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INSTITUTE OF EARTH SCIENCES
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Integrated WPT-PLC System Applied to UAV
Publication . Zouaoui, Safa; Dghais, Wael; Romba, Luís; Melício, Rui; Belgacem, Hamdi; CTS - Centro de Tecnologia e Sistemas; MDPI - Multidisciplinary Digital Publishing Institute
WPT system performances highly depend on the misalignment scenarios of the transmitter or the receiver coil. In this contribution, the authors analyze the effect of the misalignment influencing factors of the integrated WPT-PLC system receiving coil on the system performances. The simulations and experimental analysis are based on power efficiency and channel capacity metrics. The simulations are performed using finite element calculations in COMSOL Multiphysics and Advanced Design System (ADS) from Keysight technology. By analyzing the results, maximum transferred power is reached under resonance conditions. For instance, the calculated efficiencies versus the misalignment cases of the WPT-PLC system varies (η = 86% to 60%) when d = [3 cm to 7 cm], s = [3 cm to 9 cm], and for a tilt angle θ ≤ 20 deg, while the optimal data rate C(bps) is achieved while appealing different data access points and under reasonable SNR value.
Insights into the Spatial and Temporal Variability of Soil Attributes in Irrigated Farm Fields and Correlations with Management Practices
Publication . Tomaz, Alexandra; Martins, Inês; Catarino, Adriana; Mourinha, Clarisse; Dôres, José; Fabião, Marta; Boteta, Luís; Coutinho, João; Patanita, Manuel; Palma, Patrícia; GeoBioTec - Geobiociências, Geoengenharias e Geotecnologias; MDPI - Multidisciplinary Digital Publishing Institute
The evaluation of the spatial and temporal variability of soil properties can be valuable to improve crop productivity and soil health. A study of soil properties was carried out in southern Portugal, in three farm fields with irrigated annual crops (layers 0–20 cm and 20–40 cm), over three years. Factor Analysis (FA) and Discriminant Analysis (DA) were used to analyze the data. With FA, the observed variables were grouped into a smaller number of latent variables related to soil attributes. Discriminant Analysis was used to classify and identify the most dominant attributes and indicators for the time and space variability of soil parameters. The FA performed for the surface layer included factors related to texture, water and nutrient retention capacity, chemical composition, and soil fertility. In the sub-surface layer, the factor structure was similar, with four factors related to texture, chemical composition, nutrient availability, and soil fertility. The most influential factors and variables in temporal discrimination (sampling dates) in both layers were those related to chemical composition, with electric conductivity as the preponderant indicator. As for the spatial differentiation (fields), the dominant factor in the surface layer was texture, and in the sub-surface layer, nutrient availability. The most important discriminant indicators of spatial variability were fine sand proportion and available potassium, respectively, for the surface and sub-surface layers. The results obtained showed potential for the multidimensional and integrated assessment of patterns of temporal and spatial variation of soil functions from agricultural practices or soil degradation processes.
Water and carbon footprints in irrigated vineyards
Publication . Tomaz, Alexandra; Dôres, José; Martins, Inês; Catarino, Adriana; Boteta, Luís; Santos, Marta; Patanita, Manuel; Palma, Patrícia; GeoBioTec - Geobiociências, Geoengenharias e Geotecnologias; Springer Verlag Kg
This research aims to contribute to improving water and carbon efficiency in irrigated grapevine production in the dry Mediterranean climate of southern Europe. In regions with water scarcity, irrigation has become a relevant input in viticulture, essential to increase productivity and achieve profits. The joint estimation of the water footprint (WF) and the carbon footprint (CF) can help to comprehensively assess the environmental implications and sustainability associated with water-intensive grapevine cultivation. In this study, the WF and CF, of the farming stage of grapes production, were calculated for three years, in three vineyards located in southern Portugal. Data used for the calculation included meteorological data, irrigation requirements, energy use, fertilizers, and pesticide inputs. The total WF mean value for the study period was 223 m3 ton−1, lower than values found for similar conditions, but the blue component, related to irrigation, was predominant, with a higher proportion (75%) occurring during the driest year. The mean total CF was 98 kg CO2e ton−1; the major contributors were fuel use, fertilizer greenhouse gas emissions, and energy for irrigation. The factor analysis revealed relationships between footprint components, yielding latent variables participated by irrigation water and energy use, pollution loads and agrichemicals use. The examination of trade-offs and/or advantageous relations between footprints and yields showed that seasonal climate conditions play an important role via their effect on the farming practices and the inputs most influential on these indicators, namely: crop water requirement; irrigation volumes; energy for irrigation; fuel consumption; nitrogen and phosphorus fertilization rates.
