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Main concepts of the "European approach" to karst-groundwater-vulnerability assessment and mapping 总被引：4，自引：1，他引：3
D. Daly A. Dassargues D. Drew S. Dunne N. Goldscheider S. Neale I. Popescu F. Zwahlen 《Hydrogeology Journal》2002,10(2):340-345
In order to achieve some consistency in the establishment of groundwater intrinsic vulnerability maps in Europe, a new approach
is proposed by Working Group 1 of the European COST Action 620 on "Vulnerability mapping for the protection of carbonate (karst)
aquifers". A general procedure is offered which provides consistency while allowing the required flexibility for application
to a continent and under conditions of varying geology, scale, information availability, time, and resources.
The proposed methodology is designed to be clearly more physically based than the existing vulnerability-mapping techniques.
It takes the specificity of the karstic environments into account without necessarily excluding the applicability to other
geological conditions. Combined "core factors" for overlying layers and for concentration of flow account for the relative
protection of groundwater from contamination while taking into account any bypass of the overlying layers.
A precipitation factor is distinguished for describing characteristics of the input of water to the system. Differentiation
is made between groundwater resource intrinsic vulnerability mapping and source intrinsic vulnerability mapping. For the latter,
a factor describing the karst network development is relevant. This short technical note describes a first step in the work
program of Working Group 1 of the COST Action 620. Future steps are now in progress to quantify the approach and to apply
it in various European pilot areas.
Electronic Publication 相似文献
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Mihail E. Popescu 《Engineering Geology》1979,14(1):43-53
Engineering problems associated with expansive clay formations, which have a large swelling and shrinking potential, exist in different regions of Romania.In the general framework of the study of the behaviour of expansive clays, the present paper describes some particular aspects connected with the swelling and shrinkage processes and their engineering effects in Romania.The differences between swelling potential relationships, obtained by two different methods are presented and discussed. Swelling pressure tests were accomplished using the available standard techniques, as well as a specially developed cell pressure equipment.Attention is drawn to the stages of the shrinkage process as related to soil structure. It was found that, in a general case, there are three distinct?tages: initial, normal and residual shrinkage.Laboratory investigations have shown that in soils with an anisotropic structure, the directional variation of shrinkage strains is elliptical in shape, with the maximum shrinkage normal to particle orientation.The engineering aspects of the results are discussed. 相似文献
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High-latitude interplanetary mass ejections (ICMEs) observed beyond 1 AU are not studied very often. They are useful for improving
our understanding of the 3D heliosphere. As there are only few such events registered by the Ulysses spacecraft, the task of detecting their solar counterparts is a challenge, especially during high solar activity periods,
because there are dozens coronal mass ejections (CMEs) registered by SOHO that might be chosen as candidates. We analyzed
a high-latitude ICME registered by the Ulysses spacecraft on 18 January 2002. Our investigation focused on the correlation between various plasma parameters that allow
the identification to be made of the ICME and its components such as the forward shock, the magnetic cloud and the reverse
shock. 相似文献
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Counterstreaming beams of electrons are ubiquitous in coronal mass ejections (CMEs) – although their existence is not unanimously accepted as a necessary and/or sufficient signature of these events. We continue the investigation of a high-latitude CME registered by the Ulysses spacecraft on 18?–?19 January 2002 (Dumitrache, Popescu, and Oncica, Solar Phys. 272, 137, 2011), by surveying the solar-wind electron distributions associated with this event. The temporal evolution of the pitch-angle distributions reveals populations of electrons that are distinguishable through their anisotropy, with clear signatures of i) electron strahls, ii) counter-streaming in the magnetic clouds and their precursors, and iii) unidirectionality in the fast wind preceding the CME. The analysis of the counter-streams inside the CME allows us to elucidate the complexity of the magnetic-cloud structures embedded in the CME and to refine the borders of the event. Identifying such strahls in CMEs, which preserve properties of the low β [<1] coronal plasma, gives more support to the hypothesis that these populations are remnants of the hot coronal electrons that escape from the electrostatic potential of the Sun into the heliosphere. 相似文献
