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Pereira, Denis Biolkino de Sousa y William Rodrigues Ferreira. "REFLEXOS DAS OCUPAÇÕES URBANAS NA MOBILIDADE ÀS MARGENS DA RODOVIA ESTADUAL GO-060 ENTRE GOIÂNIA (GO) E TRINDADE (GO)". Revista Cerrados 18, n.º 01 (19 de mayo de 2020): 189–219. http://dx.doi.org/10.22238/rc2448269220201801189219.
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O estudo pretende compreender a dinâmica dos diversos tipos de ocupações implantadas no entorno da Rodovia Estadual GO- 060, entre a cidade de Goiânia (GO) e Trindade (GO), e os seus reflexos na mobilidade urbana. O problema se identifica na relação causa e efeito no conflito entre o espaço urbano e o sistema de transportes, em áreas conurbadas da Região Metropolitana de Goiânia (GO). O objetivo consiste em analisar as áreas de ocupação do recorte espacial, o fluxo veicular dos modos de transportes e o índice de mobilidade, em função das tipologias de ocupação, caracterizadas como polos geradores de viagens (PGVs). Para se identificar tais ocorrências, foram utilizadas metodologias adaptadas para análise espaço-temporal e redes. Os resultados mostraram as diferenças em áreas de ocupação nos PGVs Tipo Comércio/Indústria 25,74% e 30,77% e Tipo Residencial 11,41% e 38,78% para as Regiões Oeste/Mendanha e Trindade 2, para os períodos (2011/2016) e (2009/2015), respectivamente. Essa dinâmica ocupacional gerou um aumento de +87% no total de viagens do fluxo dos diversos modos de transporte e um acréscimo de +79% no índice de mobilidade para o período de 2013 a 2016, mostrando a tendência de motorização das regiões e os reflexos na mobilidade urbana.
Palavras-chave: Ocupação espacial. Sistema viário. Fluxo veicular. Transporte. Mobilidade.
REFLEXES OF URBAN OCCUPATIONS ON MOBILITY TO THE MARGINS OF THE STATE ROAD GO-060 BETWEEN GOIÂNIA (GO) AND TRINDADE (GO)
ABSTRACT
The study aims to understand the dynamics of the various types of occupations implanted around the State Highway GO-060, between the city of Goiânia (GO) and Trindade (GO), and their reflexes on urban mobility. The problem is identified in the cause and effect relationship in the conflict between urban space and the transport system in conurbated areas of the Metropolitan Region of Goiânia (GO). The objective is to analyze the areas of occupation of the spatial area, the vehicular flow of the modes of transport and the mobility index, according to the types of occupation, characterized as travel generating poles (TGPs). To identify such occurrences, methodologies adapted for spatiotemporal analysis and networks were used. The results showed the differences in occupation areas in the Trade / Industry Type 25.74% and 30.77% and Residential Type 11.41% and 38.78% for the West / Mendanha and Trindade 2 Regions for the periods (2011/2016) and (2009/2015) respectively. This occupational dynamic generated an increase of + 87% in the total travel flow of the different modes of transport and an increase of + 79% in the mobility index for the period from 2013 to 2016, showing the trend of motorization in the regions and the reflexes in urban mobility.
Keywords: Spatial occupation. Road system. Vehicular flow. Transport. Mobility.
REFLETS DES OCCUPATIONS URBAINES SUR LA MOBILITÉ LE LONG DE LA ROUTE D’ÉTAT GO-60 ENTRE GOIANIA (GO) ET TRINDADE (GO)
RÉSUMÉ
L’étude prétend comprendre la dynamique des divers types d’occupations implantées le long de la Route d’État GO-060, entre les villes de Goiânia (GO) et Trindade (GO), et ses retombées sur la mobilité urbaine. Le problème s’identifie dans la relation de cause à effet dans le conflit entre espace urbain et système de transport, dans les aires urbanisées de la Région Métropolitaine de Goiânia (GO). L’objectif est d’analyser les zones d’occupation du découpage spatial, le flux routier des modes de transport et l’indice de mobilité selon les typologies d’occupation, caractérisées comme pôles générateurs de voyages (PGVs). L’identification de ces faits s’est réalisée par l’utilisation de méthodologies adaptées à l’analyse spatio-temporelle et de réseaux. Les résultats montrent des différences de PGVs dans les zones d’occupation du type Commerce/Industrie 25,74% et 30,77% et du type résidentiel 11,41% et 38,78% pour les régions Ouest/Mendanha et Trindade 2, respectivement pour les périodes (2011/2016) et (2009/2015). Cette dynamique d’occupation révèle une augmentation de +87% du total de voyages de flux des différents modes de transport et une croissance de +79% de l’indice de mobilité pour la période de 2013 à 2016, montrant la tendance de motorisation des régions et ses reflets sur la mobilité urbaine.
Mots clés: Occupation spatial. Système routier. Flux de véhicules. Transport. Mobilité.
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Lugiéry, Charles, Guillaume Lacquement y Coline Perrin. "Des interstices agricoles investis par les Gitans et Voyageurs". Mélanges de l'École française de Rome. Italie et Méditerranée 135-2 (2023): 313–30. http://dx.doi.org/10.4000/11r7x.
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Cet article étudie la mobilisation des ressources agricoles par des groupes sociaux souvent identifiés comme Gitans ou Gens du voyage autour de Montpellier et de Perpignan. Il s’appuie sur une enquête par entretiens conduite auprès d’acteurs institutionnels et d’agriculteurs visant à comprendre le regard qu’ils portent sur les pratiques agricoles de ces groupes. La question de l’informalité est ici abordée en géographie par le prisme de l’interstice. De cette enquête se dégagent trois modalités d’investissement des interstices agricoles par les Gitans et Voyageurs : pour habiter, produire et valoriser économiquement les ressources agricoles des interstices. Cette lecture géographique des interstices montre l’ambivalence des expressions et des dynamiques socio-spatiales de l’informalité en agriculture dans les zones périurbaines quand sont concernés des groupes sociaux minoritaires.
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Larroque, Dominique, Michel Margairaz y Pierre Zembri. "Nombre de voyageurs transportés dans Paris et sa region de 1871 à 1996". Flux 50, n.º 4 (2002): 91. http://dx.doi.org/10.3917/flux.050.0091.
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Moroni, Thomas. "La régulation ordinaire des flux de voyageurs en gare : l’infrastructure à l’épreuve permanente". Flux N° 129-130, n.º 3 (14 de diciembre de 2022): 29–43. http://dx.doi.org/10.3917/flux1.129.0029.
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Garedaghi, Yagoob, Patrice Bourée y Francine Bisaro. "Cryptosporidiose au retour d’un voyage sous les tropiques, à propos de deux cas". Revue de biologie médicale N° 380, n.º 5 (1 de mayo de 2024): 51–56. http://dx.doi.org/10.3917/rbm.380.0051.
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Plus fréquente dans les zones tropicales défavorisées, la cryptosporidiose est une zoonose cosmopolite due à Cryptosporidium , un protozoaire responsable de diarrhées. Nous rapportons le cas de deux voyageurs, revenant d’une zone tropicale, confrontés à une diarrhée persistante causée par ce parasite et à la difficulté d’obtenir un traitement ad hoc par le nitazoxanide qui dispose d’une autorisation temporaire d’utilisation. La prévention de cette infection liée au péril fécal est difficile et il faut éviter d’absorber de l’eau de boisson non embouteillée et de consommer des crudités lors d’un séjour sous les tropiques.
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Ning, Jia. "Effects of Cropland Expansion on the Regional Land Surface Radiative Energy Balance and Heat Fluxes in Northern China". Applied Sciences 11, n.º 4 (9 de febrero de 2021): 1556. http://dx.doi.org/10.3390/app11041556.
