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Mixed quasi-étale surfaces and new surfaces of general type
No full textIn this thesis we define and study the mixed quasi-étale surfaces. In particularwe classify all the mixed quasi-étale surfaces whose minimal resolution of the singularities is a regular surface with p_g=0 and K^2>0.
It is a well known fact that each Riemann surface with p_g=0 is isomorphic to P^1.
At the end of XIX century M. Noether conjectured that an analogous statement holds for the surfaces: in modern words, he conjectured that every smooth projective surface with p_g=q=0 be rational.
The first counterexample to this conjecture is due to F. Enriques (1869).
He constructed the so called Enriques surfaces.
The Enriques-Kodaira classification divides compact complex surfaces in four main classes according to their Kodaira dimension k: -oo, 0, 1, 2. A surface is said to be of general type if k=2.
Nowadays this class is much less understood than the other three. The Enriques surfaces have k=0.
The first examples of surfaces of general type with p_g=0 have been constructed in the 30's by L. Campedelli e L. Godeaux.
The idea of Godeaux to construct surfaces was to consider the quotient of simpler surfaces by the free action of a finite group.
In this spirit, Beauville proposed a simple construction of surfaces of general type, considering the quotient of a product of two curves C_1 and C_2 by the free action of a finite group G. Moreover he gave an explicit example with p_g=q=0 considering the quotient of two Fermat curves of degree 5 in P^2.
There is no hope at the moment to achieve a classification of the whole class of the surfaces of general type. Since for a surface in this class the Euler characteristic of the structure sheaf \chi is strictly positive, one could hope that a classification of the boundary case \chi=1 is more affordable.
Some progresses in this direction have been done in the last years through the work of many authors, but this (a priori small) case has proved to be very challenging, and we are still very far from a classification of it. At the same time, this class of surfaces, and in particular the subclass of the surfaces with p_g=0 contains some of the most interesting surfaces of general type.
If S is a surface of general type with \chi=1, which means p_g=q, then p_g = q < 5, and if p_g=q=4, then S is birational to the product of curves of genus 2.
The surfaces with p_g = q = 3 are completely classified.
The cases p_g = q < 3 are still far from being classified.
Generalizing the Beauville example, we can consider the quotient (C_1 x C_2)/G, where the C_i are Riemann surfaces of genus at least two, and G is a finite group.
There are two cases: the mixed case where the action of G exchanges the two factors (and then C_1 = C_2); and the unmixed case where G acts diagonally.
Many authors studied the surfaces birational to a quotient of a product of two curves, mainly in the case of surfaces of general type with \chi=1.
In all these works the authors work either in the unmixed case or in the mixed case under the assumption that the group acts freely.
The main purpose of this thesis is to extend the results and the strategies of the above mentioned papers in the non free mixed case.
Let C be a Riemann surface of genus at least 2, let G be a finite group that acts on C x C with a mixed action, i.e. there exists an element in G that exchanges the two factors. Let G^0 be the index two subgroup of the elements that do not exchange the factors. We say that X=(C x C)/G is a mixed quasi-étale surface if the quotient map C x C -> (C x C)/G has finite branch locus.
We present an algorithm to construct regular surfaces as the minimal resolution of the singularities of mixed quasi-étale surfaces.
We give a complete classification of the regular surfaces with p_g=0 and K^2>0 that arise in this way.
Moreover we show a way to compute the fundamental group of these surfaces and we apply it to the surfaces we construct.
Some of our construction are more interesting than others. We have constructed two numerical Campedelli surfaces (K^2 = 2) with topological fundamental group Z/4Z. Two of our constructions realize surfaces whose topological type was not present in the literature before.
We also have three examples of Q-homology projective planes, and two of them realize new examples of Q-homology projective planes
Exploring Dynamic Constraint Enforcement and Efficiency in Access Control
No full textDynamic constraints such as Separation of Duty (SoD) prevent the possibility of frauds and enable flexible protection of sensitive resources appearing in active contexts. They are enforced in various ways depending on the access control model and the application.
Role based access control (RBAC) employs restrictions on the activation of roles and the exercise of permissions by individuals for enforcing the constraints. However, whether
a constraint specification correctly enforces a given dynamic policy is an open research question. This is mainly due to the nature of the dynamic constraint enforcement: a
constraint satisfied at a state can be violated at a future state as a result of the event sequences occurred in between. Moreover, the support of dynamic enforcement usually imposes low level extensions to the implementation, which in return requires another level of verification. In the approaches that tackle this problem at run-time, efficiency is a key concern.
