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1.
Using PISA and PIAAC data from twelve OECD countries, we examine the gap in cognitive skills among immigrants and natives and evaluate how those differences have evolved over time. We also consider how demographics, family background and school quality explain the development of cognitive skills of young people with immigrant backgrounds. The results show, first, that some convergence in skills occurs between second-generation immigrants and natives over time. Second, demographics, family background and school quality variables all contribute to the achievement gaps across different groups.  相似文献   
2.
该文认为,《"阅读·探究·体验"手册》是学生阅读的助手,设计时考虑到整体构建章节与整本书阅读相结合。同时,明确主线,整本书阅读的探究要围绕主线展开,在构建手册时,明确整本书阅读探究的核心要点。在开发《"阅读·探究·体验"手册》时,充分考虑到语文学科的核心素养,通过编制手册,提升学生的语文核心素养。  相似文献   
3.
To cope with ambiguous and/or underspecified queries, search result diversification (SRD) is a key technique that has attracted a lot of attention. This paper focuses on implicit SRD, where the subtopics underlying a query are unknown. Many existing methods appeal to the greedy strategy for generating diversified results. A common practice is using a heuristic criterion for making the locally optimal choice at each round. As a result, it is difficult to know whether the failures are caused by the optimization criterion or the setting of parameters. Different from previous studies, we formulate implicit SRD as a process of selecting and ranking k exemplar documents through integer linear programming (ILP). The key idea is that: for a specific query, we expect to maximize the overall relevance of the k exemplar documents. Meanwhile, we wish to maximize the representativeness of the selected exemplar documents with respect to the non-selected documents. Intuitively, if the selected exemplar documents concisely represent the entire set of documents, the novelty and diversity will naturally arise. Moreover, we propose two approaches ILP4ID (Integer Linear Programming for Implicit SRD) and AP4ID (Affinity Propagation for Implicit SRD) for solving the proposed formulation of implicit SRD. In particular, ILP4ID appeals to the strategy of bound-and-branch and is able to obtain the optimal solution. AP4ID being an approximate method transforms the target problem as a maximum-a-posteriori inference problem, and the message passing algorithm is adopted to find the solution. Furthermore, we investigate the differences and connections between the proposed models and prior models by casting them as different variants of the cluster-based paradigm for implicit SRD. To validate the effectiveness and efficiency of the proposed approaches, we conduct a series of experiments on four benchmark TREC diversity collections. The experimental results demonstrate that: (1) The proposed methods, especially ILP4ID, can achieve substantially improved performance over the state-of-the-art unsupervised methods for implicit SRD. (2) The initial runs, the number of input documents, query types, the ways of computing document similarity, the pre-defined cluster number and the optimization algorithm significantly affect the performance of diversification models. Careful examinations of these factors are highly recommended in the development of implicit SRD methods. Based on the in-depth study of different types of methods for implicit SRD, we provide additional insight into the cluster-based paradigm for implicit SRD. In particular, how the methods relying on greedy strategies impact the performance of implicit SRD, and how a particular diversification model should be fine-tuned.  相似文献   
4.
深海声传播信道和目标被动定位研究现状   总被引:2,自引:0,他引:2       下载免费PDF全文
随着我国海洋技术逐渐从近浅海向深远海的战略性转移,深海目标远程探测技术逐渐受到重视。海洋中目前已知的可用于远距离传播的信号是声信号,海洋是"声透明"的。基于水声传播特性的新型水声技术是实现装备探测能力突破的关键。文章主要概述了目前研究比较集中的深海表面波导、表面波导泄露、会聚区、海底弹射和可靠声路径5种深海声传播信道,以及基于可靠声路径的目标被动定位方法。旨在通过梳理深海声传播规律及相关被动定位技术,为水声技术的快速发展提供思路。  相似文献   
5.
In our present research we address the question of whether it is valid to apply the Quality Assurance and Evaluation (QAE) umbrella concept, which was formulated to explain new phenomena in European educational governance, to similar developments in Brazilian basic education. This led us to reflect on the possible pitfalls and potential strengths of using umbrella concepts as analytical tools. This article presents this exploration and its operationalisation. We confronted in-built assumptions in QAE with the contested, consensual and creative use of the notion of quality in Brazilian basic education, and looked for relationships. Our analysis shows that the Brazilian developments reiterate the relationships concerning global interconnectivity, and challenges those pertaining to conformity. We argue that the main risks of using umbrella concepts seem to concern the re-production of understandings, which frequently leads to the disregarding of deviation.  相似文献   
6.
