The objectives of this research were to study: 1) the effects of five different propagation media containing composted materials on the rooting of semi hardwood blueberry cuttings and 2) the effects of four cultivars and one genotype on rooting responses of these cuttings. The media used were: peat moss and horticulture grade per lite as control, composted pine bark fines with only one-time application of ammonium nitrate, pine bark fines with composted cotton gin waste, hardwood with and composted chicken litter and pine bark with composted chicken litter. There were no significant differences among the media for rooting from semi hardwood cuttings. Cultivars or genotype, media, and the interaction of individual media and cultivar or genotype had effect on rooting responses. Climax and Tifblue showed higher number of rooting from cuttings compared to other lines. Climax had the highest number of callus and survival percentage among all.

In response to commercial propagators’ inquiries regarding potential phytotoxicity of alcohol used in root-promoting solutions for cutting propagation, three experiments were conducted using stem cuttings of seven herbaceous and woody plant taxa. Solutions were prepared with three rates of isopropyl alcohol (0%, 25%, or 50%) in combination with three rates of indole-3-butyric acid (IBA): 0, 1000, or 2000 ppm (Expt. 1); 0, 100, and 200 ppm (Expt. 2); or a mixture of IBA and 1-naphthalene acetic acid (NAA): 0+0, 500+250, or 1000+500 ppm IBA+NAA, respectively (Expt. 3) and applied to cuttings using the basal quick-dip method (Expts. 1 and 3) or total immersion method (Expt. 2). No stem or leaf burn occurred using the basal quick-dip method (except for lantana), whereas foliar and stem burn occurred on cuttings of African wormwood, lantana, and garden geranium using the total immersion method with solutions containing alcohol (regardless of IBA rate).

Iron/manganese toxicity disorder in marigold (Tagetes erecta L.) has been related to high concentrations of Mn and low concentrations of Ca and Mg in the affected leaves. Preplant addition of micronutrients in the media combined with constant feed program and low medium pH create favorable conditions for the development of Mn toxicity in greenhouse crops. Deficiency of Ca or Mg is due in part to low medium pH and to a lack of Mg and Ca in many of the fertilizers used in greenhouse production. The objectives of this research were to determine the relationship of Mn toxicity to the incidence of Fe/Mn toxicity disorder in marigold, and to evaluate the effect of low Mg supply and/or low Ca supply on the occurrence of the toxicity. Six experiments were conducted. Plants of Tagetes erecta L. ‘First Lady’ were started from seeds and then grown in solution culture supplying different concentrations of Mn, Ca and Mg depending on the objectives of each experiment. Symptoms were described for each experiment. When the plants were harvested, their dry weights were taken and their tissues were analyzed for Mn, Fe, Ca, and Mg concentrations. The symptoms of Mg deficiency included stunting, chlorotic and necrotic areas on the leaves. The symptoms of Ca deficiency included chlorosis and curling, especially of the new leaves. The symptoms of Mn toxicity included curled leaves, bleached patches and brown spots on the leaves. These symptoms of Mn toxicity are similar to those related to Fe/Mn toxicity disorder. The incipient deficiency solution concentration of Mg was 10 mg/l (internal incipient deficiency concentration was 1.5%). The incipient deficiency solution concentration of Ca was 20 mg/l (internal incipient deficiency concentration was 0.54%). The critical toxicity concentration of Mn was 4.5 mg/l (internal critical toxicity concentration was 270 mg/kg DW). Low Ca in solution (20 mg/liter) increased the sensitivity of marigold to high levels of Mn in solution by reducing the critical toxicity concentration of Mn from 4.5 to 0.5 mg/liter. Similar results were found when both Ca and Mg were low. Iron/manganese toxicity disorder can be attributed to Mn toxicity. Low Ca supply or low Ca and Mg supplies are factors favoring the occurrence of the disorder. Low Mg supply, alone does not seem to affect Mn toxicity in marigold. Based on this research, high Ca supply could alleviate the harmful effects of Mn toxicity in marigold. Low Mn supply could prevent the toxicity problems. Agricultural practices and nutritional regimes that reduce the availability of Mn and increase the availability of Ca could reduce the occurrence of Fe/Mn toxicity disorder in marigold and similar physiological disorders in other bedding plants grown in soilless media. Monitoring Mn supply and fertilizing with Ca could prevent or reduce Mn toxicity to floriculture plants.

