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The term mismatch problem in information retrieval is a critical problem, and several techniques have been developed, such as query expansion, cluster-based retrieval and dimensionality reduction to resolve this issue. Of these techniques, this paper performs an empirical study on query expansion and cluster-based retrieval. We examine the effect of using parsimony in query expansion and the effect of clustering algorithms in cluster-based retrieval. In addition, query expansion and cluster-based retrieval are compared, and their combinations are evaluated in terms of retrieval performance by performing experimentations on seven test collections of NTCIR and TREC. 相似文献
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Lisa A. Newland Jarod T. Giger Michael J. Lawler Soonhee Roh Barbara L. Brockevelt Amy Schweinle 《Child development》2019,90(2):395-413
This study tests an ecological, relationship-based model of children's subjective well-being with 9- to 14-year-old children (n = 25,906) from 14 countries across Africa, Asia, Europe, North America, and South America. Children completed the Children's Worlds survey, a self-report measure of contextual and well-being indicators. Multilevel modeling was used to predict children's well-being (life satisfaction and self-image) at two levels, child (age, gender, home context, family relationships, peer relationships, school context, teacher relationships, and neighborhood quality), and country (gross domestic product and income inequality). Findings indicated that intercepts varied significantly across countries. The majority of variance in children's well-being was attributed to child-level rather than country-level factors. Country-level factors did not strongly predict well-being but marginally improved model fit. 相似文献
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Roh Pin Lee 《International Journal of Science Education》2016,38(6):1036-1056
Misconceptions and biases in energy perception could influence people's support for developments integral to the success of restructuring a nation’s energy system. Science education, in equipping young adults with the cognitive skills and knowledge necessary to navigate in the confusing energy environment, could play a key role in paving the way for informed decision-making. This study examined German students’ knowledge of the contribution of diverse energy sources to their nation’s energy mix as well as their affective energy responses so as to identify implications for science education. Specifically, the study investigated whether and to what extent students hold mistaken beliefs about the role of multiple energy sources in their nation’s energy mix, and assessed how misconceptions could act as self-generated reference points to underpin support/resistance of proposed developments. An in-depth analysis of spontaneous affective associations with five key energy sources also enabled the identification of underlying concerns driving people’s energy responses and facilitated an examination of how affective perception, in acting as a heuristic, could lead to biases in energy judgment and decision-making. Finally, subgroup analysis differentiated by education and gender supported insights into a ‘two culture’ effect on energy perception and the challenge it poses to science education. 相似文献
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Kyeong Hah Roh 《Educational Studies in Mathematics》2008,69(3):217-233
There are many studies on the role of images in understanding the concept of limit. However, relatively few studies have been
conducted on how students’ understanding of the rigorous definition of limit is influenced by the images of limit that the
students have constructed through their previous learning. This study explored how calculus students’ images of the limit
of a sequence influence their understanding of definitions of the limit of a sequence. In a series of task-based interviews,
students evaluated the propriety of statements describing the convergence of sequences through a specially designed hands-on
activity, called the ɛ–strip activity. This paper illustrates how these students’ understanding of definitions of the limit of a sequence was influenced
by their images of limits as asymptotes, cluster points, or true limit points. The implications of this study for teaching
and learning the concept of limit, as well as on research in mathematics education, are also discussed. 相似文献
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Understanding the mechanical properties of optically transparent polydimethylsiloxane (PDMS) microchannels was essential to the design of polymer-based microdevices. In this experiment, PDMS microchannels were filled with a 100 μM solution of rhodamine 6G dye at very low Reynolds numbers (∼10−3). The deformation of PDMS microchannels created by pressure-driven flow was investigated by fluorescence microscopy and quantified the deformation by the linear relationship between dye layer thickness and intensity. A line scan across the channel determined the microchannel deformation at several channel positions. Scaling analysis widely used to justify PDMS bulging approximation was allowed when the applied flow rate was as high as 2.0 μl/min. The three physical parameters (i.e., flow rate, PDMS wall thickness, and mixing ratio) and the design parameter (i.e., channel aspect ratio = channel height/channel width) were considered as critical parameters and provided the different features of pressure distributions within polymer-based microchannel devices. The investigations of the four parameters performed on flexible materials were carried out by comparison of experiment and finite element method (FEM) results. The measured Young''s modulus from PDMS tensile test specimens at various circumstances provided reliable results for the finite element method. A thin channel wall, less cross-linker, high flow rate, and low aspect ratio microchannel were inclined to have a significant PDMS bulging. Among them, various mixing ratios related to material property and aspect ratios were one of the significant factors to determine PDMS bulging properties. The measured deformations were larger than the numerical simulation but were within corresponding values predicted by the finite element method in most cases. 相似文献
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We investigate a new category of fuzzy-neural networks such as Hybrid Fuzzy Set-based Polynomial Neural Networks (HFSPNN). These networks consist of a genetically optimized multi-layer with two kinds of heterogeneous neurons such as fuzzy set-based polynomial neurons (FSPNs) and polynomial neurons (PNs). We have developed a comprehensive design methodology that helps determine the optimal structure of networks dynamically. The augmented genetically optimized HFSPNN (referred to as gHFSPNN) results in a structurally optimized structure and comes with a higher level of flexibility in comparison to the one we encounter in the conventional HFPNN. The GA-based design procedure being applied at each layer of gHFSPNN leads to the selection of preferred nodes (FSPNs or PNs) available within the HFSPNN. In the sequel, the structural optimization is realized via GAs, whereas the ensuing detailed parametric optimization is carried out in the setting of a standard least square method-based learning. The performance of the gHFSPNN is demonstrated through intensive experimentation where we use a number of modeling benchmarks—synthetic and experimental datasets are already being used in fuzzy or neurofuzzy modeling. 相似文献
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Kyeong Hah Roh 《Educational Studies in Mathematics》2010,73(3):263-279
This study explored students’ understanding of a logical structure in defining the limit of a sequence, focusing on the relationship
between ε and N. The subjects of this study were college students who had already encountered the concept of limit but did not have any experience
with rigorous proofs using the ε–N definition. This study suggested two statements, each of which is written by using a relationship between ε and N, similar to the ε–N definition. By analyzing the students’ responses to the validity of the statements as definitions of the limit of a sequence,
students’ understanding of such a relationship was classified into five major categories. This paper discusses some essential
components that students must conceptualize in order properly to understand the relationship between ε and N in defining the limit of a sequence. 相似文献