Features in REE and Methane Anomalies Distribution in the East China Sea Water Column: a Comparison with the South China Sea     

Le Duc Luong  Shakirov  Renat B.  Hoang  Nguyen  Shinjo  Ryuichi  Obzhirov  Anatoly  Syrbu  Nadezhda  Shakirova  Maria 《Water Resources》2019,46(5):807-816

Water Resources - This paper presents review of dissolved Rare Earth Elements (REE) and methane anomalies distribution in the East China Sea water column. In general, the REE concentrations of the...  相似文献   

Reliability index in geotechnics     

V.U. Nguyen 《Computers and Geotechnics》1985,1(2):117-138

In this paper, the reliability index β is examined for its applicability in geotechnics. A statistical finite difference scheme is proposed to evaluate partial derivatives of the limit state function, enabling the computation of the reliability index β. Through illustrative examples, it is demonstrated that the proposed procedure gives results in excellent agreement with those obtained by the Monte Carlo simulation method, and yet it involves considerable savings in computing time. Extension of the reliability index method to cover many classes of problems involving correlated variables is highlighted.  相似文献   

Palaeo-hydrogeological control on groundwater As levels in Red River delta,Vietnam     

Søren Jessen  Flemming Larsen  Dieke Postma  Pham Hung Viet  Nguyen Thi Ha  Pham Quy Nhan  Dang Duc Nhan  Mai Thanh Duc  Nguyen Thi Minh Hue  Trieu Duc Huy  Tran Thi Luu  Dang Hoang Ha  Rasmus Jakobsen 《Applied Geochemistry》2008

To study the geological control on groundwater As concentrations in Red River delta, depth-specific groundwater sampling and geophysical logging in 11 monitoring wells was conducted along a 45 km transect across the southern and central part of the delta, and the literature on the Red River delta’s Quaternary geological development was reviewed. The water samples (n = 30) were analyzed for As, major ions, Fe²⁺, H₂S, NH₄, CH₄, δ¹⁸O and δD, and the geophysical log suite included natural gamma-ray, formation and fluid electrical conductivity. The SW part of the transect intersects deposits of grey estuarine clays and deltaic sands in a 15–20 km wide and 50–60 m deep Holocene incised valley. The NE part of the transect consists of 60–120 m of Pleistocene yellowish alluvial deposits underneath 10–30 m of estuarine clay overlain by a 10–20 m veneer of Holocene sediments. The distribution of δ¹⁸O-values (range −12.2‰ to −6.3‰) and hydraulic head in the sample wells indicate that the estuarine clay units divide the flow system into an upper Holocene aquifer and a lower Pleistocene aquifer. The groundwater samples were all anoxic, and contained Fe²⁺ (0.03–2.0 mM), Mn (0.7–320 μM), SO₄ (<2.1 μM–0.75 mM), H₂S (<0.1–7.0 μM), NH₄ (0.03–4.4 mM), and CH₄ (0.08–14.5 mM). Generally, higher concentrations of NH₄ and CH₄ and low concentrations of SO₄ were found in the SW part of the transect, dominated by Holocene deposits, while the opposite was the case for the NE part of the transect. The distribution of the groundwater As concentration (<0.013–11.7 μM; median 0.12 μM (9 μg/L)) is related to the distribution of NH₄, CH₄ and SO₄. Low concentrations of As (?0.32 μM) were found in the Pleistocene aquifer, while the highest As concentrations were found in the Holocene aquifer. PHREEQC-2 speciation calculations indicated that Fe²⁺ and H₂S concentrations are controlled by equilibrium for disordered mackinawite and precipitation of siderite. An elevated groundwater salinity (Cl range 0.19–65.1 mM) was observed in both aquifers, and dominated in the deep aquifer. A negative correlation between aqueous As and an estimate of reduced SO₄ was observed, indicating that Fe sulphide precipitation poses a secondary control on the groundwater As concentration.  相似文献   

Applicability of CPT-based methods in predicting toe bearing capacities of driven piles in sand     

Le Chi Hung  Tien Dung Nguyen  Ju-Hyung Lee  Sung-Ryul Kim 《Acta Geotechnica》2016,11(2):359-372

This paper presents a study on applicability of predicting toe bearing capacities from cone penetration test (CPT) for PHC (pretensioned spun high-strength concrete) driven piles into deep sandy deposits in the Nakdong River deltaic area west of Busan City in South Korea. Using toe bearing capacities obtained from pile driving analyzer (PDA) tests as reference values, which were reliably calibrated by on-site O-cell tests, the applicability of the CPT-based methods was evaluated using a statistical rank index (RI). A total of 82 piezocone penetration test soundings and 190 PDA test piles were used for reliability analysis in this study. Three correction steps were applied to obtain reliable PDA and CPT data sets before ranking is carried out. The RI index is combined from four criteria: (1) the best-fit line, (2) the arithmetic mean and standard deviation, (3) the cumulative probabilities, and (4) the log-normal and histogram distributions. Based on these criteria the performance of some SPT-based methods in the literature is evaluated.  相似文献   

