Results 1 - 10 of 718
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[en] Highlights: ► We identify the indicators to characterise isentropic lines. ► Fluids with an isentropic index k < 1 behave differently than those with k > 1. ► The critical molar volume allows to classify fluids with k > 1 and k < 1. ► The engineering implications of the above findings are analysed. - Abstract: The three indicators of isentropic lines, namely, the isentropic index, the ratio of pressure and density p/ρ and the derivative (∂p/∂ρ)s are investigated for all of the fluids in the RefProp 9.0 program. The behaviour of these three entities is evaluated along the saturated vapour line as well as in the superheated vapour region. There is a distinct demarcation of fluids whose isentropic indices can be less than 1 and others for which this behaviour is absent. The critical molar volume is found to be the characterizing feature. Several other interesting features of those three thermodynamic properties are also highlighted. It is observed that most practical engineering compression and expansion processes occur along the decreasing direction of the sound speed.
[en] We study the properties of the second eigenvalue of the transition matrix in unimodal and bimodal map's families. We use in particular the relation with the mixing rate and apply this to classify families of isentropic bimodal maps. We present also a study which show the convergence of this quantity in those families
[en] Highlights: • Limiting partial molar isentropic compressions for small amphiphiles were experimentally determined and compiled. • A simple additive scheme was applied to 31 amphiphiles in order to estimate group contribution values and their uncertainties. • The effect of temperature was studied for temperatures ranging T = (283.15 to 303.15) K. • Few large deviations for molecules not included in the basic set, are tentatively explained. -- Abstract: A simple additive scheme based on a multi-parametric least-squares fitting method is described and employed to estimate group-contributions to limiting partial molar isentropic compressions of small amphiphile molecules in water. To complement high quality literature data for aqueous solutions of aliphatic alcohols, alkoxyalcohols, amines, alkoxyamines, aminoalcohols, amino-acids and dipeptides, new accurate densities and ultrasound speeds have been experimentally determined for several very-dilute aqueous solutions of 2-(isopropylamino)ethanol, 2-butoxyethanol and 2-isobutoxyethanol at 5 K intervals in the temperature range T = (283.15 to 303.15) K. Reliable limiting partial molar isentropic compressions for 31 amphiphiles in water at five fixed temperatures have been used to estimate group-contribution values and their associate uncertainties of the following eleven structural groups: CH3; CH2; CH; N; NH; NH2; CH2COCH2; CH2OH; CHOH; COOH; and CONH, at five different temperatures. The goodness of the fit of reconstituted against experimental values indicates that a consistent set of group-contribution values has been obtained and that their dependence on temperature deserves credit. These values and their sensibility to temperature changes have been analysed in terms of hydration processes in solution. Deviations of predicted from experimental values are found for molecules containing a vicinal diol group and dipeptides showing hindrance or enhancement of H-bond formation. These deviations for molecules not included in the basic set, are tentatively explained
[en] We propose a new model which describes relativistic hydrodynamics and generalizes the standard Euler system of isentropic perfect fluids. Remarkably, our system admits a convex extension which allows us to transform it to a symmetric hyperbolic form. This result sheds new light even on the relativistic Euler system. (paper)
[en] In this work, we explore the possible existence of several critical endpoints in the phase diagram of strongly interacting matter using an extended PNJL model with ’t Hooft determinant and eight quark interactions in the up, down and strange sectors. Besides, we also study the isentropic trajectories crossing both (light and strange) chiral phase transitions and around the critical endpoint in both the crossover and first-order transition regions.
[en] We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from previous linearly divergent channel. The divergence enhancement in the channel upstream is effective for suppressing an excessive increase in static pressure, whereby notably high isentropic efficiency is achieved.
[en] Changes of type transitions for two-component hydrodynamic type systems are discussed. It is shown that these systems generically assume the Jordan form (with Jordan block) on the transition line with hodograph equations becoming parabolic. Conditions which allow or forbid the transition from the hyperbolic domain to elliptic one are discussed. Hamiltonian systems and their special subclasses and equations, such as dispersionless nonlinear Schrödinger, dispersionless Boussinesq, one-dimensional isentropic gas dynamics equations, and nonlinear wave equations are studied. Numerical results concerning the crossing of transition line for the dispersionless Boussinesq equation are also presented. (paper)
[en] The idea of reflectionless propagation of a shock wave in a layered body is discussed. This effect can be achieved (on the basis of the data in /7/) making use of the phenomena connected with the profiling of the pressure. A reflectionless wave in a stratified medium is accompanied by a simultaneous process of the medium becoming homogeneous by means of a programmed sequence of waves. The results obtained will be applied to the problem of thermonuclear microfusion, to methods of inducing a process of isentropy and to the amplification of compression. A parallel work concerns the analogous problem of a dispersionless shock wave in a continually nonhomogeneous medium. (author)