Updated Magmatic Flux Rate Estimates for the Hawaii Plume

Science.gov (United States)

Wessel, P.

2013-12-01

Several studies have estimated the magmatic flux rate along the Hawaiian-Emperor Chain using a variety of methods and arriving at different results. These flux rate estimates have weaknesses because of incomplete data sets and different modeling assumptions, especially for the youngest portion of the chain (little or no quantification of error estimates for the inferred melt flux, making an assessment problematic. Here we re-evaluate the melt flux for the Hawaii plume with the latest gridded data sets (SRTM30+ and FAA 21.1) using several methods, including the optimal robust separator (ORS) and directional median filtering techniques (DiM). We also compute realistic confidence limits on the results. In particular, the DiM technique was specifically developed to aid in the estimation of surface loads that are superimposed on wider bathymetric swells and it provides error estimates on the optimal residuals. Confidence bounds are assigned separately for the estimated surface load (obtained from the ORS regional/residual separation techniques) and the inferred subsurface volume (from gravity-constrained isostasy and plate flexure optimizations). These new and robust estimates will allow us to assess which secondary features in the resulting melt flux curve are significant and should be incorporated when correlating melt flux variations with other geophysical and geochemical observations.

Interpretation of the measurement of ions fluxes through a biological membrane with a cellular compartment: example of the movements of sodium through the skin of frogs; Interpretation de la mesure des flux d'ions a travers une membrane biologique comportant un ''compartiment'' cellulaire; exemple des mouvements de sodium a travers la peau de grenouille

Energy Technology Data Exchange (ETDEWEB)

Morel, F [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Two-way ion fluxes which can be measured in vitro through a living epithelial membrane (such as frog skin) by the indicator method take place across the cells which behave like an intermediate ionic 'compartment'. Two membranes and four fluxes have thus to be considered. Measurements in vitro of the total sodium fluxes as a function of the sodium concentration in the medium in contact with the external face of the skin have been interpreted in this spirit. Making use of certain hypotheses, the permeability coefficients for sodium of the two cellular membranes, the four sodium fluxes, the intracellular sodium concentration and the membrane potentials have been calculated for each value of the sodium concentration in the external medium. (author) [French] Les flux ioniques bidirectionnels que l'on peut mesurer in vitro a travers une membrane epitheliale vivante (comme la peau de grenouille) a l'aide de la methode des indicateurs, s'effectuent a travers les cellules qui se comportent comme un 'compartiment' ionique intermediaire. On doit donc considerer deux membranes et quatre flux. Des mesures in vitro des flux totaux de sodium en fonction de la concentration du sodium dans le milieu baignant la face externe de la peau ont ete interpretees dans cette perspective. Moyennant certaines hypotheses, les coefficients de permeabilite pour le sodium des deux membranes cellulaires, les quatre flux de sodium ainsi que la concentration du sodium intracellulaire et les potentiels de membrane ont pu etre calcules pour chaque valeur de la concentration du sodium dans le milieu externe. (auteur)

Estimations hypoelliptiques globales et compacit\\'e de la r\\'esolvante Estimations hypoelliptiques globales et compacit\\'e de la r\\'esolvante pour des op\\'erateurs de Fokker-Planck ou des laplaciens de Witten

CERN Document Server

Helffer, B

2004-01-01

Ces derni\\`eres ann\\'ees, les estimations hypoelliptiques ont connu une nouvelle jeunesse en liaison avec des questions provenant de la th\\'eorie cin\\'etique des gaz. Dans cette direction de nombreux auteurs ont en effet eu besoin de d\\'emontrer des estimations maximales pour en d\\'eduire la compacit\\'e de l'op\\'erateur de Fokker-Planck et avoir des estimations sur la r\\'esolvante permettant d'aborder la question du retour \\`a l'\\'equilibre. Dans un article tr\\`es r\\'ecent, F.~H\\'erau et F.~Nier (inspir\\'es par des calculs explicites du livre de Risken) ont mis en \\'evidence les liens \\'etroits entre ces questions et des questions analogues pour un laplacien de Witten. L'\\'etude de ces liens est poursuivie et syst\\'ematis\\'ee dans un livre en pr\\'eparation \\'ecrit en collaboration avec F.~Nier dont nous allons pr\\'esenter quelques aspects ici en pr\\'esentant parfois un \\'eclairage diff\\'erent sur un probl\\`eme qui laisse encore beaucoup de conjectures non r\\'esolues.

Greenhouse gases regional fluxes estimated from atmospheric measurements; Estimation des flux de gaz a effet de serre a l'echelle regionale a partir de mesures atmospheriques

Energy Technology Data Exchange (ETDEWEB)

Messager, C

2007-07-15

build up a new system to measure continuously CO{sub 2} (or CO), CH{sub 4}, N{sub 2}O and SF{sub 6} mixing ratios. It is based on a commercial gas chromatograph (Agilent 6890N) which have been modified to reach better precision. Reproducibility computed with a target gas on a 24 hours time step gives: 0.06 ppm for CO{sub 2}, 1.4 ppb for CO, 0.7 ppb for CH{sub 4}, 0.2 ppb for N{sub 2}O and 0.05 ppt for SF{sub 6}. The instrument's run is fully automated, an air sample analysis takes about 5 minutes. In July 2006, I install instrumentation on a telecommunication tall tower (200 m) situated near Orleans forest in Trainou, to monitor continuously greenhouse gases (CO{sub 2}, CH{sub 4}, N{sub 2}O, SF{sub 6}), atmospheric tracers (CO, Radon-222) and meteorological parameters. Intake lines were installed at 3 levels (50, 100 and 180 m) and allow us to sample air masses along the vertical. Continuous measurement started in January 2007. I used Mace Head (Ireland) and Gif-sur-Yvette continuous measurements to estimate major greenhouse gases emission fluxes at regional scale. To make the link between atmospheric measurements and surface fluxes, we need to quantify dilution due to atmospheric transport. I used Radon-222 as tracer (radon tracer method) and planetary boundary layer heights estimates from ECMWF model (boundary layer budget method) to parameterize atmospheric transport. In both cases I compared results to available emission inventories. (author)

Estimation of Lithofacies Proportions Using Well and Well Test Data Estimation des proportions lithologiques à partir des données de puits et d'essais de puits

Directory of Open Access Journals (Sweden)

Blanc G.

2006-12-01

Full Text Available A crucial step of the two commonly used geostatistical methods for modeling heterogeneous reservoirs : the sequential indicator simulation and the truncated Gaussian simulation is the estimation of the lithofacies local proportion (or probability density functions. Well-test derived permeabilities show good correlation with lithofacies proportions around wells. Integrating well and well-test data in estimating lithofacies proportions could permit the building of more realistic models of reservoir heterogeneity. However this integration is difficult because of the different natures and measurement scales of these two types of data. This paper presents a two step approach to integrating well and well-test data into heterogeneous reservoir modeling. First lithofacies proportions in well-test investigation areas are estimated using a new kriging algorithm called KISCA. KISCA consists in kriging jointly the proportions of all lithofacies in a well-test investigation area so that the corresponding well-test derived permeability is respected through a weighted power averaging of lithofacies permeabilities. For multiple well-tests, an iterative process is used in KISCA to account for their interaction. After this, the estimated proportions are combined with lithofacies indicators at wells for estimating proportion (or probability density functions over the entire reservoir field using a classical kriging method. Some numerical examples were considered to test the proposed method for estimating lithofacies proportions. In addition, a synthetic lithofacies reservoir model was generated and a well-test simulation was performed. The comparison between the experimental and estimated proportions in the well-test investigation area demonstrates the validity of the proposed method. La méthode de simulation gaussienne seuillée et la méthode de simulation séquentielle d'indicatrices sont aujourd'hui couramment utilisées pour générer des mod

Estimating surface fluxes using eddy covariance and numerical ogive optimization

DEFF Research Database (Denmark)

Sievers, J.; Papakyriakou, T.; Larsen, Søren Ejling

2015-01-01

Estimating representative surface fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modelling efforts, low-frequency con......Estimating representative surface fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modelling efforts, low...

Modern Estimates of Global Water Cycle Fluxes

Science.gov (United States)

Rodell, M.; Beaudoing, H. K.; L'Ecuyer, T. S.; Olson, W. S.

2014-12-01

The goal of the first phase of the NASA Energy and Water Cycle Study (NEWS) Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. Here we describe results of the water cycle assessment, including mean annual and monthly fluxes over continents and ocean basins during the first decade of the millennium. To the extent possible, the water flux estimates are based on (1) satellite measurements and (2) data-integrating models. A careful accounting of uncertainty in each flux was applied within a routine that enforced multiple water and energy budget constraints simultaneously in a variational framework, in order to produce objectively-determined, optimized estimates. Simultaneous closure of the water and energy budgets caused the ocean evaporation and precipitation terms to increase by about 10% and 5% relative to the original estimates, mainly because the energy budget required turbulent heat fluxes to be substantially larger in order to balance net radiation. In the majority of cases, the observed annual, surface and atmospheric water budgets over the continents and oceans close with much less than 10% residual. Observed residuals and optimized uncertainty estimates are considerably larger for monthly surface and atmospheric water budget closure, often nearing or exceeding 20% in North America, Eurasia, Australia and neighboring islands, and the Arctic and South Atlantic Oceans. The residuals in South America and Africa tend to be smaller, possibly because cold land processes are a non-issue. Fluxes are poorly observed over the Arctic Ocean, certain seas, Antarctica, and the Australasian and Indonesian Islands, leading to reliance on atmospheric analysis estimates. Other details of the study and future directions will be discussed.

Estimating daytime ecosystem respiration from eddy-flux data

DEFF Research Database (Denmark)

Bruhn, Dan; Mikkelsen, Teis Nørgaard; Herbst, Mathias

2011-01-01

To understand what governs the patterns of net ecosystem exchange of CO2, an understanding of factors influencing the component fluxes, ecosystem respiration and gross primary production is needed. In the present paper, we introduce an alternative method for estimating daytime ecosystem respiration...... based on whole ecosystem fluxes from a linear regression of photosynthetic photon flux density data vs. daytime net ecosystem exchange data at forest ecosystem level. This method is based on the principles of the Kok-method applied at leaf level for estimating daytime respiration. We demonstrate...

Greenhouse gases regional fluxes estimated from atmospheric measurements; Estimation des flux de gaz a effet de serre a l'echelle regionale a partir de mesures atmospheriques

Energy Technology Data Exchange (ETDEWEB)

Messager, C

2007-07-15

build up a new system to measure continuously CO{sub 2} (or CO), CH{sub 4}, N{sub 2}O and SF{sub 6} mixing ratios. It is based on a commercial gas chromatograph (Agilent 6890N) which have been modified to reach better precision. Reproducibility computed with a target gas on a 24 hours time step gives: 0.06 ppm for CO{sub 2}, 1.4 ppb for CO, 0.7 ppb for CH{sub 4}, 0.2 ppb for N{sub 2}O and 0.05 ppt for SF{sub 6}. The instrument's run is fully automated, an air sample analysis takes about 5 minutes. In July 2006, I install instrumentation on a telecommunication tall tower (200 m) situated near Orleans forest in Trainou, to monitor continuously greenhouse gases (CO{sub 2}, CH{sub 4}, N{sub 2}O, SF{sub 6}), atmospheric tracers (CO, Radon-222) and meteorological parameters. Intake lines were installed at 3 levels (50, 100 and 180 m) and allow us to sample air masses along the vertical. Continuous measurement started in January 2007. I used Mace Head (Ireland) and Gif-sur-Yvette continuous measurements to estimate major greenhouse gases emission fluxes at regional scale. To make the link between atmospheric measurements and surface fluxes, we need to quantify dilution due to atmospheric transport. I used Radon-222 as tracer (radon tracer method) and planetary boundary layer heights estimates from ECMWF model (boundary layer budget method) to parameterize atmospheric transport. In both cases I compared results to available emission inventories. (author)

Evaluations of carbon fluxes estimated by top-down and bottom-up approaches

Science.gov (United States)

Murakami, K.; Sasai, T.; Kato, S.; Hiraki, K.; Maksyutov, S. S.; Yokota, T.; Nasahara, K.; Matsunaga, T.

2013-12-01

There are two types of estimating carbon fluxes using satellite observation data, and these are referred to as top-down and bottom-up approaches. Many uncertainties are however still remain in these carbon flux estimations, because the true values of carbon flux are still unclear and estimations vary according to the type of the model (e.g. a transport model, a process based model) and input data. The CO2 fluxes in these approaches are estimated by using different satellite data such as the distribution of CO2 concentration in the top-down approach and the land cover information (e.g. leaf area, surface temperature) in the bottom-up approach. The satellite-based CO2 flux estimations with reduced uncertainty can be used efficiently for identifications of large emission area and carbon stocks of forest area. In this study, we evaluated the carbon flux estimates from two approaches by comparing with each other. The Greenhouse gases Observing SATellite (GOSAT) has been observing atmospheric CO2 concentrations since 2009. GOSAT L4A data product is the monthly CO2 flux estimations for 64 sub-continental regions and is estimated by using GOSAT FTS SWIR L2 XCO2 data and atmospheric tracer transport model. We used GOSAT L4A CO2 flux as top-down approach estimations and net ecosystem productions (NEP) estimated by the diagnostic type biosphere model BEAMS as bottom-up approach estimations. BEAMS NEP is only natural land CO2 flux, so we used GOSAT L4A CO2 flux after subtraction of anthropogenic CO2 emissions and oceanic CO2 flux. We compared with two approach in temperate north-east Asia region. This region is covered by grassland and crop land (about 60 %), forest (about 20 %) and bare ground (about 20 %). The temporal variation for one year period was indicated similar trends between two approaches. Furthermore we show the comparison of CO2 flux estimations in other sub-continental regions.

Spectral estimates of net radiation and soil heat flux

International Nuclear Information System (INIS)

Daughtry, C.S.T.; Kustas, W.P.; Moran, M.S.; Pinter, P.J. Jr.; Jackson, R.D.; Brown, P.W.; Nichols, W.D.; Gay, L.W.

1990-01-01

Conventional methods of measuring surface energy balance are point measurements and represent only a small area. Remote sensing offers a potential means of measuring outgoing fluxes over large areas at the spatial resolution of the sensor. The objective of this study was to estimate net radiation (Rn) and soil heat flux (G) using remotely sensed multispectral data acquired from an aircraft over large agricultural fields. Ground-based instruments measured Rn and G at nine locations along the flight lines. Incoming fluxes were also measured by ground-based instruments. Outgoing fluxes were estimated using remotely sensed data. Remote Rn, estimated as the algebraic sum of incoming and outgoing fluxes, slightly underestimated Rn measured by the ground-based net radiometers. The mean absolute errors for remote Rn minus measured Rn were less than 7%. Remote G, estimated as a function of a spectral vegetation index and remote Rn, slightly overestimated measured G; however, the mean absolute error for remote G was 13%. Some of the differences between measured and remote values of Rn and G are associated with differences in instrument designs and measurement techniques. The root mean square error for available energy (Rn - G) was 12%. Thus, methods using both ground-based and remotely sensed data can provide reliable estimates of the available energy which can be partitioned into sensible and latent heat under non advective conditions

Analyse des systèmes de gestion des déchets par l’étude du mécanisme de répartition des déchets

OpenAIRE

Bergeron, Francis

2015-01-01

Le renforcement de l’usage concurrentiel des déchets nous amène à étudier les processus d’approvisionnement des filières de valorisation et d’élimination sous l’angle de la circulation des flux de déchets au sein d’un système de gestion des déchets. L’objectif du présent article de recherche est de concevoir un cadre théorique autour du concept de mécanisme de répartition des déchets qui désigne le processus de distribution des flux de déchets entre les filières d’élimination et de valorisati...

1km Global Terrestrial Carbon Flux: Estimations and Evaluations

Science.gov (United States)

Murakami, K.; Sasai, T.; Kato, S.; Saito, M.; Matsunaga, T.; Hiraki, K.; Maksyutov, S. S.

2017-12-01

Estimating global scale of the terrestrial carbon flux change with high accuracy and high resolution is important to understand global environmental changes. Furthermore the estimations of the global spatiotemporal distribution may contribute to the political and social activities such as REDD+. In order to reveal the current state of terrestrial carbon fluxes covering all over the world and a decadal scale. The satellite-based diagnostic biosphere model is suitable for achieving this purpose owing to observing on the present global land surface condition uniformly at some time interval. In this study, we estimated the global terrestrial carbon fluxes with 1km grids by using the terrestrial biosphere model (BEAMS). And we evaluated our new carbon flux estimations on various spatial scales and showed the transition of forest carbon stocks in some regions. Because BEAMS required high resolution meteorological data and satellite data as input data, we made 1km interpolated data using a kriging method. The data used in this study were JRA-55, GPCP, GOSAT L4B atmospheric CO2 data as meteorological data, and MODIS land product as land surface satellite data. Interpolating process was performed on the meteorological data because of insufficient resolution, but not on MODIS data. We evaluated our new carbon flux estimations using the flux tower measurement (FLUXNET2015 Datasets) in a point scale. We used 166 sites data for evaluating our model results. These flux sites are classified following vegetation type (DBF, EBF, ENF, mixed forests, grass lands, croplands, shrub lands, Savannas, wetlands). In global scale, the BEAMS estimations was underestimated compared to the flux measurements in the case of carbon uptake and release. The monthly variations of NEP showed relatively high correlations in DBF and mixed forests, but the correlation coefficients of EBF, ENF, and grass lands were less than 0.5. In the meteorological factors, air temperature and solar radiation showed

Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments

Science.gov (United States)

Durand, Pierre; Dupuis, HéLèNe; Lambert, Dominique; BéNech, Bruno; Druilhet, Aimé; Katsaros, Kristina; Taylor, Peter K.; Weill, Alain

1998-10-01

Two major campaigns (Surface of the Oceans, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were conducted in 1992 and 1993, respectively, in the Azores region. Among the various platforms deployed, instrumented aircraft and ship allowed the measurement of the turbulent flux of sensible heat, latent heat, and momentum. From coordinated missions we can evaluate the sea surface fluxes from (1) bulk relations and mean measurements performed aboard the ship in the atmospheric surface layer and (2) turbulence measurements aboard aircraft, which allowed the flux profiles to be estimated through the whole atmospheric boundary layer and therefore to be extrapolated toward the sea surface level. Continuous ship fluxes were calculated with bulk coefficients deduced from inertial-dissipation measurements in the same experiments, whereas aircraft fluxes were calculated with eddy-correlation technique. We present a comparison between these two estimations. Although momentum flux agrees quite well, aircraft estimations of sensible and latent heat flux are lower than those of the ship. This result is surprising, since aircraft momentum flux estimates are often considered as much less accurate than scalar flux estimates. The various sources of errors on the aircraft and ship flux estimates are discussed. For sensible and latent heat flux, random errors on aircraft estimates, as well as variability of ship flux estimates, are lower than the discrepancy between the two platforms, whereas the momentum flux estimates cannot be considered as significantly different. Furthermore, the consequence of the high-pass filtering of the aircraft signals on the flux values is analyzed; it is weak at the lowest altitudes flown and cannot therefore explain the discrepancies between the two platforms but becomes

Synthèse des résultats de l'enquête Récoltes et flux de graines - Campagne 2009-2010

OpenAIRE

Brochet, A.; Bilger, I.

2011-01-01

/ Cette note de synthèse présente les résultats de l'enquête statistique annuelle sur les récoltes et flux de graines forestières pour la campagne 2009-2010. Cette campagne a été marquée par des récoltes relativement importantes pour les essences feuillues, avec augmentation de plus de 300% par rapport aux mauvaises récoltes de la campagne précédentes et des récoltes faibles pour les essences résineuses, avec une diminution de 75%. Cette diminution des résineux est à mettre en relation avec ...

Scale aggregation - comparison of flux estimates from NOPEX

DEFF Research Database (Denmark)

Gottschalk, L.; Batchvarova, E.; Gryning, Sven-Erik

1999-01-01

The NOPEX two concentrated field efforts (CFEs) (June 1994 and April-July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes of latent and sensible heat, but these flux...

Pollutant Flux Estimation in an Estuary Comparison between Model and Field Measurements

Directory of Open Access Journals (Sweden)

Yen-Chang Chen

2014-08-01

Full Text Available This study proposes a framework for estimating pollutant flux in an estuary. An efficient method is applied to estimate the flux of pollutants in an estuary. A gauging station network in the Danshui River estuary is established to measure the data of water quality and discharge based on the efficient method. A boat mounted with an acoustic Doppler profiler (ADP traverses the river along a preselected path that is normal to the streamflow to measure the velocities, water depths and water quality for calculating pollutant flux. To know the characteristics of the estuary and to provide the basis for the pollutant flux estimation model, data of complete tidal cycles is collected. The discharge estimation model applies the maximum velocity and water level to estimate mean velocity and cross-sectional area, respectively. Thus, the pollutant flux of the estuary can be easily computed as the product of the mean velocity, cross-sectional area and pollutant concentration. The good agreement between the observed and estimated pollutant flux of the Danshui River estuary shows that the pollutant measured by the conventional and the efficient methods are not fundamentally different. The proposed method is cost-effective and reliable. It can be used to estimate pollutant flux in an estuary accurately and efficiently.

Estimation de la qualité des eaux de la Somme par l'étude des peuplements algaux benthiques

Directory of Open Access Journals (Sweden)

DESCY J. P.

1976-01-01

Full Text Available Une étude de la végétation algale benthique de la Somme, effectuée en septembre 1974, a permis d'établir une estimation de la qualité biologique des eaux de la Somme. La méthode utilisée, mise au point au cours de recherches dans la Meuse et la Sambre belges, est basée sur l'étude quantitative des peuplements de Diatomées benthiques

Annual sediment flux estimates in a tidal strait using surrogate measurements

Science.gov (United States)

Ganju, N.K.; Schoellhamer, D.H.

2006-01-01

Annual suspended-sediment flux estimates through Carquinez Strait (the seaward boundary of Suisun Bay, California) are provided based on surrogate measurements for advective, dispersive, and Stokes drift flux. The surrogates are landward watershed discharge, suspended-sediment concentration at one location in the Strait, and the longitudinal salinity gradient. The first two surrogates substitute for tidally averaged discharge and velocity-weighted suspended-sediment concentration in the Strait, thereby providing advective flux estimates, while Stokes drift is estimated with suspended-sediment concentration alone. Dispersive flux is estimated using the product of longitudinal salinity gradient and the root-mean-square value of velocity-weighted suspended-sediment concentration as an added surrogate variable. Cross-sectional measurements validated the use of surrogates during the monitoring period. During high freshwater flow advective and dispersive flux were in the seaward direction, while landward dispersive flux dominated and advective flux approached zero during low freshwater flow. Stokes drift flux was consistently in the landward direction. Wetter than average years led to net export from Suisun Bay, while dry years led to net sediment import. Relatively low watershed sediment fluxes to Suisun Bay contribute to net export during the wet season, while gravitational circulation in Carquinez Strait and higher suspended-sediment concentrations in San Pablo Bay (seaward end of Carquinez Strait) are responsible for the net import of sediment during the dry season. Annual predictions of suspended-sediment fluxes, using these methods, will allow for a sediment budget for Suisun Bay, which has implications for marsh restoration and nutrient/contaminant transport. These methods also provide a general framework for estimating sediment fluxes in estuarine environments, where temporal and spatial variability of transport are large. ?? 2006 Elsevier Ltd. All rights

184 Estimation des changements de la ligne de rivage de la zone ...

African Journals Online (AJOL)

youness

Estimation des changements de la ligne de rivage de la zone côtière sablonneuse de Kénitra au Maroc. Mohamed AHIZOUN1*, Eric MAIRE2, Souad HAIDA1,. José DARROZES2 et Jean-Luc PROBST3. 1 Laboratoire géophysique, mécanique des fluides, environnement et ingénierie mathématique - Equipe de recherche ...

Les flux de matières dissoutes et particulaires des Andes de Bolivie vers le rio Madeira en Amazonie brésilienne

Directory of Open Access Journals (Sweden)

1995-01-01

Full Text Available Le Rio Madeira est le principal affluent méridional de l’Amazone et le deuxième tributaire andin du bassin. L’utilisation des données obtenues en Bolivie par le PHICAB (1, et au Brésil sur le réseau du DNAEE (2, a permis de suivre l’évolution des flux de matières dissoutes et particulaires, depuis les Andes jusqu’à l’Amazone. Les flux de matières en solution [36 106 t an-1 à Villabella (3] augmentent progressivement d’amont en aval avec les débits. Les flux de matières en suspension diminuent du piedmont andin jusqu’à Villabella (258 106 t an-1 du fait d’une forte sédimentation. Ensuite, les différences notables observées au Brésil posent clairement le problème des modes d’échantillonnage et de calcul des flux sédimentaires. LOS FLUJOS DE MATERIA DISUELTA Y PARTICULAR DESDE LOS ANDES DE BOLIVIA HASTA EL RÍO MADEIRA EN EL AMAZONAS DE BRASIL. El río Madeira es el principal afluente meridional del Amazonas, y el segundo tributario andino de la cuenca. La utilización de los datos obtenidos en Bolivia por el PHICAB (1, y en el Brasil sobre la red del DNAEE (2 permite conocer la evolución de los flujos de materia disuelta y particular, desde los Andes hasta el Amazonas. Los aportes en materia disuelta [36 106 t año-1 en Villabella (3] aumentan progresivamente de aguas arriba para aguas abajo, con el caudal. Los flujos de materias en suspensión disminuyen desde el Piedemonte hasta Villabella (258 106 t año-1 por causa de una fuerte sedimentación. Después, las diferencias notables observadas en el Brasil colocan claramente el problema de los tipos de muestreo y de cálculo de los flujos de sedimentos. THE DISSOLVED AND SEDIMENT YIELDS FROM THE ANDES OF BOLIVIA TO THE MADEIRA RIVER IN THE BRAZILIAN AMAZON. The Madeira river is the main Southern tributary of the Amazon, and the second Andean tributary of the drainage basin. The use of Bolivian data from the PHICAB (1, and Brazilian data from the DNAEE (2, allow to

Estimating local atmosphere-surface fluxes using eddy covariance and numerical Ogive optimization

DEFF Research Database (Denmark)

Sievers, Jakob; Papakyriakou, Tim; Larsen, Søren

2014-01-01

Estimating representative surface-fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modeling efforts, low-frequency cont......Estimating representative surface-fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modeling efforts, low...

An observer-theoretic approach to estimating neutron flux distribution

International Nuclear Information System (INIS)

Park, Young Ho; Cho, Nam Zin

1989-01-01

State feedback control provides many advantages such as stabilization and improved transient response. However, when the state feedback control is considered for spatial control of a nuclear reactor, it requires complete knowledge of the distributions of the system state variables. This paper describes a method for estimating the flux spatial distribution using only limited flux measurements. It is based on the Luenberger observer in control theory, extended to the distributed parameter systems such as the space-time reactor dynamics equation. The results of the application of the method to simple reactor models showed that the flux distribution is estimated by the observer very efficiently using information from only a few sensors

Estimation des caractéristiques biologiques des truites de mer adultes (Salmo trutta du Rhin supérieur

Directory of Open Access Journals (Sweden)

OMBREDANE D.

1998-07-01

Full Text Available L'analyse des longueurs totales et des écailles d'un échantillon de 120 truites de mer adultes capturées essentiellement par pêche à l'électricité dans le Rhin supérieur (700 km de la mer du Nord de 1989 à 1996 a permis de caractériser la population de cette ressource piscicole en voie de restauration. L'utilisation des Captures Par Unité d'Effort (CPUE, calculées pour les pêches de 1994 à 1996, permet d'appréhender le rythme de migration et d'améliorer l'estimation des caractéristiques générales de la population. Dans cette partie du Rhin, la migration anadrome de la truite de mer se déroule en deux pics successifs de juin à décembre, les individus les plus âgés arrivant les premiers. La population est caractérisée par une très forte prédominance des groupes d'âge de mer 1 + (49,2 % et 2+ (45,8 %, soit un Age Moyen de Mer (AMM de 1,54 an. L'Age Moyen de Smoltification (AMS et de première Reproduction (AMR sont estimés respectivement à 1,30 an et 1,39 an. Par ailleurs, il est constaté que l'âge marin de première maturité des adultes du Rhin augmente quand leur âge de smoltification diminue. Les résultats sont discutés en fonction de la méthodologie employée et comparés à ceux obtenus sur d'autres populations françaises et plus nordiques. Il ressort que les caractéristiques de la population de truite de mer du Rhin traduisent bien la position latitudinale mais aussi l'importance de ce réseau hydrographique.

Comparison of surface energy fluxes with satellite-derived surface energy flux estimates from a shrub-steppe

International Nuclear Information System (INIS)

Kirkham, R.R.

1993-12-01

This thesis relates the components of the surface energy balance (i.e., net radiation, sensible and latent heat flux densities, soil heat flow) to remotely sensed data for native vegetation in a semi-arid environment. Thematic mapper data from Landsat 4 and 5 were used to estimate net radiation, sensible heat flux (H), and vegetation amount. Several sources of ground truth were employed. They included soil water balance using the neutron thermalization method and weighing lysimeters, and the measurement of energy fluxes with the Bowen ratio energy balance (BREB) technique. Sensible and latent heat flux were measured at four sites on the U.S. Department of Energy's Hanford Site using a weighing lysimeter and/or BREB stations. The objective was to calibrate an aerodynamic transport equation that related H to radiant surface temperature. The transport equation was then used with Landsat thermal data to generate estimates of H and compare these estimates against H values obtained with BREB/lysimeters at the time of overflight. Landsat and surface meteorologic data were used to estimate the radiation budget terms at the surface. Landsat estimates of short-wave radiation reflected from the surface correlate well with reflected radiation measured using inverted Eppley pyranometers. Correlation of net radiation estimates determined from satellite data, pyranometer, air temperature, and vapor pressure compared to net radiometer values obtained at time of overflight were excellent for a single image, but decrease for multiple images. Soil heat flux, G T , is a major component of the energy balance in arid systems and G T generally decreases as vegetation cover increases. Normalized difference vegetation index (NDVI) values generated from Landsat thermatic mapper data were representative of field observations of the presence of green vegetation, but it was not possible to determine a single relationship between NDVI and G T for all sites

Multi-year Estimates of Methane Fluxes in Alaska from an Atmospheric Inverse Model

Science.gov (United States)

Miller, S. M.; Commane, R.; Chang, R. Y. W.; Miller, C. E.; Michalak, A. M.; Dinardo, S. J.; Dlugokencky, E. J.; Hartery, S.; Karion, A.; Lindaas, J.; Sweeney, C.; Wofsy, S. C.

2015-12-01

We estimate methane fluxes across Alaska over a multi-year period using observations from a three-year aircraft campaign, the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Existing estimates of methane from Alaska and other Arctic regions disagree in both magnitude and distribution, and before the CARVE campaign, atmospheric observations in the region were sparse. We combine these observations with an atmospheric particle trajectory model and a geostatistical inversion to estimate surface fluxes at the model grid scale. We first use this framework to estimate the spatial distribution of methane fluxes across the state. We find the largest fluxes in the south-east and North Slope regions of Alaska. This distribution is consistent with several estimates of wetland extent but contrasts with the distribution in most existing flux models. These flux models concentrate methane in warmer or more southerly regions of Alaska compared to the estimate presented here. This result suggests a discrepancy in how existing bottom-up models translate wetland area into methane fluxes across the state. We next use the inversion framework to explore inter-annual variability in regional-scale methane fluxes for 2012-2014. We examine the extent to which this variability correlates with weather or other environmental conditions. These results indicate the possible sensitivity of wetland fluxes to near-term variability in climate.

Critical sizes and flux distributions in the shut down pile; Tailles critiques et cartes de flux a froid

Energy Technology Data Exchange (ETDEWEB)

Banchereau, A; Berthier, P; Genthon, J P; Gourdon, C; Lattes, R; Martelly, J; Mazancourt, R de; Portes, L; Sagot, M; Schmitt, A P; Tanguy, P; Teste du Bailler, A; Veyssiere, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

An important part of the experiments carried out on the reactor G1 during a period of shut-down has consisted in determinations of critical sizes, and measurements of flux distribution by irradiations of detectors. This report deals with the following points: 1- Critical sizes of the flat pile, the long pile and the uranium-thorium pile. 2- Flux charts of the same piles, and study of an exponential experiment. 3- Determination of the slit effect. 4- Calculation of the anisotropy of the lattice. 5- Description of the experimental apparatus of the irradiation measurements. (author) [French] Une part importante des experiences a froid effectuees sur le reacteur G1 a consiste en des determinations de tailles critiques et des mesures de distributions de flux par irradiations de detecteurs. Le present rapport traite les points suivants: 1- Tailles critiques de la pile plate, de la pile longue, de la pile a uranium-thorium. 2 - Cartes de flux des memes piles et etude d'une experience exponentielle. 3 - Determination de l'effet de fente. 4 - Calcul de l'anisotropie du reseau. 5 - Description de l'appareillage experimental des mesures d'irradiations. (auteur)

Critical sizes and flux distributions in the shut down pile; Tailles critiques et cartes de flux a froid

Energy Technology Data Exchange (ETDEWEB)

Banchereau, A.; Berthier, P.; Genthon, J.P.; Gourdon, C.; Lattes, R.; Martelly, J.; Mazancourt, R. de; Portes, L.; Sagot, M.; Schmitt, A.P.; Tanguy, P.; Teste du Bailler, A.; Veyssiere, A. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

An important part of the experiments carried out on the reactor G1 during a period of shut-down has consisted in determinations of critical sizes, and measurements of flux distribution by irradiations of detectors. This report deals with the following points: 1- Critical sizes of the flat pile, the long pile and the uranium-thorium pile. 2- Flux charts of the same piles, and study of an exponential experiment. 3- Determination of the slit effect. 4- Calculation of the anisotropy of the lattice. 5- Description of the experimental apparatus of the irradiation measurements. (author) [French] Une part importante des experiences a froid effectuees sur le reacteur G1 a consiste en des determinations de tailles critiques et des mesures de distributions de flux par irradiations de detecteurs. Le present rapport traite les points suivants: 1- Tailles critiques de la pile plate, de la pile longue, de la pile a uranium-thorium. 2 - Cartes de flux des memes piles et etude d'une experience exponentielle. 3 - Determination de l'effet de fente. 4 - Calcul de l'anisotropie du reseau. 5 - Description de l'appareillage experimental des mesures d'irradiations. (auteur)

A novel flux estimator based on SOGI with FLL for induction machine drives

DEFF Research Database (Denmark)

Zhao, Rende; Xin, Zhen; Loh, Poh Chiang

2016-01-01

by the initial conditions with no need for the magnitude and phase compensation. Because the dc and harmonic components are inversely proportional to the speed in the estimated flux, the performance of the single SOGI-based estimator become worse at low speed. A multiple SOGI-based flux estimator is the proposed......It is very important to estimate flux accurately in implementing high-performance control of AC motors. Theoretical analysis has been made to illustrate the performance of the pure-integration-based and the Low-Pass Filter (LPF) based flux estimators. A novel flux estimator based on Second......-Order General Integrator (SOGI) with Frequency Locked-Loop (FLL) is investigated in this paper for induction machine drives. A single SOGI instead of pure integrator or LPF is used to integrate the back electromotive force (EMF). It can solve the problems of the integration saturation and the dc drift caused...

Error estimates for ice discharge calculated using the flux gate approach

Science.gov (United States)

Navarro, F. J.; Sánchez Gámez, P.

2017-12-01

Ice discharge to the ocean is usually estimated using the flux gate approach, in which ice flux is calculated through predefined flux gates close to the marine glacier front. However, published results usually lack a proper error estimate. In the flux calculation, both errors in cross-sectional area and errors in velocity are relevant. While for estimating the errors in velocity there are well-established procedures, the calculation of the error in the cross-sectional area requires the availability of ground penetrating radar (GPR) profiles transverse to the ice-flow direction. In this contribution, we use IceBridge operation GPR profiles collected in Ellesmere and Devon Islands, Nunavut, Canada, to compare the cross-sectional areas estimated using various approaches with the cross-sections estimated from GPR ice-thickness data. These error estimates are combined with those for ice-velocities calculated from Sentinel-1 SAR data, to get the error in ice discharge. Our preliminary results suggest, regarding area, that the parabolic cross-section approaches perform better than the quartic ones, which tend to overestimate the cross-sectional area for flight lines close to the central flowline. Furthermore, the results show that regional ice-discharge estimates made using parabolic approaches provide reasonable results, but estimates for individual glaciers can have large errors, up to 20% in cross-sectional area.

Determination of the flux per electron-volt at the resonance energy of gold by means op thick gold detectors (1962); Determination des flux par electron-volt a l'energie de resonance de l'or a l'aide de detecteurs d'or epais. (1962)

Energy Technology Data Exchange (ETDEWEB)

Brisbois, J; Fogagnolo, G [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1962-07-01

We calculated the coefficients which allow determining a neutron flux at 5 eV by means of 2/10 mm thick gold detectors on Geiger-Muller counter assemblies. These coefficients were obtained comparing the thick detectors with the thin ones. (authors) [French] Nous avons calcule les coefficients permettant de determiner le flux de neutrons a 5 eV a partir de comptages de detecteurs d'or de 2/10 mm d'epaisseur sur des groupes a compteur de Geiger-Muller. Ces coefficients ont ete obtenus en comparant les detecteurs epais avec des detecteurs minces. (auteurs)

Inertial dissipation method applied to derive turbulent fluxes over the ocean during the Surface of the Ocean, Fluxes and Interactions with the Atmosphere/Atlantic Stratocumulus Transition Experiment (SOFIA/ASTEX) and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiments with low to moderate wind speeds

Science.gov (United States)

Dupuis, HéLèNe; Taylor, Peter K.; Weill, Alain; Katsaros, K.

1997-09-01

The transfer coefficients for momentum and heat have been determined for 10 m neutral wind speeds (U10n) between 0 and 12 m/s using data from the Surface of the Ocean, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiments. The inertial dissipation method was applied to wind and pseudo virtual temperature spectra from a sonic anemometer, mounted on a platform (ship) which was moving through the turbulence field. Under unstable conditions the assumptions concerning the turbulent kinetic energy (TKE) budget appeared incorrect. Using a bulk estimate for the stability parameter, Z/L (where Z is the height and L is the Obukhov length), this resulted in anomalously low drag coefficients compared to neutral conditions. Determining Z/L iteratively, a low rate of convergence was achieved. It was concluded that the divergence of the turbulent transport of TKE was not negligible under unstable conditions. By minimizing the dependence of the calculated neutral drag coefficient on stability, this term was estimated at about -0.65Z/L. The resulting turbulent fluxes were then in close agreement with other studies at moderate wind speed. The drag and exchange coefficients for low wind speeds were found to be Cen × 103 = 2.79U10n-1 + 0.66 (U10n < 5.2 m/s), Cen × 103 = Chn × 103 = 1.2 (U10n ≥ 5.2 m/s), and Cdn × 103 = 11.710n-2 + 0.668 (U10n < 5.5 m/s), which imply a rapid increase of the coefficient values as the wind decreased within the smooth flow regime. The frozen turbulence hypothesis and the assumptions of isotropy and an inertial subrange were found to remain valid at these low wind speeds for these shipboard measurements. Incorporation of a free convection parameterization had little effect.

snerti lEhissip tion flux me surements over south f y of feng l during ...

Indian Academy of Sciences (India)

his p per des ri es me surement of irEse p r meters nd estim tion of sensi le nd l tent he t fluxes y the snerti lEhissip tion99 te hnique over south f y of feng lF he d t were olle ted on. y g r u ny during fyfwi E ilot ruise during the period PQrd y to er IWWV to IPth xovem er. IWWV over south f y of feng lF he fluxes re estim ...

The inverse Numerical Computer Program FLUX-BOT for estimating Vertical Water Fluxes from Temperature Time-Series.

Science.gov (United States)

Trauth, N.; Schmidt, C.; Munz, M.

2016-12-01

Heat as a natural tracer to quantify water fluxes between groundwater and surface water has evolved to a standard hydrological method. Typically, time series of temperatures in the surface water and in the sediment are observed and are subsequently evaluated by a vertical 1D representation of heat transport by advection and dispersion. Several analytical solutions as well as their implementation into user-friendly software exist in order to estimate water fluxes from the observed temperatures. Analytical solutions can be easily implemented but assumptions on the boundary conditions have to be made a priori, e.g. sinusoidal upper temperature boundary. Numerical models offer more flexibility and can handle temperature data which is characterized by irregular variations such as storm-event induced temperature changes and thus cannot readily be incorporated in analytical solutions. This also reduced the effort of data preprocessing such as the extraction of the diurnal temperature variation. We developed a software to estimate water FLUXes Based On Temperatures- FLUX-BOT. FLUX-BOT is a numerical code written in MATLAB which is intended to calculate vertical water fluxes in saturated sediments, based on the inversion of measured temperature time series observed at multiple depths. It applies a cell-centered Crank-Nicolson implicit finite difference scheme to solve the one-dimensional heat advection-conduction equation. Besides its core inverse numerical routines, FLUX-BOT includes functions visualizing the results and functions for performing uncertainty analysis. We provide applications of FLUX-BOT to generic as well as to measured temperature data to demonstrate its performance.

Le tourisme international dans le monde : logiques des flux et confins de la touristicité

Directory of Open Access Journals (Sweden)

Corina Tatar

2008-09-01

Full Text Available L’histoire du tourisme international des cinquante dernières années peut être décomposée en trois temps : 1/ les décennies de 1950 à 1980, caractérisées par une démocratisation progressive du tourisme soutenue par une croissance économique inégalée ; 2/ la dernière décennie du vingtième siècle, celle d’une euphorie touristique qui voit les frontières s’ouvrir. La fin d’un monde bipolaire annonce bien des espoirs naïfs. Le champ des territoires ouverts au tourisme ne cesse de s’élargir. 3/ La fin du siècle annonce l’âge de maturité du tourisme. Après l’euphorie, les illusions et les désillusions d’un espace touristique mondial sans frontières, les faits, souvent dramatiques ont fait prendre conscience aux touristes la complexité d’un monde où les guerres n’ont jamais cessé. L’espace touristique mondial est articulé autour de trois bassins régionaux : plus de 75% des flux touristiques internationaux, impulsés par les riches métropoles européennes, nord-américaines et asiatique, se cantonnent à dans leur espace régional d’origine. La distribution des flux touristiques dessine une organisation en trois bassins distincts : par ordre d’importance, 1/ le bassin euro-méditerranéen, centré sur la Mer méditerranée, 2/ le bassin Asie orientale-Pacifique, autour des rivages de la mer de Chine, 3/ le bassin Amérique du Nord -Caraïbes, organisé autour de la « Méditerranée américaine ». Les discontinuités s’affirment entre des périphéries mal stabilisées, des prolongements très sélectifs, des marges oubliées ou exclues. Les climats d’insécurité qui touchent certains territoires touristiques visent à fragiliser des périphéries plus sensibles et contraignent l’espace touristique international à se rétracter.The history of international tourism of the last fifty years can be divided  into three stages: 1 / decades from 1950 to 1980, characterized by a

Inverse Estimation of Heat Flux and Temperature Distribution in 3D Finite Domain

International Nuclear Information System (INIS)

Muhammad, Nauman Malik

2009-02-01

Inverse heat conduction problems occur in many theoretical and practical applications where it is difficult or practically impossible to measure the input heat flux and the temperature of the layer conducting the heat flux to the body. Thus it becomes imperative to devise some means to cater for such a problem and estimate the heat flux inversely. Adaptive State Estimator is one such technique which works by incorporating the semi-Markovian concept into a Bayesian estimation technique thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters. The problem presented in this study deals with a three dimensional system of a cube with one end conducting heat flux and all the other sides are insulated while the temperatures are measured on the accessible faces of the cube. The measurements taken on these accessible faces are fed into the estimation algorithm and the input heat flux and the temperature distribution at each point in the system is calculated. A variety of input heat flux scenarios have been examined to underwrite the robustness of the estimation algorithm and hence insure its usability in practical applications. These include sinusoidal input flux, a combination of rectangular, linearly changing and sinusoidal input flux and finally a step changing input flux. The estimator's performance limitations have been examined in these input set-ups and error associated with each set-up is compared to conclude the realistic application of the estimation algorithm in such scenarios. Different sensor arrangements, that is different sensor numbers and their locations are also examined to impress upon the importance of number of measurements and their location i.e. close or farther from the input area. Since practically it is both economically and physically tedious to install more number of measurement sensors, hence optimized number and location is very important to determine for making the study more

EVALUATION DE L’IMPACT ENVIRONNEMENTAL : GeneSys-Colza : un modèle des effets à moyen et à long terme des systèmes de culture sur les flux de gènes entre champs de colza et repousses dans un espace agricole

Directory of Open Access Journals (Sweden)

Colbach Nathalie

2000-07-01

repousses de colza; il n’est pas non plus possible d’attendre les résultats des plates-formes pour estimer des risques à long terme. Pour ces raisons, nous avons entrepris de construire un modèle rendant compte de la répartition spatiale des systèmes de culture ainsi que de leurs effets sur la dissémination, dans le temps et l’espace, d’un transgène (par exemple un gène de résistance aux herbicides ou un gène codant pour un acide gras et sur sa persistance dans les populations de repousses de colza, sur des parcelles ayant ou non été cultivées avec la variété de colza transgénique. Les autres risques liés aux cultures transgéniques (résistance aux antibiotiques, allergies alimentaires, etc. ne sont pas considérés dans cette étude. Dans cet article, nous allons présenter les grands principes du modèle d’évolution démographique et génétique des repousses de colza fonctionnant au niveau d’un champ cultivé, puis l’intégration et le fonctionnement de ce modèle au niveau régional. Les exemples décrits lors de la présentation du modèle et des simulations se rapportent généralement à un colza transgénique résistant à un herbicide. Mais le modèle peut également être utilisé pour évaluer le flux de gènes à partir de nouvelles variétés obtenues par sélection classique et/ou pour des gènes codant pour d’autres caractéristiques telles qu’une teneur en acide gras.

Improved vertical streambed flux estimation using multiple diurnal temperature methods in series

Science.gov (United States)

Irvine, Dylan J.; Briggs, Martin A.; Cartwright, Ian; Scruggs, Courtney; Lautz, Laura K.

2017-01-01

Analytical solutions that use diurnal temperature signals to estimate vertical fluxes between groundwater and surface water based on either amplitude ratios (Ar) or phase shifts (Δϕ) produce results that rarely agree. Analytical solutions that simultaneously utilize Ar and Δϕ within a single solution have more recently been derived, decreasing uncertainty in flux estimates in some applications. Benefits of combined (ArΔϕ) methods also include that thermal diffusivity and sensor spacing can be calculated. However, poor identification of either Ar or Δϕ from raw temperature signals can lead to erratic parameter estimates from ArΔϕ methods. An add-on program for VFLUX 2 is presented to address this issue. Using thermal diffusivity selected from an ArΔϕ method during a reliable time period, fluxes are recalculated using an Ar method. This approach maximizes the benefits of the Ar and ArΔϕ methods. Additionally, sensor spacing calculations can be used to identify periods with unreliable flux estimates, or to assess streambed scour. Using synthetic and field examples, the use of these solutions in series was particularly useful for gaining conditions where fluxes exceeded 1 m/d.

Volcanic fluxes of volatiles. Preliminary estimates based on rare gas and major volatile calibration

International Nuclear Information System (INIS)

Marty, B.

1992-01-01

New estimates for volatile fluxes into the atmosphere and hydrosphere through volcanism have been computed using the measured fluxes of 3 He in oceans and SO 2 in the atmosphere, and the ratios between the volatiles in Mid-Ocean Ridge basalts and in high temperature volcanic gases. These estimates have been checked using independent estimates of the volcanic fluxes. This method provides a reliable means of tracing volatile fluxes, although its precision is restricted by the limited amount of data currently available. (author). 19 refs, 1 tab

Fast neutron flux in heavy water reactors; Flux de neutrons rapides dans les piles a eau lourde

Energy Technology Data Exchange (ETDEWEB)

Brisbois, J; Katz, S [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France)

1966-07-01

The possibility of calculating the fast neutron flux in a natural uranium-heavy water lattice by superposition of the individual contributions of the different fuel elements was verified using a one-dimension Monte-Carlo code. The results obtained are in good agreement with experimental measurements done in the core and reflector of the reactor AQUILON. (author) [French] La possibilite de calculer le flux de neutrons rapides dans un reseau d'uranium naturel a eau lourde par superposition des apports des divers barreaux, a ete verifiee en utilisant un code Monte-Carlo monodimensionel. Les resultats obtenus concordent avec des mesures experimentales effectuees dans le coeur et reacteur de la pile Aquilon. (auteurs)

Estimation of dynamic flux profiles from metabolic time series data

Directory of Open Access Journals (Sweden)

Chou I-Chun

2012-07-01

Full Text Available Abstract Background Advances in modern high-throughput techniques of molecular biology have enabled top-down approaches for the estimation of parameter values in metabolic systems, based on time series data. Special among them is the recent method of dynamic flux estimation (DFE, which uses such data not only for parameter estimation but also for the identification of functional forms of the processes governing a metabolic system. DFE furthermore provides diagnostic tools for the evaluation of model validity and of the quality of a model fit beyond residual errors. Unfortunately, DFE works only when the data are more or less complete and the system contains as many independent fluxes as metabolites. These drawbacks may be ameliorated with other types of estimation and information. However, such supplementations incur their own limitations. In particular, assumptions must be made regarding the functional forms of some processes and detailed kinetic information must be available, in addition to the time series data. Results The authors propose here a systematic approach that supplements DFE and overcomes some of its shortcomings. Like DFE, the approach is model-free and requires only minimal assumptions. If sufficient time series data are available, the approach allows the determination of a subset of fluxes that enables the subsequent applicability of DFE to the rest of the flux system. The authors demonstrate the procedure with three artificial pathway systems exhibiting distinct characteristics and with actual data of the trehalose pathway in Saccharomyces cerevisiae. Conclusions The results demonstrate that the proposed method successfully complements DFE under various situations and without a priori assumptions regarding the model representation. The proposed method also permits an examination of whether at all, to what degree, or within what range the available time series data can be validly represented in a particular functional format of

Investigating the impact of uneven magnetic flux density distribution on core loss estimation

DEFF Research Database (Denmark)

Niroumand, Farideh Javidi; Nymand, Morten; Wang, Yiren

2017-01-01

is calculated according to an effective flux density value and the macroscopic dimensions of the cores. However, the flux distribution in the core can alter by core shapes and/or operating conditions due to nonlinear material properties. This paper studies the element-wise estimation of the loss in magnetic......There are several approaches for loss estimation in magnetic cores, and all these approaches highly rely on accurate information about flux density distribution in the cores. It is often assumed that the magnetic flux density evenly distributes throughout the core and the overall core loss...

CYGNSS Surface Wind Observations and Surface Flux Estimates within Low-Latitude Extratropical Cyclones

Science.gov (United States)

Crespo, J.; Posselt, D. J.

2017-12-01

The Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, aims to improve estimates of surface wind speeds over the tropical oceans. While CYGNSS's core mission is to provide better estimates of surface winds within the core of tropical cyclones, previous research has shown that the constellation, with its orbital inclination of 35°, also has the ability to observe numerous extratropical cyclones that form in the lower latitudes. Along with its high spatial and temporal resolution, CYGNSS can provide new insights into how extratropical cyclones develop and evolve, especially in the presence of thick clouds and precipitation. We will demonstrate this by presenting case studies of multiple extratropical cyclones observed by CYGNSS early on in its mission in both Northern and Southern Hemispheres. By using the improved estimates of surface wind speeds from CYGNSS, we can obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. Surface heat fluxes, driven by surface winds and strong vertical gradients of water vapor and temperature, play a key role in marine cyclogenesis as they increase instability within the boundary layer and may contribute to extreme marine cyclogenesis. In the past, it has been difficult to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space, and deficiencies in spatial coverage and attenuation from clouds and precipitation lead to inaccurate estimates of surface flux components, such as surface wind speeds. While CYGNSS only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.

The effect of sediment thermal conductivity on vertical groundwater flux estimates

Science.gov (United States)

Sebok, Eva; Müller, Sascha; Engesgaard, Peter; Duque, Carlos

2015-04-01

The interaction between groundwater and surface water is of great importance both from ecological and water management perspective. The exchange fluxes are often estimated based on vertical temperature profiles taken from shallow sediments assuming a homogeneous standard value of sediment thermal conductivity. Here we report on a field investigation in a stream and in a fjord, where vertical profiles of sediment thermal conductivity and temperatures were measured in order to, (i) define the vertical variability in sediment thermal conductivity, (ii) quantify the effect of heterogeneity in sediment thermal conductivity on the estimated vertical groundwater fluxes. The study was carried out at field sites located in Ringkøbing fjord and Holtum stream in Western Denmark. Both locations have soft, sandy sediments with an upper organic layer at the fjord site. First 9 and 12 vertical sediment temperature profiles up to 0.5 m depth below the sediment bed were collected in the fjord and in the stream, respectively. Later sediment cores of 0.05 m diameter were removed at the location of the temperature profiles. Sediment thermal conductivity was measured in the sediment cores at 0.1 m intervals with a Decagon KD2 Pro device. A 1D flow and heat transport model (HydroGeoSphere) was set up and vertical groundwater fluxes were estimated based on the measured vertical sediment temperature profiles by coupling the model with PEST. To determine the effect of heterogeneity in sediment thermal conductivity on estimated vertical groundwater fluxes, the model was run by assigning (i) a homogeneous thermal conductivity for all sediment layers, calculated as the average sediment thermal conductivity of the profile, (ii) measured sediment thermal conductivities to the different model layers. The field survey showed that sediment thermal conductivity over a 0.5 m profile below the sediment bed is not uniform, having the largest variability in the fjord where organic sediments were also

Anthropogenic Heat Flux Estimation from Space: Results of the second phase of the URBANFLUXES Project

Science.gov (United States)

Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean-Philippe; Grimmond, Sue; Feigenwinter, Christian; Lindberg, Fredrik; Del Frate, Fabio; Klostermann, Judith; Mitraka, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans

2017-04-01

The H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the impacts of UEB fluxes on urban heat island and consequently on energy consumption in cities. In URBANFLUXES, the anthropogenic heat flux is estimated as a residual of UEB. Therefore, the rest UEB components, namely, the net all-wave radiation, the net change in heat storage and the turbulent sensible and latent heat fluxes are independently estimated from Earth Observation (EO), whereas the advection term is included in the error of the anthropogenic heat flux estimation from the UEB closure. The Discrete Anisotropic Radiative Transfer (DART) model is employed to improve the estimation of the net all-wave radiation balance, whereas the Element Surface Temperature Method (ESTM), adjusted to satellite observations is used to improve the estimation the estimation of the net change in heat storage. Furthermore the estimation of the turbulent sensible and latent heat fluxes is based on the Aerodynamic Resistance Method (ARM). Based on these outcomes, QF is estimated by regressing the sum of the turbulent heat fluxes versus the available energy. In-situ flux measurements are used to evaluate URBANFLUXES outcomes, whereas uncertainties are specified and analyzed. URBANFLUXES is expected to prepare the ground for further innovative exploitation of EO in scientific activities (climate variability studies at local and regional scales) and future and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation/adaptation. This study presents the results of the second phase of the project and detailed information on URBANFLUXES is available at: http://urbanfluxes.eu

Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

Directory of Open Access Journals (Sweden)

A. J. Spargo

2017-06-01

Full Text Available Mesospheric gravity wave (GW momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E experiments (conducted from July 1997 to June 1998 are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions. The received beams were analysed with hybrid Doppler interferometry (HDI (Holdsworth and Reid, 1998, principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997, later re-introduced by Hocking (2005 and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010 of the accuracy of the meteor radar technique.

Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

Science.gov (United States)

Spargo, Andrew J.; Reid, Iain M.; MacKinnon, Andrew D.; Holdsworth, David A.

2017-06-01

Mesospheric gravity wave (GW) momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E) experiments (conducted from July 1997 to June 1998) are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions). The received beams were analysed with hybrid Doppler interferometry (HDI) (Holdsworth and Reid, 1998), principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997), later re-introduced by Hocking (2005) and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010) of the accuracy of the meteor radar technique.

A review of land-based greenhouse gas flux estimates in Indonesia

Science.gov (United States)

Austin, Kemen G.; Harris, Nancy L.; Wijaya, Arief; Murdiyarso, Daniel; Harvey, Tom; Stolle, Fred; Kasibhatla, Prasad S.

2018-05-01

This study examines underlying reasons for differences among land-based greenhouse gas flux estimates in Indonesia, where six national inventories reported average emissions of between 0.4 and 1.1 Gt CO2e yr‑1 over the 2000–2012 period. The large range among estimates is only somewhat smaller than Indonesia’s GHG mitigation commitment. To determine the reasons for these differences, we compared input data and estimation methods, including the definitions and assumptions used for setting accounting boundaries, including emitting activities, incorporating fluxes from various carbon pools, and handling legacy fluxes. We also tested the sensitivity of methodological differences by generating our own reference emissions estimate and iteratively modifying individual components of the inventory. We found that the largest changes stem from the inclusion of legacy GHG emissions due to peat drainage (which increased emissions by at least +94% compared to the reference), methane emissions due to peat fires (+35%), and GHG emissions from belowground biomass and necromass carbon pools (+61%), modifications to assumptions of the mass of fuel burnt in peat fire events (+88%), and accounting for regrowth following a deforestation event (‑31%). These differences cumulatively explain more than half of the observed difference among inventory estimates. Understanding the various approaches to emissions estimation, and how these influence the magnitude of component GHG fluxes, is an important first step towards reconciling GHG inventories. The Indonesian government’s success in achieving its mitigation goal will depend on its ability to measure progress and evaluate the effectiveness of abatement actions, for which reliable harmonized greenhouse gas inventories are an essential foundation.

EFFET DES TRAITEMENTS THERMIQUES SUR LA REACTION ENTRE DES COUCHES MINCES DE TITANE ET DES SUBSTRATS EN ACIER

Directory of Open Access Journals (Sweden)

D Slimani

2015-06-01

Full Text Available Des couches minces du titane pur ont été déposées avec la méthode de pulvérisation cathodique sur des substrats en acier, type FF80 K-1 contenants ~1% mass. en carbone. La réaction entre les deux parties du système substrat-couche mince est activée avec des traitements thermiques sous vide dans l’intervalle de températures de 400 à900°Cpendant 30 minutes. Les Spectres de diffraction de rayons x confirment l’inter- diffusion des éléments  chimiques du système résultants la formation et la croissance des nouvelles phases en particulier le carbure binaire TiC ayant des caractéristiques thermomécaniques importantes. L’analyse morphologique des échantillons traités  avec le microscope électronique à balayage (MEB montre l’augmentation du flux de diffusion atomique avec la température de recuit, notamment la diffusion du manganèse et du fer vers la surface libre des échantillons aux températures élevées provoquant la dégradation des propriétés mécaniques des revêtements contrairement au premiers stades d’interaction où on a obtenu des bonnes valeurs de la microdureté.

Utilisation du phytoplancton pour estimer la production piscicole potentielle des étangs

Directory of Open Access Journals (Sweden)

BARBE J.

1999-07-01

Full Text Available Pour faciliter la gestion des étangs de pisciculture, il est nécessaire d'avoir un moyen pour estimer en cours de saison si l'objectif de production sera atteint, et éventuellement, intervenir sur la qualité du milieu. Les méthodes d'estimation et de prévision mentionnées dans la littérature ne sont pas applicables aux étangs de pisciculture, milieux fortement anthropisés. A partir de données (physico-chimie, plancton, production piscicole collectées sur 36 étangs en France, les auteurs proposent une méthode de prévision de la récolte piscicole à partir du phytoplancton (groupe prédominant et teneur en chlorophylle a. A l'usage, cette méthode s'est avérée satisfaisante pour prévoir des productions nettes jusqu'à plus de 500 kg/hectare.

Assessing the Importance of Prior Biospheric Fluxes on Inverse Model Estimates of CO2

Science.gov (United States)

Philip, S.; Johnson, M. S.; Potter, C. S.; Genovese, V. B.

2017-12-01

Atmospheric mixing ratios of carbon dioxide (CO2) are largely controlled by anthropogenic emissions and biospheric sources/sinks. The processes controlling terrestrial biosphere-atmosphere carbon exchange are currently not fully understood, resulting in models having significant differences in the quantification of biospheric CO2 fluxes. Currently, atmospheric chemical transport models (CTM) and global climate models (GCM) use multiple different biospheric CO2 flux models resulting in large differences in simulating the global carbon cycle. The Orbiting Carbon Observatory 2 (OCO-2) satellite mission was designed to allow for the improved understanding of the processes involved in the exchange of carbon between terrestrial ecosystems and the atmosphere, and therefore allowing for more accurate assessment of the seasonal/inter-annual variability of CO2. OCO-2 provides much-needed CO2 observations in data-limited regions allowing for the evaluation of model simulations of greenhouse gases (GHG) and facilitating global/regional estimates of "top-down" CO2 fluxes. We conduct a 4-D Variation (4D-Var) data assimilation with the GEOS-Chem (Goddard Earth Observation System-Chemistry) CTM using 1) OCO-2 land nadir and land glint retrievals and 2) global in situ surface flask observations to constrain biospheric CO2 fluxes. We apply different state-of-the-science year-specific CO2 flux models (e.g., NASA-CASA (NASA-Carnegie Ames Stanford Approach), CASA-GFED (Global Fire Emissions Database), Simple Biosphere Model version 4 (SiB-4), and LPJ (Lund-Postdam-Jena)) to assess the impact of "a priori" flux predictions to "a posteriori" estimates. We will present the "top-down" CO2 flux estimates for the year 2015 using OCO-2 and in situ observations, and a complete indirect evaluation of the a priori and a posteriori flux estimates using independent in situ observations. We will also present our assessment of the variability of "top-down" CO2 flux estimates when using different

Reconciling estimates of the ratio of heat and salt fluxes at the ice-ocean interface

Science.gov (United States)

Keitzl, T.; Mellado, J. P.; Notz, D.

2016-12-01

The heat exchange between floating ice and the underlying ocean is determined by the interplay of diffusive fluxes directly at the ice-ocean interface and turbulent fluxes away from it. In this study, we examine this interplay through direct numerical simulations of free convection. Our results show that an estimation of the interface flux ratio based on direct measurements of the turbulent fluxes can be difficult because the flux ratio varies with depth. As an alternative, we present a consistent evaluation of the flux ratio based on the total heat and salt fluxes across the boundary layer. This approach allows us to reconcile previous estimates of the ice-ocean interface conditions. We find that the ratio of heat and salt fluxes directly at the interface is 83-100 rather than 33 as determined by previous turbulence measurements in the outer layer. This can cause errors in the estimated ice-ablation rate from field measurements of up to 40% if they are based on the three-equation formulation.

Heat transfer in smooth tubes, between parallel plates, along a semi-infinite plate, in annular spaces and along tube bundles for exponential distribution of the heat flux in forced, laminar or turbulent flow; Transfert de chaleur dans des tubes lisses, entre des plaques planes paralleles, le long d'une plaque plane, dans des espaces annulaires et le long de faisceaux tubulaires pour une repartition exponentielle du flux de chaleur en ecoulement force, laminaire ou turbulent

Energy Technology Data Exchange (ETDEWEB)

Graber, H [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1969-04-01

champ de temperature ainsi que le nombre de Nusselt en ecoulement laminaire et flux de chaleur constant. En ecoulement turbulent, les lois concernant la repartition de la diffusivite de quantite de mouvement dans un tube, etablies par H. Reichardt et adaptees a l'espace annulaire et au faisceau tubulaire, permettent la determination du champ de vitesse et du coefficient de perte de charge et consequemment la solution des equations de transfert de chaleur. Les resultats du calcul numerique sont rassembles dans des tableaux et representes par des diagrammes pour un domaine etendu des differents parametres et compares avec des resultats experimentaux. Par un procede simple, on peut determiner la valeur minimale de la longueur d'etablissement du regime thermique. (auteur)

An intercomparison and validation of satellite-based surface radiative energy flux estimates over the Arctic

Science.gov (United States)

Riihelä, Aku; Key, Jeffrey R.; Meirink, Jan Fokke; Kuipers Munneke, Peter; Palo, Timo; Karlsson, Karl-Göran

2017-05-01

Accurate determination of radiative energy fluxes over the Arctic is of crucial importance for understanding atmosphere-surface interactions, melt and refreezing cycles of the snow and ice cover, and the role of the Arctic in the global energy budget. Satellite-based estimates can provide comprehensive spatiotemporal coverage, but the accuracy and comparability of the existing data sets must be ascertained to facilitate their use. Here we compare radiative flux estimates from Clouds and the Earth's Radiant Energy System (CERES) Synoptic 1-degree (SYN1deg)/Energy Balanced and Filled, Global Energy and Water Cycle Experiment (GEWEX) surface energy budget, and our own experimental FluxNet / Satellite Application Facility on Climate Monitoring cLoud, Albedo and RAdiation (CLARA) data against in situ observations over Arctic sea ice and the Greenland Ice Sheet during summer of 2007. In general, CERES SYN1deg flux estimates agree best with in situ measurements, although with two particular limitations: (1) over sea ice the upwelling shortwave flux in CERES SYN1deg appears to be underestimated because of an underestimated surface albedo and (2) the CERES SYN1deg upwelling longwave flux over sea ice saturates during midsummer. The Advanced Very High Resolution Radiometer-based GEWEX and FluxNet-CLARA flux estimates generally show a larger range in retrieval errors relative to CERES, with contrasting tendencies relative to each other. The largest source of retrieval error in the FluxNet-CLARA downwelling shortwave flux is shown to be an overestimated cloud optical thickness. The results illustrate that satellite-based flux estimates over the Arctic are not yet homogeneous and that further efforts are necessary to investigate the differences in the surface and cloud properties which lead to disagreements in flux retrievals.

Table des illustrations

OpenAIRE

2016-01-01

Tableaux Dates d’inauguration des grands hôtels japonais entre 1860 et 1945… 19 Histoire, tourisme et hôtellerie en Corée depuis les années 1870… 59-60 Dates d’inauguration des grands hôtels chinois depuis 1863… 84 Les hôtels de luxe et leurs capacités d’hébergement en Corée en 2000… 103 Les flux de personnes suscités par les hôtels « super luxe » de Séoul en 2000… 105 L’activité des grands hôtels à Séoul en 1999 (en wons)… 106 Propriété et gestion des grands hôtels à Séoul en 1999…. 110 La c...

Geothermal Heat Flux Underneath Ice Sheets Estimated From Magnetic Satellite Data

DEFF Research Database (Denmark)

Fox Maule, Cathrine; Purucker, M.E.; Olsen, Nils

The geothermal heat flux is an important factor in the dynamics of ice sheets, and it is one of the important parameters in the thermal budgets of subglacial lakes. We have used satellite magnetic data to estimate the geothermal heat flux underneath the ice sheets in Antarctica and Greenland...

Continuous measurement of neutron flux with the help of a converter; Mesure continue des flux de neutrons a l'aide d'un dispositif convertisseur

Energy Technology Data Exchange (ETDEWEB)

Mas, P; Sciers, P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-07-01

The device described in this report is working from this following principle: an element, the thermal neutron activate of which has a short period and is emitter of a {beta} particle, is surrounded with a dielectric which is itself surrounded by a conducting metal. {beta} particles are stopped in the conducting metal. Thus an electric current rises between the emitter element and the collector metal. The experimental study has been-done with rhodium as emitter. The linearity as function of thermal flux of the power of the pile, the accuracy, the efficiency of the device have been measured and are satisfactory. Just the stability of the measure equipment is not very good. This method gives, us at moment the instantaneous flux and the integrated flux, is well adapted for the measurements in pile to execute on loops. It is possible to continue to perfect the process. (authors) [French] Le dispositif decrit dans ce rapport fonctionne d'apres le principe suivant: un corps, dont le produit d'activation en neutrons thermiques a une courte periode et est emetteur d'une particule {beta}, est entoure d'un dielectrique lui-meme entoure d'un metal conducteur. Les particules {beta} sont arretees dans le metal conducteur. Il y a ainsi naissance d'un courant electrique entre le corps emetteur et le metal collecteur. L'etude experimentale a ete menee avec le rhodium comme emetteur. La linearite en fonction du flux thermique, de la puissance de la pile, la precision, le rendement du dispositif ont ete mesures et sont satisfaisants. Seule la stabilite de l'appareillage de mesure n'est pas tres bonne. Cette methode, qui peut nous donner a tout instant le flux instantane et le flux integre, est tout a fait adaptee aux mesures en pile a effectuer. sur des boucles. On peut poursuivre la mise au point du procede. (auteurs)

Inverse carbon dioxide flux estimates for the Netherlands

Energy Technology Data Exchange (ETDEWEB)

Meesters, A.G.C.A.; Tolk, L.F.; Dolman, A.J. [Faculty of Earth and Life Sciences, VU University, Amsterdam (Netherlands); Peters, W.; Hutjes, R.W.A.; Vellinga, O.S.; Elbers, J.A. [Department Meteorology and Air Quality, Wageningen University and Research Centre, Wageningen (Netherlands); Vermeulen, A.T. [Biomass, Coal and Environmental Research, Energy research Center of the Netherlands ECN, Petten (Netherlands); Van der Laan, S.; Neubert, R.E.M.; Meijer, H.A.J. [Centre for Isotope Research, Energy and Sustainability Research Institute Groningen, University of Groningen, Groningen (Netherlands)

2012-10-26

CO2 fluxes for the Netherlands and surroundings are estimated for the year 2008, from concentration measurements at four towers, using an inverse model. The results are compared to direct CO2 flux measurements by aircraft, for 6 flight tracks over the Netherlands, flown multiple times in each season. We applied the Regional Atmospheric Mesoscale Modeling system (RAMS) coupled to a simple carbon flux scheme (including fossil fuel), which was run at 10 km resolution, and inverted with an Ensemble Kalman Filter. The domain had 6 eco-regions, and inversions were performed for the four seasons separately. Inversion methods with pixel-dependent and -independent parameters for each eco-region were compared. The two inversion methods, in general, yield comparable flux averages for each eco-region and season, whereas the difference from the prior flux may be large. Posterior fluxes co-sampled along the aircraft flight tracks are usually much closer to the observations than the priors, with a comparable performance for both inversion methods, and with best performance for summer and autumn. The inversions showed more negative CO2 fluxes than the priors, though the latter are obtained from a biosphere model optimized using the Fluxnet database, containing observations from more than 200 locations worldwide. The two different crop ecotypes showed very different CO2 uptakes, which was unknown from the priors. The annual-average uptake is practically zero for the grassland class and for one of the cropland classes, whereas the other cropland class had a large net uptake, possibly because of the abundance of maize there.

Monte Carlo next-event point flux estimation for RCP01

International Nuclear Information System (INIS)

Martz, R.L.; Gast, R.C.; Tyburski, L.J.

1991-01-01

Two next event point estimators have been developed and programmed into the RCP01 Monte Carlo program for solving neutron transport problems in three-dimensional geometry with detailed energy description. These estimators use a simplified but accurate flux-at-a-point tallying technique. Anisotropic scattering in the lab system at the collision site is accounted for by determining the exit energy that corresponds to the angle between the location of the collision and the point detector. Elastic, inelastic, and thermal kernel scattering events are included in this formulation. An averaging technique is used in both estimators to eliminate the well-known problem of infinite variance due to collisions close to the point detector. In a novel approach to improve the estimator's efficiency, a Russian roulette scheme based on anticipated flux fall off is employed where averaging is not appropriate. A second estimator successfully uses a simple rejection technique in conjunction with detailed tracking where averaging isn't needed. Test results show good agreement with known numeric solutions. Efficiencies are examined as a function of input parameter selection and problem difficulty

Estimation de la prévalence de la multimorbidité au moyen du Système canadien de surveillance des maladies chroniques

Directory of Open Access Journals (Sweden)

Allison Feely

2017-01-01

Full Text Available Introduction : Le Système canadien de surveillance des maladies chroniques (SCSMC de l’Agence de la santé publique du Canada utilise une méthode validée et normalisée pour estimer la prévalence des maladies chroniques, par exemple le diabète. L’élargissement de la portée du SCSMC pour inclure la surveillance de la multimorbidité et de la présence concomitante de deux maladies chroniques ou plus pourrait mieux guider la promotion de la santé et la prévention des maladies. L’objectif de notre étude était de déterminer s’il était possible de recourir au SCSMC pour estimer la prévalence de la multimorbidité. Méthodologie : Nous avons utilisé les données administratives sur la santé de sept provinces et de trois territoires portant sur cinq affections chroniques validées (maladies cardiovasculaires, maladies respiratoires, maladies mentales, hypertension et diabète pour estimer la prévalence de la multimorbidité. Nous avons produit des estimations normalisées selon l'âge et spécifiques selon l’âge (à l’aide des données démographiques canadiennes de 1991 pour deux définitions de la multimorbidité, soit deux affections ou plus ou trois affections ou plus sur les cinq affections validées, selon le sexe, la période et la zone géographique. Résultats : Au cours de l’exercice 2011-2012, la prévalence d’au moins deux et d'au moins trois affections chroniques chez les Canadiens de 40 ans ou plus se situait à respectivement 26,5 % et 10,2 %, ce qui est comparable à d’autres estimations faites à partir des données administratives sur la santé. L'augmentation de la prévalence de la multimorbidité avec l’âge était similaire dans toutes les provinces. Les différences de prévalence entre hommes et femmes variaient selon les provinces et territoires. Nous avons également observé une variation importante des estimations au fil des années. Les résultats obtenus étaient comparables pour les

Gas loop - continuous measurement of thermal and fast neutron fluxes; Boucle a gaz - mesure continue de flux de neutrons thermiques et rapides

Energy Technology Data Exchange (ETDEWEB)

Droulers, Y; Pleyber, G; Sciers, P; Maurin, G [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-07-01

The measurement method described in this report can be applied both to thermal and fast neutron fluxes. A description is given of two practical applications in each of these two domains. This method is particularly suitable for measurements carried out on 'loop' type equipment. The measurement of the relative flux variations are carried out with an accuracy of 5 per cent. The choice of the shape of the gas circuit leaves a considerable amount of liberty for the adaptation of the measurement circuit to the experimental conditions. (authors) [French] La methode de mesure defrite dans ce rapport s1 applique aussi bien au flux de neutrons thermiques, qu'au flux de neutrons rapides. On donne la description de deux realisations pratiques dans chacun de ces domaines. Cette methode est particulierement adaptee a des mesures effectuees sur des dispositifs du type 'boucle'. La mesure des variations relatives de flux se fait avec une precision de 5 pour cent. Le choix de la configuration du circuit gazeux donne une grande souplesse dans l'adaptation du circuit de mesure aux conditions experimentales. (auteurs)

Estimation des paramètres de modèles pour la digestion anaérobie

OpenAIRE

Martinez , Ricardo

2003-01-01

La finalité de ce travail a été d'estimer de la meilleure manière possible des paramètres de différents modèles sur la respiration anaérobie. Dans un premier temps nous présentons les bases qu'on utilise pour construire les modèles du procédé biochimique. Puis nous faisons une analyse qualitative des modèles les plus connus sur le sujet. Dans un deuxième temps nous avons suggéré différents modèles, afin de mieux estimer les paramètres du modèle initial. Nous avons mis au point un programme d'...

Estimating surface fluxes over the north Tibetan Plateau area with ASTER imagery

Directory of Open Access Journals (Sweden)

Weiqiang Ma

2009-01-01

Full Text Available Surface fluxes are important boundary conditions for climatological modeling and Asian monsoon system. The recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection radiometer sensor has enabled us to estimate surface fluxes to bridge the gap between local scale flux measurements using micrometeorological instruments and regional scale land-atmosphere exchanges of water and heat fluxes that are fundamental for the understanding of the water cycle in the Asian monsoon system. A parameterization method based on ASTER data and field observations has been proposed and tested for deriving surface albedo, surface temperature, Normalized Difference Vegetation Index (NDVI, Modified Soil Adjusted Vegetation Index (MSAVI, vegetation coverage, Leaf Area Index (LAI, net radiation flux, soil heat flux, sensible heat flux and latent heat flux over heterogeneous land surface in this paper. As a case study, the methodology was applied to the experimental area of the Coordinated Enhanced Observing Period (CEOP Asia-Australia Monsoon Project (CAMP on the Tibetan Plateau (CAMP/Tibet, located at the north Tibetan Plateau. The ASTER data of 24 July 2001, 29 November 2001 and 12 March 2002 was used in this paper for the case of summer, winter and spring. To validate the proposed methodology, the ground-measured surface variables (surface albedo and surface temperature and land surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux were compared to the ASTER derived values. The results show that the derived surface variables and land surface heat fluxes in three different months over the study area are in good accordance with the land surface status. Also, the estimated land surface variables and land surface heat fluxes are in good accordance with ground measurements, and all their absolute percentage difference (APD is less than 10% in the validation sites

Flux estimation algorithms for electric drives: a comparative study

OpenAIRE

Koteich , Mohamad

2016-01-01

International audience; This paper reviews the stator flux estimation algorithms applied to the alternating current motor drives. The so-called voltage model estimation, which consists of integrating the back-electromotive force signal, is addressed. However, in practice , the pure integration is prone to drift problems due to noises, measurement error, stator resistance uncertainty and unknown initial conditions. This limitation becomes more restrictive at low speed operation. Several soluti...

Heat transfer in smooth tubes, between parallel plates, along a semi-infinite plate, in annular spaces and along tube bundles for exponential distribution of the heat flux in forced, laminar or turbulent flow; Transfert de chaleur dans des tubes lisses, entre des plaques planes paralleles, le long d'une plaque plane, dans des espaces annulaires et le long de faisceaux tubulaires pour une repartition exponentielle du flux de chaleur en ecoulement force, laminaire ou turbulent

Energy Technology Data Exchange (ETDEWEB)

Graber, H. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1969-04-01

indiquees les equations pour le calcul explicite du champ de temperature ainsi que le nombre de Nusselt en ecoulement laminaire et flux de chaleur constant. En ecoulement turbulent, les lois concernant la repartition de la diffusivite de quantite de mouvement dans un tube, etablies par H. Reichardt et adaptees a l'espace annulaire et au faisceau tubulaire, permettent la determination du champ de vitesse et du coefficient de perte de charge et consequemment la solution des equations de transfert de chaleur. Les resultats du calcul numerique sont rassembles dans des tableaux et representes par des diagrammes pour un domaine etendu des differents parametres et compares avec des resultats experimentaux. Par un procede simple, on peut determiner la valeur minimale de la longueur d'etablissement du regime thermique. (auteur)

Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

Science.gov (United States)

Tunnell, James W; Torres, Jorge H; Anvari, Bahman

2002-01-01

Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

Estimation de l'exhaustivité des données de facturation des médecins pour la détermination des cas de diabète au moyen des données sur les médicaments d'ordonnance

Directory of Open Access Journals (Sweden)

L. M. Lix

2016-01-01

Full Text Available Introduction : Les changements dans les politiques de remboursement des médecins peuvent faire obstacle à la collecte des données administratives de facturation des médecins, ce qui pourrait mener à des estimations biaisées de la prévalence et de l'incidence des maladies. L'ampleur de cette perte potentielle de données demeure cependant largement inconnue. Notre étude vise à estimer l'exhaustivité de la couverture des cas de maladie pour le Manitoba par les médecins rémunérés à l'acte (RA et par les médecins non rémunérés à l'acte (NRA. Méthodes : Les données administratives du Manitoba ont servi à créer une cohorte dont les membres (20 ans et plus devaient avoir pris un nouveau médicament pour le diabète entre le 1er avril 2007 et le 31 mars 2009. Ces membres ont été classés par mode de paiement du médecin prescripteur (c'est-à-dire rémunérés à l'acte ou non rémunérés à l'acte, puis selon s'ils avaient ou non reçu de diagnostic de diabète d'après les données de facturation des médecins et des dossiers d'hôpitaux. On a utilisé des analyses statistiques χ2 pour tester les différences de caractéristiques entre les deux groupes. Résultats : La cohorte se composait de 12 394 individus, dont 86,4 % avaient reçu une ordonnance de médicament pour le diabète d'un médecin RA. Au total, 1 172 médecins (81,8 % RA ont prescrit ce type de médicaments pour la cohorte. Les membres de la cohorte ayant reçu une ordonnance d'un médecin RA étaient plus âgés et plus susceptibles de résider dans la région sanitaire de Winnipeg que ceux qui avaient reçu une ordonnance d'un médecin NRA. Un plus grand pourcentage de cas traités par des médecins NRA n'avait pas reçu de diagnostic de diabète (18,7 %, contre 14,9 % pour les médecins RA. Conclusion : Les résultats suggèrent une perte minimale de données de facturation des médecins associée aux politiques de rémunération au Manitoba. Cette m

Estimation of the energy needs; Estimation des besoins energetiques

Energy Technology Data Exchange (ETDEWEB)

Ailleret, [Electricite de France (EDF), Dir. General des Etudes de Recherches, 75 - Paris (France)

1955-07-01

The present report draws up the balance on the present and estimable energy consumption for the next twenty years. The present energy comes mainly of the consumption of coal, oil products and essentially hydraulic electric energy. the market development comes essentially of the development the industrial activity and of new applications tributary of the cost and the distribution of the electric energy. To this effect, the atomic energy offers good industrial perspectives in complement of the energy present resources in order to answer the new needs. (M.B.) [French] Le present rapport dresse le bilan sur la consommation energetique actuelle et previsionnelle pour les vingt prochaines annees. L'energie actuelle provient principalement consommation de charbon, de produits petroliers et d'energie electrique essentiellement hydraulique. l'evolution du marche provient essentielement du developpement l'activite industriel et de nouvelles applications tributaire du cout et de la distribution de l'energie electrique. A cet effet, l'energie atomique offre de bonne perspectives industrielles en complement des sources actuelles energetiques afin de repondre aux nouveaux besoins. (M.B.)

169 Effet des flux d'eau sur la capacité de rétention des marais ...

African Journals Online (AJOL)

DieudoneZ

apport des nutriments charriés par les rivières Lwiro et Cirhanyobwa et déterminer ainsi son impact sur l'efficacité de rétention des polluants par les marais Ciranga et Kabamba. Les échantillons d'eaux récoltés dans les rivières et dans les ...

Inverse estimation of heat flux and temperature on nozzle throat-insert inner contour

Energy Technology Data Exchange (ETDEWEB)

Chen, Tsung-Chien [Department of Power Vehicle and Systems Engineering, Chung Cheng Institute of Technology, National Defense University, Ta-Hsi, Tao-Yuan 33509 (China); Liu, Chiun-Chien [Chung Shan Institute of Science and Technology, Lung-Tan, Tao-Yuan 32526 (China)

2008-07-01

During the missile flight, the jet flow with high temperature comes from the heat flux of propellant burning. An enormous heat flux from the nozzle throat-insert inner contour conducted into the nozzle shell will degrade the material strength of nozzle shell and reduce the nozzle thrust efficiency. In this paper, an on-line inverse method based on the input estimation method combined with the finite-element scheme is proposed to inversely estimate the unknown heat flux on the nozzle throat-insert inner contour and the inner wall temperature by applying the temperature measurements of the nozzle throat-insert. The finite-element scheme can easily define the irregularly shaped boundary. The superior capability of the proposed method is demonstrated in two major time-varying estimation cases. The computational results show that the proposed method has good estimation performance and highly facilitates the practical implementation. An effective analytical method can be offered to increase the operation reliability and thermal-resistance layer design in the solid rocket motor. (author)

Global CO2 fluxes estimated from GOSAT retrievals of total column CO2

Directory of Open Access Journals (Sweden)

S. Basu

2013-09-01

Full Text Available We present one of the first estimates of the global distribution of CO2 surface fluxes using total column CO2 measurements retrieved by the SRON-KIT RemoTeC algorithm from the Greenhouse gases Observing SATellite (GOSAT. We derive optimized fluxes from June 2009 to December 2010. We estimate fluxes from surface CO2 measurements to use as baselines for comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we can reproduce the observed CO2 time series at surface and TCCON sites in the tropics and the northern extra-tropics. In contrast, in the southern extra-tropics GOSAT XCO2 leads to enhanced seasonal cycle amplitudes compared to independent measurements, and we identify it as the result of a land–sea bias in our GOSAT XCO2 retrievals. A bias correction in the form of a global offset between GOSAT land and sea pixels in a joint inversion of satellite and surface measurements of CO2 yields plausible global flux estimates which are more tightly constrained than in an inversion using surface CO2 data alone. We show that assimilating the bias-corrected GOSAT data on top of surface CO2 data (a reduces the estimated global land sink of CO2, and (b shifts the terrestrial net uptake of carbon from the tropics to the extra-tropics. It is concluded that while GOSAT total column CO2 provide useful constraints for source–sink inversions, small spatiotemporal biases – beyond what can be detected using current validation techniques – have serious consequences for optimized fluxes, even aggregated over continental scales.

CARBO-CONTROLE. Quantification of the carbon flux and stocks at the european and national scale; CARBO-CONTROLE. Quantification des flux et stocks de carbone au niveau Europeen et national

Energy Technology Data Exchange (ETDEWEB)

Ciais, P

2007-07-01

The CARBO-CONTROLE project aims to evaluate the different methodologies to estimate the CO{sub 2} flux at the european, national and regional scale. The strategy is to combine a crumbling, down scaling, of the flux at a big scale, by inverting the atmospheric CO{sub 2} measures with a aggregation, up scaling, of the national stocks and flux from the climatic parameters of a model of ecosystems.They show that with the monthly data of the global network of CO{sub 2} monitoring stations, it is possible to obtain an estimation of the european flux. Meanwhile the errors bond to the leak of continental stations are of the order of the flux average. (A.L.B.)

Toward an estimation of daily european CO2 fluxes at high spatial resolution by inversion of atmospheric transport

International Nuclear Information System (INIS)

Carouge, C.

2006-04-01

Since the end of the 1980's, measurements of atmospheric carbon dioxide have been used to estimate global and regional fluxes of CO 2 . This is possible because CO 2 concentration variation is directly linked to flux variation by atmospheric transport. We can find the spatial and temporal distribution of fluxes from concentration measurements by 'inverting' the atmospheric transport. Until recently, most CO 2 inversions have used monthly mean CO 2 atmospheric concentration measurements to infer monthly fluxes. Considering the sparseness of the global CO 2 measurement network, fluxes were a priori aggregated on sub-continental regions and distributed on a fixed spatial pattern within these regions. Only one flux coefficient per month for each region was optimized. With this strong constraint, estimated fluxes can be biased by non-perfect distribution of fluxes within each region (aggregation error). Therefore, flux estimation at model resolution is being developed where the hard constraint of a fixed distribution within a region is replaced by a soft constraint of covariances between flux uncertainties. The use of continuous observations from an increasing number of measurement sites offers a new challenge for inverse modelers. We investigate the use of daily averaged observations to infer daily CO 2 fluxes at model resolution over Europe. We have developed a global synthesis Bayesian inversion to invert daily fluxes at model resolution (50 x 50 km over Europe) from daily averaged CO 2 concentrations. We have obtained estimated fluxes for the year 2001 over Europe using the 10 European continuous sites from the AEROCARB network. The global atmospheric model LMDZt is used with a nested grid over Europe. It is necessary to add a priori spatial and temporal correlations between flux errors to constrain the Bayesian inversion. We present the impact on estimated fluxes of three different spatial correlations based on distance between pixels, climate and vegetation

A punctual flux estimator and reactions rates optimization in neutral particles transport calculus by the Monte Carlo method; Mise au point d'un estimateur ponctuel du flux et des taux de reactions dans les calculs de transport de particules neutres par la methode de monte carlo

Energy Technology Data Exchange (ETDEWEB)

Authier, N

1998-12-01

One of the questions asked in radiation shielding problems is the estimation of the radiation level in particular to determine accessibility of working persons in controlled area (nuclear power plants, nuclear fuel reprocessing plants) or to study the dose gradients encountered in material (iron nuclear vessel, medical therapy, electronics in satellite). The flux and reaction rate estimators used in Monte Carlo codes give average values in volumes or on surfaces of the geometrical description of the system. But in certain configurations, the knowledge of punctual deposited energy and dose estimates are necessary. The Monte Carlo estimate of the flux at a point of interest is a calculus which presents an unbounded variance. The central limit theorem cannot be applied thus no easy confidencelevel may be calculated. The convergence rate is then very poor. We propose in this study a new solution for the photon flux at a point estimator. The method is based on the 'once more collided flux estimator' developed earlier for neutron calculations. It solves the problem of the unbounded variance and do not add any bias to the estimation. We show however that our new sampling schemes specially developed to treat the anisotropy of the photon coherent scattering is necessary for a good and regular behavior of the estimator. This developments integrated in the TRIPOLI-4 Monte Carlo code add the possibility of an unbiased punctual estimate on media interfaces. (author)

A punctual flux estimator and reactions rates optimization in neutral particles transport calculus by the Monte Carlo method; Mise au point d'un estimateur ponctuel du flux et des taux de reactions dans les calculs de transport de particules neutres par la methode de monte carlo

Energy Technology Data Exchange (ETDEWEB)

Authier, N

1998-12-01

One of the questions asked in radiation shielding problems is the estimation of the radiation level in particular to determine accessibility of working persons in controlled area (nuclear power plants, nuclear fuel reprocessing plants) or to study the dose gradients encountered in material (iron nuclear vessel, medical therapy, electronics in satellite). The flux and reaction rate estimators used in Monte Carlo codes give average values in volumes or on surfaces of the geometrical description of the system. But in certain configurations, the knowledge of punctual deposited energy and dose estimates are necessary. The Monte Carlo estimate of the flux at a point of interest is a calculus which presents an unbounded variance. The central limit theorem cannot be applied thus no easy confidencelevel may be calculated. The convergence rate is then very poor. We propose in this study a new solution for the photon flux at a point estimator. The method is based on the 'once more collided flux estimator' developed earlier for neutron calculations. It solves the problem of the unbounded variance and do not add any bias to the estimation. We show however that our new sampling schemes specially developed to treat the anisotropy of the photon coherent scattering is necessary for a good and regular behavior of the estimator. This developments integrated in the TRIPOLI-4 Monte Carlo code add the possibility of an unbiased punctual estimate on media interfaces. (author)

Formulation of the energetic spectral distribution of in pile neutron flux (energies greater than a few hundred electron volts) (1963); Formulation des repartitions spectrales energetiques de flux neutroniques en pile (energies superieures a quelques centaines d'electrons-volts) (1963)

Energy Technology Data Exchange (ETDEWEB)

Genthon, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

In the present report an expression is deduced for the spectral distribution of flux of over a few hundred electron volts; it is valid for most cases of thermal neutron reactors. This expression is: {psi}(E) = K [{psi}{sub o}(E) + h {psi}{sub e}(E)] {psi}{sub o}(E) is the so-called 'homogeneous' constituent of the flux; it corresponds approximately to the case of an infinite homogeneous medium; it is of the type: Y(V - E) e{sup (b{radical}}{sup E)}/E + Y(E-V) F E{sup {upsilon}} e{sup -{beta}}{sup E} The parameters V and F are such that {psi}{sub o}(E) and its derivative are continuous at the junction energy V. {psi}{sub e}(E) is the 'heterogeneous' constituent of the flux; it is of the type: E{sup {upsilon}} e{sup -{beta}}{sup E}. The various parameters of {psi}(E) are on the one hand characteristic of the nature of the reactor moderator, and on the other hand determined by a resonant flux measurement and one, or possibly two, measurements using a fast neutron threshold detector. We have been led furthermore to define an expression for the threshold reaction section which is more exact than the conventional transition function. (author) [French] Il est etabli, dans le present rapport, une formulation {psi}(E) des repartitions spectrales de flux au-dessus de quelques centaines d'electron-s volts, valable dans la majeure partie des cas de piles dites a neutrons thermiques. Cette formulation s'exprime: {psi}(E) = K [{psi}{sub o}(E) + h {psi}{sub e}(E)] {psi}{sub o}(E) est la composante dite 'homogene' du flux; elle correspond a peu pres au cas d'un milieu infini homogene; elle est du type: Y(V - E) e{sup (b{radical}}{sup E)}/E + Y(E-V) F E{sup {upsilon}} e{sup -{beta}}{sup E} les parametres V et F sont tels que {psi}{sub o}(E) et sa derivee soient continues a l'energie de jonction V. {psi}{sub e} est la composante dite 'heterogene' du flux ; elle est du type: E{sup {upsilon}} e{sup -{beta}}{sup E}. Les differents parametres de {psi}(E) sont, d'une part

Forest inventory-based estimation of carbon stocks and flux in California forests in 1990.

Science.gov (United States)

Jeremy S. Fried; Xiaoping. Zhou

2008-01-01

Estimates of forest carbon stores and flux for California circa 1990 were modeled from forest inventory data in support of California’s legislatively mandated greenhouse gas inventory. Reliable estimates of live-tree carbon stores and flux on timberlands outside of national forest could be calculated from periodic inventory data collected in the 1980s and 1990s;...

Evaluation of Latent Heat Flux Fields from Satellites and Models during SEMAPHORE.

Science.gov (United States)

Bourras, Denis; Liu, W. Timothy; Eymard, Laurence; Tang, Wenqing

2003-02-01

Latent heat fluxes were derived from satellite observations in the region of Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE), which was conducted near the Azores islands in the North Atlantic Ocean in autumn of 1993. The satellite fluxes were compared with output fields of two atmospheric circulation models and in situ measurements. The rms error of the instantaneous satellite fluxes is between 35 and 40 W m-2 and the bias is 60-85 W m-2. The large bias is mainly attributed to a bias in satellite-derived atmospheric humidity and is related to the particular shape of the vertical humidity profiles during SEMAPHORE. The bias in humidity implies that the range of estimated fluxes is smaller than the range of ship fluxes, by 34%-38%. The rms errors for fluxes from models are 30-35 W m-2, and the biases are smaller than the biases in satellite fluxes (14-18 W m-2). Two case studies suggest that the satellites detect horizontal gradients of wind speed and specific humidity if the magnitude of the gradients exceeds a detection threshold, which is 1.27 g kg-1 (100 km)-1 for specific humidity and between 0.35 and 0.82 m s-1 (30 km)-1 for wind speed. In contrast, the accuracy of the spatial gradients of bulk variables from models always varies as a function of the location and number of assimilated observations. A comparison between monthly fluxes from satellites and models reveals that satellite-derived flux anomaly fields are consistent with reanalyzed fields, whereas operational model products lack part of the mesoscale structures present in the satellite fields.

Contribution to the methods for estimating uranium deposits (1963); Contribution aux methodes d'estimation des gisements d'uranium (1963)

Energy Technology Data Exchange (ETDEWEB)

Carlier, A [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-02-15

index is intended to help find in this publication the definitions, formulae or theories that most interest the reader. (author) [French] Apres avoir rappele ce qu'est un gisement, de valeur economique, sur la base du marginalisme, l'auteur distingue plusieurs categories de reserves suivant le degre de connaissance du gite et suivant le poste d'exploitation ou est considere le minerai. Il rejette les anciennes categories 'a vue', 'probable' et 'possible' pour les remplacer par des categories mieux adaptees. Les reserves sensu stricto sont celles pour lesquelles on est en mesure de calculer l'erreur aleatoire d'estimation. Une notion est introduite a ce sujet, c'est le contraste naturel des teneurs dans un gite (coefficient de dispersion absolu {alpha}). L'auteur distingue 3 formes de reconnaissance des gites, la mauvaise, la bonne et l'ideale. La premiere est la reconnaissance anarchique trop souvent recontree la seconde est la reconnaissance logique fondee sur une implantation systematique des galeries, sondages, etc. La troisieme, difficile a atteindre, est celle qui minimise la depense des recherches pour une precision fixee a l'avance. Une partie de l'ouvrage traite des erreurs d'echantillonnage telles que celles resultant du quartage d'un lot (theorie de Pierre GY), ou celles issues de l'emploi de la radioactivite pour estimer les teneurs. Une autre partie traite des erreurs d'extension (assimilation du gite a ses echantillons) et donne les formules essentielles pour calculer ces erreurs aleatoires (geostatistique de Matheron). A propos de l'estimateur lui-meme, on note la disharmonie entre l'echantillon et sa zone d'influence, et le moyen de remedier a cette discordance par le 'krigeage' est fourni dans l'ouvrage. La these donne de nombreux exemples des differents parametres numeriques qui caracterisent un gite d'uranium (coefficient de dispersion absolu) ou un minerai d'uranium (parametre de liberation), ainsi que plusieurs exemples de droite de correspondance de

A procedure for the estimation over time of metabolic fluxes in scenarios where measurements are uncertain and/or insufficient

Directory of Open Access Journals (Sweden)

Picó Jesús

2007-10-01

Full Text Available Abstract Background An indirect approach is usually used to estimate the metabolic fluxes of an organism: couple the available measurements with known biological constraints (e.g. stoichiometry. Typically this estimation is done under a static point of view. Therefore, the fluxes so obtained are only valid while the environmental conditions and the cell state remain stable. However, estimating the evolution over time of the metabolic fluxes is valuable to investigate the dynamic behaviour of an organism and also to monitor industrial processes. Although Metabolic Flux Analysis can be successively applied with this aim, this approach has two drawbacks: i sometimes it cannot be used because there is a lack of measurable fluxes, and ii the uncertainty of experimental measurements cannot be considered. The Flux Balance Analysis could be used instead, but the assumption of optimal behaviour of the organism brings other difficulties. Results We propose a procedure to estimate the evolution of the metabolic fluxes that is structured as follows: 1 measure the concentrations of extracellular species and biomass, 2 convert this data to measured fluxes and 3 estimate the non-measured fluxes using the Flux Spectrum Approach, a variant of Metabolic Flux Analysis that overcomes the difficulties mentioned above without assuming optimal behaviour. We apply the procedure to a real problem taken from the literature: estimate the metabolic fluxes during a cultivation of CHO cells in batch mode. We show that it provides a reliable and rich estimation of the non-measured fluxes, thanks to considering measurements uncertainty and reversibility constraints. We also demonstrate that this procedure can estimate the non-measured fluxes even when there is a lack of measurable species. In addition, it offers a new method to deal with inconsistency. Conclusion This work introduces a procedure to estimate time-varying metabolic fluxes that copes with the insufficiency of

Estimating the amount and distribution of radon flux density from the soil surface in China

International Nuclear Information System (INIS)

Zhuo Weihai; Guo Qiuju; Chen Bo; Cheng Guan

2008-01-01

Based on an idealized model, both the annual and the seasonal radon ( 222 Rn) flux densities from the soil surface at 1099 sites in China were estimated by linking a database of soil 226 Ra content and a global ecosystems database. Digital maps of the 222 Rn flux density in China were constructed in a spatial resolution of 25 km x 25 km by interpolation among the estimated data. An area-weighted annual average 222 Rn flux density from the soil surface across China was estimated to be 29.7 ± 9.4 mBq m -2 s -1 . Both regional and seasonal variations in the 222 Rn flux densities are significant in China. Annual average flux densities in the southeastern and northwestern China are generally higher than those in other regions of China, because of high soil 226 Ra content in the southeastern area and high soil aridity in the northwestern one. The seasonal average flux density is generally higher in summer/spring than winter, since relatively higher soil temperature and lower soil water saturation in summer/spring than other seasons are common in China

Groundwater flux estimation in streams: A thermal equilibrium approach

Science.gov (United States)

Zhou, Yan; Fox, Garey A.; Miller, Ron B.; Mollenhauer, Robert; Brewer, Shannon

2018-06-01

Stream and groundwater interactions play an essential role in regulating flow, temperature, and water quality for stream ecosystems. Temperature gradients have been used to quantify vertical water movement in the streambed since the 1960s, but advancements in thermal methods are still possible. Seepage runs are a method commonly used to quantify exchange rates through a series of streamflow measurements but can be labor and time intensive. The objective of this study was to develop and evaluate a thermal equilibrium method as a technique for quantifying groundwater flux using monitored stream water temperature at a single point and readily available hydrological and atmospheric data. Our primary assumption was that stream water temperature at the monitored point was at thermal equilibrium with the combination of all heat transfer processes, including mixing with groundwater. By expanding the monitored stream point into a hypothetical, horizontal one-dimensional thermal modeling domain, we were able to simulate the thermal equilibrium achieved with known atmospheric variables at the point and quantify unknown groundwater flux by calibrating the model to the resulting temperature signature. Stream water temperatures were monitored at single points at nine streams in the Ozark Highland ecoregion and five reaches of the Kiamichi River to estimate groundwater fluxes using the thermal equilibrium method. When validated by comparison with seepage runs performed at the same time and reach, estimates from the two methods agreed with each other with an R2 of 0.94, a root mean squared error (RMSE) of 0.08 (m/d) and a Nash-Sutcliffe efficiency (NSE) of 0.93. In conclusion, the thermal equilibrium method was a suitable technique for quantifying groundwater flux with minimal cost and simple field installation given that suitable atmospheric and hydrological data were readily available.

Sea ice-atmospheric interaction: Application of multispectral satellite data in polar surface energy flux estimates

Science.gov (United States)

Steffen, Konrad; Key, J.; Maslanik, J.; Schweiger, A.

1993-01-01

This is the third annual report on: Sea Ice-Atmosphere Interaction - Application of Multispectral Satellite Data in Polar Surface Energy Flux Estimates. The main emphasis during the past year was on: radiative flux estimates from satellite data; intercomparison of satellite and ground-based cloud amounts; radiative cloud forcing; calibration of the Advanced Very High Resolution Radiometer (AVHRR) visible channels and comparison of two satellite derived albedo data sets; and on flux modeling for leads. Major topics covered are arctic clouds and radiation; snow and ice albedo, and leads and modeling.

Caractérisation et estimation du gonflement des argiles algériennes, cas des argiles de Médéa

Directory of Open Access Journals (Sweden)

Medjnoun Amal

2014-04-01

Full Text Available Le matériau argileux, dur et cassant lorsqu’il est asséché, présente la particularité de voir sa consistance se modifier en fonction de sa teneur en eau. Un certain degré d’humidité peut le transformer en un matériau plastique et malléable. Ces modifications de consistance peuvent s’accompagner, en fonction de la structure particulière de certains minéraux argileux, de variations de volume plus ou moins conséquentes qui se manifestent soit sous forme d’une forte augmentation de volume (phénomène de gonflement lorsque la teneur en eau augmente ou de rétrécissement (phénomène de retrait en période de déficit pluviométrique marqué. Ce comportement est lié essentiellement à certains paramètres environnementaux de ces sols à l’exemple de la géologie et de la lithologie du site, du climat, etc. La prévision du potentiel de gonflement des sols est possible moyennant certaines méthodes empiriques basées sur des paramètres d’identification tels que la plasticité et la granulométrie déterminées lors des campagnes de reconnaissance. Une fois le caractère de gonflement pressenti dans la phase de reconnaissance préliminaire, une estimation de l’amplitude et de la pression de gonflement peut être établie à partir des corrélations, qui tendent à mettre en relation les paramètres de gonflement avec les paramètres géotechniques issus des essais d’identification. C’est dans cet aspect que s’inscrit cet article en traitant le cas d’un site algérien. Les résultats obtenus montrent une concordance entre les méthodes empiriques appliquées. Ces résultats sont aussi comparés avec ceux obtenus des essais de gonflement à l’oedométrique. L’évolution de la structure argileuse au cours de retrait-gonflement est suivie dans l’objectif de comprendre le mécanisme de gonflement.

The influence of xenon poisoning in high-flux reactors on the choice of control rod speeds (1961); Influence de l'empoisonnement xenon dans les piles a haut flux sur le choix de la vitesse des barres de controle (1961)

Energy Technology Data Exchange (ETDEWEB)

Furet, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

- The general laws are restated concerning the changes in xenon and iodine concentrations in thermal neutron reactors, assuming an uniform neutron flux distribution in the core. It is shown how the evolution in the xenon poisoning influences the selection of the control rod speed, at start-up. Certain simple methods of calculation are developed making it possible to resolve the problem of the choice of this speed in the case where the xenon poisoning is taken into account. (author) [French] - On rappelle les lois generales relatives aux evolutions de concentration xenon et iode dans les piles atomiques a neutrons thermiques lorsqu'on suppose une repartition uniforme du flux de neutrons dans le coeur. On montre comment l'evolution de l'empoisonnement xenon influe sur le choix de la vitesse des barres de controle en periode de demarrage. On developpe certaines methodes de calculs simples permettant de resoudre le probleme du choix de la vitesse des barres de controle, dans le cas ou l'on tient compte de l'empoisonnement xenon. (auteur)

Estimates of CO2 fluxes over the city of Cape Town, South Africa, through Bayesian inverse modelling

Science.gov (United States)

Nickless, Alecia; Rayner, Peter J.; Engelbrecht, Francois; Brunke, Ernst-Günther; Erni, Birgit; Scholes, Robert J.

2018-04-01

We present a city-scale inversion over Cape Town, South Africa. Measurement sites for atmospheric CO2 concentrations were installed at Robben Island and Hangklip lighthouses, located downwind and upwind of the metropolis. Prior estimates of the fossil fuel fluxes were obtained from a bespoke inventory analysis where emissions were spatially and temporally disaggregated and uncertainty estimates determined by means of error propagation techniques. Net ecosystem exchange (NEE) fluxes from biogenic processes were obtained from the land atmosphere exchange model CABLE (Community Atmosphere Biosphere Land Exchange). Uncertainty estimates were based on the estimates of net primary productivity. CABLE was dynamically coupled to the regional climate model CCAM (Conformal Cubic Atmospheric Model), which provided the climate inputs required to drive the Lagrangian particle dispersion model. The Bayesian inversion framework included a control vector where fossil fuel and NEE fluxes were solved for separately.Due to the large prior uncertainty prescribed to the NEE fluxes, the current inversion framework was unable to adequately distinguish between the fossil fuel and NEE fluxes, but the inversion was able to obtain improved estimates of the total fluxes within pixels and across the domain. The median of the uncertainty reductions of the total weekly flux estimates for the inversion domain of Cape Town was 28 %, but reach as high as 50 %. At the pixel level, uncertainty reductions of the total weekly flux reached up to 98 %, but these large uncertainty reductions were for NEE-dominated pixels. Improved corrections to the fossil fuel fluxes would be possible if the uncertainty around the prior NEE fluxes could be reduced. In order for this inversion framework to be operationalised for monitoring, reporting, and verification (MRV) of emissions from Cape Town, the NEE component of the CO2 budget needs to be better understood. Additional measurements of Δ14C and δ13C isotope

Estimation of bulk transfer coefficient for latent heat flux (Ce)

Digital Repository Service at National Institute of Oceanography (India)

Sadhuram, Y.

The bulk transfer coefficient for latent heat flux (Ce) has been estimated over the Arabian Sea from the moisture budget during the pre-monsoon season of 1988. The computations have been made over two regions (A: 0-8 degrees N: 60-68 degrees E: B: 0...

Heat flux exchange estimation by using ATSR SST data in TOGA area

Science.gov (United States)

Xue, Yong; Lawrence, Sean P.; Llewellyn-Jones, David T.

1995-12-01

The study of phenomena such as ENSO requires consideration of the dynamics and thermodynamics of the coupled ocean-atmosphere system. The dynamic and thermal properties of the atmosphere and ocean are directly affected by air-sea transfers of fluxes of momentum, heat and moisture. In this paper, we present results of turbulent heat fluxes calculated by using two years (1992 and 1993) monthly average TOGA data and ATSR SST data in TOGA area. A comparison with published results indicates good qualitative agreement. Also, we compared the results of heat flux exchange by using ATSR SST data and by using the TOGA bucket SST data. The ATSR SST data set has been shown to be useful in helping to estimate the large space scale heat flux exchange.

Comparison of sap flux, moisture flux tower and MODIS enhanced vegetation index methods for estimating riparian evapotranspiration

Science.gov (United States)

Nagler, Pamela L.; Glenn, Edward P.; Morino, Kiyomi; Neale, Christopher M.U; Cosh, Michael H.

2010-01-01

Riparian evapotranspiration (ET) was measured on a salt cedar (Tamarix spp.) dominated river terrace on the Lower Colorado River from 2007 to 2009 using tissue-heat-balance sap flux sensors at six sites representing very dense, medium dense, and sparse stands of plants. Salt cedar ET varied markedly across sites, and sap flux sensors showed that plants were subject to various degrees of stress, detected as mid-day depression of transpiration and stomatal conductance. Sap flux results were scaled from the leaf level of measurement to the stand level by measuring plant-specific leaf area index and fractional ground cover at each site. Results were compared to Bowen ratio moisture tower data available for three of the sites. Sap flux sensors and flux tower results ranked the sites the same and had similar estimates of ET. A regression equation, relating measured ET of salt cedar and other riparian plants and crops on the Lower Colorado River to the Enhanced Vegetation Index from the MODIS sensor on the Terra satellite and reference crop ET measured at meteorological stations, was able to predict actual ET with an accuracy or uncertainty of about 20%, despite between-site differences for salt cedar. Peak summer salt cedar ET averaged about 6 mm d-1 across sites and methods of measurement.

A One-Source Approach for Estimating Land Surface Heat Fluxes Using Remotely Sensed Land Surface Temperature

Directory of Open Access Journals (Sweden)

Yongmin Yang

2017-01-01

Full Text Available The partitioning of available energy between sensible heat and latent heat is important for precise water resources planning and management in the context of global climate change. Land surface temperature (LST is a key variable in energy balance process and remotely sensed LST is widely used for estimating surface heat fluxes at regional scale. However, the inequality between LST and aerodynamic surface temperature (Taero poses a great challenge for regional heat fluxes estimation in one-source energy balance models. To address this issue, we proposed a One-Source Model for Land (OSML to estimate regional surface heat fluxes without requirements for empirical extra resistance, roughness parameterization and wind velocity. The proposed OSML employs both conceptual VFC/LST trapezoid model and the electrical analog formula of sensible heat flux (H to analytically estimate the radiometric-convective resistance (rae via a quartic equation. To evaluate the performance of OSML, the model was applied to the Soil Moisture-Atmosphere Coupling Experiment (SMACEX in United States and the Multi-Scale Observation Experiment on Evapotranspiration (MUSOEXE in China, using remotely sensed retrievals as auxiliary data sets at regional scale. Validated against tower-based surface fluxes observations, the root mean square deviation (RMSD of H and latent heat flux (LE from OSML are 34.5 W/m2 and 46.5 W/m2 at SMACEX site and 50.1 W/m2 and 67.0 W/m2 at MUSOEXE site. The performance of OSML is very comparable to other published studies. In addition, the proposed OSML model demonstrates similar skills of predicting surface heat fluxes in comparison to SEBS (Surface Energy Balance System. Since OSML does not require specification of aerodynamic surface characteristics, roughness parameterization and meteorological conditions with high spatial variation such as wind speed, this proposed method shows high potential for routinely acquisition of latent heat flux estimation

Testing an inversion method for estimating electron energy fluxes from all-sky camera images

Directory of Open Access Journals (Sweden)

N. Partamies

2004-06-01

Full Text Available An inversion method for reconstructing the precipitating electron energy flux from a set of multi-wavelength digital all-sky camera (ASC images has recently been developed by tomografia. Preliminary tests suggested that the inversion is able to reconstruct the position and energy characteristics of the aurora with reasonable accuracy. This study carries out a thorough testing of the method and a few improvements for its emission physics equations. We compared the precipitating electron energy fluxes as estimated by the inversion method to the energy flux data recorded by the Defense Meteorological Satellite Program (DMSP satellites during four passes over auroral structures. When the aurorae appear very close to the local zenith, the fluxes inverted from the blue (427.8nm filtered ASC images or blue and green line (557.7nm images together give the best agreement with the measured flux values. The fluxes inverted from green line images alone are clearly larger than the measured ones. Closer to the horizon the quality of the inversion results from blue images deteriorate to the level of the ones from green images. In addition to the satellite data, the precipitating electron energy fluxes were estimated from the electron density measurements by the EISCAT Svalbard Radar (ESR. These energy flux values were compared to the ones of the inversion method applied to over 100 ASC images recorded at the nearby ASC station in Longyearbyen. The energy fluxes deduced from these two types of data are in general of the same order of magnitude. In 35% of all of the blue and green image inversions the relative errors were less than 50% and in 90% of the blue and green image inversions less than 100%. This kind of systematic testing of the inversion method is the first step toward using all-sky camera images in the way in which global UV images have recently been used to estimate the energy fluxes. The advantages of ASCs, compared to the space-born imagers, are

Bounded estimation of flux-at-a-point for one or more detectors

International Nuclear Information System (INIS)

Steinberg, H.A.

