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51.
Quang Thanh Nguyen Sabine Caré Yves Berthaud Alain Millard Frédéric Ragueneau 《国际地质力学数值与分析法杂志》2011,35(10):1141-1159
Most reinforced concrete structures are damaged due to corrosion of reinforcements in concrete. In normal conditions the pH near the reinforcements is around 12–13 which means that steel is in a passive state. But aggressive species, such as chloride ions or carbon dioxide, may penetrate into concrete and promote active corrosion. As a consequence (hydro)oxides are produced leading to degradation of concrete structures. For instance cracking of the concrete is generated due to the pressure induced by rust. In this paper, we study the inception and the propagation of cracking on reinforced mortar plates with rebars located either in the middle or at the corner. Additional experiments have been performed on cylindrical specimens to determine the local effect of rust pressure at the interface rust/mortar. The specimens have been subjected to imposed current density in order to enhance the corrosion and digital image intercorrelation has been used to determine displacement fields. The experiments have been compared to numerical modelling. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
52.
Byron McKavanagh Bruce Boreham Kevin McCue Gary Gibson Jennifer Hafner George Klenowski 《Pure and Applied Geophysics》1995,144(1):39-57
Digital seismograms continuously recorded from 1988 to 1992 by two stations of the RESNOM seismic network in northern Baja
California, Mexico, were used to search for probable shear-wave anisotropic characteristics in the region of the Cerro Prieto
fault. Shear-wave splitting was identified in many of the three-component records analyzed. We measured the polarization direction
of the leadingS wave inside theS-wave window as well as the delay times between fast and slow phases on those records displaying shear-wave splitting. For
station CPX, which is nearest the Imperial Valley region to the north, the preferred polarization direction found in this
study (azimuth 180°±10°) coincides with the direction of the regional maximum compressive stress determined for the region.
This polarization direction can be interpreted in terms of the “Extensive Dilatancy Anisotropy” model as the effect of vertical
parallel aligned cracks. The preferred polarization direction measured at LMX, however, gives an azimuth of 45°±5°. Thus,
it appears that faults and fractures aligned oblique to the main tectonic trend have a greater influence on the anisotropic
characteristics of the crust south of Cerro Prieto volcano than that of the regional stress field. Time delays between slow
and fastS waves observed at CPX appear constant from 1988 to 1992 while delays measured at LMX for the same interval indicate a small
increase with time which cannot be attributed to azimuthal variations of paths. 相似文献
53.
Mossbauer spectra of57Fe at 77 and 295°K in the plagioclase from basalts 10044 and 12021 show that iron is in the high-spin ferrous state and located at at least two distinct positions with different coordination numbers. Some excess resonant absorption is probably due to Fe3+ although the Fe3+ doublet could not be positively resolved. The ratio Fe3+/(Fe2+ + Fe3+) is estimated to be between 0.02 and 0.1. 相似文献
54.
Distribution of heavy metals in marine bivalves, fish and coastal sediments in the Gulf and Gulf of Oman 总被引:2,自引:0,他引:2
An assessment of marine contamination due to heavy metals was made in the Gulf and Gulf of Oman based on marine biota (fish and various bivalves) and coastal sediment collected in Bahrain, Oman, Qatar, and the United Arab Emirates (UAE) during 2000-2001. Sediment metal loadings were generally not remarkable, although hot spots were noted in Bahrain (Cu, Hg, Pb, Zn) and on the east coast of the UAE (As, Co, Cr, Ni). Concentrations of As and Hg were typically low in sediments and the total Hg levels in top predator fish commonly consumed in the region were < 0.5 microg g(-1) and posed no threat to public health. Very high Cd concentrations (up to 195 microg g(-1)) in the liver of some fish from southern Oman may result from food-chain bioaccumulation of elevated Cd levels brought into the productive surface waters by upwelling in the region. Very high As concentrations (up to 156 microg g(-1)) were measured in certain bivalve species from the region. Although not certain, the As is probably derived from natural origins rather than anthropogenic contamination. 相似文献
55.
Bernhard?SchulzEmail author Klaus?Bombach Sabine?Pawlig Helene?Br?tz 《International Journal of Earth Sciences》2004,93(5):824-843
In the Austroalpine Basement to the south of the Tauern Window, distinct suites of metabasites occur with orthogneisses in pre-Early-Ordovician units. Tholeiitic and alkaline within-plate basalt-type metabasites are associated with acid meta-porphyroids in the post-Early-Ordovician Thurntaler Phyllite Group. According to their correlated trace element abundances, metabasite zircons crystallized with their host rocks. Protolith Pb–Pb zircon ages, whole-rock Ta/Yb–Th/Yb and oxygen, Sr, Nd isotope data define two principal evolution lines. An older evolution at elevated Th/Yb typical of subduction-related magmatism, started by 590-Ma N-MORB-type and 550–530 Ma volcanic arc basalt type basic suites, which mainly involved depleted mantle sources. It finished with mainly crustal-source 470–450-Ma acid magmatites. An other evolution line by tholeiitic and 430-Ma alkaline within-plate basalt-type suites in both pre- and post-Early-Ordovician units is characterized by an intraplate mantle metasomatism and enrichment trend along multicomponent sources. These magmatic evolution lines can be related to a plate tectonic scenario that involved terranes in a progressively mature Neoproterozoic to Ordovician active margin, and a subsequent Palaeo-Tethys passive margin along the north Gondwanan periphery. 相似文献
56.
