Evaluation of seismic ground motion induced by topographic irregularity   总被引：1，自引：0，他引：1  

Khoa-Van Nguyen  Behrouz Gatmiri   《Soil Dynamics and Earthquake Engineering》2007,27(2):183-188

Results of an extensive numerical study on the 2D scattering of seismic waves by local topography are presented. The investigation has been conducted using the direct boundary element method. Several types of topography (slopes, canyons and ridges) are considered. The influences of some key parameters, such as exciting frequency and geometry of the irregular feature, on surface ground motion are studied in detail. It is found that local topographic conditions play an important role in the modification of seismic ground motion at the irregular feature itself and its neighbourhood. The present results can be considered to be useful from the viewpoint of earthquake engineering and seismology.  相似文献   

Probabilistic Seismic Hazard Assessment Along the Southeastern Coast of Vietnam     

Hong Phuong  Nguyen 《Natural Hazards》2001,24(1):53-74

On the basis of the analysis of geological, tectonic characteristics and earthquake manifestation features, a causative relation between geodynamic regime and seismicity has been established for the southeastern coastal zone and continental shelf of Vietnam. The probabilistic methods have been used to evaluate ground shaking effects at Nha Trang city aswell as for the entire study area. Short, intermediate and long term predictions of ground shaking (in the form of peak ground accelerationmaps) show high risks in the coastal zone of central Vietnam and in the southeastern continental shelf of the country.  相似文献   

Simulation of acid water movement in canals   总被引：1，自引：0，他引：1  

To Van Truong  Nguyen Tat Dac  Huynh Ngoc Phienc   《Journal of Hydrology》1996,180(1-4):361-371

An attempt to tackle the problem of the propagation of acid water in canals is described, and a mathematical model to simulate the acid water movement is developed, in which the jurbanite equilibrium is found to prevail. The processes of settling owing to sedimentation, precipitation and redissolution have been considered in the modelling. Data available from Tan Thanh, in the Plain of Reeds of the Mekong Delta in Viet Nam, are used as a case study.  相似文献   

Covariations in oceanic dimethyl sulfide,its oxidation products and rain acidity at Amsterdam Island in the Southern Indian Ocean   总被引：5，自引：0，他引：5  

B. C. Nguyen  N. Mihalopoulos  J. P. Putaud  A. Gaudry  L. Gallet  W. C. Keene  J. N. Galloway 《Journal of Atmospheric Chemistry》1992,15(1):39-53

Simultaneous measurements of rain acidity and dimethyl sulfide (DMS) at the ocean surface and in the atmosphere were performed at Amsterdam Island over a 4 year period. During the last 2 years, measurements of sulfur dioxide (SO₂) in the atmosphere and of methane sulfonic acid (MSA) and non-sea-salt-sulfate (nss-SO₄ ^2-) in rainwater were also performed. Covariations are observed between the oceanic and atmospheric DMS concentrations, atmospheric SO₂ concentrations, wet deposition of MSA, nss-SO₄ ^2-, and rain acidity. A comparable summer to winter ratio of DMS and SO₂ in the atmosphere and MSA in precipitation were also observed. From the chemical composition of precipitation we estimate that DMS oxidation products contribute approximately 40% of the rain acidity. If we consider the acidity in excess, then DMS oxidation products contribute about 55%.  相似文献   

Book reviews     

Mark S. T. Bukowinski  Philip E. Wannamaker  Manfred Koch  Yukio Fujinawa  Dr. Pradeep Talwani  D. Möhlmann  Andrew H. Knoll  Lucia Lovison-Golob  Krzysztof Haman  Hanna Pawłowska  Henryk Piwkowski  Dr. Anthony Dore  Nguyen Xuan Huy  Edward R. Cook  Jan Błecki  Jacek Leliwa-Kopystynski  Magdalena Sroczynska-Kozuchowska 《Pure and Applied Geophysics》1993,140(1):139-177

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Adaptive neuro-fuzzy inference system coupled with shuffled frog leaping algorithm for predicting river streamflow time series     

Babak Mohammadi  Nguyen Thi Thuy Linh  Ali Najah Ahmed  Jana Vojteková  Yiqing Guan 《水文科学杂志》2020,65(10):1738-1751

ABSTRACT

Accurate runoff forecasting plays a key role in catchment water management and water resources system planning. To improve the prediction accuracy, one needs to strive to develop a reliable and accurate forecasting model for streamflow. In this study, the novel combination of the adaptive neuro-fuzzy inference system (ANFIS) model with the shuffled frog-leaping algorithm (SFLA) is proposed. Historical streamflow data of two different rivers were collected to examine the performance of the proposed model. To evaluate the performance of the proposed ANFIS-SFLA model, six different scenarios for the model input–output architecture were investigated. The results show that the proposed ANFIS-SFLA model (R² = 0.88; NS = 0.88; RMSE = 142.30 (m³/s); MAE = 88.94 (m³/s); MAPE = 35.19%) significantly improved the forecasting accuracy and outperformed the classic ANFIS model (R² = 0.83; NS = 0.83; RMSE = 167.81; MAE = 115.83 (m³/s); MAPE = 45.97%). The proposed model could be generalized and applied in different rivers worldwide.  相似文献   

