The Bombardier-Boeing dispute goes to the heart of the debate over what constitutes state aid and price dumping

In recent weeks the US Department of Commerce has threatened to slap a 220 percent tariff on to sales of C-series jets manufactured by the Canadian company, Bombardier. Boeing has alleged that Bombardier - which also employs thousands in Northern Ireland - has received generous state aid from the Canadian government, and is selling its jets below cost. Hervé Morvan ..

A Computational Fluid Dynamics Simulation of Oil–Air Flow Between the Cage and Inner Race of an Aero-engine Bearing

In aeroengines the shafts are supported on bearings that carry the radial and axial loads. A ball bearing is made up of an inner-race, an outer-race and a cage which contains the balls, these together comprise the bearing elements. The bearings require oil for lubrication and cooling. The design of the bearing studied in this work is such that the oil is fed to the bearing through holes/slots in the inner race. At each axial feed location the oil is fed through a number of equispaced feedholes/slots but there is a different number of holes at each location. Once the oil has passed through the bearing it sheds outwards from both sides into compartments known as the bearing chambers. A number of studies have been carried out on the dynamics of bearings. Most of the analyses consider the contributions of fluid forces as small relative to the interaction of the bearing elements. One of the most sophisticated models for a cage-raceway analysis is based on the work of Ashmore et al. [1], where the cage-raceway is considered to be a short journal bearing divided into sectors by the oil feeds. It is further assumed that the oil exits from the holes and forms a continuous block of oil that exits outwards on both sides of the cage-raceway. In the model, the Reynolds equation is used to estimate the oil dynamics. Of interest in this current work is the behaviour of the oil and air within the space bounded by the cage and inner race. The aim is to determine whether oil feed to the bearing can be modelled as coming from a continuous slot or if the discrete entry points must be modelled. A Volume of Fluid Computational Fluid Dynamics approach is applied. A sector of a ball bearing is modelled with a fine mesh and the detailed simulations show the flow behaviour for different oil splits to the three feed locations of the bearing thus providing information useful to understanding oil shedding into the bearing chambers. The work shows that different flow behaviour is predicted by models where the oil inlets through a continuous slot compared to discrete entry holes. The form and speed of oil shedding from the bearing is found to depend strongly on shaft speed with the shedding speed being slightly higher than the cage linear speed. The break-up pattern of oil on the cage inner surface suggests smaller droplets will be shed at higher shaft speed

Diagnosis and Opacity Problems for Infinite State Systems Modeled by Recursive Tile Systems

International audienceThe analysis of discrete event systems under partial observation is an important topic, with major applications such as the detection of information flow and the diagnosis of faulty behaviors. These questions have, mostly, not been addressed for classical models of recursive systems, such as pushdown systems and recursive state machines. In this paper, we consider recursive tile systems, which are recursive infinite systems generated by a finite collection of finite tiles, a simplified variant of deterministic graph grammars (slightly more general than pushdown systems). Since these systems are infinite-state in general powerset constructions for monitoring do not always apply. We exhibit computable conditions on recursive tile systems and present non-trivial constructions that yield effective computation of the monitors.We apply these results to the classic problems of state-based opacity and diagnosability (off-line verification of opacity and diagnosability, and also run-time monitoring of these properties). For a decidable subclass of recursive tile systems, we also establish the decidability of the problems of state-based opacity and diagnosability

Experimental study of the pressure loss in aero-engine air-oil separators

The results of extensive experimental testing of an aero-engine air-oil separator are presented and discussed. The study focuses on the pressure loss of the system. Oil enters the device in the form of dispersed droplets. Subsequently, separation occurs by centrifuging larger droplets towards the outer walls and by film formation at the inner surface of a rotating porous material, namely an open-cell metal foam. The work described here is part of a study led jointly by the Karlsruhe Institute of Technology (KIT) and the University of Nottingham (UNott) within a recent EU project. The goal of the research is to increase the separation efficiency to mitigate oil consumption and emissions, while keeping the pressure loss as low as possible. The aim is to determine the influencing factors on pressure loss and separation efficiency. With this knowledge, a correlation can eventually be derived. Experiments were conducted for three different separator configurations, one without a metal foam and two with metal foams of different pore sizes. For each configuration, a variety of engine-like conditions of air mass flow rate, rotational speed and droplet size was investigated. The experimental results were used to validate and improve the numerical modelling. Results for the pressure drop and its dependencies on air mass flow rate and the rotational speed were analysed. It is shown that the swirling flow and the dissipation of angular momentum are the most important contributors to the pressure drop, besides the losses due to friction and dissipation caused by the flow passing the metal foam. It was found that the ratio of the rotor speed and the tangential velocity of the fluid is an important parameter to describe the influence of rotation on the pressure loss. Contrary to expectations, the pressure loss is not necessarily increased with a metal foam installed

