Analyse mathématique, méthode de calcul de la gigue et applications aux réseaux Internet

RÉSUMÉ Internet, ces dernières années, sert de support de communication à un grand nombre d’applications. L’évolution des réseaux à haut débit ont facilité le progrès des applications multimédia comme la voix sur IP, la vidéo streaming ou la vidéo interactive en temps réel... La variation de la disponibilité des ressources du réseau ne peut pas garantir une bonne qualité à tout moment pour ces services. C’est dans ce contexte que les travaux de ce projet de doctorat s’inscrivent et précisément dans le cadre de l’optimisation de la qualité de service (QoS). Les mécanismes de contrôle de QoS sont variés. On retrouve le contrôle de délai, assuré par la stratégie d’ordonnancement des paquets. Le contrôle de débit, quant à lui, fait en sorte que le débit de la source soit égal à la bande passante disponible dans le réseau. Excepté que les applications vidéo, surtout en temps réel, sont très sensibles à la variation du délai, appelée la gigue. En effet, la qualité perçue par les clients des vidéos en ligne dépend étroitement de la gigue. Une augmentation de la gigue engendre principalement des problèmes de démarrage retardé de la vidéo, des interruptions au cours de la vidéo et des distorsions de la résolution. L’objectif de cette thèse est d’étudier le paramètre de la gigue, qui demeure peu étudiée dans la littérature sur les réseaux IP, ainsi que d’envisager l’impact de l’augmentation de ce paramètre sur la vidéo transmise sur IP, l’une des applications les plus populaires de nos jours. Toutefois, au-delà des difficultés de la modélisation du trafic et du réseau, cet objectif majeur pose de nombreuses problématiques. Comment calculer la gigue analytiquement pour un trafic modélisé par des distributions généralisées au niveau paquet ? Est-ce que les modèles proposés sont suffisamment simples et faciles à calculer ? Comment intégrer ces nouvelles formalisations pour le contrôle des performances ? Comment l’estimation analytique peut- elle minimiser le trafic des paquets de contrôle des connexions vidéo? Nous explorons tout d’abord le calcul de la gigue dans des files d’attente avec des trafics autres que le trafic Poisson. Ce dernier est largement utilisé pour modéliser le trafic sur Internet étant donnée sa simplicité en échange de la imprécision. L’idée pour le calcul de la gigue est d’utiliser, d’une part la même formule que le cas du Poisson mais en intégrant d’autres distributions, et d’autre part des approximations et des hypothèses quand la caractérisation analytique du temps de transit n’est pas possible. Nous adoptons la simulation pour valider les modèles approximatifs. L’ensemble de simulations montre que la gigue moyenne calculée par notre modèle et celle obtenue par simulation coïncident avec des intervalles de confiance adéquats. De plus, le temps de calcul estimé pour évaluer la gigue est minime, ce qui facilite l’utilisation des formules proposées dans des outils de contrôle et en optimisation.-----------ABSTRACT In recent years, we have witnessed the huge use of the Internet Protocol for delivering multimedia trafic. Developments in broadband networks led the progress in multimedia applications such as voice over IP, video streaming or real-time videos. However, the stochastic nature of the networks, in particular mobile networks, make it difficult to maintain a good quality at all times. The research of this PhD thesis deals with the improvement of the quality of service (QoS) for this kind of applications. Current network protocols provide multiple QoS control mechanism. Congestion control and transmission delay optimization are provided by packet scheduling strategies and bandwidth planning. Moreover, flow control adjusts the mismatch between the video server rate and the receiver available bandwidth. Nevertheless, video applications, in particular interactive videos, are very sensitive to delay variation, commonly called jitter. Indeed, the customers’ perceived video quality depends on it. A jitter increase may cause a large video start-up delay, video interruptions and a decrease of image quality. The main objective of this thesis is the study of jitter, which is not much studied in the IP literature. We also examine the impact of the increase of this parameter on video transmission. However, beyond the difficulties of modeling traffic and network, this major objective raises many other issues. How to calculate jitter analytically for traffic models with general distributions? Are the proposed models sufficiently simple and easy to calculate? How to integrate these new formalizations into performance monitoring? How can the analytical estimate minimize the traffic control packets exchange for each video connection? We first explore the jitter calculation in queues with traffic other than Poisson traffic, that was widely used to model Internet traffic because of its simplicity. The idea is to compute jitter with the same formula for the Poisson traffic case, but with other distributions. For this, we need some approximations and assumptions when the analytical characterization of the transit time is not possible. We adopt simulations to validate the approximate models. The set of simulations shows that the average jitter calculated by our model and by simulation coincide within an appropriate confidence intervals. Moreover, the execution time to evaluate jitter is small, which facilitates the use of the proposed formulas in control tools and in optimization models. We then study the possibility of exploiting this analytical results to control jitter buffers, an important component in the video transmission. We find that it is possible to evaluate its performances analytically by estimating jitter inside this type of buffer

