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Abstract: Switched systems, as a kind of system models with multi-modal characteristics, Therefore, switched systems have important theoretical research value. In this paper, Lyapunov function and model dependent average dwell time method (MDADT) is used to study the exponential stability of nonlinear and linear switched time delay systems. The mode dependent average dwell time scheme is introduced into the system with switched time delay. Based on the mode dependent average dwell time design, the sufficient conditions for exponential stability are given in the form of linear matrix inequalities (LMIs). Exponential stability for switched delay systems consisting of stable and unstable subsystems is addressed. Under the condition that activation time ratio between stable subsystems and unstable ones is not less than a specified constant, sufficient conditions are given to guarantee exponential stability of the switched delay systems. Subsequently, for a special class of switched delay systems, a lower bound on the mode dependent average dwell time and the activation time ratio of subsystems are calculated respectively by solving a set of linear matrix inequalities (LMIs) and certain equations. The concrete form of state exponential decay of the system is given. It is proved that under the condition of arbitrary switching, all the signals in the switched closed loop system are finally bounded, each subsystem output can track the corresponding target trajectory within a small bounded error range. Finally, the effectiveness of the proposed method is demonstrated by numerical examples and MATLAB simulation.Abstract: Switched systems, as a kind of system models with multi-modal characteristics, Therefore, switched systems have important theoretical research value. In this paper, Lyapunov function and model dependent average dwell time method (MDADT) is used to study the exponential stability of nonlinear and linear switched time delay systems. The mode dependen...Learn More
Abstract: Thermoelectric materials have the advantage of direct interaction between thermal energy and electric energy, which has attracted extensive attention. Among them, Bi2Te3-based thermoelectric materials with medium and low temperature have attracted special attention because of their high thermoelectric figure of merit in the room temperature range. Wet chemical method is widely used as an effective method to synthesize nano thermoelectric materials, which has the advantages of simple process equipment, low reaction temperature, low energy consumption and high yield. Therefore, the wet chemical preparation methods of Bi2Te3-based thermoelectric materials are analyzed and studied in this paper. The main methods are low-temperature and low-pressure wet chemical method (conventional low-temperature wet chemical method, microwave-assisted wet chemical method, ultrasonic-assisted wet chemical method) and high-temperature and high-pressure wet chemical method (hydrothermal method, solvothermal method). The phase analysis and micro-morphology analysis of the synthesized products are carried out by means of XRD, SEM and TEM, and the related chemical reaction mechanism in the synthesis process of Bi2Te3-based thermoelectric materials is explored. By changing the experimental conditions, we hope to further optimize the preparation process and analyze the reaction mechanism of chemical synthesis. In this paper, the influence factors of nano-powder morphology are studied by wet chemical method, which is of great significance to prepare Bi2Te3-based thermoelectric materials with controllable structure, good dispersion and high purity. At the same time, the optimization mechanism of thermoelectric transport performance is discussed, and the application prospect and development trend of nano-thermoelectric materials are prospected.Abstract: Thermoelectric materials have the advantage of direct interaction between thermal energy and electric energy, which has attracted extensive attention. Among them, Bi2Te3-based thermoelectric materials with medium and low temperature have attracted special attention because of their high thermoelectric figure of merit in the room temperature range. ...Learn More
