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Due to their potential applications in energy production based on waste heat, direct solar radiation or other energy sources, semiconductor materials have for years attracted the attention of theoretical and experimental researchers. The focus has been on improving the performance of thermoelectric devices through several strategies and special interest has been placed on materials with spatially inhomogeneous transport properties. Inhomogeneity can be achieved in various ways, all of them leading, to a greater or lesser extent, to an improvement of the thermoelectric performance. In this paper, general linear heat and electric charge transport processes in inhomogeneous materials are addressed. The guiding idea followed here is that there exists a relationship between inhomogeneity (structuring), minimum entropy production and performance which may be fruitfully exploited for designing more efficient thermoelectric semiconductor devices. We first show that the stationary states of such materials are minimum global entropy production states. This constitutes an extension of the validity of Prigogine's minimum entropy principle. The heat and charge transport equations obtained within the framework of classical irreversible thermodynamics are solved to find the stationary profiles of temperature and self-consistent electric potential in a one-dimensional model of a silicon–germanium alloy subjected to an external temperature difference. This allows us to assess the effect of the spatial inhomogeneity on the thermoelectric performance. We find that, regardless of the value of the applied temperature difference, the system may efficiently operate in a regime of minimum entropy production and high efficiency. [ABSTRACT FROM AUTHOR]

The following research is a literature and case review focused on the characteristics of the Millennial Generation, and their importance as consumers, through a case study of the company "Airbnb" as an example of a disruptive business model that has been able to capitalize on this generation. The structure of the work is the following: Firstly, we contextualize the research by defining the key topics, such as collaborative economy, strategic advantages, the millennial generation, then we discuss the history and strategies of the company Airbnb, as a disruptive and successful business model, explaining their general strategy and challenges they have faced, as well as their strategy specifically geared towards the Millennial niche. Finally, we conclude on the importance of disruptive business models and the challenges that companies like Airbnb are facing and will have to face in the future in order to continue in the market. The main contribution of this research is the analysis of Airbnb's strategies as they grow as a company and focus their efforts on the Millennial Generation in order to ensure their survival in an important and long-established market. [ABSTRACT FROM AUTHOR]

An equation of state for a multicomponent mixture of nonadditive hard spheres in d dimensions is proposed. It yields a rather simple density dependence and constitutes a natural extension of the equation of state for additive hard spheres proposed by us [A. Santos, S. B. Yuste, and M. López de Haro, Mol. Phys. 96, 1 (1999)]. The proposal relies on the known exact second and third virial coefficients and requires as input the compressibility factor of the one-component system. A comparison is carried out both with another recent theoretical proposal based on a similar philosophy and with the available exact results and simulation data in d=1, 2, and 3. Good general agreement with the reported values of the virial coefficients and of the compressibility factor of binary mixtures is observed, especially for high asymmetries and/or positive nonadditivities. ©2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Computer simulations have been performed on binary fluid mixtures of hard hyperspheres in four and five dimensions. The equation of state and the radial distribution function have been obtained for a variety of compositions and size ratios. The simulation results for the excess compressibility factor and the contact values of the cross radial distribution functions in both dimensions are described rather accurately by a recent theoretical proposal for these quantities up to a reduced density where some features arise which are reminiscent of a fluid-solid phase transition. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An equation of state for a fluid of hard disks is proposed: Z=[1-2η+(2η0-1)(η/η0)2]-1. The exact fit of the second virial coefficient and the existence of a single pole singularity at the close-packing fraction η0 are the only requirements imposed on its construction. A comparison of the prediction of virial coefficients and of the values of the compressibility factor Z with those stemming out of other known equations of state is made. The overall performance of this very simple equation of state is quite satisfactory. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The hydrodynamic drag on the spherical beads of a dilute suspension of multibead–spring–rod chains immersed in a Newtonian solvent in steady elongational flow is calculated with the method of induced forces. Hydrodynamic interactions between the beads cause the drag to be anisotropic in space while the friction tensors exhibit a nonanalytic dependence on the velocity gradient when nonlinear terms in the quasistatic Navier–Stokes equation are considered. A discussion of the differences with the phenomenological form usually adopted in polymer dynamics is given and potential applications of the results in rheology are highlighted. [ABSTRACT FROM AUTHOR]