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Owing to imperfect boundary conditions in laboratory soil tests and the possibility of water diffusion inside the soil specimen in undrained tests, the assumption of uniform stress/strain over the sample is not valid. This study presents a qualitative assessment of the effects of non‐uniformities in stresses and strains, as well as effects of water diffusion within the soil sample on the global results of undrained cyclic simple shear tests. The possible implications of those phenomena on the results of liquefaction strength assessment are also discussed. A state‐of‐the‐art finite element code for transient analysis of multi‐phase systems is used to compare results of the so‐called ‘element tests’ (numerical constitutive experiments assuming uniform stress/strain/pore pressure distribution throughout the sample) with results of actual simulations of undrained cyclic simple shear tests using a finite element mesh and realistic boundary conditions. The finite element simulations are performed under various conditions, covering the entire range of practical situations: (1) perfectly drained soil specimen with constant volume, (2) perfectly undrained specimen, and (3) undrained test with possibility of water diffusion within the sample. The results presented here are restricted to strain‐driven tests performed for a loose uniform fine sand with relative density Dr=40%. Effects of system compliance in undrained laboratory simple shear tests are not investigated here. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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B.?EnescuEmail author K.?Ito M.?Radulian E.?Popescu O.?Bazacliu 《Pure and Applied Geophysics》2005,162(2):249-271
The Vrancea seismic region contains an isolated cluster of events beneath the Carpathian Arc Bend in Romania, dipping to about 200 km depth. Seismic activity mainly occurs at intermediate depths (h > 60 km). The main goal of the paper is to perform an in-depth, complex analysis of the occurrence times of these intermediate-depth events. We also try to show the versatility of the methods used to characterize different aspects of the seismicity evolution and to offer a user-friendly software toolbox to do most of the related computations. The earthquake catalog used in this study spans from 1974 to 2002 and includes only the intermediate-depth events. In the first part of the paper, we analyze the multifractal characteristics of the temporal distribution of earthquakes. The study reveals two distinct scaling regimes. At small scales we found a clear nonhomogeneous, multifractal pattern, while at large scales the temporal distribution of events shows a monofractal, and close to Poissonian (random), behavior. The multifractal behavior at small scales (minutes-hours) is shown to be clearly an effect of the short aftershock sequences that occurred after some major Vrancea earthquakes. In the second part of the paper we analyze whether our temporal series shows a persistent (or anti-persistent) long-term behavior, by using the Detrended Fluctuation Analysis (DFA) method. The results suggest that the analyzed temporal series of Vrancea earthquakes is a non-correlated process. In part three of the paper we seek to determine whether the dynamics of our earthquake system (described by the occurrence time of Vrancea earthquakes) is deterministically chaotic, deriving from a rather simple evolution law, or whether it is stochastic and is generated by a system that possesses many degrees of freedom. The results suggest that our signal is stochastic (probably does not possess an attractor). The limited time-span of the catalog and the analysis performed in this paper cannot rule out the emergence of an interesting, quasi-deterministic and low-dimensional structure in the case of major Vrancea earthquakes.Acknowledgement One of the authors (BE) is grateful to the Japanese Ministry of Education for providing him a Monbusho scholarship for studying in DPRI, Kyoto University. We thank Z.R. Struzik, M Holschneider, J. Mori and D. Kaplan for their useful comments, and acknowledge the support of the staff of DPRI, Kyoto University and the National Inst. for Earth Physics, Bucharest. We thank the two reviewers, M.B. Geilikman and M. Anghel, for their useful suggestions which improved the quality of this work. 相似文献
