On-Shell Flow

In this work, the problem of constructing geometric flow equations that preserve Einstein field equations for the spacetime metric is addressed. After having briefly discussed the main features of Ricci flow, the on-shell flow equations for a system comprised of a dynamical metric and a set of matter fields are constructed. Then, two examples in which the matter content is just a single, self-interacting scalar field are analysed in detail, imposing the geometric flow equations to be the action-induced ones. In conclusion, an explicit connection to the Swampland Distance Conjecture is proposed.Comment: 72 pages, 18 figure

Analisi preliminare del comportamento aeroelastico di un'ala di nuova concezione

La presente Tesi di Laurea si pone come obbiettivo la valutazione preliminare del comportamento aeroelastico di un ala di nuova concezione. A tal fine è stata eseguita una comparazione con una tradizionale ala a freccia. Sono stati realizzati modelli FEM dettagliati della struttura dell’ala completa ai quali è stato accoppiato il corrispondente modello aerodinamico; inoltre è stata simulata la presenza delle caratteristiche inerziali dei motori, della fusoliera e del carburante imbarcato oltre alla possibilità di moto rigido del velivolo. Con i modelli sopra indicati sono state ricavate curve V-g (velocità-smorzamento) e V-f (velocità-frequenza) per varie combinazioni di quota e Mach di volo. Tutte le analisi del presente lavoro sono state eseguite utilizzando il codice ad elementi finiti MSC Nastran® Aeroelasticity. NOTE The wing configuration analyzed in the thesis has been submitted as a national patent. The wing configuration analyzed in the thesis has been submitted as the object of a Project Proposal for a Call of the FP7 research program IDEAS 2009 of the European Community

A QUIC Implementation for ns-3

Quick UDP Internet Connections (QUIC) is a recently proposed transport protocol, currently being standardized by the Internet Engineering Task Force (IETF). It aims at overcoming some of the shortcomings of TCP, while maintaining the logic related to flow and congestion control, retransmissions and acknowledgments. It supports multiplexing of multiple application layer streams in the same connection, a more refined selective acknowledgment scheme, and low-latency connection establishment. It also integrates cryptographic functionalities in the protocol design. Moreover, QUIC is deployed at the application layer, and encapsulates its packets in UDP datagrams. Given the widespread interest in the new QUIC features, we believe that it is important to provide to the networking community an implementation in a controllable and isolated environment, i.e., a network simulator such as ns-3, in which it is possible to test QUIC's performance and understand design choices and possible limitations. Therefore, in this paper we present a native implementation of QUIC for ns-3, describing the features we implemented, the main assumptions and differences with respect to the QUIC Internet Drafts, and a set of examples.Comment: 8 pages, 4 figures. Please cite it as A. De Biasio, F. Chiariotti, M. Polese, A. Zanella, M. Zorzi, "A QUIC Implementation for ns-3", Proceedings of the Workshop on ns-3 (WNS3 '19), Firenze, Italy, 201

Wavelet analysis applied to SAR images to detect atmospheric structures

The aim of this work is to evaluate the possibilities offered by the wavelet analysis in the study of the spatial structure of the radar backscatter, which is linked to the spatial structure of the marine atmospheric boundary layer. Continuous wavelet analysis has been applied to a SAR image of the sea surface, previously analysed by the more classical Conditional Sampling technique. The main problem coped with has been to select, among the large number of wavelet maps produced by the analysis (256), those containing the more energetic backscatter structures. Since the phenomenon imaged by SAR was the convective turbulence, a multiscale and quasi-periodic or intermittent process, a selection of wavelet maps according to their mean energy was unsuccessful. On the contrary, a method based on the calculation of the standard deviation of the less probable highest wavelet amplitudes led to a right selection of the wavelet maps and to a convincing reconstruction of the map of backscatter structures, which resulted similar to that provided through the Conditional Sampling

Towards the wind direction determination in RADARSAT-2 polarimetrie images

AbstractThe interpretation of SAR images of the sea surface is difficult, due to the complexity of the geophysics and of the interaction mechanisms between electromagnetic and sea waves. The determination of the wind direction is crucial for the evaluation of the wind speed, but its retrieval is still an open issue. One of the few methods able to extract the sea surface wind from SAR data only has been developed and extensively applied to Envisat ASAR images in the past years, using the two-dimensional wavelet transform to detect the backscatter signature related to locally coherent wind cells. A preliminary analysis on the applicability of this method to RADARSAT-2 fully polarimetric images has been conducted to verify if polarimetry may improve the detection of backscatter imprints related to the wind direction

Progettazione e simulazione di un sistema cruise control in ambiente Matlab Simulink

Analisi fisica del sistema e rappresentazione in Matlabope