Empleo de fosfoyeso y espuma de azucarería para mejorar la capacidad de retención de As, Cd, y Tl en un suelo ácido

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Geología y Geoquímica. Fecha de lectura: 22-04-0

Impact of Weed Control by Hand Tools on Soil Erosion under a No-Tillage System Cultivation.

In conservation agriculture, the no-tillage cultivation system and the retention of permanent vegetal cover are crucial to the control of soil erosion by water. This paper analyses the cultivation of maize under no-tillage, with particular reference to the effect produced on soil erosion when weed control is performed by a hand tool (machete), which disturbs the surface of the soil, and to the behavior of the soil cover in these circumstances. The study area is located in the humid tropical mountains of northern Nicaragua (Peñas Blancas Massif Nature Reserve). The results obtained show that 59.2% of the soil surface was affected by appreciable levels of sheet and splash erosion, although the vegetal cover of the soil was relatively high (with average weed and litter cover of 33.9% and 33.8%, respectively). The use of machetes for weed control provoked considerable soil disturbance, which explained the high rates of erosion observed. Moreover, this form of soil management disturbs the litter layer, making it less effective in preventing erosion. The litter remains loose on the soil surface, and so an increase in soil cover does not achieve a proportionate reduction in the area affected by erosion; thus, even with 80–100% weed and litter cover, 42% of the cultivated area continued to present soil erosion

An assessment of the shade and ground cover influence on the mitigation of water-driven soil erosion in a coffee agroforestry system.

Coffee cultivation under agroforestry systems is one of the main agricultural activities in Central America, but climate change is putting its sustainability at risk. Rainfall erosivity has worsened, thus driving soil losses. Although the vegetal covers in coffee agroforestry systems play a crucial role in controlling erosion, the specific influence of each cover layer remains unclear. In this study, we assessed the influence of the canopy (tree and banana cover and coffee cover) and ground cover (weed and litter) on water driven soil erosion, to determine which type of cover has the most influence on soil erosion control. The study site is situated in the core and buffer zones of the Macizo de Peñas Blancas National Park (Nicaragua), where seventeen coffee sampling plots with an agroforestry system composed of an Inga spp and Musa spp canopy cover were analysed. The results showed that the 19.2 ± 3.4% of the soil surface was affected by erosion and it was mainly related to the litter ground cover (r = –0.95, P < 0.001). Also, this cover presented the best partial correlation (ryl.tcw = –0.93, P < 0.001) when the effects of the other vegetal covers were eliminated. Specifically, the litter cover accounted for 90% of the erosion variability, while the impact of the other types of cover was negligible, accounting for just 1% of the erosion. We conclude that litter layer is more important than canopy cover for effective erosion control, and the main function of shade trees is as a source of litter biomass.Financiación para publicar en abierto: Universidad Málaga/CBUA Funding for open access publishing: Universidad Málaga/CBUA. This study was performed within the framework of the ‘International University Volunteering in Cooperation for Development’ project (funded by UMA-AACID), in collaboration with the Tropical Agricultural Research and Higher Education Centre (CATIE). It also forms part of the Project ‘Sustainable Management of Agricultural Territories in Mesoamerica (MESOTERRA). Mesoamerican Agro-Environmental Program (MAP2)’, financed by the Norwegian Ministry of Foreign Affairs. Funding for open access charge: Universidad de Málaga / CBUA

A traction Control System based on Co-evolutionary Learning in Spiking Neural Networks (SNN)

A traction control system is designed and trained for different road conditions with co-evolutionary learning based on a genetic algorithm. Common solutions do not consider the variation and oscillation created in the transition between roads defining a control logic which is highly dependent on road accuracy and a speed estimator. To solve this problem, a co-evolutionary learning process is used. This procedure trains the control algorithm, a spiking neural network, on different roads and transitions looking for the worst-case scenario. We have developed a control algorithm with a good dynamic response to constant and changing roads. This control algorithm makes the system stable when the road estimation is delayed or unstable, solving a common flaw produced by sensor noise or computation delays.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Multifunctional microcapsules based on ZnO and n-octadecane: From thermal energy storage to photocatalytic activity

Energy management is one of the most important issues to be addressed in the near future in many fields, one of which is buildings. In this sense, new phase change materials (PCM) are being widely studied for storing energy. Encapsulating PCM is a good way to incorporate these materials into different applications in which energy storage is useful. In this study, microcapsules based on ZnO containing n-octadecane as a phase change material were synthesized and characterized with regard to their structural, morphological and optical properties according to several synthesis parameters, such as the proportion of precursors, stirring rate and ageing time. The microcapsules were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–Vis spectroscopy in diffuse reflectance mode. The presence of n-octadecane inside the capsules was confirmed. Their thermal behaviour was analysed by means of differential scanning calorimetry. Heating/cooling cycles were performed, after which the microcapsules presented good stability. Furthermore, the encapsulation efficiency was estimated from melting and crystallization enthalpy values, reaching a value of 23.1%. Moreover, the isobaric specific heat of the microcapsules is higher than that of ZnO, which means that substituting ZnO with microcapsules in buildings leads to an important increase in the amount of sensible heat stored. Finally, the photocatalytic activity of the microcapsules was analysed by studying the photodegradation of Crystal Violet dye. The degradation rate increased when the microcapsules were present, so the photocatalytic activity of the microcapsules was confirmed under UV and visible irradiation, which is of interest because they can be used to remove organic pollutants from buildings.10 página

Modeling of an Overactuated Vehicle in Simscape Multibody for the Characterization of Suspension and Steering Actuation Systems.

