Hybrid power generation system for aircraft electrical emergency network

A whole structure and two management strategies are proposed here for hybridisation of a Ram air turbine (RAT) by means of supercapacitors. Such hybrid structure is dedicated to an aircraft emergency network. The structure consists in coupling, through a 270 V DC bus, a controlled source (RAT) with a storage device interfaced through a bidirectional DC–DC converter. Both the energy-management strategies are described and analysed: the first one is to assign the ‘high-frequency harmonics’ of the load power to the storage which is current controlled, whereas the RAT controls the bus voltage and then only feeds the average power, losses and low-frequency harmonics of the load. The second one proposes an energy optimised operation of the system: the RAT, being current controlled, is able to maximise the supplied power (maximum power point tracking), as for classical wind turbines. For such a strategy, the bus voltage is regulated from the storage device. The RAT sizing and its mass can then be strongly reduced by means of this hybrid structure controlled with optimised management strategies. Experiments on a lab test-bench confirm analyses presented

Minimizing Single-Usage Cache Pollution for Effective Cache Hierarchy Management

Efficient cache hierarchy management is of a paramount importance when designing high performance processors. Upon a miss, the conventional operation mode of a cache hierarchy is to retrieve back the missing block from higher levels and to store the block into all hierarchy levels. It is however difficult to assert that storing the block into intermediate levels will be really useful. In the literature, this phenomenon, referred to as cache pollution, is often associated with prefetching techniques, that is, a prefetched block could evict data that is more likely to be reused in a near future. Cache pollution could cause severe performance degradation. This paper is typically concerned with addressing this phenomenon in the highest level of cache hierarchy. Unlike past studies that treat polluting cache blocks as blocks that are never accessed (i.e. only due to prefetching), our proposal rather attempts to eliminate cache pollution that is inherent to the application. Our observations did indeed reveal that cache blocks that are only accessed once - single-usage blocks - are quite significant at runtime and especially in the highest level of cache hierarchy. In addition, most single-usage cache blocks are data that can be prefetched. We show that employing a simple prediction mechanism is sufficient to uncover most of the single-usage blocks. For a two-level cache hierarchy, these blocks are directly sent from main memory to L1 cache. Performing data bypassing on L2 cache maximizes memory hierarchy and allows hard-toprefetch memory references to remain into this cache hierarchy level. Our experimental results show that minimizing single-usage cache pollution in the L2 cache leads to a significant decrease in its miss rate; resulting therefore in noticeable performance gains

Synthesized High-Frequency Thyristor for Dielectric Barrier Discharge Excimer Lamps

Dielectric barrier discharge (DBD) lamps, being capacitive loads, must be associated with bidirectional current sources for an appropriate control of the transferred power. Pulsed current source supplies, which are known to offer very interesting performances, require specific power switches that are able to manage bidirectional voltage and unidirectional current at much higher frequencies (several hundreds of kilohertz) than commercial thyristors. This paper proposes the detailed design of such a high-speed synthesized thyristor, using discrete components: a MOSFET in series with a high-voltage (HV) diode and a logic circuit that controls its gate. This switch is associated with an optimized self-powered driver, which is a very efficient solution to handle the perturbations associated with the HV and high-frequency operation. Experimental application of this device for DBD excimer lamp supply is proposed

L' œdème aigu du poumon à troponine augmentée

L œdème aigu du poumon (OAP) est une pathologie très fréquente, surtout chez la personne âgée ; elle est responsable de dépenses de santé importantes. On distingue les insuffisances cardiaques à fraction d'éjection préservée ou altérée. Le diagnostic est réalisé à partir d'un faisceau d'arguments ; cliniques, biologiques, radiologiques et échographiques principalement. Le traitement est à la fois symptomatique et étiologique. Le pronostic est sombre. Différentes étiologies, facteurs déclenchant et diagnostics différentiels sont possibles. Il a été démontré par de récentes études que l'augmentation de la troponine au cours d'un OAP signe un mauvais pronostic. Dans notre étude, cette notion a été confirmée (allongement de la durée de séjour, élévation du taux de mortalité), et des critères corrélés à l'existence d'une coronaropathie sous-jacente en cas d'élévation de troponine ont été décelés : la présence d'antécédents coronariens connus, de plusieurs facteurs de risque cardio-vasculaires, d'une douleur thoracique, d'un taux de troponine très élevéThe acute pulmonary edema (APO) is a very frequent, especially in the elderly and is responsible for high health costs. We distinguish heart failure preserved ejection fraction in altered or preserved. The diagnosis is made from an array of arguments, clinical, biological, radiological and ultrasonographic mainly. The treatment is both symptomatic and causal. The prognosis is poor. Different etiologies, triggers and differential diagnoses are possible. It has been shown by recent studies that increased troponin during an OAP sign a poor prognosis. In our study, this notion was confirmed (longer length of stay, increased mortality), and criteria correlated with the existence of an underlying coronary artery disease in cases of elevated troponin were detected: the presence of coronary history known, several risk factors for cardiovascular disease, with chest pain, a high troponinST QUENTIN EN YVELINES-BU (782972101) / SudocSudocFranceF

