Workload assignment for global real-time scheduling on unrelated clustered platforms

Real-Time Systems - Heterogeneous MPSoCs are being used more and more, from cellphones to critical embedded systems. Most of those systems offer heterogeneous sets of identical cores. In this...     

Evaluation of performance improvement by model predictive control in a renewable energy system with hydrogen storage

Nowadays islanded microgrids mostly rely on diesel generator. In order to reduce greenhouse emissions, two islanded microgrids with hydrogen storage have been installed and are currently working autonomously in Reunion Island and France. Energy management implemented on these stations fall in the myopic control category. This study aims to determine the performance improvement that could be achieve on such stations using model predictive control. Ability to supply to the loads and energy losses minimisation are our main objectives. Lifetime degradation is also taken in consideration. Simulations shows that significant improvement can be brought, with a 76% decrease of the station's defaults time and better fill rate of hydrogen tank and batteries. In the meantime, chemical and electrical losses are reduced by 38 and 11%, and the batteries degradations are decreased by around 1%. The relevance of taking into account the electrolyser and fuel cell degradations depends on the time-step of the control. These results give a performance target in order to implement a real-time model predictive control in the microgrids, and eventually can be used to better sizing of future microgrids with similar architecture.     

Pheromone Response Inhibitors of the Corn Stalk Borer Sesamia nonagrioides. Biological Evaluation and Toxicology

The behavioral activity of some trifluoromethyl ketones (TFMKs) as inhibitors of the pheromone activity of the corn stalk borer Sesamia nonagrioides (Lef.) (Lepidoptera: Noctuidae) is reported. The most closely-related analogue to the pheromone tested, (Z)-11-hexadecenyl trifluoromethyl ketone (Z11-16:TFMK), elicited a significant decrease in the number of male catches in traps baited with mixtures with the pheromone in 1:1 and 10:1 ratios in comparison to the pheromone alone. The E isomer of the analogue as well as two highly hydrated ketones, 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP) and 1,1-difluoropentadecyl trifluoromethyl ketone, were inactive. Conversely, the saturated TFMKs n-dodecyl trifluoromethyl ketone and, particularly, n-hexadecyl trifluoromethyl ketone induced a synergistic effect when mixed with the synthetic pheromone in 10:1 ratio. However, in a wind tunnel these chemicals did not elicit any differential effect on flying moths attracted to a source containing a 10:1 blend of the analogue and the pheromone. In a dual choice bioassay with two dispensers, containing the pheromone alone, and mixtures of Z11-16:TFMK and the pheromone and separated 5 cm apart, males showed no particular preference for either dispenser. The ketone mixture, however, induced moths to execute erratic flights with frequent crosswind counter-turns and intersections with plume boundaries. The total number of contacts with the source were reduced when a control dispenser was paired with a dispenser containing Z11-16:TFMK and pheromone. Z11-16:TFMK and OTFP showed little toxicity on mice with a LD₅₀ of 1 g/kg after the 6th day of treatment. For comparitive purposes, the major component of the pheromone, Z11-16:Ac, displayed a LD₅₀ of 5 g/kg 6 days after application. Our results provide additional information about the activity of the TFMKs, which might be useful for the utilization of these chemicals in future pest control studies.     

Computer simulation of a parametric optimization problem for an industrial process

Results in functional analysis are applied to the computation of the optimal control of a parabolic distributed parameter system. The control term is a coefficient of the state equation, and is computed by the steepest descent method. An a-priori feedback is determined in the case of a constant control on the optimization interval. Numerical results are discussed.     

