频带有限信号的局部重构

本文讨论了从非均匀采样重建频带有限信号.选取不同的非均匀采样序列,利用有效算法进行重建,从得到的结果,分析采样的非均匀性对重建的影响.     

Morningness and state academic self-concept in students: Do early birds experience themselves as more competent in daily school life?

The purpose of the present study was to investigate the role of circadian preference for students’ state academic self-concept (ASC). We focused on students’ tendency to be morning-oriented (i.e., morningness) and examined the association between morningness as a trait and mean levels of state (momentary) general-school ASC in everyday school life using intensive longitudinal data collected among N = 285 (N_obs = 6,140; M_lessons = 21.54) German ninth and tenth graders. Furthermore, we tested whether the strength of this relation between morningness and state general-school ASC was modulated by the time of day (i.e., synchrony effect). Results of multilevel analyses showed that morningness was positively related to students’ mean levels of state general-school ASC. However, our results refuted a synchrony effect on state ASC, as higher morningness related to equally high mean levels of state general-school ASC both early and late in the school day with respect to a typical school schedule with lessons occurring in the morning to early afternoon. The present findings contribute to our understanding of ASC and provide relevant information about how morningness should be positioned with regard to ASC in everyday school life.     

Assessment of different genetic distances in constructing cotton core subset by genotypic values

One hundred and sixty-eight genotypes of cotton from the same growing region were used as a germplasm group to study the validity of different genetic distances in constructing cotton core subset.Mixed linear model approach was employed to unbiasedly predict genotypic values of 20 traits for eliminating the environmental effect.Six commonly used genetic distances (Euclidean,standardized Euclidean,Mahalanobis,city block,cosine and correlation distances) combining four commonly used hierarchical cluster methods (single distance,complete distance,unweighted pair-group average and Ward's methods) were used in the least distance stepwise sampling (LDSS) method for constructing different core subsets.The analyses of variance (ANOVA) of different evaluating parameters showed that the validities of cosine and correlation distances were inferior to those of Euclidean,standardized Euclidean,Mahalanobis and city block distances.Standardized Euclidean distance was slightly more effective than Euclidean,Mahalanobis and city block distances.The principal analysis validated standardized Euclidean distance in the course of constructing practical core subsets.The covariance matrix of accessions might be ill-conditioned when Mahalanobis distance was used to calculate genetic distance at low sampling percentages,which led to bias in small-sized core subset construction.The standardized Euclidean distance is recommended in core subset construction with LDSS method.     

中高级留学生识字量抽样测试报告

本报告对某大学部分中高级留学生识字量抽样测试的目的、内容、方法、结果及其对教学的启示。章认为，识字量是反映一个人汉语水平的重要参考数据，应该成为教材编写、班级划分、教材选择和课堂教学的重要依据之一。测试结果显示：中高级留学生综合识字量偏低；对汉字字音掌握较好，对字形掌握最差；对甲、乙两级汉字掌握不扎实；汉字化圈学生在识字量方面有明显优势，但高级阶段优势大幅度下降；华裔学生识字量远低于非华裔学生。作根据测试结果，对如何提高学生识字量提出了相应的建议。     

Qualitative sampling in research on international student mobility: insights from the field in Germany1

ABSTRACT

Although over the past decades the numbers of studies investigating international student mobility and migration (ISM) increased, methodological challenges in empirical research on the topic have remained mainly unaddressed. This is particularly the case for sampling, which is a crucial but often less considered part of qualitative research designs. In this article, we identify three main challenges in qualitative sampling for research into ISM: time, space and international students’ heterogeneities. In addressing those challenges, we theoretically discuss their implications and give empirical examples drawing on our research experiences. We argue for a more reflexive research procedure in studying educational mobility.     

浅谈现行统计调查存在的问题及建议

随着我国政治经济形势的发展,党和国家决策需要统计部门提供的数据越来越多。依靠以往已实行的普查、抽样调查等方法进行统计数据收集,已不能适应形势发展之需,因此,对统计调查中存在的问题必须进行分析,找出解决这些问题的办法。     

外语学习策略研究中存在的主要问题及其对策

探讨了当前国内外外语学习策略研究中存在的一些主要问题,包括术语问题、分类问题、效度和信度问题、研究内容问题、研究方法问题和代表性问题,并针对这些问题提出了相应的对策。     

大气采样技术研究

在空气环境污染物的监测中,采样是整个监测过程的第一步,是监测工作的重要环节.采样方法正确与否,关系到监测结果的可靠性和准确性.为此,采样人员在采样前必须进行误差分析,定期校准采样器,对采样系统进行气密性检查,按时校准流量,掌握程序的设置方法.最后,采集后安全及时送回实验室内分析.     

中心极限定理在抽样推断中的应用

讨论中心极限定理在抽样推断中的若干应用。     

Reconstruction algorithm in lattice-invariant signal spaces

In this paper, we mainly pay attention to the weighted sampling and reconstruction algorithm in lattice-invariant signal spaces. We give the reconstruction formula in lattice-invariant signal spaces, which is a generalization of former results in shift-invariant signal spaces. That is, we generalize and improve Aldroubi, Grochenig and Chen's results, respectively. So we obtain a general reconstruction algorithm in lattice-invariant signal spaces, which the signal spaces is sufficiently large to accommodate a large number of possible models. They are maybe useful for signal processing and communication theory.