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Land use change can impact the land surface radiation budget and energy balance by changing surface biophysical processes. Based on satellite remote sensing data and land use data from 2000 to 2015, we quantitatively estimated radiative forcing induced by cropland expansion during the early 21st century in northern China. The results showed that heat flux from the land surface to the atmosphere due to cropland expansion was quite variable in different climate zones. The heat flux increased in humid North China, whereas it decreased in arid Northwest China, semiarid Inner Mongolia, and humid Northeast China. Cropland expansion from woodland areas led to a general decline in the land surface heat flux to the atmosphere, which led to a cooling effect on the climate. The surface heat flux to the atmosphere due to cropland expansion in grassland areas displayed significant variations in different climate zones. The surface heat flux decreased only in humid Northeast China and arid Northwest China. The net surface radiation and latent heat flux both increased when grasslands were changed into cropland, but to different extents, which produced the differences in the surface heat flux to the atmosphere between different zones.
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Hatz, Christoph, Sarra Inoubli, Louis Loutan, Blaise Genton, Ron Behrens y Markus Hufnagel. "[b]Encéphalite[/b] japonaise : risque pour les populations vivant en zones d’endémie et pour les voyageurs". Revue Médicale Suisse 6, n.º 248 (2010): 956–59. http://dx.doi.org/10.53738/revmed.2010.6.248.0956.
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Cariou, Jean-Pierre y Ludovic Thobois. "Détection et analyse automatique des aérosols atmosphériques par lidar infrarouge". Photoniques, n.º 97 (julio de 2019): 30–35. http://dx.doi.org/10.1051/photon/20199730.
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Le changement climatique récent est attribué entre autres à l'impact des particules atmosphériques d’origine naturelle ou des activités humaines d’après le dernier rapport du GIEC [IPCC, Climate Change 2014: Synthesis Report]. Les aérosols affectent également les propriétés des nuages et influencent le cycle de l'eau, pouvant intensifier les moussons. En avril 2010, le volcan Eyjafjallajökull a créé un panache de plusieurs milliers de kilomètres sur l’Europe et causé la fermeture de plusieurs aéroports internationaux, clouant au sol des millions de voyageurs et causant une perte économique globale de 1,7 milliard de dollars. Tous les jours, les aérosols transfrontaliers (panaches de sable du Sahara, résidus de combustion des forêts canadiennes) affectent la santé des populations habitant notamment en zones urbaines ainsi que les activités économiques.
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O’Reilly, Carrie, Mauricio Silva, Samira Daneshgar Asl, William P. Meurer y Ian R. MacDonald. "Distribution, Magnitude, and Variability of Natural Oil Seeps in the Gulf of Mexico". Remote Sensing 14, n.º 13 (30 de junio de 2022): 3150. http://dx.doi.org/10.3390/rs14133150.
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The Gulf of Mexico is a hydrocarbon-rich region characterized by the presence of floating oil slicks from persistent natural hydrocarbon seeps, which are reliably captured by synthetic aperture radar (SAR) satellite imaging. Improving the state of knowledge of hydrocarbon seepage in the Gulf of Mexico improves the understanding and quantification of natural seepage rates in North America. We used data derived from SAR scenes collected over the Gulf of Mexico from 1978 to 2018 to locate oil slick origins (OSOs), cluster the OSOs into discrete seep zones, estimate the flux of individual seepage events, and calculate seep recurrence rates. In total, 1618 discrete seep zones were identified, primarily concentrated in the northern Gulf of Mexico within the Louann salt formation, with a secondary concentration in the Campeche region. The centerline method was used to estimate flux based on the drift length of the slick (centerline), the slick area, and average current and wind speeds. Flux estimates from the surface area of oil slicks varied geographically and temporally; on average, seep zones exhibited an 11% recurrence rate, suggesting possible intermittent discharge from natural seeps. The estimated average instantaneous flux for natural seeps is 9.8 mL s−1 (1.9 × 103 bbl yr−1), with an annual discharge of 1.73–6.69 × 105 bbl yr−1 (2.75–10.63 × 104 m3 yr−1) for the entire Gulf of Mexico. The temporal variability of average flux suggests a potential decrease following 1995; however, analysis of flux in four lease blocks indicates that flux has not changed substantially over time. It is unlikely that production activities in the Gulf of Mexico impact natural seepage on a human timescale. Of the 1618 identified seep zones, 1401 are located within U.S. waters, with 70 identified as having flux and recurrence rates significantly higher than the average. Seep zones exhibiting high recurrence rates are more likely to be associated with positive seismic anomalies. Many of the methods developed for this study can be applied to SAR-detected oil slicks in other marine settings to better assess the magnitude of global hydrocarbon seepage.
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Khamouli, Farida, Mosbah Zidani, Hichem Farh, Adel Saoudi y L'hadi Atoui. "Effects of Cellulosic and Basic Flux on the Structure, Composition and Hardness of SMAW Welds on Steel X42". International Journal of Engineering Research in Africa 27 (diciembre de 2016): 11–19. http://dx.doi.org/10.4028/www.scientific.net/jera.27.11.
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This paper studied the effects of cellulosic and basic flux on the chemical composition, microstructure, formation of inclusions and micro hardness of X42 steel SMAW welds. The commercialized chemical compositions of flux used are: E6010, E8010-P1 and E8018-G, with electrodes of low carbon content. Welding conditions are not constant. The microstructure of the fusion zone for each flux consists mainly of acicular ferrite. It is found that manganese increases in the fusion zones (C, B and A) respectively .The change in mass concentration of manganese is homogeneous through the three points with all the used flux. Regardless of the flux used, the non-metallic inclusions observed are of two types: white and black. The micro-hardness decreasing values were obtained in the fusion zones (C, B and A).
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Işık, Emre, Dieter Schmitt y Manfred Schüssler. "Modelling stellar activity cycles using deep-seated dynamos and surface flux transport". Proceedings of the International Astronomical Union 8, S294 (agosto de 2012): 431–32. http://dx.doi.org/10.1017/s1743921313002883.
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AbstractWe investigate the relations between tachocline-based dynamos and the surface flux transport mechanisms in stars with outer convection zones. Using our combined models of flux generation and transport, we demonstrate the importance of the buoyant rise of magnetic flux, which physically determines the emergence latitudes and tilt angles of bipolar magnetic regions. The combined effects of the dynamo strength, flux rise, and surface transport lead to various cyclic and non-cyclic time series of total unsigned surface magnetic flux.
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Dupuy, A., R. Moumtaz y O. Banton. "Contamination nitratée des eaux souterraines d'un bassin versant agricole hétérogène 2. Évolution des concentrations dans la nappe". Revue des sciences de l'eau 10, n.º 2 (12 de abril de 2005): 185–98. http://dx.doi.org/10.7202/705276ar.
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L'usage quasi systématique de fertilisants sur de grandes surfaces a conduit la majorité des aquifères superficiels à un grave niveau de contamination par les nitrates. Des essais de gestion environnementale de cette problématique agricole sont conduits à l'échelle du bassin versant afin d'estimer les flux de nitrates percolant vers la nappe. La présente étude reprend les résultats issus de la modélisation d'un bassin versant dans le but d'appréhender l'évolution de la concentration en nitrates dans les eaux de la nappe. L'importance des conditions hydrogéologiques dans les relations entre zones non saturée et saturée a été mise en évidence par la comparaison des concentrations calculées dans la zone non saturée et observées dans la nappe. En règle générale, les concentrations sont très semblables pour les zones proches des limites amont du bassin, et se différencient de plus en plus vers l'aval du système. Une dilution semble se produire entre les flux percolant des différentes zones non saturées et les flux d'eau et de nitrates s'écoulant dans l'aquifère. Afin de tester cette hypothèse, un modèle de dilution basé sur les flux d'eau et de nitrates dans les zones non saturée et saturée est développé. Appliqué sur l'axe d'écoulement principal du système, le modèle de dilution permet de reproduire adéquatement les concentrations observées dans la nappe à partir de celles calculées dans le sol avec une erreur maximale variant de 1 à 22%. Le couplage d'un modèle environnemental pour la zone racinaire du sol avec un modèle de dilution simple peut permettre le calcul des concentrations en nitrates dans la zone saturée. Toutefois, la prise en compte des conditions hydrogéologiques du système est nécessaire à un calcul de dilution efficace basé sur les valeurs des flux de percolation.
