Caracterización mecánica de tablas de madera de pino silvestre, usadas como barandillas en sistemas provisionales de protección de borde

El empleo de piezas de madera de pino silvestre de pequeña escuadría es una práctica muy habitual en el sector de la Construcción en la zona central de la Península Ibérica. Existen numerosos estudios sobre este tipo de material pero todos ellos se han realizado sobre piezas de gran escuadría. No obstante, se constata un vacío absoluto de informes técnicos en lo que se refiere al comportamiento mecánico de elementos de pequeña escuadría, que son los que normalmente se utilizan en protecciones colectivas (PC) y medios auxiliares de edificación (MAE). La norma UNE-EN 13374 “Sistemas provisionales de protección de borde. Especificaciones del producto, métodos de ensayo” especifica que la madera empleada en sistemas provisionales de protección de borde debe poseer como mínimo la clase resistente C14. La obtención de la clase resistente de la madera empleada en construcción para PC y MAE mediante el empleo de la norma UNE 56544 “Clasificación visual de la madera aserrada para uso estructural. Maderas de coníferas ”, dejaría fuera de uso prácticamente a todos los elementos empleados en la práctica, que suelen ser de madera de cuarta, a la que no se le puede asignar una clase resistente y además la norma supone que su resistencia es inferior a la de la clase C18 en elementos de pino silvestre. En este trabajo se ha realizado una caracterización mecánica de tablas de madera de pino silvestre de las diferentes calidades que existen en el mercado (especial, primera, segunda, tercera y cuarta) en los grosores comerciales 22, 27, 30 y 40 mm y ancho 150 mm., que son los utilizados habitualmente en (PC) y (MAE). En todos los elementos se ha realizado una clasificación visual y resistente previa según la norma UNE 56544. Posteriormente se han ensayado las piezas para determinar sus características mecánicas reales. Se han comparado los resultados con los obtenidos por otros investigadores sobre piezas de gran escuadría, buscando las posibles correlaciones entre algunas de sus propiedades.

Optical absorption analysis of quaternary molybdate- and tungstate-ordered double perovskites

Quaternary-ordered double perovskite A2MM’O6 (M=Mo,W) semiconductors are a group of materials with a variety of photocatalytic and optoelectronic applications. An analysis focused on the optoelectronic properties is carried out using first-principles density-functional theory with several U orbital-dependent one-electron potentials applied to different orbital subspaces. The structural non-equivalence of the atoms resulting from the symmetry has been taken in account. In order to analyze optical absorption in these materials deeply, the absorption coefficients have been split into inter- and intra-non-equivalent species contributions. The results indicate that the effect of the A and M’ atoms on the optical properties are minimal whereas the largest contribution comes from the non-equivalent O atoms to M transitions.

Microscopic Analysis and Applications of the Cu(Sb,Bi)S2 High Optical Absorption

Ternary Cu(Sb,Bi)S2 semiconductors are a group of materials with a wide variety of applications, especially photovoltaic. An analysis of the structural, electronic, and optical properties obtained from first-principles is presented. The microscopic justification of the high absorption coefficients is carried out by splitting the optical properties on chemical species contributions according to the symmetry. Focusing on photovoltaic applications, and from first-principles results, the efficiencies for several solar spectra are obtained as a function of the device thickness. This study indicates the great potential of these materials for photovoltaic and other optical devices.

Optical absorption and applications of the ABO4 (A=Ca, Pb and B= Mo, W) semiconductors

Ternary molybdates and tungstates ABO4 (A=Ca, Pb and B= Mo, W) are a group of materials that could be used for a variety of optoelectronic applications. We present a study of the optoelectronic properties based on first-principles using several orbitaldependent one-electron potentials applied to several orbital subspaces. The optical properties are split into chemical-species contributions in order to quantify the microscopic contributions. Furthermore, the effect of using several one-electron potentials and orbital subspaces is analyzed. From the results, the larger contribution to the optical absorption comes from the B-O transitions. The possible use as multi-gap solar cell absorbents is analyzed.

