Fotografía: viaje, coleccionismo y educación. La Hispanic Society of America, su fondo fotográfico y Murcia

This studyanalyzes the importantconnectionbetweenconceptssuch as travel, collecting and education in the construction of the photographic archive of the Hispanic Society of America and, at the same time, itputs in value the graphicdocumentsthat this institution keepabout the region of Murcia (Spain). These works are the directresult not only of documental vision of the travelingphotographerswhovisitedour country since the secondhalf of the 19th century but also of the cultural and formative expeditionsto Spain, organizedby the institutionitself directed to its curators, librarians and photographers, at the beginning of the twentieth.  Este estudio analiza la importante conexión existente entre conceptos como el viaje, el coleccionismo y la educación en la construcción del archivo fotográfico de la Hispanic Society of América; al tiempo que pone en valor los documentos gráficos que sobre la región de Murcia posee. Unas obras, estas últimas, que son fruto directo tanto de los fotógrafos viajeros que transitaron por nuestro país desde la segunda mitad del siglo XIX, en su vertiente de turista romántico o profesional, como de las expediciones a España, culturales y formativas, organizadas por la propia institución para sus conservadoras, bibliotecarias y fotógrafas, a principios del XX

Modeling OpAmp-induced harmonic distortion for switched-capacitor ΣΔ modulator design

This communication reports a new modeling of opamp-induced harmonic distortion in SC ΣΔ modulators, which is aimed to optimum design of this kind of circuit for high-performance applications. We analyze incomplete transfer of charge in a SC integrator and use power expansion and nonlinear fitting to obtain analytical models to represent harmonic distortion as function of the opamp finite gain-bandwidth (GB), slew-rate (SR) and nonlinear DC gain. Calculated models apply for all modulator architectures where harmonic distortion is dominated by the first integrator in the chain. We show that results provided by the new analytical models fit well to that obtained by simulation in time domain and have accuracy levels much larger than that provided by previously reported modeling approaches

A Tool for automated design of sigma-delta modulators using statistical optimization

A tool is presented which starting from high level specifications of SC σδ modulators (resolution, bandwidth and oversampling ratio) calculates first optimum specifications for the building blocks (op-amps, comparator, etc.), and then, optimum sizes for their schematics. At both design levels (high-level synthesis and cell dimensioning), optimization is performed via using statistical techniques and innovative heuristics, which allow global design (independent on the initial conditions) and increased computer efficiency as compared to conventional statistical optimization techniques. The tool has been conceived to be flexible at the high-level part(via the use of an architecture independent, behaviourable modeling approach) and completely open at the cell-design part. Performance of the tool is demonstrated via the automatic design of a 16bit-dynamic range, 8Khz second-order SC σδ modulator in 1.2 μm CMOS technology, for which measurements on a fabricated prototype are reported

Multi-bit cascade ΣΔ modulator for high-speed A/D conversion with reduced sensitivity to DAC errors

This paper presents a ΣΔ modulator (ΣΔM) which combines single-bit and multi-bit quantization in a cascade architecture to obtain high resolution with low oversampling ratio. It is less sensitive to the non-linearity of the DAC than those previously reported, thus enabling the use of very simple analog circuitry with neither calibration nor trimming required.Comisión Interministerial de Ciencia y Tecnología TIC97-058

La fotografía como documento sociocultural a finales del siglo XIX: Nadar y el retrato post mórtem

There is no doubt that photography was a transcendental element in nineteenth-century that definitely democratized portraiture. Citizenship found in this procedure the most effective way for their social representation. In this sense, this article deals with the important role photography played as as sociocultural document in late nineteenth-century through post mortem portrait studio. To understand this iconography we take as reference to Gaspard-Félix Tournachon «Nadar» testimony. The reflections of this photographer and theorist will help to clarify the social role of post mortem portrait at that time.No cabe duda de que la fotografía se posicionó en el siglo XIX como el elemento trascendental que democratizó definitivamente el retrato. La ciudadanía halló en este procedimiento el medio más eficaz para su representación social. En este sentido, planteamos en este artículo el importante papel que va a desempeñar la fotografía como documento sociocultural a finales del siglo XIX a través del estudio ideológico del retrato post mórtem como una modalidad usual en el ámbito familiar de aquel tiempo. Para la comprensión de esta iconografía tomamos como referente las reflexiones del fotógrafo y teórico Gaspard-Félix Tournachon «Nadar», con el fin de profundizar tanto en la función social del retrato de difuntos como en su posicionamiento dentro de la práctica fotográfica