Depth estimation of pre-Kalahari basement in Southern Angola using seismic noise measurements and drill-hole data
Publication . Carvalho, J.; Alves, D.; Borges, J.; Caldeira, B.; Cordeiro, D.; Machadinho, A.; Oliveira, A.; Ramalho, E. C.; Rodrigues, J. F.; Llorente, J. M.; Ditutala, M.; García-Lobón, J. L.; Máximo, J.; Carvalho, C.; Labaredas, J.; Ibarra, P.; Manuel, J.; GeoBioTec - Geobiociências, Geoengenharias e Geotecnologias; Elsevier BV
The remote Southern region of Angola is covered by siliciclastic Kalahari Cenozoic formations that host underground aquifers of great importance to local populations affected by water scarcity problems. These aquifers are well developed where Kalahari sands reach appropriate thicknesses. On the other hand, at the eastern end of this area, regional aeromagnetic data recently acquired suggested the possibility of the continuity of the geological structures of the Lufilian Arc, sited in the nearby Zambia and Congo, southwestwards into Angola under the Kalahari formations. Once the Lufilian Arc is associated with the presence of the so-called Central African Copperbelt, this possibility increased the interest in determining the depth to Pan-African rocks under the Kalahari basin. To estimate the thickness of Kalahari formations in this area of difficult access and poor logistics, an expedited and non-invasive geophysical method was needed. Seismic noise and the single-station Nakamura technique were chosen, but due to the large distance of the study area from the ocean, one of the major sources of seismic noise, a test survey was acquired in the Cuvelai region to assess the signal quality, where the data was calibrated using available drill-holes. >170 points of seismic ambient noise were later acquired and the horizontal/vertical (HVSR) amplitude versus frequency curves were 1D inverted for the best velocity/density model for each station. The results were compared with 1D inverted legacy vertical electrical soundings reprocessed and validated in this work, showing similar depth-to-basement, while interpreted velocities/densities of geological formations were sampled and confirmed with measurements. A depth-to-basement map was produced using seismic information, mechanical soundings, and geological information. Despite the relatively reduced geographical area covered, the map presents valuable information for hydrogeology and mineral exploration purposes and agrees with a previously available coarser map of Kalahari thickness and with observations from geological surveys simultaneously conducted at the time of the seismic surveys.
Chemical and Ecotoxicological Assessment of Agricultural Drainage Water from a Maize Crop Area
Publication . Palma, Patrícia; Catarino, Adriana; Silva, Emília; Alvarenga, Paula; GeoBioTec - Geobiociências, Geoengenharias e Geotecnologias; MDPI - Multidisciplinary Digital Publishing Institute
The use of agricultural drainage water (ADW) in irrigation is a great challenge, improving water use efficiency, nutrient circularity, and avoiding surface and ground-water contamination. The objective of this study was to evaluate the chemical and ecotoxicological characteristics of an ADW to analyze the safety of its reuse. An irrigated area with maize crops was selected (Tejo Basin, Portugal), where a subsurface structure for the recovery of ADW was installed, collecting the drainage in a pond and recycling it for crop irrigation. Water was collected monthly during the irrigation campaign of 2021 (April to August). Three herbicides and two metabolites were quantified, reaching a maximum concentration of 0.74 µg L−1 for S-metolachlor and 0.48 µg L−1 for terbuthylazine. The lethal bioassays did not detect toxicity, except for the sample collected in August toward Vibrio fisheri (EC50 = 25.2%). The samples were not toxic to Pseudokirchneriella subcapitata, with a growth inhibition rate of less than 10%. The low lethal and sublethal effects may be ascribed to the high nutrient concentration (e.g., 1.76 mg P L−1 and 98.9 mg NO3− L−1, in July) that could have masked toxic effects. Ecotoxicological responses support the option of ADW reuse in irrigation, offering a safe and sustainable solution for water and nutrient management.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDB/04683/2020