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以太网工厂自动化协议中确定性调度的研究与实现 被引量:10
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作者 孙攀 王平 谢昊飞 《计算机集成制造系统》 EI CSCD 北大核心 2007年第3期563-567,共5页
工业自动化采用以太网协议,参考了传输控制协议/网络协议的组织方式,分为物理层、数据链路层、网络层、应用层,并在其上层增加了用户层。在数据链路层,将用户层的报文分为周期报文和非周期报文,根据设备组态信息,使周期报文按照固定的... 工业自动化采用以太网协议,参考了传输控制协议/网络协议的组织方式,分为物理层、数据链路层、网络层、应用层,并在其上层增加了用户层。在数据链路层,将用户层的报文分为周期报文和非周期报文,根据设备组态信息,使周期报文按照固定的时间片发送,而非周期报文按照报文优先级大小发送,即确定性调度。运用该技术使以太网工厂自动化网络有效地避免了乱序、丢包、重发报文等情况,保证了以太网网络中报文传输的确定性和实时性。测试结果表明,所提出的调度算法完全符合以太网协议规范,精度可达到微秒级。 展开更多
关键词 以太网工厂自动化 通信调度实体 确定性调度 宏周期
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一种基于EPA标准的无线调度算法 被引量:1
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作者 高汉荣 冯冬芹 张赫男 《传感技术学报》 CAS CSCD 北大核心 2010年第2期269-273,共5页
据工业现场不同数据具有不同实时性要求的特点,在EPA有线调度算法的基础上提出了一种基于TDMA的无线调度算法。该算法根据不同的实时性要求将一个通信宏周期分为周期报文传输阶段和非周期报文传输阶段。在周期报文传输阶段,每个设备都... 据工业现场不同数据具有不同实时性要求的特点,在EPA有线调度算法的基础上提出了一种基于TDMA的无线调度算法。该算法根据不同的实时性要求将一个通信宏周期分为周期报文传输阶段和非周期报文传输阶段。在周期报文传输阶段,每个设备都被分配了时间片用于传输数据实时性要求比较高的数据,在非周期报文传输阶段,网关设备按照非周期报文的不同优先级为各设备分配时间片,该算法同时保证了通信的确定性和实时性。还提出了一种该算法通信宏周期、周期报文传输阶段长度和非周期报文传输阶段长度的确定方法。通过树型网络进行测试,结果表明该调度算法具有较低的丢包率。 展开更多
关键词 无线调度算法 EPA TDMA 通信宏周期确定
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分布式网络冗余技术对高可用性网络的贡献 被引量:4
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作者 薛百华 《仪器仪表标准化与计量》 2011年第1期31-33,48,共4页
本文介绍了分布式网络冗余协议制订的背景,分析了固定根节点的快速冗余技术和快速生成树协议组成工业控制网络的缺点和网络维护原理,并重点描述分布式网络冗余协议定义的报文类型、克服固定根节点的快速冗余技术和快速生成树协议的不足... 本文介绍了分布式网络冗余协议制订的背景,分析了固定根节点的快速冗余技术和快速生成树协议组成工业控制网络的缺点和网络维护原理,并重点描述分布式网络冗余协议定义的报文类型、克服固定根节点的快速冗余技术和快速生成树协议的不足之处的实现过程和对高可用性网络的贡献。最后简述了分布式网络冗余协议目前的应用和未来的发展方向。 展开更多
关键词 DRP 环网冗余 宏周期 高可用性
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Dynamics and Relationships of Ca,Mg,Fe in Litter,Soil Fauna and Soil in Pinus koraiensis-Broadleaf Mixed Forest 被引量:21
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作者 SONG Bo YIN Xiuqin +1 位作者 ZHANG Yu DONG Weihua 《Chinese Geographical Science》 SCIE CSCD 2008年第3期284-290,共7页
The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area. The authors collected the samples of forest litter (Tilia amurensis, Fraxinus mandshurica, Pinus koraiensis, Acer mono, ... The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area. The authors collected the samples of forest litter (Tilia amurensis, Fraxinus mandshurica, Pinus koraiensis, Acer mono, Betula costata, and mixed litter), soil in humus horizon (0--5cm) and soil horizon (5-20cm), and soil macrofauna (Oligochaeta, Geophiloporpha and Juliformia) from 2001 to 2002. The role of soil macrofauna in the material cycle was analyzed through comparing the macro-element contents among various parts of the subsystems and using enrichment index (El). The results indicate that dynamic changes of various litters are very complicated. The contents of Fe in each kind of litter increase firstly, and then decrease in the study period. The changes of macro-element contents are greater in the broad-leaf litter than in the coniferous litter, and the mixed litter is in the middle level, but the differences among them are not significant. The contents of Mg and Fe in humus are higher than those in soil, but the contents of Ca in soil are higher than that in humus. The dynamic changes of macro-element contents in soil and soil fauna are not consistent with those in litter. The diplopod presented obvious enrichment of Ca and Mg (E1〉1), but it does not significantly enrich Fe. Earthworm has a stronger enrichment ability of Fe than diplopod and scolopendra, but E1〈1. Soil fauna can make great influences on the material cycle of the subsystems. 展开更多