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Sugiana, I. Putu, Tri Prartono, Rastina Rastina y Alan Frendy Koropitan. "Warming Effect from Soil Greenhouse Gas Emission of Each Mangrove Zone during the Dry Season in Ngurah Rai Forest Park, Bali, Indonesia". Environment and Natural Resources Journal 22, n.º 5 (22 de agosto de 2024): 1–15. http://dx.doi.org/10.32526/ennrj/22/20240029.
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In addition to functioning as a carbon sink, mangrove soil also releases greenhouse gases (GHGs) through microbial metabolism. GHG flux fluctuates according to the ecological parameters of mangroves and climate variability. We quantified GHG fluxes from the soil using a closed-chamber technique and assessed soil and porewater conditions in three primary mangrove zones (each zone was dominated by one of the mangrove types) at Ngurah Rai Forest Park, Bali, Indonesia, categorized by genera: Bruguiera, Rhizophora, and Sonneratia. We found that the CO2 flux ranged from 322.5 to 3,494.5 µg/m2/h, CH4 flux ranged from -24.7 to 60.9 µg/m2/h, and N2O flux ranged from -1.2 to 2.3 µg/m2/h. None of the GHG fluxes varied significantly between mangrove zones. Overall, the highest CO2 fluxes were observed in the Bruguiera zones, while the highest CH4 and N2O fluxes were found in the Sonneratia and Rhizophora zones, respectively. A significant relationship between GHG fluxes and soil properties, including soil organic carbon (SOC), total Kjeldahl nitrogen (TKN), water content, bulk density, and soil type. The average warming effect on GHG fluxes ranged from 0.9 and 1.8 MgCO2/ha/year, accounting for only 1.1% to 2.2% of the annual plant carbon sequestration rate of 75.9 to 81.6 MgCO2/ha/year. These findings suggest that the variability of GHG fluxes is not significantly influenced by mangrove type; instead, soil conditions play a crucial role. Calculations of the net carbon stock may overlook the relatively low warming effect of GHG fluxes in this area.
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Ledley, Tamara Shapiro. "Meridional Sea-Ice Transport and its Impact on Climate". Annals of Glaciology 14 (1990): 141–43. http://dx.doi.org/10.3189/s0260305500008442.
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Sea ice is an important factor in controlling the ocean–atmosphere energy exchange in polar regions, and has an important impact on climate. This is because sea ice insulates the relatively warm ocean from the cold winter atmosphere, and has a higher surface albedo than the ocean. In this study the effect of sea-ice transport on the energy exchange between the atmosphere and ocean, and thus on climate, is examined using a coupled energy-balance climate–thermodynamic sea-ice model.Transport of sea ice produces a thinning of the zonally annually-averaged sea ice in the poleward-most zones, and an extension of the ice edge equatorward. Thinning of the poleward-most ice produces an increase in the annual sensible heat flux from the ocean to the atmosphere, which produces an increase in the mean annual atmospheric temperatures. Sensible heat flux is decreased in the zones that contain the ice edge. However, warming in the poleward-most zones produces an increased meridional energy convergence at the ice edge that offsets the decrease in the sensible heat flux to the atmosphere, resulting in a net warming.
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Ledley, Tamara Shapiro. "Meridional Sea-Ice Transport and its Impact on Climate". Annals of Glaciology 14 (1990): 141–43. http://dx.doi.org/10.1017/s0260305500008442.
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Sea ice is an important factor in controlling the ocean–atmosphere energy exchange in polar regions, and has an important impact on climate. This is because sea ice insulates the relatively warm ocean from the cold winter atmosphere, and has a higher surface albedo than the ocean. In this study the effect of sea-ice transport on the energy exchange between the atmosphere and ocean, and thus on climate, is examined using a coupled energy-balance climate–thermodynamic sea-ice model. Transport of sea ice produces a thinning of the zonally annually-averaged sea ice in the poleward-most zones, and an extension of the ice edge equatorward. Thinning of the poleward-most ice produces an increase in the annual sensible heat flux from the ocean to the atmosphere, which produces an increase in the mean annual atmospheric temperatures. Sensible heat flux is decreased in the zones that contain the ice edge. However, warming in the poleward-most zones produces an increased meridional energy convergence at the ice edge that offsets the decrease in the sensible heat flux to the atmosphere, resulting in a net warming.
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Linhoss, John E., Joseph L. Purswell y Jeremiah D. Davis. "Radiant Flux Preference of Neonatal Broiler Chicks During Brooding". Transactions of the ASABE 61, n.º 4 (2018): 1417–23. http://dx.doi.org/10.13031/trans.12775.
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Abstract. Radiant heat is the most common method of providing supplemental heat in a broiler house. However, little information exists about chick preference for radiant flux. Identifying the ranges of radiant flux that chicks prefer would allow improved management of the thermal environment. The objectives of this study were to determine the radiant flux ranges preferred by broiler chicks during the first eight days of brooding. Three trials were conducted using straight-run broiler chicks. A total of 88 chicks were randomly allocated into two mixed-gender groups and placed into identical 1 m × 4 m pens for 8 d. Heat lamps were used to create radiant flux zones of 30, 70, 175, and 450 W m-2 in each pen. Chicks were allowed to move freely between the zones, and feed and water were available in each treatment area. Chick location was recorded with a camera at 5 min intervals. For each image, non-linear regression analysis was applied to the cumulative proportion of chicks in each treatment. The resulting equations were used to calculate the range of radiant flux values for which 80% of the chicks exhibited a preference. Chicks exhibited a preference for decreasing radiant flux with age. The mean maximum preferred radiant flux for all trials decreased from 409.4 W m-2 at 1 d to 304.4 W m-2 at 8 d. The mean minimum preferred radiant flux for all trials decreased from 114.5 W m-2 at 1 d to 31.4 W m-2 at 8 d. Keywords: Broiler chicks, Brooding, Radiant flux, Radiant heaters, Thermal preference.
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Coquet, Bruno, Jean-Marc Daniel y Emmanuel Fourmann. "L’Europe et l’Afrique : flux et reflux". Politique africaine 49, n.º 1 (1993): 6–30. http://dx.doi.org/10.3406/polaf.1993.5635.
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Europe and Africa : Ebb and flow. The 1957 Treaty of Rome, initiating the construction of Europe, coincides with the independence of most African countries. During the last years, the political, commercial and financial links between these two zones, although important, cannot help divergent evolution of their respective economic situation. This paper describes and interprets the Euro-African declining commercial and financial flows since the 60’s in order to propose a global diagnosis on trade, aid, debt and foreign investments in Africa.
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Liu, Zhanpeng, Ruibin Li, Yan Wu y Naiping Gao. "Numerical study of climate characteristics on the residential scale energy balance based on some typical cities". E3S Web of Conferences 356 (2022): 04039. http://dx.doi.org/10.1051/e3sconf/202235604039.
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The energy balance of residential blocks in different climate zones is simulated and analysed. The influence of climate characteristics on the residential-scale energy budget is clarified, and the temporal evolution patterns of sensible heat flux, latent heat flux and heat storage flux in the surface energy balance are obtained. From the perspective of residential blocks energy distribution, ENVI-met simulation software is used to explore the laws of climate characteristics on the change of residential scale energy balance during summer and winter in three representative cities of typical climate zones in China.. Though surface energy balance simulations, vertical surfaces are found to be a significant source of net radiation received by settlements for northern regions and horizontal surfaces for southern regions. Most of the net radiation absorbed by the residential blocks during the day is transferred to the atmosphere in the form of sensible heat fluxes.
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Zhang, Qing, Tingting Li y Jian Yang. "Effect of Al2O3 Inclusions or Mold Flux Particles on Their Surrounding Microstructures of Sliver Defects on the Surface of Automobile Exposed Panel". Metals 13, n.º 4 (27 de marzo de 2023): 661. http://dx.doi.org/10.3390/met13040661.
