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Cyclic Codes: Low-Weight Codewords and Locators
No full textError correcting codes has become an integral part of the design of reliable data transmissions and storage systems. They are also playing an increasingly important role for other applications such as the analysis of pseudorandom sequences and the design of secure cryptosystems. Cyclic codes form a large class of widely used error correcting codes, including important codes such as the Bose-Chaudhuri-Hocquenghem (BCH) codes, quadratic residue (QR) codes and Golay codes. In this thesis I tackle two problems related to cyclic codes: finding low-weight codewords and decoding.
Computing efficiently low-weight codewords of a cyclic code is often a key ingredient of correlation attacks to LFSR-based stream ciphers. The best general purpose algorithm is based on the generalized birthday problem. In the first part of the thesis I show an alternative approach based on discrete logarithms which has - in some cases relevant for applications - much lower memory complexity requirements and a comparable time complexity. The second part of the thesis is devoted to some results concerning efficient bounded-distance decoding for cyclic codes
Towards Merging of Microfabrication and Printing of Si µ-Wires for Flexible Electronics
Get PDFThis PhD thesis focuses on the investigation and development of a feasible technology route for fabricating multifunctional flexible electronic devices through heterogeneous integration of organic/inorganic materials on polymeric substrates. The three types of printing technologies investigated during this research include: (a) Transfer printing of inorganic semiconductors processed through standard microfabrication techniques, (b) Spray coating for deposition of organic dielectrics and metal patterns, and (c) Screen-printing of solution based transducer materials. Fabrication of electronic devices based on transfer printing of high-mobility inorganic semiconductor materials (i.e. Si), aided by high-resolution possible with microfabrication technology, was explored for high performance electronics. A cost-effective processing of printable materials is desired and therefore, through printing technologies, this thesis also explored ways to bring closer the well-established microfabrication and conventional printing tools. Due to commercial interests, the major research focus in flexible electronics thus far has been on applications such as photovoltaics and displays. However, this research is focused on active/passive electronics for sensing applications like electronic skin, which is of significant interest in robotics for safe human-robot interaction and other manipulation and exploration tasks. Optimization of the Transfer Printing for translating Si microwires from SOI (silicon on insulator) wafers on secondary flexible substrates has been investigated. Processing steps have been improved for fabrication of Si microwires on donor wafers and dry transferring them onto flexible PI (polyimide) and PET (polyethylene terephthalate) substrates. The downscaling of Si in the form of microwires and using them as building block for active devices such as field effect transistors were explored in this thesis. The microwires retain the high carrier mobility, robustness, high performance and excellent stability. Arrays of MISFETs (metal insulator field effect transistors) structures were successfully fabricated and the response variations were compared. The differently doped Si microwires were analyzed in an asymmetric metal semiconductor metal (MSM) structures under planar and bend mode conditions. The optical response as well as the thermoelectric properties of the alternately doped pn-Si microwires were also investigated.
A feasible fabrication route is presented, where combination of transfer printing for Si microwires and development of the subsequent post-processes by additive manufacturing techniques i.e. Screen-printing, Spray coating and Micro-spotting are mainly investigated. The Si microwires are employed as the semiconductor in the MISFET devices whereas screen-printed metal patterns are used for back-gate and deposition of dielectric layer is performed through spray coating. In parallel, screen-printing is also used for development of large area pressure sensor patches using two different materials i.e. P(VDF-TrFE) (Polyvinylidene Fluoride Trifluoroethylene) and nanocomposites of MWCNTs/PDMS (multiwall carbon nanotubes mixed with poly(dimethylsiloxane) for measuring dynamic and static contact events. Promising results have been achieved by developing a cost-effective way of manufacturing an all Screen-Printed flexible pressure sensors using piezoelectric transducer through P(VDF-TrFE) and piezoresistive based MWCNT/PDMS nanocomposites. Active electronic circuitry is needed for signal conditioning, amplification or processing of the sensory data on the flexible foils, which is deemed to be developed through Si microwires based technology in the next phase of the project. Ultimate goal of the PhD study was to develop a fabrication platform by combining three different printing technologies for large area sensor patches. Major challenges involved in the development of flexible device designs and printing technologies are highlighted and addressed with dependable solutions. The research concludes with proposing an innovative approach towards heterogeneous integration of large area sensory cells made of organic materials to the active devices based on inorganic semiconductors such as Si microwires. This technological platform for heterogeneous integration of devices made of diverse materials (organic, inorganic etc.) on soft substrates is believed to be a step-change needed to advance flexible electronics towards manufacturing
The influence of the population contact network on the dynamics of epidemics transmission
No full textIn this thesis we analyze the relationship between epidemiology and network theory, starting from the observation that the viral propagation between interacting agents is determined by intrinsic characteristics of the population contact network. We aim to investigate how a particular network structure can impact on the long-term behavior of epidemics. This field is way too large to be fully discussed; we limit ourselves to consider networks that are partitioned into local communities, in order to incorporate realistic contact structures into the model.
