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71.
L. van Rensburg S. Claassens J. J. Bezuidenhout P. J. Jansen van Rensburg 《Environmental Geology》2009,57(2):267-273
The much publicised problem with major asbestos pollution and related health issues in South Africa, has called for action
to be taken to negate the situation. The aim of this project was to establish a prioritisation index that would provide a
scientifically based sequence in which polluted asbestos mines in Southern Africa ought to be rehabilitated. It was reasoned
that a computerised database capable of calculating such a Rehabilitation Prioritisation Index (RPI) would be a fruitful departure
from the previously used subjective selection prone to human bias. The database was developed in Microsoft Access and both
quantitative and qualitative data were used for the calculation of the RPI value. The logical database structure consists
of a number of mines, each consisting of a number of dumps, for which a number of samples have been analysed to determine
asbestos fibre contents. For this system to be accurate as well as relevant, the data in the database should be revalidated
and updated on a regular basis. 相似文献
72.
Inception of the Northern European ice sheet due to contrasting ocean and insolation forcing 总被引:1,自引:0,他引:1
Bjørg Risebrobakken Trond Dokken Eystein Jansen Yongqi Gao Helge Drange 《Quaternary Research》2007,67(1):128-135
About 115,000 yr ago the last interglacial reached its terminus and nucleation of new ice-sheet growth was initiated. Evidence from the northernmost Nordic Seas indicate that the inception of the last glacial was related to an intensification of the Atlantic Meridional Overturning Circulation (AMOC) in its northern limb. The enhanced AMOC, combined with minimum Northern hemisphere insolation, introduced a strong sea-land thermal gradient that, together with a strong wintertime latitudinal insolation gradient, increased the storminess and moisture transport to the high Northern European latitudes at a time when the Northern hemisphere summer insolation approached its minimum. 相似文献
73.
74.
Landslides - On 25 August 1933, a 7.5-magnitude earthquake struck the eastern margin of the Tibetan Plateau in Sichuan, China. The Diexi earthquake is among the largest known geohazard events... 相似文献
75.
S.P. Vriend M.G. Oosterom R.W. Bussink J.B.H. Jansen 《Journal of Geochemical Exploration》1985,23(1):13-25
Vein-type W-Sn deposits occur both in and around the Regoufe granite. The muscovite-albite granite hosts several roof pendants of schist along its eastern and northern margins. Biotite, tourmaline and K-feldspar megacrysts are virtually absent from the roof zone of the granite but sulphides are abundant. These sulphides disappear through a transition zone and the granite becomes a tourmaline-bearing porphyritic two-mica granite. Fifty-five rock samples were collected within the granite resulting in a sample density of about 10 samples per km2. The analytical results show that the granite is extremely rich in Sn, W, Li and Cs, rich in P, Ta, Rb, F and U, about normal in Cu, Zn and Nb and low in Sr, Ti and Zr in comparison with the global averages for low-Ca granites. Factor analysis was applied to the data and the resulting three factor model could be correlated to the field relations. Factor 1 reflects greisenization and albitization processes. Factor 2 scores are high in the mineralized areas and factor 3 appears to be connected with the transition zone. 相似文献
76.
Reduced-order optimal control of water flooding using proper orthogonal decomposition 总被引:1,自引:0,他引:1
Jorn F. M. van Doren Renato Markovinović Jan-Dirk Jansen 《Computational Geosciences》2006,10(1):137-158
Model-based optimal control of water flooding generally involves multiple reservoir simulations, which makes it into a time-consuming
process. Furthermore, if the optimization is combined with inversion, i.e., with updating of the reservoir model using production
data, some form of regularization is required to cope with the ill-posedness of the inversion problem. A potential way to
address these issues is through the use of proper orthogonal decomposition (POD), also known as principal component analysis,
Karhunen–Loève decomposition or the method of empirical orthogonal functions. POD is a model reduction technique to generate
low-order models using ‘snapshots’ from a forward simulation with the original high-order model. In this work, we addressed
the scope to speed up optimization of water-flooding a heterogeneous reservoir with multiple injectors and producers. We used
an adjoint-based optimal control methodology that requires multiple passes of forward simulation of the reservoir model and
backward simulation of an adjoint system of equations. We developed a nested approach in which POD was first used to reduce
the state space dimensions of both the forward model and the adjoint system. After obtaining an optimized injection and production
strategy using the reduced-order system, we verified the results using the original, high-order model. If necessary, we repeated
the optimization cycle using new reduced-order systems based on snapshots from the verification run. We tested the methodology
on a reservoir model with 4050 states (2025 pressures, 2025 saturations) and an adjoint model of 4050 states (Lagrange multipliers).
We obtained reduced-order models with 20–100 states only, which produced almost identical optimized flooding strategies as
compared to those obtained using the high-order models. The maximum achieved reduction in computing time was 35%. 相似文献
77.
