• Enhanced dielectric properties of immiscible poly (vinylidene fluoride)/low density polyethylene blends by inducing multilayered and orientated structures

      Lin, X.; Fan, L.; Ren, D.; Jiao, Z.; Yang, W.; Coates, Philip D. (2017-04-01)
      In order to improve the frequency-dependent dielectric properties of the immiscible polymeric blends which were melt-compounded by composing poly (vinylidene fluoride) (PVDF) and low density polyethylene (LDPE), the layer multiplication and the solid phase orientation technologies were respectively adopted as two effective strategies to optimize the dispersion state and the orientation of internal microstructure, aiming at reducing physical porosity and improving the barrier performance as well as crystal phase of the polymer extrudates. Results comparison showed the dielectric properties were greatly dependent on the crystal type and the physical porosity density which were also emphasized as the interfacial effect in the previous work [ref. 29: Lin X et al, J Appl Polym Sci 2015; 132(36), 42507]. It was found that the multilayer-structure manipulation could substantially improve the dispersion state between the two immiscible components, enhance the mechanical performance and reduce the internal defects and increase the dielectric constant while keeping the dielectric loss stable. By uniaxial stretching the sample sheets at a rubber state temperature of ca. 10-20˚C below the melting point, crystal transformation was induced by increasing molecular chains orientation degree which was also contributed to the enhancement of the dielectric properties. These techniques implied the potential as a promising way for inducing functional structures of polymeric blends.
    • Software rejuvenation in cluster computing systems with dependency between nodes

      Yang, M.; Min, Geyong; Yang, W.; Li, Z. (2014)
      Software rejuvenation is a preventive and proactive fault management technique that is particularly useful for counteracting the phenomenon of software aging, aimed at cleaning up the system internal state to prevent the occurrence of future failure. The increasing interest in combing software rejuvenation with cluster systems has given rise to a prolific research activity in recent years. However, so far there have been few reports on the dependency between nodes in cluster systems when software rejuvenation is applied. This paper investigates the software rejuvenation policy for cluster computing systems with dependency between nodes, and reconstructs an stochastic reward net model of the software rejuvenation in such cluster systems. Simulation experiments and results reveal that the software rejuvenation strategy can decrease the failure rate and increase the availability of the cluster system. It also shows that the dependency between nodes affects software rejuvenation policy. Based on the theoretic analysis of the software rejuvenation model, a prototype is implemented on the Smart Platform cluster computing system. Performance measurement is carried out on this prototype, and experimental results reveal that software rejuvenation can effectively prevent systems from entering into disabled states, and thereby improving the ability of software fault-tolerance and the availability of cluster computing systems.