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Indoor Localization of Wheeled Robots using Multi-sensor Data Fusion with Event-based Measurements
Get PDFIn the era in which the robots have started to live and work everywhere and in close contact with humans, they should accurately know their own location at any time to be able to move and perform safely. In particular, large and crowded indoor environments are challenging scenarios for robots' accurate and robust localization. The theory and the results presented in this dissertation intend to address the crucial issue of wheeled robots indoor localization by proposing some novel solutions in three complementary ways, i.e. improving robots self-localization through data fusion, adopting collaborative localization (e.g. using the position information from other robots) and finally optimizing the placement of landmarks in the environment once the detection range of the chosen sensors is known. As far as the first subject is concerned, a robot should be able to localize itself in a given reference frame. This problem is studied in detail to achieve a proper and affordable technique for self-localization, regardless of specific environmental features. The proposed solution relies on the integration of relative and absolute position measurements. The former are based on odometry and on an inertial measurement unit. The absolute position and heading data instead are measured sporadically anytime some landmark spread in the environment is detected. Due to the event-based nature of such measurement data, the robot can work autonomously most of time, even if accuracy degrades. Of course, in order to keep positioning uncertainty bounded, it is important that absolute and relative position data are fused properly. For this reason, four different techniques are analyzed and compared in the dissertation. Once the local kinematic state of each robot is estimated, a group of them moving in the same environment and able to detect and communicate with one another can also collaborate to share their position information to refine self-localization results. In the dissertation, it will be shown that this approach can provide some benefits, although performances strongly depend on the metrological features of the adopted sensors as well as on the communication range. Finally, as far as the problem optimal landmark placement is concerned, this is addressed by suggesting a novel and easy-to-use geometrical criterion to maximize the distance between the landmarks deployed over a triangular lattice grid, while ensuring that the absolute position measurement sensors can always detect at least one landmark
La rete di scambi epistolari fra medici italiani e di lingua tedesca nel XVI secolo: libertà di ricerca, circolazione del sapere ed esperienze confessionali
Get PDFLa Tesi studia e approfondisce, rispetto alla letteratura esistente, i rapporti culturali, scientifici e professionali tra i medici italiani e i loro colleghi di area germanofona nel Cinquecento. L’indagine si avvale del metodo di analisi della fonte epistolare, applicato a un quantitativo di unità sufficienti sia per rispondere agli interrogativi posti all’origine della ricerca, sia per integrare lo "status" delle ricerche nel campo. Accanto all’analisi di fonti manoscritte il lavoro prende in esame una serie di fonti edite, come raccolte di "Epistolae medicinales" e opere di materia medica. La Tesi è idealmente divisa in tre parti, per un totale di sei capitoli.
Nella prima di esse (capitoli primo e secondo) si indagano i nessi tra il rinnovamento della "scientia" medica del XVI secolo da una parte, e l’interesse per le coeve dottrine religioso-confessionali d’Oltralpe dall’altra, alla luce di un sistema del sapere che aspirava all’universalità, e sullo sfondo di un panorama culturale caratterizzato dalla forte interdipendenza fra le diverse discipline, nonché da molteplici nessi tra “scienza” e religione, ambiti che a loro volta non erano interpretati come compartimenti stagni. In particolar modo si prendono in esame alcuni significativi casi di medici italiani esuli "religionis causa", e si mettono in evidenza le ripercussioni che le loro peregrinazioni attraverso il suolo europeo sortirono sia sul loro modo di vivere la dimensione religiosa, sia sulla loro dimensione professionale.
La seconda parte del lavoro (capitoli terzo, quarto e quinto) esplora i tratti qualificanti della cosiddetta "Respublica medicorum" europea in una prospettiva larga di storia socio-culturale, che prende in considerazione sia fattori culturali e filosofico-“scientifici”, sia socio-economici. Sono oggetto di attenzione, quindi, le dinamiche sociali e professionali interne della comunità europea dei medici, gli aspetti relativi alla circolazione libraria e del sapere tecnico medico-botanico al suo interno, e la concreta e quotidiana attività diagnostica e terapeutica dei "physici" del Cinquecento.
