Satellite system performance assessment for in-flight entertainment and air traffic control

Concurrent satellite systems have been proposed for IFE (In-Flight Entertainment) communications, thus demonstrating the capability of satellites to provide multimedia access to users in aircraft cabin. At the same time, an increasing interest in the use of satellite communications for ATC (Air Traffic Control) has been motivated by the increasing load of traditional radio links mainly in the VHF band, and uses the extended capacities the satellite may provide. However, the development of a dedicated satellite system for ATS (Air Traffic Services) and AOC (Airline Operational Communications) seems to be a long-term perspective. The objective of the presented system design is to provide both passenger application traffic access (Internet, GSM) and a high-reliability channel for aeronautical applications using the same satellite links. Due to the constraints in capacity and radio bandwidth allocation, very high frequencies (above 20 GHz) are considered here. The corresponding design implications for the air interface are taken into account and access performances are derived using a dedicated simulation model. Some preliminary results are shown in this paper to demonstrate the technical feasibility of such system design with increased capacity. More details and the open issues will be studied in the future of this research work

Adlayer core-level shifts of admetal monolayers on transition metal substrates and their relation to the surface chemical reactivity

Using density-functional-theory we study the electronic and structural properties of a monolayer of Cu on the fcc (100) and (111) surfaces of the late 4d transition metals, as well as a monolayer of Pd on Mo bcc(110). We calculate the ground states of these systems, as well as the difference of the ionization energies of an adlayer core electron and a core electron of the clean surface of the adlayer metal. The theoretical results are compared to available experimental data and discussed in a simple physical picture; it is shown why and how adlayer core-level binding energy shifts can be used to deduce information on the adlayer's chemical reactivity.Comment: RevTeX, 7 pages, 2 figure

Comparing building blocks of life: sequence alignment and evaluation of predicted structural and functional features

Heringa, J. [Promotor]Feenstra, K.A. [Copromotor

Cursim scripsi quae potui: Tiberio Claudio Donato rilegge il suo "libro"

This paper contains a detailed analysis of the final epistle of Tiberius Claudius Donatus’ Interpretationes Vergilianae, addressed to his son Donatianus. Through a comparison with Verg. Aen. VII 641-646 (and Donatus’ interpretation of these lines) it is possible to argue that Donatus was envisioning this epistle as the conclusion of a long work (the commentary itself) and the starting point of a new endeavour: the writing of a thirteenth book covering all the Realien of the Aeneid

Tiberio Claudio Donato e i "progymnasmata"

pp. 177-199Le Interpretationes Vergilianae di Tiberio Claudio Donato rappresentano una interessante strumento per studiare la diffusione e la proposizione dei progymnasmata nella metà latina dell’Impero poiché integrano, seppur in modo parziale, le scarse informazioni offerte in proposito dalla letteratura manualistica, quasi completamente perduta. In particolare, attraverso un’analisi mirata delle ricorrenze del locus communis, sono stati individuati due differenti impieghi di questo e degli altri esercizi preliminari: uno ‘esegetico’, vale a dire un uso consapevole di questa categoria retorica come strumento di critica letteraria, e uno ‘letterario’, ossia un ricorso – spesso dissimulato – ai progymnasmata come modello formale di composizione artistica. Questo secondo aspetto permette di comprendere, almeno in parte, alcune tendenze letterarie proprie del periodo tardoantico.The work of Tiberius Claudius Donatus represents an interesting tool for study the spreading of progymnasmata in the latin part of Empire, because they integrate, even though partially, the few informations we have about ‘handbook literature’, almost completely lost. In particular, through an analisys of recurrences of the locus communis, it is possible to single out two different uses of this one and others preliminary exercises: the first ‘exegetic’, i.e. a conscius use of this retorical category as a tool of literary criticism; the second ‘literary’, i.e. a use of progymnasmata, often dissimulated, as a formal model of artistic composition

Parameterised model checking of probabilistic multi-agent systems

Swarm robotics has been put forward as a method of addressing a number of scenarios where scalability and robustness are desired. In order to deploy robotic swarms in safety-critical situations, it is necessary to verify their behaviour. Model checking gives a possible approach to do this; however, with traditional model checking techniques only systems of a finite size can be considered. This presents an issue for swarm systems, where the number of participants in the system is not known at design-time and may be arbitrarily large. To overcome this, parameterised model checking (PMC) techniques have been developed which enable the verification of systems where the number of participants is not known until run-time. However, protocols followed by robotic swarms are often stochastic in nature, and this cannot be modelled with current PMC techniques. This is the gap that this thesis aims to overcome. In particular, two parameterised semantics for reasoning about multi-agent systems are extended to incorporate probabilities. One of these semantics is synchronous, whilst the other is interleaved. Abstract models which overapproximate the systems being considered are constructed using counter abstraction techniques. These abstract models are used to develop parameterised verification procedures for a number of specification logics on both bounded and unbounded traces. The decision procedures presented are shown to be sound, and in some cases also complete. Further, the techniques are extended to allow modelling of situations where agents may exhibit faulty behaviour, as well as scenarios where the strategic capabilities of the participants needs to be verified. The procedures are all implemented in a novel verification toolkit called PSV (Probabilistic Swarm Verifier), built on top of the probabilistic model checker PRISM. This toolkit is used to verify three case studies from both swarm robotics and other application domains.Open Acces

Does one size fit all at all times ? The role of country specificities and state dependencies in predicting banking crises. National Bank of Belgium Working Paper No. 297

Given the indisputable cost of policy inaction in the run-up to banking crises as well as the negative side effects of unwarranted policy activation, policymakers would strongly benefit from early-warning thresholds that more accurately predict crises and produce fewer false alarms. This paper presents a novel yet intuitive methodology to compute country-specific and state-dependent thresholds for early-warning indicators of banking crises. Our results for a selection of early-warning indicators for banking crises in 14 EU countries show that the benefits of applying the conditional moments approach can be substantial. The methodology provides more robust signals and improves the early-warning performance at the country-specific level, by accounting for country idiosyncrasies and state dependencies, which play an important role in national supervisory authorities’ macroprudential surveillance

Capacity Dimensioning for Aeronautical Communications in North Atlantic Corridor

In the context of the Internet everywhere paradigm, aircraft passengers expect to get connectivity during flights. Several solutions based either on cellular networks in continental area or on satellite links have been designed and even deployed for some of them. But to face the increasing number of users and expected services, a migration to future satellite system such as Inmarsat's Ka band Global Xpress system have been planned. The considered geographical area of the present study is the north Atlantic corridor. In this service zone, the specific structure of aeronautical traffic must be taken into account. NAT (North Atlantic Tracks) are oceanic routes between North America and Europe that are periodically defined considering weather and wind conditions. This explains why the exact locations of the tracks change daily according to weather and also traffic demands. On each continent, specific air traffic control is provided in order to manage entrance and movement along these tracks. The proposed study makes the assumption of a flexible global coverage provided by multi beam Ka band satellites that operate in geosynchronous orbit. Aircraft flying in the north Atlantic corridor use the system in order to offer in-flight connectivity for airline passengers. Doing so, passengers may access common Internet services, namely web browsing, electronic mail, or file transfer. More specific applications for pilots and companies are also taken in consideration enhanced with new services such as real time black box data streaming. In order to assess induced traffic load and instantaneous required capacities in each spot beam, a simulation model has been specifically developed by ENAC and ISAE with Opnet Modeler software