Protocolo de Cooperación Adaptativo para Sistemas de Comunicaciones Opticas Atmosféricas

En concreto, se ha analizado un sistema de comunicaciones cooperativas formado por 3 enlaces FSO con retransmision DF usando IM/DD sobre canales con turbulencia atmosferica y desalineamiento entre el transmisor y el receptor. Se han evaluado las prestaciones de un protocolo de cooperacion adaptativo basado en la seleccion de camino óptico con mayor valor de irradiancia.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Evaluating pointing errors on ergodic capacity of DF relay-assisted FSO communication systems

Ergodic capacity of decode-and-forward (DF) relay-assisted free-space optical (FSO) communication systems when line of sight is available is analyzed over gamma-gamma fading channels with pointing errors. Novel closed-form approximate ergodic capacity expression is obtained in terms of the H-Fox function for a 3-way FSO communication system when the α-μ distribution to efficiently approximate the probability density function (PDF) of the sum of gamma-gamma with pointing errors variates is considered. Moreover, we present a novel asymptotic expression at high signal-to-noise ratio (SNR) for the ergodic capacity of DF relay-assisted FSO systems. The main contribution in this work lies in an in-depth analysis about the impact of pointing errors on the ergodic capacity for cooperative FSO systems. In order to maintain the same performance in terms of capacity, it is corroborated that the presence of pointing errors requires an increase in SNR, which is related to the fraction of the collected power at the receive aperture, i.e. A 0 . Simulation results are further demonstrated to confirm the accuracy and usefulness of the derived results.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. The authors wish to acknowledge the financial support given by Spanish MINECO Project TEC2012-32606

Estudio de la distribución de temperatura de aire en un invernadero tipo en Almería ("raspa y amagado")

RESUMEN: La Tesis Doctoral nace con el objetivo de estudiar el ambiente térmico en el interior de invernaderos y especialmente la infuencia que tiene sobre el trabajador, ya que la mayoría de estudios similares en invernaderos están centrados en el cultivo. En este trabajo se estudian las condiciones de temperatura de aire con respecto a los trabajadores, específi camente se analiza la heterogeneidad de temperatura de aire en el interior de un invernadero siguiendo los métodos recogidos en la norma ISO 7726. Para ello, se utiliza una red de sensores inalámbrica y se lleva a cabo una campaña experimental de un año de duración en un invernadero típico en Almería. Los resultados permiten caracterizar la distribución de temperatura de aire en el interior de un invernadero y con firma la existencia de heterogeneidad en la temperatura de aire conforme a la norma ISO 7726, así como identifi car patrones en su distribución. Derivado de este estudio, se encontraron di ficultades en medir con precisión y bajo coste la velocidad del viento en el interior de un invernadero, lo que lleva a realizar una calibración de un anemómetro de bajo coste. La calibración se centra en un anemómetro de hilo caliente, en el que se intenta solventar su principal inconveniente, que es la perdida de precisión causada por los cambios en la temperatura de aire o temperatura ambiente. Dicha calibración se realiza por medio de un Proceso de Regresión Gaussiana y se valida con datos reales, alcanzándose el objetivo de conseguir un dispositivo de bajo coste y capaz de realizar medidas con precisión de velocidad de aire en un rango típico de temperatura de aire. Finalmente, y también como consecuencia del estudio del ambiente térmico, se observó que los trabajadores de invernadero, a pesar de la cubierta plástica que cubre dichos invernaderos, pueden ser susceptibles de riesgos asociados a la radiación ultravioleta en piel y ojos. Por ello, mediante una red de sensores, se realiza una campaña de medida de la radiación ultravioleta durante un año de duración en el interior de un invernadero típico en Almería. Los resultados indican que se supera el límite de riesgo establecido por la Organización Mundial de la Salud, por lo que se con firma que existe riesgo sobre la salud de los trabajadores de invernaderos por radiación ultravioleta. ABSTRACT: This Doctoral Thesis was born with the aim of studying the thermal environment inside greenhouses and especially the inuence it has on the worker, since most similar studies in greenhouses are focused on the crop. In this work the air temperature conditions with respect to the workers are studied, specically the heterogeneity of air temperature inside a greenhouse is analysed following the methods gathered in ISO 7726. To achieve this goal, a network of wireless sensors and a year-long experimental campaign is carried out in a typical greenhouse in Almer a. The results allow the characterization of the air temperature distribution inside a greenhouse and con rms the existence of heterogeneity in air temperature according to the norm ISO 7726, as well identifying patterns in its distribution. Derived from this study, dificulties were found in accurately measuring and with low cost the wind speed inside a greenhouse, which leads to a calibration of a low cost anemometer. The calibration focuses on a hot-wire anemometer, which attempts to solve its main drawback, namely its loss of accuracy when air temperature or ambient temperature changes. This calibration is carried out by means of a Gaussian Regression Process and is validated with real data, reaching the goal of achieving a low-cost device capable of accurately measuring air velocity in a typical air temperature range. Finally, and also as a consequence of the study of the thermal environment, it was observed that greenhouse workers, despite the plastic cover covering such greenhouses, may be susceptible to risks associated to ultraviolet radiation on skin and eyes. For this reason, through a network of sensors, a measurement campaign of ultraviolet radiation is carried out for a year inside a typical greenhouse in Almería. The results indicate that the risk limit established by the World Health Organization is exceeded, so it is con rmed that there exist risk to the health of greenhouse workers by ultraviolet radiation