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The Al2O3 inclusions and mold flux particles are the initial causes of the sliver defects on the surface of automobile exposed panels. During the rolling process, the smashed Al2O3 inclusions or mold flux particles will hinder the growth of recrystallized grains. Compared with mold flux particles, the smashed Al2O3 inclusions have a smaller size, a denser distribution, and a larger number density, so the smashed Al2O3 inclusions have a stronger ability to hinder grain boundary migration. Therefore, the average grain size is small in the following sequence: Al2O3 defect zone with Al2O3 inclusions (Al2O3 DZ with Al2O3), mold flux defect zone with mold flux particles (MFDZ with MFP), mold flux defect zone without mold flux particles (MFDZ without MFP), Al2O3 defect zone without Al2O3 inclusions (Al2O3 DZ without Al2O3), and non-defect zone (NDZ). The influence of particles on the grain orientation of the defect zones results in the microtexture of Al2O3 DZ without Al2O3 is {111}<313>, which is close to the {111}<101> microtextures of NDZ and MFDZ without MFP, while the {001}<114> microtexture on Al2O3 DZ with Al2O3 and the {313}<111> microtexture on MFDZ with MFP are quite different from that of NDZ. Due to differences in the inclusions, orientation, and microtexture of the defect zones and NDZ, dark-gray or bright white sliver defects on the surface of the automobile exposed panel are eventually formed.
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MIGNOT, EMMANUEL, D. HURTHER y E. BARTHELEMY. "On the structure of shear stress and turbulent kinetic energy flux across the roughness layer of a gravel-bed channel flow". Journal of Fluid Mechanics 638 (7 de octubre de 2009): 423–52. http://dx.doi.org/10.1017/s0022112009990772.
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This study examines the structure of shear stress and turbulent kinetic energy (TKE) flux across the roughness layer of a uniform, fully rough gravel-bed channel flow (ks+ ≫ 100, δ/k = 20) using high-resolution acoustic Doppler velocity profiler measurements. The studied gravel-bed roughness layer exhibits a complex random multi-scale roughness structure in strong contrast with conceptualized k- or d-type roughness in standard rough-wall flows. Within the roughness layer, strong spatial variability of all time-averaged flow quantities are observed affecting up to 40% of the boundary layer height. This variability is attributed to the presence of bed zones with emanating bed protuberances (or gravel clusters) acting as local flow obstacles and bed zones of more homogenous roughness of densely packed gravel elements. Considering the strong spatial mean flow variability across the roughness layer, a spatio-temporal averaging procedure, called double averaging (DA), has been applied to the analysed flow quantities. Three aspects have been addressed: (a) the DA shear stress and DA TKE flux in specific bed zones associated with three classes of velocity profiles as previously proposed in Mignot, Barthélemy & Hurther (J. Fluid Mech., vol. 618, 2009, p. 279), (b) the global and per class DA conditional statistics of shear stress and associated TKE flux and (c) the contribution of large-scale coherent shear stress structures (LC3S) to the TKE flux across the roughness layer. The mean Reynolds and dispersive shear structure show good agreement between the protuberance bed zones associated with the S-shape/accelerated classes and recent results obtained in standard k-type rough-wall flows (Djenidi et al., Exp. Fluids, vol. 44, 2008, p. 37; Pokrajac, McEwan & Nikora, Exp. Fluids, vol. 45, 2008, p. 73). These gravel-bed protuberances act as local flow obstacles inducing a strong turbulent activity in their wake regions. The conditional statistics show that the Reynolds stress contribution is fairly well distributed between sweep and ejection events, with threshold values ranging from H = 0 to H = 8. However, the TKE flux across the roughness layer primarily results from the residual shear stress between ejection and sweep of very high magnitude (H = 10–20) and of small turbulent scale. Although LC3S are seen to penetrated the interfacial roughness layer, their TKE flux contribution is found to be negligible compared to the very energetic small-scale sweep events. These sweeps are dominantly produced in the bed zones of local gravel protuberances where the velocity profiles are inflexional of S-shape type and the mean flow properties are of mixing-layer flow type as previously shown in Mignot et al. (2009).
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Bazova, M. M. "Phosphorus Flux in Small Lakes from Different Natural-Climatic Zones". Geochemistry International 60, n.º 3 (marzo de 2022): 286–97. http://dx.doi.org/10.1134/s0016702922020021.
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Guilbeault, Martin A., Beth L. Parker y John A. Cherry. "Mass and Flux Distributions from DNAPL Zones in Sandy Aquifers". Ground Water 43, n.º 1 (enero de 2005): 70–86. http://dx.doi.org/10.1111/j.1745-6584.2005.tb02287.x.
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Stuart, Catherine A., Sandra Piazolo y Nathan R. Daczko. "The recognition of former melt flux through high-strain zones". Journal of Metamorphic Geology 36, n.º 8 (25 de junio de 2018): 1049–69. http://dx.doi.org/10.1111/jmg.12427.
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Bancelin, D., E. Pilat-Lohinger, S. Eggl, T. I. Maindl, C. Schäfer, R. Speith y R. Dvorak. "Asteroid flux towards circumprimary habitable zones in binary star systems". Astronomy & Astrophysics 581 (septiembre de 2015): A46. http://dx.doi.org/10.1051/0004-6361/201526430.
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Bancelin, D., E. Pilat-Lohinger y Á. Bazsó. "Asteroid flux towards circumprimary habitable zones in binary star systems". Astronomy & Astrophysics 591 (23 de junio de 2016): A120. http://dx.doi.org/10.1051/0004-6361/201528035.
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Li, Gang, Hongli Li, Meng Yang, Ting Lei, Mingxiang Zhang, Peter Bridgewater, Shuhong Wu y Guangchun Lei. "Seasonal and diurnal methane and carbon dioxide emissions from the littoral area of the Miyun Reservoir in Beijing, China". Marine and Freshwater Research 69, n.º 5 (2018): 751. http://dx.doi.org/10.1071/mf17114.
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Reservoirs have been regarded as hot spots for greenhouse gas emissions since the 1990s. However, there is scant research about littoral zones of reservoirs. In the present study, static closed chamber and gas chromatograph techniques were used to measure methane (CH4) and carbon dioxide (CO2) flux in the littoral area of a temperate reservoir from 2009 to 2010. The littoral area comprises three zones, namely supralittoral, eulittoral and infralittoral. The patterns of CH4 and CO2 emissions from these three littoral zones were significantly different during the sampling periods, with the eulittoral zone having the highest CH4 flux and the supralittoral zone having the highest CO2 flux. Temperature and biomass correlated with CH4 and CO2 emissions. Measurement of CO2 emissions after removing vegetation varied in each zone and according to time of sampling. A large littoral area of the reservoir sampled herein will be submerged and converted to a pelagic area with deep standing water after the South to North Water Transfer Project is completed, in 2050. The results of the present study suggest further research and monitoring are needed, and should focus on likely effects of extreme climate events and the effects of human-mediated factors on greenhouse gas emissions.
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Perdahci, Canan, Onur Hasanoglu y Yahya Sogodok. "Tunnel Illumination: Algorithm to Determine Standard Values of Luminance in Tunnel Zones Using C Programming Language Approach". Light & Engineering, n.º 06-2021 (diciembre de 2021): 102–9. http://dx.doi.org/10.33383/2021-081.
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Tunnel illumination design involves complex mathematical computation, cumbersome, and tedious to perform when done by hand. This paper proposes an algorithm to compute luminance and luminous flux of the different zones of the tunnel by following the International Commission on Illumination (CIE88:2004) standard design guidelines using the C programming language. The luminance and the luminous flux values of all the zones were calculated and compared with the CIE standard. The energy consumption of each zone is equally found to control and reduce energy wastage and payment of unwanted bills. The threshold zone length Lth, average luminance in the first half Lav, and the last half of the threshold zone are 40 m, 400 cd/m2, and 240 cd/m2, respectively, while the average luminance of the transition and interior zones are, respectively, 95.87 cd/m2 and 5.86 cd/m2. The results obtained were satisfying. The computational results showed that the proposed Algorithm could be used to design an efficient tunnel illumination system with less energy waste.
