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We study two kinds of the generalized (3+1)-dimensional cubic-quintic Schrödinger equation in PT-symmetric potentials and obtain two families (sech-type and Gaussian-type) and four kinds of analytical light bullet (LB) solutions. The stability of these solutions is tested by the linear stability analysis and the direct numerical simulation. Results imply that sech-type LB solutions are unstable for all parameters only in the extended Rosen–Morse potentials. Sech-type and Gaussian-type LB solutions are both stable below some thresholds for the imaginary part of other PT-symmetric potentials in the defocusing cubic and focusing quintic medium, while they are always unstable for all parameters in other media. Moreover, we discuss the broadened and compressed behaviors of LBs in inhomogeneous hyperbolic system and periodic amplification system. © 2014, Springer Science+Business Media Dordrecht. Source

Dai C.-Q.,Zhejiang Agriculture And forestry University | Zhang J.-F.,Zhejiang University of Media and Communications
Nonlinear Dynamics | Year: 2013

Inspired by the mapping method and the direct method of symmetry reduction method, we present a new algorithm, nonlinear Schrödinger equation-based constructive method, to solve complex nonlinear evolution equations. This method can easily construct infinite solutions of the complex nonlinear evolution equations from abundant solutions of the nonlinear Schrödinger equation, including multi-soliton solutions with and without continuous wave background, rational solutions and periodic solutions, and so on. With the aid of symbolic computation, we choose (2+1)-dimensional and (3+1)-dimensional variable-coefficient nonlinear Schrödinger equations to illustrate the validity and advantages of the proposed method. According to exact solutions, we also graphically discuss some interesting soliton-like wave dynamic behaviors, which may be observable in the future experiments. These results are helpful to increase the bit-rate of optical communication. © 2013 Springer Science+Business Media Dordrecht. Source

Wu Y.,Hangzhou Dianzi University | Zhang G.,Zhejiang University of Media and Communications
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2013

A new tolerance model by representing the position variation of control points of geometric element is proposed. The control points of point, line and plane geometric element are defined as point itself, two end points of line, any three vertices of bounding box of plane and the interior constituting points of line and plane, which are used to present the dimensional error, the position error, the orientation error and the form error. The tolerance coordinate system of target geometric element is established according to the geometric type of target geometry and datum geometry, the relative position between target geometry and datum geometry, and the precedence of datum reference frames. The degree of freedoms (DOFs) of geometry element are classified and defined under the tolerance coordinate system. The bounding box of plane is set up at the tolerance coordinate system and the variation direction of control points is defined along translational DOF of geometry element, and the variation combination of all control points are used to represent various error of geometric element. The variation of control points is controlled to follow the error probability distribution of geometric element and the definitional domain of variation parameter of control point is the tolerance zone, the restrict relationship among the control points of target element are used to represent the interaction relationship between position and orientation tolerance, and the relationship between the variation parameters of control point of target and datum element are used to represent the tolerance principles. The model is compatible with the tolerance standards and practice rules, it also suits the mathematical analysis method of many applications such as tolerance analysis, tolerance allocation and verification. © 2013 Journal of Mechanical Engineering. Source

Ai S.,Zhejiang University of Media and Communications
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2011

A novel method of bearing fault diagnosis based on demodulation technique of DTCWT. It is demonstrated that the proposed dual-tree complex wavelet transform has better shift invariance, reduced frequency aliasing effect and de-noising ability. The bearing fault vibration signals were firstly decomposed and reconstructed using dual-tree complex wavelet transform. Then the real and imaginary parts were obtained and the vibration signals were amplitude demodulated. In the end, the amplitude envelope and wavelet envelope spectrum were computed. Therefore, the characteristics of the bearing faults can be recognized according to the wavelet envelope spectrum. The experimental results show that fault diagnosis based on dual-tree complex wavelet transform can diagnose bearing faults effectively under strong noise conditions and reduce spectral aliasing. Source

Zhao Z.,Zhejiang University of Media and Communications | Luo H.,Zhejiang University
Information Technology Journal | Year: 2012

As an effective technique, reversible data hiding played an important role in multimedia security. Its key advantage lies in not only the cover image but also the secret hidden data can be recovered accurately in decoder. In recent years, many reversible data hiding schemes for images were developed, aiming to enhance the hiding capacity and stego-image visual quality. Fractal curves have been successfully applied in digital image processing. In this study, the Hilbert curve, one of the popular used Fractal curves, was applied for reversible data hiding in natural images incorporated with histogram modification. Extensive experimental results demonstrated the effectiveness of the proposed scheme. Moreover, the superior performance of higher capacity and better stego-image quality is illustrated in comparison with several available methods of the same kind. © 2012 Asian Network for Scientific Information. Source

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