Centroid propagation through optical systems with ABCD kernels and nonuniform or finite apertures

If the propagation of a light field can be satisfactorily described by a diffraction integral with an ABCD kernel, the propagation of its irradiance centroid is completely determined by the corresponding ABCD ray-transfer matrix in exactly the same way as if the centroid path were a conventional geometrical ray. However, potentially significant deviations from this geometrical propagation rule may arise in the presence of finite or nonuniform apertures truncating or otherwise modifying the input beam irradiance distributionThis work has been supported by the Spanish Ministerio de Ciencia e Innovación (MICINN), grants FIS2008-03884 and FIS2010-1574

Convective heat transfer modelling in dry-running polymer spur gears

Heat convection is an important phenomenon in the process of cooling polymer spur gears running in dry conditions, which ultimately affects the strength of the gears. In order to gain some insight into this phenomenon, a numerical heat convection model for polymer spur gears is proposed in this work, which is based on a detailed CFD simulation of the gears in operating conditions and it allows us to investigate the heat convection through their external surfaces. The performance of this numerical model is illustrated with several examples, in which a parametric study has been conducted to observe the variation of the heat transfer coefficients with the face width and the angular speed of the gears. The results obtained from this parametric study are compared to those obtained from a representative classical heat convection model, observing that the relative differences between them in terms of heat transfer coefficients can be as high as 125%. Finally, a new optimized heat convection model for polymer spur gears running in dry conditions is proposed, in which the convective heat transfer coefficients for the external surfaces of the gears are calculated from empirical equations based on the Newton’s law of cooling. This optimized model has lower computational cost than the numerical one, while it provides an important increase of the accuracy of the classical heat convection models, reducing the maximum relative differences to 10%.Funding for open access charge: CRUE-Universitat Jaume

Procesos de oxidación avanzada en el ciclo integral del agua

Ponències presentades a la I Jornada Técnica sobre Procesos de Oxidación Avanzada en el Ciclo Integral del Agua celebrada a Castelló de la Plana el 15 de gener de 2016Amb més de 5000 hm3 depurats, més de 2900 EDAR en funcionament i un mercat que supera els 1200 milions d'euros, la depuració d'aigües ha aconseguit un alt grau de maduresa. Al llarg dels diferents capítols, el llibre exposa els últims avanços en POA (Processos d'Oxidació Avançada) presentats per investigadors de referència en aquest camp, realitzant un recorregut per les principals tècniques associades, els resultats, els seus límits i les possibles aplicacions

Depuración de aguas residuales: digestión anaerobia

Col·lecció: Cátedra FACSA de Innovación en el Ciclo Integral del Agua de la Universitat Jaume I ; Núm.Serie: 2La càtedra universitat-empresa FACSA d'Innovació en el Cicle Integral de l'Aigua de la Universitat Jaume I té com a objectiu fomentar l'intercanvi d'idees, la transferència de coneixement i la trobada entre tots els actors del cicle integral de l'aigua. Aquesta publicació arreplega els treballs exposats en la 1ª Jornada Tècnica en Depuració d'Aigües Residuals: Digestió Anaeròbia, que es va celebrar en la Universitat Jaume I. La Jornada va reunir a experts de l'àmbit acadèmic i empresarial que van exposar els avanços actuals en la digestió anaeròbia. De l'exposició els experts i el posterior intercanvi d'idees i comentaris, cada ponent ha desenvolupat un capítol d'aquest llibre en què plasma les idees que va aportar, així com les conclusions generades. A més, en la web de la càtedra, www.catedradelagua.uji.es, es poden trobar les presentacions utilitzades per cada expert en la seua ponència

Evaluation of hydraulic mixing performance in a full-scale anaerobic digester with an external liquid recirculation system using CFD and experimental validation

Anaerobic digestion (AD) has become an essential process for sludge treatment and its optimum performance is related to its mixing degree. In this study, a full-scale Anaerobic Digester (ADer) with an external recirculation mixing system was studied via single-phase 3D-CFD simulations to assess the influence of recirculation flow and a 3-blade propeller. The model was validated with inert tracer tests. The design and mixing parameters were studied to characterise the mixing efficiency in different scenarios. The design parameters were assessed first, but wide deviations from the recommended values were found. Local mixing parameters were found to be useful for defining the degree and type of mixing, and are highly recommended in the CFD studies of ADers. A second-order statistical moment was proposed as a global mixing parameter to describe geometrical and local mixing, and to state a reliable homogenisation time.Funding for open access charge: CRUE-Universitat Jaume

