ESAV - DIA - Artigo em revista científica, indexada ao WoS/Scopus
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- Greenhouse Gas Emissions and Ryegrass Yield after Application of Solid-Liquid Pig Slurry and Biochar to an Agricultural SoilPublication . Pereira, José Luís da Silva; Perdigão, Adelaide; Bonifácio, Gabriel; Figueiredo, Vitor; Marques, Francisco; Trindade, Henrique; Ferreira Wessel, DulcineiaBackground: The application of animal slurry to the soil improves its quality, as manure contains many nutrients for plants. However, this could negatively impact the environment. Objective: This field study investigated the effects of the addition of biochar after the mechanical separation of Whole pig Slurry (WS) into Solid (SF) and Liquid Fractions (LF) on Greenhouse Gases (GHG) emissions (N2O, CO2, and CH4) and ryegrass (Lolium multiflorum Lam. cv magnum) yield. Methods: Biochar (1.0 kg m-2) was applied in plots alone or together with each of the three slurries (80 kg N ha-1) in a total of eight treatments with three replications, including just soil with and without biochar as controls. Soil properties, Greenhouse Gas (GHG) fluxes, and yield were measured during theautumn/winter growing season. Results: The results showed that the addition of biochar to these three slurries significantly increased the soil pH and showed no impact on the other physicochemical properties. The GHG emissions were not significantly different between treatments with and without biochar. The N use efficiency increased significantly in SF > WS > LF, whereas no differences were observed among these three slurries with and without biochar. Conclusion: It can be concluded that the addition of biochar combined with WS or SF/LF to sandy-loam soil appears to have no impact on GHG emissions and ryegrass yield during the autumn/winter season. Overall, this finding suggests that amounts higher than 1.0 kg m-2 of biochar combined with SF may need to be applied to soil to reduce GHG emissions and nitrate leaching and increase N use efficiency and crop yield
- Eating habits and food knowledge in a sample of portuguese university studentsPublication . Guiné, Raquel; Ferreira, Manuela; Duarte, João; Nunes, Bruno; Morais, Patrícia; Sanches, Rafaela; Abrantes, RomanaThe choice to adopt a healthy diet is complex, since food choices and eating behaviours are influenced by various factors, such as biological, social, environmental, demographic and psychological aspects. The transition from secondary school to university is a critical period that involves many social and physical environmental changes, which may lead to an unhealthy lifestyle. This study investigated the eating habits, food knowledge and the level of information about a healthy diet in a sample of 670 university students in Portugal. In general, the participants had a good food knowledge and satisfactory eating habits, as well as a satisfactory level of information about a healthy diet. There were found significant differences in the participants’ food knowledge among age groups and according to the area of studies. Most of the students revealed satisfactory eating habits, with significant differences between age groups, the area of studies and the practice of high competition sport. The results pointed to the necessity of improving educational programs which can contribute to increase university students’ food knowledge and consequently improve their eating habits.
- Laboratory fire spread analysis using visual and infrared imagesPublication . Martínez-de Dios, J. Ramiro; André, Jorge C.; Goncalves, J. C.; Arrue, Begoña Ch.; Ollero, Aníbal; Viegas, Domingos X.This paper presents an experimental method using computer-based image processing techniques of visual and infrared movies of a propagating fire front, taken from one or more cameras, to supply the time evolutions of the fire front shape and position, flame inclination angle, height, and base width. As secondary outputs, it also provides the fire front rate of spread and a 3D graphical model of the fire front that can be rendered from any virtual view. The method is automatic and non-intrusive, has space–time resolution close to continuum and can be run in real-time or deferred modes. It is demonstrated in simple laboratory experiments in beds of pine needles set upon an inclinable burn table, with point and linear ignitions, but can be extended to open field situations
- Laboratory fire spread analysis using visual and infrared imagesPublication . Martínez-de Dios, J. Ramiro; André, Jorge C.; Goncalves, J. C.; Arrue, Begoña Ch.; Ollero, Aníbal; Viegas, Domingos X.This paper presents an experimental method using computer-based image processing techniques of visual and infrared movies of a propagating fire front, taken from one or more cameras, to supply the time evolutions of the fire front shape and position, flame inclination angle, height, and base width. As secondary outputs, it also provides the fire front rate of spread and a 3D graphical model of the fire front that can be rendered from any virtual view. The method is automatic and non-intrusive, has space–time resolution close to continuum and can be run in real-time or deferred modes. It is demonstrated in simple laboratory experiments in beds of pine needles set upon an inclinable burn table, with point and linear ignitions, but can be extended to open field situations.