In this dissertation, we present two approaches for analyzing and enforcing dynamic constraints. The first is employed on-line and is based on software testing features available in software model checkers. The relevant components of an access control system are
modeled as a software and the execution of this software mimics the RBAC run-time. A software model checker is used to check some properties that represent constraint specifications and the actual authorization policies encoded in eXtensible Access Control Language
(XACML). We demonstrate our approach by using an open source software model checker, Java Path Finder (JPF), and its sub-projects for dierent testing scenarios. In this first approach, efficiency is not the main concern but coverage is.
The second approach relies on a propositional satisability (SAT) based run-time procedure to replace the conventional policy evaluation in RBAC systems. Efficiency and flexibility are the prominent features of this approach. Efficiency is obtained by dividing the steps involved in policy evaluation into on-line and off-line. On-line steps correspond to request answering in conventional policy evaluation and have to be done at run-time.
On-line steps can be performed as pre-processing or post-processing of the on-line steps and have no effect on policy evaluation performance. We experimentally show that our approach is efficient and scales well in realistic scenarios.
The final chapter of the thesis presents an extensive study of XACML policy evaluation performance. Policy evaluation corresponds to a function, Eval(Policy,Request), that takes a policy and a request as input, and produces an access control decision. Our experimental results show that the Eval function can create a bottleneck in application
domains where the number of policies and rules is large. We present a list of optimization techniques that can speed up the evaluation performance
Il costituzionalismo e la tutela dei diritti negli ordinamenti islamici
No full textLa tesi analizza in modo critico le peculiarità che caratterizzano il fenomeno costituzionale dell’area arabo-islamica, al fine di comprendere la distanza tra questo specifico sistema giuridico e quello del continente europeo, emblemi di due “mondi” sempre più vicini dal punto dal punto di vista sociale, ma ancora troppo distanti sul piano dei contenuti che le rispettive culture, legali e politiche, impongono sui regimi giuridici adottati. Obiettivo di questo studio è valutare fino a che punto la “dualità” legale su cui gli ordinamenti a maggioranza musulmana si sono costruiti, ravvisabile nella doppia fonte di legittimazione del diritto sacra e secolare, è tale da vincolare la compiutezza della transizione costituzionale qui avviata. La questione è trattata con particolare riguardo alla materia dell’esercizio del potere così come del riconoscimento e della tutela dei diritti, con riferimento ai due casi studio selezionati per il lavoro, Egitto e Turchia, ed alla condizione giuridica delle donne, ambito in cui la tradizione islamica riconosce ancora le principali forme di discriminazione, tanto da “svuotare” di significato il principio di uguaglianza che le Carte dell’area hanno formalmente riconosciuto.
La conoscenza di un ordinamento e dell’insieme delle specificità che lo caratterizzano è la via maestra per avviare un dialogo futuro tra culture, tale da individuare la via per la convergenza dei modelli, che, nel caso di specie, si sostiene passi attraverso un approccio “relativamente laico” al costituzionalismo, capace di garantire la tutela del pluralismo, dei diritti e dell’eguaglianza dei singoli, senza rinunciare al riferimento “morale” a cui questi ordinamenti fanno richiamo
Ultra-Low-Power Vision Systems for Wireless Applications
No full textCustom CMOS vision sensors could offer large opportunities for ultra-low power applications, introducing novel visual computation paradigms, aimed at closing the large gap between vision technology and energy-autonomous sensory systems. Energy-aware vision could offer new opportunities to all those applications, such as security, safety, environmental monitoring and many others, where communication infrastructures and power supply are not available or too expensive to be provided.
This thesis aims at demonstrating this concept, exploiting the potential of an energy-aware vision sensor, developed at FBK, that extracts the spatial contrast and delivers compressed data. As a case study, a custom stereo-vision algorithm has been developed, taking advantage of the sensor characteristics, targeted to a lower complexity and reduced memory with respect to a standard stereo-vision processing. Under specific conditions, the proposed approach has proven to be very promising, although much work has still to be done both at sensor and at processing levels.The last part of this thesis is focused on the improvement of the custom sensor. A novel vision sensor architecture has been developed, which is based on a proprietary algorithm, developed by a partner of FBK and targeted to surveillance applications. The algorithm is based on adaptive temporal contrast extraction and is very suitable to be implemented at chip level. Although the output of the algorithm has strong similarities with the spatial contrast vision sensor, it relies on temporal contrast rather than spatial one, which is much more robust for event detection applications. A first prototype of ultra-low power adaptive temporal contrast vision sensor has been developed and tested
Electrochemical and Photoelectrochemical Study of Conduction modes in Nanostructured TiO2 Films
Get PDFIn this work, two types of nano-structured TiO2 layers were obtained by two different methods.