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Jia, Dongpeng, Ning Wang, Yu Pan, Chaoyang Liu, Shiwei Wang, Kai Yang y Jian Liu. "Flow and Heat Transfer Characteristics of Supercritical N-Decane in Adjacent Cooling Channels with Opposite Flow Directions". Energies 14, n.º 4 (18 de febrero de 2021): 1071. http://dx.doi.org/10.3390/en14041071.
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To ensure the safety of a scramjet, an arrangement scheme of adjacent regenerative cooling channels with opposite flow directions is adopted to decrease the maximum wall temperature. Based on extended corresponding-state methods, the flow and heat transfer characteristics of supercritical n-decane in cooling channels with same and opposite flow directions under a pressure of 3 MPa are comprehensively investigated in this paper. Compared to adjacent cooling channels with same flow direction, the local maximum wall temperature in adjacent cooling channels with opposite directions is notably reduced. Moreover, the effects of the heat flux and gravity on the development of flow field are analysed. A pair of recirculation zones is found close to the bottom wall of the cooling channels along the flow direction, the scale of which greatly expands with increasing heat flux. Once the heat flux density reaches a critical value, a phenomenon of flow asymmetry occurs. In addition, the small recirculation zones induced by the buoyancy force narrow when the gravity and heat flux directions remain the same, and the gravity effect could inhibit the generation of small-scale vortices and flow asymmetry.
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Zhou, Wenchang, Shanshan Xiang, Yuhu Shi, Xiuhuan Xu, Huicui Lu, Wenhui Ou y Jiawei Yang. "Invasive Water Hyacinth (Eichhornia crassipes) Increases Methane Emissions from a Subtropical Lake in the Yangtze River in China". Diversity 14, n.º 12 (26 de noviembre de 2022): 1036. http://dx.doi.org/10.3390/d14121036.
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Lakes represent an important source of atmospheric methane (CH4); however, there are few studies on which lake-dwelling invasive aquatic plants generate CH4. Therefore, in this study, CH4 emissions were measured using a floating chamber and gas chromatography in a subtropical lake in China. We considered four community zones of invasive plants (Eichhornia crassipes), emergent vegetation (Zizania latifolia), floating-plant (Trapa natans) and open-water zones. The results indicate that the flux of CH4 emissions varied between −5.38 and 102.68 mg m−2 h−1. The higher emission values were attributed to lake eutrophication. Moreover, the flux of CH4 emissions in the invasive plant zone was 140–220% higher than that in the open-water and the floating-plant zones. However, there was no significant difference in CH4 emissions between the invasive plant and the emergent vegetation zones. This may be due to a higher production of plants, as well as the rapid reproductive rate of the invasive plants. Finally, CH4 emissions were positively associated with the air and water temperature; however, the emissions were also negatively associated with water depth. Our results suggest that invasive plants enhance freshwater CH4 emissions, thus contributing to global warming.
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Vergara, Oscar, Boris Dewitte, Ivonne Montes, Veronique Garçon, Marcel Ramos, Aurélien Paulmier y Oscar Pizarro. "Seasonal variability of the oxygen minimum zone off Peru in a high-resolution regional coupled model". Biogeosciences 13, n.º 15 (8 de agosto de 2016): 4389–410. http://dx.doi.org/10.5194/bg-13-4389-2016.
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Abstract. In addition to being one of the most productive upwelling systems, the oceanic region off Peru is embedded in one of the most extensive oxygen minimum zones (OMZs) of the world ocean. The dynamics of the OMZ off Peru remain uncertain, partly due to the scarcity of data and to the ubiquitous role of mesoscale activity on the circulation and biogeochemistry. Here we use a high-resolution coupled physical/biogeochemical model simulation to investigate the seasonal variability of the OMZ off Peru. The focus is on characterizing the seasonal cycle in dissolved O2 (DO) eddy flux at the OMZ boundaries, including the coastal domain, viewed here as the eastern boundary of the OMZ, considering that the mean DO eddy flux in these zones has a significant contribution to the total DO flux. The results indicate that the seasonal variations of the OMZ can be interpreted as resulting from the seasonal modulation of the mesoscale activity. Along the coast, despite the increased seasonal low DO water upwelling, the DO peaks homogeneously over the water column and within the Peru Undercurrent (PUC) in austral winter, which results from mixing associated with the increase in both the intraseasonal wind variability and baroclinic instability of the PUC. The coastal ocean acts therefore as a source of DO in austral winter for the OMZ core, through eddy-induced offshore transport that is also shown to peak in austral winter. In the open ocean, the OMZ can be divided vertically into two zones: an upper zone above 400 m, where the mean DO eddy flux is larger on average than the mean seasonal DO flux and varies seasonally, and a lower part, where the mean seasonal DO flux exhibits vertical–zonal propagating features that share similar characteristics than those of the energy flux associated with the annual extratropical Rossby waves. At the OMZ meridional boundaries where the mean DO eddy flux is large, the DO eddy flux has also a marked seasonal cycle that peaks in austral winter (spring) at the northern (southern) boundary. In the model, the amplitude of the seasonal cycle is 70 % larger at the southern boundary than at the northern boundary. Our results suggest the existence of distinct seasonal regimes for the ventilation of the OMZ by eddies at its boundaries. Implications for understanding the OMZ variability at longer timescales are discussed.
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Shakirov, R. B., A. V. Yatsuk, G. I. Mishukova, A. I. Obzhirov, I. G. Yugai, Nguyen Hon Lan y Do Huy Cuong. "About the methane flux into the atmosphere in the South-China sea". Доклады Академии наук 486, n.º 1 (10 de mayo de 2019): 103–7. http://dx.doi.org/10.31857/s0869-56524861103-107.
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The new results of gasgeochemical studies in the integrated expedition of the Russian Academy of Sciences on R/V “Akademik Boris Petrov” (Cruise 42) along the regional profile (3180 km) in the South China Sea (Bien Dong) from January 10-16, 2017 are presented. The expedition conducted in the frame of the Second International Indian Ocean Expedition (IIOE-2). For the first time, five zones of increased methane fluxes were detected. Zones with maximum values of methane fluxes correlate well with the location of hydrocarbon deposits and tectonic faults.
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Rey-Sanchez, Camilo, Gil Bohrer, Julie Slater, Yueh-Fen Li, Roger Grau-Andrés, Yushan Hao, Virginia I. Rich y G. Matt Davies. "The ratio of methanogens to methanotrophs and water-level dynamics drive methane transfer velocity in a temperate kettle-hole peat bog". Biogeosciences 16, n.º 16 (29 de agosto de 2019): 3207–31. http://dx.doi.org/10.5194/bg-16-3207-2019.
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Abstract. Peatlands are a large source of methane (CH4) to the atmosphere, yet the uncertainty around the estimates of CH4 flux from peatlands is large. To better understand the spatial heterogeneity in temperate peatland CH4 emissions and their response to physical and biological drivers, we studied CH4 dynamics throughout the growing seasons of 2017 and 2018 in Flatiron Lake Bog, a kettle-hole peat bog in Ohio. The site is composed of six different hydro-biological zones: an open water zone, four concentric vegetation zones surrounding the open water, and a restored zone connected to the main bog by a narrow channel. At each of these locations, we monitored water level (WL), CH4 pore-water concentration at different peat depths, CH4 fluxes from the ground and from representative plant species using chambers, and microbial community composition with a focus here on known methanogens and methanotrophs. Integrated CH4 emissions for the growing season were estimated as 315.4±166 mgCH4m-2d-1 in 2017 and 362.3±687 mgCH4m-2d-1 in 2018. Median CH4 emission was highest in the open water, then it decreased and became more variable through the concentric vegetation zones as the WL dropped, with extreme emission hotspots observed in the tamarack mixed woodlands (Tamarack) and low emissions in the restored zone (18.8–30.3 mgCH4m-2d-1). Generally, CH4 flux from above-ground vegetation was negligible compared to ground flux (<0.4 %), although blueberry plants were a small CH4 sink. Pore-water CH4 concentrations varied significantly among zones, with the highest values in the Tamarack zone, close to saturation, and the lowest values in the restored zone. While the CH4 fluxes and pore-water concentrations were not correlated with methanogen relative abundance, the ratio of methanogens to methanotrophs in the upper portion of the peat was significantly correlated to CH4 transfer velocity (the CH4 flux divided by the difference in CH4 pore-water concentration between the top of the peat profile and the concentration in equilibrium with the atmosphere). Since ebullition and plant-mediated transport were not important sources of CH4 and the peat structure and porosity were similar across the different zones in the bog, we conclude that the differences in CH4 transfer velocities, and thus the flux, are driven by the ratio of methanogen to methanotroph relative abundance close to the surface. This study illustrates the importance of the interactions between water-level and microbial composition to better understand CH4 fluxes from bogs and wetlands in general.
