Long-term oscillations in the sleep/wake cycle of infants

The development of circadian sleep-wakefulness rhythm was investigated by a longitudinal study of six normal infants. We propose an entropy based measure for the sleep/wake cycle fragmentation. Our results confirm that the sleep/wake cycle fragmentation and the sleep/wake ratio decrease, while the circadian power increases during the maturation process of infants. In addition to these expected linear trends in the variables devised to quantify sleep consolidation, circadian power and sleep/wake ratio, we found that they present infradian rhythms in the monthly range.     

Dynamics of momentumless turbulent wake in a shear flow of a linearly stratified medium

The numerical model of momentumless turbulent wake in a horizontally homogeneous shear flow of linearly stratified medium has been constructed. Based on this model, the investigation of the wake dynamics has been performed. The obtained data demonstrate the transformation of the zone of turbulent perturbations and internal waves generated by the wake under the action of shear flow, which leads to the deceleration of turbulence decay at large time values after the body passage.     

Dynamics of snoring sounds and its connection with obstructive sleep apnea

Snoring is extremely common in the general population and when irregular may indicate the presence of obstructive sleep apnea. We analyze the overnight sequence of wave packets — the snore sound — recorded during full polysomnography in patients referred to the Sleep Laboratory due to suspected obstructive sleep apnea. We hypothesize that irregular snore, with duration in the range between 10 and 100 s, correlates with respiratory obstructive events. We find that the number of irregular snores — easily accessible, and quantified by what we call the snore time interval index (STII) — is in good agreement with the well-known apnea–hypopnea index, which expresses the severity of obstructive sleep apnea and is extracted only from polysomnography. In addition, the Hurst analysis of the snore sound itself, which calculates the fluctuations in the signal as a function of time interval, is used to build a classifier that is able to distinguish between patients with no or mild apnea and patients with moderate or severe apnea.     

Electromagnetic scattering model of the Kelvin wake and turbulent wake by a moving ship

Taking the attenuation character of the Kelvin wake and the limitation of the traditional two-scale method into account, the practical electromagnetic (EM) scattering model of the Kelvin wake is obtained by using a facet-based model; and for a turbulent ship wake, it is produced by dealing with the wave energy loss rate due to turbulence with the width of turbulent wake closely following a moving ship. The volume scattering theory of foam or bubbles, by using the vector radiation transfer equation, is introduced to modify the traditional two-scale method, a special method for the EM scattering of a turbulent wake, which brings the scattering of ship wakes into better agreement with the real situation.     

A note on tower wake/blade interaction noise of a wind turbine

Experimental observations on wind turbine tower wake/blade interaction noise are presented. Results for circular, elliptical and square sections of the support tower legs are compared and quantified with respect to the acoustic frequency spectra produced. The results are preliminary ones obtained in a continuing study aimed at constructing a shape that may yield a lower interaction noise.     

Radar monitoring of a wake vortex: Electromagnetic reflection of wake turbulence in clear air

This article deals with X-band radar trial campaigns in 2006 and 2007 at Orly Airport, and in June 2008 at Paris-CDG Airport. An X-band Doppler radar has been deployed to assess short range (inferior to 2000 m) wake vortex monitoring capabilities in all weather conditions (dry and wet conditions). Recorded data have been correlated with electromagnetic and fluid mechanical models of wake turbulences for better and more accurate understanding of roll-up radar cross section (RCS) and Doppler signature.     

Spectroscopic detection of aircraft wake gases

Using the technique of limiting information-metric scales, the potential of laser IR absorption spectroscopy for detecting small gas components of aircraft wake was quantitatively analyzed. Formulas for minimum distinguishable and minimum detectable gas concentrations were derived. Calculation was carried out for SO₂, NO, and NO₂ under typical conditions near the Boeing 707 aircraft engine nozzle at altitude H = 12.2 km. Alternative IR laser spectroscopy methods for detecting various gas components in the near wake were considered. Two possibilities to improve the concentration measurement sensitivity were analyzed: (i) a decrease in the background absorption of CO₂ and H₂O and (ii) an increase in the absorption cross section of detected gas.     