1974-01-01

The procedure for biasing the collision density of Monte Carlo particles, so that the estimation of flux at a point detector is bounded, is described. The theory and program design of the solution of the problem of obtaining estimates for several detectors during a single Monte Carlo calculation is presented. 4 references. (U.S.)

The Chandra Source Catalog 2.0: Estimating Source Fluxes

Science.gov (United States)

Primini, Francis Anthony; Allen, Christopher E.; Miller, Joseph; Anderson, Craig S.; Budynkiewicz, Jamie A.; Burke, Douglas; Chen, Judy C.; Civano, Francesca Maria; D'Abrusco, Raffaele; Doe, Stephen M.; Evans, Ian N.; Evans, Janet D.; Fabbiano, Giuseppina; Gibbs, Danny G., II; Glotfelty, Kenny J.; Graessle, Dale E.; Grier, John D.; Hain, Roger; Hall, Diane M.; Harbo, Peter N.; Houck, John C.; Lauer, Jennifer L.; Laurino, Omar; Lee, Nicholas P.; Martínez-Galarza, Juan Rafael; McCollough, Michael L.; McDowell, Jonathan C.; McLaughlin, Warren; Morgan, Douglas L.; Mossman, Amy E.; Nguyen, Dan T.; Nichols, Joy S.; Nowak, Michael A.; Paxson, Charles; Plummer, David A.; Rots, Arnold H.; Siemiginowska, Aneta; Sundheim, Beth A.; Tibbetts, Michael; Van Stone, David W.; Zografou, Panagoula

2018-01-01

The Second Chandra Source Catalog (CSC2.0) will provide information on approximately 316,000 point or compact extended x-ray sources, derived from over 10,000 ACIS and HRC-I imaging observations available in the public archive at the end of 2014. As in the previous catalog release (CSC1.1), fluxes for these sources will be determined separately from source detection, using a Bayesian formalism that accounts for background, spatial resolution effects, and contamination from nearby sources. However, the CSC2.0 procedure differs from that used in CSC1.1 in three important aspects. First, for sources in crowded regions in which photometric apertures overlap, fluxes are determined jointly, using an extension of the CSC1.1 algorithm, as discussed in Primini & Kashyap (2014ApJ...796…24P). Second, an MCMC procedure is used to estimate marginalized posterior probability distributions for source fluxes. Finally, for sources observed in multiple observations, a Bayesian Blocks algorithm (Scargle, et al. 2013ApJ...764..167S) is used to group observations into blocks of constant source flux.In this poster we present details of the CSC2.0 photometry algorithms and illustrate their performance in actual CSC2.0 datasets.This work has been supported by NASA under contract NAS 8-03060 to the Smithsonian Astrophysical Observatory for operation of the Chandra X-ray Center.

GENOMIQUE ET LIPIDES Génomique et métabolisme des lipides des plantes

Directory of Open Access Journals (Sweden)

Delseny Michel

2002-03-01

Full Text Available Il existe dans les bases de données publiques une énorme quantité de séquences d’ADN dérivées de plantes, et notamment la séquence complète du génome d’Arabidopsis thaliana, une plante modèle pour les oléagineux, proche parente du colza. Ces données constituent une ressource importante non seulement pour la compréhension de métabolisme lipidique et de sa régulation, mais aussi pour la sélection et le développement de variétés nouvelles d’oléagineux produisant davantage d’huiles ou des huiles de composition nouvelle. Cette abondance de séquences peut être exploitée, en utilisant les recherches d’homologies, pour identifier les gènes, pour obtenir des informations sur leur fonction, comme pour repérer des gènes candidats codant des fonctions nouvelles. L’analyse de ces bases de données a révélé que la majeure partie des gènes codant des enzymes impliquées dans le métabolisme lipidique appartient à des petites familles multigéniques, reflétant la diversification des fonctions des isoformes. Une analyse du catalogue des ADNc séquencés en aveugle reflète les niveaux d’expression des différents gènes et fournit un aperçu des régulations des flux au travers des voies métaboliques conduisant à la biosynthèse des lipides de réserve. La disponibilité de mutants et de lignées transgéniques d’Arabidopsis et le développement de puces à ADN qui permettent l’analyse simultanée de plusieurs milliers de gènes conduiront à une meilleure compréhension des facteurs qui régulent le métabolisme des huiles dans les graines. Une telle connaissance facilitera la manipulation de la composition des huiles et des quantités produites dans les graines.

Immigration et affirmation : le cas des Africains en France

Directory of Open Access Journals (Sweden)

Claude Zesseu

2011-04-01

Full Text Available Cet article est un tour d’horizon des questions reliées à l’immigration et à l’intégration des Africains en France, de la période coloniale à nos jours. Il retrace les dates marquantes et les réseaux du flux migratoire Afrique-France et présente une synthèse ciblée des politiques d’immigration françaises. Il engage une réflexion sur les facteurs susceptibles d’entraver ou de favoriser l’intégration et l’affirmation socio-économique et politique des immigrants africains en France.

Preliminary estimation of Vulcano of CO2 budget and continuous monitoring of summit soil CO2 flux

OpenAIRE

Inguaggiato, S.; Mazot, A.; Diliberto, I. S.; Rouwet, D.; Vita, F.; Capasso, G.; Bobrowski, N.; Inguaggiato, C.; Grassa, F.

2008-01-01

Total CO2 output from fumaroles, soil gases, bubbling and water dissolved gases were estimated at Vulcano Island, Italy. The fumaroles output has been estimated from SO2 plume flux, while soil flux emission has been carried out through 730 CO2 fluxes measured on the island surface, performed by means of accumulation chamber method. Vulcano Island, located in the Aeolian Archipelago, is an active volcano that has been in state of solphataric activity, since the last eru...

Quantifying Surface Energy Flux Estimation Uncertainty Using Land Surface Temperature Observations

Science.gov (United States)

French, A. N.; Hunsaker, D.; Thorp, K.; Bronson, K. F.

2015-12-01

Remote sensing with thermal infrared is widely recognized as good way to estimate surface heat fluxes, map crop water use, and detect water-stressed vegetation. When combined with net radiation and soil heat flux data, observations of sensible heat fluxes derived from surface temperatures (LST) are indicative of instantaneous evapotranspiration (ET). There are, however, substantial reasons LST data may not provide the best way to estimate of ET. For example, it is well known that observations and models of LST, air temperature, or estimates of transport resistances may be so inaccurate that physically based model nevertheless yield non-meaningful results. Furthermore, using visible and near infrared remote sensing observations collected at the same time as LST often yield physically plausible results because they are constrained by less dynamic surface conditions such as green fractional cover. Although sensitivity studies exist that help identify likely sources of error and uncertainty, ET studies typically do not provide a way to assess the relative importance of modeling ET with and without LST inputs. To better quantify model benefits and degradations due to LST observational inaccuracies, a Bayesian uncertainty study was undertaken using data collected in remote sensing experiments at Maricopa, Arizona. Visible, near infrared and thermal infrared data were obtained from an airborne platform. The prior probability distribution of ET estimates were modeled using fractional cover, local weather data and a Penman-Monteith mode, while the likelihood of LST data was modeled from a two-source energy balance model. Thus the posterior probabilities of ET represented the value added by using LST data. Results from an ET study over cotton grown in 2014 and 2015 showed significantly reduced ET confidence intervals when LST data were incorporated.

Technique of nuclear reactors controls; Technique des controles des reacteurs nucleaires

Energy Technology Data Exchange (ETDEWEB)

Weill, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1953-12-15

This report deal about 'Techniques of control of the nuclear reactors' in the goal to achieve the control of natural uranium reactors and especially the one of Saclay. This work is mainly about the measurement into nuclear parameters and go further in the measurement of thermodynamic variables,etc... putting in relief the new features required on behalf of the detectors because of their use in the thermal neutrons flux. In the domain of nuclear measurement, we indicate the realizations and the results obtained with thermal neutron detectors and for the measurement of ionizations currents. We also treat the technical problem of the start-up of a reactor and of the reactivity measurement. We give the necessary details for the comprehension of all essential diagrams and plans put on, in particular, for the reactor of Saclay. (author) [French] Nous avons aborde le probleme de la ''Technique du Controle des reacteurs nucleaires'' dans le but de realiser le controle du reacteur de Saclay. C'est ainsi que nous avons ete amene a etudier le probleme dans son ensemble, tel qu'il se pose pour tout reacteur a uranium naturel. Ce travail traite principalement du domaine des mesures a caractere nucleaire et s'etend dans le domaine des mesures thermodynamque de niveaux, etc... mettant en relief les caracteristiques nouvelles exigees de la part des detecteurs du fait de leur utilisation dans le flux de neutrons thermiques. Dans le domaine de mesures nucleaires, nous indiquons principalement les realisations et les resultats obtenus pour les detecteurs de neutrons thermiques et pour la mesure de courants d'ionisations. Nous traitons egalement du probleme technique du demarrage d'un reacteur et du probleme de la mesure de la reactivite. Nous donnons les details necessaires a la comrehension de tous les schemas et plans de cablages essentiels mis au point, en particulier, pour le reacteur de Saclay. (auteur)

Gas Well Testing Analysis Using Finite-Difference Models and Optimization Techniques Analyse d'essais de puits de gaz par des modèles utilisant la méthode des différences finies et par des techniques d'optimisation

Directory of Open Access Journals (Sweden)

Darderes E. A.

2006-11-01

paramètres à partir d'essais de puits de gaz. Une des plus performantes est l'analyse du régime pseudo-permanent pour lequel on trouve, sur un graphique semi-logarithmique, une relation linéaire entre la pseudo-pression d'un gaz réel et le temps. Une autre méthode est l'ajustement à des courbes types. Les deux méthodes présentent l'inconvénient de ne pouvoir être rigoureusement appliquées qu'à des cas spécifiques. Cet article expose une méthode générale permettant d'analyser les données des essais de puits par ajustement automatisé des courbes types. Elle est basée sur le meilleur accord d'un modèle numérique avec les données obtenues dans les essais de puits de gaz grâce à des techniques d'optimisation. Le modèle numérique fournit la solution d'une équation différentielle à dérivées partielles du 2e ordre et fortement non linéaire qui régit le flux radial des gaz réels vers un puits de production. L'équation différentielle est résolue par la méthode des différences finies en tenant compte des variations des propriétés des gaz avec la pression. Pour simuler n'importe quel type d'essais de puits de gaz, on impose des conditions initiales et aux limites appropriées. On minimise les différences résiduelles entre les pressions réelles mesurées pendant l'essai et les pressions calculées par la méthode des moindres carrés. On utilise deux techniques d'optimisation pour obtenir la meilleure estimation des paramètres qui minimisent la somme des carrés des résidus : la méthode monovariante de Fibonacci [1] et la méthode polyvariante de Marquardt [1, 2]. On applique ce mode opératoire à des essais de puits menés à un débit constant et à deux débits constants. Les résultats numériques concordent très bien avec les données des essais de puits.

Large biases in regression-based constituent flux estimates: causes and diagnostic tools

Science.gov (United States)

Hirsch, Robert M.

2014-01-01

It has been documented in the literature that, in some cases, widely used regression-based models can produce severely biased estimates of long-term mean river fluxes of various constituents. These models, estimated using sample values of concentration, discharge, and date, are used to compute estimated fluxes for a multiyear period at a daily time step. This study compares results of the LOADEST seven-parameter model, LOADEST five-parameter model, and the Weighted Regressions on Time, Discharge, and Season (WRTDS) model using subsampling of six very large datasets to better understand this bias problem. This analysis considers sample datasets for dissolved nitrate and total phosphorus. The results show that LOADEST-7 and LOADEST-5, although they often produce very nearly unbiased results, can produce highly biased results. This study identifies three conditions that can give rise to these severe biases: (1) lack of fit of the log of concentration vs. log discharge relationship, (2) substantial differences in the shape of this relationship across seasons, and (3) severely heteroscedastic residuals. The WRTDS model is more resistant to the bias problem than the LOADEST models but is not immune to them. Understanding the causes of the bias problem is crucial to selecting an appropriate method for flux computations. Diagnostic tools for identifying the potential for bias problems are introduced, and strategies for resolving bias problems are described.

Greenhouse gases regional fluxes estimated from atmospheric measurements

International Nuclear Information System (INIS)

Messager, C.

2007-07-01

build up a new system to measure continuously CO 2 (or CO), CH 4 , N 2 O and SF 6 mixing ratios. It is based on a commercial gas chromatograph (Agilent 6890N) which have been modified to reach better precision. Reproducibility computed with a target gas on a 24 hours time step gives: 0.06 ppm for CO 2 , 1.4 ppb for CO, 0.7 ppb for CH 4 , 0.2 ppb for N 2 O and 0.05 ppt for SF 6 . The instrument's run is fully automated, an air sample analysis takes about 5 minutes. In July 2006, I install instrumentation on a telecommunication tall tower (200 m) situated near Orleans forest in Trainou, to monitor continuously greenhouse gases (CO 2 , CH 4 , N 2 O, SF 6 ), atmospheric tracers (CO, Radon-222) and meteorological parameters. Intake lines were installed at 3 levels (50, 100 and 180 m) and allow us to sample air masses along the vertical. Continuous measurement started in January 2007. I used Mace Head (Ireland) and Gif-sur-Yvette continuous measurements to estimate major greenhouse gases emission fluxes at regional scale. To make the link between atmospheric measurements and surface fluxes, we need to quantify dilution due to atmospheric transport. I used Radon-222 as tracer (radon tracer method) and planetary boundary layer heights estimates from ECMWF model (boundary layer budget method) to parameterize atmospheric transport. In both cases I compared results to available emission inventories. (author)

Bâle 3 : Quels impacts sur le financement des pays émergents ?

OpenAIRE

Figuet, Jean-Marc; Humblot, Thomas; Lahet, Delphine

2013-01-01

La persistance de crises bancaires démontre l'incapacité des établissements de crédit à s'autoréguler. De ce fait, le Comité de Bâle étend largement le périmètre de la nouvelle règlementation prudentielle. Sur la base de la littérature sur les déterminants des flux de capitaux transfrontières et d'un GMM système, cet article analyse l'impact potentiel de l'accord Bâle 3 sur les flux de capitaux bancaires provenant des banques de 16 pays industrialisés à destination d'un panel de 30 pays émerg...

Neutron detection in an atomic reactor core using semi-conductors; Detection des neutrons par semi-conducteur dans un coeur de reacteur atomique

Energy Technology Data Exchange (ETDEWEB)

Divoux, F [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1968-07-01

In this paper, the first part describes the principle of nuclear particle detection by means of semiconductor diodes and the general application of these. The second part describes fabrication of the device used to estimate thermic neutron fluxes in core of a swimming pool type reactor. The useful volume (2.9 mm thickness) is in the light water moderator, between combustible elements plates. The results, principally obtained in the core of Siloette reactor at the 'Centre d'Etudes Nucleaires de Grenoble' at low power, are mentioned in the third part. Flux maps have been set and comparison between converter's products: Bore 10, Lithium 6, Uranium 235 is made. (author) [French] Dans ce rapport, une premiere partie porte sur la description du principe de detection des particules nucleaires par diodes a semi-conducteur et sur l'application generale de celles-ci. Une deuxieme partie s'attache a decrire la fabrication du materiel utilise pour evaluer les flux de neutrons thermiques dans un coeur de reacteur type pile piscine. L'espace de mesure (2,9 mm d'epaisseur) se situe entre les plaques des elements combustibles, dans le moderateur eau legere. Les resultats, obtenus principalement dans le coeur du reacteur Siloette du Centre d'Etudes Nucleaires de Grenoble aux basses puissances de fonctionnement, sont rapportes dans la troisieme partie. Des cartes de flux ont ete dressees et une comparaison est faite entre les produits 'convertisseurs' suivants: Bore 10, Lithium 6, Uranium 235. (auteur)

TREEDE, Point Fluxes and Currents Based on Track Rotation Estimator by Monte-Carlo Method

International Nuclear Information System (INIS)

Dubi, A.

1985-01-01

1 - Description of problem or function: TREEDE is a Monte Carlo transport code based on the Track Rotation estimator, used, in general, to calculate fluxes and currents at a point. This code served as a test code in the development of the concept of the Track Rotation estimator, and therefore analogue Monte Carlo is used (i.e. no importance biasing). 2 - Method of solution: The basic idea is to follow the particle's track in the medium and then to rotate it such that it passes through the detector point. That is, rotational symmetry considerations (even in non-spherically symmetric configurations) are applied to every history, so that a very large fraction of the track histories can be rotated and made to pass through the point of interest; in this manner the 1/r 2 singularity in the un-collided flux estimator (next event estimator) is avoided. TREEDE, being a test code, is used to estimate leakage or in-medium fluxes at given points in a 3-dimensional finite box, where the source is an isotropic point source at the centre of the z = 0 surface. However, many of the constraints of geometry and source can be easily removed. The medium is assumed homogeneous with isotropic scattering, and one energy group only is considered. 3 - Restrictions on the complexity of the problem: One energy group, a homogeneous medium, isotropic scattering

Delayed neutron detection in canning burst detection studies (1961); Etude sur la detection des neutrons differes en vue de la detection des ruptures de gaines (1961)

Energy Technology Data Exchange (ETDEWEB)

Perlini, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

This paper describes a theoretical and experimental study on the detection of neutrons present in the primary cooling circuit of a reactor cooled by heavy or light water, with a view to the installation of a canning burst detection unit. The concentration of background neutrons is first calculated, taking into account the neutrons from nitrogen 17 decay, and the photoneutrons produced by the decay of nitrogen 16 and sodium 24. The emission of delayed fission neutrons, originating at a given crack in the canning, has been estimated. Using the D{sub 2}O circuit of the pile EL-3, three units have been developed by means of which the following three types of detector may be compared: 1) BF{sub 3} proportional counter 2) Boron scintillator 3) Fission chamber Under the present experimental conditions the BF{sub 3} counter gave the best results. The influence on these detectors of the {gamma} flux, which in certain cases reaches 200 R/h, is analysed. Finally a calibration is carried out with an experimental crack of 30 mm{sup 2} of uranium exposed to a flux of 5.8 x 10{sup 13} n.cm{sup -2}.s{sup -1}. The sensitivity obtained with the BF{sub 3} counter during this test is 2 counts/s per mm{sup 2} of exposed uranium. (author) [French] Le present rapport est une etude theorique et experimentale sur la detection des neutrons presents dans le circuit primaire de refroidissement d'un reacteur refrigere par l'eau lourde ou l'eau legere, en vue d'une installation de detection de ruptures de gaines. On fait d'abord un calcul sur la concentration des neutrons de bruit de fond en tenant compte: des neutrons de decroissance de l'azote 17 et des photoneutrons produits par les decroissances de l'azote 16 et du sodium 24. L'emission des neutrons differes de fission, qui ont pour origine une fissure de gaine donnee, a ete evaluee. Utilisant le circuit D{sub 2}O de la pile EL3, trois installations ont ete mises au point permettant de comparer les trois types de detecteurs suivants: 1

A Bayesian analysis of sensible heat flux estimation: Quantifying uncertainty in meteorological forcing to improve model prediction

KAUST Repository

Ershadi, Ali

2013-05-01

The influence of uncertainty in land surface temperature, air temperature, and wind speed on the estimation of sensible heat flux is analyzed using a Bayesian inference technique applied to the Surface Energy Balance System (SEBS) model. The Bayesian approach allows for an explicit quantification of the uncertainties in input variables: a source of error generally ignored in surface heat flux estimation. An application using field measurements from the Soil Moisture Experiment 2002 is presented. The spatial variability of selected input meteorological variables in a multitower site is used to formulate the prior estimates for the sampling uncertainties, and the likelihood function is formulated assuming Gaussian errors in the SEBS model. Land surface temperature, air temperature, and wind speed were estimated by sampling their posterior distribution using a Markov chain Monte Carlo algorithm. Results verify that Bayesian-inferred air temperature and wind speed were generally consistent with those observed at the towers, suggesting that local observations of these variables were spatially representative. Uncertainties in the land surface temperature appear to have the strongest effect on the estimated sensible heat flux, with Bayesian-inferred values differing by up to ±5°C from the observed data. These differences suggest that the footprint of the in situ measured land surface temperature is not representative of the larger-scale variability. As such, these measurements should be used with caution in the calculation of surface heat fluxes and highlight the importance of capturing the spatial variability in the land surface temperature: particularly, for remote sensing retrieval algorithms that use this variable for flux estimation.

An inverse hyperbolic heat conduction problem in estimating surface heat flux by the conjugate gradient method

International Nuclear Information System (INIS)

Huang, C.-H.; Wu, H.-H.

2006-01-01

In the present study an inverse hyperbolic heat conduction problem is solved by the conjugate gradient method (CGM) in estimating the unknown boundary heat flux based on the boundary temperature measurements. Results obtained in this inverse problem will be justified based on the numerical experiments where three different heat flux distributions are to be determined. Results show that the inverse solutions can always be obtained with any arbitrary initial guesses of the boundary heat flux. Moreover, the drawbacks of the previous study for this similar inverse problem, such as (1) the inverse solution has phase error and (2) the inverse solution is sensitive to measurement error, can be avoided in the present algorithm. Finally, it is concluded that accurate boundary heat flux can be estimated in this study

Estimating regional greenhouse gas fluxes: An uncertainty analysis of planetary boundary layer techniques and bottom-up inventories

Science.gov (United States)

Quantification of regional greenhouse gas (GHG) fluxes is essential for establishing mitigation strategies and evaluating their effectiveness. Here, we used multiple top-down approaches and multiple trace gas observations at a tall tower to estimate GHG regional fluxes and evaluate the GHG fluxes de...

Installation for the study of heat transfer with high flux density; Installation d'etude de transmission de chaleur a densite de flux elevee

Energy Technology Data Exchange (ETDEWEB)

Robin, M; Schwab, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

As a result of their very low vapor pressure, metals with a low fusion point (sodium, sodium-potassium alloys, etc.) can be used at high temperature, as heating fluids, in installations whose internal pressure is close to atmospheric pressure. Owing to the very high convection coefficients which can be reached with these fluids and to the large temperature differences utilizable, it is possible to produce through the exchange surfaces considerable heat flux densities, of the order of those which exist through the canning of fuel elements in nuclear reactors. The installation described allowed a flux density of more than 200 W/cm{sup 2} to be obtained, the heating fluid being a Na-K alloy (containing 56 per cent by weight of potassium) brought to a temperature around 550 deg. C. (author) [French] Par suite de leur tres faible pression de vapeur, les metaux a bas point de fusion (sodium, alliages sodium-potassium, etc.) peuvent etre utilises a haute temperature, comme fluides de chauffage, dans des installations dont la pression interne est voisine de la pression atmospherique. Grace aux coefficients de convection tres eleves que ces fluides permettent d'atteindre et aux importantes differences de temperature utilisables, il est possible de produire, a travers les surfaces d'echange, des densites de flux de chaleur considerables, de l'ordre de celles qui existent a travers les gaines des elements combustibles des reacteurs nucleaires. L'installation decrite a permis l'obtention d'une densite de flux de plus, de 200 W/cm{sup 2}, le fluide chauffant etant de l'alliage Na-K (a 56 pour cent en poids de potassium) porte a une temperature voisine de 550 deg. C. (auteur)

Evaluation of three Monte Carlo estimation schemes for flux at a point

International Nuclear Information System (INIS)

Kalli, H.J.; Cashwell, E.D.

1977-09-01

Three Monte Carlo estimation schemes were studied to avoid the difficulties caused by the (1/r 2 ) singularity in the expression of the normal next-event estimator (NEE) for the flux at a point. A new, fast, once-more collided flux estimator (OMCFE) scheme, based on a very simple probability density function (p.d.f.) of the distance to collision in the selection of the intermediate collision points, is proposed. This kind of p.d.f. of the collision distance is used in two nonanalog schemes using the NEE. In these two schemes, which have principal similarities to some schemes proposed earlier in the literature, the (1/r 2 ) singularity is canceled by incorporating the singularity into the p.d.f. of the collision points. This is achieved by playing a suitable nonanalog game in the neighborhood of the detector points. The three schemes were tested in a monoenergetic, homogeneous infinite-medium problem, then were evaluated in a point-cross-section problem by using the Monte Carlo code MCNG. 10 figures

Simultaneously estimation for surface heat fluxes of steel slab in a reheating furnace based on DMC predictive control

International Nuclear Information System (INIS)

Li, Yanhao; Wang, Guangjun; Chen, Hong

2015-01-01

The predictive control theory is utilized for the research of a simultaneous estimation of heat fluxes through the upper, side and lower surface of a steel slab in a walking beam type rolling steel reheating furnace. An inverse algorithm based on dynamic matrix control (DMC) is established. That is, each surface heat flux of a slab is simultaneously estimated through rolling optimization on the basis of temperature measurements in selected points of its interior by utilizing step response function as predictive model of a slab's temperature. The reliability of the DMC results is enhanced without prior assuming specific functions of heat fluxes over a period of future time. The inverse algorithm proposed a respective regularization to effectively improve the stability of the estimated results by considering obvious strength differences between the upper as well as lower and side surface heat fluxes of the slab. - Highlights: • The predictive control theory is adopted. • An inversion scheme based on DMC is established. • Upper, side and lower surface heat fluxes of slab are estimated based DMC. • A respective regularization is proposed to improve the stability of results

Heat flux estimation in an infrared experimental furnace using an inverse method

International Nuclear Information System (INIS)

Le Bideau, P.; Ploteau, J.P.; Glouannec, P.

2009-01-01

Infrared emitters are widely used in industrial furnaces for thermal treatment. In these processes, the knowledge of the incident heat flux on the surface of the product is a primary step to optimise the command emitters and for maintenance shift. For these reasons, it is necessary to develop autonomous flux meters that could provide an answer to these requirements. These sensors must give an in-line distribution of infrared irradiation in the tunnel furnace and must be able to measure high heat flux in severe thermal environments. In this paper we present a method for in-line assessments solving an inverse heat conduction problem. A metallic mass is instrumented by thermocouples and an inverse method allows the incident heat flux to be estimated. In the first part, attention is focused on a new design tool, which is a numerical code, for the evaluation of potential options during captor conception. In the second part we present the realization and the test of this 'indirect' flux meter and its associated inverse problem. 'Direct' detectors based on thermoelectric devices are compared with this new flux meter in the same conditions in the same furnace. Results prove that this technique is a reliable method, appropriate for high temperature ambiances. This technique can be applied to furnaces where the heat flux is inaccessible to 'direct' measurements.

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

Directory of Open Access Journals (Sweden)

A. Fraser

2013-06-01

Full Text Available We use an ensemble Kalman filter (EnKF, together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4 fluxes for the period June 2009–December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4 from GOSAT (Greenhouse gases Observing SATellite and/or NOAA ESRL (Earth System Research Laboratory and CSIRO GASLAB (Global Atmospheric Sampling Laboratory CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510–516 Tg yr−1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr−1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr−1 occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45% than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2 and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our

Contribution to the methods for estimating uranium deposits (1963); Contribution aux methodes d'estimation des gisements d'uranium (1963)

Energy Technology Data Exchange (ETDEWEB)

Carlier, A. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-02-15

be taken in some cases. A detailed alphabetical index is intended to help find in this publication the definitions, formulae or theories that most interest the reader. (author) [French] Apres avoir rappele ce qu'est un gisement, de valeur economique, sur la base du marginalisme, l'auteur distingue plusieurs categories de reserves suivant le degre de connaissance du gite et suivant le poste d'exploitation ou est considere le minerai. Il rejette les anciennes categories 'a vue', 'probable' et 'possible' pour les remplacer par des categories mieux adaptees. Les reserves sensu stricto sont celles pour lesquelles on est en mesure de calculer l'erreur aleatoire d'estimation. Une notion est introduite a ce sujet, c'est le contraste naturel des teneurs dans un gite (coefficient de dispersion absolu {alpha}). L'auteur distingue 3 formes de reconnaissance des gites, la mauvaise, la bonne et l'ideale. La premiere est la reconnaissance anarchique trop souvent recontree la seconde est la reconnaissance logique fondee sur une implantation systematique des galeries, sondages, etc. La troisieme, difficile a atteindre, est celle qui minimise la depense des recherches pour une precision fixee a l'avance. Une partie de l'ouvrage traite des erreurs d'echantillonnage telles que celles resultant du quartage d'un lot (theorie de Pierre GY), ou celles issues de l'emploi de la radioactivite pour estimer les teneurs. Une autre partie traite des erreurs d'extension (assimilation du gite a ses echantillons) et donne les formules essentielles pour calculer ces erreurs aleatoires (geostatistique de Matheron). A propos de l'estimateur lui-meme, on note la disharmonie entre l'echantillon et sa zone d'influence, et le moyen de remedier a cette discordance par le 'krigeage' est fourni dans l'ouvrage. La these donne de nombreux exemples des differents parametres numeriques

Estimating surface CO2 fluxes from space-borne CO2 dry air mole fraction observations using an ensemble Kalman Filter

Directory of Open Access Journals (Sweden)

S. Dance

2009-04-01

Full Text Available We have developed an ensemble Kalman Filter (EnKF to estimate 8-day regional surface fluxes of CO2 from space-borne CO2 dry-air mole fraction observations (XCO2 and evaluate the approach using a series of synthetic experiments, in preparation for data from the NASA Orbiting Carbon Observatory (OCO. The 32-day duty cycle of OCO alternates every 16 days between nadir and glint measurements of backscattered solar radiation at short-wave infrared wavelengths. The EnKF uses an ensemble of states to represent the error covariances to estimate 8-day CO2 surface fluxes over 144 geographical regions. We use a 12×8-day lag window, recognising that XCO2 measurements include surface flux information from prior time windows. The observation operator that relates surface CO2 fluxes to atmospheric distributions of XCO2 includes: a the GEOS-Chem transport model that relates surface fluxes to global 3-D distributions of CO2 concentrations, which are sampled at the time and location of OCO measurements that are cloud-free and have aerosol optical depths 2 profiles to XCO2, accounting for differences between nadir and glint measurements, and the associated scene-dependent observation errors. We show that OCO XCO2 measurements significantly reduce the uncertainties of surface CO2 flux estimates. Glint measurements are generally better at constraining ocean CO2 flux estimates. Nadir XCO2 measurements over the terrestrial tropics are sparse throughout the year because of either clouds or smoke. Glint measurements provide the most effective constraint for estimating tropical terrestrial CO2 fluxes by accurately sampling fresh continental outflow over neighbouring oceans. We also present results from sensitivity experiments that investigate how flux estimates change with 1 bias and unbiased errors, 2 alternative duty cycles, 3 measurement density and correlations, 4 the spatial resolution of estimated flux estimates, and 5 reducing the length of the lag window and the

CarbonTracker-Lagrange: A Framework for Greenhouse Gas Flux Estimation at Regional to Continental Scales

Science.gov (United States)

Andrews, A. E.

2016-12-01

CarbonTracker-Lagrange (CT-L) is a flexible modeling framework developed to take advantage of newly available atmospheric data for CO2 and other long-lived gases such as CH4 and N2O. The North American atmospheric CO2 measurement network has grown from three sites in 2004 to >100 sites in 2015. The US network includes tall tower, mountaintop, surface, and aircraft sites in the NOAA Global Greenhouse Gas Reference Network along with sites maintained by university, government and private sector researchers. The Canadian network is operated by Environment and Climate Change Canada. This unprecedented dataset can provide spatially and temporally resolved CO2 emissions and uptake flux estimates and quantitative information about drivers of variability, such as drought and temperature. CT-L is a platform for systematic comparison of data assimilation techniques and evaluation of assumed prior, model and observation errors. A novel feature of CT-L is the optimization of boundary values along with surface fluxes, leveraging vertically resolved data available from NOAA's aircraft sampling program. CT-L uses observation footprints (influence functions) from the Weather Research and Forecasting/Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) modeling system to relate atmospheric measurements to upwind fluxes and boundary values. Footprints are pre-computed and the optimization algorithms are efficient, so many variants of the calculation can be performed. Fluxes are adjusted using Bayesian or Geostatistical methods to provide optimal agreement with observations. Satellite measurements of CO2 and CH4 from GOSAT are available starting in July 2009 and from OCO-2 since September 2014. With support from the NASA Carbon Monitoring System, we are developing flux estimation strategies that use remote sensing and in situ data together, including geostatistical inversions using satellite retrievals of solar-induced chlorophyll fluorescence. CT-L enables quantitative

Using 81Kr-age of groundwater in the Guarani Aquifer, Brazil, to constrain estimates of continental degassing flux of 4He

Science.gov (United States)

Aggarwal, P. K.; Matsumoto, T.; Sturchio, N. C.; Chang, H. K.; Gastmans, D.; Lu, Z.; Jiang, W.; Müller, P.; Yokochi, R.; Han, L.; Klaus, P.; Torgersen, T.

2013-12-01

Continental degassing flux of helium is the dominant component of dissolved helium in deep groundwater together with that produced in-situ in the aquifer. A reliable estimate of the degassing flux is critical to the use of 4He as a dating tool in groundwater studies. The degassing flux is also important for understanding fluid and heat transport in the mantle and the rust. An independent tracer of groundwater age is required in order to deconvolute the two signals of the external, degassing flux and in situ production. Estimates of degassing flux mostly have relied upon shorter-lived radionuclides such as 14C and tritium and the resulting flux estimates have a significant variability (Torgersen, 2010). In the Guarani Aquifer in Brazil, an effective crustal 4He degassing flux into the aquifer was estimated from 81Kr ages ranging from about 70 Ka to 570 Ka. We then used the model framework of Toregesen and Ivey (1985), modified to include a diffusive reduction of originally uniform crustal helium flux from basement rocks through a thick sedimentary layer beneath the aquifer, to calculate a distribution of radiogenic 4He within the aquifer. With this framework, we obtain 4He ages that are consistent with ages based on 81Kr and 14C, and with a crustal degassing flux equivalent to that estimated from U and Th contents in the crust. The model framework for the Guarani Aquifer is also applied to data from other deep aquifers in Africa and Australia and our results suggest that the continental flux of 4He may be uniform, at least in stable continental areas. Additionally, a reliable estimate of the 4He degassing flux also helps to constrain the surficial discharge of deep groundwater.

Regional inversion of CO2 ecosystem fluxes from atmospheric measurements. Reliability of the uncertainty estimates

Energy Technology Data Exchange (ETDEWEB)

Broquet, G.; Chevallier, F.; Breon, F.M.; Yver, C.; Ciais, P.; Ramonet, M.; Schmidt, M. [Laboratoire des Sciences du Climat et de l' Environnement, CEA-CNRS-UVSQ, UMR8212, IPSL, Gif-sur-Yvette (France); Alemanno, M. [Servizio Meteorologico dell' Aeronautica Militare Italiana, Centro Aeronautica Militare di Montagna, Monte Cimone/Sestola (Italy); Apadula, F. [Research on Energy Systems, RSE, Environment and Sustainable Development Department, Milano (Italy); Hammer, S. [Universitaet Heidelberg, Institut fuer Umweltphysik, Heidelberg (Germany); Haszpra, L. [Hungarian Meteorological Service, Budapest (Hungary); Meinhardt, F. [Federal Environmental Agency, Kirchzarten (Germany); Necki, J. [AGH University of Science and Technology, Krakow (Poland); Piacentino, S. [ENEA, Laboratory for Earth Observations and Analyses, Palermo (Italy); Thompson, R.L. [Max Planck Institute for Biogeochemistry, Jena (Germany); Vermeulen, A.T. [Energy research Centre of the Netherlands ECN, EEE-EA, Petten (Netherlands)

2013-07-01

The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5{sup 0} resolution are applied for the western European domain where {approx}50 eddy covariance sites are operated. These inversions are conducted for the period 2002-2007. They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. Averaged over monthly periods and over the whole domain, the misfits are in good agreement with the theoretical uncertainties for prior and inverted NEE, and pass the chi-square test for the variance at the 30% and 5% significance levels respectively, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion decreases the standard deviation of the misfits by 38 %. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modelling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that this study does not engender confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than

Alize 3 - first critical experiment for the franco-german high flux reactor - calculations; Alize 3 - premiere experience critique pour le reacteur a haut flux franco-allemand. Calculs

Energy Technology Data Exchange (ETDEWEB)

Scharmer, K [Commissariat a l' Energie Atomique, Dir. des Piles Atomiques, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

The results of experiments in the light water cooled D{sub 2}O reflected critical assembly ALIZE III have been compared to calculations. A diffusion model was used with 3 fast and epithermal groups and two overlapping thermal groups, which leads to good agreement of calculated and measured power maps, even in the case of strong variations of the neutron spectrum in the core. The difference of calculated and measured k{sub eff} was smaller than 0.5 per cent {delta}k/k. Calculations of void and structure material coefficients of the reactivity of 'black' rods in the reflector, of spectrum variations (Cd-ratio, Pu-U-ratio) and to the delayed photoneutron fraction in the D{sub 2}O reflector were made. Measurements of the influence of beam tubes on reactivity and flux distribution in the reflector were interpreted with regard to an optimum beam tube arrangement for the Franco- German High Flux Reactor. (author) [French] Les resultats des experiences faites dans la maquette critique ALIZE III, refrigeree a l'eau legere et reflechie par l'eau lourde, ont ete compares aux calculs. On a utilise un modele de la theorie de diffusion a trois groupes rapides et epithermiques et deux groupes thermiques qui se recouvrent. Ce modele a permis de calculer la distribution de puissance dans le coeur en bon accord avec les mesures, meme dans le cas d'une forte variation du spectre des neutrons dans le coeur. L'erreur entre k{sub eff} calcule et mesure etait inferieure a 0,5 pour cent {delta}k/k. Le coefficient de vide et des materiaux de structure, la reactivite des barres 'noires', les variations du spectre (rapport Cd, rapport Pu/U) et la fraction des photo-neutrons retardes sont egalement calcules. Les mesures de reactivite et de perturbation de flux dans le reflecteur, dues aux canaux, ont ete interpretees du point de vue d'un arrangement optimum des canaux pour le Reacteur a Haut Flux Franco-Allemand. (auteur)

A punctual flux estimator and reactions rates optimization in neutral particles transport calculus by the Monte Carlo method

International Nuclear Information System (INIS)

Authier, N.

1998-12-01

One of the questions asked in radiation shielding problems is the estimation of the radiation level in particular to determine accessibility of working persons in controlled area (nuclear power plants, nuclear fuel reprocessing plants) or to study the dose gradients encountered in material (iron nuclear vessel, medical therapy, electronics in satellite). The flux and reaction rate estimators used in Monte Carlo codes give average values in volumes or on surfaces of the geometrical description of the system. But in certain configurations, the knowledge of punctual deposited energy and dose estimates are necessary. The Monte Carlo estimate of the flux at a point of interest is a calculus which presents an unbounded variance. The central limit theorem cannot be applied thus no easy confidence level may be calculated. The convergence rate is then very poor. We propose in this study a new solution for the photon flux at a point estimator. The method is based on the 'once more collided flux estimator' developed earlier for neutron calculations. It solves the problem of the unbounded variance and do not add any bias to the estimation. We show however that our new sampling schemes specially developed to treat the anisotropy of the photon coherent scattering is necessary for a good and regular behavior of the estimator. This developments integrated in the TRIPOLI-4 Monte Carlo code add the possibility of an unbiased punctual estimate on media interfaces. (author)

Potential for using remote sensing to estimate carbon fluxes across northern peatlands - A review.

Science.gov (United States)

Lees, K J; Quaife, T; Artz, R R E; Khomik, M; Clark, J M

2018-02-15

Peatlands store large amounts of terrestrial carbon and any changes to their carbon balance could cause large changes in the greenhouse gas (GHG) balance of the Earth's atmosphere. There is still much uncertainty about how the GHG dynamics of peatlands are affected by climate and land use change. Current field-based methods of estimating annual carbon exchange between peatlands and the atmosphere include flux chambers and eddy covariance towers. However, remote sensing has several advantages over these traditional approaches in terms of cost, spatial coverage and accessibility to remote locations. In this paper, we outline the basic principles of using remote sensing to estimate ecosystem carbon fluxes and explain the range of satellite data available for such estimations, considering the indices and models developed to make use of the data. Past studies, which have used remote sensing data in comparison with ground-based calculations of carbon fluxes over Northern peatland landscapes, are discussed, as well as the challenges of working with remote sensing on peatlands. Finally, we suggest areas in need of future work on this topic. We conclude that the application of remote sensing to models of carbon fluxes is a viable research method over Northern peatlands but further work is needed to develop more comprehensive carbon cycle models and to improve the long-term reliability of models, particularly on peatland sites undergoing restoration. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Estimating sediment and caesium-137 fluxes in the Ribble Estuary through time-series airborne remote sensing

International Nuclear Information System (INIS)

Wakefield, R.; Tyler, A.N.; McDonald, P.; Atkin, P.A.; Gleizon, P.; Gilvear, D.

2011-01-01

High spatial and temporal resolution airborne imagery were acquired for the Ribble Estuary, North West England in 1997 and 2003, to assess the application of time-series airborne remote sensing to quantify total suspended sediment and radionuclide fluxes during a flood and ebb tide sequence. Concomitant measurements of suspended particulate matter (SPM) and water column turbidity were obtained during the time-series image acquisition for the flood and ebb tide sequence on the 17th July 2003 to verify the assumption of a vertically well mixed estuary and thus justifying the vertical extrapolation of spatially integrated estimate of surface SPM. The 137 Cs activity concentrations were calculated from a relatively stable relationship between SPM and 137 Cs for the Ribble Estuary. Total estuary wide budgets of sediment and 137 Cs were obtained by combining the image-derived estimates of surface SPM and 137 Cs with estimates of water volume from a two-dimensional hydrodynamic model (VERSE) developed for the Ribble Estuary. These indicate that around 10,000 tonnes of sediment and 2.72 GBq of 137 Cs were deposited over the tidal sequence monitored in July 2003. This compared favourably with bed height elevation change estimated from field work. An uncertainty analysis on the total sediment and 137 Cs flux yielded a total budget of the order of 40% on the final estimate. The results represent a novel approach to providing a spatially integrated estimate of the total net sediment and radionuclide flux in an intertidal environment over a flood and ebb tide sequence. - Research highlights: → This paper provides a rare insight into the next flux of sediment and associated radionuclide loading into an estuary over and ebb and flood tide sequence. → The paper uses high temporal resolution airborne imagery coupled with concomitant sampling to convert total suspended sediment flux to 137 Cs loading. → For the estuary and date studied, it is estimate that an 10,000 tonnes of

Localizing by autoradiography at -195 deg radioactive areas in rats exposed to a high flux of thermal neutrons, importance of phosphorus 32 in consecutive internal irradiation; Localisation par autoradiographie a -195 deg des zones radioactives chez le rat expose a un haut flux de neutrons thermiques, importance du phosphore 32 dans l'irradiation interne consecutive

Energy Technology Data Exchange (ETDEWEB)

Chanteur, J; Pellerin, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1961-07-01

Rats weighing 25 g were exposed for 5 mn to a flux of 6.10{sup 12} thermal neutrons/cm{sup 2}/s. Anatomical autoradiography at -195 deg. C has enabled the radioactive organs to be easily localised, to follow in course of time the decrease of radioactivity, and from it to deduce the probable nature of the numerous emitters in question. In particular, the phosphorus 32 has thus appeared to be one of those responsible for internal irradiation, general, on the one hand, by activating cellular phosphorus, local, on the other, by activating bony phosphates. Owing to this, an accidental irradiation by neutrons might have consequences that are both somatic (elective irradiation of the bone marrow) and genetic (activation of nucleic acids). The gamma spectrometry has confirmed the nature of certain other emitters. (author) [French] Des rats de 25 g ont ete exposes pendant 5 mn a un flux de 6.10{sup 12} neutrons thermiques/cm{sup 2}/s. L'autoradiographie anatomique a -195 deg. C a permis de localiser facilement les organes radioactifs, de suivre dans le temps la decroissance de la radioactivite, et d'en deduire la nature probable des nombreux emetteurs en cause. En particulier, le phosphore 32 est ainsi apparu comme l'un des responsables de l'irradiation interne, d'une part generale par activation du phosphore cellulaire, d'autre part locale par activation des phosphates osseux. Une irradiations accidentelle par neutrons aurait, de ce fait, des consequences a la fois somatiques (irradiation elective de la moelle osseuse) et genetiques (activation des acides nucleiques). La spectrometrie gamma a confirme la nature de certains autres emetteurs. (auteur)

Evaluating Uncertainties in Sap Flux Scaled Estimates of Forest Transpiration, Canopy Conductance and Photosynthesis

Science.gov (United States)

Ward, E. J.; Bell, D. M.; Clark, J. S.; Kim, H.; Oren, R.

2009-12-01

Thermal dissipation probes (TDPs) are a common method for estimating forest transpiration and canopy conductance from sap flux rates in trees, but their implementation is plagued by uncertainties arising from missing data and variability in the diameter and canopy position of trees, as well as sapwood conductivity within individual trees. Uncertainties in estimates of canopy conductance also translate into uncertainties in carbon assimilation in models such as the Canopy Conductance Constrained Carbon Assimilation (4CA) model that combine physiological and environmental data to estimate photosynthetic rates. We developed a method to propagate these uncertainties in the scaling and imputation of TDP data to estimates of canopy transpiration and conductance using a state-space Jarvis-type conductance model in a hierarchical Bayesian framework. This presentation will focus on the impact of these uncertainties on estimates of water and carbon fluxes using 4CA and data from the Duke Free Air Carbon Enrichment (FACE) project, which incorporates both elevated carbon dioxide and soil nitrogen treatments. We will also address the response of canopy conductance to vapor pressure deficit, incident radiation and soil moisture, as well as the effect of treatment-related stand structure differences in scaling TDP measurements. Preliminary results indicate that in 2006, a year of normal precipitation (1127 mm), canopy transpiration increased in elevated carbon dioxide ~8% on a ground area basis. In 2007, a year with a pronounced drought (800 mm precipitation), this increase was only present in the combined carbon dioxide and fertilization treatment. The seasonal dynamics of water and carbon fluxes will be discussed in detail.

Les impacts des énergies fossiles sur l'environnement

OpenAIRE

Landrieu , Guy

1994-01-01

La satisfaction de leurs besoins en énergie est l'un des principaux facteurs de la transformation de leur environnement par les sociétés industrielles. Les combustibles carbonés fossiles, qui représentent environ 90% de la production commerciale d'énergie dans le monde, ont un rôle important dans ce processus de transformation. Une première donnée qui explique l'ampleur des impacts sur l'environnement liés aux combustibles fossiles est l'importance des flux de matières en circulation. On extr...

Anthropogenic heat flux estimation from space

NARCIS (Netherlands)

Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean Philippe; Grimmond, C.S.B.; Feigenwinter, Christian; Lindberg, Fredrik; Frate, Del Fabio; Klostermann, Judith; Mitraka, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans

2016-01-01

H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the impacts

ANthropogenic heat FLUX estimation from Space

NARCIS (Netherlands)

Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean Philippe; Grimmong, C.S.B.; Feigenwinter, Christian; Lindberg, Fredrik; Frate, Del Fabio; Klostermann, Judith; Mi, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans

2017-01-01

The H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the

Seasonal and vertical variations of sinking particle fluxes in the West Caroline Basin

OpenAIRE

Kawahata, H; Yamamuro, M; Ohta, H

1998-01-01

Des pièges à sédiments ont été déployés dans le bassin des Carolines Occidentales (ouest du Pacifique équatorial), entre la zone d'influence de la mousson d'Asie et l'océan ouvert. À la station 1, le flux annuel au piège le moins profond est 57, 10 g m-2 an-1. Les flux élevés de matière organique sont généralement associés au développement des communautés planctoniques à test silicieux et carbonaté. De plus, le rapport carbone organique/carbone minéral tend à augmenter avec la teneur en matiè...

A new empirical model to estimate hourly diffuse photosynthetic photon flux density

Science.gov (United States)

Foyo-Moreno, I.; Alados, I.; Alados-Arboledas, L.

2018-05-01

Knowledge of the photosynthetic photon flux density (Qp) is critical in different applications dealing with climate change, plant physiology, biomass production, and natural illumination in greenhouses. This is particularly true regarding its diffuse component (Qpd), which can enhance canopy light-use efficiency and thereby boost carbon uptake. Therefore, diffuse photosynthetic photon flux density is a key driving factor of ecosystem-productivity models. In this work, we propose a model to estimate this component, using a previous model to calculate Qp and furthermore divide it into its components. We have used measurements in urban Granada (southern Spain), of global solar radiation (Rs) to study relationships between the ratio Qpd/Rs with different parameters accounting for solar position, water-vapour absorption and sky conditions. The model performance has been validated with experimental measurements from sites having varied climatic conditions. The model provides acceptable results, with the mean bias error and root mean square error varying between - 0.3 and - 8.8% and between 9.6 and 20.4%, respectively. Direct measurements of this flux are very scarce so that modelling simulations are needed, this is particularly true regarding its diffuse component. We propose a new parameterization to estimate this component using only measured data of solar global irradiance, which facilitates its use for the construction of long-term data series of PAR in regions where continuous measurements of PAR are not yet performed.

Two-wavelength Method Estimates Heat fluxes over Heterogeneous Surface in North-China

Science.gov (United States)

Zhang, G.; Zheng, N.; Zhang, J.

2017-12-01

Heat fluxes is a key process of hydrological and heat transfer of soil-plant-atmosphere continuum (SPAC), and now it is becoming an important topic in meteorology, hydrology, ecology and other related research areas. Because the temporal and spatial variation of fluxes at regional scale is very complicated, it is still difficult to measure fluxes at the kilometer scale over a heterogeneous surface. A technique called "two-wavelength method" which combines optical scintillometer with microwave scintillometer is able to measure both sensible and latent heat fluxes over large spatial scales at the same time. The main purpose of this study is to investigate the fluxes over non-uniform terrain in North-China. Estimation of heat fluxes was carried out with the optical-microwave scintillometer and an eddy covariance (EC) system over heterogeneous surface in Tai Hang Mountains, China. EC method was set as a benchmark in the study. Structure parameters obtained from scintillometer showed that the typical measurement values of Cn2 are around 10-13 m-2/3 for microwave scintillometer, and values of Cn2 were around 10-15 m-2/3 for optical scintillometer. The correlation of heat fluxes (H) derived from scintillometer and EC system showed as a ratio of 1.05,and with R2=0.75, while the correlation of latent heat fluxes (LE) showed as 1.29 with R2=0.67. It was also found that heat fluxes derived from the two system showed good agreement (R2=0.9 for LE, R2=0.97 for H) when the Bowen ratio (β) was 1.03, while discrepancies showed significantly when β=0.75, and RMSD in H was 139.22 W/m2, 230.85 W/m2 in LE respectively.Experiment results in our research shows that, the two-wavelength method gives a larger heat fluxes over the study area, and a deeper study should be conduct. We expect that our investigate and analysis can be promoted the application of scintillometry method in regional evapotranspiration measurements and relevant disciplines.

Structure and kinematics of bubble flow; Structure et cinematique des ecoulements diphasiques a bulles

Energy Technology Data Exchange (ETDEWEB)

Lackme, C [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1967-07-01

This report deals with the components and use of resistivity probes in bubble flow. With a single probe, we have studied the longitudinal and radial structure of the flow. The very complicated evolution of the radial structure is shown by the measurement of the mean bubble flux at several points in the tube. A double probe associated with a device the principle of which is given in this report, permits the measure of the local velocity of bubbles. Unlike the mean bubble flux profile, the change in the velocity profile along the tube is not significant. We have achieved the synthesis of these two pieces of information, mean local bubble flux and local velocity, by computing the mean weighed velocity in the tube. This weighed velocity compares remarkably with the velocity computed from the volumetric gas flow rate and the mean void fraction. (author) [French] Ce rapport traite d'une etude methodologique des ecoulements diphasiques a bulles. Les fluides sont l'air et l'eau, ils circulent du bas vers le haut dans un tube vertical de 32 mm de diametre et 2 metres de long. Cette etude a pour but de permettre une description fine de l'ecoulement. Pour cela, il a ete necessaire de developper des appareillages nouveaux et de mettre au point les methodes d'analyses correspondantes. La valeur des mesures effectuees et des methodes utilisees apparait dans une comparaison concluante et conclusive entre des resultats de mesures globales et des resultats integres de mesures locales. (auteur)

Inverse heat transfer analysis of a functionally graded fin to estimate time-dependent base heat flux and temperature distributions

International Nuclear Information System (INIS)

Lee, Haw-Long; Chang, Win-Jin; Chen, Wen-Lih; Yang, Yu-Ching

2012-01-01

Highlights: ► Time-dependent base heat flux of a functionally graded fin is inversely estimated. ► An inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied. ► The distributions of temperature in the fin are determined as well. ► The influence of measurement error and measurement location upon the precision of the estimated results is also investigated. - Abstract: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to estimate the unknown time-dependent base heat flux of a functionally graded fin from the knowledge of temperature measurements taken within the fin. Subsequently, the distributions of temperature in the fin can be determined as well. It is assumed that no prior information is available on the functional form of the unknown base heat flux; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors and measurement location upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent base heat flux and temperature distributions can be obtained for the test case considered in this study.

Sony Labou Tansi, afflux des écrits et flux de l’écriture

Directory of Open Access Journals (Sweden)

Nicolas Martin-Granel

2014-04-01

Full Text Available Cet état des lieux des archives laissées par Sony Labou Tansi comprend deux volets. Le premier se présente comme un historique de la sauvegarde et de la valorisation des écrits qui constituent un continent immense et inédit. Leur histoire mouvementée est racontée à partir du moment où l’écriture s’arrête, lors la disparition de l’écrivain en 1995. Matériellement, les écrits sont couchés, pour la plupart, dans des cahiers d’écolier jetés en vrac au fond de la petite bibliothèque de sa maison de Makélékélé à Brazzaville. Sans date, parfois sans titre, ils représentent un véritable défi à la critique génétique qui cherche à les classer, les inventorier, les numériser et enfin à les éditer. Reconstituer leur parcours, au fil des multiples versions et transformations successives, aboutit à dresser la cartographie du labyrinthe textuel constitué non seulement du fonds SLT séparé entre la France et le Congo mais aussi des cahiers et lettres disséminés par l’auteur auprès de ses nombreux amis lecteurs et éditeurs. Dans le second volet, on s’attache à retrouver le fil conducteur de l’écriture, à en restituer la logique vitaliste et hypertextuelle. Si SLT écrivait comme on respire, son écriture, d’allure improvisée, décrite par la génétique comme « à processus », relève, du point de vue anthropologique, du prophétisme scripturaire : un dire-écrire en progression continue – contre le progrès, sans jamais se retourner vers la lecture.

