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291.
Abstract This paper proposes a framework for identifying the parameters of a lumped routing model in small to medium sized catchments where lateral inflows can be large but poorly defined. In a first step, a priori estimates of the parameters are made based on topography, aerial photographs, flood marks and field surveys. In a second step, runoff data are analysed of reservoir release events and convective events where no rainfall in the direct catchments occurred. In a third step the routing model is calibrated to the results of hydrodynamic models for scenarios of different magnitudes. In a fourth step, these pieces of information are combined, allowing for soft expert judgement to be incorporated. In a fifth step, the routing parameters are fine tuned to observed flood events where lateral inflows are estimated by a rainfall—runoff model. The framework is illustrated by the Kamp flood forecasting system in Austria that has been in operational use since 2006. 相似文献
292.
As well as world class Fe and REE resources the Bayan Obo mineral deposits also hosts significant niobium resources(estimated as 2.2 Mt Nb with an average grade of 0.13 wt% Nb).Niobium in this study is primarily hosted in aeschynite-(Ce) and(Nd),but with subsidiary amounts of pyrochlore,fergusonite-(Ce),fersmite and columbite.Here we report on the paragenetic and textural setting of aeschynite,pyrochlore and fergusonite in the main ore bodies and in a carbonatite dyke.Niobium in a carbonatite sample is hosted in a phase tentatively(due to significant Ca,Mn and Ti contents) identified as fergusonite-(Ce).Aeschynite occurs overgrowing foliation in banded ores,in fractures and vugs in aegirine-rich rocks and in calcite veins.The composition in all settings is similar,but some examples in banded ores develop significant zonation in Y,Th and the REE,inferred to relate to buffering of halogen acid species to low levels by dissolution and fluoritisation of calcite,and the preferential precipitation of LREE from solution due to lower mineral solubility products compared to the HREE.Although lower in total concentration the ratios of REE in pyrochlore are similar to those of aeschynite and suggest the same metal source.The crystallisation of pyrochlore probably relates to growth in paragenetic settings where carbonates had already been eliminated and hence the buffering of F-species activities in the hydrothermal fluid was reduced.Both aeschynite and pyrochlore show evidence of alteration.Primary alteration of aeschynite resulted in leaching of A-site cations(Ca,REE,Th) and Nb,addition of Fe,and ultimately replacement by Ba-Ti phases(baotite and bafertisite).Secondary,metamictisation enhanced,possibly supergene alteration of pyrochlore resulted in hydration,leaching of A-site cations leading to the development of lattice vacancies and increases in Si.The presence of hydrothermal Nb resources at Bayan Obo suggests there may be potential for further Nb discoveries in the area,whilst the trends in element mobility during alteration have significant implications for the utility of A-B oxides as components of materials for immobilisation of radionuclides. 相似文献
293.
Analysis methods for block toppling are most commonly undertaken in two dimensions. This paper investigates the influence
of discontinuity orientations on three-dimensional block toppling mechanisms using a three-dimensional distinct element code.
The three-dimensional models allow one to kinematically appraise if toppling conditions derived for two-dimensional geometries
can be extended into three dimensions. Two conceptual model geometries were considered in order to represent a road cut or
open-pit bench. The first geometry examined a slope with fixed vertical lateral boundaries, while the second geometry assumed
an unrestrained lateral slope as a model boundary condition. This “along-strike slope profile” of the models was found to
play an important role in the failure mechanism and displacement direction. The dip direction and dip angle of the toppling,
basal and lateral release discontinuities were varied one at the time using angular ranges of up to 30° from an assumed mutual
orthogonal relationship. This made it possible for the influence and importance of each discontinuity set to be independently
evaluated. The results are presented in a stereographic format with preliminary zones outlining discontinuity aspect combinations
that potentially result in block toppling failures. 相似文献
294.
Zhangcai QIN Xi DENG Bronson GRISCOM Yao HUANG Tingting LI Pete SMITH Wenping YUAN Wen ZHANG 《大气科学进展》2021,38(6):889-895
正"I call on all leaders worldwide to declare a State of Climate Emergency in their own countries until carbon neutrality is reached."–António GUTERRES(United Nations Secretary General), 12 December, 2020 There is no shortcut to a carbon neutral society; solutions are urgently required from both energy industrial sectors and global ecosystems. 相似文献