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•Virgin cork – plaster composites with density 1.312–0.878 g/cm3 were produced.•The additon of the cork to the plaster matrix reduces the apparant density, mechanical resistance and ...thermal conductivity.•The cork-plaster composites can be used as an insolation material.
The aim of this study is to develop a composite insulation material based on plaster and virgin cork from Corsica which has an insufficient quality for cork stoppers. This paper presents the results of design and characterization. In this study, six cork-plaster mixtures with a C/P ratio of 0.025; 0.05; 0.075; 0.10; 0.15; 0.20 were produced. The cork-plaster composites were compared with a reference sample without cork particles in terms of properties. It was observed that the compressive and flexural strength, density, and thermal conductivity decrease with the increase of the cork content. The value of thermal conductivity (0.460 – 0.168 W/(m⋅K)) shows that virgin cork-plaster composites can be used in building applications as non-structural material.
Triboelectric nanogenerators (TENGs) show exceptional promise for converting wasted mechanical energy into electrical energy. This study investigates the use of laser-induced graphene (LIG) ...composites as an exciting class of triboelectric materials in TENGs. Infrared laser irradiation is used to convert the surfaces of the two carbon sources, polyimide (PI) and cork, into LIG. This gives the bilayer composite films the high conductivity associated with LIG and the triboelectric properties of the carbon source. A LIG/PI composite is used to fabricate TENGs based on conductor-to-dielectric and metal-free dielectric-to-dielectric device geometries with open-circuit voltages >3.5 kV and peak power >8 mW. Additionally, a single sheet of PI is converted to a metal-free foldable TENG. The LIG is also embedded within a PDMS matrix to form a single-electrode LIG/PDMS composite TENG. This single-electrode TENG is highly flexible and stretchable and was used to generate power from mechanical contact with skin. The LIG composites present a class of triboelectric materials that can be made from naturally occurring and synthetic carbon sources.
•Characterization of the Iberian cork sector in structural, economic and trade terms.•Portugal and Catalonia are mainly manufacturers of high-value cork products.•Rest of Spain wastes the potential ...of its raw cork exporting it to other markets.•Cork industry should implement R&D and innovation strategies for diversification.•Cork supply chain should strengthen sustainability and ecoefficiency at all stages.
Cork oak forest grows endemically in the coastal regions of the western Mediterranean basin, particularly in the Iberian Peninsula. The cork agro-forestry systems play a key role in ecological processes, and the outer bark, or cork, can be extracted sustainability without damaging the tree or affecting biodiversity. Because of the properties of the cork, an important forestry and industrial structure has been developed around its most valuable goods. This paper describes the current global trade patterns in the Iberian Peninsula, where Portugal and Spain are world leaders. Although these countries bring most of their cork trade flows together with the rest of the world, there are clear differences between these sectors. The aim of this study was to identify these differences and to characterize each analysed sector from an economic perspective. The primary difference between the sectors lies in the characteristics of their supply chain and their capacity to generate wealth from raw cork. Portugal primarily produces and processes raw cork into products with high added value. Spain bases its cork sector on raw material and half-manufactured cork, and it is not able to use the full potential that cork provides. Catalonia is an exception because it is the global leader in the champagne stopper market. To encourage the development of the entire cork sector, every link in the supply chain should be strengthened through the establishment of companies and the generation of employment, and therefore the development of rural areas. Moreover, this industry must establish its own development strategies for the future, thereby increasing its investment in R&D and innovation in relation to the opportunities identified as follows: the potential for diversification beyond the wine market, the improvement potential for forest management and the enhancement of sustainability and eco-efficiency in every link of the cork supply chain.
•Groundwater decline following drought may reduce cork yield.•Site-specific variations in cork growth are related to groundwater levels.•Groundwater may decouple cork growth from seasonal ...fluctuations of precipitation.•A cork growth trigger value was found for groundwater levels (dry season) below −2.5m.•Cork oak woodlands can be considered groundwater dependent ecosystems.
