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Search Results: 1 - 10 of 471209 matches for " Jose A Martinez "
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Factors determining production (FDP) in basketball
Jose A. Martinez
Economics and Business Letters , 2012,
Abstract: The aim of this research was to introduce a simple and easily computable metric to assess the performance of basketball players through non-scoring box-score statistics. This metric was called Factors Determining Production (FDP). FDP was created through separating points made from the remaining variables which may bequantitatively recorded. FDP was derived from the outcome of several games, it considers both teams’ statistics, and it reflects the final result of a game with noticeable merit. This metric provides a simple linear weight formula which, together with the points made by each player, yields a comprehensible picture of how well a worker(player) performed. FDP has been validated through different statistical procedures and it overcomes Win Score from a theoretical viewpoint, because it departs production (points) from factors facilitating production.
Phase behavior of parallel hard cylinders
Jose A. Capitan,Yuri Martinez-Raton,Jose A. Cuesta
Physics , 2008, DOI: 10.1063/1.2920481
Abstract: We test the performance of a recently proposed fundamental measure density functional of aligned hard cylinders by calculating the phase diagram of a monodisperse fluid of these particles. We consider all possible liquid crystalline symmetries, namely nematic, smectic and columnar, as well as the crystalline phase. For this purpose we introduce a Gaussian parameterization of the density profile and use it to minimize numerically the functional. We also determine, from the analytic expression for the structure factor of the uniform fluid, the bifurcation points from the nematic to the smectic and columnar phases. The equation of state, as obtained from functional minimization, is compared to the available Monte Carlo simulation. The agreement is is very good, nearly perfect in the description of the inhomogeneous phases. The columnar phase is found to be metastable with respect to the smectic or crystal phases, its free energy though being very close to that of the stable phases. This result justifies the observation of a window of stability of the columnar phase in some simulations, which disappears as the size of the system increases. The only important deviation between theory and simulations shows up in the location of the nematic-smectic transition. This is the common drawback of any fundamental measure functional of describing the uniform phase just with the accuracy of scaled particle theory.
A fundamental-measure density functional for mixtures of parallel hard cylinders
Yuri Martinez-Raton,Jose A. Capitan,Jose A. Cuesta
Physics , 2008, DOI: 10.1103/PhysRevE.77.051205
Abstract: We obtain a fundamental measure density functional for mixtures of parallel hard cylinders. To this purpose we first generalize to multicomponent mixtures the fundamental measure functional proposed by Tarazona and Rosenfeld for a one-component hard disk fluid, through a method alternative to the cavity formalism of these authors. We show the equivalence of both methods when applied to two-dimensional fluids. The density functional so obtained reduces to the exact density functional for one-dimensional mixtures of hard rods when applied to one-dimensional profiles. In a second step we apply an idea put forward some time ago by two of us, based again on a dimensional reduction of the system, and derive a density functional for mixtures of parallel hard cylinders. We explore some features of this functional by determining the fluid-fluid demixing spinodals for a binary mixture of cylinders with the same volume, and by calculating the direct correlation functions.
Smectic and columnar ordering in length-polydisperse fluids of parallel hard cylinders
Yuri Martinez-Raton,Jose A. Cuesta
Physics , 2009, DOI: 10.1080/00268970902824243
Abstract: We apply a recently proposed density functional for mixtures of parallel hard cylinders, based on Rosenfeld's fundamental measure theory, to study the effect of length-polydispersity on the relative stability between the smectic and columnar liquid crystal phases.To this purpose we derive from this functional an expression for the direct correlation function and use it to perform a bifurcation analysis. We compare the results with those obtained with a second and a third virial approximation of this function. All three approximations lead to the same conclusion: there is a terminal polydispersity beyond which the smectic phase is less stable than the columnar phase. This result is in agreement with previous Monte Carlo simulations conducted on a freely rotating length-polydisperse hard spherocylinder fluid, although the theories always overestimate the terminal polydispersity because the nematic-columnar phase transition is first order and exhibits a wide coexistence gap. Both, the fundamental-measure functional and the third virial approximation, predict a metastable nematic-nematic demixing. Conversely, according to second virial approximation this demixing might be stable at high values of the polydispersity, something that is observed neither in simulations nor in experiments. The results of the fundamental-measure functional are quantitatively superior to those obtained from the other two approximations. Thus this functional provides a promising route to map out the full phase diagram of this system.
