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Floristic and structural variability of the central apennines beech forests in relation to natural and anthropogenic determinants
No full textForests are complex ecosystems, in which the floristic composition is the result of the combined effect of several factors, acting at different levels. Climate, lithology, geomorphology act at a broader scale, driving the forest's communities differentiation while, at a finer scale, the understory species composition is shaped by the forest stand structure that directly influences the environmental conditions (light, temperature, moisture) at the ground level. Fagus sylvatica forests are the most abundant broadleaved communities in central and southern Europe; in Italy they represent the typical montane vegetation in the Apennine chain, where these coenoses reach the highest elevations of their whole distributional range. Beech forests have been managed for centuries, prevalently as coppice, or coppice-with-standards (CWS), and high forest (HF). However, in recent decades deep socio-economical changes have led to the progressive abandonment of coppice cut and its conversion to high forest management. These two systems differ in cut intensity and severity (both higher in CWS): given that forest management impacts upon overstory structure and therefore determines the understory composition, management changes are likely to affect understory species composition and diversity.
In this thesis I have analyzed the effect of the main environmental drivers on beech forests communities: I then focused on the management effects on understory species and 9210* Habitat diagnostic species richness and composition (sensu Habitat Directive 92/43 EEC), in order to understand the possible implications of the old CWS conversion on the floristic composition.
The study was conducted in central Apennines, on the Montagne della Duchessa massif, where beech forests occupy a surface of more than 1200 ha; these forests have ceased to be managed since '60s, so the CWS have become older, and are destined to be converted to the HF cut.
I studied the role of the environmental factors in differentiating the beech forests communities by using a dataset of 40 relevés randomly selected. The dataset obtained has been analyzed through a cluster analysis and a Indicator Species Analysis (ISA), in order to obtain groups of relevés and to characterize them in floristic terms; the groups obtained were then compared in terms of environmental and topographic variables, Ellenberg indicator values, life forms, Social Behaviour Types (SBT) and structural parameters. Results showed that the floristic and coenological variability is shaped by a climatic and edaphic gradient, that both contribute to define two main communities: a microthermal one, placed at higher altitudes and cooler aspects (Cardamino kitaibelii - Fagetum sylvaticae), and a termophilous one, lying at lower altitudes and warmer aspects (Lathyro veneti - Fagetum sylvaticae). Social Behaviour Types and structural parameters were useful for detecting the effects of the progressive reforestation process occurring inside the microthermal community at higher elevation.
In order to investigate the differences between old CWS and HF stands in terms of understory richness and composition, I used 66 relevés, selected through a random-stratified method, so as to have a comparable number of relevés for each management category; old CWS and HF stands were compared in terms of structural attributes and floristic richness through a U Mann-Whitney test: the II results showed how management is the main factor responsible for differences in the tree layer's spatial aggregation pattern and vertical layering, and that therefore determines the amount of surface available for understory species. HF stands showed a higher mean richness of both understory and diagnostic species, these latter being more evenly distributed (higher species equitability) inside the community. This leads to the consideration that in HF stands the cut regime provided a constant canopy cover over time, and then maintained more stable microclimatic conditions favoring a higher abundance and evenness of the shade-tolerant and vernal species. Conversely, in old CWS the dense canopy negatively affected the understory richness by reducing the light-demanding species pool, while the shade-tolerant species have not yet had time to spread.
In order to understand the implications of the old CWS conversion on beech forests ecosystem's ecological functions, the same dataset was analyzed through plant functional traits, by creating a relevés x traits matrix. A Redundancy Analysis (RDA) was performed to assess the relationship between traits states and management, while a U Mann-Whitney test was used to assess differences in traits states richness between the management types. The results were consistent with the previous findings based on habitat diagnostic species, as HF stands showed a higher affinity to traits typical of mature forests, while old CWS were more related to traits related to managed stands. Moreover, HF stands showed a higher abundance of those traits related to the natural forest's seasonal change, this indicating a good species distribution among the functional niches. Even in this case, old CWS was shown to be in a transitional stage, still represented by some traits related to management, where the mature forest traits are also present, but with lower abundance.
