Dynamic Preisach hystersis model for magnetostrictive materials for energy application

Recently Magnetostrictive materials have been proposed as active materials to be used in several energy harvesting technology [1]. In this kind of application, the working condition of the material is highly dynamic and non linear. As a result static models of magnetostrictive materials are usually not very accurate and can be not reliable to develop a sufficiently accurate designof the energy harvesting devices. The presence of hysteresis requires accurate mathematical modeling in order to correctly foresee the behavior of real materials (ferromagnetic or magnetostrictive) used in control systems or in electrical machines and thus simplifying the design of such controllers or predicting with acceptable accuracy electromagnetic fields in such devices[2]. In order to overcome this problem, this paper addresses the development of Dynamic Preisach hysteresis model (DPM) for magnetostrictive materials for energy application operating in hysteretic and time varying nonlinear regimes. DPM is a development of classical Preisach Model which is able to include dynamical features in the mathematical model of hysteresis. In this paper the magnetostrictive material considered is Terfenol-D. Its hysteresis is modeled by applying the DPM whose identification procedure is performed by using a neural network procedure previously publised [3]. The neural network used is a multiplayer perceptron trained with the Levenberg-Marquadt training algorithm. This allows to obtain both Everett integrals and the Preisach distribution function, without any special conditioning of the measured data, owing to the filtering capabilities of the neural network interpolators. The model is able to reconstruct both the magnetization relation and the Field-strain relation. The model is validated through comparison and prediction of data collected from a typical Terfenol-D transducer

Bridging the knowledge gap on the distribution and typology of vermetid bioconstructions along the Maltese coastline: an updated assessment

In the Maltese Islands, insufficient attention has been paid to vermetid reefs, endemic Mediterranean bioconstructions widely distributed along the southern part of the basin. As a result, this is a largely-overlooked coastal ecosystem despite the multitude of ecosystem services it provides. The perennial urban development in the Maltese Islands calls for the adoption of urgent action to protect coastal habitats, in particular bioconstructions that increase biodiversity and contribute to mitigating the effects of climate change. The objective of our study was to extensively document the presence and typology of the vermetid reef ecosystems along the coast of Malta and Gozo, assessing the occurrence of putative anthropogenic threats on the same ecosystem. Quantitative measurements were additionally taken to morphologically characterize the recorded bioconstructions. Furthermore, we tested the human pressure effect on the density of vermetid individuals and associated biodiversity. “True” trottoirs were only documented along the south-east coast of Malta, where unfortunately land reclamation projects are expected to be implemented. Although no direct relation between a number of assessed human activities and the density of vermetid individuals was reported in the current study, we suggest the conduction of further studies to investigate the influence of specific disturbances on the conservation status of this ecosystem. This study expands the existing knowledge on the status of vermetid reefs in the Maltese Islands and calls for management and conservation actions to preserve this bioconstruction

Home advantage? Decomposition across the freshwater-estuarine transition zone varies with litter origin and local salinity

Expected increases in the frequency and intensity of storm surges and river flooding may greatly affect the relative salinity of estuarine environments over the coming decades. In this experiment we used detritus from three contrasting environments (marine Fucus vesiculosus; estuarine Spartina anglica; terrestrial Quercus robur) to test the prediction that the decomposition of the different types of litter would be highest in the environment with which they are associated. Patterns of decomposition broadly fitted our prediction: Quercus detritus decomposed more rapidly in freshwater compared with saline conditions while Fucus showed the opposite trend; Spartina showed an intermediate response. Variation in macro-invertebrate assemblages was detected along the salinity gradient but with different patterns between estuaries, suggesting that breakdown rates may be linked in part to local invertebrate assemblages. Nonetheless, our results suggest that perturbation of salinity gradients through climate change could affect the process of litter decomposition and thus alter nutrient cycling in estuarine transition zones. Understanding the vulnerability of estuaries to changes in local abiotic conditions is important given the need to better integrate coastal proceses into a wider management framework at a time when coastlines are increasingly threatened by human activities

Fish assemblages associated with coastal defence structures: Does the surrounding habitat matter?

Artificial structures are sprawling along seashores due to growing populations, coastal use and greater need for coastal erosion and flood protection. The impacts of these anthropogenic modifications of coastlines on fish populations are poorly described, and little is known about factors affecting the ecological performance of these novel habitats for fish. We compared the abundance and community structure of fish assemblages associated with artificial coastal defence structures built in either rocky or sedimentary contexts at two locations along the coast of Sicily, to explore whether the performance of the artificial habitats for fish changed in relation to the characteristics of the surrounding natural habitat. We also quantified how fish associated with artificial structures in either habitat contexts differed from that at nearby natural rocky reefs. We found that fish assemblages differed in abundance and structure between artificial coastal defences deployed in sandy contexts vs natural rocky reefs, with different ecological taxa showing greater (i.e. benthic carnivorous) or lower (i.e. serranids) abundances in the artificial habitat. We also found that fish assemblages associated to artificial structures built on rocky bottoms had inconsistent outcomes, more frequently grouping with artificial sandy habitats at one location and with natural rocky reefs at the other. These results suggest that the surrounding environmental setting could have an overriding, and so far largely overlooked, importance in affecting the performance of artificial structures as habitats and in facilitating the development of fish assemblage with distinctive composition and structure. (C) 2019 Elsevier B.V. All rights reserved

Fish assemblages associated with coastal defence structures: Does the surrounding habitat matter?

