An enhanced homogenization approach for masonry structures with compressible joints. Application to hearth thermomechanical computations     

N. J. Mathieu  K. Sab  S. A. Zaïmi 《国际地质力学数值与分析法杂志》2012,36(9):1102-1124

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The rheology of cryovolcanic slurries: Motivation and phenomenology of methanol-water slurries with implications for Titan     

Fang Zhong  Karl L. Mitchell  Mathieu Choukroun  Jeffrey S. Kargel 《Icarus》2009,202(2):607-894

The Cassini spacecraft has revealed landforms on the surface of Titan suggested to be viscous cryovolcanic flows and possibly eruptive domes. In order to relate those surface features to the processes and chemistries that produced them, it is necessary to construct flow models, which rely on characterization of the rheological properties of the eruptants. This paper describes our initial exploratory attempts to understand the rheological characteristics of cryogenic slurries, using a 40% methanol-water mixture, as a precursor to more detailed experiments. We have devised a new automated cryogenic rotational viscometer system to more fully characterize cryovolcanic slurry rheologies. A series of measurements were performed, varying first temperature, and then strain rate, which revealed development of yield stress-like behaviors, shear-rate dependence, and thixotropic behavior, even at relatively low crystal fractions, not previously reported. At fixed shear rate our data are fit well by the Andrade equation, with the activation energy modified by a solid volume fraction. At fixed temperature, depending on shearing history, a Cross model could describe our data over a wide shear rate range. A Bingham plastic model appears to be a good constitutive model for the data measured at high shear rates when the shear was global. The yield stress like behavior implies that levee formation on cryolava flows is more likely than would be inferred from the previous studies, and may provide a partial explanation for features interpreted as steep-sided volcanic constructs on Titan.  相似文献   

Albedo control of seasonal South Polar cap recession on Mars     

Frédéric Schmidt  Sylvain Douté  Bernard Schmitt  Mathieu Vincendon  Jean-Pierre Bibring  Yves Langevin  The OMEGA Team 《Icarus》2009,200(2):374-394

Over the last few decades, General Circulation Models (GCM) have been used to simulate the current martian climate. The calibration of these GCMs with the current seasonal cycle is a crucial step in understanding the climate history of Mars. One of the main climatic signals currently used to validate GCMs is the annual atmospheric pressure cycle. It is difficult to use changes in seasonal deposits on the surface of Mars to calibrate the GCMs given the spectral ambiguities between CO₂ and H₂O ice in the visible range. With the OMEGA imaging spectrometer covering the near infra-red range, it is now possible to monitor both types of ice at a spatial resolution of about 1 km. At global scale, we determine the change with time of the Seasonal South Polar Cap (SSPC) crocus line, defining the edge of CO₂ deposits. This crocus line is not symmetric around the geographic South Pole. At local scale, we introduce the snowdrop distance, describing the local structure of the SSPC edge. Crocus line and snowdrop distance changes can now be used to calibrate GCMs. The albedo of the seasonal deposits is usually assumed to be a uniform and constant parameter of the GCMs. In this study, albedo is found to be the main parameter controlling the SSPC recession at both global and local scale. Using a defrost mass balance model (referred to as D-frost) that incorporates the effect of shadowing induced by topography, we show that the global SSPC asymmetry in the crocus line is controlled by albedo variations. At local scale, we show that the snowdrop distance is correlated with the albedo variability. Further GCM improvements should take into account these two results. We propose several possibilities for the origin of the asymmetric albedo control. The next step will be to identify and model the physical processes that create the albedo differences.  相似文献   

OMEGA long wavelength channel: Data reduction during non-nominal stages     

Denis Jouglet  François Poulet  Yves Langevin  Jean-Pierre Bibring  Brigitte Gondet  Mathieu Vincendon  Michel Berthe 《Planetary and Space Science》2009,57(8-9):1032-1042

The Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA) instrument is a visible and near-infrared imaging spectrometer on board the European Mars Express (MEx) mission. The on-board calibration (OBC) performed at the beginning of observations on each orbit reveals that the photometric response of the C channel (1.0–2.5 μm) has been very stable since orbit insertion in January 2004. On the contrary the L channel (2.5–5.1 μm) response has varied significantly during the mission, and only orbits for which the response is close to nominal could be used with confidence. The spatial coverage of ice-free surfaces in this wavelength range is consequently limited to only ～30%, mainly during northern spring and summer. This paper presents the empirical method used to derive new instrumental transfer functions (ITF) for the non-nominal orbits. This method consists of analyzing the variation of the signal between several observations of a same region acquired at nominal and non-nominal calibration states. In the cases where the mineralogy and the atmospheric conditions between the two observations are the same, the variation in reflectance spectra is only due to the ITF variation, which provides a new ITF. We then associate these new ITFs with their corresponding OBCs to model a relationship between both. The resulting model enables us to provide a new ITF for each orbit for which the OBC is available. The new ITFs derived for the entire dataset have been validated (1) through a comparison of the C and L channel global albedo trends and (2) through a comparison of the surface temperatures derived from the L channel with those calculated from the General Circulation Model (GCM) numerical simulation of the LMD released in the Martian Climate Database. The non-nominal data processed with adapted ITFs for orbits up to 3050 increase the non-icy surface coverage of Mars to ～70% including all seasons.  相似文献   

Biases on the cosmological parameters and thermal Sunyaev–Zel'dovich residuals     

Nicolas Taburet  Nabila Aghanim  Marian Douspis  Mathieu Langer 《Monthly notices of the Royal Astronomical Society》2009,392(3):1153-1158

We examine the biases induced on cosmological parameters when the presence of secondary anisotropies is not taken into account in cosmic microwave background analyses. We first develop an exact analytical expression for computing the biases on parameters when any additive signal is neglected in the analysis. We then apply it in the context of the forthcoming Planck experiment. For illustration, we investigate the effect of the sole residual thermal Sunyaev–Zel'dovich signal that remains after cluster extraction. We find, in particular, that analyses neglecting the presence of this contribution introduce on the cosmological parameters n _s and τ biases, at least ∼6.5 and 2.9 times their 1σ confidence intervals. The Ω_b parameter is also biased to a lesser extent.  相似文献   

Landslide hazard and risk assessment and their application in risk management and landuse planning in eastern flank of Menoreh Mountains,Yogyakarta Province,Indonesia     

Danang Sri Hadmoko  Franck Lavigne  Junun Sartohadi  Pramono Hadi  Winaryo 《Natural Hazards》2010,54(3):623-642

The Menoreh Mountains in Yogyakarta are severely affected by landslides. Due to the high population densities, mass movements are generally damaging and fatal. More than other Javanese mountains, the Menoreh Mountains cumulate several factors causing landslides. Therefore, it is necessary to evaluate the ways to map landslide risk in order to improve the risk mitigation. The objectives of this paper are to provide landslide hazard and risk assessment that will be useful for risk prevention and landuse planning in the Menoreh Mountains. So far, risk management has been developed by the Research Centre for Disasters Gadjah Mada University in collaboration with the Regional Development Planner (BAPPEDA), which carries out fundamental and applied researches. The results of the studies have been integrated in the risk prevention and landuse planning in order to improve the integrated landslide mitigation programme.  相似文献   

Eclipsing binary Trojan asteroid Patroclus: Thermal inertia from Spitzer observations     

Michael Mueller  Franck Marchis  Joshua P. Emery  Stefano Mottola  Jérome Berthier 《Icarus》2010,205(2):505-515

We present mid-infrared observations of the binary L5-Trojan system (617) Patroclus-Menoetius before, during, and after two shadowing events, using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. For the first time, we effectively observe changes in asteroid surface temperature in real time, allowing the thermal inertia to be determined very directly. A new detailed binary thermophysical model is presented which accounts for the system’s known mutual orbit, arbitrary component shapes, and thermal conduction in the presence of eclipses.We obtain two local thermal-inertia values, representative of the respective shadowed areas: and . The average thermal inertia is estimated to be , potentially with significant surface heterogeneity. This first thermal-inertia measurement for a Trojan asteroid indicates a surface covered in fine regolith. Independently, we establish the presence of fine-grained (<a few μm) silicates on the surface, based on emissivity features near 10 and similar to those previously found on other Trojans.We also report V-band observations and report a lightcurve with complete rotational coverage. The lightcurve has a low amplitude of peak-to-peak, implying a roughly spherical shape for both components, and is single-periodic with a period equal to the period of the mutual orbit, indicating that the system is fully synchronized.The diameters of Patroclus and Menoetius are 106±11 and , respectively, in agreement with previous findings. Taken together with the system’s known total mass, this implies a bulk mass density of , significantly below the mass density of L4-Trojan asteroid (624) Hektor and suggesting a bulk composition dominated by water ice.All known physical properties of Patroclus, arguably the best studied Trojan asteroid, are consistent with those expected in icy objects with devolatilized surface (extinct comets), consistent with what might be implied by recent dynamical modeling in the framework of the Nice Model.  相似文献   

