Poly (L-lactide) was grafted onto chitosan by ring-opening copolymerization under microwave irradiation in the presence of tin octoate (Sn (Oct)2) as catalyst. The chemical structure and physical properties of the copolymers with different feeding ratios were discussed by FTIR, DTG and X-RD, taking pure chitosan as reference. The results showed that the application of microwave irradiation in the reaction could achieve the copolymer with high grafting percentage in a short time and low temperature. The thermal stability and crystallinity were decreased with the feeding ratio increasing, attributing to the increasing of grafting percentage.
Thermoelectric energy harvesting is emerging as a promising alternative energy source for drive wireless sensors in mechanical structure monitoring. Typically, the waste heat from spindle units of machine tools creates obvious potential for thermoelectric generation. However, the problem of power gap between the power level needed by wireless sensor and what thermoelectric generators (TEGs) can provide is likely to arise in the application of thermoelectric generation. Therefore, a power management system (PMS) is needed to accumulate TEG energy first and then drive the load intermittently. This study proposes a power management system to enhance the energy harvesting and usage efficiency using three capacitors. A rotating spindle platform is set up to test the PMS, and the experimental result shows that the proposed PMS worked well when the spindle speed is 3000 rpm.
Thermoelectric energy harvesting is emerging as a promising alternative energy source to drive wireless sensors in mechanical, civil, and aerospace engineering systems. Typically, the waste heat from spindle units of machine tools creates obvious potential for thermoelectric generation. The structure of heat sinks on a thermoelectric generator has a great effect on the output voltage of the thermoelectric generator due to the temperature difference between hot and cold sides induced by heat transfer, so several typical structures of heat sinks are studied under different rotation speed of the spindle. According to the simulation study, the thermal resistance of heat sinks was presented. In the experiment, the output voltages of a thermoelectric generator were measured under different rotation speed with different structures of heat sinks. Experiment and simulation shows that the two pipes structure of the heat sink can help the generator to produce more power.
In order to analyze the partial discharge of void defect discharge in solid insulator, for the PD problems that at home and abroad simulation model can’t objectively reflect the physical process of partial discharge. Based on classical three capacitor equivalent-circuit model, the change of the electric field intensity and the voltage as size of the air void differs is studied. The influence of the air void geometry properties of partial discharge is analyzed. By comparing the results of the simulation model and its results and existing research results, the correctness of the circuit simulation model is verified.
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