Artificial structures are sprawling along seashores due to growing populations, coastal use and greater need for coastal erosion and flood protection. The impacts of these anthropogenic modifications of coastlines on fish populations are poorly described, and little is known about factors affecting the ecological performance of these novel habitats for fish. We compared the abundance and community structure of fish assemblages associated with artificial coastal defence structures built in either rocky or sedimentary contexts at two locations along the coast of Sicily, to explore whether the performance of the artificial habitats for fish changed in relation to the characteristics of the surrounding natural habitat. We also quantified how fish associated with artificial structures in either habitat contexts differed from that at nearby natural rocky reefs. We found that fish assemblages differed in abundance and structure between artificial coastal defences deployed in sandy contexts vs natural rocky reefs, with different ecological taxa showing greater (i.e. benthic carnivorous) or lower (i.e. serranids) abundances in the artificial habitat. We also found that fish assemblages associated to artificial structures built on rocky bottoms had inconsistent outcomes, more frequently grouping with artificial sandy habitats at one location and with natural rocky reefs at the other. These results suggest that the surrounding environmental setting could have an overriding, and so far largely overlooked, importance in affecting the performance of artificial structures as habitats and in facilitating the development of fish assemblage with distinctive composition and structure. (C) 2019 Elsevier B.V. All rights reserved

Primary data collection and environmental/energy audit of hot mix asphalt production

The development of the road construction sector determines the consequences on consumption of non-renewable resources, energy expenditure and environmental pollution. Recent sustainability issues have highlighted the importance of efficient design and quality-oriented techniques in this sector, due to the huge amount of materials involved in construction and maintenance activities. Thus, it is necessary to properly quantify the environmental impacts of asphalt mixtures used for pavement construction, considering the whole life cycle of the products. Life cycle assessment (LCA) represents the most appropriate methodological framework for assessing the environmental burdens of a product, from raw material acquisition to final disposal. A common problem for LCA is the lack of primary data useful to calculate the product eco-profile, for a specific production process. In this context, there is generally limited reliable and accurate data regarding the asphalt plant production phase, which represents the most critical phase. Consequently, the aim of this paper is to perform an environmental/energy audit of an asphalt plant and, further, to collect and analyze primary data useful for the definition of the eco-profile of 1 metric ton of hot mix asphalt (HMA), following a “gate to gate” approach, including transport. The asphalt production is examined in a Sicilian batch-mix plant, representing one of the most commonly used for asphalt production in the Italian context. The results are of interest for asphalt mixture producers, contractors, transportation agencies and researchers seeking to quantify asphalt pavement environmental impacts in Italy, based on context-related foreground data

Experimental Test and Simulations on a Linear Generator-Based Prototype of a Wave Energy Conversion System Designed with a Reliability-Oriented Approach

In this paper, we propose a reliability-oriented design of a linear generator-based prototype of a wave energy conversion (WEC), useful for the production of hydrogen in a sheltered water area like Mediterranean Sea. The hydrogen production has been confirmed by a lot of experimental testing and simulations. The system design is aimed to enhance the robustness and reliability and is based on an analysis of the main WEC failures reported in literature. The results of this analysis led to some improvements that are applied to a WEC system prototype for hydrogen production and storage. The proposed WEC system includes the electrical linear generator, the power conversion system, and a sea-water electrolyzer. A modular architecture is conceived to provide ease of extension of the power capability of the marine plant. The experimental results developed on the permanent magnet linear electric generator have allowed identification of the stator winding typology and, consequently, ability to size the power electronics system. The produced hydrogen has supplied a low-power fuel cell stack directly connected to the hydrogen output from the electrolyzer. The small-scale prototype is designed to be installed, in the near future, into the Mediterranean Sea. As shown by experimental and simulation results, the small-scale prototype is suitable for hydrogen production and storage from sea water in this area

Algorithms for the calculation of the projected area factors of seated and standing persons

Moderate thermal environments, other than being affected by the mutual radiative heat exchange at low frequency among the internal surfaces, are often characterized by the presence of high intensity sources, that is, radiant sources showing a small area, a high emission temperature and a strongly directional beam. The sun's direct radiation can be considered to be among these radiant sources. In these cases, the computation of the mean radiant temperature and, consequently, the evaluation of the thermal comfort conditions, require knowledge of the “project area factor”, fp, of the subject. Moreover, the fp parameters are also applicable to derivation of the shape factors between subjects and the surrounding surfaces. For a manual evaluation of the projected area factors, a well-known set of graphs is available. But, when using computerized procedures, the handling of graphs can lead to troublesome operations and could involve reading errors. To avoid problems, we have developed two simple polynomial algorithms, founded on earlier data, for the automatic calculation of the projected area factors of seated and standing persons. A validation of the algorithms is also reported through the paper, for selected cases