Spatial prediction of landslide susceptibility using integrated frequency ratio with entropy and support vector machines by different kernel functions     

Wei Chen  Jiale Wang  Xiaoshen Xie  Haoyuan Hong  Nguyen Van Trung  Dieu Tien Bui  Gang Wang  Xinrui Li 《Environmental Earth Sciences》2016,75(20):1344

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A Continuous Mapping of Tidal Current Structures in the Kanmon Strait   总被引：1，自引：0，他引：1  

Keisuke?Yamaguchi  Ju?Lin  Arata?KanekoEmail author  Tokuo?Yayamoto  Noriaki?Gohda  Hong-Quang?Nguyen  Hong?Zheng 《Journal of Oceanography》2005,61(2):283-294

Tidal current structures at the Hayatomono-Seto of the Kanmon Strait are mapped continuously during March 17 to 20, 2003, including a spring tide, by the eight coastal acoustic tomography (CAT) systems distributed on both the sides of the strait. Detailed structures of strong tidal currents and their associated vortices are well reconstructed by the inverse analysis of travel-time difference data obtained from the reciprocal sound transmission between the paired CAT systems located at both sides of the strait mainly. The results are well compared to the shipboard acoustic Doppler current profiler (ADCP) data at the correlation rate of 0.84/0.82 and the RMS difference of 0.47/0.48 ms⁻¹ for the east-west/north-south current after the selection of good data. During the observation period, the maximum hourly mean volume transport for the upper 7 m layer across the strait reached 13,314 m³ s⁻¹ for the eastward and 5,547 m³ s⁻¹ for the westward. The daily mean transport is directed to the eastward and estimated 1,470 m³ s⁻¹ and 2,140 m³ s⁻¹ for March 18 and 19, respectively, when a spring tide occurs.  相似文献   

Tropical Cyclone in the North of the South China Sea as a Factor Affecting the Structure of the Vietnamese Current     

Vlasova  G. A.  Xuan  Nguyen Ba  Demenok  M. N.  Long  Bui Hong  Mau  Le Dinh  Dung  Nguyen Thi Thuy 《Izvestiya Atmospheric and Oceanic Physics》2020,56(4):390-400

Izvestiya, Atmospheric and Oceanic Physics - Tropical cyclones play a significant role in the formation of the hydrodynamic regime of the South China Sea, including its western part, which is...  相似文献   

Prediction of Blast-Induced Ground Vibration in an Open-Pit Mine by a Novel Hybrid Model Based on Clustering and Artificial Neural Network     

Nguyen  Hoang  Drebenstedt  Carsten  Bui  Xuan-Nam  Bui  Dieu Tien 《Natural Resources Research》2020,29(2):691-709

Natural Resources Research - Ground vibration (PPV) is one of the hazard effects induced by blasting operations in open-pit mines, which can affect the surrounding structures, particularly the...  相似文献   

Sedimentation in the floodplains of the Mekong Delta,Vietnam. Part I: suspended sediment dynamics          下载免费PDF全文

Nguyen Nghia Hung  José Miguel Delgado  Andreas Güntner  Bruno Merz  András Bárdossy  Heiko Apel 《水文研究》2014,28(7):3132-3144

Suspended sediment is the primary source for a sustainable agro‐ecosystem in the Mekong Delta by providing nutrient input for the subsequent cropping season. In addition, the suspended sediment concentration (SSC) plays an important role in the erosion and deposition processes in the Delta; that is, it influences the morphologic development and may counteract the deltaic subsidence and sea level rise. Despite this importance, little is known about the dynamics of suspended sediment in the floodplains of the Mekong Delta. In particular, quantitative analyses are lacking mainly because of data scarcity with respect to the inundation processes in the floodplains. In 2008, therefore, a comprehensive in situ system to monitor the dynamics of suspended sediment in a study area located in the Plain of Reeds was established, aiming at the characterization and quantification of suspended sediment dynamics in the deeply inundated parts of the Vietnamese part of the Mekong Delta. The monitoring system was equipped with seven water quality–monitoring stations. They have a robust design and autonomous power supply suitable for operation on inundated floodplains, enabling the collection of reliable data over a long period of time with a high temporal resolution. The data analysis shows that the general seasonal dynamics of suspended sediment transport in the Delta is controlled by two main mechanisms: the flood wave of the Mekong River and the tidal backwater influences from the coast. In the channel network, SSC decreases exponentially with distance from the Mekong River. The anthropogenic influence on SSC could also be identified for two periods: at the start of the floodplain inundation and at the end of the flood period, when subsequent paddy rice crops are prepared. Based on the results, we recommend an operation scheme for the sluice gates, which intends to distribute the sediment and thus the nutrients equally over the floodplain. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Predicting Blast-Induced Air Overpressure: A Robust Artificial Intelligence System Based on Artificial Neural Networks and Random Forest     

Nguyen  Hoang  Bui  Xuan-Nam 《Natural Resources Research》2019,28(3):893-907

Natural Resources Research - Blasting is the most popular method for rock fragmentation in open-pit mines. However, the side effects caused by blasting operations include ground vibration, air...  相似文献