On the inverse windowed Fourier transform

The inversion problem concerning the windowed Fourier transform is considered. It is shown that, out of the infinite solutions that the problem admits, the windowed Fourier transform is the "optimal" solution according to a maximum-entropy selection criterion.

Voltage fluctuations in IC power supply distribution

The supply voltage decrease and powerconsumption increase of modern ICs made the requirements for low voltage fluctuation caused by packaging and on-chip parasitic impedances more difficult to achieve. Most of the research works on the area assume that all the nodes of the chip are fed at thesame voltage, in such a way that the main cause of disturbance or fluctuation is the parasitic impedance of packaging. In the paper an approach to analyze the effect of high and fast current demands on the on-chip power supply network. First an approach to model the entire network by considering a homogeneous conductive foil is presented. The modification of the timing parameters of flipflops caused by spatial voltage drops through the IC surface are also investigated.

Intrinsic subspace convergence in TDD MIMO communication

In numerical linear algebra, students encounter earlythe iterative power method, which finds eigenvectors of a matrixfrom an arbitrary starting point through repeated normalizationand multiplications by the matrix itself. In practice, more sophisticatedmethods are used nowadays, threatening to make the powermethod a historical and pedagogic footnote. However, in the contextof communication over a time-division duplex (TDD) multipleinputmultiple-output (MIMO) channel, the power method takes aspecial position. It can be viewed as an intrinsic part of the uplinkand downlink communication switching, enabling estimationof the eigenmodes of the channel without extra overhead. Generalizingthe method to vector subspaces, communication in thesubspaces with the best receive and transmit signal-to-noise ratio(SNR) is made possible. In exploring this intrinsic subspace convergence(ISC), we show that several published and new schemes canbe cast into a common framework where all members benefit fromthe ISC.

Una pintura d'Antoni Viladomat i Manalt (1678-1755) a Manresa : l'Assumpta de Santa Maria de l'Alba

This painting with an exceptional iconography of the Assumption of the Virgin with All the Saints, was saved from a altarpiece in the church of Santa Maria de l'Alba in Manresa, which was burnt during the Spanish Civil War. The article attributes this painting to Antoni Viladomat i Manalt (1678-1755), one of the most relevant figures in the Catalan artistic scene in the 18th century, and it dates it to the latter years of his extensive artistic career. An analysis of the work shows that the Catalan painter incorporated some figurative elements that he borrowed from an engraving of the Swiss engraver, Jakob Frey (1681-1752), interpreted from a canvas of the Italian painter Sebastiano Conca (1680-1764). This helps to relate the canvas of the Barcelona painter-based on his previous figurative work with high Roman baroque- to the new proposals of the so-called Roman barrochetto. In addition the study hopes to offer the reader an artistically cultural view of Antoni Viladomat, openly concerned by the novelties that constantly reached Catalonia by means of the engravings

La Costa Brava ante los nuevos retos del turismo

The first section of this paper summarises the most relevant charateristics of the contemporary tourist model, also called postfordist or postmodernist. In the second part the traditional tourist model developed in the Costa Brava in the past decades, is reviewed. Emphasising the saturation of tourist facilities on the coast line, expansive urban growth, thanks to a tolerant administration, poor complementary supply and concentrated demand in few markets and the proximity of Barcelona conurbation, stressed by second homes. In the third section, some strategies developed in recent years to readapt the Costa Brava to the new tendencies in tourism, are presented. Incorporation of the inland to the tourist product, new planning policics, lessening urban densities and height, and a change in mind in favour of protected natural areas, diversification of demand with new markets, specially form Eastern Europe (although this might be considered as a continuation ofthe traditional tourist model) and the emergence of local strategies oriented towards the creation of new tourist products based upon natural and cultural resources

Estratigrafia i evolució conceptual d'un paisatge de muntanya al massís del Garraf: la Maçana-Rovirós-Térmens (Begues)

En aquest estudi, l'aplicació regressiva de tècniques com la prospecció arqueològica, la foto i cartointerpretació, els SIG i el buidatge documental han permès la reconstrucció diacrònica del paisatge de l'àrea de la Maçana-Térmens-Rovirós (Begues). L'estudi paisatgístic del Garraf revesteix un singular interès per la seva condició muntanyenca i la seva intensa antropització. Els entorns de muntanya són medis especialment sensibles a processos de canvi, especialment en el cas del massís del Garraf, proper a importants nuclis d'habitació des de l'antiguitat. El nostre treball mostrarà com, en ocasions, el canvi paisatgístic ha estat irreversible al massís.

