Academic literature on the topic 'Service quantification'

L’un des enjeux de l’agriculture moderne est la réduction de l’utilisation d’intrants chimiques, dont celle de pesticides. La régulation naturelle, en particulier la lutte biologique par conservation, est un levier prometteur de la gestion intégrée des nuisibles. Les carabes, des arthropodes abondants et diversifiés en agroécosystème, sont considérés comme de bons candidats pour la lutte biologique de par leur consommation d’une large diversité de ravageurs et d’adventices. Ce régime alimentaire opportuniste se traduit cependant par la consommation d’auxiliaires de culture et complexifie l’estimation des services apportés par les carabes. Cette thèse avait pour objectif d’apporter un éclairage sur la dynamique temporelle des interactions trophiques entre les carabes et leurs ressources en milieu agricole, afin d’estimer le potentiel de régulation de ces prédateurs.L’agriculture par conservation, comparée à l’agriculture conventionnelle, s’est révélée avoir un effet bénéfique sur les communautés de carabes et sur la régulation des pucerons. L’analyse moléculaire de contenu stomacal des carabes nous a permis de confirmer que les carabes consomment des ravageurs et qu’en leur absence ils se maintiennent grâce à des proies alternatives. Toutefois, la détection d’une interaction trophique par analyse moléculaire dépend de nombreux facteurs comme la nature de la proie, la voracité du prédateur ou sa taille. Une expérience complémentaire a montré que l’analyse moléculaire tend à sous-estimer la prédation des pucerons relativement à celle des vers de terre, soulignant à nouveau le potentiel des carabes en tant qu'agent de biocontrôle<br>One major challenge of modern agriculture is to reduce the use of chemical inputs, particularly pesticides. Natural regulation, in particular conservation biological control, is a promising lever for integrated pest management. Carabids, abundant and diverse arthropods in agroecosystems, are considered good candidates for biological control due to their consumption of a wide variety of pests and weeds. However, this opportunistic diet also results in the consumption of auxiliaries and makes it difficult to estimate the services provided by carabids. This PhD aimed to shed light on the temporal dynamics of trophic interactions between carabid beetles and their resources in agroecosystems,in order to estimate the regulation potential of these predators. Conservation agriculture, compared to conventional agriculture, had a positive effect on carabid communities and aphid regulation. Molecular gut content analysis confirmed that carabids consume pests, including aphids, and that in the absence of pests they survive thanks to alternative preys. However, the detection of a trophic interaction by molecular analysis depends on many factors as prey identity, predator voracity and predator size. An additional study showed that molecular analysis tends to underestimate aphid predation relatively to earthworm predation, highlighting again the potential of carabids as biocontrol agents

The issue of lead exposure through drinking water was re-examined in light of modern public health goals, recent high-profile cases of elevated lead in water, and emerging concerns regarding the efficacy of legally mandated remedial strategies. A critical literature review revealed that serious lead-in-water hazards are present at many US schools and homes, and that the threat to individuals is not eliminated by existing regulations. Health studies have provided strong links between lead in water and lead in blood of exposed populations, even at relatively low levels of exposure compared to reported lead occurrence in US tap water samples. As efforts shift from addressing pervasive lead sources that once elevated the blood lead of large percentages of the population, to more isolated individual cases requiring exceptional attention, the importance of carefully considering lead in water as a potential source for elevated blood lead increases. Consistent with decades of prior research linking elevated water lead to elevated blood lead (EBL), lead-contaminated water in the high-profile case of Washington DC markedly increased the incidence of EBL for very young children. Specifically, incidence of EBL for children aged ≤ 1.3 years increased more than 4 times during 2001-2003 when lead in water was high, compared to 2000 when lead in water was low. The incidence of EBL for children aged ≤ 1.3 years was highly correlated (R² = 0.81) to 90th percentile lead-in-water levels from 2000-2007, and the risk of exposure to high water lead levels varied markedly in different neighborhoods of the city. Analysis conducted herein focused on identifying "worst-case" neighborhoods and populations. Specifically, this was the first study of the Washington DC case to focus on infants who are most vulnerable to harm from lead in water, and to perform smaller area analysis at the neighborhood (i.e., zip code) level in order to capture pockets of high risk among local communities. Prior biokinetic modeling efforts, examining the potential adverse impacts of lead-in-water exposure, were re-examined to explicitly consider new public health goals. This included impacts on the most sensitive population groups (e.g., young children and particularly formula-fed infants), the potential variability in blood lead levels (BLLs) amongst exposed individuals within those groups (e.g., most sensitive children at the upper tail of the BLL distribution), more conservative BLL thresholds reflecting low-level adverse effects (e.g., 5, 2 and 1 µg/dL versus 10 µg/dL), and the possibility of acute health impacts. This re-evaluation creates a paradigm shift, in that levels of lead in water that were previously considered inconsequential are demonstrated to be of concern in specific circumstances. The replacement of lead service lines in front of consumers' homes is a costly, federally mandated remedial action if a water utility exceeds the US EPA lead action level. Because utilities do not own the entire lead service line, they often only replace the portion of the service line up to the property line, typically with copper pipe. Experiences in Washington DC, as revealed by Freedom of Information Act requests, indicated that partial pipe replacements were not decreasing lead in water, and were actually associated with relatively high incidence of childhood lead poisoning. This prompted the first comprehensive investigation of potential long-term problems arising from galvanic corrosion between the remaining lead pipe and the newly installed copper pipe. Bench-scale experiments demonstrated that galvanic connections between lead pipe (new or aged) and copper pipe increased lead release into the water by 1.1-16 times, when compared to a full length of lead pipe alone. The small area of lead pipe adjacent to the copper joint (<0.5 ft) was gravely affected by galvanic corrosion, and accumulated a thick lead-rust layer (1 inch wide) that constituted a reservoir for semi-random particulate lead detachment into the water. The work on simulated partial pipe replacements revealed that under worst-case scenarios of highly contaminated water samples, most of the lead was not quantified if water samples were not mixed thoroughly after standard preservation (i.e., after addition of 0.15% v/v HNO₃), or if water samples were transferred from one bottle to another prior to preservation. While there is no reason to believe that sample handling and pre-treatment dramatically skew regulatory compliance with the US EPA lead action level, slight variations from one approved protocol to another may cause lead-in-water health risks to be dramatically underestimated. This is of special concern in unusual situations of "worst-case" individual exposures to highly contaminated water, associated with childhood lead poisoning. This work provides the water industry and health agencies with important new insights and perspectives on an old problem. Results can improve strategies to detect and mitigate lead-in-water hazards for individuals or populations, and inform future revisions to the US EPA Lead and Copper Rule.<br>Ph. D.

