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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Secessionism on the Rise: Frames, Media Bias, and Strategies of Political Parties in Catalonia (2010-2014) and Scotland (2012-2016)

Tarasov, Andrei 15 May 2023 (has links)
Increasing calls for regional independence are being made in several European countries, and such calls are accompanied by growing public support for secessionism. Over the last decade, Catalonia and Scotland have enjoyed the highest level of political mobilization for secession in the European Union. This research highlights the role of the media in changing attitudes toward independence and studies regionalist parties' strategic choices to understand their electoral success at the regional elections at a time of fast growth of independence sentiments among the population. This study employs different methods: process tracing to focus on the specificities of the independence process in a view to understand how the secessionist agenda transformed the cases; frame analysis of media links the theoretical arguments and their representation in the public discourse; content analysis of regional parties’ electoral programs via Regional Manifesto Project approach helps to define the strategic choices of regionalist parties which brought success to their secessionist agenda at the regional elections; most-similar cases comparative analysis allows to identify commonality and differences between the cases of Catalonia and Scotland. This dissertation uncovers how: the media communicate regionalist arguments to the audience; the media justify independence claims; regionalist parties strategize their secessionist programs. First, a strong pro-region bias is the main feature of media coverage. Secondly, saliency in influenced by the political process as a largely exogeneous factor, but the framing process may also influence reality by giving particular meaning to the major political events and by framing them as political opportunities or as having transformative power. Third, the political competition structure contributes to the strategic choices of political parties. My research contributes to the framing literature by considering the role of diagnosis, prognostic, and motivational framing in the independence discourse. It highlights the extent of pro-region message flows vis-à-vis pro-center and neutral messages in media communication. My analysis contributes to previous research on regionalist parties by making an in-depth case study to differentiate between subsuming and blurring strategies adopted by secessionist actors.
232

How civil conflicts end: Fragmented and competitive armed oppositions and the outcomes of civil conflicts (1989-2017)

Longoni, Gian Marco 02 September 2021 (has links)
In the last three decades, civil conflicts have become more complex and intractable than in the past. One reason for this development is the proliferation of rebel groups within the armed oppositions involved in these conflicts. Today, armed oppositions are more likely to be movements composed of loosely connected or competing rebel groups rather than unitary blocs. Yet, despite their centrality to the dynamics of conflict, different structural characteristics of and competitive and power relations within armed oppositions have not been taken in adequate account as possible predictors of civil conflict outcomes. To further our knowledge and cover this gap in the scholarship, the dissertation investigates how and to what extent the fragmentation, internal competition, and internal power distribution of armed oppositions affect civil conflict termination. The dissertation develops a theory that sees the fragmentation of, a moderate and severe competition, and a dispersed distribution of power within armed oppositions as having an impact on the fighting effectiveness of the rebels, the countereffort of the government, bargaining problems, and the intensity of the conflict. This impact shapes, in turn, how civil conflicts end. This theory is tested with a nested analysis consisting of a large-N and a small-N analysis. Through the large-N analysis, the dissertation demonstrates that, at a general level, these characteristics of armed oppositions indeed affect how civil conflicts end. Through the small-N analysis, the dissertation further illustrates the causal mechanisms linking these characteristics to specific civil conflict outcomes. With these findings, the dissertation makes two important contributions. First, it provides generalisable conclusions that remedy the limited generalisability of the scholarship on the phenomena under study. Second, it provides indications on how to resolve conflicts in which the involved oppositions are fragmented and bedevilled by internal competition, thus helping disentangle the proverbial complexity of multi-party civil conflicts.
233

