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红果寺炼镁用白去是北京地区普查评价的第二个炼镁用白云岩矿床。矿体呈层状，单斜构造，赋存于雾迷山组三段地层中，出露较高，位于侵蚀基准面之上，适于露采。该矿的发现法区在北京地区此类矿产的勘查和白云岩的深层次开发利用，具一定意义。 相似文献
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M. Roy F. Dell’Oste J.J. Veillette A. de Vernal J.-F. Hélie M. Parent 《Quaternary Science Reviews》2011,30(5-6):682-692
Deglaciation of the James Bay region was highly dynamic, with the occurrence of ice (Cochrane) readvances into glacial Lake Ojibway around final deglaciation time, which culminated with the drainage of Ojibway waters into Hudson Bay and subsequent incursion of the Tyrrell Sea at ～8 ka. Renewed interest on these events comes from the possible link between the drainage of the ice-dammed Lake Agassiz-Ojibway and a major climate deterioration known as the 8.2-ka cooling event. Recent glaciological modeling suggests that this drainage may have occurred subglacially, a mechanism that can accommodate more than one lake discharge, as suggested by marine records. The exact number and timing of drainage events, as well as location of the lake discharge pathway(s) remain, however, largely unconstrained. Here we focus on the events that led to the drainage of Lake Ojibway by documenting late-glacial sedimentary sequences located east of James Bay. Our investigations indicate that the deglacial sequence consists of a readvance till, extensive Ojibway rhythmites, and thick marine sediments. The glaciolacustrine and marine units are separated by a 60 cm-thick horizon composed of laminated silt beds containing rounded clay balls and disseminated clasts resulting from the abrupt drainage of the lake. Radiocarbon dating of marine fossils lying above the drainage horizon indicates that the glaciolacustrine episode ended around 8128–8282 cal yr BP. Micropaleontological analyses reveal that freshwater ostracods (Candona sp.) and marine microfossils (foraminifers, dinocysts) occur together in the upper part of the Ojibway sediments. Analysis of oxygen isotopes (δ18O) of ostracods and foraminifers originating from the same stratigraphic position show highly contrasting values that suggest possible subglacial exchanges between Lake Ojibway and Tyrrell Sea waters prior to the final drainage event. The complexity of the deglacial events is further indicated by radiocarbon dating of marine shells retrieved from a Cochrane till that suggests that the last ice readvance occurred almost simultaneously with the final lake discharge. These results bring additional constraints on the drainage mechanism of the coalesced Lake Agassiz-Ojibway and indicate that the James Bay region formed an important drainage pathway for meltwaters at the end of the last deglaciation. 相似文献
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Simone Dell��Agnello Caterina Lops Giovanni O. Delle Monache Douglas G. Currie Manuele Martini Roberto Vittori Angioletta Coradini Cesare Dionisio Marco Garattini Alessandro Boni Claudio Cantone Riccardo March Giovanni Bellettini Roberto Tauraso Mauro Maiello Luca Porcelli Simone Berardi Nicola Intaglietta 《Experimental Astronomy》2011,32(1):19-35
MAGIA is a mission approved by the Italian Space Agency (ASI) for Phase A study. Using a single large-diameter laser retroreflector, a large laser retroreflector array and an atomic clock onboard MAGIA we propose to perform several fundamental physics and absolute positioning metrology experiments: VESPUCCI, an improved test of the gravitational redshift in the Earth?CMoon system predicted by General Relativity; MoonLIGHT-P, a precursor test of a second generation Lunar Laser Ranging (LLR) payload for precision gravity and lunar science measurements under development for NASA, ASI and robotic missions of the proposed International Lunar Network (ILN); Selenocenter (the center of mass of the Moon), the determination of the position of the Moon center of mass with respect to the International Terrestrial Reference Frame/System (ITRF/ITRS); this will be compared to the one from Apollo and Lunokhod retroreflectors on the surface; MapRef, the absolute referencing of MAGIA??s lunar altimetry, gravity and geochemical maps with respect to the ITRF/ITRS. The absolute positioning of MAGIA will be achieved thanks to: (1) the laboratory characterization of the retroreflector performance at INFN-LNF; (2) the precision tracking by the International Laser Ranging Service (ILRS), which gives two fundamental contributions to the ITRF/ITRS, i.e. the metrological definition of the geocenter (the Earth center of mass) and of the scale of length; (3) the radio science and accelerometer payloads; (4) support by the ASI Space Geodesy Center in Matera, Italy. Future ILN geodetic nodes equipped with MoonLIGHT and the Apollo/Lunokhod retroreflectors will become the first realization of the International Moon Reference Frame (IMRF), the lunar analog of the ITRF. 相似文献
