共查询到20条相似文献,搜索用时 15 毫秒
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Based on dynamic equations of a heterogeneous elastic medium which take into account rotational degrees of freedom of microstructure particles, a simplified mathematical model was constructed to describe the wave motions of a nematic liquid crystal under weak mechanical and temperature perturbations. It is shown that in the medium under plane deformation, the tangential stress obeys the Klein-Gordon equation of oscillatory particle rotation. Consideration is given to the possibility of initiating rotational waves in a nematic liquid crystal, which change its optical properties, due to heat sources acting at its boundary. 相似文献
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In terms of representation [1] of a decomposing binary liquid mixture as a system of two coupled self-oscillators with partial frequencies ν A and ν B , the following conjecture is verified: given frequency ratios ν A /ν B and ν A /ν C for decomposing liquid mixtures A-B and A-C at the same temperature, it is possible to determine the ν B /ν C ratio, which is independent of the choice of the A component. 相似文献
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Using Zubarev's method of nonequilibrium statistical operator, the generalized hydrodynamic equations are obtained for a model of magnetic liquid in an inhomogeneous external field. In this model the “liquid” subsystem is treated as a classical one and the “magnetic” subsystem is described by quantum mechanical methods. The properties of the transport equations are analysed in the case of a weak nonequilibrium. The equations for time correlation functions and collective mode spectrum are also found in the same manner. It is shown that the generalized hydrodynamic equations reduce to the well-known results in the limiting cases when the dynamic variables of one subsystem are formally neglected. As an illustration, a simple model of spin relaxation is considered, and the frequency matrix and the matrix of memory functions are calculated. A comparison with previous works is made. 相似文献
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We investigate the quasi-energy spectrum of a quantal parametric resonator, whose frequency is modulated by a periodic δ (t) term. The system displays two distinct phases, depending on the nature (discrete or continuous) of the quasi-energy spectrum. We investigate the dynamics in the two phases and the transition between them which is induced by varying the coupling strength. Special attention is given to those observables which might be used as indicators of stochasticity in the quantum dynamics. 相似文献
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Celliers PM Collins GW Da Silva LB Gold DM Cauble R Wallace RJ Foord ME Hammel BA 《Physical review letters》2000,84(24):5564-5567
Simultaneous measurements of shock velocity and optical reflectance at 1064, 808, and 404 nm of a high pressure shock front propagating through liquid deuterium show a continuous increase in reflectance from below 10% and saturating at approximately (40-60)% in the range of shock velocities from 12 to 20 &mgr;m/ns (pressure range 17-50 GPa). The high optical reflectance is evidence that the shocked deuterium reaches a conducting state characteristic of a metallic fluid. Above 20 &mgr;m/ns shock velocity (50 GPa pressure) reflectance is constant indicating that the transformation is substantially complete. 相似文献
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S. K. Aslanov 《Technical Physics》1999,44(11):1386-1387
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Poivet S Nallet F Gay C Teisseire J Fabre P 《The European physical journal. E, Soft matter》2004,15(2):97-116
We perform traction experiments on viscous liquids highly confined between parallel plates, a geometry known as the probe-tack test in the adhesion community. Direct observation during the experiment coupled to force measurement shows the existence of several mechanisms for releasing the stress: while fingering is favored for low traction velocities, low confinement and low viscosity, nucleation of bubbles occurs in the opposite conditions. It is possible to quantitatively predict the transition between the two regimes and, in many respects, describe the shape of the force response. Using a model for purely viscous fluids, we also present a phase diagram for the different force peak regimes that remarkably accounts for the data. Our results show that conspicuous features of the traction curve commonly thought to be characteristic of soft viscoelastic solids like adhesives are already encountered in liquid materials.Received: 30 July 2004, Published online: 26 October 2004PACS:
