A novel repetitive controller directly combined with an open loop SPWM inverter is presented in this paper. To cope with the high-resonant peak of the open loop inverter that may cause instability, a zero-phase-shift notch filter other than the inverse transfer function of the inverter or a conventional second-order filter is incorporated in the controller. The proposed method has good harmonic rejection and large tolerance to parameter variations. To further reduce the steady-state error, low-pass-filter ( ) algorithm is applied. DC bias problem is also taken into consideration and solved with the repetitive controller itself. The method is implemented with a digital signal processor and achieves low THD% (1.4%-1.7%) with nonlinear loads and fast error convergence (3-5 fundamental periods). It proves to be a cost-effective solution for common UPS products where high-quality output voltage is more stressed than fast dynamic response.

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The first copper-catalyzed asymmetric decarboxylative [4 + 1] cycloaddition of propargylic carbamates and sulfur ylides was successfully developed. This strategy led to a series of chiral indolines with synthetically flexible alkyne groups in good yields and with high enantio- and diastereoselectivities (up to 99% yield, 98% ee, and >95:5 dr). A possible mechanism and stereoinduction mode with copper-allenylidenes were proposed as the possible dipolar intermediate.

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The impact of a liquid droplet on a solid surface is one of the most common phenomena in nature and frequently encountered in numerous technological processes. Despite the significant progress on understanding the droplet impact phenomenon over the past century, the impact dynamics, especially the coupling effects between the properties of a liquid and surface wettability on the impact process, is still poorly understood. In this work, we experimentally investigated the impact of viscous droplets on superamphiphobic surfaces, with the viscosity of liquids ranging from 0.89 to 150 mPa s. We showed that an increase in liquid viscosity will slow down the impact process and cause bouncing droplets to rebound lower and fewer times. The critical impact velocity, above which droplets can rebound from the superamphiphobic surface, was found to linearly increase with the liquid viscosity. We also showed that the maximum spreading factor increases with Weber number or Reynolds number but decreases with the liquid viscosity. Scaling analyses based on energy conservation were carried out to explain these findings, and they were found to be in good agreement with our experimental results.