共查询到20条相似文献,搜索用时 15 毫秒
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KONG Shao-feng 《数字社区&智能家居》2008,(32)
网络课程中的答疑是指在网络课程的教学中对学生所遇到疑难问题的解答。通过对国内外网上答疑系统概况的分析与相关技术的研究,提出了一个具有同步和异步相结合,具有多种交互手段的多媒体网上答疑系统。系统开发过程中主要应用了ASP.NET(C#)技术、SQL 2000数据库管理技术、Flash Media Server等关键技术。系统采取多种答疑的方法:留言答疑、自动答疑、讨论答疑、在线视频答疑等,能够很好地实现两个或多个用户在线交流,交流的方式可以使用文字、音频和视频,从而实现答疑交互手段的多样性。 相似文献
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几何攻击会使水印嵌入与检测失去同步,影响水印的检测。为解决几何攻击造成的水印同步问题,基于方向可控金字塔变换域特征实现了水印图像旋转失真的检测,结合归一化小波树熵掩码及小波域人眼对比敏感度掩码完成了小波超树的自适应调制,实现了水印信息的嵌入,基于小波超树算法的抗缩放攻击能力以及采用方向可控金字塔变换设计,算法能够抵抗缩放攻击和旋转攻击。仿真结果表明,算法对几何攻击具有较强的鲁棒性。 相似文献
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多媒体系统的交互式同步模型 总被引:1,自引:1,他引:0
媒体同步是多媒体系统中的核心技术之一,目前已出现了多种同步模型。文章提出了一种基于petri网的同步模型,该模型扩展了OCPN模型,支持受用户影响的多媒体同步关系描述,是一种动态规范。 相似文献
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K. R. KRISHNAN R. MUKUNDAN D. A. RERREAULT R. F. COTELLESSA 《International journal of systems science》2013,44(7):821-837
Discrete-control correction is a method of synchronizing the clocks of a digital communication network by means of periodic corrections to their frequencies, the correction to each clock being derived from the change in the buffer level at that node. This paper presents a comprehensive treatment of this method and extends the results of earlier papers to more general situations. It is shown that there is a set of conditions, one for each node, which is sufficient to establish network synchronism. Explicit formulae are derived for the frequency of synchronism and the steady-state buffer levels. It is shown also that the master—slave scheme of synchronization, in which the clocks of the network are synchronized to a designated master clock, is obtained as the special case of discrete-control correction in which corrections are made to all the clocks except the master clock. It is pointed out that in the event of disruption of a part of the network, the surviving part or parts of the network are assured of regaining synchronism. 相似文献
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多媒体会议系统是当前计算机支持的协同工作(CSCW)系统的重要应用领域之一,为了得到更高、更好地声音及图象,会议系统中基于IP网络流媒体的传输技术,特别是数据同步,成为一个关乎系统服务质量的重要问题。本文将结合会议系统和流媒体传输的技术及特点,对多媒体会议系统中数据传输同步的问题加以研究并提出一种的同步控制方式。 相似文献
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Web服务业务流程执行语言(BPEL)是一种Web服务组合语言。本文详细分析了BPEL中的并发和同步控制、同步与异步通讯机制,并举例说明。 相似文献
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Machine Intelligence Research - Quickly getting back the synchronism of a disturbed interconnected multi area power system due to variations in loading condition is recognized as prominent issue... 相似文献
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K.R. KRISHNAN R. MUKUNDAN D.A. PERREAULT R.H. BITTEL H. HELM 《International journal of systems science》2013,44(12):1107-1118
The synchronization of a digital communication network of general structure by the method of discrete-control-correction is investigated. In this method, periodic corrections are made to the frequencies of the local clocks, according to changes in the local buffer-levels. Conditions under which synchronization is achieved are derived, and the frequency of synchronism and the steady-state buffer levels are calculated. 相似文献
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脑电(EEG)分析是研究癫痫的一个重要手段。以临床采集的健康对象和癫痫患者的头皮EEG为研究对象,计算不同导联EEG数据之间的排序互信息,结果表明癫痫患者不同导联之间的互信息明显高于健康对象,因此,排序互信息可以作为癫痫疾病诊断的重要特征。以排序互信息为依据,对癫痫脑电进行了同步性的分析,结果表明癫痫患者左脑区域内、右脑区域内及左右脑区之间的信息交流明显增强,即其同步性强于健康对象。互信息和同步性的分析方法还可对癫痫发作前期和发作阶段的EEG进行分析,对癫痫发作作出预测。 相似文献
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实时操作系统中对任务的响应时间提供了机制上的保障.但任务的同步与互斥又会削弱对任务响应的实时性,本文通过针对一个具体的实时操作系统VxWorks.详细的讨论了任务的同步与互斥机制.重点的讨论了互斥信号量机制对系统的影响。 相似文献
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分析了永磁同步电机变频驱动系统的性能特点,指出在传动性能和节能等方面具有明显优势,非常适合胶带输送机等机械设备,具有广阔的应用前景. 相似文献
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多线程技术在多任务实时处理程序中应用非常广泛,本文先介绍多线程技术及其相关概念,再对线程问的通信与同步机制进行了探讨,最后通过安防监控系统中引进多线程技术解决单线程冲突问题加以说明。 相似文献
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《Mathematics and computers in simulation》1991,33(3):209-221
This paper points out how the energy may be used to select appropriate numerical schemes. For the purpose of illustration an elastic oscillator is considered. This oscillator is modeled by a system of differential equations (zero-dimensional oscillator) and by a system of partial differential equations (one-dimensional oscillator). For the case of free oscillator the energy is preserved in time by the exact solutions. It is shown here that the numerical schemes which preserve this property better give more accurate numerical solutions at a given time and for a given time step. The one-dimensional scheme applies equally well when shock waves are involved. The relation between the solutions obtained with the two models is also discussed. 相似文献
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A microstrip open‐loop resonator oscillator operating at even modes is proposed. The even mode of the ring circuit can be predicted by using a simple transmission‐line model. The new oscillator has a characteristic similar to that of a push‐push oscillator. In addition, in comparison with the push‐push oscillator, the new oscillator with one active device can minimize the size and lower the cost. A voltage‐controlled piezoelectric transducer (PET) is used to vary the resonant frequencies of the ring resonator, which in turn tunes the oscillator with a good tuning range of 4.9% at around 12.1 GHz. This tuned oscillator should have many applications in wireless systems. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. 相似文献