Dipartimento di Fisica - Tesi di Dottorato

Permanent URI for this collectionhttps://lisa.unical.it/handle/10955/35

Questa collezione raccoglie le Tesi di Dottorato afferenti al Dipartimento di Fisica dell'Università della Calabria.

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    Black Hole Dynamics from Vacuum Spacetime to Surrounding Turbulent Plasmas
    (Università della Calabria, 2025-04-28) Imbrogno, Mario; Cipparrone, Gabriella; Servidio, Sergio
    The nonlinear behavior of black holes, governed by the Einstein field equations, cou- pled with the turbulent dynamics of plasma in relativistic regimes, constitutes the cornerstone of both general relativity and high-energy astrophysics. In this thesis, we employ advanced numerical simulations and cutting-edge techniques in numer- ical relativity and plasma physics to investigate these extreme systems and probe the intricate nonlinear interactions between black holes and relativistic plasmas. The investigation begins with simulations of black hole systems in vacuum space- times, using the 3+1 formalism to explore both binary and multi-body interactions. The three-body problem is examined by transitioning from Newtonian mechanics to general relativity. In the classical framework, the interactions are modeled in a typ- ically chaotic configuration, identifying extreme gravitational interactions (EGIs) as transients characterized by complex and highly energetic dynamics. We concentrate on selecting these EGIs as initial data for the general relativistic case, performing a series of numerical relativity simulations to establish a comprehensive set of cases. The analysis of three-body black hole dynamics reveals intricate gravitational wave- forms, which are crucial for interpreting observational data and refining detection strategies. Within the 3+1 framework and in the presence of matter, a novel loga- rithmic formulation has been developed to enhance numerical stability in scenarios characterized by steep gradients, such as those found in stellar atmospheres. Pre- liminary applications of this formulation include the propagation of classical sound waves and the study of the Kelvin-Helmholtz instability. In the second part, we perform simulations using the BHAC code within theGRMHD framework to model the accreting plasma flow near black holes. These simulations provide significant insights into the behavior of matter in magnetically dominated regions, such as those surrounding Sgr A* and M87*, bridging theoretical models with observational data and offering new perspectives on high-energy astrophysi- cal processes, including jet formation, accretion mechanisms, and magnetic recon- nection. Our results demonstrate the presence of a strong turbulent cascade that transfers energy from large (inhomogeneous) accretion scales down to smaller (ho- mogeneous) lengths. This process, therefore, may conDue to the cross-scale cascade, our focus ultimately shifts to local plasma be- havior, where we explore fully kinetic plasma turbulence through high-resolution, direct numerical simulations based on the PIC method. These simulations incor- porate realistic mass ratios between particle species, allowing for a detailed exam- ination of particle acceleration mechanisms within plasma turbulence. We observe the formation of long-lived vortices with profiles typical of macroscopic, magneti- cally dominated force-free states. Inspired by the Harris pinch model for inhomo- geneous equilibria, we describe these metastable solutions using a self-consistent kinetic model in a cylindrical coordinate system centered on a representative vortex, starting from an explicit form of the particle velocity distribution function. Turbu- lence is mediated by these long-lived structures, accompanied by transients in which such vortices merge and self-similarly form new metastable equilibria. For future re- search, we plan to broaden the scope of this investigation by including positrons as a third particle species, enabling a more comprehensive analysis of multi-species plasma behavior and elucidating the dominant processes governing energy transfer, particle energization, and the resulting electromagnetic emissions.tinue to kinetic scales, where collisionless, relativistic physics becomes dominant.
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    Raman spectroscopic characterization of thin films to be used in Electrochromic Devices
    (Università della Calabria, 2023-05-16) Nucera, Antonello; Cipparrone, Gabriella; Castriota, Marco
    Electrochromism is related to the optical properties of some materials when subject to an electric potential. These properties are exploited in special electrochromic devices formed by these materials and others that together provide for their implementation and operation. In recent years, the overall performance of these devices has increased considerably, although further improvements are currently being studied by the scientific community. The aim of this thesis work has been the study of materials for potential use in electrochromic devices, the creation of an electrochromic device capable of modulating solar radiation as well as a part of the heat associated with it and its complete characterization. The instrumental analyses used for the characterization of the various materials and devices were Raman spectroscopy, Cyclic Voltammetry and UV-visible spectroscopy. Raman spectroscopy is a formidable investigation technique because it is non-destructive and it can reveal a lot of structural chemical and physical information from the samples analysed. In recent years it has gained great importance in the analysis of biological samples because of the development of the Raman technique named as SERS (Surface Enhanced Raman Spectroscopy). The results of the thesis are presented in different chapters that deal with the theoretical concepts related to electrochromism (chapters 1 and 2) and those related to the investigation techniques used during the course (chapter 3). The results of the analyses are set out in Chapter 4. Chapter 5 presents the conclusions and future perspectives. In the first part of Chapter 4, Raman analyses have been conducted on different polymeric materials such as polymethylmethacrylates (PMMA) and polyethylene oxide (PEO) as well as natural polymers such as chitosan for potential operational (the former) and environmental benefits (the second) that these can bring in the realization of an electrochromic device. Polyelectrolyte materials can be used as an electrolyte layer in electrochromic device, in this thesis work the SERS effect of polyelectrolyte layers on the Raman spectrum of acetic acid has been observed. Chitosan films doped with zinc complex have been analysed by Raman spectroscopy. The interpretation of the results obtained made it possible to establish that the interaction between