Phase-field and reduced peridynamic theories for fracture problems

Cavuoto, Riccardo 11 November 2021 (has links)
Several aspects of fracture nucleation and growth in brittle porous ceramics and in thin films are investigated, through analytical, numerical modelling, and experimental validation. A mechanical experimental characterization has been developed for a porous ceramic, namely, a 3D apatite, characterised by an oriented porosity and used for biomedical applications. The ceramic is produced from wood, so that the resulting porosity evidences a multi-scale nature, a feature determining peculiar failure mechanisms and an unprecedented porosity/strength ratio. In particular, the material exhibits an exfoliation-type failure, resulting in a progressive loss in mechanical properties, occurring for compression tests parallel to the grains and for highly slender specimens. Similar cohesive-brittle behaviour is also found when the compression is applied in the direction orthogonal to the porous channels, regardless of the shape ratio of the specimen. An in-depth analysis of this response is performed by means of a phase-field model. After calibrating the model, stress-strain curves and fracturing patterns are accurately reproduced. Furthermore, the effects of multi-scale porosity on mechanical behaviour are determined. Various strategies available in the literature for evaluating the properties of porous materials are compared to the proposed phase-field approach. The results open new possibilities for the prediction and characterization of complex fracturing phenomena occurring in highly porous ceramics, so to facilitate medical applications as structural bone repair. An application of the peridynamic theory of continuum mechanics is developed to obtain a dimensional reduced formulation for the characterisation of through-thickness delamination of plates. The kinematic of the plate is carefully chosen to be composed of an absolutely continuous part and a zone where jumps in the displacements are allowed; in this way, the reduced form of the elastic bond-based peridynamic energy and the reduced Lagrangian are explicitly retrieved in a closed-form. The reduction generates a hierarchy of terms, characterizing the energy stored inside the plane element. A semi-analytical solution, obtained by means of a minimization procedure, is obtained for a test case and compared with finite element simulations. Despite the fact that the numerical model is fully three-dimensional (in other words, it is not reduced), this model leads to the same moment-curvature diagrams and nucleation/growth of the delamination surface found with the reduced formulation. Finally, the convergence of the proposed reduced model to local elastic theory at vanishing internal length is determined, so that a reduced-localized cohesive model for fracture is retrieved.
234