Conception d'un réseau de secours électrique pour l'aéronautique

L avènement de l avion plus électrique implique de nombreux changements dans les réseaux de bords, y compris la partie essentielle du réseau électrique utilisée en secours. L objet de notre étude est la conception du réseau de secours électrique. Pour cela, une modélisation adaptée de chaque équipement utilisé en dernier secours est nécessaire, et particulièrement les sources électriques de secours et les actionneurs de commande de vol. La modélisation sous forme de Bond Graph est largement employée dans cette thèse, pour sa pertinence à représenter les systèmes multi-physiques et les échanges de puissance. Le concept d hybridation de deux sources de nature différente est introduit dans le but d exploiter au mieux leurs performances. Plusieurs architectures sont proposées et dimensionnées, en utilisant notamment des lois de redimensionnement par similitudes. Un gain de masse potentiel sur l ensemble du réseau est estimé par rapport à des solutions conventionnelles.The more electric aircraft involves a lot of changes about electrical networks, including the essential part used in case of an emergency. The aim of this study is to design the emergency electrical network. Therefore, a suitable modeling of each device used in emergency is necessary, in particular the electrical power emergency sources and the flight control surface actuators. Bond Graph methodology is used in this thesis, due to its convenience for multi-domain representation and power transfers. The hybrid concept with two different electrical power sources is proposed to take advantage of each of the two sources. Several architectures are proposed and sized. Models based on similarity relations are used to resize the electrical sources for example. A significant gain on the system mass is estimated regarding conventional solutions.TOULOUSE-ENSEEIHT (315552331) / SudocSudocFranceF

Minimizing Single-Usage Cache Pollution for Effective Cache Hierarchy Management

Efficient cache hierarchy management is of a paramount importance when designing high performance processors. Upon a miss, the conventional operation mode of a cache hierarchy is to retrieve back the missing block from higher levels and to store the block into all hierarchy levels. It is however difficult to assert that storing the block into intermediate levels will be really useful. In the literature, this phenomenon, referred to as cache pollution, is often associated with prefetching techniques, that is, a prefetched block could evict data that is more likely to be reused in a near future. Cache pollution could cause severe performance degradation. This paper is typically concerned with addressing this phenomenon in the highest level of cache hierarchy. Unlike past studies that treat polluting cache blocks as blocks that are never accessed (i.e. only due to prefetching), our proposal rather attempts to eliminate cache pollution that is inherent to the application. Our observations did indeed reveal that cache blocks that are only accessed once - single-usage blocks - are quite significant at runtime and especially in the highest level of cache hierarchy. In addition, most single-usage cache blocks are data that can be prefetched. We show that employing a simple prediction mechanism is sufficient to uncover most of the single-usage blocks. For a two-level cache hierarchy, these blocks are directly sent from main memory to L1 cache. Performing data bypassing on L2 cache maximizes memory hierarchy and allows hard-toprefetch memory references to remain into this cache hierarchy level. Our experimental results show that minimizing single-usage cache pollution in the L2 cache leads to a significant decrease in its miss rate; resulting therefore in noticeable performance gains

High-frequency structure design and RF stability analysis of a 4-vane radio frequency quadrupole with pi-mode stabilizer loops

International audienceCompact accelerator-based neutron source facilities are garnering attention and play an important and expanding role in material and engineering sciences, as well as in neutron science education and training. Neutrons are produced by bombarding a low-energy proton beam onto a beryllium or lithium target. In such an accelerator-based neutron source, a radio frequency quadrupole (RFQ) is usually utilized to accelerate a high-intensity proton beam to a few MeV. This study mainly covers the high-frequency structure design optimizations of a 4-vane RFQ with pi-mode stabilizer loops (PISLs) and its RF stability analysis. A 176 MHz RFQ accelerator is designed to operate at a 10% duty factor and could accelerate an 80 mA proton beam from 65 keV to 2.5 MeV within a length of 5.3 m. The adoption of PISLs ensures high RF stability, eases the operation of the accelerator, and implies less stringent alignment and machining tolerances

X-Rays Energy Measurements During the RFQ Conditioning at the European Spallation Source

International audienceThe Radio Frequency Quadrupole (RFQ) was conditioned at the European Spallation Source during spring 2021. We used part of the conditioning time to estimate the accelerating potential within the RFQ analyzing the x-rays bremsstrahlung radiation emitted by the electrons released and accelerated in the RFQ. The results of these measurements are in good agreement with the theoretical prediction