Labour flexibility and productivity in the hotel sector

In this paper, we analyze the effect of labour flexibility on productivity in the Andalusian hotel industry using raw data of our own database and applying an expanded version of the standard production function by distinguishing between part-time, temporary, and full-time labour inputs. Our results show that productivity is lower the higher the percentage of temporary and part-time workers and there are no differences between the impacts on productivity of both types of labour contract. Future studies should analyze the differential impact of all the types of contracts discussed on the mean cost per employee in this sector.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

La población de Guadalajara,1500-1650

Tesis inédita leída el 17-12-2008 en la Universidad Autónoma de Madrid, Facultad de Filosofía y Letras, Departamento de Historia Modern

Diseño de un sistema de control basado en linealización por realimentación para un robot móvil tipo Ackerman con velocidad variable y movimiento en doble sentido describiendo trayectorias óptimas

Desde varios años, las investigaciones en el tema del uso de robots móviles han ido en aumento con el objetivo de poder utilizar los robots móviles para múltiples actividades que suelen ser difícil para una persona realizar; es por eso que, se ha ido desarrollando técnicas de control para distintos tipos de robots móviles, así como también en la mejora de su desempeño en trayectorias a recorrer frente a entornos al cual se aplique. El desarrollo se enfoca principalmente en el control del robot móvil, ya que existen varios métodos para controlarlos, ya sea de manera lineal o de manera no lineal, dependiendo sea el caso, llevándolos a llegar a su objetivo siguiendo ciertas trayectorias especificas o trayectorias más cortas a su objetivo. Para los casos de trayectorias específicas, suelen definirse formas geométricas conocidas y fáciles de realizar; sin embargo, para el caso de trayectorias con la distancia más corta, aún sigue habiendo más investigación a nivel aplicativo. Es por eso que se busca desarrollar un método para la generación de trayectoria mínima enfocado para un robot móvil tipo Ackerman, que permita llevarlo a su objetivo, considerando que el robot móvil funcionará con movimiento en avance y retroceso en cualquier momento. Esta investigación busca aplicar una técnica de control no lineal, para así trabajar en todo el espacio de funcionamiento del vehículo, que le permita al robot móvil describir trayectorias óptimas, la cual va a ser diseñada en base al análisis de movimiento que tiene un tipo Ackerman, considerando que se puede cambiar de velocidad en una misma trayectoria; para lo cual se ha realizado la obtención del modelo del tipo Ackerman y así definir correctamente el controlador a utilizar, mientras que a su vez se desarrolla el algoritmo de generación de trayectoria mínima y al final realizar la corroboración del funcionamiento en base a simulación y luego con un prototipo. El desarrollo de la investigación se ha realizado analizando diferentes técnicas de control, decidiendo al final utilizar un control basado en linealización por realimentación utilizando el método de flatness diferencial, el cual permite introducir de manera práctica una trayectoria deseada a seguir por el robot móvil en sus variables de posición. Dicha trayectoria deseada ha sido diseñada mediante un análisis geométrico compuesto por segmentos de rectas y curvas de circunferencia, basado en la teoría de Dubins y Reed & Shepp, permitiendo describir la ruta más corta posible desde el punto de origen a su punto de destino. Las pruebas realizadas de su funcionamiento han sido simuladas bajo un software que permitió validar el controlador y la correcta generación de una ruta mínima; y también se realizó pruebas en un prototipo para corroborar que puede ser aplicable en un sistema real Al final de la investigación se muestra como el controlador permite llevar al robot móvil a su objetivo describiendo trayectorias optimas, generando la velocidad y el ángulo de dirección adecuados que permitan guiarlo por dicha ruta; considerando también un sistema de navegación para la aplicación real del sistema.Tesi

Effect of the synthesis method on the performance of Ni-CeO2-ZrO2 catalysts for the hydrogenolysis of glycerol with endogenous hydrogen

In this work, we investigated the influence of the synthesis method of Ni-based CeZr catalysts on their physicochemical and catalytic properties in the hydrogenolysis (HDO) of glycerol with H2 in-situ produced by the aqueous-phase reforming (APR). Conventional impregnation method involved surface nickel deposition (NiCeZr-IM). The one-pot methods, which involved nickel embedment into CeZr lattice, included sol-gel (NiCeZr-SC) and coprecipitation (NiCeZr-CA and ultrasound-assisted NiCeZR-CS) methods. Differences in textural, structural, morphological, redox, and surface properties, together with and catalytic performance in the glycerol APR-HDO, were investigated systematically. As well, spent catalysts were deeply characterized. There were notable differences among textural properties, which significantly affected their activity in glycerol conversion. The structural characterization confirmed the successful integration of Ni into the CeZr lattice, especially for the catalysts synthesized using one-pot methods. One-pot synthesized catalysts showed stronger Ni-CeZr interaction, which affect the reducibility. The catalysts prepared by coprecipitation contained the highest metal-to-acid ratio, making them very active for C-O bond hydrogenation. Post-reaction characterization discloses a leaching of the nickel, in greater amount for both coprecipitated catalysts. This study revealed the potential of Ni-based catalysts derived from subsurface insertion of nickel into the CeZr matrix for the hydrogenolysis of glycerol without external hydrogen.Ministerio de Ciencia e Innovación, PID2019-106692RB-I0