Electrolytic oxidation as a sustainable method to transform urine into nutrients

© 2020 by the authors. In this work, the transformation of urine into nutrients using electrolytic oxidation in a single-compartment electrochemical cell in galvanostatic mode was investigated. The electrolytic oxidation was performed using thin film anode materials: boron-doped diamond (BDD) and dimensionally stable anodes (DSA). The transformation of urine into nutrients was confirmed by the release of nitrate (NO3-) and ammonium (NH4 +) ions during electrolytic treatment of synthetic urine aqueous solutions. The removal of chemical oxygen demand (COD) and total organic carbon (TOC) during electrolytic treatment confirmed the conversion of organic pollutants into biocompatible substances. Higher amounts of NO3-and NH4 + were released by electrolytic oxidation using BDD compared to DSA anodes. The removal of COD and TOC was faster using BDD anodes at different current densities. Active chlorine and chloramines were formed during electrolytic treatment, which is advantageous to deactivate any pathogenic microorganisms. Larger quantities of active chlorine and chloramines were measured with DSA anodes. The control of chlorine by-products to concentrations lower than the regulations require can be possible by lowering the current density to values smaller than 20 mA/cm2. Electrolytic oxidation using BDD or DSA thin film anodes seems to be a sustainable method capable of transforming urine into nutrients, removing organic pollution, and deactivating pathogens

Variable Levels of Tolerance to water Stress (Drought) and Associated Biochemical Markers in Tunisian Barley Landraces

[EN] Due to its high tolerance to abiotic stress, barley (Hordeum vulgare) is cultivated in many arid areas of the world. In the present study, we evaluate the tolerance to water stress (drought) in nine accessions of ¿Ardhaoui¿ barley landraces from different regions of Tunisia. The genetic diversity of the accessions is evaluated with six SSR markers. Seedlings from the nine accessions are subjected to water stress by completely stopping irrigation for three weeks. A high genetic diversity is detected among the nine accessions, with no relationships between genetic distance and geographical or ecogeographical zone. The analysis of growth parameters and biochemical markers in the water stress-treated plants in comparison to their respective controls indicated great variability among the studied accessions. Accession 2, from El May Island, displayed high tolerance to drought. Increased amounts of proline in water-stressed plants could not be correlated with a better response to drought, as the most tolerant accessions contained lower levels of this osmolyte. A good correlation was established between the reduction of growth and degradation of chlorophylls and increased levels of malondialdehyde and total phenolics. These biochemical markers may be useful for identifying drought tolerant materials in barleyPietro Gramazio is grateful to Universitat Politecnica de Valencia for a pre-doctoral (Programa FPI de la UPV-Subprograma 1/2013 call) contract.Dbira, S.; Al Hassan, M.; Gramazio, P.; Ferchichi, A.; Vicente, O.; Prohens, J.; Boscaiu, M. (2018). Variable Levels of Tolerance to water Stress (Drought) and Associated Biochemical Markers in Tunisian Barley Landraces. Molecules. 23(3). doi:10.3390/molecules23030613S23

Comparative analysis of the responses to water stress in eggplant (Solanum melongena) cultivars

