Archivio Istituzionale della Ricerca- Università del Salento
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Surfaces of three-dimensional homogeneous plane waves
No full textWe investigate the geometry of surfaces in three-dimensional homogeneous non-symmetric plane waves. In particular, we obtain the full classification and explicit description of their totally geodesic and parallel examples and prove the nonexistence of proper totally umbilical surfaces. Moreover, we characterize their minimal surfaces, providing some explicit examples
Higher-Order Theories for the Vibration Analysis of Anisotropic Doubly Curved Irregular Shells with Holes and Discontinuities
No full textNew advances in many engineering fields require refined modeling strategies to analyze the static and the dynamic behavior of complex structural components and sub-systems with a reduced computational effort. In this context, the present contribution proposes an innovative approach, based on higher-order theories and a unified formulation, to analyze the statics and vibrations of doubly-curved shell structures with irregular domains, including discontinuities and holes of different shapes. The geometry of the panel is described using the principal coordinates, whereas the fundamental equations are derived from the Hamiltonian principle, and are described in their weak form using higher-order interpolations for the unknowns on a discrete computational grid. The constitutive properties of layers are derived from various analytical homogenization techniques, primarily for composite materials, lattice honeycomb and anisogrid cells, Carbon Nanotubes (CNTs), and Functionally Graded Materials (FGMs), among others. Various loading and boundary conditions are modelled, while various methodologies are provided to recover stress and strain components, based on either a Generalized Differential Quadrature (GDQ) and Generalized Integral Quadrature (GIQ) method. Various numerical examples are presented which validate the accuracy and efficiency of the model against the reference solutions from commercial softwares. In addition, the effects of the polynomial-based interpolations of different orders are explored followed by a parametric study aimed at evaluating the sensitivity of the governing parameters to the overall response of structures with different curvatures and materials
Nature-inspired sustainable graphene oxide photocatalyst for sunlight-driven H2 production
No full textMost carbon-based materials are traditionally derived from fossil resources, and their synthesis often requires hazardous chemicals. Developing sustainable approaches is therefore an essential method that uses renewable feedstocks, minimizes solvents and reagents. This study utilizes waste coffee silverskin (CSS), a byproduct of coffee roasting, as a renewable carbon precursor (CP) for sustainable energy applications. Herein, an eco-friendly, low-cost, and sustainable method to synthesize silverskin graphene oxide (SGO) from CSS via the ozone oxidation method is presented. This greener approach avoids the use of toxic oxidants and gives higher surface oxygenation, defect density, and hydrophilicity compared to conventional methods for graphene oxide (GO) production, thereby offering a novel and more sustainable pathway. It also enables the separation of the charge, and the extension of the interfacial interactions helps to achieve efficient solar interfacial interaction with catalysts for H2 production. Structural and compositional analysis (UV-Vis, FTIR, XRD, Raman, TGA-DSC, SEM-EDX, TEM, XPS) confirmed the presence of oxygen functionalities (C/O atomic ratio 0.31 ± 0.02) with a band gap of 2.4 eV and revealed good thermal stability. The results confirmed the successful synthesis of SGO with good catalytic activity. Its potential as a metal-free semiconductor in photocatalysis under different water matrices was indeed demonstrated splitting water into H2 gas under sunlight irradiation, achieving a hydrogen generation of 24.34 mmolg−1 2 h−1 and 27.50 mmolg−1 2 h−1, respectively, in ultrapure water and secondary treated wastewater. This work highlights a sustainable pathway for managing waste, promoting sustainable hydrogen production, and the potential of biomass-derived carbon catalysts for clean energy
Volatile Organic Compounds (VOCs) in Neurodegenerative Diseases (NDDs): Diagnostic Potential and Analytical Approaches