Deposition reactors for solar grade silicon: a comparative thermal analysis of a Siemens reactor and a fluidized bed reactor

Polysilicon production costs contribute approximately to 25-33% of the overall cost of the solar panels and a similar fraction of the total energy invested in their fabrication. Understanding the energy losses and the behaviour of process temperature is an essential requirement as one moves forward to design and build large scale polysilicon manufacturing plants. In this paper we present thermal models for two processes for poly production, viz., the Siemens process using trichlorosilane (TCS) as precursor and the fluid bed process using silane (monosilane, MS).We validate the models with some experimental measurements on prototype laboratory reactors relating the temperature profiles to product quality. A model sensitivity analysis is also performed, and the efects of some key parameters such as reactor wall emissivity, gas distributor temperature, etc., on temperature distribution and product quality are examined. The information presented in this paper is useful for further understanding of the strengths and weaknesses of both deposition technologies, and will help in optimal temperature profiling of these systems aiming at lowering production costs without compromising the solar cell quality.

Optoelectronic property analysis of MCrO4 (M=Ba, Sr) with a response to visible light irradiation

Ternary MCrO4 (M = Ba, Sr) semiconductors are materials with a variety of photocatalyst and optoelectronic applications. We present detailed microscopic analyses based on first principles of the structure, the electronic properties and the optical absorption in which the difference between symmetrically non-equivalent atoms has been considered. The high absorption coefficients of these materials are split into chemical species contributions in accordance with the symmetry. The high optical absorption in these materials is mainly because of the Cr–O inter-species transitions.

Age regression from soft aligned face images using low computational resources

The initial step in most facial age estimation systems consists of accurately aligning a model to the output of a face detector (e.g. an Active Appearance Model). This fitting process is very expensive in terms of computational resources and prone to get stuck in local minima. This makes it impractical for analysing faces in resource limited computing devices. In this paper we build a face age regressor that is able to work directly on faces cropped using a state-of-the-art face detector. Our procedure uses K nearest neighbours (K-NN) regression with a metric based on a properly tuned Fisher Linear Discriminant Analysis (LDA) projection matrix. On FG-NET we achieve a state-of-the-art Mean Absolute Error (MAE) of 5.72 years with manually aligned faces. Using face images cropped by a face detector we get a MAE of 6.87 years in the same database. Moreover, most of the algorithms presented in the literature have been evaluated on single database experiments and therefore, they report optimistically biased results. In our cross-database experiments we get a MAE of roughly 12 years, which would be the expected performance in a real world application.

Thermal shields for heat loss reduction in Siemens-type CVD reactors

The use of thermal shields to reduce radiation heat loss in Siemens-type CVD reactors is analyzed, both theoretically and experimentally. The potential savings from the use of the thermal shields is first explored using a radiation heat model that takes emissivity variations with wavelength into account, which is important for materials that do not behave as grey bodies. The theoretical calculations confirm that materials with lower surface emissivity lead to higher radiation savings. Assuming that radiation heat loss is responsible for around 50% of the total power consumption, a reduction of 32.9% and 15.5% is obtained if thermal shields with constant emissivities of 0.3 and 0.7 are considered, respectively. Experiments considering different thermal shields are conducted in a laboratory CVD reactor, confirming that the real materials do not behave as grey bodies, and proving that significant energy savings in the polysilicon deposition process are obtained. Using silicon as a thermal shield leads to energy savings of between 26.5-28.5%. For wavelength-dependent emissivities, the model shows that there are significant differences in radiation heat loss, of around 25%, when compared to that of constant emissivity. The results of the model highlight the importance of having reliable data on the emissivities within the relevant range of wavelengths, and at deposition temperatures, which remains a pending issue.

Demonstration of the operation principles of intermediate band solar cells at room temperature

In this work we report, for the first time at room temperature, experimental results that prove, simultaneously in the same device, the two main physical principles involved in the operation of intermediate band solar cells: (1) the production of sub-bandgap photocurrent by two optical transitions through the intermediate band; (2) the generation of an output voltage which is not limited by the photon energy absorption threshold. These principles, which had always required cryogenic temperatures to be evidenced all together, are now demonstrated at room temperature on an intermediate band solar cell based on InAs quantum dots with Al0.3Ga0.7As barriers.