La terza ed ultima parte (capitolo sesto) si avvale delle analisi precedenti, per definire i tratti dell’ambivalenza della scienza medica del Cinquecento. Inoltre, in questa sezione si formulano le prime riflessioni sulle caratteristiche della rete professionale dei "physici" in un’ottica comparativa rispetto alla categoria dei giuristi. L’attenzione, quindi, si sposta sulle "institutiones" dell’Arte, dello "Studium" e del "Collegium" medico-fisico, e sul contesto normativo da esse prodotte, il quale a sua volta attivava precisi meccanismi socio-professionali
Automotive Brake Materials: Characterization of Wear Products and Relevant Mechanisms at High Temperature
Get PDFWear is an ubiquitous phenomenon affecting an extremely wide number of technological system, often determining their premature failure. In this regard, wear and friction behavior of friction materials and the characterization of wear debris from brake disc system is an important step to understand the dominant wear mechanisms active in a given tribological system, in order to improve its performances and to increase the expected lifetime. In the thesis, four tribological task has been performed, under the code name Case I, II, III & IV. This thesis present the work on the development of a characterization methodology of a wear debris from brake pad-disc system, M1 and M2 friction materials at elevated temperatures and study of the wear and frictional behavior of a heat treated cast iron disc.
In Case I, the dry sliding behavior of two friction materials (M1 & M2) have been investigated. The sliding tests were carried out on a pin-on-disc test rig, using a cast iron disc as a counterface, under mild conditions (the applied nominal pressure was 2 MPa and the sliding speed was 3.14 m/s). The results shows that friction material M2 is characterized by a lower friction coefficient than friction material M1, and the friction coefficient is stable during the test. In addition, friction material M2 shows a lower wear rate than M1. The results were explained by considering the characteristics of the friction layer that is established during the test. On the bases of the experimental observations, the lower friction and wear of friction material M2 was attributed to the formation a quite uniform and well compacted friction layer, due to the presence of ingredients, such as Zr oxides, able to form small particles during sliding that are compacted and held together by the presence of metallic ingredients, such as copper. The absence of Zr-oxides in the formulation of M1friction material and the presence, in their place, of hard and abrasives Mg, Zn and Al-oxides, impeded the formation of wide covering friction layer, increasing friction and wear. The different frictional properties of the brake pads determine their driving performances, and the different wear behavior determine their in-service deterioration and also their attitude to emit particulate matter in the environment, which is nowadays a concern of increasing importance. Under the Case II, a streamline characterization protocol for wear debris emitted under wear testing conditions (Case I - M1 friction material) used for disc brake assemblies is presented. An important aspect of the experimental test methodology concerns the powder collection methodology on different substrates: aluminum foil, for a gravitational integral collection, and polycarbonate filters of an ELPI+ impactor equipment, on which particles are selectively trapped, according to their average size. The protocol is based on the application of different materials characterization tools, like scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The deliberate aim of the study was to identify suitable selection parameters, like specimen availability and average particle size, for an effective and smart application of the mentioned experimental techniques so to optimize testing times and obtain statistical reliable results. The proposed characterization approach could be profitably employed also in other contexts, like environmental and health monitoring, as far as particulate matter, even from other sources than brake systems, is concerned. We extended the work in Case I by investigating further wear mechanisms of M1 & M2 pins at elevated temperatures i.e., 170°C, 200°C, 250°C, 300°C and 350°C, under Case III. The results showed a clear evolution of frictional parameters with temperature. For M1, the working temperature were 155°C, 200°C, 250°C and 300°C, the absence of frictional parameters with temperature and wear behavior of M1 is higher than M2 with one degree higher order of magnitude. Wear tracks on the discs form from the piling up of wear fragments produced both by the tribo-oxidation of the disc itself and from the wearing out of the pin materials. This accumulation of wear debris on the disc surface nearly compensate for the weight loss associated with disc wear. The observed tribological behaviour is very much influenced by the thermal degradation of the phenolic binder of the friction material. The thermal decomposition kinetics was confirmed by thermogravimetric analyses, conducted on purpose on the pin material, and by Raman spectroscopy results, that confirmed the presence of carbonaceous products on the worn out pin surface. For M2, the working temperature were 170°C, 200°C, 250°C, 300°C and 350°C, above 170°C a transition from mild to severe wear was observed. Correspondingly, the friction layers, in particular, the secondary plateaus, which develop on the pins and disc surface during sliding displayed quite different features, as proved by electron microscopy observations and X-ray spectroscopy analyses. As concerns the pins, at 25°C and 170°C, the friction layer consists of primary and well compacted secondary plateaus. At 200°C and above, a progressive reduction of the pin surface coverage by the secondary component of the friction layer and a corresponding thinning of this component are observed. Secondary plateaus are barely present on the samples tested at 350°C. Although referring to rather extreme conditions and simplified sliding conditions, the results obtained in this study provide useful indications on the role that the thermal stability of the organic component may have in determining wear rate in brake systems in which the temperature rise may be induced by actual operational conditions. The Case IV work aims at illustrating the role of conventional heat-treatments on the friction and wear behavior of the above system. Wear rates of both disc and M2 friction material were reduced by almost one order of magnitude when the disc is preliminarily heat-treated and then grinded to remove the surface decarburized layer that forms during the adopted treatment cycle. Heat-treatment and heat-treatment plus ground results in the reduction of the friction coefficient, which was comparatively low for the grounded samples (grinded to remove the surface decarburized layer). The friction and wear behavior along with the contact temperature evolutions were rationalized according to the materials characteristics and the observed wear mechanisms