The gross structure of hierarchical networks of this kind can be described by a quotient graph. The rationale of this approach is that individuals infect those belonging to the same community with higher probability than individuals in other communities. We describe the epidemic process as a continuous-time individual-based susceptible–infected–susceptible (SIS) model using a first-order mean-field approximation, both in homogeneous and in heterogeneous setting. For this mean-field model we show that the spectral radius of the smaller quotient graph, in connection with the infecting and curing rates, is related to the epidemic threshold, and it gives conditions in order to decide whether the overall healthy-state defines a globally asymptotically stable or an unstable equilibrium.
Moreover we show that above the threshold another steady-state exists that can be computed using a lower-dimensional dynamical system associated with the evolution of the process on the quotient graph. Our investigations are based on the graph-theoretical notion of equitable partition and of its recent and rather flexible generalization, that of almost equitable partition. We also consider the important issue related to the control of the infectious disease. Taking into account the connectivity of the network, we provide a cost-optimal distribution of resources to prevent the disease from persisting indefinitely in the population; for a particular case of two-level immunization problem we report on the construction of a polynomial time complexity algorithm. In the second part of the thesis we include stochasticity in the model, considering the infection rates in the form of independent stochastic processes. This allows us to get stochastic differential equation for the probability of infection in each node. We report on the existence of the solution for all times. Moreover we show that there exist two regions, given in terms of the coefficients of the model, one where the system goes to extinction almost surely, and the other where it is stochastic permanent
Advanced Methods for the Analysis of Radar Sounder Data Acquired at the Ice Sheets
Get PDFThe World Climate Research Programme (WCRP) has recently reconfirmed the importance of a better understanding of the Cryosphere for advancing the analysis, modeling and prediction of climate change and its impact on the environment and society. One of the most complete collection of information about the ice sheets and glaciated areas is contained in the data (radargrams) acquired by Radar Sounder (RS) instruments. The need to better understand the structure of the ice sheets and the availability of enourmous quantities of radargrams call for the development of automatic techniques for an efficient extraction of information from RS data. This topic has been only marginally addressed in the literature. Thus, in this thesis we address this challenge by contributing with four novel automatic techniques for the analysis of radargrams acquired at the ice sheets.
The first contribution of this thesis presents a system for the automatic classification of ice subsurface targets in RS data. The core of the system is represented by the extraction of a set of features for target discrimination. The features are based on both the specific statistical properties of the RS signal and the spatial distribution of the ice subsurface targets. The second contribution is an unsupervised model-based technique for the automatic detection and property estimation of ice subsurface targets. This is done by using the parameters of the RS system combined with the output of an automatic image segmentation algorithm. The third contribution presents an automatic technique for the local 3D reconstruction of the ice sheet. It is based on the use of RS and altimeter (ALT) data, and relies on the use of a geostatistical interpolation method and on several statistical measures for validating the interpolation results and the quality of interpolation. The fourth contribution presents a technique for the automatic estimation of radar power losses in ice as a continuous non-linear function of depth, by using RS and ice core data. The technique relies on the detection of ice layers in the RS data, the computation of their reflectivity from the ice core data and the use of the radar equation for loss estimation. Qualitative and quantitative experimental results obtained on real RS data confirm the effectiveness of the first three techniques. Also, preliminary results have been obtained by applying the fourth technique to real RS and ice core data acquired in Greenland.
