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Lindström, Robin. "Flexibility or coerced resilience: Analysing the role of flex crops in the global production ecosystem." Thesis, Stockholms universitet, Stockholm Resilience Centre, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-194678.
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Large parts of Earth’s natural ecosystems have been converted into simplified production system. These production systems, named the Global Production Ecosystems (GPE) are characterised by homogenised and industrial production, that delivers predictable yields of biomass and is highly connected through global trade. The anthropogenic inputs required to keep this predictability is likely to cause environmental degradation and could cause novel risks in the long term. The rise of flex crops is a phenomenon that is likely to further promote this homogenisation and industrialisation. These are crops with multiple and flexible uses that are increasingly targeted by agribusinesses to feed the demands of food, feed, fuel and other industrial products. This study examines global flex crops production ecosystem through the lens of resilience thinking, by analysing production data over time, including the social and environmental impacts of inputs, and assess the national concentration of production. I find that flex crops have expanded and intensified more so than similar crops. Since 1961 flex crops harvested area have increased in more than 150% in size, while similar crops have increased 10%. At the same time yields for flex crops have almost tripled, while similar crops have doubled their yield. I also find that in some aspects flex crops are heavily reliant on anthropogenic inputs. On a global scale the use of inputs is generally concentrated to a small number of countries, but that the average use of inputs varies greatly between countries. These findings indicate that the development of flex crops is an important to research to understand the GPE and that using resilience thinking is key to understand this phenomenon.
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Smith, Joshua Dwayne. "Impacts of Cover Crops on Carbon Dioxide and Nitrous Oxide Flux from a Row Crop Agricultural Field in Central Illinois." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1391.
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In the United States, there is renewed interest in incorporating cover crops into agricultural systems to provide a variety of potential benefits related to soil quality, water quality, and greenhouse gas emissions. This study focused on assessing whether cover crops influence N2O and CO2 emissions in a central Illinois agricultural research field over two years (2011-2013) of cover crop growing seasons. Three winter cover crop systems, annual ryegrass (Lolium multiflorum), cereal rye (Secale cereale), and a cereal rye (2011)/ hairy vetch (Vicia villosa) (2012) rotation were planted after fall 2011 and 2012 harvests. The field included a total of eight main plots, two of each treatment, and two no cover crop control plots. Soil carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were measured from the plots in a single corn (Zea mays) - soybean (Glycine max) system for two cover crop growing seasons. Fluxes of CO2 and CO2 were measured in March 2012, August 2012, and February 2013. The CO2 flux measurements were performed by using an infrared gas analyzer. The N2O fluxes were analyzed from samples collected at 0, 10, 20, 30 min intervals from the same closed dynamic chamber system. Both CO2 and N2O fluxes were computed from respective gas concentrations over time. Data were analyzed with a repeated measures mixed model procedure. N2O fluxes from the cereal rye/hairy vetch plots were greater than the no cover control and annual ryegrass plots, suggesting that cover crops may not decrease N2O fluxes immediately after being incorporated into a cropping system. In contrast, CO2 fluxes did not significantly differ among the treatments, but the cereal rye/hairy vetch plot sequestered ~100 kg C ha-1 of soil organic carbon (SOC). Overall, it was observed that some cover crop plots can have higher N2O fluxes than plots without cover crops, but cover crops have the long-term potential to sequester C in croplands demonstrating that their use should still be considered a sustainable agriculture practice.
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Thomas, Benjamin Mark. "The role of vesicular-arbuscular mycorrhizal fungi in Linum usitatissimum L. production in Southern Australian soils." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pht4541.pdf.
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Bibliography: leaves 106-132. This project investigated the role of VAM fungi in the growth and nutrition of Linum usitatissimum L. in agricultural soils in southern Australia. It had two general aims: (1) to examine the role of indigenous VAM fungi in the growth and nutrition of linseed in field soil collected near Clare, South Australia; and (2) to examine the effect of VAM fungi on the Zn nutrition of Linola.
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Keller, Steven Ede. "Flux-limited Diffusion Coefficient Applied to Reactor Analysis." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16126.
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A new definition of the diffusion coefficient for use in reactor physics calculations is evaluated in this thesis. It is based on naturally flux-limited diffusion theory (FDT), sometimes referred to as Levermore-Pomraning diffusion theory. Another diffusion coefficient more loosely based on FDT is also evaluated in this thesis. Flux-limited diffusion theory adheres to the physical principle of flux-limiting, which is that the magnitude of neutron current is not allowed to exceed the scalar flux. Because the diffusion coefficients currently used in the nuclear industry are not flux-limited they may violate this principle in regions of large spatial gradients, and because they encompass other assumptions, they are only accurate when used in the types of calculations for which they were intended.
The evaluations were performed using fine-mesh diffusion theory. They are in one spatial dimension and in 47, 4, and 2 energy groups, and were compared against a transport theory benchmark using equivalent energy structures and spatial discretization.
The results show that the flux-limited diffusion coefficient (FD) outperforms the standard diffusion coefficient in calculations of single assemblies with vacuum boundaries, according to flux- and eigenvalue-errors. In single assemblies with reflective boundary conditions, the FD yielded smaller improvements, and tended to improve only the fast-group results. The results also computationally confirm that the FD adheres to flux-limiting, while the standard diffusion coefficient does not.
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Schaare, P. N. "Areal variations in heat flux density over crop surfaces." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370557.
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Zydney, Andrew Lawrence. "Cross-flow membrane plasmapheresis : an analysis of flux and hemolysis." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15235.
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Jamboonsri, Watchareewan. "IMPROVEMENT OF NEW OIL CROPS FOR KENTUCKY." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/120.
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Three oil crops, chia (Salvia hispanica L.), flax (Linum usitatissimum L.), and castor (Ricinus communis L.), were studied because of their nutritional and industrial values. Chia and flax are rich in an ω3 fatty acid, α-linolenic acid, and castor is a very high oil producer and high in a hydroxy fatty acid. Ethyl methanesulfonate (EMS) and gamma rays were employed to mutagenize chia seeds to produce early flowering mutants. The M1 population was grown and induced to flower by short-day photoperiods. The M2 population was planted in the field in Lexington, KY in 2008. Early flowering plants were found 55 days after planting while non-mutagenized plants did not produce any flower buds until the 7th of October, 82 days after planting, at a daylength of 11 hours and 32 minutes. 0.012% of the EMS-treated M2 population and 0.024% of the gamma radiation-treated population flowered much earlier than the controls. M3 early flowering mutant lines were able to flower at photoperiods of 12-15 hours in a greenhouse. Selected lines produced flower buds on the 7th of July, 47 days after planting, at a daylength of 14 hours and 41 minutes in the field in Lexington, Kentucky.
Different varieties of flax were evaluated for seed yield and field performance in Kentucky. Plant height and yield data were collected from three growing seasons. Yields from 2006 trial varied from 368-1,267 kg/ha. Yields from 2007 and 2008 were much lower due to drought. The variety ‘Carter’ gave the highest yield every season. Flax can be grown in Kentucky but yields are low.
Two high-yield castor varieties, ‘Carmencita’ and ‘TTU-LRC’, were crossed in greenhouse. The F1 population was grown in the field. Inflorescences were covered to ensure self-pollination. The F2 population showed a high degree of segregation for plant height, stem color, capsule color and seed yield in the following growing season. Data on plant height, number of branches, color, and yield was collected from 89 F2 individuals. Fifteen lines with the highest yield were selected to plant in the field in spring of 2009. New high-yield castor varieties are being developed for production in Kentucky.
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Dalton, James A. "Contribution of upward soil water flux to crop water requirements." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/344938/.
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Celebi, Selahattin. "Flux line cutting and cross-flow in tubes of high T(c) superconductors." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6904.
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We present strong evidence that helical flux lines can concurrently, enter and leave the wall of hollow cylinders of sintered high superconductors at T$\sb{\rm c}$ 77 K, hence cut and traverse each other. Tubes of two different materials, denoted BiSCCO and YBCO, have been studied. The evidence for flux line cutting and cross-flow is examined in the perspective of basic concepts. The traffic of the flux lines is also described formally. The penetration fields across the wall and into the grains of the sintered ceramic tubes are determined from their magnetic response to an applied axial field H$\sb{//}$ and from their flux trapping behaviour when subjected to two standard procedures, denoted H$\sb{\rm cool}$ and H$\sb{\rm cycle}$. This provides information on j$\sb{\rm c\perp m}$ and j$\sb{\rm c\perp g}$, the intergrain and intragrain critical current densities for depinning of flux lines. The penetration fields are seen to correlate with salient features (peaks and valleys) of the flux line cutting and cross flow phenomena. This enables us to claim that we are witnessing flux line cutting and cross flow in the weak link regime in the BiSCCO tube and in this regime as well as in the interior of the grains in the YBCO tube. The Clem/Perez-Gonzalez phenomenological theory is exploited in a simplified framework to describe the crucial features of the data semi-quantitatively. This analysis confirms the above conclusions and provides estimates of j$\sb{\rm c//m}$ and j$\sb{\rm c//g}$, the critical current densities for intergranular and intragranular flux line cutting and their dependence on the magnetic flux density.
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Somoano, Rodríguez Miguel. "Performance and flow dynamics in cross-flow turbines." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/553240.
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Aquesta tesi doctoral presenta l'estudi que l'autor va realitzar per comprendre l'efecte de l'angle pitch de la pala sobre les interaccions pala-estela que tenen lloc dins el rotor i, per tant, sobre el rendiment d'una turbina de flux creuat amb tres pales rectes.
En primer lloc, hem estudiat experimentalment el rendiment d'aquest tipus de turbina en un túnel de vent de capa límit. Ho vam fer per a diferents pitches fixos de les pales, i amb diferents nombres de Reynolds basats en el diàmetre de la turbina que cobreixen la regió de transició en què el parell produït per les pales va superar el parell resistiu oposat. La forma i els valors de la corba de rendiment van canviar dràsticament amb només un increment de l'angle pitch fix. Com més gran sigui el nombre de Reynolds, menor és el tip speed ratio òptim i més cap al toe-out es mou l'angle pitch ideal.
Posteriorment, vam estudiar experimentalment la dinàmica de flux dins el rotor per diferents pitches de la pala en un tanc d'aigua amb carro, usant Digital Particle Image Velocimetry. Els assajos es van realitzar a un nombre de Reynolds basat en el diàmetre de la turbina constant, i per a un rang de tip speed ratios. L'atenció se centra en l'anàlisi de les interaccions pala-estela dins el rotor. Angles toe-in i excessius toe-out s'han associat a baixos rendiments d'aquest tipus de turbines. La investigació ens ha permès relacionar les interaccions pala-estela amb les diferències de rendiment en aquest tipus de turbines, en funció del tip speed ratio i de l'angle pitch de la pala.Esta tesis doctoral presenta el estudio que el autor realizó para comprender el efecto del ángulo pitch de la pala sobre las interacciones pala-estela que tienen lugar dentro del rotor y, por lo tanto, sobre el rendimiento de una turbina de de flujo cruzado con tres palas rectas. En primer lugar, hemos estudiado experimentalmente el rendimiento de este tipo de turbina en un túnel de viento de capa límite. Lo hicimos para diferentes pitches fijos de las palas, y con diferentes números de Reynolds basados en el diámetro de la turbina que cubren la región de transición en la que el par producido por las palas superó al par resistivo opuesto. La forma y los valores de la curva de rendimiento cambiaron drásticamente con sólo un incremento del ángulo pitch fijo. Cuanto mayor sea el número de Reynolds, menor es el tip speed ratio óptimo y más hacia el toe-out se mueve el ángulo pitch ideal. Posteriormente, estudiamos experimentalmente la dinámica de flujo dentro del rotor para diferentes pitches de la pala en un tanque de agua con carro, usando Digital Particle Image Velocimetry. Los ensayos se realizaron a un número de Reynolds basado en el diámetro de la turbina constante, y para un rango de tip speed ratios. La atención se centra en el análisis de las interacciones pala-estela dentro del rotor. Ángulos toe-in y excesivos toe-out se han asociado a bajos rendimientos de este tipo de turbinas. La investigación nos ha permitido relacionar las interacciones pala-estela con las diferencias de rendimiento en este tipo de turbinas, en función del tip speed ratio operativo y del ángulo pitch de la pala.
This doctoral thesis presents the study that the author have carried out in order to understand the effect of the blade pitch angle on the blade-wake interactions that take place inside the rotor, and hence on the performance of a three straight bladed cross-flow turbine. Firstly, we have experimentally studied the performance of this kind of turbine in a boundary layer wind tunnel. We did it for different fixed blade pitches, and at different turbine diameter Reynolds numbers covering the transitional region in which the torque produced by the blades overtook the opposed resistive torque. Shape and values of the performance curve changed drastically with just an increment of the fixed pitch angle. The higher the Reynolds number, the lower the optimal tip speed ratio and the more towards toe-out the ideal pitch angle is moved. Afterwards, we study experimentally the flow dynamics inside the rotor for different blade pitches in a water towing tank, using planar Digital Particle Image Velocimetry. Tests were made at a constant turbine diameter Reynolds number, and for a range of tip speed ratios. The focus is given to the analysis of the blade-wake interactions inside the rotor. Toe-in and excessive toe-out angles have been associated to low performances of this type of turbines. The investigation has allowed us to relate the blade-wake interactions with the performance differences in this type of turbines, as a function of both the operational tip speed ratio and the blade pitch angle.
