幂律流体在圆管内湍流流动剪切率的近似计算

根据剪切率和能量耗散率的定义，建立了幂律流体湍流剪切率与能量耗散率的关系式。参照文献上对不可压缩牛顿流体湍流能量耗散率的近似算法，提出了一种幂律流体管内湍流能量耗散率的近似算法，从而得到了幂律流体管内湍流剪切率的实用近似算式，再利用湍流剪切率与脉动流剪切率的关系即可得到脉动流剪切率。计算得到的湍流剪切率分布及其随流动特性指数变化的特征与已知规律相符。     

ICRF Experiments and GAMMA 10 Potential Formation on the Tandem Mirror

Target plasmas, on which the formation of the electrostatic potentials and the improvement of the confinement are studied, are produced with ICRF in the GAMMA 10 tandem mirror. The ion temperature of more than 10 keV has been achieved in relatively low density plasmas. When the strong ICRF heating is applied, it is observed that the high frequency and the low frequency fluctuations are excited and suppress the increase of the plasma parameters. Recently, a new high power gyrotron system has been constructed and the ECRH power in plug extends up to 370 kW. The improvement of the confinement due to the formation of the potential in the axial direction and the strong radial electric field shear has been observed.     

Daily Fluctuations in Self-Control Demands and Alcohol Intake.

Predictions made by the self-control strength model were tested in a sample of underage social drinkers using ecological momentary assessment methodology. On days that participants experienced more self-control demands than average, they were more likely to violate their self-imposed drinking limit after controlling for mood and urge to drink. There was no relationship between self-control demands and urge or intention to drink, nor were self-control demands related to plans to limit drinking. When individuals planned to limit their alcohol intake, they were more affected by self-control demands than when they did not plan to limit their alcohol intake. Trait self-control moderated these relationships. Consistent with the self-control strength model, it appears that exerting self-control in nondrinking areas undermines individuals' capacity to exert self-control of drinking in daily life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measurement of transport properties of liquids with equilibrium and nonequilibrium Rayleigh scattering

We have developed an experimental arrangement for measuring Rayleigh scattering in liquids and liquid mixtures that are either in thermal equilibrium or in thermal nonequilibrium states. As an illustrative example we report experimental values for the thermal dilfusivity, the mass diffusion coefficient, the Rayleigh-factor ratio, and the Suret coefficient of an equimolar mixture of liquid toluene andn-hexane.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994 Boulder Colorado U S A     

Broadening of the vibrational linewidth in a mixture due to critical concentration fluctuations

Vibrational Raman spectroscopy is a very usful technique for studying the dynamical behavior of a system, in particular in the critical region. In a mixture, composition fluctuations play an important role and on the basis of the results for pure substances one would expect an increase of the linewidth in approaching the critical point. However, in previous experiments such an effect was not detected. The reasons for this failure will be discussed. Recently, we have observed a considerable broadening of the linewidth in approaching the critical point in the system helium-nitrogen under high pressure. However, it is well-known that broadening may occur through various other mechanisms such as changes in density, composition fluctuations far from the critical point, aggregation, etc. On the basis of the helium-nitrogen data the pitfalls in the experimental determination of critical broadening are discussed. The data analysis takes into account the contribution of noncritical effects. Consequences are drawn for the interpretation of spectroscopic data in terms of concentration of species in supercritical solvents. Moreover, we discuss the possibility of a difference between the local composition and the bulk composition and demonstrate from our line shift data that this is not a critical effect.Invited paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Decay rate of critical fluctuations in steam and in dilute steam-NaCl mixtures

The decay rate of critical fluctuations in steam and in a steam-NaCl mixture has been investigated experimentally with the aid of photon correlation spectroscopy. For pure steam, the measurements have been performed along seven isochores [(¦– _c¦)/_c<0.09] as a function of the temperatureT for (T–T_t)<1 K. The results have been compared with the values predicted by the renormalization-group theory written as a modification of the classical mode coupling theory. The agreement between experiment and theory is satisfactory along the critical isochore, but larger deviations are noted for _c when approching the transition temperatureT _t. The decay rate of a 0.1% (molar) dilute mixture of NaCl in H₂O has been measured along some near-critical isochores as a function of temperature. Its behavior, which is very different from that observed for pure steam, is dicussed.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Temperature fluctuations in a solid-nitrogen cooled secondary frequency standard

Liquid helium and liquid nitrogen are commonly used as coolants for highly frequency stable oscillators. In this paper, we present the use of solid nitrogen as an alternative coolant. Solid nitrogen solidifies near 52 K under vacuum and we show that the temperature fluctuations in the solid are an order of magnitude lower than in the liquid. This has the advantage of reducing the temperature control requirements necessary to limit temperature induced frequency fluctuations in cryogenic microwave resonator-oscillators.     

Transport properties of fluids near critical points

The paper reviews the theoretical and experimental results for the asymptotic behavior of the dynamics of critical fluctuations in fluids and fluid mixtures near a critical point. The implications of these results for the development of accurate representative equations for the viscosity and thermal conductivity of gases in the critical region are discussed.Invited lecture presented at the 10th International Conference on the Properties of Steam, Moscow, USSR, September 2–7, 1984.     

Imperfections and resonant tunneling in quantum-well heterostructures

We discuss effects of structural imperfections on the I-V characteristics and local density-of-states of semiconductor double-barrier heterostructures. Using a linear-chain model for GaAs/AlGaAs structures, we simulate fluctuations in layer thicknesses, defects at the heterointerfaces, and disorder.     

Renormalization Group Theory for Fluids to Greater Density Distances from the Critical Point

A recently developed renormalization group (RG) theory for fluids begins with an expression for the free energy for repulsive interactions only, then employs an RG procedure to take into account contributions to the free energy that come from fluctuations of all wavelengths in the presence of attractive inter-molecular interactions of limited range. The theory has had some success in describing volumetric properties of real fluids at the critical point and out to distances within approximately ±50% of the critical point density. In the calculations, the density dependence of the radial distribution function for the repulsive interactions was ignored. The theory has now been modified to take that density dependence into account. Predictions of the theory as thus amended are compared with volumetric measurements made in argon near the critical point temperature for densities from zero to more than twice the critical point density.