Statistical Thinking Enables Good Science

ABSTRACT

Scientific research of all kinds should be guided by statistical thinking: in the design and conduct of the study, in the disciplined exploration and enlightened display of the data, and to avoid statistical pitfalls in the interpretation of the results. However, formal, probability-based statistical inference should play no role in most scientific research, which is inherently exploratory, requiring flexible methods of analysis that inherently risk overfitting. The nature of exploratory work is that data are used to help guide model choice, and under these circumstances, uncertainty cannot be precisely quantified, because of the inevitable model selection bias that results. To be valid, statistical inference should be restricted to situations where the study design and analysis plan are specified prior to data collection. Exploratory data analysis provides the flexibility needed for most other situations, including statistical methods that are regularized, robust, or nonparametric. Of course, no individual statistical analysis should be considered sufficient to establish scientific validity: research requires many sets of data along many lines of evidence, with a watchfulness for systematic error. Replicating and predicting findings in new data and new settings is a stronger way of validating claims than blessing results from an isolated study with statistical inferences.     

Adaptive order selection for autoregressive models

Autoregressive model is a popular method for analysing the time dependent data, where selection of order parameter is imperative. Two commonly used selection criteria are the Akaike information criterion (AIC) and the Bayesian information criterion (BIC), which are known to suffer the potential problems regarding overfit and underfit, respectively. To our knowledge, there does not exist a criterion in the literature that can satisfactorily perform under various situations. Therefore, in this paper, we focus on forecasting the future values of an observed time series and propose an adaptive idea to combine the advantages of AIC and BIC but to mitigate their weaknesses based on the concept of generalized degrees of freedom. Instead of applying a fixed criterion to select the order parameter, we propose an approximately unbiased estimator of mean squared prediction errors based on a data perturbation technique for fairly comparing between AIC and BIC. Then use the selected criterion to determine the final order parameter. Some numerical experiments are performed to show the superiority of the proposed method and a real data set of the retail price index of China from 1952 to 2008 is also applied for illustration.     

论理工科全日制专业学位研究生培养质量的提升

中国专业学位研究生教育起步较晚,人们对此类研究生培养定位的认识不够明确,为此,构建合理的专业学位研究生培养方案对提升全日制专业学位研究生培养质量有重要意义。要进一步提高理工科专业学位研究生培养质量可从以下几方面着手:调整课程设置,优化教师队伍,加强实训基地建设,建立专业学位培养评价体系等,为培养更多应用型、复合型、高层次专门人才打下基础。     

复合型人才培养新途径的探索

介绍了西安交通大学主、辅修双学位人才培养的实践 ,分析了主、辅修制对复合型人才培养所起到的积极作用。提出高等学校要贯彻教育方针 ,深化高等教育改革 ,逐步构建富有时代特征的多样化的人才培养模式 ,培养基础扎实、知识面宽、能力强、素质高的复合型人才