A hybrid method for detecting the onset of local necking by monitoring the bulge forming load

Strain-based Forming Limit Diagrams (FLD), which are typically obtained under linear or quasi-linear loading conditions, describe the limiting strains in terms of the major and minor in-plane strains before the onset of necking or the final failure (FFD). These strains can be detected by analysing the strain field in the vicinity of necking or cracking defects. It has generally been agreed that the loading versus time signal is not suitable for detecting necking processes. A novel hybrid method of detecting the onset of necking based on the experimental and simulated bulging load is presented in this paper. This method consists mainly in comparing the experimental forming load, i.e., a load showing plastic instability, with the numerical predictions obtained by performing finite element simulation. The simulation of the bulging process does not include any damage or failure criteria. A homogeneous forming load can therefore be simulated without requiring any information about the localization. This method was applied to detecting the onset of local necking in circular and elliptic quasistatic bulge tests on sheet material, with a diameter of 200 mm. Two materials were tested, a 0.8 mm thick DP450 Dual Phase steel sheet and a 1 mm thick AA6016-T4 aluminium sheet. The onset of necking observed with our method was compared with the results obtained by performing Hogström’s analysis based on the measured strain field over time and similar necking strains were obtained. Beside, the Bressian Williams Hill (BWH) shear criterion was identified for each test from experimental results. A slight scattering of the shear stress values was observed.     

Minimal schedulability interval for real-time systems of periodic tasks with offsets

We consider real-time systems in highly safety context where tasks have to meet strict deadlines. Tasks are periodic, may have offsets, share critical resources and be precedence constrained. Off-line scheduling should be of great help for such systems, but methods proposed in the literature cannot deal with them. Our aim is to extend and improve the well-known cyclicity result of Leung and Merill to every scheduling algorithm and to systems of interacting tasks with offsets. One of the main benefit of our result is to enable the use of off-line scheduling methods for those real-time critical systems.     

Effect of potential cycling on structure and activity of Pt nanoparticles dispersed on different carbon supports

Platinum particles synthesized via the Bönnemann methods were dispersed on two different Vulcan XC72 carbon supports. One was used after thermal treatment at 400 °C under nitrogen atmosphere, the other after oxidation of its surface by acid leaching using diluted HNO₃ in water (1/3). Characterization of the carbon support indicated that HNO₃ treatment leads to the decrease of the BET surface and to the increase of the surface acidity of the carbon support. After dispersion of the platinum catalyst, TEM results indicated that the mean particle size was a little higher on the non-oxidized support (Pt/XC72) than that on the functionalized one (Pt/XC72_HNO3), being 2.5 and 2.0 nm, respectively. However, potential cycles from 0.05 to 1.25 V vs. RHE led to a higher increase of the particle size when catalyst is dispersed on the functionalized support, reaching after 400 potential cycles 5.5 nm against 4.0 nm with the non-functionalized one. The effect of the upper limit (1.0 and 1.25 V vs. RHE) of the potential cycles on the active surface area and on the activity towards the oxygen reduction reaction (orr) was determined for both catalysts. Results indicated that the particle growth was not the main degradation process over the whole duration of the electrochemical experiments, but that dissolution/redeposition (Otswald ripening) was also involved. The predominant role of each degradation process depends on the number of cycles, on the upper potential limit and on the carbon surface state, and could be temporally separated. However, the lower activity towards orr was recorded for the (Pt/XC72_HNO3) cycled up to 1.0 V vs. RHE.     

Coefficient control for a distributed parabolic system

A simulation study for the optimal control of a system described by a set of two coupled parabolic equations is presented. The control is a function of time and appears as a coefficient in the state equation. The optimality conditions lead to a two points boundary value problem which is solved by an iterative ‘steepest descent method“. Numerical results related to different criterions are presented.     

Reaction mechanisms of the radio frequency glow discharged deposition process in silane-helium

The kinetics of a low pressure (0.2 Torr) r.f. discharge in SiH₄-He has been studied. The measured mass transport rate towards the wall is compared with the transport rate derived from a simplified mono-dimensional kinetic model. The silane decomposition is assumed to proceed mainly through electron impact, and only neutral radicals SiH_n have been considered for the diffusional mass transport. A good agreement is found between the experimental and theoretical rates.The measurement of the mean electron density means that an activation constant for silane can be determined. The neutral species evolving from the plasma have been studied by mass spectrometry. The formation of disilane has been observed for pressures above about 0.5 Torr.