Due to their advantages over the traditional manual approach, e.g., efficiency, objectivity, possibility of jointly analyzing multisensor data (e.g., RS, ALT), the proposed methods can support the scientific community to enhance the data usage for a better modeling and understanding of the ice sheets. Moreover, they will become even more important in the near future, since the volume of data is expected to grow from the increase in airborne and possible Earth Observation spaceborne RS missions
Smart Energy City Development in Europe: Towards Successful Implementation
Get PDFSmart energy city (SEC) development is a component of the urban development initiative smart city, which has been a popular response to the global energy challenge in Europe during the past two decades. SEC development aims to increase the sustainability of urban energy systems and services. Since 2011, SEC development has been supported by the European Commission as part of the Strategic Energy Technology plan (SET-Plan) and through the European Union Programmes for Research and Technological Development (specifically FP7 and Horizon 2020). This, along with the promising vision of SEC development and considerable financial support by the private sector, has encouraged numerous European cities to initiate SEC projects. Successful implementation of these projects at the urban scale is crucial to achievement of urban energy objectives and sustainability of future urban development.
The here presented thesis aims to support urban decision-makers towards successful implementation of urban scale smart energy city development in Europe. The study includes three stages. The first stage is dedicated to conceptual analysis. Within this stage, I conceptualized smart city through a keyword analysis of existing literature on the concept. Then, within the context of the smart city concept, I defined SEC development through literature review and expert knowledge elicitation. The second stage is dedicated to empirical investigation. Using the definition of SEC development, I distinguished and investigated 43 previously implemented SEC projects to identify common barriers that hinder successful implementation of SEC development. In addition, I proposed a new multi-dimensional methodology that allows a simultaneous prioritization of barriers against their probability, the level of impact, scale, origin, and relationship with other barriers. The third stage of the thesis is dedicated to learning methodologies that allow efficient transfer of knowledge from the past SEC experiences to the new SEC developments. I introduced the application of two learning methodologies that support decision-makers to predict barriers to the implementation of a new SEC project: case-based learning and decision tree learning. The former predicts barriers based on internal similarities between the new SEC project and the past projects. The latter uses the past projects and creates a predictive model for each barrier based on internal and external project characteristics. These models are later used to predict barriers to a new SEC project. Both methodologies were tested in a new SEC project, named SINFONIA. The conceptual analysis revealed that application of information and communication technologies, the collaboration of multiple stakeholders, integration of multiple urban domains, and sustainability evaluation are the constant characteristics (i.e. principles) of smart city and SEC development. It resulted in, to the best of my knowledge, the first multi-dimensional and comprehensive definition of SEC development, revealing its principles, objectives, domains of intervention, stakeholders, time and spatial dimensions. Furthermore, a list of smart energy solutions in each SEC domain of intervention was provided. The empirical investigation of the past SEC projects resulted in the identification of 35 common barriers to the implementation of SEC development, categorized in policy, administrative, legal, financial, market, environmental, technical, social, and information and awareness dimensions. The barrier prioritization showed that barriers related to collaborative planning, external funding of the project, providing skilled personnel, and fragmented ownership should be the key action priorities for SEC project coordinators. Application of case-based learning methodology resulted in identifying five past SEC projects that were the most similar to the SINFONIA project in terms of project internal characteristics. Investigating the barriers to the similar projects revealed that fragmented ownership is the most probable barrier to implementation of SINFONIA project. Application of the decision trees methodology resulted in generation of 20 barrier models, four of which showed a very good performance in prediction of barriers: lack of values and interest in energy optimization measures, time-consuming requirements by European Commission concerning reporting and accountancy, economic crisis, and local unfavorable regulations for innovative technologies. None of these four barriers were predicted to occur in the SINFONIA project. The application of this method in the SINFONIA showed a higher predicting power when a barrier was absent.