Effect of Sb on the quantum efficiency of GaInP solar cells

The energy bandgap of GaInP solar cells can be tuned by modifying the degree of order of the alloy. In this study, we employed Sb to increase the energy bandgap of the GaInP and analyzed its impact on the performance of GaInP solar cells. An effective change in the cutoff wavelength of the external quantum efficiency of GaInP solar cells and an effective increase of 50 mV in the open-circuit voltage of GaInP/Ga(In)As/Ge triple junction solar cells were obtained with the use of Sb. Copyright © 2016 John Wiley & Sons, Ltd.

Inorganic Photovoltaics - Planar and Nanostructured Devices

Since its invention in the 1950s, semiconductor solar cell technology has evolved in great leaps and bounds. Solar power is now being considered as a serious leading contender for replacing fossil fuel based power generation. This article reviews the evolution and current state, and potential areas of near future research focus, of leading inorganic materials based solar cells, including bulk crystalline, amorphous thin-films, and nanomaterials based solar cells. Bulk crystalline silicon solar cells continue to dominate the solar power market, and continued efforts at device fabrication improvements, and device topology advancements are discussed. III-V compound semiconductor materials on c-Si for solar power generation are also reviewed. Developments in thin-film based solar cells are reviewed, with a focus on amorphous silicon, copper zinc tin sulfide, cadmium telluride, as well as nanostructured Cadmium telluride. Recent developments in the use of nano-materials for solar power generation, including silicon and gallium arsenide nanowires, are also reviewed.

Optimizing phosphorus diffusion for photovoltaic applications: peak doping, inactive phosphorus,gettering, and contact formation

The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl3 source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860 °C for 60 min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density Npeak = 8.0 × 1018 cm−3 and a junction depth dj = 0.4 μm, resulting in a sheet resistivityρsh = 380 Ω/sq and a saturation current-density J0 below 10 fA/cm2. With these properties, the POCl3 process can compete with ion implantation or doped oxide approaches.

Solar driven energy conversion applications based on 3C-SiC

There is a strong and growing worldwide research on exploring renewable energy resources. Solar energy is the most abundant, inexhaustible and clean energy source, but there are profound material challenges to capture, convert and store solar energy. In this work, we explore 3C-SiC as an attractive material towards solar-driven energy conversion applications: (i) Boron doped 3C-SiC as candidate for an intermediate band photovoltaic material, and (ii) 3C-SiC as a photoelectrode for solar-driven water splitting. Absorption spectrum of boron doped 3C-SiC shows a deep energy level at ~0.7 eV above the valence band edge. This indicates that boron doped 3C-SiC may be a good candidate as an intermediate band photovoltaic material, and that bulk like 3C-SiC can have sufficient quality to be a promising electrode for photoelectrochemical water splitting.

Ultra high temperature latent heat energy storage and thermophotovoltaic energy conversion

A conceptual energy storage system design that utilizes ultra high temperature phase change materials is presented. In this system, the energy is stored in the form of latent heat and converted to electricity upon demand by TPV (thermophotovoltaic) cells. Silicon is considered in this study as PCM (phase change material) due to its extremely high latent heat (1800 J/g or 500 Wh/kg), melting point (1410 C), thermal conductivity (~25 W/mK), low cost (less than $2/kg or $4/kWh) and abundance on earth. The proposed system enables an enormous thermal energy storage density of ~1 MWh/m3, which is 10e20 times higher than that of lead-acid batteries, 2e6 times than that of Li-ion batteries and 5e10 times than that of the current state of the art LHTES systems utilized in CSP (concentrated solar power) applications. The discharge efficiency of the system is ultimately determined by the TPV converter, which theoretically can exceed 50%. However, realistic discharge efficiencies utilizing single junction TPV cells are in the range of 20e45%, depending on the semiconductor bandgap and quality, and the photon recycling efficiency. This concept has the potential to achieve output electric energy densities in the range of 200-450 kWhe/m3, which is comparable to the best performing state of the art Lithium-ion batteries.

[Colección de fotografías sobre la ciudad de Valencia (1914 a 1930) [ [Material gráfico].]

