PLA Air Force Aviation University
PLA Air Force Aviation University
Wang B.H.,PLA Air Force Aviation University |
Hui H.T.,National University of Singapore
IEEE Transactions on Signal Processing | Year: 2011
Using the beamspace preprocessing in RF chains, the fast Fourier transform (FFT)-based antenna selection scheme can reduce the performance degradation of traditional antenna selection schemes in correlated multiple-input multiple-output (MIMO) channels. Based on this technique, an antenna selection method in beamspace is developed for MIMO systems using compact uniform circular arrays (UCAs) at the receiver. To take advantages of the FFT-based antenna selection scheme for application in practical scenarios, a parametric physical model that considers the geometrical properties of the scattering environment is introduced to include realistic fading conditions into the channel matrix. Furthermore, due to the limited spatial phase modes of UCAs, the channel matrix resulting from the beamspace preprocessing only possesses a limited and small number of nonzero rows. This substantially reduces the computational load in the following beam selection procedure. More importantly, the optimal beam selection can be realized even without channel state information (CSI) at the receiver. This characteristic is especially useful for compact UCAs with a large number of elements. Besides, it is also found that the severe mutual coupling effect resulting from compact UCAs does not affect these favorable characteristics of the FFT-based preprocessing technique. Numerical examples considering strong mutual coupling in compact UCAs are provided to verify and validate the proposed method. © 2006 IEEE.
Guo L.,PLA Air Force Aviation University |
Li R.,PLA Air Force Aviation University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013
The entanglement-assisted (EA) formalism is a generalization of the standard stabilizer formalism, and it can transform arbitrary quaternary classical linear codes into entanglement-assisted quantum error correcting codes (EAQECCs) by using of shared entanglement between the sender and the receiver. Using the special structure of linear EAQECCs, we derive an EA-Plotkin bound for linear EAQECCs, which strengthens the previous known EA-Plotkin bound. This linear EA-Plotkin bound is tighter then the EA-Singleton bound, and matches the EA-Hamming bound and the EA-linear programming bound in some cases. We also construct three families of EAQECCs with good parameters. Some of these EAQECCs saturate this linear EA-Plotkin bound and the others are near optimal according to this bound; almost all of these linear EAQECCs are degenerate codes. © 2013 American Physical Society.
Liu S.,PLA Air Force Aviation University |
Xu J.,PLA Air Force Aviation University |
Xu J.,Northwest University, China
International Journal of Rock Mechanics and Mining Sciences | Year: 2013
Dynamic mechanical experiments are carried out on marble under different temperatures and different impact loadings by using the high temperature split Hopkinson pressure bar (SHPB) experimental system which is set up by integrating the 100. mm diameter SHPB with high temperature device. Combining the transformation of mineral components with the change of mineral particles under high temperatures, the dynamic mechanical characteristics are analyzed and the essence of rock fracture is explored. The experimental results show that the stress-strain curves under impact loadings and different temperatures have the same change law below 800 °C. When temperature exceeds 800 °C, the densification stage prolongs, the curve moves towards right quickly, the slope decreases and the yielding stage extends evidently. The dynamic mechanical characteristics of marble take on obvious temperature effects. The peak stress, peak strain and elastic modulus with the same impact velocity fluctuate in different extents with the increase of temperature before 400 °C. When temperature is above 400 °C, the peak stress, peak strain and elastic modulus increase or decline nearly linearly with the increase of temperature. There is remarkable difference among dynamic failure modes of marble under different temperatures. Especially, when temperature reaches 1000 °C, the fragments are powder and uniform particles. © 2013.
Guo S.-X.,PLA Air Force Aviation University
JVC/Journal of Vibration and Control | Year: 2010
Based on an appropriate uncertainty description, a new robust reliability method for stability issue of dynamic systems is developed to deal with bounded uncertainties. The presented methods provide necessary and sufficient conditions for quadratic stability and stabilization of uncertain systems and are suitable both for cases where the bounds of uncertain parameters are known and where they are unknown. Using this method, a robust reliability measure of the stability of parametric uncertain systems can be provided, and the maximum robustness bounds of uncertain parameters such that the system can be stable can be obtained. The design of a controller for stabilizing uncertain systems is carried out by solving a robust-reliability-based convex optimization problem. This makes it possible to take both the robustness with respect to uncertainties and the control cost into account simultaneously in the controller design. Moreover, the presented procedures are within the framework of linear matrix inequality and can be implemented conveniently. Two examples are provided to demonstrate the effectiveness and feasibility of the proposed methods. By numerical simulations and compared with existing results, it is shown that increasing conservatism in controller design by traditional methods does not mean increasing reliability, and so it is significant to take the robust reliability into account in the controller design of uncertain systems. © 2010 SAGE Publications Los Angeles.
Guo S.,PLA Air Force Aviation University
Systems and Control Letters | Year: 2014
The problem of non-fragile guaranteed cost control of uncertain systems is studied from a new point of view of reliability against uncertainties. An efficient robust reliability method for the analysis and design of non-fragile guaranteed cost controller of parametric uncertain systems is presented systematically. By the method, a robust reliability measure of an uncertain control system satisfying required robust performance can be obtained, and the robustness bounds of uncertain parameters such that the control cost of a system is guaranteed can be provided. The optimal non-fragile guaranteed cost controller obtained in the paper may possess optimal guaranteed cost performance satisfying the precondition that the system is robustly reliable with respect to uncertainties occurring in both the controlled plant and controller gain. The presented formulations are in the framework of linear matrix inequality and thus can be carried out conveniently. The presented method provides an essential basis for the tradeoff between reliability and control cost in controller design of uncertain systems. Two numerical examples are provided to demonstrate the efficiency and feasibility of the presented method. It is shown that the coordination and simultaneous realization of the system performance, control cost, and robust reliability in control design of uncertain systems are significant. © 2013 Elsevier B.V. All rights reserved.