Nickel aluminate spinel-derived catalysts for the aqueous phase reforming of glycerol: Effect of reduction temperature

Bulk nickel aluminate (NiAl2O4) was synthesised by co-precipitation at a Ni/Al mole ratio of 1:2 (stoichiometric ratio). The prepared sample was reduced at different temperatures, in the 300 to 850 ºC range, and obtained assays were analysed by a wide range of analytical techniques (XFR, XRD, H2-chemisoprtion, H2-TPR, DRS UV-vis NIR, FTIR, 27Al MAS NMR, NH3-TPD, CO2-TPD, TPO) and tested for the APR of glycerol. The spinel precursor allowed the formation of small and stable Ni particles (< 14 nm) upon reduction with good performance in the APR of glycerol (NiAl-850 93% conversion, 57% conversion to gas, at 250 ºC/45 bar and WHSV 24.5 h-1). Hydrogen was the main gaseous product and the activation temperature did not substantially alter selectivity to gaseous products; however, selectivity to intermediate oxygenated liquid compounds was substantially modified. Overall, glycerol dehydrogenation route was dominant at high reduction temperature. The good stability of the spinel led to stable H2 yield in the long-term runs (50 hours) and proved potential to be used in the APR of glycerol.Ministerio de Economía y Competitividad, ENE2016-7450-

Aqueous-Phase Glycerol Conversion over Ni-Based Catalysts Synthesized by Nanocasting

[EN] A morphological strategy consisting of nanocasting synthesis of nickel aluminate spinel precursor was addressed. Two nanocasted catalysts were synthesized involving different template-removal procedures (i.e., Teflon-assisted calcination vs. NaOH washing) for spinel recovery. As a reference, spinel NiAl2O4 supported by SBA-15 and bare nickel aluminate spinel were selected. The obtained solids were characterized in detail, examining their textural, acid–base, structural and compositional characteristics, either in the calcined or reduced forms. The as-obtained catalysts’ performance was evaluated in the aqueous-phase reforming of glycerol at 235 °C and 35 bar. Exhausted samples were also characterized to enlighten changes in catalyst properties during the aqueous-phase reaction. NiAl/SBA-15 and NiAl-NCF catalyst showed very poor catalytic performance for the glycerol transformation. NiAl-NCN catalyst presented improved activity with respect to NiAl, with a 20% higher hydrogen production rate but, as a drawback, higher methane formation for a whole range of glycerol conversions. Exhausted catalyst indicated nickel oxidized in liquid phase reaction.This research was supported by grant PID2019-106692EB-I00 funded by MCIN/AEI/ 10.13039/501100011033

Bimetallic Pt-Co Catalysts for the Liquid-Phase WGS

[EN] Bimetallic Pt-Co catalysts derived from cobalt aluminate spinel were investigated in the liquid-phase water–gas shift (WGS) reaction and CO hydrogenation. Liquid-phase WGS is a key reaction in the aqueous-phase reforming (APR) of polyols; thus, WGS activity is essential to formulate good APR catalysts. In this work, catalysts with different Pt/Co molar ratios were synthesized together with a reference Pt/alumina. All the synthesized catalysts were characterized by various techniques in order to gain knowledge on their structural and surface characteristics. WGS activity was tested with a feedstream of CO/H2O = 1/15 (space-time of 76.8 kg·s/molCO), isothermal operation at 260 ºC and 50 bar, for 10 TOS. Bimetallic Pt-Co catalysts showed improved activity in liquid-phase WGS in comparison to bare Co or Pt catalysts, which was ascribed to the synergistic effect. Despite being subjected to an increased hydrogen concentration in the feedstream (H2/CO between 0 and 12/3), these catalysts maintained a preferential selectivity towards WGS activity. In addition, the effect of temperature (220–260 ºC) and pressure (25–50 bar) was investigated over a catalyst with 0.3Pt/CoAl. CO conversion and CO2 yield were more sensitive to temperature, while a higher pressure favored methane production. The measured activation energy in the 220–260 ºC temperature range was 51.5 kJ/mol.This research was funded by Mineco (ENE2016-74850-R and PID2019-106692EB-I00) and FEDER. The APC was funded by ENE2016-74850-R. A.J.R. was supported by a PhD research fellowship provided by the University of the Basque Country UPV/EHU (PIF-17/319)