[27]. Pasadizo que une la Catedral con el Palacio Arzobispal de Valencia en la calle de la Barcella, 1917 (1 par estereoscópico) (1 fot.) -- [28]. Puerta románica de la Catedral de Valencia, 1917 (1 par estereoscópico) (1 fot.) -- [29-30]. Fuente monumento al Márques de Campo situado en la plaza Emilio Castelar, 1917 (3 pares estereoscópicos) (2 fot.) -- [31]. Patio interior sin identificar, un hombre y un policia (1 par estereoscópico) (1 fot.) -- [32]. Estatua ecuestre de Don Jaime I El Conquistador en el Parterre, 1917 (1 par estereoscópico) (1 fot.) -- [32 A y B]. Máximo López Roglá en el Parterre (2 par estereoscópico) (2 fot.) -- [33-35]. Nieve en Valencia, en la alameditas de Serranos, niños jugando con la nieve en la Glorieta, 30-12-1917 (3 pares estereoscópicos) (3 fot.) -- [36-38]. Claustro del Patriarca con la escultura del Beato Juan de Ribera, en una de las fotos un grupo de seminaristas, 1917 (5 pares estereoscópicos) (3 fot.) -- [39-40]. Museo del Patriarca de Valencia, relicarios, Cruz Patriarcal (2 pares estereoscópicos) (2 fot.) -- [41-48]. Antiguo Hospital Padre Jofré, acceso desde la calle, patio de entrada y estatua del Padre Jofré, pórtico del Real Monasterio de la Santísima Trinidad, miembros de la Congregación de la Inmaculada y San Luís, los congregantes con los enfermos en el patio del hospital, 1913 (8 pares estereoscópicos) (8 fot.) -- [49]. Estandarte de la Academia Valencianista del Centro Escolar y Mercantil, 1917 (1 par estereoscópico) (1 fot.) -- [50-51].Miembros de la Congregación de la Inmaculada y San Luís y de la Academia Valencianista del Centro Escolar y Mercantil (calle libreros 2) junto a la falla, en una de las fotos llevan el estandarte de la Academia (2 pares estereoscópicos) (2 fot.) -- [52]. Sede de la Academia Valencianista del Centro Escolar y Mercantil (2 pares estereoscópicos) (1 fot.) -- [53-69]. Fallas, año 1917 (21 pares estereoscópicos) (14 fot.) -- [70]. Mercado de Colón, carruaje con caballo junto a la puerta principal, 1917 (1 par estereoscópico) (1 fot.) -- [71]. Palacio de la Exposición, 1917 (1 par estereoscópico) (1 fot.) -- [72-87]. Los Jardines de Viveros: ruinas en primer plano al fondo la torre del Palacio de Ripalda, jaulas de los pájaros, Francisco Roglá López en Viveros, Isabel Orrico Vidal con sus hijos y las niñeras en Viveros en distintos situaciones y contemplando el estanque con el Museo de San Pío V al fondo, 1922 (19 pares estereoscópicos) (17 fot.) -- [88-90]. La Hípica (5 pares estereoscópicos) (3 fot.) -- [91-94]. Jugando al tenis en un campo habilitado para el tenis entre pinos (8 pares estereoscópicos) (4 fot.) -- [95-97]. El Puerto de Valencia, 1921 (4 pares estereoscópicos) (3 fot.) -- [98-104]. Llegada al puerto de Valencia de cuatro submarinos, entre ellos el submarino Monturiol, escoltados por torpederos y acompañados por el buque de salvamento Canguro, 8 de septiembre de 1921 (7 pares estereoscópicos) (7 fot.) -- [105-107A-D]. Playa y Balneario de las Arenas: un hombre y tres mujeres patinando en las Arenas; Isabel Orrico Vidal (izquierda), Ignacio Roglá Orrico (bebe) en brazos de Pilar (la niñera de Chiva), Manolo Orrico Vidal con su mujer Mercedes Gay, la niñera con Luisito Roglá Orrico, los niños más mayores son Merceditas Orrico Gay y Paquito Roglá Orrico; en las Arenas a la izquierda de la foto Ignacio Roglá Orrico (bebe), Ana María Rodríguez Gay, Paquito Roglá Orrico, Manolo Orrico Vidal, Merceditas Orrico Gay, en el centro Mercedes Gay Lloveras (sentada) y Gonzalo Rodríguez Gay, a la derecha Gonzalo Rodríguez, Ana Gay Lloveras, Isabel Orrico Vidal con Luisito