Nonparametric tests for right-censored data with biased sampling

Testing the equality of two survival distributions can be difficult in a prevalent cohort study when non random sampling of subjects is involved. Due to the biased sampling scheme, independent censoring assumption is often violated. Although the issues about biased inference caused by length-biased sampling have been widely recognized in statistical, epidemiological and economical literature, there is no satisfactory solution for efficient two-sample testing. We propose an asymptotic most efficient nonparametric test by properly adjusting for length-biased sampling. The test statistic is derived from a full likelihood function, and can be generalized from the two-sample test to a k-sample test. The asymptotic properties of the test statistic under the null hypothesis are derived using its asymptotic independent and identically distributed representation. We conduct extensive Monte Carlo simulations to evaluate the performance of the proposed test statistics and compare them with the conditional test and the standard logrank test for different biased sampling schemes and right-censoring mechanisms. For length-biased data, empirical studies demonstrated that the proposed test is substantially more powerful than the existing methods. For general left-truncated data, the proposed test is robust, still maintains accurate control of type I error rate, and is also more powerful than the existing methods, if the truncation patterns and right-censoring patterns are the same between the groups. We illustrate the methods using two real data examples.     

On the Sustainable Development of the Design of Semiotics and Ecological Aesthetics

Semiotics is the meta-science of researching the general theories of symbols.Design is the result of the production practice of the human society,and what are designed is to meet the first demand of the human society and is the most important cultural creation;i.e.,the material cultural creation.All the cultural phenom ena are symbol phenomena,so the design phenomenon is also a kind of symbol phenomenon.The ecological aesthetics is a new aesthetic form,studying ecology itself,and it develops from the ecological aesthetic standard.This paper attempts to illustrate the relation of the two fields and find out how to realize sustainable development with the lead of the social values and the mainstream culture.     

Analysis of the Modes of Characteristics of Chinese National Culture

A.L. Kroeber, the anthropologist, regards those stable relationships and structures in the culture as a kind of mode, while the other one, Ruth Benedict considers cultural patternas way of group behavior relative to individual behavior. As a type of cultural gestalt and mode,     

一类食饵具有群体防御能力捕食系统的稳定性与定性分析

本文研究了一类具有较强群体防御能力捕食系统[dx/dt=x(a-x)-yx^2e^-kx dy/dt=-dy=cyx^2e^-kx的稳定性并进行定性分析，得到若干新结果。     

略述内蒙古北部边疆部分地区的“石头墓”和“石板墓”

1975年6月至3月间,原内蒙古文物工作队组织部分同志对内蒙古大青山以北,乌兰察布盟四子王旗的红格尔(大庙)地区和锡林郭勒盟的东苏尼特旗,阿巴嘎纳尔旗以及西乌珠穆沁旗等地,进行了一次广泛的古文化遗迹调查。为了进一步了解探索在调查中发现的“石头墓”和“石板墓”的文化内涵,对红格尔地区的宫胡洞、潮鲁温克钦、乌兰胡洞三处古墓群和石头圈、石头堆有重点的进行了试掘工作,对在东苏尼特旗海留吐沟附近发现的石头圈也进行了部分清理,现根据这次调查试掘,提出一些粗浅看法,以期起到抛砖引玉的作用。