Dr. Manfred Behrens Armin Jansen Dipl.-Geol. Dr. Paul Wurster 《International Journal of Earth Sciences》1967,56(1):748-765
Zusammenfassung An vier feldgeologisch untersuchten Beispielen, dem Gräfenthaler Horst im Frankenwald, der Fränkischen Linie bei Kronach, der Kulmbacher Verwerfung bei Kirchleus und an Verwerfungszonen im Steigerwald wird gezeigt, daß die fränkischen Verwerfungen als Flächen eines zusammenhängenden Strukturfeldes angesehen werden können, das trotz seiner verschiedenartigen Erscheinungsformen im Grund- und Deckgebirge auf eine gemeinsame Ursache zurückgehen dürfte.
Herrn Professor Dr.Roland Brinkmann zum 70. Geburtstag gewidmet. 相似文献
Four areas in Northern Bavaria, the Gräfenthaler Horst in the Frankenwald, the Franconian Line near Kronach, the Kulmbach Fault near Kirchleus and fault zones in the Steigerwald, were investigated by different field methods. The authors are in the opinion that these Franconian faults are elements of a connecting structural region though different tectonic phenomena may be observed on the surface.
Résumé Dans le nord de la Bavière des grands accidents tectoniques de direction NW/ SE, dont quelques-uns traversent le socle hercynien, d'autres la couverture mésozoique avoisinante, ont été étudiés par des methodes diverses. Quoique leurs caractères changent selon l'étage affectée, ces accidents sont des élements d'un seul domaine structural et ont apparement une origine commune.
. , , , .
Herrn Professor Dr.Roland Brinkmann zum 70. Geburtstag gewidmet. 相似文献
78.
Steven Franke Hannes Eisermann Wilfried Jokat Graeme Eagles Jölund Asseng Heinrich Miller Daniel Steinhage Veit Helm Olaf Eisen Daniela Jansen 《地球表面变化过程与地形》2021,46(13):2728-2745
The landscape of Antarctica, hidden beneath kilometre-thick ice in most places, has been shaped by the interactions between tectonic and erosional processes. The flow dynamics of the thick ice cover deepened pre-formed topographic depressions by glacial erosion, but also preserved the subglacial landscapes in regions with moderate to slow ice flow. Mapping the spatial variability of these structures provides the basis for reconstruction of the evolution of subglacial morphology. This study focuses on the Jutulstraumen Glacier drainage system in Dronning Maud Land, East Antarctica. The Jutulstraumen Glacier reaches the ocean via the Jutulstraumen Graben, which is the only significant passage for draining the East Antarctic Ice Sheet through the western part of the Dronning Maud Land mountain chain. We acquired new bed topography data during an airborne radar campaign in the region upstream of the Jutulstraumen Graben to characterise the source area of the glacier. The new data show a deep relief to be generally under-represented in available bed topography compilations. Our analysis of the bed topography, valley characteristics and bed roughness leads to the conclusion that much more of the alpine landscape that would have formed prior to the Antarctic Ice Sheet is preserved than previously anticipated. We identify an active and deeply eroded U-shaped valley network next to largely preserved passive fluvial and glacial modified landscapes. Based on the landscape classification, we reconstruct the temporal sequence by which ice flow modified the topography since the beginning of the glaciation of Antarctica. 相似文献
79.
Late Holocene Baltic Sea outflow changes reconstructed using C37:4 content from marine cores 下载免费PDF全文
Veronica Rohde Krossa Matthias Moros Thomas Blanz Eystein Jansen Ralph Schneider 《Boreas: An International Journal of Quaternary Research》2015,44(1):81-93
The Baltic Sea is an intra‐continental brackish water body. Low saline surface water, the so‐called Baltic outflow current, exits the Baltic Sea through the Kattegat into the Skagerrak. Ingressions of saline oxygen‐rich bottom water enter the Baltic Sea basins via the narrow and shallow Kattegat and are of great importance for the ecological and ventilation state of the Baltic Sea. Over recent decades, progress has been made in studying Holocene changes in saline water inflow. However, reconstructions of past variations in Baltic Sea outflow changes are sparse and hampered because of the lack of suitable proxies. Here, we used the relative proportion of tetra‐unsaturated C37 ketones (C37:4 %) in long‐chain alkenones produced by coccolithophorids as a proxy for outflowing Baltic Sea water in the Skagerrak. To evaluate the applicability of the proxy, we compared the biomarker results with grain‐size records from the Kattegat and Mecklenburg Bay in addition to previously published salinity reconstructions from the Kattegat over the last 5000 years. All Skagerrak records showed an increase in C37:4 % that is accompanied by enhanced bottom water currents in the Kattegat and western Baltic Sea over the past 3500 cal. a BP, indicating an increase in Baltic Sea outflow. This probably reflects higher precipitation in the Baltic Sea catchment area owing to a re‐organization of North Atlantic atmospheric circulation with an increased influence of wintertime Westerlies over the Baltic catchment from the mid‐ to the late Holocene. 相似文献
80.
Linear regression models relating annual average sediment yield with a number of climatic and topographic variables, are developed for rivers (basin area >5,000 km2) in bach of the world's major climatic zones. The models are seen to be of value as a predictive cool to assess the scale of the sediment problem in rivers where no sediment data exist. Despite the limitations imposed by the use of numerical optimisation in their development, the relative significance of different climatic and topographic factors is demonstrated, and an estimate of the annual global denudation, based on the equations, compares satisfactorily with existing figures. 相似文献