Cork oak (Quercus suber L.) woodlands in the Mediterranean basin may cope with drought continuing to grow during the dry summer period. This growth pattern relies on the presence of extensive and deep root systems and on their access to groundwater. When the water table level is not within the reach of roots or decreases below a certain level following periods of drought, tree growth and survival might be affected. So far, little is known about the sensitivity and resilience of cork oak to both the rising and lowering of the water table over a long-term period, e.g., during one cork production cycle (9–10years). In this study, we determined whether changes in groundwater levels influence cork growth in two cork oak woodlands located at the Tagus alluvium aquifer in southwestern Portugal. The selected areas have contrasting groundwater levels and an integrated framework was developed combining: (a) a standardized annual cork growth index series for tree (cork) growth assessment; (b) a monthly Standardized Precipitation Evapotranspiration Index (SPEI) for drought periods assessment and; (c) a Geographical Information System (GIS)-based model for mapping the mean water table depth in the dry period. Results showed a decrease of cork growth index (up to 40%) immediately following a severe drought, which lowered the water table in the dry period. Moreover, in the site with deeper groundwater levels the reduction of cork growth index was higher. The mean water table depth (in dry period) of −2.5m was found to be a trigger value for cork growth. Our findings suggest that, under shallow water table conditions groundwater mitigates the seasonal fluctuations of precipitation and trees may use groundwater to decouple cork growth from the annual precipitation regime. We conclude that, under changing Mediterranean environments, with expected increase in drought events, the decrease of groundwater levels may severely affect cork (and tree) growth and ultimately tree survival. The management and conservation of cork oak woodlands should therefore rely on adequate policies for the sustainability of groundwater resources.
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•Wines matured in different vessels had similar VOC profiles after 6 months.•Differences in the VOC content of wines among vessels are maximized after 4.5 months.•Using screwcaps led ...to wines with higher contents of VOCs, regardless of the vessel used.•Natural cork combined with alternative vessels increases the ionene content in wine.
A Sauvignon Blanc wine was subjected to a maturation period of six months by using four different types of vessels in triplicate: cylindrical stainless steel tanks, oval-shaped polyethylene tanks, cubic-shaped polyethylene tanks, and clay jars. After maturation in the different vessels, wines were bottled using three different closures (natural cork, synthetic cork, and screwcaps). The volatile compound profiles of the wine samples were recorded by SPME-GC–MS throughout vessel maturation as well as after the bottle storage period. In general terms, wines stored in stainless steel tanks showed the highest contents of volatile compounds when compared with the other tested vessels. Moreover, wines from bottles capped with screwcaps showed the highest contents of most of the volatile compounds when compared with the other closures. Moreover, an interaction between the vessel and the closure was observed: when screwcaps were used during bottle aging, the resulting wines were very similar to those matured in stainless steel vessels. These results suggest that the use of screwcaps hides the differences originating from wine composition during maturation in vessels other than stainless steel.
Summary
Interaction effects of different stressors, such as extreme drought and plant invasion, can have detrimental effects on ecosystem functioning and recovery after drought. With ongoing climate ...change and increasing plant invasion, there is an urgent need to predict the short‐ and long‐term interaction impacts of these stressors on ecosystems.
We established a combined precipitation exclusion and shrub invasion (Cistus ladanifer) experiment in a Mediterranean cork oak (Quercus suber) ecosystem with four treatments: (1) Q. suber control; (2) Q. suber with rain exclusion; (3) Q. suber invaded by shrubs; and (4) Q. suber with rain exclusion and shrub invasion. As key parameter, we continuously measured ecosystem water fluxes.
In an average precipitation year, the interaction effects of both stressors were neutral. However, the combination of imposed drought and shrub invasion led to amplifying interaction effects during an extreme drought by strongly reducing tree transpiration. Contrarily, the imposed drought reduced the competitiveness of the shrubs in the following recovery period, which buffered the negative effects of shrub invasion on Q. suber.
Our results demonstrate the highly dynamic and nonlinear effects of interacting stressors on ecosystems and urges for further investigations on biotic interactions in a context of climate change pressures.
Suppose that X,X′ are simply-connected closed exotic 4-manifolds. It is well-known that X′ is obtained by an order 2 cork twist of X. We give an infinite family of exotic 4-manifolds not generated by ...any infinite order cork. This is the first example admitting such a condition. We prove a necessary condition of 4-dimensional Ozsváth-Szabó invariants for a family to be generated by an infinite order cork and as an application give non-contractible relatively exotic 4-manifolds that are never induced by any cork. Furthermore, we give an estimate of the number of Ozsváth-Szabó invariants of 4-manifolds generated by a cork.
•Impact of considering cork absorption during preparation of concretes was assessed.•Lightweight cork concretes were produced.•Considering cork absorption modified the concrete ...microstructure.•Concretes considering cork absorption showed enhanced hygrothermal properties.•Maximum compressive strength was recorded for concretes neglecting cork absorption.