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Abu Talib, Abd Rahim, Andrew J. Neely, Peter T. Ireland y Andrew J. Mullender. "Detailed Investigation of Heat Flux Measurements Made in a Standard Propane-Air Fire-Certification Burner Compared to Levels Derived From a Low-Temperature Analog Burner". Journal of Engineering for Gas Turbines and Power 127, n.º 2 (1 de abril de 2005): 249–56. http://dx.doi.org/10.1115/1.1806454.
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This paper presents detailed heat flux measurements on a flat plate subjected to the ISO2685 [The International Organization for Standardization (ISO), 1992, “Aircraft—Environmental Conditions and Test Procedures for Airborne Equipment—Resistance to Fire in Designated Fire Zones,” ISO2685:1992(E)] standard, propane fueled burner used throughout the industry in aero-engine fire-certification. The authors have developed a custom-built heat transfer gauge to measure the heat flux from the burner under isothermal wall conditions. The heat flux from the standard burner is normally calibrated using either a water-cooled copper tube or a Gardon gauge, each sited at a single position in the flame. There are no reports in the literature of a detailed survey of heat flux distribution for the burner and the results are of considerable interest to engineers involved in fire-certification. The reported measurements constitute the first, detailed distribution of heat flux from the actual burner flame during a fire test. These measurements provided benchmark data which allowed the heat flux distribution from the ISO burner to be compared to levels derived from the low-temperature analog burner developed by the authors. The analog burner uses liquid crystals to measure heat transfer coefficient and adiabatic wall temperature on scale models of engine components and provides key data to facilitate the successful design of components used in fire zones. The objective of this paper is to further validate the low-temperature analog burner technique developed by the authors which simulates the standard large propane-air burner for fire-certification in aero engine.
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Kurazhkovskii, A. Yu, A. Yu Kazansky, A. A. Shchetnikov, T. A. Blyakharchuk y D. A. Philippov. "Studying the dynamics of cosmic dust flux on the earth’s surface from peat deposits". Физика Земли, n.º 3 (10 de mayo de 2019): 150–60. http://dx.doi.org/10.31857/s0002-333720193150-160.
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Peat cores sampled from different climatic zones are studied. The petromagnetic and microprobe methods are used to find peat layers enriched with cosmic dust. It is established that the behavior of saturation isothermal remanent magnetization (SIRM) of peat deposits from the zones where the aeolian transfer of terrigenous particles is negligible can be used for studying the dynamics of the fall of cosmic matter on the Earth’s surface. The cosmic dust flux can be conditionally divided into the background and burst components. Here, the background flux of cosmic dust varies cyclically. The characteristic times of these cycles are about 100 years. The cyclicity in the background flux of cosmic material most clearly manifested itself in the interval of 1200 to 500 years ago. The most significant burst in the influx of cosmic material (by an order of magnitude above the background) is revealed in the layer that was formed about 5000 years ago. The microprobe studies established that the mineralogical content of cosmic dust differs between the background and burst fluxes.
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NIU, Xiaodong. "A dataset of carbon and water fluxes in a natural oak forest of Baotianman in Henan Province (2017-2018)". China Scientific Data 8, n.º 4 (31 de diciembre de 2023): 1–5. http://dx.doi.org/10.11922/11-6035.csd.2023.0124.zh.
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Using the eddy covariance flux observation technique based on micrometeorology theory, we directly measured the functions and processes of the productivity, energy partitioning and water use of natural oak forest ecosystems at a transitional area between subtropical and warm temperate zones, which can provide an important data basis for studying the mechanism of carbon and water cycle in forest ecosystems. This study focused on a natural oak forest located at the Baotianman Ecological Research Station. We employed a combination of the eddy covariance system and an environmental gradient system for long-term and continuous observations, and we further organized, quality-controlled, and analyzed the monitoring data collected from January 2017 to December 2018. The dataset includes various data variables, such as air temperature and humidity, soil temperature and humidity, wind speed, wind direction, photosynthetically active radiation, upward/downward shortwave radiation, upward/downward longwave radiation, net radiation, sensible heat flux, latent heat flux and carbon flux. The dataset is composed of the observation data on half-hourly, daily monthly, and yearly scales. It is expected to provide a database for studying the response and adaption mechanisms of typical forest ecosystems to climate change in transitional areas between subtropical and warm temperate zones.
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Wasson, J. G., J. L. Guyot y H. Sanejouand. "Premières données concernant le Carbone Organique transporté par le Rio Desaguadero (Altiplano Bolivien)". Revue des sciences de l'eau 4, n.º 3 (12 de abril de 2005): 363–79. http://dx.doi.org/10.7202/705105ar.
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Le Rio Desaguadero relie le lac Titicaca (alt. 3 810 m) au lac Poopo (alt. 3 670 m) dans le bassin endoréique de l'Altiplano, en Bolivie, (fig. 1). Le bassin versant est constitué de terrains sédimentaires et volcaniques, avec une végétation steppique et aucune source de pollution organique. Le climat très variable présente d'une alternance de saisons humide et sèche. Le Rio Mauri fournit 90 % du flux de MES estimé à 6,6.106 t an-1 (d'après GUYOT et al., 1990). Des analyses de COT et d'autres paramètres chimiques ont été réalisées sur 15 stations en 3 campagnes (fig. 2 et tableau 1). Une ACP (fig. 3) révèle une corrélation entre COT et MES, correspondant à deux épisodes de crues (déc. 87 et fév. 88) (tableau 2). Des hypothèses concernant l'origine du carbone organique et les flux sont avancées (tableau 3). Un flux de base, principalement du COD provenant du lac Titicaca, représenterait 18 000 t an-1. Mais le COP, quoique fortement corrélé aux MES, n'a pas la même origine que celles-ci (fig. 4); il proviendrait principalement des zones connexes au Rio Desaguadero riches en végétation aquatique. La contribution de ces flux aux bilans du carbone organique paraît négligeable pour le lac Titicaca et peu importante pour le lac Poopo. Mais le maintien des interconnexions entre le Rio Desaguadero et ses zones humides doit être intégré dans les projets d'aménagement.
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CORDIER, STEPHANE. "HYPERBOLICITY OF GRAD’S EXTENSION OF HYDRODYNAMIC MODELS FOR IONOSPHERIC PLASMA PART I: THE SINGLE SPECIES CASE". Mathematical Models and Methods in Applied Sciences 04, n.º 05 (octubre de 1994): 625–45. http://dx.doi.org/10.1142/s0218202594000352.
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We present the fluid equations derived by Schunck following Grad’s approach to solve Boltzmann equation for near Maxwellian distribution functions. We study the hyperbolic part of these systems usually referred to as five-, eight-, 10-, 13- and 16-moment approximation. We show that the hyperbolicity of the systems involving the heat flux as an independent variable always requires a limitation on the heat flux. This limitation fails in the auroral ionospheric zones for the terrestrial plasma.
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Küker, Manfred y Günther Rüdiger. "Differential rotation and meridional flows in stellar convection zones". Proceedings of the International Astronomical Union 9, S302 (agosto de 2013): 194–95. http://dx.doi.org/10.1017/s174392131400204x.
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AbstractDifferential rotation and meridional flow are key ingredients in flux transport dynamo models of the solar activity cycle. As the subsurface flow pattern is not sufficiently constrained by observations, it is a major source of uncertainty in solar and stellar dynamo models. We discuss the current mean field theory of stellar differential rotation and meridional flows and its predicitons for the Sun and stars on the lower main sequence.