Finally, given that in a forest ecosystem understory represent more than 90% of species richness, and is the most sensitive to disturbance, the modern silvi-cultural strategies should take into account the management effects on forest biodiversity, and adopt sustainable interventions able to favor the typical biodiversity of the ecosystems we want to manage. This thesis provides useful information for management purposes, as our findings show that, in the forests studied, the old CWS conversion to HF could be a good management strategy if our aim is the conservation over time of the species typically related to mature forest conditions
Immigrate e lavoro autonomo in Italia : nuove forme di integrazione?
No full textLa ricerca è stata organizzata in diverse fasi corrispondenti a un progressivo approfondimento dell’oggetto indagato: l’esperienza di alcune donne immigrate che hanno scelto la strada del lavoro autonomo e imprenditoriale. Una prima fase è stata dedicata all’analisi della letteratura su più livelli ripercorrendo in primo luogo il modo in cui sono state studiate le grandi migrazioni internazionali e isolando il tema delle “migrazioni di genere”. Inevitabile e necessario è stato lo sguardo alla letteratura internazionale ed europea che ha fornito una prima cornice di riferimento anche riguardo al tema specifico del genere. Rispetto a questo concetto chiave, la letteratura italiana sulle migrazioni ha mostrato un certo ritardo e, soprattutto, la tendenza a far diventare la migrazione femminile un interesse di pochi verso poche specifiche tematiche: il lavoro domestico e di cura e la prostituzione.
La volontà di studiare questa area del mercato del lavoro è nata in stretta connessione con l’ipotesi di fondo: può l’autonomia lavorativa, con le relative ambizioni e prospettive di mobilità, aprire la strada a una forma di inclusione sociale più profonda di una formale accettazione e tolleranza? Come si definisce la soggettività di queste donne?
L’indagine ha coinvolto dieci donne attive nella città di Roma secondo un criterio di significatività dato non tanto dall’essere un campione statisticamente rappresentativo, quanto dalla possibilità di far emergere dei tratti comuni e differenti nella definizione della loro soggettività di immigrate provenienti da diverse aree geo-culturali. In questo senso l’analisi è stata condotta secondo un approccio qualitativo per mezzo di racconti di vita seguiti poi da un intenso lavoro di carattere interpretativo. Il primo tramite di contatto è stato la Cna World di Roma, gruppo di interesse della Confederazione Nazionale dell’Artigianato e della Piccola e Media Impresa che si occupa in particolare dell’imprenditoria straniera.
È emerso un quadro piuttosto vivace e non privo di contraddizioni sul modo in cui è vissuta la condizione di immigrate. Da un lato è espressa una sincera soddisfazione per quanto si è realizzato in ambito lavorativo, si dichiarano, con altrettanto coinvolgimento, ottimi rapporti con gli italiani e un percorso di inserimento “felice” e “fortunato”. Quando però si va a scavare un po’ più in profondità queste stesse affermazioni rivelano una realtà complessa e ricca di punti interrogativi. Il luogo di lavoro è lo spazio dove passano la maggior parte del loro tempo, pur con varie sfumature, la socialità appare ristretta a relazioni poco profonde sia con gli autoctoni sia con i loro connazionali con i quali raramente si mantengono legami forti. Il tema della cittadinanza è un terreno scosceso e in qualche modo rivelatore di una realtà che necessita di essere approfondita. Emerge una visione essenzialmente strumentale e strategica in base alla quale si guarda a una generale facilitazione in termini di gestione delle pratiche burocratiche connesse, in primo luogo, al mondo del lavoro e alla tutela dei figli. Sembrerebbe mancare qualsiasi senso di coinvolgimento e attribuzione di un significato di appartenenza dietro all’etichetta “cittadinanza”. Appartenenza e inclusione che, pur lontane dal compiersi, sembrano essere ricercate più nella buona riuscita del percorso lavorativo e nella conseguente “approvazione” da parte degli italiani
Alleviation of Rotorcraft BV1 noise and vibrations through control algorithms based on efficient aeroelastic/aeroacoustic formulations
No full textBecause of their peculiar ability to take off vertically and their excellent handling qualities in hover and low speed flight conditions, helicopters can play several roles beyond the capabilities of fixedwing aircraft. However, the high levels of vibrations and noise generated represent nowadays critical issues limiting the helicopters operations both in civilian and military cenarios. Among the several sources contributing to the overall levels of vibration and noise, the main rotor plays a fundamental role through complex aerodynamic and aeroelastic phenomena affecting its operation.
