排序方式： 共有49条查询结果，搜索用时 15 毫秒
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Mahnoosh Biglari Claudio Mancuso Anna d’Onofrio Mohammad Kazem Jafari Ali Shafiee 《Computers and Geotechnics》2011
Existing models for predicting the small strain behaviour of unsaturated soil are not capable of predicting the initial shear stiffness during suction reduction under normally consolidated conditions. This problem has been addressed in the present study by combining an existing elastoplastic model and recent experimental data to provide a new model for the initial shear stiffness. The model, which is similar to that typically adopted for saturated soils, uses the average skeleton stress and an additional function of the degree of saturation. This new model not only captures the behaviour of the new experimental results, but it also describes a unique relationship between saturated and unsaturated soils. 相似文献
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A solution to the coincidence and Big Rip problems on the bases of an anisotropic space-time is proposed. To do so, we study the interaction between viscous dark energy and dark matter in the scope of the Bianchi type-I Universe. We parameterize the viscosity and the interaction between the two fluids by constants ζ 0 and σ respectively. A detailed investigation on the cosmological implications of this parametrization has been made. We have also performed a geometrical diagnostic by using the statefinder pairs {s,r} and {q,r} in order to differentiate between different dark energy models. Moreover, we fit the coupling parameter σ as well as the Hubble’s parameter H 0 of our model by minimizing the χ 2 through the age differential method, involving a direct measurement of H. 相似文献
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Assessment of groundwater quality using multivariate statistical techniques in Hashtgerd Plain, Iran 总被引：4，自引：3，他引：1
Multivariate statistical techniques, such as cluster analysis (CA), factor analysis (FA), principal component analysis (PCA),
and discriminant analysis (DA), were applied for the evaluation of variations and the interpretation of a large complex groundwater
quality data set of the Hashtgerd Plain. In view of this, 13 parameters were measured in groundwater of 26 different wells
for two periods. Hierarchical CA grouped the 26 sampling sites into two clusters based on the similarity of groundwater quality
characteristics. FA based on PCA, was applied to the data sets of the two different groups obtained from CA, and resulted
in three and five effective factors explaining 79.56 and 81.57% of the total variance in groundwater quality data sets of
the two clusters, respectively. The main factors obtained from FA indicate that the parameters influencing groundwater quality
are mainly related to natural (dissolution of soil and rock), point source (domestic wastewater) and non-point source pollution
(agriculture and orchard practices) in the sampling sites of Hashtgerd Plain. DA provided an important data reduction as it
uses only three parameters, i.e., electrical conductivity (EC), magnesium (Mg2+) and pH, affording more than 98% correct assignations, to discriminate between the two clusters of groundwater wells in the
plain. Overall, the results of this study present the effectiveness of the combined use of multivariate statistical techniques
for interpretation and reduction of a large data set and for identification of sources for effective groundwater quality management. 相似文献
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Fabrizio Cecca Kazem Seyed-EmamiJohann Schnyder Mohamed BenzaggaghMahmoud Reza Majidifard Mohammed Mohammadi Monfared 《Cretaceous Research》2012,33(1):106-115
An early Berriasian (Berriasella jacobi Zone) ammonite fauna is described for the first time from the Alborz Mountains in northwest Iran. It has been collected from a section located near the village of Shal (Talesh region); in addition to rare phylloceratids, lytoceratids and Neolissoceras, the majority of ammonites belong to the neocomitid subfamily Berriasellinae. With the exception of a new genus and species, Taleshites fuersichi, these taxa are common in European and North African Tethyan successions. Associated calpionellids confirm the early Berriasian age of the ammonite-bearing levels. 相似文献
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Kazem Faghei 《Astrophysics and Space Science》2013,345(1):125-132
