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Dual-Responsive Shape Memory and Thermally Reconfigurable Reduced Graphene Oxide-Vitrimer Composites
Guo-kang Chen,Kun Wu,Qian Zhang,Yan-cen Shi,Man-geng Lu 한국고분자학회 2019 Macromolecular Research Vol.27 No.6
In this paper, we have prepared shape memory reduced graphene oxidevitrimer composites via in situ reduction of graphene oxide (GO) during the curing reaction. Because of good compatibility between GO and epoxy resin, reduced graphene oxide (rGO) has a good dispersion in the epoxy matrix. Conventional thermoset shape memory polymers can only maintain one permanent shape, while these obtained composites can be randomly reconfigured into other shapes via dynamic covalent transesterification reaction at 200 °C above transesterification temperature (TV). They can recover quickly from fixed shapes to their initial shapes with shape fixity ratio higher than 95% and shape recovery ratio higher than 97%. Besides, the rGO-vitrimers show good mechanical properties and thermal stabilities. In addition, sequent nearinfrared (NIR) irradiation can control the shape recovery, because rGO can serve as an energy convertor to convert NIR irradiation into thermal energy.
Causal analysis of natural gas station pipelines vibration and reduction measures
Wenwu Yang,Xin Li,Yuhan Tao,Kang Cen,Yunqiao Wen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9
The existing studies on the strong vibration problem of the outbound process pipeline of a natural gas transfer station focus on the pipeline process with a compressor. This work proposes a structural innovation to eliminate the pipeline vibration without compressor by experiment and numerical simulation. A simulation model was established based on the physical dimensions. Hammer test and finite element method validated the proposed model for natural gas stations pipelines. It was found that in branch 1 and 2 occur the first two coupled modes. In addition, three kinds of vibration reduction schemes, such as increasing sleeve and increasing pipe diameter, are proposed to increase the pipe rigidity and reduce the excitation force to control the vibration. It is revealed that adding sleeves to the branch pipes 1 and 2 can better suppress pipe vibration by referring to related evaluation standards. This case shows that performing variable-condition vibration testing and spectrum characteristics analysis of pipelines can easily reveal the main vibration sources and provide solutions for pipeline vibration reduction treatment.