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121.
We present a geoid solution for the Weddell Sea and adjacent continental Antarctic regions. There, a refined geoid is of interest, especially for oceanographic and glaciological applications. For example, to investigate the Weddell Gyre as a part of the Antarctic Circumpolar Current and, thus, of the global ocean circulation, the mean dynamic topography (MDT) is needed. These days, the marine gravity field can be inferred with high and homogeneous resolution from altimetric height profiles of the mean sea surface. However, in areas permanently covered by sea ice as well as in coastal regions, satellite altimetry features deficiencies. Focussing on the Weddell Sea, these aspects are investigated in detail. In these areas, ground-based data that have not been used for geoid computation so far provide additional information in comparison with the existing high-resolution global gravity field models such as EGM2008. The geoid computation is based on the remove–compute–restore approach making use of least-squares collocation. The residual geoid with respect to a release 4 GOCE model adds up to two meters and more in the near-coastal and continental areas of the Weddell Sea region, also in comparison with EGM2008. Consequently, the thus refined geoid serves to compute new estimates of the regional MDT and geostrophic currents. 相似文献
122.
Klaus Peter Jochum Steven A. Wilson Wafa Abouchami Marghaleray Amini Jérome Chmeleff Anton Eisenhauer Ernst Hegner Linda M. Iaccheri Bruno Kieffer Joachim Krause William F. McDonough Regina Mertz‐Kraus Ingrid Raczek Roberta L. Rudnick Denis Scholz Grit Steinhoefel Brigitte Stoll Andreas Stracke Sonia Tonarini Dominique Weis Ulrike Weis Jon D. Woodhead 《Geostandards and Geoanalytical Research》2011,35(2):193-226
This paper contains the results of an extensive isotopic study of United States Geological Survey GSD‐1G and MPI‐DING reference glasses. Thirteen different laboratories were involved using high‐precision bulk (TIMS, MC‐ICP‐MS) and microanalytical (LA‐MC‐ICP‐MS, LA‐ICP‐MS) techniques. Detailed studies were performed to demonstrate the large‐scale and small‐scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD‐1G and the MPI‐DING glasses are suitable reference materials for microanalytical and bulk analytical purposes. 相似文献
123.
Joachim T. Haug Carolin Haug Dieter Waloszek Günter Schweigert 《Swiss Journal of Geoscience》2011,104(1):85-98
Developmental biology has become a major issue for understanding the evolution of Arthropoda. While usually only the ontogenies of extant species are studied, developmental information of fossil arthropods may exhibit developmental patterns not present in living ones. Crustacea possess, basically, a more gradual development than, for example, pterygote insects and would, therefore, be appropriate candidates for the study of fossil ontogenies. Remarkably, famous fossil deposits like the Devonian Rhynie Chert or the Early Palaeozoic ‘Orsten’-type deposits do not comprise the generally macroscopic malacostracan Crustacea (although most probably adult malacostracan fossils have already been found in the Cambrian). By contrast, the Late Jurassic Solnhofen Lithographic Limestones of southern Germany provide thousands of specimens (although only few morphotypes) that can be identified as malacostracan larvae, together with juvenile specimens differing in certain morphological aspects from their conspecific adults. More recent investigations with up-to-date imaging methodology on additional malacostracan crustacean larvae yielded also reconstructible developmental sequences of species from the Solnhofen deposits. The very similar fossil deposits of the Cretaceous lithographic limestones of Lebanon have also yielded malacostracan larvae and juvenile specimens. We present a summary of the occurrences of crustacean fossils providing developmental information and a demonstration of the potential of the lithographic limestones in this context. The importance of developmental data for understanding crustacean evolution is also highlighted. 相似文献
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125.
Joachim Neugebauer 《地学学报》1994,6(4):359-365
Fault blocks passing bends or stepovers in a fault zone must adapt their margins to the uneven fault trace. Two cases of adaption are distinguished for extensional bends or stepovers (transtension): (1) The fault margins close up behind a single bend ('knickpoint') of a strike-slip fault and a 'closing-up structure' (new term) arises or (2) fault-block margins are extended behind a releasing bend (double bend) or stepover parallel to the displacement and a pull-apart basin originates. The dosing up described here is accomplished by acute-angled synthetic strike-slip faults that dissect the straight fault in front of a knickpoint to form a zig-zag block boundary behind it. Crustal extension is also involved in the closing-up structure, but in a different way from typical pull-apart basins.