Most infrastructures in the world are made with reinforced concrete (RC), and one of the ‎crucial concerns in North America is corrosion of steel reinforcement in RC structures. ‎Corrosion can lead to severe degradation which can affect the serviceability and ultimate limit ‎state, and cause failure. One solution for overcoming this phenomenon is the use of corrosion-‎resistant fibre-reinforced polymer (FRP) reinforcement. In addition to corrosion resistance, ‎FRPs also present other advantages such as high strength and light weight compared to steel ‎reinforcing bars. Their mechanical properties differ from those of steel; therefore, the flexural ‎and shear behaviour of FRP-RC members requires investigation. In general, predictions from flexural design equations are close to results from experimental ‎data. However, shear strength predictions based on different modelling approaches can vary ‎greatly. Thus, in the last century, one of the main controversies in the field of structural ‎engineering attracting continuous attention is the shear behaviour of RC members. In previous ‎studies, factors such as concrete strength, reinforcement ratio, beam depth, beam width, size ‎effect, aggregate size, fracture energy and shear slenderness have been investigated in an effort ‎to solve the riddle of shear in beams. Recently, a new rational theory named "Shear Crack ‎Propagation Theory" (SCPT) was introduced that combines crack kinematics with constitutive ‎material behaviour to predict shear behaviour over the entire loading process, rather than only ‎focusing on the point of failure. To date, the SCPT has only been used to predict the shear behaviour of RC beams containing ‎steel reinforcement. The present study is the first to apply the SCPT to RC beams with non-‎metallic reinforcement. The numerical analysis using SCPT on RC members was validated ‎against published test data and examines the role of important parameters such as ‎reinforcement modulus of elasticity, reinforcement ratio, bond condition, and dowel resistance.‎

No description available.

No description available.

