Evaluation of food risk parameters in the Day River Flood Diversion Area,Red River Delta,Vietnam     

Nguyen Mai Dang  Mukand S. Babel  Huynh T. Luong 《Natural Hazards》2011,56(1):169-194

An interdisciplinary approach is necessary for flood risk assessment. Questions are often raised about which factors should be considered important in assessing the flood risk in an area and how to quantify these factors. This article defines and quantitatively evaluates the flood risk factors that would affect the Day River Flood Diversion Area in the context of integrated flood management in the Red River Delta, Vietnam. Expert analysis, in conjunction with field survey and Analytical Hierarchy Process (AHP), is applied to define and quantify parameters (indicators, subcomponents, and components) that contribute to flood risk. Flood duration is found to be the most prominent indicator in determining flood hazard. Residential buildings, population, and pollution are other fairly significant indicators contributing to flood vulnerability from the economic, social, and environmental perspectives, respectively. The study results will be useful in developing comprehensive flood risk maps for policy-makers and responsible authorities. Besides, local residents will also be able to implement suitable measures for reducing flood risk in the study area.  相似文献   

Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C     

Neubeck A  Duc NT  Bastviken D  Crill P  Holm NG 《Geochemical transactions》2011,12(1):6-10

Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.  相似文献   

Sea urchin development in a global change hotspot, potential for southerly migration of thermotolerant propagules     

M. Byrne  P. SelvakumaraswamyM.A. Ho  E. WoolseyH.D. Nguyen 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(5):712-719

The distribution of the sea urchin Heliocidaris erythrogramma coincides with the southeast Australia global change hot spot where marine ecosystems are warming significantly due to changes in ocean circulation. To address questions on future vulnerabilities, the thermotolerance of the planktonic life phase of H. erythrogramma was investigated in the climate and regionally relevant setting of projected near-future (2100) ocean warming. Experimental treatments ranged from 18 to 26 °C, with 26 °C representing +3-4 °C above recent ambient sea-surface temperatures. Developmental success across all stages (gastrula, 24 h; larva, 72 h; juvenile, 120 h) decreased with increasing temperature. Development was tolerant to a +1-2 °C increase above ambient, but significant deleterious effects were evident at +3-4 °C. However, larvae that developed through the early bottleneck of normal development at 26 °C metamorphosed successfully. The inverse relationship between temperature and planktonic larval duration (PLD) was seen in a 25% decrease in the PLD of H. erythrogramma at 24 and 26^oC. Ocean warming may be advantageous to a subset of larvae through early settlement and reduction of the vulnerable planktonic period. This positive effect of temperature may help buffer the negative effects of ocean warming. In parallel studies with progeny derived from northern (Coffs Harbour) and southern (Sydney) H. erythrogramma, northern embryos had significantly higher thermotolerance. This provides the possibility that H. erythrogramma populations might keep up with a warming world through poleward migration of thermotolerant propagules, facilitated by the strong southward flow of the East Australian Current. It is uncertain whether H. erythrogramma populations at the northern range of this species, with no source of immigrants, will have the capacity to persist in a warm ocean. Due to its extensive latitudinal distribution, its potential developmental thermotolerance and independence of its lecithotrophic larvae from exogenous food and the need to make a functional skeleton, H. erythrogramma may be particularly robust to ocean change.  相似文献   

A coupled damage–plasticity model for concrete based on thermodynamic principles: Part I: model formulation and parameter identification     

Giang D. Nguyen  Guy T. Houlsby 《国际地质力学数值与分析法杂志》2008,32(4):353-389

The development of a coupled damage‐plasticity constitutive model for concrete is presented. Emphasis is put on thermodynamic admissibility, rigour and consistency both in the formulation of the model, and in the identification of model parameters based on experimental tests. The key feature of the thermodynamic framework used in this study is that all behaviour of the model can be derived from two specified energy potentials, following procedures established beforehand. Based on this framework, a constitutive model featuring full coupling between damage and plasticity in both tension and compression is developed. Tensile and compressive responses of the material are captured using two separate damage criteria, and a yield criterion with a multiple hardening rule. A crucial part of this study is the identification of model parameters, with these all being shown to be identifiable and computable based on standard tests on concrete. Behaviour of the model is assessed against experimental data on concrete. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

SOME PRELIMINARY RESULTS FROM STUDY OF CRUSTAL DEFORMATION IN VIETNAM     

Cao Dinh Trieu  Le Van Dung  Nguyen Huu Tuyen  Pham Nam Hung 《大地测量与地球动力学》2003,23(Z1)

