排序方式： 共有102条查询结果，搜索用时 312 毫秒
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首先介绍数据库的基本概念,包括dBASE, FoxPro, Microsoft Access and Paradox软件的定义.然后解释数据库的结构包括表(Table)、记录(Record)和字段(Field)的定义,并举例说明.还详细介绍不同类型的数据库关系,包括单个对单个、单个对多个、多个对多个的关系.最后介绍Dreamwear环境下动态数据库的设计方法和数据库连接方法. 相似文献
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Learning from imbalanced datasets is difficult. The insufficient information that is associated with the minority class impedes making a clear understanding of the inherent structure of the dataset. Most existing classification methods tend not to perform well on minority class examples when the dataset is extremely imbalanced, because they aim to optimize the overall accuracy without considering the relative distribution of each class. In this paper, we study the performance of SVMs, which have gained great success in many real applications, in the imbalanced data context. Through empirical analysis, we show that SVMs may suffer from biased decision boundaries, and that their prediction performance drops dramatically when the data is highly skewed. We propose to combine an integrated sampling technique, which incorporates both over-sampling and under-sampling, with an ensemble of SVMs to improve the prediction performance. Extensive experiments show that our method outperforms individual SVMs as well as several other state-of-the-art classifiers. 相似文献
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企业作为创新的传统主体一直受到学界和业界的重视和实践,而作为创新动力重要源泉的消费者的作用同样不容忽视,其活跃的思维方式、独特的视角在一定使能技术支持下,在产品创新过程中同样大有作为.如何将传统的企业创新资源与消费者这两种创新资源有机地集成在一起是一个现实的问题.以创新的过程作为切入点,根据创新不同阶段的特征以及对创新能力的需求,探讨了企业、消费者这两种创新资源的能力特征以及参与创新活动的形式.为实现资源的动态整合,提出了一种立体集成模式,从创新活动形式、资源主体以及创新阶段三个维度探讨了面向创新过程的资源集成方式. 相似文献
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通过利用信息技术营造一种新型教学环境，改变教学结构，革新教育技术的教材、教法，对CAI教学手段进行创新，拓展CAI领域，目的在于将技术合理地整合于教学当中，将教学环境最大程度的开放，探讨一种合理的教育模式，促进教学改革．通过课程整合，定量、定性的提高学生综合素质，最终把学生培养成能适应社会需求的创新性人才． 相似文献
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Persistent and toxic organic pollutants are serious environmental concerns in many parts of the world. These pollutants are often difficult to deal with using conventional treatment processes. Photocatalysis is an emerging technology which uses environmentally-friendly oxidants (oxygen, hydrogen peroxide, ozone),photocatalysts (titanium dioxide, ferrous ions or its complexes) and ultraviolet (UV) radiation to degrade and mineralize the toxic organic pollutants. The major drawback is that photocatalytic processes need to be activated by ultraviolet light, which accounts for only about 4% of the incoming solar energy; the overall reaction efficiency is still very low. 相似文献
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Multi-candidate reduction: Sentence compression as a tool for document summarization tasks 总被引：2，自引：0，他引：2
David Zajic Bonnie J. Dorr Jimmy Lin Richard Schwartz 《Information processing & management》2007,43(6):1549
This article examines the application of two single-document sentence compression techniques to the problem of multi-document summarization—a “parse-and-trim” approach and a statistical noisy-channel approach. We introduce the multi-candidate reduction (MCR) framework for multi-document summarization, in which many compressed candidates are generated for each source sentence. These candidates are then selected for inclusion in the final summary based on a combination of static and dynamic features. Evaluations demonstrate that sentence compression is a valuable component of a larger multi-document summarization framework. 相似文献
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Improving Person-Fit Assessment by Correcting the Ability Estimate and Its Reference Distribution 总被引：1，自引：0，他引：1
The standardized log-likelihood of a response vector (lz ) is a popular IRT-based person-fit test statistic for identifying model-misfitting response patterns. Traditional use of lz is overly conservative in detecting aberrance due to its incorrect assumption regarding its theoretical null distribution. This study proposes a method for improving the accuracy of person-fit analysis using lz which takes into account test unreliability when estimating the ability and constructs the distribution for each lz through resampling methods. The Type I error and power (or detection rate) of the proposed method were examined at different test lengths, ability levels, and nominal α levels along with other methods, and power to detect three types of aberrance—cheating, lack of motivation, and speeding—was considered. Results indicate that the proposed method is a viable and promising approach. It has Type I error rates close to the nominal value for most ability levels and reasonably good power. 相似文献
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通过面对现代社会的入侵,生活在偏僻地区的土著居民传统文化也受到了相应的损害,如何保护土著文化不仅有助于民族之间的相互交流,同时也体现了对其他民族文化的尊重.本文以最有代表性的三种土著居民为例,提出利用现代教育技术保护土著文化的一些建议. 相似文献
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Donald R. Baum Jimmy E. Hernandez Ariah Orchard 《Early Years: An International Journal of Research and Development》2019,39(3):260-275
This study considers the extent to which access to basic education and student learning outcomes have become more equalized or more disparate in Tanzania following the implementation of the international Education for All (EFA) initiative, and whether early childhood education access and performance follow similar patterns. To answer these questions, we apply a mixed-methods research design, which includes a longitudinal analysis of changes in educational opportunity and a critical discourse analysis (CDA) of key education policy documents in Tanzania. Findings from our quantitative analysis suggest that social inequality is persistent across time and consistent across access and learning outcomes at the early childhood and basic education levels. The implication is that, to date, the EFA agenda has only served to reproduce social inequalities in Tanzania, with the exception of increased opportunity for girls. These results align with CDA findings assessing the global and national policy discourse, which find educational inequalities to be prioritized in language but not adequately in final targets and strategies. Given the resiliency of such education inequalities, it would appear that policy capable of removing social barriers to educational opportunity requires more attention to specific at-risk student populations. 相似文献