Les infrasons sont des ondes acoustiques de fréquence inférieure à environ 20 Hz qui sont produits par une grande variété de sources naturelles (éruptions volcaniques, séismes, etc.) ou artificielles (explosions chimiques, avions, tirs de mine, etc.). Ils peuvent se propager dans l’atmosphère terrestre jusqu’à de très grandes distances, de quelques centaines à plusieurs milliers de kilomètres, et transportent des informations importantes concernant leur source. Pour cette raison, la mesure des ondes infrasonores représente aujourd’hui une des principales techniques utilisées dans le cadre du Traité d’interdiction complète des essais nucléaires (TICE) pour la détection, la localisation et l’identification de sources. La modélisation de la propagation atmosphérique des infrasons a été classiquement réalisée par des approximations géométriques, comme le tracé de rayons, ou par la résolution d’équations paraboliques. Grâce à un coût de calcul raisonnable, allant de quelques secondes à une heure, ces approches sont largement employées dans le domaine opérationnel. Leur efficience est néanmoins obtenue au détriment de la complexité physique de la propagation atmosphérique. Les avancées récentes de la simulation numérique directe en aéroacoustique rendent cependant envisageable la résolution directe des équations de Navier-Stokes instationnaires et compressibles, permettant ainsi de décrire sans approximation la propagation infrasonore. Dans la présente thèse, trois objectifs principaux ont été poursuivis. En utilisant une méthode de tracé de rayons, une caractérisation des effets non linéaires, visqueux, thermiques et de relaxation sur les ondes infrasonores produites par des sources explosives a été d’abord effectuée. La propagation non linéaire des signaux infrasonores dans l’atmosphère terrestre a été ensuite examinée à l’aide de simulations tridimensionnelles directes des équations de Navier-Stokes instationnaires et compressibles. Des sources de très grande amplitude et de fréquence de l’ordre de 0.1 Hz ont été considérées. Les calculs ont été menés jusqu’à des distances de propagation de plusieurs centaines de kilomètres et jusqu’à des altitudes de l’ordre de 140 km. Une étude détaillée de la diffusion par les petites échelles de l’atmosphère a été effectuée. Une première analyse de la pénétration en zone d’ombre provoquée par des phénomènes de diffraction au niveau des caustiques a été également réalisée. Des cas test bidimensionnels ont été enfin formulés et des solutions de référence ont été déterminées afin de permettre la validation numérique de codes de calcul et l’évaluation des erreurs commises par les approximations usuelles. / Infrasounds are acoustic signals of frequency lower than about 20 Hz. They are generated by a large variety of natural events, such as volcanic eruptions or earthquakes, and by artificial sources, like nuclear or chemical explosions and supersonic booms. Infrasonic waves can propagate through the different atmospheric layers up to very large distances, from few hundreds to thousands of kilometres, and can potentially carry relevant information about their source. For this reason, within the framework of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), infrasound recordings are widely employed to monitor clandestine nuclear tests. Infrasound modelling has classically been based on simplified equations. Ray tracing and parabolic models have been the most commonly used techniques. Their efficiency in terms of computational cost is however obtained at the expense of generality and some of the main phenomena affecting infrasound propagation are inherently excluded by these methods. Over the past decade, progress has been made towards the simulation of acoustic propagation by directly solving the fluid dynamics equations. Understandably, this approach is expected to allow a finer description of atmospheric propagation and to lead to a better interpretation of experimental observations. In the present thesis, three main objectives have been achieved. First of all, using ray theory, a characterization of nonlinear effects and absorption induced by thermo-viscous and vibrational relaxation phenomena on the propagation of infrasonic signals generated by explosive sources has been carried out. Direct numerical simulations of the three-dimensional unsteady compressible Navier-Stokes equations have been then performed to calculate the sound field generated by an infrasonic source in a realistic atmosphere. Computations have been carried out using a low-dispersive and low-dissipative finite-difference time-domain method, for very large source amplitudes and for source frequencies of order of 0.1 Hz, up to altitudes of 140 km and ranges of few hundreds of kilometres. The scattering from small-scale inhomogeneities, of characteristic dimension of the same order as the wavelength of the infrasonic wave, has been investigated. The penetration in the shadow zone induced by diffraction phenomena at the thermospheric caustic has also been studied. Two-dimensional benchmarks specific to infrasound atmospheric propagation have been finally formulated and reference solutions have been computed. They aim to allow the assessment of the accuracy of numerical solvers as well as the evaluation of the range of validity of the classical approaches.

abstract: Blockchain scalability is one of the issues that concerns its current adopters. The current popular blockchains have initially been designed with imperfections that in- troduce fundamental bottlenecks which limit their ability to have a higher throughput and a lower latency. One of the major bottlenecks for existing blockchain technologies is fast block propagation. A faster block propagation enables a miner to reach a majority of the network within a time constraint and therefore leading to a lower orphan rate and better profitability. In order to attain a throughput that could compete with the current state of the art transaction processing, while also keeping the block intervals same as today, a 24.3 Gigabyte block will be required every 10 minutes with an average transaction size of 500 bytes, which translates to 48600000 transactions every 10 minutes or about 81000 transactions per second. In order to synchronize such large blocks faster across the network while maintain- ing consensus by keeping the orphan rate below 50%, the thesis proposes to aggregate partial block data from multiple nodes using digital fountain codes. The advantages of using a fountain code is that all connected peers can send part of data in an encoded form. When the receiving peer has enough data, it then decodes the information to reconstruct the block. Along with them sending only part information, the data can be relayed over UDP, instead of TCP, improving upon the speed of propagation in the current blockchains. Fountain codes applied in this research are Raptor codes, which allow construction of infinite decoding symbols. The research, when applied to blockchains, increases success rate of block delivery on decode failures. / Dissertation/Thesis / Masters Thesis Computer Science 2018