The rotorcraft research community is currently involved in exploring several active and passive approaches suited to reduce these annoying effects, and a lot of attention is particularly given to noise aerodynamically generated by main rotor when blade-vortex interactions (BVIs) occur. In this context, the aim of the thesis is to provide efficient formulations for performing fast and accurate rotor aeroelastic and aeroacoustic analyses. The availability of numerically efficient tools is extremely useful, for example, in early stages of design, optimization, and control synthesis, due to the high number of simulations that might be required. Some applications of the numerical tools
developed are also presented in the thesis, in order to investigate different active and passive approaches for reducing vibration and BVI noise due to the helicopter main rotor. In particular, a procedure of advanced blade optimization is investigated as passive approach. In this procedure,
blade shape and its mechanical/structural properties are selected using a genetic optimization algorithm, in order to reduce annoying vibratory loads at different flight conditions. In examining active control approaches, benefits achievable through the active twist rotor (ATR) solution are evaluated, investigating control effectiveness of both high-frequency and low-frequency actuators.
The optimal, multi-cyclic, control theory is applied to identify the control law driving the ATR actuation. In all the applications proposed, rotor simulations are obtained by combining aerodynamic, aeroelastic and aeroacoustic tools able to accurately capture wake-blade mutual positions, which plays a crucial role in vibration and noise generation. In particular, rotor aeroelastic behaviour is described by a non-linear, beam-like model, coupled with a quasi-steady sectional aerodynamic formulation, taking into account three-dimensional effects by a free-wake inflow correction. The evaluation of the wake inflow is obtained by a boundary element method (BEM) suited for the analysis of helicopter rotors in arbitrary flight conditions, including those
affected by strong aerodynamic body-wake interactions. Concerning the noise emitted by the rotor, it is evaluated through solution of the well-known Ffowcs Williams and Hawkings equation, which governs the propagation of acoustic disturbances aerodynamically generated by moving bodies.
Specifically, the boundary integral Formulation 1A developed by Farassat is used. In this thesis, an accurate and efficient approach is presented for predicting blade airloads used for the aeroacoustic solution. It relies on the Küssner-Schwarz aerodynamic sectional theory, coupled with wake inflow
information obtained through three-dimensional, free-wake aerodynamic solutions of trimmed rotor aeroelastic responses. In order to provide inflow corrections to sectional formulations used for both the aeroelastic solution and the blade airloads prediction, surrogate inflow models are also
introduced in the thesis, as good trade-off solution between accuracy and computational efficiency.
Furthermore, different algorithms for blade optimization and active control synthesis, aimed at efficiently exploiting aeroelastic and aeroacoustic models for the specific considered applications, are described. Several numerical investigations are presented to demonstrate the capability of the proposed approaches and examine their performance in the optimization and active control applications considered. In particular, single-point and multi-point optimization procedures are successfully applied to define low-vibrating rotor blades at the flight condition(s) considered, showing difficulties to guarantee significant vibratory loads reductions in off-design flight conditions, even if multi-point optimization is considered. A sensitivity analysis of the results
obtained to the aerodynamic models used is carried out, confirming suitability of the surrogate models introduced in optimization problems. A final acoustic assessment of the optimal rotor obtained is performed, confirming the more acoustically annoying nature of low-vibrating rotors.
