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201.
Sung Hi Choi Samuel B. Mukasa Alexandre V. Andronikov Maria C. Marcano 《Contributions to Mineralogy and Petrology》2007,153(4):443-463
An origin of the Tinaquillo Peridotite Complex in northern Venezuela, and a model for the tectonic framework of the boundary
zone between the southern Caribbean Plate margin and the South American Plate (SAP) during Late Jurassic to Mid-Cretaceous
time are developed using newly measured Sr, Nd, Pb and Hf isotopic compositions as well as major and trace element geochemistry
for some hornblendite veins and their spinel peridotite host rocks. Depleted geochemical characteristics, principally major
element concentrations, and Nd and Hf isotopes (e.g., εNd = + 27; εHf = +50; ca. 3.4 Ga-Nd model age) of the Tinaquillo peridotites suggest a genetic link between this complex and the Guiana
Shield farther to the south within Venezuela. Scattered zones within the Tinaquillo peridotite were overprinted by what we
interpret as channelized hydrous fluids (<∼3%) derived from the eastward-dipping subduction of the Farallon Plate beneath
the SAP in the Late Jurassic, leading to modification of the original Sr, Nd and Hf isotopic compositions as well as the incompatible
element concentrations. The hornblendite veins have Sr, Nd, Pb and Hf isotopic compositions, falling within the range of present-day
Pacific/Atlantic MORB, but trace element abundance patterns with combinations of arc- and MORB-like characteristics. These
results rule out the possibility of local melting of the host peridotites to produce magmas from which the hornblendite veins
formed. We suggest that during inception of the westward-dipping subduction of the Protocaribbean Plate immediately following
polarity reversal in the Mid-Cretaceous, melts infiltrated the mantle lithosphere and produced the veins. 相似文献
202.
Stream water-use is essential for both agricultural and hydrological management and yet not many studies have explored its non-stationarity and nonlinearity with meteorological variables. This study proposed a deep-learning based model to estimate agricultural water withdrawal using hydro-meteorological variables, which projected the changes of agricultural water withdrawal influenced by climate change of future. The relationships between meteorological variables and stream water-use rate (WUR) were quantified using a deep belief network (DBN). The influences of precipitation, potential evapotranspiration, and monthly averaged WUR on the performance of the developed DBN model were tested. As a result, this DBN with potential evapotranspiration (PET) provided better performances than precipitation to estimate the WUR. The PET of multi-model scenarios for Representative Concentration Pathways 8.5 would be increased as time goes by, and thus leads to increase WUR estimated by DBN in three basins, located in South Korea during the future period. On the contrary, water availability expected to decrease compared to the current. Therefore, managing water-uses and improving efficiencies can be prepared for the change in agricultural water-use by climate change in the future. 相似文献
203.
1 IntroductionOpenclustersareidealtargetswithwhichtoinvestigatethestructureandevolutionoftheGalacticdiskaswellastheformationandevolutionofstarsandstellarclusters.Thereareabout1 ,2 0 0knownopenclustersintheCatalogueofOpenClusterData (Lynga 1 987) .Inspiteofmany… 相似文献
204.
A detailed analysis of high-resolution seismic data (Chirp, 2–7 kHz) in the Ulleung Basin reveals spatial variation in echo
characteristics and geometry of large-scale debris lobes. In the proximal part, the debris lobes are dominated by hummocky
surface echoes and gradually transitional downslope to seafloor-tangent hyperbolic and smooth prolonged bottom echoes, reflecting
progressive decrease in size, spacing, and relief of surface forms. The strongly convex-upward upper surface with steep blunt
margins in the proximal part is gradually transitional downslope to slightly convex- upward or nearly flat form with less
blunt margins. The gradual downslope decrease in both scale and spacing of surface forms and convexity of upper surface within
each debris lobe is suggestive of progressive dilution in flow concentration within a debris flow, probably due to mixing
of ambient water and removal of suspended sediment by deposition during downslope movement.
Received: 3 February 1999 / Revision received: 27 April 1999 相似文献
205.