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R. Krivonos A. Tkachenko R. Burenin E. Filippova I. Lapshov I. Mereminskiy S. Molkov M. Pavlinsky S. Sazonov M. Gubarev J. Kolodziejczak S. L. O’Dell D. Swartz Vyacheslav E. Zavlin B. D. Ramsey 《Experimental Astronomy》2017,44(1):147-164
The Astronomical Röntgen Telescope X-ray Concentrator (ART-XC) is a hard X-ray telescope with energy response up to 30 keV, to be launched on board the Spectrum Röntgen Gamma (SRG) spacecraft in 2018. ART-XC consists of seven identical co-aligned mirror modules. Each mirror assembly is coupled with a CdTe double-sided strip (DSS) focal-plane detector. Eight X-ray mirror modules (seven flight and one spare units) for ART-XC were developed and fabricated at the Marshall Space Flight Center (MSFC), NASA, USA. We present results of testing procedures performed with an X-ray beam facility at MSFC to calibrate the point spread function (PSF) of the mirror modules. The shape of the PSF was measured with a high-resolution CCD camera installed in the focal plane with defocusing of 7 mm, as required by the ART-XC design. For each module, we performed a parametrization of the PSF at various angular distances Θ. We used a King function to approximate the radial profile of the near on-axis PSF (Θ < 9 arcmin) and an ellipse fitting procedure to describe the morphology of the far off-axis angular response (9 < Θ < 24 arcmin). We found a good agreement between the seven ART-XC flight mirror modules at the level of 10%. The on-axis angular resolution of the ART-XC optics varies between 27 and 33 arcsec (half-power diameter), except for the spare module. 相似文献
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We analyze decadal climate variability in the Mediterranean region using observational datasets over the period 1850–2009 and a regional climate model simulation for the period 1960–2000, focusing in particular on the winter (DJF) and summer (JJA) seasons. Our results show that decadal variability associated with the winter and summer manifestations of the North Atlantic Oscillation (NAO and SNAO respectively) and the Atlantic Multidecadal Oscillation (AMO) significantly contribute to decadal climate anomalies over the Mediterranean region during these seasons. Over 30% of decadal variance in DJF and JJA precipitation in parts of the Mediterranean region can be explained by NAO and SNAO variability respectively. During JJA, the AMO explains over 30% of regional surface air temperature anomalies and Mediterranean Sea surface temperature anomalies, with significant influence also in the transition seasons. In DJF, only Mediterranean SST still significantly correlates with the AMO while regional surface air temperature does not. Also, there is no significant NAO influence on decadal Mediterranean surface air temperature anomalies during this season. A simulation with the PROTHEUS regional ocean–atmosphere coupled model is utilized to investigate processes determining regional decadal changes during the 1960–2000 period, specifically the wetter and cooler 1971–1985 conditions versus the drier and warmer 1986–2000 conditions. The simulation successfully captures the essence of observed decadal changes. Model set-up suggests that AMO variability is transmitted to the Mediterranean/European region and the Mediterranean Sea via atmospheric processes. Regional feedbacks involving cloud cover and soil moisture changes also appear to contribute to observed changes. If confirmed, the linkage between Mediterranean temperatures and the AMO may imply a certain degree of regional decadal climate predictability. The AMO and other decadal influences outlined here should be considered along with those from long-term increases in greenhouse gas forcings when making regional climate out-looks for the Mediterranean 10–20?years out. 相似文献
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Steric sea level rise over the Mediterranean Sea: present climate and scenario simulations 总被引：3，自引：0，他引：3
A. Carillo G. Sannino V. Artale P. M. Ruti S. Calmanti A. Dell’Aquila 《Climate Dynamics》2012,39(9-10):2167-2184
A regional atmosphere–ocean coupled model has been used to estimate sea level rise in the Mediterranean basin under present and future conditions. A present climate simulation has been forced by ERA40 reanalysis covering the period 1958–2001. Moreover a simulation has been forced by the global coupled model ECHAM5-MPIOM under present climate conditions for the period 1951–2000. Two other 50-year simulations have been performed under the SRESA1B scenario for the twenty-first century and differ only in temperature and salinity profiles used to relax the ocean model in the Atlantic buffer zone. The present climate simulation has been verified in terms of temperature, salinity and sea level against observed data, showing good performances both in mean values and variability over the whole Mediterranean Sea and over different sub-basins. The future scenario simulations show that the steric sea level averaged over the entire basin rises of about 2 or 7?cm in 50?years depending on the Atlantic boundary conditions. The difference of about 1?°C and 0.5?psu in the upper layers of the Atlantic sea reflects mainly on the halosteric component that contributes negatively to the sea level rise, when fresher and colder boundary conditions are used in the Atlantic buffer zone, and positively in the other case. The impact of the boundary conditions is not uniform in the basin and is particularly strong in some easternmost regions. 相似文献
