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81.
S. Turck-Chièze P. Lamy C. Carr P. H. Carton A. Chevalier I. Dandouras J. M. Defise S. Dewitte T. Dudok de Wit J. P. Halain S. Hasan J. F. Hochedez T. Horbury P. Levacher M. Meissonier N. Murphy P. Rochus A. Ruzmaikin W. Schmutz G. Thuillier S. Vivès 《Experimental Astronomy》2009,23(3):1017-1055
The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar
variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere
layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding
space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties,
atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of
the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements
of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space
in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by
putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of
the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies.
The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona
and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle)
and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement
of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred
orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft
due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and
D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM)
and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA
missions (PICARD, LYRA, maybe ASPIICS). 相似文献
82.
83.
Simultaneous identification of a single pollution point-source location and contamination time under known flow field conditions 总被引:3,自引:0,他引:3
A theoretical framework is presented that allows direct identification of a single point-source pollution location and time in heterogeneous multidimensional systems under known flow field conditions. Based on the concept of the transfer function theory, it is shown that an observed pollution plume contains all the necessary information to predict the concentration at the unknown pollution source when a reversed flow field transport simulation is performed. This target concentration C0 is obtained from a quadratic integral of the observed pollution plume itself. Backwards simulation of the pollution plume leads to shrinkage of the C0-contour due to dispersion. When the C0-contour reduces to a singular point, i.e. becomes a concentration maximum, the position of the pollution source is identified and the backward simulation time indicates the time elapsed since the contaminant release. The theoretical basis of the method is first developed for the ideal case that the pollution plume is entirely known and is illustrated using a synthetic heterogeneous 2D example where all the hydro-dispersive parameters are known. The same example is then used to illustrate the procedure for a more realistic case, i.e. where only few observation points exist. 相似文献
84.
Submersible investigations with the ROV Victor 6000 of some pockmark structures on the seafloor of the Congo deep-sea fan
have shown that they are active venting sites of methane-rich fluids, associated with abundant fauna and carbonate crusts.
Moreover, methane hydrates have been observed both outcropping and deep in the sediments in the centre of the “Regab” giant
pockmark. Authigenic carbonates, mostly calcite sometimes mixed with aragonite, are cementing the sedimentary matrix components
and fauna; diatoms are abundant but only as moulds, indicating that biogenic silica dissolution occurred in situ synchronous
with carbonate precipitation. The occurrence of diagenetic barite and pyrite in some carbonate crusts demonstrates that they
can be formed either within the sulphate/methane transition zone or deeper in sulphate-depleted sediments. The oxygen isotopic
compositions of the diagenetic carbonates (3.17–6.01‰ V-PDB) indicate that precipitation occurred with bottom seawater mixed
with a variable contribution of water from gas hydrate decomposition. The very low carbon isotopic compositions of the diagenetic
carbonates (−57.1 to −27.75‰ V-PDB) demonstrate that carbon derives mostly from the microbial oxidation of methane. 相似文献
85.
D. B. Seaton D. Berghmans B. Nicula J.-P. Halain A. De Groof T. Thibert D. S. Bloomfield C. L. Raftery P. T. Gallagher F. Auchère J.-M. Defise E. D’Huys J.-H. Lecat E. Mazy P. Rochus L. Rossi U. Schühle V. Slemzin M. S. Yalim J. Zender 《Solar physics》2013,286(1):43-65
The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope onboard ESA’s Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. Given the limited resources of the PROBA2 microsatellite, the SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS–APS detector. This article provides reference documentation for users of the SWAP image data. 相似文献
86.
87.
Aurélia Mouret Pierre Anschutz Bruno Deflandre Gwénaëlle Chaillou Christelle Hyacinthe Jonathan Deborde Henri Etcheber Jean-Marie Jouanneau Antoine Grémare Pascal Lecroart 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(4):528-540
The relationship between particulate organic carbon (POC) concentrations measured in modern sediment and fluxes of exported POC to the sediment surface needs to be understood in order to use POC content as a proxy of paleo-environmental conditions. The objective of our study was to compare POC concentrations, POC mineralization rates calculated from O2 consumption and POC burial rates. Benthic O2 distributions were determined in 58 fine-grained sediment cores collected at different periods at 14 stations in the southeastern part of the Bay of Biscay with depths ranging from 140 to 2800 m. Depth-dependent volume-specific oxygen consumption rates were used to assess rates of aerobic oxidation of organic matter (OM), assuming that O2 consumption solely was related to heterotrophic activity at the sediment–water interface. Heterogeneity of benthic O2 fluxes denoted changes in time and space of fresh organic material sedimentation. The most labile fraction of exported POC engendered a steep decrease in concentration in the upper 5 mm of vertical O2 profiles. The rupture in the gradient of O2 microprofile may be related to the bioturbation-induced mixing depth of fast-decaying carbon. Average diffusive O2 fluxes showed that this fast-decaying OM flux was much higher than buried POC, although diffusive O2 fluxes underestimated the total sediment oxygen demand, and thus the fast-decaying OM flux to the sediment surface. Sedimentary POC burial was calculated from sediment mass accumulation rate and the organic carbon content measured at the top of the sediment. The proportion of buried POC relative to total exported POC ranged at the most between 50% and 10%, depending on station location. Therefore, for a narrow geographic area like the Bay of Biscay, burial efficiency of POC was variable. A fraction of buried POC consisted of slow-decaying OM that was mineralized within the upper decimetres of sediment through oxic and anoxic processes. This fraction was deduced from the decrease with depth in POC concentration. At sites located below 500 m water depth, where the fast-decaying carbon did not reach the anoxic sediment, the slow-decaying pool may control the O2 penetration depth. Only refractory organic material was fossilized in sedimentary records at locations where labile OM did not reach the anoxic portion of the sediment. 相似文献
88.
Jean Pierre Baudin 《Marine environmental research》1982,7(3):227-233
Uptake of 65Zn by Gammarus aequicauda results in a concentration factor of approximately 50 and it is characterised by a maximal accumulation level attained as early as the third day of the experiment. After ingestion by the gammarids of twenty contaminated meals which are distributed over a 45-day period, a transfer of 65Zn between the food and the consumer can be observed but there is no sign of the biomagnification phenomenon. The retention rate of the radionuclide is only about 1·5% and the 65Zn concentration in the gammarids remains markedly inferior to that of the ingested food.The elimination of the 65Zn fixed directly from water takes place according to an exponential model which corresponds to the existence of three biological half-lives of the radionuclide, . The excretion of 65Zn accumulated from food is a simple exponential phenomenon which corresponds to only one biological half-life of approximately 17 days. 相似文献
89.
90.
Spectra of Hα, Hβ and Hδ have been taken under good seeing conditions with the vacuum tower telescope of Sacramento Peak Observatory. Intensity curves are given at various wavelengths in these lines to permit further comparison with a theoretical model. Moreover, considering in each case the range of height in which the lines are almost optically thin and using a few approximations, the following results are derived: between 2000 and 6000 km above the limb the average thermal + turbulent velocity of the atoms is found to increase from 20 km s?1 to 30 km s?1 and the mean number of hydrogen atoms per cm3 in level 2 is given by $$\log n_2 {\text{ = }}4.5{\text{ }} - {\text{ 0}}{\text{.00056(}}z - 2000)$$ z being the altitude above the limb in km. For line profile computations a new interpolation formula is presented; it gives good profiles with a small number of scans, saving microphotometer time. 相似文献