Generalized projective synchronization between two chaotic gyros with nonlinear damping

In this paper, the chaotic generalized projective synchronization of a controlled, noised gyro with an expected gyro is investigated by a simple control law. Based on the theory of discontinuous dynamical systems, the necessary and sufficient conditions for such a synchronization are achieved. From such conditions, non-synchronization, partial and full synchronizations between the two coupled gyros are discussed. The switching scenarios between desynchronized and synchronized states of the two dynamical systems are shown. Numerical simulations are illustrated to verify the effectiveness of this method.     

On the systematic energy difference between states of positive and negative parity

Comparison of the nuclear spectra in the mass region A = 10–40 shows a systematic difference between states of positive and negative parity. This systematic difference can be explained quantitatively with methods derived from statistical spectroscopy. The influence of spurious states is corrected for.     

On the relation between subglottal pressure and fundamental frequency in phonation

The change in fundamental frequency with subglottal pressure in phonation is quantified on the basis of the ratio between vibrational amplitude and vocal fold length. This ratio is typically very small in stringed instruments, but becomes quite appreciable in vocal fold vibration. Tension in vocal fold tissues is, therefore, not constant over the vibratory cycle, and a dynamic tension gives rise to amplitude-frequency dependence. It is shown that the typical 2-6 Hz/cm H2O rise in fundamental frequency with subglottal pressure observed in human and canine larynges is a direct and predictable consequence of this amplitude-frequency dependence. Results are presently limited to phonation in the chest register.     

On the relation between the phonation threshold lung pressure and the oscillation frequency of the vocal folds

This Letter presents an extension of a previous equation for the phonation threshold pressure by Titze [I. R. Titze, J. Acoust. Soc. Am. 83, 1536-1552 (1988)]. The extended equation contains the vocal-fold oscillation frequency as an explicit factor. It is derived from the mucosal wave model of the vocal folds by considering the general case of an arbitrary time delay for the mucosal wave to travel the glottal height. The results are illustrated with a numerical example, which shows good qualitative agreement with experimental measures.     

On the relation between Vicsek and Kuramoto models of spontaneous synchronization

The Vicsek model for self-propelling particles in 2D is investigated with respect to the addition of the stochastic perturbation of dynamic equations. We show that this model represents in essence the same type of bifurcations under a different type of noise as the celebrated Kuramoto model of spontaneous synchronization. These models demonstrate similar behavior at least within the mean-field approach. To prove this we consider two types of noise for the Vicsek model which are commonly considered in the literature: the intrinsic and the extrinsic ones (according to the terminology of Pimentel et al. [J.A. Pimentel, M. Aldana, C. Huepe, H. Larralde, Intrinsic and extrinsic noise effects on phase transitions of network models with applications to swarming systems, Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 77 (6) (2008) doi:10.1103/PhysRevE.77.061138. URL: http://dx.doi.org/10.1103/PhysRevE.77.061138]). The qualitative correspondence with the bifurcation of stationary states in the Kuramoto model is stated. A new type of stochastic perturbation—the “mixed” noise is proposed. It is constructed as the weighted superposition of the intrinsic and the extrinsic noises. The corresponding phase diagram “noise amplitude vs. interaction strength” is obtained. The possibility of the tricritical behavior for the Vicsek model is predicted.     

Detection of the difference between two images: An improved method

The method for the detection of the difference between two images, proposed by the authors, can be modified to improve the signal/noise ratio. An amplitude distribution proportional to cos²? is obtained in the Fourier plane using three exposures in the ratio 1 : 2 : 1. In the neighbourhood of ? = Π/2 the gradient of this distribution is one order of magnitude inferior to that of cos? obtained with two equal exposures. Consequently a wider slit can be used as a filter. A further improvement can be obtained if the number of exposures is increased.     

On mechanisms of the helix pitch variation in a thin cholesteric layer confined between two surfaces

Two possible mechanisms of the temperature-induced variation and jump of the helix pitch in a spatially bounded planar layer of a cholesteric liquid crystal (LC) was considered within the framework of the continuum theory of elasticity. These mechanisms are related to the existence of two configuration curves of the system free energy. The states with local free energy minima on each of the configuration curves correspond to topologically equivalent configurations of the LC director distribution and are quasi-equivalent in this sense. The transitions between such quasi-equivalent states are especially important in the first mechanism of the helix pitch jump proceeding without participation of defects. The second mechanism is related to transitions between the ground states of different configuration curves corresponding to topologically nonequivalent configurations. This mechanism requires either participation of disclination lines or the formation of defects.     