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Wickremasinghe, Don Athula A. "HARP Targets Pion Production Cross Section and Yield Measurements: Implications for MiniBooNE Neutrino Flux." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439295324.
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Kularatne, Kottabogoda Angidigedera Samantha Rangajeewa. "Factors influencing sediment re-suspension and cross-shore suspended sediment flux in the frequency domain." University of Western Australia. School of Environmental Systems Engineering, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0005.
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[Truncated abstract] With rapidly increasing population densities along coastlines and rising global sea levels, coastal protection has become a major concern for coastal communities. Predicting sediment transport in nearshore regions, however, is one of the most challenging tasks faced by coastal researchers in designing coastal structures or beach nourishment schemes. Although nearshore sediment transport mainly occurs in the longshore direction, cross-shore sediment transport is crucial in determining the shoreline evolution and beach morphology . . . This study investigated the factors influencing sediment re-suspension and cross-shore suspended sediment flux in the frequency domain through a series of field measurements conducted at several different locations and a numerical model. Only oscillatory flow components were examined and the mean flow components were not considered. Although many different factors such as cross-shore location with respect to breaker line, significant wave height to water depth ratio (Hs/h), normalised horizontal velocity skewness (
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Medina, Ricardo. "Measurement of neutron flux and spectrum-averaged cross sections for an in-pile PWR loop." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14095.
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Van, Koninckxloo Michel. "Ecophysiological approach of the fertilization of crops on the basis of the nutrients productivity and nutrients flux density concepts." Doctoral thesis, Universite Libre de Bruxelles, 1990. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213159.
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Mponda, O. K. K. "Involving farmers in the design of low-input control programme for sesame flea beetle (Alocypha bimaculata, Jacoby) in S.E. Tanzania." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320951.
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Brown, Mitic Constance Maria. "Flux associations and their relationship to the underlying heterogeneous surface characteristics." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35988.
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This thesis consists of analysis of three different data sets: (i) Aircraft-based eddy correlation data collected above irrigated and non-irrigated agricultural land in Southern California during the California Ozone Deposition Experiment (CODE) summer 1991; (ii) micrometeorological tower data, collected over grape and cotton canopies as part of CODE; (iii) aircraft-based eddy correlation flux data above two grid sites in the Canadian boreal forest during the Boreal Ecosystem-Atmosphere Study (BOREAS), spring and summer of 1994 and 1996.Results from the CODE aircraft data document composition and size of the dominant structures, which transport heat and gases (H2O, CO 2 and ozone) over water stressed and non-water stressed surfaces, and the relative frequency with which structures carrying only a single scalar, or given combinations of scalars, were encountered along the flight paths. Interpretation of results provides further evidence for the existence of a second (nonphysiological) sink for ozone. The relative preponderance of structures that carry moisture, carbon dioxide and ozone simultaneously, particularly in the gradient-up mode, reflects the importance of vegetation as co-located source/sink for these scalars. The detrending procedures described in this study may help to define a more effective separation between local and mesoscale events in biosphere-atmosphere interaction.
Results from the CODE tower data indicates a single vegetated ozone sink for the grape site, but a vegetated as well as a non-vegetated sink for the cotton site. For both sites, structures simultaneously transporting significant flux contributions of CO2, H2O, heat and ozone dominate during unstable conditions. During stable conditions, unmixed single flux structures dominated over cotton but not over grape. The results of this study contribute empirical evidence about the relationship between ozone uptake and the physical and physiological state of vegetation, as well as the limitations placed on eddy scales in simulation models.
Results from the BOREAS aircraft data shows a decoupling between the surface and the atmosphere, where the patterns of vegetation, greenness and surface temperature may be quite dissimilar to those of the fluxes of sensible heat, latent heat and---to a lesser degree---CO2. Reasons for this lie in the extraordinary boundary layer conditions, high vapour pressure deficit, moist soil and hot canopies, and the response of the vegetation to these conditions. Analysis of the coherent structure compositions to some extent permits the characterization of the different sources and sinks. Overall, this study shows the importance of understanding the various interacting components of soil, vegetation and atmosphere when attempting to design process-based models for predictions in 'micrometeorologiacally' complex ecosystems.
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Riccio, Ciro. "Mesure du flux et de la section efficace des antineutrinos dans le détecteur proche de l'expérience T2K." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS013/document.
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T2K (Tokai to Kamioka) est une expérience d’oscillation de neutrinos muoniques sur une longue ligne de base, située au Japon. Elle est conçue pour mesurer le changement de saveur des neutrinos d’un faisceau produit à l’aide d’un accélérateur au laboratoire JPARC de Tokai. Les détecteurs proche et lointain sont placés légèrement hors axe par rapport au faisceau. Depuis la découverte en 2013 de l’apparition de neutrinos électroniques, T2K a inversé la polarité des cornes magnétiques intervenant dans la production du faisceau, afin de produire un faisceau d’antineutrinos et d’augmenter la sensibilité de l’expérience à la violation de la charge-parité dans le secteur leptonique. Le faisceau produit est alors dominé par les antineutrinos muoniques avec une composante mesurable de neutrinos muoniques. L’analyse simultanée, dans les données prises avec le faisceau de neutrinos et le faisceau d’antineutrinos, des interactions par courant chargé dans le détecteur proche ND280, permet de réduire l’impact sur les analyses d’oscillation des incertitudes liées au flux de (anti)neutrinos et à leur section efficace d’interaction. Les données de ND280 permettent également de mesurer les sections efficaces d’interaction des antineutrinos d’énergie proche de 600 MeV. La bonne connaissance du processus d’interaction des (anti)neutrinos avec les noyaux atomiques est cruciale pour interpréter les résultats de l’expérience en termes d’oscillations. De nombreux modèles théoriques ont été développés pour décrire les effets nucléaires lors des interactions des (anti)neutrinos, mais une vison globale cohérente n’a pas encore émergé. En particulier, des mesures variées de section efficace d’interaction par courant chargé sans production de pion dans l’état final suggèrent la possibilité pour les neutrinos d’interagir avec des paires de nucléons corrélés, entrainant l’éjection de plus d’un nucleon hors du noyau (composante dite “multi-nucléon”). Divers modèles ont proposé des estimations différentes de ce processus et une mesure précise et sans ambiguité n’est pas encore disponible. Ce travail de thèse se concentre sur trois études. La première détaille la sélection des interactions de neutrinos muoniques par courant chargé dans le détecteur proche hors axe. Dans un premier temps l’échantillon de données était divisé en deux selon le nombre de traces chargées de l’événement, puis l’accumulation de davantage de données a permis la séparation de l’échantillon en trois lots selon le contenu en pions de l’événement. La seconde étude consiste en la mesure simultanée de la section efficace d’interaction des neutrinos et des antineutrinos muoniques par courant chargé, conduisant à un état final sans pion mesuré dans le détecteur ND280. Ces sections efficaces sont extraites en fonction de l’impulsion et de l’angle du muon issu de l’interaction, permettant ainsi d’évaluer la somme, la différence et l’asymétrie entre les sections efficaces des neutrinos et des antineutrinos. La somme permet d’isoler la composante d’interférence vecteur-axial de la section efficace, et la différence est sensible à la composante multi-nucléons. L’asymétrie permet d’estimer directement le biais éventuel sur la mesure de la phase de violation de CP dû à la modélisation des sections efficaces, dans l’analyse d’oscillation de neutrinos. La dernière partie de la thèse étudie la proposition d’utiliser la technologie dite de multi-PMT pour le detector Hyper-Kamiokande, version à plus grande échelle de Super-Kamiokande, ainsi que la possibilité d’étudier le flux de neutrinos avec un détecteur basé sur le rayonnement Cherenkov dans l’eau, et placé à environ 2 km de l’origine du faisceau de neutrinos. Un multi-PMT est une sphère de plastique contenant 26 tubes photomultiplicateurs, qui pourrait améliorer l’efficacité des futurs détecteurs basés sur le rayonnement Cherenkov dans l’eauT2K (Tokai to Kamioka) is a long-baseline neutrino oscillation experiment installed in Japan and designed to measure neutrino flavor oscillation using an off-axis neutrino beam produced at the J-PARC accelerator facility in Tokai. Since its discovery of electron neutrino appearance in 2013, T2K has switched its beam magnet polarities to run in antineutrino beam mode in order to enhance its sensitivity to the charge-parity violation in the leptonic sector. The beam is dominated by muon antineutrinos, but it also contains a sizable contamination from muon neutrinos. The analysis of both neutrino and antineutrino charged-current interactions in the off-axis near detector ND280, provides a significant reduction of the flux prediction and cross-section modeling systematic uncertainties in the oscillation analysis. ND280 data also gives us the opportunity to measure antineutrinos cross-sections at the energy around 600 MeV. Information on (anti)neutrino scattering is vital for the interpretation of neutrino oscillation. Many theoretical models have been developed to describe the nuclear effects in (anti)neutrino scattering, but a consistent picture has yet to emerge. In particular, various measurements of charged-current cross-section without production of pions in the final state have suggested the presence of another channel where neutrinos interact with pairs of correlated nucleons and more than one nucleon is knocked-out from the nucleus (multi-nucleon component). Various models have proposed different estimations of such process and a precise and unambiguous measurement is not yet available. This thesis work is focused on three different arguments. First the selections of CC interactions of muon neutrinos in antineutrino beam in the off-axis near detector. In a first iteration this sample has been divided into two sub-sample based on the track multiplicity, then with more statistic a separation into three sub-samples based on the pion content in each event was possible. Then on the simultaneous measurement of the double-differential muon neutrino and antineutrino charged-current cross-section without pions in the final state using the off-axis near detector. The neutrino and antineutrino cross-sections will be simultaneously extracted as a function of muon momentum and angle with a likelihood fit, including proper estimation of the correlations, allowing the evaluation of the sum, difference and asymmetry between the two cross-sections. The sum isolates the axial-vector interference term of the cross-section, and the difference enhances the sensitivity to the multinucleon component. The asymmetry is a direct estimation on any possible bias due to mismodeling of (anti)neutrino interactions on the measurement of the CP violation phase in neutrino oscillation. The last topic concerns the proposal of the multi-PMT technology as detector for Hyper-Kamiokande, the upgrade of Super-Kamiokande, and the intermediate water v Cherenkov proposed to study the neutrino flux at ~2 $km$ from the beam production point. A multi-PMT is a plastic sphere filled with 26 photomultiplier tube that could improve the efficiency of the Cherenkov detectors foreseen in the future
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Ballard, Todd Curtis. "Mathematical Models of Zea mays: Grain Yield and Aboveground Biomass Applied to Ear Flex and within Row Spacing Variability." TopSCHOLAR®, 2008. http://digitalcommons.wku.edu/theses/41.
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Field studies were conducted during the summers of 2007 and 2008 at the Agricultural Research and Education Complex, Western Kentucky University, Warren County, KY and commercial production fields in Caldwell County, KY, Warrick County IN, and Vanderburgh County, IN. The goals of these studies were to further validate the Duncan grain yield model, the Russell aboveground biomass model, and to study the effect of inconsistent spacing within rows on Zea mays L. yield. Plant spacing other than uniform decreases grain yield and profitability. The population experiments conducted at the Warren County location were a randomized complete block design with three planting densities, three varieties (c.v. DeKalb DKC6547, DeKalb DKC6346, DeKalb DKC6478) in 2007 and (DeKalb DKC6478, DeKalb DKC6342, and DeKalb DKC6544) in 2008, and three replications. Seeds were planted in rows 76 cm apart and 9.1 m long with four rows per plot in a no-till system on a Crider Silt Loam with pH of 6.8 and 1.5% organic matter. The effect of variable within row spacing was evaluated in commercial production fields by randomly selecting five adjacent rows of 5.3 meters in length at each location. Grain yield for each row was then curve fitted both linearly and exponentially.
Minimizing interspecies competition was essential to evaluating the effects of competition within Zea mays L. A burn-down application of 2,4-D and glyphosate was used prior to planting. The most common weeds in the plots were Sorghum halepense L. (johnsongrass), Trifolium repens L. (white clover), and Taraxacum officinale L. (common dandelion) . Glyphosate was reapplied throughout the growing season due to reemergence of S. halepense and Ipomoea hederacea Jacq. (ivyleaf morningglory).
The weight of each ear was recorded and one row from each plot was randomly selected to shell. The moisture content was measured from a subsample twice each row using an electrical conductivity moisture meter. The mean of the two moisture readings was used as the moisture content from the plot. Cob weights from shelled ears were recorded to determine the grain/cob mass ratio. This ratio was used to project the grain weight for the remaining harvested rows.