Analytical estimation show low depth-independent water loss due to vapor flux from deep aquifers

Science.gov (United States)

Selker, John S.

2017-06-01

Recent articles have provided estimates of evaporative flux from water tables in deserts that span 5 orders of magnitude. In this paper, we present an analytical calculation that indicates aquifer vapor flux to be limited to 0.01 mm/yr for sites where there is negligible recharge and the water table is well over 20 m below the surface. This value arises from the geothermal gradient, and therefore, is nearly independent of the actual depth of the aquifer. The value is in agreement with several numerical studies, but is 500 times lower than recently reported experimental values, and 100 times larger than an earlier analytical estimate.

Residual-based a posteriori error estimation for multipoint flux mixed finite element methods

KAUST Repository

Du, Shaohong; Sun, Shuyu; Xie, Xiaoping

2015-01-01

A novel residual-type a posteriori error analysis technique is developed for multipoint flux mixed finite element methods for flow in porous media in two or three space dimensions. The derived a posteriori error estimator for the velocity and pressure error in L-norm consists of discretization and quadrature indicators, and is shown to be reliable and efficient. The main tools of analysis are a locally postprocessed approximation to the pressure solution of an auxiliary problem and a quadrature error estimate. Numerical experiments are presented to illustrate the competitive behavior of the estimator.

Residual-based a posteriori error estimation for multipoint flux mixed finite element methods

KAUST Repository

Du, Shaohong

2015-10-26

A novel residual-type a posteriori error analysis technique is developed for multipoint flux mixed finite element methods for flow in porous media in two or three space dimensions. The derived a posteriori error estimator for the velocity and pressure error in L-norm consists of discretization and quadrature indicators, and is shown to be reliable and efficient. The main tools of analysis are a locally postprocessed approximation to the pressure solution of an auxiliary problem and a quadrature error estimate. Numerical experiments are presented to illustrate the competitive behavior of the estimator.

Satellite data based approach for the estimation of anthropogenic heat flux over urban areas

Science.gov (United States)

Nitis, Theodoros; Tsegas, George; Moussiopoulos, Nicolas; Gounaridis, Dimitrios; Bliziotis, Dimitrios

2017-09-01

Anthropogenic effects in urban areas influence the thermal conditions in the environment and cause an increase of the atmospheric temperature. The cities are sources of heat and pollution, affecting the thermal structure of the atmosphere above them which results to the urban heat island effect. In order to analyze the urban heat island mechanism, it is important to estimate the anthropogenic heat flux which has a considerable impact on the urban energy budget. The anthropogenic heat flux is the result of man-made activities (i.e. traffic, industrial processes, heating/cooling) and thermal releases from the human body. Many studies have underlined the importance of the Anthropogenic Heat Flux to the calculation of the urban energy budget and subsequently, the estimation of mesoscale meteorological fields over urban areas. Therefore, spatially disaggregated anthropogenic heat flux data, at local and city scales, are of major importance for mesoscale meteorological models. The main objectives of the present work are to improve the quality of such data used as input for mesoscale meteorological models simulations and to enhance the application potential of GIS and remote sensing in the fields of climatology and meteorology. For this reason, the Urban Energy Budget concept is proposed as the foundation for an accurate determination of the anthropogenic heat discharge as a residual term in the surface energy balance. The methodology is applied to the cities of Athens and Paris using the Landsat ETM+ remote sensing data. The results will help to improve our knowledge on Anthropogenic Heat Flux, while the potential for further improvement of the methodology is also discussed.

The advantages, and challenges, in using multiple techniques in the estimation of surface water-groundwater fluxes.

Science.gov (United States)

Shanafield, M.; Cook, P. G.

2014-12-01

When estimating surface water-groundwater fluxes, the use of complimentary techniques helps to fill in uncertainties in any individual method, and to potentially gain a better understanding of spatial and temporal variability in a system. It can also be a way of preventing the loss of data during infrequent and unpredictable flow events. For example, much of arid Australia relies on groundwater, which is recharged by streamflow through ephemeral streams during flood events. Three recent surface water/groundwater investigations from arid Australian systems provide good examples of how using multiple field and analysis techniques can help to more fully characterize surface water-groundwater fluxes, but can also result in conflicting values over varying spatial and temporal scales. In the Pilbara region of Western Australia, combining streambed radon measurements, vertical heat transport modeling, and a tracer test helped constrain very low streambed residence times, which are on the order of minutes. Spatial and temporal variability between the methods yielded hyporheic exchange estimates between 10-4 m2 s-1 and 4.2 x 10-2 m2 s-1. In South Australia, three-dimensional heat transport modeling captured heterogeneity within 20 square meters of streambed, identifying areas of sandy soil (flux rates of up to 3 m d-1) and clay (flux rates too slow to be accurately characterized). Streamflow front modeling showed similar flux rates, but averaged over 100 m long stream segments for a 1.6 km reach. Finally, in central Australia, several methods are used to decipher whether any of the flow down a highly ephemeral river contributes to regional groundwater recharge, showing that evaporation and evapotranspiration likely accounts for all of the infiltration into the perched aquifer. Lessons learned from these examples demonstrate the influences of the spatial and temporal variability between techniques on estimated fluxes.

Numerical tools to estimate the flux of a gas across the air–water interface and assess the heterogeneity of its forcing functions

Directory of Open Access Journals (Sweden)

V. M. N. C. S. Vieira

2013-03-01

Full Text Available A numerical tool was developed for the estimation of gas fluxes across the air–water interface. The primary objective is to use it to estimate CO2 fluxes. Nevertheless application to other gases is easily accomplished by changing the values of the parameters related to the physical properties of the gases. A user-friendly software was developed allowing to build upon a standard kernel a custom-made gas flux model with the preferred parameterizations. These include single or double layer models; several numerical schemes for the effects of wind in the air-side and water-side transfer velocities; the effects of atmospheric stability, surface roughness and turbulence from current drag with the bottom; and the effects on solubility of water temperature, salinity, air temperature and pressure. An analysis was also developed which decomposes the difference between the fluxes in a reference situation and in alternative situations into its several forcing functions. This analysis relies on the Taylor expansion of the gas flux model, requiring the numerical estimation of partial derivatives by a multivariate version of the collocation polynomial. Both the flux model and the difference decomposition analysis were tested with data taken from surveys done in the lagoon system of Ria Formosa, south Portugal, in which the CO2 fluxes were estimated using the infrared gas analyzer (IRGA and floating chamber method, whereas the CO2 concentrations were estimated using the IRGA and degasification chamber. Observations and estimations show a remarkable fit.

Mesure et modélisation multidimensionnelle des transferts thermiques gaz-paroi dans le cas des moteurs à allumage commandé Measurement and Multidimensional Modeling of Gas-Wall Heat Transfers in Spark-Ignition Engines

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Gilaber P.

2006-11-01

Full Text Available A cette fin, deux étapes de recherche ont été mises en oeuvre : une phase expérimentale et une phase calcul. Dans la phase expérimentale, des mesures ont été faites sur un moteur monocylindre équipé de flux-mètres à réponse rapide. Chaque flux-mètre est composé d'un cylindre d'acier, contenant deux thermocouples. Dans le but de montrer l'influence de l'aérodynamique sur les échanges thermiques, un anémomètre à Laser a été utilisé à l'aide d'une entretoise placée entre culasse et cylindre. L'entretoise comportait deux hublots et deux flux-mètres permettant la mesure simultanée des flux thermiques et des paramètres aérodynamiques à l'extérieur de la couche limite. Deux flux-mètres supplémentaires ont été placés dans la culasse et le système d'acquisition permettait d'enregistrer simultanément dix voies de mesure à chaque degré vilebrequin, parmi lesquelles deux composantes de vitesse et la pression cylindre. Une étude paramétrique a révélé les tendances suivantes : - les pertes globales aux parois au cours d'un cycle thermodynamique diminuent lorsque le régime augmente, mais la valeur maximale des flux locaux augmente en raison de l'élévation du niveau de turbulence; - le remplissage a peu d'effet sur l'aérodynamique; son influence sur les transferts thermiques est due principalement à l'augmentation de la densité des gaz, qui se traduit par une augmentation des flux. Dans la phase calcul, deux idées de base ont guidé notre travail : - pour des raisons de temps de calcul prohibitif, il est impossible de mailler la couche limite; les échanges thermiques ont donc été estimés à l'aide d'une loi de paroi; - on fait l'hypothèse que les champs locaux de densité, vitesse et turbulence conditionnent fortement les flux thermiques; ce seront les paramètres de la loi de paroi. Dans cet esprit, le modèle de transferts thermiques de DIWAKAR a été introduit dans le code multi-dimensionnel KIVA. Une

Compliments, motivation et estime de soi : l'effet paradoxal de féliciter les capacités des enfants

DEFF Research Database (Denmark)

Hansen, Mikkel

2014-01-01

motivation may suffer when given feedback that evaluates their person. We discuss links between different types of feedback and children’s motivational frameworks, including their self-esteem. // RÉSUMÉ L’objectif de compliments tels que « T’es très fort, très intelligent » est d’encourager les enfants, mais...... des recherches récentes montrent que de telles propositions en feedback peuvent dissuader les enfants de s’engager dans des tâches difficiles, réduisant ainsi leurs apprentissages. Nous exposerons les travaux de Dweck (e.g., 2000) qui démontrent comment les compliments centrés sur l’évaluation de la...... personne influent négativement sur la motivation intrinsèque du sujet. Nous discuterons des liens existant entre différents types de feedback et les cadres motivationnels où évoluent les enfants, ainsi que de leur estime de soi....

Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective

DEFF Research Database (Denmark)

Morillas, L.; Garcia Garcia, Monica; Nieto Solana, Hector

2013-01-01

A two-source model (TSM) for surface energy balance, considering explicitly soil and vegetation components, was tested under water stress conditions. The TSM evaluated estimates the sensible heat flux (H) using the surface-air thermal gradient and the latent heat flux (LE) as a residual from the ...

ETUDES ANALYTIQUES : Détection des OGM : du libre choix des consommateurs aux études de biovigilance

Directory of Open Access Journals (Sweden)

Bertheau Yves

2000-07-01

Full Text Available Les récentes affaires de semences conventionnelles de colza et de maïs contaminées par des traces d’OGM ont à nouveau, s’il en était besoin, rappelé à notre bon souvenir les besoins en méthodes de détection et d’identification des OGM fiables et sensibles. Les développements se poursuivent, certes bien plus lentement qu’initialement espéré du fait du nombre important de facteurs à maîtriser et du caractère relativement inédit de ce travail. Concernant des matrices alimentaires variées, cette détection se heurte au manque de recul dans plusieurs domaines tels que celui de l’extraction et la purification d’acides nucléiques en quantité et en qualité. Bien que développées pour satisfaire aux besoins réglementaires européens concernant l’alimentation humaine, ces méthodes devraient être aisément applicables dans d’autres domaines concernés par les OGM (étude des transferts de gènes par flux pollinique, éventuels transferts horizontaux, suivi des acides nucléiques lors de l’ingestion.... Au-delà des OGM, les méthodes mises en œuvre devraient présenter un intérêt dans d’autres domaines comme la microbiologie, l’épidémiologie ou l’authentification des composants biologiques d’un produit.

Towards scale-independent land-surface flux estimates in Noah-MP

Science.gov (United States)

Thober, Stephan; Mizukami, Naoki; Samaniego, Luis; Attinger, Sabine; Clark, Martyn; Cuntz, Matthias

2017-04-01

Land-surface models use a variety of process representations to calculate terrestrial energy, water and biogeochemical fluxes. These process descriptions are usually derived from point measurements which are, in turn, scaled to much larger resolutions ranging from 1 km in catchment hydrology to 100 km in climate modelling. Both, hydrologic and climate models are nowadays run on different spatial resolutions, using the exactly same land surface representations. A fundamental criterion for the physical consistency of land-surface simulations across scales is that a flux estimated over a given area is independent of the spatial model resolution (i.e., the flux-matching criterion). The Noah-MP land surface model considers only one soil and land cover type per model grid cell without any representation of their subgrid variability, implying a weak flux-matching. A fractional approach simulates the subgrid variability but it requires a higher computational demand than using effective parameters and it is used only for land cover in current land surface schemes. A promising approach to derive scale-independent parameters is the Multiscale Parameter Regionalization (MPR) technique, which consists of two steps: first, it applies transfer functions directly to high-resolution data (such as 100 m soil maps) to derive high-resolution model parameter fields, acknowledging the full subgrid variability. Second, it upscales these high-resolution parameter fields to the model resolution by using appropriate upscaling operators. MPR has shown to improve substantially the scalability of the mesoscale Hydrologic Models mHM (Samaniego et al., 2010 WRR). Here, we apply the MPR technique to the Noah-MP land-surface model for a large sample of basins distributed across the contiguous USA. Specifically, we evaluate the flux-matching criterion for several hydrologic fluxes such as evapotranspiration and drainage at scales ranging from 3 km to 48 km. We investigate the impact of different

Création du groupe FMR (Flux, Matrices, Réseaux

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Laurent Beauguitte

2013-06-01

Full Text Available Laurent Beauguitte et César Ducruetont pris l’initiative de créer un groupe de travail sur les réseaux en vue d’intégrer dans l’approche géographique les outils et méthodes issues de l’analyse des réseaux (planaires, sociaux, complexes. Ces derniers paraissent en effet fournir des pistes intéressantes pour l’analyse des flux de toute nature (commerciaux, humains, informationnels, financiers. Ce groupe tient une réunion mensuelle depuis le 26 octobre 2010 à Paris. Trois axes de travail sont...

The Boston Methane Project: Mapping Surface Emissions to Inform Atmospheric Estimation of Urban Methane Flux

Science.gov (United States)

Phillips, N.; Crosson, E.; Down, A.; Hutyra, L.; Jackson, R. B.; McKain, K.; Rella, C.; Raciti, S. M.; Wofsy, S. C.

2012-12-01

Lost and unaccounted natural gas can amount to over 6% of Massachusetts' total annual greenhouse gas inventory (expressed as equivalent CO2 tonnage). An unknown portion of this loss is due to natural gas leaks in pipeline distribution systems. The objective of the Boston Methane Project is to estimate the overall leak rate from natural gas systems in metropolitan Boston, and to compare this flux with fluxes from the other primary methane emissions sources. Companion talks at this meeting describe the atmospheric measurement and modeling framework, and chemical and isotopic tracers that can partition total atmospheric methane flux into natural gas and non-natural gas components. This talk focuses on estimation of surface emissions that inform the atmospheric modeling and partitioning. These surface emissions include over 3,300 pipeline natural gas leaks in Boston. For the state of Massachusetts as a whole, the amount of natural gas reported as lost and unaccounted for by utility companies was greater than estimated landfill emissions by an order of magnitude. Moreover, these landfill emissions were overwhelmingly located outside of metro Boston, while gas leaks are concentrated in exactly the opposite pattern, increasing from suburban Boston toward the urban core. Work is in progress to estimate spatial distribution of methane emissions from wetlands and sewer systems. We conclude with a description of how these spatial data sets will be combined and represented for application in atmospheric modeling.

Estimating surface turbulent heat fluxes from land surface temperature and soil moisture using the particle batch smoother

Science.gov (United States)

Lu, Yang; Dong, Jianzhi; Steele-Dunne, Susan; van de Giesen, Nick

2016-04-01

This study is focused on estimating surface sensible and latent heat fluxes from land surface temperature (LST) time series and soil moisture observations. Surface turbulent heat fluxes interact with the overlying atmosphere and play a crucial role in meteorology, hydrology and other climate-related fields, but in-situ measurements are costly and difficult. It has been demonstrated that the time series of LST contains information of energy partitioning and that surface turbulent heat fluxes can be determined from assimilation of LST. These studies are mainly based on two assumptions: (1) a monthly value of bulk heat transfer coefficient under neutral conditions (CHN) which scales the sum of the fluxes, and (2) an evaporation fraction (EF) which stays constant during the near-peak hours of the day. Previous studies have applied variational and ensemble approaches to this problem. Here the newly developed particle batch smoother (PBS) algorithm is adopted to test its capability in this application. The PBS can be seen as an extension of the standard particle filter (PF) in which the states and parameters within a fix window are updated in a batch using all observations in the window. The aim of this study is two-fold. First, the PBS is used to assimilate only LST time series into the force-restore model to estimate fluxes. Second, a simple soil water transfer scheme is introduced to evaluate the benefit of assimilating soil moisture observations simultaneously. The experiments are implemented using the First ISLSCP (International Satellite Land Surface Climatology Project) (FIFE) data. It is shown that the restored LST time series using PBS agrees very well with observations, and that assimilating LST significantly improved the flux estimation at both daily and half-hourly time scales. When soil moisture is introduced to further constrain EF, the accuracy of estimated EF is greatly improved. Furthermore, the RMSEs of retrieved fluxes are effectively reduced at both

Estimation of catchment averaged sensible heat fluxes using a large aperture scintillometer

Directory of Open Access Journals (Sweden)

Samain Bruno

2012-05-01

Full Text Available Evapotranspiration rates at the catchment scale are very difficult to quantify. One possible manner to continuously observe this variable could be the estimation of sensible heat fluxes (H across large distances (in the order of kilometers using a large aperture scintillometer (LAS, and inverting these observations into evapotranspiration rates, under the assumption that the LAS observations are representative for the entire catchment. The objective of this paper is to assess whether measured sensible heat fluxes from a LAS over a long distance (9.5 km can be assumed to be valid for a 102.3 km2 heterogeneous catchment. Therefore, a fully process-based water and energy balance model with a spatial resolution of 50 m has been thoroughly calibrated and validated for the Bellebeek catchmentin Belgium. A footprint analysis has been performed. In general, the sensible heat fluxes from the LAS compared well with the modeled sensible heat fluxes within the footprint. Moreover, as the modeled Hwithin the footprint has been found to be almost equal to the modeled catchment averaged H, it can be concluded that the scintillometer measurements over a distance of 9.5 km and an effective heightof 68 m are representative for the entire catchment.

A Novel Methodology to Estimate Metabolic Flux Distributions in Constraint-Based Models

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Francesco Alessandro Massucci

2013-09-01

Full Text Available Quite generally, constraint-based metabolic flux analysis describes the space of viable flux configurations for a metabolic network as a high-dimensional polytope defined by the linear constraints that enforce the balancing of production and consumption fluxes for each chemical species in the system. In some cases, the complexity of the solution space can be reduced by performing an additional optimization, while in other cases, knowing the range of variability of fluxes over the polytope provides a sufficient characterization of the allowed configurations. There are cases, however, in which the thorough information encoded in the individual distributions of viable fluxes over the polytope is required. Obtaining such distributions is known to be a highly challenging computational task when the dimensionality of the polytope is sufficiently large, and the problem of developing cost-effective ad hoc algorithms has recently seen a major surge of interest. Here, we propose a method that allows us to perform the required computation heuristically in a time scaling linearly with the number of reactions in the network, overcoming some limitations of similar techniques employed in recent years. As a case study, we apply it to the analysis of the human red blood cell metabolic network, whose solution space can be sampled by different exact techniques, like Hit-and-Run Monte Carlo (scaling roughly like the third power of the system size. Remarkably accurate estimates for the true distributions of viable reaction fluxes are obtained, suggesting that, although further improvements are desirable, our method enhances our ability to analyze the space of allowed configurations for large biochemical reaction networks.

Estimating carbon flux phenology with satellite-derived land surface phenology and climate drivers for different biomes: a synthesis of AmeriFlux observations.

Directory of Open Access Journals (Sweden)

Wenquan Zhu

Full Text Available Carbon Flux Phenology (CFP can affect the interannual variation in Net Ecosystem Exchange (NEE of carbon between terrestrial ecosystems and the atmosphere. In this study, we proposed a methodology to estimate CFP metrics with satellite-derived Land Surface Phenology (LSP metrics and climate drivers for 4 biomes (i.e., deciduous broadleaf forest, evergreen needleleaf forest, grasslands and croplands, using 159 site-years of NEE and climate data from 32 AmeriFlux sites and MODIS vegetation index time-series data. LSP metrics combined with optimal climate drivers can explain the variability in Start of Carbon Uptake (SCU by more than 70% and End of Carbon Uptake (ECU by more than 60%. The Root Mean Square Error (RMSE of the estimations was within 8.5 days for both SCU and ECU. The estimation performance for this methodology was primarily dependent on the optimal combination of the LSP retrieval methods, the explanatory climate drivers, the biome types, and the specific CFP metric. This methodology has a potential for allowing extrapolation of CFP metrics for biomes with a distinct and detectable seasonal cycle over large areas, based on synoptic multi-temporal optical satellite data and climate data.

Experimental study of the Rapsodie protections; Etude experimentale des protections de rapsodie

Energy Technology Data Exchange (ETDEWEB)

Chapelet, M; Edeline, J; Lhiaubet, G [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1968-07-01

This report gives details of the protection tests which have been carried out by the Protection Sub-Commission during the starting-up trials on the reactor Rapsodie. The main types of tests reported concern the flux measurements in the core, the reflectors, the sodium and the near biological protections, the radio-protection measurements in the premises, and the activation of the principal fluids. In the last part, the results obtained are analyzed and compared to the forecast calculations. (author) [French] Ce rapport rend compte des essais de protection qui ont ete effectues dans le cadre des essais de demarrage de RAPSODIE par la Sous Commission Protection. Les principaux types d'essais rapportes sont les mesures de flux dans le coeur, les reflecteurs, le sodium et les protections biologiques proches, les mesures de radioprotection dans les locaux, et l'activation des principaux fluides. Dans la derniere partie, les resultats obtenus sont analyses et compares aux calculs previsionnels. (auteur)

Estimation of phosphorus flux in rivers during flooding.

Science.gov (United States)

Chen, Yen-Chang; Liu, Jih-Hung; Kuo, Jan-Tai; Lin, Cheng-Fang

2013-07-01

Reservoirs in Taiwan are inundated with nutrients that result in algal growth, and thus also reservoir eutrophication. Controlling the phosphorus load has always been the most crucial issue for maintaining reservoir water quality. Numerous agricultural activities, especially the production of tea in riparian areas, are conducted in watersheds in Taiwan. Nutrients from such activities, including phosphorus, are typically flushed into rivers during flooding, when over 90% of the yearly total amount of phosphorous enters reservoirs. Excessive or enhanced soil erosion from rainstorms can dramatically increase the river sediment load and the amount of particulate phosphorus flushed into rivers. When flow rates are high, particulate phosphorus is the dominant form of phosphorus, but sediment and discharge measurements are difficult during flooding, which makes estimating phosphorus flux in rivers difficult. This study determines total amounts of phosphorus transport by measuring flood discharge and phosphorous levels during flooding. Changes in particulate phosphorus, dissolved phosphorus, and their adsorption behavior during a 24-h period are analyzed owing to the fact that the time for particulate phosphorus adsorption and desorption approaching equilibrium is about 16 h. Erosion of the reservoir watershed was caused by adsorption and desorption of suspended solids in the river, a process which can be summarily described using the Lagmuir isotherm. A method for estimating the phosphorus flux in the Daiyujay Creek during Typhoon Bilis in 2006 is presented in this study. Both sediment and phosphorus are affected by the drastic discharge during flooding. Water quality data were collected during two flood events, flood in June 9, 2006 and Typhoon Bilis, to show the concentrations of suspended solids and total phosphorus during floods are much higher than normal stages. Therefore, the drastic changes of total phosphorus, particulate phosphorus, and dissolved phosphorus in

Comparison of sensible heat flux estimates using AVHRR with scintillometer measurements over semi-arid grassland in northwest Mexico

NARCIS (Netherlands)

Watts, C.J.; Chehbouni, A.; Rodriguez, J.C.; Kerr, Y.H.; Hartogensis, O.K.; Bruin, de H.A.R.

2000-01-01

The problems associated with the validation of satellite-derived estimates of the surface fluxes are discussed and the possibility of using the large aperture scintillometer is investigated. Simple models are described to derive surface temperature and sensible heat flux from the advanced very high

Flux des polluants liés aux activités anthropiques, risques sur les ...

African Journals Online (AJOL)

Les activités anthropiques interfèrent sur les eaux de surface en créant des problèmes environnementaux et sanitaires. Les activités domestiques, agricoles, industrielles, hospitalières, et les activités de pêche artisanale et de tourisme, sont les plus incriminées. La pollution des eaux de surface par les métaux lourds, les ...

Estimation of net ecosystem carbon exchange for the conterminous United States by combining MODIS and AmeriFlux data

Energy Technology Data Exchange (ETDEWEB)

Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Bolstad, Paul V.; Burns, Sean P.; Chen, Jiquan; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Law, Beverly E.; Litvak, Marcy; Ma, Siyan; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Noormets, Asko; Oechel, Walter C.; Oren, Ram; Richardson, Andrew D.; Schmid, Hans Peter; Scott, Russell L.; Starr, Gregory; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.; Paw, Kyaw; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.

2008-10-01

Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board the National Aeronautics and Space Administration's (NASA) Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a modified regression tree approach. The predictive model was trained and validated using eddy flux NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE well (r = 0.73, p < 0.001). We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day interval in 2005 using spatially explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE as determined from measurements and the literature. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets over large areas.

Effects of variations of stage and flux at different frequencies on the estimates using river stage tomography

Science.gov (United States)

Wang, Y. L.; Yeh, T. C. J.; Wen, J. C.

2017-12-01

This study is to investigate the ability of river stage tomography to estimate the spatial distribution of hydraulic transmissivity (T), storage coefficient (S), and diffusivity (D) in groundwater basins using information of groundwater level variations induced by periodic variations of stream stage, and infiltrated flux from the stream boundary. In order to accomplish this objective, the sensitivity and correlation of groundwater heads with respect to the hydraulic properties is first conducted to investigate the spatial characteristics of groundwater level in response to the stream variations at different frequencies. Results of the analysis show that the spatial distributions of the sensitivity of heads at an observation well in response to periodic river stage variations are highly correlated despite different frequencies. On the other hand, the spatial patterns of the sensitivity of the observed head to river flux boundaries at different frequencies are different. Specifically, the observed head is highly correlated with T at the region between the stream and observation well when the high-frequency periodic flux is considered. On the other hand, it is highly correlated with T at the region between monitoring well and the boundary opposite to the stream when the low-frequency periodic flux is prescribed to the stream. We also find that the spatial distributions of the sensitivity of observed head to S variation are highly correlated with all frequencies in spite of heads or fluxes stream boundary. Subsequently, the differences of the spatial correlations of the observed heads to the hydraulic properties under the head and flux boundary conditions are further investigated by an inverse model (i.e., successive stochastic linear estimator). This investigation uses noise-free groundwater and stream data of a synthetic aquifer, where aquifer heterogeneity is known exactly. The ability of river stage tomography is then tested with these synthetic data sets to

The Vertical Flux Method (VFM) for regional estimates of temporally and spatially varying nitrate fluxes in unsaturated zone and groundwater

Science.gov (United States)

Green, C. T.; Liao, L.; Nolan, B. T.; Juckem, P. F.; Ransom, K.; Harter, T.

2017-12-01

Process-based modeling of regional NO3- fluxes to groundwater is critical for understanding and managing water quality. Measurements of atmospheric tracers of groundwater age and dissolved-gas indicators of denitrification progress have potential to improve estimates of NO3- reactive transport processes. This presentation introduces a regionalized version of a vertical flux method (VFM) that uses simple mathematical estimates of advective-dispersive reactive transport with regularization procedures to calibrate estimated tracer concentrations to observed equivalents. The calibrated VFM provides estimates of chemical, hydrologic and reaction parameters (source concentration time series, recharge, effective porosity, dispersivity, reaction rate coefficients) and derived values (e.g. mean unsaturated zone travel time, eventual depth of the NO3- front) for individual wells. Statistical learning methods are used to extrapolate parameters and predictions from wells to continuous areas. The regional VFM was applied to 473 well samples in central-eastern Wisconsin. Chemical measurements included O2, NO3-, N2 from denitrification, and atmospheric tracers of groundwater age including carbon-14, chlorofluorocarbons, tritium, and triogiogenic helium. VFM results were consistent with observed chemistry, and calibrated parameters were in-line with independent estimates. Results indicated that (1) unsaturated zone travel times were a substantial portion of the transit time to wells and streams (2) fractions of N leached to groundwater have changed over time, with increasing fractions from manure and decreasing fractions from fertilizer, and (3) under current practices and conditions, 60% of the shallow aquifer will eventually be affected by NO3- contamination. Based on GIS coverages of variables related to soils, land use and hydrology, the VFM results at individual wells were extrapolated regionally using boosted regression trees, a statistical learning approach, that related

Contribution à l’identification des déterminants fondamentaux en évaluation des banques

Directory of Open Access Journals (Sweden)

Badr Habba

2016-03-01

Full Text Available Ce papier étudie l’influence des facteurs fondamentaux sur l’évaluation des banques. Dans un premier temps, nous avons sélectionné, sur la base d’une revue de la littérature, les caractéristiques fondamentales susceptibles d’influencer l’évaluation des banques. Ensuite, nous avons estimé un modèle économétrique mettant en relation la valeur des banques et six variables explicatives à l’aide de l’économétrie des données de panel. L’échantillon est constitué d’un panel de 82 banques cotées entre 2005 et 2013. Les résultats obtenus montrent qu’il existe une influence très significative de la qualité du portefeuille bancaire de crédits, du niveau de capitalisation, du niveau de diversification du portefeuille d’activités, de l’efficience et de la taille de la banque sur l’évaluation des firmes bancaires.

How Choice of Depth Horizon Influences the Estimated Spatial Patterns and Global Magnitude of Ocean Carbon Export Flux

Science.gov (United States)

Palevsky, Hilary I.; Doney, Scott C.

2018-05-01

Estimated rates and efficiency of ocean carbon export flux are sensitive to differences in the depth horizons used to define export, which often vary across methodological approaches. We evaluate sinking particulate organic carbon (POC) flux rates and efficiency (e-ratios) in a global earth system model, using a range of commonly used depth horizons: the seasonal mixed layer depth, the particle compensation depth, the base of the euphotic zone, a fixed depth horizon of 100 m, and the maximum annual mixed layer depth. Within this single dynamically consistent model framework, global POC flux rates vary by 30% and global e-ratios by 21% across different depth horizon choices. Zonal variability in POC flux and e-ratio also depends on the export depth horizon due to pronounced influence of deep winter mixing in subpolar regions. Efforts to reconcile conflicting estimates of export need to account for these systematic discrepancies created by differing depth horizon choices.

Rocket Motor Plume Technology (L’Etude des Jets des Moteures-Fusees)

Science.gov (United States)

1993-06-01

souhait6 que des I ’utilisation de distributions granulom ~triquesprcdesimars celsd itacif- dons un but diff~rent de cclui pour lequel ment une base...4-5 while beyond the third cell, wave processes are linear and equally parcelled into 1, 3, and 10prm radius particulates. no further damping occurs...aN where N denotes the time step level, and, the . + , flux vectors E and F, (which are nonlinear functions of Q) have been linearized about WN, e.g

Concentration, flux, and trend estimates with uncertainty for nutrients, chloride, and total suspended solids in tributaries of Lake Champlain, 1990–2014

Science.gov (United States)

Medalie, Laura

2016-12-20

The U.S. Geological Survey, in cooperation with the New England Interstate Water Pollution Control Commission and the Vermont Department of Environmental Conservation, estimated daily and 9-month concentrations and fluxes of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids from 1990 (or first available date) through 2014 for 18 tributaries of Lake Champlain. Estimates of concentration and flux, provided separately in Medalie (2016), were made by using the Weighted Regressions on Time, Discharge, and Season (WRTDS) regression model and update previously published WRTDS model results with recent data. Assessment of progress towards meeting phosphorus-reduction goals outlined in the Lake Champlain management plan relies on annual estimates of phosphorus flux. The percent change in annual concentration and flux is provided for two time periods. The R package EGRETci was used to estimate the uncertainty of the trend estimate. Differences in model specification and function between this study and previous studies that used WRTDS to estimate concentration and flux using data from Lake Champlain tributaries are described. Winter data were too sparse and nonrepresentative to use for estimates of concentration and flux but were sufficient for estimating the percentage of total annual flux over the period of record. Median winter-to-annual fractions ranged between 21 percent for total suspended solids and 27 percent for dissolved phosphorus. The winter contribution was largest for all constituents from the Mettawee River and smallest from the Ausable River. For the full record (1991 through 2014 for total and dissolved phosphorus and chloride and 1993 through 2014 for nitrogen and total suspended solids), 6 tributaries had decreasing trends in concentrations of total phosphorus, and 12 had increasing trends; concentrations of dissolved phosphorus decreased in 6 and increased in 8 tributaries; fluxes of total phosphorus decreased in 5 and

Synthesizing Global and Local Datasets to Estimate Jurisdictional Forest Carbon Fluxes in Berau, Indonesia.

Science.gov (United States)

Griscom, Bronson W; Ellis, Peter W; Baccini, Alessandro; Marthinus, Delon; Evans, Jeffrey S; Ruslandi

2016-01-01

Forest conservation efforts are increasingly being implemented at the scale of sub-national jurisdictions in order to mitigate global climate change and provide other ecosystem services. We see an urgent need for robust estimates of historic forest carbon emissions at this scale, as the basis for credible measures of climate and other benefits achieved. Despite the arrival of a new generation of global datasets on forest area change and biomass, confusion remains about how to produce credible jurisdictional estimates of forest emissions. We demonstrate a method for estimating the relevant historic forest carbon fluxes within the Regency of Berau in eastern Borneo, Indonesia. Our method integrates best available global and local datasets, and includes a comprehensive analysis of uncertainty at the regency scale. We find that Berau generated 8.91 ± 1.99 million tonnes of net CO2 emissions per year during 2000-2010. Berau is an early frontier landscape where gross emissions are 12 times higher than gross sequestration. Yet most (85%) of Berau's original forests are still standing. The majority of net emissions were due to conversion of native forests to unspecified agriculture (43% of total), oil palm (28%), and fiber plantations (9%). Most of the remainder was due to legal commercial selective logging (17%). Our overall uncertainty estimate offers an independent basis for assessing three other estimates for Berau. Two other estimates were above the upper end of our uncertainty range. We emphasize the importance of including an uncertainty range for all parameters of the emissions equation to generate a comprehensive uncertainty estimate-which has not been done before. We believe comprehensive estimates of carbon flux uncertainty are increasingly important as national and international institutions are challenged with comparing alternative estimates and identifying a credible range of historic emissions values.

Estimation of Net Ecosystem Carbon Exchange for the Conterminous UnitedStates by Combining MODIS and AmeriFlux Data

Energy Technology Data Exchange (ETDEWEB)

Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Law, Beverly E.; Richardson, Andrew D.; Chen, Jiquan; Oren, Ram; Starr, Gregory; Noormets, Asko; Ma, Siyan; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.; Bolstad, Paul V.; Burns, Sean P.; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Falk, Matthias; Fischer, Marc L.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Litvak, Marcy; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Oechel, Walter C.; U, Kyaw Tha Paw; Schmid, Hans Peter; Scott, Russell L.; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.

2009-03-06

Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely-sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board NASA's Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a regression tree approach. The predictive model was trained and validated using NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE reasonably well at the site level. We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day period in 2005 using spatially-explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets for large areas.

RECRUTEMENT DES CIVELLES (ANGUILLA ANGUILLA SUR LA COTE MEDITERRANEENNE FRANÇAISE : ANALYSE COMPAREE DES CARACTERISTIQUES BIOMETRIQUES ET PIGMENTAIRES DES SAISONS 1974-75 ET 2000-01.

Directory of Open Access Journals (Sweden)

LEFEBVRE F.

2003-07-01

Full Text Available Une campagne d’échantillonnage des civelles Anguilla anguilla a été menée de novembre 2000 à mai 2001 au grau de la Fourcade (Saintes-Maries-de-la-Mer, côte méditerranéenne française. Des civelles ont été capturées sur toute la période d’échantillonnage, mais les maxima d’abondance se situent en janvier-février et, dans une moindre mesure, en avril. Afin d’optimiser le recrutement dans les lagunes littorales intérieures, la mesure de gestion proposée est donc de favoriser l’ouverture des martelières au milieu de l’hiver. Le suivi des proportions mensuelles des différents stades pigmentaires (de V A à VI A4 permet de conclure à un vieillissement généralisé des civelles en recrutement de novembre à mars, puis à l’arrivée d’un deuxième flux de civelles jeunes en avril. Parallèlement, il est observé une diminution très nette des masses et des longueurs moyennes mensuelles, et ce, même en ne considérant qu’un stade pigmentaire donné (en l’occurrence V B. Ces résultats sur l’évolution des caractéristiques biométriques et pigmentaires sont en accord avec les deux séries de travaux déjà menés sur la façade méditerranéenne française (années 30 et 70, ainsi qu’avec les données publiées en différents points de la façade atlantique. L’analyse comparée de ces données avec celles issues de la dernière étude en date sur la côte méditerranéenne française (Bages-Sigean, Languedoc-Roussillon, campagne 1974-75 ; LECOMTE-FINIGER, 1976 montre une composition pigmentaire mensuelle totalement différente, et révèle une diminution significative de la longueur des civelles, de l’ordre de 5 % en 25 ans.

Estimate of the latent flux by the energy balance in protected cultivation of sweet pepper

International Nuclear Information System (INIS)

Cunha, A.R. da; Escobedo, J.F.; Klosowski, E.S.

2002-01-01

The aim of this work was to characterize and bring into relationship the net radiation with the latent heat flux equivalent to water mm, in sweet pepper crops in the field and in protected cultivation. The estimate of latent heat flux was made by the energy balance method through the Bowen ratio. Instantaneous measures were made of net radiation (Rn), sensitive (H) and latent (LE) heat fluxes, heat flux into the soil (G), and of psychrometers gradients in the crop canopy. In protected cultivation, the conversion of the available net radiation in total dry matter and fruit productivity was more efficient than in the field, in spite of lower amounts of global solar radiation received by the crop. Ratios of G/Rn and LE/Rn were lower, and that of H/Rn was higher in protected cultivation, with an equivalent latent heat flux in millimeters, 45.43% lower than that determined in the field. Available net radiation and energy losses were also lower in protected cultivation, showing a higher water use efficiency. (author) [pt

The functioning of the reactors G2-G3 at Marcoule and E.D.F. 1; Experience de fonctionnement des reacteurs G2-G3 de Marcoule et enseignements des essais de demarrage du reacteur E.D.F. 1 de Chinon

Energy Technology Data Exchange (ETDEWEB)

Boussard, R; Conte, F [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires; Stolz, J M [Electricite de France (EDF), 75 - Paris (France)

1964-07-01

After resuming briefly the characteristics of the installations G2-G3 at Marcoule and EDF 1 at Chinon, the authors review the main aspects of the tests, the starting and the exploitation of these reactors. Among the various points examined, particular emphasis is given to the devices of original nature such as tubular fuel elements, flattening of the neutron flux by stuffing, behaviour of the reactor tanks and the cooling circuits, the blowers, unloading devices, regulation and functioning of the informations. This analysis deals equally with the performances obtained and the difficulties and the various incidents experienced during the initial starting period. Among the more interesting results, the progressive increase in the power of the Marcoule reactors is mentioned, obtained through a better knowledge of the parameters covering the functioning of the reactors such as the distribution of the flux and the temperatures etc... acquired during the course of the exploitation of the reactor. The conclusion reached by the authors is that the experience gained on these installations has shown: - that during an initial period, adjustments became necessary, all of which turned out to be possible, - that an analysis of their functioning has permitted the progressive movement towards a truly industrial exploitation. (authors) [French] Les auteurs, apres un bref rappel des caracteristiques des installations G2 - G3 de MARCOULE et E.D.F. 1 de CHINON, passent en revue les principaux aspects des essais, de la mise en service et de l'exploitation de ces centrales. Parmi les divers points examines, une attention speciale est accordee aux dispositifs presentant un caractere original tels que elements combustibles tubulaires, aplatissement du flux neutronique par gavage, comportement des caissons des reacteurs et des circuits de refroidissement, soufflantes, appareils de dechargement, regulation et fonctionnement des informations. L'analyse presentee porte tant sur les

Effect of recent observations on Asian CO2 flux estimates by transport model inversions

International Nuclear Information System (INIS)

Maksyutov, Shamil; Patra, Prabir K.; Machida, Toshinobu; Mukai, Hitoshi; Nakazawa, Takakiyo; Inoue, Gen

2003-01-01

We use an inverse model to evaluate the effects of the recent CO 2 observations over Asia on estimates of regional CO 2 sources and sinks. Global CO 2 flux distribution is evaluated using several atmospheric transport models, atmospheric CO 2 observations and a 'time-independent' inversion procedure adopted in the basic synthesis inversion by the Transcom-3 inverse model intercomparison project. In our analysis we include airborne and tower observations in Siberia, continuous monitoring and airborne observations over Japan, and airborne monitoring on regular flights on Tokyo-Sydney route. The inclusion of the new data reduces the uncertainty of the estimated regional CO 2 fluxes for Boreal Asia (Siberia), Temperate Asia and South-East Asia. The largest effect is observed for the emission/sink estimate for the Boreal Asia region, where introducing the observations in Siberia reduces the source uncertainty by almost half. It also produces an uncertainty reduction for Boreal North America. Addition of the Siberian airborne observations leads to projecting extra sinks in Boreal Asia of 0.2 Pg C/yr, and a smaller change for Europe. The Tokyo-Sydney observations reduce and constrain the Southeast Asian source

An iterative procedure for estimating areally averaged heat flux using planetary boundary layer mixed layer height and locally measured heat flux

Energy Technology Data Exchange (ETDEWEB)

Coulter, R. L.; Gao, W.; Lesht, B. M.

2000-04-04

Measurements at the central facility of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) are intended to verify, improve, and develop parameterizations in radiative flux models that are subsequently used in General Circulation Models (GCMs). The reliability of this approach depends upon the representativeness of the local measurements at the central facility for the site as a whole or on how these measurements can be interpreted so as to accurately represent increasingly large scales. The variation of surface energy budget terms over the SGP CART site is extremely large. Surface layer measurements of the sensible heat flux (H) often vary by a factor of 2 or more at the CART site (Coulter et al. 1996). The Planetary Boundary Layer (PBL) effectively integrates the local inputs across large scales; because the mixed layer height (h) is principally driven by H, it can, in principal, be used for estimates of surface heat flux over scales on the order of tens of kilometers. By combining measurements of h from radiosondes or radar wind profiles with a one-dimensional model of mixed layer height, they are investigating the ability of diagnosing large-scale heat fluxes. The authors have developed a procedure using the model described by Boers et al. (1984) to investigate the effect of changes in surface sensible heat flux on the mixed layer height. The objective of the study is to invert the sense of the model.

Measurement of a neutral particle flux by a thermal method using the junction temperature effect; Mesure d'un flux de particules neutres par une methode thermique mettant a contribution l'effet de temperature des jonctions

Energy Technology Data Exchange (ETDEWEB)

Caron, Anthime [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires. Services Scientifiques

1966-07-01

Among all the methods suitable for measuring neutral particle fluxes obtained by proton charge exchange in an organic gas, the thermal method has been chosen. The energy imparted by the neutral particles to the target in the form of heat leads to the latter temperature increasing; this temperature is usually followed with a thermocouple. In order to increase the sensitivity and the elegance of the apparatus the thermocouple has been replaced by a junction whose characteristics are known to vary with temperature. A calibration is carried out using a beam of charged particles. The response obtained is linear. Measurements have been made with a power of up to 1 mW; the accuracy increases with the energy provided; for 4 joules an accuracy of 10 per cent is obtained. The apparatus may be improved in particular by extending the measurement range towards low power values, and by increasing the accuracy. (author) [French] Parmi toutes les methodes utilisees pour la mesure d'un flux de particules neutres, obtenues par echange de charge de protons dans un gaz organique, nous avons choisi la methode thermique. L'energie cedee par les particules neutres a la cible sous forme de chaleur provoque une elevation de temperature de celle-ci; cette temperature est habituellement reperee par thermocouple. Pour accroitre la sensibilite et la finesse de l'appareillage, nous avons substitue au thermocouple une jonction dont on sait que les caracteristiques varient avec la temperature. Un etalonnage est realise par un faisceau de particules chargees. La reponse obtenue est lineaire. Des puissances de l'ordre du mW ont ete mesurees; la precision croit avec l'energie apportee; elle est de 10 pour cent quand celle-ci est de 4 joules. L'appareillage peut etre notablement perfectionne, pour reculer la gamme des mesures vers les basses puissances et accroitre la precision. (auteur)

Estimation of transient heat flux density during the heat supply of a catalytic wall steam methane reformer

Science.gov (United States)

Settar, Abdelhakim; Abboudi, Saïd; Madani, Brahim; Nebbali, Rachid

2018-02-01

Due to the endothermic nature of the steam methane reforming reaction, the process is often limited by the heat transfer behavior in the reactors. Poor thermal behavior sometimes leads to slow reaction kinetics, which is characterized by the presence of cold spots in the catalytic zones. Within this framework, the present work consists on a numerical investigation, in conjunction with an experimental one, on the one-dimensional heat transfer phenomenon during the heat supply of a catalytic-wall reactor, which is designed for hydrogen production. The studied reactor is inserted in an electric furnace where the heat requirement of the endothermic reaction is supplied by electric heating system. During the heat supply, an unknown heat flux density, received by the reactive flow, is estimated using inverse methods. In the basis of the catalytic-wall reactor model, an experimental setup is engineered in situ to measure the temperature distribution. Then after, the measurements are injected in the numerical heat flux estimation procedure, which is based on the Function Specification Method (FSM). The measured and estimated temperatures are confronted and the heat flux density which crosses the reactor wall is determined.

A comprehensive biogeochemical record and annual flux estimates for the Sabaki River (Kenya)

Science.gov (United States)

Marwick, Trent R.; Tamooh, Fredrick; Ogwoka, Bernard; Borges, Alberto V.; Darchambeau, François; Bouillon, Steven

2018-03-01

Inland waters impart considerable influence on nutrient cycling and budget estimates across local, regional and global scales, whilst anthropogenic pressures, such as rising populations and the appropriation of land and water resources, are undoubtedly modulating the flux of carbon (C), nitrogen (N) and phosphorus (P) between terrestrial biomes to inland waters, and the subsequent flux of these nutrients to the marine and atmospheric domains. Here, we present a 2-year biogeochemical record (October 2011-December 2013) at biweekly sampling resolution for the lower Sabaki River, Kenya, and provide estimates for suspended sediment and nutrient export fluxes from the lower Sabaki River under pre-dam conditions, and in light of the approved construction of the Thwake Multipurpose Dam on its upper reaches (Athi River). Erratic seasonal variation was typical for most parameters, with generally poor correlation between discharge and material concentrations, and stable isotope values of C (δ13C) and N (δ15N). Although high total suspended matter (TSM) concentrations are reported here (up to ˜ 3.8 g L-1), peak concentrations of TSM rarely coincided with peak discharge. The contribution of particulate organic C (POC) to the TSM pool indicates a wide biannual variation in suspended sediment load from OC poor (0.3 %) to OC rich (14.9 %), with the highest %POC occurring when discharge is Wet season flows (October-December and March-May) carried > 80 % of the total load for TSM (˜ 86 %), POC (˜ 89 %), dissolved organic carbon (DOC; ˜ 81 %), PN (˜ 89 %) and particulate phosphorus (TPP; ˜ 82 %), with > 50 % of each fraction exported during the long wet season (March-May). Our estimated sediment yield (85 Mg km-2 yr-1) is relatively low on the global scale and is considerably less than the recently reported average sediment yield of ˜ 630 Mg km-2 yr-1 for African river basins. Regardless, sediment and OC yields were all at least equivalent or greater than reported yields

Fast flux measurements by means of threshold detectors on the reactor 'Melusine'; Mesures de flux rapides a l'aide de detecteurs a seuil sur le reacteur 'Melusine'

Energy Technology Data Exchange (ETDEWEB)

Leger, P; Sautiez, B [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Using existing data on the (n,p) and (n,{alpha}) threshold reactions we have carried out fast flux measurements on the swimming pool type reactor 'Melusine'. Four common elements: P, S, Mg, Al were chosen because from the point of view of fast spectrum analysis they represent a fairly good energy range from 2.4 MeV to 8 MeV. The fission flux value found in the central element at a power of 1 MW is 1.4 x 10{sup 13} n/cm{sup 2}/s {+-} 0.14. (author) [French] A l'aide des donnees actuelles sur les reactions a seuil (n,p) et (n,{alpha}) nous avons realise des mesures de flux rapide dans le reacteur du type piscine 'Melusine'. Quatre corps courants: P, S, Mg, Al, ont ete choisis parce qu'ils constituent au point de vue de l'analyse du spectre rapide un assez bon etalement en energie de 2,4 MeV A 8 MeV. La valeur du flux de fission trouve dans l'element central a une puissance de 1 MW est de 1,4.10{sup 13} n/cm{sup 2}/s {+-} 0,14. (auteur)

Best estimate approach for the evaluation of critical heat flux phenomenon in the boiling water reactors

Energy Technology Data Exchange (ETDEWEB)

Kaliatka, Tadas; Kaliatka, Algirdas; Uspuras, Eudenijus; Vaisnoras, Mindaugas [Lithuanian Energy Institute, Kaunas (Lithuania); Mochizuki, Hiroyasu; Rooijen, W.F.G. van [Fukui Univ. (Japan). Research Inst. of Nuclear Engineering

2017-05-15

Because of the uncertainties associated with the definition of Critical Heat Flux (CHF), the best estimate approach should be used. In this paper the application of best-estimate approach for the analysis of CHF phenomenon in the boiling water reactors is presented. At first, the nodalization of RBMK-1500, BWR-5 and ABWR fuel assemblies were developed using RELAP5 code. Using developed models the CHF and Critical Heat Flux Ratio (CHFR) for different types of reactors were evaluated. The calculation results of CHF were compared with the well-known experimental data for light water reactors. The uncertainty and sensitivity analysis of ABWR 8 x 8 fuel assembly CHFR calculation result was performed using the GRS (Germany) methodology with the SUSA tool. Finally, the values of Minimum Critical Power Ratio (MCPR) were calculated for RBMK-1500, BWR-5 and ABWR fuel assemblies. The paper demonstrate how, using the results of sensitivity analysis, to receive the MCPR values, which covers all uncertainties and remains best estimated.

Seroprevalence des anticorps anti-HBc chez les donneurs de sang ...

African Journals Online (AJOL)

'hépatite virale demeure une priorité pour les centres de qualification des produits sanguins labiles au Togo. Objectif: Déterminer la séroprévalence des anticorps anti-HBc au sein des donneurs de sang en vue d'estimer le niveau de risque ...

Fate modeling of mercury species and fluxes estimation in an urban river

International Nuclear Information System (INIS)

Tong, Yindong; Zhang, Wei; Chen, Cen; Chen, Long; Wang, Wentao; Hu, Xindi; Wang, Huanhuan; Hu, Dan; Ou, Langbo; Wang, Xuejun; Wang, Qiguang

2014-01-01

The fate and transfer of mercury in urban river is an important environmental concern. In this study, QWASI (Quantitative Water–Air–Sediment Interaction) model was selected to estimate the levels of total mercury and three mercury species in water and sediment, and was used to quantify the fluxes of mercury at water/air and sediment/water interfaces of an urban river. The predicted mercury levels in water and sediments were closed to the measured values. Water inflow, re-suspension of sediment and diffusion from sediment to water are major input sources of mercury in water. The net mercury transfer flux from water to air was 0.16 ng/(m 2 h). At the sediment/water interface, a net total mercury transfer of 1.32 ng/(m 2 h) from water to sediment was seen. In addition to the existing dynamic flux chambers measurement, this model method could provide a new perspective to identify the distribution and transfer of mercury in the urban river. -- Highlights: • QWASI could be a good tool to quantify transfer and fate of mercury in environment. • Distribution and flux of mercury species in an urban river was modeled. • Mercury in water mainly came from water inflow, sediment re-suspension and diffusion. • Net mercury transfer from water to air and sediment were 0.16 and 1.32 ng/(m 2 h). -- Quantitative Water–Air–Sediment Interaction model was used to quantify the transfer and fate of mercury in an urban river

A combined ANN-GA and experimental based technique for the estimation of the unknown heat flux for a conjugate heat transfer problem

Science.gov (United States)

M K, Harsha Kumar; P S, Vishweshwara; N, Gnanasekaran; C, Balaji

2018-05-01

The major objectives in the design of thermal systems are obtaining the information about thermophysical, transport and boundary properties. The main purpose of this paper is to estimate the unknown heat flux at the surface of a solid body. A constant area mild steel fin is considered and the base is subjected to constant heat flux. During heating, natural convection heat transfer occurs from the fin to ambient. The direct solution, which is the forward problem, is developed as a conjugate heat transfer problem from the fin and the steady state temperature distribution is recorded for any assumed heat flux. In order to model the natural convection heat transfer from the fin, an extended domain is created near the fin geometry and air is specified as a fluid medium and Navier Stokes equation is solved by incorporating the Boussinesq approximation. The computational time involved in executing the forward model is then reduced by developing a neural network (NN) between heat flux values and temperatures based on back propagation algorithm. The conjugate heat transfer NN model is now coupled with Genetic algorithm (GA) for the solution of the inverse problem. Initially, GA is applied to the pure surrogate data, the results are then used as input to the Levenberg- Marquardt method and such hybridization is proven to result in accurate estimation of the unknown heat flux. The hybrid method is then applied for the experimental temperature to estimate the unknown heat flux. A satisfactory agreement between the estimated and actual heat flux is achieved by incorporating the hybrid method.

Fast neutron dosimetry and spectrometry using radioactivation (1963); Dosimetrie et spectrometrie des neutrons rapides par radioactivation (1963)

Energy Technology Data Exchange (ETDEWEB)

Lamberieux, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

The author first recalls rapidly a few generalities concerning induced radioactivity detectors and gives, in an appendix, tables summarizing the properties of detector elements which may be used in radioprotection. The excitation functions found in the literature and also given. The technological characteristics of the detectors used are given, together with the counting methods. The many advantages of activation dosimetry for strong or periodic neutron fluxes and for those in the presence of {gamma}-radiation are stressed. The main problem in activation dosimetry is, however, the calculation of the dose absorbed from the results of the measurements. It is shown how the dose is expressed, fairly accurately, as a function of the radioactivities induced in a series of detectors. As an example, the spectrometry and the dosimetry of the neutron flux emitted by a Po-Be source are presented. (author) [French] L'auteur fait d'abord un bref rappel des generalites sur les detecteurs a radioactivite induite, accompagne, en annexe, des tableaux resumant les proprietes d'elements detecteurs utilisables en radioprotection. Les fonctions d'excitation trouvees dans la litterature y sont egalement annexees. On donne ensuite les caracteristiques technologiques des detecteurs employes ainsi que les methodes de comptage utilisees. On souligne les nombreux avantages de la dosimetrie par activation dans les flux de neutrons intenses ou periodiques et en presence de rayonnement {gamma}. Il reste que le probleme central de la dosimetrie par activation est le calcul de la dose absorbee a partir des resultats de mesure. On montre comment la dose s'exprime, de maniere approchee, en fonction des radioactivites induites dans une serie de detecteurs. A titre d'exemple, la spectrometrie et la dosimetrie du flux de neutrons emis par une source de Po-Be sont presentees. (auteur)

A sampling strategy for estimating plot average annual fluxes of chemical elements from forest soils

NARCIS (Netherlands)

Brus, D.J.; Gruijter, de J.J.; Vries, de W.

