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Bambi Hu

Publications and source records attributed to Bambi Hu.

30 records · Page 2Linked to original sources
PubMed2003

Frequency and phase locking of noise-sustained oscillations in coupled excitable systems: array-enhanced resonances.

We study the interplay among noise, weak driving signal and coupling in excitable FitzHugh-Nagumo neurons. Due to coupling, noise-sustained oscillations become locked to the signal as functions of both signal frequency and noise intensity. Higher order m:n locking tongues and various array-enhanced resonance features are demonstrated. This resonance and locking behavior due to a time scale matching between noise-sustained oscillations and the signal is fundamentally different from stochastic resonance in usual noisy threshold elements.

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PubMed2003

Analytical approach to the drift of the tips of spiral waves in the complex Ginzburg-Landau equation.

In this paper, we investigate the motion of spiral waves in the complex Ginzburg-Landau equation (CGLE) analytically and numerically. We find that the tip of the spiral wave drifts primarily in the direction of the electric field and there is a smaller component of the drift that is perpendicular to the field when a uniform field is applied to the system. The velocity of the tip is uniform and its component along the electric field is equal to the strength of the field. When the CGLE system is driven by white noise, a diffusion law for the vortex core of the spiral wave is derived at long time explicitly. The diffusion constant is found to be D=T/C(2), in which T is the noise strength and C is the core asymptotic factor of the spiral wave. When the external force is a simple oscillation we find that the tip of the spiral wave drifts if the frequency of the external force is the same as that of the system. Our analytical results are verified using numerical simulations.

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PubMed2002

Turbulence control by developing a spiral wave with a periodic signal injection in the complex Ginzburg-Landau equation.

Turbulence control in the two-dimensional complex Ginzburg-Landau equation is investigated. An approach is proposed for the purpose of control. In the presence of a small spiral wave seed initiation, a fully developed turbulence can be completely annihilated by injecting a single periodic signal into a small fixed space area around the spiral wave tip. The control is achieved in a parameter region where the spiral wave of the uncontrolled system is absolutely unstable. The robustness, convenience, and high control efficiency of this method are emphasized, and the mechanism underlying these practical advantages is intuitively understood.

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PubMed2002

Fluctuation of the strength function.

We consider a single state stochastically coupled to its stochastic background states. The fluctuation of the strength function of the single state is systematically studied. We find that the upper and lower deviations of the strength function only depend on the ratio of the spreading width over the decay width of the single state and on the ratio of the common decay width over the mean level spacing of the background states. Based on the two fit formulas for the upper and lower deviations, the uncertainties of the full width at half maximum (FWHM) and lifetime of a single state are estimated. They predict the experimental error bars of the FWHM and lifetime. A comparison of the uncertainties with the experimental error bars is made for nuclear giant dipole resonance, which illuminates our theoretical predictions.

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PubMed2002

Transition among synchronized states mediated by attractor-repeller collision crisis.

We studied the transition from a single-value generalized synchronization state to a double-value one in a unidirectionally coupled two-dimensional map system. It is found that this discontinuous transition is mediated by the attractor-repeller collision crisis and is different from the blowout bifurcation in many respects. By using the unstable periodic orbits decomposition method, it is shown that the attractor is generally nondifferential in the parameter regime about the transition. Based on the nondifferential character of the attractor, we propose a mechanism for the attractor-repeller collision crisis.

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PubMed2002

Shnirelman peak in level spacing statistics of Calogero-like three-body problem.

Statistical properties of quantum quasidegeneracy in a Calogero-like three-body problem is presented. The hidden continuous symmetry of a Calogero problem is broken by adding a three-body interaction, which results in discrete symmetry. This symmetry is sufficient to get the Shnirelman peak in level spacing statistics. Our calculation immediately implicates the application of Shnirelman theorem in real physical quantum systems.

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PubMed2002

Finite thermal conductivity in 1D models having zero Lyapunov exponents.

Heat conduction in three types of 1D channels is studied. The channels consist of two parallel walls, right triangles as scattering obstacles, and noninteracting particles. The triangles are placed along the walls in three different ways: (i) periodic, (ii) disordered in height, and (iii) disordered in position. The Lyapunov exponents in all three models are zero because of the flatness of triangle sides. It is found numerically that the temperature gradient can be formed in all three channels, but the Fourier heat law is observed only in two disordered ones. The results show that there might be no direct connection between chaos (in the sense of positive Lyapunov exponent) and normal thermal conduction.

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PubMed2002

Electronic properties of the 1D Frenkel-Kontorova model.

The energy spectra and quantum diffusion of an electron in a 1D incommensurate Frenkel-Kontorova model are studied numerically. We found that the spectral and dynamical properties of an electron display quite different behaviors in the invariance circle regime and in the Cantorus regime. In the former case, it is similar to that of the Harper model, whereas in the latter case, it is similar to that of the Fibonacci model. The relationship between spectral and transport properties is discussed.

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PubMed2001

Stochastic resonance of small-world networks.

Stochastic resonance (SR) of a coupled array of bistable oscillators with small-world connectivity is numerically studied. At certain coupling strength, it is found that both temporal SR and spatial synchronization of the oscillators can be considerably improved by increasing the order of randomness of the network due to the long-range couplings. Moreover, our results show that a small fraction of long-range couplings is sufficient to obtain great improvement in SR and synchronization.

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PubMed2001

Driven dynamics: a photodriven Frenkel-Kontorova model.

In this study, we examine the dynamics of a one-dimensional Frenkel-Kontorova chain consisting of nanosize clusters (the "particles") and photochromic molecules (the "bonds"), also being subjected to a periodic substrate potential. Whether the whole chain should be running or be locked depends on both the frequency and the wavelength of the light (keeping the other parameters fixed), as observed through numerical simulation. In the locked state, the particles are bound at the bottom of the external potential and vibrate backwards and forwards at a constant amplitude. In the running state, the initially fed energy is transformed into directed motion as a whole. It is of interest to note that the driving energy is introduced to the system by the irradiation of light, and the driven mechanism is based on the dynamical competition between the inherent lengths of the moving object (the chain) and the supporting carrier (the isotropic surface). However, the most important feature is that the light-induced conformational changes of the chromophore lead to the time-and-space dependence of the rest lengths of the bonds.

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