Self-adjointe extensions for symmetric Laplacians on polygons.

By the results contained in the paper by Birman and Skvortsov “On the square summability of the highest derivatives of the solution to the Dirichlet problem in a region with piecewise smooth boundary" the Laplace operator o on a plane curvilinear polygon with domain the Sobolev space H2() and homogeneous Dirichlet boundary conditions is a closed symmetric operator with deficiency indices (n, n), where n is the number of non-convex corners. Therefore on a non-convex polygon, o has infinite self-adjoint extensions. Such extensions have been recently determined by means of Kreǐn's resolvent formula. The purpose of this thesis is to extend such results to the case of different, more general, boundary conditions. In the first part of the thesis we consider the case of mixed Dirichlet-Neumann conditions, thus allowing each side j of the polygon boundary to support either a Dirichlet or a Neumann homogeneous boundary condition. In this case, building on results by Grisvard, while in the pure Neumann case the dimensions of the defect spaces is the same as in the case of the pure Dirichlet case already studied by Birman and Skvortsov, the mixed case has a different behavior, allowing both convex cases and non-convex cases with double vertex contribution. After explicitly characterizing the defect sub- space we determined the self-adjoint extensions by a Kreǐn's resolvent formula proceeding analogously to the pure Dirichlet case, however taking into account the double contribution due to the vertices with mixed boundary conditions. In the second part of the thesis we further extend our analysis by allowing some sides j to support Robin boundary conditions. While this is a deformation of the case considered in the first part, some not completely trivial calculations are necessary in order to get results similar to the ones concerning the mixed Dirichlet-Neumann case. By such calculations, one can recover results anologous to the ones in the first part. However also different behaviors are possible: 1. for any > 0, for any 0 < j < , there are parameter values which give dj = 1; 2. for any x < j (3/2) , x 1.43, there are parameter values which give dj = 2. Moreover, as expected, the dj 's converge to the ones corresponding to the mixed Dirichlet-Neumann case as the j 's converge to either 0 or 1 accordingly to the different possible cases and as in the mixed Dirichlet-Neumann a Kreǐn's formula giving the classification of all the self-adjoint extension is provided in Chapter 4

Self-adjointe extensions for symmetric Laplacians on polygons.

By the results contained in the paper by Birman and Skvortsov \u201cOn the square summability of the highest derivatives of the solution to the Dirichlet problem in a region with piecewise smooth boundary" the Laplace operator \uf044o\uf057 on a plane curvilinear polygon \uf057 with domain the Sobolev space H2(\uf057) and homogeneous Dirichlet boundary conditions is a closed symmetric operator with deficiency indices (n, n), where n is the number of non-convex corners. Therefore on a non-convex polygon, \uf044o\uf057 has infinite self-adjoint extensions. Such extensions have been recently determined by means of Kre\u1d0n's resolvent formula. The purpose of this thesis is to extend such results to the case of different, more general, boundary conditions. In the first part of the thesis we consider the case of mixed Dirichlet-Neumann conditions, thus allowing each side \uf047j of the polygon boundary to support either a Dirichlet or a Neumann homogeneous boundary condition. In this case, building on results by Grisvard, while in the pure Neumann case the dimensions of the defect spaces is the same as in the case of the pure Dirichlet case already studied by Birman and Skvortsov, the mixed case has a different behavior, allowing both convex cases and non-convex cases with double vertex contribution. After explicitly characterizing the defect sub- space we determined the self-adjoint extensions by a Kre\u1d0n's resolvent formula proceeding analogously to the pure Dirichlet case, however taking into account the double contribution due to the vertices with mixed boundary conditions. In the second part of the thesis we further extend our analysis by allowing some sides \uf047j to support Robin boundary conditions. While this is a deformation of the case considered in the first part, some not completely trivial calculations are necessary in order to get results similar to the ones concerning the mixed Dirichlet-Neumann case. By such calculations, one can recover results anologous to the ones in the first part. However also different behaviors are possible: 1. for any \uf065 > 0, for any 0 < \uf077j < \uf065, there are parameter values which give dj = 1; 2. for any x\uf070 < \uf077j \uf0a3 (3/2) \uf070, x \uf040 1.43, there are parameter values which give dj = 2. Moreover, as expected, the dj 's converge to the ones corresponding to the mixed Dirichlet-Neumann case as the \uf061j 's converge to either 0 or 1 accordingly to the different possible cases and as in the mixed Dirichlet-Neumann a Kre\u1d0n's formula giving the classification of all the self-adjoint extension is provided in Chapter 4