Duncan’s grain yield model and Russell’s biomass model were curve fitted to the data for areas of 0.00040 hectares at the p < 0.05 significance level or greater in all population density plots. Individual plant grain masses were curve fitted to Duncan’s model with p < 0.05 significance in 3 out of 15 plots. Grain mass was negatively correlated (R < 0) with standard deviation of within row spacing in 14 of 15 plots. A linear fit to this trend was significant in only 2 of 15 plots. The Duncan yield curve and the Russell aboveground biomass model fit all 6 genotype by environment interactions for 2007 and 2008 to the α = 0.05 level of confidence when evaluated over a 5.3 meter length on 76.2 cm wide rows. Individual plants fit linearly at α = 0.05 in 9 out of 15 plots. Individual plants fit the Duncan yield curve at α = 0.05 in 4 out of 15 plots.
Standard deviation of within row spacing fit grain yield loss significantly at &#; = 0.05 in two of 15 plots. The individual plant spacing and local population density collectively fit nine plots significantly at α = 0.05 or better.
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Raaf, Jennifer Lynne. "A Measurement of the Neutrino Neutral Current π0 Cross Section at MiniBooNE." Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1116006438.
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Thesis (Ph. D.)--University of Cincinnati, 2005.Title from electronic thesis title page (viewed Jul. 11, 2006). Includes abstract. Keywords: neutrino; neutral current; cross section; single pion; resonant; coherent; flux-averaged. Includes bibliographical references.
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Cosic, Alija. "Analysis of a novel Transversal Flux Machine with a tubular cross-section for Free Piston Energy Converter application." Doctoral thesis, KTH, Elektriska maskiner och effektelektronik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25834.
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Constantly growing need for oil, all over the world, has caused oil price to rise rapidly during the last decade. High oil prices have made fuel economy as one of the most important factors when consumers are buying their cars today. Realizing this, many car manufacturers have developed or are looking for some alternative solutions in order to decrease fuel consumption. Combining two different technologies in a vehicle, the so called hybrid vehicle, can be seen as the first step toward a better and more sustainable development. There are several different solutions for hybrid vehicles today, among the best known are the Serie Electric Hybrid Vehicle (SEHV), the Parallel Electric Hybrid Vehicle (PEHV) and the Serie-Parallel Hybrid Electric Vehicle (SPEHV). By integrating a combustion engine with a linear electric machine into one unit, a system that is called Free Piston Energy Converter (FPEC) is achieved. The FPEC is suitable for use in a SEHV. Other application areas like stand alone generator are also possible. In this report a novel Transverse Flux Machine (TFM) with a tubular cross section of the translator has been investigated. Application of the machine in a FPEC has put tough requirement on the translator weight, specific power and force density. Different configurations of the winding arrangements as well as the magne tarrangement have been investigated. It has been concluded that the buried magnet design suffers from high leakage flux and is thus not asuitable TFM concept. Instead the surface mounted magnet design has been chosen for further investigation. An analytical model has been developed and a prototype machine has been built based on the analytical results. In order to have a better understanding of the machine characteristic a 3D-FEM analysis has been performed. The results from the analytical model, FEM model and measurements are analyzed and compared. The comparison between the measured and FEM-simulated results shows very good agreement. Furthermore, the results from the analytical model indicates that it can be successfully developed for further analysis and optimization of the design to give a cost-effective solution of the novel generato for mass production.Det ständigt växande behovet av oljan runt om i världen, har fått oljepriset att stiga snabbt under det senaste decenniet. Detta har gjort bränsleekonomin till en av de viktigaste faktorer när konsumenterna väljer sina bilar i dag. Många biltillverkare har därför utvecklat eller söker efter alternativa lösningar till dagens förbränningsmotorer i hopp om att minska bränsleförbrukningen. Ett hybridfordon, ett fordon som är försedd med fler än en energiomvandlare, kan ses som ett första steg mot en bättre och mer hållbar utveckling. Det finns flera olika lösningar för hybridfordon i dag, bland de mest kända är Seriehybrid, Parallellhybrid och Serie-Parallelhybridfordon. Genom att integrera en förbränningsmotor med en linjär elektriskmaskin, erhålls ett system som kallas Frikolvsenergiomvandlare. Dennna typ av energiomvandlare lämpar sig bäst för användning i en seriehybridfordon, men andra användningsområden som fristående generator är också möjliga. I denna avhandling har en ny typ av Transversalflödesmaskin (TFM) med en cirkulärt tvärsnitt undersökts. Tillämpningen av maskinen i en Frikolvsenergiomvandlare har medfört tuffa krav på translatorvikten, specifikeffekten och kraftdensiteten. Olika lindnings- och magnetkonfiguratationer har undersökts. Forskningen har visat att designen med begravdamagneter lider av stort läckflöde och är därför inte lämplig för det nya TFM koncept. Istället har designen med ytmonterade magneter valts för vidare undersökning. En analytisk modell har utvecklats och en prototyp maskin har byggts med utgångspunkt i analysresultaten. För att få en bättre förståelse avmaskinkarakteristiken har en 3D-FEM modell tagits fram och analyserats. Resultaten från den analytiska modellen, FEM modellen och mätningar har analyserats och jämförts. Överensstämmelsen mellan de simulerade och de uppmätta resultaten är mycket bra. Dessutom, resultaten från den analytiska modellen visar på att modellen kan framgångsrikt användas för fortsatt analys och optimering av maskinen för att ge en kostnadseffektivlösning för masstillverkning.
QC 20101102
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Niaghi, Ali Rashid. "Advanced Evapotranspiration Measurement for Crop Water Management in the Red River Valley." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/31644.
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As the main component of terrestrial energy and water balance, evapotranspiration (ET) moves a large amount of water and energy in the form of latent heat flux from bare soil and vegetated surfaces into the atmosphere. Despite the development of many methods and equations through past decades, accurate ET estimation is still a challenging task, especially for the Red River Valley of the North (RRV) that has limited updated information on ET either for landscape or agricultural water management.
The overall objective of first study was to evaluate the ASCE-EWRI reference ET (ETo) method by developing an accurate crop coefficient (Kc) using an eddy covariance (EC) system over an unirrigated turfgrass site. The results showed that with mean ETgrass/ETo ratio as 0.96 for the entire growing seasons of turfgrass, the ASCE-EWRI ETo method is valid for guiding the turfgrass irrigation management in cold climate conditions. In a Controlled drainage with subirrigation (CD+SI) field, an EC system was used to measure and quantify energy flux components along with soil water content (SWC) and water table depth (WTD) measurements during four corn growing. This study showed that the subsurface drainage along with the CD + SI system can be used for optimal water management with an improvement of 26.7% and 6.6% of corn yield during wet and dry year, respectively.
For the final task, ET was measured using EC, Bowen ratio system (BREB), and soil water balance (SWB) method during the corn growing season. The comparison of the EC and the BREB system illustrated the advantages of using the residual method to close the energy balance closure of EC. Among the different time approaches for SWB method, ET by the SWB method using the average soil water contents between 24:00 to 2:00 time period showed non-significant differences (alpha = 0.05) compared to the BREB system during the observation periods.USDA National Institute of Food and Agriculture project
USDA NCR SARE project
ND Soybean Council
ND Water Resources Research Institute
ND Agricultural Experimental Station
USDA Hatch project
NASA ROSES Project
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Artur, Sagradyan. "Method for detection of corrosion-induced loss of cross-section of prestressing steel based on magnetic flux leakage with residual magnetization." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225551.
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Hu, Chih-Chieh. "Mechanistic modeling of evaporating thin liquid film instability on a bwr fuel rod with parallel and cross vapor flow." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28148.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Abdel-Khalik, Said; Committee Member: Ammar, Mostafa H.; Committee Member: Ghiaasiaan, S. Mostafa; Committee Member: Hertel, Nolan E.; Committee Member: Liu, Yingjie.
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El, Rayess Youssef. "Microfiltration tangentielle appliquée à l'oenologie : compréhension et maîtrise des phénomènes de colmatage." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0089/document.
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La clarification des vins par procédés membranaires en particulier la microfiltration tangentielle a toujours été limitée par le colmatage, générant des flux de perméation faibles incompatibles avec la rentabilité économique. La compréhension, la maîtrise, ainsi que l'anticipation des phénomènes de colmatage font l'objet de ce travail. Dans un premier temps, la contribution individuelle puis en mélange des composés du vin (tannins, pectines, mannoprotéines et levures) au colmatage d'une membrane céramique multicanaux a été évaluée. Une approche fondamentale a permis de proposer des mécanismes de colmatage : la présence des pectines induit les flux de perméation les plus faibles en formant un gel à la surface de la membrane tandis que les levures semblent au contraire avoir un effet protecteur dans le cas d'un vin brut. Parce qu'il représente le flux au-delà duquel un colmatage irréversible apparaît à la surface de la membrane, le flux critique pour l'irréversibilité est un paramètre clef pour contrôler le colmatage. Dans le cas de la filtration de vin, aucun flux critique n'a pu être déterminé ce qui a conduit à définir un critère identifiant une zone de travail où le degré de colmatage reste acceptable. La dernière partie de cette thèse est consacrée à l'étude de la filtration dynamique (RVF) pour une éventuelle application dans le secteur vinicole. Cette technique est testée en présence de deux membranes organiques différentes: PES (hydrophile) et PTFE (hydrophobe). Les observations ont permis de mettre en évidence l'efficacité du système contre le colmatage des membranes PES induite par l'action de l'agitateur. Le colmatage des membranes PTFE est énormément affecté par les interactions molécules/membrane rendant la filtration dynamique inefficace pour lutter contre le colmatage de ces membranesWine clarification by membrane processes mainly cross-flow microfiltration has been limited by membrane fouling generating low permeate fluxes with economic efficiency. Understanding, controlling and anticipation of fouling are the main goals of this work. In a first time, the individual contribution of wine compounds (tannins, pectins, mannoproteins and yeasts) to a multichannel ceramic membrane fouling was evaluated. The fouling mechanisms were analyzed using a fundamental approach. The presence of pectins induce the lowest fluxes by a gel-type formation at the membrane surface while yeasts presence tends to reduce fouling in the case of crude wine (case of mixed components). Because it represents the flux beyond which irreversible fouling appears on the membrane surface, the critical flux for irreversibility is a key parameter to control fouling. No critical flux for irreversibility could be measured, hence a criterion that identifies a range of operating conditions where the degree of fouling remains acceptable was proposed. The last part of this work was devoted to the study of dynamic filtration (RVF) for further application in wine sector. This technique was tested with two different membranes: hydrophilic PES and hydrophobic PTFE. Results have allowed to demonstrate the efficiency of the system to reduce fouling in the case of PES membrane. Fouling of PTFE membrane is greatly influenced by molecules / membrane interaction making dynamic filtration ineffective in reducing of membrane fouling
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Mohaghegh, Motlagh Seyed Amir H. "An Investigation into the Impact of Cell Metabolic Activity on Biofilm Formation and Flux Decline during Cross-flow Filtration of Cellulose Acetate Ultrafiltration Membranes." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1310138074.
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DIAS, MAURO da S. "Desenvolvimento e aplicacao de um detector para a medida absoluta da taxa de fluencia de neutrons na regiao de MeV." reponame:Repositório Institucional do IPEN, 1988. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9898.
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Made available in DSpace on 2014-10-09T12:32:36Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:17Z (GMT). No. of bitstreams: 1 03269.pdf: 4525465 bytes, checksum: 8d08a1f89182180eaf465278796a6732 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Murugesan, Viyash. "Optimization of Nanocomposite Membrane for Membrane Distillation." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36534.
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In this study, effects of nanoparticles, including 7 nm TiO2, 200 nm TiO2, and hydrophilic and hydrophobic SiO2 with mean diameter in the range of 15–20 nm and their concentration on the membrane properties and vacuum membrane distillation (VMD) performance were evaluated. The effect of membrane thickness and support materials were also investigated. The membranes were characterised extensively in terms of morphology (SEM), water contact angle, water liquid entrance pressure (LEPw), surface roughness, and pore size. While the best nanocomposite membranes with 200 nm TiO2 Nanoparticles(NPs) were obtained at 2% particle concentration, the optimal particle concentration was 5% when 7 nm TiO2 was integrated. Using nanocomposite membrane containing 2 wt% TiO2 – 200 nm nanoparticles, VMD flux of 2.1 kg/m2h and LEPw of 34 PSI was obtained with 99% salt rejection. Furthermore, it was observed that decreasing the membrane thickness would increase the portion of finger-like layer in membrane and reduce the spongy-like layer when hydrophilic nanoparticles were used. Using continuous flow VMD, a flux of 3.1 kg/m2h was obtained with neat PVDF membranes, which was 600% higher than the flux obtained by the static flow VMD with the same membrane at the same temperature and vacuum pressure. The fluxes of both static and flow-cell VMD increased with temperature. Furthermore, it was evident that the continuous flow VMD at 2 LPM yielded 300% or higher flux than static VMD at any given temperature, indicating strong effects of turbulence provided in the flow-cell VMD.