Roglá Orrico y Francisco Roglá López (6 pares estereoscópicos) (6 fot.) -- [109]. En la playa de la Malvarrosa barca tirada por bueyes, 1922 (1 pares estereoscópicos) (1 fot.) -- [110-117]. Fiesta de la Virgen de los Desamparados, tapíz de flores con la imagen de la Virgen colocada en el retablo de flor, salida de la Virgen de la Basílica en el traslado a la Catedral, salida de la Virgen de la Catedral para la procesión de la tarde (9 pares estereoscópicos) (7 fot.) -- [118-120]. Carroza del MArqués de Llanera (actualmente en el Museo Nacional de Cerámica y Artes Suntuarias "González Martí" por la calle Carniceros esquina con la calle Arolas, vista lateral de la carroza, procesión del Corpus? (5 pares estereoscópicos) (3 fot.) -- [121-122]. Gigantes y Cabezudos junto a la Catedral, Fiesta del Corpus (2 pares estereoscópicos) (2 fot.) -- [123]. Isabel Orrico Vidal en el balcón del nº 11 de la calle de la Paz (1 par estereoscópico) (1 fot.) -- [124]. Procesión del domingo de Ramos (1 par estereoscópico) (1 fot.) -- [125-136]. Desfile del cortejo fúnebre por la calle (de la Paz?) de los restos de Sorolla el 13 de agosto de 1923 (16 pares estereoscópicos) (10 fot.) -- [137]. Detalle de la fuente de la Alameda (1 par estereoscópico) (1 fot.) -- [138-139]. Francisco Roglá López con su caballo en la Alameda, carruaje por la Alameda (2 pares estereoscópicos) (2 fot.) -- [140-143]. Jura de bandera en la Alameda (4 pares estereoscópicos) (4 fot.) -- [144A, B, C, D, E]. Fuente con estatua de la Alameda, José Roglá López leyendo el periódico junto a la fuente, con un grupo de amigos, grupo de amigos y un barquillero en el Paseo de la Alameda, José Roglá López con unos amigos en una fuente de la Alameda que ahora está en el barrio del Carmen (5 fot.) -- [145]. Grupo de coches de la época en la plaza de la Virgen (1 fot.) -- [146A, B]. Pareja de novios saliendo de la Basílica de la Virgen? (2 pares estereoscópicos) (2 fot.) -- [147-148]. Niños de la Asociación de San Vicente Ferrer que representan los milagros en los altares (2 pares estereoscópicos) (2 fot.) -- [149-150]. Actos festivos, dos mujeres llevando una bandera con gente alrededor (2 fot.) -- [151-152]. Plaza de toros de Valencia, 1930 (2 fot.) -- [153]. Rosalía Roglá López con su abuela materna en el piso de la calle Liñán nº 3, a través de los cristales se ve el edificio de la Lonja (1 par estereoscópico) (1 fot.) -- [154]. Rosalía Roglá López en el balcón de su piso de la calle Liñán nº 3, al fondo a la izquierda se ve la plaza del mercado y la Lonja (1 par estereoscópico) (1 fot.) -- [155]. José Roglá López de pié junto a la ventana leyendo un periódico (1 fot.) -- [156-157]. Isabel Orrico Vidal en la Alameditas de Serranos, al fondo el Museo San Pío V (2 fot.) -- [158-159]. Ignacio Roglá Orrico, Luís Roglá Orrico y Francisco Roglá Orrico sentados en un banco en la Glorieta, los tres niños junto al monumento al Dr. Gómez Ferrer de la Glorieta, 1928 (2 fot.) -- [160-161]. Ignacio Roglá Orrico, Luís Roglá Orrico en el jardín de los Viveros, los dos niños con Paco bebiendo en una fuente de Viveros junto al estanque, 1929 (2 fot.) -- [162]. Grupo familiar sentado en el jardín de los Viveros, Manolo Orrico Gay, Manolo Orrico Vidal, Luís Roglá Orrico, Isabel Orrico Vidal, Mercedes Gay Lloveras y Mercedes Orrico Gay, 1930 (1 par estereoscópico) (1 fot.) -- [163]. Isabel Orrico Vidal junto a Luís Roglá Orrico en bicicleta en el jardín de los Viveros, 1930 (1 par estereoscópico) (1 fot.) -- [164]. Manolo Orrico Gay y Luís Roglá Orrico (detrás) en bicicleta por el jardín de los Viveros (1 par estereoscópico) (1 fot.)