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Innovative Techniques for Antenna Synthesis in Modern Wireless Communication Systems
No full textThis thesis deals with the study and development of innovative techniques for the synthesis of antennas able to fulfill the tight requirements of modern wireless communication systems. By exploiting the advantages given by the use of geometries based on spline and fractal shapes, the aim of the proposed synthesis techniques is the design of small Ultra-Wideband (UWB) and multi-band antennas. The synthesis of UWB antennas is carried out by means of two different approaches which consider the antenna characterization in the frequency and in the time domain, respectively. The antenna structure is based on a spline representation which allows the description of complex contour by means of a limited set of control parameters. Regarding the synthesis of multi-band antennas, an approach based on the perturbation of fractal geometries is proposed. The perturbation breaks the fixed relationships among resonances typical of standard fractal geometries, allowing the use of fractal antennas for practical applications. By exploiting the knowledge acquired during the synthesis of UWB spline-shaped antennas, a preliminary assessment of an approach for the design of multi-band antennas with spline-based geometries is also reported. Finally, the integration of UWB antennas in array layouts is addressed. Towards this end, first a methodology for the design of aperiodic UWB linear arrays populated by spline-shaped radiating elements is proposed. Successively, the design of an array of UWB elements for imaging applications is described. In order to assess the effectiveness as well as the reliability of the proposed antenna synthesis approaches, both numerical and experimental results are reported
Gli "Statuta Almae Urbis": il diritto municipale a Roma nella seconda metà del XVI secolo.
Get PDFGli statuti municipali della città di Roma, riformati nel 1580, rappresentano il fulcro attorno al quale è stata condotta la ricerca. Dopo una breve riflessione sul mancato interesse suscitato per più secoli da questa "forma iuris" negli storici, l'attenzione si è spostata sull'oggetto 'statuti'. La particolarità della città e i diversi fori di competenza dei numerosi tribunali romani sono serviti a comprendere in parte il perché di un nuovo "corpus" normativo. Ma un'analisi più dettagliata di coloro che furono gli artefici della riforma ha permesso di chiarire numerosi aspetti di un processo durato più di cinquant'anni. L'emergere alla fine di una figura, un giurista romano, Luca Peto, che si dedicò alla riforma istituzionale del comune di Roma e al rinnovamento degli statuti, ha fatto sì che anche alcuni passaggi fondamentali avvenuti durante la riforma uscissero dall'ombra. Ciò ha reso più comprensibile la distribuzione della materia statutaria nei libri del "corpus", mettendo in evidenza anche una continuità con il passato che sembrava scomparsa. Gli "statuta Urbis" anche dopo l'approvazione di Gregorio XIII continuarono ad essere interpretati in maniera differente dai giurisperiti. Ne conseguì un dibattito che rimase vivo fino alla metà del Settecento
Improving the consideration of cumulative effects in Strategic Environmental Assessment of spatial plans: A case study in the peri-urban region of Milan
No full textMost of the significant changes on the environment have resulted from individually minor but collectively significant human actions and decisions. This kind of consequences has been defined Cumulative Effects (CE) and their systematic consideration can be attributed to the scientific basis and institutional context of Environmental Assessment (EA) theory and practice. However, although Strategic Environmental Assessment (SEA) has been largely recognised as one of the most appropriate procedure to support spatial and land use plans in managing CE; the advancement in integrating the assessment of CE into SEA practice has been often stated slow to evolve, suggesting a gap between SEA theory and practice in treating cumulative effects and confirming that further investigation on this subject is required.
This research aimed to propose and apply a methodological approach to improve the consideration of CE in SEA of spatial plans, by focusing on the Italian spatial planning system and urban regions. It was developed according to the main findings and shortcomings emerging from the academic literature and the exploration of SEA practice through: an international expert survey; a systematic review of SEA documents; and a couple of real-life SEA case studies following during the research period. Among the most important were: the lack of scoping of relevant resources (or Valued Ecosystem Component); the scarce exploration of future decisions and consequences; and the requirement of a more evidence-based assessment of CE.
The methodological approach was then developed for SEA of regional spatial plans, consisting of four main tasks: the selection of significant valued resources; the identification of other relevant decisions (projects, plans and policies) which together with the spatial plan could contribute to CE; the generation of land use scenarios; and the prediction of CE through indicators.
