Neural Networks Applications for the Remote Sensing of Hydrological Parameters

The main artificial neural networks (ANN)‐based retrieval algorithms developed at the Institute of Applied Physics (IFAC) are reviewed here. These algorithms aim at retrieving the main hydrological parameters, namely the soil moisture content (SMC), the plant water content (PWC) of agricultural vegetation, the woody volume of forests (WV) and the snow depth (SD) or snow water equivalent (SWE), from data collected by active (SAR/scatterometers) and passive (radiometers) microwave sensors operating from space. Taking advantage of the fast computation, ANN are able to generate output maps of the target parameter at both local and global scales, with a resolution varying from hundreds of meters to tens of kilometres, depending on the considered sensor. A peculiar strategy adopted for the training, which has been obtained by combining satellite measurements with data simulated by electromagnetic models (based on the radiative transfer theory, RTT), made these algorithms robust and site independent. The obtained results demonstrated that ANN are a powerful tool for estimating the hydrological parameters at different spatial scales, provided that they have been trained with consistent datasets, made up by both experimental and theoretical data

Microwave Indices from Active and Passive Sensors for Remote Sensing Applications

Past research has comprehensively assessed the capabilities of satellite sensors operating at microwave frequencies, both active (SAR, scatterometers) and passive (radiometers), for the remote sensing of Earth’s surface. Besides brightness temperature and backscattering coefficient, microwave indices, defined as a combination of data collected at different frequencies and polarizations, revealed a good sensitivity to hydrological cycle parameters such as surface soil moisture, vegetation water content, and snow depth and its water equivalent. The differences between microwave backscattering and emission at more frequencies and polarizations have been well established in relation to these parameters, enabling operational retrieval algorithms based on microwave indices to be developed. This Special Issue aims at providing an overview of microwave signal capabilities in estimating the main land parameters of the hydrological cycle, e.g., soil moisture, vegetation water content, and snow water equivalent, on both local and global scales, with a particular focus on the applications of microwave indices

The Horizontal Branch in the UV Colour Magnitude Diagrams. II. The case of M3, M13 and M79

We present a detailed comparison between far-UV/optical colour Magnitude Diagrams obtained with high-resolution Hubble Space Telescope data and suitable theoretical models for three Galactic Globular Clusters: M3, M13 and M79. These systems represents a classical example of clusters in the intermediate metallicity regime that, even sharing similar metal content and age, show remarkably different Horizontal Branch morphologies. As a consequence, the observed differences in the colour distributions of Horizontal Branch stars cannot be interpreted in terms of either first (metallicity) or a second parameter such as age. We investigate here the possible role of variations of initial Helium abundance (Y). Thanks to the use of a proper setup of far-UV filters, we are able to put strong constraints on the maximum Y (Y_{max}) values compatible with the data. We find differences Delta Y_{max} ~ 0.02-0.04 between the clusters with M13 showing the largest value (Y_{max} ~ 0.30) and M3 the smallest (Y_{max} ~ 0.27). In general we observe that these values are correlated with the colour extensions of their Horizontal Branches and with the range of the observed Na-O anti-correlations.Comment: Accepted for publication by MNRAS. 15 pages, 15 figures, 1 tabl

DECENTRALIZATION AND GOVERNANCE IN DEVELOPING COUNTRIES: THE CASE OF GHANA

2003/2004Il presente lavoro di ricerca ha l'obiettivo di analizzare il fenomeno del decentramento politico e amministrativo nei paesi in via di sviluppo, servendosi di un percorso metodologico che parte dallo studio ed applicazione del concetto di governance e, allo stesso tempo, si avvale di un'attenta analisi geopolitica del caso empirico del Ghana. Il concetto di decentramento entra a fare parte della ridefinizione del ruolo dello Stato, fronte alla globalizzazione e alle nuove pressioni localistiche e multipolari. Esso rappresenta un tema di grande attualità nel dibattito sulle strategie di sviluppo, tanto che molti paesi meno avanzati hanno già intrapreso da anni riforme nella direzione di un rafforzamento delle autorità locali, spesso dietro pressione dei paesi donatori e di organizzazioni internazionali. I risultati di queste riforme sono stati di diversa natura, anche a secondo dei settori e dei continenti interessati. L'Africa, dove queste riforme sono spesso state legate a "tentativi" di democratizzazione, è forse il continente dove il decentramento ha trovato terreno meno fertile, producendo risultati deludenti e risposte contraddittorie. Il caso studio preso in esame è quello della Repubblica del Ghana. In questo paese il decentramento si è rivelato non solo il primo passo verso un processo di democratizzazione del Paese, ma anche una strategia di azione in risposta alle enormi disuguaglianze tra le regioni Nord e il Sud. La storia del decentramento ghanese trova le Decentralization and Governance in Deve/oping Countries: The Case o/Ghana sue origini nell'amministrazione coloniale britannica e nella sua indirect rule esercitata attraverso le autorità tradizionali. Solamente nel 1988 tuttavia il decentramento trova uno sviluppo significativo, legandosi con successo al processo di transizione democratica. L'analisi dei processi di governance fa emergere tuttavia che il decentramento in Ghana soffre della mancanza di un forte sostegno pubblico verso le proprie istituzioni, di una rappresentazione spesso carente delle classi meno abbienti, ma soprattutto dell'assenza di sistemi efficaci di accountability (rendere conto delle proprie azioni). È significativo osservare come le assemblee distrettuali, ossia le organizzazioni amministrative del territorio più importanti, dipendono ancora fortemente dalle decisioni del governo centrale e sono spesso vittime dell'influenza di elites locali. In questo contesto il processo di decentramento ha finito per riprodurre le inefficienze e i favoritismi del potere centrale a livello locale. Per far fronte a queste difficoltà, il Ghana dovrà mettere in piedi degli aggiustamenti istituzionali che migliorino i sistemi di accountability e dovrà cercare di rafforzare la credibilità delle assemblee distrettuali, dotandole di mezzi adeguati. Il paese dovrà inoltre creare nuovi spazi di comunicazione e di dialogo a livello locale, che permettano alle comunità e ai gruppi meno avvantaggiati, di meglio comprendere e quindi partecipare ai processi democratici locali, liberandosi dallo strapotere delle elites locali.XVII Ciclo1976Versione digitalizzata della tesi di dottorato cartacea

