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Search Results: 1 - 10 of 359391 matches for " Santos Sharpe Andrés "
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The Higher Education System in Argentina. Networks, Genealogies and Conflicts  [PDF]
Santos Sharpe Andrés
Creative Education (CE) , 2015, DOI: 10.4236/ce.2015.618200
Abstract: The present manuscript aims to identify the genealogies, understood in a Foucaultian perspective, which leads to the actual Higher Education System in Argentina, by distinguishing how series of events are organized, distributed, organized in terms of institutional relations, signifying chains in the social amalgam and educational networks. This analysis will allow understanding the hierarchical relationships between higher education institutions and how the differences on cultural and curricular traditions and history also motivate (though not impose) the differences on the students and on policies. Finally, it is as well an accurate description of the Higher Education System in Argentina with a strong emphasis on universities.
Comment on `A general integral identity'
Andrés Santos
Physics , 2011, DOI: 10.1088/1751-8113/44/42/428001
Abstract: A simple heuristic proof of an integral identity recently derived (Glasser ML 2011 J. Phys. A: Math. Theor. 44 225202) is presented.
Chemical-Potential Route: A Hidden Percus-Yevick Equation of State for Hard Spheres
Andrés Santos
Physics , 2012, DOI: 10.1103/PhysRevLett.109.120601
Abstract: The chemical potential of a hard-sphere fluid can be expressed in terms of the contact value of the radial distribution function of a solute particle with a diameter varying from zero to that of the solvent particles. Exploiting the explicit knowledge of such a contact value within the Percus--Yevick (PY) theory, and using standard thermodynamic relations, a hitherto unknown PY equation of state, $p/\rho k_BT=-(9/\eta)\ln(1-\eta)-(16-31\eta)/2(1-\eta)^2$, is unveiled. This equation of state turns out to be better than the one obtained from the conventional virial route. Interpolations between the chemical-potential and compressibility routes are shown to be more accurate than the widely used Carnahan--Starling equation of state. The extension to polydisperse hard-sphere systems is also presented.
Playing with Marbles: Structural and Thermodynamic Properties of Hard-Sphere Systems
Andrés Santos
Physics , 2013,
Abstract: These lecture notes present an overview of equilibrium statistical mechanics of classical fluids, with special applications to the structural and thermodynamic properties of systems made of particles interacting via the hard-sphere potential or closely related model potentials. The exact statistical-mechanical properties of one-dimensional systems, the issue of thermodynamic (in)consistency among different routes in the context of several approximate theories, and the construction of analytical or semi-analytical approximations for the structural properties are also addressed.
Homogeneous Free Cooling State in Binary Granular Fluids of Inelastic Rough Hard Spheres
Andrés Santos
Physics , 2010, DOI: 10.1063/1.3562637
Abstract: In a recent paper [A. Santos, G. M. Kremer, and V. Garz\'o, \emph{Prog. Theor. Phys. Suppl.} \textbf{184}, 31-48 (2010)] the collisional energy production rates associated with the translational and rotational granular temperatures in a granular fluid mixture of inelastic rough hard spheres have been derived. In the present paper the energy production rates are explicitly decomposed into equipartition rates (tending to make all the temperatures equal) plus genuine cooling rates (reflecting the collisional dissipation of energy). Next the homogeneous free cooling state of a binary mixture is analyzed, with special emphasis on the quasi-smooth limit. A previously reported singular behavior (according to which a vanishingly small amount of roughness has a finite effect, with respect to the perfectly smooth case, on the asymptotic long-time translational/translational temperature ratio) is further elaborated. Moreover, the study of the time evolution of the temperature ratios shows that this dramatic influence of roughness already appears in the transient regime for times comparable to the relaxation time of perfectly smooth spheres.