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Nielsen, Christine. "Constraining the flux and cross section models using carbon and oxygen targets in the off-axis near detector for the 2016 joint oscillation analysis at T2K." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61056.
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The T2K experiment is a long baseline neutrino experiment designed to measure various neutrino oscillation parameters, particularly θ₁₃ and θ₂₃, at world-leading precisions. T2K uses muon neutrino and antineutrino beams produced at the Japan Proton Accelerator Research Complex. The off-axis beam strikes near detectors 280 m from the source (ND280) and the water Cherenkov detector, Super-Kamiokande, 295 km away. The far detector performs the primary oscillation analysis, while ND280 provides cross-section and flux constraints to reduce uncertainties in the oscillation analyses. ND280 consists of several different detectors, with the main target mass being the Fine Grained Detectors, one of which provides an active carbon target and one which provides a combined water-carbon target. This thesis describes the fitting methods used for T2K's oscillation analyses and near detector constraints, with a focus on the near detector fit. The addition of water target data in the near detector fit improves cross-section uncertainties at both near and far detectors. The near detector fit is a maximum likelihood fit to observed neutrino interaction rates in ND280 to constrain the cross-section and flux at the far detector. Event cuts identify and separate charged-current neutrino interactions into topology-based samples, with selection uncertainties and correlations handled through extensive detector systematic studies. The near detector fit to data including a water target shows consistent fitted cross-section and flux with previous ND280 fits, and significantly reduces the uncertainty on the neutrino energy spectrum predictions at the far detector. In addition, nuclear model dependencies in the cross-section model used at T2K were investigated using the near detector fit, and the T2K model was shown to be sufficient in accounting for nuclear effects.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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JOLIMOY, CYRILLE. "Sensibilisation de la recherche des anticorps anti-idiotypes par absorption des anticorps anti-hla de classe i sur plaquettes : mise au point des cross-matches par cytometrie en flux." Dijon, 1994. http://www.theses.fr/1994DIJOM088.
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Rakotovololona, Lucia. "Quantification expérimentale et modélisation de la production, des flux d'eau et d'azote en systèmes de culture biologiques." Thesis, Paris, Institut agronomique, vétérinaire et forestier de France, 2018. http://www.theses.fr/2018IAVF0024.
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Dans le contexte actuel de changements globaux, faire face au défi multiple et interconnecté de la sécurité alimentaire et des impacts environnementaux s’avère fondamental pour la durabilité des systèmes agricoles. La thèse s’attache ainsi à évaluer les performances agronomiques et environnementales des systèmes en AB, en couplant un suivi expérimental réalisé sur un réseau de 35 parcelles agricoles dans la région Hauts-de-France, avec la modélisation du continuum sol-plante-atmosphère afin de mieux comprendre les processus expliquant les dynamiques de l’eau et de l’azote dans ces systèmes, en vue de promouvoir des pratiques de gestion durables.Dans un premier temps, le drainage d’eau et la lixiviation d’azote ont été quantifiés en couplant les données sol-culture-climat et le modèle LIXIM. L’analyse de la lixiviation des parcelles agricoles a permis de déterminer que les facteurs qui expliquent la variabilité. Outre le fort effet sol et l’importance des conditions climatiques sur le drainage, ils sont principalement liés à la combinaison de précédent cultural et de gestion de la couverture du sol en automne. Ces deux derniers jouent en effet sur la quantité d’azote minéral présent avant la période de drainage et expliquent la position du nitrate dans le profil de sol. Nos résultats ont montré le rôle dichotomique des légumineuses dans les systèmes de grandes cultures en AB, et la faible performance des cultures intermédiaires car semées tardivement en automne dans ce contexte.Dans un second temps, le diagnostic des déterminants de l’écart au rendement des cultures ou yield gap a été réalisé via une approche par modélisation déterministe. Le modèle sol-culture STICS a servi à estimer les différents niveaux de rendement potentiel et décomposer le yield gap, en s’appuyant sur le cas du blé tendre et du triticale. Les résultats montrent que le stress en azote permet d’expliquer la majeure partie du yield gap survenant en AB, et dans une moindre mesure les facteurs liés à la pression biotique, pour des systèmes recourant à peu ou pas d’apport azoté exogène.Finalement, le défi de la fourniture en azote dans les systèmes de grandes cultures en AB a été abordé afin de contribuer à une meilleure efficience d’utilisation de l’azote et une amélioration de la productivité des parcelles. Le modèle STICS a permis de simuler l’impact de pratiques de gestion alternatives de l’azote, par expérimentation numérique menée dans le cadre d’une approche participative, mobilisant les agriculteurs, les conseillers techniques et les chercheurs. Les résultats indiquent l’importance de la succession et des pratiques culturales, en particulier la mise en place de cultures intermédiaires et la gestion du retournement des luzernières. L’optimisation des pratiques des agriculteurs restent ainsi possible, en réduisant les émissions potentielles d’azote par lixiviation ou par pertes gazeuses, sans léser la fourniture en N pour les cultures.Dans les contextes pédo-technico-climatiques étudiés, les systèmes de grandes cultures en AB peuvent ainsi combiner performance agronomique et faibles impacts environnementaux, lorsque la gestion de l’azote est bien maîtriséeNowadays, in a context of global changes, addressing the interlinked challenges of food security and environmental impacts is fundamental for the sustainability of agricultural systems. Therefore, the thesis aimed to assess agronomic and environmental performances of organic systems, by coupling the experimental monitoring of a 35 organic fields network in the Northern region of France with modeling the soil-crop continuum, to better understand the underlying processes in water and nitrogen dynamics within those systems, and to promote a more sustainable management.Water drainage and nitrate leaching were assessed by coupling soil, crop and climate data within LIXIM model. Then we analyzed N leaching pattern under diverse organic arable fields to explain its main driving factors. Leaving aside the strong soil type effect and the importance of climatic conditions on drainage, the combination of previous crops and autumn field management appeared to be a key determinant of nitrate leaching in the studied organic systems, as they both drive the amount of soil mineral nitrogen before draining period and explain the position of nitrate in the soil profile. We also showed the dichotomous role of legumes as preceding crop in organic cropping systems and the poor performance of the standard catch crops, sown in late summer in this context.Yield gap of cereals was investigated using a deterministic modeling approach as a diagnosis tool, to contribute in improving the productivity of organic agriculture. The soil-crop model STICS was used to estimate the potential yields of each studied winter wheat and winter triticale crop fields in their given soil and climate conditions. Our results reasserted how nitrogen stress could explain a major part of the yield gap occurring in organic crops and outweigh biotic limiting factors impacts, for cropping systems relying on few or no manures for nitrogen supply.Lastly, we aimed to address the challenge of nitrogen supply in organic arable systems for a better nitrogen use efficiency and improved crop yields. We used the model STICS to simulate the impact of alternative nitrogen management practices by carrying out a numerical experiment in a participatory approach involving farmers, technical advisors and researchers. The findings emphasized the importance of crop succession design and management practices, particularly the implementation of catch crops and the timing of the destruction of perennial legume crops. Optimizing the farmer’s actual practices could then be possible, reducing the potential emissions of nitrogen via leaching or gaseous losses, without decreasing the nitrogen supply for the following crop.Organic arable cropping systems, within the studied soil, technics and climate contexts, can achieve agronomic performances combined with low environmental impacts, with well-managed nitrogen practices
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Rodjom, Abbey M. "Greenhouse Gas Fluxes of Soil in a Miscanthus x giganteus Crop Grown for Cellulosic Bioenergy on Abandoned Agricultural Land." Ohio University Honors Tutorial College / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1524837572902621.
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Wade, James David. "Magnetic Sensor for Nondestructive Evaluation of Deteriorated Prestressing Strand." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271287017.
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Älfvåg, Hector. "Parametric Study of Separation in Outlet Diffuser of Rocket Nozzle Cooling Channel Rig : The Effect of Heat Flux and Angle of Outlet Diffuser for Rectangular-to-Circular Cross Section Transitions." Thesis, KTH, Farkostteknik och Solidmekanik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299946.
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The use of natural gas with high methane content as rocket fuel has gained substantial industrial attention over the past number of years. Several actors including SpaceX and Blue Origin are developing natural gas powered rocket engines. Attention is also shown from GKN Aerospace, a Sweden-based aerospace engine development company, who together with KTH Royal Institute of Technology has initiated the MERiT project. The project is intended to investigate different aspects of methane powered engines. The project is centered around a physical test rig of a rocket nozzle cooling channel along with an ANSYS CFX simulationmodel of the same rig to investigate the operation. The rig is heated from one side to simulate the boundary conditions of a real rocket nozzle. This report is a follow-up to the previous work by Pettersson (2019), which determined rig design points for two channel geometries (channel 3, channel 4) and studied the behaviours and limitations in regards to overheating, cooling and coking. The channels feature outlet diffusers transitioning from rectangular to circular cross sections. The inputs investigated were mass flow, inlet temperature, outlet pressure and heat flux. Following the discovery of flow separation occurring in the rig at certain design points, it was suggested that a parametric study of the outlet diffuser angle could investigate the effect on separation in the outlet diffuser of the rig channel geometry. This is the task at hand in this thesis, and a complementary investigation on the effect heat flux has on separation is also performed for single selected diffuser angles. To achieve this, the full rig model geometry is first reduced to its core components to reduce simulation run time, and the parametric diffuser is implemented for both channel geometries. The mesh and the model definition is then adjusted to accommodate the changes made, by for example replacing the full rig heater block with a constant heat flux boundary condition. After this, a total of 40 test cases of different diffuser angle and heat flux combinations are used to establish trends in the behaviour of the separation. The results show that separation occurs more easily for the channel 3 configuration, which sees separation occur for lower diffuser angles and heat flux settings. The separation grows diminishinly as the heat flux and diffuser angle is increased. The separation onset location is found to consistently be in the corners of the outlet diffuser, after which it expands and rotates into the symmetry plane further downstream. The channel 4 solution convergence is found to be increasingly poor for higher diffuser angles, which suggests the solutions may be transient in nature. The Reynolds and Mach number is found to be correlated to the heat flux applied but no conclusion can be made about their link to separation for the cases studied.Användningen av naturgas med hög metanhalt som raketbränsle har fått stor industriell uppmärksamhet under de senaste åren. Flera aktörer inklusive SpaceX och Blue Origin utvecklar naturgasdrivna raketmotorer. Intresset visas även från GKN Aerospace, ett Sverige-baserat företag som bland annat utvecklar raketmotorer, som tillsammans med KTH Royal Institute of Technology har påbörjat ett projekt kallat MERiT. Projektet är avsett att undersöka olika aspekter av metandrivna raketmotorer. Projektet kretsar kring en fysisk testrigg modellerad efter ett raketmunstyckes kylkanal och en simuleringstvilling i ANSYS CFX av samma rigg för att undersöka funktionaliteten av metan i den här kontexten. Riggen värms upp från ena sidan för att simulera randvillkoren hos ett riktigt raketmunstycke i drift. Denna rapport är en uppföljning till ett tidigare arbete av Pettersson (2019), som bestämde testriggens giltiga designpunkter för två kanalgeometrier (kanal 3, kanal 4) och studerade beteenden och begränsningarna när det gäller överhettning, kylning och koksning. Inputs som undersöktes var massflöde, inlopsstemperatur, utloppstryck och värmeväxling. Kanalerna har en diffusor vid utloppet som övergår från ett cirkulärt till rektangulärt tvärsnitt. Efter att flödessepareration upptäcktes i riggen vid vissa designpunkter föreslogs det att en parametrisk studie av diffusorvinkeln kunde undersöka hur separationen beror på diffusorvinkeln i utloppets diffuser. Detta är uppgiften här och en kompletterande undersökning av värmeväxlingens effekt på flödesseparation utförs också för enstaka valda diffusorvinklar. För att genomföra detta reducerades först testriggen till dess fundamentala delar för att minska simuleringarnas beräkningstid, efter vilket den parametriska diffusorn var implementerad för båda kanalgeometrier. Meshningen uppdaterades för att ta hänsyn till förändringarna i geometrin, och ändringar gjordes även i modeldefinitionen för att återställa korrekt funktion. Dessa ändringar inkluderar att ersätta värmeblocket från den fullständiga riggen med ett randvillkor med konstant värmeväxling. Därefter testades total 40 olika fall av diffusorvinkel och värmeväxling med syftet att fastslå trender i beteendet hos flödesseparationen med avseende på värmeväxling och diffusorvinkel. Resultaten visar att separation inträffar först för kanal 3, som påträffar flödesseparation för både lägre diffusorvinklar och värden av värmeväxling. Mängden separation växer avtagande när diffusorvinkeln och värmeväxlingen ökas. För de studerade fallen börjar alltid separationen i hörnet på utloppets diffusor, för att sedan expandera nedströms och rotera in i symmetriplanet. Lösningskonvergensen för kanal 4 visar sig vara sämre och sämre för ökande diffusorvinklar, vilket möjligen tyder på att de sanna lösningarna är transienta. Reynoldstalet och machtalet visar på korrelation till värmeväxlingens värde, men ingen slutsats kan dras om hur separationen påverkas av dessa tal för de studerade fallen.
