A numerical model of nearshore waves, currents, and sediment transport   总被引：1，自引：0，他引：1  

Pham Thanh Nam  Magnus Larson  Hans Hanson  Le Xuan Hoan   《Coastal Engineering》2009,56(11-12):1084-1096

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Predictability of the wintertime 500 hPa geopotential height over Ural-Siberia in the NCEP climate forecast system     

Qiao  Shaobo  Zou  Meng  Cheung  Ho Nam  Zhou  Wen  Li  Qingxiang  Feng  Guolin  Dong  Wenjie 《Climate Dynamics》2020,54(3):1591-1606

Climate Dynamics - Using hindcast and forecast data from the National Centers for Environmental Prediction (NCEP) climate forecast system version 2 (CFSv2) for the period 1982–2017, we...  相似文献   

Mechanism of tremolite carbonation     

Kyoung Won RyuMyung Gyu Lee  Young Nam Jang 《Applied Geochemistry》2011,26(7):1215-1221

The direct aqueous carbonation of fibrous tremolite was investigated by TEM, powder XRD, and FT-IR to elucidate the transformation mechanism of tremolite into calcite. The TEM study revealed that tremolite dissolves along the weak cleavage on (1 0 0) and (1 1 0) and the cleavage fragment fibers. The preferential release of Ca, relative to Si or Mg, into the solution resulted in the crystallization of compositionally homogeneous calcite and in the concurrent formation of proto-saponite. X-ray diffraction analysis revealed that the amount of product calcite increased rapidly within 15 min. Subsequently, after a 5 h carbonation period, it increased slowly to about 60%. The product calcite is euhedral. In contrast, the unreacted tremolite grains retain the original crystal structure even after prolonged carbonation. The morphological modification of tremolite from fibrous to round may have important implications for the elimination of its toxicity.  相似文献   

Simulation of marine controlled source electromagnetic measurements using a parallel fourier <Emphasis Type="Italic">hp</Emphasis>-finite element method     

David Pardo  Myung Jin Nam  Carlos Torres-Verdín  Michael G. Hoversten  Iñaki Garay 《Computational Geosciences》2011,15(1):53-67

We introduce a new numerical method to simulate geophysical marine controlled source electromagnetic (CSEM) measurements for the case of 2D structures and finite 3D sources of electromagnetic (EM) excitation. The method of solution is based on a spatial discretization that combines a 1D Fourier transform with a 2D self-adaptive, goal-oriented, hp-Finite element method. It enables fast and accurate simulations for a variety of important, challenging and practical cases of marine CSEM acquisition. Numerical results confirm the high accuracy of the method as well as some of the main physical properties of marine CSEM measurements such as high measurement sensitivity to oil-bearing layers in the subsurface. In our model, numerical results indicate that measurements could be affected by the finite oil-bearing layer by as much as 10⁴% (relative difference). While the emphasis of this paper is on EM simulations, the method can be used to simulate different physical phenomena such as seismic measurements.  相似文献   

A numerical model of beach morphological evolution due to waves and currents in the vicinity of coastal structures   总被引：2，自引：0，他引：2  

Pham Thanh Nam  Magnus Larson  Hans Hanson  Le Xuan Hoan 《Coastal Engineering》2011

A numerical model was developed of beach morphological evolution in the vicinity of coastal structures. The model includes five sub-models for random wave transformation, surface roller development, nearshore wave-induced currents, sediment transport, and morphological evolution. The model was validated using high-quality data sets obtained during experiments with a T-head groin and a detached breakwater in the basin of the Large-scale Sediment Transport Facility at the Coastal and Hydraulics Laboratory in Vicksburg, Miss, USA. The simulations showed that the model reproduced well the wave conditions, wave-induced currents, and beach morphological evolution in the vicinity of coastal structures. Both salient and tombolo formation behind a T-head groin and a detached breakwater were simulated with good agreement compared to the measurements.  相似文献   

Geotechnical parameter estimation in tunnelling using relative convergence measurement     

Kook‐Hwan Cho  Min‐Kwang Choi  Seok‐Woo Nam  In‐Mo Lee 《国际地质力学数值与分析法杂志》2006,30(2):137-155

Accurate estimation of geotechnical parameters is an important and difficult task in tunnel design and construction. Optimum evaluation of the geotechnical parameters have been carried out by the back‐analysis method based on estimated absolute convergence data. In this study, a back‐analysis technique using measured relative convergence in tunnelling is proposed. The extended Bayesian method (EBM), which combines the prior information with the field measurement data, is adopted and combined with the 3‐dimensional finite element analysis to predict ground motion. By directly using the relative convergence as observation data in the EBM, we can exclude errors that arise in the estimation of absolute displacement from measured convergence, and can evaluate the geotechnical parameters with sufficient reliability. The proposed back‐analysis technique is applied and validated by using the measured data from two tunnel sites in Korea. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Geohazards rooted from the northern margin of the Sea of Marmara since the late Pleistocene: a review of recent results     

