1869 research outputs found
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Contrast Field and Contrast Source Formulations for Microwave Imaging: A Comparative Analysis
No full textInverse scattering techniques are aimed at recovering the profiles, positions and constitutive parameters of unknown objects belonging to an inaccessible region illuminated by known and successive probing fields from the measurements of the scattered field (i.e., the problem data) collected by a set of sensors in an external observation domain. Within such a framework, different methods have been proposed, based either on system matrix inversion or optimization approaches. Since multiple scattering effects cannot be neglegted, full non�]linear formulations have to be used. The contrast field inversion (CFI) and the contrast source inversion (CSI) have been widely employed in a lot of practical applications (e.g., biomedical diagnosis or UXO and landmines detection, NDT/NDE, archeology, etc.). CFI�]based techniques recast the inversion problem to the minimization of a cost function of two integral terms both non�]linear related to the so�]called Data and State/Object Equations [1][2]. The goal is to determine the unknown contrast function and total field within the investigation domain. On the other hand, in the CSI algorithm the contrast sources (i.e., the equivalent currents defined in the support of the scatterers) and the contrast itself are iteratively reconstructed [3][4][5]. In such a case, the cost function is still composed by two�]terms, but only one is non�]linear. This contribution proposes a comparison between the CFI and CSI methods in terms of solution accuracy, robustness to local minima and noise, and computational efficiency. The analysis is aimed at pointing out potentialities and limitations of both the inversion formulations when dealing with synthetic as well as experimental datasets. Towards this end, a set of representative results obtained with different minimization techniques both deterministic [6] and stochastic [7] are reported and compared
Fuzzy-Logic Reasoning for Estimating the Reliability of Noisy Data in Inverse Scattering Problems
No full textInverse scattering data, even though collected in a controlled environment, are usually corrupted by electromagnetic noise, which strongly affects the effectiveness of the reconstruction techniques because of the intrinsic ill-positioning of the problem. In order to limit the effects of the noise on the retrieval procedure and to fully exploit the limited information content available from the measurements, an innovative inversion scheme based on the integration of an adaptive multi-scale procedure and a fuzzy-logic-based decision strategy is proposed. The approach is based on an adaptive, coarse-to-fine successive representation of the unknown object obtained through a sequence of nonlinear reconstructions where suitable weighting coefficients are defined using fuzzy logic. Numerical examples from synthetic and experimental test cases are given to illustrate the advantages brought by the proposed approach in terms of reconstruction quality
On The Use Of SVM For Electromagnetic Subsurface Sensing
No full textIn this paper, a classification approach for the real-time identification of “occupation” areas (instead of the detection of each subsurface object) in sub-surface sensing applications is applied. A suitable SVM-based strategy is developed for determining the probability of occurrence of buried targets and to define a “risk map” of the investigation domain. To assess the effectiveness of the proposed approach and to evaluate its robustness, selected numerical results related to a two-dimensional geometry are presented
Improving the Numerical Effectiveness of a Class of Microwave Imaging Techniques For NDE/NDT with the SMW Updating Formula
No full textThis paper presents an innovative microwave imaging technique suitable for NDT/NDE applications. To reduce the number of problem unknowns as well a the computational load by improving the convergence rate of the process, the available a-priori information is exploited by introducing a computationally-effective procedure for the prediction of the electric field based on the updating Sherman-Morrison-Woodbury (SMW) formula. The numerical results as well as comparisons with state-of-the-art methods confirm the effectiveness, the feasibility, and the robustness of the proposed approach
Youtube attracca (per ora) in un porto sicuro: in Tema di Responsabilità del Service Provider: Nota a Viacom Int'l, Inc. v. YouTube, Inc., 718 F. Supp. 2d 514 (S.D.N.Y. 2010) = Youtube Docks in a Safe Harbor (for now): On Service Provider’s Liability: Note to Viacom Int'l, Inc. v. YouTube, Inc., 718 F. Supp. 2d 514 (S.D.N.Y. 2010)
