Segmented polymer networks containing amino‐dendrimers

Polymer networks in which poly(propylene imine) dendrimers (Astramol?) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry     

井下煤仓全深度分段爆破成井技术

介绍了在煤矿现有设备条件下，全深度一次钻孔分段爆破掘进煤仓的设计与应用情况，论述了爆破方案确定，参数设计及主要措施，通过实践取得了良好效果。     

Increasing Reliability in Cable-Free Radio LANs Low Level Forwarding in HIPERLAN

Radio LANs are emerging in the computing world. They are supported by distinct configurations: on the one hand radio LANs with base stations and a wired backbone, on the other hand radio LANs implementing Intra-forwarding. Adding a new node in a radio LAN with Intra-forwarding, increases the reliability, while this reliability decreases with ad hoc or hub configurations. This advantage of Intra-forwarding is quantified. Intra-forwarding, as defined in the HIPERLAN standard, is based on a hop-by-hop policy and link check procedures. It is shown how point-to-point packets and broadcast packets are forwarded. The three basic components of Intra-forwarding needed to build and update the Intra-forwarding database are described. The originality of this approach is the use of multipoint relays which enable better scalability. The correctness of the Intra-forwarding protocol is proved and its cost is evaluated.     

基于空洞模型的地理位置路由改进算法研究

针对现有WSN中地理位置路由遇路由空洞后会产生冗余路由的问题,提出一种基于感知空洞形状的分段贪婪路由(Easy Modeling Greedy Routing,EMGR)算法。EMGR引入虚拟坐标概念,利用空洞边界探测包收集空洞边界节点信息,将其映射到虚拟坐标系中;根据空洞边界节点在虚拟坐标系的不同分布,定义凹、凸域来概括路由空洞形状;根据不同的空洞形状找到合适的中转节点,采用分段贪婪路由方式传输数据。仿真实验结果表明,相较于GPSR算法,EMGR算法产生的路由跳数减少了35%,网络能耗低,路径扩张率和网络时延小。     

自适应Fourier分解思想在再生核W2 1 [a,b]空间的应用

在再生核$W_2^1[a, b]$空间中研究自适应正交贪婪分解算法, 利用能量下降最快的原理自适应性地构造出最佳$n$项逼近函数, 并从理论上证明其收敛性成立。最后, 实验验证了在$W_2^1[a, b]$再生核空间中, 利用正交贪婪原理构造的$n$项数值原函数比用等分结点构造出的最佳$n$项数值原函数收敛效果更优。     

一种应用层组播可靠性技术

组播是一种高效的多点通信方式,IP组播效率高,但需专门的组播路由器,代价大,至今未能大规模部署.应用层组播数据的复制转发功能由终端主机完成,不涉及现有网络基础设施的更新,在Internet上容易实现,但终端主机的稳定性和安全性不如组播路由器,容易导致单点失效,且数据恢复困难.为解决应用层组播存在的可靠性问题,提出了一种树环结构的应用层组播方案,通过环结构来增加数据传输的可靠性,并采用主动随机转发技术来解决树环结构的多点失效问题.该方案既有效解决了应用层组播可靠传输问题,又降低了恢复时延和系统开销.     

Time-optimized contextual information forwarding in mobile sensor networks

We study on the forwarding of quality contextual information in mobile sensor networks (MSNs). Mobile nodes form ad-hoc distributed processing networks that produce accessible and quality-stamped information about the surrounding environment. Due to the dynamic network topology of such networks the context quality indicators seen by the nodes vary over time. A node delays the context forwarding decision until context of better quality is attained. Moreover, nodes have limited resources, thus, they have to balance between energy conservation and quality of context. We propose a time-optimized, distributed decision making model for forwarding context in a MSN based on the theory of optimal stopping. We compare our findings with certain context forwarding schemes found in the literature and pinpoint the advantages of the proposed model.     

Gas-liquid mass transfer in taylor flow through a capillary

The gas-liquid mass transfer in two-phase flow through a capillary has been measured for water-air, ethanol-air and ethylene glycol-air systems. A semi-theoretical model has been developed and compared with experimental results. and a full computer simulations of the flow pattern and mass transfer using a flow simulation program have been made. The measured values are about 30% less than the calculated values.     

Context-aware adaptive IP mobility anchoring

The novel distributed mobility management trend is a promising direction to cope with the increasing mobile data traffic and flatten network architectures. Most of the novel mobility approaches distribute the mobility anchors through the access level, as opposed to the centralized mobility anchoring model. Other recent approaches argue that mobility anchors closer to the content servers may be the solution to optimize the mobility performance. However, none of the mobility anchoring models is ideal for all scenarios, since it depends on the user, the session and the network. Hence, we propose an IP mobility approach driven by the context of the user, sessions and the network, where the mobility anchors for IP address allocation and for routing/forwarding are distributed through the network nodes, while the mobility context is managed by the mobile devices. Although each session is properly anchored in the establishment phase, the routing/forwarding is adapted over time, according to the user, the session and the network context: the proposed approach is able to signal different mobility anchors to optimize the routing path to new and ongoing sessions of the user. The outcome of the evaluation shows that the proposed approach overall reduces the data cost, the data delay, the tunneled packets and the tunnel length, when compared with other anchoring models.     

基于贪心核特征提取方法的中期峰值负荷预测

针对中期电力负荷预测, 提出基于贪心核主元回归(GKPCR)、贪心核岭回归(GKRR) 的特征提取建模方法. 通过对核矩阵的稀疏逼近, GKPCR和GKRR两种贪心核特征提取方法旨在寻找特征空间中数据的低维表示, 计算需求低, 适用于大数据集的在线学习. 将所提出的方法应用于不同地区的电力负荷中期峰值预测, 并与现有预测方法进行了比较. 实验结果表明, 在同等条件下, 所提出的方法能有效地改进预测精度, 而且性能更好, 显示了其有效性和应用潜力.