First, during an exploratory study, a set of nano-columnar TiO2 films and niobium doped TiO2 films was obtained on stainless steel, by a RF reactive sputtering technique. The argon gas is ionized by a high negative voltage applied to the TiO2 target (cathode), and a plasma is created between the cathode and the substrate (anode). Positively charged ions (Ar+) are accelerated toward the TiO2 target (a co-target Nb is placed beside the TiO2 cathode for Nb doping) and their impact sputters atoms off the target. These atoms travel across the chamber and a fraction of them land on stainless steel, resulting in a film TiO2 and Nb-doped film TiO2. With adjusting the RF power applied on the co – target, different concentrations of Nb in the TiO2 film could be controlled. The results of EIS (Electrochemical Impedance Spectroscopy) mainly showed the presence of a barrier layer (junction metal/semiconductor or metal/oxide/semiconductor) between the TiO2 layer and the stainless steel in the absence and presence of niobium. The carrier density is estimated at almost 1018 cm-3.
In the second part of this thesis, two types of TiO2 nano-tubular arrays with nanotubes (NT) aligned perpendicular to the titanium substrate were obtained by anodization of a titanium foil, in two different solutions containing fluoride ions. The NT obtained in a tetrabutylammonium / formamide solution (named: TiO2-NT(TB)) are rough, while the second solution, ethylene glycol , allows to synthesize smoother and denser tubes (named: TiO2-NT(EG)).
All the nanotubular arrays were characterized by EIS and showed in the high frequency range a contribution related to the presence of surface states, and a contribution at low frequencies related to the capacity of the space charge layer. In the dark, in the Na2SO4 solution with neutral pH, the EIS study of TiO2-NT (TB) anatase showed that these two contributions vary with the applied potential. The capacity of surface states varied exponentially in a wide range of potential, but in addition the presence of a localized energy state in the gap could be evidenced. This localized state is the signature of the adsorption of molecular water. After UV exposure during 3h, and back to the dark, the quasi irreversible disappearance of the localized energy states is related to photo-induced adsorbed water dissociation at some sites on the surface of NT. Furthermore, the increase by a factor 112 of the capacity of the space charge layer was observed after UV exposure. This increase can be explained by the photo activation of the surface of NT, which was inactive before UV exposure. This activation is related to the dissociation of adsorbed molecular water and the insertion of hydrogen into the walls of NT.
A geometric model considering the variation of the band bending taking place inside the wall of NT is proposed to replace the classical Mott-Schottky relation, which is only valid for a plate condensator. This model allows understanding the variation of the space charge layer as a function of the applied potential. With this new model, a carrier density of about 1018 cm-3 et 1020 cm-3 respectively before and after UV illumination were determined, confirming that the photo-induced activation of the wall of NT is linked to the phenomenon of doping due to hydrogen insertion.
In the case of TiO2 –NT(EG), the contribution of adsorption of molecular water was not observed. The spectrum of EIS before and after UV exposure did not show a significant change and the capacities of space charge layer after illumination only increased by a factor 8. The simulation with the model shows that the carrier density is about 1020cm-3 before and after illumination. In other words, these tubes of TiO2 –NT(EG), are already activated before illumination and the photo-induced effects are less important compared to the TiO2 –NT(TB) array.
For a better identification of the chemical nature of the surface state in the case of rough tubes of TiO2 –NT(TB), EIS measurements were performed in the same manner, but in acidic (pH=3.5) and basic (pH=12.5) media, in order to compare the behaviour to that observed in the neutral Na2SO4 solution.
In the alkaline electrolyte, the band bending varies only slightly with the applied potential, reflecting a shift of band edge and the filling/emptying of the surface states during polarization. Moreover, the exponential distribution of capacities of surface states is more spread out (850 meV) in alkaline solution than in the neutral solution (257meV), showing clearly the particular role of the OH groups at the surface of the tubes.
In the acidic electrolyte, a phenomenon of diffusion –insertion of protons should be taken into account for interpreting the spectra of EIS. H atoms play the role of electron donors able to increase the carrier density in the wall of the tubes. The comparison between the behaviours in the 3 media clearly associates the surface states to hydroxyl groups.
