Dependence of the viscosity of nanofluids on nanoparticle size and material

The viscosity of nanofluids as a function of nanoparticle size and material is modeled and analyzed. Dependences of the viscosity of nanofluids based on liquid argon with aluminum and lithium nanoparticles are obtained. The nanoparticle size ranges from 1 to 4 nm. The volume concentration of nanoparticles is varied from 1% to 12%. It is shown that the viscosity of the nanofluid increases with decreasing nanoparticle size and, in addition, depends on the nanoparticle material.     

温度对液体黏度影响的实验研究

利用自主开发的多光电门可变温式液体黏度测试仪研究了液体黏度随温度变化的关系,得到了实验曲线,显示了不同温度区段的变化特性.     

High pressure guided falling body viscometer. Representation of alkanes viscosity as a function of temperature and pressure

Abstract

A guided falling body viscometer developed in our laboratory for the measure of the viscosity coefficient of liquids (up to 400MPa; temperature range: -10 to 200°C) is described here.

This study presents a method developed from experimental results concerning the viscosity of pure linear alkanes (n-C₁₀ to n-C₁₈) and their mixtures in reservoir fluid conditions (up to 100MPa and 20 to 100°C). For such groups, we propose a representative formulation (based on a Vogel type analytical expression and using the same set of empirical coefficients for all compounds) which needs only knowledge of molecular weight.     

Effects of viscosity on water waves

Summary The paper deals with the behaviour of a viscous liquid whose flow preserves the structure of the material columns. A balance law for energy is established which accounts for Navier-Stokes dissipation; on appealing to the invariance of such a low under rigid motions, balance equations for mass and linear momentum are derived. It is an outstanding consequence of the theory that the simultaneous occurence of viscosity and inertia terms makes long gravity waves be governed by the combined Korteweg-de Vries and Burgers equation.

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Riassunto Si considera il comportamento di un liquido viscoso il cui flusso conserva la struttura delle colonne materiali. Si formula un bilancio dell'energia che contiene il termine dissipativo di Navier-Stokes; applicando quindi l'invarianza di tale legge di bilancio per moti rigidi si deducono le leggi di bilancio per la massa e la quantità di moto. è una rilevante conseguenza della teoria che, per la simultanea presenza di termini inerziali e viscosità, le onde lunghe di gravità sono governate dall'equazione combinata di Korteweg-de Vries e Burgers.

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Резюме Рассматривается поведение вязкой жидкости, поток которой сохраняет структуру столба вешества. Формулируется баланс энергии, который содержит диссипативный член Навье-Стокса. Используя инвариантность этого закона относительно недформируемых движений, выводятся уравнения баланса для массы и импульса. Получено важное следствие зтой теории: одновременное появление членов, связанных с вязкостью и инерцией, приводит к что длинные гравитационные волны определяются объединенным уравнением Кортевега-де Вриса и ъургерса.

     

Dependence of hot carriers temperature on lattice temperature in CdS

Non-equilibrium carrier distributions were obtained in CdS at various temperatures from 77 to 400K. A study is made of the influence of the lattice temperature on the carrier temperature. It is found that the higher the lattice temperature the lower is the difference between carrier and lattice temperatures, though carriers are always thermalized among themselves. The results can be accounted for by carrier relaxation through optical polar phonon emission.     

Dependence of single-bubble sonoluminescence on ambient pressure

Kondic et al.'s theory makes several specific predictions on the dependence of single-bubble sonoluminescence (SBSL) on ambient pressure. We have carried out experiments to verify these predictions for air bubbles in a water-glycerine mixture at about 17.5 kHz. The results show an increase in SBSL with reduced ambient pressure down to a critical value below which SBSL is extinguished. The results are all in good agreement with Kondic et al.'s theory and are also compatible with the dissociation hypothesis of Lohse et al.     

Dependence of electromagnetically induced transparency on temperature

We performed an experimental study on the dependence of the linewidth of electromagetically induced transparency (EIT) on the temperature of medium in a Λ-type configuration using caesium vapour. We found that the transparent window is narrowed in the EIT whose two ground levels are composed of two hyperfine levels, and broadened in the case when the two ground levels are degenerated Zeeman sublevels, as the temperature of vapour cell is increased. The explanation for the phenomena is given qualitatively.     

High pressure studies of viscosity effects on isomerization

Abstract

The viscosity dependence of the isomerization process with comparatively low potential barrier was studied as a model of one-dimensional barrier crossing.

We found that the ground-state isomerization of DODCI fails to fit the Kramers equation. We analyzed this non-Kramers behavior by means of an approach of frequency dependent friction.     

