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移动自组织网络的动态拓扑特性给其分簇路由协议的设计带来了一定的挑战,而分簇算法作为分簇路由协议中重要的技术手段,如何建立一种有效稳定的分簇机制,对分簇路由协议的性能至关重要。本文在大规模网络环境下,提出一种稳定的分簇算法,并在此基础上提出一种分簇路由协议。为提高网络性能,该分簇路由协议簇间采用被动模式,簇内采用主动模式,并且各个分簇由簇首、网关、访客和普通簇节点组成。仿真结果表明:该分簇算法减少了簇的数量和簇成员在簇间的切换次数,提高了分簇的稳定性。相应的分簇路由协议较该类协议也降低了网络的平均端到端时延和平均路由开销,提高了数据包接收的成功率。 相似文献
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微重力作为典型的空间环境因素,对植物生长发育的影响机制是空间生命科学的研究热点。微重力环境直接或间接影响植物代谢,并引起许多生理适应。 随着系统生物学的发展,代谢网络模型使微重力环境下的植物代谢建模成为可能。采用流平衡分析方法对模式植物拟南芥不同组织的代谢网络进行分析,研究微重力对拟南芥生长发育的影响机制。通过比较空间与地面条件下拟南芥的生物质产量,发现空间条件下拟南芥黄化幼苗、幼苗、芽、根、下胚轴的生物量分别下降了33.00%,51.52%,6.89%,12.53%,11.70%,与空间环境下拟南芥的长势变化趋势一致。代谢通路富集分析发现,微重力使得拟南芥的碳固定等通路下调,而磷酸戊糖途径上调,初步解析了微重力对拟南芥生长发育的影响机制,也验证了流平衡方法用于微重力生物学效应研究中的可行性。 相似文献
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对比分析了目前2种BACnet(楼宇自动控制网络数据通信协议)与Internet的互联技术,即B/IP PAD(BACnet/Internet协议包封装/拆装设备)和BACnet/IP,并指出了这2种技术所存在的问题.提出了一种基于BACnet网关的互联模型,此网关工作在BACnet网络层,需要配置一个独立的IP地址和一个BACnet网络号,同时也必须维护一个对等网关的IP地址与BACnet网络号的本地数据库.该模型通过BACnet网关来完成不同协议之间的语义转换、广播及管理等功能,为BACnet网络与Internet之间提供了统一的网络接口,增强了楼宇控制网络与Internet融合的能力,并大大简化了BACnet网络与Internet的互联过程.在研究此模型的体系结构和工作流程的基础上探讨了该模型的实现方法. 相似文献
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1 前言
在,人类环境和地球未来的可持续发展问题是世界各国关注的焦点.欧洲为了表明它在制定区域性国际政策、提出可持续发展议程,以及必要时商讨国际协议等方面的能力,已正式启动了“全球环境和安全监测”(GMES)计划.该计划将联合欧洲各自分散的对地观测力量,使其成为综合的观测网络,并能提供运营服务. 相似文献
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强实时条件下光纤通道仲裁环带宽分配方法 总被引:7,自引:0,他引:7
光纤通道是一个为适应高性能信息传输要求而提出的计算机通讯协议,仲裁环是光纤通道的基本拓扑结构之一.为解决网络消息集实时发送的问题,研究了光纤通道仲裁环拓扑在强实时条件下的通信性能.依据实时系统中的周期任务模型和光纤通道仲裁环协议规定的访问公平机制,采用负载匹配算法提出了一种适用于仲裁环网络的带宽分配方法.推导并证明了采用该方法时在最坏情况下消息集强实时的网络可达负载率不低于50%. 相似文献
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无线传感器网络(WSNs)的应用前景非常广阔,得到了越来越广泛的关注,其中网络节能、降低功耗、延长寿命是WSNs必须解决的问题。对WSNs中典型的分簇路由协议进行了详细分析,通过对比研究,提出了一种基于节点间相关性的能量有效分簇路由协议——BCCP协议。在BCCP协议中,能耗均衡分簇算法利用节点间位置相关性与节点剩余能量,降低分簇迭代次数,得到分布均匀的簇首节点,降低簇内成员节点与簇首节点的通信能耗,以此降低网络能耗;降低能耗分簇算法利用节点间数据相似性与节点间协同性,降低簇内通信、簇间通信的数据量,以此降低网络能耗。实验结果表明,BCCP协议在能耗均衡、网络存活节点数、降低能耗方面与其他方法相比均有明显的优势。 相似文献
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确定性网络的同步性在航天电子系统中至关重要。为保证确定性网络在发生故障的情况下也能正常地进行时间同步,采用spaceVPX标准中典型的双星拓扑交换结构,配置基于时间触发以太网协议的可容错系统。针对此架构,对使用以太网的航天系统中发生故障的单容错结构进行了仿真,并模拟了几种时间同步协议控制帧异常的情况:协议控制帧包括冷启动帧、冷启动应答帧、集成帧,从故障交换机的端口发送到网络中的一个终端系统后,对于时间触发网络的同步网络所产生的影响。仿真结果表明,故障交换机会逐渐延长处于正常工作的终端系统的启动时间,不利于整个确定网络系统的同步过程,但是,如果设置不同协议控制帧的周期超过一定的数值后,单点故障不会影响双冗余系统的启动时间。 相似文献
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确定性无线传感器网络定向扩散路由协议 总被引:1,自引:0,他引:1
提出了一种新的确定性无线传感器网络定向扩散路由协议以延长网络生存期.Sink以泛洪方式周期性地广播Interest,网络节点依据收到Interest的时间先后设置与邻近节点的梯度值,最先到达的梯度值最大.选择梯度最大方向上的节点建立数据传输路径.通过调整剩余能量的阈值限制低能量节点加入路径以均衡节点能耗.定性分析和仿真结果表明,在单sink单事件及多sink多事件应用场合,所提出的协议在能耗及可靠性方面均优于定向扩散协议,且更易于实际实现.同时定性分析还说明所提协议能获得更好的时延及时延抖动性能. 相似文献
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H. Cottin P. Coll D. Coscia N. Fray Y.Y. Guan F. Macari F. Raulin C. Rivron F. Stalport C. Szopa D. Chaput M. Viso M. Bertrand A. Chabin L. Thirkell F. Westall A. Brack 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments. 相似文献
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空间数据系统咨询委员会(CCSDS)针对空间通信的特点制定了空间通信协议标准SCPS(Space Communications Protocal Specification)。文章从CCSDS标准在中国空间技术的实际应用出发,对CCSDS SCPS协议中网络层协议(NP)和传输层协议(TP)进行研究,分析其特点和适用性,并与TCP/IP协议进行对比,最后设计演示验证系统对所提方案进行验证并得出结论:在空间通信环境下,采用SCPS协议后的性能优于采用TCP/IP协议。 相似文献
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The Strategic Priority Program on Space Science in 2011-2017 (hereafter referred to as SPP I), which officially went ahead in 2011, marks that a new chapter of Chinese space endeavor has been opened. The 4 satellites, Wukong/DAMPE, SJ-10, Mozi/QUESS and Insight/HXMT, has been achieving promising scientific results since their launch, e.g., Wukong directly detected a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons. To enable the sustainable development of China's space science endeavor, the Strategic Priority Program Ⅱ on Space Science (hereafter referred to as SPP Ⅱ) was officially approved in late 2017. SPP Ⅱ includes 4 satellites-EP, ASO-S, SMILE and GECAM, Intensive Study of Future Space Science Missions, Advanced Research of Space Science Missions and Payloads, Space Science Mission Concept Research, and Data Analysis Research. Dedicated to exploring the unknown, the program is aiming to address scientific questions such as the origin and evolution of the universe and life, search for extraterrestrial life, and the impact of the Sun and the solar system on Earth and human development. Chinese space science community is committed to contributing to the progress of human civilization. 相似文献
