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Modified Two-Scale Model for Low-Grazing-Angle Scattering from Two-Dimensional Sea Surface

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Chinese Physics Letters 2002年第5期19卷 666-669页

作者： Zhang Yan-Dong wu Zhen-sen School of Sciences Xidian University Xi'an 710071

A hybrid model for describing a fully developed two-dimensional sea surface is presented, which incorporates the sea spectrum into a fractal model, and an improved two-scale model is applied to calculate the scattering coefficient. In this model the slope distribution of the large-scale surface is obtained with a numerical method instead of being assumed, and the projecting and ray tracing methods are applied to obtain the shadow function for arbitrary incident and scattering angles. Moreover the effect of curvature of the large-scale undulating surface on the scattered wave is taken into account. Hence the precision of the results is greatly increased at low-grazing angles. Finally the amplitude and fractal characteristics of the scattered wave are analysed, which are of great significance for distinguishing and detecting targets on the sea.

关键词： Numerical methods

Moment Method with Wavelet Expansions for Fractal Rough Surface Scattering

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Chinese Physics Letters 2002年第11期19卷 1617-1620页

作者： Guo Li-Xin wu Zhen-sen School of Science Xidian University Xi'an 710071

We study the moment method (MM) to deal with Harr wavelet basis due to the problem of electromagnetic scattering from the fractal rough surface. The vanishing moment properties and the capability of the wavelets to adjust themselves to the fractal surface lead to a sparse impedance matrix and faster computation. Compared to the measured data and the conventional MM, the result shows that the wavelet basis functions provide substantial reductions in both memory requirements and computation time.

关键词： Method of moments

Scattering from Rough Surfaces with Extended Self-Similarity

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Chinese Physics Letters 2002年第11期19卷 1613-1616页

作者： Zhang Yan-Dong wu Zhen-sen School of Sciences Xidian University Xi'an 710071

An extended self-similarity (ESS) model is developed by extending the self-similarity condition in fractional Brownian motion (FBM), then the incremental Fourier synthesis algorithm is introduced to generate ESS rough surfaces, and an estimation algorithm is presented to extract the generalized multiscale Hurst parameter, which can also be modified to estimate the Hurst parameter for FBM more accurately. Finally, the scattering coefficient from ESS rough surfaces is calculated with the scalar Kirchhoff approximation, and its variation with the parameters in the ESS model is obtained. Compared with experimental measurements, it can be concluded that the ESS model provides a good tool to model natural rough surfaces.

关键词： Brownian movement

Chaos Control and Bifurcation Behavior for a Sprott E System with Distributed Delay Feedback

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International Journal of Automation and computing 2015年第2期12卷 182-191页

作者： Chang-Jin Xu Yu-sen wu Guizhou Key Laboratory of Economics System Simulation Guizhou University of Finance and Economics School of Mathematics and Statistics Henan University of Science and Technology

In this paper, the problem of controlling chaos in a Sprott E system with distributed delay feedback is considered. By analyzing the associated characteristic transcendental equation, we focus on the local stability and Hopf bifurcation nature of the Sprott E system with distributed delay feedback. Some explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions are derived by using the normal form theory and center manifold theory. Numerical simulations for justifying the theoretical analysis are provided.

关键词： Sprott E system chaos control stability Hopf bifurcation distributed delay.

Chaos Control of a Chemical Chaotic System via Time-delayed Feedback Control Method

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International Journal of Automation and computing 2014年第4期11卷 392-398页

In this paper, the control of chemical chaotic dynamical system is investigated by time-delayed feedback control *** controllability and the stability of the equilibriums and local Hopf bifurcation of the system are verified. Some numerical simulations which show the effectiveness of the time-delayed feedback control method are provided.

