共查询到17条相似文献,搜索用时 140 毫秒
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IEEE1588协议定义的精确时间协议(Precision Time Protocol,PTP)能够实现地面以太网网络节点中的时钟同步,达到亚微秒级时间同步精度。相比于稳定的地面以太网环境,深空网络环境具有长时延、时延抖动及信道不对称等特点。对PTP协议在深空邻近空间无线信道下的时间同步性能进行了研究。首先,介绍了PTP协议的同步原理。其次,对深空邻近无线网络信道环境对于适用于地面以太网环境的PTP协议时间同步性能的影响进行了分析,并提出采用卡尔曼滤波算法和设定主从时钟钟差阈值相结合的方法,对PTP协议进行适应性改进。最后,采用损伤仪和测试仪模拟深空邻近无线网络信道环境,利用时钟分析仪对软件结合硬件实现的PTP协议进行了时间同步性能测试。测试结果表明,改进后的PTP协议提高了在深空邻近空间无线信道下时间同步的精度和稳定性。 相似文献
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《计算机测量与控制》2014,(4)
随着网络技术的飞速发展,分布式应用系统的规模越来越大,网络中各远距离节点间的时间同步性要求越来越高;这种高同步性要求在诸如分布式数据采集和测试测量系统中尤为重要。IEEE 1588——精确时间协议(PTP,Precision Time Protocol)为此提供了一个很好的解决方案,它是一种主要基于以太网的精确时钟同步技术,其同步成本低、精度高、协议开放,广泛应用于各种通信、测试测量设备;文章着重介绍了如何在分布式数据采集系统中实现IEEE 1588PTP协议,其实现原理可应用到其它类似基于IEEE 1588PTP协议的分布式应用中;采用此方法构建的分布式数据采集系统同步精度达到了纳秒级。 相似文献
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IEEE 1588时钟同步协议用于解决分布式网络测控系统中远距离仪器设备之间的同步问题;在分析IEEE 1588时钟同步实现原理的基础上,提出一种嵌入式Linux设备的高精度IEEE 1588时钟同步实现方案;采用专用PHY芯片DP83640在物理层为PTP报文加盖硬件时间戳,设计网络设备驱动与PTP硬件时钟控制驱动,并在用户层利用Linux系统标准API实现IEEE 1588协议软件;实验结果表明,两台设备直接相连时,时钟同步精度可稳定在±100ns以内。 相似文献
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为了解决飞行试验复杂遥测网络系统中各子系统间的时间同步问题,文章从探讨遥测网络中试验对象节点之间的时间同步概念着手,介绍了使用网络时间同步协议(NTP)或精确时钟同步协议(PTP)实现遥测网络试验对象节点间时间同步的原理和方法,提出了一种基于IEEE 1588协议的遥测网络时间同步技术实现方案和时间同步检测方法,分析了遥测网络传输时延和影响试验对象节点之间时间同步的主要因素,并给出了修正思路。该技术和方法为未来空地一体化综合测试网络时间同步提供了借鉴作用。 相似文献
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该文基于IEEE1588精准时间同步协议(PTP协议),结合DP83640以太网控制芯片阐述了PTP协议同步报文发送和接收原理,通过在物理层加盖时间戳和调节本地时钟的频率和相位,DP83640能够提供精准的IEEE1588时钟,有效地解决由于软件带来的时钟抖动问题。 相似文献
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该文基于IEEE1588精准时间同步协议(PTP协议),结合DP83640以太网控制芯片阐述了PTP协议同步报文发送和接收原理,通过在物理层加盖时间戳和调节本地时钟的频率和相位,DP83640能够提供精准的IEEE1588时钟,有效地解决由于软件带来的时钟抖动问题。 相似文献
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详细讲述了PTP(precise time protocol)的时钟同步原理,分析了影响时钟同步精度的因素,并给出了一种在基于LAN的ARM硬件平台上纯软件实现IEEE1588协议的方案. 相似文献
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This paper describes the use of peak-to-peak (PTP) force diagrams for machining stability prediction and validates its suitability for milling processes where the workpiece is considerably more flexible than the machine-tool system. These diagrams result from numerous executions of a time domain simulation which includes both the tool and workpiece dynamics and a mechanistic force model. The applicability of the PTP force diagram is validated experimentally through peripheral milling tests of thin-walled structures. Measured and simulated cutting forces are compared. It is shown that the PTP diagrams offer the global stability information which is provided by the traditional lobe diagram, while preserving the detailed, local information provided by time domain simulation. 相似文献
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PTP1B plays an important role as a negative regulator in insulin and leptin signaling pathways. Potent and orally active PTP1B inhibitors can act as potential agents for the treatment of Type 2 diabetes and obesity. CoMFA (Comparative Molecular Field Analysis) and de novo ligand design using LeapFrog (LF) studies were performed on pyridazine analogs, reported to be selective and non-competitive inhibitors of PTP1B. A robust model was developed which produced statistically significant results with cross-validated and conventional correlation coefficients of 0.619 and 0.990, respectively. Further, the robustness of the model was verified by bootstrapping analysis. LeapFrog (LF) program is a de novo drug discovery tool, which uses CoMFA maps to generate hypothetical cavity and ligands. As the crystal structure of PTP1B-pyridazine complex is not yet known, the contours of CoMFA model was used to serve as a pharmacophoric model to generate hypothetical cavity for LeapFrog calculations. Ligands were optimized using this concept. 相似文献
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M. Dell'Amico F. Maffioli P. Vrbrand 《International Transactions in Operational Research》1995,2(3):297-308
We consider a variant of the Travelling Salesman Problem which is to determine a tour visiting each vertex in the graph at most at one time; if a vertex is left unrouted a given penalty has to be paid. The objective function is to find a balance between these penalties and the cost of the tour. We call this problem the Profitable Tour Problem(PTP). If, in addition, each vertex is associated with a prize and there is a knapsack constraint which guarantees that a sufficiently large prize is collected, we have the well-known Prize-collecting Travelling Salesman Problem (PCTSP). In this paper we summarize the main results presented in the literature, then we give lower bounds for the asymmetric version of PTP and PCTSP. Moreover, we show, through computational experiments, that large size instances of the asymmetric PTP can be solved exactly. 相似文献