Although it is normally considered that hydrothermal synthesis is difficult to be controlled,the controllable synthesis of zeolite and related materials is believed to be possible by tuning the crystal nucleation proc...Although it is normally considered that hydrothermal synthesis is difficult to be controlled,the controllable synthesis of zeolite and related materials is believed to be possible by tuning the crystal nucleation process based on the study in this work.Herein,a switch crystallization strategy(SCS)is developed to prepare zeolite lamellas by the combination of crystallizations under rotating and static hydrothermal conditions.Particularly,by the initial crystallization under relatively high rotation rate conditions for 12 hours and the consequent static crystallization for 10 days(R+S route),MWW zeolite lamellas with a unique centre-crossed morphology and hierarchically porous structure can be directly synthesized(centre-crossed zeolite lamellas,CCZL).Through systematic studies of crystallization conditions and processes,it is found that the rotation rate of the autoclave has an important influence on the particle size and morphology of the zeolite precursor prepared by‘R+S’route,and the formation of CCZL is ascribed to the vital roles of external forces aroused by rotation in the electrostatic and van der Waals interactions among various reaction species in the gel mixture during the nucleation stage.Moreover,the CCZL materials show efficient catalytic performance in the acid-catalysis condensation reaction of ethylene glycol with benzaldehyde or cyclohexanone,which is ascribed to their excellent physical and chemical properties,including a large BET surface area,suitable acid property,highly exposed and accessible catalytic sites over the centre-crossed MWW zeolite lamellas,and so on.展开更多
The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the...The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the critical load from the preferred feeder to the alternate feeder when a voltage sag or a fault occurs on the preferred feeder. A forced commutation technique is proposed and implemented to turn off the preferred feeders＇ thyristor, thus avoiding cross current to flow and minimizing the transfer time. Simulation results show that the forced commutation technique is more effective as compared to the recently proposed time delay technique for STS operation. Two different feeders, namely New Exchange, the preferred feeder, and Sector 1-10/2, the alternate feeder of Islamabad Electric Supply COmpany （IESCO）, Pakistan, have been selected for case studies. The software PSCAD/EMTDC professional package has been used for simulation.展开更多
The problem of admissibility analysis and control synthesis of discrete-time switched linear singular （SLS） systems for arbitrary switching laws is solved. By using the switched Lyapunov function approach, some new ...The problem of admissibility analysis and control synthesis of discrete-time switched linear singular （SLS） systems for arbitrary switching laws is solved. By using the switched Lyapunov function approach, some new sufficient conditions under which the SLS system is admissible for arbitrary switching laws are derived in terms of linear matrix inequalities （LMIs）. Based on the admissibility results, control synthesis is then to design switched state feedback and static output feedback controllers, guaranteeing that the resulting closed-loop system is admissible. The presented results can be viewed as the extensions of previous works on switched Lyapunov function approach from the regular switched systems to singular switched cases. Examples are provided to demonstrate the reduced conservatism and effectiveness of the proposed conditions.展开更多
The admissibility analysis and robust admissible control problem of the uncertain discrete-time switched linear singular (SLS) systems for arbitrary switching laws are investigated. Based on linear matrix inequalities...The admissibility analysis and robust admissible control problem of the uncertain discrete-time switched linear singular (SLS) systems for arbitrary switching laws are investigated. Based on linear matrix inequalities, some sufficient conditions are given for: A) the existence of generalized common Lyapunov solution and the admissibility of the SLS systems for arbitrary switching laws, B) the existence of static output feedback control laws ensuring the admissibility of the closed-loop SLS systems for arbitrary switching laws and norm-bounded uncertainties.展开更多
This paper is concerned with the problems of robust admissibility and static output feedback( SOF)stabilization for a class of discrete-time switched singular systems with norm-bounded parametric uncertainties.The obj...This paper is concerned with the problems of robust admissibility and static output feedback( SOF)stabilization for a class of discrete-time switched singular systems with norm-bounded parametric uncertainties.The objective is to design a suitable robust SOF controller guaranteeing the regularity,causality and asymptotic stability of the resulting closed-loop system under arbitrary switching laws. Based on the basic matrix inequality sufficient condition for checking the admissibility of switched singular systems,together with some matrix inequality convexifying techniques,the SOF controller synthesis is developed for the underlying systems. It is shown that the controller gains can be obtained by solving a set of strict linear matrix inequalities( LMIs). A simulation example is given to show the effectiveness of the proposed method.展开更多
基金the financial support by the National Natural Science Foundation of China(21571055,U20A20122,and 22072038)State Key Laboratory of Fine Chemicals,Dalian University of Technology(KF2115).