Novel PM Tool Steel with improved hardness and toughness

Deirmina, Faraz January 2017 (has links)
Ultrafine grained (~ 1μm) steels have been the subject of extensive research work during the past years. These steels generally offer interesting perspectives looking for improved mechanical properties. UFG Powder Metallurgy hot work tool steels (HWTS) can be fabricated by high energy mechanical milling (MM) followed by spark plasma sintering (SPS). However, similarly to most UFG and Nano-Crystalline (NC) metals, reduced ductility and toughness result from the early plastic instabilities in these steels. Industrialization of UFG PM Tool Steels requires the application of specific metallurgical tailoring to produce tools with sound mechanical properties or in a more optimistic way, to break the Strength-Toughness “trade-off†in these materials. Among the possible ways proposed to restore ductility and toughness without losing the high strength, “Harmonic microstructure†design seems to be a very promising endeavor in this regard. Harmonic microstructure materials consist of a tunable volume fraction of evenly spaced “isolated†coarse-grained particles (CG) surrounded by a 3D interconnected network of UFG particles. CGs provide ductility and toughness, while high strength is guaranteed by the interconnected network of UFGs. This peculiar design offers an extra work hardening due to the generation of geometrically necessary dislocations at the interfaces of UFGs and confined CGs that are essentially present to accommodate the strain gradient imposed by the inhomogeneous (bimodal grained) microstructure. The first part of this work is devoted to the development of PM tool steels with harmonic microstructure. Due to the difficulties of processing hard tool steel particles according to the methods reported in the literature, an economical, simple alternative approach is also proposed. Near full density “Harmonic structure“ AISI H13 samples were produced using different volume fractions of UFG/NC mechanically milled (MM) and CG as-atomized particles followed by short time (30 min) low-temperature (1100°C) SPS. A combination of high hardness and significantly improved fracture toughness was achieved for the blends containing more that 50% UFG particles. The optimized mechanical properties was achieved by the mixture of 60% UFG particles where the sample showed a hardness near to the value predicted by the rule of mixtures (i.e. 405 HV10 vs. 406 HV10) while apparent fracture toughness (Kapp) was about 10% higher than that of predicted by the same rule (i.e. 52.0 MPa*m1/2 vs. ~47.0 MPa*m1/2). A toughening effect was evidenced for the samples essentially showing harmonic microstructure. Toughening was interpreted to be the result of the deviatory effect of coarse-grained round atomized particles together with energy dissipation by decohesion at the CG/UFG or UFG/UFG interfaces leading to a local drop of the driving force for the crack propagation. The design allowed to easily adjust the strength and toughness to meet the specific application-oriented requirements. The harmonic steel was also subjected to Thermal Fatigue (TF) testing. The preliminary results confirmed that this microstructure combined the beneficial effects of both of its constituents, i.e., the low crack nucleation rate of CG H13 and the low crack propagation rate of UFG H13, thus showing the lowest pyrocracking factor. Moreover, TF crack deflection as an extrinsic toughening mechanism was evidenced in Harmonic Microstructure. The second part of this work deals with the production and characterization of a PM HWTS reinforced with partially stabilized zirconia (PSZ). HWTS composites show improved hardness and remarkable wear resistance but generally also a systematic lower fracture toughness than the base material. Deteriorated toughness in metal matrix composites (MMCs) with a high strength matrix is mainly interpreted as a result of early damage initiation at the hard particles (HPs) or Matrix-HP interface. This damage can be even anticipated in the presence of readily damaged HPs (i.e. processing related flaws). Selection of PSZ as reinforcement was aimed at improving the strength and fracture toughness of the composite by taking advantage of the transformation toughening effect of PSZ. Two different types of PSZ, different volume fractions (10 and 20 vol. %) and sizes of reinforcement were used. Mechanical Alloying (MA) was used to process the composite powders to refine the matrix microstructure and both the matrix and PSZ particle size hence increasing the strength of the PSZ particles according to the Griffith strength formalism, and also to overcome the aggregation problems. Powders were consolidated by (SPS). The influence of processing parameters on density and microstructure was investigated. Short time (30 min) low-temperature (1100°C) consolidation by SPS allowed preserving the refined microstructure while achieving a maximum relative density of 98.6%. Moreover, short time sintering did not allow the extensive formation of thermodynamically plausible reaction products at the PSZ-H13 interface. As a result of dispersion hardening, the hardness of the as-sintered composites (i.e. maximum hardness of ~ 920 HV10) was increased compared to the mechanically milled UFG H13 (i.e. ~ 755 HV10), while in comparison to the as-atomized H13 (i.e. ~ 640 HV10) the improved hardness was ascribed to the synergic effect of dispersion hardening, microstructural refinement and strain hardening induced by MA. In these composites, tempering resistance at 550°C and 650°C was significantly improved due to the dispersion hardening effect. The hot compressive yield strength of the composites at 650°C and 450°C was increased up to 1.8 times the unreinforced UFG H13. t to m transformation during hot compression was evidenced and contributed to the strengthening. The hardness of the composites in heat treated condition (i.e. ~ 600 HV10) was significantly improved compared to that of the unreinforced matrix (i.e. ~ 420 HV10) while the apparent fracture toughness was drastically decreased to half the Kapp of the base material (19 MPa*m1/2 vs. 36 MPa*m1/2). However, the fracture toughness was slightly higher than that of a TiC reinforced H13 (i.e. 17 MPa*m1/2) with the same hardness (i.e. ~ 600 HV10).
235

Essays on Loan Markets in Less-Developed Economies

Yaldiz, Elmas January 2013 (has links)
Financial constraints are one of the most important obstacles for businesses particularly in less–developed and developing economies. Collateral requirements are frequently addressed as one the most important obstacles to starting and running a business especially for small and medium enterprises (SMEs), in these countries. This thesis consists of four empirical papers each corresponding to a chapter on loan markets in less-developed economies. After the introduction chapter, the second chapter investigates both the presence of collateral and the collateral to loan ratios on loans extended to SMEs are examined. The informal credit mostly serves credit-constrained borrowers (mostly SMEs, poor households, informal businesses, borrowers in rural areas that are located far from formal creditors, and people who are not able to meet collateral requirements of formal creditors) in the formal financial markets. The third chapter aims to understand why and to what extend SMEs use informal credit from various sources, moneylenders and family/friends and suppliers/customers as forms of informal credit. The fourth chapter examines the financial constraints faced by female entrepreneurs. The primary data source in these second, third and fourth chapters is the Business Environment and Enterprise Performance Surveys which are mainly based on Eastern European and Central Asian countries. These surveys are joint projects of the European Bank for Reconstruction and Development and the World Bank. Chapter five of this thesis takes a different strand and focuses on the effect of banks’ market power on banks’ risk. The empirical analysis is based on data from Turkish banks and helps to shed light on the relation between market power and financial stability. Finally chapter six highlights the main conclusions and addresses potential future research directions.
236