Déterminer si un problème de satisfaction de contraintes (CSP) a une solution ou non est NP-complet. Les CSP sont résolus par inférence (c’est-à-dire, en appliquant un algorithme de cohérence), par énumération (c’est-à-dire en effectuant une recherche avec retour sur trace ou backtracking), ou, plus souvent, en intercalant les deux mécanismes. La propriété de cohérence la plus courante appliquée en cours du backtracking est la GAC (Generalized Arc Consistency). Au cours des dernières années, de nouveaux algorithmes pour appliquer des cohérences plus fortes que le GAC ont été proposés et montrés comme étant nécessaires pour résoudre les problèmes difficiles.Nous nous attaquons à la question de balancer d’une part le coût et, d’autre part, le pouvoir d’élagage des algorithmes de cohérence et posons cette question comme étant celle de déterminer où, quand et combien une cohérence doit-elle être appliquée en cours de backtracking. Pour répondre à la question « où », nous exploitons la structure topologique d'une instance du problème et focalisons la cohérence forte là où des structures cycliques apparaissent. Pour répondre à la question « quand », nous proposons une stratégie simple, réactive et efficace qui surveille la performance du backtracking puis déclenche une cohérence forte lorsque l’effort du retour sur trace devient alarmant. Enfin, pour la question du « combien », nous surveillons les mises à jour provoquées par la propagation des contraintes et interrompons le processus dès qu’il devient inactif ou coûteux même avant qu’il n’atteigne un point fixe. Les évaluations empiriques sur des problèmes de référence établissent l’efficacité de nos stratégies. / Determining whether or not a Constraint Satisfaction Problem (CSP) has a solution is NP-complete. CSPs are solved by inference (i.e., enforcing consistency), conditioning (i.e., doing search), or, more commonly, by interleaving the two mechanisms. The most common consistency property enforced during search is Generalized Arc Consistency (GAC). In recent years, new algorithms that enforceconsistency properties stronger than GAC have been proposed and shown to be necessary to solve difficult problem instances.We frame the question of balancing the cost and the pruning effectiveness of consistency algorithms as the question of determining where, when, and how much of a higher-level consistency to enforce during search. To answer the ‘where’ question, we exploit the topological structure of a problem instance and target high-level consistency where cycle structures appear. To answer the ‘when’ question, we propose a simple, reactive, and effective strategy that monitors the performance of backtrack search and triggers a higher-level consistency as search thrashes. Lastly, for the question of ‘how much,’ we monitor the amount of updates caused by propagation and interrupt the process before it reaches a fixpoint. Empirical evaluations on benchmark problems demonstrate the effectiveness of our strategies.

Dans le domaine du transport de fret, il est nécessaire d’assurer le suivi des wagons, d’identifier les wagons sensibles (transport de matières dangereuses, denrées périssables…) ainsi que de collecter les informations associées (contenu, poids, localisation) pour faciliter la gestion logistique. Le but de cette thèse est de proposer un système de communication sans fil à courte portée qui répond à ces besoins. Les contraintes de l’environnement ferroviaire et de l’embarqué telles que la flexibilité, le coût de l’installation, la faible consommation d’énergie, et le risque de présence de perturbations électromagnétiques rend l’insertion des technologies sans fil dans le milieu ferroviaire plus complexe. Une étude comparative des systèmes de communication existants a permis d’identifier la technologie ZigBee comme étant la plus adaptée au problème étudié. Une comparaison des différents scénarios possibles du positionnement des dispositifs ZigBee a été réalisée et validée par des mesures en présence de véhicules et de conteneurs. L’impact des perturbations électromagnétiques issues des installations d’alimentation ferroviaire et des émetteurs RF environnants, a été étudié. Une analyse d’autres types de perturbations générées intentionnellement pour nuire au système proposé à des fins malveillantes, a été également menée. / In railway freight transport, wagons tracking is necessary to identify sensitive elements (transport of hazardous materials, perishable goods ...) and the associated information (content, weight, location) could be useful for logistic management. The aim of this thesis is to propose a short-range wireless communication system, which meets these needs. The constraints of rail environment such as flexibility, technical installation difficulties, low energy consumption and the risk of electromagnetic disturbances, causes more difficulties to insert wireless technologies in railway environment. A comparative study of existing communication systems has identified the ZigBee technology as the most appropriate to design the communication between wagons and between wagon and infrastructure for the studied application. A comparison of different possibilities for positioning of ZigBee devices was carried out. Experimentations have been realized in presence of vehicles and containers. The impact of electromagnetic disturbances issued from rail power infrastructure and from surrounding RF transmitters, has been studied. Disturbances intentionally generated to damage the proposed system, have been also analyzed.