Görür  Naci  Çağatay  M. Namık 《Natural Hazards》2010,54(2):583-603

Natural Hazards - Owing to its special geodynamic setting on the western extension of the North Anatolian Fault (NAF) and oceanographic setting between Mediterranean and the Black Seas, the Sea of...  相似文献   

Post-subduction margin structures along Boyd Strait, Antarctic Peninsula     

Young Keun Jin  Robert D. Larter  Yeadong Kim  Sang Heon Nam  Kyu Jung Kim 《Tectonophysics》2002,346(3-4)

The Pacific margin of the Antarctic Peninsula to the southwest of the Hero Fracture Zone (HFZ) is a former subducting margin which became inactive following the arrival of ridge crest segments of the Antarctic–Phoenix ridge at the margin during the Tertiary. In contrast, the part of the margin to the northeast of the HFZ remains active. Tertiary convergence was approximately perpendicular to the margin and ongoing motion is thought to have the same orientation. A new seismic reflection profile running along Boyd Strait, just northeast of the landward projection of the HFZ, shows major structural components similar to those typically observed along the margin to the southwest of the HFZ. In order of increasing proximity to the margin, these components are: the inner shelf, the shelf basin, the mid-shelf basement high (MSBH), and the outer shelf. The continuation of the post-subduction margin structures to the active margin suggests that the boundary between crust with passive and active margins characteristics is not sharply defined. Our postulated scenario for tectonic evolution along Boyd Strait is that: (1) before the arrival of the last ridge crest segment to the southwest of the HFZ, the inner shelf and the shelf basin were part of a Cretaceous–Tertiary arc and forearc area, (2) after the arrival, thermal effects resulting from interaction of the ridge crest with the margin just southwest of the HFZ lead to the formation of the MSBH to the northeast, but MSBH uplift in Boyd Strait did not prevent concurrent cross-shelf sediment transport contributing to development of an extensive outer shelf on the seaward flank of the MSBH, (3) Recent extension in Bransfield Strait, a marginal basin to the northeast of the landward projection of the HFZ, has caused about 10 km of seaward deflection in the strike of the part of the MSBH to the northeast of the projection of the HFZ.  相似文献   

Radial Deformations Induced by Groundwater Flow on Deep Circular Tunnels     

S.-W. Nam  A. Bobet 《Rock Mechanics and Rock Engineering》2007,40(1):23-39

Summary. The magnitude and distribution of ground deformations around a tunnel are often monitored during construction and provide key information about ground-support interaction and ground behavior. Thus it is important to determine the effects of different parameters on ground deformations to accurately and effectively evaluate what contributes to ground and support behavior observed during excavation. This paper investigates one such relation: the effects of seepage on radial deformations. A number of numerical analyses have been conducted with the following assumptions: deep circular unsupported tunnel, elastic ground, isotropic far field stresses, dry ground or saturated ground with steady-state water seepage. The analyses cover a wide range of tunnel sizes, effective stresses, and pore pressures. Results from the numerical simulations confirm previous analytical solutions for normalized radial deformations behind the face (i.e. on the tunnel side of the face) of a tunnel excavated in dry ground, and have been used to propose a new analytical formulation for normalized radial displacements ahead and behind the tunnel face for both dry and saturated ground with water flow. Water seepage substantially increases the magnitude and distribution of the normalized radial deformations ahead of the face and at the tunnel face, but does not change much the displacement distribution behind the tunnel face.  相似文献   

Crustal anatexis and formation of two types of granitic magmas in the Kontum massif, central Vietnam: Implications for magma processes in collision zones   总被引：1，自引：0，他引：1  

M. Owada  Y. Osanai  N. Nakano  T. Matsushita  Tran Ngoc Nam  T. Tsunogae  T. Toyoshima  Pham Binh  H. Kagami 《Gondwana Research》2007,12(4):428-437

Asia grew in the Late Permian by the collision of a number of micro-continents. Syn- to post-collisional magmatism occurred along the continental collision zones . In this study, we report two types of granitic rocks, garnet granite (Grt granite) and orthopyroxene granite (Opx granite), from the Kontum massif, central Vietnam, which is situated on the continental collision zone between the South China and Indochina cratons. These granitic rocks were formed at ca. 250 Ma when high-temperature (HT) and ultrahigh-temperature (UHT) metamorphism took place in the same zone. Based on the petrological and geochemical features compared with previously reported experimental results, garnet-bearing granite is derived from pelitic gneisses by partial melting, whereas orthopyroxene-bearing granite is produced by the partial melting of garnet-bearing mafic granulites. We inferred that a significantly high-geothermal gradient is required to produce Vietnamese granitic magmatism and related HT to UHT metamorphism. This geotherm may be attributed to upwelling mantle plume beneath the Kontum massif during the Late Permian.  相似文献