PLA Air Force Aviation University
PLA Air Force Aviation University
Song W.,PLA Air Force Aviation University |
Zhang H.,PLA Air Force Aviation University
Journal of Computational Physics | Year: 2017
Through introducing the alternating direction implicit (ADI) technique and the memory-optimized algorithm to the shift operator (SO) finite difference time domain (FDTD) method, the memory-optimized SO-ADI FDTD for nonmagnetized collisional plasma is proposed and the corresponding formulae of the proposed method for programming are deduced. In order to further the computational efficiency, the iteration method rather than Gauss elimination method is employed to solve the equation set in the derivation of the formulae. Complicated transformations and convolutions are avoided in the proposed method compared with the Z transforms (ZT) ADI FDTD method and the piecewise linear JE recursive convolution (PLJERC) ADI FDTD method. The numerical dispersion of the SO-ADI FDTD method with different plasma frequencies and electron collision frequencies is analyzed and the appropriate ratio of grid size to the minimum wavelength is given. The accuracy of the proposed method is validated by the reflection coefficient test on a nonmagnetized collisional plasma sheet. The testing results show that the proposed method is advantageous for improving computational efficiency and saving computer memory. The reflection coefficient of a perfect electric conductor (PEC) sheet covered by multilayer plasma and the RCS of the objects coated by plasma are calculated by the proposed method and the simulation results are analyzed. © 2017 Elsevier Inc.
Shi Y.,PLA Air Force Aviation University
Journal of Physical Organic Chemistry | Year: 2017
The density functional theory methods are used to design a series of new highly energetic tetrazolone-based molecules by the combination of the linked tetrazolone framework and versatile substitutes. The molecular and electronic structures, physicochemical, and energetic properties were analyzed and predicted. The decomposition mechanisms were computationally simulated, and 3 potential decomposition channels were proposed. These newly designed tetrazolone-based compounds show high densities (up to 2.08 g/cm3) and highly positive heats of formation (407.0-1377.9 kJ/mol) due to all right content of nitrogen and oxygen. Most of them exhibit good detonation velocity (8.31-9.62 km/s) and detonation pressure (32.40-43.86 GPa), and some are comparative to excellent explosive CL-20. Results show that compounds 6, 10, 11, 12, 15, 16, 17, 22, 23, and 24 own superior detonation performance than widely used explosive HMX and may be promising candidates of green high-performance energetic materials. © 2017 John Wiley & Sons, Ltd.
Xu H.-X.,Nanjing Southeast University |
Xu H.-X.,PLA Air Force Aviation University |
Wang G.-M.,PLA Air Force Aviation University |
Tao Z.,Nanjing Southeast University |
Cui T.J.,Nanjing Southeast University
Scientific Reports | Year: 2014
A three-dimensional (3D) highly-directive emission system is proposed to enable beam shaping and beam steering capabilities in wideband frequencies. It is composed of an omnidirectional source antenna and several 3D gradient-refractive-index (GRIN) lenses. To engineer a broadband impedance match, the design method for these 3D lenses is established under the scenario of free-space excitation by using a planar printed monopole. For realizations and demonstrations, a kind of GRIN metamaterial is proposed, which is constructed by non-uniform fractal geometries. Due to the non-resonant and deep-subwavelength features of the fractal elements, the resulting 3D GRIN metamaterial lenses have extra wide bandwidth (3 to 7.5 GHz), and are capable of manipulating electromagnetic wavefronts accurately, advancing the state of the art of available GRIN lenses. The proposal for the versatile highly-directive emissions has been confirmed by simulations and measurements, showing that not only the number of beams can be arbitrarily tailored but also the beam directions can be steerable. The proposal opens a new way to control broadband highly-directive emissions with pre-designed directions, promising great potentials in modern wireless communication systems.
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.
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.