https://hdl.handle.net/10955/35 2026-04-21T03:13:24Z https://hdl.handle.net/10955/5599 Chemical characterization of atmospheric aerosols from natural and anthropogenic sources in the Mediterranean area Moretti, Sacha; Carbone, Vincenzo; Sprovieri, Francesca; Naccarato, Attilio The Mediterranean Sea basin constitutes a semi-enclosed area where atmospheric particles originating from natural and anthropogenic continental sources and gas-to-particle conversion processes are present at all times. The area is, in fact, located to the south of highly populated European countries characterized by industrial, semi-industrial, and rural economies, and to the north of Africa, which includes the Sahara desert. Detailed wind trajectory analysis reported in previous research studies show that more than 60% of air masses crossing the Mediterranean originate from the north-northwest sector, containing particles emitted or derived from industrial and urban sources, whereas 13–16% of air masses coming from the Sahara region carrying predominantly mineral dust. The transport of Saharan dust occurs mostly during the spring and summer seasons and causes sporadic crustal aerosol pulses to the Mediterranean area. On the other hand, aerosol scavenging by precipitation during the rainy season (from October to May) reduces aerosol concentrations. Summer is also characterized by low inversion layers and strong sunlight conditions, causing photochemical smog. Moreover, forest fires, which occur during the summer months in the Mediterranean region and in North Africa, increase black carbon and fine particle emissions. In this frame, it is clear enough that specific meteorological conditions result in high temporal variability of aerosol concentrations. There is strong evidence on the relationship between short-term and long-term exposure to atmospheric particles, with adverse health effects. Therefore, the study on atmospheric Particulate Matter (PM) (solid or liquid particles dispersed in the atmosphere which may persist for long times to undergo transport and diffusion phenomena), and the relative chemical composition of the two particle size fractions PM2.5, (aerodynamic diameter ≤ 2.5 μm) and PM10 (aerodynamic diameter ≤ 10 μm), is essential to evaluate the effect of the PM on human health and environment. The present work of thesis developed during the Ph.D. is focused on the chemical characterization of aerosol in the Mediterranean area through a monitoring program which has foreseen a number of oceanographic campaigns performed in the Mediterranean sea onboard the CNR-research vessel in the framework of the ongoing MEDOCEANOR measurements program as well as long-term measurements carried out on-land, specifically at the high altitude GAW observatory “Monte Curcio” of the CNR-IIA (1780 m a.s.l.), located on the Sila massif, Southern Italy, and thus able to intercept long-range transport air masses and across a number of monitoring sites (i.e., coastal, urban, rural sites etc.) distributed in the south of Italy as part of the I-AMICA regional network. The concentration of aerosol size fractions and its chemical composition performed at permanent ground-based stations as well as during oceanographic measurement campaigns have been analyzed in order to assess a spatially and temporally consistent measurement data across Mediterranean basin, and to investigate the main natural and anthropogenic sources affecting the air quality using source apportionment techniques. The seasonal oceanographic campaigns developed along different routes in the western sector of the Mediterranean Sea basin, and aimed to study the influence of natural and anthropogenic sources of PM and associated levels of pollutants. Chemical analysis assisted by the receptor models, identified, in particular, six main sources: crustal, volcanic, biomass burning, marine spray, industrial and vehicular traffic. The carbonaceous content in the PM sampled in Monte Curcio station shows seasonal trends for Organic Carbon (OC) and Elemental Carbon (EC) in both PM size fractions. The concentrations during the warm season are higher than those observed during the cold season and the annual levels of EC and OC were lower than those observed at the other four monitoring sites as part of the regional network “I-AMICA” distributed in southern Italy (Capo Granitola, Lamezia Terme, Lecce; Naples) due to different environmental conditions (eg, coastal/marine, suburban and urban) characterizing these sampling sites compared to “Monte Curcio” remote site. In particular, both OC and EC average concentrations were minimal at Monte Curcio and increased in the following order: remote < coastal/marine < suburban < urban (i.e., Monte Curcio < Capo Granitola < Lamezia Terme < Lecce < Naples). The Secondary Organic Carbon (SOC) was mainly present in PM2.5 at all sites, and higher SOC/OC ratios were observed at the urban and suburban site. Indeed, the yearly average SOC in Monte Curcio station has been estimated as 52% of OC in PM2.5 and representing, on average, the major mass contributes to PM2.5 during the cold season. Furthermore, the receptor models used shown differences among the possible sources of carbonaceous aerosol between different seasons. The cold season was characterized by aerosol mainly coming from the long-range transport, while during the warm season it is influenced by local and regional sources. In the following Chapters, the results have been presented and discussed. Università della Calabria. Dipartimento di Fisica. Dottorato di Ricerca in Scienze e Tecnologie Fisiche, Chimiche e dei Materiali in convenzione con il CNR. Ciclo XXXI 2019-10-14T00:00:00Z https://hdl.handle.net/10955/5592 Optimal design and numerical modelling of imperfection sensitive shell structures Liguori, Francesco Salvatore; Garcea, Giovanni; Bartolino, Roberto