- Study of the aerodynamic sealing of a cold store – Experimental and numerical approachesPublication . Goncalves, J.C.; Costa, J.J.; Figueiredo, A.R.; Lopes, A.M.G.An experimental study was conducted in a laboratory scale model in order to characterize the airflow generated by an air curtain device (ACD) on the aerodynamic sealing of refrigerated spaces. The laboratory scale model consists of two similar adjacent rooms connected by a door over which the ACD device was installed. The tracer gas technique was used to calculate the sealing effect achieved with the air curtain at different jet velocities. A three-dimensional numerical model was also developed to simulate the heat and mass transfer phenomena, as well as the aerodynamic sealing performance of an ACD. The numerical study was carried out using a commercial CFD code (ANSYS-CFX®) and the turbulence effects were approached by two different turbulence models (k–ε and k–ω SST). The experimental and numerical results show a good agreement for validation purposes. No significant differences were found in the results obtained with the two turbulence models, although the k–ω SST model seems to be more appropriate for the simulations. The existence of an optimum discharge air jet velocity was confirmed. The results also indicate that the air curtain is more efficient in reducing the mass transfer than the energy flow rate across the doorway.
- CFD modelling of aerodynamic sealing by vertical and horizontal air curtainsPublication . Goncalves, J.C.; Costa, J.J.; Figueiredo, A.R.; Lopes, A.M.G.This work presents a comparative study of the aerodynamic sealing of doorways of refrigerated rooms, obtained by vertical and horizontal air curtain devices (ACD). The sealing efficiency is estimated for different situations, with the ACD installed inside, outside or on both sides of the door. For this purpose, a numerical model was developed for the simulation of the turbulent non-isothermal 3D airflow generated by the air curtain in the transient period after the door is opened. The buoyancyinduced airflow field when the ACD is turned off and the door is open was taken as a reference to assess the sealing efficiency. Numerical results are plausible and comply with the physical interpretation of the convective phenomena. In line with previous investigations, the optimum velocity of the air jet was found, corresponding to the highest sealing effect. The advantage of installing the ACD outside the refrigerated room was shown by the present simulations. According to the present study, downward blowing air curtains present better sealing efficiency (over 70%) compared to horizontal jet air curtains (about 55%). Although the direct air recirculation provides a better sealing efficiency (over 80%), the system complexity and the installation and maintenance costs inhibit its common use.
- Angular variation of fire rate of spreadPublication . André, Jorge C. S.; Goncalves, J. C.; Vaz, Gilberto C.; Viegas, Domingos X.Laboratory fire tests were performed in still air, for variable inclinations (10°, 15°) and fuel bed dimensions (1.28 × 2.50–3.0 × 4.6 m2), with homogeneous fuel beds of pine needles and pine wood excelsior. The fire ignition was made at a point, along a closed line with no fuel inside and along a straight edge of the fuel bed. The tests were recorded with an infrared camera and various techniques were developed to implement direct and indirect empirical methods of construction of the ‘orientation function’ of the fire in the given fuel bed and ambient conditions, showing how the rate of spread of a steady straight fire front depends on its orientation on the terrain. The direct method uses a set of straight fire fronts with various orientations whereas the indirect method uses essentially a point ignited fire front. Contrary to what is assumed in BehavePlus model, the orientation function is observed to depend significantly on the properties of the fuel bed. In all tests with closed fire fronts, the full steadiness required by the indirect method was not achieved (namely, at the head of the front), although, for slope angle of 10°, the corresponding errors induced on the orientation function were small.