Optimization of multi-stage thickening of biomass in a demonstrative full–scale microalgae-based wastewater treatment system

This study gathers the results of the operation and optimization of the thickening of microalgal biomass produced at demonstrative scale in photobioreactors fed with agricultural runoff and domestic wastewater. The optimization was conducted during two months. The system consisted in two gravity thickeners connected in series in a multi-stage approach. The objective of thickening was to concentrate the microalgae grown in photobioreactors (total solids (TS) concentration of 0.1–1 g/L) into a biomass with 20 g/L of TS, which was considered optimal for the subsequent anaerobic digestion process. First, the utilization of one single thickener alone allowed to achieve a concentration factor (CF) of 1.9 and recovery efficiency (RE) of 28%. However, the final concentration of TS in the thickened biomass (6.4 g/L) was still much lower than the target concentration. The installation of the second thickener connected in series with the first one significantly improved the overall performance. Indeed, a TS concentration of 26.5 g/L was finally achieved, with an overall CF of 3.6. The results of the study suggest that the multi-stage thickening process is a suitable strategy and it is highly advisable to achieve a successful microalgal biomass thickening at full-scale. In addition, other three points have been identified as key factors to be taken into account for biomass tickening: proper adjustment of the purge flowrate, coordination between purges times and volumes in the different stages, and proper adjustment of the operation of the scrapers.The authors would like to thank the European Commission (INCOVER, GA 689242) and the Government of Catalonia (Consolidated Research Group 2017 SGR 1029) for their financial support. E. Uggetti and R. Díez-Montero would also like to thank the Spanish Ministry of Industry and Economy for their research grants (RYC2018-025514-I and IJC2019-042069-I, respectively).Peer ReviewedPostprint (published version

Advanced biokinetic and hydrodynamic modelling to support and optimize the design of full-scale high rate algal ponds

