Real-Time Fixed and Dynamic Priority Driven Scheduling Algorithms: Theory and Experience

Projet REFLECSThere are two main positions regarding real-time scheduling algorithms. The first is based on fixed priorities and the second makes use of dynamic priorities such as deadlines. These two approaches have never really been compared because the emphasis has always been on the ease of implementation rather than the efficiency of the algorithms and the complexity of the associated feasibility conditions. In addition to traditional real-time applications, we believe that starting to look at these two criteria will be very important in the perspective of providing admission control mechanisms and real-time guarantees on large distributed systems like the Internet network. To that end, our purpose is first to provide a general framework based, on the one hand, a representation of preemptive, real-time scheduling in an algebraic structure that enables us to evaluate the distance of the optimality of any scheduling algorithm ; and on the other hand, a consistent representation of the associated feasibility conditions that enables us to evaluate the number of basic operations. As a second step, considering several kinds of traffics, we initiate the comparison by a straight, but limited, application of our general framework. Our preliminary results will notably highlight, in the cases where deadlines are all greater than periods, that fixed priority schedulers (like deadline monotonic) behave as well as EDF while the worst-case response time analysis is less complex. The same remark is valid when the task sets are almost homogeneous but is in favor of EDF in the general case or when a simple feasibility analysis is needed. Therefore, it might be of interest, given a real-time scheduling context (spanning from small embedded system to large distributed system), to take into account these two extra criteria in order to find a right trade-off among several possible solutions

NMDA receptor dysfunction contributes to impaired brain-derived neurotrophic factor-induced facilitation of hippocampal synaptic transmission in a Tau transgenic model.

While the spatiotemporal development of Tau pathology has been correlated with occurrence of cognitive deficits in Alzheimer's patients, mechanisms underlying these deficits remain unclear. Both brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor TrkB play a critical role in hippocampus-dependent synaptic plasticity and memory. When applied on hippocampal slices, BDNF is able to enhance AMPA receptor-dependent hippocampal basal synaptic transmission through a mechanism involving TrkB and N-methyl-d-Aspartate receptors (NMDAR). Using THY-Tau22 transgenic mice, we demonstrated that hippocampal Tau pathology is associated with loss of synaptic enhancement normally induced by exogenous BDNF. This defective response was concomitant to significant memory impairments. We show here that loss of BDNF response was due to impaired NMDAR function. Indeed, we observed a significant reduction of NMDA-induced field excitatory postsynaptic potential depression in the hippocampus of Tau mice together with a reduced phosphorylation of NR2B at the Y1472, known to be critical for NMDAR function. Interestingly, we found that both NR2B and Src, one of the NR2B main kinases, interact with Tau and are mislocalized to the insoluble protein fraction rich in pathological Tau species. Defective response to BDNF was thus likely related to abnormal interaction of Src and NR2B with Tau in THY-Tau22 animals. These are the first data demonstrating a relationship between Tau pathology and synaptic effects of BDNF and supporting a contribution of defective BDNF response and impaired NMDAR function to the cognitive deficits associated with Tauopathies

Stabilité et atomisation d'une nappe annulaire liquide soumise à deux courants gazeux avec effets de swirl : application aux futurs moteurs fusée cryotechniques

Dans une optique d'amélioration ou de construction de moteurs fusée dérivés du modèle Vulcain, ce projet propose une nouvelle géométrie d'injecteur permettant l'atomisation efficace d'une nappe annulaire liquide en un brouillard de gouttelettes, nécessaire à un rendement élevé de combustion de propergols. Les images de tomographie et de visualisations rapides ont permis de comprendre les mécanismes de rupture de la nappe liquide par un courant interne et/ou externe tandis que la phase diluée a été caractérisée par les techniques de Vélocimétrie par Images de Particules et d'Interférométrie par Phase Doppler. Plusieurs modes de rupture ont été identifiés dépendant principalement du rapport du flux de quantité de mouvement gaz/liquide et une étude fréquentielle a été réalisée sur les battements de la nappe. Le mode qui nous intéresse plus particulièrement, nommé « arbre de Noël », permet une atomisation primaire beaucoup plus efficace que celui d'un jet liquide assisté par une couronne annulaire de gaz mais aussi d'obtenir une granulométrie plus faible des gouttes produites. L'étude des différents paramètres : rapport des densités de flux de quantité de mouvement gaz/liquide, pression ambiante et rotation du gaz a montré que les deux premiers cités ont une influence très importante sur la granulométrie tandis que la longueur de rupture de la nappe dépend principalement du premier et du dernier. La rotation du gaz modifie fortement la forme du profil de vitesse en sortie d'injecteur et donc du spray généré par la suite. Elle permet également une fluctuation plus faible de la longueur de rupture de la nappe et surtout une bonne homogénéisation de la vitesse des gouttes. Bien que ce type d'atomisation soit déjà particulièrement efficace, l'ajout d'une couronne de gaz externe améliore nettement l'atomisation