Unlocking North Africa’s Potential through Regional Integration : Challenges and Opportunities

Efforts to promote regional integration in North Africa to date have often been constrained by political differences as well as diversity in economic performance, pace of economic reforms and openness, and disparities in legal and regulatory frameworks. Overlapping preferential trade agreements also emerged as a constraint to regional integration efforts on the back of complex rules of origin and a large number of ‘behind the border’ barriers. Together, these impediments have increased transaction costs. Importantly, the existence of these barriers reflects weak commitment to the integration process, as national governments have failed to translate decisions taken at the regional level into action at the country level. In the wake of the Arab Spring, the emerging political landscape in North Africa promises to give new impetus to regional integration efforts, as new democratically-elected governments seek to promote inclusive growth and build institutions for good governance. The diversity of resource endowments in the region, coupled with the existing physical infrastructure, represent an important opportunity to further development through integration. This book examines the key issues and challenges facing regional integration in the North African countries across a number of thematic areas including: (i) energy, (ii) climate change and environment, (iii) financial sector, (iv) trade facilitation and transport, (v) human development and, (vi) information and communication technology. It provides proposals for the Bank’s continued engagement in the region, geared towards exploiting the full potential of regional integration in North Africa for the promotion of a new, inclusive, sustainable economic growth model

A Weakly Pareto Compliant Quality Indicator

In multi-objective optimization problems, the optimization target is to obtain a set of non-dominated solutions. Comparing solution sets is crucial in evaluating the performances of different optimization algorithms. The use of performance indicators is common in comparing those sets and, subsequently, optimization algorithms. A good solution set must be close to the Pareto-optimal front, well-distributed, maximally extended and fully filled. Therefore, an effective performance indicator must encompass these features as a whole and must be Pareto dominance compliant. Unfortunately, some of the known indicators often fail to properly reflect the quality of a solution set or cost a lot to compute. This paper demonstrates that the Degree of Approximation (DOA) quality indicator, is a weakly Pareto compliant unary indicator that gives a good estimation of the match between the approximated front and the Pareto-optimal front. Moreover, DOA computation is easy and fast

Green Systems Integrated to the Building Envelope: Strategies and Technical Solution for the Italian Case

Green roofs and green and living walls are increasingly seen in cities, because they are an important strategy that addresses some key urban environmental issues and allows the achievement of different benefits. Among these, the most relevant ones are reduction of the \u201cUrban Heat Island\u201d effect, of rainfall contributions to the sewer system, of environmental impact and energy saving, and retention of harmful substance. The study aims to analyze different systems of greenery systems integrated (GSI), green roofs (GR), and green and living walls (GW-LW), as a possible retrofit technique of the envelope of heritage buildings and especially their applications in the context of historic cities in Italy, pointing out positive and negative aspects. Particularly, it pays attention to the green retrofitting of buildings and to the technical problems related to the installation of systems, since at the moment there are already several studies that show the environmental and microclimatic benefits of the integration of vegetation in architecture. This study tries to highlight the series of design procedures necessary both in the preliminary phase and then in the executive phase to relate the GSI to the existing building envelopes. The GR, from the results of the simulations conducted, demonstrate a greater simplicity in their construction, with improvements also from the point of view of the working loads on the existing structures, since the interventions are performed more easily than those on the facade. The study highlights the architectural needs that are not always considered such as the increase in the thickness of the roof and the related need to raise its edges, changing the perspective of the building. On the other hand, the GW and the LW show some complexity in their construction because they must deal with facades often rich in decorative elements and where openings aect the assemblage and connection works such as the tinsmiths of the intrados of the openings. It must be taken into consideration the necessity of having to drill masonry, often inhomogeneous, to connect fixings and the problems of stability this entails must be carefully analyzed

Comparison of Machine Learning Methods Applied to SAR Images for Forest Classification in Mediterranean Areas

In this paper, multifrequency synthetic aperture radar (SAR) images from ALOS/PALSAR, ENVISAT/ASAR and Cosmo‐SkyMed sensors were studied for forest classification in a test area in Central Italy (San Rossore), where detailed in‐situ measurements were available. A preliminary discrimination of the main land cover classes and forest types was carried out by exploiting the synergy among L‐, C‐ and X‐bands and different polarizations. SAR data were preliminarily inspected to assess the capabilities of discriminating forest from non‐forest and separating broadleaf from coniferous forests. The temporal average backscattering coefficient (°) was computed for each sensor‐polarization pair and labeled on a pixel basis according to the reference map. Several classification methods based on the machine learning framework were applied and validated considering different features, in order to highlight the contribution of bands and polarizations, as well as to assess the classifiers’ performance. The experimental results indicate that the different surface types are best identified by using all bands, followed by joint L‐ and X‐ bands. In the former case, the best overall average accuracy (83.1%) is achieved by random forest classification. Finally, the classification maps on class edges are discussed to highlight the misclassification errors