8-Vertex Correlation Functions and Twist Covariance of q-KZ Equation

We study the vertex operators $\Phi(z)$ associated with standard quantum groups. The element $Z = RR^{t}$ is a "Casimir operator" for quantized Kac-Moody algebras and the quantum Knizhnik-Zamolodchikov (q-KZ) equation is interpreted as the statement $:Z\Phi(z): = \Phi(z)$. We study the covariance of the q-KZ equation under twisting, first within the category of Hopf algebras, and then in the wider context of quasi Hopf algebras. We obtain the intertwining operators associated with the elliptic R-matrix and calculate the two-point correlation function for the eight-vertex model.Comment: 31 pages. Plain Te

Quasi-isotropic spacecraft antenna system Final report

Spacecraft quasi-isotropic antenna system for space telemetr

Application of the SAFT-γ Mie group contribution equation of state to fluids of relevance to the oil and gas industry

Calculated data for all the figures presented in publication

Dual-shaped offset reflector antenna designs from solutions of the geometrical optics first-order partial differential equations

In obtaining solutions to the first-order nonlinear partial differential equations (PDEs) for synthesizing offset dual-shaped reflectors, it is found that previously observed computational problems can be avoided if the integration of the PDEs is started from an inner projected perimeter and integrated outward rather than starting from an outer projected perimeter and integrating inward. This procedure, however, introduces a new parameter, the main reflector inner perimeter radius p(o), when given a subreflector inner angle 0(o). Furthermore, a desired outer projected perimeter (e.g., a circle) is no longer guaranteed. Stability of the integration is maintained if some of the initial parameters are determined first from an approximate solution to the PDEs. A one-, two-, or three-parameter optimization algorithm can then be used to obtain a best set of parameters yielding a close fit to the desired projected outer rim. Good low cross-polarization mapping functions are also obtained. These methods are illustrated by synthesis of a high-gain offset-shaped Cassegrainian antenna and a low-noise offset-shaped Gregorian antenna

Modelling the phase and chemical equilibria of aqueous solutions of alkanolamines and carbon dioxide using the SAFT-γ SW group contribution approach

p>All computational data for figures presented in the publication/p

Distopía y apocalipsis en la poesía de Óscar Hahn y Gonzalo Millán

The article analyses dystopian and apocalyptic elements in two contemporary Chilean poets, Óscar Hahn and Gonzalo Millán, as part of a reflection on the alienation and degradation that characterizes urban life. However, from the deepest structures of these poets' texts, it detects a tension between the dystopian-apocalyptic discourse and the utopian discourse which creates diverse allegorical and literary meanings

Design considerations for the beam-waveguide retrofit of a ground antenna station

Retrofitting an antenna that was originally designed without a beam waveguide introduces special difficulties because it is desirable to minimize alteration of the original mechanical truss work and to image the actual feed without distortion at the focal point of the dual-shaped reflector. To obtain an acceptable image, certain Geometrical Optics (GO) design criteria are followed as closely as possible. The problems associated with applying these design criteria to a 34-meter dual-shaped DSN (Deep Space Network) antenna are discussed. The use of various diffraction analysis techniques in the design process is also discussed. GTD and FFT algorithms are particularly necessary at the higher frequencies, while Physical Optics and Spherical Wave Expansions proved necessary at the lower frequencies

Intraband Optical Absorption In Superlattices In An In-plane Magnetic Field

The absorption coefficient of GaAs-AlxGa1-xAs superlattices in an in-plane magnetic field is studied in the case of intraband transitions between electronic magnetic levels. A detailed analysis of the absorption peaks and their dependence on the magnetic-field intensity, superlattice period, and temperature, is performed. By taking into account the detailed properties of the magnetic subbands, the joint density of states, the transition matrix elements, and the effective sheet concentration of electrons involved in the optical transitions, a simple theoretical explanation is given for some experimental results previously reported. © 1993 The American Physical Society.4874516452

Data Analysis with Intersection Graphs

AbstractThis paper presents a new framework for multivariate data analysis, based on graph theory, using intersection graphs [1]. We have named this approach DAIG – Data Analysis with Intersection Graphs. This new framework represents data vectors as paths on a graph, which has a number of advantages over the classical table representation of data. To do so, each node represents an atom of information, i.e. a pair of a variable and a value, associated with the set of observations for which that pair occurs. An edge exists between a pair of nodes whenever the intersection of their respective sets is not empty. We show that this representation of data as an intersection graph allows an easy and intuitive geometric interpretation of data observations, groups of observations, and results of multivariate data analysis techniques such as biplots, principal components, cluster analysis, or multidimensional scaling. These will appear as paths on the graph, relating variables, values and observations. This approach allows for a compact and memory efficient representation of data that contains many missing values or multi-valued attributes. The basic principles and advantages of this approach are presented with an example of its application to a simple toy problem. The main features of this methodology are illustrated with the aid software specifically developed for this purpose