Long-term exposure to high-temperature and high-humidity environments inevitably causes performance degradation of flexible thin-film gallium arsenide (GaAs) solar cell modules, which poses a critical challenge for solar-powered unmanned aerial vehicles deployed in southern coastal regions of China. This work evaluates the moisture and heat resistance of flexible GaAs modules with different encapsulation designs via accelerated aging tests. Two sample groups were fabricated with identical ethylene-tetra-fluoro-ethylene (ETFE) front sheets and polyolefin elastomer (POE) encapsulant, but with distinct backsheet materials: polyimide (PI) for Group A and polyethylene terephthalate (PET) for Group B. All samples were exposed to 85 °C / 85
The history of the development of forced supercharging of piston compressors is briefly presented. Simplifying schemes and main results of previous authors are presented. Based on the experience of previous authors, a scheme for forced supercharging of a household piston compressor was proposed and the existing experimental stand was modified in order to increase its energy efficiency. By using forced supercharging, it was possible to increase the compressor’s performance (the delivery efficiency increased by an average of 9
An important and relevant aspect of thermodynamic calculation of a piston compressor is considered, namely, calculation of friction forces acting in a row. The analysis showed that the discrepancy between the calculated and actual friction force values can reach up to 90
This work investigates the impact of gate-length (LG) and gate-to-source spacing (LGS) scaling on the electrical, RF, and breakdown characteristics of a quaternary In0.78Al0.13Ga0.09N/GaN HEMT employing a sapphire substrate and gate field-plate architecture. Owing to the enhanced spontaneous and piezoelectric polarization associated with the In-rich quaternary barrier, a deep quantum well is formed at the heterointerface, leading to strong 2DEG confinement and improved carrier transport. Detailed TCAD simulations are performed to analyze the influence of geometric scaling on transfer characteristics, transconductance, capacitances, electric-field distribution, cutoff frequency, and breakdown behavior. The optimized structure exhibits a maximum ID of approximately 1.08 A/mm, a peak transconductance of 0.46 S/mm, ultra-low off-state leakage current in the order of 10−16 A/mm, and an Ion/Ioff ratio exceeding 1015. Furthermore, a peak fT of 40 GHz and a maximum breakdown voltage of 497 V are achieved through appropriate optimization of gate length and field-plate dimensions. The electrostatic potential and electric-field analyses reveal improved field redistribution and reduced field crowding, contributing to enhanced reliability and high-voltage operation. The obtained results demonstrate that the proposed In0.78Al0.13Ga0.09N/GaN HEMT offers an excellent balance between high-frequency performance and breakdown capability for next-generation RF and power electronic applications.
The work investigates relaxation processes in polyvinylidene fluoride (PVDF) films modified by ion irradiation with heavy ions 132Xe26+ followed by chemical etching. Dielectric spectroscopy and thermally stimulated depolarization methods were used for analysis, which made it possible to cover a wide frequency range from 10–5 to 106 Hz. Two relaxation processes were considered: α relaxation in the glass transition temperature region (Tg ≈ − 40°C) and αc relaxation, which manifests itself near room temperature. After chemical etching, an additional relaxation process was detected at about −10°C, associated with the formation of relaxers on the pore surface. It was shown that changes in etching time and pore diameter significantly affect the intensity of relaxation processes.