Then, the methodological approach was tested in a case study selected within the peri-urban region of Milan, representing one of the most urbanised and industrialised part of Italy, with significant urban pressures on existing protected areas and remaining rural patches. Firstly, the regional green infrastructure was selected as the most important regional valued resource (or VEC); then, three important ‘future policies’ were identified (i.e. highway transportation corridor, protected areas conservation plans, and rural policies). Subsequently, a set of future land use scenarios were developed and made spatially explicit, starting from a couple of regional land use maps. Then, the regional cumulative effects on the selected valued resource (e.g. habitat fragmentation, surface runoff, etc.) were assessed against a range of future conditions through a core set of indicators, mainly quantitative and spatially explicit, simulating relevant environmental processes, such as hydrological cycle, local surface temperature, ecological connectivity. They were all selected and computed starting from land cover data, allowing the combined effects to be quantified and land use scenarios to be compared. The results mainly showed that the method provided an applicable means to, firstly, transfer policies and decisions into maps, and then, predict their combined effects on selected VEC. Moreover, it can be straightforwardly included in SEA of regional spatial plans in order to support a more evidence-based CE analysis, by adding spatial thinking to decision-makers and improving the understanding and the perception of the cumulative consequences of their “minor” decisions under uncertain future policy contexts
1D Mobile-Bed Model for Uniform and Non-Uniform Sediment Transport in Free Surface Flows
No full textIn the last fifty years, new engineering problems, connected with gravel extraction, installation of dams and disposal of mine waste into rivers, have risen to the extent that sediment transport modeling is assuming a key role in realistic river hydraulic simulations. Floods, meandering, sediment load computation, river bed aggradation or degradation, channel design and navigation are some of the problems concerning the sediment transport in rivers. The description of the river dynamics and morphodynamics is then relevant and a clearer analysis of the existing models is necessary.
Standard mathematical models for sediment transport in rivers employ simplified continuity equations. These equations, essentially mono-phase model, are only valid for low sediment concentrations and Froude number. A rather complete approach, quasi-two phase model, is presented and thanks to the coupling between morphodynamics and hydrodynamics it can be applied also to higher concentration regimes and Froude number.
Finally, numerical simulation of river dynamics has to consider the non-uniformity of sediments.
In this work, a more traditional scheme, in which the grain size distribution curve is divided into a discrete number of classes and the transport is calculated for each class, is compared with a novel formulation. This method is based on the series expansion of sediment transport formulas. In conclusion, the algorithm can be integrated with a description of grain sorting and non-uniform sediment transport in order to better describe the river dynamics and morphology
Ultracold Bosonic Gases: Superfluidity and Quantum Interferometry
No full textThe aims of this dissertation are twofold. Firstly, the study of superfluidity, presented in the first part, has more a fundational character, since we investigate some well known problems, already raised in the context of superfluid helium, in order to gain a deeper understanding, by exploiting the cleannes of dilute BECs systems, as well as analyzing the new features emerging from the unique dilute BECs properties. We study the BEC flow through weak-links, first analyzing the various regimes of transport by the current-phase relation and the Josephson plasma oscillations, and then turning to the superfluid instability, determining critical velocities and examining the dissipation dynamics in different geometries and dimensionalities. Secondly, the analysis of quantum interferometry, given in the second part, has instead a more technological character, since we propose two possible implementation of interferometric protocols in double-well traps, with application to the measurement of weak-forces, and study their sensitivity in detail, especially in relation to its possible quantum enhancement
Planning African rural towns: the case of Caia and Sena, Mozambique.
No full textOver the last few years, academic research and international aid organizations have been underlining the important role that the small towns of Sub-Saharan Africa have in promoting development in the surrounding rural areas and in reversing the polarization trend of major urban centers. Nevertheless, defining the particular characteristics of these towns—which the majority of African population lives in or refers to—and analyzing the relevant transformations that they are experiencing are still unsolved issues. Moreover, until now, policies, programs and projects related to African urban development have focused mainly on major urban centers, while small towns have an almost complete lack of planning on how to accommodate people coming from the surrounding rural areas and how to provide them with services.
The aim of the research is to define a conceptual and methodological framework to support the spatial planning activity of local administrators and technicians in Mozambique small towns.
To reach the objective of a spatial planning process that results from the thorough comprehension of this particular typology of human settlement, the research was based mainly on the analysis of case studies: Caia and Sena, two vilas rurales situated in a rural district in central Mozambique along the Zambezi River. Together with literature review, a field research was conducted by the author in the district of Caia that consisted of the analysis of already existing data and documents, direct observation, interviews with institutional and non-institutional actors, and a household survey in Sena. Afterwards, a SWOT analysis was used as a tool to manage such a greatly varied amount of information. The research process allowed to identify the main features of the small towns, that are here denominated as “rural towns”, and to understand the major trends related to the “rur-urbanization” process.
The rural town is defined as a hybrid settlement pattern in which persisting elements of the rural world melt together with emerging urban characteristics. Vilas rurales, in fact, are traditionally rural contexts characterized by a dominance of vernacular settlement patterns and architectures. The socio-economic and cultural features of the towns, as well as their physical structure, are rapidly changing as a consequence of the ongoing “modernization”. The risk is that a rapid and uncontrolled urbanization process could threaten the natural, economic and cultural bases of the small towns without adequately replacing them. Thereby, some suggestions follow on how spatial planning can contribute to the sustainable growth of the rural towns.