[EN] Little information is available on the physiological and biochemical responses to water stress in eggplant (Solanum melongena). We valuated four genetically diverse eggplant varieties (MEL3-MEL6) under control and water stress conditions. Measurements were taken for plant growth, tissue water content, levels of chlorophylls a and b, carotenoids, roline, malondialdehyde, total phenolics, total flavonoids, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase APX), and glutathione reductase (GR) activities. For most traits, the water stress treatment had a greater contribution than the variety effect to the total sums of squares in an ANOVA analysis, except for total flavonoids, SOD, APX, and GR. The water stress treatment had a strong effect on plant growth and tissue water content. In general, water tress reduced the three photosynthetic pigments, increased proline, malondialdehyde, total phenolics, and total flavonoids, although some varietal differences were ob- served. Different patterns were also detected in the activities of the four enzymes evaluated, but few differences were observed for individual varieties between the control and water stress treatments. Many significant phe- notypic orrelations were observed among the traits studied, but only eight environmental correlations were detected. A PCA analysis distinctly separated individuals according to the treatment, and revealed a clearer separation of varieties under water stress than under control conditions, pointing to varietal differences in the responses to stress. Our results suggest that proline could be used as a marker for drought stress tolerance in this species. The information obtained provides new insight on the physiological and biochemical responses of eggplant to drought stressAuthors are grateful to the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No 677379 (G2P-SOL project: Linking genetic resources, genomes and phenotypes of Solanaceous crops), to Ministerio de Economfa, Industria y Competitividad and Fondo Europeo de Desarrollo Regional (grant AGL2015-64755-R from MINECO/FEDER), to Ministerio de Ciencia, Innovation y Universidades, Agencia Estatal de Investigation and Fondo Europeo de Desarrollo Regional (grant RTI-2018-094592-B-100 from MCIU/AEI/FEDER, UE), to the Generalitat Valenciana and Fondo Social Europeo (Ayuda a Grupos Emergentes; GV/2019/033), to the Vicerrectorado de Investigacien, Innovation y Transferencia de la Universitat Politecnica de Valencia (Ayuda a Primeros Proyectos de Investigation; PAID-06-18), and to the initiative "Adapting Agriculture to Climate Change: Collecting, Protecting and Preparing Crop Wild Relatives", which is supported by the Government of Norway. This latter project is managed by the Global Crop Diversity Trust with the Millennium Seed Bank of the Royal Botanic Gardens, Kew and implemented in partnership with national and international gene banks and plant breeding institutes around the world. For further information see the project website: http://www.cwrdiversity.org/. Mariola Plazas is grateful to Generalitat Valenciana and Fondo Social Europeo for a post-doctoral contract (APOSTD/2018/014). The contribution of Huu Trong Nguyen to this paper has been developed as a result of a mobility stay funded by Erasmus + KA1 Erasmus Mundus Joint Master Degrees Programme of the European Commission under the PLANT HEALTH project.Plazas, M.; Nguyen, HT.; González-Orenga, S.; Fita, A.; Vicente, O.; Prohens Tomás, J.; Boscaiu, M. (2019). Comparative analysis of the responses to water stress in eggplant (Solanum melongena) cultivars. Plant Physiology and Biochemistry. 143:72-82. https://doi.org/10.1016/j.plaphy.2019.08.031S728214

The contribution of mediated oxidation mechanisms in the electrolytic degradation of cyanuric acid using diamond anodes