Marie Alexandrine Sicre Laurent Labeyrie Ullah Ezat Josette Duprat Jean Louis Turon Sabine Schmidt Elisabeth Michel Alain Mazaud 《Earth and Planetary Science Letters》2005,240(3-4):724-731
The lack of temporal resolution and accurate chronology of Southern Ocean marine cores has hampered comparison of glacial millennial-scale oscillations between the Southern Ocean, Antarctic ice and other records from both hemispheres. In this study, glacial climate variability is investigated over the last 50 ka using a multi-proxy approach. A precise chrono-stratigraphy was developed on the high-sedimentation rate core MD94-103 (Indian Southern Ocean, 45°35′S 86°31′E, 3560 m water depth) by geomagnetic synchronization between the later core and NAPIS75, and 14C dates. High-resolution time-series of δ18O in planktonic foraminifera Globigerina bulloides and Neogloboquadrina pachyderma, and sea surface temperatures (SSTs) estimated from the alkenone UK′37 index and foraminifera assemblages have been generated. Temporal evolution of the two temperature proxy records is notably different during the last glacial period. While foraminifera data indicate a consistent cooling towards the last glacial maximum, anomalous warm glacial alkenone temperatures suggest a strong advection of warm “detrital” alkenones by surface waters of the Agulhas current. Superimposed to this general trend, during Heinrich events, foraminiferal SSTs point to warmer surface waters, while concurrent alkenone SSTs exhibit apparent coolings probably caused by enhanced local alkenone production. By analogy to modern observations, possible influence of ENSO-like conditions on the subantarctic Southern Ocean SSTs is discussed. 相似文献
57.
Sabine Charmasson Olivier Radakovitch Mireille Arnaud Patrick Bouisset Anne-Sylvie Pruchon 《Estuaries and Coasts》1998,21(3):367-378
Various anthropogenic radionuclides and210Pb were analyzed in a 4.3-m-long core, sampled near the Rhône River mouth in March 1991, to evaluate the extent of industrial releases that accumulate in this area. The whole core was significantly marked by radionuclide inputs from the nuclear facilities located along the river (137Cs,134Cs,60Co). Irregular profiles in natural and artificial radionuclides should be related to variations in their respective inputs from the Rhône River to the Mediterranean Sea. Minimum concentrations were found during high flow periods. Using both the137Cs/134Cs profile in the core and the range of this ratio in Rhône waters, mean apparent accumulation rates were estimated to range between 37 cm yr?1 and 48 cm yr?1. This core would then represent a sedimentary record over a 7–10 year period. However, the presence of a signal from the Chernobyl accident, which occurred on April 26, 1986, was not clearly observed in the core. Inventories of both artificial and natural radionuclides were greater than expected from atmospheric inputs. The increased sedimentation occurring in close vicinity to the mouth of the Rhône River is thus responsible for trapping of elements transported by the river to the Mediterranean Sea. In this area, inventories of artificial radionuclides are well in excess of aerial deposition from Chernobyl and atmospheric weapons tests and are linked primarily to industrial releases. 相似文献
58.
In the last decades, employment policy design and implementation partly shifted from the national to local and regional scales
in most European countries. In addition, the European Union appeared as an important new actor in this policy field in the
late 1990s. We argue that the new geographical multi-scaling of employment policy can be used strategically by feminists to
promote different aspects of gender equality simultaneously: Feminist claims related to gender equity, i.e., demands to secure equal participation of women and men in the labour market, should be advocated at the national scale.
Claims related to the recognition of gender difference, i.e., demands related to typical female and male employment needs and their social recognition should be promoted at the
local scale. The regional scale is the most appropriate one to advance gender plurality, i.e., non-traditional employment of women and men. In the empirical part of the paper we discuss how the ideal leverage
of claims at different spatial scales and inter-linkage between scales could operate. We will show that the link to EU policy
strengthens feminist claims in the highly gender-differentiated societies and political settings of Austria and Germany.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
59.
The subject of measuring the performance of registries has been a topic of policy discussions in recent years at the regional level due to the recasting of the European Union (EU) port state control (PSC) directive which introduces incentives for flags which perform better. Since the current method used in the EU region entails some shortcomings, it has therefore been the subject of substantial scrutiny. Furthermore, the International Maritime Organization (IMO) developed a set of performance indicators which however lacks the ability to measure compliance as set out in one of its strategic directions towards fostering global compliance. This article develops a methodology to measure flag state performance which can be applied on the regional or global level and to other areas of legislative interest (e.g. recognized organizations, Document of Compliance Companies). The proposed methodology overcomes some of the shortcomings of the present method and presents a more refined, less biased approach of measuring performance. To demonstrate its usefulness, it is applied to a sample of 207,821 observations for a 3-year time frame and compared to the current method. 相似文献
60.
Sabine Richling 《Astrophysics and Space Science》2003,284(2):361-364
The Lyα line emission of high-redshift galaxies depends on the density and temperature distribution of the gas, the kinematics
and the dust content. We use a finite element method to model theLyα radiation of different 3D configurations considering
complete frequency redistribution and the influence of velocity fields. Our results show that the central absorption feature
of the double-peaked Lyα line profile observed in many radio galaxies with z=2-4 is probably the consequence of frequency redistribution rather than foreground absorption. The blue peak of the profile
is enhanced for models with in fall motion and the red peak for models with outflow motion. In particular, we attempt to model
the extendedLyα emission of high-redshift radio galaxies, where we consider results of corresponding hydrodynamical simulations
to select possible model configurations. We find that Lyα photons scattered outside a jet-influenced low-density region are
able to produce an extended Lyα halo.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献