2010-01-01

A sampling strategy for estimating spatially averaged annual element leaching fluxes from forest soils is presented and tested in three Dutch forest monitoring plots. In this method sampling locations and times (days) are selected by probability sampling. Sampling locations were selected by

Émissions azotées au champ et performances des machines lors de l'épandage de boues issues du traitement des eaux usées

OpenAIRE

Pradel, M.; Pacaud, T.; Cariolle, M.

2011-01-01

/ Ce document est un rapport de synthèse des travaux réalisés dans le cadre du projet Ecodefi sur l'estimation des émissions azotées lors de l'épandage de boues issues du traitement des eaux usées en lien avec les performances technologiques des machines utilisées à cet effet.

Estimation of aerosol plutonium transport by the dust-flux method: a perspective on application of detailed data

International Nuclear Information System (INIS)

Shinn, J.H.

1976-01-01

Two methods of dust-flux measurements are discussed which have been utilized to estimate aerosol plutonium deposition and resuspension. In previous studies the methods were found to be sufficiently detailed to permit parameterization of dust-flux to the erodibility of the soil, and a seventh-power dependency of dust-flux (or plutonium flux) to wind speed was observed in worst case conditions. The eddy-correlation method is technically more difficult, requires high-speed data acquisition, and requires an instrument response time better than one second, but the eddy-correlation method has been shown feasible with new fast-response sensors, and it is more useful in limited areas because it can be used as a probe. The flux-gradient method is limited by critical assumptions and is more bulky, but the method is more commonly used and accepted. The best approach is to use both methods simultaneously. It is suggested that several questions should be investigated by the methods, such as saltation stimulation of dust-flux, simultaneous suspension and deposition, foliar deposition and trapping, erodibility of crusted surfaces, and horizontally heterogeneous erodibility

Data Driven Estimation of Transpiration from Net Water Fluxes: the TEA Algorithm

Science.gov (United States)

Nelson, J. A.; Carvalhais, N.; Cuntz, M.; Delpierre, N.; Knauer, J.; Migliavacca, M.; Ogee, J.; Reichstein, M.; Jung, M.

2017-12-01

The eddy covariance method, while powerful, can only provide a net accounting of ecosystem fluxes. Particularly with water cycle components, efforts to partitioning total evapotranspiration (ET) into the biotic component (transpiration, T) and the abiotic component (here evaporation, E) have seen limited success, with no one method emerging as a standard.Here we demonstrate a novel method that uses ecosystem WUE to predict transpiration in two steps: (1) a filtration step that to isolate the signal of ET for periods where E is minimized and ET is likely dominated by the signal of T; and (2) a step which predicts the WUE using meteorological variables, as well as information derived from the carbon and energy fluxes. To assess the the underlying assumptions, we tested the proposed method on three ecological models, allowing validation where the underlying carbon:water relationships, as well as the transpiration estimates, are know.The partitioning method shows high correlation (R²>0.8) between Tmodel/ET and TTEA/ET across timescales from half-hourly to annually, as well as capturing spatial variability across sites. Apart from predictive performance, we explore the sensitivities of the method to the underlying assumptions, such as the effects of residual evaporation in the training dataset. Furthermore, we show initial transpiration estimates from the algorithm at global scale, via the FLUXNET dataset.

Atmosphere–Surface Fluxes of CO2 using Spectral Techniques

DEFF Research Database (Denmark)

Sørensen, Lise Lotte; Larsen, Søren Ejling

2010-01-01

Different flux estimation techniques are compared here in order to evaluate air–sea exchange measurement methods used on moving platforms. Techniques using power spectra and cospectra to estimate fluxes are presented and applied to measurements of wind speed and sensible heat, latent heat and CO2...... fluxes. Momentum and scalar fluxes are calculated from the dissipation technique utilizing the inertial subrange of the power spectra and from estimation of the cospectral amplitude, and both flux estimates are compared to covariance derived fluxes. It is shown how even data having a poor signal......-to-noise ratio can be used for flux estimations....

Les risques industriels et le prix des logements

DEFF Research Database (Denmark)

Grislain-Letrémy, Céline; Katossky, Arthur

2013-01-01

Le prix des logements peut diminuer du fait de la proximité d’installations industrielles. Cet effet dépend de la perception du risque par les riverains et est donc potentiellement modifié par des événements changeant la perception du risque, tels que les plans de prévention des risques technolog......Le prix des logements peut diminuer du fait de la proximité d’installations industrielles. Cet effet dépend de la perception du risque par les riverains et est donc potentiellement modifié par des événements changeant la perception du risque, tels que les plans de prévention des risques...... proximité d’installations industrielles dans les agglomérations françaises de Bordeaux, Dunkerque et Rouen. La méthode des prix hédoniques permet d’estimer l’effet de la proximité des usines sur les prix des logements. Les résultats suggèrent que les écarts de prix ne sont modifiés ni par les incidents...

Estimating spatially distributed turbulent heat fluxes from high-resolution thermal imagery acquired with a UAV system.

Science.gov (United States)

Brenner, Claire; Thiem, Christina Elisabeth; Wizemann, Hans-Dieter; Bernhardt, Matthias; Schulz, Karsten

2017-05-19

In this study, high-resolution thermal imagery acquired with a small unmanned aerial vehicle (UAV) is used to map evapotranspiration (ET) at a grassland site in Luxembourg. The land surface temperature (LST) information from the thermal imagery is the key input to a one-source and two-source energy balance model. While the one-source model treats the surface as a single uniform layer, the two-source model partitions the surface temperature and fluxes into soil and vegetation components. It thus explicitly accounts for the different contributions of both components to surface temperature as well as turbulent flux exchange with the atmosphere. Contrary to the two-source model, the one-source model requires an empirical adjustment parameter in order to account for the effect of the two components. Turbulent heat flux estimates of both modelling approaches are compared to eddy covariance (EC) measurements using the high-resolution input imagery UAVs provide. In this comparison, the effect of different methods for energy balance closure of the EC data on the agreement between modelled and measured fluxes is also analysed. Additionally, the sensitivity of the one-source model to the derivation of the empirical adjustment parameter is tested. Due to the very dry and hot conditions during the experiment, pronounced thermal patterns developed over the grassland site. These patterns result in spatially variable turbulent heat fluxes. The model comparison indicates that both models are able to derive ET estimates that compare well with EC measurements under these conditions. However, the two-source model, with a more complex treatment of the energy and surface temperature partitioning between the soil and vegetation, outperformed the simpler one-source model in estimating sensible and latent heat fluxes. This is consistent with findings from prior studies. For the one-source model, a time-variant expression of the adjustment parameter (to account for the difference between

Graphite reactor physics; Physique des piles a graphite

Energy Technology Data Exchange (ETDEWEB)

Bacher, P; Cogne, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Noc, B [Electricite de France (EDF), 75 - Paris (France)

1964-07-01

The study of graphite-natural uranium power reactor physics, undertaken ten years ago when the Marcoule piles were built, has continued to keep in step with the development of this type of pile. From 1960 onwards the critical facility Marius has been available for a systematic study of the properties of lattices as a function of their pitch, of fuel geometry and of the diameter of cooling channels. This study has covered a very wide field: lattice pitch varying from 19 to 38 cm. uranium rods and tubes of cross-sections from 6 to 35 cm{sup 2}, channels with diameters between 70 and 140 mm. The lattice calculation methods could thus be checked and where necessary adapted. The running of the Marcoule piles and the experiments carried out on them during the last few years have supplied valuable information on the overall evolution of the neutronic properties of the fuel as a function of irradiation. More detailed experiments have also been performed in Marius with plutonium-containing fuels (irradiated or synthetic fuels), and will be undertaken at the beginning of 1965 at high temperature in the critical facility Cesar, which is just being completed at Cadarache. Spent fuel analyses complement these results and help in their interpretation. The thermalization and spectra theories developed in France can thus be verified over the whole valid temperature range. The efficiency of control rods as a function of their dimensions, the materials of which they are made and the lattices surrounding them has been measured in Marius, and the results compared with calculation on the one hand and with the measurements carried out in EDF 1 on the other. Studies on the control proper of graphite piles were concerned essentially with the risks of spatial instability and the means of detecting and controlling them, and with flux distortions caused by the control rods. (authors) [French] Entreprise il y a dix ans a l'occasion de la construction des piles de Marcoule, l'etude de la

Combining tracer flux ratio methodology with low-flying aircraft measurements to estimate dairy farm CH4 emissions

Science.gov (United States)

Daube, C.; Conley, S.; Faloona, I. C.; Yacovitch, T. I.; Roscioli, J. R.; Morris, M.; Curry, J.; Arndt, C.; Herndon, S. C.

2017-12-01

Livestock activity, enteric fermentation of feed and anaerobic digestion of waste, contributes significantly to the methane budget of the United States (EPA, 2016). Studies question the reported magnitude of these methane sources (Miller et. al., 2013), calling for more detailed research of agricultural animals (Hristov, 2014). Tracer flux ratio is an attractive experimental method to bring to this problem because it does not rely on estimates of atmospheric dispersion. Collection of data occurred during one week at two dairy farms in central California (June, 2016). Each farm varied in size, layout, head count, and general operation. The tracer flux ratio method involves releasing ethane on-site with a known flow rate to serve as a tracer gas. Downwind mixed enhancements in ethane (from the tracer) and methane (from the dairy) were measured, and their ratio used to infer the unknown methane emission rate from the farm. An instrumented van drove transects downwind of each farm on public roads while tracer gases were released on-site, employing the tracer flux ratio methodology to assess simultaneous methane and tracer gas plumes. Flying circles around each farm, a small instrumented aircraft made measurements to perform a mass balance evaluation of methane gas. In the course of these two different methane quantification techniques, we were able to validate yet a third method: tracer flux ratio measured via aircraft. Ground-based tracer release rates were applied to the aircraft-observed methane-to-ethane ratios, yielding whole-site methane emission rates. Never before has the tracer flux ratio method been executed with aircraft measurements. Estimates from this new application closely resemble results from the standard ground-based technique to within their respective uncertainties. Incorporating this new dimension to the tracer flux ratio methodology provides additional context for local plume dynamics and validation of both ground and flight-based data.

Estimating the Total Heat Flux from the ASHES Hydrothermal Vent Field Using the Sentry Autonomous Underwater Vehicle

Science.gov (United States)

Crone, T. J.; Kinsey, J. C.; Mittelstaedt, E. L.

2017-12-01

Hydrothermal venting at mid-ocean ridges influences ocean chemistry, the thermal and chemical structure of the oceanic crust, and the evolution of unique and diverse autolithotrophically-supported ecosystems. Axially-hosted hydrothermal systems are responsible for 20-25% of the total heat flux out of Earth's interior, and likely play a large role in local as well as global biogeochemical cycles. Despite the importance of these systems, only a few studies have attempted to constrain the volume and heat flux of an entire hydrothermal vent field. In July of 2014 we used the Sentry autonomous underwater vehicle (AUV) to survey the water column over the ASHES hydrothermal vent field which is located within the caldera of Axial Seamount, an active submarine volcano located on the Juan de Fuca Ridge. To estimate the total heat and mass flux from this vent field, we equipped Sentry with a Nortek acoustic Doppler velocimeter (ADV), an inertial measurement unit (IMU), two acoustic Doppler current profilers (ADCPs), and two SBE3 temperature probes, allowing us to obtain precise measurements of fluid temperature and water velocity. The survey was designed using a control volume approach in which Sentry was pre-programmed to survey a 150-m-square centered over the vent field flying a grid pattern with 5-m track line spacing followed by a survey of the perimeter. This pattern was repeated multiple times during several 10-h dives at different altitudes, including 10, 20, 40, and 60 m above the seafloor, and during one 40-h survey at an altitude of 10 m. During the 40-h survey, the pattern was repeated nine times allowing us to obtain observations over several tidal cycles. Water velocity data obtained with Sentry were corrected for platform motion and then combined with the temperature measurements to estimate heat flux. The analysis of these data will likely provide the most accurate and highest resolution heat and mass flux estimates at a seafloor hydrothermal field to date.

Influence of Mean Rooftop-Level Estimation Method on Sensible Heat Flux Retrieved from a Large-Aperture Scintillometer Over a City Centre

Science.gov (United States)

Zieliński, Mariusz; Fortuniak, Krzysztof; Pawlak, Włodzimierz; Siedlecki, Mariusz

2017-08-01

The sensible heat flux ( H) is determined using large-aperture scintillometer (LAS) measurements over a city centre for eight different computation scenarios. The scenarios are based on different approaches of the mean rooftop-level (zH) estimation for the LAS path. Here, zH is determined separately for wind directions perpendicular (two zones) and parallel (one zone) to the optical beam to reflect the variation in topography and building height on both sides of the LAS path. Two methods of zH estimation are analyzed: (1) average building profiles; (2) weighted-average building height within a 250 m radius from points located every 50 m along the optical beam, or the centre of a certain zone (in the case of a wind direction perpendicular to the path). The sensible heat flux is computed separately using the friction velocity determined with the eddy-covariance method and the iterative procedure. The sensitivity of the sensible heat flux and the extent of the scintillometer source area to different computation scenarios are analyzed. Differences reaching up to 7% between heat fluxes computed with different scenarios were found. The mean rooftop-level estimation method has a smaller influence on the sensible heat flux (-4 to 5%) than the area used for the zH computation (-5 to 7%). For the source-area extent, the discrepancies between respective scenarios reached a similar magnitude. The results demonstrate the value of the approach in which zH is estimated separately for wind directions parallel and perpendicular to the LAS optical beam.

Estimating Tritium Fluxes from the Shallow Unsaturated Zone to the Atmosphere in an Arid Environment Dominated by Creosote Bush (USGS-ADRS)

Science.gov (United States)

Garcia, C. A.; Andraski, B. J.; Wheatcraft, S. W.; Johnson, M. J.; Michel, R. L.; Stonestrom, D. A.

2006-12-01

Understanding the transport and fate of tritium is essential when evaluating options for low-level radioactive waste (LLRW) isolation. The magnitude and spatio-temporal variability of tritium transport from the shallow unsaturated zone to the atmosphere are being investigated adjacent to a LLRW facility at the U.S. Geological Survey's Amargosa Desert Research Site (ADRS) in Southern Nevada. Site and community-scale tritium fluxes from the subsurface to the atmosphere were quantified using a simple gas-phase diffusive loading approach combining evaporation and transpiration fluxes with mass fractions of gas-phase tritium concentrations. A Priestly-Taylor model, calibrated with quarterly bare-soil evaporation measurements, was used to estimate continuous bare-soil evaporation from measured continuous eddy-covariance evapotransporation. Continuous transpiration was computed as the difference between measured evapotranspiration and estimated bare-soil evaporation. Tritium concentrations in plant water and soil-water vapor were measured along two transects perpendicular to the LLRW using azeotropic distillation of creosote bush (Larrea tridentata) foliage and soil vapor extraction from 0.5 and 1.5 m depths below land surface. A preliminary daily tritium flux estimate at a single plant site was 1.66 × 10-11 gm-2. Spatio- temporal variability over a 75-ha area and 2-yr period will be quantified using a combination of tritium concentration maps and continuous evaporation and transpiration flux estimates. Quantifying tritium fluxes from the shallow unsaturated zone to the atmosphere on a site and community-scale will improve knowledge and understanding of vertical contaminant transport in arid environments.

Estimation of the heat/Na flux using lidar data recorded at ALO, Cerro Pachon, Chile

Science.gov (United States)

Vargas, F.; Gardner, C. S.; Liu, A. Z.; Swenson, G. R.

2013-12-01

In this poster, lidar nigh-time data are used to estimate the vertical fluxes of heat and Na at the mesopause region due to dissipating gravity waves presenting periods from 5 min to 8 h, and vertical wavelengths > 2 km. About 60 hours of good quality data were recorded near the equinox during two observation campaigns held in Mar, 2012 and Apr, 2013 at the Andes Lidar Observatory (30.3S,70.7W). These first measurements of the heat/Na flux in the southern hemisphere will be discussed and compared with those from the northern hemisphere stations obtained at the Starfire Optical Range, NM, and Maui, HW.

A state-space modeling approach to estimating canopy conductance and associated uncertainties from sap flux density data.

Science.gov (United States)

Bell, David M; Ward, Eric J; Oishi, A Christopher; Oren, Ram; Flikkema, Paul G; Clark, James S

2015-07-01

Uncertainties in ecophysiological responses to environment, such as the impact of atmospheric and soil moisture conditions on plant water regulation, limit our ability to estimate key inputs for ecosystem models. Advanced statistical frameworks provide coherent methodologies for relating observed data, such as stem sap flux density, to unobserved processes, such as canopy conductance and transpiration. To address this need, we developed a hierarchical Bayesian State-Space Canopy Conductance (StaCC) model linking canopy conductance and transpiration to tree sap flux density from a 4-year experiment in the North Carolina Piedmont, USA. Our model builds on existing ecophysiological knowledge, but explicitly incorporates uncertainty in canopy conductance, internal tree hydraulics and observation error to improve estimation of canopy conductance responses to atmospheric drought (i.e., vapor pressure deficit), soil drought (i.e., soil moisture) and above canopy light. Our statistical framework not only predicted sap flux observations well, but it also allowed us to simultaneously gap-fill missing data as we made inference on canopy processes, marking a substantial advance over traditional methods. The predicted and observed sap flux data were highly correlated (mean sensor-level Pearson correlation coefficient = 0.88). Variations in canopy conductance and transpiration associated with environmental variation across days to years were many times greater than the variation associated with model uncertainties. Because some variables, such as vapor pressure deficit and soil moisture, were correlated at the scale of days to weeks, canopy conductance responses to individual environmental variables were difficult to interpret in isolation. Still, our results highlight the importance of accounting for uncertainty in models of ecophysiological and ecosystem function where the process of interest, canopy conductance in this case, is not observed directly. The StaCC modeling

Estimation of (Cl-Mn) /Fe flux ratio at relativistic energies using steady-state leaky-box model modified for re accelerations

International Nuclear Information System (INIS)

Majumdar, R.; Basu, B.; Bhattacharyya, D.P.

1997-01-01

The (Cl-Mn) /Fe flux ratio at the top of the atmosphere has been estimated from source composition. The authors have adopted the SSLB model modified for weak shocks to estimate the enhancement of (Cl-Mn) /Fe flux ratio due to re acceleration. The observed active detector results of Lezniak and Webber, Caldwell, Orth et al., Engelmann et al., and our passive detector results are fairly supported by the expected results from the SSLB model modified with re acceleration after Ferrando for energies ≤ 100 GeV / n

Analysis and development of spatial hp-refinement methods for solving the neutron transport equation; Analyse et developpement de methodes de raffinement hp en espace pour l'equation de transport des neutrons

Energy Technology Data Exchange (ETDEWEB)

Fournier, D.

2011-10-10

flux behaviour is very different depending on the energy, there is no reason to use the same spatial discretization. Such an approach implies to modify the initial estimators in order to take into account the coupling between groups. This study is done from a theoretical as well as from a numerical point of view. (author) [French] Pour la conception des coeurs de reacteurs de 4eme generation, une precision accrue est requise pour les calculs des differents parametres neutroniques. Les ressources memoire et le temps de calcul etant limites, une solution consiste a utiliser des methodes de raffinement de maillage afin de resoudre l'equation de transport des neutrons. Le flux neutronique, solution de cette equation, depend de l'energie, l'angle et l'espace. Les differentes variables sont discretisees de maniere successive. L'energie avec une approche multigroupe, considerant les differentes grandeurs constantes sur chaque groupe, l'angle par une methode de collocation, dite approximation SN. Apres discretisation energetique et angulaire, un systeme d'equations hyperboliques couplees ne dependant plus que de la variable d'espace doit etre resolu. Des elements finis discontinus sont alors utilises afin de permettre la mise en place de methodes de raffinement dite hp. La precision de la solution peut alors etre amelioree via un raffinement en espace (h-raffinement), consistant a subdiviser une cellule en sous-cellules, ou en ordre (p-raffinement) en augmentant l'ordre de la base de polynomes utilisee. Dans cette these, les proprietes de ces methodes sont analysees et montrent l'importance de la regularite de la solution dans le choix du type de raffinement. Ainsi deux estimateurs d'erreurs permettant de mener le raffinement ont ete utilises. Le premier, suppose des hypotheses de regularite tres fortes (solution analytique) alors que le second utilise seulement le fait que la solution est a variations bornees. La

PCB in soils and estimated soil-air exchange fluxes of selected PCB congeners in the south of Sweden

International Nuclear Information System (INIS)

Backe, Cecilia; Cousins, Ian T.; Larsson, Per

2004-01-01

PCB concentrations were studied in different soils to determine the spatial variation over a region of approximately 11 000 km 2 . PCB congener pattern was used to illustrate the spatial differences, as shown by principal component analysis (PCA). The relationship to different soil parameters was studied. PCB concentrations in soil showed a large variation between sampling-areas with median concentrations ranging between 2.3 and 332 ng g -1 (dw). Highest concentrations were found at two sites with sandy soils, one with extremely high organic carbon content. Both sites were located on the west coast of southern Sweden. Soils with similar soil textures (i.e. sandy silt moraine) did not show any significant differences in PCB concentrations. PCB congener composition was shown to differ between sites, with congener patterns almost site-specific. PCB in air and precipitation was measured and the transfer of chemicals between the soil and air compartments was estimated. Soil-air fugacity quotient calculations showed that the PCBs in the soil consistently had a higher fugacity than the PCBs in the air, with a median quotient value of 2.7. The gaseous fluxes between soil and air were estimated using standard modelling equations and a net soil-air flux estimated by subtracting bulk deposition from gaseous soil-air fluxes. It was shown that inclusion of vertical sorbed phase transport of PCBs in the soil had a large effect on the direction of the net soil-air exchange fluxes. - Soil-air exchange of PCBs is investigated and modelled across Sweden

Réalisation d'un appareillage a lame vibrante pour l'étude des lignes de flux dans les supraconducteurs à haute température critique

Science.gov (United States)

Woirgard, J.; Salmon, E.; Gaboriaud, R. J.; Rabier, J.

1994-03-01

éalisés sur une couche mince épitaxiée de 1000 Å d'épaisseur d'YBaCuO ont permis de mettre en évidence un pic d'amortissement, de grande amplitude, qui pourrait être dû à la fusion du réseau de vortex. Prochainement, cet appareillage sera employé pour l'étude de l'ancrage des lignes de flux sur les défauts du réseau cristallin, défauts naturels ou artificiels créés par implantation ionique dans les films minces ou par déformation plastique dans les échantillons massifs.

Reactor AQUILON. The hardening of neutron spectrum in natural uranium rods, with a computation of epithermal fissions (1961); Pile AQUILON. Durcissement du spectre des neutrons dans les barreaux d'uranium et calcul des fissions epithermiques (1961)

Energy Technology Data Exchange (ETDEWEB)

Durand -Smet, R; Lourme, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

- Microscopic flux measurements in reactor Aquilon have allowed to investigate the thermal and epithermal flux distribution in natural uranium rods, then to obtain the neutron spectrum variations in uranium, Wescott '{beta}' term of the average spectrum in the rod, and the ratio of epithermal to therma fissions. A new definition for the infinite multiplication factor is proposed in annex, which takes into account epithermal parameters. (authors) [French] - Un certain nombre de mesures effectuees dans la pile Aquilon ont permis d'etablir la distribution fine des flux thermique et epithermique dans les barreaux d'uranium, et d'en deduire les variations du spectre des neutrons dans l'uranium, le terme {beta} du spectre de Wescott moyen dans le barreau et le nombre de fissions epithermiques. En annexe, il est propose une definition nouvelle du coefficient de multiplication infini, qui fait intervenir les parametres epithermiques. (auteurs)

Angio-RM morphologique et dynamique sans injection de contraste dans l’exploration des pathologies neurovasculaires à l’étage cervical et encéphalique

OpenAIRE

Raoult , Hélène

2014-01-01

ProblématiqueL’angio-IRM (ARM) est devenue incontournable dans la prise en charge des pathologies neurovasculaires. Elle permet en effet d’évaluer les pathologies modifiant la dynamique circulatoire, telles les sténoses artérielles, plus fréquentes à l’étage cervical et générant des flux sanguins accélérés voire turbulents en amont et ralentis en aval; ou bien les shunts artério-veineux, telles les malformations artério-veineuses encéphaliques, caractérisés par des flux accélérés et complexes...

Tests on dynamic corrosion by water. Influence of the passage of a heat flux on the corrosion kinetics. pH measurement in water at high temperature; Essais de corrosion dynamique par l'eau. Influence du passage d'un flux thermique sur la cinetique de corrosion. Mesure du pH dans l'eau a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Coriou, H; Grall, L; Hure, J; Saint-James, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Berthod, [Societe Grenobloise d' Etudes et d' Applications Hydrauliques, 38 (France); peintre, Le [Centre National de la Recherche Scientifique (CNRS), 38 - Grenoble (France)

1958-07-01

The passage of a heat flux through the surface of a metal placed in a corrosive medium influences the rate of corrosion, these being higher than under adiabatic conditions. The apparatus developed for corrosion tests is described, it is possible to obtain with this equipment: 1) Heat fluxes greater than 200 W/cm{sup 2}, across aluminium canning, which is cooled by water (temperature 50 deg. C), circulating with flow rates of the order of 5 to 6 m/s. 2) Heat fluxes which can go up to 150 W/cm{sup 2}, across canning of zircaloy or stainless steel. The cooling fluid is pressurized water at a temperature around 280 deg. C, the flow-rate of circulation reaching 6 m/s. The results obtained on aluminium canning are studied from the viewpoint of corrosion, paying particular attention to cavitation phenomena which can cause serious damage in certain special circumstances. After developing a glass electrode system capable of supporting high pressures, the authors have investigated materials capable of functioning as a hydrogen electrode and of resisting satisfactorily corrosion by water at 200 deg. C. Various possibilities have been examined: electrodes of special glasses, quartz, metals, with a membrane etc... The results of the various tests and the practical limits of utilisation are given. (author)Fren. [French] Le passage d'un flux thermique a travers la surface d'un metal place dans un milieu corrosif influence les vitesses de corrosion, celles-ci etant plus elevees que dans des conditions adiabatiques. On decrit les appareils mis au point, pour essais de corrosion. Ils permettent d'obtenir: 1) A travers des gaine aluminium des flux thermiques depassant 200 W /cm{sup 2}. Les gaines sont refroidies par l'eau (temperature 50 deg. C), circulant a des vitesses de l'ordre de 5 a 6 m/s. 2) A travers des gaines en zircaloy ou acier inoxydable des flux thermiques pouvant s'elever a 150 W/cm{sup 2}. Le fluide de refroidissement est de l'eau sous pression a une temperature

Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850-2000

International Nuclear Information System (INIS)

Houghton, R.A.

2003-01-01

Recent analyses of land-use change in the US and China, together with the latest estimates of tropical deforestation and afforestation from the FAO, were used to calculate a portion of the annual flux of carbon between terrestrial ecosystems and the atmosphere. The calculated flux includes only that portion of the flux resulting from direct human activity. In most regions, activities included the conversion of natural ecosystems to cultivated lands and pastures, including shifting cultivation, harvest of wood (for timber and fuel) and the establishment of tree plantations. In the US, woody encroachment and woodland thickening as a result of fire suppression were also included. The calculated flux of carbon does not include increases or decreases in carbon storage as a result of environmental changes (e.g.; increasing concentrations of CO 2 , N deposition, climatic change or pollution). Globally, the long-term (1850-2000) flux of carbon from changes in land use and management released 156 PgC to the atmosphere, about 60% of it from the tropics. Average annual fluxes during the 1980s and 1990s were 2.0 and 2.2 PgC/yr, respectively, dominated by releases of carbon from the tropics. Outside the tropics, the average net flux of carbon attributable to land-use change and management decreased from a source of 0.06 PgC/yr during the 1980s to a sink of 0.02 PgC/yr during the 1990s. According to the analyses summarized here, changes in land use were responsible for sinks in North America and Europe and for small sources in other non-tropical regions. The revisions were as large as 0.3 PgC/yr in individual regions but were largely offsetting, so that the global estimate for the 1980s was changed little from an earlier estimate. Uncertainties and recent improvements in the data used to calculate the flux of carbon from land-use change are reviewed, and the results are compared to other estimates of flux to evaluate the extent to which processes other than land-use change and

An Optimal Estimation Method to Obtain Surface Layer Turbulent Fluxes from Profile Measurements

Science.gov (United States)

Kang, D.

2015-12-01

In the absence of direct turbulence measurements, the turbulence characteristics of the atmospheric surface layer are often derived from measurements of the surface layer mean properties based on Monin-Obukhov Similarity Theory (MOST). This approach requires two levels of the ensemble mean wind, temperature, and water vapor, from which the fluxes of momentum, sensible heat, and water vapor can be obtained. When only one measurement level is available, the roughness heights and the assumed properties of the corresponding variables at the respective roughness heights are used. In practice, the temporal mean with large number of samples are used in place of the ensemble mean. However, in many situations the samples of data are taken from multiple levels. It is thus desirable to derive the boundary layer flux properties using all measurements. In this study, we used an optimal estimation approach to derive surface layer properties based on all available measurements. This approach assumes that the samples are taken from a population whose ensemble mean profile follows the MOST. An optimized estimate is obtained when the results yield a minimum cost function defined as a weighted summation of all error variance at each sample altitude. The weights are based one sample data variance and the altitude of the measurements. This method was applied to measurements in the marine atmospheric surface layer from a small boat using radiosonde on a tethered balloon where temperature and relative humidity profiles in the lowest 50 m were made repeatedly in about 30 minutes. We will present the resultant fluxes and the derived MOST mean profiles using different sets of measurements. The advantage of this method over the 'traditional' methods will be illustrated. Some limitations of this optimization method will also be discussed. Its application to quantify the effects of marine surface layer environment on radar and communication signal propagation will be shown as well.

Production des micro-algues des claires ostréicoles en relation avec l'azote organique dissous excrété par les huîtres

OpenAIRE

Robert, Jean-michel; Maestrini, Serge; Heral, Maurice; Zanette, Yvan

1981-01-01

L'utilisation de tests biologiques dans l'étude de la fertilité des eaux de claires ainsi que l'analyse chimique des réserves en sels nutritifs des mêmes eaux montrent qu'une part importante de la biomasse micro-algale peut être produite dans ces bassins, par assimilation par les cellules de substances organiques dissoutes. Ainsi, pour l'azote, des estimations indirectes aboutissent à des quantités de cet élément assimilé sous forme organique variant entre 0,6 et 30,7 µg-at.I-1 selon les mode...

A Bayesian analysis of sensible heat flux estimation: Quantifying uncertainty in meteorological forcing to improve model prediction

KAUST Repository

Ershadi, Ali; McCabe, Matthew; Evans, Jason P.; Mariethoz, Gregoire; Kavetski, Dmitri

2013-01-01

The influence of uncertainty in land surface temperature, air temperature, and wind speed on the estimation of sensible heat flux is analyzed using a Bayesian inference technique applied to the Surface Energy Balance System (SEBS) model

Vécu des situations scolaires, estime de soi et Développement : du jugement moral a la période de la latence

Directory of Open Access Journals (Sweden)

Emile-Henri Riard

2011-06-01

Full Text Available Suivant une approche de psychologie sociale clinique, le point de vue adopté dans cet article est triple : 1- considérer les situations scolaires “ ordinaires ” comme potentiellement génératrices de difficultés; 2- s’inscrire en amont de l’adolescence afin d’améliorer la compréhension de cette dernière; 3 – considérer le vécu des élèves. La recherche menée en France (enfants de 6 à 11 ans, par questionnaire (48 situations relevant de la scolarité : classe, cour de récréation, trajet domicile/école et domicile ont été proposées ; test d’estime de soi (Coopersmith ; développement moral (Kohlberg. Variables : âge, sexe, mode d’habitat, position scolaire, classement, département. Les résultats (analyse de variance démontrent un fonctionnement “ en bloc ” du niveau de vécu de difficulté. Ressortent comme variables significatives, par ordre d’importance décroissante: le sexe (les garçons ressentent davantage les difficultés que les filles; l’âge (le niveau de difficulté vécue décroît avec l’âge mais concerne surtout la cour de récréation ; le mode d’habitat (collectif. La classe est l’espace le plus porteur de différences de vécu de difficultés indépendamment des variables. Le niveau d’autonomie et l’estime de soi sont schématiquement inversement proportionnés au niveau de difficulté vécu. La conclusion met l’accent sur l’importance des effets interactif et d’accumulation des situations.

Estimating Antarctic Geothermal Heat Flux using Gravity Inversion

Science.gov (United States)

Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; Golynsky, A. V.; Sasha Rogozhina, Irina

2013-04-01

Geothermal heat flux (GHF) in Antarctica is very poorly known. We have determined (Vaughan et al. 2012) top basement heat-flow for Antarctica and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning (Chappell & Kusznir 2008). Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental and oceanic lithosphere. The sensitivity of present-day Antarctic top basement heat-flow to initial continental radiogenic heat productivity, continental rift and margin breakup age has been examined. Knowing GHF distribution for East Antarctica and the Gamburtsev Subglacial Mountains (GSM) region in particular is critical because: 1) The GSM likely acted as key nucleation point for the East Antarctic Ice Sheet (EAIS); 2) the region may contain the oldest ice of the EAIS - a prime target for future ice core drilling; 3) GHF is important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology (Bell et al. 2011). An integrated multi-dataset-based GHF model for East Antarctica is planned that will resolve the wide range of estimates previously published using single datasets. The new map and existing GHF distribution estimates available for Antarctica will be evaluated using direct ice temperature measurements obtained from deep ice cores, estimates of GHF derived from subglacial lakes, and a thermodynamic ice-sheet model of the Antarctic Ice Sheet driven by past climate reconstructions and each of analysed heat flow maps, as has recently been done for the Greenland region (Rogozhina et al. 2012). References Bell, R.E., Ferraccioli, F., Creyts, T.T., Braaten, D., Corr, H., Das, I., Damaske, D., Frearson, N

Optimum input leads for cryogenic apparatus; Optimisation des descentes de courant dans des enceintes cryogeniques

Energy Technology Data Exchange (ETDEWEB)

Der Nigohossian, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-02-15

The electrical leads used to introduce a current into a cryostat cause a heat influx due to thermal conduction and to Joule heating. It is very important to be able to minimize this flux. Theoretical calculation of optimized leads takes into account the varying heat and electrical conductivities of the leads as well as the heat exchange coefficient with the effluent gas. Practical results have been summarized in different tables which permit for a specific material i.e. copper, aluminium, brass, stainless steel with the intensity and end temperatures being known (i.e. 4,2 or 18,5 deg. K at the cold end; 77,295 or 320 deg. K at the warm end) to deduce the minimum heat flow and the length-cross section ratio of the optimized leads. A general method is indicated, which would allow to solve the same problem for other materials. (author) [French] Les conducteurs electriques assurant la liaison d'appareillages situes dans des cryostats apportent tant par effet Joule que par conductibilite thermique une certaine quantite de chaleur qu'il est tres important de pouvoir minimiser. L'etude theorique de l'optimisation des descentes de courant tient compte des variations des conductibilites thermique et electrique ainsi que de l'influence des echanges avec le gaz. Pratiquement les resultats ont ete resumes dans differents tableaux ce qui permet, pour un materiau donne tel que cuivre, aluminium, laiton, acier inoxydable, connaissant l'intensite et les temperatures d'extremites 4,2 et 18,5 deg. K d'une part, et 77,295 et 330 deg. K d'autre part, de deduire la consommation minimale et le rapport longueur-section d'un conducteur optimise. Une methode generale est indiquee, qui permet de resoudre le probleme pour d'autres materiaux. (auteur)

Pool size measurements facilitate the determination of fluxes at branching points in nonstationary metabolic flux analysis: The case of Arabidopsis thaliana

Directory of Open Access Journals (Sweden)

Robert eHeise

2015-06-01

Full Text Available Pool size measurements are important for the estimation of absolute intracellular fluxes in particular scenarios based on data from heavy carbon isotope experiments. Recently, steady-state fluxes estimates were obtained for central carbon metabolism in an intact illuminated rosette of Arabidopsis thaliana grown photoautotrophically (Szecowka et al., 2013; Heise et al., 2014. Fluxes were estimated therein by integrating mass-spectrometric data of the dynamics of the unlabeled metabolic fraction, data on metabolic pool sizes, partitioning of metabolic pools between cellular compartments and estimates of photosynthetically inactive pools, with a simplified model of plant central carbon metabolism. However, the fluxes were determined by treating the pool sizes as fixed parameters. Here we investigated whether and, if so, to what extent the treatment of pool sizes as parameters to be optimized in three scenarios may affect the flux estimates. The results are discussed in terms of benchmark values for canonical pathways and reactions, including starch and sucrose synthesis as well as the ribulose-1,5-bisphosphate carboxylation and oxygenation reactions. In addition, we discuss pathways emerging from a divergent branch point for which pool sizes are required for flux estimation, irrespective of the computational approach used for the simulation of the observable labelling pattern. Therefore, our findings indicate the necessity for development of techniques for accurate pool size measurements to improve the quality of flux estimates from nonstationary flux estimates in intact plant cells in the absence of alternative flux measurements.

South American smoke coverage and flux estimations from the Fire Locating and Modeling of Burning Emissions (FLAMBE') system.

Science.gov (United States)

Reid, J. S.; Westphal, D. L.; Christopher, S. A.; Prins, E. M.; Gasso, S.; Reid, E.; Theisen, M.; Schmidt, C. C.; Hunter, J.; Eck, T.

2002-05-01

The Fire Locating and Modeling of Burning Emissions (FLAMBE') project is a joint Navy, NOAA, NASA and university project to integrate satellite products with numerical aerosol models to produce a real time fire and emissions inventory. At the center of the program is the Wildfire Automated Biomass Burning Algorithm (WF ABBA) which provides real-time fire products and the NRL Aerosol Analysis and Prediction System to model smoke transport. In this presentation we give a brief overview of the system and methods, but emphasize new estimations of smoke coverage and emission fluxes from the South American continent. Temporal and smoke patterns compare reasonably well with AERONET and MODIS aerosol optical depth products for the 2000 and 2001 fire seasons. Fluxes are computed by relating NAAPS output fields and MODIS optical depth maps with modeled wind fields. Smoke emissions and transport fluxes out of the continent can then be estimated by perturbing the modeled emissions to gain agreement with the satellite and wind products. Regional smoke emissions are also presented for grass and forest burning.

Évaluation de la diversité et estimation de la biomasse des arbres d ...

African Journals Online (AJOL)

SARAH

31 janv. 2016 ... d'alignement des communes du Plateau et de Cocody (Abidjan - Côte d'Ivoire. 9141 ..... variations des valeurs d'équivalent CO2 par type d'espace suivent .... rôle compensatoire dans les émissions du dioxyde de carbone.

La régulation des industries culturelles à l’heure d’Internet et les enjeux pour la diversité culturelle: Le cas des quotas radiophoniques français

Directory of Open Access Journals (Sweden)

Alexandre Joux

2016-06-01

Full Text Available La convention sur la protection et la promotion de la diversité des expressions culturelles, adoptée à l’UNESCO en 2005, redonne à l’instance internationale sa légitimité pour traiter des sujets liés aux politiques culturelles nationales. Ceux-ci avaient été déportés vers l’OMC dans les années 1990 à l’occasion des débats sur l’exception culturelle. Dix ans après l’adoption de la Convention de 2005, le développement de plates-formes mondiales de distribution des biens et services culturels remet toutefois en question, non pas les politiques culturelles nationales que la convention a sanctuarisés, mais leur efficacité à l’heure d’Internet. Ces évolutions obligent à comprendre la diversité culturelle au prisme de l’analyse économique pour imaginer des formes nouvelles et internationales de régulation des flux des produits des industries culturelles, ce qu’a révélé le débat français sur le projet de modification, en 2015, des quotas radiophoniques. Les quotas et les contraintes de programmation qu’ils imposent, en ne s’appliquant pas aux plates-formes de streaming musical, pourraient en effet et paradoxalement fragiliser les acteurs régulés sur qui repose la politique de diversité, sauf à étendre aux acteurs non-médiatiques le principe des quotas.

EVALUATION DE L’IMPACT ENVIRONNEMENTAL : Vers une compréhension de la dynamique des populations de colza « échappées » des cultures à l’échelle d’une région agricole

Directory of Open Access Journals (Sweden)

Pessel Fabrice-Del

2000-07-01

Full Text Available Dans le cadre des études de risques agro-environnementaux, comme dans celui de la mise en place de stratégies de gestion des cultures transgéniques (par exemple la segmentation des filières de production OGM/non OGM, s’il est indispensable de quantifier les différents processus d’échappement des transgènes depuis les parcelles cultivées (flux de pollen et/ou de graines, il est également nécessaire de déterminer leurs potentialités de maintien en dehors des parcelles cultivées (aptitudes écologiques des hybrides interspécifiques et/ou de la plante dans des environnements hors des parcelles cultivées. En effet, des populations, dans lesquelles seraient présents un ou plusieurs transgènes, seraient suceptibles de se comporter comme des réservoirs et/ou des relais de pollutions génétiques entre deux filières de production avec et sans OGM. À plus long terme, la connaissance des processus gouvernant la dynamique et la persistance de ces populations s’avère indispensable pour une gestion efficace des différentes situations de crise possibles (sanitaire, écologique ou agronomique, en particulier pour déterminer la durée des suivis après un arrêt éventuel des cultures transgéniques.

Estimation of subcriticality and fuel concentration by using 'pattern matching' of neutron flux distribution under non uniformed system

International Nuclear Information System (INIS)

Ishitani, Kazuki; Yamane, Yoshihiro

1999-01-01

In nuclear fuel reprocessing plants, monitoring the spatial profile of neutron flux to infer subcriticality and distribution of fuel concentration using detectors such as PSPC, is very beneficial in sight of criticality safety. In this paper a method of subcriticality and fuel concentration estimation which is supposed to use under non-uniformed system is proposed. Its basic concept is the pattern matching between measured neutron flux distribution and beforehand calculated one. In any kind of subcriticality estimation, we can regard that measured neutron counts put any kind of black box, and then this black box outputs subcriticality. We proposed the use of artificial neural network or 'pattern matching' as black box which have no theoretical clear base. These method are wholly based on the calculated value as recently advancement of computer code accuracy for criticality safety. The most difference between indirect bias estimation method and our method is that our new approach target are the unknown non-uniform system. (J.P.N.)

New data-driven estimation of terrestrial CO2 fluxes in Asia using a standardized database of eddy covariance measurements, remote sensing data, and support vector regression

Science.gov (United States)

Ichii, Kazuhito; Ueyama, Masahito; Kondo, Masayuki; Saigusa, Nobuko; Kim, Joon; Alberto, Ma. Carmelita; Ardö, Jonas; Euskirchen, Eugénie S.; Kang, Minseok; Hirano, Takashi; Joiner, Joanna; Kobayashi, Hideki; Marchesini, Luca Belelli; Merbold, Lutz; Miyata, Akira; Saitoh, Taku M.; Takagi, Kentaro; Varlagin, Andrej; Bret-Harte, M. Syndonia; Kitamura, Kenzo; Kosugi, Yoshiko; Kotani, Ayumi; Kumar, Kireet; Li, Sheng-Gong; Machimura, Takashi; Matsuura, Yojiro; Mizoguchi, Yasuko; Ohta, Takeshi; Mukherjee, Sandipan; Yanagi, Yuji; Yasuda, Yukio; Zhang, Yiping; Zhao, Fenghua

2017-04-01

The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial CO2 fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated CO2 fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8 days are reproduced (e.g., r2 = 0.73 and 0.42 for 8 day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r2 = 1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land CO2 fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land CO2 fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land CO2 fluxes. These data-driven estimates can provide a new opportunity to assess CO2 fluxes in Asia and evaluate and constrain terrestrial ecosystem models.

Seasonal variation, flux estimation, and source analysis of dissolved emerging organic contaminants in the Yangtze Estuary, China.

Science.gov (United States)

Zhao, Heng; Cao, Zhen; Liu, Xue; Zhan, Yi; Zhang, Jing; Xiao, Xi; Yang, Yi; Zhou, Junliang; Xu, Jiang

2017-12-15

The occurrence and seasonal variation of 24 dissolved emerging organic contaminants in the Yangtze Estuary were studied, including 12 non-antibiotic pharmaceuticals, seven sulfonamides, two macrolides and three chloramphenicols. Sulfadiazine, erythromycin, thiamphenicol and paracetamol were the primary contaminants in sulfonamides, macrolides, chloramphenicols and non-antibiotic pharmaceutical groups, respectively. Compared to the concentrations at Datong, chloramphenicols at Xuliujing were significantly higher in autumn and winter, while macrolides were lower in spring. Based on the flux estimation, approximately 37.1 tons of sulfonamides, 17.4 tons of macrolides, 79.2 tons of chloramphenicols and 14.1 tons of non-antibiotic pharmaceuticals were discharged into the Yangtze Estuary from June 2013 to May 2014. However, the total flux from the Huangpu River only represented 5% of the total. The pharmaceutical sources were speculated on by analyzing the seasonal variations in pharmaceutical concentrations and fluxes at various sites. Both environmental and social factors might affect the fluxes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measurement of a thermal neutron flux using air activation; Mesure de flux de neutrons thermiques par activation d'air

Energy Technology Data Exchange (ETDEWEB)

Guyonvarh, M; Lecomte, P; Le Meur, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

It is necessary to know, in irradiation loops, the thermal neutron flux after the irradiation device has been introduced and without being obliged to wait for the discharge of this device. In order to measure the flux and to control it continuously, one possible method is to place in the flux a coiled steel tube through which air passes. By measuring the activity of argon 41, and with a knowledge of the flow rate and the temperature of the air, it is possible to calculate the flux. An air-circulation flux controller is described and the relationship between the flux and the count rate is established The accuracy of an absolute measurement is about 14 per cent; that of a relative measurement is about 3 per cent. The measurement can be carried out equally well whether the reactor is operating at maximum or at low power. The measurement range goes from 10{sup 9} to lO{sup 15} n.cm{sup -2}.sec{sup -1}, and it would be possible after a few modifications to measure fluxes between 10{sup 5} and 10{sup 15} n.cm{sup -2}.sec{sup -1}. Finally, the method is very safe to operate: there is little risk of irradiation because of the low specific activity of the argon-41 formed, and no risk of contamination because the decay product of argon-41 is stable. This method, which is now being used in loops, is thus very practical. (authors) [French] Sur des boucles d'irradiation il est necessaire de connaitre le flux de neutrons thermiques apres mise en place du dispositif d'irradiation et sans etre oblige d'attendre le detournement de ce dispositif. Pour mesurer le flux et le controler en permanence, une methode consiste a placer sous flux un serpentin en acier dans lequel on fait circuler de l'air. La mesure d'activite d'argon 41 permet de calculer le flux, connaissant le debit et la temperature de l'air. Un controleur de flux par circulation d'air est decrit et la relation entre le flux et le taux de comptage est etablie. La precision d'une mesure absolue est de l'ordre de 14 pour

Diffusion of graphite. The effect of cylindrical canals; Longueur de diffusion du graphite effet des canaux cylindriques

Energy Technology Data Exchange (ETDEWEB)

Carle, R; Clouet d' Orval, C; Martelly, J; Mazancourt, T de; Sagot, M; Lattes, R; Teste du Bailler, A [Commissariat a l' Energie Atomique, Dir. Industrielle, Saclay (France). Centre d' Etudes Nucleaires; Robert, C [Ecole Normale Superieure, 75 - Paris (France)

1957-07-01

Experiments on thermal neutron diffusion in the graphite used as moderator in the pile G1 have been carried out. The object of these experiments is to determine: - the intrinsic quality of this graphite, characterised by its diffusion length L or its Laplacian 1/L{sup 2} - the effect of the canals, which modifies anisotropically the macroscopic diffusion equation and is characterized by two principal diffusion regions (or two principal Laplacian), valid respectively for the diffusion in the direction of the canals and in a perpendicular direction. In order to determine them two experiments are necessary, in which the second derivatives of the flux in relation to the space coordinates are very different. These experiments form the object of the first two parts. Part 1: Diffusion along the axis of a flux coming from the pile source, and limited radially by a quasi cylindrical screen of cadmium bars. This screen, or Faraday cage is designed to give to the thermal flux produced the same radius of extrapolation to zero as that of the pile source. The determination of L (with the graphite full) has been made under the same conditions. The measurements have been interpreted in two ways. The influence of the brackets holding the detectors is discussed. Part 2: Radial diffusion in the graphite surrounding the 'long' cylindrical pile. This is well described by a sum of Bessel functions. Part 3: Results (valid for d = 1.61 t = 17 deg. C). For the graphite without cavity L = 52.7 {+-} 0.4 cm. The effect of the canals on the diffusion area and its anisotropy are in excellent agreement with the theory of Behrens: L(parallel) = 64.6 cm and L(perpendicular) 62.2 cm. Appendix: Theory of the Faraday cage. (author) [French] Des experiences de diffusion des neutrons thermiques dans le graphite constituant le moderateur de la pile G1 ont ete effectuees. Elles ont pour objet de determiner: - la qualite intrinseque de ce graphite, caracterisee par sa longueur de diffusion L ou son

Response of actinides to flux changes in high-flux systems

International Nuclear Information System (INIS)

Sailor, W.C.

1993-01-01

When discussing the transmutation of actinides in accelerator-based transmutation of waste (ATW) systems, there has been some concern about the dynamics of the actinides under high transient fluxes. For a pure neptunium feed, it has been estimated that the 238 Np/ 237 Np ratio increase due to an increasing flux may lead to an unstable, positive reactivity growth. In this analysis, a perturbation method is used to calculate the response of the entire set of actinides in a general way that allows for more species than just neptunium. The time response of the system can be calculated; i.e., a plot of fuel composition and reactivity versus time after a change in flux can be made. The effects of fission products can also be included. The procedure is extremely accurate on short time scales (∼ 1000 s) for the flux levels we contemplate. Calculational results indicate that the reactivity insertions are always smaller than previously estimated

Study of heat flux deposition in the Tore Supra Tokamak; Etude des depots de chaleur dans le tokamak Tore Supra

Energy Technology Data Exchange (ETDEWEB)

Carpentier, S.

2009-02-15

Accurate measurements of heat loads on internal tokamak components is essential for protection of the device during steady state operation. The optimisation of experimental scenarios also requires an in depth understanding of the physical mechanisms governing the heat flux deposition on the walls. The objective of this study is a detailed characterisation of the heat flux to plasma facing components (PFC) of the Tore Supra tokamak. The power deposited onto Tore Supra PFCs is calculated using an inverse method, which is applied to both the temperature maps measured by infrared thermography and to the enthalpy signals from calorimetry. The derived experimental heat flux maps calculated on the toroidal pumped limiter (TPL) are then compared with theoretical heat flux density distributions from a standard SOL-model. They are two experimental observations that are not consistent with the model: significant heat flux outside the theoretical wetted area, and heat load peaking close to the tangency point between the TPL and the last closed field surface (LCFS). An experimental analysis for several discharges with variable security factors q is made. In the area consistent with the theoretical predictions, this parametric study shows a clear dependence between the heat flux length lambda{sub q} (estimated in the SOL (scrape-off layer) from the IR measurements) and the magnetic configuration. We observe that the spreading of heat fluxes on the component is compensated by a reduction of the power decay length lambda{sub q} in the SOL when q decreases. On the other hand, in the area where the derived experimental heat loads are not consistent with the theoretical predictions, we observe that the spreading of heat fluxes outside the theoretical boundary increases when q decreases, and is thus not counterbalanced. (author)

Uncertainties in surface mass and energy flux estimates due to different eddy covariance sensors and technical set-up

Science.gov (United States)

Arriga, Nicola; Fratini, Gerardo; Forgione, Antonio; Tomassucci, Michele; Papale, Dario

2010-05-01

Eddy covariance is a well established and widely used methodology for the measurement of turbulent fluxes of mass and energy in the atmospheric boundary layer, in particular to estimate CO2/H2O and heat exchange above ecologically relevant surfaces (Aubinet 2000, Baldocchi 2003). Despite its long term application and theoretical studies, many issues are still open about the effect of different experimental set-up on final flux estimates. Open issues are the evaluation of the performances of different kind of sensors (e.g. open path vs closed path infra-red gas analysers, vertical vs horizontal mounting ultrasonic anemometers), the quantification of the impact of corresponding physical corrections to be applied to get robust flux estimates taking in account all processes concurring to the measurement (e.g. the so-called WPL term, signal attenuation due to air sampling system for closed path analyser, relative position of analyser and anemometer) and the differences between several data transmission protocols used (analogue, digital RS-232, SDM). A field experiment was designed to study these issues using several instruments among those most used within the Fluxnet community and to compare their performances under conditions supposed to be critical: rainy and cold weather conditions for open-path analysers (Burba 2008), water transport and absorption at high air relative humidity conditions for closed-path systems (Ibrom, 2007), frequency sampling limits and recorded data robustness due to different transmission protocols (RS232, SDM, USB, Ethernet) and finally the effect of the displacement between anemometer and analyser using at least two identical analysers placed at different horizontal and vertical distances from the anemometer. Aim of this experiment is to quantify the effect of several technical solutions on the final estimates of fluxes measured at a point in the space and if they represent a significant source of uncertainty for mass and energy cycle

Water, Energy, and Carbon with Artificial Neural Networks (WECANN): a statistically based estimate of global surface turbulent fluxes and gross primary productivity using solar-induced fluorescence

Science.gov (United States)

Hamed Alemohammad, Seyed; Fang, Bin; Konings, Alexandra G.; Aires, Filipe; Green, Julia K.; Kolassa, Jana; Miralles, Diego; Prigent, Catherine; Gentine, Pierre

2017-09-01

A new global estimate of surface turbulent fluxes, latent heat flux (LE) and sensible heat flux (H), and gross primary production (GPP) is developed using a machine learning approach informed by novel remotely sensed solar-induced fluorescence (SIF) and other radiative and meteorological variables. This is the first study to jointly retrieve LE, H, and GPP using SIF observations. The approach uses an artificial neural network (ANN) with a target dataset generated from three independent data sources, weighted based on a triple collocation (TC) algorithm. The new retrieval, named Water, Energy, and Carbon with Artificial Neural Networks (WECANN), provides estimates of LE, H, and GPP from 2007 to 2015 at 1° × 1° spatial resolution and at monthly time resolution. The quality of ANN training is assessed using the target data, and the WECANN retrievals are evaluated using eddy covariance tower estimates from the FLUXNET network across various climates and conditions. When compared to eddy covariance estimates, WECANN typically outperforms other products, particularly for sensible and latent heat fluxes. Analyzing WECANN retrievals across three extreme drought and heat wave events demonstrates the capability of the retrievals to capture the extent of these events. Uncertainty estimates of the retrievals are analyzed and the interannual variability in average global and regional fluxes shows the impact of distinct climatic events - such as the 2015 El Niño - on surface turbulent fluxes and GPP.

Efficacité des néonicotinoïdes et des pyréthrinoïdes utilisés contre le ...

African Journals Online (AJOL)

Efficacité des néonicotinoïdes et des pyréthrinoïdes utilisés contre le foreur des tiges du cacaoyer ( Eulophonotus myrmeleon Felder : Lepidoptera, Cossidae). Implications dans la stratégie de protection de la cacaoculture en Côte d'Ivoire.