The importance of thermal conduction on hot accretion flow is confirmed by observations of hot gas that surrounds Sgr A? and a few other nearby galactic nuclei. On the other hand, the existence of outflow in accretion flows is confirmed by observations and magnetohydrodynamic (MHD) simulations. In this research, we study the influence of both thermal conduction and outflow on hot accretion flows with ordered magnetic field. Since the inner regions of hot accretion flows are, in many cases, collisionless with an electron mean free path due to Coulomb collision larger than the radius, we use a saturated form of thermal conduction, as is appropriate for weakly collisional systems. We also consider the influence of outflow on accretion flow as a sink for mass, and the radial and the angular momentum, and energy taken away from or deposited into the inflow by outflow. The magnetic field is assumed to have a toroidal component and a vertical component as well as a stochastic component. We use a radially self-similar method to solve the integrated equations that govern the behavior of such accretion flows. The solutions show that with an ordered magnetic field, both the surface density and the sound speed decrease, while the radial and angular velocities increase. We found that a hot accretion flow with thermal conduction rotates more quickly and accretes more slowly than that without thermal conduction. Moreover, thermal conduction reduces the influences of the ordered magnetic field on the angular velocities and the sound speed. The study of this model with the magnitude of outflow parameters implies that the gas temperature decreases due to mass, angular momentum, and energy loss. This property of outflow decreases for high thermal conduction. 相似文献
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The morphotectonics of Zagros Structural Belt (ZSB) of SW Iran has been controlled by collision tectonics of the Arabian and Iranian plates. Morphotectonically ZSB has been distinguished into four lithotectonics units namely, Imbricate Zone (IZ), Sanandaj-Sirjan Zone (SSZ), Zagros Folded Belt (ZFB) and Molasses Cover Sequence (MCS). The collision generated morphogeny and vertical tectonics in ZSB. The opening of the Red Sea has contributed to vertical tectonics @ 1 mm/year, and during the last 4–5 million years a relief of about 4 km has been generated in ZSB which resulted in development of erosional cycles. The Sanandaj-Sirjan Zone (SSZ) and Imbricate Zone (IZ) became positive tectonic topography with opening of Red Sea. The exogenic geomorphic processes resulted in the erosion and SSZ was exhumed to lower level than IZ. The ZFB and MCS underwent vertical tectonics @ 1 mm/year. The Neo-tectonism is expressed as anomalous drainage and compressed meanders in MCS. The humid cycles (?) during the Quaternary period resulted in fluvial erosion and cuesta, hogbacks, structural and erosional hills and valleys were carved in ZSB in Iran. The NW-SE tectonic trend of ZFB has determined the morphotectonics and the geomorphic grain of ZSB of in SW Iran. 相似文献
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Whole rock major and trace element geochemistry together with zircon U-Pb ages and Sr-Nd isotope compositions for the Middle Eocene intrusive rocks in the Haji Abad region are presented. The granitoid hosts, including granodiorite and diorite, yielded zircon U-Pb ages with a weighted mean value of 40.0 ± 0.7 Ma for the granodiorite phase. Mafic microgranular enclaves(MMEs) are common in these plutons, and have relatively low SiO_2 contents(53.04-57.08 wt.%) and high Mg#(42.6-60.1), probably reflecting a mantle-derived origin. The host rocks are metaluminous(A/CNK = 0.69-1.03), arc-related calc-alkaline, and I-type in composition, possessing higher SiO_2 contents(59.7-66.77 wt.%) and lower Mg#(38.6-52.2); they are considered a product of partial melting of the mafic lower crust. Chondritenormalized REE patterns of the MMEs and granitoid hosts are characterized by LREE enrichment and show slight negative Eu anomalies(Eu/Eu* = 0.60-0.93). The host granodiorite samples yield(87Sr/86Sr);ratios ranging from 0.70498 to 0.70591,positive eNd(t) values varying from +0.21 to +2.3, and TDM2 ranging from 760 to 909 Ma, which is consistent with that of associated mafic microgranular enclaves(87Sr/86Sr)i = 0.705111-0.705113, εNd(t)= +2.14 to +2.16, TDM2 = 697-785 Ma). Petrographic and geochemical characterization together with bulk rock Nd-Sr isotopic data suggest that host rocks and associated enclaves originated by interaction between basaltic lower crust-derived felsic and mantlederived mafic magmas in an active continental margin arc environment. 相似文献