the natural polymer and the zinc complex takes place at the level of the N-H and O-H groups. Bipyridine ligands are often used in the formation of metallopolymer molecules with electrochromic properties. In this thesis, the SERS effect of a gold plate on the Raman spectra of bipyridine samples has been studied, showing an interesting improvement of bipyridine Raman signals. Graphite and graphene can improve the conductivity of electrochromic devices by improving their performance. In this thesis work, through the use of Raman spectroscopy, the structural characteristics of functionalized graphite and graphene nanoplates have been shown. The SERS effect of Ag thin layer on the Raman spectra of deposited 6G rhodamine has been demonstrated. The Raman characterization of TiO2 films has been shown. In the second part of Chapter 4, electrochromic devices consisting of an electrochromic solution of viologen and ferrocene to which glycerolate bisphenol A has been added in certain proportions have been developed. The optical properties of the devices have been studied with UV-vis-NIR spectroscopy before and after polymerization induced by exposure to UV light. In particular, the analysis of the transmission properties of the devices in the coloured and transparent states (ON and OFF states, respectively) have been shown. In addition, the electrochemical properties of the devices have been studied by means of cyclic voltammetry measurements that show the differences between the ON and OFF states of the devices. Concluding remarks have been made in the last chapter of the thesis, with research on electrochromic technology continuing with further structural analysis of materials.
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    Innovative hybrid-composite membranes based on 2D materials for desalination of saline waters
    (Università della Calabria, 2023-01-20) Frappa, Mirko; Cipparrone, Gabriella; Gugliuzza, Annarosa; Drioli, Enrico
    Water is essential for the life of all living organisms and its conservation and responsible use is one of the global challenges that humanity will have to face in the near future. The recovery of water and salts from the sea represents the main source and today represents an important opportunity within the logic of sustainable water management. Water reuse is the use of treated wastewater for beneficial purposes, which increases a community's available water supply and makes it more reliable, especially in times of drought. Access to clean water resources, however, requires urgent economic and ecological needs on a global level, urging more efficient technologies. Indeed, due to its energy consumption, seawater desalination is generally an expensive process. Currently, technological progress has led to the development of a series of technologies that make the wastewater treatment process increasingly concrete and efficient. Among them, membrane processes represent a valid alternative thanks to the numerous advantages offered such as low environmental impact, high efficiency and sufficient related costs. Research, respecting the environment, is increasingly focused on improving these techniques in terms of production and costs. In this sense, two eco-sustainable techniques have been developed based on the use of porous and hydrophobic membranes: membrane distillation (MD) and membrane crystallization (MCr). These two technologies do not yet have the production capacity to replace reverse osmosis, which is currently the leading process for desalination. However, integrating these processes with RO could increase the recovery factor close to one hundred percent. In fact, in addition to increasing the production of clean water, it is also possible to recover the salts dissolved in sea water thanks to the MCr process. Hence the basic idea of this work where we wanted to introduce several innovative materials in membrane systems with the aim of improving and optimizing the MD / MCr processes. In this case, three classes of materials have been taken into consideration for the preparation of the polymeric membranes. The first material is Graphene consisting of a monatomic layer of carbon atoms. The second type of material proposed is part of the family of transition metals and are Monolayer dicalcogenides. Among the dicalcogenides, Bismuth Tellurium and metal organic frameworks (MOF) have been taken in consideration. Graphene and dicalcogenated metals have been exfoliated by the WET-Jet Milling technique and supplied by BeDimensional S.P.A. while the Zirconium based MOF [MIL-140B] has been provided by Nanjing Tech University (China). The materials have been used for the preparation of PVDF-based membranes, characterized and tested in MD and MCr in order to evaluate the correlated effects on productivity and selectivity.
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    Scaling properties and multifractal dynamic of greenhouses gases
    (Università della Calabria, 2023-07-11) Tripicchio, Giovanni; Cipparrone, Gabriella; Sprovieri, Francesca; Carbone, Francesco
    This work presents an extensive analysis of scaling properties of the intra-day components that constitute the temporal behaviour of GHG tracers (CO2, CH4 and CO), recorded during the period from 2015 to 2017 at Monte Curcio Observatory. Through the application of Empirical Mode Decomposition and Mutual Information methods, fast and slow components have been highlighted, which characterize the dynamics of GHG tracers at small and large scales, respectively. From analyses of these two components, it was possible to investigate the scaling properties related to the Hurst coe cient. The results highlight di erent local properties that characterize the uctuations of the two components, particularly according to the scale and time period under investigation. The discrepancy of scaling exponents suggests that the dynamics of slow components are related to di erent phenomena that contribute more energy (force) to the process, while fast components are governed by small-scale turbulent processes. The Hurst coe cient of slow component for CO2 exhibits a large-scale temporal modulation, which may be related to the main environmental drivers responsible for dynamics of CO2 concentrations. In this context, the photosynthesis-respiration process has been considered, through the analysis of the vegetation indexes EVI and NDVI, and the variation of the Planetary Boundary Layer (PBL) height. The high correlation value measured between the monthly variations of these two indexes and the variation of Hs coe cient suggests that these phenomena played a primary role in de ning the intra-day fractal properties of the CO2. The results obtained are useful to the parametrization of sub-grid processes in atmosphericclimatic models, while providing a temporal evolution of the emission maps of the analyzed GHG tracers.
