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排序方式: 共有239条查询结果,搜索用时 31 毫秒
231.
Jean Beaujean Jean‐Michel Lemieux Alain Dassargues René Therrien Serge Brouyère 《Ground water》2014,52(6):864-874
A general physically based method is presented to assess the vulnerability of groundwater to external pressures by numerical simulation of groundwater flow. The concept of groundwater vulnerability assessment considered here is based on the calculation of sensitivity coefficients for a user‐defined groundwater state for which we propose several physically based indicators. Two sensitivity analysis methods are presented: the sensitivity equation method and the adjoint operator method. We show how careful selection of a method can significantly minimize the computational effort. An illustration of the general methodology is presented for the Herten aquifer analog (Germany). This application to a simple, yet insightful, case demonstrates the potential use of this general and physically based vulnerability assessment method to complex aquifers. 相似文献
232.
In earthquake occurrence studies, the so-called q value can be considered both as one of the parameters describing the distribution of interevent times and as an index of
non-extensivity. Using simulated datasets, we compare four kinds of estimators, based on principle of maximum entropy (POME),
method of moments (MOM), maximum likelihood (MLE), and probability weighted moments (PWM) of the parameters (q and τ
0) of the distribution of inter-events times, assumed to be a generalized Pareto distribution (GPD), as defined by Tsallis
(1988) in the frame of non-extensive statistical physics. We then propose to use the unbiased version of PWM estimators to
compute the q value for the distribution of inter-event times in a realistic earthquake catalogue simulated according to the epidemic type
aftershock sequence (ETAS) model. Finally, we use these findings to build a statistical emulator of the q values of ETAS model. We employ treed Gaussian processes to obtain partitions of the parameter space so that the resulting
model respects sharp changes in physical behaviour. The emulator is used to understand the joint effects of input parameters
on the q value, exploring the relationship between ETAS model formulation and distribution of inter-event times. 相似文献
233.
Local soil failure before general slope failure 总被引:1,自引:0,他引:1
Gianfranco Urciuoli Luciano Picarelli Serge Leroueil 《Geotechnical and Geological Engineering》2007,25(1):103-122
Slopes are generally characterized by non-uniform stress field. Additional stresses induced by changes in boundary conditions
can emphasize local differences in the stress level. As a consequence, every failure process is, at first, local, with formation
of plastic zones, then general. This is the subject of this paper, which concerns clay slopes, whose failure generally implies
formation of a shear zone. A special consideration is addressed to the simple and special case of infinite slope which is
also featured by transition from local to general failure, even if stress conditions are uniform along the potential failure
plane. 相似文献
234.
Zhenxia Liu Serge Berné Yoshiki Saito Hua Yu Alain Trentesaux Katsuto Uehara Ping Yin J. Paul Liu Chaoxing Li Guanghai Hu Xiangqin Wang 《Continental Shelf Research》2007
On the basis of bathymetric and seismic data and data from piston cores collected by the Chinese–French marine geology and geophysics investigation of 1996, we discuss the internal architecture and mobility of tidal sand ridges in the East China Sea (ECS). We characterized the sand ridges on the middle to outer shelf of the ECS as tide-dominated sand ridges with southwest dipping beds, indicating that the regional net sediment transport is toward the southwest. As the sand ridges gradually migrate toward the southwest, new sand ridges are continually replacing old ones, and several generations of sand ridges have developed in the study area. 相似文献
235.
Christian Beck Pieter Van Rensbergen Marc De Batist Fernand Berthier Serge Lallier 《Journal of Paleolimnology》2001,25(4):551-553
Volume Contents
Volume contents 相似文献236.
Serge D. Elie 《GeoJournal》2018,83(5):897-913
This article depicts the initial human–environmental relations that prevailed during the pre-modern period of Soqotra’s history prior to its incorporation into a state-led modernization process and its subsequent enclosure within a United Nations-designed conservation zoning plan and ecotourism economy. The term ecological primordialism is coined to highlight the primacy of the environment as the enabling and constraining context for the constitution of the Soqotran community. It entails a symbiotic relationship between an ecosystem and a human social system, which structured the contingent relations between the raw materials for livelihood making and community formation: people, resources and space. The article elucidates how Soqotrans managed this mostly constraining human–environment nexus through a series of adaptive practices: their taxonomic appropriation and practical domestication of the island’s environmental resources; their transformation of the landscape into a domain of livelihood; their organization of dispersed settlements into a socio-political unit; their demarcation of the island into geographical zones of cultural differentiation; and their establishment of mutual aid institutions that simultaneously regulated resource use while integrating all islanders into relations of social kinship. The article concludes with a cautionary tale about the use of anachronistic human–environment relations as the basis of conservation policy. 相似文献
237.