Measurements of near-IR water vapor absorption at high pressure and temperature

Tunable diode lasers (TDLs) are used to measure high resolution (0.1 cm^-1), near-infrared (NIR) water vapor absorption spectra at 700 K and pressures up to 30 atm within a high-pressure and -temperature optical cell in a high-uniformity tube furnace. Both direct absorption and wavelength modulation with second harmonic detection (WMS-2f) spectra are obtained for 6 cm^-1 regions near 7204 cm^-1 and 7435 cm^-1. Direct absorption measurements at 700 K and 10 atm are compared with simulations using spectral parameters from HITRAN and a hybrid database combining HITRAN with measured spectral constants for transitions in the two target spectral regions. The hybrid database reduces RMS error between the simulation and the measurements by 45% for the 7204 cm^-1 region and 28% for the 7435 cm^-1 region. At pressures above 10 atm, the breakdown of the impact approximation inherent to the Lorentzian line shape model becomes apparent in the direct absorption spectra, and measured results are in agreement with model results and trends at elevated temperatures reported in the literature. The wavelength-modulation spectra are shown to be less affected by the breakdown of the impact approximation and measurements agree well with the hybrid database predictions to higher pressures (30 atm). PACS 33.20.Ea; 42.62.Fi; 52.25.Os     

Effects of pressure and temperature on the solubility of monosodium L-glutamate monohydrate in water

Abstract

The solubility of monosodium L-glutamate monohydrate (MSG.H₂O) in water was measured at pressures in the range of 0.10-300MPa and 298.15K. The density of MSG solution at high concentrations and heat of solution at saturated concentration were also measured at atmospheric pressure. The solubility, m_s, increased with increasing pressure and the pressure coefficient, Θ_p, [?(? In m_s,? p)_T] at 0.10 MPa was (2.0 ± 0.1) × 10-¹⁰Pa-1. It agrees well with (2.1 ±0.2)× 10-¹⁰ Pa-¹ thermodynamically estimated using the partial molar volume, the activity coefficient of the solute in solution, and the molar volume of the crystal. The excellent agreement at 0.10MPa gives us confidence in the solubility data at higher pressures. The heat of solution data and other pertinent values were used to calculate the temperature coefficient of solubility, Θ_T [? (? In m_s/?(1/T))_p], by a thermodynamic equality. The resulting Θ_T compares well with the data directly measured by Ogawa.     

Dependence of permittivity of diluted octanol on temperature

The dielectric constant of octanol diluted in decane, cyclohexane and carbon tetrachloride for different concentrations has been measured as a function of temperature. The experimental data were adjusted with a modified Onsager's equation to which a term that diminishes the dipolar interaction was added. This empirical equation has already been employed and published earlier for pentanol solutions in the same solvents. Good agreement has been found between experimental and predicted permittivity values and the results obtained for the diverse solvents used are compared and analysed, together with the parameters resulting from the fittings. The differences in behaviour between octanol and pentanol are analysed.     

铁电体中相界运动对压力的依赖性

在平均场理论的框架内研究了KNbO3 中的顺电—铁电相界在静水压的运动。纠缠解被用于不同压力下相界宽度和速度的计算。计算基于居里—外斯常数的实验数值和自由能的金兹堡—朗道展开式的参数。非经验性地研究了对静水压和三相点的响应。     

Application of SH surface acoustic waves for measuring the viscosity of liquids in function of pressure and temperature

Viscosity measurements were carried out on triolein at pressures from atmospheric up to 650 MPa and in the temperature range from 10 °C to 40 °C using ultrasonic measuring setup. Bleustein–Gulyaev SH surface acoustic waves waveguides were used as viscosity sensors. Additionally, pressure changes occurring during phase transition have been measured over the same temperature range. Application of ultrasonic SH surface acoustic waves in the liquid viscosity measurements at high pressure has many advantages. It enables viscosity measurement during phase transitions and in the high-pressure range where the classical viscosity measurement methods cannot operate. Measurements of phase transition kinetics and viscosity of liquids at high pressures and various temperatures (isotherms) is a novelty. The knowledge of changes in viscosity in function of pressure and temperature can help to obtain a deeper insight into thermodynamic properties of liquids.     

Dependence of the surface energy of metals on pressure

A theoretical model has been developed within the method of electron-density functional to describe the effect of pressure on the surface energy of pure metals.     

Dependence of the type of fracture on temperature and strain rate

A way to determine conditions for the viscous-brittle transition preceding the fracture of a solid is suggested. The viscous-brittle transition is viewed as the result of competition between different fracture mechanisms. The model suggested in this work is valid in wide ranges of strain rates and temperatures. The temperature and strain rate intervals within which brittle fracture is most probable are calculated for several materials.     

Dependence of magnetic ordering temperature of doped and undoped EuFe2As2 on hydrostatic pressure to 0.8 GPa

The ac susceptibility of single crystalline tetragonal EuFe₂As₂, EuFe₂As_1.4P_0.6, and EuFe_1.715Co_0.285As₂ has been measured over the temperature and hydrostatic (He-gas) pressure ranges 10–60 K and 0–0.8 GPa, respectively. For all three samples the magnetic ordering temperature (17–19 K) from the Eu sublattice increases linearly with pressure, presumably due to the enhanced exchange coupling between Eu-layers. No evidence for a superconducting transition was observed in the susceptibility for any sample over the measured temperature/pressure range.