In the last part of this thesis, experiments were performed on TiO2 –NT(TB) in a NaOH electrolyte, using Intensity Modulated Photocurrent Spectroscopy (IMPS), and the results are discussed in comparison with a thin compact film deposed on a titanium foil par PVD
Roads and Verticality: Strategy and design in mountain landscape
Get PDFThis PhD thesis provides design strategies to control changes produced in mountains places and landscapes following constructions of roads. Strategies are based on the activation of unexpressed potentialities in places, although compromised, characterized by presence of roads. With the term unexpressed potentialities we refer to functions, attitudes, uses which, during the process of road realization, have not found an appropriate design solution. Topic of the thesis is to demonstrate that these design gaps can be properly addressed by an architecture project, obtaining two results: create a link between places, landscapes and roads and consolidate the participation of architecture discipline in a field (roads production) in which, today in Italy, it is less integrated than others.
Changes in mountain landscapes are characterized by morphology and orography of the territory crossed: the factor that most influences in this direction is the verticality of the space.
This specificity is discussed in the thesis through the analysis of road segments, infrastructure nodes or other specific situations, divided according to the topography in which there are: high gradients, slope or bottom of valleys. Specific characteristics which correspond to the three different orographic situations are explained by an interpretative study of the cross section, highlighting the potentiality of the space related with its vertical dimension.
Most study cases belong to the geographical area of Trentino Alto Adige, an Italian region characterized by mountain landscapes. Some study cases are taken from other Italian regions or known experiences of the international context.
The proposed strategies are developed through study of architectural projects, joined by devices that interpret the vertical (overlapping, slope and difference in altitude) of the spaces, reproposable in cases of mountain road. All strategies can be applied at any step of road production, from concept to design to construction. In addition, and we assume that this is the most frequent case, can be applied ex post, when the road is built, intervening to change situations already in place
Innovative methods for the reconstruction of new generation satellite remote sensing images
No full textRemote sensing satellites have demonstrated to be a helpful instrument. Indeed, satellite images have been successfully exploited to deal with several applications including environmental monitoring and prevention of natural disasters. In the last years, the increasing of the availability of very high spatial resolution (VHR) remote sensing images resulted in new potentially relevant applications related to land cover control and environmental management. In particular, optical sensors may suffer from the presence of clouds and/or of shadows. This involves the problem of missing data, which may result in an important problem especially in the case of VHR images.
In this thesis, new methodologies of detection and reconstruction of missing data region in VHR images are proposed and applied on areas contaminated by the presence of clouds and/or shadows. In particular, the proposed methodological contributions include: i) a multiresolution inpainting strategy to reconstruct cloud-contaminated images; ii) a new combination of radiometric information and spatial position information in two specific kernels to perform a better reconstruction of cloud-contaminated regions by adopting a support vector regression (SVR) method; iii) the exploitation of compressive sensing theory adopting three different strategies (orthogonal matching pursuit, basis pursuit and a genetic algorithm solution) for the reconstruction of cloud-contaminated images; iv) a complete processing chain which exploits a support vector machine (SVM) classification and morphological filters for the detection and a linear regression for the reconstruction of specific shadow areas; and v) several evaluation criteria capable to assess the reconstructability of shadow areas. All of them are specifically developed to work with VHR images.
Experimental results conducted on real data are reported in order to show and confirm the validity of all the proposed methods. They all suggest that, despite the complexity of the problems, it is possible to recover in a good way missing areas obscured by clouds or shadows
L'intertextualité comme procédé dramaturgique dans Hécube et Les Troyennes d'Euripide
No full textThis study investigates the question of how intertextuality is used as a dramaturgical device in Euripides’ Hecuba and Troades. The intertexts considered here are the Homeric epics and Aeschylus’ Agamemnon.
After a presentation of the problems raised by the use of the notion of “intertextuality” in the field of ancient Greek literature, and more specifically Greek theatre, the two dramas are each studied in depth.
Chapters I to IV are concerned with the stasima of these plays and raise the question of the specific manner in which intertextuality is inscribed in the lyrical language of the chorus. The stasima are considered from a global perspective in order to highlight their function as a guiding thread running through each drama.