Solar water splitting for hydrogen production: development of photocatalysts based on earth abundant and biocompatible materials (TiO2 and Fe2O3)
No full textFossil fuels have been critical to the development of modern society, but concerns over pollution, environmental degradation and climate change demand humans transition to renewable sources of energy. Solar energy is, among renewables, by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. The principal problem related to solar energy use is its intermittency. Collecting and storing solar energy in chemical bonds (solar fuel), as nature accomplishes through photosynthesis, is possible through photo-electrochemical water splitting, a clean and sustainable way for hydrogen production. The materials used as photo-electrodes in a photo-electrochemical cell must fulfil a variety of thermodynamic and kinetic requirements to ensure good efficiency and durability. Since there is no material in nature satisfying all these requirements, tailoring the optical, electrical, and morphological properties of the existing materials to construct photo-electrodes with the desired performance is a big task for materials scientists. In this thesis, we study TiO2 based photo-catalysts and Fe2O3 based water oxidation catalysts. TiO2 thin films were deposited by radio frequency magnetron sputtering technique and their optical, electrical and morphological properties were changed to enhance the visible light absorption and/or limit the recombination rate of charge carriers. More specifically, the effect of compensated (V and N) and non compensated (Cu and N) n-p codoping of TiO2 was studied. The role of coupling TiO2 thin films with indium tin oxide films in single and multilayer structures, compact and porous morphologies was underlined. The effect of hydrogen doping in passivating dangling bonds in TiO2 was demonstrated. Fe2O3 nanoparticles assembled coatings were synthesized by pulsed laser deposition and studied for the functionalization of electrodes and absorbers surfaces as water oxidation catalysts. The response of the optical and electrochemical properties of the coating to the tuning of film morphology was studied, ranging from a low-transmittance compact layer to a porous nanoparticle-assembled coating, which resulted to be highly transparent. Materials properties were characterized by various techniques such as Raman spectroscopy, x-ray diffraction, UV-vis spectroscopy, x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, and scanning electron microscopy. Electrochemical and photo-electrochemical properties of the samples were studied by testing them as electrodes in a photoelectrochemical cell. Both materials were chosen because they are widespread, non-hazardous, biocompatible and scalable. This enables the large-scale application of photo-electrochemical water splitting and the full exploitation of the green potential of this technology
Test-retest Reliability of Intrinsic Human Brain Default-Mode fMRI Connectivity: Slice Acquisition and Physiological Noise Correction Effects
Get PDFThis thesis aims at evaluating, in two separate studies, strategies for physiological noise and head motion correction in resting state brain FC-fMRI. In particular, as a general marker of noise correction performance we use the test-retest reproducibility of the DMN. The guiding hypothesis is that methods that improve reproducibility should reflect more efficient corrections and thus be preferable in longitudinal studies. The physiological denoising study evaluated longitudinal changes in a 3T harmonized multisite fMRI study of healthy elderly participants from the PharmaCog Consortium (Jovicich et al., 2016). Retrospective physiological noise correction (rPNC) methods were here implemented to investigate their influence on several DMN reliability measures within and between 13 MRI sites. Each site involved five different healthy elderly participants who were scanned twice at least a week apart (5 participants per site). fMRI data analysis was performed once without rPNC and then with WM/CSF regression, with physiological estimation by temporal ICA (PESTICA) (Beall & Lowe, 2007) and FMRIB's ICA-based Xnoiseifier (FSL-FIX) (Griffanti et al., 2014; Salimi-Khorshidi et al., 2014). These methods differ for their data-based computational approach to identify physiological noise fluctuations and need to be applied at different stages of data preprocessing. As a working hypothesis, physiological denoising was in general expected to improve DMN reliability. The head motion study evaluated longitudinal changes in the DMN connectivity from a 4T single-site study of 24 healthy young volunteers who were scanned twice within a week. Within each scanning session, RS-fMRI scans were acquired once using interleaved and then sequential slice-order acquisition methods. Furthermore, brain volumes were corrected for motion using once rigid-body volumetric and then slice-wise methods. The effects of these choices were then evaluated computing multiple DMN reliability measures and investigating single regions within the DMN to assess the existence of inter-regional effects associated with head-motion. In this case, we expected to find slice-order acquisition effects in reliability estimates under standard volumetric motion correction and no slice-order acquisition effect under 2D slice-based motion correction.