Heat flux estimation for neutral beam line components using inverse heat conduction procedures

International Nuclear Information System (INIS)

Bharathi, P.; Prahlad, V.; Quereshi, K.; Bansal, L.K.; Rambabu, S.; Sharma, S.K.; Parmar, S.; Patel, P.J.; Baruah, U.K.; Patel, Ravi

2015-01-01

In this work, we describe and compare the analytical IHCP methods such-as semi-infinite method, finite slab method and a numerical method called Stolz method for estimating the incident heat flux from the experimentally measured temperature data. In case of analytical methods, the finite time response of the sensor is needed to be accounted for an accurate power density estimations. The modified models corrected for the response time of the sensors are also discussed in this paper. Application of these methods using example temperature waveforms obtained on the SST1-NBI test stand is presented and discussed. For choosing the suitable method for the calorimetry on beam line components, the estimated results are also validated using the ANSYS analysis done on these beam Iine components. As a conclusion, the finite slab method corrected for the influence of the sensor response time found out to be the most suitable method for the inversion of temperature data in case of neutral beam line components

A comprehensive biogeochemical record and annual flux estimates for the Sabaki River (Kenya

Directory of Open Access Journals (Sweden)

T. R. Marwick

2018-03-01

Full Text Available Inland waters impart considerable influence on nutrient cycling and budget estimates across local, regional and global scales, whilst anthropogenic pressures, such as rising populations and the appropriation of land and water resources, are undoubtedly modulating the flux of carbon (C, nitrogen (N and phosphorus (P between terrestrial biomes to inland waters, and the subsequent flux of these nutrients to the marine and atmospheric domains. Here, we present a 2-year biogeochemical record (October 2011–December 2013 at biweekly sampling resolution for the lower Sabaki River, Kenya, and provide estimates for suspended sediment and nutrient export fluxes from the lower Sabaki River under pre-dam conditions, and in light of the approved construction of the Thwake Multipurpose Dam on its upper reaches (Athi River. Erratic seasonal variation was typical for most parameters, with generally poor correlation between discharge and material concentrations, and stable isotope values of C (δ13C and N (δ15N. Although high total suspended matter (TSM concentrations are reported here (up to ∼ 3.8 g L−1, peak concentrations of TSM rarely coincided with peak discharge. The contribution of particulate organic C (POC to the TSM pool indicates a wide biannual variation in suspended sediment load from OC poor (0.3 % to OC rich (14.9 %, with the highest %POC occurring when discharge is < 100 m3 s−1 and at lower TSM concentrations. The consistent 15N enrichment of the particulate nitrogen (PN pool compared to other river systems indicates anthropogenic N loading is a year-round driver of N export from the Sabaki Basin. The lower Sabaki River was consistently oversaturated in dissolved methane (CH4; from 499 to 135 111 % and nitrous oxide (N2O; 100 to 463 % relative to atmospheric concentrations. Wet season flows (October–December and March–May carried > 80 % of the total load for TSM (∼ 86 %, POC (∼ 89 %, dissolved

On the use of radiative surface temperature to estimate sensible heat flux over sparse shrubs in Nevada

Science.gov (United States)

Chehbouni, A.; Nichols, W. D.; Qi, J.; Njoku, E. G.; Kerr, Y. H.; Cabot, F.

1994-01-01

The accurate partitioning of available energy into sensible and latent heat flux is crucial to the understanding of surface atmosphere interactions. This issue is more complicated in arid and semi arid regions where the relative contribution to surface fluxes from the soil and vegetation may vary significantly throughout the day and throughout the season. A three component model to estimate sensible heat flux over heterogeneous surfaces is presented. The surface was represented with two adjacent compartments. The first compartment is made up of two components, shrubs and shaded soil, the second of open 'illuminated' soil. Data collected at two different sites in Nevada (U.S.) during the Summers of 1991 and 1992 were used to evaluate model performance. The results show that the present model is sufficiently general to yield satisfactory results for both sites.

Estimating energy fluxes within the stream-aquifer interface of the Avenelles basin

Science.gov (United States)

Berrhouma, Asma; Rivière, Agnès; Goblet, Patrick; Cucchi, Karina; Rubin, Yoram; Baudin, Aurélien; Ansart, Patrick; Flipo, Nicolas

2017-04-01

The understanding of water temperature evolution and its associated energy fluxes is important to follow the aquatic habitats evolution and to predict future modifications induced by climate change. The spatio-temporal energy balance dynamics within the stream-aquifer interface is complex because of the multitude of physical, morphological and meteorological parameters on which it depends. This critical interface is involving numerous physical and bio-geochemical processes which are taking place at different time and spatial scales. The energy balance estimation at this interface depends mainly on the direction, magnitude and variability of water exchanges and the temporal variation of river and aquifer temperatures as well as the thermal porous media properties. In this work, a combined numerical and experimental approach is used to study the temporal and spatial evolution of the energy budget along 6 km of the stream network of the Avenelles watershed. With an area of 46 km2, the Avenelles watershed is located 70 km east from Paris. The Avenelles river presents different types of connectivity with the underlying aquifers. Five Local Monitoring Stations (LOMOS) have been deployed along the hydraulic corridor to monitor the water and thermal exchanges between the stream and aquifer over years, based on continuous pressure and temperature measurements in the river, the hyporheic zone (HZ) and the underlying aquifer. A 2D finite element thermo-hydrogeological model (METIS) coupled with a parameters screening script is used to determine the hydrogeological and thermal properties of the HZ and of the underlying aquifers by inversion at five LOMOS. Once the local models are calibrated, water and heat fluxes through the stream - aquifer interface are assessed over years (2012-2015) along the stream network. This work offers a new understanding of the stream-aquifer interface functioning, shifting from a pure hydrological characterizing toward a more subtle view that

Migration des civelles d'anguilles (Anguilla anguilla L. dans les estuaires, modalités du phénomène et caractéristiques des individus

Directory of Open Access Journals (Sweden)

ELIE P.

1994-10-01

Full Text Available Nous avons réalisé une analyse de la littérature consacrée à la migration estuarienne de la civelle d'anguille (Anguilla anguilla L. et nous l'avons confrontée à des chroniques de données originales (abondance, structure en poids et en stades pigmentaires issues de l'estuaire de la Gironde. Ceci nous a permis de dégager la façon dont se déroule la migration. Il en ressort que les modalités du déroulement de la migration sont bien connues et relativement stables d'une année à l'autre, mais nous en sommes encore réduits à des hypothèses en ce qui concerne l'explication de son allure générale et de sa variabilité interannuelle. L'analyse des caractéristiques des individus montre une haute régularité interannuelle, on peut même parler d'un patron standard de l'évolution des individus en migration. L'action des principaux facteurs environnementaux sur les individus en migration apparaît assez nette, même si nous ne sommes pas en mesure actuellement de hiérarchiser leurs effets sur des flux migrants. Ce travail met en évidence la nécessité, pour appréhender les phénomènes migratoires et à plus forte raison pour établir un prémodèle de migration, de tenir compte de l'ensemble des aspects de la migration (tendance, facteurs modulateurs, épiphénomènes et caractéristiques des individus e n migration et d'utiliser des horloges écologiques adaptées.

Estimation of microwave source location in precipitating electron fluxes according to Viking satellite data

International Nuclear Information System (INIS)

Khrushchinskij, A.A.; Ostapenko, A.A.; Gustafsson, G.; Eliasson, L.; Sandal, I.

1989-01-01

According to the Viking satellite data on electron fluxes in the 0.1-300 keV energy range, the microburst source location is estimated. On the basis of experimental delays in detected peaks in different energy channels and theoretical calculations of these delays within the dipole field model (L∼ 4-5.5), it is shown that the most probable source location is the equatorial region with the centre, 5-10 0 shifted towards the ionosphere

Safety precautions in atomic pile control (1962); Securite dans le controle des piles atomiques (1962)

Energy Technology Data Exchange (ETDEWEB)

Furet, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-01

We have been led to study the problem of safety in atomic pile control as a result of our participation on the one hand in the planning of C.E.A. atomic piles, and on the other hand in the pile safety sub omission considering atomic pile safety of operational or planned C.E.A. piles. We have thus had to consider the wishes occurring in piles during their operation and also their behaviour in the dynamic state The present work deals mainly with the importance of intrinsic safety devices, with the influence of reactivity variations on the power fluctuations during accidental operation, and with the development of robust and reliable safety appliances. The starting p accident has been especially studied both for low-flux piles where a compromise is necessary between the response time of the safety appliances and the statistical fluctuations and for high lux piles where xenon poisoning has an effect on the lower limit of the velocity of reactivity liberation. The desirability has been stressed of automation as a safety factor in atomic pile control. The details required for an understanding of the diagrams of the apparatus are given. (author) [French] Nous avons aborde le probleme de la securite dans le controle des piles atomiques a la suite de notre participation d'une part aux avant rojets de piles atomiques du CE.A. et d'autre part a l'examen au sein de la sous ommission de surete des piles, de la securite des piles du CE.A. en fonctionnement ou en projet. Nous avons ete amenes a nous interesser alors aux risques encourus par les piles pendant leur fonctionnement et par la meme a leur comportement en regime dynamique. Ce travail traite principalement de l'importance des securites intrinseques, de l'influence des variations de reactivite sur les evolutions de puissance en regime d'accident et du developpement d'appareillages de securite robustes et de fonctionnement tres sur. L'accident de demarrage a ete particulierement developpe aussi bien pour les piles a bas

Safety precautions in atomic pile control (1962); Securite dans le controle des piles atomiques (1962)

Energy Technology Data Exchange (ETDEWEB)

Furet, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-01

We have been led to study the problem of safety in atomic pile control as a result of our participation on the one hand in the planning of C.E.A. atomic piles, and on the other hand in the pile safety sub omission considering atomic pile safety of operational or planned C.E.A. piles. We have thus had to consider the wishes occurring in piles during their operation and also their behaviour in the dynamic state The present work deals mainly with the importance of intrinsic safety devices, with the influence of reactivity variations on the power fluctuations during accidental operation, and with the development of robust and reliable safety appliances. The starting p accident has been especially studied both for low-flux piles where a compromise is necessary between the response time of the safety appliances and the statistical fluctuations and for high lux piles where xenon poisoning has an effect on the lower limit of the velocity of reactivity liberation. The desirability has been stressed of automation as a safety factor in atomic pile control. The details required for an understanding of the diagrams of the apparatus are given. (author) [French] Nous avons aborde le probleme de la securite dans le controle des piles atomiques a la suite de notre participation d'une part aux avant rojets de piles atomiques du CE.A. et d'autre part a l'examen au sein de la sous ommission de surete des piles, de la securite des piles du CE.A. en fonctionnement ou en projet. Nous avons ete amenes a nous interesser alors aux risques encourus par les piles pendant leur fonctionnement et par la meme a leur comportement en regime dynamique. Ce travail traite principalement de l'importance des securites intrinseques, de l'influence des variations de reactivite sur les evolutions de puissance en regime d'accident et du developpement d'appareillages de securite robustes et de fonctionnement tres sur. L'accident de demarrage a ete particulierement

Estimating daily forest carbon fluxes using a combination of ground and remotely sensed data

Science.gov (United States)

Chirici, Gherardo; Chiesi, Marta; Corona, Piermaria; Salvati, Riccardo; Papale, Dario; Fibbi, Luca; Sirca, Costantino; Spano, Donatella; Duce, Pierpaolo; Marras, Serena; Matteucci, Giorgio; Cescatti, Alessandro; Maselli, Fabio

2016-02-01

Several studies have demonstrated that Monteith's approach can efficiently predict forest gross primary production (GPP), while the modeling of net ecosystem production (NEP) is more critical, requiring the additional simulation of forest respirations. The NEP of different forest ecosystems in Italy was currently simulated by the use of a remote sensing driven parametric model (modified C-Fix) and a biogeochemical model (BIOME-BGC). The outputs of the two models, which simulate forests in quasi-equilibrium conditions, are combined to estimate the carbon fluxes of actual conditions using information regarding the existing woody biomass. The estimates derived from the methodology have been tested against daily reference GPP and NEP data collected through the eddy correlation technique at five study sites in Italy. The first test concerned the theoretical validity of the simulation approach at both annual and daily time scales and was performed using optimal model drivers (i.e., collected or calibrated over the site measurements). Next, the test was repeated to assess the operational applicability of the methodology, which was driven by spatially extended data sets (i.e., data derived from existing wall-to-wall digital maps). A good estimation accuracy was generally obtained for GPP and NEP when using optimal model drivers. The use of spatially extended data sets worsens the accuracy to a varying degree, which is properly characterized. The model drivers with the most influence on the flux modeling strategy are, in increasing order of importance, forest type, soil features, meteorology, and forest woody biomass (growing stock volume).

Santé des adolescents et des jeunes au Burkina Faso : état des ...

African Journals Online (AJOL)

Il s'est agi d'une étude évaluative ayant utilisé une revue documentaire associée à une interview des acteurs clés et un atelier de validation et d'identification des interventions pertinentes pour un plan stratégique national. La situation de la santé des adolescents et des jeunes est caractérisée par des grossesses précoces ...

Fate factors and emission flux estimates for emerging contaminants in surface waters

Directory of Open Access Journals (Sweden)

Hoa T. Trinh

2016-01-01

Full Text Available Pharmaceuticals, personal care products, hormones, and wastewater products are emerging environmental concerns for manifold reasons, including the potential of some compounds found in these products for endocrine disruption at a very low chronic exposure level. The environmental occurrences and sources of these contaminants in the water, soil, sediment and biota in European nations and the United States are well documented. This work reports a screening-level emission and fate assessment of thirty compounds, listed in the National Reconnaissance of the United States Geological Survey (USGS, 1999–2000 as the most frequently detected organic wastewater contaminants in U.S. streams and rivers. Estimations of the surface water fate factors were based on Level II and Level III multimedia fugacity models for a 1000 km2 model environment, the size of a typical county in the eastern United States. The compounds are categorized into three groups based upon the sensitivity of their predicted surface water fate factors to uncertainties in their physicochemical property values and the landscape parameters. The environmental fate factors, mass distributions, and loss pathways of all of the compounds are strongly affected by their assumed modes of entry into the environment. It is observed that for thirteen of the thirty organic wastewater contaminants most commonly detected in surface waters, conventional treatment strategies may be ineffective for their removal from wastewater effluents. The surface water fate factors predicted by the fugacity models were used in conjunction with the surface water concentrations measured in the USGS reconnaissance to obtain emission flux estimates for the compounds into U.S. streams and rivers. These include estimated fluxes of 6.8 × 10−5 to 0.30 kg/h km2 for the biomarker coprostanol; 1.7 × 10−5 to 6.5 × 10−5 kg/h km2 for the insect repellent N,N-diethyltoluamide; and 4.3 × 10−6 to 3.1 × 10−5 kg/h km2 for

La fabrique des sciences des institutions aux pratiques

CERN Document Server

Benninghoff, Martin; Crettaz von Roten, Fabienne; Merz, Martina

2006-01-01

Aujourd'hui, les façons de produire, d'organiser, d'évaluer et d'utiliser les savoirs sont en profond débat. De plus en plus, l'Etat, la société civile et l'économie tentent d'influencer les activités des universités et des laboratoires de recherche. Ces développements mettent à l'épreuve tout à la fois les fondements des systèmes d'enseignement supérieur et de recherche, l'autonomie des institutions scientifiques, la définition des frontières des savoirs et l'acceptation des sciences. Dans des contextes suisses et européens, cet ouvrage s'intéresse aux manières dont les sciences et les technologies sont fabriquées, en analysant leurs institutions et les pratiques. A partir d'une approche relationnelle, les sciences et les technologies sont conçues comme des phénomènes profondément sociaux, culturels et politiques. Une telle démarche déstabilise les visions parfois idéalisées et stéréotypées de la construction des savoirs. Des études de cas détaillées décrivent des phénomè...

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Directory of Open Access Journals (Sweden)

S. Hartery

2018-01-01

Full Text Available Methane (CH4 is the second most important greenhouse gas but its emissions from northern regions are still poorly constrained. In this study, we analyze a subset of in situ CH4 aircraft observations made over Alaska during the growing seasons of 2012–2014 as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE. Net surface CH4 fluxes are estimated using a Lagrangian particle dispersion model which quantitatively links surface emissions from Alaska and the western Yukon with observations of enhanced CH4 in the mixed layer. We estimate that between May and September, net CH4 emissions from the region of interest were 2.2 ± 0.5 Tg, 1.9 ± 0.4 Tg, and 2.3 ± 0.6 Tg of CH4 for 2012, 2013, and 2014, respectively. If emissions are only attributed to two biogenic eco-regions within our domain, then tundra regions were the predominant source, accounting for over half of the overall budget despite only representing 18 % of the total surface area. Boreal regions, which cover a large part of the study region, accounted for the remainder of the emissions. Simple multiple linear regression analysis revealed that, overall, CH4 fluxes were largely driven by soil temperature and elevation. In regions specifically dominated by wetlands, soil temperature and moisture at 10 cm depth were important explanatory variables while in regions that were not wetlands, soil temperature and moisture at 40 cm depth were more important, suggesting deeper methanogenesis in drier soils. Although similar environmental drivers have been found in the past to control CH4 emissions at local scales, this study shows that they can be used to generate a statistical model to estimate the regional-scale net CH4 budget.

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Science.gov (United States)

Hartery, Sean; Commane, Róisín; Lindaas, Jakob; Sweeney, Colm; Henderson, John; Mountain, Marikate; Steiner, Nicholas; McDonald, Kyle; Dinardo, Steven J.; Miller, Charles E.; Wofsy, Steven C.; Chang, Rachel Y.-W.

2018-01-01

Methane (CH4) is the second most important greenhouse gas but its emissions from northern regions are still poorly constrained. In this study, we analyze a subset of in situ CH4 aircraft observations made over Alaska during the growing seasons of 2012-2014 as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). Net surface CH4 fluxes are estimated using a Lagrangian particle dispersion model which quantitatively links surface emissions from Alaska and the western Yukon with observations of enhanced CH4 in the mixed layer. We estimate that between May and September, net CH4 emissions from the region of interest were 2.2 ± 0.5 Tg, 1.9 ± 0.4 Tg, and 2.3 ± 0.6 Tg of CH4 for 2012, 2013, and 2014, respectively. If emissions are only attributed to two biogenic eco-regions within our domain, then tundra regions were the predominant source, accounting for over half of the overall budget despite only representing 18 % of the total surface area. Boreal regions, which cover a large part of the study region, accounted for the remainder of the emissions. Simple multiple linear regression analysis revealed that, overall, CH4 fluxes were largely driven by soil temperature and elevation. In regions specifically dominated by wetlands, soil temperature and moisture at 10 cm depth were important explanatory variables while in regions that were not wetlands, soil temperature and moisture at 40 cm depth were more important, suggesting deeper methanogenesis in drier soils. Although similar environmental drivers have been found in the past to control CH4 emissions at local scales, this study shows that they can be used to generate a statistical model to estimate the regional-scale net CH4 budget.

Advances in Support of the CMAQ Bidirectional Science Option for the Estimation of Ammonia Flux from Agricultural cropland

Science.gov (United States)

Proposed Session: Emissions Inventories, Models and processes: Last year a new CMAQ bidirectional option for the estimation of ammonia flux (emission and deposition) was released. This option essentially replaces NEI crop ammonia emissions with emissions calculated dynamically...

Tests on dynamic corrosion by water. Influence of the passage of a heat flux on the corrosion kinetics. pH measurement in water at high temperature; Essais de corrosion dynamique par l'eau. Influence du passage d'un flux thermique sur la cinetique de corrosion. Mesure du pH dans l'eau a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Coriou, H.; Grall, L.; Hure, J.; Saint-James, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Berthod [Societe Grenobloise d' Etudes et d' Applications Hydrauliques, 38 (France); Le peintre [Centre National de la Recherche Scientifique (CNRS), 38 - Grenoble (France)

1958-07-01

The passage of a heat flux through the surface of a metal placed in a corrosive medium influences the rate of corrosion, these being higher than under adiabatic conditions. The apparatus developed for corrosion tests is described, it is possible to obtain with this equipment: 1) Heat fluxes greater than 200 W/cm{sup 2}, across aluminium canning, which is cooled by water (temperature 50 deg. C), circulating with flow rates of the order of 5 to 6 m/s. 2) Heat fluxes which can go up to 150 W/cm{sup 2}, across canning of zircaloy or stainless steel. The cooling fluid is pressurized water at a temperature around 280 deg. C, the flow-rate of circulation reaching 6 m/s. The results obtained on aluminium canning are studied from the viewpoint of corrosion, paying particular attention to cavitation phenomena which can cause serious damage in certain special circumstances. After developing a glass electrode system capable of supporting high pressures, the authors have investigated materials capable of functioning as a hydrogen electrode and of resisting satisfactorily corrosion by water at 200 deg. C. Various possibilities have been examined: electrodes of special glasses, quartz, metals, with a membrane etc... The results of the various tests and the practical limits of utilisation are given. (author)Fren. [French] Le passage d'un flux thermique a travers la surface d'un metal place dans un milieu corrosif influence les vitesses de corrosion, celles-ci etant plus elevees que dans des conditions adiabatiques. On decrit les appareils mis au point, pour essais de corrosion. Ils permettent d'obtenir: 1) A travers des gaine aluminium des flux thermiques depassant 200 W /cm{sup 2}. Les gaines sont refroidies par l'eau (temperature 50 deg. C), circulant a des vitesses de l'ordre de 5 a 6 m/s. 2) A travers des gaines en zircaloy ou acier inoxydable des flux thermiques pouvant s'elever a 150 W/cm{sup 2}. Le fluide de refroidissement est de l

Estimation des changements de la ligne de rivage de la zone côtière ...

African Journals Online (AJOL)

Les plages du littoral de Kénitra ont connu des modifications au cours de ces quatre dernières décennies. La mise en valeur économique de certaines plages par des aménagements touristiques et l'extraction massive de sables pour les travaux d'aménagements urbains sont à l'origine d'une déstabilisation des échanges ...

Bilan des flux de matières particulaires et dissoutes du Sassandra à ...

African Journals Online (AJOL)

2Centre de Recherches Océanologiques, Rue des pêcheurs, BP V 18 Abidjan – Cote d'Ivoire. *Auteur pour les ... situé entre 5° et 9° 50 de latitude nord, et 6° 50 et ... Il existe de nombreuses techniques de mesures ..... Diagnostic et prévision.

Estimation of net ecosystem exchange at the Skukuza flux site, Kruger National Park, South Africa

CSIR Research Space (South Africa)

Nickless, A

2011-03-01

Full Text Available , Manlay R., Ngom D., Ntoupka M., Ouattara S., Savadogo P., Sawadogo L., Seghieri J.,Tiveau D. ?valuation de la productivit? et de la biomasse des savanes s?ches africaines : l?apport du collectif SAVAFOR. Bois et For?ts des Tropiques, 60... (citato 1 volta) UNFCCC United Nations Framework Convention on Climate Change UNOPS United Nations Office for Project Services UR2PI Unit? de Recherche sur la Productivit? des Plantations Industrielles (ex CTFT) Key note speeches on Africa...

Some advance on the comprehension of SR analysis for estimating the flux of a scalar

Science.gov (United States)

Castellví, Dr

2009-04-01

In agronomy, the eddy covariance, EC, method likely is the preferred for measuring surface scalar fluxes. For latent heat flux, however, weighing lysimeters maybe preferred in agriculture, but they are rarely affordable and not portable. The dissipation method, DM, is considered the most reliable technique for measuring scalar fluxes over open water because instrument motion contaminates the EC measurements. The main advantage of DM over EC is that it is less sensitive to low frequency instrument platform motions (such as ship and buoys), sensor alignment, precise orientation and stringent steadiness in the mean meteorological conditions (Fairall and Larsen, 1986; Kader, 1992; Edson and Fairall, 1998). Over land, keeping in mind that the EC and DM methods require the same measurements for scalar flux measurement, the DM has several disadvantages versus the EC. Direct measurement of the scalar variance dissipation rate, VDR, requires to capture eddies in the Kolmogorov's microscale (thus scalar time series measured at frequencies in the order of kHz are needed). Therefore, it is not practical. Indirect methods to estimate VDR (such as spectral analysis and second or third order structure functions) requires implementing iterative methods involving similarity relationships that are not well established (Hsieh and Katul, 1997; Castellvi and Snyder, 2008). Currently, there is ample evidence that the DM as explained in traditional micrometeorological books (such as, Panofsky and Dutton, 1984; Brutsaert, 1988; Kaimal and Finnigan; 1994) is, in general, not correct. Accordingly, it likely explains why DM is typically omitted in revisits of micrometeorological methods for estimating scalar fluxes in agronomy. Within the last decade, over some agricultural surfaces, evidence has been shown on the advantages over other micrometeorological methods and the reliability (i.e., close performance to the EC method) of Surface Renewal, SR, theory in conjunction with the Analysis of

Surface layer scintillometry for estimating the sensible heat flux component of the surface energy balance

Directory of Open Access Journals (Sweden)

M. J. Savage

2010-01-01

Full Text Available The relatively recently developed scintillometry method, with a focus on the dual-beam surface layer scintillometer (SLS, allows boundary layer atmospheric turbulence, surface sensible heat and momentum flux to be estimated in real-time. Much of the previous research using the scintillometer method has involved the large aperture scintillometer method, with only a few studies using the SLS method. The SLS method has been mainly used by agrometeorologists, hydrologists and micrometeorologists for atmospheric stability and surface energy balance studies to obtain estimates of sensible heat from which evaporation estimates representing areas of one hectare or larger are possible. Other applications include the use of the SLS method in obtaining crucial input parameters for atmospheric dispersion and turbulence models. The SLS method relies upon optical scintillation of a horizontal laser beam between transmitter and receiver for a separation distance typically between 50 and 250 m caused by refractive index inhomogeneities in the atmosphere that arise from turbulence fluctuations in air temperature and to a much lesser extent the fluctuations in water vapour pressure. Measurements of SLS beam transmission allow turbulence of the atmosphere to be determined, from which sub-hourly, real-time and in situ path-weighted fluxes of sensible heat and momentum may be calculated by application of the Monin-Obukhov similarity theory. Unlike the eddy covariance (EC method for which corrections for flow distortion and coordinate rotation are applied, no corrections to the SLS measurements, apart from a correction for water vapour pressure, are applied. Also, path-weighted SLS estimates over the propagation path are obtained. The SLS method also offers high temporal measurement resolution and usually greater spatial coverage compared to EC, Bowen ratio energy balance, surface renewal and other sensible heat measurement methods. Applying the shortened surface

Estimation de la survie des alevins de carpe (C. carpio au cours de leur premier mois d'existence

Directory of Open Access Journals (Sweden)

MOREAU J.

1979-10-01

Full Text Available Des observations réalisées sur deux stations piscicoles de Madagascar, dans des étangs ne recevant ni engrais ni nourriture, révèlent qu'au cours de leur premier mois les alevins de carpe (C. carpio subissent des mortalités voi-sines de 50 %. Ces dernières sont encore plus élevées en début et en fin de saison de reproduction. Au début, les fortes mortalités sont dues à la température trop basse et aux disponibilités alimentaires insuffisantes ; en fin de saison de reproduction, la température trop élevée et la mauvaise qualité des œufs sont sans doute en cause. Une fumure adéquate des étangs de grossissement des alevins et une alimentation correcte des géniteurs permettront peut-être de diminuer ces mortalités.

Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations

Science.gov (United States)

Guzinski, R.; Anderson, M. C.; Kustas, W. P.; Nieto, H.; Sandholt, I.

2013-07-01

The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time-differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish

Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day–night MODIS observations

Directory of Open Access Journals (Sweden)

R. Guzinski

2013-07-01

Full Text Available The Dual Temperature Difference (DTD model, introduced by Norman et al. (2000, uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST to estimate surface energy fluxes. By using a time-differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the

Detection and location of can rupture in reactors cooled by a flow of water; Detection et localisation des ruptures de gaines sur les reacteurs refroidis par circulation d'eau

Energy Technology Data Exchange (ETDEWEB)

Le Meur, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-07-01

This report brings together the principal methods of fission-product detection used for water reactors. The position, type and method of adjustment is given for each detector. The methods for localizing the defective elements are explained, in particular those using water sampling or decreases in the flux. A few installations are briefly described. They correspond to particular types of reactors using boiling, pressurized or cold water. Amongst the many methods used, it can be noted that when the fuel is resistant, the installations are fairly compact. In nuclear super-heated reactors on the other hand, the study of fuel behaviour calls for larger installations. An identification of defective elements exists when the reactor structure allows it. If this is not possible, a localization in a group of elements is obtained by a flux depression. (author) [French] Ce rapport rassemble les principales methodes de detection de produits de fission utilisees pour des reacteurs a eau. On indique pour les detecteurs leurs emplacements, leurs types, leurs reglages. On explique quelles sont les methodes de localisation des elements defectueux, en particulier celles utilisant des prelevements d'eau ou des depressions de flux. Quelques installations sont decrites sommairement. Elles correspondent a des types particuliers de reacteurs a eau bouillante, pressurisee ou froide. Parmi les nombreuses methodes utilisees, on constate que les installations sont peu importantes, lorsque le combustible est resistant. Par contre dans les reacteurs a surchauffe nucleaire l'etude du comportement du combustible necessite des installations plus importantes. Une identification d'elements defectueux existe lorsque la structure du reacteur le permet. A defaut une localisation dans un groupe d'elements est obtenue par depression de flux. (auteur)

Impact de la preparation des anodes crues et des conditions de cuisson sur la fissuration dans des anodes denses

Science.gov (United States)

Amrani, Salah

fabriquees industriellement. Cette technique a consiste a determiner le profil des differentes proprietes physiques. En effet, la methode basee sur la mesure de la distribution de la resistivite electrique sur la totalite de l'echantillon est la technique qui a ete utilisee pour localiser la fissuration et les macro-pores. La microscopie optique et l'analyse d'image ont, quant a elles, permis de caracteriser les zones fissurees tout en determinant la structure des echantillons analyses a l'echelle microscopique. D'autres tests ont ete menes, et ils ont consiste a etudier des echantillons cylindriques d'anodes de 50 mm de diametre et de 130 mm de longueur. Ces derniers ont ete cuits dans un four a UQAC a differents taux de chauffage dans le but de pouvoir determiner l'influence des parametres de cuisson sur la formation de la fissuration dans ce genre de carottes. La caracterisation des echantillons d'anodes cuites a ete faite a l'aide de la microscopie electronique a balayage et de l'ultrason. La derniere partie des travaux realises a l'UQAC contient une etude sur la caracterisation des anodes fabriquees au laboratoire sous differentes conditions d'operation. L'evolution de la qualite de ces anodes a ete faite par l'utilisation de plusieurs techniques. L'evolution de la temperature de refroidissement des anodes crues de laboratoire a ete mesuree; et un modele mathematique a ete developpe et valide avec les donnees experimentales. Cela a pour objectif d'estimer la vitesse de refroidissement ainsi que le stress thermique. Toutes les anodes fabriquees ont ete caracterisees avant la cuisson par la determination de certaines proprietes physiques (resistivite electrique, densite apparente, densite optique et pourcentage de defauts). La tomographie et la distribution de la resistivite electrique, qui sont des techniques non destructives, ont ete employees pour evaluer les defauts internes des anodes. Pendant la cuisson des anodes de laboratoire, l'evolution de la resistivite

Estimation of the thermal neutron flux in a PET cyclotron room via radioactive analysis of the bolts of a wall socket in the room

International Nuclear Information System (INIS)

Ogata, Y.; Ishigure, N.; Mochizuki, S.; Ito, K.; Hatano, K.; Abe, J.; Miyahara, H.; Masumoto, K.; Nakamura, H.; Matsumura, H.

2008-01-01

Full text: Since positron emission nuclides for PET (Positron Emission Tomography) have short half-lives, they are mainly produced by on-site cyclotrons. Significant amounts of neutrons are generated together with the operating of the cyclotron, and then materials in the room are activated. To quantify the neutron flux density will lead the prediction of the extent of the activation. We tried to estimate the neutron flux of the room via the radioactive analysis of bolts in the room. The cyclotron (Cypris HM-18, Sumitomo Heavy Industry) is able to accelerate protons and deuterons up to 18 and 10 MeV, respectively. The routine charge current is 20μA. The cyclotron is housed in a room with 1 m thickness concrete wall. A couple of bolts of a wall socket were removed to investigate the components and the radioactivities, which were analyzed by fluorescent X-ray spectroscopy and by gamma-ray spectroscopy, respectively. We compared the neutron flux estimated by the bolts analysis with the results measured by the gold foil activation method. The weight sum of the bolts was 1.257 g. They were made of nickel plated brass, and predominantly consisted of Cu (63%) and Zn (34%). Four nuclides, 69m Zn, 65 Zn, 64 Cu, and 60 Co, were detected in the bolts. The activity of 64 Cu half-life of 12.7 h, led the last few days history of neutron flux, and the activity of 65 Zn, 244 d, led the last few years history. The analysis of the bolts activity estimated the thermal neutron flux at 4∼6x10 5 cm -2 s -1 . This figure agreed with the value, 6∼9x10 5 cm -2 s -1 , computed from the activated gold foil near the bolts. Bolts are quite generally installed in such a room. Therefore, the radioactive analysis of the bolts leads convenient and effective estimation of neutron flux there. Consequently, the radioactive analysis of the bolts in the cyclotron room allowed us to estimate the neutron flux in the room. (author)

Une estimation de la précarité des patients recourant à la médecine générale en centres de santé. Le cas des centres de santé du projet Epidaure-CDS

OpenAIRE

Anissa Afrite; Julien Mousques; Yann Bourgueil

2015-01-01

Le projet exploratoire Epidaure-CDS a pour objectif principal d’analyser la spécificité des centres de santé (CDS) dans l’offre de soins et de déterminer s’ils jouent un rôle particulier dans la réduction des inégalités sociales de santé, notamment en facilitant l’accès aux soins primaires pour les personnes en situation de précarité ou de vulnérabilité sociale, ce qui n’a été que peu exploré jusqu’à présent. Il s’agit ici d’estimer en quoi la population recourant à la médecine générale dans ...

Tombes et cimetières éthiopiens : des rois, des saints, des anonymes1

OpenAIRE

Derat, Marie-Laure

2009-01-01

L’histoire des tombes et cimetières éthiopiens, dans la longue durée, en est encore à ses balbutiements. Si les tombes des saints et des rois nous sont un peu mieux connus grâce à des textes témoignant à la fois des enjeux entourant les sépultures de ces personnages hors du commun et des soins apportés à leur inhumation, en revanche, les cimetières ordinaires échappent encore largement à l’enquête, en grande partie parce que le commun des mortels est inhumé dans l’anonymat et dans un grand dé...

Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

African Journals Online (AJOL)

Face à ce constat, le défi de la recherche serait la détermination du niveau actuel de contamination des légumes feuilles et des eaux du barrage et celui de l'État serait l'initiation de programmes de sensibilisation des producteurs par rapport à une gestion plus rigoureuse des pesticides. Mots-clés : pratiques paysannes, ...

A state-space modeling approach to estimating canopy conductance and associated uncertainties from sap flux density data

Science.gov (United States)

David M. Bell; Eric J. Ward; A. Christopher Oishi; Ram Oren; Paul G. Flikkema; James S. Clark; David Whitehead

2015-01-01

Uncertainties in ecophysiological responses to environment, such as the impact of atmospheric and soil moisture conditions on plant water regulation, limit our ability to estimate key inputs for ecosystem models. Advanced statistical frameworks provide coherent methodologies for relating observed data, such as stem sap flux density, to unobserved processes, such as...

Use of a numerical simulation approach to improve the estimation of air-water exchange fluxes of polycyclic aromatic hydrocarbons in a coastal zone.

Science.gov (United States)

Lai, I-Chien; Lee, Chon-Lin; Ko, Fung-Chi; Lin, Ju-Chieh; Huang, Hu-Ching; Shiu, Ruei-Feng

2017-07-15

The air-water exchange is important for determining the transport, fate, and chemical loading of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in aquatic systems. Investigations of PAH air-water exchange are mostly based on observational data obtained using complicated field sampling processes. This study proposes a new approach to improve the estimation of long-term PAH air-water exchange fluxes by using a multivariate regression model to simulate hourly gaseous PAH concentrations. Model performance analysis and the benefits from this approach indicate its effectiveness at improving the flux estimations and at decreasing the field sampling difficulty. The proposed GIS mapping approach is useful for box model establishment and is tested for visualization of the spatiotemporal variations of air-water exchange fluxes in a coastal zone. The air-water exchange fluxes illustrated by contour maps suggest that the atmospheric PAHs might have greater impacts on offshore sites than on the coastal area in this study. Copyright © 2017 Elsevier Ltd. All rights reserved.

Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

Directory of Open Access Journals (Sweden)

H. Aaltonen

2012-06-01

Full Text Available Soil provides an important source of volatile organic compounds (VOCs to atmosphere, but in boreal forests these fluxes and their seasonal variations have not been characterized in detail. Especially wintertime fluxes are almost completely unstudied. In this study, we measured the VOC concentrations inside the snowpack in a boreal Scots pine (Pinus sylvestris L. forest in southern Finland, using adsorbent tubes and air samplers installed permanently in the snow profile. Based on the VOC concentrations at three heights inside the snowpack, we estimated the fluxes of these gases. We measured 20 VOCs from the snowpack, monoterpenes being the most abundant group with concentrations varying from 0.11 to 16 μg m⁻³. Sesquiterpenes and oxygen-containing monoterpenes were also detected. Inside the pristine snowpack, the concentrations of terpenoids decreased from soil surface towards the surface of the snow, suggesting soil as the source for terpenoids. Forest damages (i.e. broken treetops and branches, fallen trees resulting from heavy snow loading during the measurement period increased the terpenoid concentrations dramatically, especially in the upper part of the snowpack. The results show that soil processes are active and efficient VOC sources also during winter, and that natural or human disturbance can increase forest floor VOC concentrations substantially. Our results stress the importance of soil as a source of VOCs during the season when other biological sources, such as plants, have lower activity.

La convergence des rôles respectifs des relationnistes et des journalistes influence-t-elle la perception qu'ils ont les uns des autres?

DEFF Research Database (Denmark)

Valentini, Chiara

2017-01-01

la convergence des rôles respectifs des praticiens des relations publiques et des journalistes a un effet favorable sur la perception qu’ils ont les uns des autres. L’effet est plus marqué chez les praticiens des relations publiques, car leur vision de la profession en journalisme correspond à celle...

Mécanique des sols et des roches

CERN Document Server

Vullier, Laurent; Zhao, Jian

2016-01-01

La mécanique des sols et la mécanique des roches sont des disciplines généralement traitées séparément dans la littérature. Pour la première fois, un traité réunit ces deux spécialités, en intégrant également les connaissances en lien avec les écoulements souterrains et les transferts thermiques. A la fois théorique et pratique, cet ouvrage propose tout d'abord une description détaillée de la nature et de la composition des sols et des roches, puis s'attache à la modélisation de problèmes aux conditions limites et présente les essais permettant de caractériser les sols et les roches, tant d'un point de vue mécanique qu'hydraulique et thermique. La problématique des sols non saturés et des écoulements multiphasiques est également abordée. Une attention particulière est portée aux lois de comportement mécanique et à la détermination de leurs paramètres par des essais in situ et en laboratoire, et l'ouvrage offre également une présentation détaillée des systèmes de classi...

Optimal estimation of the surface fluxes of methyl chloride using a 3-D global chemical transport model

Directory of Open Access Journals (Sweden)

X. Xiao

2010-06-01

Full Text Available Methyl chloride (CH₃Cl is a chlorine-containing trace gas in the atmosphere contributing significantly to stratospheric ozone depletion. Large uncertainties in estimates of its source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission estimates are used to construct a priori maps of the surface fluxes of CH₃Cl. The Model of Atmospheric Transport and Chemistry (MATCH, driven by NCEP interannually varying meteorological data, is then used to simulate CH₃Cl mole fractions and quantify the time series of sensitivities of the mole fractions at each measurement site to the surface fluxes of various regional and global sources and sinks. We then implement the Kalman filter (with the unit pulse response method to estimate the surface fluxes on regional/global scales with monthly resolution from January 2000 to December 2004. High frequency observations from the AGAGE, SOGE, NIES, and NOAA/ESRL HATS in situ networks and low frequency observations from the NOAA/ESRL HATS flask network are used to constrain the source and sink magnitudes. The inversion results indicate global total emissions around 4100 ± 470 Gg yr⁻¹ with very large emissions of 2200 ± 390 Gg yr⁻¹ from tropical plants, which turn out to be the largest single source in the CH₃Cl budget. Relative to their a priori annual estimates, the inversion increases global annual fungal and tropical emissions, and reduces the global oceanic source. The inversion implies greater seasonal and interannual oscillations of the natural sources and sink of CH₃Cl compared to the a priori. The inversion also reflects the strong effects of the 2002/2003 globally widespread heat waves and droughts on global emissions from tropical plants, biomass burning and salt marshes, and on the soil sink.

Study of a photomultiplier for the measurement of low light flows by photon counting; Etude d'un photomultiplicateur en vue de la mesure des faibles flux lumineux par comptage de photons

Energy Technology Data Exchange (ETDEWEB)

Haye, Kleber

1964-03-20

After a recall of the history of the discovery and use of the photoemission effect, a presentation of the main characteristics of photomultipliers, a discussion of performance and weaknesses of electron multiplier-based cells, this research thesis addresses the study of low light flows. The author tried to determine whether it was possible, at ambient temperature, to reduce the influence of the thermoelectric effect. In order to do so, he made a detailed study of the amplitude spectrum of pulses of photoelectric origin. In order to analyse the influence of temperature of photomultiplier characteristics, he studied, with respect to temperature, the variation of the counting rate corresponding to darkness, the variation of pulse amplitude spectrum, and relative variations of the quantum efficiency for various wavelengths. In parallel with the study by counting, a study has been performed by using the well known mean current measurement [French] Si l'on veut etudier de faibles flux lumineux, c'est surtout l'effet thermoelectronique qui limite a temperature ambiante le domaine possible des mesures. Les electrons qui arrivent en effet a quitter la photocathode ou les dynodes donnent naissance a des groupes supplementaires d'electrons venant s'ajouter a ceux causes par effet photoelectrique. En utilisant une methode de mesure par comptage des groupes d'electrons, nous nous sommes attaches a determiner s'il etait possible a temperature ordinaire de reduire 1'influence de l'effet thermoelectronique. Pour cela, nous avons fait une etude detaillee du spectre d'amplitude des impulsions d'origine photoelectrique. Toutefois, la solution la plus efficace pour combattre l'effet thermoelectronique etant le refroidissement, nous avons essaye d'analyser l'influence de la temperature sur les caracteristiques du photomultiplicateur. Nous avons ainsi etudie en fonction de la temperature la variation du taux de comptage correspondant a l'obscurite, la variation du spectre d

Environmental controls of daytime leaf carbon exchange: Implications for estimates of ecosystem fluxes in a deciduous forest

Science.gov (United States)

Heskel, M.; Tang, J.

2017-12-01

Leaf-level photosynthesis and respiration are sensitive to short- and long-term changed in temperature, and how these processes respond to phenological and seasonal transitions and daily temperature variation dictate how carbon is first assimilated and released in terrestrial ecosystems. We examined the short-term temperature response of daytime leaf carbon exchange at Harvard Forest across growing season, with the specific objective to quantify the light inhibition of dark respiration and photorespiration in leaves and use this to better inform daytime carbon assimilation and efflux estimates at the canopy scale. Dark and light respiration increased with measurement temperature and varied seasonally in a proportional manner, with the level of inhibition remaining relatively constant through the growing season. Higher rates of mitochondrial respiration and photorespiration at warmer temperatures drove a lower carbon use efficiency. Using temperature, light, and canopy leaf area index values to drive models, we estimate partitioned ecosystem fluxes and re-calculate gross primary production under multiple scenarios that include and exclude the impact of light inhibition, thermal acclimation, and seasonal variation in physiology. Quantifying the contribution of these `small fluxes' to ecosystem carbon exchange in forests provides a nuanced approach for integrating physiology into regional model estimates derived from eddy covariance and remote-sensing methods.

Air-sea fluxes and satellite-based estimation of water masses formation

Science.gov (United States)

Sabia, Roberto; Klockmann, Marlene; Fernandez-Prieto, Diego; Donlon, Craig

2015-04-01

Recent work linking satellite-based measurements of sea surface salinity (SSS) and sea surface temperature (SST) with traditional physical oceanography has demonstrated the capability of generating routinely satellite-derived surface T-S diagrams [1] and analyze the distribution/dynamics of SSS and its relative surface density with respect to in-situ measurements. Even more recently [2,3], this framework has been extended by exploiting these T-S diagrams as a diagnostic tool to derive water masses formation rates and areas. A water mass describes a water body with physical properties distinct from the surrounding water, formed at the ocean surface under specific conditions which determine its temperature and salinity. The SST and SSS (and thus also density) at the ocean surface are largely determined by fluxes of heat and freshwater. The surface density flux is a function of the latter two and describes the change of the density of seawater at the surface. To obtain observations of water mass formation is of great interest, since they serve as indirect observations of the thermo-haline circulation. The SSS data which has become available through the SMOS [4] and Aquarius [5] satellite missions will provide the possibility of studying also the effect of temporally-varying SSS fields on water mass formation. In the present study, the formation of water masses as a function of SST and SSS is derived from the surface density flux by integrating the latter over a specific area and time period in bins of SST and SSS and then taking the derivative of the total density flux with respect to density. This study presents a test case using SMOS SSS, OSTIA SST, as well as Argo ISAS SST and SSS for comparison, heat fluxes from the NOCS Surface Flux Data Set v2.0, OAFlux evaporation and CMORPH precipitation. The study area, initially referred to the North Atlantic, is extended over two additional ocean basins and the study period covers the 2011-2012 timeframe. Yearly, seasonal

Heat flux estimate of warm water flow in a low-temperature diffuse flow site, southern East Pacific Rise 17°25‧ S

Science.gov (United States)

Goto, Shusaku; Kinoshita, Masataka; Mitsuzawa, Kyohiko

2003-09-01

A low-temperature diffuse flow site associated with abundant vent fauna was found by submersible observations on the southern East Pacific Rise at 17°25‧ S in 1997. This site was characterized by thin sediment covered pillow and sheet lavas with collapsed pits up to ˜15 m in diameter. There were three warm water vents (temperature: 6.5 to 10.5 °C) within the site above which the vented fluids rise as plumes. To estimate heat flux of the warm water vents, a temperature logger array was deployed and the vertical temperature distribution in the water column up to 38 m above the seafloor was monitored. A stationary deep seafloor observatory system was also deployed to monitor hydrothermal activity in this site. The temperature logger array measured temperature anomalies, while the plumes from the vents passed through the array. Because the temperature anomalies were measured in only specific current directions, we identified one of the vents as the source. Heat flux from the vent was estimated by applying a plume model in crossflow in a density-stratified environment. The average heat flux from September 13 to October 18, 1997 was 39 MW. This heat flux is as same order as those of high-temperature black smokers, indicating that a large volume flux was discharged from the vent (1.9 m3/s). Previous observations found many similar warm water flow vents along the spreading axis between 17°20‧ S 30‧ S. The total heat flux was estimated to be at least a few hundred mega-watts. This venting style would contribute to form effluent hydrothermal plumes extended above the spreading axis.

Estimation of the soil heat flux/net radiation ratio based on spectral vegetation indexes in high-latitude Arctic areas

International Nuclear Information System (INIS)

Jacobsen, A.; Hansen, B.U.

1999-01-01

The vegetation communities in the Arctic environment are very sensitive to even minor climatic variations and therefore the estimation of surface energy fluxes from high-latitude vegetated areas is an important subject to be pursued. This study was carried out in July-August and used micro meteorological data, spectral reflectance signatures, and vegetation biomass to establish the relation between the soil heat flux/net radiation (G / Rn) ratio and spectral vegetation indices (SVIs). Continuous measurements of soil temperature and soil heat flux were used to calculate the surface ground heat flux by use of conventional methods, and the relation to surface temperature was investigated. Twenty-seven locations were established, and six samples per location, including the measurement of the surface temperature and net radiation to establish the G/Rn ratio and simultaneous spectral reflectance signatures and wet biomass estimates, were registered. To obtain regional reliability, the locations were chosen in order to represent the different Arctic vegetation communities in the study area; ranging from dry tundra vegetation communities (fell fields and dry dwarf scrubs) to moist/wet tundra vegetation communities (snowbeds, grasslands and fens). Spectral vegetation indices, including the simple ratio vegetation index (RVI) and the normalized difference vegetation index (NDVI), were calculated. A comparison of SVIs to biomass proved that RVI gave the best linear expression, and NDVI the best exponential expression. A comparison of SVIs and the surface energy flux ratio G / Rn proved that NDVI gave the best linear expression. SPOT HRV images from July 1989 and 1992 were used to map NDVI and G / Rn at a regional scale. (author)

Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

African Journals Online (AJOL)

SARAH

30 sept. 2017 ... ... de Biochimie et Immunologie Appliquée, Centre de Recherche en Sciences Biologiques, Alimentaires et .... l'intoxication des agriculteurs et des consommateurs, ... source d'alimentation en eau et au pouvoir d'achat des.

Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy

Science.gov (United States)

Acton, W. Joe F.; Schallhart, Simon; Langford, Ben; Valach, Amy; Rantala, Pekka; Fares, Silvano; Carriero, Giulia; Tillmann, Ralf; Tomlinson, Sam J.; Dragosits, Ulrike; Gianelle, Damiano; Hewitt, C. Nicholas; Nemitz, Eiko

2016-06-01

This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs) 4 m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone + methacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton-transfer-reaction mass spectrometer (PTR-MS) and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) together with the methods of virtual disjunct eddy covariance (using PTR-MS) and eddy covariance (using PTR-ToF-MS). Isoprene was the dominant emitted compound with a mean daytime flux of 1.9 mg m-2 h-1. Mixing ratios, recorded 4 m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28-day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTR-ToF-MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m-2 h-1 was calculated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) isoprene emission algorithms (Guenther et al., 2006). A detailed tree-species distribution map for the site enabled the leaf-level emission of isoprene and monoterpenes recorded using gas-chromatography mass spectrometry (GC-MS) to be scaled up to produce a bottom-up canopy-scale flux. This was compared with the top-down canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant-species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates.

S'associer à des bailleurs de fonds partenaires | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

3 nov. 2010 ... Le CRDI estime que les partenariats lui sont essentiels pour l'aider à réaliser sa mission. C'est aussi ce qu'a réaffirmé le Conseil des gouverneurs en mars 2010 en approuvant le premier cadre quinquennal des partenariats avec les bailleurs de fonds. Les partenariats favorisent la collaboration entre les ...

A direct estimate of poleward volume, heat, and freshwater fluxes at 59.5°N between Greenland and Scotland

Science.gov (United States)

Rossby, T.; Reverdin, Gilles; Chafik, Leon; Søiland, Henrik

2017-07-01

The meridional overturning circulation (MOC) in the North Atlantic plays a major role in the transport of heat from low to high latitudes. In this study, we combine recent measurements of currents from the surface to >700 m from a shipboard acoustic Doppler current profiler with Argo profiles (to 2000 m) to estimate poleward volume, heat, and freshwater flux at 59.5°N between Greenland and Scotland. This is made possible thanks to the vessel Nuka Arctica that operates on a 3 week schedule between Greenland and Denmark. For the period late 2012 to early 2016, the deseasoned mean meridional overturning circulation reaches a 18.4 ± 3.4 Sv maximum at the σθ = 27.55 kg m-3 isopycnal, which varies in depth from near the surface in the western Irminger Sea to 1000 m in Rockall Trough. The total heat and freshwater fluxes across 59.5°N = 399 ± 74 TW and -0.20 ± 0.04 Sv, where the uncertainties are principally due to that of the MOC. Analysis of altimetric sea surface height variations along exactly the same route reveals a somewhat stronger geostrophic flow north during this period compared to the 23 year mean suggesting that for a long-term mean the above flux estimates should be reduced slightly to 17.4 Sv, 377 TW, and -0.19 Sv, respectively, with the same estimate uncertainties. The ADCP program is ongoing.

Experiments on neutron-attenuation by water-lead mixtures; Etude experimentale de l'attenuation des neutrons dans les melanges plomb-eau

Energy Technology Data Exchange (ETDEWEB)

Beauge, R; Millot, J P; Rastoin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

The penetration of fission neutrons in water-lead mixtures has been investigated in the NAIADE facility. The slopes of the thermal and fast fluxes (the latter measured with a dosimeter) remain similar when the volume proportion of water is greater than 65 per cent. For smaller water contents, the measurements show the evidence of streaming presumably due to slowing-down neutrons of energy smaller than 300 keV. (author) [French] La propagation des neutrons de fission a ete etudiee dans les melanges plomb-eau au moyen du dispositif NAIADE. La pente du flux thermique et la pente du flux rapide (obtenue au moyen d'un dosimetre) restent voisines lorsque la proportion d'eau dans le melange depasse 65 pour cent en volume. Pour des proportions inferieures les mesures mettent en evidence un 'streaming' de neutrons en ralentissement d'energie probablement inferieure a 300 keV. (auteur)

Modelisation des effets physico-techniques pour la conception des ...

African Journals Online (AJOL)

automatisation dans les installations industrielles a besoin d'une régulation automatique des commandes des processus technologiques pour lesquelles certaines contraintes sont à relever compte tenu des exigences des innovations scientifiques de ...

Quantifying and reducing the differences in forest CO₂-fluxes estimated by eddy covariance, biometric and chamber methods: A global synthesis

Energy Technology Data Exchange (ETDEWEB)

Wang, Xingchang; Wang, Chuankuan; Bond-Lamberty, Benjamin

2017-12-15

Carbon dioxide (CO₂) fluxes between terrestrial ecosystems and the atmosphere are primarily measured with eddy covariance (EC), biometric, and chamber methods. However, it is unclear why the estimates of CO₂-fluxes, when measured using these different methods, converge at some sites but diverge at others. We synthesized a novel global dataset of forest CO₂-fluxes to evaluate the consistency between EC and biometric or chamber methods for quantifying CO₂ budget in forests. The EC approach, comparing with the other two methods, tended to produce 25% higher estimate of net ecosystem production (NEP, 0.52Mg C ha-1 yr-1), mainly resulting from lower EC-estimated Re; 10% lower ecosystem respiration (Re, 1.39Mg C ha-1 yr-1); and 3% lower gross primary production (0.48 Mg C ha-1 yr-1) The discrepancies between EC and the other methods were higher at sites with complex topography and dense canopies versus those with flat topography and open canopies. Forest age also influenced the discrepancy through the change of leaf area index. The open-path EC system induced >50% of the discrepancy in NEP, presumably due to its surface heating effect. These results provided strong evidence that EC produces biased estimates of NEP and Re in forest ecosystems. A global extrapolation suggested that the discrepancies in CO₂ fluxes between methods were consistent with a global underestimation of Re, and overestimation of NEP, by the EC method. Accounting for these discrepancies would substantially improve the our estimates of the terrestrial carbon budget .

Integration of ground and satellite data to estimate the forest carbon fluxes of a Mediterranean region

Science.gov (United States)

Chiesi, M.; Maselli, F.; Moriondo, M.; Fibbi, L.; Bindi, M.; Running, S. W.

