Some medium properties at friuli (Italy) from amplitude spectrum analysis: A possible change in time or in space     

M. Granet  P. Hoang Trong 《Tectonophysics》1980,68(3-4)

We have studied the relation log M₀+ versus M_L in Friuli (Italy) by considering the amplitude spectra of local earthquakes. We show a possible time variation of the apparent average stress in the focal region between the two periods of May and November, 1976. Furthermore, the quality factor Q_p obtained from the same spectra indicates a spatial variation which could be correlated to the difference in the seismicity level.  相似文献   

Investigation of the accelerated carbonation of a MgO-based binder used to treat contaminated sediment     

Hoang Q. H. Phan  Kyung-Yup Hwang  Jun-Young Ahn  Tae Yoo Kim  Cheolyong Kim  Inseong Hwang 《Environmental Earth Sciences》2017,76(22):771

A MgO-based binder developed to simultaneously solidify/stabilize contaminated sediment and store CO₂ has been described previously. The objectives of the study presented here were to investigate the kinetics of the carbonation reactions of the binder and the extent to which carbonation occurred and to identify the optimal conditions for using the binder. The carbonation reaction was clearly faster and the degree of carbonation higher at CO₂ concentrations of 50 and 100% than in the ambient atmosphere (which contains 0.04% CO₂). A modified unreactive core model adequately described the kinetics. The rate constants were 0.0217–0.319 h^?1 and were proportional to the degree of carbonation. A high degree of carbonation, 93.8%, was achieved at a CO₂ concentration of 100%. The water to sediment ratio strongly affected carbonation, the optimal ratio being around 0.7. The relative humidity did not strongly affect the carbonation performance. The carbonation products were magnesite (MgCO₃) and nesquehonite (MgCO₃·3H₂O). X-ray diffraction analysis showed that brucite (Mg(OH)₂) was not present, suggesting that brucite was very quickly transformed into magnesium carbonates, the presence of which was confirmed by thermal gravimetric analysis. The results indicated that, in 7 d, 1 kg of binder could sequester up to 0.507 kg of CO₂ in a 100% CO₂ atmosphere. The results indicate that the MgO-based binder has great potential to be used to sequester CO₂ under accelerated carbonation conditions.  相似文献   

Assessing Possible Impacts of Climate Change on Species Important for Forestry in Vietnam   总被引：1，自引：0，他引：1  

Trevor H. Booth  Nguyen Hoang Nghia  Miko U. F. Kirschbaum  Clive Hackett  Tom Jovanovic 《Climatic change》1999,41(1):109-126

The likely effects on two tree species of a range of scenarios of climatic and atmospheric change expected by the year 2050 are investigated using a climatic mapping program, a simple simulation model and a process-based simulation model. Styrax tonkinensis is a native species for which relatively little information is available. Acacia mangium is an introduced species, which is important for pulp production in several other countries, and for which there is considerable information for growth and utilization. A climatic mapping program is used to show areas which may be suitable for these species under present and predicted conditions. Two simulation models are used to investigate likely effects on productivity of the two species for a range of climatic change scenarios for Hanoi and Ho Chi Minh City. The estimated changes in production are predicted to be relatively small, though uncertainities associated with the simulations are quite high. However, the models highlight areas where more data are needed and also suggest some key regions in Vietnam which would be worth monitoring to detect early signs of the effects of climatic and atmospheric change.  相似文献   

Non-stationary future return levels for extreme rainfall over Extremadura (southwestern Iberian Peninsula)     

Francisco Javier Acero  Sylvie Parey  Thi Thu Huong Hoang  Didier Dacunha-Castelle  José Agustín García  María Cruz Gallego 《水文科学杂志》2017,62(9):1394-1411

Based on a previous study for temperature, a new method for the calculation of non-stationary return levels for extreme rainfall is described and applied to Extremadura, a region of southwestern Spain, using the peaks-over-threshold approach. Both all-days and rainy-days-only datasets were considered and the 20-year return levels expected in 2020 were estimated taking different trends into account: first, for all days, considering a time-dependent threshold and the trend in the scale parameter of the generalized Pareto distribution; and second, for rainy days only, considering how the mean, variance, and number of rainy days evolve. Generally, the changes in mean, variance and number of rainy days can explain the observed trends in extremes, and their extrapolation gives more robust estimations. The results point to a decrease of future return levels in 2020 for spring and winter, but an increase for autumn.  相似文献   

Toward state-of-the-art techniques in predicting and controlling slope stability in open-pit mines based on limit equilibrium analysis,radial basis function neural network,and brainstorm optimization     

Shang  Li  Nguyen  Hoang  Bui  Xuan-Nam  Vu  Thai Ha  Costache  Romulus  Hanh  Le Thi Minh 《Acta Geotechnica》2022,17(4):1295-1314

Acta Geotechnica - This study aims to propose state-of-the-art techniques in predicting and controlling slope stability in open-pit mines based on limit equilibrium analysis, artificial neural...  相似文献   

Prediction of Blast-induced Air Over-pressure in Open-Pit Mine: Assessment of Different Artificial Intelligence Techniques     

Bui  Xuan-Nam  Nguyen  Hoang  Le  Hai-An  Bui  Hoang-Bac  Do  Ngoc-Hoan 《Natural Resources Research》2020,29(2):571-591