Klimt and the post mortem portrait. From the professional to the sentimental

Este artículo analiza la vertiente conceptual y plástica de los retratos post mortem efectuados por Gustav Klimt. Una labor que ejerce excepcionalmente, como otros pintores de la historia del arte, aunque el caso de este artista es destacado por abordarla desde el campo profesional al personal. En este aspecto, el presente texto pone de relieve los significativos trabajos realizados por Klimt, entre 1883 y 1912, tanto por encargos privados, como son los proyectos dedicados a Lott, Eitelberger, Natter o Munk; como por intereses íntimos y familiares, cuando registra a su hijo Otto Zimmerman, en 1902, en el lecho de muerte.This article analyzes the conceptual and plastic aspects of Gustav Klimt’s post mortem portraits. A task that he carries out ex-ceptionally, like other painters in the history of art, although the case of this artist is notable for approaching it from the professional to the personal field. In this aspect, this text highlights the significant works carried out by Klimt, between 1883 and 1912, both for private com-missions, such as the projects dedicated to Lott, Eitelberger, Natter or Munk; as for intimate and family interests, when he registers his son Otto Zimmerman, in 1902, on his deathbed

El retrato en la práctica fotográfica de finales del siglo XX y principios del XXI en la región de Murcia

The article has with topic the production of the photographic portrait at the end of the 20th century and beginning of the XXIst in the Region of Murcia. Along the text there is revealed the important tradition that has been practised as I generate inside the contemporary photography of this zone.El artículo tiene con tema la producción del retrato fotográfico a finales del siglo XX y principios del XXI en la Región de Murcia. A lo largo del texto se pone de manifiesto la importante tradición que se ha practicado como genero dentro de la fotografía contemporánea de esta zona

Study of the growth mechanisms of low-pressure chemically vapour deposited silica films

7 pages, 5 figures.-- Issue title: "Proceedings of the Twelfth European Conference on Chemical Vapour Deposition" (Sitges, Barcelona, Spain, Sep 5-10, 1999).We have studied the surface morphology evolution of SiO2 films grown at 20 nm/min in a low-pressure chemical vapour deposition reactor from SiH4/O2 mixtures at low (611 K) and high (723 K) temperatures. Films have been deposited for times ranging from 10 min up to 48 hours. It is shown that the SiO2 growth at high temperature becomes stable, whereas at low temperature it is unstable (i.e., the surface roughness increases continuously with deposition time). This clear difference is explained on the basis of the different growth mechanisms operating under both experimental conditions. These results are compared with the predictions of the few theoretical works on growth evolution by chemical vapour deposition.This work was partially realized within the frame of the CONICET-CSIC research cooperation program, partially supported by Ministerio de Educación y Cultura (Programa de Cooperación Científica con Iberoamérica), by the 7220-ED/082 project from ECSC and by the 07M/0710/97 project from CAM. F. Ojeda gratefully acknowledges the grant financed by the Comunidad de Madrid (683/96, BOCM 22/4/96).Publicad

Modelling of silica film growth by chemical vapour deposition: Influence of the interface properties

12 pages, 6 figures.-- Issue title: "Thirteenth European Conference on Chemical Vapor Deposition" (Glyfada, Athens, Greece, Aug 26-31, 2001).We have studied the main physical mechanisms involved in the growth of Chemical Vapor Deposition (CVD) systems. We have characterized W films by Scanning Tunneling Microscopy, and SiO2 films by Atomic Force Microscopy (AFM) and Infrared and Raman spectroscopies. Tungsten CVD films display an unstable growth mode since the surface roughness increases continuously with deposition time. In order to assess the physical origin of the instability we have grown silica films in a low-pressure CVD reactor from SiH4/O2 mixtures at 0.3 nm/s at low (611 K) and high (723 K) temperatures. Silica films deposited at high temperature are rougher than those grown at low temperature. Moreover, they become asymptotically stable in contrast to those deposited at low temperature which are unstable. These different behaviors are explained within the framework of the dynamic scaling theory by the interplay for each growth condition between surface diffusion relaxation processes, shadowing effects, lateral growth, short-range memory effects and the relative concentration of active sites, mainly SiH and strained siloxane groups, and passive sites. A continuum growth equation taking into account these effects is proposed to explain the observed growth behavior for both sets of films. Computer simulations of this equation reproduce the experimental behavior.This work was partially supported by the 7220-DE/082 project from ECSC, the 07M/0710/97 project from CAM and Ministerio de Educación y Cultura (MEC, programa de Cooperación Científica con Iberoamérica) and the DGES project BFM2000-0006 from MBC. It was pertormed also within the framework of the CSIC/CONICET research cooperation program.Publicad