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基于效用EPON分布式动态带宽分配实现机制 被引量:9
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作者 张晋豫 刘犁 《软件学报》 EI CSCD 北大核心 2008年第7期1693-1706,共14页
EPON(Ethernet-based passive optical network)作为基于光纤的宽带网络接入技术,已经成为下一代接入网络的关键技术之一,但是IEEE 802.3ah EPON的Polling机制存在带宽使用率不高的问题,其DBA(dynamic bandwidth allocation)算法产生UWR... EPON(Ethernet-based passive optical network)作为基于光纤的宽带网络接入技术,已经成为下一代接入网络的关键技术之一,但是IEEE 802.3ah EPON的Polling机制存在带宽使用率不高的问题,其DBA(dynamic bandwidth allocation)算法产生UWR(unused window remainder),USR(unused slot remainder),UQR(unused queue remainder)和UPR(unused package remainder),浪费了许多带宽资源.IPACT(interleaved polling with adaptive cycle time)EPON提出了一个带宽使用率较高的新的Poling机制,但没有解决DBA算法存在的缺点.在IPACT基础上,提出了一个基于效用的分布式EPON DBA实现机制,实现了对不同SLA(service level agreement)用户的相同业务类应用的差分处理.通过一种集中递归效用算法,有效地消除了再生UWR,通过一种分布式递归效用算法,有效地消除了UQR,通过一个分布式UPR消除机制,减少了UPR.提出了一个基于交织接力棒的USR消除机制,提高了消除USR条件满足的概率,通过将交棒者的USR追加到接棒者的授权中,提高了带宽的使用效率.仿真结果很好地验证了该机制的优点. 展开更多
关键词 以太无源光网络 动态带宽分配 服务质量 服务等级协议
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Design of Greenhouse Environment Control System Based on Internet of Things 被引量:9
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作者 Shen Wei-zheng Wang Shi-yu +2 位作者 Nagi Eltieb Babker Eltieb Hou Han-dan Zheng Cheng 《Journal of Northeast Agricultural University(English Edition)》 CAS 2018年第2期54-64,共11页
There are some disadvantages, such as complicated wiring, high cost, poor monitoring flexibility, low accuracy and high energy consumption in traditional greenhouse environment monitoring system which based on previou... There are some disadvantages, such as complicated wiring, high cost, poor monitoring flexibility, low accuracy and high energy consumption in traditional greenhouse environment monitoring system which based on previous wireless sensor networks (WSN). Aiming at these problems, a greenhouse environmental parameter monitoring system had been designed based on internet of things technology in this paper. A set of control system with good robustness, strong adaptive ability and small overshoot was set up by combining the fuzzy proportion-integral-derivative (PID) control. The system was composed of a number of independent greenhouse monitoring systems. The server could provide remote monitoring access management services after the collected data were transmitted. The data transmission part of greenhouse was based on ZigBee networking protocol. And the data were sent to intelligent system via gateway connected to the internet. Compared to the classical PID control and fuzzy control, the fuzzy PID control could quickly and accurately adjust the corresponding parameters to the set target. The overshoot was also relatively small. The simulation results showed that the amount of overshoot was reduced 20% compared with classical PID control. 展开更多
关键词 GREENHOUSE environmental monitoring remote service fuzzy PID control
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Plane extraction for navigation of humanoid robot
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作者 张彤 肖南峰 《Journal of Central South University》 SCIE EI CAS 2011年第3期627-632,共6页
In order to make the humanoid robot walk freely in complicated circumstance, the reliable capabilities for obtaining plane information from its surroundings are demanded. A system for extracting planes from data taken... In order to make the humanoid robot walk freely in complicated circumstance, the reliable capabilities for obtaining plane information from its surroundings are demanded. A system for extracting planes from data taken by stereo vision was presented, After the depth image was obtained, the pixels of each line were scanned and split into straight line segments. The neighbouring relation of line segments was kept in link structure. The groups of three line segments were selected as seed regions. A queue was maintained for storing seed regions, and then the plane region was expanded around the seed region. The process of region growing continued until the queue of seed regions was empty. After trimming, the edges of the planes became smooth. In the end, extracted planes were obtained. In the experiment, two models were used: pipe and stairs. Two planes in pipe mode/and six planes in stairs model were extracted exactly. The speed and precision of algorithm can satisfy the demands of humanoid robot's navigation. 展开更多
关键词 humanoid robot NAVIGATION line segments splitting region growing plane extraction depth image
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