Southeast University

About: Southeast University is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Computer science & MIMO. The organization has 66363 authors who have published 79434 publications receiving 1170576 citations. The organization is also known as: SEU.

State Estimation for Coupled Uncertain Stochastic Networks With Missing Measurements and Time-Varying Delays: The Discrete-Time Case

Abstract: This paper is concerned with the problem of state estimation for a class of discrete-time coupled uncertain stochastic complex networks with missing measurements and time-varying delay. The parameter uncertainties are assumed to be norm-bounded and enter into both the network state and the network output. The stochastic Brownian motions affect not only the coupling term of the network but also the overall network dynamics. The nonlinear terms that satisfy the usual Lipschitz conditions exist in both the state and measurement equations. Through available output measurements described by a binary switching sequence that obeys a conditional probability distribution, we aim to design a state estimator to estimate the network states such that, for all admissible parameter uncertainties and time-varying delays, the dynamics of the estimation error is guaranteed to be globally exponentially stable in the mean square. By employing the Lyapunov functional method combined with the stochastic analysis approach, several delay-dependent criteria are established that ensure the existence of the desired estimator gains, and then the explicit expression of such estimator gains is characterized in terms of the solution to certain linear matrix inequalities (LMIs). Two numerical examples are exploited to illustrate the effectiveness of the proposed estimator design schemes.

Energy-Efficient Resource Assignment and Power Allocation in Heterogeneous Cloud Radio Access Networks

Abstract: Taking full advantage of both heterogeneous networks and cloud access radio access networks, heterogeneous cloud radio access networks (H-CRANs) are presented to enhance both spectral and energy efficiencies, where remote radio heads (RRHs) are mainly used to provide high data rates for users with high quality of service (QoS) requirements, whereas the high-power node (HPN) is deployed to guarantee seamless coverage and serve users with low-QoS requirements. To mitigate the intertier interference and improve energy efficiency (EE) performances in H-CRANs, characterizing user association with RRH/HPN is considered in this paper, and the traditional soft fractional frequency reuse (S-FFR) is enhanced. Based on the RRH/HPN association constraint and the enhanced S-FFR, an energy-efficient optimization problem with the resource assignment and power allocation for the orthogonal-frequency-division-multiple-access-based H-CRANs is formulated as a nonconvex objective function. To deal with the nonconvexity, an equivalent convex feasibility problem is reformulated, and closed-form expressions for the energy-efficient resource allocation solution to jointly allocate the resource block and transmit power are derived by the Lagrange dual decomposition method. Simulation results confirm that the H-CRAN architecture and the corresponding resource allocation solution can enhance the EE significantly.

Finite time integral sliding mode control of hypersonic vehicles

Abstract: This study investigates the tracking control problem for the longitudinal model of an airbreathing hypersonic vehicle (AHV) with external disturbances. By introducing finite time integral sliding mode manifolds, a novel finite time control method is designed for the longitudinal model of an AHV. This control method makes the velocity and altitude track the reference signals in finite time. Meanwhile, considering the large chattering phenomenon caused by high switching gains, an improved sliding mode control method based on nonlinear disturbance observer is proposed to reduce chattering. Through disturbance estimation for feedforward compensation, the improved sliding mode controller may take a smaller value for the switching gain without sacrificing disturbance rejection performance. Simulation results are provided to confirm the effectiveness of the proposed approach.

Consensus of Data-Sampled Multi-Agent Systems With Random Communication Delay and Packet Loss

Abstract: The consensus problem is considered for a team of second-order mobile agents communicating via a network with noise, variable delays and occasional packet losses. A queuing mechanism is applied and the switching process of the interaction topology of the network is modeled as a Bernoulli random process. In such a framework, a necessary and sufficient condition is presented for the mean-square robust consensus. Moreover, a necessary and sufficient condition of the solvability of the mean-square robust consensus problem is established. An approach to designing consensus protocol is proposed and numerical examples are given to illustrate the results.

Preparation of copper nanoparticles coated cellulose films with antibacterial properties through one-step reduction.

Abstract: Regenerated cellulose (RC) films coated with copper (Cu) nanoparticles were prepared from cellulose-cuprammonium solution through coagulation in aq. NaOH and subsequent reduction in aq. NaBH4. Structure and morphology of the nanocomposite films were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results established the migration of Cu(2+) from the inner to the surface of the RC films during the coagulation of cellulose-cuprammonium solution and the reduction from Cu(2+) to Cu(0). Cu nanoparticles were found to be firmly embedded on the surface of the RC films. The RC films coated with Cu nanoparticles showed efficient antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The dramatic reduction of viable bacteria could be observed within 0.5 h of exposure, and all of the bacteria were killed within 1 h.