The effect of including corrections to the Oseen hydrodynamic interaction in the rheological properties of polymer solutions is investigated. The case of a dilute suspension of Rouse–Zimm–Bueche dumbbells in steady shear flow is examined within the consistent averaging approximation due to Öttinger [J. Chem. Phys. 83, 6535 (1985)]. A reduction of the values of the material functions as compared to the results obtained in the Oseen approximation is observed. The effect is most important at zero shear rate and the highest allowed value of the hydrodynamic interaction parameter. It decreases when either the shear rate is increased or the hydrodynamic interaction parameter is lowered. The ratio of the second to the first normal stress coefficients is always a small positive quantity. [ABSTRACT FROM AUTHOR]

The extended thermodynamic treatment developed in part I for a fluid with internal degrees of freedom, is used to calculate its Rayleigh–Brillouin spectrum. A hydrodynamic model is first constructed which involves unspecified phenomenological coefficients. When these coefficients are identified in terms of experimental parameters, reasonably good agreement is obtained between the calculated and measured dynamic structure factor of CS2 at 20 °C with a density 1.262 g/cm3 and for k=8.608×10 cm-1. It is also shown that when the relaxation times of the trace and the nondeviatoric part of the stress tensor of the fluid tend to zero, the results previously derived by Mountain are recovered. The possible connections between this extended thermodynamic approach and Rytov’s hydrodynamic theory are also hinted at. [ABSTRACT FROM AUTHOR]

Approximate analytical expressions for the values of the derivatives of the radial distribution function at contact in a hard-sphere fluid are derived. These expressions are obtained within a rational function approximation (RFA) method recently developed. The results are compared with those based on the Percus-Yevick approximation, as well as with those obtained from expressions for the cavity function inside the core or through computer simulations. While the qualitative dependence on the packing fraction is similar for the values of the first two derivatives at contact in all cases, the one corresponding to the third derivative is definitely different in our approach from that previously reported. The integral moments of the total correlation function as given by the RFA method are also computed. [ABSTRACT FROM AUTHOR]

Using the revised Enskog theory we derive equations for the thermal diffusion ratios kTi and thermal diffusion factors αij of multicomponent hard-sphere mixtures for systems in mechanical equilibrium. The first ten Enskog approximations to the thermal diffusion factor αij[N] (N=1,2,...,10) are evaluated numerically for a variety of system parameter choices appropriate to binary and ternary mixtures. We find that the first Enskog approximation does not vanish; the sequence of Enskog approximations converges most rapidly when the mass of the spheres are nearly equal. The seventh Enskog approximation was estimated to lie within about 1% of the exact value for all choices of system parameters. A comprehensive numerical study of the properties of the thermal diffusion factor for binary mixtures is given, including special mixtures such as the dusty gas, the Lorentz, quasi-Lorentz and Rayleigh gases, and isotopic mixtures. Particular emphasis is placed on showing how the properties of α12 change as the density is increased. The most striking difference between the low-density (Boltzmann) and high-density values for α12 is that the region of the mass ratio—diameter ratio plane for which α12 is either strictly positive or negative, as a function of composition, is much smaller at high densities. Also, at higher densities α12 is not a monotonic function of the mole fraction. For ternary mixtures in which two of the components are isotopes we show how the properties of the third component affect the separation of the two isotopes. [ABSTRACT FROM AUTHOR]

The equilibrium concentration autocorrelation function for an inert binary mixture is calculated by means of extended irreversible thermodynamics. The ensuing generalized transport coefficient is explicitly evaluated and the corresponding k-dependent relaxation time is also obtained. The connection with neutron scattering experiments is suggested and expressions for the dynamic structure factor and the half-width dispersion relation are given. [ABSTRACT FROM AUTHOR]

Two related approaches, one fairly recent [A. Trokhymchuk et al., J. Chem. Phys.123, 024501 (2005)] and the other one introduced 15 years ago [S. B. Yuste and A. Santos, Phys. Rev. A43, 5418 (1991)], for the derivation of analytical forms of the radial distribution function of a fluid of hard spheres are compared. While they share similar starting philosophy, the first one involves the determination of 11 parameters while the second is a simple extension of the solution of the Percus-Yevick equation. It is found that the second approach has a better global accuracy and the further asset of counting already with a successful generalization to mixtures of hard spheres and other related systems. [ABSTRACT FROM AUTHOR]