Modeling of microstructured materials via finite element formulation of strain gradient elasticity

Nardin, Mattia 18 April 2023 (has links)
Through the last decades several nonlocal models of linear elasticity have been introduced as enhancements of the Cauchy-elastic model, often with the purpose of providing an improved mechanical description of solids at the microscale level. Although many efforts have been devoted to the analytical formulation of these advanced constitutive models, a definitive interpretation of the relevant static quantities is still incomplete and Finite Element (FE) solvers are practically unavailable. In this thesis, after providing a mechanical interpretation to the static quantities involved in strain gradient (of Mindlin type) elastic materials, an overview on the possible quadrilateral Hermitian finite elements is given to treat quasi-static plane problems. Beside the classical finite elements inspired by those adopted for modeling Kirchhoff plates, an alternative quadrilateral self-constrained finite element formulated through Lagrange multipliers is also proposed. With reference to a hexagonal lattice structure, for which the equivalent constitutive tensors have been recently derived as closed-form expressions, the developed FE codes are exploited to assess the reliability of modelling lattices through higher-order constitutive equations. These analyses are developed for one-dimensional and two dimensional problems, where the former are considered for both homogeneous layers (with a finite size in one direction) and rod-type structures (with a finite uniform cross section along one direction). It is confirmed that higher-order modelling improves the mechanical description. In particular, the macroscale response is shown to be strongly affected by higher-order contributions in the presence of extreme elastic contrast between microstructural elements. Indeed, in this last case, only higher-order modeling captures a non-null residual stiffness, which vanishes in the framework of classical models. Therefore, higher-order modeling becomes important not only to describe the mechanical response at a microlevel, but also for macrolevel modelling, when extreme mechanical properties are addressed. The presented results pave the way to a refined modelling of architected materials leading to improved design of microstructures displaying innovative mechanical features.
237

Integration in times of crisis. Testing Neofunctional hypotheses: a political economy investigation of crisis-led integration.

Nicoli, Francesco January 2017 (has links)
For more than 10 years, from the launch of the Single Currency to the global financial crisis, the process of deepening European integration stagnated, while emphasis was on widening the borders of the Union. In the wake of the Eurocrisis, however, two phenomena have captured the attention of political economists interested in European integration: the outstanding amount of new institutions, policies, and legislation which have been set in place to counter the crisis, and the rising popular rejection of the very concept of European unity. The old functionalist adage that “integration advances through crises” appears to be, prima facie, corroborated; nevertheless, the dynamics of (political) fragmentation seems to follow a similar pattern, as Postfunctionalists would expect. Two interrelated questions emerge: is the Eurocrisis a true functional crisis? Did the Eurocrisis trigger a new, “transformative” cycle of integration, embodied in its Postfunctional dynamics? In the attempt to address this research puzzle, this doctoral dissertation attempts to operationalize the research problem through six standalone papers clustered in two parts. In addition, Chapter 1 reconstructs the key elements of systemic functionalism, guiding the reader through the theoretical pillars of this work presenting its overall logic – questions, methodologies, and chapter connections. Part One of the dissertation (Chapters 1-4) deals with the fundamental question concerning the Neofunctional nature of the Eurocrisis, attempting to clarify to what extent the Eurocrisis can be really qualified as a “functional crisis”. Chapter 2 provides a comprehensive historical account of functional crises through the first 60 years of European Integration; Chapter 3 provides an econometric test of the endogenous nature of the Eurocrisis; Chapter 4 provides a qualitative assessment of the functional nature of the institutions introduced during the crisis. Part Two of the dissertation (Chapters 5-7) dives into the possible Postfunctional implications of the Eurocrisis, analyzing to what extent the crisis is contributing to create a mobilized European public sphere. In particular, Chapter 5 provides a theoretical analysis of how the crisis is changing the legitimacy of the EU; Chapter 6 provides an econometric assessment of the crisis’ impact on citizens’ preferences for further economic integration; finally, Chapter 7 provides an analysis of the crisis’ impact on the performance of extreme Eurosceptic parties.
238

Experimental and Novel Analytic Results for Couplings in Ordered Submicroscopic Systems: from Optomechanics to Thermomechanics