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Multiyear simulation of the African climate using a regional climate model (RegCM3) with the high resolution ERA-interim reanalysis 总被引：2，自引：2，他引：0
Mouhamadou Bamba Sylla E. Coppola L. Mariotti F. Giorgi P. M. Ruti A. Dell’Aquila X. Bi 《Climate Dynamics》2010,35(1):231-247
This study examines the ability of the latest version of the International Centre for Theoretical Physics (ICTP) regional
climate model (RegCM3) to reproduce seasonal mean climatologies, annual cycle and interannual variability over the entire
African continent and different climate subregions. The new European Center for Medium Range Weather Forecast (ECMWF) ERA-interim
reanalysis is used to provide initial and lateral boundary conditions for the RegCM3 simulation. Seasonal mean values of zonal
wind profile, temperature, precipitation and associated low level circulations are shown to be realistically simulated, although
the regional model still shows some deficiencies. The West Africa monsoon flow is somewhat overestimated and the Africa Easterly
Jet (AEJ) core intensity is underestimated. Despite these biases, there is a marked improvement in these simulated model variables
compared to previous applications of this model over Africa. The mean annual cycle of precipitation, including single and
multiple rainy seasons, is well captured over most African subregions, in some cases even improving the quality of the ERA-interim
reanalysis. Similarly, the observed precipitation interannual variability is well reproduced by the regional model over most
regions, mostly following, and sometimes improving, the quality of the ERA-interim reanalysis. It is assessed that the performance
of this model over the entire African domain is of sufficient quality for application to the study of climate change and climate
variability over the African continent. 相似文献
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C.R. O&#x;Dell 《Icarus》1973,19(1):137-146
A new model for the nucleus of comets is presented, hypothesizing formation at large heliocentric distances from many independent solid bodies. It is shown that such a configuration would collapse to a single assemblage if it is to survive into the inner solar system. Prior to collapse, the bodies would be subject to coating by interstellar gas and particles, which would form the material lost into the coma at subsequent inner solar system perihelia. Quantitative estimates place an upper limit to the body sizes of 2.3m and a lower limit of the number as 3 × 101° with sizes of a few tenths of a micron and numbers of about 1033 most probable. The major structural and evolutionary features of such comet nuclei are consistent with the Whipple icy-conglomerate model. 相似文献
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Bruce B. Hicks William R. Pendergrass Barry D. Baker Rick D. Saylor Debra L. O’Dell Neal S. Eash Jeffrey T. McQueen 《Boundary-Layer Meteorology》2018,167(2):285-301
The assumption that the roughness Reynolds number \(( Re_{*})\) can be used as a basis for quantifying the boundary-layer property \({ kB}^{-1} (= \ln (z_{0}/z_{0T}))\) as in some modern numerical models is questioned. While \({ Re}_{*}\) is a useful property in studies of pipe flow, it appears to have only marginal applicability in the case of treeless terrain, as studied in the two experimental situations presented here. For both the daytime and night-time cases there appears to be little correlation between \({ kB}^{-1}\) and \({ Re}_{*}\). For daytime, the present studies indicate that the assumption \({ kB}^{-1} \approx 2\) is acceptable, while for night-time, the scatter involved in relating \({ kB}^{-1}\) to \({ Re}_{*}\) suggests there is little reason to assume a direct relationship. However, while the scatter affecting all of the night-time results is large, there remains a significant correlation between the heat and momentum fluxes upon which an alternative methodology for describing bulk air–surface exchange at night could be constructed. The friction coefficient (\(C_{f}\)) and the turbulent Stanton number \(({ St}_{*})\) are discussed as possible alternatives for describing bulk properties of the air layer adjacent to the surface. While describing the surface roughness in terms of the friction coefficient provides an attractive simplification relative to the conventional methodologies based on roughness length and stability considerations, use of the Stanton number shares many of uncertainties that affect \({ kB}^{-1}\). The transitions at dawn and dusk remain demanding situations to address. 相似文献