Multi-Elemental Analysis of ATHO-G Rhyolitic Glass (MPI-DING Reference Material) by Femtosecond and Nanosecond LA-ICP-MS: Evidence for Significant Heterogeneity of B,V, Zn,Mo, Sn,Sb, Cs,W, Pt and Pb at the Millimetre Scale     

Anastassia Y. Borisova  Rémi Freydier  Mireille Polvé  Klaus Peter Jochum  Frederic Candaudap 《Geostandards and Geoanalytical Research》2010,34(3):245-255

This paper reports on the application of variants of LA-ICP-MS – including infrared femtosecond laser ablation (fs-LA) inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) and nanosecond laser ablation (ns-LA) coupled with single-collector sector-field (SF-) ICP-MS – to the in situ determination of trace elements in different splits of the reference material (RM) ATHO-G (MPI-DING). Analyses of the materials performed by fs- and ns-LA-ICP-MS demonstrated the efficiency of the techniques with typical accuracy at a level of ≤ ± 20%. One ‘anomalous’ split, however, displayed a significant discrepancy from the reference concentrations for B, V, Zn, Mo, Sn, Sb, Cs, W and Pb. Three- to six-fold enrichment of V, Mo, Cs and Pt relative to the reference contents in this split is likely to have been due to direct contact of the silicate melt with Pt crucible walls and ceramics. Boron, Zn, Sn, Sb, W and Pb depletion relative to the reference concentrations is probably due to siderophile element adsorption by the Pt walls and/or related to the formation of volatile-depleted compositional cords during the preparation process. Our results imply that additional precautions should be taken against volatile/siderophile element heterogeneity in marginal/surface layers (≤ 10 mm) during the preparation of RMs by the fusion technique.  相似文献   

Mission design for Human Outer Planet Exploration (HOPE) using a magnetoplasma spacecraft     

Sang-Young Park  Hans Seywald  Frederic H. Stillwagen 《Planetary and Space Science》2006,54(8):737-749

To send humans beyond Mars, a Human Outer Planet Exploration (HOPE) mission has been studied for new spacecraft concepts and technologies. In this paper, an interplanetary trajectory and a preliminary spacecraft design are presented for the HOPE visit to Callisto, one of Jupiter's moons. To design a round-trip trajectory for the mission, the characteristics of the spacecraft and its trajectories are analyzed. A detailed optimization approach is formulated to utilize a Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine with capabilities of variable specific impulse, variable engine efficiency, and engine on-off control. It is mainly illustrated that a 30 MW powered spacecraft can make the mission possible in a 5-year round trip constraint around the year 2045. Trajectories with different power and reactor options are also discussed. The results obtained in this study can be used for formulating an overall concept for the mission.  相似文献   

ECMWF seasonal forecast system 3 and its prediction of sea surface temperature   总被引：1，自引：1，他引：0  

Timothy N. Stockdale  David L. T. Anderson  Magdalena A. Balmaseda  Francisco Doblas-Reyes  Laura Ferranti  Kristian Mogensen  Timothy N. Palmer  Franco Molteni  Frederic Vitart 《Climate Dynamics》2011,37(3-4):455-471

The latest operational version of the ECMWF seasonal forecasting system is described. It shows noticeably improved skill for sea surface temperature (SST) prediction compared with previous versions, particularly with respect to El Nino related variability. Substantial skill is shown for lead times up to 1?year, although at this range the spread in the ensemble forecast implies a loss of predictability large enough to account for most of the forecast error variance, suggesting only moderate scope for improving long range El Nino forecasts. At shorter ranges, particularly 3?C6?months, skill is still substantially below the model-estimated predictability limit. SST forecast skill is higher for more recent periods than earlier ones. Analysis shows that although various factors can affect scores in particular periods, the improvement from 1994 onwards seems to be robust, and is most plausibly due to improvements in the observing system made at that time. The improvement in forecast skill is most evident for 3-month forecasts starting in February, where predictions of NINO3.4 SST from 1994 to present have been almost without fault. It is argued that in situations where the impact of model error is small, the value of improved observational data can be seen most clearly. Significant skill is also shown in the equatorial Indian Ocean, although predictive skill in parts of the tropical Atlantic are relatively poor. SST forecast errors can be especially high in the Southern Ocean.  相似文献   