All over the world, universities have to cope with the mission to promote the employability of their graduates, implying that competences should be trained which are relevant for the professional experience. In this context, it is of special interest where graduates work and what they are doing at work. In this study we focus on educational science graduates (N = 1565) and compare them to graduates of other study programmes (N = 10,224). Using data of the German DZHW graduate panel 2005 (N = 11,789), we address the questions (1) in which fields graduates of educational science work, (2) whether a theoretical-based four-dimensional internal structure of graduates’ job-related requirements and competences can be confirmed, (3) what kind of self-rated requirements educational science graduates experience at work, and (4) which self-rated levels of competences they possess, compared to other graduates. The analyses show that most graduates of educational science find an appropriate job in a clearly educational setting and that generic competences (systematic, social, and personal competences) are rated as more important than knowledge processing.  相似文献   
7.
丁利 《现代情报》2018,38(1):100-107
旅游政务微博已成为政府官方旅游机构发布和传播旅游信息的重要载体,其信息服务质量的优化对于完善旅游信息服务体系建设和提升旅游品牌形象尤为关键。本研究借鉴扎根理论,对游客的网络评论数据进行三级编码,归纳了网络游客信息需求的4个核心范畴,从而构建了旅游政务微博公共信息服务质量优化的理论模型,最终依据模型提出相关的优化建议。  相似文献   
8.
In this work, we present the first quality flaw prediction study for articles containing the two most frequent verifiability flaws in Spanish Wikipedia: articles which do not cite any references or sources at all (denominated Unreferenced) and articles that need additional citations for verification (so-called Refimprove). Based on the underlying characteristics of each flaw, different state-of-the-art approaches were evaluated. For articles not citing any references, a well-established rule-based approach was evaluated and interesting findings show that some of them suffer from Refimprove flaw instead. Likewise, for articles that need additional citations for verification, the well-known PU learning and one-class classification approaches were evaluated. Besides, new methods were compared and a new feature was also proposed to model this latter flaw. The results showed that new methods such as under-bagged decision trees with sum or majority voting rules, biased-SVM, and centroid-based balanced SVM, perform best in comparison with the ones previously published.  相似文献   
9.
[目的/意义]研究方法在学术研究中发挥着至关重要的作用。确认图书馆情报学领域主要的研究方法,并对它们进行了解熟悉,以在开展研究时能合理选择、灵活使用,确保研究质量。[方法/过程]对近2 000篇图书馆情报学领域的研究文献以及相关研究方法论文进行内容分析,在此基础上对研究方法的类分命名、图书馆情报学界主要的研究方法的确定、特点和使用注意事项进行介绍和讨论。[结果/结论]研究方法应以数据收集法而不是数据分析法命名。图书馆情报学领域常用的研究方法包括实验法、问卷法、理论研讨法、内容分析法、访谈法和书目计量法,每种方法都有各自的特点。因而在选择使用时,既应根据具体研究课题及研究方法之特性,也要考虑使用注意事项,并尽量在同一研究中采用两种或更多的方法,以扬长避短,更有效地展开研究。  相似文献   
10.
This study enhances the existing literature on online trust by integrating the consumers’ product evaluations model and technology adoption model in e-commerce environments. In this study, we investigate how perceived value influences the perceptions of online trust among online buyers and their willingness to repurchase from the same website. This study proposes a research model that compares the relative importance of perceived value and online trust to perceived usefulness in influencing consumers’ repurchase intention. The proposed model is tested using data collected from online consumers of e-commerce. The findings show that although trust and e-commerce adoption components are critical in influencing repurchase intention, product evaluation factors are also important in determining repurchase intention. Perceived quality is influenced by the perceptions of competitive price and website reputation, which in turn influences perceived value; and perceived value, website reputation, and perceived risk influence online trust, which in turn influence repurchase intention. The findings also indicate that the effect of perceived usefulness on repurchase intention is not significant whereas perceived value and online trust are the major determinants of repurchase intention. Major theoretical contributions and practical implications are discussed.  相似文献   
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