A large wet snow avalanche cycle in West Greenland quantified using remote sensing and in situ observations     

Abermann  Jakob  Eckerstorfer  Markus  Malnes  Eirik  Hansen  Birger Ulf 《Natural Hazards》2019,97(2):517-534

Natural Hazards - On 11 April 2016 we observed high slushflow and wet snow avalanche activity at the environmental monitoring station Kobbefjord in W-Greenland. Snow avalanches released as a result...  相似文献   

First U–Pb geochronology on detrital zircons from Early-Middle Cambrian strata of the Torgau-Doberlug Syncline (eastern Germany) and palaeogeographic implications     

Abubaker  Atnisha  Hofmann  Mandy  Gärtner  Andreas  Linnemann  Ulf  Elicki  Olaf 《International Journal of Earth Sciences》2017,106(7):2445-2459

International Journal of Earth Sciences - LA-ICP-MS U–Pb data from detrital zircons of the Ediacaran to Cambrian siliciclastic sequence of the Torgau-Doberlug Syncline (TDS, Saxo-Thuringia,...  相似文献   

Comparison of geotechnical uncertainties linked to different soil characterization methods     

Mwajuma Ibrahim Lingwanda  Anders Prästings  Stefan Larsson  Dalmas L. Nyaoro 《Geomechanics and Geoengineering》2017,12(2):137-151

One of the essential inputs in settlement prediction models is the soil modulus, which may be obtained from laboratory tests or estimated from in situ measurements. The total uncertainty in predicting the confined modulus of a sandy soil is quantified with data from side-by-side in situ testing using the standard penetration test, the static cone penetration test, the light dynamic probing and the laboratory oedometer test. To estimate transformation errors, correlations are proposed between in situ and laboratory data. The results indicate that similar magnitudes of total uncertainties are associated with the in situ methods, which are approximately twice as high as those from the direct oedometer method. The quantified uncertainties are an important input for reliability-based designs of foundations under similar soil conditions.  相似文献   

A Note on Velocity Spectra in the Marine Boundary Layer   总被引：1，自引：1，他引：0  

Ann-Sofi Smedman  Ulf Högström  Anna Sjöblom 《Boundary-Layer Meteorology》2003,109(1):27-48

Spectra of longitudinal and vertical velocity have been studied at a marine site, östergarnsholm, in the Baltic Sea during a period of six days with near-neutral or slightly unstable conditions, when the wave state gradually changed from pure wind sea to strong swell having approximately the same direction as the wind. During the pure wind sea phase, spectra are shown to adhere closely to general forms for the neutral atmospheric surface layer obtained from a new theory. As soon as the wave age goes slightly beyond that representative of pure wind sea conditions, the spectra deviate in shape from the ideal forms. The spectral modification appears to start at a frequency typical of the swell component. As the wave age increases, it progresses in frequency as a downscale cascade, which is particularly prominent in the spectrum of the vertical component but which is also observed in the longitudinal component. In addition, there is a strong effect in the low-frequency part of the spectra. It is interpreted as an indirect effect of large-scale inactive turbulence, which becomes progressively more important as wave-age increases. It is found that the ratio of the spectrum of the vertical component and the spectrum of the corresponding longitudinal component attains the theoretically predicted value of 4/3 for cases of developing sea (gale force wind) for frequencies above approximately 4 Hz but never much exceeds unity for cases with swell. It is argued that this is an indication of local anisotropy and that the inertial-dissipation method for determination of the momentum flux is inappropriate in the case of mixed seas or swell.  相似文献   

SMART-1 mission description and development status     

G. D. Racca  A. Marini  L. Stagnaro  J. van Dooren  L. di Napoli  B. H. Foing  R. Lumb  J. Volp  J. Brinkmann  R. Grünagel  D. Estublier  E. Tremolizzo  M. McKay  O. Camino  J. Schoemaekers  M. Hechler  M. Khan  P. Rathsman  G. Andersson  K. Anflo  S. Berge  P. Bodin  A. Edfors  A. Hussain  J. Kugelberg  N. Larsson  B. Ljung  L. Meijer  A. Mrtsell  T. Nordebck  S. Persson  F. Sjberg 《Planetary and Space Science》2002,50(14-15)

SMART-1 is the first of the Small Missions for Advanced Research in Technology of the ESA Horizons 2000 scientific programme. The SMART-1 mission is dedicated to testing of new technologies for future cornerstone missions, using Solar-Electric Primary Propulsion (SEPP) in Deep Space. The chosen mission planetary target is the Moon. The target orbit will be polar with the pericentre close to the South-Pole. The pericentre altitude lies between 300 and 2000 km, while the apocentre will extend to about 10,000 km. During the cruise phase, before reaching the Moon, the spacecraft thrusting profile allows extended periods for cruise science. The SMART-1 spacecraft will be launched in the spring of 2003 as an auxiliary passenger on an Ariane 5 and placed into a Geostationary Transfer Orbit (GTO). The expected launch mass is about 370 kg, including 19 kg of payload. The selected type of SEPP is a Hall-effect thruster called PPS-1350. The thruster is used to spiral out of the GTO and for all orbit maneuvers including lunar capture and descent. The trajectory has been optimised by inserting coast arcs and the presence of the Moon's gravitational field is exploited in multiple weak gravity assists.The Development Phase started in October 1999 and is expected to be concluded by a Flight Acceptance Review in January 2003. The short development time for this high technology spacecraft requires a concerted effort by industry, science institutes and ESA centres. This paper describes the mission and the project development status both from a technical and programmatic standpoint.  相似文献   

