Dynamic Scheduling of Real-Time Tasks on Multicore Architectures

2 pages acceptée pour élaboration d'un posterWe present a new dynamic scheduling on multicore architectures. This is an improvement of the Optimal Finish Time (OFT) scheduler introduced by Lemerre reducing preemptions. Our result is compared with other schedulers and we show that our algorithm can handle with more general scheduling problems

Placement, ordonnancement et mécanismes de migration de tâches temps-réel pour des architectures distribuées multicoeurs

Les systèmes temps-réel embarqués critiques intègrent un nombre croissant de fonctionnalités comme le montrent les domaines de l'automobile ou de l'aéronautique. Ces systèmes doivent offrir un niveau maximal de sûreté de fonctionnement en disposant des mécanismes pour traiter les défaillances éventuelles et doivent être également performants, avec le respect de contraintes temps-réel strictes. Ces systèmes sont en outre contraints par leur nature embarquée : les ressources sont limitées, tels que par exemple leur espace mémoire et leur capacité de calcul. Dans cette thèse, nous traitons deux problématiques principales de ce type de systèmes. La première porte sur la manière d'apporter une meilleure tolérance aux fautes dans les systèmes temps-réel distribués subissant des défaillances matérielles multiples et permanentes. Ces systèmes sont souvent conçus avec une allocation statique des tâches. Une approche plus exible effectuant des recon gurations est utile si elle permet d'optimiser l'allocation à chaque défaillance rencontrée, pour les ressources restantes. Nous proposons une telle approche hors-ligne assurant un dimensionnement adapté pour prendre en compte les ressources nécessaires à l'exécution de ces actions. Ces recon gurations peuvent demander une réallocation des tâches ou répliques si l'espace mémoire local est limité. Dans un contexte temps-réel strict, nous dé nissons notamment des mécanismes et des techniques de migration garantissant l'ordonnançabilité globale du système. La deuxième problématique se focalise sur l'optimisation de l'exécution des tâches au niveau local dans un contexte multicoeurs préemptif. Nous proposons une méthode d'ordonnancement optimal disposant d'une meilleure extensibilité que les approches existantes en minimisant les surcoûts : le nombre de changements de contexte préemptions et migrations locales) et la complexité de l'ordonnanceurCritical real-time embedded systems are integrating an increasing number of functionalities, as shown in automotive domain or aeronautics. These systems require high dependability including mechanisms to handle possible failures and have to be effective, meeting hard real-time constraints. These systems are also constrained by their embedded nature : resources are limited, such as their memory and their computing capacities. In this thesis, we focus on two main problems for this type of systems. The rst one is about a way to bring a better fault-tolerance in distributed real-time systems when multiple and permanent hardware failures can occur. In classical systems, the design is limited to a static task assignment. A more exible approach exploiting recon gurations is useful if it allows to optimize assignment at each failure for the remaining resources. We propose an off-line approach to obtain an adapted sizing taking into account necessary resources to execute these actions. These recon gurations may require to reallocate tasks or replicas if memory capacities are limited. In a hard real-time context, we de ne mechanisms and migration techniques to guarantee global schedulability of the system. The second problem focus on optimizing performance to run tasks at a local level in a multicore preemptive context. We propose an optimal scheduling method allowing a better scalability than existing approaches by minimizing overheads : the number of context switches (local preemptions and migrations) and the scheduler complexityTOULOUSE-INP (315552154) / SudocSudocFranceF

Lateral speckle size in Phase Retrieval systems

Phase Retrieval (PR) techniques provide a complimentary approach to Digital Holography (DH) for estimating the complex amplitude of a wavefield. If one uses a Gerchberg-Saxon type iterative approach, generally two intensity distributions at different optical planes are captured. Fast Fourier Transform (FFT) based algorithms are then employed to iteratively recover the phase information. Once we have estimated the complex amplitude of the wavefield we can use numerical propagation algorithms to calculate the distribution at any optical plane. We expect however that the finite size of the camera aperture and the sampling effect introduced by the camera pixels will act to reduce the performance of the optical system. In this manuscript we attempt to examine these performance limiting factors in more detail using a special field as the input into our system; namely a speckle field. This particular type of field contains high spatial frequencies which in turn are related to the lateral speckle size. A series of PR experiments at different capture planes are conducted and we report on how the system performance is effected

Green on-site power generation : environmental considerations on small-scale biomass gasifier fuel-cell CHP systems for the residential sector