Cavitation and primary atomization in real injectors at low injection pressure condition

International audienc

Real-Time Fixed And Dynamic Priority Driven Scheduling Algorithms: Theory And Experience

There are two main positions regarding real-time scheduling algorithms. The first is based on fixed priorities and the second makes use of dynamic priorities such as deadlines. These two approaches have never really been compared because the emphasis has always been on the ease of implementation rather than the efficiency of the algorithms and the complexity of the associated feasibility conditions. In addition to traditional real-time applications, we believe that starting to look at these two criteria will be very important from the point of view of providing admission control mechanisms and real-time guarantees on large distributed systems like the Internet network. To that end, our purpose is first to provide a general framework based, on the one hand, a representation of preemptive, real-time scheduling in an algebraic structure that enables us to evaluate the distance of the optimality of any scheduling algorithm ; and on the other hand, a consistent representation of the assoc..

Empirical Protocol to Correct Laser-Diffraction Measurements from Multiple-Scattering Effects

The present work addresses the problem of multiple-scattering effects on Laser-Diffraction spray drop-size distribution measurements. The Laser-Diffraction Technique (LDT) is a rather straightforward diagnostic often used in industries and universities to characterize liquid sprays. Recent LDT equipments have been especially conceived for highly transient and dense sprays such as those encountered in car injection applications (direct gasoline injection or diesel injection). In particular, they are equipped with an optional algorithm to correct the effects of multiple-scattering that occurs when the spray density is great. However, experimental investigations of the literature reported that this algorithm was not able to treat all situations. An explanation for this could be found in the assumptions of the model that are often not satisfied by real sprays. For several years, an alternative to this approach has been explored: it consists in establishing an empirical correction protocol. In a recent approach, this empirical correction protocol received a mathematical description. The work in the present contribution generalizes this mathematical model and demonstrates that it is able to describe the influence of multiplescattering for other working conditions. The sprays investigated here are produced by a three-jet gasoline direct injection device. We found that the mathematical model was adaptable to this case. Therefore, the present empirical correction protocol appears to be easily applicable and should be recommended at least to test a theoretical model or at most to replace it

Injector Internal Geometry and Sub-Atmospheric Back Pressure Influence on Low Weber Number Liquid Flow

International audienceThe experimental work presented in this paper investigates the influence of the injector internal geometry on the primary atomization process in sub-atmospheric back pressure condition. A series of four injectors is studied. High-rate shadowgraph films of the liquid flow issuing from the nozzle are performed (66 667 fr/s). In order to have exploitable images, the injection pressure is maintained low (less than 1 MPa). On each image, the interface length per unit liquid surface area, e 2 (0), is measured. The examination of this parameter and of the images reveals that under atmospheric pressure, the primary atomization process is rather independent of the injectors. However, as the ambient pressure decreases, the injectors show different behaviour and the atomization process becomes intermittent. This behaviour is attributed to the apparition of cavitation in the injector. The characteristics of this intermittency are evaluated. Among other results, we observed that atomization process produced by cavitating flows are more sensitive to the injector internal geometry, the intermittency is due to the production of vortex cavitation, and, contrary to what is usually reported in the literature, cavitation does not enhance atomization in the present case. These results, as well as others, are presented and discussed in this paper

Dopamine Agonists and Impulse Control Disorders: A Complex Association

International audienceImpulse control disorders (ICDs) are a well-known adverse effect of dopamine agonists (DAAs). This critical review aims to summarize data on the prevalence and factors associated with the development of an ICD simultaneous to DAA use. A search of two electronic databases was completed from inception to July 2017. The search terms were medical subject headings (MeSH) terms including "dopamine agonists" AND "disruptive disorders", "impulse control disorders", or "conduct disorders". Articles had to fulfill the following criteria to be included: (i) the target problem was an ICD; (ii) the medication was a dopaminergic drug; and (iii) the article was an original article. Of the potential 584 articles, 90 met the criteria for inclusion. DAAs were used in Parkinson's disease (PD), restless legs syndrome (RLS) or prolactinoma. The prevalence of ICDs ranged from 2.6 to 34.8% in PD patients, reaching higher rates in specific PD populations; a lower prevalence was found in RLS patients. We found only two studies about prolactinoma. The most robust findings relative to the factors associated with the development of an ICD included the type of DAA, the dosage, male gender, a younger age, a history of psychiatric symptoms, an earlier onset of disease, a longer disease duration, and motor complications in PD. This review suggests that DAA use is associated with an increased risk in the occurrence of an ICD, under the combined influence of various factors. Guidelines to help prevent and to treat ICDs when required do exist, although further studies are required to better identify patients with a predisposition

Real-time fixed and dynamic priority driven scheduling algorithms : theory and experience

Theme 1 - Reseaux et systemes - Projet REFLECSSIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 14802 E, issue : a.1996 n.3081 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

NUMERICAL SIMULATION OF PRIMARY ATOMIZATION: INTERACTION WITH EXPERIMENTAL ANALYSIS

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