No full textNeurodegenerative diseases (NDDs) are a group of progressive diseases affecting neuronal cells in specific areas of the brain, causing cognitive decline and movement impairment. Nowadays, NDDs play a significant role in the global burden of disease, and their incidence is increasing, particularly due to population aging. NDD onset is multi-factorial; based on the current knowledge, genetic, environmental, and cellular factors are believed to contribute to their occurrence and progression. Taking into account that at an early stage, the symptoms are not clearly defined, and diagnosis may be delayed, the development of innovative and non-invasive methodological approaches for early diagnosis of NDDs is strategic for timely and tailored disease management, as well as for the overall improvement of patients' quality of life. The present review aims to provide, in the first part, an overview based on the current level of knowledge on the environmental risk factors that can explicate a role in the onset of the most common NDDs and on the main pathogenic mechanisms involved in disease initiation and progression. The second part aims to define the current state of the art regarding the significance of Volatile Organic Compounds (VOCs) in the volatome of different human biological matrices (exhaled breath, feces, and skin sebum) as candidate biomarkers of specific NDDs, with the aim of developing non-invasive diagnostic approaches for the early diagnosis and personalized management of the patients. A critical synthesis and discussion on the applied methodological approaches and on the relevant outcomes obtained across the studies is reported
Multi-criteria Evaluation: An Approach Based on Distance Operators
No full textIn this paper, we propose an extension of the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method, a widely used method for multi-criteria problems, taking the similarity between the variables into account, in order to penalize scenarios in which there is considerable variability. The motivation for our approach lies in the concept of sustainability, where a high value of one criterion cannot compensate for a too-low value of others, and therefore more balanced scenarios are thus preferred
MLUCM BEP + BEM: an offline one-dimensional multi-layer urban canopy model based on the BEP + BEM scheme
No full textThe MLUCM BEP + BEM model advances urban microclimate modelling by combining a multi-layer canopy approach with Building Effect Parameterization (BEP) and a Building Energy Model (BEM). It includes updated turbulent length scales and eddy diffusivity coefficients that account for atmospheric stability, along with explicit representation of urban vegetation, such as street trees and green spaces. The model runs offline with low computational demands, making it suitable for standalone use, integration with climate projections, and long-term simulations to evaluate emission scenarios and adaptation strategies. Validation against data from the Urban-PLUMBER project at a suburban site in Preston (Melbourne, Australia) demonstrates that MLUCM BEP + BEM reliably reproduces shortwave (SWup) and longwave (LWup) radiation, as well as latent (Qle), sensible (Qh), and momentum (Qtau) fluxes. Its overall performance is on par with, and in several cases surpasses, that of other established urban models with particularly notable improvements in the simulation of momentum flux (Qtau). Some refinements are still needed, particularly in modelling tree-soil moisture dynamics to reduce surface energy budget imbalances. Thanks to its flexibility and efficiency, MLUCM BEP + BEM is well-suited for assessing urban overheating, building energy demand, and the effectiveness of mitigation strategies such as green roofs, cool materials, and photovoltaic systems under various future climate scenarios
Numerical Homogenization Approach for the Analysis of Honeycomb Sandwich Shell Structures
No full textThis study conducts a thorough examination of honeycomb sandwich panels with a lattice core, adopting advanced computational techniques for their modeling. The research extends its analysis to investigate the natural frequency behavior of sandwich panels, encompassing the comprehensive assessment of the entire panel structure. At its core, the research applies the Representative Volume Element (RVE) theory to establish the equivalent material properties, thereby enhancing the predictive capabilities of lattice structure simulations. The methodology applies these properties in the core of infinite panels, which are modeled using double periodic boundary conditions to explore their natural frequencies. Expanding beyond mere material characterization, the study introduces a novel approach to defining the material within the panel cores. By incorporating alternate materials such as steel and AlSiC, and by strategically modifying their ratios, the research streamlines the process of material variation without resorting to repetitive 3D operations on the constituent cells. This optimizes not only the computational resources but also offers insights into the structural response under diverse material compositions. Furthermore, the investigation extends its scope to analyze the influence of curvature on the structural behavior of lattice structures. Panels are modeled with varying degrees of curvature, ranging from single to double curvatures, including cylindrical and spherical configurations, across a spectrum of radii. A rigorous analysis is performed to study the effect of curvature on the mechanical performance and stability of lattice structures, offering valuable insights for design optimization and structural engineering applications. By building upon the existing knowledge and introducing innovative methodologies, this study contributes to improving the understanding of lattice structures and their applicability in diverse engineering contexts