文摘Although it is normally considered that hydrothermal synthesis is difficult to be controlled,the controllable synthesis of zeolite and related materials is believed to be possible by tuning the crystal nucleation process based on the study in this work.Herein,a switch crystallization strategy(SCS)is developed to prepare zeolite lamellas by the combination of crystallizations under rotating and static hydrothermal conditions.Particularly,by the initial crystallization under relatively high rotation rate conditions for 12 hours and the consequent static crystallization for 10 days(R+S route),MWW zeolite lamellas with a unique centre-crossed morphology and hierarchically porous structure can be directly synthesized(centre-crossed zeolite lamellas,CCZL).Through systematic studies of crystallization conditions and processes,it is found that the rotation rate of the autoclave has an important influence on the particle size and morphology of the zeolite precursor prepared by‘R+S’route,and the formation of CCZL is ascribed to the vital roles of external forces aroused by rotation in the electrostatic and van der Waals interactions among various reaction species in the gel mixture during the nucleation stage.Moreover,the CCZL materials show efficient catalytic performance in the acid-catalysis condensation reaction of ethylene glycol with benzaldehyde or cyclohexanone,which is ascribed to their excellent physical and chemical properties,including a large BET surface area,suitable acid property,highly exposed and accessible catalytic sites over the centre-crossed MWW zeolite lamellas,and so on.
文摘The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the critical load from the preferred feeder to the alternate feeder when a voltage sag or a fault occurs on the preferred feeder. A forced commutation technique is proposed and implemented to turn off the preferred feeders＇ thyristor, thus avoiding cross current to flow and minimizing the transfer time. Simulation results show that the forced commutation technique is more effective as compared to the recently proposed time delay technique for STS operation. Two different feeders, namely New Exchange, the preferred feeder, and Sector 1-10/2, the alternate feeder of Islamabad Electric Supply COmpany （IESCO）, Pakistan, have been selected for case studies. The software PSCAD/EMTDC professional package has been used for simulation.
基金supported partly by the National Natural Science Foundation of China(6057400660835001)+1 种基金the Key Project of Chinese Ministry of Education(108060)the Jiangsu Planned Projects for Postdoctoral Research Funds(0802010c).
文摘The problem of admissibility analysis and control synthesis of discrete-time switched linear singular （SLS） systems for arbitrary switching laws is solved. By using the switched Lyapunov function approach, some new sufficient conditions under which the SLS system is admissible for arbitrary switching laws are derived in terms of linear matrix inequalities （LMIs）. Based on the admissibility results, control synthesis is then to design switched state feedback and static output feedback controllers, guaranteeing that the resulting closed-loop system is admissible. The presented results can be viewed as the extensions of previous works on switched Lyapunov function approach from the regular switched systems to singular switched cases. Examples are provided to demonstrate the reduced conservatism and effectiveness of the proposed conditions.
基金Supported by National Natural Science Foundation of P. R. China (6022130, 60334040, 60428304)
文摘The admissibility analysis and robust admissible control problem of the uncertain discrete-time switched linear singular (SLS) systems for arbitrary switching laws are investigated. Based on linear matrix inequalities, some sufficient conditions are given for: A) the existence of generalized common Lyapunov solution and the admissibility of the SLS systems for arbitrary switching laws, B) the existence of static output feedback control laws ensuring the admissibility of the closed-loop SLS systems for arbitrary switching laws and norm-bounded uncertainties.
基金Sponsored by the National Natural Science Foundation of China Grant No.61004038
文摘This paper is concerned with the problems of robust admissibility and static output feedback( SOF)stabilization for a class of discrete-time switched singular systems with norm-bounded parametric uncertainties.The objective is to design a suitable robust SOF controller guaranteeing the regularity,causality and asymptotic stability of the resulting closed-loop system under arbitrary switching laws. Based on the basic matrix inequality sufficient condition for checking the admissibility of switched singular systems,together with some matrix inequality convexifying techniques,the SOF controller synthesis is developed for the underlying systems. It is shown that the controller gains can be obtained by solving a set of strict linear matrix inequalities( LMIs). A simulation example is given to show the effectiveness of the proposed method.