Both studies used ICA to characterize the DMN using group-ICA and dual regression procedures (Beckmann et al., 2009). This methodology proved successful at defining consistent DMN connectivity metrics in longitudinal and clinical RS-fMRI studies (Zuo & Xing, 2014). Automatic DMN selection procedures and other quality assurance analyses were made to supervise ICA performance. Both studies considered several test-retest (TRT) reliability estimates (Vilagut, 2014) for some DMN connectivity measurements: absolute percent error between the sessions, intraclass correlation coefficients (ICC) between sessions and multiple sites, the Jaccard index to evaluate the degree of voxel-wise spatial pattern actiavtion overlap between sessions
Tra Guerra e Pace. Il Ministero della Cultura Popolare dalla <<non belligeranza>> alla disfatta in Grecia
No full textL’obiettivo di questa ricerca è provare ad analizzare l’evoluzione dell’apparato del Ministero della Cultura Popolare sia nei suoi aspetti amministrativi e sia nei suoi compiti propri della propaganda all’interno di un arco temporale compreso tra la dichiarazione di «non belligeranza» fino all’insuccesso dell’invasione greca. In questa tesi vengono presi in considerazioni molteplici aspetti che hanno influito sulla politica propagandistica del MinCulPop: l’immaginario costruito artificiosamente per gli italiani, gli aspetti burocratici, il peso della guerra sulle attività e sulle risorse del dicastero per dare un quadro di questi diciannove mesi della propaganda fascista. Questioni chiave come i mutamenti nella struttura del Ministero, i contrasti amministrativi con autorità civili e militari, l’accentramento di competenze differenti e l’assorbimento di Enti e Istituti sono trattati in maniera complementare ad altre tematiche come i mezzi e le tematiche affrontate dalla propaganda fascista in Italia e all’estero, tutti aspetti che possono fornire una chiave di lettura dell’evoluzione dell’opera del Ministero della Cultura Popolare. L’analisi non vuole soffermarsi quindi all’elencazione delle veline o degli ordini alla stampa, opera per di più egregiamente svolta in passato da Nicola Tranfaglia, ma dare una visione di insieme della macchina propagandistica italiana nel tempestoso periodo che ha preceduto l’ingresso nel secondo conflitto mondiale dell’Italia e il primo impatto con la guerra, guerra divenuta reale e non più solamente giornalistica.