2009-04-01

reference series of monthly gross primary production (GPP) estimates. In particular this model estimates forest GPP as function of photosynthetically active radiation absorbed by vegetation (Veroustraete et al., 2002) combined with ground based estimates of incoming solar radiation and air temperature. These GPP values are used as reference data to both calibrate and integrate the functions of a more complex bio-geochemical model, BIOME-BGC, which is capable of simulating all main ecosystem processes. This model requires: daily climate data, information on the general environment (i.e. soil, vegetation and site conditions) and parameters describing the ecophysiological characteristics of vegetation. Both C-Fix and BIOME-BGC compute GPP as an expression of total, or potential, productivity of an ecosystem in equilibrium with the environment. This makes the GPP estimates of the two models practically inter-comparable and opens the possibility of using the more accurate GPP estimates of C-Fix to both calibrate BIOME-BGC and stabilize its outputs (Chiesi et al., 2007). In particular, by integrating BIOME-BGC respiration estimates to those of C-Fix, forest fluxes for the entire region are obtained, which are referable to ecosystems at equilibrium (climax) condition. These estimates are converted into NPP and NEE of real forests relying on a specifically developed conceptual framework which uses the ratio of actual over potential stand volume as indicator of ecosystem distance from climax. The accuracy of the estimated net carbon exchanges is finally evaluated against ground data derived from a recent forest inventory and from two eddy covariance flux towers located in Tuscany (San Rossore and Lecceto). The results of both these comparisons were quite positive, indicating the good capability of the method for forest carbon flux estimation in Mediterranean areas.

Estimation of suspended sediment flux in streams using continuous turbidity and flow data coupled with laboratory concentrations

Science.gov (United States)

Jack Lewis

2002-01-01

The widening use of sediment surrogate measurements such as turbidity necessitates consideration of new methods for estimating sediment flux. Generally, existing methods can be simply be used in new ways. The effectiveness of a method varies according to the quality of the surrogate data and its relation to suspended sediment concentration (SSC). For this discussion,...

Surface renewal analysis for estimating turbulent surface fluxes

International Nuclear Information System (INIS)

Castellvi, F.

2009-01-01

A decade ago, the need for a long-term surface monitoring was recognized to better understand the soil-vegetation-atmosphere scalar exchange and interaction processes. the AmeriFlux concept emerged in the IGBP workshop (La Thuile, IT, 1995). Continuous acquisition of surface fluxes for different species such as temperature, water vapour, CO x , halocarbon, ozone, etc.,) and momentum allows determination of the influence of local (canopy) exchanges, fossil fuel emission, large-scale biotic exchange on ambient concentrations which are crucial to take decisions for protecting natural environments and water resources, to develop new perspective for modern agriculture and forest management and to better understand the global climate change. (Author)

Vecteurs Singuliers des Theories des Champs Conformes Minimales

Science.gov (United States)

Benoit, Louis

En 1984 Belavin, Polyakov et Zamolodchikov revolutionnent la theorie des champs en explicitant une nouvelle gamme de theories, les theories quantiques des champs bidimensionnelles invariantes sous les transformations conformes. L'algebre des transformations conformes de l'espace-temps presente une caracteristique remarquable: en deux dimensions elle possede un nombre infini de generateurs. Cette propriete impose de telles conditions aux fonctions de correlations qu'il est possible de les evaluer sans aucune approximation. Les champs des theories conformes appartiennent a des representations de plus haut poids de l'algebre de Virasoro, une extension centrale de l'algebre conforme du plan. Ces representations sont etiquetees par h, le poids conforme de leur vecteur de plus haut poids, et par la charge centrale c, le facteur de l'extension centrale, commune a toutes les representations d'une meme theorie. Les theories conformes minimales sont constituees d'un nombre fini de representations. Parmi celles-ci se trouvent des theories unitaires dont les representation forment la serie discrete de l'algebre de Virasoro; leur poids h a la forme h_{p,q}(m)=[ (p(m+1) -qm)^2-1] (4m(m+1)), ou p,q et m sont des entiers positifs et p+q= 2. Ces representations possedent un sous-espace invariant engendre par deux sous-representations avec h_1=h_{p,q} + pq et h_2=h_{p,q} + (m-p)(m+1-q) dont chacun des vecteurs de plus haut poids portent le nom de vecteur singulier et sont notes respectivement |Psi _{p,q}> et |Psi_{m-p,m+1-q}>. . Les theories super-conformes sont une version super-symetrique des theories conformes. Leurs champs appartiennent a des representation de plus haut poids de l'algebre de Neveu-Schwarz, une des deux extensions super -symetriques de l'algebre de Virasoro. Les theories super -conformes minimales possedent la meme structure que les theories conformes minimales. Les representations sont elements de la serie h_{p,q}= [ (p(m+2)-qm)^2-4] /(8m(m+2)) ou p,q et m sont

Experiments on neutron-attenuation by ordinary concrete; Etude experimentale de l'attenuation des neutrons dans le beton ordinaire

Energy Technology Data Exchange (ETDEWEB)

Beauge, R; Millot, J P; Rastoin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

The penetration of fission-neutrons in water and glass mixtures has been investigated in the NAIADE facility. The slopes of the thermal and fast fluxes (the latter measured with a dosimeter) remain similar when the volume proportion of water is greater than 15 per cent. For smaller water-contents the measurements show the evidence of streaming, presumably due to slowing-down neutrons of energy smaller than 300 keV. Since a volume proportion of about 15 per cent of water in glass corresponds to the composition of ordinary concrete, the present work enables to predict the effects of a desiccation of concrete. Moreover, it is seen that there is no interest in increasing the proportion of water in ordinary concrete beyond the usual values (15-20 per cent). (author) [French] La propagation des neutrons de fission a ete etudiee dans les melanges verre-eau au moyen du dispositif NAIADE. La pente du flux thermique et la pente du flux rapide (obtenue au moyen d'un dosimetre) restent voisines lorsque la proportion d'eau dans le melange depasse 15 pour cent en volume. Pour des proportions d'eau inferieures les mesures mettent en evidence un 'streaming' de neutrons en ralentissement d'energie probablement inferieure a 300 keV. La composition des melanges verre-eau aux environs de 15 pour cent d'eau en volume correspondant au beton ordinaire, la presente etude permet de prevoir les effets d'une dessication du beton, et montre, en outre, qu'il n'y a pas interet a essayer d'augmenter la proportion d'eau dans le beton ordinaire au dela des valeurs usuelles (15 a 20 pour cent). (auteur)

Study of thermocouples for control of high temperatures; Etude de thermocouples pour le reperage des hautes temperatures

Energy Technology Data Exchange (ETDEWEB)

Villamayor, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Faculte des Sciences de l' Universite de Lyon - 69 (France)

1967-07-01

Previous works have shown that the tungsten-rhenium alloys thermocouples were a good instrument for control of high temperatures. From its, the author has studied the W/W 26 per cent and W 5 per cent Re/W 26 per cent Re french manufactured thermocouples and intended for control of temperatures in nuclear reactors until 2300 deg. C. In 'out-pile' study he determines the general characteristics of these thermocouples: average calibration curves, thermal shocks influence, response times, and alloys allowing the cold source compensation. The evolution of these thermocouples under thermal neutron flux has been determined by 'in-pile' study. The observations have led the author to propose a new type of thermocouples settled of molybdenum-columbium alloys. (author) [French] Des travaux anterieurs ont montre que les thermocouples des alliages tungstene-rhenium etaient susceptibles de reperer avec precision des hautes temperatures. A partir de la, l'auteur a etudie las thermocouples W/W 26 pour cent Re et W 5 pour cent Re/W 26 pour cent Re de fabrication francaise et destines au controle des temperatures dans les reacteurs nucleaires, jusqu'a 2300 deg. C Dans l'etude 'hors-pile' il a determine les caracteristiques generales de ces thermocouples: courbes d'etalonnage moyen, influence des chocs thermiques, temps de reponse, et alliages assurant la compensation de soudure froide. L'etude 'en-pile' a permis de rendre compte de l'evolution de ces thermocouples sous flux neutroniques. Les phenomenes observes ont conduit l'auteur a proposer un nouveau type de thermocouples constitues d'alliages molybdene-niobium. (auteur)

A comparison of ground-based and aircraft-based methane emission flux estimates in a western oil and natural gas production basin

Science.gov (United States)

Snare, Dustin A.

Recent increases in oil and gas production from unconventional reservoirs has brought with it an increase of methane emissions. Estimating methane emissions from oil and gas production is complex due to differences in equipment designs, maintenance, and variable product composition. Site access to oil and gas production equipment can be difficult and time consuming, making remote assessment of emissions vital to understanding local point source emissions. This work presents measurements of methane leakage made from a new ground-based mobile laboratory and a research aircraft around oil and gas fields in the Upper Green River Basin (UGRB) of Wyoming in 2014. It was recently shown that the application of the Point Source Gaussian (PSG) method, utilizing atmospheric dispersion tables developed by US EPA (Appendix B), is an effective way to accurately measure methane flux from a ground-based location downwind of a source without the use of a tracer (Brantley et al., 2014). Aircraft measurements of methane enhancement regions downwind of oil and natural gas production and Planetary Boundary Layer observations are utilized to obtain a flux for the entire UGRB. Methane emissions are compared to volumes of natural gas produced to derive a leakage rate from production operations for individual production sites and basin-wide production. Ground-based flux estimates derive a leakage rate of 0.14 - 0.78 % (95 % confidence interval) per site with a mass-weighted average (MWA) of 0.20 % for all sites. Aircraft-based flux estimates derive a MWA leakage rate of 0.54 - 0.91 % for the UGRB.

Volatilité des prix et régulation des marchés. Instruments de gestion du risque

OpenAIRE

Cordier, Jean

2014-01-01

La présentation porte d'abord sur une présentation de la volatilité des prix, définition et estimation pour les principaux produits agricoles. La seconde partie développe le concept d'efficience des marchés, dans les trois dimensions du marché physique (espace, forme et temps). Le marché de gré à gré, dit OTC en anglais, est décrit dans sa dimension physique puis financière. Les nouveaux instruments d'investissement sur les produits agricoles sont alors introduits pour évoquer la volatilité e...

Joint estimation of the fast and thermal components of a high neutron flux with a two on-line detector system

International Nuclear Information System (INIS)

Filliatre, P.; Oriol, L.; Jammes, C.; Vermeeren, L.

2009-01-01

A fission chamber with a 242 Pu deposit is the best suited detector for on-line measurements of the fast component of a high neutron flux (∼10 14 ncm -2 s -1 or more) with a significant thermal component. To get the fast flux, it is, however, necessary to subtract the contribution of the thermal neutrons, which increases with fluence because of the evolution of the isotopic content of the deposit. This paper presents an algorithm that permits, thanks to measurements provided by a 242 Pu fission chamber and a detector for thermal neutrons, to estimate the thermal and the fast flux at any time. An implementation allows to test it with simulated data.

Utilisation sans risque des eaux usées, des excréta et des eaux ...

International Development Research Centre (IDRC) Digital Library (Canada)

Les responsables de ce projet piloteront l'application et l'adaptation des principes directeurs relatifs à l'utilisation sans risque des eaux usées, des excreta et des eaux grises en agriculture et en aquaculture (Guidelines for the Safe Use of Wastewater, Excreta and Greywater in Agriculture and Aquaculture), que ...

FluxPyt: a Python-based free and open-source software for 13C-metabolic flux analyses.

Science.gov (United States)

Desai, Trunil S; Srivastava, Shireesh

2018-01-01

13 C-Metabolic flux analysis (MFA) is a powerful approach to estimate intracellular reaction rates which could be used in strain analysis and design. Processing and analysis of labeling data for calculation of fluxes and associated statistics is an essential part of MFA. However, various software currently available for data analysis employ proprietary platforms and thus limit accessibility. We developed FluxPyt, a Python-based truly open-source software package for conducting stationary 13 C-MFA data analysis. The software is based on the efficient elementary metabolite unit framework. The standard deviations in the calculated fluxes are estimated using the Monte-Carlo analysis. FluxPyt also automatically creates flux maps based on a template for visualization of the MFA results. The flux distributions calculated by FluxPyt for two separate models: a small tricarboxylic acid cycle model and a larger Corynebacterium glutamicum model, were found to be in good agreement with those calculated by a previously published software. FluxPyt was tested in Microsoft™ Windows 7 and 10, as well as in Linux Mint 18.2. The availability of a free and open 13 C-MFA software that works in various operating systems will enable more researchers to perform 13 C-MFA and to further modify and develop the package.

Modélisation de la réponse des flux de respiration d'un sol forestier selon les principales variables climatiques

Directory of Open Access Journals (Sweden)

Marc Aubinet

2004-01-01

Full Text Available Modelling of the response of forest soil respiration fluxes to the main climatic variables. The objective of this article is to model the carbon dioxide (CO2 efflux to the atmosphere due to soil respiration. First, we will synthesize the main components of soil respiration fluxes as found in the literature. Then, we will present a system of automatic measurements, which was set up in a forest stand in Vielsalm (Ardennes, Belgium. This system recorded measurements of soil efflux and of climatic variables every 30 minutes. Its spatial resolution was limited to six collars of 20 cm diameter in a two-meter diameter curve. The measurements were analyzed according to their climatic components: temperature and relative soil water content. We analyzed 2 2 , 9 2 6 cycles of soil respiration measurements, and we followed a strict procedure of data selection in order to characterize soil respiration fluxes according to the main environmental components. We modelized those soil temperature-dependent fluxes with a Q1 0 function and A r r h e n i u s ' law with temperature-adjusted activation energ y, which both gave very similar results. Our best estimation for Q1 0 is 3.86 and for A in Arrhenius ' l a w, 17,479. We then adjusted two line segments beneath and beyond 0 . 2 7 m3.m- 3 of water in the soil in order to describe the response of respiration fluxes to soil moisture content. The soil temperature at 4.5 cm could explain over 86 % of the soil respiration fluxes. Relative moisture content narrows this by 2 % .

Ajout d’équivalents des groupes alimentaires au Questionnaire canadien de fréquence alimentaire II pour estimer l’Indice canadien de saine alimentation-2005

Directory of Open Access Journals (Sweden)

Maria McInerney

2018-01-01

Full Text Available Introduction : Il a été prouvé qu’un régime alimentaire de piètre qualité augmente le risque de maladies chroniques courantes susceptibles de nuire à la qualité de vie et d'alourdir le fardeau qui pèse sur le système de santé. Les recommandations fondées sur des données probantes du Guide alimentaire canadien (GAC fournissent des conseils nutritionnels destinés à améliorer la qualité du régime alimentaire. L’Indice canadien de saine alimentation (ICSA, un outil de mesure de la qualité du régime alimentaire, permet d'évaluer la conformité au GAC. Le Questionnaire canadien de fréquence alimentaire II (QFA-C II [Canadian Diet History Questionnaire II, C-DHQ II], mis au point récemment, pourrait quant à lui servir à estimer l’ICSA au sein de la population canadienne si on pouvait ajouter à sa base de données sur les éléments nutritifs les équivalents des groupes alimentaires (correspondant aux portions du GAC. Nous décrivons dans cet article des méthodes destinées à enrichir cette base de données sur les éléments nutritifs du QFA-C II en vue d’estimer l’ICSA. Méthodologie : Nous avons créé des équivalents des groupes alimentaires à partir de données provenant de diverses bases de données sur les aliments et les éléments nutritifs, en particulier l’Enquête sur la santé dans les collectivités canadiennes, cycle 2.2 Nutrition de 2004. Nous avons ajouté ces variables à la base de données sur les éléments nutritifs du QFA-C II. Nous avons déterminé les scores de l’ICSA et avons effectué des analyses descriptives pour les participants qui ont répondu au QFA-C II dans le cadre d’une étude transversale canadienne. Résultats : Le score moyen de l’ICSA dans notre échantillon de 446 adultes de 20 à 83 ans était de 64,4 (écart-type : 10,8. Les femmes, les non-fumeurs et les personnes ayant un niveau de scolarité supérieur au secondaire ont obtenu de manière statistiquement

ANALYSE DES PERCEPTIONS LOCALES ET DES FACTEURS ...

African Journals Online (AJOL)

AISA

1Faculté des Sciences Agronomiques (FSA), Université d'Abomey-Calavi (UAC), 01 BP 526 Cotonou Bénin. Email : cgbemavo@yahoo.fr. 2Institut National des Recherches Agricoles du Bénin, Centre de Recherches Agricoles d'Agonkanmey (CRA-A),. Laboratoire des Sciences du Sol, Eau et Environnement (LSSEE).

{gamma} activity and heating of rods in EL2 and EL3; Activitiy {gamma} et echauffement des barres de EL2 et EL3

Energy Technology Data Exchange (ETDEWEB)

Lalere, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-07-01

A method is described for calculating the {gamma} activity of uranium rods, given the mean flux in which they are irradiated, the time they remain in the pile and the duration of deactivation. This calculation leads to numerical formulae which may be applied to the rods of the two reactors. It allows the saturation activities to be foreseen both for EL2 and for EL3, taking into recount the minimum times necessary for extraction. Measurements have been carried out, and the results are in good agreement with those foreseen by calculation. In the last section this method is used to calculate the heating of the irradiated rods. (author) [French] Une methode est indiquee ici, qui permet de calculer l'activite {gamma} des barres d'uranium connaissant le flux moyen dans lequel elles ont ete irradiees, leur temps de sejour en pile et la duree de la desactivation. Ce calcul conduit a des formules numeriques que l'on peut appliquer aux barres des deux reacteurs. Il permet de prevoir les activites atteintes a saturation, tant a EL2 qu'a EL3, compte tenu des temps minima necessaires a l'extraction. Des mesures ont ete faites: les resultats sont en bon accord avec les previsions du calcul. Enfin, en derniere partie, cette methode est utilisee pour calculer l'echauffement des barres irradiees. (auteur)

variabilite des productions et des revenus des exploitations

African Journals Online (AJOL)

3Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UMR Innovation,. Montpellier, France. Doubangolo COULIBALY, Email kone_b@yahoo.fr. RESUME. La durabilité des systèmes de production à base de coton dans un contexte de variabilité des prix aux producteurs et de ...

Le statut vitaminique des individus et des populations…

Directory of Open Access Journals (Sweden)

Icart Jean-Claude

2000-05-01

Full Text Available Comme le souligne un récent rapport du Haut comité de santé publique, le statut vitaminique des individus et des populations demeure une question d’actualité. Si les études ne révèlent plus de signes évocateurs de carence, au plus des problèmes de déficiences pour certains groupes à risque, des interrogations, demeurent malgré le contexte d’abondance, concernant la couverture des besoins, laquelle pourrait s’avérer inférieure aux valeurs considérées comme satisfaisantes.

Application des TIC à l'atténuation des effets des catastrophes dans ...

International Development Research Centre (IDRC) Digital Library (Canada)

L'Amérique centrale est souvent aux prises avec des inondations et des ... (SIG) et de traitement des images, afin de cartographier les dangers et de modéliser les ... de l'Institut d'étude du développement international de l'Université McGill.

Génétique et adaptation : le point des connaissances chez les volailles

OpenAIRE

Mignon-Grasteau , Sandrine; Faure, J.M.

2002-01-01

De nombreuses études ont porté sur la génétique des capacités d’adaptation des oiseaux, qui ont été modifiées par la domestication, puis la sélection artificielle. Ces études comprennent des comparaisons entre lignées, des estimations de paramètres génétiques et des expériences de sélection. Elles portent sur de nombreux caractères, parmi lesquels le comportement sexuel, alimentaire ou social, la sensibilité au stress. Ces comportements liés aux capacités d’adaptation de l’animal sont général...

Estimation of Atmospheric Methane Surface Fluxes Using a Global 3-D Chemical Transport Model

Science.gov (United States)

Chen, Y.; Prinn, R.

2003-12-01

Accurate determination of atmospheric methane surface fluxes is an important and challenging problem in global biogeochemical cycles. We use inverse modeling to estimate annual, seasonal, and interannual CH4 fluxes between 1996 and 2001. The fluxes include 7 time-varying seasonal (3 wetland, rice, and 3 biomass burning) and 3 steady aseasonal (animals/waste, coal, and gas) global processes. To simulate atmospheric methane, we use the 3-D chemical transport model MATCH driven by NCEP reanalyzed observed winds at a resolution of T42 ( ˜2.8° x 2.8° ) in the horizontal and 28 levels (1000 - 3 mb) in the vertical. By combining existing datasets of individual processes, we construct a reference emissions field that represents our prior guess of the total CH4 surface flux. For the methane sink, we use a prescribed, annually-repeating OH field scaled to fit methyl chloroform observations. MATCH is used to produce both the reference run from the reference emissions, and the time-dependent sensitivities that relate individual emission processes to observations. The observational data include CH4 time-series from ˜15 high-frequency (in-situ) and ˜50 low-frequency (flask) observing sites. Most of the high-frequency data, at a time resolution of 40-60 minutes, have not previously been used in global scale inversions. In the inversion, the high-frequency data generally have greater weight than the weekly flask data because they better define the observational monthly means. The Kalman Filter is used as the optimal inversion technique to solve for emissions between 1996-2001. At each step in the inversion, new monthly observations are utilized and new emissions estimates are produced. The optimized emissions represent deviations from the reference emissions that lead to a better fit to the observations. The seasonal processes are optimized for each month, and contain the methane seasonality and interannual variability. The aseasonal processes, which are less variable, are

La gestion des résultats des entreprises innovantes

OpenAIRE

Dumas, Guillaume

2014-01-01

Cette thèse s’intéresse à la gestion des résultats dans le cadre des entreprises innovantes. Elle est constituée de trois articles. Dans le premier, il s’agit d’examiner si les résultats des entreprises innovantes sont gérés et si le stade de développement des innovations influence cette gestion des résultats. Il apparaît que les résultats des entreprises innovantes sont gérés à la hausse. Cette gestion ne semble intervenir qu’au cours de l’activité d’innovation (c’est-à-dire lorsque les entr...

Evaluation of NASA's Carbon Monitoring System (CMS) Flux Pilot: Terrestrial CO2 Fluxes

Science.gov (United States)

Fisher, J. B.; Polhamus, A.; Bowman, K. W.; Collatz, G. J.; Potter, C. S.; Lee, M.; Liu, J.; Jung, M.; Reichstein, M.

2011-12-01

NASA's Carbon Monitoring System (CMS) flux pilot project combines NASA's Earth System models in land, ocean and atmosphere to track surface CO2 fluxes. The system is constrained by atmospheric measurements of XCO2 from the Japanese GOSAT satellite, giving a "big picture" view of total CO2 in Earth's atmosphere. Combining two land models (CASA-Ames and CASA-GFED), two ocean models (ECCO2 and NOBM) and two atmospheric chemistry and inversion models (GEOS-5 and GEOS-Chem), the system brings together the stand-alone component models of the Earth System, all of which are run diagnostically constrained by a multitude of other remotely sensed data. Here, we evaluate the biospheric land surface CO2 fluxes (i.e., net ecosystem exchange, NEE) as estimated from the atmospheric flux inversion. We compare against the prior bottom-up estimates (e.g., the CASA models) as well. Our evaluation dataset is the independently derived global wall-to-wall MPI-BGC product, which uses a machine learning algorithm and model tree ensemble to "scale-up" a network of in situ CO2 flux measurements from 253 globally-distributed sites in the FLUXNET network. The measurements are based on the eddy covariance method, which uses observations of co-varying fluxes of CO2 (and water and energy) from instruments on towers extending above ecosystem canopies; the towers integrate fluxes over large spatial areas (~1 km2). We present global maps of CO2 fluxes and differences between products, summaries of fluxes by TRANSCOM region, country, latitude, and biome type, and assess the time series, including timing of minimum and maximum fluxes. This evaluation shows both where the CMS is performing well, and where improvements should be directed in further work.

Estimation of annual suspended-sediment fluxes, 1931-95, and evaluation of geomorphic changes, 1950-2010, in the Arkansas River near Tulsa, Oklahoma

Science.gov (United States)

Lewis, Jason M.; Smith, S. Jerrod; Buck, Stephanie D.; Strong, Scott A.

2011-01-01

An understanding of fluvial sediment transport and changing channel morphology can assist planners in making responsible decisions with future riverine development or restoration projects. Sediment rating curves can serve as simple models and can provide predictive tools to estimate annual sediment fluxes. Sediment flux models can aid in the design of river projects by providing insight to past and potential future sediment fluxes. Historical U.S. Geological Survey suspended-sediment and discharge data were evaluated to estimate annual suspended-sediment fluxes for two stations on the Arkansas River located downstream from Keystone Dam in Tulsa County. Annual suspended-sediment fluxes were estimated from 1931-95 for the Arkansas River at Tulsa streamflow-gaging station (07164500) and from 1973-82 for the Arkansas River near Haskell streamflow-gaging station (07165570). The annual flow-weighted suspended-sediment concentration decreased from 1,970 milligrams per liter to 350 milligrams per liter after the completion of Keystone Dam at the Tulsa station. The streambed elevation at the Arkansas River at Tulsa station has changed less than 1 foot from 1970 to 2005, but the thalweg has shifted from a location near the right bank to a position near the left bank. There was little change in the position of most of the banks of the Arkansas River channel from 1950 to 2009. The most substantial change evident from visual inspection of aerial photographs was an apparent decrease in sediment storage in the form of mid-channel and meander bars. The Arkansas River channel between Keystone Dam and the Tulsa-Wagoner County line showed a narrowing and lengthening (increase in sinuosity) over the transition period 1950-77 followed by a steady widening and shortening of the river channel (decrease in sinuosity) during the post-dam (Keystone) periods 1977-85, 1985-2003, and 2003-10.

Squeezing Flux Out of Fat

DEFF Research Database (Denmark)

Gonzalez-Franquesa, Alba; Patti, Mary-Elizabeth

2018-01-01

Merging transcriptomics or metabolomics data remains insufficient for metabolic flux estimation. Ramirez et al. integrate a genome-scale metabolic model with extracellular flux data to predict and validate metabolic differences between white and brown adipose tissue. This method allows both metab...

Upscaling Our Approach to Peatland Carbon Sequestration: Remote Sensing as a Tool for Carbon Flux Estimation.

Science.gov (United States)

Lees, K.; Khomik, M.; Clark, J. M.; Quaife, T. L.; Artz, R.

2017-12-01

Peatlands are an important part of the Earth's carbon cycle, comprising approximately a third of the global terrestrial carbon store. However, peatlands are sensitive to climatic change and human mismanagement, and many are now degraded and acting as carbon sources. Restoration work is being undertaken at many sites around the world, but monitoring the success of these schemes can be difficult and costly using traditional methods. A landscape-scale alternative is to use satellite data in order to assess the condition of peatlands and estimate carbon fluxes. This work focuses on study sites in Northern Scotland, where parts of the largest blanket bog in Europe are being restored from forest plantations. A combination of laboratory and fieldwork has been used to assess the Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP) and respiration of peatland sites in different conditions, and the climatic vulnerability of key peat-forming Sphagnum species. The results from these studies have been compared with spectral data in order to evaluate the extent to which remote sensing can function as a source of information for peatland health and carbon flux models. This work considers particularly the effects of scale in calculating peatland carbon flux. Flux data includes chamber and eddy covariance measurements of carbon dioxide, and radiometric observations include both handheld spectroradiometer results and satellite images. Results suggest that despite the small-scale heterogeneity and unique ecosystem factors in blanket bogs, remote sensing can be a useful tool in monitoring peatland health and carbon sequestration. In particular, this study gives unique insights into the relationships between peatland vegetation, carbon flux and spectral reflectance.

Neutronic study of the two french heavy water reactors; Etude neutronique des deux piles francaises a eau lourde

Energy Technology Data Exchange (ETDEWEB)

Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

The two french reactors - the reactor of Chatillon, named Zoe, and the reactor of Saclay - P2 - were the object of detailed neutronic studies which the main ideas are exposed in this report. These studies were mostly done by the Department of the Reactor Studies (D.E.P.). We have thus studied the distribution of neutronic fluxes; the factors influencing reactivity; the link between reactivity and divergence with the formula of Nordheim; the mean time life of neutrons; neutron spectra s of P2; the xenon effect; or the effect of the different adjustments of the plates and controls bar. (M.B.) [French] Les deux reacteurs francais - la pile de Chatillon, appelee ZOE, et la pile de Saclay, designee dans la suite par P2 - ont fait l'objet d'etudes neutroniques detaillees dont les principales sont exposees dans ce rapport. Ces etudes ont ete pour la plupart effectuees dans le cadre du Departement des Etudes de Piles (D.E.P.). Nous avons ainsi entre autre etudie la distribution du flux neutronique; les facteurs influencants la reactivite; le lien entre reactivite et divergence par la formule de Nordheim; le temps de vie moyen des neutrons; les spectres de neutrons de P2; l'effet xenon; ou encore l'effet des differents reglages des plaques et barres de controles. (M.B.)

Joint estimation of the fast and thermal components of a high neutron flux with a two on-line detector system

Energy Technology Data Exchange (ETDEWEB)

Filliatre, P. [CEA, DEN, SPEx/LDCI, F-13108 Saint-Paul-lez-Durance (France); Laboratoire Commun d' Instrumentation CEA-SCK-CEN (France)], E-mail: philippe.filliatre@cea.fr; Oriol, L.; Jammes, C. [CEA, DEN, SPEx/LDCI, F-13108 Saint-Paul-lez-Durance (France); Laboratoire Commun d' Instrumentation CEA-SCK-CEN (France); Vermeeren, L. [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Laboratoire Commun d' Instrumentation CEA-SCK-CEN (France)

2009-05-21

A fission chamber with a {sup 242}Pu deposit is the best suited detector for on-line measurements of the fast component of a high neutron flux ({approx}10{sup 14}ncm{sup -2}s{sup -1} or more) with a significant thermal component. To get the fast flux, it is, however, necessary to subtract the contribution of the thermal neutrons, which increases with fluence because of the evolution of the isotopic content of the deposit. This paper presents an algorithm that permits, thanks to measurements provided by a {sup 242}Pu fission chamber and a detector for thermal neutrons, to estimate the thermal and the fast flux at any time. An implementation allows to test it with simulated data.

Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy

Directory of Open Access Journals (Sweden)

W. J. F. Acton

2016-06-01

Full Text Available This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs 4 m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone + methacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton-transfer-reaction mass spectrometer (PTR-MS and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS together with the methods of virtual disjunct eddy covariance (using PTR-MS and eddy covariance (using PTR-ToF-MS. Isoprene was the dominant emitted compound with a mean daytime flux of 1.9 mg m−2 h−1. Mixing ratios, recorded 4 m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28-day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTR-ToF-MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m−2 h−1 was calculated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN isoprene emission algorithms (Guenther et al., 2006. A detailed tree-species distribution map for the site enabled the leaf-level emission of isoprene and monoterpenes recorded using gas-chromatography mass spectrometry (GC–MS to be scaled up to produce a bottom-up canopy-scale flux. This was compared with the top-down canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant-species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates.

LARGE-SCALE MAGNETIC HELICITY FLUXES ESTIMATED FROM MDI MAGNETIC SYNOPTIC CHARTS OVER THE SOLAR CYCLE 23

Energy Technology Data Exchange (ETDEWEB)

Yang Shangbin; Zhang Hongqi, E-mail: yangshb@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing (China)

2012-10-10

To investigate the characteristics of large-scale and long-term evolution of magnetic helicity with solar cycles, we use the method of Local Correlation Tracking to estimate the magnetic helicity evolution over solar cycle 23 from 1996 to 2009 using 795 MDI magnetic synoptic charts. The main results are as follows: the hemispheric helicity rule still holds in general, i.e., the large-scale negative (positive) magnetic helicity dominates the northern (southern) hemisphere. However, the large-scale magnetic helicity fluxes show the same sign in both hemispheres around 2001 and 2005. The global, large-scale magnetic helicity flux over the solar disk changes from a negative value at the beginning of solar cycle 23 to a positive value at the end of the cycle, while the net accumulated magnetic helicity is negative in the period between 1996 and 2009.

LARGE-SCALE MAGNETIC HELICITY FLUXES ESTIMATED FROM MDI MAGNETIC SYNOPTIC CHARTS OVER THE SOLAR CYCLE 23

International Nuclear Information System (INIS)

Yang Shangbin; Zhang Hongqi

2012-01-01

To investigate the characteristics of large-scale and long-term evolution of magnetic helicity with solar cycles, we use the method of Local Correlation Tracking to estimate the magnetic helicity evolution over solar cycle 23 from 1996 to 2009 using 795 MDI magnetic synoptic charts. The main results are as follows: the hemispheric helicity rule still holds in general, i.e., the large-scale negative (positive) magnetic helicity dominates the northern (southern) hemisphere. However, the large-scale magnetic helicity fluxes show the same sign in both hemispheres around 2001 and 2005. The global, large-scale magnetic helicity flux over the solar disk changes from a negative value at the beginning of solar cycle 23 to a positive value at the end of the cycle, while the net accumulated magnetic helicity is negative in the period between 1996 and 2009.

131 IDENTITES ET APPRENTISSAGE DES LANGUES ...

African Journals Online (AJOL)

22 juin 2017 ... 1Département de Langues Africaines et Linguistique, Faculté des Arts, Lettres et Sciences Humaines,. Université de .... En revanche, une catégorie de répondants estime que la langue ... de s'exposer soi-même. Ils précisent ...

Injectabilite des coulis de ciment dans des milieux fissures

Science.gov (United States)

Mnif, Thameur

Le travail presente ici est un bilan du travaux de recherche effectues sur l'injectabilite des coulis de ciment dans lu milieux fissures. Un certain nombre de coulis a base de ciment Portland et microfin ont ete selectionnes afin de caracteriser leur capacite a penetrer des milieux fissures. Une partie des essais a ete menee en laboratoire. L'etude rheologique des differents melanges a permis de tester l'influence de l'ajout de superplastifiant et/ou de fumee de silice sur la distribution granulometrique des coulis et par consequent sur leur capacite a injecter des colonnes de sable simulant un milieu fissure donne. La classe granulometrique d'un coulis, sa stabilite et sa fluidite sont apparus comme les trois facteurs principaux pour la reussite d'une injection. Un facteur de finesse a ete defini au cours de cette etude: base sur la classe granulometrique du ciment et sa stabilite, il peut entrer dans la formulation theorique du debit d'injection avant application sur chantier. La deuxieme et derniere partie de l'etude presente les resultats de deux projets de recherche sur l'injection realises sur chantier. L'injection de dalles de beton fissurees a permis le suivi de l'evolution des pressions avec la distance au point d'injection. L'injection de murs de maconnerie a caractere historique a montre l'importance de la definition de criteres de performance des coulis a utiliser pour traiter un milieu donne et pour un objectif donne. Plusieurs melanges peuvent ainsi etre predefinis et mis a disposition sur le chantier. La complementarite des ciments traditionnels et des ciments microfins devient alors un atout important. Le choix d'utilisation de ces melanges est fonction du terrain rencontre. En conclusion, cette recherche etablit une methodologie pour la selection des coulis a base de ciment et des pressions d'injection en fonction de l'ouverture des fissures ou joints de construction.

La gouvernance des risques naturels et la problematique des ...

African Journals Online (AJOL)

Depuis quelques années, la gouvernance des risques naturels dus aux inondations remet en cause les processus de mise en oeuvre des politiques urbaines et la qualité de la structure des aménagements dans les grandes villes du Golfe de Guinée. La perception de la gouvernance et l'application des politiques de ...

Au cœur des services : les larmes au travail

OpenAIRE

Soares, Angelo

2014-01-01

Nous avons cru pendant longtemps qu’il était possible de laisser nos émotions à la porte des organisations. Cela simplifie excessivement la complexité et l’hétérogénéité du travail et, par conséquent, on finit par sous-estimer les effets du travail sur la santé. Notre objectif est de comprendre une forme particulière de l’expression des émotions des travailleuses et travailleurs : les larmes au travail. Pour comprendre cette question, nous utilisons une approche qualitative avec les travaille...

Radioactive contamination of foodstuffs: determination of permissible levels; Contamination radioactive des denrees alimentaires: determination des niveaux admissibles

Energy Technology Data Exchange (ETDEWEB)

Ledermann, S [Commissariat a l' Energie Atomique, Fontenay- aux-Roses (France). Centre d' Etudes Nucleaires

1965-07-01

In a latent air-soil contamination situation, the population would receive 80 per cent of its contamination through foodstuffs. The supervision of this food poses many problems: sampling, radionuclide dosages, etc. It is also necessary to estimate the maximum permissible concentration of radionuclides in foodstuffs, once the maximum exposure limit for the human body has been fixed. The passage of this level to the maximum concentrations is not simple since a) each radionuclide has its own particular effect on the body; b) their concentrations vary from one foodstuff to another, and c) the average amounts of foodstuffs vary from one population to another. Two methods are given here for estimating the maximum permissible concentrations in foodstuffs, together with the first diets likely to become critical when several of them are to be considered simultaneously. The results depend on the way in which the present situation can change to become critical. This evolutionary path can only be estimated approximately. Two methods are therefore given for studying the sensitivity of the results. As an example, a numerical application of these methods using data actually available is given. The data used is naturally incomplete and this will always be true. This application test indicates however two fields in which an improvement is absolutely necessary. 1 - The obtention of multiple observations (simultaneous dosage of at least 2 radionuclides in the same foodstuff, and simultaneous dosage of at least two foodstuffs for the same radionuclide); this assumes a combined effort by the various organisms; 2 - The reaching of an agreement on the dosage methods used by the various organisms since the results actually available are not comparable. (authors) [French] Dans une situation de contamination air-sol latente, la contamination des populations se ferait a 80 pour cent par l'alimentation. Surveiller cette alimentation pose des problemes complexes: echantillonnage, dosage des

Estimation of CO2 flux from targeted satellite observations: a Bayesian approach

International Nuclear Information System (INIS)

Cox, Graham

2014-01-01

We consider the estimation of carbon dioxide flux at the ocean–atmosphere interface, given weighted averages of the mixing ratio in a vertical atmospheric column. In particular we examine the dependence of the posterior covariance on the weighting function used in taking observations, motivated by the fact that this function is instrument-dependent, hence one needs the ability to compare different weights. The estimation problem is considered using a variational data assimilation method, which is shown to admit an equivalent infinite-dimensional Bayesian formulation. The main tool in our investigation is an explicit formula for the posterior covariance in terms of the prior covariance and observation operator. Using this formula, we compare weighting functions concentrated near the surface of the earth with those concentrated near the top of the atmosphere, in terms of the resulting covariance operators. We also consider the problem of observational targeting, and ask if it is possible to reduce the covariance in a prescribed direction through an appropriate choice of weighting function. We find that this is not the case—there exist directions in which one can never gain information, regardless of the choice of weight. (paper)

Nitrous oxide fluxes from grassland in the Netherlands. 1. Statistical analysis of flux-chamber measurements

NARCIS (Netherlands)

Velthof, G.L.; Oenema, O.

1995-01-01

Accurate estimates of total nitrous oxide (N2O) losses from grasslands derived from flux-chamber measurements are hampered by the large spatial and temporal variability of N2O fluxes from these sites. In this study, four methods for the calculation o

Comparative Assessment of Two Vegetation Fractional Cover Estimating Methods and Their Impacts on Modeling Urban Latent Heat Flux Using Landsat Imagery

Directory of Open Access Journals (Sweden)

Kai Liu

2017-05-01

Full Text Available Quantifying vegetation fractional cover (VFC and assessing its role in heat fluxes modeling using medium resolution remotely sensed data has received less attention than it deserves in heterogeneous urban regions. This study examined two approaches (Normalized Difference Vegetation Index (NDVI-derived and Multiple Endmember Spectral Mixture Analysis (MESMA-derived methods that are commonly used to map VFC based on Landsat imagery, in modeling surface heat fluxes in urban landscape. For this purpose, two different heat flux models, Two-source energy balance (TSEB model and Pixel Component Arranging and Comparing Algorithm (PCACA model, were adopted for model evaluation and analysis. A comparative analysis of the NDVI-derived and MESMA-derived VFCs showed that the latter achieved more accurate estimates in complex urban regions. When the two sources of VFCs were used as inputs to both TSEB and PCACA models, MESMA-derived urban VFC produced more accurate urban heat fluxes (Bowen ratio and latent heat flux relative to NDVI-derived urban VFC. Moreover, our study demonstrated that Landsat imagery-retrieved VFC exhibited greater uncertainty in obtaining urban heat fluxes for the TSEB model than for the PCACA model.

Analytical Model for Estimating the Zenith Angle Dependence of Terrestrial Cosmic Ray Fluxes.

Directory of Open Access Journals (Sweden)

Tatsuhiko Sato

Full Text Available A new model called "PHITS-based Analytical Radiation Model in the Atmosphere (PARMA version 4.0" was developed to facilitate instantaneous estimation of not only omnidirectional but also angular differential energy spectra of cosmic ray fluxes anywhere in Earth's atmosphere at nearly any given time. It consists of its previous version, PARMA3.0, for calculating the omnidirectional fluxes and several mathematical functions proposed in this study for expressing their zenith-angle dependences. The numerical values of the parameters used in these functions were fitted to reproduce the results of the extensive air shower simulation performed by Particle and Heavy Ion Transport code System (PHITS. The angular distributions of ground-level muons at large zenith angles were specially determined by introducing an optional function developed on the basis of experimental data. The accuracy of PARMA4.0 was closely verified using multiple sets of experimental data obtained under various global conditions. This extension enlarges the model's applicability to more areas of research, including design of cosmic-ray detectors, muon radiography, soil moisture monitoring, and cosmic-ray shielding calculation. PARMA4.0 is available freely and is easy to use, as implemented in the open-access EXcel-based Program for Calculating Atmospheric Cosmic-ray Spectrum (EXPACS.

Estimating Hydrologic Fluxes, Crop Water Use, and Agricultural Land Area in China using Data Assimilation

Science.gov (United States)

Smith, Tiziana; McLaughlin, Dennis B.; Hoisungwan, Piyatida

2016-04-01

Crop production has significantly altered the terrestrial environment by changing land use and by altering the water cycle through both co-opted rainfall and surface water withdrawals. As the world's population continues to grow and individual diets become more resource-intensive, the demand for food - and the land and water necessary to produce it - will continue to increase. High-resolution quantitative data about water availability, water use, and agricultural land use are needed to develop sustainable water and agricultural planning and policies. However, existing data covering large areas with high resolution are susceptible to errors and can be physically inconsistent. China is an example of a large area where food demand is expected to increase and a lack of data clouds the resource management dialogue. Some assert that China will have insufficient land and water resources to feed itself, posing a threat to global food security if they seek to increase food imports. Others believe resources are plentiful. Without quantitative data, it is difficult to discern if these concerns are realistic or overly dramatized. This research presents a quantitative approach using data assimilation techniques to characterize hydrologic fluxes, crop water use (defined as crop evapotranspiration), and agricultural land use at 0.5 by 0.5 degree resolution and applies the methodology in China using data from around the year 2000. The approach uses the principles of water balance and of crop water requirements to assimilate existing data with a least-squares estimation technique, producing new estimates of water and land use variables that are physically consistent while minimizing differences from measured data. We argue that this technique for estimating water fluxes and agricultural land use can provide a useful basis for resource management modeling and policy, both in China and around the world.

Revisiting the paper “Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective”

DEFF Research Database (Denmark)

Kustas, William P.; Nieto, Hector; Morillas, Laura

2016-01-01

The recent paper by Morillas et al. [Morillas, L. et al. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective, Remote Sens. Environ. 136, 234–246, 2013] evaluates the two-source model (TSM) of Norman et al. (1995) with re......The recent paper by Morillas et al. [Morillas, L. et al. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective, Remote Sens. Environ. 136, 234–246, 2013] evaluates the two-source model (TSM) of Norman et al. (1995......) with revisions by Kustas and Norman (1999) over a semiarid tussock grassland site in southeastern Spain. The TSM - in its current incarnation, the two-source energy balance model (TSEB) - was applied to this landscape using ground-based infrared radiometer sensors to estimate both the composite surface...... greenness and local leaf area index values as well as modifications to the coefficients of the soil resistance formulation to account for the very rough (rocky) soil surface conditions with a clumped canopy. This indicates that both limitations in remote estimates of biophysical indicators of the canopy...

Non-stationary (13)C-metabolic flux ratio analysis.

Science.gov (United States)

Hörl, Manuel; Schnidder, Julian; Sauer, Uwe; Zamboni, Nicola

2013-12-01

(13)C-metabolic flux analysis ((13)C-MFA) has become a key method for metabolic engineering and systems biology. In the most common methodology, fluxes are calculated by global isotopomer balancing and iterative fitting to stationary (13)C-labeling data. This approach requires a closed carbon balance, long-lasting metabolic steady state, and the detection of (13)C-patterns in a large number of metabolites. These restrictions mostly reduced the application of (13)C-MFA to the central carbon metabolism of well-studied model organisms grown in minimal media with a single carbon source. Here we introduce non-stationary (13)C-metabolic flux ratio analysis as a novel method for (13)C-MFA to allow estimating local, relative fluxes from ultra-short (13)C-labeling experiments and without the need for global isotopomer balancing. The approach relies on the acquisition of non-stationary (13)C-labeling data exclusively for metabolites in the proximity of a node of converging fluxes and a local parameter estimation with a system of ordinary differential equations. We developed a generalized workflow that takes into account reaction types and the availability of mass spectrometric data on molecular ions or fragments for data processing, modeling, parameter and error estimation. We demonstrated the approach by analyzing three key nodes of converging fluxes in central metabolism of Bacillus subtilis. We obtained flux estimates that are in agreement with published results obtained from steady state experiments, but reduced the duration of the necessary (13)C-labeling experiment to less than a minute. These results show that our strategy enables to formally estimate relative pathway fluxes on extremely short time scale, neglecting cellular carbon balancing. Hence this approach paves the road to targeted (13)C-MFA in dynamic systems with multiple carbon sources and towards rich media. © 2013 Wiley Periodicals, Inc.

Models of the Strongly Lensed Quasar DES J0408-5354

Energy Technology Data Exchange (ETDEWEB)

Agnello, A.; et al.

2017-02-01

We present gravitational lens models of the multiply imaged quasar DES J0408-5354, recently discovered in the Dark Energy Survey (DES) footprint, with the aim of interpreting its remarkable quad-like configuration. We first model the DES single-epoch $grizY$ images as a superposition of a lens galaxy and four point-like objects, obtaining spectral energy distributions (SEDs) and relative positions for the objects. Three of the point sources (A,B,D) have SEDs compatible with the discovery quasar spectra, while the faintest point-like image (G2/C) shows significant reddening and a `grey' dimming of $\\approx0.8$mag. In order to understand the lens configuration, we fit different models to the relative positions of A,B,D. Models with just a single deflector predict a fourth image at the location of G2/C but considerably brighter and bluer. The addition of a small satellite galaxy ($R_{\\rm E}\\approx0.2$") in the lens plane near the position of G2/C suppresses the flux of the fourth image and can explain both the reddening and grey dimming. All models predict a main deflector with Einstein radius between $1.7"$ and $2.0",$ velocity dispersion $267-280$km/s and enclosed mass $\\approx 6\\times10^{11}M_{\\odot},$ even though higher resolution imaging data are needed to break residual degeneracies in model parameters. The longest time-delay (B-A) is estimated as $\\approx 85$ (resp. $\\approx125$) days by models with (resp. without) a perturber near G2/C. The configuration and predicted time-delays of J0408-5354 make it an excellent target for follow-up aimed at understanding the source quasar host galaxy and substructure in the lens, and measuring cosmological parameters. We also discuss some lessons learnt from J0408-5354 on lensed quasar finding strategies, due to its chromaticity and morphology.

Promouvoir l'entrepreneuriat inclusif des jeunes et des femmes ...

International Development Research Centre (IDRC) Digital Library (Canada)

Le projet vise à analyser la contribution réelle et potentielle de l'entrepreneuriat inclusif au bien-être des jeunes et des femmes en Côte d'Ivoire, au Burkina Faso et au Kenya. Après un état des lieux de la pratique de l'entrepreneuriat inclusif dans chacun des pays ciblés, l'équipe de recherche étudiera son incidence sur ...

Modeling radon flux from the earth's surface

International Nuclear Information System (INIS)

Schery, S.D.; Wasiolek, M.A.

1998-01-01

We report development of a 222 Rn flux density model and its use to estimate the 222 Rn flux density over the earth's land surface. The resulting maps are generated on a grid spacing of 1 0 x 1 0 using as input global data for soil radium, soil moisture, and surface temperature. While only a first approximation, the maps suggest a significant regional variation (a factor of three is not uncommon) and a significant seasonal variation (a factor of two is not uncommon) in 222 Rn flux density over the earth's surface. The estimated average global flux density from ice-free land is 34 ± 9 mBq m -2 s -1 . (author)

Theoretical and Experimental Methods in Hypersonic Flows (Les Methodes Theoriques et Experimentales pour l’Etude Des Ecoulements Hypersoniques)

Science.gov (United States)

1993-04-01

vibrationicl (fans des tuNZ~rcs tesi pri~sentee. Pour les conditions g~n~iatr-iccs consid~r~es, 1 onisation I es tenoes tie flux die Moude parfait son...lenus figures possibles, deux initialisations du champ valcurs de Y/delta (Y ktant Is distance A Ia peau wont disponibles : et DELTA , I’kpaissenr de...maillage support on calcule Plus de details sont disponibles dans les les distances des nocuds A la peau tres references . prkciskment. Le code N.S

Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: Model estimates for different shelf environments and sensitivity to global change

NARCIS (Netherlands)

Krumins, V.; Gehlen, M.; Arndt, S.; Van Cappellen, P.; Regnier, P.

2013-01-01

We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC) and alkalinity (AT) from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation,

Prise en charge des urgences au service d'accueil des urgences ...

African Journals Online (AJOL)

Introduction: La prise en charge des patients dans les services d'accueil des urgences est une des meilleures vitrines d'un système de santé. En Afrique subsaharienne, la gestion des urgences se heurte à des difficultés humaines et matérielles. Le but de ce travail était d'évaluer les difficultés de prise en charge au Service ...

Résoudre le problème de l'emploi des jeunes en Afrique | CRDI ...

International Development Research Centre (IDRC) Digital Library (Canada)

17 déc. 2015 ... L'emploi des jeunes est l'un des défis les plus pressants auxquels est confrontée l'Afrique subsaharienne. L'ONU estime que le groupe des jeunes de 15 à 24 ans augmentera d'environ six millions par année au cours de la prochaine décennie; d'ici 2050, l'âge médian sera à peine de 24 ans. La plupart ...

Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

Directory of Open Access Journals (Sweden)

M. Lockwood

2004-04-01

Full Text Available Results from all phases of the orbits of the Ulysses spacecraft have shown that the magnitude of the radial component of the heliospheric field is approximately independent of heliographic latitude. This result allows the use of near-Earth observations to compute the total open flux of the Sun. For example, using satellite observations of the interplanetary magnetic field, the average open solar flux was shown to have risen by 29% between 1963 and 1987 and using the aa geomagnetic index it was found to have doubled during the 20th century. It is therefore important to assess fully the accuracy of the result and to check that it applies to all phases of the solar cycle. The first perihelion pass of the Ulysses spacecraft was close to sunspot minimum, and recent data from the second perihelion pass show that the result also holds at solar maximum. The high level of correlation between the open flux derived from the various methods strongly supports the Ulysses discovery that the radial field component is independent of latitude. We show here that the errors introduced into open solar flux estimates by assuming that the heliospheric field's radial component is independent of latitude are similar for the two passes and are of order 25% for daily values, falling to 5% for averaging timescales of 27 days or greater. We compare here the results of four methods for estimating the open solar flux with results from the first and second perehelion passes by Ulysses. We find that the errors are lowest (1–5% for averages over the entire perehelion passes lasting near 320 days, for near-Earth methods, based on either interplanetary magnetic field observations or the aa geomagnetic activity index. The corresponding errors for the Solanki et al. (2000 model are of the order of 9–15% and for the PFSS method, based on solar magnetograms, are of the order of 13–47%. The model of Solanki et al. is based on the continuity equation of open flux, and uses the

OGM Diffusion des OGM et impact pour les agriculteurs : quels sont les liens ?

Directory of Open Access Journals (Sweden)

Lemarie Stéphane

2001-05-01

Full Text Available Les OGM actuellement sur le marché présentent des innovations sur des fonctions de protection des plantes. Selon les problèmes de protection des plantes, les gains des agriculteurs liés à l’adoption des OGM sont très variables. Cette hétérogénéité pose d’importants problèmes méthodologiques pour pouvoir estimer correctement la distribution des gains pour l’ensemble des agriculteurs. Une synthèse de plusieurs études américaines est réalisée ici et met bien en évidence la diversité des méthodes utilisées, chacune d’elles présentant ses avantages et ses limites. Globalement, si la diffusion des OGM est un fait indéniable, les études ne permettent pas de tirer des conclusions aussi nettes quant à l’impact des OGM pour tous les agriculteurs qui adoptent ces produits, et cela en particulier pour le soja. Cette absence de conclusion s’explique en grande partie par la difficulté à mesurer certains facteurs qui influencent le comportement d’adoption, comme par exemple la simplification de la conduite des cultures. En contrepartie, il faut noter que les études présentées ici ne prennent pas en compte un certain nombre d’effets indirects qui peuvent faire diminuer les gains des agriculteurs.

Estimation of sensible and latent heat flux from natural sparse vegetation surfaces using surface renewal

Science.gov (United States)

Zapata, N.; Martínez-Cob, A.

2001-12-01

This paper reports a study undertaken to evaluate the feasibility of the surface renewal method to accurately estimate long-term evaporation from the playa and margins of an endorreic salty lagoon (Gallocanta lagoon, Spain) under semiarid conditions. High-frequency temperature readings were taken for two time lags ( r) and three measurement heights ( z) in order to get surface renewal sensible heat flux ( HSR) values. These values were compared against eddy covariance sensible heat flux ( HEC) values for a calibration period (25-30 July 2000). Error analysis statistics (index of agreement, IA; root mean square error, RMSE; and systematic mean square error, MSEs) showed that the agreement between HSR and HEC improved as measurement height decreased and time lag increased. Calibration factors α were obtained for all analyzed cases. The best results were obtained for the z=0.9 m ( r=0.75 s) case for which α=1.0 was observed. In this case, uncertainty was about 10% in terms of relative error ( RE). Latent heat flux values were obtained by solving the energy balance equation for both the surface renewal ( LESR) and the eddy covariance ( LEEC) methods, using HSR and HEC, respectively, and measurements of net radiation and soil heat flux. For the calibration period, error analysis statistics for LESR were quite similar to those for HSR, although errors were mostly at random. LESR uncertainty was less than 9%. Calibration factors were applied for a validation data subset (30 July-4 August 2000) for which meteorological conditions were somewhat different (higher temperatures and wind speed and lower solar and net radiation). Error analysis statistics for both HSR and LESR were quite good for all cases showing the goodness of the calibration factors. Nevertheless, the results obtained for the z=0.9 m ( r=0.75 s) case were still the best ones.

Connaissances, attitudes et pratiques des prestataires de santé des ...

African Journals Online (AJOL)

... des prestataires interrogés avaient respectivement une bonne connaissance des facteurs de risque et des moyens de dépistage. Les signes évocateurs et les examens complémentaires nécessaires au diagnostic du cancer du sein étaient connus par 15,3 % des prestataires. La définition du cancer du sein et les moyens ...

