Ion heat and parallel momentum transport by stochastic magnetic fields and turbulence

The theory of turbulent transport of parallel momentum and ion heat by the interaction of stochastic magnetic fields and turbulence is presented. Attention is focused on determining the kinetic stress and the compressive energy flux. A critical parameter is identified as the ratio of the turbulent scattering rate to the rate of parallel acoustic dispersion. For the parameter large, the kinetic stress takes the form of a viscous stress. For the parameter small, the quasilinear residual stress is recovered. In practice, the viscous stress is the relevant form, and the quasilinear limit is not observable. This is the principal prediction of this paper. A simple physical picture is developed and shown to recover the results of the detailed analysis.

Reciprocal-condition-number-based borehole acoustic dispersion curve prediction

The prediction of dispersion curves is an essential part of understanding borehole acoustic modes. Traditional dispersion curve calculation requires finding zeros of the determinant of the characteristic matrix of a borehole system. This approach is subject to interpretational ambiguity because the determinant can be scaled arbitrarily. We have developed an alternative approach based on the reciprocal condition number (RCN) of the characteristic matrix. The RCN quantifies the singularity of a matrix on a fixed scale between zero and unity; thus, it represents wave modal strengths. We find that our method and traditional methods give identical dispersion-curve locations for simple models and that our method provides more insights on the wave modal amplitudes of complicated models with multiple layers, such as those incorporating logging tools and casing strings. Finally, we determine how our method can be used as the basis of sensitivity analysis to indicate how the dispersion curves are dependent on the model parameters.

Spectral properties of anterior sibilant fricatives in Northern Peninsular Spanish and sibilant-merging and non-merging varieties of Basque

This paper focuses on the spectral properties of anterior sibilant fricatives in Northern Peninsular Spanish, and sibilant-merging and non-merging varieties of Basque. Non-merging varieties of Basque have two voiceless anterior sibilant fricatives, characterized as apico-alveolar and lamino-alveolar. In other Basque varieties, however, these two phonemes have merged with varying results. Twenty-four participants divided into four different groups have been studied. One group is a set of monolingual Spanish speakers from north-central Spain, while the remaining three are Basque–Spanish bilingual groups with different sibilant fricative systems in Basque. The goal is to describe the spectral properties of anterior sibilant fricatives and examine the effect of the L1-Basque sibilant system upon L2-Spanish. The Basque varieties chosen are: (i) Azpeitia Basque, where merging in favor of the lamino-alveolar sibilant fricative has occurred; (ii) Lemoa Basque, where the merging in favor of the apico-alveolar sibilant fricative is widespread; and (iii) Goizueta Basque, where no merging has happened. Participants took part in an elicitation task where they produced sentences containing target words with an intervocalic anterior sibilant fricative in Basque and Spanish. Bayesian probability was used for inferential statistics. Speakers of the non-merging Basque variety show the narrowest acoustic dispersion of /s/ in Spanish, as opposed to broader diffusion in the other three groups. Regarding L1 transfer, while the Azpeitia group does not show transfer into Spanish, the Lemoa and Goizueta groups do. Results show that /s/ is more fronted for monolingual Spanish speakers from north-central Spain than the previous literature has reported.

Kinetic and Activation Characteristics of Structure Rearrangement Processes in Ethoxylated Isononylphenol Derivates

The paper presents the calculation results of the kinetic and activation characteristics of fast and ultrafast structure rearrangement processes in liquid hydroxyethylated derivates of isononylphenol (ОНФn). Parameters were calculated using the relaxation theory of acoustic spectroscopy of liquids based on the analysis of the acoustic spectra of speed and sound absorption of the hydroxyethylated derivates of isononylphenol. The paper shows that two simple regions of acoustic dispersion can describe the acoustic spectra in the frequency range from 12 MHz to 2 GHz and the temperature range from 253 K to 323 K. The dispersion region data in the hydroxyethylated derivates of isononylphenol correspond to the interconnected reactions of OH ... O bonding and breaking in chain associates and spatially branched network structures. It is noted that the change in the spatial structure of liquid hydroxyethylated derivates of isononylphenol can be considered as a set of the large number of independent (for non-collective processes) and interconnected (for collective processes) local rearrangements of the liquid structure as a result of the thermal motion of molecules. The proposed molecular mechanism of acoustic relaxation and the kinetic model of fast and ultrafast structure rearrangement processes of the hydroxyethylated derivates of isononylphenol made it possible to explain the main experimental results and to calculate the kinetic and activation characteristics of the structure rearrangement processes of the hydroxyethylated derivates of isononylphenol. This model and the kinetic and activation parameters of the hydroxyethylated derivates of isononylphenol can find application in development of various technologies for using nonionic surfactants.

Автоволновой импульс в среде с дисбалансом между тепловыделением и теплоотводом при произвольной величине тепловой дисперсии

An analytical method for determining the amplitude and velocity of an autowave pulse emerging in isentropically unstable heat-releasing media is presented. The method is suitable for any values of acoustic dispersion and growth rate and requires the knowledge of heat-loss function only without the need for a numerical solution of a complete system of gas-dynamic equations.