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Pietro Ubertini Neil Gehrels Ian Corbett Paolo de Bernardis Marcos Machado Matt Griffin Michael Hauser Ravinder K. Manchanda Nobuyuki Kawai Shuang-Nan Zhang Mikhail Pavlinsky 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The use of space techniques continues to play a key role in the advance of astrophysics by providing access to the entire electromagnetic spectrum from radio to high energy γ rays. The increasing size, complexity and cost of large space observatories places a growing emphasis on international collaboration. Furthermore, combining existing and future datasets from space and “ground based” observatories is an emerging mode of powerful and relatively inexpensive research to address problems that can only be tackled by the application of large multi-wavelength observations. While the present set of astronomical facilities is impressive and covers the entire electromagnetic spectrum, with complementary space and “ground based” telescopes, the situation in the next 10–20 years is of critical concern. The James Webb Space Telescope (JWST), to be launched not earlier than 2018, is the only approved future major space astronomy mission. Other major highly recommended space astronomy missions, such as the Wide-field Infrared Survey Telescope (WFIRST), the International X-ray Observatory (IXO), Large Interferometer Space Antenna (LISA) and the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), have yet to be approved for development. 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(9):2223-2234
Since more than one decade ago, several institutions started to offer a large variety of Operative Space Weather (SWx) products. This is of major importance because Space Weather events can affect aviation communications, global positioning systems, grid electric power, satellite technologies, and human health in space. The scientific potential on solar-terrestrial physics in Argentina motivated the creation of an interdisciplinary Laboratory of Space Weather in Argentina. The Argentinean Space Weather Laboratory (in Spanish ‘Laboratorio Argentino de Meteorología del esPacio’, LAMP) was initiated in 2016, and it carries out daily monitoring of real-time information (space and ground-based instruments) on Space Weather. The information is synthesized on a weekly bulletin as a summary of the Space Weather conditions, and it is posted on a website (spaceweather.at.fcen.uba.ar). The analyzed information includes own data and of other centers that offer them publicly, and it is also analyzed and discussed later on, during monthly briefings. In particular, one of the regional products that is included in the briefing discussions and it was developed by LAMP in collaboration with INPE-EMBRACE, involves Vertical Total Electron Content (VTEC) maps in the Argentinean region. LAMP set up a Space Weather Laboratory in the Antarctic peninsula, in the Argentine Marambio base, where a Water Cherenkov radiation Detector (WCD) was installed during the Argentinean Antarctic campaign (January-March of 2019). This detector is the southern node of a Latin American Collaboration (LAGO, Latin American Giant Observatory), which is a network of WCDs installed throughout more than 10 Latin American countries. 相似文献
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Martin Schlueter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
A numerical study of the MIDACO optimization software on the well known GTOP benchmark set, published by the European Space Agency (ESA), is presented. The GTOP database provides trajectory models of real-world interplanetary space missions such as Cassini, Messenger or Rosetta. The trajectory models are formulated as constrained nonlinear optimization problems and are known to be difficult to solve. 相似文献