Overactuated systems are increasingly among us. They are used for applications in vehicles, aeronautics and robotics, among others [1, 2]. These systems have a number of advantages, among which we can mention that there are multiple (or infinite) solutions for a given problem. More specifically, in the case of overactuated vehicles, similar states of the system can be achieved in many different ways. These systems are still under development, especially in the field of vehicle dynamics. For example, there are various steer-by-wire algorithms, when the steering of the vehicles is independent, or brake blending strategies. In this work, a part of an overactuated vehicle is designed and validated. This multiphysics model allows to know the plant of the system in much more depth in order to develop control algorithms. More specifically, by modeling the delay of the systems and the nonlinear relationships inherent to multibody systems, much more accurate predictive control can be performed. These results allow a previous validation of the control algorithms in the test platform vehicle being manufactured and developed by the research group, greatly accelerating the control process of each of the overactuated systems of the vehicle.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Stability and Thermal Properties Study of Metal Chalcogenide-Based Nanofluids for Concentrating Solar Power

Nanofluids are colloidal suspensions of nanomaterials in a fluid which exhibit enhanced thermophysical properties compared to conventional fluids. The addition of nanomaterials to a fluid can increase the thermal conductivity, isobaric-specific heat, diffusivity, and the convective heat transfer coefficient of the original fluid. For this reason, nanofluids have been studied over the last decades in many fields such as biomedicine, industrial cooling, nuclear reactors, and also in solar thermal applications. In this paper, we report the preparation and characterization of nanofluids based on one-dimensional MoS2 and WS2 nanosheets to improve the thermal properties of the heat transfer fluid currently used in concentrating solar plants (CSP). A comparative study of both types of nanofluids was performed for explaining the influence of nanostructure morphologies on nanofluid stability and thermal properties. The nanofluids prepared in this work present a high stability over time and thermal conductivity enhancements of up to 46% for MoS2-based nanofluid and up to 35% for WS2-based nanofluid. These results led to an increase in the efficiency of the solar collectors of 21.3% and 16.8% when the nanofluids based on MoS2 nanowires or WS2 nanosheets were used instead of the typical thermal oil

Synthesis and characterization of metal oxide-based microcapsules including phase change materials for energy storage applications

In this study, microcapsules based on Cu2O containing different phase change materials (PCM) were prepared and characterized. The elemental, structural and electronic properties of the Cu2O-based microcapsules were characterized using several techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and Fourier-transform infrared spectroscopy. In addition, the thermal properties of the microcapsules prepared were characterized in order to analyse their possible application as a thermal energy storage medium. Heating/cooling cycles using a differential scanning calorimetry technique were performed, and the phase change temperature and enthalpy were estimated. We observed good stability after the cycles. Furthermore, the encapsulation efficiency was estimated from melting and crystallization enthalpy values, reaching a value of 14.8% for the paraffin wax-based microcapsules. Finally, isobaric specific heat was measured to evaluate the storage capability of the encapsulated PCMs with regard to pure Cu2O to evaluate their possible application as a thermal storage system. An increase of around 140% was found in the isobaric specific heat for the microcapsules based on paraffin wax with regard to pure Cu2O. © 2023, The Author(s)

Design and testing of a steering damper for motorcycles based on a shear-thickening fluid.

Política de acceso abierto tomada de: https://v2.sherpa.ac.uk/id/publication/11350This work is intended to show the feasibility of the utilisation of a shear-thickening fluid as working fluid in a steering damper for motorcycles. To that end, a prototype of a steering damper has been designed and then tested under different working conditions. Unlike conventional models, this new steering damper bases its performance on the combination of very simple rod geometries and a shear-thickening fluid of different concentrations. The experiments carried out with a test machine demonstrate that, despite its simplicity and reduced cost of manufacturing, the prototype shows similar behaviour to a conventional high-performance racing steering damper. The Bouc–Wen model has been used to reproduce the behaviour of the shear-thickening fluid-based damper prototype. The parameters of the model have been obtained following an optimization process to fit the model’s response to the experimental data when exciting the damper at different speeds. Results show that the damper’s behaviour can be properly modelled with a single combination of parameters

Modeling of the Influence of Operational Parameters on Tire Lateral Dynamics

Tires play a critical role in vehicle safety. Proper modeling of tire–road interaction is essential for optimal performance of active safety systems. This work studies the influence of temperature, longitudinal vehicle speed, steering frequency, vertical load, and inflation pressure on lateral tire dynamics. To this end, a tire test bench that allows the accurate control of these parameters and the measurement of the variables of interest was used. The obtained results made it possible to propose a simple model that allowed the determination of relaxation length as a function of tire vertical load and vehicle linear speed, and the determination of a representative tread temperature. Additionally, a model has been proposed to determine the lateral friction coefficient from the aforementioned temperature. Finally, results also showed that some variables had little influence on the parameters that characterize lateral dynamicsThis work is partly supported partly by the Spanish Ministry of Science and Innovation under grant PID2019-105572RB-I00, partly by the Economy, Knowledge, Enterprise and Universities Council of the Andalusian Regional Government under grant UMA18-FEDERJA-109, partly by the Spanish Ministry of Education, Culture and Sport under grant FPU18/00450, and partly by the University of Malaga.Partial funding for open access charge: Universidad de Málag