Then, the high-frequency ATR control application is numerically investigated. Two different closed-loop controls are obtained, leading to significant reductions of the higher-harmonic noise in some areas of the acoustic field through limited blade twist imposed. In both cases, vibratory levels appears to be unaffected by control actuation, confirming the advantage of high-frequency controllers in terms of drawbacks onset. Finally, attention is focused on low-frequency ATR control strategy. In a preliminary analysis, 2/rev frequency appears to be effective in reducing BVI noise, with limited drawbacks in terms of increase of vibratory loads and low-frequency acoustic disturbance with respect to other frequencies considered. Hence, a 2/rev closed-loop noise control is numerically applied, showing an overall satisfactory reduction of the BVI noise in the acoustic field, with limited increase of low-frequency noise and vibratory hub loads
Brain waves for biometric user recognition
No full textBrain signals are being investigated within the medical field for more than a century to study brain diseases like epilepsy, spinal cord injuries, Alzheimer, Parkinson, schizophrenia, and stroke among the others. They are also used as the basis of brain computer interface and brain machine interface with assistance, rehabilitative and entertainment applications. Despite the broad interest in clinical applications, the use of brain signals sensed by means of electroencephalogram has been only recently investigated by the scientific community as a biometric characteristic, and the use of brain waves for the purpose of automatic people recognition is only at an embryonic stage. However, brain signals present some peculiarities, not shared by the most commonly used biometrics, like face, iris, and fingerprints, concerning secretness, privacy compliance, robustness against spoofing attacks, possibility to perform continuous identification, intrinsic liveness detection, and universality. Moreover since 70s there is evidence that EEG signals are genetically influenced and that they carry personality correlates. These peculiarities make the use of brain signals appealing. On the other hand there are many challenges related to the use of brain signals which need to be properly addressed in order to deploy biometric systems based on brain activity in real life applications. Among these challenges, the definition of the brain response elicitation protocol and the convenience of the acquisition process should be addressed, to cite a few.
In this work of doctoral thesis the aforementioned issues are further developed. The first chapters provide a comprehensive and critical review of state of the art methods for electroencephalogram based automatic user recognition that have been proposed in literature so far, also pointing out neurophysiological evidences related to the performed claims. The methods implemented and the experiments carried on within the present work are reported and detailed in the next chapters, together with the results obtained from the analysis of data
L'approbatio degli statuti comunali nei domini della Chiesa tra legislazione, dottrina e prassi
No full textGli statuti comunali, espressioni del sistema di diritto comune, costituirono nel medioevo e nell’età moderna un’importante fonte del diritto. La loro approvazione da parte dell’ autorità papale rappresentò per questa uno strumento politico-giuridico per affermare il suo potere nei confronti delle varie comunità, rivestendo pertanto un ruolo rilevante nel disciplinare i rapporti centro-periferia. Questo scritto si propone di verificare come concretamente l’istituto abbia operato nei domini della Chiesa, avvalendosi delle diverse le ricostruzioni proposte dalla storiografia e attraverso lo studio della documentazione d’archivio che rappresenta in gran parte il riflesso delle scelte organizzative del potere temporale
Iftiimin Suugaanta Soomaalida: waxa ay tahay, waxa ay tarto iyo waxyaha ay ka koobanto
No full textMaqaalkaani wuxuu ka hadlayaa "suugaan" waxa loola jeedo, qaybaha ay u kala baxdo iyo qiimaha ay suugaantu u leedahay guud ahaan ummadda dunida, gaar ahaanna Soomaalida.L'articolo illustra il significato del termine "suugaan" (letteratura), i generi letterari e l'importanza che la letteratura ha generalmente per tutte le popolazioni del mondo, e in particolar modo per i Somali.The article illustrates the meaning of the word "suugaan" (literature), the literary genres and the importance literture has for every society and in particular for Somali society.Cabdirashid M. Ismaaciil, Cabdalla C. Mansuur, Saynab A. Sharci (eds.
