A series of 5-substituted-3-[5-hydroxy-4-pyrone-2-yl-methymercapto]-4-amino-1,2,4-triazole derivatives were synthesized by nucleophilic substitution reaction of 5-hydroxy-2-chloromethyl -4H-pyran-4-one with 5-substituted-3-mercapto-4-amino-1,2,4-triazole, and their inhibitory effects on mushroom tyrosinase were evaluated. The results indicated that most of the synthesized compounds exhibited significant inhibitory activity. Specifically, 5-(4-chlorophenyl)-3-[5-hydroxy-4-pyrone-2-yl-methymercapto]-4-amino-1,2,4-triazole (6j) exhibited the most potent tyrosinase inhibitory activity with IC50 value of 4.50 ± 0.34 μm. The kinetic studies of the compound (6j) demonstrated that the inhibitory effects of the compound on the tyrosinase were belonging to competitive inhibitors. Meanwhile, the structure-activity relationship was also discussed.
The piezoelectric micro-positioning platform(PMP) has advantages in high displacement resolution and fast response, however, the serious hysteresis nonlinearity in the PMP restricts its positioning accuracy. This paper presents a discretization of Krasnosel'skii-Pokrovskii model to describe the hysteresis nonlinearity of the PMP. Then, the density function is identified online by the adaptive linear neural network. To compensate the intrinsic hysteresis nonlinearity in the PMP, a feedforward compensation control method is implemented by an innovative iterative learning control algorithm. Moreover, a hybrid control method based on iterative learning and fractional order PID control is proposed to further improve the control accuracy. A series of comparative experiments are carried out to validate the feasibility and effectiveness of the proposed control method.INDEX TERMS Piezoelectric micro-positioning platform, hysteresis nonlinearity, iterative learning control, fractional order PID.
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