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Collaborative filtering(CF) has been widely applied to recommender systems,since it can assist users to discover their favorite items.Similarity measurement that measures the similarity between two users or items is critical to CF.However,traditional similarity measurement approaches for memory-based CF can be strongly improved.In this paper,we propose a novel similarity measurement,named Jaccard Uniform Operator Distance(JacUOD),to effectively measure the similarity.Our JacUOD approach aims at unifying similarity comparison for vectors in different multidimensional vector spaces.Compared with traditional similarity measurement approaches,JacUOD properly handles dimension-number difference for different vector spaces.We conduct experiments based on the well-known MovieLens datasets,and take user-based CF as an example to show the effectiveness of our approach.The experimental results show that our JacUOD approach achieves better prediction accuracy than traditional similarity measurement approaches. 相似文献
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基于目标距离评估的启发式Web Services组合算法 总被引:6,自引:0,他引:6
随着可用Web Services数量的快速增长,如何根据用户的需求来自动组合Web Services,生成满足用户需求的组合业务,成为一项亟待解决的课题.提出了一种基于用户需求目标距离评估的启发式算法,通过该算法,动态调用Web Services来自动生成满足用户所需目标的Web Service组合,同时,该算法还能够根据Web Services组合经验,对以后的Web Services组合方案进行调整.实验结果表明:该算法能够很好地适应网络上Web Services的不稳定情况,与同类算法进行性能比较,也显示出基于目标距离评估的算法具有较好的性能. 相似文献
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无线局域网支持实时业务的研究 总被引:1,自引:0,他引:1
在分析当今两大主流无线局域网MAC层机制的基础上研究了无线局域网对实时业务的支持,分析了不同媒体接入策略对实时业务的影响。 相似文献
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动力电池的荷电状态(State of Charge,SOC)是电动汽车的重要参数之一,直接影响电动汽车的安全控制与可续行里程的评估.电池总容量作为估算电池SOC的重要变量之一,其与使用环境温度密切相关,而在SOC估计算法中常被认为是恒定值,从而影响不同环境温度下锂电池SOC估计精度.为实现对锂电池SOC的准确估计,考虑温度对锂电池容量等特性参数的影响,通过引入温度补偿模型,并结合扩展卡尔曼滤波(Extended Kalman Filter,EKF)算法实现对锂电池SOC的动态估计.在不同环境温度下模拟电动汽车实际工况对锂电池进行放电试验,并比较未经温度补偿的SOC算法与补偿后的SOC算法精度.研究结果表明,所提出的方法适用于不同温度的锂电池,能实现较为精确的估计. 相似文献
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在综合考虑标签交换路径(LSP)排队时延和丢包率的基础上,定义了一个能反映LSP负荷的指标:可分配流量(DT).并基于DT提出一种多协议标签交换(MPLS)动态流量分配机制(DTMD),该机制只需要边缘路由器的参与,具有很好的可扩展性.仿真表明,DTMD具有较好的收敛性和稳定性,并能适应网络状态的动态变化;与单纯基于时延的流量分配机制相比,DTMD具有更好的公平性,能将流量更均衡地分配到各条并行LSP中. 相似文献
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IEEE 802.11 Medium Access Control (MAC) is proposed to support asynchronous and time bounded delivery of radio packets. Distributed Coordination b-kmction (DCF), which uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and binary slotted exponen-tial backoff, is the basis of the 802.11 MAC. This paper proposes a throughput enhancement for DCF by adjusting the Contention Window (CW) setting scheme. Moreover, an analytical model based on Markov chain is introduced to compute the enhanced throughput. The accuracy of the model and the enhancement of the proposed scheme are verified by elaborate simulations. 相似文献
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