The findings of the here presented thesis contribute to successful implementation of SEC development by supporting decision-makers in different phases of SEC projects. The results of the conceptual analysis contribute to a common understanding and foster the dialogue on the concept among various SEC stakeholders, particularly decision-makers and urban planners. The results of the empirical investigation lead to a better comprehension and evaluation of the barriers to the implementation of SEC projects in order to efficiently allocate resources to mitigate barriers. The proposed learning methodologies proved to be promising in helping decision-makers to identify similar projects to a new SEC development and to predict barriers to the implementation of new SEC projects.
The thesis concludes that SEC is an outstanding urban development that can make a valuable contribution to the sustainability of urban energy systems. The specific characteristics of SEC development pose new challenges to the future smart and sustainable urban planning. Nevertheless, SEC development brings about unprecedented opportunities for integration and application of advanced quantitative techniques with current urban planning methods. This allows efficient knowledge transfer in not only intra-urban but also inter-urban levels in order to provide a collaborative, integrated and constructive movement towards successful implementation of SEC projects and sustainability of future urban development
Acquisition and Exclusion of Pathogenicity Island 1 (PAPI-1) in Pseudomonas Aeruginosa
Get PDFHorizontal gene transfer (HGT) allows rapid exchanges of large genetic elements and is known to play an important role in bacterial evolution and adaptation. Conjugative transfer of genomic islands (GIs) has recently been reported in the opportunistic pathogen Pseudomonas aeruginosa. PAPI-1, one of the largest pathogenicity islands of P. aeruginosa, encodes several putative virulence genes and a major regulator of biofilm formation and antibiotic-resistant traits and was found to be horizontally transferable into strains lacking it. The conjugation of PAPI-1 island transfer is mediated by type IV pilus, which is encoded by ten genes located in PAPI-1. Nevertheless, the acquisition mechanism of PAPI-1 is currently not well understood.
The first part of this thesis was aimed at identifying the receptor for conjugative transfer on the bacterial cell surface. Based on previous knowledge on bacterial conjugation, we designed and performed a series of mating experiments and analyzed transfer efficiency between PAPI-1 donor and recipient strains. Our data showed that A-band lipopolysaccharide (LPS) is required to initiate PAPI-1 transfer, supporting the idea that this structure acts as a receptor for conjugative type IV pilus in recipient strains. These results were verified by PAPI-1 transfer inhibition experiments with outer membrane (OM) or LPS preparations. The addition of a low amount of OM or LPS derived from strains producing A-band decreased PAPI-1 transfer efficiency by 80% compared to controls.
In the second part, we demonstrated that P. aeruginosa strains which already acquired a copy of PAPI-1 almost completely lost the ability to receive additional copies of the island. Combination of strains with or without PAPI-1 were mated in-pair to investigate the redundancy in PAPI-1 transfer. The surface exclusion of PAPI-1 was characterized by investigating the effects of the addition of OM and LPS derived from strains with or without PAPI-1. In addition, LPS of the different strains were analyzed by western blot using antibodies directed against different parts of the molecule and by testing the in-vitro binding capacity of LPS to pilin protein. All experiments indicated that the strains carrying PAPI-1 produced much less A-band LPS compared to those lacking the island and lost the ability to bind to conjugative pilin. Finally, the screening of a series of mutants highlighted a role for two PAPI-1 genes in an entry exclusion activity, possibly through PAPI-1 island destabilization.
