503 research outputs found
The Skipping Behavior of Users of Music Streaming Services and its Relation to Musical Structure
The behavior of users of music streaming services is investigated from the
point of view of the temporal dimension of individual songs; specifically, the
main object of the analysis is the point in time within a song at which users
stop listening and start streaming another song ("skip"). The main contribution
of this study is the ascertainment of a correlation between the distribution in
time of skipping events and the musical structure of songs. It is also shown
that such distribution is not only specific to the individual songs, but also
independent of the cohort of users and, under stationary conditions, date of
observation. Finally, user behavioral data is used to train a predictor of the
musical structure of a song solely from its acoustic content; it is shown that
the use of such data, available in large quantities to music streaming
services, yields significant improvements in accuracy over the customary
fashion of training this class of algorithms, in which only smaller amounts of
hand-labeled data are available
Study and development of a reliable fiducials-based localization system for multicopter UAVs flying indoor
openThe recent evolution of technology in automation, agriculture, IoT, and aerospace fields
has created a growing demand for mobile robots capable of autonomous operation and
movement to accomplish various tasks. Aerial platforms are expected to play a central
role in the future due to their versatility and swift intervention capabilities. However,
the effective utilization of these platforms faces a significant challenge due to localization,
which is a vital aspect for their interaction with the surrounding environment.
While GNSS localization systems have established themselves as reliable solutions for
open-space scenarios, the same approach is not viable for indoor settings, where localization
remains an open problem as it is witnessed by the lack of extensive literature on
the topic.
In this thesis, we address this challenge by proposing a dependable solution for small
multi-rotor UAVs using a Visual Inertial Odometry localization system. Our KF-based
localization system reconstructs the pose by fusing data from onboard sensors. The primary
source of information stems from the recognition of AprilTags fiducial markers,
strategically placed in known positions to form a “map”.
Building upon prior research and thesis work conducted at our university, we extend
and enhance this system. We begin with a concise introduction, followed by a justification
of our chosen strategies based on the current state of the art. We provide an
overview of the key theoretical, mathematical, and technical aspects that support our
work. These concepts are fundamental to the design of innovative strategies that address
challenges such as data fusion from different AprilTag recognition and the elimination
of misleading measurements. To validate our algorithms and their implementation,
we conduct experimental tests using two distinct platforms by using localization
accuracy and computational complexity as performance indices to demonstrate the
practical viability of our proposed system.
By tackling the critical issue of indoor localization for aerial platforms, this thesis tries
to give some contribution to the advancement of robotics technology, opening avenues
for enhanced autonomy and efficiency across various domains.The recent evolution of technology in automation, agriculture, IoT, and aerospace fields
has created a growing demand for mobile robots capable of autonomous operation and
movement to accomplish various tasks. Aerial platforms are expected to play a central
role in the future due to their versatility and swift intervention capabilities. However,
the effective utilization of these platforms faces a significant challenge due to localization,
which is a vital aspect for their interaction with the surrounding environment.
While GNSS localization systems have established themselves as reliable solutions for
open-space scenarios, the same approach is not viable for indoor settings, where localization
remains an open problem as it is witnessed by the lack of extensive literature on
the topic.
In this thesis, we address this challenge by proposing a dependable solution for small
multi-rotor UAVs using a Visual Inertial Odometry localization system. Our KF-based
localization system reconstructs the pose by fusing data from onboard sensors. The primary
source of information stems from the recognition of AprilTags fiducial markers,
strategically placed in known positions to form a “map”.
Building upon prior research and thesis work conducted at our university, we extend
and enhance this system. We begin with a concise introduction, followed by a justification
of our chosen strategies based on the current state of the art. We provide an
overview of the key theoretical, mathematical, and technical aspects that support our
work. These concepts are fundamental to the design of innovative strategies that address
challenges such as data fusion from different AprilTag recognition and the elimination
of misleading measurements. To validate our algorithms and their implementation,
we conduct experimental tests using two distinct platforms by using localization
accuracy and computational complexity as performance indices to demonstrate the
practical viability of our proposed system.