The central idea that is proposed herein is to preserve the rural characteristics, which are widely present within the rural towns, and to integrate them with the emerging “urban” features. This strategy aims to support the subsistence activities adopted by the majority of the population and to outline a spatial planning process that responds to the specific characteristics of this typology of human settlement by culturally appropriate means.
The thesis consists of three parts. The first part presents the results of the literature review. The origin of the debate on small and intermediate urban centers of Third World countries in the late 1970s is presented in Chapter 1 while Chapter 2 actualizes this debate, also in the light of major processes occurring at global level and affecting African small towns. Chapter 3 stresses the big gap in urbanization theory and practices related to small towns of Africa and focuses on their characteristic of being predominantly vernacular settlements in which a “deculturation” process” is taking place as a consequence of the imposition/adoption of western cultural models. The second part of the thesis presents the analysis of case studies. The research methodology is outlined in Chapter 4. In Chapter 5, Caia and Sena are contextualized within their macro-institutional and regional contexts. Then, an analysis of the rural towns is proposed at the local level. Chapter 6 offers a snapshot of the emerging lifestyles in Sena through the results of the household survey. The rur-urbanization process is described in Chapter 7, first by analysing the spatial evolution of Caia and Sena from a historical perspective and, then, by proposing four key topics that identify the main features of the rural towns and describe the major trends related to the rur-urbanization process. The third part of the research, Chapter 8, presents the conclusions. First of all a definition and an assessment of the rural town is offered. Moreover, a conceptual framework is presented that relates key topics, risks, planning principles and actions related to the spatial planning activity in the rural towns. Finally, a methodological framework is proposed that translates the conceptual framework into more operational terms by outlining a spatial planning process aimed at the rural towns
Advanced Techniques based on Mathematical Morphology for the Analysis of Remote Sensing Images
No full textRemote sensing optical images of very high geometrical resolution can provide a precise and detailed representation of the surveyed scene.
Thus, the spatial information contained in these images is fundamental for any application requiring the analysis of the image. However, modeling the spatial information is not a trivial task. We addressed this problem by using operators defined in the mathematical morphology framework in order to extract spatial features from the image.
In this thesis novel techniques based on mathematical morphology are presented and investigated for the analysis of remote sensing optical images addressing different applications.
Attribute Profiles (APs) are proposed as a novel generalization based on attribute filters of the Morphological Profile operator. Attribute filters are connected operators which can process an image by removing
flat zones according to a given criterion. They are flexible operators since they can transform an image according to many different attributes (e.g., geometrical, textural and spectral).
Furthermore, Extended Attribute Profiles (EAPs), a generalization of APs, are presented for the analysis of hyperspectral images. The EAPs are employed for including spatial features in the thematic classification of hyperspectral images.
Two techniques dealing with EAPs and dimensionality reduction transformations are proposed and applied in image classification. In greater detail, one of the techniques is based on Independent Component Analysis and the other one deals with feature extraction techniques.
Moreover, a technique based on APs for extracting features for the detection of buildings in a scene is investigated.
Approaches that process an image by considering both bright and dark components of a scene are investigated. In particular, the effect of applying attribute filters in an alternating sequential setting is investigated. Furthermore, the concept of Self-Dual Attribute Profile (SDAP) is introduced. SDAPs are APs built on an inclusion tree instead of a min- and max-tree, providing an operator that performs a multilevel filtering of both the bright and dark components of an image.
Techniques developed for applications different from image classification are also considered. In greater detail, a general approach for image simplification based on attribute filters is proposed. Finally, two change detection techniques are developed.
The experimental analysis performed with the novel techniques developed in this thesis demonstrates an improvement in terms of accuracies in different fields of application when compared to other state of the art methods
A theory of constructive and predictable runtime enforcement mechanisms
No full textNowadays owners and users of software systems want their executions to be reliable and secure. Runtime enforcement is a common mechanism for ensuring that system or program executions adhere to constraints specified by a security policy. It is based on two properties: the enforcement mechanism should leave legal executions without changes(transparency) and make sure that illegal executions are amended (soundness).
From the theory side, the literature proposes the precise characterization of legal executions that represent a security policy and thus is enforced by mechanisms like security automata or edit automata. Unfortunately, transparency and soundness do not distinguish what happens when an execution is actually illegal (the practical case). They only tell that the outcome of an enforcement mechanism should be "legal", but not how far the illegal execution should be changed.