No full textLa nota affronta la complessa questione della responsabilità indiretta dell’Internet Service Provider per le violazioni del diritto d’autore perpetrate in via diretta dagli utenti finali. Viacom è uno tra i più grandi creatori e distributori al mondo di programmi televisivi, film ed altre forme di intrattenimento. YouTube è un sito internet dove ciascuno può visualizzare in streaming video caricati dagli utenti stessi o da società di intrattenimento. Viacom ritiene che YouTube sia responsabile in via vicaria, in via concorrente e per l’induzione alla violazione del copyright effettuata dagli users del sito web. YouTube, grazie alle proprie politiche riesce ad attraccare ad uno dei “safe harbors” previsti dalla normativa americana. Lo stesso non è accaduto nello scontro fra il medesimo portale e il gruppo italiano RTI, ma in entrambe i casi si tratta solo del primo grado di giudizio. ENGLISH ABSTRACT The comment analyzes the problematic issue of Internet Service Provider’s indirect liability for users’ copyright infringement. Viacom is one of the biggest producers and distributors of TV programs, movies and other entertainment works. YouTube is a website where anybody can watch videos in streaming uploaded by other users or by entertainment companies. Viacom holds YouTube liable for vicarious and contributory copyright infringement made by its users and for inducing this SUCH illegal activity. YouTube, thanks to its policies, docks in a DMCA “safe harbor”. The present case is different from that previously occurred in Italy between YouTube and RTI (an entertainment companies group), nonetheless there is still room for further developments at the appellate level. Originally Published in March 2011. Questo paper © Copyright 2011 by Federica Giovanella è pubblicato con Creative Commons Attribuzione-Non commerciale-Non opere derivate 2.5 Italia License. Maggiori informazioni circa la licenza all’URL: http://creativecommons.org/licenses/by-nc-nd/2.5/it
Towards the Integration of Knowledge Organization Systems with the Linked Data Cloud
No full textIn representing the shared view of all the people involved, building a Knowledge Organization System (KOS) from scratch is extremely costly, and it is therefore fundamental to reuse existing resources. This can be done by progressively extending the KOS with knowledge coming from similar KOS and by promoting interoperability among them. The linked data initiative is indeed fostering people to share and integrate their datasets into a giant network of interconnected resources. This enables different applications to interoperate and share their data. However, the integration should take into account the purpose of the datasets and make explicit the semantics. In fact, the difference in the purpose is reflected in the difference in the semantics. With this paper we (a) highlight the potential problems that may arise by not taking into account purpose and semantics, (b) make clear how the difference in the purpose is reflected in totally different semantics and (c) provide an algorithm to translate from one semantic into another as a preliminary step towards the integration of ontologies designed for different purposes. This will allow reusing the ontologies even in contexts different from those in which they were designed
La disciplina del trasporto pubblico locale: recenti sviluppi e prospettive
No full textIl volume, che fa seguito all'incontro seminariale dal titolo “La disciplina del trasporto pubblico locale: recenti sviluppi e prospettive” svoltosi presso la Facoltà di Giurisprudenza dell’Università degli Studi di Trento in data 1° aprile 2011, si manifesta quale esposizione dei relativi risultati scientifici raggiunti, sotto forma di raccolta dei contributi in quella occasione presentati e, quindi, aggiornati e rivisitati per la presente pubblicazione. In tale contesto, il volume si propone di offrire, in una prospettiva teorico-pratica, una analisi della disciplina giuridica sottesa alla riforma del trasporto pubblico locale in Italia, che si estenda alla indagine dei più recenti sviluppi in tal senso previsti dal Legislatore, nel contempo delineando interessanti soluzioni interpretative al problema della abrogazione dell’art. 23-bis del d.l. 25 giugno 2008, n. 112
Models and Performance of VANET based Emergency Braking
No full textThe network research community is working in the field of automotive to provide VANET based safety applications to reduce the number of accidents, deaths, injuries and loss of money. Several approaches are proposed and investigated in VANET literature, but in a completely network-oriented fashion. Most of them do not take into account application requirements and no one considers the dynamics of the vehicles. Moreover, message repropagation schemes are widely proposed without investigating their benefits and using very complicated approaches. This technical report, which is derived from the Master Thesis of Michele Segata, focuses on the Emergency Electronic Brake Lights (EEBL) safety application, meant to send warning messages in the case of an emergency brake, in particular performing a joint analysis of network requirements and provided application level benefits. The EEBL application is integrated within a Collaborative Adaptive Cruise Control (CACC) which uses network-provided information to automatically brake the car if the driver does not react to the warning. Moreover, an information aggregation scheme is proposed to analyze the benefits of repropagation together with the consequent increase of network load. This protocol is compared to a protocol without repropagation and to a rebroadcast protocol found in the literature (namely the weighted p-persistent