Characterization and utilization of noisy displacement signals from simple shear device using linear and kernel regression methods     

Eric Yee  Jonathan P. Stewart  Frederic P. Schoenberg 《Soil Dynamics and Earthquake Engineering》2011

Small strain testing of dynamic soil properties such as threshold strains, γ_tv, are often conducted using specialized devices such as dual-specimen simple-shear, as devices configured for large strain testing produce noisy signals in the small strain range. Working with a simple shear device originally developed for large-strain testing, we extend its low-strain capabilities by characterizing noisy signals and utilizing several statistical methods to extract meaningful responses in the small strain range. We utilize linear regression of a transformed variable to estimate the cyclic shear strain from a noisy signal and the confidence interval on its amplitude. We utilize Kernel regression with the Nadaraya–Watson estimator and a Gaussian kernel to evaluate vertical strain response. A practical utilization of these techniques is illustrated by evaluating threshold shear strains for volume change with a procedure that takes into account uncertainties in the measured shear and vertical strains.  相似文献   

Comments on “SHORT NOTE: Extending simplified high-degree synthesis methods to second latitudinal derivatives of geopotential”     

David Frederic Crouse 《Journal of Geodesy》2014,88(10):1007-1008

This comment corrects a number of errors in the paper “SHORT NOTE: Extending simplified high-degree synthesis methods to second latitudinal derivatives of geopotential”.  相似文献   

Storm influence on SPM concentrations in a coastal turbidity maximum area with high anthropogenic impact (southern North Sea)     

Michael Fettweis  Frederic Francken  Dries Van den Eynde  Toon Verwaest  Job Janssens  Vera Van Lancker 《Continental Shelf Research》2010

Multi-sensor tripod measurements in the high-turbidity area of the Belgian nearshore zone (southern North Sea) allowed investigating storm effects on near bed suspended particulate matter (SPM) concentrations. The data have shown that during or after a storm the SPM concentration increases significantly and that high concentrated mud suspensions (HCMS) are formed. Under these conditions, about 3 times more mass of SPM was observed in the water column, as compared to calm weather conditions. The following different sources of fine-grained sediments, influencing the SPM concentration signal, have been investigated: wind direction and the advection of water masses; the previous history and occurrence of fluffy layers; freshly deposited mud near the disposal grounds of dredged material, navigation channels and adjacent areas; and the erosion of medium-consolidated mud of Holocene age.  相似文献   

An analysis of the July 2006 heatwave extent in Europe compared to the record year of 2003   总被引：2，自引：1，他引：1  