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Guinet, Maé. "Quantification des flux d’azote induits par les cultures de légumineuses et étude de leurs déterminants : comparaison de 10 espèces de légumineuses à graines." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK011/document.
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Dans le contexte de la transition agroécologique en faveur de systèmes de culture plus économes en intrants azotés, la réintroduction des légumineuses a un rôle majeur à jouer pour atteindre la durabilité de ces systèmes. Peu de références sont actuellement disponibles sur les intérêts agronomiques et écologiques des différentes espèces, notamment à l’échelle de la rotation. Dans ce cadre, notre objectif principal consiste à mieux quantifier les flux d’azote impliqués au cours et après culture de légumineuses, et ce pour une gamme élargie d’espèces. Notre travail expérimental porte donc sur la caractérisation des flux d’azote induits dans le sol et dans les cultures de légumineuses aux caractéristiques morphologiques contrastées en parallèle de la mesure des déterminants de ces flux. Les objectifs spécifiques consistent à : i) quantifier la fixation symbiotique en fonction du niveau du stock d’azote minéral du sol, la minéralisation de l’azote des résidus de légumineuses après enfouissement et les pertes d’azote en dehors du système sol-plante (lixiviation, émission de protoxyde d’azote), ii) identifier les « traits de plantes » explicatifs des fonctions liées à ces flux d’azote. Pour atteindre ces objectifs, les différents flux d’azote ont été quantifiés au cours d’une expérimentation au champ avec implantation d’une culture de légumineuses en première année suivie par une culture de blé en année 2 qui a été menée en 2014-2015 et reconduite sur la campagne 2016-2017. En parallèle, les traits des plantes, notamment racinaires, ont été caractérisés plus finement au cours d’expérimentations conduites en conditions contrôléesIn the context of agroecological transition, the reintroduction of legume crops should play a key role in cropping system sustainability by allowing a reduction of nitrogen (N) inputs. But few references are available concerning the agronomical and ecological services provided by a wide range of legume crops, particularly within crops succession scale. Thus, the main objective of our study is to quantify the N fluxes during and after the legume crops taking into account 10 legume crops (peas, lupin, faba bean, soybean...). Our experiment consists in i) quantifying symbiotic N fixation depending on the amount of soil inorganic N, the mineralisation of N present in legume crop residues after soil incorporation and N losses outside of the soil-plant system (leaching, emission of nitrous oxide), ii) identifying plant biological traits associated to N fluxes. Thus, different N fluxes were quantified during a two-year field experiment, i.e. the first year (2014) legume crops were implanted and followed by wheat the second year (14-15) after incorportation of legume residues. This experiment was repeated in 2016-2017.In parallel, plant root traits were characterised during greenhouse hydroponic experiments
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Hassini, Sanaa. "Développement des plate-formes logistiques au Maroc : enjeux et perspectives." Thesis, Paris 1, 2015. http://www.theses.fr/2015PA010061.
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Depuis les années 70, la production et la commercialisation des biens et services, la circulation des capitaux et des systèmes se sont fortement internationalisées. Ce phénomène a poussé les entreprises à optimiser leurs chaînes logistiques pour rester compétitives. Le Maroc s'inscrit dans la même tendance, vue sa position géographique joue un rôle de carrefour et de hub des échanges commerciaux. Le développement d'une réelle compétitivité logistique constitue un pilier du programme gouvernemental 2010-2020, d'où le lancement de la stratégie nationale pour le développement de la compétitivité logistique, dont principalement le contrat programme régissant le développement des plateformes logistiques, dites zones logistiques multi flux. La stratégie vise la réduction du poids du coût logistique de 5 points pour 2015, la création de 70 zones logistiques dans 17 villes sur environ 3 300 hectares. La mise en œuvre de ce programme logistique nécessite un effort cohérent, s'inscrivant dans le temps et des arbitrages complexes à opérer sur des domaines ne relevant pas des prérogatives d'un seul intervenant de la chaîne logistique. À la lumière de ces propos, nous avons vu en cette problématique un enjeu majeur nécessitant des actions managériales, une réflexion académique aussi par un focus sur le principe de la Supply Chain et plus précisément la logistique des plateformes. L'agencement et la connectivité des plateformes logistiques s'avère décisionnelle pour la réussite d'une politique commerciale compétitive d'une entreprise : nous ne pouvons pas concevoir des flux juste en mouvement, in fine, ils commencent d'un point de création de valeur vers un point de consommation et que ce sont ces nœuds (plateformes) qui œuvrent pour l'optimisation de l'organisation de toute la chaîne. Un retour vers l'histoire de la logistique, ses définitions et son évolution managériale dans le temps s'avérait nécessaire pour expliciter l'approche transversale et intégrée de la chaîne logistique ; et s'attarder par la suite sur les composantes, intégration des flux physiques et d'information, sur le poids de la stratégie logistique comme arme de différenciation vis-à-vis de la concurrence et sur les leviers d'optimisation des plateformes logistiques dans ces modèles. Le dernier chapitre traitera de la compétitivité logistique au Maroc, au regard des standards précités et les axes de développement du réseau des zones logistiques comme première orientation du contrat programme logistique nationalSince earlier years, production and sales of goods and services. capital flows and systems are highly internationalized. This has led companies to optimize their supply chain to remain competitive. Morocco is part of the same trend, for its geographical position acts as a hub and crossroads of trade. The development of logistics real competitiveness is a pillar of the government program 2010-2020. Hence the launch of the national strategy for the development of logistics competitiveness, mainly the program contract governing the development of logistics platforms. The strategy aims to reduce the weight of the logistics cost of 5 points for 2015, creating 70 logistics warehouses in 17 cities on 3 300 hectares. The implementation of the logistics program requires a coherent effort, registering in time and complex trade-offs in different areas in the supply chain. In the light of these remarks, we have seen this problem a major issues requiring managerial actions, academic reflection as a focus on the basics of suppl y chain and specifically logistics platforms. The layout and connectivity of logistics platforms proves the success of a competitive sales policy of a company : we cannot just design flow, ultimately, they start a creative point value to a consumption point and that it is these nodes (platforms) working to optimize the organization of the whole chain. A return to the story of logistics was important to present it, its definitions and managerial changes over time was needed to explain the cross and integrated approach to the supply chain; and linger afterwards on the components. integration of physical and information flows. the weight of the logistics strategy as a weapon of differentiation regarding the competition and logistics platforms optimization levers in these models. The final part will present logistics competitiveness in Morocco, in view of the above standards and network development axes logistics areas as a first orientation of the national logistics program
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Carvalho, João Luís Nunes. "Dinâmica do carbono e fluxo de gases do efeito estufa em sistemas de integração lavoura-pecuária na Amazônia e no Cerrado." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-19042010-164213/.
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Mudanças de uso e manejo influenciam o acúmulo de carbono (C) no solo e o fluxo de gases do efeito estufa (GEE). No Brasil, sobretudo nos biomas Amazônia e Cerrado, historicamente vegetações nativas são convertidas em pastagens e agricultura emitindo consideráveis quantidades de GEE para a atmosfera. Áreas sob pastagens e agricultura vêm sendo convertidas em sistemas mais intensificados e tecnicamente mais avançados, tais como os sistemas de integração lavoura-pecuária (ILP), os quais têm a capacidade de acumular C no solo e mitigar as emissões de GEE para atmosfera. O objetivo deste estudo foi avaliar as modificações nos estoques de C do solo e nos fluxos de GEE em áreas sob mudança de uso da terra nos biomas Amazônia e Cerrado. Foram avaliadas áreas sob vegetação nativa, pastagens, sucessão de cultivos e ILP em diferentes condições edafoclimáticas. O manejo da fertilidade do solo sob pastagem afeta produção de biomassa, que por sua vez influencia o acúmulo ou perda de C. Pastagem cultivada em solo fértil acumulou 0,46 Mg de C ha-1 ano-1. Sob baixa fertilidade natural, obsrvou-se perdas de 0,15 e 1,53 Mg de C ha-1 ano-1, respectivamente para pastagem não degradada e degradada. A conversão de vegetação nativa e pastagem para agricultura, mesmo cultivada sob SPD, reduziu o estoque de C, exibindo perdas de 0,69 a 1,44 Mg ha-1 ano-1. A implantação de sistemas de ILP em áreas sob sucessão de cultivos aumentou os estoques de C no solo, com taxas varaindo de 0,82 a 2,58 Mg ha-1 ano-1. Aplicando a modelagem matemática, com o modelo Century, verificou-se as mesmas tendências de acúmulo ou perdas de C no solo. Entretanto, o modelo subestimou os estoques de C em todas as áreas avaliadas. Em Montividiu, a avalaição do fluxo de GEE em diferentes usos e manejos da terra, evidenciou maior emissão CCO2 na pastagem (10820 kg ha-1) e esta foi significativamente maior em relação à sucessão de cultivos (4987 kg ha-1) e ILP (6565 kg ha-1). Emissão de N-N2O foi maior em ILP (2,00 kg ha-1 ano-1) e menor na vegetação nativa (0,35 kg ha-1 ano-1). Os fluxos de C-CH4 resultaram em emissão de 1,67 kg ha-1 ano-1 na pastagem e em absorção nas demais áreas. Em ILP, os manejos aplicados à soqueira do algodoeiro, resultaram em diferenças nos fluxos de GEE. O manejo químico, sem perturbação do solo, reduziu a emissão de CO2, aumentou a emissão de N2O e não influenciou os fluxos de CH4. Utilizando as taxas de acúmulos de C e os fluxos de GEE obteve-se o seqüestro de C no solo. As taxas de seqüestro, expressas em C equivalente, evidenciaram perdas da ordem de 0,43 e 0,77 Mg ha-1 ano-1, respectivamente para a conversão de Cerrado para pastagem e sucessão de cultivos. Implantação de ILP em áreas sob sucessão de cultivos resultou em seqüestro de C pelo solo, independente do manejo aplicado. Manejo químico seqüestrou 1,05 Mg de C ha-1 ano-1. Manejo mecânico com o equipamento Cotton 1000 e grade aradora seqüestraram 0,58 e 0,71 Mg de C ha-1 ano-1, respectivamente. A implantação de sistemas ILP se mostrou uma excelente alternativa para acumular C no solo e mitigar as emissões de GEE para atmosfera.Changes on land use and management influence the accumulation of carbon (C) in soil and the greenhouse gas (GHG) fluxes. In Brazil, especially in Amazonia and Cerrados biomes, the native vegetation has been historically converted in pastures and agriculture causing considerable amount of GHG emissions to the atmosphere. Recently, pastures and agricultural activities have been adopting more intensified and technically advanced land management systems, such as the integrated crop-livestock (ICL) system, which has the capacity to increase soil C accumulation and promote GHG mitigation. The objective of this study was to evaluate the alterations in soil C stock and GHG fluxes in areas under land use changes in the Amazonia and Cerrados biomes. The study focused on areas under native vegetation, pasture, crop succession and ICL under different edaphoclimatic conditions. The fertility management of soil under pasture affects the biomass production which, in turn, influences not only the soil C accumulation but also the C loss. This study showed that pasture cultivated in fertile soil presented an accumulation of 0.46 Mg of C ha-1 year-1. Under naturally low soil fertility, losses of 0.15 and 1.53 Mg of C ha-1 year -1 were observed in non-degraded and degraded pastures, respectively. Conversion of native vegetation and pasture to agriculture, even when cultivated under no-tillage, caused the reduction of C stock and showed losses from 0.69 to 1.44 Mg ha-1 year -1. The implementation of ICL systems in crop succession areas caused the increase of soil C stock with rates ranging from 0.82 to 2.58 Mg ha-1 year -1. By applying the Century model, the same tendencies in soil C accumulation and C loss were observed. However, the model underestimated the C stock in all areas under evaluation. In Montividiu, Goiás State, the evaluation of GHG fluxes from different land uses and management showed that pasture produced higher C-CO2 emissions (10829 kg ha-1 year -1) than crop succession (4987 kg ha-1 year -1) and ICL (6565 kg ha- 1 year -1). The N-N2O emission was higher from ICL (2.00 kg ha-1 year-1) and lower from native vegetation (0.35 kg ha-1 year-1). Regarding the C-CH4 emissions from pastures, the fluxes were in the order of 1.67 kg ha-1year-1 while the other areas showed sink. In ICL, the soil management applied to the cotton stalk resulted in GHG flux differences. Chemical management with no soil disturbance reduced the CO2 emissions, increased N2O emissions and showed no influence on CH4 fluxes. Carbon sequestration rates, expressed in C equivalent, showed losses in the order of 0.43 and 0.77 Mg ha-1 year-1, respectively, from the conversion of Cerrado to pasture and crop succession. The implementation of ICL in areas under crop succession resulted in C sequestration in soil, regardless the type of management applied. Chemical management produced C sequestration of 1.05 Mg ha-1 year -1. Mechanical management with Cotton 1000 equipment and full tillage produced the sequestration of 0.58 and 0.71 Mg of C ha-1 year-1, respectively. The implementation of ICL systems showed to be an excellent alternative for soil C accumulation and mitigation of GHG emission.
