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Summary: Mechanical properties of fibres reinforced composite materials depend on the type of fibres used, their percentage as well as their arrangement and orientation. As computer technology continues to improve, high‐resolution computed tomography has proven to be an ideal instrument to analyse the structure of this kind of materials. In this context, various approaches have been proposed to detect the fibre orientation distribution and the relative degree of anisotropy of these composite materials. Some of these approaches are based on 'individual' measurements that isolate and reconstruct each single fibre and measure its properties. On the other hand, other approaches capture the characteristics of the fibre distribution by means of 'global' measurements computed on the entire set of tomographic data. The first methods are more precise but also more complex because they demand a procedure able to segment and separate each single fibre in the polymer, whereas the latter are easier to implement and can be applied even if fibre segmentation and separation is not effective or practicable. In this paper, a global method based on the technique called volume orientation – originally proposed several years ago to study the anisotropy of bone structures – is applied to fibre reinforced composite materials. This new approach does not require data acquired at very high resolution nor very complex procedures for individual segmentation of the fibres, but only binarised data through common thresholding procedures. The effectiveness of the proposed new approach is demonstrated by comparing it to the results obtained from a method based on individual measurements: when resolution and images quality are good enough, the volume orientation method gives results quite similar to the other approach. The analysis of three different case studies demonstrates its flexibility and its validity as an alternative to methods based on the separation of individual fibres, which are not always usable. The samples have been carefully selected in order to range between different attenuation contrast levels and also include a specimen subjected to mechanical testing which can be of great practical interest. Lay Description: Mechanical properties of fibres reinforced composite materials depend on the type of fibres used, their percentage as well as their arrangement and orientation. Today, both destructive and nondestructive techniques can be used in order to assess the fibre orientation. As computer technology continues to improve, high‐resolution computed tomography has proven to be an ideal instrument to analyse the structure of this kind of materials, and then the fibre orientation distribution inside the material. In this context, various strategies have been proposed. Some of them require measurements that isolate and reconstruct each single fibre and measure its properties. On the other hand, other approaches capture the characteristics of the fibre distribution by means of 'global' measurements computed on the entire set of tomographic data. The first methods are more precise but also more complex because they demand a procedure able to detect and separate each single fibre in the polymer, whereas the latter are easier to implement and can be applied even if fibre segmentation and separation is not effective or practicable. In this paper, a global method based on the technique called volume orientation – originally proposed several years ago to study the microstructure of bone tissues – is applied to fibre reinforced composite materials. The aim of this work is to demonstrate that this new approach is easier to use. As a matter of fact, it does not require data acquired at very high resolution nor very complex procedures for individual segmentation of the fibres, but only binarised data through common thresholding procedures. The effectiveness of the proposed new approach is shown by comparing it to the results obtained from a method based on individual measurements: when spatial resolution and images quality are good enough, the volume orientation method gives results quite similar to the other already used approach. The analysis of three different case studies demonstrates its flexibility and its validity as an alternative to methods based on the separation of individual fibres, which are not always usable. The samples have been carefully selected in order to range between different attenuation contrast levels and different nature of the fibres (mineral, vegetable or synthetic). A specimen subjected to mechanical testing is also included, because of its great practical interest. [ABSTRACT FROM AUTHOR]

Summary: Structural anisotropy of two‐phase materials can be evaluated through global measurements, as volume orientation or mean‐intercept length methods do, or through statistics performed on a set of individual measurements. This last procedure is encouraged by recent improvements in the spatial resolution of conventional X‐ray tomography. In this paper, the above‐described approaches were compared in three case studies: a foam subjected to an in situ compression test, a second foam with a completely different cell morphology and a plastic material reinforced with short fibres. The approach based on the subdivision into distinguishable objects of the considered material phase has proved to be more sensitive in highlighting small deformations in the structure or small irregularities in an otherwise isotropic structure. On the other hand, the other approach is more general and is always usable. The two methods for calculating the fabric tensor tend to converge as the average anisotropy of individual objects in the statistical population increases. The use of Lambert's cylindrical equal‐area projection of cell/fibre directions or local volume orientations is suggested, because the density of points is preserved from the sphere to the plane surface. Finally, a quick vector method to evaluate the anisotropy of the directions distribution has been presented, by defining a coherence index of the average direction. [ABSTRACT FROM AUTHOR]