This study contributes with a step forward in the understanding of the acquisition of genomic islands in P. aeruginosa, which may be generalized to other gram-negative bacteria and may lead to the future development of new strategies to limit the spread of virulence or resistance functions in populations of pathogenic bacteria
Il potere dell'evoluzione: il dibattito sulla variabilità delle specie a Torino dall'Età napoleonica allo Stato unitario
Get PDFNel corso dell'Ottocento, Torino fu uno dei principali centri di elaborazione e diffusione delle teorie evoluzionistiche in Italia. Le ricerche furono indirizzate dapprima dal modello trasformistico di Lamarck e, a partire dagli anni '60, dalla teoria darwiniana. Il lavoro ricostruisce lo sviluppo delle indagini in zoologia e in alcune discipline ad essa collegate, come la paleontologia e l'antropologia, approfondendo anche il dibattito nato sui periodici scientifici, le opere divulgative e i giornali. Tale ricostruzione si accompagna ad uno studio delle interferenze tra gli orientamenti teorici adottati dagli scienziati e le fasi del cambiamento politico-sociale che si succedettero nel corso del secolo
Ceramic aerogels of the Si-C-N-O system from pre-ceramic polymer
No full textResearch in materials science field is often driven by the necessity to overcome problems in fast, reliable and possibly cost effective ways. Many times the starting point to find a solution is a literature survey, to understand if someone already encountered a similar problem and proposed an answer, or if some authors developed a material that can be used to solve the issue. The work performed within this thesis however fits in another type of approach, i.e. research for the research's sake. In this kind of approach the efforts are not dedicated directly to solve a given, precise and detailed problem, but to invent and develop new types of materials, characterizing them so that other researchers can take benefits from both the synthetic way and the measured properties of the new material produced. In particular, this PhD thesis deals with the combination of two "exotic" class of materials, which are aerogels and polymer derived ceramics. Aerogel is actually a shape, more than a material, from the proper chemical point of view. This kind of shape, anyway, is so peculiar that many of the properties are common to all the aerogels' products, similarly to what happen for other class of materials like conductivity for metals, hardness for ceramics and high specific strength for polymers. These common properties are: low density, high specific surface and predominantly mesoporous microstructure. Polymer derived ceramic (PDC) denotes a family of ceramic materials that can be obtained by a controlled thermolysis of a polymeric precursor. These polymers are usually Si based and contain functional groups that allow to control the final chemistry of the ceramic produced, along with the great advantage that the shape can be set already in the polymeric state. Successfully combining the two techniques, i.e. to produce polymer derived ceramic aerogel, is the core of this thesis. Preference was given to the use of commercially available pre-ceramic polymers so ceramic aerogels belonging to the SiOCN system were produced, starting from polycarbosilane (SMP-10), polysilazane (PSZ-20) and polysiloxane (PMHS). A reliable procedure was set up to produce aerogels with different composition and microstructure, leading to a wide range of properties in terms of density, specific surface, high temperature stability, electrochemical functionality etc., as will be better depicted through the thesis. Additionally, some application of the materials produced were tested, in which the aerogel shape, combined with the proper chemistry, was expected to give interesting results
Secure Business Process Engineering: a socio-technical approach
Get PDFDealing with security is a central activity for todays organizations. Security breaches impact on the activities executed in organizations, preventing them to execute their business processes and, therefore, causing millions of dollars of losses. Security by design principles underline the importance of considering security as early as during the design of organizations to avoid expensive fixes during later phases of their lifecycle. However, the design of secure business processes cannot take into account only security aspects on the sequences of activities. Security reports in the last years demonstrate that security breaches are more and more caused by attacks that take advantage of social vulnerabilities. Therefore, those aspects should be analyzed in order to design a business process robust to technical and social attacks. Still, the mere design of business processes does not guarantee that their correct execution, such business processes have to be correctly implemented and performed. We propose SEcure Business process Engineering (SEBE), a method that considers social and organizational aspects for designing and implementing secure business processes. SEBE provides an iterative and incremental process and a set of verification of transformation rules, supported by a software tool, that integrate different modeling languages used to specify social security aspects, business processes and the implementation code. In particular, SEBE provides a new modeling language which permits to specify business processes with security concepts and complex security constraints. We evaluated the effectiveness of SEBE for engineering secure business processes with two empirical evaluations and applications of the method to three real scenarios
Codici quattrocenteschi di "pìstole" e "dicerie". Per lo studio della tradizione
Get PDFIl lavoro completa il censimento dei codici di lettere e orazioni in volgare del XV secolo e avvia uno studio d'insieme, di carattere filologico e critico-letterario, dell'intera tradizione