Dissociative recombination of nitrile ions with implications for Titan's upper atmosphere     

E. Vigren  J. Semaniak  M. Hamberg  V. Zhaunerchyk  M. Kaminska  R.D. Thomas  M. af Ugglas  M. Larsson  W.D. Geppert 《Planetary and Space Science》2012,60(1):102-106

Nitrile ions are abundant in Titan's upper atmosphere and are expected to be lost mainly via dissociative recombination with free electrons. We review in this paper a series of experimental results on the dissociative recombination reactions of nitrile ions known/expected to be present in Titan's upper atmosphere. The experiments were all performed at the heavy ion storage ring CRYRING in Stockholm, Sweden, and the results presented here include information on rate coefficients at electron temperatures relevant for Titan's upper atmosphere as well as information on the product branching fractions of the reactions. We discuss implications of the results for Titan's atmosphere. As an example the presented results support a statement by Krasnopolsky (2009) that nitriles do not degrade to yield N₂ again in Titan's atmosphere, indicating that condensation and polymerization with precipitation to the surface are their ultimate fate.  相似文献   

An EELS study of near edge structures of the oxygen K-edge in spinels     

Susanne Nyquist  Ulf Hålenius 《Physics and Chemistry of Minerals》2014,41(4):255-265

Spectra of seven aluminate, ferrite and chromate spinels were collected at the oxygen K-edge in order to examine the effect of octahedral ion composition on the near edge structures and explore whether these may shed some light on previously reported major variations in the optical absorption coefficient (ε) for the spin-allowed d–d band transitions due to tetrahedrally coordinated Fe²⁺ in optical spectra of oxide spinels. Interpretation of the energy loss near edge structure (ELNES) spectra was aided using the multiple scattering code FEFF8.40. For the chromate samples spin polarised calculations were included. Gold’s iterative deconvolution method was utilized to improve on energy resolution, resulting in spectra equal in merit to those recorded by technically superior instruments. Results include absolute energy positions and interpretation of ELNES features in terms of transitions to available states. We conclude that the major causes of differences in the optical absorption coefficient mentioned above are hybridization between oxygen p- and octahedral metal orbitals. Our study does not support the idea presented by other authors that there exists a local antiferromagnetic ordering in MgCr₂O₄ at room temperature.  相似文献   

Precise U–Pb baddeleyite ages of mafic dykes and intrusions in southern West Greenland and implications for a possible reconstruction with the Superior craton     

Mimmi K.M. Nilsson  Ulf Söderlund  Richard E. Ernst  Michael A. Hamilton  Anders Scherstén  Paul E.B. Armitage 《Precambrian Research》2010

The Archaean block of southern Greenland constitutes the core of the North Atlantic craton (NAC) and is host to a large number of Precambrian mafic intrusions and dyke swarms, many of which are regionally extensive but poorly dated. For southern West Greenland, we present a U–Pb zircon age of 2990 ± 13 Ma for the Amikoq mafic–ultramafic layered intrusion (Fiskefjord area) and four baddeleyite U–Pb ages of Precambrian dolerite dykes. Specifically, a dyke located SE of Ameralik Fjord is dated at 2499 ± 2 Ma, similar to a previously reported ⁴⁰Ar/³⁹Ar age of a dyke in the Kangâmiut area. For these and related intrusions of ca. 2.5 Ga age in southern West Greenland, we propose the name Kilaarsarfik dykes. Three WNW-trending dykes of the MD3 swarm yield ages of 2050 ± 2 Ma, 2041 ± 3 Ma and 2029 ± 3 Ma. A similar U–Pb baddeleyite age of 2045 ± 2 Ma is also presented for a SE-trending dolerite (Iglusuataliksuak dyke) in the Nain Province, the rifted western block of the NAC in Labrador. We speculate that the MD3 dykes and age-equivalent NNE-trending Kangâmiut dykes of southern West Greenland, together with the Iglusuataliksuak dyke (after closure of the Labrador Sea) represent components of a single, areally extensive, radiating swarm that signaled the arrival of a mantle plume centred on what is presently the western margin of the North Atlantic craton. Comparison of the magmatic ‘barcodes’ from the Nain and Greenland portions of the North Atlantic craton with the established record from the north-eastern Superior craton shows matches at 2500 Ma, 2214 Ma, 2050–2030 Ma and 1960–1950 Ma. We use these new age constraints, together with orientations of the dyke swarms, to offer a preliminary reconstruction of the North Atlantic craton near the north-eastern margin of the Superior craton during the latest Archaean and early Palaeoproterozoic, possibly with the Core Zone craton of eastern Canada intervening.  相似文献