A practical synthesis and detailed development process of 2H-1,3-benzoxazine derivatives catalyzed by aldimine and trifluoromethanesulfonic acid is described. A broad range of substrates with diverse steric and electronic properties were explored. Aliphatic/aromatic/heteroaromatic substrates all proceed well under conditions which have been optimized into a robust, scalable process.

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In this study, the performance of an electromagnetic vibration energy harvester (EM-VEH) based on micro-electro-mechanical systems 3D coils was presented theoretically and experimentally. The VEH employs two 3D coils and E-shape iron cores inserted into the coils to reduce the magnetic leakage and to improve the output power. In this structure, the planar spring stiffness and the attraction between the iron core and magnet are nonlinear, which can broad the bandwidth. In the theoretical work, a magnetic dipole model with the integral form was derived to describe the nonlinear interaction and estimate the dynamic response, which agreed well with the finite element method results. The influence of load resistance, excitation acceleration, and initial magnet offset (IMO) was measured and analyzed experimentally. The results showed that the IMO had a significant influence on the output performance. The maximum output power of one coil can reach 57.65 μW for 250 μm IMO based on 1 g excitation with the normalized power density (NPD) of 5.08 μW/cm3 g2, along with a half power bandwidth of 4 Hz. For a smaller IMO of 174 μm, the output power reduced at 22.23 μW with the same excitation condition, while the half power bandwidth was broadened to 13 Hz. With the increase in excitation, the output power and bandwidth can be improved while the NPD reduces. The tested results proved that the structure proposed in this study can significantly enhance the output performance compared with published data.

In this study, we conducted a systematic exploration of a micro-electromagnetic vibration energy harvester with a bi-magnet structure and microelectromechanical systems 3D coils. First, we establish a physical model of stiffness and damping characteristics based on the superposition principle for the bi-magnet structure which has also been verified experimentally. Then, we investigate the influence of magnet gap and air gap on the stiffness and the magnetic flux change rate, mainly focusing on the distance and the potential barrier between the two potential wells. Finally, we fabricate and assemble the bi-magnet VEH prototype and tested the output performance under 1 and 6g excitation, which correspond the intra-well vibration and inter-well vibration, respectively. The tested results show that under 1g excitation, the prototype can output 155.38 μW power with 32 Hz half-power bandwidth and 4939.06 μW·Hz integrated power, which are obviously higher than those for mono-magnet under same excitation. When the excitation raises to 6g, the output power is improved to 362.98 μW with the half power bandwidth and integrated power enhanced to 56 Hz and 9289.96 μW·Hz, respectively. The tested results also prove that the structure proposed in this study can significantly enhance the output performance compared with a mono-magnet structure and other published data.