The main objective of this paper to examine the impact of varying the considered level of cork absorption during preparation of cork concrete. For this purpose, experiments were carried out on cork concretes considering three different levels of cork absorption, namely: (i) no water, (ii) water corresponding to 2 h of cork absorption and (iii) cork saturation water. For each level of absorption, three cork percentages (25, 50 and 75%) were studied. Concretes were tested in terms of consistency, density, microstructure and hygro-thermo-mechanical properties. Microstructure’ results highlighted the impact of considering cork absorption on the porosity of concrete, its pore size distribution and the Interfacial Transition Zone (ITZ) between cork and matrix. By increasing the considered level of cork absorption, the hygric performance of cork concretes was substantially improved. For instance, by going from zero to a saturation level, an increase of 20% was recorded on Moisture Buffer Value (MBV) of concrete with 75% of cork. The best thermal conductivity was obtained for concretes incorporating water corresponding to 2 h of cork absorption. However, the highest specific heat (Cp), value that insure high thermal inertia, was recorded for concretes containing cork saturation water. Depending on water amount and cork percentage, thermal conductivity of concretes ranged between 140 and 1230 mW/(m.K). Notwithstanding the decrease of compressive strength with increasing cork absorption water, the produced concretes exhibited good performance for the use as non-structural materials.
This paper investigates the reliability of free and open-source algorithms used in the geographical object-based image classification (GEOBIA) of very high resolution (VHR) imagery surveyed by ...unmanned aerial vehicles (UAVs). UAV surveys were carried out in a cork oak woodland located in central Portugal at two different periods of the year (spring and summer). Segmentation and classification algorithms were implemented in the Orfeo ToolBox (OTB) configured in the QGIS environment for the GEOBIA process. Image segmentation was carried out using the Large-Scale Mean-Shift (LSMS) algorithm, while classification was performed by the means of two supervised classifiers, random forest (RF) and support vector machines (SVM), both of which are based on a machine learning approach. The original, informative content of the surveyed imagery, consisting of three radiometric bands (red, green, and NIR), was combined to obtain the normalized difference vegetation index (NDVI) and the digital surface model (DSM). The adopted methodology resulted in a classification with higher accuracy that is suitable for a structurally complex Mediterranean forest ecosystem such as cork oak woodlands, which are characterized by the presence of shrubs and herbs in the understory as well as tree shadows. To improve segmentation, which significantly affects the subsequent classification phase, several tests were performed using different values of the range radius and minimum region size parameters. Moreover, the consistent selection of training polygons proved to be critical to improving the results of both the RF and SVM classifiers. For both spring and summer imagery, the validation of the obtained results shows a very high accuracy level for both the SVM and RF classifiers, with kappa coefficient values ranging from 0.928 to 0.973 for RF and from 0.847 to 0.935 for SVM. Furthermore, the land cover class with the highest accuracy for both classifiers and for both flights was cork oak, which occupies the largest part of the study area. This study shows the reliability of fixed-wing UAV imagery for forest monitoring. The study also evidences the importance of planning UAV flights at solar noon to significantly reduce the shadows of trees in the obtained imagery, which is critical for classifying open forest ecosystems such as cork oak woodlands.
Existing water quality index (WQI) models assess water quality using a range of classification schemes. Consequently, different methods provide a number of interpretations for the same water ...properties that contribute to a considerable amount of uncertainty in the correct classification of water quality. The aims of this study were to evaluate the performance of the water quality index (WQI) model in order to classify coastal water quality correctly using a completely new classification scheme. Cork Harbour water quality data was used in this study, which was collected by Ireland's environmental protection agency (EPA). In the present study, four machine-learning classifier algorithms, including support vector machines (SVM), Naïve Bayes (NB), random forest (RF), k-nearest neighbour (KNN), and gradient boosting (XGBoost), were utilized to identify the best classifier for predicting water quality classes using widely used seven WQI models, whereas three models are completely new and recently proposed by the authors. The KNN (100% correct and 0% wrong) and XGBoost (99.9% correct and 0.1% wrong) algorithms were outperformed in predicting the water quality accurately for seven WQI models. The model validation results indicate that the XGBoost classifier outperformed, including accuracy (1.0), precision (0.99), sensitivity (0.99), specificity (1.0), and F1 (0.99) score, in order to predict the correct classification of water quality. Moreover, compared to WQI models, higher prediction accuracy, precision, sensitivity, specificity, and F1 score were found for the weighted quadratic mean (WQM) and unweighted root mean square (RMS) WQI models, respectively, for each class. The findings of this study showed that the WQM and RMS models could be effective and reliable for assessing coastal water quality in terms of correct classification. Therefore, this study could be helpful in providing accurate water quality information to researchers, policymakers, and water research personnel for monitoring using the WQI model more effectively.
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