高压变频器在电厂凝结水泵上的应用

文章论述了高压变频器在燃煤发电厂大容量电动机上应用的必要性,介绍了凝结水泵的变频改造方案,分析了高压变频器改造的经济性,为同类型发电厂的节能降耗提供了借鉴经验和参考。     

汽车保险精算定价模型研究综述

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。     

基于AD9834的简易信号源设计

采用模拟电路设计的信号源存在频率精度不高、调试与维修不方便以及直接升级困难等缺点。为了克服这些缺点,提出利用直接数字频率合成技术（AD9834）产生要求的正弦测井激励信号,利用小功率低压器件的串联实现信号的大功率大电压输出,利用电源跟踪技术在一定程度上降低功率器件的损耗,提高电路的工作效率。实验结果表明,信号源输出频率1～15Hz,频率分辨率为0.004Hz。     

THE INTELLECTUAL FOUNDATION OF THE JOURNAL OF BUSINESS LOGISTICS AND ITS EVOLUTION BETWEEN 1978 AND 2007

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.     

Term frequency – function of document frequency: a new term weighting scheme for enterprise information retrieval

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.     

Business models and their relationship with marketing: A systematic literature review

The purpose of this paper is to identify the degree to which the marketing discipline has hitherto engaged with business model literature. The results of a systematic review of business model literature are presented and utilise both the citation counts and the h-index to objectively demonstrate the limited engagement that the marketing discipline has had with business model literature, and the limited degree that the discipline has influenced that literature. The key findings reveal a growing, but formative body of literature that, hitherto, has been dominated by non-marketing disciplines and which has only just begun to be addressed by present day marketing scholars. Using the most influential articles identified in the analysis, the paper concludes with a case for the empirical development of the business model concept with industrial marketing scholarship. Such development is argued to be grounded in the potential of open business models, co-created with multiple stakeholders in a supply chain and the end users of a value proposition.     

节能技术在建筑设备工程中的应用与探讨

伴随着我国经济高速发展、产业结构调整及世界性能源紧缺的大背景下,建筑节能已经成为建筑行业必须面对、考虑和解决的问题。本文从建筑设备工程所涉及的给排水管网系统的减压节流、水泵的变频控制,空气调节系统节能技术,电气系统节能技术等几方面进行阐述。节能技术在建筑设备工程中的应用与开展,有着重大的社会效益、经济效益和业主效益,同时也是社会和建筑行业发展的必然。     

《高频电子线路》课程教学中的几个重要环节

《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。     

高等师范院校古代汉语教学语料库字频研究

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。     

谈高低频电路接地

在电子线路中,合理的接地方式能够有效抑制噪声和提高抗干扰能力。文章分析了电子线路中产生噪声干扰的一些原因,并讨论了一点接地及多点接地等接地方式消除噪声的方法。