World Library and Information Congress: 75th IFLA General Conference and Assembly.

L"edició del 2009 de la trobada de l"IFLA s"ha celebrat a Milà. La maquinària de l"organització va funcionar amb precisió per a aquest esdeveniment. Després d"anys de regularitat en les trobades per tot el món, l"IFLA funciona com un autòmat, una d"aquestes màquines perfectes, tant que podria continuar uncionant en les formes amb exemplar artifici. És un trobada singular, que aplega, a la vegada, la reunió de l"organització, un congrés mundial i una fira comercial; tot això amanit amb una ciutat diferent cada any i un finançament que depèn de la bona marxa de tot l"esdeveniment. En certa mesura, l"IFLA és un aparador de la professió, al qual assisteixen bibliotecaris de tot el món i de centenars d"institucions, amb tot el que suposa d"artificiositat en la representació d"entitats i promoció; un espai de reflexió, amb ponències i debats de molt variat interès que poden trobar-se, generalment, en altres esdeveniments; i una posada a punt dels treballs de tots els comitès, que tenen un complex desenvolupament previ i una àrdua tasca desenvolupada amb generositat per tots els participants.

The maximum voltage drop in an on-chip power distribution network: analysis of square, triangular and hexagonal power pad arrangements

A mathematical model of the voltage drop which arises in on-chip power distribution networks is used to compare the maximum voltage drop in the case of different geometric arrangements of the pads supplying power to the chip. These include the square or Manhattan power pad arrangement, which currently predominates, as well as equilateral triangular and hexagonal arrangements. In agreement with the findings in the literature and with physical and SPICE models, the equilateral triangular power pad arrangement is found to minimize the maximum voltage drop. This headline finding is a consequence of relatively simple formulas for the voltage drop, with explicit error bounds, which are established using complex analysis techniques, and elliptic functions in particular.

Boris Vian dans ses poèmes

El artículo se propone mostrar cómo el estudio de los poemas y canciones de Boris Vian sólo cobra sentido mediante un análisis de conjunto. Tras la aparente dispersión de temas y estilos, bajo la apariencia superficial, cómica y en ocasiones incluso grotesca y banal de sus poemas y canciones, se oculta una unidad y una coherencia profundas y minuciosamente calculadas. Para expresarla Vian huye de las limitaciones de la lógica heredada de Aristóteles y opta por utilizar la técnica del collage, yuxtaponiendo una pluralidad de situaciones y acciones en las que lo real se entremezcla con lo imaginario, cuyo resultado final es la representación de una realidad única, indivisible y a la vez relativa y singular en función de cada individuo, en la que los aparentes antagonismos se revelan como elementos complementarios en el proceso de individualización y conocimiento del «yo» interior.

Sarraïns sota el domini de la família Montcada: les aljames de la baronia d'Aitona al segle XV

L'any 1212 la família Montcada es fa amb el control de l´àrea del Baix Segre, una de les mes densament habitades en època islàmica. Dos segles després, tot i la profunda implantació del sistema feudal, la comunitat musulmana no només hi conserva una forta presencia poblacional sinó que a més mante vives bona part de les seves institucions. Aquesta comunitat -organitzada en aljames- es concentra en les viles d’Aitona, Seròs i Mequinensa, on constitueix el gruix de la població. Aquesta tensió entre els antics i els nous marcs de relacions en que es mou la comunitat islàmica (materialitzats en sistemes de tinença com l’emfiteusi) conferí a la zona un caire marcadament singular.

Conditional equilibrium constants in multicomponent heterogeneous adsorption: The conditional affinity spectrum

The concept of conditional stability constant is extended to the competitive binding of small molecules to heterogeneous surfaces or macromolecules via the introduction of the conditional affinity spectrum (CAS). The CAS describes the distribution of effective binding energies experienced by one complexing agent at a fixed concentration of the rest. We show that, when the multicomponent system can be described in terms of an underlying affinity spectrum [integral equation (IE) approach], the system can always be characterized by means of a CAS. The thermodynamic properties of the CAS and its dependence on the concentration of the rest of components are discussed. In the context of metal/proton competition, analytical expressions for the mean (conditional average affinity) and the variance (conditional heterogeneity) of the CAS as functions of pH are reported and their physical interpretation discussed. Furthermore, we show that the dependence of the CAS variance on pH allows for the analytical determination of the correlation coefficient between the binding energies of the metal and the proton. Nonideal competitive adsorption isotherm and Frumkin isotherms are used to illustrate the results of this work. Finally, the possibility of using CAS when the IE approach does not apply (for instance, when multidentate binding is present) is explored. © 2006 American Institute of Physics.

