Building multivariable prognostic and diagnostic models: transformation of the predictors by using fractional polynomials

To be useful to clinicians, prognostic and diagnostic indices must be derived from accurate models developed by using appropriate data sets. We show that fractional polynomials, which extend ordinary polynomials by including non-positive and fractional powers, may be used as the basis of such models. We describe how to fit fractional polynomials in several continuous covariates simultaneously, and we propose ways of ensuring that the resulting models are parsimonious and consistent with basic medical knowledge. The methods are applied to two breast cancer data sets, one from a prognostic factors study in patients with positive lymph nodes and the other from a study to diagnose malignant or benign tumours by using colour Doppler blood flow mapping. We investigate the problems of biased parameter estimates in the final model and overfitting using cross-validation calibration to estimate shrinkage factors. We adopt bootstrap resampling to assess model stability. We compare our new approach with conventional modelling methods which apply stepwise variables selection to categorized covariates. We conclude that fractional polynomial methodology can be very successful in generating simple and appropriate models.     

高职新生数学学习状况研究与转化策略

通过对高等职业技术学校一年级新生数学学习状况的调查研究，看到高职一年级新生数学学习中存在的问题．并就解决这些问题提出了三个转化策略：积极归因训练；培养非智力因素，让学生以良好的学习习惯对待学习；转变学生对学习数学的认知。最后，谈到培养学生元认知的重要性．     

A Note on the Characterization of Positive Linnik Laws

Recently, Jayakumar & Pillai (1996) gave an interesting characterization of the positive Linnik laws in terms of the spectrum function of an infinitely divisible law. This paper improves their result and simplifies their proof. It proves another characterization result in terms of the Pareto law. Further, it represents the positive Linnik random variable as a function of independent gamma random variables.     

社会转型期高校师生关系

教育教学活动中师生关系至关重要。在社会转型期我们应该建构一种基于双方各自本份的具有伦理情感、独立精神、平等人格的＂本份观＂师生关系,以尽量减少转型期＂失范＂对于教育教学活动的影响。从而,努力走出一条以文化传承为旨归,求智育人,现代西方自由主义教育理念与中国传统教育理念相结合的具有民族特色的教育和谐之路。     

五代社会心理转型与诗风变化关系考论

五代政局动荡,人民苦难深重,由此形成了反常的社会心理。官僚及士人道统沦丧成为整个社会的风尚,知识分子普遍对政治表示了绝望,不再热心于实现救民立功、立德立名的抱负,社会风气向着缺少廉耻、不问世务、寄情声色发展。同政治局势动荡变化所导致的社会心理转型相一致,五代诗歌风格较之晚唐发生了转变,呈现出萧瑟衰萎、清冷感伤、绮艳靡丽、缺少怨刺等特征。     

转型期的行政权嬗变:中国行政改革之透析

转型期的行政权嬗变表现为传统的行政权某些特征依然存在,现代的行政权特征又大量出现,构成传统的行政权与现代的行政权整合与交融态势.它从一个层面透视了当代中国公共行政改革历程,同时也是对其改革向度的折射,为当代中国公共行政的发展及行为选择提供了思考.     

Identifying Nonlinear Relationships in Regression using the ACE Algorithm

This paper introduces an alternating conditional expectation (ACE) algorithm: a non-parametric approach for estimating the transformations that lead to the maximal multiple correlation of a response and a set of independent variables in regression and correlation analysis. These transformations can give the data analyst insight into the relationships between these variables so that this can be best described and non-linear relationships uncovered. Using the Bayesian information criterion (BIC), we show how to find the best closed-form approximations for the optimal ACE transformations. By means of ACE and BIC, the model fit can be considerably improved compared with the conventional linear model as demonstrated in the two simulated and two real datasets in this paper.     

Banach空间中Hammerstein型积分微分方程初值问题的一种拟上下解法

通过建立一个新的比较原理,利用L-拟上下解方法和混合单调迭代法,研究了Banach空间中一阶非线性积分微分方程初值问题解的存在唯一性,并给出了近似解的迭代序列和误差估计式.     

Generalized Self-Consistency: Multinomial logit model and Poisson likelihood

A generalized self-consistency approach to maximum likelihood estimation (MLE) and model building was developed in Tsodikov [2003. Semiparametric models: a generalized self-consistency approach. J. Roy. Statist. Soc. Ser. B Statist. Methodology 65(3), 759–774] and applied to a survival analysis problem. We extend the framework to obtain second-order results such as information matrix and properties of the variance. Multinomial model motivates the paper and is used throughout as an example. Computational challenges with the multinomial likelihood motivated Baker [1994. The Multinomial–Poisson transformation. The Statist. 43, 495–504] to develop the Multinomial–Poisson (MP) transformation for a large variety of regression models with multinomial likelihood kernel. Multinomial regression is transformed into a Poisson regression at the cost of augmenting model parameters and restricting the problem to discrete covariates. Imposing normalization restrictions by means of Lagrange multipliers [Lang, J., 1996. On the comparison of multinomial and Poisson log-linear models. J. Roy. Statist. Soc. Ser. B Statist. Methodology 58, 253–266] justifies the approach. Using the self-consistency framework we develop an alternative solution to multinomial model fitting that does not require augmenting parameters while allowing for a Poisson likelihood and arbitrary covariate structures. Normalization restrictions are imposed by averaging over artificial “missing data” (fake mixture). Lack of probabilistic interpretation at the “complete-data” level makes the use of the generalized self-consistency machinery essential.     

“双元结构”下的概念转换

由于中国成年人在学习外语时有"双元结构"的存在,因而造成了成年人在进行语义理解时对不同语言的不同原型不能理解和转换,这时就需要借助概念进行转换,而在概念转换时激活不同文化模式下认知域,从而达到匹配语义、理解语义的目的,当不能匹配时,就需文化的介入,进而完成概念转换.