82.35.Gh Polymers on surfaces; adhesion - 47.55.Bx Cavitation - 83.50.Jf Extensional flow and combined shear and extension 相似文献
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纸杯中残留苯并(a)芘在食品模拟物中的相对迁移率研究 总被引:1,自引:0,他引:1
采用具有高分辨、高灵敏度的导数-恒能量同步荧光法分析测定了不同条件下,纸杯中残留苯并(a)芘在水性模拟液和脂肪模拟液中的迁移量.探讨了模拟物的种类、浸泡时间和温度对纸杯中苯并(a)芘的相对迁移率的影响.结果表明:该分析方法的回收率为89.2~104.3%;纸杯中残留苯并(a)芘在脂肪模拟液中的相对迁移率明显高于水性模拟液的,纸杯盛装冷水时无苯并(a)芘浸出.而用于盛装热水可浸出苯并(a)芘;温度越高,浸泡时间越长,纸杯中苯并(a)芘向食品模拟液的相对迁移率也越大. 相似文献
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El-Sayed MF 《The European physical journal. E, Soft matter》2004,15(4):443-455
A linear electrohydrodynamic instability analysis is presented for an inviscid dielectric liquid sheet emanated into an inviscid dielectric gas medium in the presence of a horizontal electric field. The influence of Weber number, gas-to-liquid density ratio, and the applied electric field on the evolution of two-, and three-dimensional disturbances of symmetrical and antisymmetrical types is studied. It is found, for antisymmetrical waves, that two-dimensional disturbances always prevail over three-dimensional disturbances, regardless of Weber number or gas-to-liquid density ratio values, especially for long waves; while for short waves, both two- and three-dimensional disturbances grow at approximately the same rate. It is also found, for symmetrical waves, that two-dimensional disturbances always dominate the instability process at low Weber number, and when the Weber number is large, symmetrical three-dimensional disturbances become more unstable than two-dimensional ones for long waves. The effect of increasing the gas-to-liquid density ratio is to promote the dominance of long three-dimensional symmetrical waves over their two-dimensional counterpart. Finally, the equilibrium Weber number at which the growth rates of two- and three-dimensional modes are equal is discussed for both symmetrical- and antisymmetrical-disturbances cases.-1 相似文献
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Philipp Wagener Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2010,101(2):435-439
We present a novel approach for laser fragmentation of melamine cyanurate microcrystals suspended in liquid into colloidal
nanoparticles. Laser fragmentation is done by irradiating a liquid jet of melamine cyanurate suspended in water with intense
picosecond pulses. The free liquid jet is generated by a nozzle with small diameter and provides a thin liquid filament (d
fil<1 mm) perpendicular to the focused laser beam. This geometry allows tight focusing resulting in high intensities without
the danger of damaging an optical element like windows necessary in conventional flow cells or cuvettes. It reduces losses
of excitation light by avoiding scattering or absorption in front of the focus. We stabilized the nanoparticles electrosterically
in-situ with neutral and polyelectrolytic polymers preventing agglomeration and precipitation. The threshold for sufficient
stabilization of laser-fragmented nanoparticles (d
hydrodyn≈200 nm) is reached at a mass fraction of 0.25 wt% dextrin as a neutral polymer and 0.01 wt% polyacrylic acid as a polyelectrolytic
polymer. Hydrodynamic size and zeta-potential of the nanoparticles can be controlled by mass fraction of the stabilization
agent. 相似文献
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The polyamorphism of liquid silica (SiO2) at 3200?K and in a wide pressure range is investigated by molecular dynamics simulation. Results show that the structure of liquid SiO2 consists of five order-parameters that do not depend on compression. Three order parameters that relate to the short-range order are SiOx coordination units (x?=?4, 5, 6) and two order parameters that relate to the intermediate-range order are OSi2 and OSi3 linkages. The structure of liquid silica under compression can be described by the two-state model: low-density and high-density states. The low-density state is formed by clustering of OSi2 linkages (in the low-density state, the short-range order (SRO) is mainly characterized by SiO4 coordination units), conversely, clustering of OSi3 linkages will form high-density state (in the high-density state, the SRO is mainly characterized by SiO5 and SiO6 coordination units). Under compression, in the liquid silica co-exist two phases: low-density and high-density phases. The size of phase regions significantly depends on compression. 相似文献
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