Air over-pressure (AOp) is one of the products of blasting operations for rock fragmentation in open-pit mines. It can cause structural vibration, smash glass doors, adversely affect the surrounding environment, and even be fatal to humans. To assess its dangerous effects, seven artificial intelligence (AI) methods for predicting specific blast-induced AOp have been applied and compared in this study. The seven methods include random forest, support vector regression, Gaussian process, Bayesian additive regression trees, boosted regression trees, k-nearest neighbors, and artificial neural network (ANN). An empirical technique was also used to compare with AI models. The degree of complexity and the performance of the models were compared with each other to find the optimal model for predicting blast-induced AOp. The Deo Nai open-pit coal mine (Vietnam) was selected as a case study where 113 blasting events have been recorded. Indicators used for evaluating model performances include the root-mean-square error (RMSE), determination coefficient (R²), and mean absolute error (MAE). The results indicate that AI techniques provide better performance than the empirical method. Although the relevance of the empirical approach was acceptable (R²?=?0.930) in this study, its error (RMSE?=?7.514) is highly significant to guarantee the safety of the surrounding environment. In contrast, the AI models offer much higher accuracies. Of the seven AI models, ANN was the most dominant model based on RMSE, R², and MAE. This study demonstrated that AI techniques are excellent for predicting blast-induced AOp in open-pit mines. These techniques are useful for blasters and managers in controlling undesirable effects of blasting operations on the surrounding environment.

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Novel Soft Computing Model for Predicting Blast-Induced Ground Vibration in Open-Pit Mines Based on Particle Swarm Optimization and XGBoost     

Zhang  Xiliang  Nguyen  Hoang  Bui  Xuan-Nam  Tran  Quang-Hieu  Nguyen  Dinh-An  Bui  Dieu Tien  Moayedi  Hossein 《Natural Resources Research》2020,29(2):711-721

Natural Resources Research - Blasting is a useful technique for rocks fragmentation in open-pit mines, underground mines, as well as for civil engineering work. However, the negative impacts of...  相似文献   

Prediction of Blast-Induced Ground Vibration in Open-Pit Mines Using a New Technique Based on Imperialist Competitive Algorithm and M5Rules     

Fang  Qiancheng  Nguyen  Hoang  Bui  Xuan-Nam  Nguyen-Thoi  Trung 《Natural Resources Research》2020,29(2):791-806

Natural Resources Research - In this paper, blast-induced ground vibration (BIGV) was considered as the primary objective, and a new artificial intelligence system was proposed to predict BIGV with...  相似文献   

Improving watershed management practices in humid regions          下载免费PDF全文

Fasikaw A. Zimale  Seifu A. Tilahun  Tigist Y. Tebebu  Christian D. Guzman  Linh Hoang  Elliot M. Schneiderman  Eddy J. Langendoen  Tammo S. Steenhuis 《水文研究》2017,31(18):3294-3301

In many parts of the world, watershed management practices have been extremely effective. However, implementation of soil and water conservation technologies in the humid African highlands, while beneficial in the short term, were remarkably unsuccessful in the long term. Insights from community knowledge perspectives have revealed that alternative methods are needed. Although conservation practices are designed to conserve water in semi‐arid areas, safely draining excess water is needed in humid areas. The objective of this paper is to review current watershed management approaches used in humid regions as exemplified by those used in Ethiopian highlands and then based on these findings propose more effective practices. Although current government sponsored practices primarily protect the hillsides, direct run‐off is generated from areas that become saturated on valley bottoms near rivers and on specific parts of the hillsides with degraded soils (or with highly permeable surface soils) and with perched water tables on slowly permeable horizons at shallow depths. In these areas, direct run‐off is increasing with deforestation and the soil degradation, demanding additional drainage ways that evolve in the form of gullies. Therefore, watershed management interventions for erosion control should prioritize revegetation of degraded areas, increasing sustainable infiltration, and rehabilitating gullies situated at saturated bottomlands.  相似文献   

Present-day stress and pore pressure fields in the Cuu Long and Nam Con Son Basins, offshore Vietnam   总被引：1，自引：0，他引：1  

Nguyen Thi Thanh Binh  Tomochika Tokunaga  Hoang Phuoc Son  Mai Van Binh 《Marine and Petroleum Geology》2007,24(10):607-615

Knowledge of the in situ, or contemporary stress field is vital for planning optimum orientations of deviated and horizontal wells, reservoir characterization and a better understanding of geodynamic processes and their effects on basin evolution.This study provides the first documented analysis of in situ stress and pore pressure fields in the sedimentary formations of the Cuu Long and Nam Con Son Basins, offshore Vietnam, based on data from petroleum exploration and production wells.In the Cuu Long Basin, the maximum horizontal stress is mainly oriented in NNW–SSE to N–S in the northern part and central high. In the Nam Con Son Basin, the maximum horizontal stress is mainly oriented in NE–SW in the northern part and to N–S in the central part of the basin.The magnitude of the vertical stress has a gradient of approximately 22.2 MPa/km at 3500 m depth. Minimum horizontal stress magnitude is approximately 61% of the vertical stress magnitude in normally pressured sequences.The effect of pore pressure change on horizontal stress magnitudes was estimated from pore pressure and fracture tests data in depleted zone caused by fluid production, and an average pore pressure–stress coupling ratio (ΔS_h/ΔP_p) obtained was 0.66. The minimum horizontal stress magnitude approaches the vertical stress magnitude in overpressured zones of the Nam Con Son Basin, suggesting that an isotropic or strike-slip faulting stress regime may exist in the deeper overpressured sequences.  相似文献