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Jardou, Ali. "Compétence de communication interculturelle et mobilité étudiante : le cas des apprenants primoarrivants en France et des classes plurilingues et multiculturelles de FLE." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAL010/document.
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Dans le contexte actuel de mondialisation de l’enseignement supérieur, cette recherche propose de réfléchir sur la compétence de communication interculturelle (CCI) des étudiants étrangers en mobilité entrante vers la France ainsi que sur la manière dont l’enseignement/apprentissage de la CCI est abordé en classe de FLE.En partant des compétences et des savoirs nécessaires à la communication en langue étrangère et de l’apport théorique de la perspective interculturelle qui s’est développée en didactique des langues à partir des années 80, nous analysons un corpus de 26 entretiens d’apprenants primoarrivants de 12 nationalités différentes afin d’interroger leur expérience aussi bien en salle de classe qu’en dehors de celle-ci.Le choix de la classe de langue comme lieu de rencontre interculturelle se justifie parce que ces classes plurilingues et multiculturelles en milieu homoglotte constituent, pour ces publics, un espace privilégié d’apprentissage de la différence tout en permettant une médiation culturelle avec la réalité sociale dans laquelle l’apprenant cherche une modalité d’insertion en tant qu’acteur social.Le retour sur expérience de nos interviewés —avec l’analyse de leurs perceptions, représentations préalables et difficultés d’ordre linguistique et/ou socioculturel identifiées dans leur discours— permet de mieux comprendre les effets pragmatiques de cette compétence dans la communication et la place qui doit lui être accordée en cours de langue.À cheval entre la sociolinguistique et la didactique du FLE, ce travail de doctorat vise à mieux connaître les facteurs qui influencent la construction de la CCI et les différentes dynamiques qui l’impactent, afin de mieux pouvoir œuvrer pour son développementIn the current context of the globalization of higher education, this research suggests a reflection on the cross-cultural communication skills (known as CCI in French) of exchange students coming to France. This study also looks at the way in which CCI is taught and learned in the ‘French as a foreign language’ (FLE) class.Based on the skills and knowledge needed to communicate in a foreign language and the theoretical contribution of the intercultural perspective, which has been developed into language didactics since the 80s, we analyze a corpus of 26 interviews with newly arrived learners from 12 different nationalities in order to consider their experience both inside and outside the classroom.The choice of the FLE class in a French-speaking country as a cross-cultural meeting place is justified because it constitutes, for these students from all different backgrounds, a privileged place for learning about difference while allowing a cultural mediation with the social reality in which they seek a means of insertion as social actors.The analysis of our interviewees’ feedback –through a detailed assessment of their perceptions, prior representations and the language-related difficulties and/or socio-cultural issues we were able to identify in their speech- allows a better understanding of the pragmatic effects of this skill-set while communicating and the place it deserves in a language course.Somewhere in between sociolinguistics and the didactics of French as a foreign language, this PhD seeks to improve our understanding of the key factors in the build-up of cross-cultural communication skills as well as the various dynamics that have an impact on this skill-set in order to enhance them
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Falahati, Hamid. "The Characterization of Bimodal Droplet Size Distributions in the Ultrafiltration of Highly Concentrated Emulsions Applied to the Production of Biodiesel." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/19585.
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A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor.Natural Sciences and Engineering Research Council of Canada (NSERC)
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Júnior, Felisberto Alves Ferreira. "Medida da secção de choque térmica e da integral de ressonância da reação 41K(n,)42K." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-03112008-104617/.
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Pastilhas de nitrato de potássio foram irradiadas no núcleo do reator de pesquisas IEA-R1m do Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, operando a 2 MW de potência, para determinar a secção de choque térmica e integral de ressonância da reação 41K(n,g)42K. O fluxo de nêutrons foi monitorado com folhas de liga ouro-alumínio. As atividades induzidas nos alvos foram determinadas por espectroscopia gama com detectores de germânio hiper puro. Os cálculos realizados se basearam no formalismo de Westcott. Foram realizadas simulações com o código MCNP (Monte Carlo N-Particle) para determinar a auto-blindagem e a depressão do fluxo de nêutrons nas pastilhas durante as irradiações e os fatores de correção da eficiência de detecção para fontes volumétricas, que leva em conta a absorção de raios gama nas mesmas. Foi efetuado um tratamento estatístico das incertezas envolvidas e determinadas as covariâncias entre os resultados, incluindo aquelas decorrentes das incertezas do padrão de referência (ouro). Os resultados obtidos foram comparados com os de outros autores. Foi testada a possibilidade de se observar o produto da reação 41K(n,g)42K(n,g)43K.Pellets of potassium nitrate were irradiated in the IPEN/CNEN-SP (Instituto de Pesquisas Energeticas e Nucleares, Comissao de Energia Nuclear, Sao Paulo, SP) IEAR1m reactor core operating at 2 MW power in order to determine the 41K(n,g)42K reaction thermal cross-section and resonance integral. The neutron flux was monitored by Au-Al alloy foils, and the Westcott formalism was applied. Neutron self-shielding, flux depression and gamma-ray self-absorption in the relatively large samples, as well as the gamma-ray detection efficiency correction factor, were determined by simulation with MCNP code. The data reduction statistical methods included the determination of the covariances between the obtained results and the standard cross-sections used (Au). The results were compared to those already published. The observation of the consecutive neutron capture reaction leading to 43K was tried.
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Dashdorj, D. "Spin distribution in preequilibrium reactions for 48Ti + n." Washington, D.C : Oak Ridge, Tenn. : United States. Dept. of Energy ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2005.
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Thesis (Ph.D.); Submitted to North Carolina State Univ., Raleigh, NC (US); 6 Apr 2005.Published through the Information Bridge: DOE Scientific and Technical Information. "UCRL-TH-211400" Dashdorj, D. 04/06/2005. Report is also available in paper and microfiche from NTIS.
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Rezgui, Cyrine. "Etude du potentiel d'introduction de la culture du pois d'hiver dans les successions culturales en Normandie : conséquences sur les communautés microbiennes du sol et les flux d'azote Impacts of the winter pea crop (instead of rapeseed) on soil microbial communities, nitrogen balance and wheat yield Quantification et analyse des exsudats racinaires de pois, de blé et de colza : mise au point d’une méthodologie de collecte des exsudats racinaires N rhizodeposition quantification and root exudates characterization of pea (Pisum Sativum L.), rapeseed (Brassica napus L.) and wheat (Triticum aestivum L.) under controlled conditions Linking soil microbial community to C and N dynamics during crop residues decomposition." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR047.
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La transition agroécologique vise la triple performance agronomique, écologique et sociétale des exploitations agricoles. Un certain nombre de pratiques agricoles permet d’envisager la construction et le développement de systèmes de culture répondant à ces contraintes. Les légumineuses, par leur capacité à fixer l’azote atmosphérique, sont une alternative intéressante aux intrants azotés. Outre l’absence de fertilisation lors de leur culture, elles fournissent de l’azote à la culture suivante. Il existe cependant un manque de références sur certaines légumineuses à graines et notamment la culture du pois d’hiver. En effet, si des données acquises dans différentes régions françaises sont disponibles, aucune référence n’a été publiée pour la Normandie où la culture du pois d’hiver connaît un récent regain d’intérêt. Cette thèse propose d’évaluer, sur une période de deux ans, l’effet du remplacement du colza par le pois d’hiver en tête de rotation en réalisant une analyse comparative de ces deux successions (pois d’hiver-blé et colza-blé). L’objectif était d’évaluer l’effet de ce changement de tête de rotation (pois d’hiver vs colza) sur l’état biologique du sol et les flux d’azote à différentes échelles spatiotemporelles. Les résultats ont révélé une forte variabilité spatio-temporelle dans la réponse des communautés microbiennes du sol, et mis en évidence l’importance du contexte pédoclimatique dans le déterminisme de l’abondance et de l’activité des communautés microbiennes du sol. Ils ont montré par ailleurs, l’effet positif du pois d’hiver sur la disponibilité de l’azote minéral au cours du cycle cultural et pour les cultures suivantes, ici le blé puis l’orge. Les apports d’azote minéral dans le sol lié à la contribution des parties racinaires via la rhizodéposition et à la dégradation des résidus de culture après récolte ont été évalués au cours de ce travail de thèse. En effet, si la rhizodéposition s’est révélée plus importante sous pois d’hiver, elle n’a pas eu d’impact significatif sur les communautés microbiennes rhizosphériques. Contrairement à ces observations, la dégradation des résidus de culture a significativement modifié la composition des communautés bactériennes en lien avec leur composition biochimique initiale. La succession culturale incluant le pois a enrichi le sol en azote minéral mais des risques de perte d’azote par lixiviation de l’ordre de 23 kg N. ha-1 ont été estimés. Ces constats soulignent l’importance d’adapter la conduite des systèmes de culture incluant le pois d’hiver, en limitant les pertes d’azote par lixiviation et en maximisant son utilisation par les cultures suivantes. Les résultats de ces travaux ont confirmé la diminution des quantités d’engrais azoté utilisées dans la succession contenant le pois, sans préjudice de productivité, ni pour le pois, ni pour la culture suivante, ici, le blé. Finalement, introduire le pois d’hiver dans la rotation de culture en région Normandie, semble permettre de répondre à la problématique d’augmentation du coût des intrants, et aux enjeux de transition agroécologique et d’autonomie protéique régionaleThe agroecological transition targets triple agronomic, ecological, and societal performance of farms. Some new agricultural practices had emerged to develop a new cropping system to respond to these constraints. Legumes constitute an interesting alternative. Indeed, legumes are advantageous for soils due to their symbiotic relationship with nitrogen-fixing bacteria. The presence of compatible rhizobia combined to nitrogen-limited conditions promotes symbiosis which is the most efficient way for legumes to acquire more nitrogen. Compared with non-nodulated plants, symbiosis provides a competitive advantage by increasing soil nitrogen pool. However, some grain legumes, notably winter pea, are rarely studied, especially in the Normandy region where no reference has been published for this crop. The objective of this study is to compare two crop successions for a period of two years (winter pea-wheat and rapeseed-wheat), in order to assess the effect of replacing rapeseed by winter pea at the head of the rotation .We evaluated the effect of these two crops (winter pea vs rapeseed) on the biological state of the soil and nitrogen fluxes at different spatio-temporal scales. The results showed a significant spatio-temporal effect on the response of soil microbial communities and highlighted the importance of the pedoclimatic context in determining the abundance and activity of soil microbial communities. A positive effect of winter pea has been demonstrated on the availability of mineral nitrogen during the crop cycle and for following crops (wheat and barley). The supply of nitrogen to the soil is linked to the rhizodeposition of nitrogen via plants roots and the degradation of crop residues after harvest. Our results showed that winter pea exhibited the greatest amount of nitrogen rhizodeposition. However, rhizodeposition did not have a significant impact on rhizospheric microbial communities. Contrary to these observations, the degradation of crop residues significantly modified the composition of bacterial communities linked to their initial biochemical composition. Crop succession including winter pea enriched the soil with mineral nitrogen but simulation with STICS software revealed a nitrogen leaching around of 23 kg N. ha-1 during the cropping cycle. These findings underline the importance of adapting an adequate crop management system, including winter pea, to limit nitrogen losses. The results showed also that wheat yields after winter pea without the use of nitrogen fertilizers were equivalent to those obtained after rapeseed. However, rapeseed required significant nitrogen fertilization. Including winter pea in crop rotation in Normandy region may be a key to enhance productivity, to respond to the challenges of agroecological transition, regional protein autonomy, and to reduce environmental and economic costs, by reducing notably, the costs of fertilizers production and uses
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Dominguez, Bermudez Favio Enrique. "Simulation numérique de parcs d'hydroliennes à axe vertical carénées par une approche de type cylindre actif." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI020.