关键词： Chemical system chaos stability Hopf bifurcation time delay

Bifurcation Control for a Duffing Oscillator with Delayed Velocity Feedback

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International Journal of Automation and computing 2016年第6期13卷 596-606页

作者： Chang-Jin Xu Yu-sen wu Guizhou Key Laboratory of Economics System Simulation Guizhou University of Finance and Economics Guiyang 550004 China School of Mathematics and Statistics Henan University of Science and Technology Luoyang 471023 China

In this paper, a Duffing oscillator model with delayed velocity feedback is considered. Applying the time delayed feedback control method and delayed differential equation theory, we establish some criteria which ensure the stability and the existence of Hopf bifurcation of the model. By choosing the delay as bifurcation parameter and analyzing the associated characteristic equation,the existence of bifurcation parameter point is determined. We found that if the time delay is chosen as a bifurcation parameter,Hopf bifurcation occurs when the time delay is changed through a series of critical values. Some numerical simulations show that the designed feedback controllers not only delay the onset of Hopf bifurcation, but also enlarge the stability region for the model.

关键词： bifurcation oscillator Feedback asymptotically dynamical Velocity enlarge perturbation imaginary unstable

Exact Calculations of Vertex ^-sγb and ,^-sZb in the Unitary Gauge

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Communications in Theoretical Physics 2007年第3X期48卷 502-508页

作者： wu Lu-sen XIAO Zhen-Jun Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing 210097 China

In this paper, we present the exact calculations for the vertex ^-sγb and ^sZb in the unitary gauge. We find that （a） the divergent- and μ-dependent terms are left in the effective vertex function Г^γμ（p, k） for b → sγ transition even after we sum up the contributions from four related Feynman diagrams; （b） for an on-shell photon, such terms do not contribute et al.; （c） for off-shell photon, these terms will be canceled when the contributions from both vertex ^sγb and ^sZb are taken into account simultaneously, and therefore the finite and gauge-independent function Zo（xt） = Co（xt）＋ Do（xt）/4, which governs the semi-leptonic decay b → sl^- l^＋, is derived in the unitary gauge.

关键词： unitary gauge Feynman diagram vertex

Mlock:building delegable metadata service for the parallel file systems

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Science China(Information Sciences) 2015年第3期58卷 66-79页

作者： ZHANG Quan FENG Dan WANG Fang wu sen wuhan National Laboratory for Optoelectronics School of Computer Huazhong University of Science and Technology Information & Telecommunication Company State Grid Hubei Electric Power Company

The ever-growing demand for high performance computation calls for progressively larger parallel distributed file systems to match their *** file systems can achieve high performance for large I/O operations through distributing load across numerous data ***,they fail to provide quality service for applications pertaining to small *** this paper,we propose a delegable metadata service(DMS)for hiding latency of metadata accesses and optimizing small-file *** addition,four techniques have been designed to maintain consistency and efficiency in DMS:pre-allocate serial metahandles,directory-based metadata replacement,packing transaction operations and fine-grained lock *** schemes have been employed in Cappella parallel distributed file system,and various experiments complying with industrial standards have been conducted for evaluation of its *** results show that our design has achieved significant improvement in performance of both metadata operations and small-file ***,this scheme is widely applicable for integration within many other distributed file systems.

关键词： delegable metadata service metadata performance consistency small file parallel file system

Preparation of NH_4ZrH(PO_4)_2·H_2O via solid-state reaction at low heat and its catalytic performance in the synthesis of butyl acetate

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Rare Metals 2008年第5期27卷 550-554页

作者： wu Wenwei LAI Shuibin wu Xuehang LIAO sen HOU Shengyi School of Chemistry and Chemical Engineering Guangxi University Nanning 530004 China

Nanocrystalline NH4ZrH（PO4）2·H2O was obtained by grinding ZrOC12·8H2O and （NH4）2HPO4 in the presence of surfactant PEG-400 via solid-state reaction at room temperature. The product NH4ZrH（PO4）2·H2O and its product of thermal decomposition were characterized using thermogravimetry and differential thermal analyses （TG/DTA）, Fourier transform infrared spectroscopy （FT-IR）, X-ray powder diffraction （XRD）, and transmission electron microscopy （TEM）. Nanocrystalline NHaZrH（PO4）2·H2O with an average particle size of 17 nm was obtained when the product was kept at80℃ for 3 h. Its crystalline framework was stable at temperatures below 250℃. In addition, the catalytic performance of NH4ZrH（PO4）2·H2O in the synthesis of butyl acetate was investigated. The results show that NH4ZrH（PO4）2·H2O behaved as an excellent heterogeneous catalyst in the synthesis of butyl acetate.

关键词： nanocrystalline solid-state reaction butyl acetate catalysis