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231.
The electrical conductivity of Posidonia black shales — from magnetotelluric exploration to rock samples
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We carried out a magnetotelluric field campaign in the South–East Lower Saxony Basin, Germany, with the main goal of testing this method for imaging regional Posidonia black shale sediments. Two‐dimensional inversion results of the magnetotelluric data show a series of conductive structures correlating with brine‐saturated sediments but also with deeper, anthracitic Westphalian/Namurian coals. None of these structures can be directly related with the Posidonia black shale, which appears to be generally resistive and therefore difficult to resolve with the magnetotelluric method. This assumption is supported by measurements of electrical resistivity on a set of Posidonia shale samples from the Hils syncline in the Lower Saxony basin. These rock samples were collected in shallow boreholes and show immature (0.53% Ro), oil (0.88% Ro), and gas (1.45% Ro) window thermal maturities. None of the black shale samples showed low electrical resistivity, particularly those with oil window maturity show resistivity exceeding 104 Ωm. Moreover, we could not observe a direct correlation between maturity and electrical resistivity; the Harderode samples showed the highest resistivity, whereas the Haddessen samples showed the lowest. A similar trend has been seen for coals in different states of thermal maturation. Saturation of the samples with distilled and saline water solutions led to decreasing electrical resistivity. Moreover, a positive correlation of electrical resistivity with porosity is observed for the Wickensen and Harderode samples, which suggests that the electrical resistivity of the Posidonia black shale is mainly controlled by porosity. 相似文献
232.
233.
A new mass rig system is proposed to minimize the deficiencies in current shaking table testing setups. This is accomplished by placing the inertial mass on a convex path designed to impose P‐Delta demands on slender cantilever columns. The design and performance of the mass rig system, and the principles used in deriving the equations of motion and their analytical validation against results obtained from shaking table tests, are presented. Formulation of the governing equations of motion was based on Lagrangian mechanics and solved using an implicit linear acceleration method with an adaptive time step formulation. Friction developed in the sliding system was also incorporated in the equations of motion. Experimental results validated the accuracy in the derivation and solution of the equations of motion. Validated by analytical and experimental results, P‐Delta effects were found to increase the displacement demands on slender columns in the low‐frequency range of acceleration input, while in the high‐frequency range P‐Delta effects led to no increase and in some cases even a reduction in displacement demands. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
234.
João Janeiro Anna ZacharioudakiEhsan Sarhadi Augusto NevesFlávio Martins 《Marine pollution bulletin》2014
A new approach towards the management of oil pollution accidents in marine sensitive areas is presented in this work. A set of nested models in a downscaling philosophy was implemented, externally forced by existing regional operational products. The 3D hydrodynamics, turbulence and the oil transport/weathering models are all linked in the same system, sharing the same code, exchanging information in real time and improving its ability to correctly reproduce the spill. A wind-generated wave model is also implemented using the same downscaling philosophy. Observations from several sources validated the numerical components of the system. The results obtained highlight the good performance of the system and its ability to be applied for oil spill forecasts in the region. The success of the methodology described in this paper was underline during the Costa Concordia accident, where a high resolution domain was rapidly created and deployed inside the system covering the accident site. 相似文献
235.
Fully probabilistic seismic risk assessment considering local site effects for the portfolio of buildings in Medellín,Colombia 总被引:1,自引:0,他引:1
Mario A. Salgado-Gálvez Daniela Zuloaga-Romero Gabriel A. Bernal Miguel G. Mora Omar-Darío Cardona 《Bulletin of Earthquake Engineering》2014,12(2):671-695
A fully probabilistic seismic risk analysis using a comprehensive approach is conducted for Medellin, the second largest city of Colombia, using a building by building database constructed and complemented from aerial images, considering characteristics such as building use categories, socio-economic levels and replacement values. The seismic hazard used for the analysis corresponds to the most updated study available in the country with the same model that was included in the national building code maps definition. Spectral transfer functions are determined for each of the seismic microzonation zones in order to take into account the dynamic soil response and amplification effects in the risk analysis. Several building types are defined for the city and individual vulnerability functions are assigned to each of them. Risk results are presented in the state of the art metrics such as the loss exceedance curve, probable maximum losses for different return periods, average annual losses and risk maps. The obtained results can be classified by use and socio-economic sectors as well as by structural systems that may help the stakeholders to identify where the risk concentrates. 相似文献
236.
Susana Bolhão Muiños James R. Hein Martin Frank José Hipólito Monteiro Luís Gaspar Tracey Conrad 《Marine Georesources & Geotechnology》2013,31(1):40-70
Eighteen deep-sea ferromanganese crusts (Fe-Mn crusts) from 10 seamounts in the northeast Atlantic were studied. Samples were recovered from water depths of ~1,200 to ~4,600 m from seamounts near Madeira, the Canary and Azores islands, and one sample from the western Mediterranean Sea. The mineralogical and chemical compositions of the samples indicate that the crusts are typical continental margin, hydrogenetic Fe-Mn crusts. The Fe-Mn crusts exhibit a Co + Cu + Ni maximum of 0.96 wt%. Platinum-group element contents analyzed for five samples showed Pt contents from 153 to 512 ppb. The resource potential of Fe-Mn crusts within and adjacent to the Portuguese Exclusive Economic Zone (EEZ) is evaluated to be comparable to that of crusts in the central Pacific, indicating that these Atlantic deposits may be an important future resource. 相似文献
237.