Dimensional crossover of the fundamental-measure functional for parallel hard cubes
Jose A. Cuesta,Yuri Martinez-Raton
Physics , 1997, DOI: 10.1103/PhysRevLett.78.3681
Abstract: We present a regularization of the recently proposed fundamental-measure functional for a mixture of parallel hard cubes. The regularized functional is shown to have right dimensional crossovers to any smaller dimension, thus allowing to use it to study highly inhomogeneous phases (such as the solid phase). Furthermore, it is shown how the functional of the slightly more general model of parallel hard parallelepipeds can be obtained using the zero-dimensional functional as a generating functional. The multicomponent version of the latter system is also given, and it is suggested how to reformulate it as a restricted-orientation model for liquid crystals. Finally, the method is further extended to build a functional for a mixture of parallel hard cylinders.
Phase behaviour of additive binary mixtures in the limit of infinite asymmetry
Yuri Martinez-Raton,Jose A. Cuesta
Physics , 1998, DOI: 10.1103/PhysRevE.58.R4080
Abstract: We provide an exact mapping between the density functional of a binary mixture and that of the effective one-component fluid in the limit of infinite asymmetry. The fluid of parallel hard cubes is thus mapped onto that of parallel adhesive hard cubes. Its phase behaviour reveals that demixing of a very asymmetric mixture can only occur between a solvent-rich fluid and a permeated large particle solid or between two large particle solids with different packing fractions. Comparing with hard spheres mixtures we conclude that the phase behaviour of very asymmetric hard-particle mixtures can be determined from that of the large component interacting via an adhesive-like potential.
Phase diagrams of Zwanzig models: The effect of polydispersity
Yuri Martinez-Raton,Jose A. Cuesta
Physics , 2003, DOI: 10.1063/1.1571055
Abstract: The first goal of this article is to study the validity of the Zwanzig model for liquid crystals to predict transitions to inhomogeneous phases (like smectic and columnar) and the way polydispersity affects these transitions. The second goal is to analyze the extension of the Zwanzig model to a binary mixture of rods and plates. The mixture is symmetric in that all particles have equal volume and length-to-breadth ratio, $\kappa$. The phase diagram containing the homogeneous phases as well as the spinodals of the transitions to inhomogeneous phases is determined for the cases $\kappa=5$ and 15 in order to compare with previous results obtained in the Onsager approximation. We then study the effect of polydispersity on these phase diagrams, emphasizing the enhancement of the stability of the biaxial nematic phase it induces.
Enhancement by polydispersity of the biaxial nematic phase in a mixture of hard rods and plates
Yuri Martinez-Raton,Jose A. Cuesta
Physics , 2002, DOI: 10.1103/PhysRevLett.89.185701
Abstract: The phase diagram of a polydisperse mixture of uniaxial rod-like and plate-like hard parallelepipeds is determined for aspect ratios $\kappa=5$ and 15. All particles have equal volume and polydispersity is introduced in a highly symmetric way. The corresponding binary mixture is known to have a biaxial phase for $\kappa=15$, but to be unstable against demixing into two uniaxial nematics for $\kappa=5$. We find that the phase diagram for $\kappa=15$ is qualitatively similar to that of the binary mixture, regardless the amount of polydispersity, while for $\kappa=5$ a sufficient amount of polydispersity stabilizes the biaxial phase. This provides some clues for the design of an experiment in which this long searched biaxial phase could be observed.
The space of solutions to the Hessian one equation in the finitely punctured plane
Jose A. Galvez,Antonio Martinez,Pablo Mira
Mathematics , 2004,
Abstract: We construct the space of solutions to the elliptic Monge-Ampere equation det(D^2 u)=1 in the plane R^2 with n points removed. We show that, modulo equiaffine transformations and for n>1, this space can be seen as an open subset of R^{3n-4}, where the coordinates are described by the conformal equivalence classes of once punctured bounded domains in the complex plane of connectivity n-1. This approach actually provides a constructive procedure that recovers all such solutions to the Monge-Ampere equation, and generalizes a theorem by K. Jorgens.
The Bonnet problem for surfaces in homogeneous 3-manifolds
Jose A. Galvez,Antonio Martinez,Pablo Mira
Mathematics , 2006,
Abstract: We solve the Bonnet problem for surfaces in the homogeneous 3-manifolds with a 4-dimensional isometry group. More specifically, we show that a simply connected real analytic surface in H^2xR or S^2xR is uniquely determined pointwise by its metric and its principal curvatures if and only if it is not a minimal or a properly helicoidal surface. In the remaining three types of homogeneous 3-manifolds, we show that except for constant mean curvature surfaces and helicoidal surfaces, all simply connected real analytic surfaces are pointwise determined by their metric and principal curvatures.
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