1　IntroductionOneofthemaintasksinstudyinggeodynamicprocessisevaluatingtherateofearthcrustmove ments.Normally ,themethodsforstudyingearthcrustmovementareestablishedonthebasisoftheobjectofstudyandtherequirementsfortheresultstobeobtainedasfollows.1 )Tostudythemovingprocessofcrustplatesinalargeareaandwithinacertaintectonicperiod ,geologicmethodsareusuallyused .2 )Geodeticmeasurementsarecarriedoutinanareacoveringfromsomekm2 totensofkm2 andal lowtodeterminethedisplacementoftheearthcrustwithinaperio…  相似文献   

Nonlinear longitudinal dynamics of an orbital lifting vehicle     

Nguyen X. Vinh  Arthur J. Dobrzelecki 《Celestial Mechanics and Dynamical Astronomy》1971,3(4):427-460

This paper presents an analytical study of the longitudinal dynamics of a thrusting, lifting, orbital vehicle in a nearly circular orbit. The translational motion is composed of a nonlinear oscillation, or phugoid, and a spiral mode which results in either decay or dilatation of the orbit depending on the perturbed initial conditions. The nonlinear effects on the phugoid period and damping are small in the altitude range considered. Elements of the orbit such as radial distance, velocity, and flight path angle were obtained explicitly as functions of time. The behavior of the variations of these elements is correctly predicted. Explicit expressions for period and damping of the angle-of-attack mode were derived. It is shown that a critical altitude may exist at which the phugoid mode and the angle-of-attack mode have nearly equal periods. Near this resonance altitude linearized solutions are no longer valid and a study of the nonlinear equations shows that there is a strong interactions between the translational and the rotational modes resulting in a switching of the two frequencies of oscillations.This work was supported by NASA Contract No. NASr 54(06).  相似文献   

Predicting water flow in fully and partially saturated porous media: a new fractal-based permeability model     

A.  Nguyen Van Nghia  Jougnot  Damien  Thanh  Luong Duy  Van Do  Phan  Thuy  Tran Thi Chung  Hue  Dang Thi Minh  Hung  Nguyen Manh 《Hydrogeology Journal》2021,29(6):2017-2031

Hydrogeology Journal - Predicting the permeability of porous media in saturated and partially saturated conditions is of crucial importance in many geo-engineering areas, from water resources to...  相似文献   

Regional-scale landslide risk assessment on Mt. Umyeon using risk index estimation     

Nguyen  Ba-Quang-Vinh  Kim  Yun-Tae 《Landslides》2021,18(7):2547-2564

Landslides - The frequency of landslides and their magnitude are increasing worldwide due to global climate change, causing damage to people and infrastructure. Therefore, landslide risk assessment...  相似文献   

Improved flood susceptibility mapping using a best first decision tree integrated with ensemble learning techniques     

Binh Thai Pham  Abolfazl Jaafari  Tran Van Phong  Hoang Phan Hai Yen  Tran Thi Tuyen  Vu Van Luong  Huu Duy Nguyen  Hiep Van Le  Loke Kok Foong 《地学前缘(英文版)》2021,12(3):101105

Improving the accuracy of flood prediction and mapping is crucial for reducing damage resulting from flood events. In this study, we proposed and validated three ensemble models based on the Best First Decision Tree (BFT) and the Bagging (Bagging-BFT), Decorate (Bagging-BFT), and Random Subspace (RSS-BFT) ensemble learning techniques for an improved prediction of flood susceptibility in a spatially-explicit manner. A total number of 126 historical flood events from the Nghe An Province (Vietnam) were connected to a set of 10 flood influencing factors (slope, elevation, aspect, curvature, river density, distance from rivers, flow direction, geology, soil, and land use) for generating the training and validation datasets. The models were validated via several performance metrics that demonstrated the capability of all three ensemble models in elucidating the underlying pattern of flood occurrences within the research area and predicting the probability of future flood events. Based on the Area Under the receiver operating characteristic Curve (AUC), the ensemble Decorate-BFT model that achieved an AUC value of 0.989 was identified as the superior model over the RSS-BFT (AUC = 0.982) and Bagging-BFT (AUC = 0.967) models. A comparison between the performance of the models and the models previously reported in the literature confirmed that our ensemble models provided a reliable estimate of flood susceptibilities and their resulting susceptibility maps are trustful for flood early warning systems as well as development of mitigation plans.  相似文献   

The analysis of ballistic capabilities for countering disturbances associated with temporary emergency electric propulsion shutdown     

M. S. Konstantinov  D. N. Nguyen 《Solar System Research》2016,50(7):560-567

The paper analyzes the possibility for countering ballistic perturbations of the interplanetary transfer trajectory of the spacecraft with electric propulsion (EP) associated with the temporary impossibility of the normal use of the EP in phases of the heliocentric transfer. The main result of the present study is the method for the determination of a new nominal trajectory, at any point of which the allowed duration of the emergency shutdown of electric propulsion is large enough. The numerical analysis is given for one of the possible scenarios of spacecraft injection into the operational heliocentric orbit for solar research.  相似文献