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21.
The analytic construction of the direct periodic orbits in the circular 3-body problem is given in explicit form to the linear terms in . It is shown to be in good agreement with the numerically found orbits for large values of . 相似文献
22.
On the coronograph spectrophotographic records taken on 31.372 UT, August 1979, some faint emission features were found which can be ascribed to Siii and Niii. These emissions were obviously a transient phenomena which were detected only 10 hr after the supposed fall of Comet 1979 XI in the Sun's photosphere. It cannot be excluded that the appearance of Si and Ni lines was triggered by the evaporation of dust particles with a high abundance of heavier elements in the solar corona. This assumption is also supported by intensity distribution of the Fex coronal line around the Sun's limb. The maximum coincide with the position angle of the projected path of the comet. 相似文献
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We have revised the regional crustal structure, oceanic age distribution, and conjugate margin segmentation in and around the Lena Trough, the oceanic part of the Fram Strait between the Norwegian–Greenland Sea and the Eurasia Basin (Arctic Ocean). The Lena Trough started to open after Eurasia–Greenland relative plate motions changed from right-lateral shear to oblique divergence at Chron 13 times (33.3 Ma; earliest Oligocene). A new Bouguer gravity map, supported by existing seismic data and aeromagnetic profiles, has been applied to interpret the continent–ocean transition and the influence of Eocene shear structures on the timing of breakup and initial seafloor spreading. Assuming that the onset of deep-water exchange depended on the formation of a narrow, oceanic corridor, the gateway formed during early Miocene times (20–15 Ma). However, if the initial Lena Trough was blocked by terrigenous sediments or was insufficiently subsided to allow for deep-water circulation, the gateway probably formed with the first well developed magnetic seafloor spreading anomaly around Chron 5 times (9.8 Ma; Late Miocene). Paleoceanographic changes at ODP Site 909 (northern Hovgård Ridge) are consistent with both hypotheses of gateway formation. We cannot rule out that a minor gateway formed across stretched continental crust prior to the onset of seafloor spreading in the Lena Trough. The gravity, seismic and magnetic observations question the prevailing hypotheses on the Yermak Plateau and the Morris Jesup Rise as Eocene oceanic plateaus and the Hovgård Ridge as a microcontinent. 相似文献
25.
The largest karst cave discovered in a tunnel during motorway construction in Slovenia’s Classical Karst (Kras) 总被引:1,自引:0,他引:1
Karst researchers of the Karst Research Institute ZRC SAZU are regularly consulted during the planning of Slovenia’s motorways
and invited to observe and monitor construction in the karst areas. More than 350 caves have been discovered in the course
of building 60 km of new motorways over the past decade. Access to the most important caves is preserved by concrete tubes
closed with metal covers at the roadside. The largest cave system in a tunnel, named LC-S647, is almost entirely preserved.
The protection of this cave will serve as a good example for the preservation of natural heritage in the future. Construction
work for the motorway uncovered a high degree of karstification. In particular, the discovery of this cave in the Kastelec
tunnel LC-S647 showed the existence of a major cave system in the geological and speleological past. A number of unconnected
passages have also been found. Caves discovered during highway construction have brought new knowledge about the cavernosity
and the geological history of this part of the karst. 相似文献
26.
We propose a simple pressure test that can be used in the field to determine the effective permeability of existing wellbores.
Such tests are motivated by the need to understand and quantify leakage risks associated with geological storage of CO2 in mature sedimentary basins. If CO2 is injected into a deep geological formation, and the resulting CO2 plume encounters a wellbore, leakage may occur through various pathways in the “disturbed zone” surrounding the well casing.
The effective permeability of this composite zone, on the outside of the well casing, is an important parameter for models
of leakage. However, the data that exist on this key parameter do not exist in the open literature, and therefore specific
field tests need to be done in order to reduce the uncertainty inherent in the leakage estimates. The test designed and analyzed
herein is designed to measure effective wellbore permeability within a low-permeability caprock, bounded above and below by
permeable reservoirs, by pressurizing the reservoir below and measuring the response in the reservoir above. Alternatively,
a modified test can be performed within the caprock without directly contacting the reservoirs above and below. We use numerical
simulation to relate pressure response to effective well permeability and then evaluate the range of detection of the effective
permeability based on instrument measurement error and limits on fracture pressure. These results can guide field experiments
associated with site characterization and leakage analysis. 相似文献
27.
Jan Kaiser 《Geochimica et cosmochimica acta》2008,72(5):1312-1334
Mass-spectrometric stable isotope measurements of CO2 use molecular ion currents at mass-to-charge ratios m/z 44, 45 and 46 to derive the elemental isotope ratios n(13C)/n(12C) and n(18O)/n(16O), abbreviated 13C/12C and 18O/16O, relative to a reference. The ion currents have to be corrected for the contribution of 17O-bearing isotopologues, the so-called ‘17O correction’. The magnitude of this correction depends on the calibrated isotope ratios of the reference. Isotope ratio calibrations are difficult and are therefore a matter of debate. Here, I provide a comprehensive evaluation of the existing 13C/12C (13R), 17O/16O (17R) and 18O/16O (18R) calibrations of the reference material Vienna Standard Mean Ocean Water (VSMOW) and CO2 generated from the reference material Vienna Pee Dee Belemnite (VPDB) by reaction with 100% H3PO4 at 25 °C (VPDB-CO2). I find , 18RVSMOW/10−6 = 2005.20 ± 0.45, 13RVPDB-CO2/10-6= 11124 ± 45, and 18RVPDB-CO2/10-6=2088.37±0.90. I also rephrase the calculation scheme for the 17O correction completely in terms of relative isotope ratio differences (δ values). This reveals that only ratios of isotope ratios (namely, 17R/13R and 13R17R/18R) are required for the 17O correction. These can be, and have been, measured on conventional stable isotope mass spectrometers. I then show that the remaining error for these ratios of isotope ratios can lead to significant uncertainty in the derived relative 13C/12C difference, but not for18O/16O. Even though inter-laboratory differences can be corrected for by a common ‘ratio assumption set’ and/or normalisation, the ultimate accuracy of the 17O correction is hereby limited. Errors of similar magnitude can be introduced by the assumed mass-dependent relationship between 17O/16O and 18O/16O isotope ratios. For highest accuracy in the 13C/12C ratio, independent triple oxygen isotope measurements are required. Finally, I propose an experiment that allows direct measurement of 13R17R/18R. 相似文献
28.
Gravitational spreading of mountain ridges displays primary disequilibrium of flysch mountain areas of the Czech Carpathians.
The progression of various types of mass movements is a product of long-term ridge disintegration and is predisposed by the
geological structure of the area and the upper Tertiary-Quaternary morphogenesis of the mountain area. Deep-seated slope deformations
are spatially interconnected by the occurrence of some other types of slope deformations (e.g. debris flows, debris slides,
slumps, rock avalanches, etc.), which pose a considerable risk for the existence of human society. An important causative
factor in these dynamically developing hazardous processes is, among other factors, the way in which land has been used in
the last three centuries. Therefore, the occurrence of various types of slope deformations is studied in terms of their relation
to deep-seated gravitational deformations and in terms of other limiting factors (structural geological, morphological and
climatic factors, manmade impacts, etc.). The paper presents several case studies of slope deformations (Velká Čantoryje Mt,
Lysá hora Mt, Ropice Mt and Smrk Mt) in the area of the Outer Carpathians within the territory of the Czech Republic and also
adverts to some consequences in terms of the socioeconomic structure of the landscape. 相似文献
29.
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