Contemporary combined heat and power (CHP) systems are often based on fossil fuels, such as natural gas or heating oil. Thereby, small-scale cogeneration systems are intended to replace or complement traditional heating equipment in residential buildings. In addition to space heating or domestic hot water supply, electricity is generated for the own consumption of the building or to be sold to the electric power grid. The adaptation of CHP-systems to renewable energy sources, such as solid biomass applications is challenging, because of feedstock composition and heat integration. Nevertheless, in particular smallscale CHP technologies based on biomass gasification and solid oxide fuel cells (SOFCs) offer significant potentials, also regarding important co-benefits, such as security of energy supply as well as emission reductions in terms of greenhouse gases or air pollutants. Besides emission or air quality regulations, the development of CHP technologies for clean on-site small-scale power generation is also strongly incentivised by energy efficiency policies for residential appliances, such as e.g. Ecodesign and Energy Labelling in the European Union (EU). Furthermore, solid residual biomass as renewable local energy source is best suited for decentralised operations such as micro-grids, also to reduce long-haul fuel transports. By this means such distributed energy resource technology can become an essential part of a forward-looking strategy for net zero energy or even smart plus energy buildings. In this context, this paper presents preliminary impact assessment results and most recent environmental considerations from the EU Horizon 2020 project "FlexiFuel-SOFC" (Grant Agreement no. 641229), which aims at the development of a novel CHP system, consisting of a fuel flexible smallscale fixed-bed updraft gasifier technology, a compact gas cleaning concept and an SOFC for electricity generation. Besides sole system efficiencies, in particular resource and emission aspects of solid fuel combustion and net electricity effects need to be considered. The latter means that vastly less emission intensive gasifier-fuel cell CHP technologies cause significant less fuel related emissions than traditional heating systems, an effect which is further strengthened by avoided emissions from more emission intensive traditional grid electricity generation. As promising result, operation "net" emissions of such on-site generation installations may be virtually zero or even negative. Additionally, this paper scopes central regulatory instruments for small-scale CHP systems in the EU to discuss ways to improve the framework for system deployment

Green on-site power generation : environmental considerations on small-scale biomass gasifier fuel-cell CHP systems for the residential sector

Contemporary combined heat and power (CHP) systems are often based on fossil fuels, such as natural gas or heating oil. Thereby, small-scale cogeneration systems are intended to replace or complement traditional heating equipment in residential buildings. In addition to space heating or domestic hot water supply, electricity is generated for the own consumption of the building or to be sold to the electric power grid. The adaptation of CHP-systems to renewable energy sources, such as solid biomass applications is challenging, because of feedstock composition and heat integration. Nevertheless, in particular smallscale CHP technologies based on biomass gasification and solid oxide fuel cells (SOFCs) offer significant potentials, also regarding important co-benefits, such as security of energy supply as well as emission reductions in terms of greenhouse gases or air pollutants. Besides emission or air quality regulations, the development of CHP technologies for clean on-site small-scale power generation is also strongly incentivised by energy efficiency policies for residential appliances, such as e.g. Ecodesign and Energy Labelling in the European Union (EU). Furthermore, solid residual biomass as renewable local energy source is best suited for decentralised operations such as micro-grids, also to reduce long-haul fuel transports. By this means such distributed energy resource technology can become an essential part of a forward-looking strategy for net zero energy or even smart plus energy buildings. In this context, this paper presents preliminary impact assessment results and most recent environmental considerations from the EU Horizon 2020 project "FlexiFuel-SOFC" (Grant Agreement no. 641229), which aims at the development of a novel CHP system, consisting of a fuel flexible smallscale fixed-bed updraft gasifier technology, a compact gas cleaning concept and an SOFC for electricity generation. Besides sole system efficiencies, in particular resource and emission aspects of solid fuel combustion and net electricity effects need to be considered. The latter means that vastly less emission intensive gasifier-fuel cell CHP technologies cause significant less fuel related emissions than traditional heating systems, an effect which is further strengthened by avoided emissions from more emission intensive traditional grid electricity generation. As promising result, operation "net" emissions of such on-site generation installations may be virtually zero or even negative. Additionally, this paper scopes central regulatory instruments for small-scale CHP systems in the EU to discuss ways to improve the framework for system deployment

Green on-site power generation: environmental considerations on small-scale biomass gasifier fuel-cell CHP systems for the residential sector

