Monte Carlo analysis of voltage noise in sub-micrometre semiconductor structures under large-signal regime

Sea analiza el método de Monte Carlo y el ruidoUsing an ensemble Monte Carlo technique, we investigate voltage noise(related to diffusion noise sources) in GaAs n+nn+ structures operating underlarge-amplitude periodic signals. A pronounced noise contribution aroundthe frequency of the excitation signal f0 is evidenced. This contribution is mainly associated with the time-varying field sustained by the n region. Its presence and importance depends on the length of the n region and the value of f0. This additional contribution in the voltage noise spectrum tends to disappear for values of f0 beyond the cut-off of the noise related to the n region. On the other hand, the level of low-frequency noise under large-signal conditions is higher than under mall-signal operation due to theincrease of the effective resistance of the structures

La imagen fotográfica como documento arqueológico. Los archivos en la Universidad Autónoma de Madrid

Actas de las Primeras Jornadas Imagen, Cultura y Tecnología celebradas del 1 al 5 de julio de 2002 en la Universidad Carlos III de Madri

Ener3DMap-SolarWeb roofs: A geospatial web-based platform to compute photovoltaic potential

[EN] The effective exploitation and management of renewable energies requires knowledge not only of the energy intensity at the exploitation site but also of the influence of the geometry of the site and its surroundings. For this reason, the efficient processing and interpretation of combined geospatial and energy data is a key issue. This paper presents the development of a web-based tool for the automatic computation of photovoltaic potential on rooftops and on parcels without buildings. The tool called Ener3DMap-SolarWeb Roofs is based on Leaflet and supports WMS, GeoJSON, GeoCSV and KML formats, among others. With these data formats, base maps, geometric data from the rooftops automatically computed from LiDAR and imagery data with self-developed processing algorithms, cadastral data and a solar radiation model are integrated in the tool. These different types of data, the high level of automation and the different scales for which energy data is calculated (hourly, monthly and annually) are the main contributions of the presented tool compared to other existing solutions. The capacities of the tool are tested through its application to analyze the solar potential of rooftops with different shapes and for different solar panel configurations. The accuracy of the results is ensured through the integration of a validated methodology for the computation of geometry and a validated solar radiation model, PVGIS

Submillimeter-Wave Oscillations in Recessed InGaAs/InAlAs Heterostructures: Origin and Tunability

By means of an ensemble Monte Carlo simulator, the appeareance of THz oscillations in InAlAs/InGaAs slot diodes is predicted when the applied bias exceeds the threshold for intervalley transfer. Such high frequency is attained by the presence of a Gunn-like effect in the recess-to-drain region of the device channel whose dynamics is controlled by ballistic gamma valley electrons. In this work we explain the mechanism at the origin of this effect and also the influence of the bias conditions, delta-doping, recess-to-drain distance and recess length on the frequency of the ultra-fast Gunn like oscillations. The simulations show that a minimum value for the delta-doping is necessary to have enough carrier concentration under the recess and allow the oscillations to emerge. Finally, we show that shortening the devices (small recess and recess-to-drain lengths) increases of the oscillation frequency, so providing an interesting frequency tuneability of this THz source.ROOTHz (FP7-243845

Reproduction, longevity and life table parameters of Monosteira unicostata (Hemiptera: Tingidae) at constant temperatures

Information on the effect of temperature on biological parameters of phytophagous insects is one of the tools in IPM programs, as it allows prediction of risk situations in the field. This work reports the effect of temperature on reproductive parameters and longevity of one of the most important current pests of almond orchards in the Mediterranean basin, the poplar lace bug, Monosteira unicostata (Mulsant & Rey) (Hemiptera: Tingidae). The temperatures tested were 22, 25, 28, 31, 34 and 37ºC, always at 60 ± 10% relative humidity and under a L16:D8 photoperiod. Extreme temperatures had an adverse effect on preoviposition period, total fecundity and daily fecundity while increasing values of oviposition period and adults longevity were registered for decreasing temperatures. Male longevity was higher than female longevity, and mortality pattern differed between sexes for all temperatures but 37ºC. The nonlinear Lactin model described accurately the effect of temperature on the intrinsic rate of natural increase of M. unicostata populations and predicted the optimum temperature for population increase at 34.1ºC, at which the population doubling time is 3.6 days. Produced values of lower and upper thresholds for M. unicostata populations were 14.8 and 38.8ºC, respectively. This characterizes the poplar lace bug as a very important pest in the Mediterranean basin, with an increasing potential risk in a global warming scenario