Alison de Oliveira Moraes Fabiano da Silveira Rodrigues Waldecir Jo?o Perrella Eurico Rodrigues de Paula 《Surveys in Geophysics》2012,33(5):1107-1131
Ionospheric scintillations are fluctuations in the phase and/or amplitude of trans-ionospheric radio signals caused by electron density irregularities in the ionosphere. A better understanding of the scintillation pattern is important to make a better assessment of GPS receiver performance, for instance. Additionally, scintillation can be used as a tool for remote sensing of ionospheric irregularities. Therefore, the study of ionospheric scintillation has both scientific as well as technological implications. In the past few years, there has been a significant advance in the methods for analysis of scintillation and in our understanding of the impact of scintillation on GPS receiver performance. In this work, we revisit some of the existing methods of analysis of scintillation, propose an alternative approach, and apply these techniques in a comprehensive study of the characteristics of amplitude scintillation. This comprehensive study made use of 32?days of high-rate (50?Hz) measurements made by a GPS-based scintillation monitor located in S?o José dos Campos, Brazil (23.2°S, 45.9°W, ?17.5° dip latitude) near the Equatorial Anomaly during high solar flux conditions. The variability of the decorrelation time (τ0) of scintillation patterns is presented as a function of scintillation severity index (S 4). We found that the values of τ0 tend to decrease with the increase of S 4, confirming the results of previous studies. In addition, we found that, at least for the measurements made during this campaign, averaged values of τ0 (for fixed S 4 index values) did not vary much as a function of local time. Our results also indicate a significant impact of τ0 in the GPS carrier loop performance for S 4?≥?0.7. An alternative way to compute the probability of cycle slip that takes into account the fading duration time is also presented. The results of this approach show a 38% probability of cycle slips during strong scintillation scenarios (S 4 close to 1 and τ0 near 0.2?s). Finally, we present results of an analysis of the individual amplitude fades observed in our set of measurements. This analysis suggests that users operating GPS receivers with C/N 0 thresholds around 30?dB-Hz and above can be affected significantly by low-latitude scintillation. 相似文献
238.
Alexandre A. Costa António Arêde Aníbal Costa Jo?o Guedes Bruno Silva 《Bulletin of Earthquake Engineering》2012,10(1):135-159
Stone masonry is one of the oldest building techniques used worldwide and it is known to exhibit poor behaviour under seismic
excitations. In this context, this work aims at assessing the in-plane behaviour of an existing double-leaf stone masonry
pier by experimental testing. Additionally, a detailed 3D finite element numerical analysis based on micro-modelling of the
original pier is presented (fully describing the geometry and division of each individual elements, namely infill, blocks
and joints) aiming at simulating the experimental test results. This numerical strategy can be seen as an alternative way
of analysing this type of constructions, particularly useful for laboratory studies, and suitable for the calibration of simplified
numerical models. As part of a wider research activity, this work is further complemented with the presentation of an effective
retrofit/strengthening technique (reinforced connected plaster) to achieve a significant improvement of its in-plane cyclic
response which is experimentally verified in the results presented herein. 相似文献
239.
Helen Glenn Diana TingleySonia Sánchez Maroño Dennis HolmGurpreet Padda Ingi Runar EdvardssonAlexis Conides Kostas KapirisMintewab Bezabih Premachandra WattageSakari Kuikka 《Marine Policy》2012,36(1):54-72
This paper explores the issue of “trust” in the fisheries science community, a key corollary of effective risk communication. It presents the findings of a survey undertaken in Iceland, Greece, Spain, United Kingdom and Faroe Islands during 2008. The findings reveal differing levels of trust and mistrust in the fisheries science community between countries and between stakeholder groups, demonstrating areas for future attention in the interests of improving fisheries science and management. As this paper explores, unfortunately the “trust” necessary for effective stakeholder cooperation and participation within current fisheries science is currently somewhat lacking. The cited reasons behind this lack of trust include: a lack of soundness, credibility, responsiveness, flexibility and stakeholder involvement, flawed data and weak science, poor communications and political and lobby group interference. Notable from the results is a lack of consensus on the existence of a common language and vision. It is evident, however, that certain aspects of fisheries science are strong contributors to trust and that there are opportunities for improvement. 相似文献
240.
Catarina Frazão Santos Zara Gonçalves Teixeira João Janeiro Renata Sousa Gonçalves Rhema Bjorkland Michael Orbach 《Marine Policy》2012
The EU Marine Strategy Framework Directive (MSFD) is considered to be the environmental pillar of the EU Integrated Maritime Policy, establishing a framework within which member states must take the necessary measures to achieve, or maintain, good environmental status in their marine waters. This study presents Portugal's contributions to the Directive development, describes the Portuguese institutional framework within the MSFD and, finally, highlights the opportunities and threats to the success of the MSFD implementation in Portugal. The latter entails an analysis of the Directive's long term adequacy in its link to (1) marine spatial planning, (2) climate change and (3) the economic/financial crisis. With one of Europe's largest exclusive economic zones. Portugal's interest in the MSFD is paramount. Efforts towards the approval of the final document were assured during the Portuguese presidency of the European Council of Ministers, in 2007, while chairing a thorough discussion between the Council and the European Parliament. In the Portuguese context, the Directive implementation will rely on the Water Institute as the authoritative entity, which will be responsible for coordinating all necessary efforts at the national level. The success of such process depends on a close cooperation among the institutions involved as well as on how approved measures account for long term issues. In addition, the MSFD implementation must be built on lessons learned within the Water Framework Directive, in order to be successful. Although it poses a methodological challenge to Portugal, the MSFD implementation is expected to contribute significantly to the improvement of coastal/marine conservation and management at the national level. 相似文献