关键词 soil fauna litter decomposition macro-element cycle Liangshui Natural Reserve
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Ground State Properties of Superheavy Nuclei in Macroscopic-Microscopic Model 被引量:1
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作者 ZHI Qi-Jun REN Zhong-Zhou +1 位作者 ZHANG Xiao-Ping ZHENG Qiang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2008年第9期707-714,共8页
The ground state properties of superheavy nuclei are systematically calculated by the macroscopic-microscopic (MM) model with the Nilsson potential.The calculations well produced the ground state binding energies,α-d... The ground state properties of superheavy nuclei are systematically calculated by the macroscopic-microscopic (MM) model with the Nilsson potential.The calculations well produced the ground state binding energies,α-decay energies,and half lives of superheavy nuclei.The calculated results are systematically compared with availableexperimental data.The calculated results are also compared with theoretical results from other MM models and fromrelativistic mean-field model.The calculations and comparisons show that the MM model is reliable in superheavy regionand that the MM model results are not very sensitive to the choice of microscopic single-particle potential. 展开更多
关键词 macroscopic-microscopic model.superheavy nuclei binding energy half life
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Laser-Manipulating Macroscopic Quantum States of a Bose-Einstein Condensate Held in a Kronig-Penny Potential
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作者 ZHU Qian-Quan HAI Wen-Hua DENG Hai-Ming 《Communications in Theoretical Physics》 SCIE CAS CSCD 2009年第7期68-74,共7页
We investigate the boundary vaJue problem (BVP) of a quasi-one-dimensional Gross-Pitaevskii equation with the Kronig-Penney potential (KPP) of period d, which governs a repulsive Bose-Einstein condensate. Under th... We investigate the boundary vaJue problem (BVP) of a quasi-one-dimensional Gross-Pitaevskii equation with the Kronig-Penney potential (KPP) of period d, which governs a repulsive Bose-Einstein condensate. Under the zero and periodic boundary conditions, we show how to determine n exact stationary eigenstates {Rn} corresponding to different chemical potentials {μn} from the known solutions of the system. The n-th eigenstate P~ is the Jacobian elliptic function with period 2din for n = 1,2,…, and with zero points containing the potential barrier positions. So Rn is differentiable at any spatial point and R2 describes n complete wave-packets in each period of the KPP. It is revealed that one can use a laser pulse modeled by a 5 potential at site xi to manipulate the transitions from the states of {Rn} with zero Point x≠xi to the states of {Rn'} with zero Point x= Xi. The results suggest an experimental scheme for applying BEC to test the BVP and to observe the macroscopic quantum transitions. 展开更多
关键词 Bose-Einstein Condenstate Kronig-Penney potential boundary value problem laser-manipulating macroscopic quantum state
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