La asamblea de clase en educación infantil: un espacio para crecer como grupo

La Educación Infantil es una etapa de pleno valor educativo y con una identidad propia. En este trabajo mostramos el interés de la práctica de la asamblea de clase como espacio en el que desarrollar de forma interrelacionada la competencia social y cívica y la competencia en comunicación lingüística de niños menores de 6 años. Para ello, explicamos el sentido de la asamblea de clase en esta etapa, atendiendo a la dificultad que entraña la comunicación compartida en aula. Posteriormente, exponemos cómo a partir de una adecuada gestión docente de la reunión de grupo es posible fomentar el desarrollo de la autonomía moral en los niños, así como proporcionar oportunidades para la experimentación comunicativa en contexto, que redundarán en el desarrollo de las capacidades de los niños

Experimental simulation of simultaneous vision

Purpose. To present and validate a prototype of an optical instrument that allows experimental simulation of pure bifocal vision. To evaluate the influence of different power additions on image contrast and visual acuity. Methods. The instrument provides the eye with two superimposed images, aligned and with the same magnification, but with different defocus states. Subjects looking through the instrument are able to experience pure simultaneous vision, with adjustable refractive correction and addition power. The instrument is used to investigate the impact of the amount of addition of an ideal bifocal simultaneous vision correction, both on image contrast and on visual performance. The instrument is validated through computer simulations of the letter contrast and by equivalent optical experiments with an artificial eye (camera). Visual acuity (VA) was measured in four subjects (age: 34.3 ± 3.4 years; spherical error: -2.1 ± 2.7 diopters [D]) for low and high contrast letters and different amounts of addition. Results. The largest degradation in contrast and visual acuity (~25%) occurred for additions around ±2 D, while additions of ±4 D produced lower degradation (14%). Low additions (1-2 D) result in lower VA than high additions (3-4 D). Conclusions. A simultaneous vision instrument is an excellent tool to simulate bifocal vision and to gain understanding of multifocal solutions for presbyopia. Simultaneous vision induces a pattern of visual performance degradation, which is well predicted by the degradation found in image quality. Neural effects, claimed to be crucial in the patients' tolerance of simultaneous vision, can be therefore compared with pure optical effects. Copyright 2013 The Association for Research in Vision and Ophthalmology, Inc.Supported by Spanish Government Grant FIS2011-25637 and European Advanced Grant ERC-2011-AdG-294099 to SM.Peer Reviewe

Rammed earth walls in Mediterranean climate: material characterization and thermal behaviour

Rammed earth is considered a very sustainable construction system due to its low embodied energy, long service life and high recyclability. However, authors found that there is a lack of experimental results at real scale regarding rammed earth thermal behaviour. For this reason, this paper is first focused on the characterization of two different types of earth in order to check the suitability of being used in rammed earth walls. After the characterization, two experimental cubicle-shape buildings were built in Barcelona and Puigverd de Lleida (Spain) in order to test the thermal behaviour of their walls in two different climatic conditions. Temperature profiles inside walls have been monitored using thermocouples and temperature profile of southern walls was analysed in free floating conditions during summer and winter periods of 2013. Results show that thermal amplitude from outside to inside temperatures are decreased by rammed earth walls, achieving constant temperatures in inner surface of southern walls.Peer ReviewedPostprint (published version

Thermodynamic analysis of a dual power-hydrogen production system based on chemical-looping combustion

Chemical-looping hydrogen generation (CLHG) is a chemical-looping combustion variant that allows simultaneous production of power and hydrogen. A thermodynamic analysis from the exergy method point of view of an integrated syngas-fueled CLHG cycle is carried out with the aim of contributing to the conceptual understanding and development of CLHG systems. The cycle working point is optimized in a range of conditions. The proposed system shows a very interesting potential for power, hydrogen and process heating coproduction with high efficiency