Adding Robustness in Dynamic Preemptive Scheduling

In this paper we introduce a robust earliest deadline scheduling algorithm for deal ing with hard aperiodic tasks under overloads in a dynamic realtime environment The algorithm synergistically combines many features including dynamic guarantees graceful degradation in overloads deadline tolerance resource reclaiming and dy namic reguarantees A necessary and sucient schedulability test is presented and an ecient On guarantee algorithm is proposed The new algorithm is evaluated via simulation and compared to several baseline algorithms The experimental results show excellent performance of the new algorithm in normal and overload conditions Static realtime systems are designed for worst case situations Assuming that all the assumptions made in the design and analysis are correct we can say that the level of guarantee for these systems is absolute and all tasks will make their deadlines Unfortunately static systems are not always possible becaus

Real-time robust adaptive modeling and scheduling for an electronic commerce server

With the increasing importance and pervasiveness of Internet services, it is becoming a challenge for the proliferation of electronic commerce services to provide performance guarantees under extreme overload. This paper describes a real-time optimization modeling and scheduling approach for performance guarantee of electronic commerce servers. We show that an electronic commerce server may be simulated as a multi-tank system. A robust adaptive server model is subject to unknown additive load disturbances and uncertain model matching. Overload control techniques are based on adaptive admission control to achieve timing guarantees. We evaluate the performance of the model using a complex simulation that is subjected to varying model parameters and massive overload

Mise au point d’un test in vitro de comportement au sel de quatre génotypes d’agrumes

Introduction : La salinité des sols et des eaux d’irrigation constituent une contrainte abiotique dont les conséquences impactent autant la production que la qualité des agrumes. L’utilisation d’un porte-greffe résistant à ces conditions apparaît la solution la plus adaptée.Objectifs : Cette étude est la comparaison de comportement de  génotypes d’agrumes, en termes de résistance à la salinité in vitro au niveau des cals et des cellules cultivées parallèlement sur milieu liquide et solide.Méthodologie et résultat : À cet égard, des cals de quatre génotypes d’agrumes : mandarinier Cléopâtre (citrus reshni hort ex Tan), mandarinier commun (citrus delicosa Ten.), pomelo Star Ruby ruby (citrus paradisi Macfad.cv Star Ruby) et orange Shamouti (citrus sinensis) ont été maintenus sur des milieux MT renfermant des doses de NaCl 0, 50, 100, 150 et 200 mM. Les résultats ont montré que les différents niveaux de stress de salinité ont eu un effet significatif sur la croissance des cellules. En outre, la salinité a augmenté de façon significative le niveau de chlorures des génotypes testés.Conclusions et application des résultats : Un comportement différentiel sur les niveaux de tolérance à la salinité a été révélé, entre génotypes d’une part, et entre types de milieu d’autre part. Le mandarinier Cléopâtre et le pomelo Star Ruby ont montré la meilleure réponse sous stress salin. La culture des suspensions cellulaires peut être un outil efficace pour étudier le comportement des génotypes d'agrumes vis-à-vis la salinité.Mots clefs : Agrumes, salinité, tolérance, cals, suspension cellulaire Introduction: Soil and water salinity is an important abiotic stress that can affect both production and quality of citrus fruits. The use of tolerant rootstocks under these conditions would be a promising solution.Objectives: The aim of this study was to compare in vitro behaviour of four citrus genotypes in terms of salt tolerance using callus and cells grown in parallel on liquid and solid media.Methodology and Results: In this regard, calluses of four genotypes of citrus: Cleopatra mandarin (Citrus reshni hort ex Tan), Willow leaf mandarin (Citrus delicosa Ten.), ‘Star Ruby’ grapefruit (Citrus paradisi Ruby), and ‘Shamouti’ sweet orange (Citrus sinensis) were maintained on MT media containing different NaCl doses, i.e.: 0, 50, 100, 150, and 200 mM. The results showed that the different salt levels used had a significant effect on cell growth, resulting in a decrease in fresh and dry weights. In addition, salinity increased considerably Chloride concentrations in the tested genotypes.Conclusions and application of findings: A differential behaviour of salt tolerance was found between citrus calluses used depending on genotype on one hand, and type of medium on other hand. Compared to the other genotypes, Cleopatra mandarin and Star Ruby grapefruit showed the best performance under salt stress conditions. These results suggest that  culture cell suspensions can be an effective tool for studying the behaviour of citrus species under salinity.Keywords: Citrus, salinity, tolerance, callus, cell suspensio