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401.
The dynamic response of rigid and flexible walls retaining dry cohesionless soil is examined in light of experimental results and analytical elastodynamic and limit analysis solutions. Following a brief review of the problem, experimental findings from three different testing programs on retaining walls are presented, and compared with theoretical predictions based on the above-mentioned approaches. Reasonable agreement is found depending on the assumptions. It is shown that wall flexibility – which is not taken into account in classical design approaches – should be considered to establish the point of application of seismic thrust on the wall. Detailed calculations and set of graphs and charts are presented, which highlight salient aspects of the problem. 相似文献
402.
Aggeliki Adamaki Eleftheria E. Papadimitriou George M. Tsaklidis Vassilios Karakostas 《Acta Geophysica》2011,59(4):748-769
Aftershock rates seem to follow a power law decay, but the assessment of the aftershock frequency immediately after an earthquake,
as well as during the evolution of a seismic excitation remains a demand for the imminent seismic hazard. The purpose of this
work is to study the temporal distribution of triggered earthquakes in short time scales following a strong event, and thus
a multiple seismic sequence was chosen for this purpose. Statistical models are applied to the 1981 Corinth Gulf sequence,
comprising three strong (M = 6.7, M = 6.5, and M = 6.3) events between 24 February and 4 March. The non-homogeneous Poisson process outperforms the simple Poisson process
in order to model the aftershock sequence, whereas the Weibull process is more appropriate to capture the features of the
short-term behavior, but not the most proper for describing the seismicity in long term. The aftershock data defines a smooth
curve of the declining rate and a long-tail theoretical model is more appropriate to fit the data than a rapidly declining
exponential function, as supported by the quantitative results derived from the survival function. An autoregressive model
is also applied to the seismic sequence, shedding more light on the stationarity of the time series. 相似文献
403.
Sabine Geiß Nicole Lettmann Aurélien Rey Herbert Lepper Birgit Körner Silvio Mais Theodor Prey Bettina Hilger Moana Engelke Stephan Lebertz Claudine Chatellier George Sawal Dirk Löffler Tom Schillings 《洁净——土壤、空气、水》2011,39(6):537-542
A first preliminary interlaboratory trial was planned to prepare ISO/DIS 12010: Water quality – determination of short chain polychlorinated alkanes (SCCP) in water – method using GC/MS and electron capture negative ionisation (ECNI). The task was to determine the sum of short chain polychlorinated n‐alkanes with carbon chain lengths of C10–C13 and a chlorine content between 49 and 67% in water by GC‐ECNI‐MS and quantification by multiple linear regression described in ISO/DIS 12010 as the compulsory method. Distributed samples were obtained from a real water extract spiked with a target concentration of 0.4 µg/mL sum of SCCP, i.e. the environmental quality target level according to the Water Framework Directive. The interlaboratory trial included the calibration, a column chromatographic clean up, a concentration step and an integration of chromatographic unresolved humps as well as the quantification with multiple linear regression. Reproducibility standard deviations between 21.5 and 22.9% were achieved by 17 participating laboratories from four countries. The method outlined no significant difference of the results between the standard solution and a real water matrix extract. On the basis of this succeeded preliminary interlaboratory trial the final interlaboratory trial for validation of ISO 12010 was prepared in autumn 2010. 相似文献
404.
George C.LEE 《地震工程与工程振动(英文版)》2011,10(1):I0001-I0001
Dear Contributors,Readers and Friends: 2011 milestones the tenth anniversary of the Journal of Earthquake Engineering and Engineering Vibration.we first want to take this opportunity to express our gratitude to those retiring members of the Editorial Board for their valuable contributions in the past,and to welcome those who joined the Editorial Board this year. As we mentioned in our message to you in December 2010,effective 20ll,the journal is officially co-sponsored by the Huixian Earthquake 相似文献
405.
Joseph G. Meert Anatoly S. Gibsher Natalia M. Levashova Warren C. Grice George D. Kamenov Alexander B. Ryabinin 《Gondwana Research》2011,19(4):867-880
The Cambrian explosion, c. 530–515 Ma heralded the arrival of a diverse assembly of multicellular life including the first hard-shelled organisms. Fossils found in Cambrian strata represent the ancestors of most modern animal phyla. In contrast to the apparent explosiveness seen in the Cambrian fossil record, studies of molecular biology hint that the diversification observed in Cambrian strata was rooted in ancestry extending back into the Ediacaran (635–542 Ma). Fossil evidence for this mostly cryptic phase of evolution is derived from the soft-bodied fossils of the Ediacaran biota found throughout the world and bilaterian embryos found in the Doushantuo lagerstätte in South China. The first appearance of Ediacara fauna is thought to have followed the last of the ~ 750–635 Ma Neoproterozoic glacial episodes by 20–30 million years. In this paper, we present evidence for the oldest discovery of the ‘Ediacara’ discoidal fossils Nimbia occlusa and Aspidella terranovica (?) that predate the early Cryogenian glaciations by more than fifty million years. There is considerable disagreement over the significance of discoidal Ediacaran fossils, but our findings may support earlier suggestions that metazoan life has roots extending deeper into the Proterozoic Eon. We also confirm the presence of a Late Cryogenian (e.g. “Marinoan”) glaciation on the Lesser Karatau microcontinent including dropstones and striated clasts within the glacial strata. 相似文献
406.
