The debonding of particle/matrix interfaces has an important effect on the behavior of composite materials. During last decades, great efforts have been made to simulate the behavior of the interface. Boundary element method, as an alternative effective numerical method, has great advantages in simu...
The stress and the debonding of the interface in coating layers structure due to thermal loading are investigated by using boundary element methods(BEM). The nearly-singular integrals that arise in the boundary integral equation(BIE) for such thin layered structures cannot be accurately evaluated us...
This paper presents the concept and measurements of a new microwave rectifier based on the time reversal duality of power amplifiers. It is shown that the proposed rectifier can simultaneously provide high efficiency at large input power range over much more improved bandwidth compared to the conventional rectifier from time reversal duality. It is also reported that the proposed rectifier allows reconfiguration of the efficiency at input power range without placing the tunable elements. A 10 W wideband power amplifier with 79%drain efficiency at 1.85 GHz is used to validate the concept. By making the gate bias network short-terminated and replacing the drain termination with the DC load resistor for power amplifier, the circuit can operate as microwave rectifier with taking part of bandwidth from power amplifier. Measurements show the efficiency bandwidth with larger than 70 % rectifying efficiency at 15 dB input power range over a 1.7–1.95 GHz frequency range. The measurements thereby validate the presented concept and demonstrate the potential of the proposed rectifier for use in future wireless energy harvesting applications.
Inversion is a critical and challenging task in geophysical research. Geophysical inversion can be formulated as an optimization problem to find the best parameters whose forward synthesis data most fit the observed data. The inverse problems are usually highly non-linear, multi-modal as well as ill-posed, so conventional optimization algorithms cannot handle it very efficiently. In the past decades, genetic algorithm (GA) and its many variants are widely applied to inverse problems and achieve great success. Swarm intelligence algorithms are a family of global optimizers inspired by swarm phenomena in nature, and have shown better performance than GA for diverse optimization problems. However, swarm intelligence algorithms are not utilized for geophysical inversion problems until recently and only limited number of works are reported. In this paper, we try to apply two swarm intelligence algorithms, Particle Swarm Optimization (PSO) and Fireworks Algorithm (FWA), to the regional seismic waveform inversion. To explore the advantages and disadvantages of swarm intelligence algorithms over GA, synthetic experiments are conducted by using these two swarm intelligence algorithm and several GA variants as well as Differential Evolution (DE). The experimental results show that, both swarm intelligence algorithms outperform the widely used GA, DE, and the models estimated by swarm intelligence algorithms are closer to the true solution. The promising results imply that swarm intelligence algorithms are a potentially more powerful tool for inversion problems.
This paper presents an analysis for the impedance transformation ratio of microwave rectifier, implemented as an energy recycling unit suitable for RF outphasing transmitters. The experimental demonstration is realised by two single-ended microwave rectifiers with different impedance transformation ratios to separately replace the power-wasting resistive load of an isolating combiner in a multilevel LINC system. The measurement results show that the implemented rectifier can improve the overall efficiency of the multilevel LINC system from original 39.5 % to 46.7 % and 44.9 % respectively, without affecting linearity.