Full textAbstract:
La récupération, grâce aux hydroliennes, de l’énergie cinétique de courants marins et fluviaux constitue une source d’énergie renouvelable considérable et prédictible. La simulation fine, par une description statistique instationnaire de type URANS, de l’écoulement autour d’une hydrolienne isolée à axe vertical, bi-rotor et munie d’un carénage (hydrolienne de type HARVEST) donne accès à une estimation précise de la puissance produite. Cependant, le coût élevé de cette approche URANS la rend inadaptée à la simulation d’un parc de machines. Une analyse de la littérature conduit à retenir un modèle basse-fidélité de type Blade Element Momentum (BEM) pour décrire à moindre coût l’effet du rotor de la turbine sur l’écoulement, dans le contexte d’une description 2D (coupe horizontale). La performance de l’hydrolienne est alors prédite par un calcul RANS incluant des termes sources distribués dans un anneau rotor virtuel et conservant le maillage des parties fixes (carénage). Ces termes sources sont construits grâce à une procédure originale exploitant les conditions locales de l’écoulement en amont des cellules du rotor virtuel et le débit de l’écoulement traversant l’hydrolienne. Les coefficients hydrodynamiques utilisés pour le calcul des termes sources BEM-RANS sont construits une fois pour toutes en exploitant une série de simulations URANS préliminaires ; ils intègrent les effets du carénage et le fonctionnement de chaque rotor à une vitesse de rotation optimale (maximisant la puissance produite) grâce au système de régulation de l’hydrolienne. Le modèle BEM-RANS développé est validé par comparaison avec des simulations URANS de référence : il fournit une estimation fiable de la puissance produite (erreur de quelques % par rapport à l’approche URANS) pour un coût réduit de plusieurs ordres de grandeur. Ce modèle est appliqué à l'analyse de la puissance produite par une rangée d’hydroliennes HARVEST dans un canal pour différents facteurs de blocage et d’espacement latéral ainsi qu’à une ferme marine composée de trois hydroliennesThe capture, thanks to hydrokinetic turbines, of the kinetic energy generated by sea and river currents provides a significant and predictable source of renewable energy. The detailed simulation, using an unsteady statistical description of URANS type, of the flow around an isolated water turbine of HARVEST type (cross flow vertical axis ducted water turbine) provides an accurate estimate of the power output. However, the cost of the URANS approach is much too expensive to be applied to a farm of several turbines. A review of the literature leads to select a low-fidelity model of Blade Element Momentum (BEM) type to describe at a reduced cost the rotor effect on the flow, in a 2D context (horizontal cross-section). The turbine performance is then predicted using a steady RANS simulation including source terms distributed within a virtual rotor ring and preserving the mesh of the turbine fixed parts (duct). These source terms are derived using an original procedure which exploits both the local flow conditions upstream of the virtual rotor cells and the flow rate through the turbine. The hydrodynamic coefficients used to compute the BEM-RANS source terms are built once for all from a series of preliminary URANS simulations; they include the effects of the duct on the flow and the rotor operating at optimal rotational speed (maximizing the power output) thanks to the turbine regulation system. The BEM-RANS model is validated against reference URANS simulations: it provides a reliable prediction for the power output (within a few % of the URANS results) at a computational cost which is lowered by several orders of magnitude. This model is applied to the analysis of the power produced by a row of Vertical Axis Water Turbines in a channel for various values of the blockage ratio and lateral spacing as well as to a 3-machine sea farm
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Marelli, Luana Maria. "Desenvolvimento e estudo de um reator UASB com unidade de filtração, utilizado para o tratamento de esgoto sanitário." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-01032007-140140/.
Full textAbstract:
Para o tratamento de esgoto sanitário foi desenvolvido e estudado um reator UASB (Upflow Anaerobic Sludge Blanket), associado com unidade de filtração. O estudo se iniciou pela operação do reator UASB durante 642 dias, onde a fase líquida afluente e efluente foi monitorada. Em seguida uma unidade de filtração foi acoplada ao reator UASB e foram avaliados as características de filtração, o desempenho do tratamento e a eficiência do processo de limpeza química de três filtros. Os materiais poliméricos utilizados como filtros foram o polipropileno, o poliéster e o geossintético de poliéster, com diâmetro médio de poros de um mícron (1μm). As características de filtração avaliadas foram o fluxo do permeado e os mecanismos de obstrução de cada material polimérico (resistência à filtração: total, do material, da camada de biossólidos e de entupimento). O desempenho global do sistema de tratamento foi avaliado em termos de remoção de demanda química de oxigênio (DQO) e de sólidos suspensos totais (SST). Para recuperação dos filtros foi utilizada primeiramente a limpeza química com solução ácida (ácido clorídrico-HCl) e em série a limpeza com solução alcalina (hipoclorito de sódio e hidróxido de sódio- NaOCl e NaOH). Dentre os três materiais poliméricos utilizados verificou-se que, o geossintético (poliéster) foi o filtro que apresentou melhores características de filtração e desempenho global, ou seja, com este material a resistência da camada foi predominante (obstrução é reversível), a concentração de sólidos suspensos totais do permeado estabilizou em 25 mg/L e a eficiência média global de remoção da demanda química de oxigênio (DQO) foi de 78%. Dentre os procedimentos de limpeza química utilizada nos três filtros, verificou-se que a solução ácida (HCl) aplicada em série com a solução alcalina (NaOCl e NaOH) apresentou maior eficiência que a limpeza somente com a solução ácida (recuperação do fluxo inicial do permeado acima de 90%).An anaerobic reactor (UASB Upflow Anaerobic Sludge Blanket) coupled to a filtration unit for the treatment of domestic sewage was developed and studied. The study began by operating the UASB reactor for 642 days, during which time the influent and effluent liquid phase were monitored. The filtration unit was then coupled to the UASB reactor and the filtration characteristics, the performance of the treatment, and the efficiency of the cleaning process of three polymeric filters were evaluated. The polymeric materials used for the filters were polypropylene, polyester and geosynthetic polyester, all with an average pore size of one micron (1μm). The filtration characteristics evaluated were the permeate flux and the fouling mechanisms (total filtration resistance of the material and the cake, and clogging) during filtration. The systems overall performance was evaluated in terms of chemical oxygen demand (COD) and removal of total suspended solids (TSS). The filters were cleaned chemically, first with an acid solution (HCl), followed by alkaline solutions (NaOH and NaOCl) applied in series. A comparison of the three filtering materials indicated that the geosynthetic material (polyester) possessed the best overall characteristics of filtration and performance. In other words, i.e., cake resistance (reversible fouling) predominated with this material, the concentration of total suspended solids (TSS) in the permeate stabilized at 25 mg/L, and the overall removal efficiency of chemical oxygen demand (COD) was 78%. Of the various chemical cleaning procedures tested on the three polymeric filters, the acid (HCl) and alkaline solutions (NaOH and NaOCl) applied in series provided more efficient flux recovery (over 90% of the initial permeate) than chemical cleaning only with acid (HCl).
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Sivaraman, Gokul. "Development of PMSM and drivetrain models in MATLAB/Simulink for Model Based Design." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-301027.
Full textAbstract:
When developing three-phase drives for Electric Vehicles (EVs), it is essential to verify the controller design. This will help in understanding how fast and accurately the torque of the motor can be controlled. In order to do this, it is always better to test the controller using the software version of the motor or vehicle drivetrain than using actual hardware as it could lead to component damage when replicating extreme physical behavior. In this thesis, plant modelling of Permanent Magnet Synchronous Machine (PMSM) and vehicle drivetrain in MATLAB/Simulink for Model Based Design (MBD) is presented. MBD is an effective method for controller design that, if adopted can lead to cost savings of 25%-30% and time savings of 35%-40% (according to a global study by Altran Technologies, the chair of software and systems engineering and the chair of Information Management of the University of Technology in Munich) [1]. The PMSM plant models take effects like magnetic saturation, cross- coupling, spatial harmonics and temperature into account. Two PMSM models in d-q frame based on flux and inductance principles were implemented. Flux, torque maps from Finite Element Analysis (FEA) and apparent inductance from datasheets were used as inputs to the flux- and inductance-based models, respectively. The FEA of PMSM was done using COMSOL Multiphysics. The PMSM model results were compared with corresponding FEA simulated results for verification. A comparison of these PMSM models with conventional low fidelity models has also been done to highlight the impact of inclusion of temperature and spatial harmonics. These motor models can be combined with an inverter plant model and a controller can be developed for the complete model. Low frequency oscillations of drivetrain in EVs lead to vibrations which can cause discomfort and torsional stresses. In order to control these oscillations, an active oscillation damping controller can be implemented. For implementation of this control, a three-mass mechanical plant model of drivetrain with an ABS (Anti-lock Braking System) wheel speed sensor has been developed in this thesis. Analysis of the model transfer function to obtain the pole zero maps was performed. This was used to observe and verify presence of low frequency oscillations in the drivetrain. In order to include the effects of ABS wheel speed sensor and CAN communication, a model was developed for the sensor.Testning av regulatorernas inställningar med hänsyn till snabbhet och noggrannhet i momentreglering är avgörande i trefasiga drivsystem för elektriska fordon. Oftast är det bättre att simulera i stället för att utföra experimentella tester där komponenter kan skadas på grund av fysisk stress. Detta kallas för Model Based Design (MBD). MBD är an effektiv metod för utformningen av styrningen som kan leda till kostnadsbesparingar på 25%-30% och tidsbesparingar på 35%-40% enligt en studie från Altran Technologies i samarbete med Tekniska universitet i München, TUM. Detta examensarbete behandlar en modell för en synkronmaskin med permanentmagneter (PMSM) samt en modell för drivlinan utvecklad i Matlab/Simulink för MBD. PMSMs modellen inkluderar magnetisk mättnad och tvärkoppling, MMF övervågor och temperatur. Två PMSM modeller har utvecklats. Den första baseras på magnetiskt flöde som erhålls från finita element beräkningar i COMSOL Multiphysics medan den andra bygger på induktanser givna från datablad. En jämförelse av dessa PMSM-modeller med konventionella low fidelity-modeller har också gjorts för att illustrera påverkan temperaturberoende och MMF övervågor. Modellerna kan kombineras med en växelriktarmodell för att utveckla en hel styrenhet. Lågfrekventa oscillationer i drivlinan leder till vibrationer som kan orsaka vridspänningar och försämra komforten i elfordonet. En aktiv dämpningsregulator kan implementeras för att kontrollera spänningarna men en mekanisk drivlinemodell med tre massor och en ABS (anti-lock braking system) hastighetssensor behövs. Den mekaniska modellen har implementerats och analyserats även beaktande en modell för en CAN kommunikationskanal. Oscillationer med låg frekvens kunde observeras i modellen.
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Tsaousis, Georgios. "Le difficile équilibre entre sécurité et protection des données : comparaison des cadres juridiques français et grec sous l'influence du droit européen." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOD003.
Full textAbstract:
Confronté à sa propre violence, voire aux forces de la nature, l’homme n’a cessé d’exprimer un besoin, celui d’être rassuré et protégé. Ainsi le droit à la sécurité est dès la création des sociétés organisées un principe primordial de leur existence. Depuis les attentats du 11 septembre 2001 la question de la sécurité préoccupe fortement l’actualité politico-médiatique. La mise en place de politiques de sécurité performantes est un objectif qui excite les foules, un facteur qui renforce l’exécutif. Cet objectif est caractérisé comme « besoin social impérieux ». Toutefois sur le plan purement textuel le droit à la sécurité n’apparaît pas d’une façon explicite comme norme constitutionnelle. La sécurité usant des techniques les plus avancées exige, sur le plan juridique, une adaptation du droit à l’ère numérique. Les systèmes de vidéosurveillance, les téléphones portables, la toile et les fichiers automatisés constituent les nouvelles armes de l’appareil policier. A ce titre le traitement des données représente le noyau dur des nouvelles orientations de sécurité. Toutefois l’utilisation des nouvelles technologies pour des raisons liées au maintien du bon ordre nécessite également un autre devoir: le respect des libertés fondamentales préoccupation manifeste du droit. Pour autant, la surestimation des politiques de sécurité et la prolifération des mesures sécuritaires sont susceptibles d’entraîner une certaine dégradation ou un affaiblissement du droit à la protection des données principe fondamental du droit de l’UE dès l’adoption du traité de Lisbonne. Face à ce défi, le droit cherche un juste équilibre entre vie privée et sécurité. Certes, l’équation est ancienne, mais ses modes de résolutions évoluent en raison des innovations technologiques, qui se rient des frontières et mettent à mal le principe de souveraineté territorial inhérent à l’Etat. Les droits nationaux, supportent également mal cette abolition des frontières. La comparaison, des ordres juridiques grecs et français, avec certes leurs différences, en sont de belles illustrations notamment dans le cadre de l’UE où la sécurité nationale en demeurant de la seule responsabilité des Etats membres crée des disparités entre les législations nationales. Dans cet environnement les AAI de protection des données des pays comparés se trouvent à la marge, captives dans des cadres juridiques précis. Seule le juge reste pour faire le contrepoids face aux abus des services policiers. Dans l’état actuel des traités constitutifs, la protection des données traitées à des fins policières par la juridiction luxembourgeoise est impossible. Ainsi la Cour EDH constitue la seule juridiction européenne dotée d’opérer une conciliation des deux exigences fondamentales: maintien de l’ordre public et protection des données. En effet, elle n’exerce qu’un contrôle de proportionnalité des mesures appliquées. Ainsi, l’établissement d’un juste équilibre au moins au sein de l’UE conduit in fine le droit à s’orienter vers la mise en œuvre d’une approche unique des politiques de sécurité à travers d’une éventuelle révision des traitésConfronted by his own violence and the forces of nature, man has consistently expressed the need to be protected. Since the creation of organized societies, the right of security has been a fundamental principle of his existence. Since the attacks of September 11th, 2001, the question of security is being brought up constantly in the media. The implementation of effective security policies is an exciting objective, a factor that strengthens the executive power. This objective has been characterized as a "pressing social need". However, in the purely textual level, the right of security does not appear explicitly as a constitutional norm. Security using the most advanced techniques requires, legally, the adaptation of law to the digital era. CCTV systems, mobile phones, the word-wide-web and automatic archiving constitute the new weapons of the police apparatus. As such, data processing forms the core of the new security guidelines. Nevertheless, using new technologies for reasons related to the maintenance of public order also requires another duty: respect for fundamental freedoms, law's obvious concern. However, the overestimation of security policies and the proliferation of security measures may cause some degradation and loss of the right of data protection, a fundamental principle of EU law since the adoption of the Lisbon Treaty. Faced with this challenge, law seeks the right balance between privacy and security. Of course, the equation is old, but the ways to solve it evolve due to technological advances that laugh at borders and undermine the state's inherent principle of territorial sovereignty. National laws also handle poorly the abolition of frontiers. Comparison between Greek and French legal systems, albeit with their differences, is a beautiful illustration of this fact, notably within the EU where national security, remaining the sole responsibility of the member states, creates disparities between national laws. In this environment the Independent Administrative Authorities of data protection of the compared countries remain at the margin, trapped in specific legal frameworks. Only the judge remains to the counterweight police abuse. In the current state of the constitutive treaties, protection of processed data for police purposes by the Luxembourg court is impossible. And the ECHR is the only european court capable of providing a balance between the two basic requirements: maintenance of public order and data protection. Indeed, it only exercises a proportionality test of the applied measures. Thus, establishment of a balance at least within the EU ultimately leads law towards the implementation of a unique approach to security policies through a possible revision of the Treaties
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Ben, Ameur Chiheb. "TCP Protocol Optimization for HTTP Adaptive Streaming." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S127/document.