Contemporary combined heat and power (CHP) systems are often based on fossil fuels, such as natural gas or heating oil. Thereby, small-scale cogeneration systems are intended to replace or complement traditional heating equipment in residential buildings. In addition to space heating or domestic hot water supply, electricity is generated for the own consumption of the building or to be sold to the electric power grid. The adaptation of CHP-systems to renewable energy sources, such as solid biomass applications is challenging, because of feedstock composition and heat integration. Nevertheless, in particular smallscale CHP technologies based on biomass gasification and solid oxide fuel cells (SOFCs) offer significant potentials, also regarding important co-benefits, such as security of energy supply as well as emission reductions in terms of greenhouse gases or air pollutants. Besides emission or air quality regulations, the development of CHP technologies for clean on-site small-scale power generation is also strongly incentivised by energy efficiency policies for residential appliances, such as e.g. Ecodesign and Energy Labelling in the European Union (EU). Furthermore, solid residual biomass as renewable local energy source is best suited for decentralised operations such as micro-grids, also to reduce long-haul fuel transports. By this means such distributed energy resource technology can become an essential part of a forward-looking strategy for net zero energy or even smart plus energy buildings. In this context, this paper presents preliminary impact assessment results and most recent environmental considerations from the EU Horizon 2020 project "FlexiFuel-SOFC" (Grant Agreement no. 641229), which aims at the development of a novel CHP system, consisting of a fuel flexible smallscale fixed-bed updraft gasifier technology, a compact gas cleaning concept and an SOFC for electricity generation. Besides sole system efficiencies, in particular resource and emission aspects of solid fuel combustion and net electricity effects need to be considered. The latter means that vastly less emission intensive gasifier-fuel cell CHP technologies cause significant less fuel related emissions than traditional heating systems, an effect which is further strengthened by avoided emissions from more emission intensive traditional grid electricity generation. As promising result, operation "net" emissions of such on-site generation installations may be virtually zero or even negative. Additionally, this paper scopes central regulatory instruments for small-scale CHP systems in the EU to discuss ways to improve the framework for system deployment

Green on-site power generation: environmental considerations on small-scale biomass gasifier fuel-cell CHP systems for the residential sector

Contemporary combined heat and power (CHP) systems are often based on fossil fuels, such as natural gas or heating oil. Thereby, small-scale cogeneration systems are intended to replace or complement traditional heating equipment in residential buildings. In addition to space heating or domestic hot water supply, electricity is generated for the own consumption of the building or to be sold to the electric power grid. The adaptation of CHP-systems to renewable energy sources, such as solid biomass applications is challenging, because of feedstock composition and heat integration. Nevertheless, in particular smallscale CHP technologies based on biomass gasification and solid oxide fuel cells (SOFCs) offer significant potentials, also regarding important co-benefits, such as security of energy supply as well as emission reductions in terms of greenhouse gases or air pollutants. Besides emission or air quality regulations, the development of CHP technologies for clean on-site small-scale power generation is also strongly incentivised by energy efficiency policies for residential appliances, such as e.g. Ecodesign and Energy Labelling in the European Union (EU). Furthermore, solid residual biomass as renewable local energy source is best suited for decentralised operations such as micro-grids, also to reduce long-haul fuel transports. By this means such distributed energy resource technology can become an essential part of a forward-looking strategy for net zero energy or even smart plus energy buildings. In this context, this paper presents preliminary impact assessment results and most recent environmental considerations from the EU Horizon 2020 project "FlexiFuel-SOFC" (Grant Agreement no. 641229), which aims at the development of a novel CHP system, consisting of a fuel flexible smallscale fixed-bed updraft gasifier technology, a compact gas cleaning concept and an SOFC for electricity generation. Besides sole system efficiencies, in particular resource and emission aspects of solid fuel combustion and net electricity effects need to be considered. The latter means that vastly less emission intensive gasifier-fuel cell CHP technologies cause significant less fuel related emissions than traditional heating systems, an effect which is further strengthened by avoided emissions from more emission intensive traditional grid electricity generation. As promising result, operation "net" emissions of such on-site generation installations may be virtually zero or even negative. Additionally, this paper scopes central regulatory instruments for small-scale CHP systems in the EU to discuss ways to improve the framework for system deployment.Energy Technolog

Development of a new highly efficient and fuel flexible medium-scale CHP technology based on fixed-bed updraft biomass gasification and a SOFC

The H2020 project HiEff-BioPower aims at the development of a new, innovative, fuel flexible and highly efficient medium-scale biomass CHP technology. It consists of (i) a fuel-flexible fixed-bed updraft gasifier, a novel primary gas treatment zone placed downstream the gasifier for gas and tar reforming, (ii) a novel compact gas cleaning system for dust, HCl and S removal as well as final tar cracking within one process step, (iii) a solid oxide fuel cell (SOFC) and (iv) a heat recovery system which supplies heat for internal heating purposes and for external utilisation. The technology shall distinguish itself by a wide fuel spectrum applicable (wood pellets, wood chips, short rotation coppice (SRC), selected agricultural fuels like agro-pellets, fruit stones/shells), high gross electric (40%) and overall (90%) efficiencies as well as equal-zero gaseous and PM emissions. During the first project year of the 4-year project the system design has been worked out and the interfaces between the different plant units have been defined. Based on preliminary experimental (partly lab-scale) work, process simulations and computational fluid dynamics (CFD) simulations a first testing plant consisting of the gasifier, the gas cleaning unit and a slip-stream SOFC system has been developed and designed. The fuel flexible gasifier has been constructed and has already successfully been taken into operation. The remaining plant components are presently manufactured and the construction of the first testing plant is expected to be finalised in June 2018