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991.
Lai YC Kandangath A Krishnamoorthy S Gaudet JA de Moura AP 《Physical review letters》2005,94(21):214101
We propose a scheme to induce chaos in nonlinear oscillators that either are by themselves incapable of exhibiting chaos or are far away from parameter regions of chaotic behaviors. Our idea is to make use of small, judiciously chosen perturbations in the form of weak periodic signals with time-varying frequency and phase, and to drive the system into a hierarchy of nonlinear resonant states and eventually into chaos. We demonstrate this method by using numerical examples and a laboratory experiment with a Duffing type of electronic circuit driven by a phase-locked loop. The phase-locked loop can track the instantaneous frequency and phase of the Duffing circuit and deliver resonant perturbations to generate robust chaos. 相似文献
992.
993.
994.
Granucci G Mazzoni M Persico M Toniolo A 《Physical chemistry chemical physics : PCCP》2005,7(13):2594-2598
We have determined the lowest excited states of bilirubin IX by TD-DFT calculations. The lowest pair of excited states, S(1) and S(2), turn out to be of charge-transfer (CT) nature. Although DFT based methods tend to underestimate the energy of CT states, the small oscillator strengths we have computed indicate that such states may actually exist in this spectral region, but would have escaped spectroscopic detection. The next pair of excited states, S(3) and S(4), account for the most prominent spectral feature of bilirubin. They can be accurately described by the exciton coupling model, as we show by a thorough analysis of wavefunctions and properties. This finding therefore supports the interpretation of bilirubin photoisomerization behaviour, based on the exciton coupling model. 相似文献
995.
Laio A Rodriguez-Fortea A Gervasio FL Ceccarelli M Parrinello M 《The journal of physical chemistry. B》2005,109(14):6714-6721
Metadynamics is a powerful technique that has been successfully exploited to explore the multidimensional free energy surface of complex polyatomic systems and predict transition mechanisms in very different fields, ranging from chemistry and solid-state physics to biophysics. We here derive an explicit expression for the accuracy of the methodology and provide a way to choose the parameters of the method in order to optimize its performance. 相似文献
996.
Bertolini D Cinacchi G De Gaetani L Tani A 《The journal of physical chemistry. B》2005,109(51):24480-24488
We report a molecular dynamics simulation study on the isotropic phase of an idealized calamitic liquid crystal model with a length-to-width ratio of approximately 5-6. The study focuses on the characterization of single-particle and collective orientational dynamics on approaching the phase transition to the nematic phase. Recent experimental and simulation works have suggested that a power law behavior exists at relatively short times in the decay of the time derivative of the orientational correlation functions. Qualitatively, our simulation data are consistent with these findings. Both single-particle and collective time correlation function derivatives possess, in their respective log-log plots, a linear region at very short times, whose slope is essentially independent from the thermodynamic state. Nevertheless, the single-particle orientational correlation functions are better described by a function which is the sum of a fast exponential, an intermediate stretched-exponential and a slow exponential, while the collective orientational correlation functions are satisfactorily described by a sum of two exponentials, at higher density, or by just one exponential, at lower density. 相似文献
997.
Christian Fabry Alessandro Fonda 《NoDEA : Nonlinear Differential Equations and Applications》2000,7(1):23-42
We study the existence of large-amplitude periodic or almost periodic solutions of second order differential equations with
asymmetric nonlinearities, when the system is close to "nonlinear resonance".
Received September 1998 相似文献
998.
999.
Riassunto In questo lavoro si considerano sottoinsiemi compatti olomorficamente convessi di uno spazio analitico non ridotto e si prova
che questi sono caratterizzati, come nel caso ridotto, dagli analoghi dei teoremiA eB di Cartan. Si dà inoltre una caratterizzazione di certi morfismi in un compatto olomorficamente convesso.
Lavoro eseguito nell'ambito del G.N.S.A.G.A. del C.N.R. 相似文献
Summary In this paper we consider compact holomorphically convex subsets of a non reduced analytic space and we prove that they are characterized, as in the reduced case, by the analogous of Cartan's theoremsA andB. We give also a characterization of some morphisms in a compact holomorphically convex set.
Lavoro eseguito nell'ambito del G.N.S.A.G.A. del C.N.R. 相似文献
1000.