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991.
Hervé Jourde Axel Roesch Vincent Guinot Vincent Bailly-Comte 《Environmental Geology》2007,51(5):725-730
This paper describes the role of groundwater contribution to surface flow at the Causse d’Aumelas, a karst system near Montpellier
(France), which is traversed by an intermittent river, the Coulazou. A first hydrologic model integrating a digital terrain
model shows the inability of a standard rainfall-runoff model to replicate recorded flood hydrographs. While the flood peaks
are routed through the karstic system along the Coulazou without a phase lag, the peak magnitude is somewhat modified. These
results indicate an initial karst system recharge followed by a significant contribution to surface flow. A hydrodynamic analysis
of ground-water flow confirms these results: the karst system first absorbs part of the rainfall, which induces a general
water table rise within the aquifer, and then contributes to surface flow in the Coulazou. 相似文献
992.
Nemesio M. Pérez Pedro A. Hernández Eleazar Padrón Gladys Melián Rayco Marrero Germán Padilla José Barrancos Dácil Nolasco 《Pure and Applied Geophysics》2007,164(12):2431-2448
Precursory geochemical signatures of radon degassing in the subsurface of the Tenerife Island were observed several months
prior to the recent 2004 seismic-volcanic crisis. These premonitory signatures were detected by means of a continuous monitoring
of 222Rn and 220Rn activity from a bubbling CO2-rich gas spot located at 2.850 m depth inside a horizontal gallery for groundwater exploitation at Tenerife. Multivariate
Regression Analysis (MRA) on time series of the radon activity was applied to eliminate the radon activity fluctuation due
to external variables such as barometric pressure, temperature and relative humidity as well as power supply. Material Failure
Forecast Method (FFM) was successfully applied to forecast the anomalous seismicity registered in Tenerife Island in 2004.
The changes in the 222Rn/220Rn ratio observed after the period of anomalous seismicity might suggest a higher gas flow rate and/or changes in the vertical
permeability induced by seismic activity. 相似文献
993.
The authors describe a simple model of an ionization-front propagating in a homogeneous expanding Nova shell. They have estimated the ejected shell mass, the shell ionization time and the Ly-c output from the remnant for several Novae, and present some correlations between these quantities and other Nova parameters. 相似文献
994.
A method is proposed to calculate the distribution of energy during the quasi-static confined comminution of particulate assemblies. The work input, calculated by integrating the load-displacement curve, is written as the sum of the elastic deformation energy, the breakage energy and the redistribution energy. Experimental results obtained on samples subjected to compression stresses ranging between 0.4 and 92 MPa are used to calibrate the model. The elastic energy stored in the samples is obtained by simulating the compression test on the final particle size distributions (PSDs) with the discrete element method and by extracting the contact forces. A PSD evolution law is proposed to account for particle breakage. The PSD is related to the total particle surface in the sample, which allows calculating the breakage energy. The redistribution energy, which comprises the kinetic energy of particles being rearranged and the friction energy dissipated at contacts, is obtained by subtracting the elastic energy and breakage energy from the work input. Results show that: (1) at least 60% of the work input is dissipated by particle redistribution; (2) the fraction of elastic deformation energy increases, and the fraction of redistribution energy decreases as the compression stress increases; (3) the breakage energy accounts for less than 5% of the total input energy, and this value is independent of the compressive stress; (4) the energy dissipated by redistribution is between 14 and 30 times larger than the breakage energy. 相似文献
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Khan Mohammad Zaved Kaiser Rahman Ataur Rahman Mohammad Azizur Renzaho André M. N. 《Natural Hazards》2021,108(2):2211-2224
Natural Hazards - Natural hazards like floods and droughts affect many aspects of life. The study in particular examined the impacts of droughts on under-five mortality rate in Southern Africa,... 相似文献