La navigation Web est l'un des principaux services de l’Internet où un large éventail d'acteurs est impliqué et évolue de manière constante. Les nouveaux protocoles de l’Internet, les réseaux de diffusion de contenu (CDN) ou encore les évolutions des différents navigateurs Web sont destinés à améliorer les temps de chargement des pages. Pour mieux comprendre la Qualité d'Expérience (QoE) perçue par les utilisateurs, il est donc essentiel d’identifier comment le contenu des pages est constitué et délivré et de fournir une métrique de QoE pertinente. Dans cette thèse, nous avons conçu un nouvel outil, Web View, destiné à effectuer des sessions de navigation Web automatisées et mesurant de nombreuses informations liées à l’écosystème du Web. Nous avons aussi défini une nouvelle métrique Web, le Time for Full Visual Rendering (TFVR). À partir de plus de 18 trillions de mesures effectuées pendant 2,5 ans sur les 10,000 sites Web les plus visités (selon la classification Alexa), nous avons utilisé des techniques statistiques pour identifier les paramètres clés qualifiant et quantifiant la qualité de la navigation Web. Cet ensemble de facteurs a été confirmé par un processus d'apprentissage automatique, donnant en sortie un ensemble de règles pour prédire les temps de chargement des pages Web. Pour les pages Web où des fluctuations dans les temps de chargement sont fréquentes, nous avons utilisé des modèles de chaines de Markov cachées suivant un processus de Dirichlet hiérarchique (HDP-HMM) pour enrichir notre modèle et ainsi augmenter le taux de prédiction correspondant. L'évaluation de notre modèle basé sur un arbre de décision sur des sites Web jamais mesurés montre que nous pouvons prédire correctement la qualité de la navigation Web. Ces travaux visent ainsi à permettre aux opérateurs de réseaux et aux fournisseurs de services d’augmenter la Qualité de Service (QoS) offerte à leurs clients<br>Web browsing is one of the main Internet services where a wide set of actors are involved and evolves constantly. New Internet protocols, Content Delivery Networks (CDN) or web browsers’evolutions are meant to improve web pages’ loading times. In order to better understand the Quality of Experience (QoE) perceived by end-users, it is of prime importance to identify how web pages’ content is composed and delivered as well as providing are levant QoE metric. In this thesis, we have designed a new tool, Web View, meant to perform automatic Web browsing and measures several aspects of the Web browsing eco-system. We have also introduced a new web metric, the Time for Full Visual Rendering (TFVR). From more than 18 Trillion measurements performed over 2.5 years on the Top 10,000 Alexa websites, we have used statistical techniques to identify the key parameters qualifying and quantifying web browsing quality. This set of factors has been confirmed by a machine learning process, which gives as output the set of rules to predict web pages’ loading times. For websites where fluctuations in loading times happen regularly, we have used the Hierarchical Dirich let Process Hidden Markov Model (HDP-HMM) to enrich our rulesbased models in order to increase the correctness in prediction rates. The evaluation of our decision treebased model on never assessed websites shows that we can correctly predict web browsing quality. This work aims at helping network operators and service providers to increase the Quality of Service (QoS) offered to their customers