George G. Waldbusser Erin P. Voigt Heather Bergschneider Mark A. Green Roger I. E. Newell 《Estuaries and Coasts》2011,34(2):221-231
Anthropogenic carbon dioxide (CO2) emissions reduce pH of marine waters due to the absorption of atmospheric CO2 and formation of carbonic acid. Estuarine waters are more susceptible to acidification because they are subject to multiple
acid sources and are less buffered than marine waters. Consequently, estuarine shell forming species may experience acidification
sooner than marine species although the tolerance of estuarine calcifiers to pH changes is poorly understood. We analyzed
23 years of Chesapeake Bay water quality monitoring data and found that daytime average pH significantly decreased across
polyhaline waters although pH has not significantly changed across mesohaline waters. In some tributaries that once supported
large oyster populations, pH is increasing. Current average conditions within some tributaries however correspond to values
that we found in laboratory studies to reduce oyster biocalcification rates or resulted in net shell dissolution. Calcification
rates of juvenile eastern oysters, Crassostrea virginica, were measured in laboratory studies in a three-way factorial design with 3 pH levels, two salinities, and two temperatures.
Biocalcification declined significantly with a reduction of ∼0.5 pH units and higher temperature and salinity mitigated the
decrease in biocalcification. 相似文献
407.
Amy Gartman Mustafa Y��cel Andrew S. Madison David W. Chu Shufen Ma Christopher P. Janzen Erin L. Becker Roxanne A. Beinart Peter R. Girguis George W. Luther III 《Aquatic Geochemistry》2011,17(4-5):583-601
The sulfide (H2S/HS?) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [ $ {\text{S}}_{\text{x}}^{2 - } $ ] and thiosulfate [ $ {\text{S}}_{ 2} {\text{O}}_{ 3}^{ 2- } $ ], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H2S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are <10?3 ??M/min and are consistent with slow oxidation and the observed lack of sulfur oxidation intermediates. It is known that the thermodynamics for the first electron transfer step for sulfide and oxygen during sulfide oxidation in these systems are unfavorable, and that the kinetics for two electron transfers are not rapid. Here, we suggest that different metal catalyzed and/or biotic reaction pathways can readily produce sulfur oxidation intermediates. Via shipboard high-pressure incubation experiments, we show that snails with chemosynthetic endosymbionts do release polysulfides and may be responsible for our field observations of polysulfides. 相似文献
408.
János Kovács Szabolcs Á. Fábián Gábor Varga Karoly Németh Corina Risso Francisco Nullo Gabor Kereszturi Titusz Bugya Szabolcs Á. Fábián Noémi L. Görcs István P. Kovács Bertalan Radvánszky Gabriella Barta Rudolf Musil Alice Ghiselli Marzio Merazzi Andrea Strini Roberto Margutti Michele Mercuriali Rauf Gardashov Daria Gushchina Boris Dewitte Martin Michálek Marián Putiš Christoph A. Hauzenberger Jindřich Šancer Martin Štrejbar Aneta Maleňáková George Migiros George D. Bathrellos Hariklia D. Skilodimou Theodoros Karamousalis 《Central European Journal of Geosciences》2011,3(2):229-229
409.
Ali Al-Lazki Cindy Ebinger Michael Kendall George Helffrich Sylvie Leroy Christel Tiberi Graham Stuart Khalfan Al-Toobi 《Arabian Journal of Geosciences》2011,5(5):925-934
In this study, we used data recorded by two consecutive passive broadband deployments on the Gulf of Aden northern margin, Dhofar region, Sultanate of Oman. The objective of these deployments is to map the young eastern Gulf of Aden passive continental margin crust and upper mantle structure and rheology. In this study, we use shear-wave splitting analysis to map lateral variations of upper mantle anisotropy beneath the study area. In this study, we found splitting magnitudes to vary between 0.33 and 1.0 s delay times, averaging about 0.6 s for a total of 17 stations from both deployment periods. Results show distinct abrupt lateral anisotropy variation along the study area. Three anisotropy zones are identified: a western zone dominated by NW–SE anisotropy orientations, an eastern zone dominated with NE–SW anisotropy orientations, and central zone with mixed anisotropy orientations similar to the east and west zones. We interpret these shorter wavelength anisotropy zones to possibly represent fossil lithospheric mantle anisotropy. We postulate that the central anisotropy zone may be representing a Proterozoic suture zone that separates two terranes to the east and west of it. The anisotropy zones west and east were being used indicative of different terranes with different upper mantle anisotropy signatures. 相似文献
410.
Obianwu I. Victor Chimezie C. Innocent Akpan E. Anthony George N. Jimmy 《Central European Journal of Geosciences》2011,3(4):368-374
Twenty seven vertical electrical sounding (VES) profiles surrounding four known traverses were obtained in Ngor-Okpala local government area of Imo state to examine the subsurface geomaterials and the associated groundwater potential. The VES data, constrained by borehole data, provided useful information about the subsurface hydrogeologic and lithologic conditions. From the validated interpretation, the area assessed has loamy soil, medium grained sands, well-sorted medium-grained/gravelly sands and river sand as the lithologic succession from top to the bottom of the depth penetrated. The aquifers in the area were found in the medium-grained sands and well-sorted medium-coarse-grained sands. The aquifer depth for all-season groundwater that would be devoid of draw-down can be found at a depth range of 42–50 m. The resistivity maps of selected depths exhibit sharp resistivity changes at depth due mainly to undulating subsurface topography. A map of the distribution of the kσ-values shows that good quality groundwater can be found in most parts of the area. 相似文献