A causa del breve arco temporale da me trattato una suddivisione in aree tematiche piuttosto che cronologica appare più adatta per mettere in rilievo i risultati della ricerca. Nonostante l’esame dell’indice possa dare già ad un primo sguardo l’idea generale dei contenuti dell’opera, alcuni macro-temi meritano un’introduzione più approfondita. Il primo capitolo prova ad analizzare alcune caratteristiche sulle disposizioni provenienti dal ministro e dal suo Gabinetto per dirigere il lavoro della stampa finalizzato a costruire un quadro fittizio delle politiche del Regime come quella autarchica, per descrivere il conflitto europeo e soprattutto per creare un’immagine dei contendenti che potesse influenzare l’opinione pubblica secondo la convenienza del momento. Quindi la distinzione di tre momenti che hanno visto la mutazione delle disposizioni secondo uno schema di reazione a stimoli esterni e di un continuo adattamento ai mutamenti politici e militari in atto. Un accenno a questa suddivisione era già stato fatto da Arnold Vincent in “The Illusion of Victory: Fascist Propaganda and the Second World War”, in queste pagine si proverà a contestualizzare questa scansione temporale soffermandosi sugli argomenti chiave che individuano nella «non belligeranza, nella preparazione all’ingresso in guerra e nel periodo di belligeranza i tre momenti evolutivi della propaganda. Nel secondo capitolo ci si concentrerà sulla struttura del Ministero della Cultura Popolare e il processo che prova ad integrare fasce sempre più ampie di popolazione all’interno delle sue attività e di accentrare nella sua amministrazione il maggiori numero di organi che possano coadiuvare questo lavoro. Sono riportati i tentativi per coinvolgere i centri rurali e le inevitabili frizioni scaturite con altri centri di potere da questa operazione, inoltre non verrà trascurata l’analisi dei mezzi più moderni che la propaganda dell’epoca aveva a disposizione quali la radio e il cinema. Nell’ultima parte della tesi invece il focus sarà indirizzato sull’espansione all’estero delle attività del MinCulPop e sull’impatto che la guerra e l’alleanza con la Germania hanno determinato nei successi e negli insuccessi del dicastero di Pavolini. All’interno di queste considerazioni si prova a far luce sullo stato dei rapporti con le Forze Armate e sulle eventuali esperienze di collaborazione senza tralasciare i limiti dell’azione propagandistica del fascismo oltre i confini nazionali. Infine delle necessarie riflessioni saranno portate avanti sul peso dell’apparato propagandistico di Berlino all’interno della vita dell’Asse, in bilico tra un potente alleato e un concorrente scomodo
Switching Behavior: An Experimental Approach to Equilibrium Selection
No full textThe aim of this thesis is to investigate experimentally the reliability of the predictions of evolutionary game theory concerning equilibrium selection. Particularly, I analyze how an adjustment of the initial conditions, which were stated to be one of the essential factors in determining long-run stochastic equilibrium, may change the outcome of the game. The current work studies equilibrium selection in the framework of technology adoption in the presence of an established convention. It consists of three chapters. The first provides an extensive survey of theoretical and experimental literature on equilibrium selection, technology adoption and the emergence of conventions. The second chapter presents an experiment that investigates whether a new technology, represented by an introduction of either a risk-dominant or a payoff dominant strategy, is capable to break a conventional equilibrium and provoke the adoption of another one. In the third chapter I present an experiment that studies whether adding a dominated strategy to a coordination game facilitates transition from one equilibrium to another by changing their basins of attraction
Towards an Ontology of Software
No full textSoftware is permeating every aspect of our personal and social life. And yet, the cluster of concepts around the notion of software, such as the notions of a software product, software requirements, software specifications, are still poorly understood with no consensus on the horizon. For many, software is just code, something intangible best defined in contrast with hardware, but it is not particularly illuminating. This erroneous notion, software is just code, presents both in the ontology of software literature and in the software maintenance tools. This notion is obviously wrong because it doesn’t account for the fact that whenever someone fixes a bug, the code of a software system changes, but nobody believes that this is a different software system. Several researchers have attempted to understand the core nature of software and programs in terms of concepts such as code, copy, medium and execution. More recently, a proposal was made by Irmak to consider software as an abstract artifact, distinct from code, just because code may change while the software remains the same. We share many of his intuitions, as well as the methodology he adopts to motivate his conclusions, based on an analysis of the condition under which software maintains its identity despite change. However, he leaves the question of ‘what is the identity of software’ open, and we answer this question here. Trying to answer the question left open by Irmak, the main objective of this dissertation is to lay the foundations for an ontology of software, grounded on the foundational ontology DOLCE. This new ontology of software is intended to facilitate the communication within the community by reducing terminological ambiguities, and by resolving
inconsistencies. If we had a better footing on answering the question ‘What is software?’, we'd be in a position to build better tools for maintaining and managing a software system throughout its lifetime. The research contents of the thesis consist of three results. Firstly, we dive into the ontological nature of software, recognizing it as an abstract information artifact. To support this proposal the first main contribution of the dissertation is demonstrated from three dimensions: (1) We distinguish software (non-physical object) from hardware (physical object), and demonstrate the idea that the rapid changing speed of software is supported by the easy changeability of its medium hardware; (2) Furthermore, we discuss about the artifactual nature of software, addressing the erroneous notion, software is just code, presents both in the ontology of software literature and in the software maintenance tools; (3)At last, we recognize software as an information artifact, and this approach ensures that software inherits all the properties of an information artifact, and the study and research could be directly reused for software then.