Ji W.-J.,PLA Air Force Aviation University |
Tong C.-M.,PLA Air Force Aviation University
Progress in Electromagnetics Research | Year: 2010
An efficient approach called general sparse matrix canonical grid (G-SMCG) method is proposed to analyze the electromagnetic scattering from 2-D dielectric rough surface with a conducting object partially buried. In this paper, the scattering of 3-D arbitrarily shaped object is computed by using the traditional method of moments (MoM) with RWG basis function, and the scattering of rough surface is analyzed by using the SMCG method. The coupling interactions between an object and rough surface are calculated by iterative method. Combing the ocean rough surface with PiersonJMoskowitz (PM) spectrum, the bistatic scattering coefficients of typical objects buried in the ocean surface have been computed by using the proposed method. Then the accuracy and efficiency of this method are discussed. Finally, the bistatic scattering coefficients of a ship located on ocean surface are calculated, and the influence of sea state and wind direction on the scattering coefficients is indicated.
Li J.,PLA Air Force Aviation University |
Yang Y.,PLA Air Force Aviation University
Journal of Theoretical Biology | Year: 2011
Vaccination is important for the control of some infectious diseases. This paper considers two SIR-SVS epidemic models with vaccination, where it is assumed that the vaccination for the newborns is continuous in the two models, and that the vaccination for the susceptible individuals is continuous and impulsive, respectively. The basic reproduction numbers of two models, determining whether the disease dies out or persists eventually, are all obtained. For the model with continuous vaccination for the susceptibles, the global stability is proved by using the Lyapunov function. Especially for the endemic equilibrium, to prove the negative definiteness of the derivative of the Lyapunov function for all the feasible values of parameters, it is expressed in three different forms for all the feasible values of parameters. For the model with pulse vaccination for the susceptibles, the global stability of the disease free periodic solution is proved by the comparison theorem of impulsive differential equations. At last, the effect of vaccination strategies on the control of the disease transmission is discussed, and two types of vaccination strategies for the susceptible individuals are also compared. © 2011 Elsevier Ltd.
Wang J.,PLA Air Force Aviation University |
Hu J.,PLA Air Force Aviation University
IET Control Theory and Applications | Year: 2011
A robust adaptive neural network controller is proposed for a class of uncertain non-linear time-delay systems in strict feedback form with both completely unknown control gains and unknown non-symmetric dead-zone non-linearity based on backstepping design. The proposed design approach does not require a priori knowledge of the signs of the unknown control gains. The unknown time delays are compensated for constructing appropriate Lyapunov-Krasovskii functionals. By utilising integral Lyapunov design and sliding-mode control strategy, the controller singularity problem and the effect of dead-zone input non-linearity are avoided perfectly. From Lyapunov stability theorem, it is proved that the proposed design approach is able to guarantee semi-globally uniformly ultimately boundedness of all the signals in the closed-loop system, and the tracking error of the system is proven to be converged to a small neighbourhood of the origin. The simulation results demonstrate the effectiveness of the proposed approach. © 2011 The Institution of Engineering and Technology.
Guo S.,PLA Air Force Aviation University
Journal of Systems Engineering and Electronics | Year: 2011
A robust reliability method for stability analysis and reliability-based stabilization of time-delay dynamic systems with uncertain but bounded parameters is presented by treating the uncertain parameters as interval variables. The performance function used for robust reliability analysis is defined by a delayindependent stability criterion. The design of robust controllers is carried out by solving a reliability-based optimization problem in which the control cost satisfying design requirements is minimized. This kind of treatment makes it possible to achieve a balance between the reliability and control cost in the design of controller when uncertainties must be taken into account. By the method, a robust reliability measure of the degree of stability of a time-delay uncertain system can be provided, and the maximum robustness bounds of uncertain parameters such that the time-delay system to be stable can be obtained. All the procedures are based on the linear matrix inequality approach and therefore can be carried out conveniently. The effectiveness and feasibility of the proposed method are demonstrated with two practical examples. It is shown by numerical simulations and comparison that it is meaningful to take the robust reliability into account in the control design of uncertain systems.
Li J.,PLA Air Force Aviation University |
Yang Y.,PLA Air Force Aviation University |
Zhou Y.,Xi'an Jiaotong University
Nonlinear Analysis: Real World Applications | Year: 2011
For an epidemic model with latent stage and vaccination for the newborns and susceptibles, we establish that the global dynamics are completely determined by the basic reproduction number R0. More specifically, we prove that, if R0≤1, then the disease-free equilibrium is globally asymptotically stable, that is, the disease dies out eventually; if R0>1, then there exists a unique endemic equilibrium and it is globally asymptotically stable in the interior of the feasible region, that is, the disease persists in the population. In this paper, by the proof of global stability, we propose an approach for determining the Lyapunov function and proving the negative definiteness or semidefiniteness of its derivative. Our proof shows that, for a given Lyapunov function, its derivative should be arranged in different forms for the different values of parameters to prove the negative definiteness or semidefiniteness of its derivative. © 2011 Elsevier Ltd. All rights reserved.