rebroadcast). The scenario is a highway stretch in which a platoon of vehicles brake down to a complete stop. Simulations are performed using the NS_3 network simulation in which two mobility models have been embedded. The first one, which is called Intelligent Driver Model (IDM) emulates the behavior of a driver trying to reach a desired speed and braking when approaching vehicles in front. The second one (Minimizing Overall Braking Induced by Lane change (MOBIL)), instead, decides when a vehicle has to change lane in order to perform an overtake or optimize its path. The original simulator has been modified by - introducing real physical limits to naturally reproduce real crashes; - implementing a CACC; - implementing the driver reaction when a warning is received; - implementing different network protocols. The tests are performed in different situations, such as different number of lanes (one to five), different average speeds, different network protocols and different market penetration rates and they show that: - the adoption of this technology considerably decreases car accidents since the overall average maximum deceleration is reduced; - network load depends on application-level details, such as the implementation of the CACC; - VANET safety application can improve safety even with a partial market penetration rate; - message repropagation is important to reduce the risk of accidents when not all vehicles are equipped; - benefits are gained not only by equipped vehicles but also by unequipped ones
Two-layered architecture for peer-to-peer concept search
No full textThe current search landscape consists of a small number of centralized search engines posing serious issues including centralized control, resource scalability, power consumption and inability to handle long tail of user interests. Since, the major search engines use syntactic search techniques, the quality of search results are also low, as the meanings of words are not considered effectively. A collaboratively managed peer-to-peer semantic search engine realized using the edge nodes of the internet could address most of the issues mentioned. We identify the issues related to knowledge management, word-to-concept mapping and efficiency in realizing a peer-to-peer concept search engine, which extends syntactic search with background knowledge of peers and searches based on concepts rather than words. We propose a two-layered architecture for peer-to-peer concept search to address the identified issues. In the two-layered approach, peers are organized into communities and background knowledge and document index are maintained at two levels. Universal knowledge is used to identify the appropriate communities for a query and search within the communities proceed based on the background knowledge developed independently by the communities. We developed proof-of-concept implementations of peer-to-peer syntactic search, straightforward single-layered and the proposed two-layered peer-to-peer concept search approaches. Our evaluation concludes that the proposed two-layered approach improves the quality and network efficiency substantially compared to a straightforward single-layered approach
Overview of the Italian Pension System
Get PDFThis report provides a general introduction to the Italian pension system. To this end, firstly a contextual framework of the pension system is given by presenting Italian demographics and economic indicators. Secondly, the history of the system is analyzed, including the main reforms of the past two decades. After having determined the context, the public and mandatory first pillar of the pension system is discussed. The first pillar has traditionally been Italy's main pillar, providing generous replacement rates. The characteristics of the contributions-based scheme introduced in the 1995 reform are outlined, followed by a presentation of forecasted effects of the reform on public pension expenditure and replacement rates obtained. The reforms have changed the outlook for the younger generation of workers, increasing the importance of the complementary pillars. The voluntary second and third pillars are then thoroughly analyzed, by presenting both the theoretical and regulatory framework and market data. The report has been constructed in the context of the APG World of Pensions Scholarship. The aim is to provide an overview of the entire Italian pension system, with specific attention for the complementary pillars. In addition, literature is analyzed in order to identify recommended further steps. On a personal note, drafting this document has been useful in comprehending the current state-of-the-art of the pension system. Moreover, the report can be used as a general introduction to the Italian pension system by future participants of the Scholarship or others interested in this subject. This overview is not aimed to be a final product but should instead be frequently updated, as the system is constantly developing (especially now as pension issues are high on the agenda of policy makers) and new market data becomes available. All views expressed in this article are those of the author and do not necessarily represent the views of, and should not be attributed to, APG and PensPlan