Secondly, we propose an ontology founded on the concepts adopted from Requirements Engineering (RE), such as the notions of World and Machine phenomena. In this ontology, we make a sharp distinction between different kinds of software artifacts (software program, software system, and software product), and describe the ways they are inter-connected in the context of a software engineering process. Additionally, we study software from a Social Perspective, explaining the concepts of licensable software product and licensed software product. Also, we discuss about the possibility to adopt our ontology of software in software configuration management systems to provide a better understanding and control of software changes. Thirdly, we note the important role played by assumptions in getting software to fulfill its requirements. The requirements for most software systems -- the intended states-of-affairs these systems are supposed to bring about -- concern their operational environment, usually a social world. But these systems don’t have any direct means to change that environment in order to bring about the intended states-of-affairs. In what sense then can we say that such systems fulfill their requirements? One of the main contributions of this dissertation is to account for this paradox. We do so by proposing a preliminary ontology of assumptions that are implicitly used in software engineering practice to establish that a system specification S fulfills its requirements R given a set of assumptions A, and our proposal is illustrated with a meeting scheduling example
Ecosystem services for watershed management and planning
Get PDFHuman wellbeing in cities, often associated to availability of engineered structures, is increasingly linked to the conservation of ecosystems. This is the case of the urban water sector where the focus is shifting from adequate infrastructural arrangements to the key role of ecosystem services, thus offering a unique opportunity to achieve sustainability transitions. The urban water sector entails significant complexities and uncertainties, which no longer can be addressed effectively with traditional approaches. A new paradigm of “adaptation and integration”, emerging as a collective effort of stakeholders that engage themselves in a process of social learning, is needed. However, real-life implementation is arduous: it requires linking diverse stakeholders and knowledge systems, across management levels and institutional boundaries. Three innovative concepts can help face this challenge, namely, ecosystem services, boundary work and learning organizations. Ecosystem services provide a holistic approach for framing socio-ecological issues and for integrating different biophysical and socio-economic data. Boundary work, i.e. the effort put in place to facilitate transfer of knowledge into action, informs active management of the tension at the interface between stakeholders that have differing views on what constitutes relevant knowledge. A learning organization is one that is skilled at creating and acquiring knowledge and modifying its behavior to reflect new insights. In this study, these three concepts are jointly explored to build operative approaches to support the implementation of adaptive management. To this end, the work is driven by four specific objectives presented hereafter. The first objective is to frame the urban water sector from an ecosystem services perspective, synthesizing the most relevant aspects related to the exchange of water between watershed and city, and within the city. The proposed framework highlights the role of the urban water sector in (i) linking ecosystem service production and benefit areas, (ii) bridging spatial scales ranging from the watershed to the household level and (iii) adopting ecosystem service-based responses to drivers of water vulnerability. The second objective is to explore practices of boundary work in adaptive watershed management. Thus, an empirical investigation of how boundary work can facilitate knowledge co-generation and cooperative application in a case study of adaptive management in the Fuhrberg watershed (Germany) is conducted. The results suggest that scientific insights have been crucial for "enlightenment", "decision-support", and in "negotiations" between a water utility and stakeholders in Fuhrberg watershed management. The successful implementation of adaptive watershed management is attributed to boundary work deployed by the water utility and ultimately to its high institutional capacity. This study, which is one of the first empirical assessments of boundary work in practice, presents many promising approaches for initiating boundary work in the case of water utilities. Yet, more comparative research is required to understand the influence of contextual differences on appropriate methods and potential outcomes of boundary work. The third objective is to build and test an approach for designing and assessing impact of watershed investments, aiming to implement adaptive management. The proposed approach is structured to facilitate negotiations among stakeholders. Its strategic component includes setting the agenda, defining investment scenarios, and assessing the performance of watershed investments. Its technical component consists of tailoring spatially explicit ecosystem service models, generating future land use scenarios, and modeling impacts on ecosystem services. The approach is applied to a case study in a data-scarce context: Toker Watershed (Eritrea), considering soil erosion -related challenges. It produced spatially explicit data, which has been aggregated to assess quantitatively the performance of watershed investments, in terms of changes in selected ecosystem services, thus answering key management and planning questions. By addressing stakeholders’ concerns of credibility, saliency, and legitimacy, the approach is expected to facilitate the negotiation of objectives, definition of scenarios, and assessment of watershed investments. The fourth objective is to explore water utilities as learning organization implementing adaptive watershed management. A conceptual framework for evaluating the institutional capacity of water utilities is used to characterize the water utilities in Hanover and Asmara. In particular, the institutional capacity of the “Hannover Water Utility” and “Asmara Water Supply Department” is investigated based on the available information from documents, literature and the previous results, and an interview with a key informant. The results show that the institutional capacity of Hanover Water Utility can be classified as Level 5 – “Progressive water utility” and Asmara Water Supply Department can be classified as Level 2 – “Basic water utility”. An empirical pathway to test the results, by involving senior managers and informed scientists from both case studies, is proposed. In any case, the preliminary results highlight the attributes that determine the capacity of water utilities to become a central actor in the in the implementation of an adaptive watershed management. This research, by jointly exploring the innovative concepts of ecosystem services, boundary work and learning organizations, builds operative approaches that can support the implementation of adaptive watershed management. Further work is needed to address some of the complexities and uncertainties underlying the proposed approaches, including data resolution, model calibration, and above all participation of real-life stakeholder
From data to mathematical analysis and simulation in models in epidemiology and ecology
No full textThis dissertation is divided into three different parts.