High rate algal ponds (HRAP) are known for their suitability to treat wastewater and to produce microalgal biomass, which can be converted into bioproducts. However, full-scale application of HRAP is still limited to few cases, and design procedures are not consolidated or standardized. In this study, a demonstrative-scale HRAP system for secondary wastewater treatment to be implemented in India (treatment capacity of 50 m3·d-1) has been designed combining conventional dimensioning techniques and advanced modelling tools. The objective of the study was to assist, verify and optimize the conventional dimensioning of the secondary HRAP by means of simulations predicting the behaviour of the system in the specific local conditions under different configurations and operational strategies. Biokinetic modelling and hydrodynamic analysis using Computational Fluid Dynamics (CFD) were carried out. The simulations performed with the biokinetic model showed that the optimal hydraulic retention time to enhance nutrient removal and biomass production is 4 days. For the hydrodynamic modelling, a 3D model of the HRAP was built to simulate the hydrodynamic behaviour of 36 different designs. Simulations allowed quantifying the presence of low velocity zones as well as the land use efficiency of the different designs in terms of the useful area vs. the total occupied area. Two baffles and tear-shapes with a diameter equal to ¼ of the channel width was the most efficient configuration. Moreover, a technical–economic assessment of the system was carried out, resulting in an investment cost of 483 € per population equivalent and an operational cost of 0.19 € per m3 of treated wastewaterAuthors would like to thank the European Commission for the financial support (PAVITR project, GA 821410) and the Department of Sciences and Technology from Government of India for the financial support (GA DST/IMRCD/India-EU/Water Call2/PAVITR/2018). Authors are also grateful to the Government of Catalonia (Consolidated Research Group 2017 SGR 1029). E. Uggetti and R. Díez-Montero would also like to thank the Spanish Ministry of Industry and Economy for their research grants (RYC2018-025514-I and IJC2019-042069-I, respectively).Peer ReviewedPostprint (published version

Statistical Channel Impulse Response Modeling for Optical Wireless Communication in Turbid Waters

Underwater optical wireless communication (UOWC) systems support high-speed, reliable and cost-effective implementations that are demanded for extending the telecommunication networks to oceans. UOWC systems suffer from attenuation and scattering processes. Particularly, the scattering process can change the direction of the emitted photons, especially in turbid waters. In this way, quantifying the signal attenuation and the time dispersion produced by absorption and scattering is a crucial work. Hence, we propose a new closed-form solution for modeling the channel impulse response for UOWC systems in turbid water that is validated through Monte Carlo simulations and can be used for system design and optimization purposes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Influence of liquid-to-biogas ratio and alkalinity on the biogas upgrading performance in a demo scale algal-bacterial photobioreactor

The influence of the liquid-to-biogas ratio (L/G) and alkalinity on methane quality was evaluated in a 11.7 m3 outdoors horizontal semi-closed tubular photobioreactor interconnected to a 45-L absorption column (AC). CO2 concentrations in the upgraded methane ranged from <0.1 to 9.6% at L/G of 2.0 and 0.5, respectively, with maximum CH4 concentrations of 89.7% at a L/G of 1.0. Moreover, an enhanced CO2 removal (mediating a decrease in CO2 concentration from 9.6 to 1.2%) and therefore higher CH4 contents (increasing from 88.0 to 93.2%) were observed when increasing the alkalinity of the AC cultivation broth from 42 ± 1 mg L−1 to 996 ± 42 mg L−1. H2S was completely removed regardless of the L/G or the alkalinity in AC. The continuous operation of the photobioreactor with optimized operating parameters resulted in contents of CO2 (<0.1%–1.4%), H2S (<0.7 mg m−3) and CH4 (94.1%–98.8%) complying with international regulations for methane injection into natural gas grids.Peer ReviewedPostprint (published version

Sludge treatment wetland for treating microalgae digestate grown in agricultural runoff: a technical, economic, and environmental assessment