DES Science Portal: Computing Photometric Redshifts

Energy Technology Data Exchange (ETDEWEB)

Gschwend, Julia [LIneA, Rio de Janeiro

2016-01-01

An important challenge facing photometric surveys for cosmological purposes, such as the Dark Energy Survey (DES), is the need to produce reliable photometric redshifts (photo-z). The choice of adequate algorithms and configurations and the maintenance of an up-to-date spectroscopic database to build training sets, for example, are challenging tasks when dealing with large amounts of data that are regularly updated and constantly growing. In this paper, we present the first of a series of tools developed by DES, provided as part of the DES Science Portal, an integrated web-based data portal developed to facilitate the scientific analysis of the data, while ensuring the reproducibility of the analysis. We present the DES Science Portal photometric redshift tools, starting from the creation of a spectroscopic sample to training the neural network photo-z codes, to the final estimation of photo-zs for a large photometric catalog. We illustrate this operation by calculating well calibrated photo-zs for a galaxy sample extracted from the DES first year (Y1A1) data. The series of processes mentioned above is run entirely within the Portal environment, which automatically produces validation metrics, and maintains the provenance between the different steps. This system allows us to fine tune the many steps involved in the process of calculating photo-zs, making sure that we do not lose the information on the configurations and inputs of the previous processes. By matching the DES Y1A1 photometry to a spectroscopic sample, we define different training sets that we use to feed the photo-z algorithms already installed at the Portal. Finally, we validate the results under several conditions, including the case of a sample limited to i<22.5 with the color properties close to the full DES Y1A1 photometric data. This way we compare the performance of multiple methods and training configurations. The infrastructure presented here is an effcient way to test several methods of

Estimating chemical composition of atmospheric deposition fluxes from mineral insoluble particles deposition collected in the western Mediterranean region

Directory of Open Access Journals (Sweden)

Y. Fu

2017-11-01

Full Text Available In order to measure the mass flux of atmospheric insoluble deposition and to constrain regional models of dust simulation, a network of automatic deposition collectors (CARAGA has been installed throughout the western Mediterranean Basin. Weekly samples of the insoluble fraction of total atmospheric deposition were collected concurrently on filters at five sites including four on western Mediterranean islands (Frioul and Corsica, France; Mallorca, Spain; and Lampedusa, Italy and one in the southern French Alps (Le Casset, and a weighing and ignition protocol was applied in order to quantify their mineral fraction. Atmospheric deposition is both a strong source of nutrients and metals for marine ecosystems in this area. However, there are few data on trace-metal deposition in the literature, since their deposition measurement is difficult to perform. In order to obtain more information from CARAGA atmospheric deposition samples, this study aimed to test their relevance in estimating elemental fluxes in addition to total mass fluxes. The elemental chemical analysis of ashed CARAGA filter samples was based on an acid digestion and an elemental analysis by inductively coupled plasma atomic emission spectroscopy (ICP-AES and mass spectrometry (MS in a clean room. The sampling and analytical protocols were tested to determine the elemental composition for mineral dust tracers (Al, Ca, K, Mg and Ti, nutrients (P and Fe and trace metals (Cd, Co, Cr, Cu, Mn, Ni, V and Zn from simulated wet deposition of dust analogues and traffic soot. The relative mass loss by dissolution in wet deposition was lower than 1 % for Al and Fe, and reached 13 % for P due to its larger solubility in water. For trace metals, this loss represented less than 3 % of the total mass concentration, except for Zn, Cu and Mn for which it could reach 10 %, especially in traffic soot. The chemical contamination during analysis was negligible for all the elements except for Cd

Estimation of In-canopy Flux Distributions of Reactive Nitrogen and Sulfur within a Mixed Hardwood Forest in Southern Appalachia

Science.gov (United States)

Wu, Z.; Walker, J. T.; Chen, X.; Oishi, A. C.; Duman, T.

2017-12-01

Estimating the source/sink distribution and vertical fluxes of air pollutants within and above forested canopies is critical for understanding biological, physical, and chemical processes influencing the soil-vegetation-atmosphere exchange. The vertical source-sink profiles of reactive nitrogen and sulfur were examined using multiple inverse modeling methods in a mixed hardwood forest in the southern Appalachian Mountains where the ecosystem is highly sensitive to loads of pollutant from atmospheric depositions. Measurements of the vertical concentration profiles of ammonia (NH3), nitric acid (HNO3), sulfur dioxide (SO2), and ammonium (NH4+), nitrate (NO3-), and sulfate (SO42-) in PM2.5 were measured during five study periods between May 2015 and August 2016. The mean concentration of NH3 decreased with height in the upper canopy and increased below the understory toward the forest floor, indicating that the canopy was a sink for NH3 but the forest floor was a source. All other species exhibited patterns of monotonically decreasing concentration from above the canopy to the forest floor. Using the measured concentration profiles, we simulated the within-canopy flow fields and estimated the vertical source-sink flux profiles using three inverse approaches: a Eulerian high-order closure model (EUL), a Lagrangian localized near-field (LNF) model, and a new full Lagrangian stochastic model (LSM). The models were evaluated using the within- and above-canopy eddy covariance flux measurements of heat, CO2 and H2O. Differences between models were analyzed and the flux profiles were used to investigate the origin and fate of reactive nitrogen and sulfur compounds within the canopy. The knowledge gained in this study will benefit the development of soil-vegetation-atmosphere models capable of partitioning canopy-scale deposition of nitrogen and sulfur to specific ecosystem compartments.

The impact of lateral carbon fluxes on the European carbon balance

International Nuclear Information System (INIS)

Ciais, P.; Hauglustaine, D.; Borges, A.V.; Abril, G.; Meybeck, M.; Folberth, G.; Janssens, I.A.

2008-01-01

To date, little is known about the impact of processes which cause lateral carbon fluxes over continents, and from continents to oceans on the CO 2 - and carbon budgets at local, regional and continental scales. Lateral carbon fluxes contribute to regional carbon budgets as follows: Ecosystem CO 2 sink=Ecosystem carbon accumulation + Lateral carbon fluxes. We estimated the contribution of wood and food product trade, of emission and oxidation of reduced carbon species, and of river erosion and transport as lateral carbon fluxes to the carbon balance of Europe (EU-25). The analysis is completed by new estimates of the carbon fluxes of coastal seas. We estimated that lateral transport (all processes combined) is a flux of 165 Tg C yr -1 at the scale of EU-25. The magnitude of lateral transport is thus comparable to current estimates of carbon accumulation in European forests. The main process contributing to the total lateral flux out of Europe is the flux of reduced carbon compounds, corresponding to the sum of non-CO 2 gaseous species (CH 4 , CO, hydrocarbons,... ) emitted by ecosystems and exported out of the European boundary layer by the large scale atmospheric circulation. (authors)

Neutron moderation at very low temperatures (1691); Moderation des neutrons aux tres basses temperatures (1961)

Energy Technology Data Exchange (ETDEWEB)

Lacaze, A [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1961-04-15

Starting from Harwell experiment carried out inside a low-power reactor, we intended to maintain a liquid hydrogen cell in a channel of the EL3 reactor (at Saclay) whose thermal neutrons flux is 10{sup 14} neutrons/cm{sup 2}/s. We tried to work out a device giving off an important beam of cold neutrons and able to operate in a way as automatic as possible during many consecutive day without a stop. Several circuits have already been achieved at very low temperatures but they brought out volumes and fluxes much lower than those we used this time. The difficulties we have met in carrying out such a device arose on the one hand from the very high energy release to which any kind of experiment is inevitably submitted when placed near the core of the reactor, on the other, hand from the very little room which is available in experimental channels of reactors. In such condition, it is necessary to use a moderator as effective as possible. This study is divided into three parts ; in the first part, we try to determine: a) conditions in which moderation takes place, hence the volume of the cell; b) materials likely to be used at low temperature and in pile; c) cooling system; hence we had to study fluid flow conditions at very low temperatures in very long ducts. The second part is devoted to the description of the device. The third part ventilates the results we have obtained. (author) [French] Partant de l'experience de Harwell faite dans une pile de faible puissance, nous nous sommes propose de maintenir une cellule d'hydrogene liquide dans un canal de la pile EL3 de Saclay dont le flux de neutrons thermiques est de 10{sup 14} neutrons par seconde et par cm{sup 2}. Nous avons cherche a realiser une installation donnant un faisceau de neutrons froids important, et pouvant fonctionner d'une maniere aussi automatique que possible, pendant des periodes de plusieurs jours sans arret. Plusieurs circuits aux tres basses temperatures ont deja ete realises, mais ils ne mettaient

La demande de bois-énergie à Ouagadougou : esquisse d’évaluation de l’impact physique et des échecs des politiques de prix

Directory of Open Access Journals (Sweden)

Boukary Ouedraogo

2006-03-01

Full Text Available Cet article vise à évaluer non seulement la demande de bois-énergie de la ville de Ouagadougou, l’impact de cette demande sur le patrimoine forestier de l’aire d’approvisionnement de cette ville, mais aussi l’esquisse d’une évaluation des échecs des politiques de prix du bois-énergie. Les méthodes d’évaluation de la consommation de cette source d’énergie sont passées en revue au regard des conditions d’offre de la ressource et des données existantes sur la demande de cette ressource. Les données sur les inventaires forestiers de l’aire d’approvisionnement de Ouagadougou en bois-énergie, ainsi que des enquêtes sur les ménages et les artisans ont permis d’estimer la consommation de Ouagadougou en bois-énergie et son impact sur l’épuisement des ressources forestières du pays.This paper aims at evaluating not only the wood-energy demand of Ouagadougou, the physic impact of this city wood energy consumption on the forest of its provisioning area, together with the causes of wood-energy price policy failures. The evaluation’s methods of wood energy consumption are reviewed in comparison with the resource supply conditions and the availability on data of wood resource demand. The data on the forest inventories of the wood-energy provisioning surface of Ouagadougou, as well as investigations into the households and the craftsmen allows estimating the consumption of Ouagadougou in wood-energy and its impact on the forest resources’ depletion. some complementary analysis have been done on the main causes of wood energy price policy failures.

Estimating biological elementary flux modes that decompose a flux distribution by the minimal branching property

DEFF Research Database (Denmark)

Chan, Siu Hung Joshua; Solem, Christian; Jensen, Peter Ruhdal

2014-01-01

biologically feasible EFMs by considering their graphical properties. A previous study on the transcriptional regulation of metabolic genes found that distinct branches at a branch point metabolite usually belong to distinct metabolic pathways. This suggests an intuitive property of biologically feasible EFMs......, i.e. minimal branching. RESULTS: We developed the concept of minimal branching EFM and derived the minimal branching decomposition (MBD) to decompose flux distributions. Testing in the core Escherichia coli metabolic network indicated that MBD can distinguish branches at branch points and greatly...... knowledge, which facilitates interpretation. Comparison of the methods applied to a complex flux distribution in Lactococcus lactis similarly showed the advantages of MBD. The minimal branching EFM concept underlying MBD should be useful in other applications....

Eddy covariance N2O flux measurements at low flux rates: results from the InGOS campaign in a Danish willow field.

Science.gov (United States)

Ibrom, Andreas; Brümmer, Christian; Hensen, Arjan; van Asperen, Hella; Carter, Mette S.; Gasche, Rainer; Famulari, Daniela; Kutsch, Werner; Pilegaard, Kim; Ambus, Per

2014-05-01

Nitrous oxide (N2O) fluxes from soils are characterised by their high spatial and temporal variability. The fluxes depend on the availability of the substrates for nitrification and denitrification and soil physical and chemical conditions that control the metabolic microbial activity. The sporadic nature of the fluxes and their high sensitivity to alterations of the soil climate put very high demands on measurement approaches. Laser spectroscopy enables accurate and fast response detection of atmospheric N2O concentrations and is used for eddy covariance (EC) flux measurements. Alternatively N2O fluxes can be measured with chambers together with high precision analysers. Differences in the measurement approaches and system designs are expected to have a considerable influence on the accuracy of the flux estimation. This study investigates how three different eddy covariance systems perform in a situation of low N2O fluxes from a flat surface. Chamber flux measurements with differing chamber and analyser designs are used for comparison. In April 2013, the EU research infrastructure project InGOS (http://www.ingos-infrastructure.eu/) organised a campaign of N2O flux measurements in a willow plantation close to the Risø Campus of the Technical University of Denmark. The willow field was harvested in February 2013 and received mineral fertiliser equivalent to 120 kg N ha-1 before the campaign started. Three different eddy covariance systems took part in the campaign: two Aerodyne quantum cascade laser (QCL) based systems and one Los Gatos Research off-axis integrated-cavity-output spectroscopy (ICOS) system for N2O and CO. The sonic anemometers were all installed at 2 m height above the bare ground. Gill R3 type sonic anemometers were used with QCL systems and a Gil HS-50 with the ICOS system. The 10 Hz raw data were analysed with group specific softwares and procedures. The local conditions in the exceptionally cold and dry spring 2013 did not lead to large N2O flux

[Project for] a high-flux extracted neutron beam reactor [for physicists]; Un [projet de] reacteur a haut flux et faisceaux sortis [pour physiciens

Energy Technology Data Exchange (ETDEWEB)

Ageron, P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-07-01

tubes and the experimental equipment which can support doses much higher than the ones which are biologically permissible. The final part of the communication describes the studies carried out on the realization of a liquid hydrogen cold sink, one of the most important experimental devices envisaged. (authors) [French] Les besoins francais en canaux pour sortie de neutrons de differentes energies sont brievement indiques. L'interet bien connu des neutrons froids (plus de 4 Angstroem) est souligne. Les grandes lignes d'un reacteur permettant de satisfaire les physiciens sont esquissees. Ce sont les suivantes: 1 - Flux dans l'eau lourde du reflecteur de l'ordre de 7. 10{sup 14} thermiques. 2 - Souplesse d'emploi maximum obtenue par: - separation physique du coeur et du reflecteur, - independance des experiences entre elles, - possibilite de modification, sans interruption notable du fonctionnement de la pile, des experiences physiques jusqu'a - et y compris - la nature du reflecteur utilise, - reduction au minimum des protections fixes; emploi largement generalise des protections liquides (eau) et fluidisees (sables). 3 - Continuite technologique aussi grande que possible avec les reacteurs de recherche francais existant ou en construction (SILOE, PEGASE, OSIRIS). 4 - Surete de fonctionnement recherche par la simplicite de conception. 5 - Minimisation des frais de construction. La reduction des frais d'exploitation est recherchee plutot indirectement par la simplicite des solutions et la reduction du personnel d'exploitation, que directement par la minimisation des consommations d'elements combustibles et d'energie. La solution preconisee peut etre decrite comme un reacteur de type piscine a coeur clos, non pressurise, tres sous modere par l'eau legere de refroidissement. Entourant le reacteur, se trouvent un certain nombre de 'canaux boucles' comprenant chacun: - une portion du reflecteur (eau lourde dans l'exemple decrit), - une portion de canal d'extraction de neutrons

Usages des TIC et socialisation professionnelle des enseignants-chercheurs

OpenAIRE

Lavielle-Gutnik, Nathalie; Massou, Luc

2013-01-01

En prenant appui sur une nouvelle analyse des données recueillies dans l’enquête Tec-Meus (2008-2011, MSH Lorraine) sur la place accordée par des enseignants-chercheurs en sciences humaines et sociales aux technologies de l’information et de la communication (TIC) dans leur activité d’enseignement, nous souhaitons nous focaliser dans cet article sur la compréhension des processus de socialisation professionnelle en jeu dans leur usage déclaré des TIC. Par socialisation professionnelle, nous e...

Source, flux and balance of atmospheric deposition of metals at Ile-de-France; Source, flux et bilan des retombees atmospheriques de metaux en Ile de France

Energy Technology Data Exchange (ETDEWEB)

Azimi, S

2004-07-15

evidenced. At the Seine River catchment scale, the atmospheric deposition levels were of the same order of magnitude as Seine River particle contents measured at the catchment estuary (Poses). The flux ratio between atmospheric inputs and Seine particles ranged between 0.8 and 4.8 for Al, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn. The importance of atmospheric deposition of metals was estimated on agricultural and urban areas. In the first case, the atmospheric fallout appears as the main input way of Cu, Ni and Pb to agro-systems while Cd is mainly introduced by fertilizers. These two input ways induced an increase of Cd, Ni and Pb in the cultivated horizon with an annual balance reaching 0.33, 0.014 and 0.014 %, respectively, of actual stocks while the Cu showed a decrease with an annual balance reaching 0.024 %. In the second case, atmospheric deposition was compared to roof and street runoff. The atmospheric deposition is the main introducing way of most of considered elements, compared to roof runoff excepting Cu, Pb, Ti and Zn which are mainly emitted by the latter. Nevertheless, compared to street runoff, atmospheric deposition levels are 1.5 to 27 times lower than street cleaning ones showing that atmospheric introducing way is not the main introducing way of metals in urban areas. The source investigation on atmospheric deposition was performed using several tools developed during this study. The results allow the characterisation of the anthropogenic sources considered using specific elements or ratios. These tools were applied to the atmospheric deposition data but they did not allowed the determination of anthropogenic activities because of the atmospheric mixture. (author)

Evaluer des études de gestion des entreprises : combiner des éléments principales avec des éléments pratiques

NARCIS (Netherlands)

Pennink, B.J.W.

2002-01-01

Evaluer la recherche de gestion demande une combinaison des critères classiques et des critères pratiques. Par cette combinaison il est possible de trouver une réponse cerrecte concernant la validité et l'effet de la recherche. Dans cet article nous allons décrire comment une combinaison des

Aspects des Onychomycoses chez des patients camerounais de ...

African Journals Online (AJOL)

... biologiques et évolutifs des onychomycoses chez des patients camerounais. Méthode : Il s'agit d'une étude rétrospective et descriptive menée de mars 2011 à mars 2014 dans l'unité de dermatologie de l'hôpital général de Douala (HGD), incluant des patients chez lesquels le diagnostic d'onychomycose avait été posé.

Couplage des équations électriques et magnétiques

Science.gov (United States)

Lombard, P.; Meunier, G.

1993-03-01

The non-linear analysis of electrical devices is often limited by the complexity of the power supply. In effect, in the case of solid conductors, the voltage is required, while in the case of stranded conductors, the current must be known. These restrictions are due to the nature of the field equations. A new formulation is proposed which allows the possibility to choose the power supply and choose any kind of connection between components. Two types of “magnetic conductors” are considered: solid conductors, in which eddy current can be induced and stranded conductors without eddy current. An equation combining the magnetic potential, the current and the voltage is established for each conductor. This equation is introduced into a conventional circuit analysis method. The magnetic field and circuit equations can be solved simultaneously in the resulting system. An implicit method is used to discretize the equation in time. A NewtonRaphson linearization algorithm is used to handle problems that include materials with non linear properties. This formulation is used in the commercial program FLUX2D. To illustrate one of the many applications, an A.C. electromagnet is studied. L'analyse des dispositifs électrotechniques est souvent limitée par les sources d'alimentation. En effet, dans le cas de conducteurs massifs, la valeur de la tension est requise, alors que, dans le cas de conducteurs bobinés, le courant doit être connu. Ces restrictions sont dues à la nature des équations de champ. Une nouvelle formulation est proposée qui permet de choisir la source d'alimentation et d'autoriser tous les types de connexions entre les composants. Deux types de “conducteurs magnétiques” sont considérés : les conducteurs massifs, dans lesquels des courants de Foucault peuvent être induits et les conducteurs bobinés sans courants de Foucault. Une équation associant le potentiel vecteur magnétique, le courant et la tension est établie pour chaque type de

Some ways for the investigation of the solar modulation of cosmic electrons; Moyens d'etude de la modulation solaire des electrons cosmiques

Energy Technology Data Exchange (ETDEWEB)

Mercier, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

In this report, we are investigating the solar modulation of cosmic electrons, in different ways. By comparing the calculated intensity with the measured intensity of positrons, we can evaluate the solar modulation of positrons, hence the modulation of negatons, since the modulation of negatons is probably the same that for positrons. By comparing the electron spectrum in interstellar space needed to explain the galactic background radio emission with that observed near the earth, we can deduce information about the modulation of electrons. We can investigate the modulation through the observation of its variations during the solar cycle. This different ways lead us to compatible results. In spite of the fact that the precision of the experimental data is poor, the modulation can be represented by: a constant or a form in exp(- K/Ro{beta}) under the rigidity Ro {approx_equal} 0,5 BV; a form in exp(- K/R) or exp(- K/R{beta}) above this rigidity. In addition, the investigation of both electrons and protons displays that the diffusion-convection theory is inadequate to explain all the features of the solar modulation. (author) [French] Dans le present rapport, nous etudions la modulation solaire des electrons cosmiques a l'aide de plusieurs methodes. Par comparaison entre l'intensite calculee et l'intensite mesuree des positons, on peut evaluer la modulation solaire des positons, et aussi des negatons, puisque la modulation des negatons est probablement la meme que celle des positons. Par le calcul, a partir du bruit de fond radio, du flux des electrons a l'exterieur du systeme solaire et sa confrontation avec le flux observe a l'orbite de la Terre permet l'etude de la modulation solaire des electrons. On peut aussi analyser ce phenomene de modulation pour l'etude de ses variations au cours du cycle solaire. Ces diverses methodes donnent des resultats compatibles. En depit de la precision mediocre des donnees experimentales, on peut caracteriser la modulation par: une

PFA toolbox: a MATLAB tool for Metabolic Flux Analysis.

Science.gov (United States)

Morales, Yeimy; Bosque, Gabriel; Vehí, Josep; Picó, Jesús; Llaneras, Francisco

2016-07-11

Metabolic Flux Analysis (MFA) is a methodology that has been successfully applied to estimate metabolic fluxes in living cells. However, traditional frameworks based on this approach have some limitations, particularly when measurements are scarce and imprecise. This is very common in industrial environments. The PFA Toolbox can be used to face those scenarios. Here we present the PFA (Possibilistic Flux Analysis) Toolbox for MATLAB, which simplifies the use of Interval and Possibilistic Metabolic Flux Analysis. The main features of the PFA Toolbox are the following: (a) It provides reliable MFA estimations in scenarios where only a few fluxes can be measured or those available are imprecise. (b) It provides tools to easily plot the results as interval estimates or flux distributions. (c) It is composed of simple functions that MATLAB users can apply in flexible ways. (d) It includes a Graphical User Interface (GUI), which provides a visual representation of the measurements and their uncertainty. (e) It can use stoichiometric models in COBRA format. In addition, the PFA Toolbox includes a User's Guide with a thorough description of its functions and several examples. The PFA Toolbox for MATLAB is a freely available Toolbox that is able to perform Interval and Possibilistic MFA estimations.

A note on the effective evaluation height for flux-gradient relationships and its application to herbicide fluxes

Science.gov (United States)

Volatilization represents a significant loss pathway for many pesticides, herbicides and other agrochemicals. One common method for measuring the volatilization of agrochemicals is the flux-gradient method. Using this method, the chemical flux is estimated as the product of the vertical concentratio...

Architecture, des normes et des systèmes d'information libres, phase ...

International Development Research Centre (IDRC) Digital Library (Canada)

Architecture, des normes et des systèmes d'information libres, phase II (OASIS II) - Renforcement des capacités dans l'ensemble de l'Afrique. Sur presque tout le continent africain, la prestation des services de santé est limitée en raison des maigres ressources disponibles et de la charge de morbidité de plus en plus ...

Proton ejection project for Saturne; Projet d'ejection des protons de saturne

Energy Technology Data Exchange (ETDEWEB)

Bronca, G; Gendreau, G

1959-07-01

The reasons for choosing the ejection system are given. The characteristics required for the ejected beam are followed by a description of the ejection process, in chronological order from the viewpoint of the protons: movement of the particles, taking into account the various elements which make up the system (internal magnet, external magnet, quadrupoles, ejection correction coils, thin and thick cables,...) and specification of these elements. Then follows an estimation of the delay in manufacture and the cost of the project. Finally, the characteristics of the magnets and quadrupoles are listed in an appendix. (author) [French] On donne d'abord les raisons du choix du systeme d'ejection, puis le principe. Apres les caracteristiques requises pour le faisceau ejecte, on decrit le processus d'ejection selon l'ordre chronologique vu par les protons: mouvement des particules compte tenu des divers elements composant le systeme (aimant interne, aimant externe, quadrupoles, enroulements correcteurs ejection, cibles mince et epaisse,. ..) et cahier de charge de ces elements. On estime, ensuite les delais de realisation et le cout du projet. Enfin, un resume des caracteristiques des aimants et quadrupoles est donne en appendice. (auteur)

Exploitation du savoir autochtone afin de créer des emplois pour les ...

International Development Research Centre (IDRC) Digital Library (Canada)

La Commission des Nations unies pour la démarginalisation estime que quatre milliards de personnes ne peuvent pas exercer leurs droits juridiques à cause des coûts, du dysfonctionnement, de la corruption ou de l'abus de pouvoir. Il existe un besoin reconnu en institutions intermédiaires, comme les médias, les partis ...

Estimation of Surface Energy Fluxes from Bare Ground in a Tropical ...

African Journals Online (AJOL)

This investigation was designed to test the performance of Priestley Taylor method in the partitioning of the available energy into sensible and latent heat fluxes in a tropical site. Compared to eddy covariance measured fluxes, the conventional Priestley Taylor constant (αPT) of 1.25 gave low coefficient of determination and ...

A multi-method and multi-scale approach for estimating city-wide anthropogenic heat fluxes

Science.gov (United States)

Chow, Winston T. L.; Salamanca, Francisco; Georgescu, Matei; Mahalov, Alex; Milne, Jeffrey M.; Ruddell, Benjamin L.

2014-12-01

A multi-method approach estimating summer waste heat emissions from anthropogenic activities (QF) was applied for a major subtropical city (Phoenix, AZ). These included detailed, quality-controlled inventories of city-wide population density and traffic counts to estimate waste heat emissions from population and vehicular sources respectively, and also included waste heat simulations derived from urban electrical consumption generated by a coupled building energy - regional climate model (WRF-BEM + BEP). These component QF data were subsequently summed and mapped through Geographic Information Systems techniques to enable analysis over local (i.e. census-tract) and regional (i.e. metropolitan area) scales. Through this approach, local mean daily QF estimates compared reasonably versus (1.) observed daily surface energy balance residuals from an eddy covariance tower sited within a residential area and (2.) estimates from inventory methods employed in a prior study, with improved sensitivity to temperature and precipitation variations. Regional analysis indicates substantial variations in both mean and maximum daily QF, which varied with urban land use type. Average regional daily QF was ∼13 W m-2 for the summer period. Temporal analyses also indicated notable differences using this approach with previous estimates of QF in Phoenix over different land uses, with much larger peak fluxes averaging ∼50 W m-2 occurring in commercial or industrial areas during late summer afternoons. The spatio-temporal analysis of QF also suggests that it may influence the form and intensity of the Phoenix urban heat island, specifically through additional early evening heat input, and by modifying the urban boundary layer structure through increased turbulence.

From COS ecosystem fluxes to GPP: integrating soil, branch and ecosystem fluxes.

Science.gov (United States)

Kooijmans, L.; Maseyk, K. S.; Vesala, T.; Mammarella, I.; Baker, I. T.; Seibt, U.; Sun, W.; Aalto, J.; Franchin, A.; Kolari, P.; Keskinen, H.; Levula, J.; Chen, H.

2016-12-01

The close coupling of Carbonyl Sulfide (COS) and CO2 due to a similar uptake pathway into plant stomata makes COS a promising new tracer that can potentially be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. Although ecosystem-scale measurements have been made at several sites, the contribution of different ecosystem components to the total COS budget is often unknown. Besides that, the average Leaf Relative Uptake (LRU) ratio needs to be better determined to accurately translate COS ecosystem fluxes into GPP estimates when the simple linear correlation between GPP estimates and COS plant uptake is used. We performed two campaigns in the summer of 2015 and 2016 at the SMEAR II site in Hyytiälä, Finland to provide better constrained COS flux data for boreal forests. A combination of COS measurements were made during both years, i.e. atmospheric profile concentrations up to 125 m, eddy-covariance fluxes and soil chamber fluxes. In addition to these, branch chamber measurements were done in 2016 in an attempt to observe the LRU throughout the whole season. The LRU ratio shows an exponential correlation with photosynthetic active radiation (PAR) but is constant for PAR levels above 500 µmol m-2 s-1. Mid-day LRU values are 1.0 (aspen) and 1.5 (pine). The correlation between LRU and PAR can be explained by the fact that COS is hydrolyzed with the presence of the enzyme carbonic anhydrase, and is not light dependent, whereas the photosynthetic uptake of CO2 is. We observed nighttime fluxes on the order of 25-30 % of the daily maximum COS uptake. Soils are a small sink of COS and contribute to 3 % of the total ecosystem COS flux during daytime. In a comparison between observed and simulated fluxes from the Simple Biosphere (SiB) model, the modelled COS and CO2 ecosystem fluxes are on average 40 % smaller than the observed fluxes, however, the Ecosystem Relative Uptake (ERU) ratios are identical at a value of 1.9 ± 0

L'exode des cerveaux et le renforcement des capacités en Afrique ...

International Development Research Centre (IDRC) Digital Library (Canada)

1 févr. 2011 ... Ce phénomène ébranle les assises économiques et politiques de bien des pays africains. ... le défi consiste à recruter ces cerveaux. ... des missions africaines, des organisations non gouvernementales et des groupes de la diaspora réunis pour parler de l'exode des cerveaux en Afrique et des stratégies à ...

Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations

DEFF Research Database (Denmark)

Guzinski, Radoslaw; Anderson, M.C.; Kustas, W.P.

2013-01-01

The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time-differential temperature...... agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological ObsErvatory (HOBE) in western Denmark, indicating realistic patterns based on land use....

Influence de l'occupation des terres sur la dynamique des ...

African Journals Online (AJOL)

L'objectif de la présente étude est d'évaluer l'impact de mise en culture, des pâturages, des jachères et l'influence des villages sur la dynamique des communautés végétales de la commune de ..... mais il n'y a que peu de recrutement. Au-delà de cinq ans, taille et phytovolume diminuent, témoignant du vieillissement de la ...

Reliable estimation of neutron flux in BWR reactor vessel using the tort code (2) application to neutron and gamma flux estimation

Energy Technology Data Exchange (ETDEWEB)

Kurosawa, M. [Toshiba Corp., Yokohama (Japan); Tsukiyama, T.; Hayashi, K. [Hitachi Engineering Co. Ltd., Hitachi-shi (Japan)

2001-07-01

A neutron and gamma flux distribution around the core of BWR commercial plant in Japan was calculated, using a three-dimensional transport code, TORT in DOORS32 code system. In the external of the core, the bottom of the model was at an elevation of 150 cm below the bottom of active fuel, the top of the model was at an elevation of the top of the shroud head dome and the radial part of the model was to the outside of the reactor pressure vessel. The top guide beams were modeled explicitly to obtain the neutron and gamma flux distribution both in the beams and outside beams. The each control rod guide tube was also modeled with homogeneous region which included the blade wing and poison tubes so that we could obtain the neutron and gamma flux distribution around the each control rod guide tube. The calculation model mentioned above needed very large memory size which exceeded a few decade giga-bytes. As the using the splicing/coupling method had uncertainly at the splicing/coupling boundary, in this work the calculation was performed without this splicing/coupling method. On the other hand, radioactivity data were measured for a few pieces of the top guide beam, shroud and in-core monitor guide tube in the same plant which was analyzed in the above calculation. So the calculation results were able to be compared with those measured data as benchmarking and at the end of this task, the C/M values at these measured points were obtained and calculation model using TORT was evaluated. (authors)

Scaling of surface energy fluxes using remotely sensed data

Science.gov (United States)

French, Andrew Nichols

Accurate estimates of evapotranspiration (ET) across multiple terrains would greatly ease challenges faced by hydrologists, climate modelers, and agronomists as they attempt to apply theoretical models to real-world situations. One ET estimation approach uses an energy balance model to interpret a combination of meteorological observations taken at the surface and data captured by remote sensors. However, results of this approach have not been accurate because of poor understanding of the relationship between surface energy flux and land cover heterogeneity, combined with limits in available resolution of remote sensors. The purpose of this study was to determine how land cover and image resolution affect ET estimates. Using remotely sensed data collected over El Reno, Oklahoma, during four days in June and July 1997, scale effects on the estimation of spatially distributed ET were investigated. Instantaneous estimates of latent and sensible heat flux were calculated using a two-source surface energy balance model driven by thermal infrared, visible-near infrared, and meteorological data. The heat flux estimates were verified by comparison to independent eddy-covariance observations. Outcomes of observations taken at coarser resolutions were simulated by aggregating remote sensor data and estimated surface energy balance components from the finest sensor resolution (12 meter) to hypothetical resolutions as coarse as one kilometer. Estimated surface energy flux components were found to be significantly dependent on observation scale. For example, average evaporative fraction varied from 0.79, using 12-m resolution data, to 0.93, using 1-km resolution data. Resolution effects upon flux estimates were related to a measure of landscape heterogeneity known as operational scale, reflecting the size of dominant landscape features. Energy flux estimates based on data at resolutions less than 100 m and much greater than 400 m showed a scale-dependent bias. But estimates

Gaseous mercury fluxes from the forest floor of the Adirondacks

International Nuclear Information System (INIS)

Choi, Hyun-Deok; Holsen, Thomas M.

2009-01-01

The flux of gaseous elemental mercury (Hg 0 ) from the forest floor of the Adirondack Mountains in New York (USA) was measured numerous times throughout 2005 and 2006 using a polycarbonate dynamic flux chamber (DFC). The Hg flux ranged between -2.5 and 27.2 ng m -2 h -1 and was positively correlated with temperature and solar radiation. The measured Hg emission flux was highest in spring, and summer, and lowest in winter. During leaf-off periods, the Hg emission flux was highly dependent on solar radiation and less dependent on temperature. During leaf-on periods, the Hg emission flux was fairly constant because the forest canopy was shading the forest floor. Two empirical models were developed to estimate yearly Hg 0 emissions, one for the leaf-off period and one for the leaf-on period. Using the U.S. EPA's CASTNET meteorological data, the cumulative estimated emission flux was approx. 7.0 μg Hg 0 m -2 year -1 . - Empirical models based on the Hg emission measurements from the forest floor of the Adirondacks indicate the estimated emission flux was approx. 7.0 μg Hg 0 m -2 year -1 in 2006

Satellite-based Calibration of Heat Flux at the Ocean Surface

Science.gov (United States)

Barron, C. N.; Dastugue, J. M.; May, J. C.; Rowley, C. D.; Smith, S. R.; Spence, P. L.; Gremes-Cordero, S.

2016-02-01

Model forecasts of upper ocean heat content and variability on diurnal to daily scales are highly dependent on estimates of heat flux through the air-sea interface. Satellite remote sensing is applied to not only inform the initial ocean state but also to mitigate errors in surface heat flux and model representations affecting the distribution of heat in the upper ocean. Traditional assimilation of sea surface temperature (SST) observations re-centers ocean models at the start of each forecast cycle. Subsequent evolution depends on estimates of surface heat fluxes and upper-ocean processes over the forecast period. The COFFEE project (Calibration of Ocean Forcing with satellite Flux Estimates) endeavors to correct ocean forecast bias through a responsive error partition among surface heat flux and ocean dynamics sources. A suite of experiments in the southern California Current demonstrates a range of COFFEE capabilities, showing the impact on forecast error relative to a baseline three-dimensional variational (3DVAR) assimilation using Navy operational global or regional atmospheric forcing. COFFEE addresses satellite-calibration of surface fluxes to estimate surface error covariances and links these to the ocean interior. Experiment cases combine different levels of flux calibration with different assimilation alternatives. The cases may use the original fluxes, apply full satellite corrections during the forecast period, or extend hindcast corrections into the forecast period. Assimilation is either baseline 3DVAR or standard strong-constraint 4DVAR, with work proceeding to add a 4DVAR expanded to include a weak constraint treatment of the surface flux errors. Covariance of flux errors is estimated from the recent time series of forecast and calibrated flux terms. While the California Current examples are shown, the approach is equally applicable to other regions. These approaches within a 3DVAR application are anticipated to be useful for global and larger

Des dispositions responsables à prendre pour la protection des ...

African Journals Online (AJOL)

En considérant l'effet néfaste des maladies, des parasites, du changement climatique et d'autres facteurs environnementaux (les OGM par exemple) sur la survie des abeilles, la baisse de leurs populations dans certaines parties du monde ne saurait être attribuée aux seules pesticides. En plus, l'impact de ces derniers sur ...

Gestion des risques

CERN Document Server

Louisot, Jean-Paul

2009-01-01

Depuis le début du lie siècle, la gestion des risques connaît une véritable révolution culturelle. Jusqu'alors fonction technique, centrée autour de l'achat de couverture d'assurances, elle est devenue une discipline managériale et transversale : une valise d'instruments que chaque manager doit connaître et appliquer quels que soient son domaine de compétence et ses missions au sein de l'organisation. En effet, la gestion des risques est une culture qui doit être assimilée par chacun des acteurs. C'est précisément l'ambition des 101 questions rassemblées dans cet ouvrage : apporter à chaque manager d'entreprise, de collectivité, d'établissement de santé..., des réponses claires au " pourquoi " et au " comment " : Comment identifier les risques ? Comment analyser les risques ? Quels sont les objectifs de la gestion des risques ? Une carte des risques pour quoi faire ? Pourquoi faut-il financer les risques ? Les entreprises ont-elles des responsabilités pénales ? En quoi consiste la gestion...

Comportement des polluants des eaux pluviales urbaines en ...

African Journals Online (AJOL)

développement et la croissance des organismes vivant dans l'eau et particulièrement les micro- organismes. Le suivi des températures enregistrées oscille entre 9 et 16°C dans les trois sites d'observation durant la période ... de la lumière du soleil. Le site C est bien aéré et .... Effets de différents modes de gestion des eaux ...

Caractérisation des plantes médicinales à flavonoïdes des marchés ...

African Journals Online (AJOL)

Les espèces guinéo-congolaises sont les plus abondantes et le mode de dissémination majoritaire des diaspores est la zoochorie. Les plantes à flavonoïdes les plus utilisées sont : Combretum micranthum, Aloe vera, Ageratum conyzoïdes et Cylicodiscus gabonensis. Elles rentrent dans le traitement de 73 maladies parmi ...

MODIS-Based Estimation of Terrestrial Latent Heat Flux over North America Using Three Machine Learning Algorithms

Directory of Open Access Journals (Sweden)

Xuanyu Wang

2017-12-01

Full Text Available Terrestrial latent heat flux (LE is a key component of the global terrestrial water, energy, and carbon exchanges. Accurate estimation of LE from moderate resolution imaging spectroradiometer (MODIS data remains a major challenge. In this study, we estimated the daily LE for different plant functional types (PFTs across North America using three machine learning algorithms: artificial neural network (ANN; support vector machines (SVM; and, multivariate adaptive regression spline (MARS driven by MODIS and Modern Era Retrospective Analysis for Research and Applications (MERRA meteorology data. These three predictive algorithms, which were trained and validated using observed LE over the period 2000–2007, all proved to be accurate. However, ANN outperformed the other two algorithms for the majority of the tested configurations for most PFTs and was the only method that arrived at 80% precision for LE estimation. We also applied three machine learning algorithms for MODIS data and MERRA meteorology to map the average annual terrestrial LE of North America during 2002–2004 using a spatial resolution of 0.05°, which proved to be useful for estimating the long-term LE over North America.

Arctic Ocean CO2 uptake: an improved multiyear estimate of the air-sea CO2 flux incorporating chlorophyll a concentrations

Science.gov (United States)

Yasunaka, Sayaka; Siswanto, Eko; Olsen, Are; Hoppema, Mario; Watanabe, Eiji; Fransson, Agneta; Chierici, Melissa; Murata, Akihiko; Lauvset, Siv K.; Wanninkhof, Rik; Takahashi, Taro; Kosugi, Naohiro; Omar, Abdirahman M.; van Heuven, Steven; Mathis, Jeremy T.

2018-03-01

We estimated monthly air-sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014. This was done by mapping partial pressure of CO2 in the surface water (pCO2w) using a self-organizing map (SOM) technique incorporating chlorophyll a concentration (Chl a), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO2 mixing ratio, and geographical position. We applied new algorithms for extracting Chl a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl a values. The overall relationship between pCO2w and Chl a was negative, whereas the relationship varied among seasons and regions. The addition of Chl a as a parameter in the SOM process enabled us to improve the estimate of pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180 ± 130 Tg C yr-1. Seasonal to interannual variation in the CO2 influx was also calculated.

ADAPTIVE FLUX OBSERVER FOR PERMANENT MAGNET SYNCHRONOUS MOTORS

Directory of Open Access Journals (Sweden)

A. A. Bobtsov

2015-01-01

Full Text Available The paper deals with the observer design problem for a flux in permanent magnet synchronous motors. It is assumed that some electrical parameters such as resistance and inductance are known numbers. But the flux, the angle and the speed of the rotor are unmeasurable. The new robust approach to design an adaptive flux observer is proposed that guarantees globally boundedness of all signals and, moreover, exponential convergence to zero of observer error between the true flux value and an estimate obtained from the adaptive observer. The problem of an adaptive flux observer design has been solved with using the trigonometrical properties and linear filtering which ensures cancellation of unknown terms arisen after mathematical calculations. The key idea is the new parameterization of the dynamical model containing unknown parameters and depending on measurable current and voltage in the motor. By applying the Pythagorean trigonometric identity the linear equation has found that does not contain any functions depending on angle or angular velocity of the rotor. Using dynamical first-order filters the standard regression model is obtained that consists of unknown constant parameters and measurable functions of time. Then the gradient-like estimator is designed to reconstruct unknown parameters, and it guarantees boundedness of all signals in the system. The proposition is proved that if the regressor satisfies the persistent excitation condition, meaning the “frequency-rich” signal, then all errors in observer exponentially converges to zero. It is shown that observer error for the flux explicitly depends on estimator errors. Exponential convergence of parameter estimation errors to zero yields exponential convergence of the flux observer error to zero. The numerical example is considered.

Nouvelle approche à la prise en charge des condylomes

Science.gov (United States)

Lopaschuk, Catharine C.

2013-01-01

Résumé Objectif Faire le résumé des anciens et des nouveaux moyens de traitement des verrues génitales ou condylomes et déterminer comment les utiliser de manière appropriée. Sources des données Une recherche documentaire a été effectuée dans les bases de données suivantes: MEDLINE, PubMed, EMBASE, base de données des synthèses systématiques et registre central des études contrôlées de la Collaboration Cochrane (en anglais), ACP Journal Club et Trip. Les bibliographies des articles extraits ont aussi été examinées. Les études cliniques, les articles de révision qualitative, les rapports consensuels et les guides de pratique clinique ont été retenus. Message principal Les verrues symptomatiques sont présentes chez au moins 1 % des personnes âgées entre 15 et 49 ans et on estime que jusqu’à 50 % des gens sont infectés par le virus du papillome humain à un moment donné de leur vie. L’imiquimod et la podophyllotoxine sont 2 nouveaux traitements pour les verrues génitales externes qui sont moins douloureux et peuvent être appliqués par les patients à la maison. De plus, il a été démontré que le vaccin quadrivalent contre le virus du papillome humain est efficace pour prévenir les condylomes et le cancer du col. Les plus anciennes méthodes thérapeutiques ont aussi leur place dans certaines situations, comme les verrues intravaginales, urétrales, anales ou récalcitrantes ou encore pour les patientes enceintes. Conclusion Les nouveaux traitements des verrues génitales externes peuvent réduire la douleur causée par la thérapie et le nombre de visites au cabinet. Les autres méthodes thérapeutiques demeurent utiles dans certaines situations.

Optimal determination of the parameters controlling biospheric CO{sub 2} fluxes over Europe using eddy covariance fluxes and satellite NDVI measurements

Energy Technology Data Exchange (ETDEWEB)

Aalto, Tuula [Finnish Meteorological Inst., Helsinki (Finland). Air Quality Research; Ciais, Philippe; Moulin, Cyril [UMR CEA-CNRS, Gif-sur-Yvette (France). Laboratoire des Sciences du Climat et de l' Environnement; Chevillard, Anne [CEA, Fontenay-aux-Roses (France). DPRE/SERGD/LEIRPA

2004-04-01

Ecosystem CO{sub 2} flux measurements using the eddy covariance method were compared with the biospheric CO{sub 2} exchange estimates of a regional scale atmospheric model. The model described the seasonal patterns quite well, but underestimated the amplitude of the fluxes, especially at the northern sites. Two model parameters, photosynthetic efficiency for light use and Q{sub 10} for soil respiration, were re-evaluated on a diurnal and seasonal basis using the results from flux measurements. In most cases the photosynthetic efficiency was higher than the earlier estimate. The resulting flux was very sensitive to the value of photosynthetic efficiency, while changes in Q{sub 10} did not have a significant effect.

Méthode d'estimation des tassements des sols fins sous les remblais d'infrastructures ferroviaires pour lignes à grande vitesse

Science.gov (United States)

Said Alami, Soukaina; Reiffsteck, Philippe; Cuira, Fahd

2018-02-01

Le besoin de maîtriser les déformations des sols sous les remblais destinés à recevoir les structures de lignes à grande vitesse, en fait un enjeu important pour ces projets. Toutefois, de nombreuses difficultés ont été soulevées liées principalement au grand nombre d'incertitudes qui entourent le phénomène. En effet, la caractérisation géologique et géotechnique dépend de sondages et d'essais où le risque de remaniement est important et dont l'interprétation est, souvent, délicate. Cet article présente une procédure de calcul qui permettrait en pratique d'évaluer le tassement sous remblai avec une bonne précision et qui a été validée sur un certain nombre d'ouvrages. Pour cela, des corrections sont introduites aux méthodes usuelles de calcul permettant d'approcher les valeurs mesurées sur chantier.

When to use discrete event simulation (DES) for the economic evaluation of health technologies? A review and critique of the costs and benefits of DES.

Science.gov (United States)

Karnon, Jonathan; Haji Ali Afzali, Hossein

2014-06-01

Modelling in economic evaluation is an unavoidable fact of life. Cohort-based state transition models are most common, though discrete event simulation (DES) is increasingly being used to implement more complex model structures. The benefits of DES relate to the greater flexibility around the implementation and population of complex models, which may provide more accurate or valid estimates of the incremental costs and benefits of alternative health technologies. The costs of DES relate to the time and expertise required to implement and review complex models, when perhaps a simpler model would suffice. The costs are not borne solely by the analyst, but also by reviewers. In particular, modelled economic evaluations are often submitted to support reimbursement decisions for new technologies, for which detailed model reviews are generally undertaken on behalf of the funding body. This paper reports the results from a review of published DES-based economic evaluations. Factors underlying the use of DES were defined, and the characteristics of applied models were considered, to inform options for assessing the potential benefits of DES in relation to each factor. Four broad factors underlying the use of DES were identified: baseline heterogeneity, continuous disease markers, time varying event rates, and the influence of prior events on subsequent event rates. If relevant, individual-level data are available, representation of the four factors is likely to improve model validity, and it is possible to assess the importance of their representation in individual cases. A thorough model performance evaluation is required to overcome the costs of DES from the users' perspective, but few of the reviewed DES models reported such a process. More generally, further direct, empirical comparisons of complex models with simpler models would better inform the benefits of DES to implement more complex models, and the circumstances in which such benefits are most likely.

Experimental study of heat transfer for parallel flow in tube bundles with constant heat flux and for medium Prandtl numbers; Etude experimentale du transfert de chaleur dans des faisceaux tubulaires en ecoulement parallele pour une densite de flux thermique constante dans le domaine des nombres de Prandtl moyens

Energy Technology Data Exchange (ETDEWEB)

Rieger, M [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-06-01

The heat transfer parameters were determined experimentally in electrically heated tube bundles for turbulent flow parallel to the axis. The tubes were arranged in a pattern of equilateral triangles. The ratios of the distance between the axes of the tubes to their external diameter were 1.60 and 1.25 in the two test sections studied. The experiments were carried out with distilled water and with a mixture of 60 per cent ethylene glycol and 40 per cent water. The values obtained for the Prandtl numbers in this way fell within the range from 2.3 to 18. The Reynolds numbers were varied between 10{sup 4} and 2.10{sup 5}. The relation between the mean heat transfer coefficients and the friction factor in the tube bundles was found from the experiments as: Nu = [Re Pr {zeta}/8]/[1+{radical}({zeta}/8) 8.8 (Pr-1.3) Pr{sup -0.22}]. The experimentally determined mean Nusselt numbers were also given by the following function: Nu = (0.0122 + 0.00245 p/d) Re{sup 0.86} Pr{sup 0.4}, with a maximum deviation of {+-}4 per cent. For certain local Nusselt numbers, deviations of up to 20 per cent with respect to the relations given were observed. (author) [French] Dans des faisceaux tubulaires a chauffage electrique parcourus par un ecoulement turbulent parallele a l'axe, on a determine experimentalement les parametres du transfert de chaleur. Les centres des sections droites des tubes etaient des sommets de triangles equilateraux. Les rapports de la distance a l'axe des tubes et leur diametre exterieur dans les deux veines de mesure etudiees etaient de 1.60 et 1.25. Des essais furent effectues avec de l'eau distillee ainsi qu'avec un melange de 60 pour cent de glycol ethylenique et 40 pour cent d'eau. Les valeurs des nombres de Prandtl obtenues ainsi etaient situees entre 2.3 a 18. On a fait varier les nombres de Reynolds entre 10{sup 4} et 2.10{sup 5}. La relation entre les nombres caracteristiques de transfert de chaleur moyens et la perte de charge dans les faisceaux tabulaires

Estimation of Throughfall and Stemflow Bacterial Flux in a Subtropical Oak-Cedar Forest

Science.gov (United States)

Bittar, Thais B.; Pound, Preston; Whitetree, Ansley; Moore, L. Dean; Van Stan, John T.

2018-02-01

Transport pathways of microbes between ecosystem spheres (atmosphere, phyllosphere, and pedosphere) represent major fluxes in nutrient cycles and have the potential to affect microbially mediated biogeochemical processes. Novel data on bacterial fluxes from the phyllosphere to the pedosphere during rainfall via throughfall (rain dripping from/through the canopy) and stemflow (rain funneled down tree stems) are reported. Bacterial concentrations were quantified using flow cytometry and validated with quantitative polymerase chain reaction assays in rainfall samples from an oak-cedar forest in coastal Georgia (southeastern U.S.). Bacteria concentrations (cells mL-1) and storm-normalized fluxes (cells m-2 h-1, cells m-2 mm-1) were greater for cedar versus oak. Total bacterial flux was 1.5 × 1016 cells ha-1 yr-1. These previously unexamined bacterial fluxes are interpreted in the context of major elemental pools and fluxes in forests and could represent inoculum-level sources of bacteria (if alive), and organic matter and inorganic solute inputs (if lysed) to soils.

Information derived from French studies and achievements in the field of uranium isotope separation; Enseignements tires des etudes et realisations francaises relatives a la separation des isotopes de l'uranium

Energy Technology Data Exchange (ETDEWEB)

Frejacques, C; Galley, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

The work carried out in the field of uranium isotope separation, by gaseous diffusion and by ultracentrifugation, is reviewed. An economic estimate of the various parameters involved in the cost is given, and it is shown that only very large gaseous diffusion plants, corresponding to a programme of enriched uranium reactors of at least 4000 MWe to be installed yearly, can give an economically acceptable enriched uranium production. (authors) [French] La communication passe en revue les realisations effectuees dans le domaine de la separation des isotopes de l'uranium, par diffusion gazeuse et par ultracentrifugation. Elle donne une estimation economique des differents parametres intervenant dans les couts et met en evidence que seules les tres grandes usines de diffusion gazeuse, correspondant a un programme d'installation de reacteurs a uranium enrichi d'au moins 4000 MWe nouveaux par an, peuvent conduire a des productions d'uranium enrichi economiquement acceptables. (auteurs)

Influence of Sky Conditions on Estimation of Photosynthetic Photon Flux Density for Agricultural Ecosystem

Science.gov (United States)

Yamashita, M.; Yoshimura, M.

2018-04-01

Photosynthetic photon flux density (PPFD: µmol m-2 s-1) is indispensable for plant physiology processes in photosynthesis. However, PPFD is seldom measured, so that PPFD has been estimated by using solar radiation (SR: W m-2) measured in world wide. In method using SR, there are two steps: first to estimate photosynthetically active radiation (PAR: W m-2) by the fraction of PAR to SR (PF) and second: to convert PAR to PPFD using the ratio of quanta to energy (Q / E: µmol J-1). PF and Q/E usually have been used as the constant values, however, recent studies point out that PF and Q / E would not be constants under various sky conditions. In this study, we use the numeric data of sky-conditions factors such cloud cover, sun appearance/hiding and relative sky brightness derived from whole-sky image processing and examine the influences of sky-conditions factors on PF and Q / E of global and diffuse PAR. Furthermore, we discuss our results by comparing with the existing methods.

Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated?

Science.gov (United States)

Le Gland, Guillaume; Mémery, Laurent; Aumont, Olivier; Resplandy, Laure

2017-07-01

Radium-228 (228Ra), an almost conservative trace isotope in the ocean, supplied from the continental shelves and removed by a known radioactive decay (T1/2 = 5. 75 years), can be used as a proxy to constrain shelf fluxes of other trace elements, such as nutrients, iron, or rare earth elements. In this study, we perform inverse modeling of a global 228Ra dataset (including GEOSECS, TTO and GEOTRACES programs, and, for the first time, data from the Arctic and around the Kerguelen Islands) to compute the total 228Ra fluxes toward the ocean, using the ocean circulation obtained from the NEMO 3.6 model with a 2° resolution. We optimized the inverse calculation (source regions, cost function) and find a global estimate of the 228Ra fluxes of 8.01-8. 49 × 1023 atoms yr-1, more precise and around 20 % lower than previous estimates. The largest fluxes are in the western North Atlantic, the western Pacific and the Indian Ocean, with roughly two-thirds in the Indo-Pacific Basin. An estimate in the Arctic Ocean is provided for the first time (0.43-0.50 × 1023 atoms yr-1). Local misfits between model and data in the Arctic, the Gulf Stream and the Kuroshio regions could result from flaws of the ocean circulation in these regions (resolution, atmospheric forcing). As radium is enriched in groundwater, a large part of the 228Ra shelf sources comes from submarine groundwater discharge (SGD), a major but poorly known pathway for terrestrial mineral elements, including nutrients, to the ocean. In contrast to the 228Ra budget, the global estimate of SGD is rather unconstrained, between 1.3 and 14. 7 × 1013 m3 yr-1, due to high uncertainties on the other sources of 228Ra, especially diffusion from continental shelf sediments. Better precision on SGD cannot be reached by inverse modeling until a proper way to separate the contributions of SGD and diffusive release from sediments at a global scale is found.

Using Gravity Inversion to Estimate Antarctic Geothermal Heat Flux

Science.gov (United States)

Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; (Sasha) Golynsky, A. V.; Rogozhina, Irina

2014-05-01

New modelling studies for Greenland have recently underlined the importance of GHF for long-term ice sheet behaviour (Petrunin et al. 2013). Revised determinations of top basement heat-flow for Antarctica and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning (Chappell & Kusznir 2008), using BedMap2 data have provided improved estimates of geothermal heat flux (GHF) in Antarctica where it is very poorly known. Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental and oceanic lithosphere. The sensitivity of present-day Antarctic top basement heat-flow to initial continental radiogenic heat productivity, continental rift and margin breakup age has been examined. Recognition of the East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km (Ferraccioli et al. 2011) and is comparable in scale to the well-studied East African rift system, highlights that crustal variability in interior Antarctica is much greater than previously assumed. GHF is also important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology (Bell et al. 2011). References Bell, R.E., Ferraccioli, F., Creyts, T.T., Braaten, D., Corr, H., Das, I., Damaske, D., Frearson, N., Jordan, T., Rose, K., Studinger, M. & Wolovick, M. 2011. Widespread persistent thickening of the East Antarctic Ice Sheet by freezing from the base. Science, 331 (6024), 1592-1595. Chappell, A.R. & Kusznir, N.J. 2008. Three-dimensional gravity inversion for Moho depth at rifted continental margins