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31.
In this paper, we provide a new insight into clustering with a spring–mass dynamics, and propose a resulting hierarchical clustering algorithm. To realize the spectral graph partitioning as clustering, we model a weighted graph of a data set as a mass–spring dynamical system, where we regard a cluster as an oscillating single entity of a data set with similar properties. And then, we describe how oscillation modes are related with eigenvectors of a graph Laplacian matrix of the data set. In each step of the clustering, we select a group of clusters, which has the biggest number of constituent clusters. This group is divided into sub-clusters by examining an eigenvector minimizing a cost function, which is formed in such a way that subdivided clusters will be balanced with large size. To find k clusters out of non-spherical or complex data, we first transform the data into spherical clusters located on the unit sphere positioned in the (k−1)-dimensional space. In the sequel, we use the previous procedure to these transformed data. The computational experiments demonstrate that the proposed method works quite well on a variety of data sets, although its performance degrades with the degree of overlapping of data sets. 相似文献
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This paper addresses synchronization problem for discrete-time complex dynamical networks with interval time-varying delays. In order to achieve the synchronization, a feedback controller subjected to randomly occurring perturbations will be considered. The randomly occurring perturbations are assumed to belong to the Binomial sequence. By constructing a suitable Lyapunov–Krasovskii functional, and utilizing reciprocally convex approach and Finsler?s lemma, the synchronization criteria for the networks are established in terms of linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. The networks are represented by the use of Kronecker product technique. The effectiveness of the proposed methods will be verified via numerical examples. 相似文献
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This paper reports a method to control the fluid flow in paper-based microfluidic devices simply by pressing over the channel surface of paper, thereby decreasing the pore size and permeability of a non-woven polypropylene sheet. As a result, fluid resistance is increased in the pressed region and causes flow rate to decrease. We characterize the decrease of flow rate with respect to different amounts of pressure applied, and up to 740% decrease in flow velocity was achieved. In addition, we demonstrate flow rate control in a Y-shaped merging paper and sequential delivery of multiple color dyes in a three-branched paper. Furthermore, sequential delivery of multiple fluid samples is performed to demonstrate its application in multi-step colorimetric immunoassay, which shows a 4.3-fold signal increase via enhancement step. 相似文献
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Yeonjeong Park 《Assessment & Evaluation in Higher Education》2017,42(4):531-547
As the advance of learning technologies and analytics tools continues, learning management systems (LMSs) have been required to fulfil the growing expectations for smart learning. However, the reality regarding the level of technology integration in higher education differs considerably from such expectations or the speed of advances in educational technologies. This research aimed to evaluate the current activation levels and usage patterns of a LMS. A large data-set was analysed, which included the online activity information from 7940 courses. Through data pre-processing, general indicators reflecting login frequencies of the virtual campus and activity-based indicators presenting the activation patterns of diverse functions provided by Moodle were derived. Activity theory was applied to interpret the results of analysis, since it has been recognised as a powerful framework to understand phenomena encompassing interactive systems. Further, time-series investigation over three consecutive semesters allowed observation of historical changes. The results revealed considerably low use of the virtual campus with only slight changes, as well as significantly different activity patterns across course attributes and colleges. Contradictions among components in the activity system are discussed, along with the implications for improving teaching and learning with LMS in higher education. 相似文献
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Jee Young Noh Laura Marie Elenbaas Kyung Ja Park Young Sun Chung Melanie Killen 《Early education and development》2017,28(2):240-254
Research Findings: To test children’s use of testimony of others, 3 – 9 years (N = 227) made judgments about a potential peer transgression in which the intentions of the protagonist were ambiguous, after hearing two different forms of testimony. The 2 forms of testimony were (a) opposing opinion-based testimony from an adult authority versus a peer consensus group and (b) knowledge-based testimony (eyewitness testimony) that was counter to the participants’ initial judgments. Findings revealed that when testimony was presented in an opinion-based format, children were likely to side with the opinion that reflected their own interpretation of the peer encounter, regardless of whether the opinion came from a peer consensus or an adult authority. However, when knowledge-based testimony was introduced in support of the opposite of children’s initial interpretation of the ambiguous peer encounter, children most often changed their initial judgment to align with the new testimony. That is, children used knowledge-based testimony but not opinion-based testimony to evaluate a potential transgression. Practice or Policy: These findings demonstrate that the way in which testimony is delivered to children has a direct influence on their decision making about peer interactions and has relevance for teacher–student discourse in the classroom. 相似文献
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Charlotte Johnston Laura Belschner Joanne L. Park Kurtis Stewart Amira Noyes Mark Schaller 《Parenting, science and practice》2017,17(1):51-72
Objective. Parenting behavior is presumed to be related to the thoughts about child behavior that parents report in a controlled and explicit manner and to more implicit parent cognitions that occur outside of conscious awareness and are less accessible to verbal report. Design. We examined mothers’ attitudes toward their children as correlates of self-reported parenting behavior. We used a combination of a self-report questionnaire and a reaction-time method (the Implicit Association Test) to assess explicit and implicit attitudes, respectively. We also assessed mothers’ implicit and explicit attributions for child misbehavior in relation to parenting, using a questionnaire measure of attributions completed under high-cognitive load (implicit attributions) or under low-cognitive load (explicit attributions). Mothers of 124, 6- to 10-year-olds (52% male) participated. Results. Attitudes assessed by self-report questionnaire and the Implicit Association Test were uniquely associated with negative parenting. The cognitive load manipulation moderated associations between attributions and parenting, such that child-blaming attributions were inversely associated with positive parenting only under conditions of high-cognitive load. Conclusions. Compared to traditional self-report questionnaires, methods such as the Implicit Association Test or cognitive load manipulations may more effectively assess implicit parent cognitions. 相似文献
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The geography of opportunity: spatial heterogeneity in founding rates and the performance of biotechnology firms 总被引:3,自引:0,他引:3
One of the most commonly observed features of the organization of markets is that similar business enterprises cluster in physical space. In this paper, we develop an explanation for firm co-location in high-technology industries that draws upon a relational account of new venture creation. We argue that industries cluster because entrepreneurs find it difficult to leverage the social ties necessary to mobilize essential resources when they reside far from those resources. Therefore, opportunities for high tech entrepreneurship mirror the distribution of critical resources. The same factors that enable high tech entrepreneurship, however, do not necessary promote firm performance. In the empirical analyses, we investigate the effects of geographic proximity to established biotechnology firms, sources of biotechnology expertise (highly-skilled labor), and venture capitalists on the location-specific founding rates and performance of biotechnology firms. The paper finds that the local conditions that promote new venture creation differ from those that maximize the performance of recently established companies. 相似文献