Piccolo, Valentina January 2019 (has links)
Theoretical modelling of challenging multiscale problems arising in complex (and sometimes bioinspired) solids are presented. Such activities are supported by analytical, numerical and experimental studies. For instance, this is the case for studying the response of hierarchical and nano-composites, nanostructured solid/semi-fluid membranes, polymeric nanocomposites, to electromagnetic, mechanical, thermal, and sometimes biological, electrical, and chemical agents. Such actions are notoriously important for sensors, polymeric films, artificial muscles, cell membranes, metamaterials, hierarchical composite interfaces and other novel class of materials. The main purpose of this project is to make significant advancements in the study of such composites, with a focus on the electromagnetic and mechanical performances of the mentioned structures, with particular regards to novel concept devices for sensing. These latter ones have been studied with different configuration, from 3D colloidal to 2D quasi-hemispherical micro voids elastomeric grating as strain sensors. Exhibited time-rate dependent behavior and structural phenomena induced by the nano/micro-structure and their adaptation to the applied actions, have been explored. Such, and similar, ordered submicroscopic systems undergoing thermal and mechanical stimuli often exhibit an anomalous response. Indeed, they neither follow Fourier’s law for heat transport nor their mechanical time-dependent behavior exhibiting classical hereditariness. Such features are known both for natural and artificial materials, such as bone, lipid membranes, metallic and polymeric “spongy” composites (like foams) and many others. Strong efforts have been made in the last years to scale-up the thermal, mechanical and micro-fluidic properties of such solids, to the extent of understanding their effective bulk and interface features. The analysis of the physical grounds highlighted above has led to findings that allow the describing of those materials’ effective characteristics through their fractional-order response. Fractional-order frameworks have also been employed in analyzing heat transfer to the extent of generalizing the classical Fourier and Cattaneo transport equations and also for studying consolidation phenomenon. Overall, the research outcomes have fulfilled all the research objectives of this thesis thanks to the strong interconnection between several disciplines, ranging from mechanics to physics, from structural health monitoring to chemistry, both from an analytical and numerical point of view to the experimental one.
239

Strategies for cells encapsulation and deposition

Gasperini, Luca January 2013 (has links)
A computer aided manufacturing approach to encapsulate viable mammalian cells in hydrogels and use these capsules as the building blocks for scaffolds. A novel 3D capable contactless bioprinter is presented that encapsulates cells in a alginate hydrogel through an electro hydro dynamic process and deposit these capsules on a specifically engineered substrate manufacturing scaffold without the need for further postprocessing.
240

Nanostructured hybrid organic/inorganic materials by the nanobuilding blocks (NBB) approach

Tagliazucca, Valeria January 2010 (has links)
The thesis work aimed to find appropriate syntheses procedures for the preparation of Nano Building Blocks (NBB) and Nano Particles (NP), starting from organo silanes as molecular precursors, using the Sol-Gel method. NBB were obtained by either non-hydrolytic or in situ water production (ISWP) route, depending on the reactive function’s loading. The obtained NBB were characterised by means of FT-IR, ATR/FT-IR, RAMAN, multinuclear NMR spectroscopies, SEM, N2 physisorption, Thermal analyses (TG/DTA), DSC. NBBs were used to prepare methacrylate-based matrices, which were subsequently exploited in order to produce patternable films by the two photon polymerisation technique (TPP). Epoxy-based matrices were also prepared and the films obtained were patterned by the UV photolithography technique. Both techniques gave high surface resolution patterning. NP were obtained with a modified Stöber method and organosilica NP were obtained. The NP were characterised by FT-IR and NMR spectroscopies. Morphology was observed and sizes calculated using SEM; N2- physisorption and thermal analyses (TG/DTA) were also carried out in order to complete the characterization. DSC measurements were performed on methacryloxypropyl-functionalised NP in order to control the ability to polymerise of the particles. Films of the different organic-modified NP were obtained by spin coating and contact angle measurements were performed. FE-SEM was used in order to observe an eventual change in morphology after thermal treatment under reduced atmosphere. The ability to retain the shape depends on the functional group on the NP. Finally a preliminary study on dye doping was accomplished. The NP were efficiently doped with a fluorescent dye: Rhodamine 6G (R6G). Absorption and emission spectra were recorded with a spectrofluorometer. It is observable that the emission spectra is influenced by the NP’s matrix.

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