A Bhatnagar-Gross-Krook-like Model Kinetic Equation for a Granular Gas of Inelastic Rough Hard Spheres
Andrés Santos
Physics , 2010, DOI: 10.1063/1.3562623
Abstract: The Boltzmann collision operator for a dilute granular gas of inelastic rough hard spheres is much more intricate than its counterpart for inelastic smooth spheres. Now the one-body distribution function depends not only on the translational velocity of the center of mass but also on the angular velocity of the particle. Moreover, the collision rules couple both velocities, involving not only the coefficient of normal restitution but also the coefficient of tangential restitution. The aim of this paper is to propose an extension to inelastic rough particles of a Bhatnagar-Gross-Krook-like kinetic model previously proposed for inelastic smooth particles. The Boltzmann collision operator is replaced by the sum of three terms representing: (i) the relaxation to a two-temperature local equilibrium distribution, (ii) the action of a nonconservative drag force proportional to the peculiar velocity, and (iii) the action of a nonconservative torque equal to a linear combination of the angular velocity and its mean value. The three coefficients in the force and torque are fixed to reproduce the Boltzmann collisional rates of change of the mean angular velocity and of the two granular temperatures (translational and rotational). A simpler version of the model is also constructed in the form of two coupled kinetic equations for the translational and rotational velocity distributions. The kinetic model is applied to the simple shear flow steady state and the combined influence of the two coefficients of restitution on the shear and normal stresses and on the translational velocity distribution function is analyzed.
Comments on "State equation for the three-dimensional system of 'collapsing' hard spheres"
Andrés Santos
Physics , 2009, DOI: 10.1142/S021798490902148X
Abstract: A recent paper [I. Klebanov et al. \emph{Mod. Phys. Lett. B} \textbf{22} (2008) 3153; arXiv:0712.0433] claims that the exact solution of the Percus-Yevick (PY) integral equation for a system of hard spheres plus a step potential is obtained. The aim of this paper is to show that Klebanov et al.'s result is incompatible with the PY equation since it violates two known cases: the low-density limit and the hard-sphere limit.
Solutions of the moment hierarchy in the kinetic theory of Maxwell models
Andrés Santos
Physics , 2009, DOI: 10.1007/s00161-009-0113-5
Abstract: In the Maxwell interaction model the collision rate is independent of the relative velocity of the colliding pair and, as a consequence, the collisional moments are bilinear combinations of velocity moments of the same or lower order. In general, however, the drift term of the Boltzmann equation couples moments of a given order to moments of a higher order, thus preventing the solvability of the moment hierarchy, unless approximate closures are introduced. On the other hand, there exist a number of states where the moment hierarchy can be recursively solved, the solution generally exposing non-Newtonian properties. The aim of this paper is to present an overview of results pertaining to some of those states, namely the planar Fourier flow (without and with a constant gravity field), the planar Couette flow, the force-driven Poiseuille flow, and the uniform shear flow.
Note: An exact scaling relation for truncatable free energies of polydisperse hard-sphere mixtures
Andrés Santos
Physics , 2012, DOI: 10.1063/1.3702439
Abstract: A theoretical model for polydisperse systems of hard spheres is said to be truncatable when the excess free energy depends on the size distribution through a finite number $K$ of moments. This Note proves an exact scaling relation for truncatable free energies, which allows to reduce the effective degrees of freedom to $K-2$ independent combinations of the moments.
Class of consistent fundamental-measure free energies for hard-sphere mixtures
Andrés Santos
Physics , 2012, DOI: 10.1103/PhysRevE.86.040102
Abstract: In fundamental-measure theories the bulk excess free-energy density of a hard-sphere fluid mixture is assumed to depend on the partial number densities ${\rho_i}$ only through the four scaled-particle-theory variables ${\xi_\alpha}$, i.e., $\Phi({\rho_i})\to\Phi({\xi_\alpha})$. By imposing consistency conditions, it is proven here that such a dependence must necessarily have the form $\Phi({\xi_\alpha})=-\xi_0\ln(1-\xi_3)+\Psi(y)\xi_1\xi_2/(1-\xi_3)$, where $y\equiv {\xi_2^2}/{12\pi \xi_1 (1-\xi_3)}$ is a scaled variable and $\Psi(y)$ is an arbitrary dimensionless scaling function which can be determined from the free-energy density of the one-component system. Extension to the inhomogeneous case is achieved by standard replacements of the variables ${\xi_\alpha}$ by the fundamental-measure (scalar, vector, and tensor) weighted densities ${n_\alpha(\mathbf{r})}$. Comparison with computer simulations shows the superiority of this bulk free energy over the White Bear one.
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