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301.
本文介绍了快速傅立叶变换的离散算法,并在此基础上设计程序。设计所用的分析信号由电网电压经互感器得到,所用单片机型号为dsPIC30F4011,安装在APP009实验电路板上。程序设计部分主要包括A/D转换部分及FFT变换部分等。实验中,通过A/D转换进行采样,得到一组离散的采样点,通过快速傅立叶变换(FFT)对采样信号进行频谱分析.实验结果表明该测试仪可以实现对电网的各次谐波进行有效检测。 相似文献
302.
目前整车E/E架构由于面临来自不同控制器和传感器的数据交互需求而变得愈加复杂,所需要解决的问题包括:功能复杂性,通信带宽,计算能力,灵活性,可拓展性等。其中域控制器上层应用算法对获取数据的同步尤其敏感,数据融合需要针对同一时间点获取到的数据做融合处理。因此,对域控制器内部的异构多核、外部控制器数据以及传感器数据时间同步的研究尤其重要。基于此,文章详细介绍了域控制器片内及片外时间同步的方法,解决了域控制器内外部数据时间不同步的技术缺陷。 相似文献
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To improve the detection rate and lower down the false positive rate in intrusion detection system,dimensionality reduction is widely used in the intrusion detection system.For this purpose,a data processing (DP) with support vector machine (SVM) was built.Different from traditionally identifying the redundant data before purging the audit data by expert knowledge or utilizing different kinds of subsets of the available 41-connection attributes to build a classifier,the proposed strategy first removes the attributes whose correlation with another attribute exceeds a threshold,and then classifies two sequence samples as one class while removing either of the two samples whose similarity exceeds a threshold.The results of performance experiments showed that the strategy of DP and SVM is superior to the other existing data reduction strategies (e.g.,audit reduction,rule extraction,and feature selection),and that the detection model based on DP and SVM outperforms those based on data mining,soft computing,and hierarchical principal component analysis neural networks. 相似文献
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We evaluate the economic effects of investment in the road network on private regional activity. We employ provincial Spanish panel data from 1980 to 2007 to perform non-parametric frontier techniques based on Data Envelopment Analysis and to obtain the Malmquist productivity indexes, thus enabling us to examine the evaluation of the productivity growth via technological changes or efficiency gains. Additionally, we analyze the role of transport infrastructure on the evolution of Total Factor Productivity and its components through econometric techniques. Our results show important spillover effects. Moreover, our findings have significant implications for policy makers if we take into account the fact that the use of the road network in economic activity or in commercial relations greatly influences productivity growth. 相似文献
307.
The public transport networks of dense cities such as London serve passengers with widely different travel patterns. In line with the diverse lives of urban dwellers, activities and journeys are combined within days and across days in diverse sequences. From personalized customer information, to improved travel demand models, understanding this type of heterogeneity among transit users is relevant to a number of applications core to public transport agencies’ function. In this study, passenger heterogeneity is investigated based on a longitudinal representation of each user’s multi-week activity sequence derived from smart card data. We propose a methodology leveraging this representation to identify clusters of users with similar activity sequence structure. The methodology is applied to a large sample (n = 33,026) from London’s public transport network, in which each passenger is represented by a continuous 4-week activity sequence. The application reveals 11 clusters, each characterized by a distinct sequence structure. Socio-demographic information available for a small sample of users (n = 1973) is combined to smart card transactions to analyze associations between the identified patterns and demographic attributes including passenger age, occupation, household composition and income, and vehicle ownership. The analysis reveals that significant connections exist between the demographic attributes of users and activity patterns identified exclusively from fare transactions. 相似文献
308.
《铁路数据通信网设计规范》已经发布实施。概述了铁路数据通信网承载的业务,提出铁路数据通信网工程设计应遵循的共性要求,介绍了在网络结构、业务接入、路由策略、MPLSVPN部署、QoS、网络安全等方面的工程设计中,应如何理解、贯彻重点内容。 相似文献
309.
胡旭 《辽宁省交通高等专科学校学报》2010,12(2):53-55
我们已进入信息化社会,很多人都需要利用计算机处理每天的学习和工作,当我们在网上使用一些如邮箱、聊天、网上银行等功能时,需要设置口令来保护自己的信息,本文介绍了黑客攻击用户帐户的常用方法,用户设置口令的要求与技巧。 相似文献
310.