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Concept

Situation de compétition

Résumé

Une situation de compétition (ou situation de concurrence, accès concurrent, concurrence critique, course critique, séquencement critique ; race condition en anglais, littéralement « situation de course »), est une situation caractérisée par un résultat différent selon l'ordre dans lequel agissent les acteurs du système. Le terme est plutôt employé à propos de programmes informatiques et de systèmes électroniques. C'est généralement considéré comme un défaut car source de panne ou de blocage. Une situation de compétition peut survenir dès que plusieurs acteurs tentent d'accéder au même moment à une ressource partagée (fichier, imprimante, etc.) et qu'au moins l'un d'entre eux est susceptible de modifier son état. Cette définition implique que les systèmes dont les ressources partagées sont immuables (dont l'état ne peut pas changer) soient immunisés contre ce problème. Les situations de compétition sont des problèmes particulièrement difficiles à identifier et à corriger puisqu'ils

Source officielle

https://fr.wikipedia.org/wiki/Situation_de_comp%C3%A9tition

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Cours associés (24)

We introduce formal verification as an approach for developing highly reliable systems. Formal verification finds proofs that computer systems work under all relevant scenarios. We will learn how to use formal verification tools and explain the theory and the practice behind them.

Test of VLSI Systems covers theoretical knowledge related to the major algorithms used in VLSI test, and design for test techniques. Basic knowledge related to computer-aided design for test techniques, and their integration into a design-flow are presented.

IC Design II presents the fundamentals of digital integrated circuit design. The methods and techniques aiming at the fabrication and development of digital integrated circuits are reviewed, the major design style pertaining to digital logic and memory are presented.

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Séances de cours associées (41)

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Publications associées (60)

Evaluation and optimization of renewable energy in the Quartier Nord

Yuchen Yang

The energy demand increases worldwide and due to the fact that fossil fuel is still dominating the energy mix, the corresponding CO2 emission becomes a more serious problem that threatens the global environment. The building sector is the largest energy consumer and it is of vital significance to reduce the primary energy consumption thus the CO2 emission in this sector. Under this constraint, the standards were set up to design buildings with relatively low energy consumption. Following the standard, the proposal phase of the buildings can be well regulated. However, it is equally important to check the energy consumption of the building in operating condition. In this project, a specific building was selected and its energy consumption condition was simulated both at building and neighbourhood level respectively. EnergyPlus was chosen to run the simulation at single building level and the results were compared with Minergie standard and the monitored data for the building. Another software, CitySim working at a larger scale, is also used. In order to validate the accuracy of the simulations, a benchmark was done based on the calculations of the idea load of the building in EnergyPlus and CitySim. The sources of errors were analysed in detail. At last, renewable resources were also integrated into the building to explore its plotentialof being a net-zero energy building.

2015

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Data-based identification of a parametric heat pump model

Franca Schmid

At the LENI a heat pump model has been developed, which aims to simulate a single state compression heat pump in both steady state and transient regime. For gaining the experimental data and for the simulation the same set of input data is used. The goal is to approximate the output values of the model ym to the ones measured in the experiments. Therefore a certain number of parameters need to be defined in order of obtaining the highest accuracy possible. At the beginning these different parameters γ need to be found and a criterion needs to be appointed which can be used to judge the accuracy of the model. The first approach to the identification is to only work with the steady states. This includes to select steady values out of a data sheet and to change the model so that only steady states are computed. As soon as the model is successfully running for the steady states an optimizer needs to be chosen to finally output the best values of parameters. Subsequently the improvement of the output vector ym needs to be checked. As during the examination some computational problems have been revealed, which interfered with the optimization, various influences on the heat pump model were investigated. It was tried to find the reason for numerical problems and to eliminate those in order to finally be able to optimise the parameters. To identify the model in the transient regime the model needs to be linearised at a typical operation condition. The new chosen criterion must also take into account the transient regimes and the optimality of the solution has to be proved. The numerical problems which exist for the steady state also influence the transient regime. As the emphasis was therefore put on finding the origin of the instabilities, the identification of the transient regime was only briefly worked on.

2010

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Nonreciprocal surface acoustic wave propagation via magneto-rotation coupling

Dirk Grundler

A fundamental form of magnon-phonon interaction is an intrinsic property of magnetic materials, the “magnetoelastic coupling.” This form of interaction has been the basis for describing magnetostrictive materials and their applications, where strain induces changes of internal magnetic fields. Different from the magnetoelastic coupling, more than 40 years ago, it was proposed that surface acoustic waves may induce surface magnons via rotational motion of the lattice in anisotropic magnets. However, a signature of this magnon-phonon coupling mechanism, termed magneto-rotation coupling, has been elusive. Here, we report the first observation and theoretical framework of the magneto-rotation coupling in a perpendicularly anisotropic film Ta/CoFeB(1.6 nanometers)/MgO, which consequently induces nonreciprocal acoustic wave attenuation with an unprecedented ratio of up to 100% rectification at a theoretically predicted optimized condition. Our work not only experimentally demonstrates a fundamentally new path for investigating magnon-phonon coupling but also justifies the feasibility of the magneto-rotation coupling application.

2020

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