The management and disposal of wastewater treatment sludge can be a costly and resource-intensive process. To provide a cost-effective and sustainable alternative, Sludge Treatment Wetlands (STW) have emerged as a viable solution for enhancing sludge quality through dewatering and biodegradation. In this study, the effectiveness of a full-scale STW for stabilizing and dewatering digested microalgal biomass from a domestic and agricultural wastewater treatment system was evaluated. The properties of the treated digestate in the STW were assessed after 35 weeks of operation and a resting period of 4 weeks. The dry matter content was found to be 12.8%, and the average macronutrient content was K: 3.8 mg/g DW, P: 4.9 mg/g DW, and Ca: 95 mg/g DW. The highest contents of micronutrients were for Fe: 7.8 mg/g DW and Mg: 7.6 mg/g DW, while heavy metals and pathogen contents were below the EC limits for sewage sludge reuse in agriculture. The STW was found to be a cost-effective and environmentally friendly option for treating mixed wastewater-based sludge for land application. The STW outperformed reference systems using centrifuge dewatering techniques, particularly in terms of eutrophication potential and acidification potential. However, the STW’s economic performance was slightly worse than that of the dewatering system in terms of unit production cost. This study is the first in the literature to investigate the use of STW for treating digested microalgae and its possible reuse in arable land, suggesting that STW infrastructures have great potential for the development of sustainable and eco-friendly sludge treatment technologies.This research was funded by the European Commission (H2020 project INCOVER, GA 689242). E. Gonzalez-Flo would like to thank the European Union-Next Generation EU, Ministry of Universities and Recovery, Transformation and Resilience Plan for her research grant [2021UPF-MS12]. A. Ortiz would like to thank the European Union Next-Generation EU, Ministry of Universities and Recovery, Transformation and Resilience Plan for his research grant [2022UPC-MSC-94120].Peer ReviewedBy Eva Gonzalez-Flo 1 , Antonio Ortiz 2, Carlos A. Arias 3, Rubén Díez-Montero 2,4, Norbert Kohlheb 5, Ulf-Henning Schauser 6, Joan García 2 and Peder K. S. Gregersen 7. 1 GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Escola d’Enginyeria de Barcelona Est (EEBE), Universitat Politècnica de Catalunya-BarcelonaTech, Av. Eduard Maristany 16, Building C5.1, E-08019 Barcelona, Spain 2 GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya-BarcelonaTech, c/Jordi Girona 1-3, Building D1, E-08034 Barcelona, Spain 3 Department of Biology, Aarhus University, 8000 Aarhus, Denmark 4 GIA-Group of Environmental Engineering, Department of Water and Environmental Sciences and Technologies, Universidad de Cantabria, Avda. Los Castros s/n, 39005 Santander, Spain 5 Helmholtz-Zentrum Fuer Umveltforschung GMBH–UFZ (“UFZ”), 04318 Leipzig, Germany 6 N.A.T., Ingenieurökologisches Planungsbüro, 24340 Eckernförde, Germany 7 Center for Recirkulering v/Peder S, 6870 Gregersen Ölgod, DenmarkPostprint (published version

The importance of atmospheric correction for airborne hyperspectral remote sensing of shallow waters: application to depth estimation

Accurate determination of water depth is indispensable in multiple aspects of civil engineering (dock construction, dikes, submarines outfalls, trench control, etc.). To determine the type of atmospheric correction most appropriate for the depth estimation, different accuracies are required. Accuracy in bathymetric information is highly dependent on the atmospheric correction made to the imagery. The reduction of effects such as glint and cross-track illumination in homogeneous shallow-water areas improves the results of the depth estimations. The aim of this work is to assess the best atmospheric correction method for the estimation of depth in shallow waters, considering that reflectance values cannot be greater than 1.5% because otherwise the background would not be seen. This paper addresses the use of hyperspectral imagery to quantitative bathymetric mapping and explores one of the most common problems when attempting to extract depth information in conditions of variable water types and bottom reflectances. The current work assesses the accuracy of some classical bathymetric algorithms (Polcyn? Lyzenga, Philpot, Benny?Dawson, Hamilton, principal component analysis) when four different atmospheric correction methods are applied and water depth is derived. No atmospheric correction is valid for all type of coastal waters, but in heterogeneous shallow water the model of atmospheric correction 6S offers good results