study on qos-based routing algorithm for double-layered satellite networks

具有星际链路的双层通信星座网络可为全球提供宽带实时多媒体通信服务,路由算法设计是其中关键技术之一.本文详细介绍了由低轨卫星与中轨卫星构成的空间信息通信网双层星座系统体系结构,提出了一种新的具有QoS保证的双层卫星网络路由算法.仿真结果表明提出的路由算法可以满足系统的QoS业务要求的延迟、丢包率与抖动等指标

a time-division qos routing protocol for three-layered satellite networks

提出了一种基于低轨/中轨/高轨(LEO/MEO/GEO)卫星网络体系结构(TLSN)和时空分割思想的QoS路由协议(TDRP),详细阐述了时空分割思想和时隙优化方法,重点研究了QoS路由的实现框架和路由算法(BDA)的实现原理.在此基础上,卫星网络体系结构和路由协议的性能得到了详细分析和仿真验证.相同负载情况下,TLSN中端到端时延和时延抖动性能明显好于LEO卫星网络;同Dijkstra算法相比,BDA算法在端到端时延、时延抖动、丢包率、吞吐量方面具有更好的QoS保证能力

Effect of PEG Molecular Weight in Hydrophilic-segment on the Crystallization of Cast Film of Water-borne Polyurethane

采用二级扩链技术 ,合成了同时具备阴离子型和非离子型大分子链结构的水性聚氨酯分散液 .以红外光谱技术 ,就预聚反应时间和温度对反应程度的影响进行了表征 ,认为当初始合成温度为 70℃时 ,以丁酮为稀释剂、DMPA为离子型亲水单体、乙二醇为一级扩链剂、三乙胺为中和剂、三乙烯四胺为二级扩链剂 ,控制nNCO/nOH=1.3,预聚反应 5h ,扩链反应 2～ 4h ,可获得具有良好稳定性的水性聚氨酯分散液 .采用XRD、DSC等技术 ,研究了亲水链段PEG分子量对水性聚氨酯浇铸膜结晶性的影响 ,证实了所合成的水性PU结晶形态属于单斜晶系 ,且软链段结晶致密程度随PEG分子量的增大而增加The polyurathane are the segmented copolymers that consist of alternating soft and hard segment units. In order to obtain a better synthesizing way of water borne polyurethane (WBPU) dispersion, the WBPU whose macromolecular chain structure combined of anionic and nonionic types was prepared by a new technology of second order expanded chain. Quasi quantitative analytical method of FTIR spectra was adopted to characterize the effect of pre polymerization's condition(time & temperature)on pre polymerization's process, and the stable WBPU dispersion was obtained in the following optimal condition: 70 ℃, dimethylolpropionic acid(DMPA) as ionic hydrophilic monomer, polyethylene glycol(PEG) as first order expanded chain agent, triethylamine(TEA) as neutralizing agent, triethylenetetramine (TETA) as second order expanded chain agent, n NCO /n OH =1.3, prepolymerization period 5 h, and expanded chain period 2～4 h. It was indicated by test of forming cast film that it was easy to form cast film with higher PEG molecule weight. Wide angle X ray diffraction (XRD), differential scanning calorimetric (DSC) methods were used to study the effect of PEG molecular weight in hydrophilic segment on the crystallization of WBPU cast films. The results indicated that crystal form of WBPU was monoclinic, and along with the PEG molecule weight increased, the percentage of soft segment and molecular chain pliancy increased resulting in higher crystallinity and tightness