- Angular variation of fire rate of spreadPublication . André, Jorge C. S.; Goncalves, J. C.; Vaz, Gilberto C.; Viegas, Domingos X.Laboratory fire tests were performed in still air, for variable inclinations (108, 158) and fuel bed dimensions (1.28 2.50–3.0 4.6m2), with homogeneous fuel beds of pine needles and pine wood excelsior. The fire ignition was made at a point, along a closed line with no fuel inside and along a straight edge of the fuel bed. The tests were recorded with an infrared camera and various techniques were developed to implement direct and indirect empirical methods of construction of the ‘orientation function’ of the fire in the given fuel bed and ambient conditions, showing how the rate of spread of a steady straight fire front depends on its orientation on the terrain. The direct method uses a set of straight fire fronts with various orientations whereas the indirect method uses essentially a point ignited fire front. Contrary to what is assumed in BehavePlus model, the orientation function is observed to depend significantly on the properties of the fuel bed. In all tests with closed fire fronts, the full steadiness required by the indirect method was not achieved (namely, at the head of the front), although, for slope angle of 108, the corresponding errors induced on the orientation function were small.
- Effects of Pre- and Post-Harvest Factors on the Selected Elements Contents in Fruit JuicesPublication . Paula, Francisco; Guiné, Raquel; Cruz-Lopes, Luísa; Duarte, Armando; Fragata, Anabela; Reis, ManuelPre- and post-harvest factors determine the levels of the selected risk elements in100% fruit juices. The juices samples closely followed the Brix international reference values. Fruit juices presented the following order of the elements mean concentrations: cadmium (1.597 μg/l), chromium (2.767 μg/l), lead (20.75 μg/l), nickel (73.37 μg/l), zinc (545.9 μg/l), and iron (1792 μg/l), measured by AAS. The pre-harvest factors (origin, fruit, and agriculture) and the post-harvest factors (blending, packaging, conservation, pasteurisation, and process) were evaluated according to the manufacturers information and were correlated with the elements concentrations of fruit juices. A strong relationship was detected between the fruit species used for the juice production (i.e. pre-harvest factor) and their elements concentrations. Furthermore, multiple correspondence analysis was used for reducing the data dimension by grouping the factors. The zinc concentration was detected as a potential proxy for the identification of the fruit juices manufacturing process.
- Modelling the Influence of Origin, Packing and Storage on Water Activity, Colour and Texture of Almonds, Hazelnuts and Walnuts Using Artificial Neural NetworksPublication . Guiné, Raquel; Almeida, Cátia; Correia, Paula; Mendes, MateusThe present work assessed the influence of different factors on some physical and chemical properties of nuts. The factors evaluated were the presence or absence of the inner skin, geographical origin, storage conditions (ambient temperature, in a stove at 30 and 50 °C, in a chamber at 30 and 50 °C and 90 % RH, refrigerated and freezing) and type of package (none, low density polyethylene and low density polyethylene). The fruits studied were almonds, hazelnuts and walnuts from different countries. The properties measured were moisture content, water activity, colour coordinates (L*, a* and b*) and texture parameters (hardness and friability). Experimental data were modelled using neural networks. The results showed that the almonds from Spain and Romania had aw greater than 0.6, and therefore, its stability was not guaranteed, contrarily to the other samples that presented values of aw lower than 0.6. The colour coordinate lightness varied from 40.60 to 49.30 in the fresh samples but decreased during storage, indicating darkening. In general, an increase in hardness and friability was observed with the different storage conditions. Neuron weight analysis has shown that the origin was a good predictor for moisture content and texture; whereas, the storage condition was a good predictor for aw and colour. In conclusion, it was possible to verify that the properties of nuts are very different depending on origin; they are better preserved at lower temperatures and the type of package used did not impact the properties studied.