On the difference between proton and neutron spin-orbit splittings in nuclei

The latest experimental data on nuclei at ¹³²Sn permit us for the first time to determine the spin-orbit splittings of neutrons and protons in identical orbits in this neutron-rich doubly magic region and compare the case to that of ²⁰⁸Pb. Using the new results, which are now consistent for the two neutron-rich doubly magic regions, a theoretical analysis defines the isotopic dependence of the mean-field spin-orbit potential and leads to a simple explicit expression for the difference between the spin-orbit splittings of neutrons and protons. The isotopic dependence is explained in the framework of different theoretical approaches. Received: 13 February 2002 / Accepted: 20 February 2002     

On the relation between mechanisms for single-transverse-spin asymmetries

Recent studies have shown that two widely-used mechanisms for single-transverse-spin asymmetries based on either twist-three contributions or on transverse-momentum-dependent (Sivers) parton distributions become identical in a kinematical regime of overlap. This was demonstrated for the so-called soft-gluon-pole and hard-pole contributions to the asymmetry associated with a particular quark–gluon correlation function in the nucleon. In this Letter, using semi-inclusive deep inelastic scattering as an example, we extend the study to the contributions by soft-fermion poles and by another independent twist-three correlation function. We find that these additional terms organize themselves in such a way as to maintain the mutual consistency of the two mechanisms for single-spin asymmetries.     

On the Collision between two PNG Droplets

In this article we study the interface generated by the collision between two crystals growing layer by layer on a one-dimensional substrate through random decomposition of particles. We relate this interface with the notion of β-path in an equivalent directed polymer model and, by using asymptotics results from J. Baik and E. Rains, J. Stat. Phys., 100:523–541 (2000). and some hydrodynamic tools introduced by E. Cator and P. Groeneboom, Ann. Probab., 33:879–903 (2005), we derive a law of large numbers for such a path and obtain some bounds for its fluctuations. 2000 Mathematics Subject Classification: 60C05, 60K35     

On the difference in the rise times of the two SES electric field components

The study of low frequency signal transmission in conductive media, reveals that the electric and magnetic fields follow diffusion type equations. In a previous paper (Varotsos et al.1)) experimental evidence was forwarded that for epicentral distances of the order of 100 km, the SES electric field variations precede those of the magnetic ones by a time of the order of 1 sec. In the present paper, we present evidence that this peculiarity still pertains (but to a smaller extent), when studying the differences in the components of the electric field. This cannot be probably observed in the scale of laboratory measurements, lying usually within the error bars of the current experimental facilities. A tentative theoretical justification, termed as τ-approximation, is presented which accounts for the measurements of electric field components. The present findings can provide a unique tool for the discrimination between remote and nearby sources by using data from electric measurements alone.     

Theoretical study on the statistical properties of phase difference between two interfering speckle fields

The statistical properties of phase difference between two interfering speckle fields are studied theoretically with the general expression of the free standard deviation of the phase difference of speckle fields. The experimental results of the standard deviations of phase difference between two interfering partially developed speckle fields in the diffractive region [Opt. Quantum Electron. 19 (1987) 59] are studied and discussed theoretically with the general expression of the free standard deviation of phase difference of speckle fields. The theoretical standard deviations of phase difference for the case of two interfering fully developed Gaussian speckle fields are compared with that which are numerically calculated from the Gaussian theory.     

Statistical properties of the phase difference between two interfering speckle fields in speckle interferometry

The statistical properties of the phase difference between the two interfering partially correlated and partially developed speckle fields were studied experimentally as a function of the intensity correlation coefficient. The gaussian statistics are assumed for the formation of speckle fields in the diffraction region and the correlation coefficient between the two speckle intensities is used to evaluate the phase difference. The standard deviation of the phase difference can be uniquely determined in the fully developed speckle field from the correlation coefficient of the two speckle intensities. However, it was found in the partially developed speckle field that the standard deviation of the phase difference between the two speckle fields cannot be uniquely determined from the correlation coefficient of the two speckle intensities.     

热声发动机起消振过程中压比演化规律研究

实验研究了热声发动机起振过程中典型的非线性现象,即双阈起消振现象。实验结果表明,充气压力以及加热功率对于双阈起振现象有着明显的影响,而双阈消振现象则主要由充气压力和消振时刻系统压力振幅决定。该研究有助于增进对热声振荡现象的进一步理解与认识。     

On the modal density and damping of cylindrical pipes

Measurements of the resonant frequencies and quality factors of a series of long, small diameter cylindrical pipes are presented. The dependence of the modal densities, calculated from these measurements, on pipe length, wall thickness and pipe material is in close agreement with theoretical statistical predictions. Measurements of the damping of steel pipes for several different end conditions are also presented. Different, but always well-ordered, variation of modal quality factor with mode order is found in each case. For free-free ends the modal quality factors are large (>1000) and determined by internal material damping, except for modes for which the acoustic radiation damping is large; the effect of radiation damping is most important for those modes which have high wave speeds at low frequencies. The quality factors for rigid end conditions are similar to those for free ends, except for translational modes of low axial order which are damped by vibration of the end supports. For end conditions which allow relative motion between the pipe and the end supports, there is considerable additional damping, probably ascribable to gas pumping in the joints.     

关于“滴状冷凝中液滴内外压强差及临界半径”的评注

从力学和热力学角度简要证明了滴状冷凝时壁面球冠形液滴内外压强差不同于冷凝器内部球 形液滴的内外压强差，并指出有关文献对壁面自由能增量的理解存在概念上的混乱。 关键词： 滴状冷凝 压差 自由能