Current enhancement through a time dependent constriction in fractional topological insulators

We analyze the backscattering current induced by a time dependent constriction as a tool to probe fractional topological insulators. We demonstrate an enhancement of the total current for a fractional topological insulator induced by the dominant tunneling excitation, contrary to the decreasing present in the integer case for not too strong interactions. This feature allows to unambiguously identify fractional quasiparticles. Furthermore, the dominant tunneling processes, which may involve one or two quasiparticles depending on the interactions, can be clearly determined.Comment: 6 pages, 3 figure

Valutazione e mitigazione dei rischi geo-idrologici derivanti da eventi catastrofici nell'area del Parco Nazionale delle Cinque Terre

This research is included in the field of studies for the evaluation and mitigation of geo-hydrological risks deriving from catastrophic rainfall events conducted in the Cinque Terre National Park area (Liguria) by the Department of Earth Sciences of the Environment and Life of University of Genoa (Italy). This activity made it possible to create and test a mathematical simulation model, in a physically based GIS environment, capable of carrying out 3D slope stability analysis (extended to a spatial domain) according to the pluviometric conditions assumed in the calculations. The experimentation first highlighted the limits of application of the "infinte slope" limit equilibrium method (LEM) used for the spatially 3D slope stability analysis in a GIS computerized geographical environment, also indicating improvement solutions for a more correct use. The input parameters of the soils (geotechnical, hydrogeological and geometric) entering the above mathematical expression were then examined. Their spatial distribution and their relationship with the local geo-morphometric-environmental control factors, on a basin and regional scale, were assessed, as well as their influence on the results was tested by comparing them with real phenomena and geomorphological processes observed in the chosen pilot area (i.e. Vernazza catchment affected on 25/10/2011 by a catastrophic rainfall event). All this experimentation led to the formulation of innovative calculation procedures and methods which were then coded in the Python programming language and developed in the open source QGIS application system in the form of executable "scripts". The predictive ability of the new model was tested in the aforementioned basin, comparing the spatial output data derived from the mathematical simulation with the real distribution of the surface landslides obtained from the analysis of aerial photos and site surveys. In summary, the system showed excellent potential for the preventive localization of soil mobilization phenomena on the slopes of a territorial domain where, in a neighborhood of 25 m away from the focal landslide areas, it was able to identify the 84% of the phenomena that actually occurred with a probability of 93% of the total of the aforementioned areas (with only 7% of false alarms)

Rosa Mucignat, Realism and Space in the Novel, 1795–1869. Imagined Geographies

Review of the book Realism and Space in the Novel, 1795–1869. Imagined Geographies by Rosa Mucignat.Problema a lungo trascurato dalla teoria e dalla critica letteraria, nel corso degli ultimi due decenni il rapporto tra letteratura e spazio è stato assunto, nelle sue varie declinazioni, come consapevole oggetto di indagine, sulla scia dello spatial turn che ha coinvolto i diversi campi del sapere nella seconda metà del Novecento. Lo studio di Rosa Mucignat, pubblicato nel 2013 per Ashgate e riedito nel 2016 da Routledge, si colloca all’interno di questo filone della comparatistica letteraria, occupandosi del ruolo della rappresentazione dello spazio nel romanzo realista

Towards the understanding of the transient behaviour and sources of variability on the process outcomes in inertia friction welding

