Search results for " Representation."
showing 10 items of 791 documents
Graphical representation of non-absorbing polarization devices
2000
A graphical representation of general non-absorbing polarization devices operating under normal plane-wave incidence is presented. The representation is based on a four-dimensional spherical parametrization of the Jones matrix of this kind of polarization devices. The graphical representation takes the form of a solid cylinder. The projection of the point representing the device over the base of the cylinder gives the corresponding polarization eigenvectors represented in the complex plane, while the height of the point in the cylinder is the phase of its eigenvalue. Some simple examples like wave-plates and rotators are discussed. The representation may represent a useful tool to identify …
The local group K(4) in the algebraic approach to vibrational spectra of tetrahedral molecules: Application to silane
1992
Abstract In a previous paper, Michelot and Moret-Bailly (J. Phys., 48, 51 (1987)) proposed an algebraic treatment of vibrational stretching modes in polyatomic molecules. They used the properties of the group chain U(p + 1) ⊃ U(p) ⊃ S(p) ⊃ G for the study of p identical oscillators. The molecule, with p equivalent bonds described as a system of p oscillators, has a symmetry group G. We develop in this paper an application to p = 4 equivalent oscillators. We show that, for a tetrahedral molecule, the group chain U(5) ⊃ U(4) ⊃ S(4) ≈ Td can be completed, in a local point of view, with a particular group K(4): U(5) ⊃ U(4) ⊃ K(4) ⊃ S(4) ≈ T d This group provides us with available labels which c…
The time-harmonic Maxwell equations
1996
In this chapter we shall see that the solution of the time-harmonic Maxwell equations with real coefficients can be transformed to time independent partial differential equations with complex coefficients. Then we introduce a finite element approximation proposed in [Křižek, Neittaanmaki, 1989]. A similar technique is analyzed in [Křižek, Neittaanmaki, 1984b], [Monk, 1992a] (for fully time dependent problems see, e.g., [Monk 1992b,c]).
Maxwell’s Equations
2012
The empirical basis of electrodynamics is defined by Faraday’s law of induction, by Gauss’ law, by the law of Biot and Savart and by the Lorentz force and the principle of universal conservation of electric charge. These laws can be tested – confirmed or falsified – in realistic experiments. The integral form of the laws deals with physical objects that are one-dimensional, two-dimensional, or three-dimensional, that is to say, objects such as linear wires, conducting loops, spatial charge distributions, etc. Thus, the integral form depends, to some extent, on the concrete experimental set-up. To unravel the relationships between seemingly different phenomena, one must switch from the integ…
The bound state in the spectrum of the Lee–Friedrichs Hamiltonian
2000
Abstract The spectrum of the Lee–Friedrichs Hamiltonian, describing a two-level system embedded in a continuum, is considered. An appropriate discretization of the field modes is performed before taking the continuum limit. It is shown that the existence of an eigenstate with negative energy (bound state) is related to the nonanalyticity of the Friedrichs spectral representation. This negative energy state is a dressed state and its physical properties are studied in some significant cases.
Hidden Oscillations In The Closed-Loop Aircraft-Pilot System And Their Prevention* *This work was supported by Russian Science Foundation (project 14…
2016
Abstract The paper is devoted to studying and prevention of a special kind of oscillations-the Pilot Involved Oscillations (PIOs) which may appear in man-machine closed-loop dynamical systems. The PIO of categories II and III are defined as essentially non-linear unintended steady fluctuations of the piloted aircraft, generated due to pilot efforts to control the aircraft with a high precision. The main non-linear factor leading to the PIO is, generally, rate limitations of the aircraft control surfaces, resulting in a delay in the response of the aircraft to pilot commands. In many cases, these oscillations indicate presence of hidden, rather than self-excited attractors in the aircraft-pi…
A Statistical Matrix Representation Using Sliced Orthogonal Nonlinear Correlations for Pattern Recognition
2000
In pattern recognition, the choice of features to be detected is a critical factor to determine the success or failure of a method; much research has gone into finding the best features for particular tasks [1]. When images are detected by digital cameras, they are usually acquired as rectangular arrays of pixels, so the initial features are pixel values. Some methods use those pixel values directly for processing, for instance in normal matched filtering [2], whereas other methods execute some degree of pre-processing, such as binarizing the pixel values [3].
Maps in picturebooks: cognitive status and narrative functions
2015
This article focuses on the relation between maps, mental representations, description, and narration in picturebooks. It is shown that maps are cognitively demanding, since they presuppose the development of cognitive abilities and the comprehension of complex visual codes, including recognition of the specific combination of signs and names representing land- and cityscapes, geographical abstraction as well as the symbolization, highlighting, and suppression of information. After a survey of findings from cognitive psychology and geography literacy about children’s map acquisition, the article gives an overview on some types of maps in picturebooks that are interesting from a narrative po…
Participación política y periodismo: análisis de la cobertura de Televisión Española de la segunda asamblea ciudadana de Podemos / Political particip…
2018
ResumenEl incremento de la participación en la vida de los partidos políticos se ha mostrado como un ideal en los últimos años de la democracia española. Podemos, una de las formaciones de la llamada nueva política ha utilizado el voto telemático para establecer interconexión con sus inscritos y decidir sus estructuras organizativas y sus documentos políticos. A pesar de la ampliación de posibilidades de participación en las decisiones internas, la definición de visibilidades mediáticas se circunscribe al tándem Iglesias-Errejón y el debate interior encuentra límites en su representación externa. Este estudio trata de analizar los discursos derivados de la cobertura de Televisión Española d…
Electoral Rules and Proportionality in Spain: Estimating the Impact of some Swedish Rules Through the 2011 Electoral Data
2016
In democratic countries policy making is always framed by many procedures and rules. Some of these rules are particularly critical for allowing more or less proportionality in legislative chambers, though the behavior of political actors also matter. The rules used for technically converting votes into political representatives often exercise such an important role in western countries. In this chapter we provide an estimation of the impact upon proportionality between seats and votes that might have resulted in the 2011 Spanish general elections if some Swedish electoral rules had been applied, ceteris paribus. As we are aware that electoral reforms favouring proportionality may hinder the…