In this thesis we address the gap between the theory of runtime enforcement and the practical case. First, we explore a set of policies that represent legal executions in terms of repeated legal iterations and propose a constructive enforcement mechanism that can deal with illegal executions by eliminating illegal iterations. Second, we introduce a new notion of predictability, that puts a restriction on the way illegal executions are modified by an enforcement mechanism. Third, we propose an automatic construction of enforcement mechanisms that is able to tolerate some insignificant errors of the user and we prove it to have a sufficient degree of predictability.
The main case study of this thesis is a business process from a medical organization. A number of discussions with the partners from this organization shows the validity of the approaches described in this thesis in practical cases
Silicon Nanocrystal Based Light Emitting Devices for Silicon Photonics
No full textThis thesis presents experimental work developing silicon nanocrystal based light emitting devices for silicon photonics. The chapters are organized as follows:
In chapter 2, fabrication and characterization of silicon nanocrystal based devices are presented. In collaboration with Intel Corporation and Bruno Kessler Foundation and thanks to the support of European Commission through the project No. ICT-FP7-224312 HELIOS and through the project No. ICT-FP7-248909 LIMA, it is shown that layers and devices containing silicon nanocrystals can be formed in a production silicon-fab on 4 and 8 inch silicon substrates via PECVD and subsequent thermal annealing. Devices produced by single layer and multilayer deposition are studied and compared in terms of structural properties, conduction mechanisms and electroluminescence properties. Power efficiency is evaluated and studied in order to understand the relation between exciton recombination and electrical conduction. A band gap engineering method is proposed in order to better control carrier injection and light emission in order to enhance the electroluminescence power efficiency.
In chapter 3, the power efficiency of silicon nanocrystal light-emitting devices is studied in alternating current regime. An experimental method based on impedance spectroscopy is proposed and an electrical model based on the constant phase element (CPE) is derived. It is, then, given a physical interpretation of the electrical model proposed by considering the disordered composition of the active material. The electrical model is further generalized for many kinds of waveforms applied and it is generalized for the direct current regime. At the end, time-resolved electroluminescence and carrier injection in alternate current regime are presented.
In chapter 4, erbium implanted silicon rich oxide based devices are presented. The investigation of opto-electrical properties of LED in direct current and alternate current regime are studied in order to understand the injection mechanism and estimate the energy transfer between silicon nanocrystals and erbium. At the end a device layout and process flow for an erbium doped silicon nanocrystal based laser structure are shown.
In chapter 5, some other applications of silicon nanocrystal are presented. An example of all-silicon solar cell is shown. The photovoltaic properties and carrier transport of silicon nanocrystal based solar are studied. At the end, the combination of emitting and absorbing properties of silicon nanocrystal based LED are used to develop an all-silicon based optical transceiver
Out of Equilibrium: Modelling and Simulating Traverse
No full textManaging disequilibrium and its consequent traverse is one of the important topics in economic theory. During such traverse, the evolving economic system faces various imbalances and coordination problems that arise within and outside the sys-tem. In order to traverse the disequilibrium, the economic system should innovate, create, and manage its resources in a viable manner. This dissertation reports stud-ies in modelling ‘disequilibrium traverse economies’, in the sense of Hicksian Neo-Austrian, Time-to-Build, theory. In the first chapter, we discuss the origins of traverse analysis and the role of ‘time-to-build’ framework in modelling macro-dynamics. We also provide a review of the literature concerning ‘time-to-build’ tradition in modelling traverse and business cycles. Then, we discuss in detail how this framework actually enters into these models and the assumptions that underpin them. In the second chapter, we provide an overview of different notions of viability, which are widely used in economic literature, and formulate viability conditions for Amendola and Gaffard’s Neo-Austrian model. We then simulate the model, with and without the viability conditions, to study the dynamics of the evolving system. The main aim of this chapter is to explore and analyse the importance of viability creating mechanisms during dynamic traverse.
In chapter three, we analyse some of the classics in business cycle theory and how the ‘time-to-build’ framework plays an important role in modelling economic fluctuations. The contribution of this chapter is to provide insights on various as-sumptions and the choice of mathematical formalisms that underpin these business cycle models. In conclusion, we also suggest that the Neo-Austrian tradition should be placed as a part of the rich tradition of business cycle theory. In the fourth chapter, we take the ‘time-to-build’ model and improve the framework by endogenizing one of the main engines of growth, i.e., innovations, in a non-stochastic, non ad-hoc, manner. We model innovations using Turing Machine metaphor, so that we can encapsulate the intrinsic uncertainties of Research and Development processes in an insightful way. The enhanced ‘time-to-build’ model thus developed is then simulated for various policy parameters, such as - R&D policies, interest rates, and bankruptcy policies, and the resulting traverses are studied. In the last chapter, we provide a comprehen-sive summary of the novel contributions of the dissertation and list some of the future research paths that can be traversed