971 resultados para Gramàtica comparada i general -- Nominals -- Congressos


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Mode of access: Internet.

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Any (N+M)-parameter Lie group G with an N-parameter subgroup H can be realized as a global group of diffeomorphisms on an M-dimensional base space B, with representations in terms of transformation laws of fields on B belonging to linear representations of H. The gauged generalization of the global diffeomorphisms consists of general diffeomorphisms (or coordinate transformations) on a base space together with a local action of H on the fields. The particular applications of the scheme to space-time symmetries is discussed in terms of Lagrangians, field equations, currents, and source identities. Journal of Mathematical Physics is copyrighted by The American Institute of Physics.

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Digital image

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The solution of the time-dependent Schrodinger equation for systems of interacting electrons is generally a prohibitive task, for which approximate methods are necessary. Popular approaches, such as the time-dependent Hartree-Fock (TDHF) approximation and time-dependent density functional theory (TDDFT), are essentially single-configurational schemes. TDHF is by construction incapable of fully accounting for the excited character of the electronic states involved in many physical processes of interest; TDDFT, although exact in principle, is limited by the currently available exchange-correlation functionals. On the other hand, multiconfigurational methods, such as the multiconfigurational time-dependent Hartree-Fock (MCTDHF) approach, provide an accurate description of the excited states and can be systematically improved. However, the computational cost becomes prohibitive as the number of degrees of freedom increases, and thus, at present, the MCTDHF method is only practical for few-electron systems. In this work, we propose an alternative approach which effectively establishes a compromise between efficiency and accuracy, by retaining the smallest possible number of configurations that catches the essential features of the electronic wavefunction. Based on a time-dependent variational principle, we derive the MCTDHF working equation for a multiconfigurational expansion with fixed coefficients and specialise to the case of general open-shell states, which are relevant for many physical processes of interest. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3600397]

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UANL

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El trabajo de campo ha sido realizado por un equipo de quince colaboradores coordinados por Mercè Morey López

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The calculation of accurate and reliable vibrational potential functions and normal co-ordinates is discussed, for such simple polyatomic molecules as it may be possible. Such calculations should be corrected for the effects of anharmonicity and of resonance interactions between the vibrational states, and should be fitted to all the available information on all isotopic species: particularly the vibrational frequencies, Coriolis zeta constants and centrifugal distortion constants. The difficulties of making these corrections, and of making use of the observed data are reviewed. A programme for the Ferranti Mercury Computer is described by means of which harmonic vibration frequencies and normal co-ordinate vectors, zeta factors and centrifugal distortion constants can be calculated, from a given force field and from given G-matrix elements, etc. The programme has been used on up to 5 × 5 secular equations for which a single calculation and output of results takes approximately l min; it can readily be extended to larger determinants. The best methods of using such a programme and the possibility of reversing the direction of calculation are discussed. The methods are applied to calculating the best possible vibrational potential function for the methane molecule, making use of all the observed data.

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Regiones y Departamentos. Relatos de nuestra identidad es una serie que aborda las características turísticas, culturales e históricas de la provincia de Mendoza. En los 14 programas se han destacado y revalorizado las particularidades de cada uno de los departamentos de esta provincia argentina que se dividen en distintas regiones: Valle de Uco, Gran Mendoza, Zona Sur, Zona Este y Zona Nordeste. ZONA SUR I, es un documental que recorre los departamentos de General Alvear, Malargüe y San Rafael rescatando sus características sociales, culturales y turísticas. El bloque 1destaca la historia de San Rafael, departamento habitado, en principio, por los Puelches, cazadores recolectores nómades, y más tarde son los Pehuenches quienes logran concentrar el poder y hasta adquieren el poder de gobernar, hasta 1805 con la construcción del Fuerte histórico de San Rafael. El aluvión y la llegada del ferrocarril fueron los acontecimientos que hicieron que se traslade a la ciudad. El bloque 2 resalta las características económicas y sociales de los departamentos de General Alvear y Malargüe. El primero con una creciente industria agroindustrial y el segundo apoyándose en las bondades de su naturaleza. En este bloque conocemos también la historia de los hermanos Pincheira, reconocidos bandidos por sus acciones violentas. Finalmente, en el bloque 3 se muestran las posibilidades turísticas de General Alvear y Malargüe, que van desde el turismo religioso, de aventura, rural, cultural , de naturaleza entre otros.