By tackling the critical issue of indoor localization for aerial platforms, this thesis tries
to give some contribution to the advancement of robotics technology, opening avenues
for enhanced autonomy and efficiency across various domains
Vegetative incompatibility and potential involvement of a mycovirus in the Italian population of Geosmithia morbida
Studies carried out during an Italian outbreak of the Thousand Cankers Disease of walnut, demonstrated that non-coalescing cankers on host plants, separated by equidistant uninfected zones, were associated with incompatible strains of Geosmithia morbida. Confirmation of the vegetative incompatibility of paired fungal isolates, randomly collected from black walnuts, was obtained from observations of a clear separation zones and the absence of anastomoses. Pairing tests with two incompatible monoconidial strains indicated differences in morphology and growth rates. Electron microscopy revealed the presence of icosahedral mycovirus-like particles in one of the monoconidial strains that demonstrated low degrees of virulence in planta compared with a particlefree monoconidial strain. The occurrence of a vegetative incompatibility system in recently introduced populations of G. morbida has considerable implications for fungal biology. Incompatibility in G. morbida and potential direct or indirect roles of the observed virus-like particles have potential ecological and epidemiological consequences. \ua9 Firenze University Press
Analysing the relationship between ectomycorrhizal infection and forest decline using marginal models
This statistical survey originates from the problem of discovering which relationship exists between root ectomycorrhizal infection and health status of forest plants. The sampling scheme takes observations from roots that come from sectors around the tree resulting in a hierarchical association structure of the observations. Marginal regression models are used to analyze the mean effect of the ectomycorrhizal state on a response variable proxy for the health degree of the plants
Evaluating the impact of Hymenoscyphus fraxineus in Trentino (Alps, Northern Italy): first investigations
The spread of Hymenoscyphus fraxineus has been causing great concern regarding the survival of European ash (Fraxinus excelsior) throughout Europe since the 1990s. The disease was first recorded in Trentino (southern Alps, Italy) in 2012 and has spread throughout the mountain landscape, where ash trees are scattered in small and isolated stands in different valleys. The status of the disease was checked by monitoring the damage to natural regeneration and adult trees in 90 sites spread over the whole region. The survey confirmed the complete colonization by the pathogen of the whole investigated area, with high levels of damage to both young and adult ash trees. Regeneration (both seedlings and saplings) was observed to be affected by the fungus in 88 plots out of 90. Out of 4486 examined young European ashes, 2261 (50.4%) were affected and 789 (17.6%) were already dead. Ten of the 384 assayed flowering ashes (Fraxinus ornus) showed symptoms on branches and apical stems, similar to those observed for European ash. Isolation and molecular analysis proved the presence of the fungus on both symptomatic European and flowering ashes. The examined 386 adult trees showed different levels of damage, sometimes reaching more than 75% of the crown. Some individual trees (42) growing close to severely damaged trees appeared fully healthy, which suggests the possible existence of some resistant/tolerant individuals in the examined populations
Colored black holes and Kac-Moody algebra
We demonstrate that the near horizon symmetries of black holes in Einstein-Yang-Mills (EYM) theory are generated by an infinite-dimensional algebra that contains, in addition to supertranslations and superrotations, a non-Abelian loop algebra. This means that the Virasoro-Kac-Moody structure of EYM in asymptotically flat spacetimes has an exact analog in the near horizon region.Fil: Giribet, Gaston Enrique. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FĂsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FĂsica de Buenos Aires; ArgentinaFil: Montecchio, Luciano. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FĂsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FĂsica de Buenos Aires; Argentin
The symmetries of magnetized horizons
We study stationary black holes in the presence of an external strong
magnetic field. In the case where the gravitational backreaction of the
magnetic field is taken into account, such an scenario is well described by the
Ernst-Wild solution to Einstein-Maxwell field equations, representing a
charged, stationary black hole immersed in a Melvin magnetic universe. This
solution, however, describes a physical situation only in the region close to
the black hole. This is due to the following two reasons: Firstly, Melvin
spacetime is not asymptotically locally flat; secondly, the non-static
Ernst-Wild solution is not even asymptotically Melvin due to the infinite
extension of its ergoregion. All this might seem to be an obstruction to
address an scenario like this; for instance, it seems to be an obstruction to
compute conserved charges as this usually requires a clear notion of
asymptotia. Here, we circumvent this obstruction by providing a method to
compute the conserved charges of such a black hole by restricting the analysis
to the near horizon region. We compute the Wald entropy, the mass, the electric
charge, and the angular momentum of stationary black holes in highly magnetized
environments from the horizon perspective, finding results in complete
agreement with other formalisms.Comment: 17 pages. v2, typos corrected and discussions extende
Ottimizzazione dell'esercizio di un impianto per la distillazione discontinua di una miscela eptano/tetraidrofurano
Questa Tesi di Laurea tratta dell'ottimizzazione di una distillazione discontinua di una miscela di eptano e tetraidrofurano. Il lavoro svolto può essere diviso in un'analisi iniziale dell'esercizio, in modo da individuare come andare a procedere per l'ottimizzazione. In seguito si è pensato di modificare l'esercizio dell'impianto sostituendo tutte le fasi della distillazione con un'unica fase costituita da una distillazione a riflusso totale o a riflusso costante. Entrambi i metodi sono stati sviluppati e state effettuate varie prove per poi andare ad applicare la distillazione a riflusso totale. Per concludere la Tesi si è pensato a come gestire i sottoprodotti che venivano a formarsi nella distillazione e infine si sono teorizzati degli sviluppi futuriope
A closer glance at black hole pair creation
We consider accelerated black hole horizons with and without defects. These
horizons appear in the -metric solution to Einstein equations and in its
generalization to the case where external fields are present. These solutions
realize a variety of physical processes, from the decay of a cosmic string by a
black hole pair nucleation to the creation of a black hole pair by an external
electromagnetic field. Here, we show that such geometries exhibit an infinite
set of symmetries in their near horizon region, generalizing in this way
previous results for smooth isolated horizons. By considering the limit close
to both the black hole and the acceleration horizons, we show that a sensible
set of asymptotic boundary conditions gets preserved by supertranslation and
superrotation transformations. By acting on the geometry with such
transformations, we derive the superrotated, supertranslated version of the
-metric and compute the associated conserved charges.Comment: 22 pages. v2, substantially extended; two new sections, one author
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