松嫩平原土壤有机质含量高光谱反演研究

采集松嫩平原典型类型土壤样本252个.室内条件下测定了风干后土样的光谱.对原始光谱数据作预处理后,分别运用多元线性逐步回归法和偏最小二乘法建立土壤有机质含量高光谱预测模型.结果表明,采用2种方法建立的模型均可满足有机质含量速测要求,但偏最小二乘法得到的模型更具稳健性.     

负反馈放大器回归比的测试

不论何种类型的负反馈放大器，只要在反馈环路某点处断开反馈环，测试出反馈放大器的回归比，就可方便地分析研究负反馈对放大器性能的影响．     

Scale and Translation Invariant Collaborative Filtering Systems

Collaborative filtering systems are prediction algorithms over sparse data sets of user preferences. We modify a wide range of state-of-the-art collaborative filtering systems to make them scale and translation invariant and generally improve their accuracy without increasing their computational cost. Using the EachMovie and the Jester data sets, we show that learning-free constant time scale and translation invariant schemes outperforms other learning-free constant time schemes by at least 3% and perform as well as expensive memory-based schemes (within 4%). Over the Jester data set, we show that a scale and translation invariant Eigentaste algorithm outperforms Eigentaste 2.0 by 20%. These results suggest that scale and translation invariance is a desirable property.     

国外高校的人文科学教育及启示——以英、美、日为例

我国高校若干年来形成了重理工轻人文、重专业技能轻综合素质的不良倾向。在国外,学者们则较早地注意到科学(科技)教育与人文教育的割裂与失衡的危机,并对两者的整合提出了许多思路且付诸实践。英、美、日高校的人文教育都经历了"兴盛——衰落——回归"的历程,具有代表性。该文对这三个国家高校人文科学教育的思潮及实践作一概述,以期对我国高等教育改革提供某些借鉴。     

Adaptive progressive download based on the MPEG-4 file format

In this paper we describe how progressive download and adaptive streaming can be combined into a simple and efficient streaming framework. Based on the MPEG-4 file format (MP4) we use HTTP for transport and argue that these two components are sufficient for specifying an open streaming architecture. The client selects appropriate chunks from the MP4 file to be transferred based on (1) the header information (i.e. the "moov" box) in the first part of the file and (2) his observation of network throughput. The framework is completely client driven which allows for better server scalability and reduces signalling overhead. We discuss architecture and implementation issues such as complexity, interoperability and scalability and compare to 3GPP PSS Re1-6 adaptive streaming when appropriate. Measurements from a simple MP4/HTTP streaming client are presented showing that appropriate chunks are selected such that increased reliability is achieved.     

中国公民对民主政治体制态度的实证分析--就"世界价值观调查"中"无回答"的处理与Russell J. Dalton教授商榷

本文通过对“世界价值观调查”的数据分析证实,对“无回答”数据的不同处理会导致截然不同的结论。一些学者在不分析“无回答”数据的基础上,得出在中国有96%的人赞成民主政治体制的结论。但是,该调查中分别有近20%和42%的人对各种政治体制持有“不知道”和“混合”态度,而明确赞成民主体制的只占31%。逻辑斯蒂回归分析表明这两类人与明确赞成民主体制的人具有显著的差异,并且数据显示他们是现实政治体制的高度拥护者。因此不能将“无回答”数据忽略,分析“无回答”数据是作出科学结论前的一个必要环节。     

Learning by progressive inquiry in a physics lesson with the support of cloud-based technology

ABSTRACT

Background

Inquiry-based learning has been widely adopted in educational practice especially in science education. Scaffolding plays an important role in fostering learning in sophisticated inquiry. Meanwhile, it is important not to undermine the open-endedness of inquiry activities and the nature of student-centred learning.     

农村留守儿童社会支持与孤独感的关系

通过对264名留守儿童和213名非留守儿童进行问卷调查,探讨了不同情况下,社会支持对留守儿童孤独感的影响.结果表明:留守与非留守儿童在孤独感上没有显著差异;同学支持和母亲支持对非留守儿童的孤独感有显著负向影响,而同学支持、父亲支持和教师支持同时对留守儿童的孤独感具有显著负向影响;高自尊组留守儿童的孤独感显著低于低自尊组;只有同学支持对于低自尊组留守儿童的孤独感具有显著负向影响,而同学支持和教师支持同时对高自尊组留守儿童的孤独感也具有显著负向影响.     

Separating the Odds: Thresholds for Entropy in Logistic Regression

Abstract

Researchers are often reluctant to rely on classification rates because a model with favorable classification rates but poor separation may not replicate well. In comparison, entropy captures information about borderline cases unlikely to generalize to the population. In logistic regression, the correctness of predicted group membership is known, however, this information has not yet been utilized in entropy calculations. The purpose of this study was to, 1) introduce three new variants of entropy as approximate-model-fit measures, 2) establish rule-of-thumb thresholds to determine whether a theoretical model fits the data, and 3) investigate empirical Type I error and statistical power associated with those thresholds. Results are presented from two Monte Carlo simulations. Simulation results indicated that EFR-rescaled was the most representative of overall model effect size, whereas EFR provided the most intuitive interpretation for all group size ratios. Empirically-derived thresholds are provided.     

体育多种预测方法的比较研究

运用3种不同的方法所建立的多元回归预测模型,其回归预测值的准确度均达到了99.26%以上,其回归的预测值与实际值的方差分析检验均呈无差异性,P》0.50水平.说明3种不同的方法所建立的预测模型的预测值均具有显著性意义.在3种建模方法中,均有评价作用,且其评价目的也不尽相同.在体育运动实践中可依据研究的目的,选择建模方法,以提高体育预测研究的效益.