M. Rebetez  O. Dupont  M. Giroud 《Theoretical and Applied Climatology》2009,95(1-2):1-7

  相似文献   

Edge Flow and Canopy Structure: A Large-Eddy Simulation Study   总被引：4，自引：4，他引：0  

Sylvain Dupont  Yves Brunet 《Boundary-Layer Meteorology》2008,126(1):51-71

Sharp heterogeneities in forest structure, such as edges, are often responsible for wind damage. In order to better understand the behaviour of turbulent flow through canopy edges, large-eddy simulations (LES) have been performed at very fine scale (2 m) within and above heterogeneous vegetation canopies. A modified version of the Advanced Regional Prediction System (ARPS), previously validated in homogeneous conditions against field and wind-tunnel measurements, has been used for this purpose. Here it is validated in a simple forest-clearing-forest configuration. The model is shown to be able to reproduce accurately the main features observed in turbulent edge flow, especially the “enhanced gust zone” (EGZ) present around the canopy top at a few canopy heights downwind from the edge, and the turbulent region that develops further downstream. The EGZ is characterized by a peak in streamwise velocity skewness, which reflects the presence of intense intermittent wind gusts. A sensitivity study of the edge flow to the forest morphology shows that with increasing canopy density the flow adjusts faster and turbulent features such as the EGZ become more marked. When the canopy is characterized by a sparse trunk space the length of the adjustment region increases significantly due to the formation of a sub-canopy wind jet from the leading edge. It is shown that the position and magnitude of the EGZ are related to the mean upward motion formed around canopy top behind the leading edge, caused by the deceleration in the sub-canopy. Indeed, this mean upward motion advects low turbulence levels from the bottom of the canopy; this emphasises the passage of sudden strong wind gusts from the clearing, thereby increasing the skewness in streamwise velocity as compared with locations further downstream where ambient turbulence is stronger.  相似文献   

EXOTIME: searching for planets around pulsating subdwarf B stars     

Sonja Schuh  Roberto Silvotti  Ronny Lutz  Björn Loeptien  Elizabeth M. Green  Roy H. Østensen  Silvio Leccia  Seung-Lee Kim  Gilles Fontaine  Stéphane Charpinet  Myriam Francœur  Suzanna Randall  Cristina Rodríguez-López  Valerie van Grootel  Andrew P. Odell  Margit Paparó  Zsófia Bognár  Péter Pápics  Thorsten Nagel  Benjamin Beeck  Markus Hundertmark  Thorsten Stahn  Stefan Dreizler  Frederic V. Hessman  Massimo Dall’Ora  Dario Mancini  Fausto Cortecchia  Serena Benatti  Riccardo Claudi  Rimvydas Janulis 《Astrophysics and Space Science》2010,329(1-2):231-242

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time scales of several years with two immediate observational goals:

1. determine $\dot{P}$ of the pulsational periods P
2. search for signatures of substellar companions in O–C residuals due to periodic light travel time variations, which would be tracking the central star’s companion-induced wobble around the centre of mass

These sets of data should therefore, at the same time, on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the $\dot{P}$ (comparison with “local” evolutionary models), and on the other hand allow one to investigate the preceding evolution of a target in terms of possible “binary” evolution by extending the otherwise unsuccessful search for companions to potentially very low masses. While timing pulsations may be an observationally expensive method to search for companions, it samples a different range of orbital parameters, inaccessible through orbital photometric effects or the radial velocity method: the latter favours massive close-in companions, whereas the timing method becomes increasingly more sensitive toward wider separations. In this paper we report on the status of the on-going observations and coherence analysis for two of the currently five targets, revealing very well-behaved pulsational characteristics in HS?0444+0458, while showing HS?0702+6043 to be more complex than previously thought.  相似文献   

Suitability of airborne laser scanning for the assessment of forest protection effect against rockfall     

Jean-Matthieu Monnet  Franck Bourrier  Sylvain Dupire  Frederic Berger 《Landslides》2017,14(1):299-310

Rockfall simulation models are now able to quantify the protective effect of forest with the integration of rock impacts on trees. Those models require spatially explicit forest characteristics which are costly to acquire in operational conditions. The present study compares rockfall simulation results obtained with different forest input data sources: field data with different levels of spatial detail and two methods based on airborne Lidar data. Three different forest stands are tested with several virtual terrain configurations. When rockfall energies are below 200 kJ, the forest protection effect is significant. For higher energies, it also exists but it is minor compared to the effects of topography and rock volume. For all forest input data sources, the estimated rockfall intensity is within ?13 and 16 % of the reference value, whereas the frequency is generally overestimated. Both Lidar methods yield a satisfactory forest protection effect evaluation, but single tree detection tends to underestimate it. Improvements are possible regarding the spatial heterogeneity of stem density and the diameter distribution by tree species.  相似文献