In this study, the authors propose a novel circuit topology based on the current non-linear parity-time (PT)-symmetry principle. The exact analytical solutions of transfer efficiency and resonant frequency are deduced, a state switching phenomenon is observed, and the mathematical expression of the critical coupling coefficient (κ c) corresponding to the state switching point is provided. When the coupling coefficient (κ) is ≥κ c , the system has two real frequencies and can maintain near 100% transfer efficiency theoretically. When κ < κ c , the system has only one real frequency, and the transfer efficiency attenuates rapidly. The correctness of the theoretical model is verified by simulation and experiment. Results show that when the distance between the two coils (38 cm in diameter) varies from 10 to 42.5 cm, the transfer efficiency remains ∼95%, without the need for any tuning. Theoretical analysis and experimental verification show that κ c increases when the load resistance increases and the natural resonant frequency or the self-inductance of the Rx coil decreases. Furthermore, the system can maintain the equivalent current of the Tx and Rx circuits when κ ≥ κ c , which is convenient for controlling the circuit current, and suitable for the case of small load and large current.

With the rapid development of self-powered electronics such as wearables, implantable devices, and sensor networks, there is an increasing demand for power sources that have a high power density and a long lifespan to keep the entire system operational. Flexible piezoelectric materials with the capability of mechanical-to-electrical energy conversion have attracted significant interest because of their immense potential for harvesting human biomechanical energy. Herein, 3 mol.% yttrium stabilized zirconia ribbon ceramic is selected as a unique substrate to manufacture a large-scale and all-ceramic flexible Pb(Zr 0.52 Ti 0.48 )O 3 piezoelectric energy harvester via the cost-effective one-step process. The flexible piezoelectric energy harvester delivers excellent performance with an open-circuit voltage of ~105 V and short-circuit current of ~0.58 µA under mechanical strain equivalent to human movement. Moreover, the output voltage of a flexible piezoelectric energy harvester varies linearly with strain, allowing it a promising candidate as a self-powered strain sensor. Of particular importance is that a large-scale piezoelectric energy harvester (4 × 4 cm 2 ) can simultaneously light up eight commercial light emitting diodes without any external power source and circuit. This research provides an innovative approach to the fabrication of high-performance and large-scale flexible piezoelectric energy harvesters as well as self-powered micromechanical devices.

In this paper, an optimal-damage-effectiveness cooperative-control strategy based on a damage-efficiency model and a virtual-force method is proposed to solve the pursuit–evasion problem with multiple guided missiles. Firstly, different from the overly ideal assumption in the traditional pursuit–evasion problem, an optimization problem that maximizes the damage efficiency is established and solved, making the optimal-damage-effectiveness strategy more meaningful for practical applications. Secondly, a modified virtual-force method is proposed to obtain this optimal-damage-effectiveness control strategy, which solves the numerical solution challenges brought by the high-complexity damage function. Thirdly, adaptive gain is designed in this strategy based on guidance-integrated fuze technology to achieve robust maximum damage efficiency in unpredictable interception conditions. Finally, the effectiveness and robustness of the proposed strategy are verified by numerical simulations.

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