ABSTRACT
In order to make a piezoelectric vibration energy harvester collect more energy on a broader frequency range, nonlinearity is introduced into the system, allowing the harvester to produce multiple steady states and deflecting the frequency response curve. However, the harvester can easily maintain intra-well motion rather than inter-well motion, which seriously affects its efficiency. The aim of this paper is to analyze how to take full advantage of the nonlinear characteristics to widen the bandwidth of the piezoelectric vibration energy harvester and obtain more energy. The influence of the inter-permanent magnet torque on the bending of the piezoelectric cantilever beam is considered in the theoretical modeling. The approximate analytical solutions of the primary and 1/3 subharmonic resonance of the harvester are obtained by using the complex dynamic frequency (CDF) method so as to compare the energy acquisition effect of the primary resonance and subharmonic resonance, determine the generation conditions of subharmonic resonance, and analyze the effect of primary resonance and subharmonic resonance on broadening the bandwidth of the harvester under different external excitations. The results show that the torque significantly affects the equilibrium point and piezoelectric output of the harvester. The effective frequency band of the bistable nonlinear energy harvester is 270% wider than that of the linear harvester, and the 1/3 subharmonic resonance broadens the band another 92% so that the energy harvester can obtain more than 0.1 mW in the frequency range of 18 Hz. Therefore, it is necessary to consider the influence of torque when modeling. The introduction of nonlinearity can broaden the frequency band of the harvester when it is in primary resonance, and the subharmonic resonance can make the harvester obtain more energy in the global frequency range.
ABSTRACT
Objective To explore the effects of compound lidocaine cream applied to postoperative wound and nasal packing on postoperative sinus pain after endoscopic sinus surgery . Methods From April 2015 to June 2016, 100 cases of endoscopic sinus surgery were carried out in our hospital under general anesthesia .The patients were randomly divided into two groups , with 50 cases in each group .The group A was given compound lidocaine cream 4 g on the nasal surgery wound and medical inflation sponge for intranasal packing;the group B was given saline 4 g on the nasal surgery wound and medical inflation sponge for intranasal packing . The heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured at the time of extubation (T0), 1 h after extubation (T1), 4 h after extubation (T2), 10 h after extubation (T3), and 12 h after extubation (T4), respectively.The visual analogue scale (VAS) of pain after extubation was recorded . Results The HR, SBP and DBP at T0, T1, T2 and T3 in the group A were significantly lower than those in the group B (P0.05), while the DBP was significantly lower in the group A than that in the group B (t=-2.562, P=0.012).The VAS scores were significantly lower in the group A than those in the group B at T 0, T1, T2 and T3 (P=0.000).No statistical difference was seen in VAS scores at T4 between the two groups (t=-1.199, P=0.233). Conclusions Application of compound lidocaine cream on nasal endoscopic wound and intranasal packing can effectively relieve the pain after endoscopic sinus surgery .The method has good analgesic effects and is worthy of popularization and application .
