We report on optical waveguiding in the channel region of an epitaxial GaN film defined by a SiN cladding layer of a stripe window pattern. We carried out numerical analyses on the various possible effects that might contribute to the overcompensation of the negative loading effect of a SiN cladding window. This includes the photoelastic, piezoelectric, and electro-optic effects in GaN induced by a SiN window layer. The analysis result suggests that the observed phenomenon can be ascribed to a combination of both the photoelastic and electro-optic effects, and especially that the spontaneous polarization field in undoped GaN with a low background carrier concentration might play an important role in forming a channel waveguide in the window region.

In this study, we analyzed the thermal performance of electric vehicle lithium batteries with phase-change materials (PCMs) at 26 °C. PCMs and temperature sensors are the major factors affecting the thermal performance. To improve the heat transfer rate of PCMs in a lithium polymer pouch battery with 16 Ah capacity, a battery thermal management system with different PCMs, namely, RT15, RT31, EG5, and EG26, is proposed and experimentally investigated. The results show that the temperature of the battery surface without PCMs increased to 35.9 °C at different discharge rates at a room temperature of 25 °C. In the case of the battery with EG26, its surface temperature was 30.5 °C, which shows a temperature difference of 5.4 °C from the battery without a PCM. A low temperature-rise rate and a uniform temperature distribution were observed in the batteries with PCMs. In addition, a numerical simulation using the computational fluid dynamics software FLUENT was also carried out. The numerical simulation results are in good agreement with experimental data, such as the temperatures of batteries monitored with sensors.

No abstract

No abstract

No abstract