The difficulty in creating high-quality joints in high-strength/high-temperature materials for aerospace applications fostered the interest in solid-state friction-based joining techniques. Among these, inertia friction welding (IFW) found numerous industrial applications to join axisymmetric components since highly repeatable and fully automated, does not require filler material, shielding gas or vacuum, produces a small heat-affected zone and is not affected by bulk melting. Two workpieces, one rotating and the other stationary, are pressed together and the frictional heat generated at the weld interface causes a localised plastic deformation and their junction. IFW found large interest among researchers and several studies focused on the modelling of the thermo-mechanical evolution of the joint to predict the welding response to changes in process parameters. To cope with the complexity of the phenomena occurring during welding, these models usually rely on simplifications in term of weld geometry, alignment and interaction between the workpieces, machine behaviour, process loads and clamping conditions. In addition, despite many studies showed that dynamic effects can deeply affect the process evolution and the quality of the outcomes in manufacturing processes that share similarities with IFW, no study presented a satisfactory dynamic analysis of IFW. To fill these research gaps, three main objectives were addressed: (i) development of a novel monitoring system for the in-process characterisation of the IFW machine that can act as a diagnostic tool; (ii) investigate the machine response to the process conditions and assess the validity of the axisymmetric assumption conventionally adopted to study IFW; (iii) modelling the effect of the imperfect contact between the workpieces on the pressure distribution at the weld interface and the dynamic behaviour of the system. The monitoring system developed is a significant step forward from the existing systems. In fact, the simultaneous measurement of complementary parameters related to the weld evolution provided a holistic view of the process that proved fundamental in giving physical meaning to the phenomena observed. From data extracted with a set of rundown tests and steel welds, a non-negligible relative runout between the headstock and tailstock was measured. The imperfect contact between the workpieces caused by the runout was correlated to a pressure variation in the circumferential direction at the weld interface and radial non-axisymmetric loads particularly evident in the initial stages of the process. These findings are important because not only differ from the idealised conditions conventionally assumed but also, when combined with the compliance of the machine, can foster a larger misalignment. This research allowed to shed light on the actual interaction between the workpieces and point out that when local phenomena at the weld interface need to be evaluated, the traditional axisymmetric assumption can fail in providing realistic results. In addition, the versatility of the monitoring system makes it ideal as a research platform for further studies and tool to assess the equivalency of different machines

Reluctant Geographer. R.K. Narayan and the World of Malgudi

Il presente lavoro è dedicato allo studio della geografia immaginaria creata dallo scrittore indiano di lingua inglese R.K. Narayan (1906-2001), allo scopo non solo di indagare la relazione che si stabilisce tra spazio, personaggi e racconto, ma anche di rilevare l’interazione tra il mondo narrativo e le rappresentazioni dominanti dello spazio indiano elaborate nel contesto coloniale e postcoloniale. Dopo un primo capitolo di carattere teorico-metodologico (che interroga le principali riflessioni seguite allo "spatial turn" che ha interessato le scienze umane nel corso del Novecento, i concetti fondamentali formulati nell’ambito della teoria dei "fictional worlds", e i più recenti approcci al rapporto tra spazio e letteratura), la ricerca si articola in due ulteriori sezioni, che si rivolgono ai quattordici romanzi dell’autore attraverso una pratica interpretativa di ispirazione geocritica e “spazializzata”. Nel secondo capitolo, che concerne la dimensione “verticale” che si estende dal cronotopo dei romanzi a quello dell’autore e dei lettori, si procede al rilevamento, all’interno del mondo narrativo, di tre macro-paesaggi, successivamente messi a confronto con le rappresentazioni endogene e esogene dello spazio extratestuale; da questo confronto, la cittadina di Malgudi emerge come proposta autoriale di riorganizzazione sociale e urbana dal carattere innovativo e dallo statuto eterotopico, sia in rapporto alla tradizione letteraria dalla quale origina, sia rispetto alle circostanze ambientali dell’India meridionale in cui essa è finzionalmente collocata. Seguendo una dinamica “orizzontale”, il terzo capitolo esamina infine il rapporto tra lo spazio frazionato di Malgudi, i luoghi praticati dai suoi abitanti e la relazione che questi instaurano con il territorio transfrontaliero e con la figura del forestiero; inoltre, al fine di stabilire la misura in cui la natura dello spazio narrativo influisce sulla forma del racconto, si osservano le coincidenze tra il tema dell’incompiutezza che pervade le vicende dei personaggi e la forma aperta dei finali romanzeschi.The purpose of this dissertation is to study the spatial dimension in the novels of Indian English writer R.K. Narayan (1906-2001), in order to evaluate its interaction with dominant ideological representations of the Indian space and shed new light to the relation holding between space, plot and narrative form. The first chapter investigates a range of theoretical and critical sources, including: works addressing the so-called “spatial turn” in the field of humanities; literary theories based on the conceptual framework of possible worlds; and works on the representation of space in fiction. Chapter two and three examine Narayan’s fourteen novels using methodological tools mainly inspired by Westphal’s geocriticism and Friedman’s spatialization. Specifically, the second chapter works at the interface between fiction and reality, disclosing the linkage between the three broad spatial landscapes of the novels and their actual geographical referents. Malgudi thus emerges as a heterotopian site of newness, a “thirdspace” different from colonial and postcolonial conceptions of both city and village in the Indian context. The third chapter assesses the complex geographical dimension of the town and identifies the spatial trajectories covered by the characters, kinetic correlatives for their inner crisis in the face of modernity. Moreover, it explores the connection between narrative space, thematic content and narrative structure (i.e., open endings). This study thus aims at reinstating Narayan’s work out of the precinct of the Indian English novels portraying picturesque, mythologized and hegemonic versions of the national imaginary, into the context of a literature concerned with defining creative, alter-native spaces for the postcolonial nation. In so doing, my research project tests the explanatory possibilities of critical practices in the field of geocriticism on Narayan’s œuvre, contributing to the insertion of his diachronically changing small-town geography in the ever-growing, puzzle-like picture of rural and urban India