NO emissions as observed by SPICAV during stellar occultations     

Emilie Royer  Franck Montmessin  Jean-Loup Bertaux 《Planetary and Space Science》2010,58(10):1314-1326

Ultraviolet (UV) nightglow data from the SPICAV instrument (SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus) onboard the Venus Express spacecraft, currently in orbit around Venus, are presented. In its extended source mode, SPICAV has shown that the Venus nightglow in the UV contains essentially Lyman-α and Nitric Oxide (NO) emissions. In the stellar mode, when the slit of the spectrometer is removed, an emission is also observed at the limb in addition to the stellar spectrum. A forward model allows us to identify this feature as being an NO emission. Due to radiative recombination of N and O atoms produced on the dayside of Venus, and transported to the nightside, NO nightglow provides important constraints to the Solar-to-Anti Solar thermospheric circulation prevailing above 90 km. The forward model presented here allows us to derive the altitude of the peak of emission of the NO layer, found at 113.5±6 km, as well as its scale height, of 3.4±1 km and its brightness. The latter is found to be very variable with emissions between 19 Kilo-Rayleigh (kR) and 540 kR. In addition, the NO nightglow is sometimes very patchy, as we are able to observe two distinct emission zones in the field of view. Finally, systematic extraction of this emission from stellar occultations extends the database of the NO emission already reported elsewhere using limb observations.  相似文献   

The spray contribution to net evaporation from the sea: A review of recent progress   总被引：6，自引：0，他引：6  

Edgar L Andreas  James B. Edson  Edward C. Monahan  Mathieu P. Rouault  Stuart D. Smith 《Boundary-Layer Meteorology》1995,72(1-2):3-52

The part that sea spray plays in the air-sea transfer of heat and moisture has been a controversial question for the last two decades. With general circulation models (GCMs) suggesting that perturbations in the Earth's surface heat budget of only a few W m^–2 can initiate major climatic variations, it is crucial that we identify and quantify all the terms in that heat budget. Thus, here we review recent work on how sea spray contributes to the sea surface heat and moisture budgets. In the presence of spray, the near-surface atmosphere is characterized by a droplet evaporation layer (DEL) with a height that scales with the significant-wave amplitude. The majority of spray transfer processes occur within this layer. As a result, the DEL is cooler and more moist than the atmospheric surface layer would be under identical conditions but without the spray. Also, because the spray in the DEL provides elevated sources and sinks for heat and moisture, the vertical heat fluxes are no longer constant with height. We use Eulerian and Lagrangian models and a simple analytical model to study the processes important in spray droplet dispersion and evaporation within this DEL. These models all point to the conclusion that, in high winds (above about 15 m/s), sea spray begins to contribute significantly to the air-sea fluxes of heat and moisture. For example, we estimate that, in a 20-m/s wind, with an air temperature of 20°C, a sea surface temperature of 22°C, and a relative humidity of 80%, the latent and sensible heat fluxes resulting from the spray alone will have magnitudes of order 150 and 15 W/m², respectively, in the DEL. Finally, we speculate on what fraction of these fluxes rise out of the DEL and, thus, become available to the entire marine boundary layer.  相似文献   

Thermodynamic properties of the forsterite-fayalite (Mg2SiO4-Fe2SiO4) solid solution. determination of heat of formation     

P. Thierry  C. Chatillon-Colinet  J. C. Mathieu  J. R. Regnard  J. Amossé 《Physics and Chemistry of Minerals》1981,7(1):43-46

A high temperature calorimetric solution method involving the use of a sodium and lithium metaborate (NaBO₂+LiBO₂) molten bath at 1,180 K, has been developed in order to measure the enthalpy of formation of the forsterite-fayalite (Mg₂SiO₄-Fe₂SiO₄) system. The samples used for these measurements have been obtained by synthesis. They have been carefully controlled by chemical and X-ray analysis and Mössbauer spectroscopy. The results obtained for forsterite and fayalite agree closely with the data commonly found in the literature. Owing to the uncertainty of the experimental results, it is not possible to determine conclusively whether an enthalpy of mixing exists in this system.  相似文献