A nonparametric hypothesis test for heteroscedasticity

In this paper, a hypothesis test for heteroscedasticity is proposed in a nonparametric regression model. The test statistic, which uses the residuals from a nonparametric fit of the mean function, is based on an adaptation of the well-known Levene's test. Using the recent theory for analysis of variance when the number of factor levels goes to infinity, the asymptotic distribution of the test statistic is established under the null hypothesis of homocedasticity and under local alternatives. Simulations suggest that the proposed test performs well in several situations, especially when the variance is a nonlinear function of the predictor.     

胡适与民国时期安徽大学的初创

作为一位皖籍著名学者,胡适并不仅仅关注中国和世界,他同样十分关注家乡安徽的教育文化事业.1921年8月,胡适首先发出筹建安徽大学的呼吁.之后,他对推动安徽大学的筹建起了重要和积极的作用.1928年4月安徽大学成立后,他曾是安徽大学首位校长的主要人选,并且与安徽大学最初几位校长关系密切,对他们有重要影响.     

浅谈如何做好燃气安全监管工作

随着市场经济的不断推进,行业垄断的格局被逐渐打破,多元化的经济成分融人,给燃气市场的发展带来了新的活力,同时也促进了社会各行业的经济发展,使人们的生产、生活质量得到很大提高.     

论马克思主义文明和谐观的理论方法

研究马克思主义的文明和谐观,有必要去伪存真,还理论以本来面目,坚持马克思主义对历史的本质的考察所做的双向维度,从源头上把握马克思主义文明理论的最高和谐境界,从而建构起科学的文明和谐观念。马克思主义唯物史观站在以科学实践观为核心的辩证唯物主义,或实践唯物主义的哲学高度上,才真正实现跨越传统决定论和非决定论的藩篱,并将两者辩证地统一起来,为其文明和谐观奠定了深厚的基础。唯物史观在考察文明演进的过程中,综合了社会历史观和主体价值观的双向视角,从而科学论证了人类文明的和谐走向不仅是纯粹的道德理想,还是历史现实自身的运动。唯物史观以文明的和谐程度为文明进步的重要标志,并且首先表现为生产力与人的双重评价尺度的和谐统一。     

Subsampling-extrapolation bandwidth selection in bivariate kernel density estimation

This paper focuses on bivariate kernel density estimation that bridges the gap between univariate and multivariate applications. We propose a subsampling-extrapolation bandwidth matrix selector that improves the reliability of the conventional cross-validation method. The proposed procedure combines a U-statistic expression of the mean integrated squared error and asymptotic theory, and can be used in both cases of diagonal bandwidth matrix and unconstrained bandwidth matrix. In the subsampling stage, one takes advantage of the reduced variability of estimating the bandwidth matrix at a smaller subsample size m (m < n); in the extrapolation stage, a simple linear extrapolation is used to remove the incurred bias. Simulation studies reveal that the proposed method reduces the variability of the cross-validation method by about 50% and achieves an expected integrated squared error that is up to 30% smaller than that of the benchmark cross-validation. It shows comparable or improved performance compared to other competitors across six distributions in terms of the expected integrated squared error. We prove that the components of the selected bivariate bandwidth matrix have an asymptotic multivariate normal distribution, and also present the relative rate of convergence of the proposed bandwidth selector.     

Graphical representation of survival curves in the presence of time-dependent categorical covariates with application to liver transplantation

Graphical representation of survival curves is often used to illustrate associations between exposures and time-to-event outcomes. However, when exposures are time-dependent, calculation of survival probabilities is not straightforward. Our aim was to develop a method to estimate time-dependent survival probabilities and represent them graphically. Cox models with time-dependent indicators to represent state changes were fitted, and survival probabilities were plotted using pre-specified times of state changes. Time-varying hazard ratios for the state change were also explored. The method was applied to data from the Adult-to-Adult Living Donor Liver Transplantation Cohort Study (A2ALL). Survival curves showing a ‘split’ at a pre-specified time t allow for the qualitative comparison of survival probabilities between patients with similar baseline covariates who do and do not experience a state change at time t. Time since state change interactions can be visually represented to reflect changing hazard ratios over time. A2ALL study results showed differences in survival probabilities among those who did not receive a transplant, received a living donor transplant, and received a deceased donor transplant. These graphical representations of survival curves with time-dependent indicators improve upon previous methods and allow for clinically meaningful interpretation.     

Prediction of future failures times based on Type-I hybrid censored samples of random sample sizes

In this article, we consider the prediction of future failure times based on Type-I hybrid censored samples. Point predictors and prediction intervals using different procedures are discussed for a general model. The exponential and Rayleigh distributions are used as illustrative examples to show the most simplified forms of the so obtained predictors as well as prediction intervals. Intensive simulation study and a real life dataset are presented to illustrate our findings and results.     

Moving targets: determinants of nutritional preferences and habitat use in an urban ant community

Urban environments are often associated with reduced biodiversity, presumably because they are typically more fragmented, warmer, and drier than nearby non-urban environments. However, urban landscapes offer significant complexity that have allowed some taxonomic groups to flourish. Understanding how urban-exploiting animals navigate this spatiotemporal heterogeneity is important given the continued global urban land expansion. Here, we examined the factors influencing resource-use in an urban community of ants, which represent a widespread and important taxon in urban ecosystems. In particular, we sought to integrate ants’ nutritional, thermal, and spatial niches to better understand how urban animals successfully access critical resources throughout their active season. Meteorological season (spring, summer, and fall) and/or species (n?=?9) influenced ants’ preferences for nutrition (ratio of ingested protein-to-carbohydrate ratio), as well as the temperature, type (impervious vs. non-impervious), and shade status (shaded vs. non-shaded) of surfaces used during activity. Our data also indicate links among habitat variables, as well as between nutritional preferences and habitat use. Together, our results suggest that species and seasonality influence ecological (combined nutritional, thermal, and spatial) niches in an urban community. We encourage future work in urban ecosystems that continues to integrate more features of the ecological niche, and to examine the outcomes of variation in niches (e.g., non-overlapping niches may explain both the persistence of some native animals and the success of invaders).     

对欧洲人道主义精神核心价值理念的反思

人道主义思想是欧洲文艺复兴以来主流文化价值体系的反映,19世纪的一批现实主义作家对人道主义思想作了艺术的诠释,人道主义精神的核心价值理念主要体现在对革命和暴力的审视与批判上,由此形成了一套独特的文学话语体系,而对人道与革命之间非此即彼关系的僵化认识恰恰成为我们质疑、批判人道主义思想的一个基本出发点。在反思人道主义核心价值理念时,首先应该还原历史语境和文学语境,并在对人道和革命的关系进行新的定位的同时,对人道主义精神的历史合理性作出充分肯定。     

高校图书馆与新时期信息素质教育

信息是当今社会最重要的资源之一,人们对信息的需求正呈现出多层次、多样化的形式。在新的信息环境下,高校图书馆应与时俱进地积极转变观念,拓展教学内容,规范相关要求,在信息素质教育中作出突出的贡献。