摘要：Oscillation of fluid flow may cause the dynamic instability of nanotubes,which should be valued in the design of hanoelectromechanical *** dynamic instability of the fluid-conveying nanotube transporting the pulsating harmonic flow is *** nanotube is composed of two surface layers made of functionally graded materials and a viscoelastic *** nonlocal strain gradient model coupled with surface effect is established based on Gurtin-Murdoch's surface elasticity theory and nonlocal strain gradient ***,the size-dependence of the nanofluid is *** the slip flow *** stability boundary is obtained by the two-step perturbation-Galerkin truncation-Incremental harmonic balance(IHB)method·and compared with the linear solutions by using Bolotin's ***,the Runge-Kutta method is utilized to plot the amplitudefrequency bifurcation curves inside/outside the *** reveal the influence of nonlocal stress,strain gradient,surface elasticity and slip flow on the *** also suggest that the stability boundary obtained by the IHB method represents two bifurcation points when sweeping from high frequency to low ***,when sweeping to ***,there exists a hysteresis boundary where amplitude jump will occur.

摘要：In power systems, the Hopf bifurcation (HB) can occur before the saddle-node bifurcation (SNB) and be-comes one of main reasons of voltage instability and collapse, so the bifurcation control for HB has impor-tant significance in improving power system voltage stability. In this paper, the numerical bifurcation analy-sis software MATCONT was used to study bifurcation behavior of a single-machine dynamic-load (SMDL) system with SVC, and the simulation analysis results show that a unstable Hopf bifurcation (UHB) point oc-curring before SNB point and engendering potential harm to voltage stability. To delay or eliminate the UHB phenomenon and enhance voltage stability of the SMDL system with SVC, we designed a sliding mode variable structure controller. The switching function and control variables of the controller are clearly de-scribed and the derivations are directly provided in detail in this paper. The MATLAB simulation results prove that the designed controller can eliminate the UHB point effectively and ensure safe and stable opera-tion of the system.

摘要：In this paper, firstly, a mathematical model for a specific kind of welted bifurcation is established, the parametric equation for the intersecting curve is resulted in. Secondly, a method for partitioning finite element meshes of the welted bifurcation is put forward, its main idea is that developing the main pipe surface and the branch pipe surface respectively, dividing meshes on each developing plane and obtaining meshes points, then transforming their plane coordinates into space coordinates. Finally, an applied program for finite element meshes auto-generation is simply introduced, which adopt ObjectARX technique and its running result can be shown in AutoCAD. The meshes generated in AutoCAD can be exported conveniently to most of finite element analysis soft wares, and the finite element computing result can satisfy the engineering precision requirement.

摘要：In this paper, a new four-dimensional autonomous hyperchaotic system is designed for generating complex chaotic signals. In the design, its parameters are selected according to the requirements for chaos and hyperchaos. The hyperchaotic nature is verified theoretically by using the bifurcation analysis and demonstrated experimentally by the implementation of an analogue electronic circuit. Moreover, the Field Programmable Gate Array （FPGA） technology is applied to implementing a continuous system in a digital form by using a chip of Altera Cyclone II EP2C35F484C8. The digital sequence generated from the FPGA device is observed in our experimental setup.

摘要：In recent years, the chaos based cryptographic algorithms have suggested some new and efficient ways to develop secure image encryption techniques, but the drawbacks of small key space and weak security in one-dimensional chaotic cryptosystems are obvious. In this paper, permutation and sub- stitution methods are incorporated to present a stronger image encryption algorithm. Spatial chaotic maps are used to realize the position permutation, and to confuse the relationship between the ci- pher-image and the plain-image. The experimental results demonstrate that the suggested encryption scheme of image has the advantages of large key space and high security; moreover, the distribution of grey values of the encrypted image has a random-like behavior.

摘要：Nonlinear dynamic analysis was performed on a planetary gear transmission system with meshing beyond the pitch *** parameters of the planetary gear system were optimized,and a two-dimensional nonlinear dynamic model was established using the lumped-mass ***-varying meshing stiffness was calculated by the energy *** model consumes the backlash,bearing clearance,time-varying meshing stiffness,time-varying bearing stiffness,and time-varying friction *** time-varying bearing stiffness was calculated according to the Hertz contact *** load distribution among the gears was computed,and the time-varying friction coefficient was calculated according to elastohydrodynamic lubrication(EHL)*** dynamical equations were solved via numerical *** global bifurcation characteristics caused by the input speed,backlash,bearing clearance,and damping were *** system was in a chaotic state at natural frequencies or frequency *** system transitioned from a single-period state to a chaotic state with the increase of the *** bearing clearance of the sun gear had little influence on the bifurcation *** amplitude was restrained in the chaotic state as the damping ratio increased.