Archivio Istituzionale della Ricerca- Università del Salento
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Urban Mining in Europe: Exploring the Recovery Potential of Critical Elements for Battery Manufacturing
No full textModelling multivariate spatio-temporal data with identifiable variational autoencoders
Get PDFModelling multivariate spatio-temporal data with complex dependency structures is a challenging task but can be simplified by assuming that the original variables are generated from independent latent components. If these components are found, they can be modelled univariately. Blind source separation aims to recover the latent components by estimating the unknown linear or nonlinear unmixing transformation based on the observed data only. In this paper, we extend recently introduced identifiable variational autoencoder to the nonlinear nonstationary spatio-temporal blind source separation setting and demonstrate its performance using comprehensive simulation studies. Additionally, we introduce two alternative methods for the latent dimension estimation, which is a crucial task in order to obtain the correct latent representation. Finally, we illustrate the proposed methods using a meteorological application, where we estimate the latent dimension and the latent components, interpret the components, and show how nonstationarity can be accounted and prediction accuracy can be improved by using the proposed nonlinear blind source separation method as a preprocessing method
Influence of the lemon (Citrus Limon L.) juice amount on the green synthesis of CuO nanoparticles: Characterization, stability and thermal conductivity
Get PDFIn this study, the effect of three L/M ratios on the morphology and thermal conductivity of CuO plant-mediated synthesis was evaluated for the first time. The work was structured as follows: In section 3.1, an overall description of the three synthesis processes was set up. In section 3.2, a complete characterization of the three synthesized CuO NPs through electron microscopy (SEM, TEM), FTIR, XRD and TGA/DTA was conducted. In section 3.3, the stability of the three CuO NPs dispersed in EG/DW (60:40) was accomplished by dynamic light scattering (DLS) and zeta potential measurements. The fact of having three NPs with the same chemical nature but different sizes and powder qualities in terms of disaggregation made it possible to perform a comparative study of the experimental thermal conductivities under uniform standards. Additionally, these experimental TC data of the three CuO-EG/DW nanofluids were compared with those obtained from two mathematical models. These results are presented in section 3.4
Improving spatial clustering through a weight system on multilevel permanent museum attraction probability
No full textMuseums are extensively distributed all over the Italian territory. In this context, the iden- tification of spatial patterns, referred to specific characteristics of museums evaluated at regional level, can support the enhancement of the cultural and natural heritage as well as the social and economic growth. In the literature, many studies were focused on the visitors’ profile or on the managerial performance and economic efficiency of the muse- ums. However, none of them analysed the effects of the permanent presence of museums and their spatial contiguity by using both spatial machine learning models and statistical models. To this aim an innovative approach, which combines multilevel binary model and spatial clustering, as a machine learning unsupervised technique, is proposed to investigate the pattern recognition of the permanent museums all over the Italian territory and provide relevant information in terms of similarity among the spatial cluster formed. The logit of the museums to remain open all over the year, also with respect to different types of institu- tion (private/public) and a different spatial/geographical constraints are jointly considered. In addition, a weight system is defined in order to introduce a regional measure of muse- ums prevalence with respect to other types of cultural institutions. The ISTAT microdata concerning the Italian survey on museums and cultural entities are considered. The results highlight the great potentiality of this spatial clustering approach in delivering a better understanding of the role of museums as factor of challenge of urban development, provid- ing in the meantime suggestions for tourism providers and museum managers
Optimal transport between algebraic hypersurfaces
Get PDFWhat is the optimal way to deform a projective hypersurface into another one? In this paper we will answer this question adopting the point of view of measure theory, introducing the optimal transport problem between complex algebraic projective hypersurfaces. First, a natural topological embedding of the space of hypersurfaces of a given degree into the space of measures on the projective space is constructed. Then, the optimal transport problem between hypersurfaces is defined through a constrained dynamical formulation, minimizing the energy of absolutely continuous curves which lie on the image of this embedding. In this way an inner Wasserstein distance on the projective space of homogeneous polynomials is introduced. This distance is finer than the Fubini–Study one. The innner Wasserstein distance is complete and geodesic: geodesics corresponds to optimal deformations of one algebraic hypersurface into another one. Outside the discriminant this distance is induced by a smooth Riemannian metric, which is the real part of an explicit Hermitian structure. Moreover, this Hermitian structure is Kähler and the corresponding metric is of Weil–Petersson type. To prove these results we develop new techniques, which combine complex and symplectic geometry with optimal transport, and which we expect to be relevant on their own. We discuss applications on the regularity of the zeroes of a family of multivariate polynomials and on the condition number of polynomial systems solving
The role of active breaks and curriculum-based active breaks in enhancing executive functions and math performance, and in reducing math anxiety in primary school children: a systematic review
Get PDFPhysical activity is recognized as crucial for children’s development in many aspects. However, its integration into the classroom remains a challenge, particularly in STEM subjects, despite this area being a central component of school curricula worldwide. This systematic review investigates the characteristics and the relationships between active breaks (AB) and curriculum-based active breaks (CB) interventions on executive functions, attention, on-task behavior, performance in STEM, and math anxiety in primary school children. A database search, following the PRISMA 2020 guidelines, was conducted in March 2024, identifying 19 eligible studies for descriptive analysis and assessed for risk of bias. A total of 13 studies focused on AB, four on CB, and two compared the two conditions. Only one paper considered math anxiety. The results revealed mixed effects on executive functions and attention, with some studies reporting improvements and others finding no significant changes. Math performance improved with both AB and CB interventions, especially when AB lasted 10 to 20 min. Most interventions were led by teachers, though few studies incorporated intervention fidelity. Overall, the inconsistent findings highlight the need for further research to determine the optimal characteristics for effective interventions and reliable assessment methods and to explore long-term effects and the appropriate level of teacher involvement
Volumetric drag coefficients for generic urban configurations: Insights from canopy flow analysis
No full textAlternative drag approaches for representing unresolved buildings were proposed in literature for computational fluid dynamics (CFD) simulation of macroscopic urban airflow. As a contribution, the present work derives the volumetric drag coefficient (Cd*) through canopy drag and velocity analysis and provides appropriate correlations for Cd*against urban morphological parameters. A total of 72 cases across various urban configurations are investigated, categorized by building typology, horizontal layout, height variability, and plan area density (λp, from 0.0625 to 0.57). Reynolds-Averaged Navier-Stokes (RANS) simulations with periodic boundary conditions are performed to model fully developed flows. Results for the normalized drag force and superficial velocity and their relations with λp are evaluated. Subsequent evaluation of the profiles for the sectional coefficients (Cd*(Z)) reveals four distinct types with variations in uniform-height cases and combinations in varying-height cases. A throughout correlations analysis, facilitated by data transformation, identifies the straightforward relations between Cd* and frontal area density (λf) and tortuosity (τ). The followed stepwise regression provides a recommended formula for Cd*, demonstrating a proper fit with the simulated values. These findings facilitate the understanding and appropriate estimation of Cd* and Cd*(Z), promoting the application of macroscopic turbulence models, for neighborhood-scale wind and air quality studies