Full textAbstract:
Le streaming adaptatif sur HTTP, désigné par HAS, est une technique de streaming vidéo largement déployée sur Internet. Elle utilise TCP comme protocole de transport. Elle consiste à segmenter la vidéo stockée sur un serveur web en petits segments indépendants de même durée de lecture et transcodés à plusieurs niveaux de qualité, désignés par "chunks". Le player, du côté du client HAS, demande périodiquement un nouveau chunk. Il sélectionne le niveau de qualité en se basant sur l’estimation de la bande passante du/des chunk(s) précédent(s). Étant donné que chaque client HAS est situé au sein d’un réseau d’accès, notre étude traite un cas fréquent dans l’usage quotidien: lorsque plusieurs clients partagent le même lien présentant un goulot d’étrangement et se trouvent en compétition sur la bande passante. Dans ce cas, on signale une dégradation de la qualité d’expérience (QoE) des utilisateurs de HAS et de la qualité de service (QoS) du réseau d’accès. Ainsi, l’objectif de cette thèse est d’optimiser le protocole TCP pour résoudre ces dégradations de QoE et QoS. Notre première contribution propose une méthode de bridage du débit HAS au niveau de la passerelle. Cette méthode est désignée par "Receive Window Tuning Method" (RWTM): elle utilise le principe de contrôle de flux de TCP et l’estimation passive du RTT au niveau de la passerelle. Nous avons comparé les performances de RWTM avec une méthode récente implémentée à la passerelle qui utilise une discipline particulière de gestion de la file d’attente, qui est désignée par "Hierarchical Token Bucket shaping Method" (HTBM). Les résultats d’évaluations indiquent que RWTM offre une meilleure QoE et une meilleure QoS de réseau d’accès que HTBM. Notre deuxième contribution consiste à mener une étude comparative combinant deux méthodes de bridages, RWTM et HTBM, avec quatre variantes TCP largement déployées, NewReno, Vegas, Illinois et Cubic. Les résultats d'évaluations montrent une discordance importante entre les performances des différentes combinaisons. De plus, la combinaison qui améliore les performances dans la majorité des scénarios étudiés est celle de RWTM avec Illinois. En outre, une mise à jour efficace de la valeur du paramètre "Slow Start Threshold", sthresh, peut accélérer la vitesse de convergence du player vers la qualité optimale. Notre troisième contribution propose une nouvelle variante de TCP adaptée aux flux HAS, qu’on désigne par TcpHas; c’est un algorithme de contrôle de congestion de TCP adapté aux spécifications de HAS. TcpHas estime le niveau de la qualité optimale du flux HAS en se basant sur l’estimation de la bande passante de bout en bout. Ensuite, TcpHas applique un bridage au trafic HAS en fonction du débit d’encodage du niveau de qualité estimé. TcpHas met à jour ssthresh pour accélérer la vitesse de convergence. Une étude comparative a été réalisée avec la variante Westwood+. Les résultats d’évaluations montrent que TcpHas est plus performant que Westwood+HTTP adaptive streaming (HAS) is a streaming video technique widely used over the Internet. It employs Transmission Control Protocol (TCP) as transport protocol and it splits the original video inside the server into segments of same duration, called "chunks", that are transcoded into multiple quality levels. The HAS player, on the client side, requests for one chunk each chunk duration and it commonly selects the quality level based on the estimated bandwidth of the previous chunk(s). Given that the HAS clients are located inside access networks, our investigation involves several HAS clients sharing the same bottleneck link and competing for bandwidth. Here, a degradation of both Quality of Experience (QoE) of HAS users and Quality of Service (QoS) of the access network are often recorded. The objective of this thesis is to optimize the TCP protocol in order to solve both QoE and QoS degradations. Our first contribution consists of proposing a gateway-based shaping method, that we called Receive Window Tuning Method (RWTM); it employs the TCP flow control and passive round trip time estimation on the gateway side. We compared the performances of RWTM with another gateway-based shaping method that is based on queuing discipline, called Hierarchical Token Bucket shaping Method (HTBM). The results of evaluation indicate that RWTM outperforms HTBM not only in terms of QoE of HAS but also in terms of QoS of access network by reducing the queuing delay and significantly reducing packet drop rate at the bottleneck.Our second contribution consists of a comparative evaluation when combining two shaping methods, RWTM and HTBM, and four very common TCP variants, NewReno, Vegas, Illinois and Cubic. The results show that there is a significant discordance in performance between combinations. Furthermore, the best combination that improves performances in the majority of scenarios is when combining Illinois variant with RWTM. In addition, the results reveal the importance of an efficient updating of the slow start threshold value, ssthresh, to accelerate the convergence toward the best feasible quality level. Our third contribution consists of proposing a novel HAS-based TCP variant, that we called TcpHas; it is a TCP congestion control algorithm that takes into consideration the specifications of HAS flow. Besides, it estimates the optimal quality level of its corresponding HAS flow based on end-to-end bandwidth estimation. Then, it permanently performs HAS traffic shaping based on the encoding rate of the estimated level. It also updates ssthresh to accelerate convergence speed. A comparative performance evaluation of TcpHas with a recent and well-known TCP variant that employs adaptive decrease mechanism, called Westwood+, was performed. Results indicated that TcpHas largely outperforms Westwood+; it offers better quality level stability on the optimal quality level, it dramatically reduces the packet drop rate and it generates lower queuing delay
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Küttler, Sulivan. "Dimensionnement optimal de machines synchrones pour des applications de véhicules hybrides." Phd thesis, Université de Technologie de Compiègne, 2013. http://tel.archives-ouvertes.fr/tel-01023815.
Full textAbstract:
Les travaux de recherche présentés dans ce document portent sur le dimensionnement de machines synchrones pour des applications de véhicules hybrides. L'utilisation de la machine électrique au sein du véhicule hybride est caractérisée par des appels de puissance de courtes durées. Cette thèse propose donc une stratégie de dimensionnement permettant de minimiser considérablement le volume de l'actionneur par la prise en compte des limites thermiques réelles lors du cycle de conduite. La stratégie de dimensionnement est composée de deux étapes. La première étape est l'optimisation du dimensionnement de l'actionneur à partir des points de fonctionnement du cycle. Nous autorisons des niveaux d'induction dans le fer élevés et des niveaux de densité de courant dans les conducteurs dépassant les niveaux habituellement autorisés pour un fonctionnement en régime permanent thermique. Ces deux points ont un impact réel sur le volume de la machine. Cela-dit, à ce stade, la thermique de la machine n'est prise en compte qu'indirectement en fixant une densité de courant dans les conducteurs. La seconde étape permet alors de vérifier la thermique par une simulation sur cycle pour ensuite réajuster si besoin la densité de courant et reprendre la première étape d'optimisation de la machine. Des modèles adaptés au processus d'optimisation ont alors été mis en place et offrent un bon compromis entre le temps de calcul et la précision requise. Par conséquent, un modèle magnétique prenant en compte la saturation croisée dans la machine utilisant la méthode nodale a été développé ; un modèle permettant une meilleure prise en compte des pertes fer notamment dans le zone de défluxage a également été développé ainsi qu'un modèle thermique en transitoire utilisant également la méthode nodale. Le modèle thermique étant la clé de la stratégie de dimensionnement, une grande attention y a été portée. Ce modèle permet de prendre en compte la direction des flux dans les trois dimensions et fournit de bonnes estimations des températures dans la machine notamment aux endroits les plus chauds comme les encoches et les têtes de bobines. Ces résultats ont été corroborés par des essais expérimentaux réalisés dans les bancs IFPEN sur une machine spécialement instrumentée en thermocouples. Cela a permis de valider le comportement thermique en régime permanent thermique et en régime transitoire thermique. Ces modèles ont ensuite été implantés dans une modélisation multi-physique pour l'outil d'optimisation et pour l'outil de simulation. Une étude de cas a été présentée pour un véhicule hybride Kangoo où la machine doit pouvoir assurer son fonctionnement pour un cycle Artémis urbain. Les résultats de la stratégie de dimensionnement permettent alors de conclure que sur cycle, le volume extérieur des parties actives de la machine électrique peut-être réduit de 40 % par rapport à un dimensionnement établi par les règles de l'art en régime permanent. De plus, la réduction du volume de fer dans la machine induit également une réduction des pertes fer ce qui nous permet de conclure que, toujours sur cycle, son rendement moyen reste élevé.
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Ballard, Todd Curtis. "Mathematical models of Zea mays : grain yield and above ground biomass applied to ear flex and within row spacing variability /." 2008. http://digitalcommons.wku.edu/theses/41.
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Ngomane, Dambuza. "Moderation of growth and sucrose flux in sugarcane by temperature." Thesis, 2005. http://hdl.handle.net/10413/4490.
Full textAbstract:
Sugarcane plants (cultivar NCo376) were studied to assess the effects of temperature and
season (spring and autumn equinox) on the morphological and physiological response of
stalk components. Plants were grown from single-eyed setts for ca. five months and then
placed into three temperature controlled glasshouses (22/12°C (C), 27/17°C (W) and
32/22°C (H) day/night temperatures). The plants were sampled twice weekly over a one
month period., and intemodes 4, 6 and 10 of the primary haulms of each plant sampled for
growth and sugar analysis.
During spring, the leaf emergence rates were 0.0303, 0.1095 and 0.1682 leaves d(-1) at
temperatures C, W and H, respectively; and 0.0327, 0.0824 and 0.113 leaves d(-1) in
autumn. The phyllochron intervals were 114°Cd in spring and 147°Cd in autumn. Highest
green leaf blade area of the primary haulms was achieved at H (438.0 and 511.7 cm2 in
spring and autumn, respectively). The stalk extension rates were 1.22, 1.02, 0.38 cm d(-1)
(spring) and 1.35, 0.98, 0.45 cm d(-1) (autumn), respectively, in descending order of
temperature. Total biomass and stalk biomass per plant were not affected by temperature,
despite the differences in stem elongation. Internodes of plants at C were shorter but
thicker and heavier than the comparable internodes of plants at W and H.
In autumn, the mature internode sucrose concentrations were 35.5, 29.2 and 25.5% at C,
W and H, respectively; corresponding to mean RS% of 5.7, 9.8 and 13.3%, and fibre %
of 58.8, 61.1 and 61.3%, at the respective ascending order of temperature. Sucrose % in
the mature internodes in spring were 27.8, 20.9 and 19.9% at C, W and H, respectively;
corresponding to RS% of 5.9, 9.76 and 10.9% and fibre % of 66.3, 69.4 and 69.2% at the
respective ascending order of temperature. Temperature effect on the concentration of the
stalk components of the immature internodes was in general not significant. Sucrose
partitioning coefficients in the mature internodes were 0.25, 0.21 and 0.20 in spring and
0.50, 0.32 and 0.21 in autumn (at C, W and H, respectively). Data that resulted from this
study, which is isolated to temperature and cultivar NCo376 can be used in models of
sugarcane that simulate leaf appearance and senescence, assimilate partitioning between
leaf and stalk and assimilate partitioning between the stalk components namely sucrose,
reducing sugars and fibre.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
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Jhala, Amitkumar Jayendrasinh. "Environmental biosafety of genetically engineered crops flax (Linum usitatissimum L.) as a model system /." 2010. http://hdl.handle.net/10048/874.
Full textAbstract:
Thesis (Ph. D.)--University of Alberta, 2010.Title from pdf file main screen (viewed on April 22, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Plant Science, Department of Agricultural, Food and Nutritional Science, University of Alberta. Includes bibliographical references.