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O. Vaduvescu M. Birlan A. Tudorica A. Sonka F.N. Pozo A.D. Barr D.J. Asher J. Licandro J.L. Ortiz E. Unda-Sanzana M. Popescu A. Nedelcu D. Dumitru R. Toma I. Comsa C. Vancea D. Vidican C. Opriseanu T. Badescu M. Badea M. Constantinescu 《Planetary and Space Science》2011,59(13):1632-1646
We report on the follow-up and recovery of 100 program NEAs, PHAs and VIs using the ESO/MPG 2.2 m, Swope 1 m and INT 2.5 m telescopes equipped with large field cameras. The 127 fields observed during 11 nights covered 29 square degrees. Using these data, we present the incidental survey work which includes 558 known MBAs and 628 unknown moving objects mostly consistent with MBAs from which 58 objects became official discoveries. We planned the runs using six criteria and four servers which focus mostly on faint and poorly observed objects in need of confirmation, follow-up and recovery. We followed 62 faint NEAs within one month after discovery and we recovered 10 faint NEAs having big uncertainties at their second or later opposition. Using the INT we eliminated four PHA candidates and VIs. We observed in total 1286 moving objects and we reported more than 10,000 positions. All data were reduced by the members of our network in a team effort, and reported promptly to the MPC. The positions of the program NEAs were published in 27 MPC and MPEC references and used to improve their orbits. The O−C residuals for known MBAs and program NEAs are smallest for the ESO/MPG and Swope and about four times larger for the INT whose field is more distorted. For the astrometric reduction, the UCAC-2 catalog is recommended instead of USNO-B1. The incidental survey allowed us to study statistics of the MBA and NEA populations observable today with 1–2 m facilities. We calculate preliminary orbits for all unknown objects, classifying them as official discoveries, later identifications and unknown outstanding objects. The orbital elements a, e, i calculated by FIND_ORB software for the official discoveries and later identified objects are very similar with the published elements which take into account longer observational arcs; thus preliminary orbits were used in statistics for the whole unknown dataset. We present a basic model which can be used to distinguish between MBAs and potential NEAs in any sky survey. Based on three evaluation methods, most of our unknown objects are consistent with MBAs, while up to 16 unknown objects could represent NEO candidates and four represent our best NEO candidates. We assessed the observability of the unknown MBA and NEA populations using 1 and 2 m surveys. Employing a 1 m facility, one can observe today fewer unknown objects than known MBAs and very few new NEOs. Using a 2 m facility, a slightly larger number of unknown than known asteroids could be detected in the main belt. Between 0.1 and 0.8 new NEO candidates per square degree could be discovered using a 2 m telescope. 相似文献
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Irina Popescu Gilles Lericolais Nicolae Panin Marc De Batist Hervé Gillet 《Geo-Marine Letters》2007,27(2-4):173-183
This study is a synthesis of gas-related features in recent sediments across the western Black Sea basin. The investigation
is based on an extensive seismic dataset, and integrates published information from previous local studies. Our data reveal
widespread occurrences of seismic facies indicating free gas in sediments and gas escape in the water column. The presence
of gas hydrates is inferred from bottom-simulating reflections (BSRs). The distribution of the gas facies shows (1) major
gas accumulations close to the seafloor in the coastal area and along the shelfbreak, (2) ubiquitous gas migration from the
deeper subsurface on the shelf and (3) gas hydrate occurrences on the lower slope (below 750 m water depth). The coastal and
shelfbreak shallow gas areas correspond to the highstand and lowstand depocentres, respectively. Gas in these areas most likely
results from in situ degradation of biogenic methane, probably with a contribution of deep gas in the shelfbreak accumulation.
On the western shelf, vertical gas migration appears to originate from a source of Eocene age or older and, in some cases,
it is clearly related to known deep oil and gas fields. Gas release at the seafloor is abundant at water depths shallower
than 725 m, which corresponds to the minimum theoretical depth for methane hydrate stability, but occurs only exceptionally
at water depths where hydrates can form. As such, gas entering the hydrate stability field appears to form hydrates, acting
as a buffer for gas migration towards the seafloor and subsequent escape. 相似文献