Modelling of Droplet Capture in an Open-Cell Metal Foam at the Pore and Macroscopic Scales

Open-cell metal foams are often used in applications where particulate and/or droplet capture is important. Here a Computational Fluid Dynamics (CFD) modelling approach is described which models the metal foam at both the pore-scale and the macroscopic scale. At the pore-scale, the detailed internal geometry of the foam is included and the flow field and droplet tracking and capture is modelled explicitly. At this scale, a coefficient is found for each metal foam that relates the distance a droplet can freely travel through the foam to both the droplet diameter and the Darcian velocity in the porous medium. Then, at the macroscopic scale, the coefficient from the pore-scale droplet capture simulations is used in a novel stochastic particle extinction model. Here, the droplets travel through a porous zone and are removed from the model, the probability of which is determined by the coefficient from the pore-scale modelling. A test case is described in which the macroscopic model is verified against the pore-scale model with acceptable levels of accuracy

Design and experimental validation of an active acoustic liner for aircraft engine noise reduction

The use of acoustic liners in aviation industry is a quite common solution for reducing the engines acoustic emissions. Although the current solutions based on single or multilayer liners are efficient and compact for the mid and high frequencies, noise mitigation in the low frequencies would require large volumes, making the integration in the nacelle difficult. Moreover, the passive liners are tuned to attenuate fixed frequencies and are optimized for specific flights regimes. An active electroacoustic skin based on a distribution of loudspeaker and microphones is presented here. The acoustic impedance is controlled by an embedded electronic system and can be changed in real time. Compared to a conventional passive liner, it is shown that the resonance frequency of the active skin can be adjusted to better match the flight phase and that the performance is better at low frequency. An experimental campaign in a wind tunnel has been performed and is presented here

Porcine neurofibromatosis : a new syndrome

A genetically dominant neoplasic disease similar to human neurofibromatosis has just been discovered in pigs. Two of the three clinical forms known in man have been identified in several pig farms: one with large subcutaneous tumours, the other exclusively intradermal. Clinical and pathology studies have been performed on these lesions. Tumour cells are being cultured and the sequencing of their genome is underway. This research is especially important because no animal model of this very common disease in man was available until now.Une affection tumorale similaire à la neurofibromatose de l'Homme vient d'être découverte chez le porc. Cette maladie, de caractère génétique dominant, a été retrouvée dans plusieurs élevages sous deux des trois formes rencontrées chez l'Homme, l'une à grosses tumeurs sous-cutanées et l'autre, strictement intradermique. Ces lésions ont été étudiées aux plans clinique et anatomopathologique. Les cellules tumorales ont été mises en culture et le séquençage de leur génome entrepris. Ce travail revêt une importance toute particulière car il n'existait jusqu'alors aucun modèle animal de cette maladie très fréquente chez l'Homme

Value of syndromic surveillance within the Armed Forces for early warning during a dengue fever outbreak in French Guiana in 2006

<p>Abstract</p> <p>Background</p> <p>A dengue fever outbreak occured in French Guiana in 2006. The objectives were to study the value of a syndromic surveillance system set up within the armed forces, compared to the traditional clinical surveillance system during this outbreak, to highlight issues involved in comparing military and civilian surveillance systems and to discuss the interest of syndromic surveillance for public health response.</p> <p>Methods</p> <p>Military syndromic surveillance allows the surveillance of suspected dengue fever cases among the 3,000 armed forces personnel. Within the same population, clinical surveillance uses several definition criteria for dengue fever cases, depending on the epidemiological situation. Civilian laboratory surveillance allows the surveillance of biologically confirmed cases, within the 200,000 inhabitants.</p> <p>Results</p> <p>It was shown that syndromic surveillance detected the dengue fever outbreak several weeks before clinical surveillance, allowing quick and effective enhancement of vector control within the armed forces. Syndromic surveillance was also found to have detected the outbreak before civilian laboratory surveillance.</p> <p>Conclusion</p> <p>Military syndromic surveillance allowed an early warning for this outbreak to be issued, enabling a quicker public health response by the armed forces. Civilian surveillance system has since introduced syndromic surveillance as part of its surveillance strategy. This should enable quicker public health responses in the future.</p