In this work, the contribution of mediated oxidation mechanisms in the electrolytic degradation of cyanuric acid using boron-doped diamond (BDD) anodes was investigated in different electrolytes. A complete mineralization of cyanuric acid was obtained in NaCl; however lower degrees of mineralization of 70% and 40% were obtained in Na2SO4 and NaClO4, respectively. This can be explained by the nature of the oxidants electrogenerated in each electrolyte. It is clear that the contribution of active chlorine (Cl2, HClO, ClO−) electrogenerated from oxidation of chlorides on BDD is much more important in the electrolytic degradation of cyanuric acid than the persulfate and hydroxyl radicals produced by electro-oxidation of sulfate and water on BDD anodes. This could be explained by the high affinity of active chlorine towards nitrogen compounds. No organic intermediates were detected during the electrolytic degradation of cyanuric acid in any the electrolytes, which can be explained by their immediate depletion by hydroxyl radicals produced on the BDD surface. Nitrates and ammonium were the final products of electrolytic degradation of cyanuric acid on BDD anodes in all electrolytes. In addition, small amounts of chloramines were formed in the chloride medium. Low current density (≤ 10 mA/cm2) and neutral medium (pH in the range 6–9) should be used for high efficiency electrolytic degradation and negligible formation of hazardous chlorate and perchlorate

Mechanism and kinetics of electrochemical degradation of uric acid using conductive-diamond anodes

Uric acid (UA) is one of the principal effluents of urine wastewaters, widely used in agriculture as fertilizer, which is potentially dangerous and biorefractory. Hence, the degradation of UA (2,6,8-trihydroxy purine) in aqueous solution of pH 3.0 has been studied by conductive-diamond electrochemical oxidation. Hydroxyl radicals formed from water oxidation at the surface of boron-doped diamond anodes were the main oxidizing agents. Effects of current density and supporting electrolyte on the degradation rate and process efficiency are assessed. Results show that the increase of current density from 20 to 60 mA cm–2 leads to a decrease in the efficiency of the electrochemical process. In addition, the best degradation occurred in the presence of NaCl as conductive electrolyte. Interestingly, an almost total mineralization of 50 ppm UA was obtained when anodic oxidation was performed at low current densities (20 mA cm–2) and in the presence of NaCl. This result confirmed that the electrolysis using diamond anodes is a very interesting technology for the treatment of UA. The identification of UA transformation products was performed by high-performance liquid chromatography (HPLC). HPLC analysis of treated solutions revealed that oxalic acid and urea were the two intermediates found. Oxalic acid was the most persistent product. Based on detected intermediates and bibliographic research, a mechanism of UA mineralization by anodic oxidation has been proposed. Ionic chromatography analysis confirmed the release of NO− 3 and NO+ 4 ions during UA mineralization

Mechanistic and kinetic studies of the degradation of diethyl phthalate (DEP) by homogeneous and heterogeneous Fenton oxidation

In this work, the degradation of diethyl Phthalate (DEP) by homogeneous and heterogeneous Fenton oxidation was investigated. The influence of several parameters was determined such as the initial pH, the catalyst concentration, the hydrogen peroxide concentration and the initial concentration of DEP on the oxidative degradation kinetics and mineralization efficiency. Different iron sources were tested (Ferrous sulfate, Ferric oxide, Pyrite and FeF2) leading to homogeneous and heterogeneous Fenton system. Ferrous sulfate is used for deeper investigation given its fast catalytic decomposition of hydrogen peroxide directly to generate hydroxyl radicals OH known as the Fenton reaction. The experimental results showed that DEP was completely removed by the hydroxyl radicals (•OH) action generated from Fenton’s reaction under the optimal conditions 100 ppm DEP, [H2O2] = 1000 ppm, [Fe2+] = 50 ppm, and pH = 3.2. Furthermore, under these conditions, more than 95% of the initial TOC was removed, meaning almost complete mineralization of the organic compounds after 300 min of treatment. The absolute rate constant for the DEP oxidation reaction by the hydroxyl radical was determined using the competition kinetics method and found to be 4.4x109 M−1 s−1. HPLC analysis of treated solutions revealed that phtalic acid, 1,2-dihydroxybenzene, 1,2,4-trihydroxybenzene, maleic acid, formic acid and oxalic acid were the intermediates found. Oxalic acid was the major and most persistent oxidized product found at the end of the treatment. Based on the identified reaction intermediates by HPLC and TOC results, a mechanism was proposed for the mineralization of DEP during Fenton process. Finally, it can be said that the Fenton process is a suitable and efficient method for DEP removing and its intermediates from water.Scopu