Advanced polymeric foams are used in a wide range of industrial and R&D applications. Their properties strongly depend upon the cell structure. Traditionally, their microstructure has been studied using optical or electron microscopy, limiting the investigations to sample’s surface only. To overcome this shortcoming, the use of X-ray micro-tomography imaging is here adopted to allow for a complete 3D, non-destructive analysis of advanced polymeric foams. This work brings to fruition high resolution and low-contrast imaging techniques to perform quantitative analyses onto polymeric foams, where the low contrast of reconstructed structural features might hamper accurate quantitative analyses. Local structural features of individual cells are statistically evaluated, showing the key role of the achieved resolution. [ABSTRACT FROM AUTHOR]

As the size of vessels progressively increases to compete in the global trade, the impact evaluation of navigation in waterways and shallow coastal ecosystems become more important. Therefore, suitable tools to investigate processes are required to support a sustainable management of ship traffic. This work tests a new methodology, based on a numerical model chain, that reproduces the hydrodynamic field close to the ship hull and the ship-induced wave propagation in the surrounding shallow areas. The model chain includes an unstructured hydrodynamic model forced by the near-field estimation of a computational fluid dynamics simulation. The modeling system has been applied to a major navigation channel and surrounding tidal flats in the Venice Lagoon (Italy). Field observations and a theoretical framework were used to characterize the ship waves and to validate the modeling system. Results show that the deeper the initial depression, the larger the dissipation over the tidal flat. In these conditions smaller vessels sailing at higher speed produce smaller waves with low amplitudes compared to larger ships traveling at lower speed. We considered vessels moving at different speeds providing useful information to evaluate impacts and to define criteria for decision support systems for a sustainable management of navigation. [ABSTRACT FROM AUTHOR]

Heat management in hydrogen storage tanks is a mandatory issue in order to ensure high level performances both in terms of hydrogen release/uptake kinetics and storage capacity. Previous research has ascertained that powders tend to pack and sinter during charge/discharge cycling giving rise to non-reacting material. Moreover powders, with intrinsically low thermal conductivity, can show problems related to hydrogen permeability, and suffer from hydraulic losses and particle entrainment by gas flow. To overtake these problems and to keep high performances, hydride powders mixed with high thermal conductivity additives are compacted in pellets. Some materials, like Expanded Natural Graphite (ENG), besides improving the pellet mechanical stability during cycling, can impart a thermal conductivity higher by order of magnitudes with respect to a simple powdered bed. On the basis of these considerations, pelleting can be very effective in improving tank performances. However pellets tend to swell and lose compactness during long term operation, returning back to the powder form with a detrimental effect on tank performances. In this work the swelling process caused by cycling of pellets simulating tank exercise has been studied. The pellets, which are constituted by ball milled magnesium hydride (MgH 2 ) with the addition of niobium oxide (Nb 2 O 5 ) and ENG, have been deeply studied by different microscopic methods including Scanning Electron Microscopy (SEM), Helium Ion Microscopy (HeIM) and high resolution Computed Tomography (CT) with the purpose of ascertaining microstructural modification and degradation mechanism in order to define strategies for material preparation able to reduce the entity of the swelling process. [ABSTRACT FROM AUTHOR]

A flexible pilot plant, fed with primary settled wastewater, was used to study (1) organic carbon and nitrification in a two(three)-stagecontinuous-flow aerobic process and (2) organic carbon and nitrogen removal in a heterotrophic moving-bed sequencing batch biofilm reactor (MBSBBR) for denitrification and in a continuous-flow autotrophic moving-bed biofilm reactor (MBBR) for nitrification. In both experiments the same polyethylene biofilm carriers were used. Filtered COD removal rates in aerobic conditions appear to be proportional to the corresponding loading rates up to 8 gCOD m-2 d-1. Nitrification tests, performed in oxygen limiting conditions and ammonia limiting conditions, showed that the reaction rate was nearly first order with respect to dissolved oxygen due to liquid film diffusion. Denitrification tests, performed without external carbon sources, showed that the denitrification rate never fell below 0.3 gN03--N m-2 d-1 even at very low biodegradable filtered COD loading rates. [ABSTRACT FROM AUTHOR]