A new type of troposphere zenith path delay product of the international GNSS service 总被引:3,自引:2,他引:1
The International GNSS Service (IGS) has been producing the total troposphere zenith path delay (ZPD) product that is based on combined ZPD contributions from several IGS Analysis Centers (AC) since GPS week 890 in 1997. A new approach to the production of the IGS ZPD has been proposed that replaces the direct combination of diverse ZPD products with point positioning estimates using the IGS Combined Final orbit and clock products. The new product was formally adopted in 2007 after several years of concurrent production with the legacy product. We describe here the advantages of the new approach for the IGS ZPD product, which enhance the value of the new ZPD product for climate studies. We also address the impact the IGS adoption in November 2006 of new GPS antenna phase center standards has had on the new ZPD product. Finally we describe plans to further enhance the ZPD products. 相似文献
206.
In this paper, the recent development in modeling seabed dissipative mechanisms in shallow water is reviewed. Specifically, laminar and turbulent boundary layer solutions as well as viscous mud flow solutions under transient waves are presented. These analytical solutions are compared with experimental data for both solitary waves and cnoidal waves. Very goed agreement is ohtained. The Boussinesq equations with boundary layer effects and the muddy seabed effects are also shown. 相似文献
207.
A single specimen ofAlbula leptocephalus (55.7 mm SL) was collected from the southern coastal waters of Korea using an aquatic lamp. It is characterized
by having a ribbonlike body with a small head and a well-forked caudal fin. Although the general appearance was similar to
the leptocephalus ofA. vulpes including myomere counts and fin ray counts, the melanophore deposition was different from that ofA. vulpes. This leptocephalus specimen was confirmed withA. forsteri using the cytochrome b mtDNA (Cytb) analysis. The genetic distance ofCytb between the present leptocephalus andA. forsteri is 0.006-0.038, which falls into the cutoff point separatingAlbula species into eight deep lineages including the four valid species. Its genetic characteristic have more similarities to those
of Fiji than those of Hawaii and the Northern territory of Australia. 相似文献
208.
Influence of frequency‐dependent soil–structure interaction on the fragility of R/C bridges
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Bridge performance under earthquake loading can be significantly influenced by the interaction between the structure and the supporting soil. Even though the frequency dependence of the interaction mentioned in this study has long been documented, the simplifying assumption that the dynamic stiffness is dominated by the mean or predominant excitation frequency is still commonly made, primarily as a result of the associated numerical difficulties when the analysis has to be performed in the time domain. This study makes use of the advanced lumped parameter models recently developed 1 in order to quantify the impact of the assumption on the predicted fragility of bridges mentioned in this study. This is achieved by comparing the predicted vulnerability for the case of a reference, well studied, actual bridge using both conventional, frequency‐independent, Kelvin–Voigt models and the aforementioned lumped parameter formulation. Analysis results demonstrate that the more refined consideration of frequency dependence of soil–structure interaction at the piers and the abutments of a bridge not only leads to different probabilities of failure for given intensity measures but also leads to different hierarchy and distribution of damage within the structure for the same set of earthquake ground motions even if the overall probability of exceeding a given damage state is the same. The paper concludes with the comparative assessment of the effect for different soil conditions, foundation configurations, and ground motion characteristics mentioned in this study along with the relevant analysis and design recommendations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
209.
Recently, a mesh-size insensitive structural stress definition (Battelle structural stress method) has been proposed. This method gives a stress state at a weld toe with a relatively coarse mesh, such as up to 2t (t=plate thickness) or irregular mesh shapes. The structural stress definition is based on the elementary structural mechanics theory and provides an effective measure of a stress state in front of a weld toe. In this present study, a fatigue strength assessment was carried out for a side shell connection of a container vessel using both the hot spot stress and the structural stress methods. A consistent approach to computing extrapolated hot spot stress for design purposes based on converged hot spot stresses is described and current fatigue guidance is evaluated. Fatigue strength predicted by the two methods, i.e. hot spot stress and structural stress approaches, at hot spot locations of a typical ship structure are compared and discussed. 相似文献
210.