A brand-new design philosophy tends to harness the load-carrying capacity hidden beyond the onset of buckling phenomena in shell structures. However, when designing in the postbuckling range, among other effects, attention should be given at imperfection sensitivity which may generate catastrophic and unexpected consequences on the optimised structures. Therefore, what would be necessary is an optimisation strategy able to deal with the complex geometries of full-scale structures and, meanwhile, efficiently gather the complexity of their postbuckling response. The aim of this work is to meet this demand by proposing numerical methods that face the problem from different sides, namely the geometrically nonlinear description of the shell, the solution algorithm and the optimisation strategy. As a starting point, a convenient format to describe geometrically nonlinear shell structures is identified in the solid-shell model. On the basis of this model, a discretised environment is constructed using isogeometric analysis (IGA) that, by taking advantage from the high continuity of the interpolation functions, leads to a reduced number of variables with respect to standard finite elements. Afterwards, an IGA-based multimodal Koiter’s method is proposed to solve the geometrically nonlinear problem. This method meets the aforementioned requirements of efficiency, accuracy and is capable of providing information on the worst-case imperfection with no extra computational cost with respect to the analysis of a perfect structure. Additionally, a new strategy for improving the accuracy of the standard version of Koiter’s algorithm in the presence of geometrical imperfections is devised. The last part of the thesis concerns the optimal design of full-scale structures undergoing buckling phenomena. In particular, the design focuses on variable angle tow laminates, namely multi-layered composites in which fibre tows can describe curvilinear paths, thereby providing great stiffness-tailoring capacity. Two optimisation strategies are proposed, both based on the use of Koiter’s method to evaluate the postbuckling response. The first one makes use of a fibre path parameterisation and stochastic Monte Carlo random search as a global optimiser. The second one is based on direct stiffness modelling using lamination parameters as intermediate optimisation variables that lead to a reduction of the nonlinearity of the optimisation problem and remove the direct dependence from the number of layers. Università della Calabria. Dipartimento di Fisica. Dottorato di Ricerca in Scienze e Tecnologie Fisiche, Chimiche e dei Materiali. Ciclo XXXII 2020-02-24T00:00:00Z https://hdl.handle.net/10955/5575 Ion energization in the terrestrial magnetosphere Catapano, Filomena; Zimbardo, Gaetano; Delcourt, Dominique; Carbone, Vincemzo; Retinò, Alessandro Università della Calabria. Dipartimento di Fisica. Scuola di Dottorato in scienze e tecnologie fisiche, chimiche e dei materiali, Ciclo XXXI 2019-10-29T00:00:00Z https://hdl.handle.net/10955/5564 Optical and mechanical responses of liquid crystals under confinement Zheng, Weichao; Cipparrone, Gabriella; Zappone, Bruno The optics of liquid crystals (LCs) lay an important foundation for LC displays and the mechanics of LCs are the backbones of LC elastomers that are promising materials for artificial muscles. Despite broad prospects for applications, it is still a challenge to precisely measure both optics and mechanics at the nanoscale. Here both optical and mechanical responses are simultaneously probed by the Surface Forces Apparatus to understand how optical anisotropies of LCs interact with the birefringence of the mica, and how mechanical anisotropies of LCs interact with anchoring conditions and the confinement. Optically, the birefringence of nematics adds complexities to the two intrinsic birefringent mica surfaces for multiple-beam interference. The phase retardation by multiple birefringent layers is a result of composition by the phase retardation from each layer and their relative intersection angles, which is intuitively understood by the parallelogram rule that is similar to the geometrical composition of forces but with double intersection angle. The simulation based on 4x4 matrices is used to reconstruct the interaction of fringes and to compare the deviation of average wavelengths in the same chromatic order and isotropic wavelengths generated by the average refractive indices. Mechanically, LC behaviours result from the competition among surface anchoring, elasticity of LCs and confinements. During the retraction of surfaces, the neck of cholesteric layers is broken by the innermost circular dislocation defect that serves as a bulk crack with the opening mode of fracture, producing periodical twist transitions and structural forces. During the approach of surfaces, three regimes, constrained, stick-slip and sliding-slip, of cholesteric mechanical windings are observed with the time evolution of the surface anchoring. The onset of three regimes and the retardation of twist transitions results from the balance between the twist elastic torque and the frictional surface torque, namely the anchoring torque and the viscous torque, which is analogous to friction torque in rotational friction. The deviation of the anchoring angle on surfaces provides evidence of interfacial ruptures, with tearing or sliding mode, described by the paradigm of fracture mechanics for the onset from static frictions to kinetic frictions. This thesis sheds light on the understanding of boundary effects on permeative flows, frictions, fractures, yield stress materials, adhesions and biomechanics. Università della Calabria. Dipartimento di Fisica. Dottorato di ricerca in Scienze e Tecnologie Fisiche, chimiche e dei Materiali. Ciclo XXXII 2020-11-25T00:00:00Z