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91.
Victor Ginting Felipe Pereira Michael Presho Shaochang Wo 《Computational Geosciences》2011,15(4):691-707
In this paper, we develop a procedure for subsurface characterization of a fractured porous medium. The characterization involves
sampling from a representation of a fracture’s permeability that has been suitably adjusted to the dynamic tracer cut measurement
data. We propose to use a type of dual-porosity, dual-permeability model for tracer flow. This model is built into the Markov
chain Monte Carlo (MCMC) method in which the permeability is sampled. The Bayesian statistical framework is used to set the
acceptance criteria of these samples and is enforced through sampling from the posterior distribution of the permeability
fields conditioned to dynamic tracer cut data. In order to get a sample from the distribution, we must solve a series of problems
which requires a fine-scale solution of the dual model. As direct MCMC is a costly method with the possibility of a low acceptance
rate, we introduce a two-stage MCMC alternative which requires a suitable coarse-scale solution method of the dual model.
With this filtering process, we are able to decrease our computational time as well as increase the proposal acceptance rate.
A number of numerical examples are presented to illustrate the performance of the method. 相似文献
92.
93.
Tadeu José Pereira Gilda Silva Maria José Costa José Lino Costa 《Estuarine, Coastal and Shelf Science》2011
The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the “characteristic” morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics. 相似文献
94.
Sin Chan Chou Andr de Arruda Lyra Jorge Lus Gomes Daniel Andrs Rodriguez Minella Alves Martins Nicole Costa Resende Priscila da Silva Tavares Claudine Pereira Dereczynski Isabel Lopes Pilotto Alessandro Marques Martins Lus Felipe Alves de Carvalho Jos Luiz Lima Onofre Idalcio Major Manuel Penhor Adrito Santana 《Climate Dynamics》2020,54(9):4021-4042
Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work. 相似文献
95.
V.F. Litvin F.M. Holzmann B.S. Taibin S.A. Matveev W. Pereira V.V. Orlov 《Astrophysics and Space Science》1997,253(2):181-187
The main aim of this paper is to search for matter clumps in scales with redshifts z∼1 using a new enlarged version of the
QSO catalogue. This work confirms the evidence of the existence of anomalous spots in the sky, where the Hubble diagram shows
an extreme behaviour, as well as the existence of a spot where there is maximum density of absorbers. In addition to this,
the work also reveals a second anomaly of the same type, though of smaller intensity. An estimate is carried out of the statistical
significance of these anomalies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
96.
Cristina I.Pereira Celene B.Milanes Rafael Sarda Benjamin Cuker Camilo M.Botero 《地学前缘(英文版)》2021,12(6):36-45
Defining impact significance is the main technical task that influences decision-making during the Environmental Licensing Procedure(ELP).The ELP begins with screening to determine potentially signif-icant impacts of the proposed project.Scoping then follows to address any interventions deemed worthy of attention in the production of an Environmental Impact Assessment(EIA).This will include consider-ation of relevant landforms and geomorphological processes.However,preliminary assessments of envi-ronmental impacts often lack the scientific robustness to procure substantive and transactive effectiveness.This review presents an examination of the established practices of screening and scoping while highlighting the foremost challenges to improve the technical grounds of the ELP.The analysis of screening and scoping practices stresses the need for novel methods that ensure the sequential reasoning between their criteria while improving the preliminary evaluation of impact significance.Reducing the inherent subjectivity of discretionary judgment requires scientific methodologies that acknowledge the interaction between the natural system and human interventions,which has been addressed by geomor-phological research.The knowledge consolidated in this review opens the gate to explore the compatibil-ity between the United Nations strategy of Ecosystem Approach(EA)with the ELP through a novel geomorphological interpretation of the EIA.Therefore,this diagnosis demonstrate that screening and scoping practices would benefit from reliable methods that balance the precautionary principle with the efficient character required in the ELP. 相似文献
97.
Darde Benjamin Roux Jean-Noël Pereira Jean-Michel Dangla Patrick Talandier Jean Vu Minh Ngoc Tang Anh Minh 《Acta Geotechnica》2021,16(2):507-524
Acta Geotechnica - Bentonite pellet mixtures are candidate material for the sealing of galleries in radioactive waste disposals. The hydromechanical behaviour of assemblies of bentonite pellets is... 相似文献
98.
An initial on-going survey of the activity concentrations of 226Ra, 232Th and 40K for sand samples collected within the coastal strip of 290 Ramsar site evaluated the external hazard index, the outdoor annual effective dose equivalent and the radium equivalent activity, to elucidate potential risks for the resident inhabitants. The range of mean activity concentrations in the whole area for 226Ra, 232Th and 40K were between 4.12?±?0.26 and 48.3?±?1.4, 5.47?±?0.55 and 194?±?13, 77.7?±?4.2 and 445?±?18 Bq kg?1, respectively. The Barra de Valizas–Aguas Dulces region had the highest activity concentrations of 226Ra and 232Th. The annual effective dose equivalent for this region was higher than the mean worldwide value, whereas it is lower than the recommended values for public exposure. 相似文献
99.
Pereira M. F. Díez Fernández R. Gama C. Hofmann M. Gärtner A. Linnemann U. 《International Journal of Earth Sciences》2018,107(1):251-267
International Journal of Earth Sciences - Zircon grains extracted from S-type granites of the Mêda-Escalhão-Penedono Massif (Central Iberian Zone, Variscan Orogen) constrain the timing of... 相似文献
100.
Physical controls on sand composition and relative durability of detrital minerals during ultra‐long distance littoral and aeolian transport (Namibia and southern Angola) 下载免费PDF全文
Eduardo Garzanti Alberto Resentini Sergio Andò Giovanni Vezzoli Alcides Pereira Pieter Vermeesch 《Sedimentology》2015,62(4):971-996
Sediment in coastal Namibia to southern Angola is supplied dominantly from the Orange River with minor additional fluvial input and negligible modifications by chemical processes, which makes this a great test case for investigating physical controls on sand texture and composition. This study monitored textural, mineralogical and geochemical variability in beach and aeolian‐dune sands along a ca 1750 km stretch of the Atlantic coast of southern Africa by using an integrated set of techniques, including image analysis, laser granulometry, optical microscopy, Raman spectroscopy and bulk‐sediment geochemistry. These results contrast with previous reports that feldspars and volcanic detritus break down during transport, that sand grains are rounded rapidly in shallow‐marine environments, and that quartzose sands may be produced by physical processes. Mechanical wear is unable to modify the relative abundance of detrital components, including pyroxene and mafic volcanic rock fragments traditionally believed to be destroyed rapidly. The sole exceptions are poorly lithified or cleaved sedimentary/metasedimentary rock fragments, readily lost at the transition to the marine environment, and slow‐settling flaky micas, winnowed and deposited offshore. Coastal sediments tend to be depleted in relatively mobile amphibole, preferentially entrained offshore or re‐deposited in sheltered beaches, while less mobile garnet is retained onshore. No detrital mineral displays a significant increase in grain roundness after 300 to 350 km of longshore transport in high‐energy littoral environments from the Orange mouth to south of the Namib Erg, but all minerals get rapidly rounded after passing into the dunefield. Pyroxene and opaques get rounded faster than harder quartz and garnet, but sand mineralogy remains unchanged. Excepting strong transient selective‐entrainment effects, physical processes are unable to modify sand composition significantly. Selective mechanical breakdown can be largely neglected in quantitative provenance analysis of sand and sandstone even in the case of ultra‐long‐distance transport in high‐energy environments dominated by strong persistent winds and waves. 相似文献