Design and manufacture of hybrid aluminum/composite co-cured tubes with viscoelastic interface layer

Abstract The development of hybrid FRP-metal axisymmetric components is a matter of increasing interest in the automotive and aerospace industry for a lightweight design. The hybridization of the technology enables a cost reduction of components production and an increase of mechanical performances together with the ability of machining the surface of the metal tube; this technique guarantees a production improvement since the coating of the tube is no longer required and the pieces can be manufactured in one-step curing cycle. The improvement in bending and torsional stiffness, corrosion resistance and mass reduction of hybrid tubes, in comparison to the single material-built component, has been already demonstrated. A great challenge is to find a way to make hybrid tubes with external metal, avoiding delaminations and detachments that could occur during and after the curing process, due to the different coefficients of thermal expansion between FRP and metal along the axial direction of the tube. For this reason, a component manufacturing process has been studied by experimental and numerical analysis (FEM), including custom process machines and inserting a viscoelastic layer as an interface between the two tubes. Genetic algorithm method has been used to optimize the stacking sequence of a hybrid co-cured metal/composite tube to maximize the flexural stiffness, while applying a strength constraint condition

MiR-33a Controls hMSCS Osteoblast Commitment Modulating the Yap/Taz Expression Through EGFR Signaling Regulation

Mesenchymal stromal cells (hMSCs) display a pleiotropic function in bone regeneration. The signaling involved in osteoblast commitment is still not completely understood, and that determines the failure of current therapies being used. In our recent studies, we identified two miRNAs as regulators of hMSCs osteoblast differentiation driving hypoxia signaling and cytoskeletal reorganization. Other signalings involved in this process are epithelial to mesenchymal transition (EMT) and epidermal growth factor receptor (EGFR) signalings through the regulation of Yes-associated protein (YAP)/PDZ-binding motif (TAZ) expression. In the current study, we investigated the role of miR-33a family as a (i) modulator of YAP/TAZ expression and (ii) a regulator of EGFR signaling during osteoblast commitments. Starting from the observation on hMSCs and primary osteoblast cell lines (Nh-Ost) in which EMT genes and miR-33a displayed a specific expression, we performed a gain and loss of function study with miR-33a-5p and 3p on hMSCs cells and Nh-Ost. After 24 h of transfections, we evaluated the modulation of EMT and osteoblast genes expression by qRT-PCR, Western blot, and Osteoimage assays. Through bioinformatic analysis, we identified YAP as the putative target of miR-33a-3p. Its role was investigated by gain and loss of function studies with miR-33a-3p on hMSCs; qRT-PCR and Western blot analyses were also carried out. Finally, the possible role of EGFR signaling in YAP/TAZ modulation by miR-33a-3p expression was evaluated. Human MSCs were treated with EGF-2 and EGFR inhibitor for different time points, and qRT-PCR and Western blot analyses were performed. The above-mentioned methods revealed a balance between miR-33a-5p and miR-33a-3p expression during hMSCs osteoblast differentiation. The human MSCs phenotype was maintained by miR-33a-5p, while the maintenance of the osteoblast phenotype in the Nh-Ost cell model was permitted by miR-33a-3p expression, which regulated YAP/TAZ through the modulation of EGFR signaling. The inhibition of EGFR blocked the effects of miR-33a-3p on YAP/TAZ modulation, favoring the maintenance of hMSCs in a committed phenotype. A new possible personalized therapeutic approach to bone regeneration was discussed, which might be mediated by customizing delivery of miR-33a in simultaneously targeting EGFR and YAP signaling with combined use of drugs