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51.
This paper studies the use of patent statistics in identifying four aspects of technological structure, namely, the potential knowledge pool, cumulativeness, inter-firm homogeneity in technology levels, and the scope of innovations. The firms are sampled from the chemical (CHEM), the computer (COM) and the electrical and electronic (EE) industries worldwide. Using the proxies defined, we find that (i) the contributions of intra-industry spillover are low, at 12%, 10%, and 9% for the three industries respectively; (ii) they can internalize 15%, 19% and 13% of their previous research efforts respectively; and (iii) a positive relationship between knowledge spillover and technology overlap, and between scope of innovation and number of patents being cited in future. 相似文献
52.
《Enterprise Information Systems》2013,7(4):433-444
In today's business environment, enterprises are increasingly under pressure to process the vast amount of data produced everyday within enterprises. One method is to focus on the business intelligence (BI) applications and increasing the commercial added-value through such business analytics activities. Term weighting scheme, which has been used to convert the documents as vectors in the term space, is a vital task in enterprise Information Retrieval (IR), text categorisation, text analytics, etc. When determining term weight in a document, the traditional TF-IDF scheme sets weight value for the term considering only its occurrence frequency within the document and in the entire set of documents, which leads to some meaningful terms that cannot get the appropriate weight. In this article, we propose a new term weighting scheme called Term Frequency – Function of Document Frequency (TF-FDF) to address this issue. Instead of using monotonically decreasing function such as Inverse Document Frequency, FDF presents a convex function that dynamically adjusts weights according to the significance of the words in a document set. This function can be manually tuned based on the distribution of the most meaningful words which semantically represent the document set. Our experiments show that the TF-FDF can achieve higher value of Normalised Discounted Cumulative Gain in IR than that of TF-IDF and its variants, and improving the accuracy of relevance ranking of the IR results. 相似文献
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对基于高等师范学校古代汉语教学的语料库相关数据结果做了定量分析,阐述了语料库的用字概况,提出了字区划分的标准,研制了分区字频表。 相似文献
56.
We provide a structural approach to identify instantaneous causality effects between durations and stock price volatility. So far, in the literature, instantaneous causality effects have either been excluded or cannot be identified separately from Granger type causality effects. By giving explicit moment conditions for observed returns over (random) duration intervals, we are able to identify an instantaneous causality effect. The documented causality effect has significant impact on inference for tick-by-tick data. We find that instantaneous volatility forecasts for, e.g., IBM stock returns must be decreased by as much as 40% when not having seen the next quote change before its (conditionally) median time. Also, instantaneous volatilities are found to be much higher than indicated by standard volatility assessment procedures using tick-by-tick data. For IBM, a naive assessment of spot volatility based on observed returns between quote changes would only account for 60% of the actual volatility. For less liquidly traded stocks at NYSE this effect is even stronger. 相似文献
57.
《高频电子线路》课程是工程电子、通信类专业的一门重要专业基础课程,该课程主要学习通信系统中构成发射机、接收机的单元电路。文章针对学生学习高频电路困难的现状进行分析,从而探讨了在教学中如何从五个方面使学生对该课程产生兴趣并以清晰地思路学好本课程。 相似文献
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汽车保险精算定价模型研究综述 总被引:1,自引:0,他引:1
郁佳敏 《上海金融学院学报》2010,(1):14-19
汽车保险定价模型在非寿险精算领域内占有重要地位,本文对车险定价模型一百多年来的研究进展作了综述性的回顾。首先,本文介绍了车险定价模型的先验估费方法;其次着重介绍了时齐的后验估费方法,以及时变的先验后验相结合的精算模型;最后提出了车险定价模型的未来发展方向。 相似文献
60.
Herbert Kotzab Ph.D. 《Journal of Business Logistics》2010,31(2):63-109
Many logistics and supply chain management researchers have so far studied the nature of logistics and supply chain management research in terms of its domain and scope, its epistemological assumptions, and its evolution. However, the knowledge repository on which the scientific research community draws, that is, its intellectual foundation, has not yet been studied. Studying the intellectual foundation of research provides an unbiased and comprehensive picture of the development, dissemination, and utilization of its knowledge. In this article, we identify the most contributive works—in terms of citations received—that have been used in 497 articles published in the Journal of Business Logistics (JBL) between 1978 and 2007. By means of citation and co‐citation analysis, the intellectual structure of research in JBL is revealed and transformations therein are explored. Overall, the most frequently‐cited literature can be classified into six themes: physical distribution; inventory models; customer service; interorganizational relationships; competitive strategy; and empirical methodologies for socio‐scientific research. Furthermore, we determined a development in citation frequencies to these themes: literature related to physical distribution and inventory management declined over the three decades under study, whereas literature related to competitive strategy and empirical methods gained in importance. This development indicates a shift from an operational focus to a prioritization of managerial issues. Moreover, our results demonstrate a shift towards more relational and institutional research in logistics (management), which has been typically linked with the notion of supply chain management since the 1990's. 相似文献