University of Science and Technology Beijing

About: University of Science and Technology Beijing is a education organization based out in Beijing, China. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 41558 authors who have published 44473 publications receiving 623229 citations. The organization is also known as: Beijing Steel and Iron Institute.

Discrete-Time Deterministic $Q$ -Learning: A Novel Convergence Analysis

Abstract: In this paper, a novel discrete-time deterministic $ Q$ -learning algorithm is developed. In each iteration of the developed $ Q$ -learning algorithm, the iterative $ Q$ function is updated for all the state and control spaces, instead of updating for a single state and a single control in traditional $ Q$ -learning algorithm. A new convergence criterion is established to guarantee that the iterative $ Q$ function converges to the optimum, where the convergence criterion of the learning rates for traditional $ Q$ -learning algorithms is simplified. During the convergence analysis, the upper and lower bounds of the iterative $ Q$ function are analyzed to obtain the convergence criterion, instead of analyzing the iterative $ Q$ function itself. For convenience of analysis, the convergence properties for undiscounted case of the deterministic $ Q$ -learning algorithm are first developed. Then, considering the discounted factor, the convergence criterion for the discounted case is established. Neural networks are used to approximate the iterative $ Q$ function and compute the iterative control law, respectively, for facilitating the implementation of the deterministic $ Q$ -learning algorithm. Finally, simulation results and comparisons are given to illustrate the performance of the developed algorithm.

Modeling and Observer-Based Vibration Control of a Flexible Spacecraft With External Disturbances

Abstract: This paper outlines the vibration reduction of a spacecraft with flexible appendage subject to external disturbances. The hybrid dynamic model of the spacecraft is described by both partial differential equations and ordinary differential equations. A vibration control scheme consisting of two boundary control laws and a distributed control law is developed to restrain the spacecraft's vibration and track the desired attitude. An infinite-dimensional disturbance observer is introduced as a feedforward compensator to handle unknown external disturbances. Based on the semigroup theory, the extended LaSalle's invariance principle and Lyapunov analysis, the well-posedness and stabilities of the designed control system are both discussed. Simulation results are given for validating the effectiveness of the developed vibration control scheme.

Electronic structure engineering of Cu2O film/ZnO nanorods array all-oxide p-n heterostructure for enhanced photoelectrochemical property and self-powered biosensing application.

Abstract: We have engineered the electronic structure at the interface between Cu2O and ZnO nanorods (NRs) array, through adjusting the carrier concentration of Cu2O. The electrodeposition of Cu2O at pH 11 acquired the highest carrier concentration, resulting in the largest interfacial electric field between Cu2O and ZnO, which finally led to the highest separation efficiency of photogenerated charge carriers. The optimized Cu2O/ZnO NRs array p-n heterostructures exhibited enhanced PEC performance, such as elevated photocurrent and photoconversion efficiency, as well as excellent sensing performance for the sensitive detection of glutathione (GSH) in PBS buffer even at applied bias of 0 V which made the device self-powered. Besides, the favorable selectivity, high reproducibility and extremely wide detection range, make such heterostructure a promising candidate for PEC biosensing applications, probably for the extended field of PEC water splitting or other solar photovoltaic beacons.