Dynamics of Polaron at Polymer/Polymer Interface

The migration of a polaron at polymer/polymer interface is believed to be of fundamental importance for the transport and light-emitting properties of conjugated polymer-based light emitting diodes. Based on the one- dimensional tight-binding Su-Schrieffer-Heeger （SSH） model, we have investigated polaron dynamics in a one- dimensional polymer/polymer system by using a nonadiabatic evolution method. In particular, we focus on how a polaron migrates through the conjugated polymer/polymer interface in the presence of external electric field. The results show that the migration of polaron at the interface depends sensitively on the hopping integrals, the potential barrier induced by the energy mismatch, and the strength of applied electric field which increases the polaron kinetic energy.     

RDX/AMMO推进剂的分子动力学

利用分子动力学方法研究了含能材料环三亚甲基三硝胺(RDX)、3-叠氮甲基-3-甲基氧丁环(AMMO)和RDX/AMMO推进剂. 结果表明AMMO与RDX(010)面分子之间相互作用最强,其次是(100)和(001)面．用相关函数g(r)描述了RDX和AMMO之间的相互作用．计算了RDX/AMMO推进剂的弹性系数、柯西压、泊松比 等性能．研究结果表明,AMMO的加入能够改善RDX的弹性力学性能,它们的相对改善效应为(100)>(010)>(001)．RDX/AMMO推进剂的能量性能显示,AMMO的加入降低了RDX的比冲,但其仍高于双基推进剂.     

1D theory of laser plasma wake

In this paper, we get the 1D approximate analytical solution of the plasma     

Dynamics of spin-1/2 quantum plasmas

The fully nonlinear governing equations for spin-1/2 quantum plasmas are presented. Starting from the Pauli equation, the relevant plasma equations are derived, and it is shown that nontrivial quantum spin couplings arise, enabling studies of the combined collective and spin dynamics. The linear response of the quantum plasma in an electron-ion system is obtained and analyzed. Applications of the theory to solid state and astrophysical systems as well as dusty plasmas are pointed out.     

1D theory of laser plasma wake

In this paper, we get the 1D approximate analytical solution of the plasma electrostatic wake driven by the laser, and get the modified oscillating frequency of this wake. Finally we analyze the longitudinal beam dynamics in this electrostatic wake, and find that the high order terms don’t change the topology of the longitudinal phase space.     

Analysis of turbulent axisymmetric inner near wake

An analysis is presented describing the characteristics of mean velocity profile in the axisymmetric turbulent inner near-wake flow behind a body of revolution. The near wake is developing under zero streamwise pressure gradient and the upstream turbulent boundary layer is fully developed. It is shown that the boundary layer condition that exists at the trailing edge can be used to describe the mean velocity profiles in the inner near wake. It is shown that the logarithmic layer of the upstream turbulent boundary layer continues to be valid for some more distance in the near wake, and as the streamwise distance is increased, the logarithmic layer is slowly getting destroyed. It is also shown that the central line velocity exhibits a logarithmic behaviour for large streamwise distance. Results of the analysis have been validated using available experimental data.     

Local instability characteristics and frequency determination of self-excited wake flows

As suggested by the strong effect resonances and feedback mechanisms can exert upon vortices shed from blunt bodies, it is proposed that the discrete frequency, self-excited vortex shedding process itself is governed by a resonance-like mechanism. With the assumption that to a first approximation the shedding frequency is determined by the behaviour in the linear regime, the resonance hypothesis is found to lead to a bifurcation condition (direct resonance condition) of the local instability eigenvalue. In a corresponding initial value formulation the same condition separates a subcritical region of locally absolute instability from a supercritical region of locally convective instability. The critical basic wake profile corresponding to the bifurcation condition is found to be near the end of the potential core. The pertinent frequency is close to experimentally found values if, in the absence of numerically determined (physically unstable) solutions of the steady Navier-Stokes equations, the steady basic wake flow is modelled realistically. For asymmetrical steady wakes a limiting asymmetry seems to exist beyond which no time-harmonic resonance could be determined. This provides a link to mixing layers where apparently only convective instabilities are possible.