High efficiency and low footprint wooden housing prototypes for Latin America

El abandono de técnicas constructivas tradicionales y la sustitución de estas por materiales industrializados de bajas prestaciones ha sustituido en apenas unas décadas los conocimientos constructivos evolucionados durante siglos y perfectamente adaptados a la realidad climática, constructiva, económica y social de su emplazamiento, por modelos inhabitables de un altísima huella ecológica. Con el objetivo de revertir esta tendencia se ha realizado una investigación, centrada en el ámbito ecuatoriano, sobre elementos constructivos, materiales, tecnologías y sistemas que incrementen al máximo la sostenibilidad de la edificación. La investigación se centra en torno a la aplicación de aislamientos térmicos naturales, sistemas de captación solar por efecto invernadero, fachadas ventiladas y cubiertas vegetales. La monitoreo del modelo construido avala las estrategias de eficiencia energética implementadas al obtenerse temperaturas muy estables siempre dentro de la envolvente de confort (20-21ºC), mientras las edificaciones del entorno sufren sobrecalentamientos o requieren de sistemas de calefacción convencionales.The abandonment of traditional construction techniques and the replacement of these by industrialized low-performance materials has replaced in just a few decades the constructive knowledge developed over the centuries perfectly adapted to the climatic, constructive, economic and social reality of the site by uninhabitable models of a very high footprint ecological With the aim of reversing this trend, research has been carried out, focused on the Ecuadorian environment, on constructive elements, materials, technologies and systems that maximize the sustainability of the building. The research focuses on the application of natural thermal insulation, solar capture systems by greenhouse effect, ventilated facades and green roofs. The monitoring of the built model supports the energy efficiency strategies implemented to obtain very stable temperatures always within the comfort envelope (20-21ºC), while the surrounding buildings suffer overheating or require conventional heating systems.Facultad de Arquitectura y Urbanism

Bio‑hydrogen and valuable chemicals from industrial waste glycerol via catalytic aqueous-phase transformation

Waste glycerol obtained as by-product of biodiesel production has been submitted to a sequential physico-chemical treatment in order to make it suitable for continuous Aqueous-Phase Reforming (APR) in a tubular reactor. Special focus was given to the impact of impurities. APR was performed using 0.3%Pt/CoAl2O4 catalyst, at 260 °C and 50 bar within WHSV range 6–55 h−1 to cover whole conversion ranges. Glycerol conversion and yield to hydrogen reached 99.7% and 45.4%, respectively at WHSV = 6 h−1. The liquid product distribution strongly varied with glycerol conversion, maximum C-yield to 1,2-propylene glycol was attained in the 60–90% glycerol conversion range. APR of methanol and acetic acid aqueous feedstreams were investigated independently. It was concluded that acetic acid exerts a negative influence on catalyst stability since glycerol conversion decreased by 41% after 5 h TOS. Extensive characterization of fresh and exhausted catalysts revealed strong Co leaching, especially for acetic acid APR, oxidation of metals, and carbonaceous deposits. The basis for the regeneration of the spent catalyst, consisting of a reductive treatment at 500 °C, has been established. This work is expected to have significant implications for the development of APR technology for crude glycerol from biodiesel industry.This research was supported by grant PID2019-106692EB-I00 funded by MCIN/AEI/10.13039/501100011033. The authors thank for technical support provided by SGIker of UPV/EHU and European funding (ERDF and ESF)

Aqueous-phase reforming of glycerol over Pt-Co catalyst: Effect of process variables

This study examined the influence of process variables (glycerol concentration in feed, coupled temperature/pressure and space velocity) in the catalytic performance in the APR of glycerol over 0.3Pt/CoAl catalyst in a continuous fixed-bed reactor in order to maximize the production of H2. The effect of glycerol concentration in the feed was studied from 5 to 20 wt%, the coupled temperature/pressure varied from 225 °C/25 bar to 260 °C/50 bar and the spatial velocity was changed from 0.68 to 17 h-1. Our results reflected that H2 production was favored at higher reaction temperature/pressure (3.62 vs. 2.49 molH2/molGly-converted, at the most severe and mild conditions, respectively), lower WHSV (3.89 vs. 1.27 molH2/molGly-converted, at the lowest and highest space velocity, respectively) and more diluted feedstocks (3.95 vs. 1.44 molH2/molGly-converted, at the most diluted and concentrated freestreams, respectively). A threshold value at 10 wt% glycerol was found for the ratio of dehydrogenation to dehydration liquid products. The post-reaction catalyst was also characterized by several techniques, showing that Co leaching was the major drawback, especially at the mildest operation conditions, while carbonaceous deposits are negligible.Ministerio de Ciencia e Innovación, PID2019-106692RB-I0