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    Hunting stabilization effects of the high-energy resummation at the LHC
    (Università della Calabria, 2022-03-14) Mohammed, Maher Abdelrahim Mohammed; Cipparrone, Gabriella; Papa, Alessandro
    Studying semi-hard processes in the large center-of-mass energy limit gives us an opportunity to further test perturbative QCD in an unexplored kinematical configuration, contributing to a better understanding of the dynamics of strong interactions. For semi-hard reactions in kinematics at large center-of-mass energy ps, the BFKL resummation of energy logarithms comes into play, since large energy logarithms compensate the smallness of QCD coupling as and must therefore be accounted for to all perturbative orders. Tracing the path toward performing precision calculations via BFKL resummation of high-energy logarithms, in this thesis we present phenomenological analyses for distinct inclusive processes, highlighting the recognized problem of instabilities under higher-order corrections and energy-scales variations, that would abort any possibility to investigate semi-hard reactions with high-precision at natural energy-scales. At the same time, we present new reactions that seem to act as fair stabilizers of the highenergy series. First, the inclusive production at the LHC of a charged light hadron and of a jet, featuring a wide separation in rapidity, is presented making use of optimization methods to fix energy-scale. We report some predictions, tailored on the CMS and CASTOR acceptances, for the cross section averaged over the azimuthal angle between the identified jet and hadron and for azimuthal correlations. Then, we propose as a novel probe channel for the manifestation of the BFKL dynamics, the inclusive hadroproduction of a Higgs boson and of a jet, featuring large transverse momenta and well separated in rapidity. We present predictions for azimuthal Higgs-jet correlations and other observables, to be possibly compared with typical experimental analyses at the LHC. Finlay, we propose the inclusive semi-hard production, in proton-proton collisions, of two bottom-flavored hadrons, as well as of a single bottom-flavored hadron accompanied by a light jet, as novel channels for targeting stabilization effects of the high-energy resummation under higher-order corrections. Moreover, we propose the study of double differential distributions in the transverse momenta of the two finalstate particles as a common basis to investigate the interplay of different resummation approaches.
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    Multifunctional mesogenic microparticles: optomechanics and photonics
    (Università della Calabria, 2023-02-15) Pellizzi, Nicola; Cipparrone, Gabriella; Mazzulla, Alfredo; Pagliusi, Pasquale
    The development of efficient and cost-effective micromachines is a challenge for applied and fundamental science given their wide fields of interest. Light has become a suitable tool to move small objects in a non-contact way, given its capabilities in exerting forces and torques. However, when complex machining is required, the assembly of micro-objects with proper architecture able to play a specific role in the dynamics, is extremely helpful. To this aim, the design of opto-responsive micrometric devices was carried out by exploiting the dielectric-metal coupling. Such structures are able to couple with different forces carried by the optical field, and selectively acquire orbital and rotational momentum, depending on the presence of a raspberry-like gold nanoparticles shell. Furthermore, the particles can have a chiral supramolecular structure due to the cholesteric nature of the mesogenic precursor. This allows the study of collective optomechanical phenomena and to the use of these as laser resonance cavities. The study, therefore, of how these microparticles under appropriate structures of the field are able to couple with it, giving rise to the birth of collective phenomena of angular momentum transfer. The addition of fluorescent molecules in the polymeric core enables laser emission and demonstrate higher resistance to degradation of the core-shell particles, which represents the current limit of similar organic microresonators. Bragg and whispering gallery emissive modes were observed and an increase in operating cycles was obtained. 6 The thesis is completed with a detailed part concerning the production protocol and variants useful for obtaining versatile structures in both photonic and optomechanical fields. A profound characterization was carried out in order to appropriately exploit the different properties offered by this technology.
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    Chemical characterization of atmospheric aerosols from natural and anthropogenic sources in the Mediterranean area
    (Università della Calabria, 2019-10-14) 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.
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    Optimal design and numerical modelling of imperfection sensitive shell structures
    (Università della Calabria, 2020-02-24) 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.
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    Ion energization in the terrestrial magnetosphere
    (Università della Calabria, 2019-10-29) Catapano, Filomena; Zimbardo, Gaetano; Delcourt, Dominique; Carbone, Vincemzo; Retinò, Alessandro
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    Optical and mechanical responses of liquid crystals under confinement
    (Università della Calabria, 2020-11-25) 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.