Increment of specific heat capacity of solar salt with SiO2 nanoparticles

Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable.Universitat Jaume I (project P1-1B2013-43

Multibeam second-harmonic generation by spatiotemporal shaping of femtosecond pulses

We present a technique for efficient generation of the second-harmonic signal at several points of a nonlinear crystal simultaneously. Multispot operation is performed by using a diffractive optical element that splits the near-infrared light of a mode-locked Ti:sapphire laser into an arbitrary array of beams that are transformed into an array of foci at the nonlinear crystal. We show that, for pulse temporal durations under 100 fs, spatiotemporal shaping of the pulse is mandatory to overcome chromatic dispersion effects that spread both in space and time the foci showing a reduced peak intensity that prevents nonlinear phenomena. We experimentally demonstrate arbitrary irradiance patterns for the second-harmonic signal consisting of more than 100 spots with a multipass amplifier delivering 28 fs, 0.8 mJ pulses at 1 kHz repetition rate.This work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) and FEDER through the projects FIS2010-15746, FIS2009-09522, and SAUUL (CSD2007-00013) and the Fundació Caixa Castelló (P1- 1B2010-26)

Dispersion management in two-photon microscopy by using diffractive optical elements

We demonstrate efficient generation of wide-field fluorescence signals in two-photon microscopy exploiting diffractive optical elements and short pulses by using a dispersion-compensated beam delivery optics module. Computer-generated holograms are codified onto a phase-only spatial light modulator, which allows for arbitrary single-shot patterning of the sample. Spatiotemporal shaping of the pulse is mandatory to overcome spatial chirp and pulse-front tilt effects that spread both in space and time the irradiance patterns, thus limiting not only the spatial resolution but also the signal-to-noise ratio in two-photon microscopy. By using a multipass amplifier delivering 30 fs, 0.8 mJ pulses at 1 kHz repetition rate, we experimentally demonstrated arbitrary single-shot fluorescence irradiance patterns in Rhodamine B

Free-Motion Beam Propagation Factor Measurement by Means of a Liquid Crystal Spatial Light Modulator

In contrast to the mechanical scanning procedure described in the standard ISO/DIS 11146, the use of electronically tunable focal length lenses has proved its capability for the measurement of the laser beam propagation factor ( ) without moving components. Here, we demonstrate a novel experimental implementation where we use a low-cost programmable liquid crystal spatial light modulator (SLM) for sequentially codifying a set of lenses with different focal lengths. The use of this kind of modulators introduces some benefits such as the possibility for high numerical aperture or local beam control of the phase of the lenses which allows for minimizing systematic errors originated by lens aberrations. The beamwidth, according to the second-order moment of the irradiance, is determined for each focal length by using a digital sensor at a fixed position with respect to the spatial light modulator. After fitting the measured data to the theoretical focusing behavior of a real laser beam, the beam propagation factor is obtained. We successfully validated the results in the laboratory where a full digital control of the measurement procedure without mechanical scanning was demonstrated

Enhanced field-of-view integral imaging display using multi-Köhler illumination

A common drawback in 3D integral imaging displays is the appearance of pseudoimages beyond the viewing angle. These pseudoimages appear when the light rays coming from each elemental image are not passing through the corresponding microlens, and a set of barriers must be used to avoid this flipping effect. We present a pure optical arrangement based on Köhler illumination to generate these barriers thus avoiding the pseudoimages. The proposed system does not use additional lenses to project the elemental images, so no optical aberrations are introduced. As an added benefit, Köhler illumination provides a higher contrast 3D display.This work was supported in part by the Plan Nacional I + D + I, under Grants DPI2012-32994 and ENE2013-48565-C2-2-P, Ministerio de Economía y Competitividad (Spain), and also by the Generalitat Valenciana (Spain) under Grant PROMETEOII/2014/072. The work of Ángel Tolosa was supported by the Generalitat Valenciana under IVACE Grant PROMECE 2014