The following chapters deal with extended portions of Hecuba and Troades. The use of intertextuality in the representation of the sacrifice of Polyxena is studied in Chapter V, whereas Chapter VI deals with the double intertextual allusion (both to the Odyssey and to the Agamemnon) engaged in by Euripides in his representation of Hecuba’s revenge (in Hecuba).
Chapters VII and VIII are about the Troades, focusing firstly on the Cassandra scene, which is compared with the Cassandra scene in Aeschylus’ Agamemnon, reworked here by Euripides. Secondly there is the scene involving Helen, where Euripides builds up the tensions of the agôn by basing it on a precise passage of Iliad III – which, in the light of the positions taken by the two characters, he purposely renders even more problematic than it is in Homer.
The conclusion presents the results of this inquiry into the functioning and possible purposes of intertextuality in Greek tragedy
Dealing with Semantic Heterogeneity in Classifications
No full textMany projects have dealt with mappings between classifications both in computer science and digital library communities. The adopted solutions range from fully manual to fully automatic approaches. Manual approaches are very precise, but automation becomes unavoidable when classifications contain thousands of nodes with millions of candidate correspondences. As fun-damental preliminary step towards automation, S-Match converts classifications into formal on-tologies, i.e. lightweight ontologies. Despite many solutions to the problem have been offered, with S-Match representing a state of the art matcher with good accuracy and run-time perfor-mance, there are still several open problems. In particular, the problems addressed in this thesis include: (a) Run-time performance. Due to the high number of calls to the SAT reasoning engine, semantic matching may require exponential time; (b) Maintenance. Current matching tools offer poor support to users for the process of creation, validation and maintenance of the correspond-ences; (c) Lack of background knowledge. The lack of domain specific background knowledge is one important cause of low recall. As significant progress to (a) and (b), we describe MinSMatch, a semantic matching tool we developed evolving S-Match that computes the minimal mapping between two lightweight ontologies. The minimal mapping is that minimal subset of correspondences such that all the others can be efficiently computed from them and are therefore said to be redundant. We provide a formal definition of minimal and, dually, redundant map-pings, evidence of the fact that the minimal mapping always exists and it is unique and a correct and complete algorithm for computing it. Our experiments demonstrate a substantial improve-ment in run-time. Based on this, we also developed a method to support users in the validation task that allows saving up to 99% of the time. We address problem (c) by creating and by making use of an extensible diversity-aware knowledge base providing a continuously growing quantity of properly organized knowledge. Our approach is centered on the fundamental notions of domain and context. Domains, developed by adapting the faceted approach from library science, are the main means by which diversity is captured and allow scaling as with them it is possible to add new knowledge as needed. Context allows a better disambiguation of the terms used and re-ducing the complexity of reasoning at run-time. As proof of the applicability of the approach, we developed the Space domain and applied it in the Semantic Geo-Catalogue (SGC) project
Helsinki disentangled (1973-75): West Germany, the Netherlands, the EPC and the principle of the protection of human rights
No full textThis work is situated at the intersection between the historiographies on European integration, the Cold War, and human rights, and scrutinizes the Conference on Security and Cooperation in Europe (CSCE, 1973-75) from the specific angle of the history of European integration. According to a narrative that has become standard in historiography, the EC countries achieved remarkable cohesion in the CSCE process through the newly-created European Political Cooperation (EPC), an informal intergovernmental mechanism set up in 1970.
This thesis argues instead that the EPC was less successful in achieving cohesion and a common position of the ECâs member states than has been claimed so far. Human rights was a divisive issue, and ideas of détente differed widely in the West European camp. The thesis emphasizes the political fault lines among the nine member states, and in particular between West Germany and the Netherlands, two countries that stand out for their quite different negotiating style and equally different political goals. The author argues that while West German and Dutch foreign policy eventually achieved a degree of coordination, common understanding was lacking. West Germany and the Netherlands often fought for very different goals. In the case of West Germany, its key goal at the CSCE was human relief, a long-standing goal of West German policy that had marked Ostpolitik since its very beginnings: the conspicuous sufferings of German people and the personal experiences of German leaders had a powerful impact on West German foreign policy. The Dutch by contrast thought of human rights as a principle of international law to be used in an ideological confrontation. The work emphasizes the multifaceted nature of the domestic discussions about human rights at the time, points out that the very idea of human rights needs to be historicized, and highlights the role played by domestic influences and by individuals, with a specific focus on domestic political actors, like the Dutch foreign minister Max van der Stoel, who emerges as a staunch â and relatively poorly known - key-advocate of human rights