In the first part we analyse collected data on the occurrence of influenza-like illness (ILI) symptoms regarding the 2009 influenza A/H1N1 virus pandemic in two primary schools of Trento, Italy. These data were used to calibrate a discrete-time SIR model, which was designed to estimate the probabilities of influenza transmission within the classes, grades and schools using Markov Chain Monte Carlo (MCMC) methods. We found that the virus was mainly transmitted within class, with lower levels of transmission between students in the same grade and even lower, though not significantly so, among different grades within the schools. We estimated median values of R0 from the epidemic curves in the two schools of 1.16 and 1.40; on the other hand, we estimated the average number of students infected by the first school case to be 0.85 and 1.09 in the two schools. This discrepancy suggests that household and community transmission played an important role in sustaining the school epidemics. The high probability of infection between students in the same class confirms that targeting within-class transmission is key to controlling the spread of influenza in school settings and, as a consequence, in the general population.
In the second part, by starting from a basic host-parasitoid model, we study the dynamics of a 2 hosts-1 parasitoid model assuming, for the sake of simplicity, that larval stages have a fixed duration. If each host is subjected to density-dependent mortality in its larval stage, we obtain explicit conditions for coexistence of both hosts, as long as each 1 host-parasitoid system would tend to an equilibrium point.
Otherwise, if mortality is density-independent, under the same conditions host coexistence is impossible.
On the other hand, if at least one of the 1 host-parasitoid systems has an oscillatory dynamics (which happens under some parameter values), we found, through numerical bifurcation, that coexistence is favoured. It is also possible that coexistence between the two hosts occurs even in the case without density-dependence. Analysis of this case has been based on methods of approximation of the dominant characteristic multipliers of the monodromy operator using a recent method introduced by Breda et al.
Models of this type may be relevant for modelling control strategies for Drosophila suzukii, a recently introduced fruit fly that caused severe production losses, based on native parasitoids of indigenous fruit flies.
In the third part, we present a starting point to analyse raw data collected by Stacconi et al. in the province of Trento, Italy. We present an extensions of the model presented in Part 2 where we have two hosts and two parasitoids. Since its analysis is complicated, we begin with a simpler one host-one parasitoid model to better understand the possible impact of parasitoids on a host population. We start by considering that the host population is at an equilibrium without parasitoids, which are then introduced as different percentages of initial adult hosts. We compare the times needed by parasitoids to halve host pupae and we found that the best percentage choice is 10%. Thus we decide to fix this percentage of parasitoid introduction and analyse what happens if parasitoids are introduced when the host population is not at equilibrium both by introducing always the same percentage or the same amount of parasitoids. In this case, even if the attack rate is at 1/10 of its maximum value, parasitoids would have a strong effect on host population, shifting it to an oscillatory regime. However we found that this effect would require more than 100 days but we also found that it can faster if parasitoids are introduced before the host population has reached the equilibrium without parasitoids. Thus there could be possible releases when host population is low. Last we investigate also what happens if in nature mortality rates of these species increase and we found that there is not such a big difference respect to the results obtained using laboratory data