Synchronous Transformations of Mineral and Organic Constituents of Sedimentary Rocks in Geological Structure with an Initial Extension and Subsequent Compression Tectonic Regime     

Petrova  V. V.  Nginh  Le Thi  Stukalova  I. E.  Sokolova  A. L.  Huyen  Nguyen Xuan  Pha  Phang Dong 《Lithology and Mineral Resources》2003,38(3):209-222

Sedimentary rocks of the section in the Red River fold zone of northern Viet Nam are considered. It is shown that secondary mineral parageneses formed in two stages. The first stage (35–17 Ma ago) corresponded to the period of structure extension and sediment subsidence to a depth of about 6 km. This period and subsequent 10 Ma were marked by the formation of a usual dia- and catagenetic zoning of metasedimentary rocks. The second stage (5–7 Ma ago) corresponded to processes of compression that were responsible for the deformation of rocks into gentle folds and 1.5 to 2.2 times contraction of the section thickness in different places. The sequential–mineralogical zoning was disturbed at this stage. Smectites and mixed-layer minerals were replaced by chlorites and hydromicas. Organic material also responded to compression simultaneously with inorganic components. The bituminous component was released from humic matter and rocks became enriched in hydrocarbons.  相似文献   

Small-scale marine fisheries policy in Vietnam   总被引：1，自引：0，他引：1  

Robert Pomeroy  Kim Anh Thi Nguyen  Ha Xuan Thong 《Marine Policy》2009

Vietnam's marine fisheries are considered to be small scale and are concentrated in coastal near-shore waters. This has resulted in heavy pressure on near-shore fisheries resources. Near-shore fisheries are considered by fishers and the government to be over-exploited, causing hardship for many coastal communities. This paper reviews and analyzes changes in policy towards small-scale fisheries in Vietnam over the last two decades. The primary issues facing the small-scale fisheries in Vietnam are to restructure the near-shore fisheries and to address over-capacity. Recommended actions include improved fisheries statistics, resources for provincial fisheries staff, and a coordinated and integrated approach involving a mixed strategy of resource management; resource restoration; economic and community development; and new governance arrangements.  相似文献   

Petroleum composition in the Cuu Long Basin (Mekong Basin) offshore southern Vietnam     

Jørgen A. Bojesen-Koefoed  H. Peter Nytoft  Nguyen Thi Dau 《Marine and Petroleum Geology》2009

The Cuu Long Basin (Mekong Basin) is a rift basin off southern Vietnam, and the most important petroleum producing basin in the country. However, information on petroleum type and characteristics has hitherto been largely unavailable to the public. This paper presents petroleum geochemical data on nine oil samples from four different producing fields in the Cuu Long Basin: the Dragon (Rong), Black Lion (Sutu-Den), Sunrise (Rang ?ong) and White Tiger (Bach Ho) Fields. The oils are highly paraffinic with bimodal normal alkane distributions and show moderate pristane to phytane ratios and a conspicuous hyperbolic decrease in abundance with increasing carbon number of hopane homologues from C₃₀ to C₃₅. The TPP-index of Holba et al. (Holba, A.G., Dzou, L.I., Wood, G.D., Ellis, L., Adam, P., Schaeffer, P., Albrecht, P., Greene, T., Hughes, W.B., 2003. Application of tetracyclic polyprenoids as indicators of input from fresh–brackish water environments. Organic Geochemistry 34, 441–469) is equal to 1 in all samples which in combination with tricyclic triperpane T26/T25 ratios >1 and the n-alkane and hopane distributions mentioned above provide a strong indication of an origin from lacustrine source rocks. This is supported by the absence of marine C₃₀ desmethyl steranes (i.e. 24-n-propylcholestanes) and marine diatom-derived norcholestanes. Based on the overall biological marker distributions, the lakes probably belonged to the overfilled or balanced-fill types defined by Bohacs et al. (Bohacs, K.M., Carroll, A.R., Neal, J.E., Mankiewicz, P.J., 2000. Lake-basin type, source potential, and hydrocarbon character. An integrated sequence-stratigraphic–geochemical framework. AAPG Studies in Geology 46, 3–34). The oils were generated from source rocks at early- to mid-oil-window maturity, presumably Oligocene lacustrine shales that are present in the syn-rift succession. Oils from individual fields may, however, be distinguished by a combination of biological marker parameters, such as the oleanane index, the gammacerane index, the relative abundance of tricyclic terpanes, the proportions of diasteranes and 28-norspergulane, complemented by other parameters. The oils of the Cuu Long Basin show an overall similarity to the B-10 oil from the Song Hong Basin off northern Vietnam, but are markedly different from the seepage oils known from Dam Thi Nai on the coast of central Vietnam.  相似文献   

Non‐local damage modelling of concrete: a procedure for the determination of model parameters     

Giang D. Nguyen  Guy T. Houlsby 《国际地质力学数值与分析法杂志》2007,31(7):867-891

This paper presents a procedure for the determination of parameters of non‐local damage models. This is to assure a consistent response of a non‐local damage model, as choice of the internal length and other parameters of the model are varied. Correlations between the internal length and other parameters governing the local constitutive behaviour of the model are addressed and exploited. Focus is put on the relationship between the internal length of the non‐local model and the width of the fracture process zone. Numerical examples are used to demonstrate the rigour of the proposed method. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献