Wireless sensor networks (WSN), as a new type of environment monitoring system, has became a hot research topic in recent years. This paper mainly focuses on the problem of signal conflicting in WSN. The link quality (quality between two neighboring nodes) can be guaranteed by the layout of network, but, the end-to-end routing quality can not be guaranteed in the same way because of random signal conflicting (even if CSMA/CA is used in WSN). The end-to-end routing will have higher performance if the routing has lower signal conflicting probability. So, the main work of this paper is designing a routing protocol to find out the routing with the lowest signal conflicting probability. This paper proposed a Minimum conflicting probability routing protocol (MCR) in link quality guaranteed WSN. Firstly, MCR combines the degree value with workload of nodes, forming a new degree and cache based routing metric (DBM). Secondly, MCR finds out the best routing by the Random Walk theory on basis of DBM. The simulation results show that, MCR protocol is more effective to avoid the signal conflicting, it has a higher end-to-end reliability and a more stable network throughput than other routing protocols in the same link quality guaranteed WSN.
Cluster-assembled Tb-Fe nanostructured films were prepared by the low energy cluster beam deposition method. The microstructure, magnetization and magnetostriction were investigated for the films. It is shown that the film is assembled by monodisperse spherical nanoparticles with average diameter of ～30?nm which are distributed uniformly. The cluster-assembled Tb-Fe nanostructured films exhibit good magnetization and possess giant magnetostriction with saturation value of ～1060 × 10(-6), much higher than that of the common Tb-Fe films. The origin of good magnetization and giant magnetostriction for the cluster-assembled Tb-Fe nanostructured film was discussed. The present work opens a new avenue to produce the nanostructured magnetostrictive alloy in application of a nano-electro-mechanical system. 相似文献
In the Temecula Valley of California the proximity of citrus groves to vineyards influences the incidence and severity of
Pierce’s disease (PD) in grapes, a disease caused by the gram-negative bacterium, Xylella fastidiosa. Although the glassy-winged sharpshooter (GWSS), the major insect vector of the bacterium, feeds on and moves back and forth
between citrus groves and vineyards, there are no visible symptoms of disease caused by X. fastidiosa in citrus. Previous evidences suggested that while grapevines are susceptible to the PD strain of X. fastidiosa, citrus trees are resistant or tolerant but could be a reservoir to harbor the pathogen for the GWSS acquisition. We investigated
the mechanisms of host plant resistance/susceptibility by examining the in vitro effect of xylem fluid from grapefruit, orange, lemon, and grape on the growth, aggregation, and attachment of a X. fastidiosa strain isolated from grape. Our results revealed that xylem fluid from grapefruit, orange, and lemon trees caused the bacterial
cells to form aggregations of large whitish clumps, whereas the xylem fluid from grape vines created a visible thick biofilm.
The densities of X. fastidiosa cells in grapefruit xylem fluid treatment were significantly higher at 6, 8, and 9 d postinoculation compared with those
in grape xylem fluid treatment. The cell densities of X. fastidiosa cultures in orange or lemon xylem fluid were generally lower than those in grape xylem fluid treatment, whereas citrus xylem
fluid significantly inhibited X. fastidiosa biofilm formation compared to grape xylem fluid. 相似文献
Cationic ring opening polymerization of octamethylcyclotetrasiloxane （Da） initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments.Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance （IH-NMR） and gel perneation chromotography. The width of molecular mass distribution was found ranging between 1.2 and 1.4, which is extraordinarlly narrow compared with that of cationic polymerizations reported elsewhere （〉 1.9）. The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mechanism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated. 相似文献
