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Matlab/Simulink, Chemkin, as well as the finite element method (FEM) have been used to investigate the performance of the novel development of a two-stroke free-piston engine for electrical power generation. It is called free-piston linear alternator (FPLA). The motion differences between the FPLA and the internal combustion engine (ICE) are also presented. The effects of various resistance loads and equivalence ratios are studied. The simulation results show that the FPLA has a buildup nature to change the top dead center (TDC) according to loads and other parameters. The high compression ratio can be achieved easily by decreasing the equivalence ratio, which is an effective way to increase the indicated thermal efficiency. Besides, the peak temperature is much lower than the traditional engine under the same condition, which could reduce the temperature-dependent emissions.

Metal oxide nanocrystals have been pursued for various applications in photovoltaics as a buffer layer. However, it remains a challenging task to adjust their energy levels to achieve a better match of the donor–acceptor system. Herein, we report the fabrication of graphene quantum dots (GQDs) with bright blue photoluminescence by a top-down strategy based on laser fragmentation with posthydrothermal treatment. The GQDs demonstrate appropriate energy level positions and are used as an intermediate buffer layer between TiO2 and P3HT to form a cascade energy level architecture. The introduction of the GQDs into a bulk heterojunction hybrid solar cell has led to an enhancement of the power conversion efficiency.

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