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BOP, Ibra, Lansana SANE, Seydou Nourou DIOP y Biram Dieng. "THEORICAL INVESTIGATION ON THE EFFECTS OF THE FIN-TUBE CONTACT ZONES ON THE EXCHANGED CONVECTIVE HEAT FLUX BETWEEN A FINNED-TUBE AIR-COOLED CONDENSER AND ITS SURROUNDING ENVIRONMENT". International Journal of Advanced Research 11, n.º 08 (31 de agosto de 2023): 352–66. http://dx.doi.org/10.21474/ijar01/17398.
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Adding fins on the tubes of an air-cooled condenser allows to increase its heat transfer area.The purpose of this work is to investigate on the effects of the tube-fin contact zones on thecondenserconvectiveheattransferwiththesurroundingair.Itproposesamethodofdetermining the condenser outer surface and a ratio which compares the losses to the heat fluxgainsduetotheinputoffins.Thisratiocharacterizestheinfluenceofthefin-tubecontactzoneson the exchanged convective heat flux and informs whether or not their effect has to be takeninto account. The developed model allowed to obtain relations which give the condensereffective exchange outer surface which participates to convective heat transfers. The obtainedresults using Matlab software show that the ratio of the losses to the heat flux gains does notdepend on the number of fins. However, it increases with the number of tubes, with their outerdiameterandwiththefinthickness.Itisfoundthat,whenthisratioislessthan0.026,theeffectsof the fin-tube contact zones on the condenser convective heat transfer can be neglected.Otherwise,theseeffectshavetobetakenintoaccountwhendeterminingthecondenserexchanged heat fluxwith its outer environment.
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Zhu, J., L. Shu, C. Lu, J. Li, S. Chen, S. Li y G. Wang. "Study of heterogeneous vertical hyporheic flux via streambed temperature at different depths". Proceedings of the International Association of Hydrological Sciences 368 (6 de mayo de 2015): 168–73. http://dx.doi.org/10.5194/piahs-368-168-2015.
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Abstract. The hyporheic flux can be characterized using the heat-tracing method. Based on the analytical solution of the one-dimensional steady-state heat transport equation under vertical groundwater discharge conditions, hyporheic flux was obtained via a curve fitting method. The temperature data used was obtained from monitoring three different sections of the DaWen River, Shandong Province. The distribution of the depth of the hyporheic zone was analysed by a curve relating groundwater temperature and the depth of the hyporheic zone. The study results showed that the vertical hyporheic flux was significantly heterogeneous along the three sections. The hyporheic flux ranged from 99.61 to 356.25 L/m2 per day. In the summer, the low temperature area on streambed profile was in accordance with the high value areas of hyporheic flux. There were several strong discharge zones within the same section and these flux values were normally distributed. The depth of the hyporheic zone was inversely proportional to the hyporheic flux and the hyporheic zone depth, also, presented great spatial heterogeneity.
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Kalitov, M. A. y N. P. Kornyshev. "Mathematical description of the processes of synthesis of digital multispectral images". Journal of Physics: Conference Series 2052, n.º 1 (1 de noviembre de 2021): 012018. http://dx.doi.org/10.1088/1742-6596/2052/1/012018.
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Abstract The article discusses the features of the formation of digital multispectral images corresponding to narrow registration zones. The processes of signal transformations are analyzed during the synthesis of such images from the original multispectral images with overlapping spectral flux registration zones. Questions of the mathematical description of the differential and multiplicative method for the synthesis of spectrozonal images are discussed. Analytical expressions are given that correspond to signal transformations of the original digital multispectral images in their differential and multiplicative synthesis.
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Li, Yong, Na Li, Jiacheng Feng, Jianing Qian y Yajie Shan. "Temporal Temperature Distribution in Shallow Sediments of a Large Shallow Lake and Estimated Hyporheic Flux Using VFLUX 2 Model". Water 13, n.º 3 (26 de enero de 2021): 300. http://dx.doi.org/10.3390/w13030300.
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Identifying and quantifying exchange flux across sediment-water interface is crucial when considering water and nutrient contributions to a eutrophic lake. In this study, observed temporal temperature distributions in shallow sediment of Lake Taihu (Eastern China) based on three-depth sensors at 14 sites throughout 2016 were used to assess temporal water exchange patterns. Results show that temporal temperature in shallow sediments differed with sampling sites and depths and the temperature amplitudes also clearly shrunk as the offshore distance increasing. Exchange fluxes estimated using the VFLUX 2 model based on temperature amplitude show that alternating-direction temporal flow exists in the eastern zone of Lake Taihu with averages of −13.0, −0.6, and 3.4 mm day−1 (negative represents discharging into the lake) at three nearshore sites (0.5, 2.0, and 6.0 km away from the shoreline, respectively). Whereas downwelling flow occurred throughout almost the entire year with averages of 37.7, 23.5, and 6.6 mm day−1 at the three southern nearshore sites, respectively. However, upwelling flow occurred throughout almost the entire year and varied widely in the western zone with averages of −74.8, 45.9, and −27.0 mm day–1 and in the northern zone with averages of −76.2, −55.3, and −51.1 mm day−1. The estimated fluxes in the central zone were relatively low and varied slightly during the entire year (−15.1 to 22.5 mm day−1 with an average of −0.7 mm day−1). Compared with the sub sensor pair (at 5 and 10 cm), the estimated hyporheic fluxes based on the top sensor pair (at 0 and 5 cm) varied within wider ranges and exhibited relatively larger values. Effects of upwelling flow at the western and northern zones need to be paid attention to on nearshore water quality particularly during winter and spring seasons. Estimated flow patterns at the four zones summarily reflect the seasonal water interaction near the sediment surface of Lake Taihu and are beneficial to improve its comprehensive management. Thermal dispersivity usually used for estimating the thermal diffusivity is more sensitive for upward hyporheic flux estimating even if with a low flux. Temperature amplitude ratio method can be used to estimate the exchange flux and suitable for low flux conditions (either upwelling or downwelling). A better evaluation of the exchange flux near inclined nearshore zones might need an optimized installation of temperature sensors along with the potential flow path and/or a vertical two-dimensional model in the future.
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Langhirt, Mark A., Charles W. Holland, Ying-Tsong Lin, Sheri Martinelli y Daniel C. Brown. "Implementation and validation of a three-dimensional semi-coherent energy flux model for underwater acoustic propagation". Journal of the Acoustical Society of America 152, n.º 4 (octubre de 2022): A291. http://dx.doi.org/10.1121/10.0016316.
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The energy flux method uses a continuum of adiabatic Wentzel–Kramers–Brillouin modes to integrate intensity directly as a function of propagation angle. Work published a decade ago extended the energy flux method to include semi-coherent interference between neighboring modes to capture convergence zones. This study seeks to generalize the energy flux method to three-dimensional inhomogeneous underwater environments by converting a cross-product of double mode-sums to a double integration over solid angle. Theoretical derivations for a proof of concept model were presented previously, and current work has been focused on the numerical implementation of the model. Model validation will be discussed with comparisons to analytical solutions and other three-dimensional underwater acoustic propagation models.
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Kruegler, James, Jesus Gomez-Velez, Laura K. Lautz y Theodore A. Endreny. "Dynamic Evapotranspiration Alters Hyporheic Flow and Residence Times in the Intrameander Zone". Water 12, n.º 2 (5 de febrero de 2020): 424. http://dx.doi.org/10.3390/w12020424.