Affinity distribution functions in multicomponent heterogeneous adsorption. Analytical inversion of isotherms to obtain affinity spectra

An analytical approach for the interpretation of multicomponent heterogeneous adsorption or complexation isotherms in terms of multidimensional affinity spectra is presented. Fourier transform, applied to analyze the corresponding integral equation, leads to an inversion formula which allows the computation of the multicomponent affinity spectrum underlying a given competitive isotherm. Although a different mathematical methodology is used, this procedure can be seen as the extension to multicomponent systems of the classical Sips’s work devoted to monocomponent systems. Furthermore, a methodology which yields analytical expressions for the main statistical properties (mean free energies of binding and covariance matrix) of multidimensional affinity spectra is reported. Thus, the level of binding correlation between the different components can be quantified. It has to be highlighted that the reported methodology does not require the knowledge of the affinity spectrum to calculate the means, variances, and covariance of the binding energies of the different components. Nonideal competitive consistent adsorption isotherm, widely used in metal/proton competitive complexation to environmental macromolecules, and Frumkin competitive isotherms are selected to illustrate the application of the reported results. Explicit analytical expressions for the affinity spectrum as well as for the matrix correlation are obtained for the NICCA case. © 2004 American Institute of Physics.

Complexation to macromolecules with a large number of sites

This paper presents an approach based on the saddle-point approximation to study the equilibrium interactions between small molecules and macromolecules with a large number of sites. For this case, the application of the Darwin–Fowler method results in very simple expressions for the stoichiometric equilibrium constants and their corresponding free energies in terms of integrals of the binding curve plus a correction term which depends on the first derivatives of the binding curve in the points corresponding to an integer value of the mean occupation number. These expressions are simplified when the number of sites tends to infinity, providing an interpretation of the binding curve in terms of the stoichiometric stability constants. The formalism presented is applied to some simple complexation models, obtaining good values for the free energies involved. When heterogeneous complexation is assumed, simple expressions are obtained to relate the macroscopic description of the binding, given by the stoichiomeric constants, with the microscopic description in terms of the intrinsic stability constants or the affinity spectrum. © 1999 American Institute of Physics.

Tradición y modernidad en las políticas educativas en España: una revisión de las últimas décadas

En el presente artículo trazamos un panorama aproximativo de algunas de las cuestiones más relevantes que determinan, al tiempo que reflejan, las políticas educativas en España desde la década de 1980 hasta la actualidad. Esta revisión de los últimos 25 años permitirá apreciar, siquiera de manera epidérmica e inevitablemente parcial, la tensión o dialéctica entre la tradición-caracterizada por la persistencia de formas caducas en la concepción y en la provisión educativa- y la modernidad-portadora de la tendencia al cambio y a la innovación, si bien no exenta de ambigüedad y contradicción en su propio desarrollo-. Nos detenemos en aquellos ejes a partir de los cuales se articula nuestra reflexión, tales como las políticas educativas, la organización del sistema educativo, la convergencia europea, las organizaciones transnacionales reguladoras de las políticas educativas y prospectivas, finalizando con algunas conclusiones que, aun siendo abiertas, plantean la persistencia de las dinámicas reproductoras. Nuestro análisis se ciñe, para esta ocasión, al ámbito de la educación formal, sin dejar de reconocer la importancia creciente de los espacios de educación no formal e informal, y de los sectores emergentes derivados de los mismos. Como se verá, nuestro planteamiento se enmarca dentro de una interpretación singular acerca de las derivaciones y consecuencias de la modernidad tardía en la que se inscribe nuestro período de estudio

The differentiable chain functor is not homotopy equivalent to the continuous chain functor

Let $S_*$ and $S_*^\{infty}$ be the functors of continuous and differentiable singular chains on the category of differentiable manifolds. We prove that the natural transformation $i: S_*^\infty \rightarrow S_*$, which induces homology equivalences over each manifold, is not a natural homotopy equivalence.