Serge Ngendakumana Peter A. Minang Mireille Feudjio Stijn Speelman Patrick Van Damme Zacharie Tchoundjeu 《Climate Policy》2014,14(6):769-787
The reducing emissions from deforestation and forest degradation (REDD+) initiative has emerged in recent years as a mechanism to simultaneously address climate change, biodiversity, and poverty reduction challenges at the margins of tropical forests. Congo Basin countries, including Cameroon, have embraced the opportunities that REDD+ provides, with great expectations. Yet, it needs to be investigated whether the enabling institutional environment, which is required for implementing REDD+, is present. Understanding is still limited on how to build adequate and strong institutional relations that could shape the reforms towards the establishment of efficient emissions reductions schemes. Furthermore, uncertainty remains on the operational mechanisms of REDD+, suggesting that, to catalyse effectiveness, there is a need to come up with a governance model nested in relevant policy frameworks. This study builds on a modified ‘4Is’ framework – Institutions, Interests, Ideas and Information – to analyse REDD+ and explore stakeholders' perceptions on the local forest governance potential. A structural implementation model to optimize the effectiveness of REDD+ is developed. Findings suggest that governments need to review existing policies to take into account participation, local people rights, and information access as a way to stimulate actors' willingness to contribute to emissions reductions and carbon stock increases under REDD+ regimes. 相似文献
238.
Carolina Bernal Frédéric Christophoul Jean-Claude Soula José Darrozes Luc Bourrel Alain Laraque José Burgos Séverine Bès de Berc Patrice Baby 《International Journal of Earth Sciences》2012,101(7):1913-1928
The successive courses of the Rio Pastaza in the upper Amazonian Puyo plateau (Ecuador) during the past century have been followed using historical maps, aerial photographs, satellite imagery, topographic and river long profiles, and field studies. The abrupt change in direction of the Rio Pastaza from transverse to longitudinal was a result of two avulsions occurred between 1906 and 1976 at the braided-meandering transition of the former alluvial plain. These avulsions are related to aggradation at the toe of a braided piedmont fan prograding on to a hinterland-dipping topographic slope formed by ongoing tectonic backtilting. The main avulsion proceeded by annexation of a south-dipping depression created in front of the cordillera by backtilting of the plateau. A partial and gradual avulsion having occurred upstream of the former site between 1976 and 2008 is marked by the progressive predominance of a newly formed inner branch. Tectonic backtilting enhanced aggradation upstream of the initial site while it offered the newly avulsed channel a still more favorable way along the cordillera by creating a westward lateral slope. The correlation between ENSO events and the occurrence of the 1976–2008 avulsions strongly suggests that the triggers of the avulsions were the floods caused by the high water and sediment discharges associated with ENSO (La Ni?a) events contrasting with the regular monthly discharge and the lack of actual ‘normal’ floods during the inter-ENSO periods. 相似文献
239.
Jérôme Carrayrou Joachim Hoffmann Peter Knabner Serge Kräutle Caroline de Dieuleveult Jocelyne Erhel Jan Van der Lee V. Lagneau K. Ulrich Mayer Kerry T. B. MacQuarrie 《Computational Geosciences》2010,14(3):483-502
Although multicomponent reactive transport modeling is gaining wider application in various geoscience fields, it continues
to present significant mathematical and computational challenges. There is a need to solve and compare the solutions to complex
benchmark problems, using a variety of codes, because such intercomparisons can reveal promising numerical solution approaches
and increase confidence in the application of reactive transport codes. In this contribution, the results and performance
of five current reactive transport codes are compared for the 1D and 2D subproblems of the so-called easy test case of the
MoMaS benchmark (Carrayrou et al., Comput Geosci, 2009, this issue). This benchmark presents a simple fictitious reactive transport problem that highlights the main numerical difficulties
encountered in real reactive transport problems. As a group, the codes include iterative and noniterative operator splitting
and global implicit solution approaches. The 1D easy advective and 1D easy diffusive scenarios were solved using all codes,
and, in general, there was a good agreement, with solution discrepancies limited to regions with rapid concentration changes.
Computational demands were typically consistent with what was expected for the various solution approaches. The differences
between solutions given by the three codes solving the 2D problem are more important. The very high computing effort required
by the 2D problem illustrates the importance of parallel computations. The most important outcome of the benchmark exercise
is that all codes are able to generate comparable results for problems of significant complexity and computational difficulty. 相似文献