The closing-up structure illustrated was developed behind an extensional knickpoint in the North Anatolian Fault west of Lake Abant, NW Turkey, where the process of closing up continues to this day. The kinematic model of this closing-up structure is supported by displacements and ruptures observed during the 1967 Mudurnu valley earthquake and the 1957 Abant earthquake. 相似文献
The closing-up structure illustrated was developed behind an extensional knickpoint in the North Anatolian Fault west of Lake Abant, NW Turkey, where the process of closing up continues to this day. The kinematic model of this closing-up structure is supported by displacements and ruptures observed during the 1967 Mudurnu valley earthquake and the 1957 Abant earthquake. 相似文献
126.
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128.
Tobias Goerdt Ben Moore J. I. Read Joachim Stadel Marcel Zemp 《Monthly notices of the Royal Astronomical Society》2006,368(3):1073-1077
The dark matter dominated Fornax dwarf spheroidal has five globular clusters orbiting at ∼1 kpc from its centre. In a cuspy cold dark matter halo the globulars would sink to the centre from their current positions within a few Gyr, presenting a puzzle as to why they survive undigested at the present epoch. We show that a solution to this timing problem is to adopt a cored dark matter halo. We use numerical simulations and analytic calculations to show that, under these conditions, the sinking time becomes many Hubble times; the globulars effectively stall at the dark matter core radius. We conclude that the Fornax dwarf spheroidal has a shallow inner density profile with a core radius constrained by the observed positions of its globular clusters. If the phase space density of the core is primordial then it implies a warm dark matter particle and gives an upper limit to its mass of ∼0.5 keV, consistent with that required to significantly alleviate the substructure problem. 相似文献
129.
Consistency of seven different GNSS global ionospheric mapping techniques during one solar cycle 总被引:1,自引:0,他引:1
David Roma-Dollase Manuel Hernández-Pajares Andrzej Krankowski Kacper Kotulak Reza Ghoddousi-Fard Yunbin Yuan Zishen Li Hongping Zhang Chuang Shi Cheng Wang Joachim Feltens Panagiotis Vergados Attila Komjathy Stefan Schaer Alberto García-Rigo José M. Gómez-Cama 《Journal of Geodesy》2018,92(6):691-706
In the context of the International GNSS Service (IGS), several IGS Ionosphere Associated Analysis Centers have developed different techniques to provide global ionospheric maps (GIMs) of vertical total electron content (VTEC) since 1998. In this paper we present a comparison of the performances of all the GIMs created in the frame of IGS. Indeed we compare the classical ones (for the ionospheric analysis centers CODE, ESA/ESOC, JPL and UPC) with the new ones (NRCAN, CAS, WHU). To assess the quality of them in fair and completely independent ways, two assessment methods are used: a direct comparison to altimeter data (VTEC-altimeter) and to the difference of slant total electron content (STEC) observed in independent ground reference stations (dSTEC-GPS). The main conclusion of this study, performed during one solar cycle, is the consistency of the results between so many different GIM techniques and implementations. 相似文献
130.
Jin Luo Haifeng Zhao Wei Huang YongQiang Zhu Wei Xiang Joachim Rohn 《Environmental Earth Sciences》2018,77(4):152
Thermal properties of ground heat exchanger (GHE) such as effective thermal conductivity and borehole thermal resistance are commonly measured in the field by thermal response tests (TRTs). TRT has been proved to be a consolidated method to determine thermal properties of traditional borehole heat exchangers (BHEs). However, there is still lack of data for adopting TRT on energy piles with often a large diameter and deficiency in validation of TRT results with geological materials. In this study, ground thermal properties for typical configured GHEs of energy piles are investigated. Three TRTs are conducted and the obtained results are analyzed. Effective thermal conductivity, λeff, of the ground derived by following the traditional linear source model shows large deviation as compared to the thermal conductivity of the geological materials. In order to determine λeff properly, the linear source model is modified and an equivalent radius, req, of energy piles is considered. The λeff estimated by the modified model shows a good agreement with thermal conductivity of the in situ geological materials. In addition, there has been no obvious correlation between borehole thermal resistances and thermal efficiency due to heat transport of energy piles that depends not only by borehole thermal resistance but also by the pile’s diameter and ground conditions. The findings drawn from this study indicate that the modified model is reasonable and useful in determining thermal properties of energy piles. 相似文献