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Hyporheic zones (HZs) influence biogeochemistry at the local reach scale with potential implication for water quality at the large catchment scale. The characteristics of the HZs (e.g., area, flux rates, and residence times) change in response to channel and aquifer physical properties, as well as to transient perturbations in the stream–aquifer system such as floods and groundwater withdraws due to evapotranspiration (ET) and pumping. In this study, we use a numerical model to evaluate the effects of transient near-stream evapotranspiration (ET) on the area, exchange flux, and residence time (RT) of sinuosity-induced HZs modulated by regional groundwater flow (RGF). We found that the ET fluxes (up to 80 mm/day) consistently increased HZ area and exchange flux, and only increased RTs when the intensity of regional groundwater flow was low. Relative to simulations without ET, scenarios with active ET had more than double HZ area and exchange flux and about 20% longer residence times (as measured by the median of the residence time distribution). Our model simulations show that the drawdown induced by riparian ET increases the net flux of water from the stream to the nearby aquifer, consistent with field observations. The results also suggest that, along with ET intensity, the magnitude of the HZ response is influenced by the modulating effect of both gaining and losing RGF and the sensitivity of the aquifer to daily cycles of ET withdrawal. This work highlights the importance of representing near-stream ET when modeling sinuosity-induced hyporheic zones, as well as the importance of including riparian vegetation in efforts to restore the ecosystem functions of streams.
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Işik, Emre. "Stellar activity cycles in a model for magnetic flux generation and transport". Proceedings of the International Astronomical Union 7, S286 (octubre de 2011): 291–95. http://dx.doi.org/10.1017/s1743921312004991.
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AbstractWe present results from a model for magnetic flux generation and transport in cool stars and a qualitative comparison of models with observations. The method combines an αΩ-type dynamo at the base of the convection zone, buoyant rise of magnetic flux tubes, and a surface flux transport model. Based on a reference model for the Sun, numerical simulations were carried out for model convection zones of G- and K-type main sequence and subgiant stars. We investigate magnetic cycle properties for stars with different rotation periods, convection zone depths, and dynamo strengths. For a Sun-like star with Prot=9 d, we find that a cyclic dynamo can underly an apparently non-cyclic, ‘flat’ surface activity, as observed in some stars. For a subgiant K1 star with Prot=2.8 d the long-term activity variations resemble the multi-periodic cycles observed in V711 Tau, owing to high-latitude flux emergence, weak transport effects and stochastic processes of flux emergence.
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Bobylev, Pavel G., Andrey V. Pavlov, Vyacheslav M. Proskurin, Yuriy V. Andreyev, Vladimir Yu Mityakov y Sergey Z. Sapozhnikov. "Gradient Heatmetry in a Burners Adjustment". Inventions 7, n.º 4 (13 de diciembre de 2022): 122. http://dx.doi.org/10.3390/inventions7040122.
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Measuring the heat flux in the furnace of industrial boilers is an urgent task in the power industry. Installing the measuring instruments directly into the furnace is a laborious and complex process. It requires a complete shutdown of the boiler, which incurs economic costs. It is most efficient to use portable probes with measuring insert. The created cooled probe with a heterogeneous gradient heat flux sensor is a unique and versatile tool that allows for the configuration and control of the operation of power boilers. This article compares experimental values with calculation methods. The obtained heat flux per unit area is in good agreement with the theoretical concepts when the values are averaged. The technique used in this paper makese it possible to determine the maximum heat-stressed zones and areas with stable or unstable combustion. The main combustion zones that are typical for the flaring of any fuel are identified. This approach allows us to consider various approaches to heat transfer enhancement during the combustion of both liquid and gaseous fuels. Comparison of experimental results with the data of other authors is not quite exact due to the complexity of the experiment. The study of burners in this configuration has not previously been considered in the literature.
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HURTHER, D., U. LEMMIN y E. A. TERRAY. "Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)". Journal of Fluid Mechanics 574 (15 de febrero de 2007): 465–93. http://dx.doi.org/10.1017/s0022112006004216.
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Acoustic Doppler velocity profiler (ADVP) measurements of instantaneous three-dimensional velocity profiles over the entire turbulent boundary layer height, δ, of rough-bed open-channel flows at moderate Reynolds numbers show the presence of large scale coherent shear stress structures (called LC3S herein) in the zones of uniformly retarded streamwise momentum. LC3S events over streamwise distances of several boundary layer thicknesses dominate the mean shear dynamics. Polymodal histograms of short streamwise velocity samples confirm the subdivision of uniform streamwise momentum into three zones also observed by Adrian et al. (J. Fluid Mech., vol. 422, 2000, p. 1). The mean streamwise dimension of the zones varies between 1δ and 2.5δ. In the intermediate region (0.2<z/δ<0.75), the contribution of conditionally sampled u'w' events to the mean vertical turbulent kinetic energy (TKE) flux as a function of threshold level H is found to be generated by LC3S events above a critical threshold level Hmax for which the ascendant net momentum flux between LC3S of ejection and sweep types is maximal. The vertical profile of Hmax is nearly constant over the intermediate region, with a value of 5 independent of the flow conditions. Very good agreement is found for all flow conditions including the free-stream shear flows studied in Adrian et al. (2000). If normalized by the squared bed friction velocity, the ascendant net momentum flux containing 90% of the mean TKE flux is equal to 20% of the shear stress due to bed friction. In the intermediate region this value is nearly constant for all flow conditions investigated herein. It can be deduced that free-surface turbulence in open-channel flows originates from processes driven by LC3S, associated with the zonal organization of streamwise momentum. The good agreement with mean quadrant distribution results in the literature implies that LC3S identified in this study are common features in the outer region of shear flows.
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Du, Changmin, Shouzheng Jiang, Chuqiang Chen, Qianyue Guo, Qingyan He y Cun Zhan. "Machine Learning-Based Estimation of Daily Cropland Evapotranspiration in Diverse Climate Zones". Remote Sensing 16, n.º 5 (20 de febrero de 2024): 730. http://dx.doi.org/10.3390/rs16050730.
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The accurate prediction of cropland evapotranspiration (ET) is of utmost importance for effective irrigation and optimal water resource management. To evaluate the feasibility and accuracy of ET estimation in various climatic conditions using machine learning models, three-, six-, and nine-factor combinations (V3, V6, and V9) were examined based on the data obtained from global cropland eddy flux sites and Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data. Four machine learning models, random forest (RF), support vector machine (SVM), extreme gradient boosting (XGB), and backpropagation neural network (BP), were used for this purpose. The input factors included daily mean air temperature (Ta), net radiation (Rn), soil heat flux (G), evaporative fraction (EF), leaf area index (LAI), photosynthetic photon flux density (PPFD), vapor pressure deficit (VPD), wind speed (U), and atmospheric pressure (P). The four machine learning models exhibited significant simulation accuracy across various climate zones, reflected by their global performance indicator (GPI) values ranging from −3.504 to 0.670 for RF, −3.522 to 1.616 for SVM, −3.704 to 0.972 for XGB, and −3.654 to 1.831 for BP. The choice of suitable models and the different input factors varied across different climatic regions. Specifically, in the temperate–continental zone (TCCZ), subtropical–Mediterranean zone (SMCZ), and temperate zone (TCZ), the models of BPC-V9, SVMS-V6, and SVMT-V6 demonstrated the highest simulation accuracy, with average RMSE values of 0.259, 0.373, and 0.333 mm d−1, average MAE values of 0.177, 0.263, and 0.248 mm d−1, average R2 values of 0.949, 0.819, and 0.917, and average NSE values of 0.926, 0.778, and 0.899, respectively. In climate zones with a lower average LAI (TCCZ), there was a strong correlation between LAI and ET, making LAI more crucial for ET predictions. Conversely, in climate zones with a higher average LAI (TCZ, SMCZ), the significance of the LAI for ET prediction was reduced. This study recognizes the impact of climate zones on ET simulations and highlights the necessity for region-specific considerations when selecting machine learning models and input factor combinations.
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Ludwig, W., S. Eggl, D. Neubauer, J. Leitner, M. G. Firneis y R. Hitzenberger. "Effective stellar flux calculations for limits of life-supporting zones of exoplanets". Monthly Notices of the Royal Astronomical Society 458, n.º 4 (7 de marzo de 2016): 3752–59. http://dx.doi.org/10.1093/mnras/stw509.
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Salvatierra, L. M., O. A. Lambri, C. L. Matteo, P. A. Sorichetti, C. A. Celauro y R. E. Bolmaro. "Growing of crystalline zones in EPDM irradiated with a low neutron flux". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 225, n.º 3 (septiembre de 2004): 297–304. http://dx.doi.org/10.1016/j.nimb.2004.04.166.
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