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201.
202.
Proloy Deb Duong Anh Tran Parmeshwar D. Udmale 《Theoretical and Applied Climatology》2016,124(3-4):641-652
This paper presents applications of the peaks-over-threshold methodology for both the univariate and the recently introduced bivariate case, combined with a novel bootstrap approach. We compare the proposed bootstrap methods to the more traditional profile likelihood. We have investigated 63 years of the European Climate Assessment daily precipitation data for five Hungarian grid points, first separately for the summer and winter months, then aiming at the detection of possible changes by investigating 20 years moving windows. We show that significant changes can be observed both in the univariate and the bivariate cases, the most recent period being the most dangerous in several cases, as some return values have increased substantially. We illustrate these effects by bivariate coverage regions. 相似文献
203.
Characteristic Features of REE and Pb–Zn–Ag Mineralizations in the Na Son Deposit,Northeastern Vietnam
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Can Pham‐Ngoc Daizo Ishiyama Tuan Anh Tran Mihoko Hoshino Sachihiro Taguchi 《Resource Geology》2016,66(4):404-418
The Na Son deposit is a small‐scale Pb–ZnPb–Zn–Ag deposit in northeast Vietnam and consists of biotite–chlorite schist, reddish altered rocks, quartz veins and syenite. The biotite–chlorite schist is intruded by syenite. Reddish altered rocks occur as an alteration halo between the biotite–allanite‐bearing quartz veins and the biotite–chlorite schist. Allanite occurs in the biotite–allanite‐bearing quartz veins and in the proximal reddish altered rocks. Rare earth element (REE) fluorocarbonate minerals occur along fractures or at rim of allanite crystals. The later horizontal aggregates of sulfide veins and veinlets cut the earlier reddish altered rocks. The earlier Pb–Zn veins consist of a large amount of galena and lesser amounts of sphalerite, pyrite and molybdenite. The later Cu veins cutting the Pb–Zn veins include chalcopyrite and lesser amounts of tetrahedrite and pyrite. The occurrences of two‐phase H2O–CO2 fluid inclusions in quartz from biotite–allanite‐bearing quartz veins and REE‐bearing fluorocarbonate minerals in allanite suggest the presence of CO2 and F in the hydrothermal fluid. The oxygen isotopic ratios of the reddish altered rocks, biotite–chlorite schist, and syenite range from +13.9 to +14.9 ‰, +11.5 to +13.3 ‰, and +10.1 to +11.6 ‰, respectively. Assuming an isotopic equilibrium between quartz (+14.6 to +15.8 ‰) and biotite (+8.6 ‰) in the biotite–allanite‐bearing quartz vein, formation temperature was estimated to be 400°C. At 400°C, δ18O values of the hydrothermal fluid in equilibrium with quartz and biotite range from +10.5 to +11.7 ‰. These δ18O values are consistent with fluid that is derived from metamorphism. Assuming an isotopic equilibrium between galena (+1.5 to +1.7 ‰) and chalcopyrite (+3.4 ‰), the formation temperature was estimated to be approximately 300°C. The formation temperature of the Na Son deposit decreased with the progress of mineralization. Based on the geological data, occurrence of REE‐bearing minerals and oxygen isotopic ratios, the REE mineralization is thought to result from interaction between biotite–chlorite schist and REE‐, CO2‐ and F‐bearing metamorphic fluid at 400°C under a rock‐dominant condition. 相似文献
204.
Dieu Tien Bui Tran Anh Tuan Harald Klempe Biswajeet Pradhan Inge Revhaug 《Landslides》2016,13(2):361-378
Preparation of landslide susceptibility maps is considered as the first important step in landslide risk assessments, but these maps are accepted as an end product that can be used for land use planning. The main objective of this study is to explore some new state-of-the-art sophisticated machine learning techniques and introduce a framework for training and validation of shallow landslide susceptibility models by using the latest statistical methods. The Son La hydropower basin (Vietnam) was selected as a case study. First, a landslide inventory map was constructed using the historical landslide locations from two national projects in Vietnam. A total of 12 landslide conditioning factors were then constructed from various data sources. Landslide locations were randomly split into a ratio of 70:30 for training and validating the models. To choose the best subset of conditioning factors, predictive ability of the factors were assessed using the Information Gain Ratio with 10-fold cross-validation technique. Factors with null predictive ability were removed to optimize the models. Subsequently, five landslide models were built using support vector machines (SVM), multi-layer perceptron neural networks (MLP Neural Nets), radial basis function neural networks (RBF Neural Nets), kernel logistic regression (KLR), and logistic model trees (LMT). The resulting models were validated and compared using the receive operating characteristic (ROC), Kappa index, and several statistical evaluation measures. Additionally, Friedman and Wilcoxon signed-rank tests were applied to confirm significant statistical differences among the five machine learning models employed in this study. Overall, the MLP Neural Nets model has the highest prediction capability (90.2 %), followed by the SVM model (88.7 %) and the KLR model (87.9 %), the RBF Neural Nets model (87.1 %), and the LMT model (86.1 %). Results revealed that both the KLR and the LMT models showed promising methods for shallow landslide susceptibility mapping. The result from this study demonstrates the benefit of selecting the optimal machine learning techniques with proper conditioning selection method in shallow landslide susceptibility mapping. 相似文献
205.
The length variations and the ultrasonic wave velocities were measured along principal single crystal calcite axes under high pressure.We have observed that six independent elastic constants undergo drastic changes at the calcite I—calcite II transition point at 14.6 kbar. Furthermore, we have determinated the length and volumetric variations in the phases I and II and during the I–II transition.These results allow us to deduce the following important points: influence of the planar CO3 groups on the strong linear compressibility anisotropy in phase I; reciprocal relation between the decrease of elastic constants at the transition point and the anomaly of compressibility of the calcite II; compatibility of our data with the monoclinic structure of calcite II. 相似文献
206.
Van Tien Pham Trinh Phan Trong Luong Le Hong Nhat Le Minh Duc Dao Minh Hieu Tran Trung Cuong Tran Quoc Nhan Tran Thanh 《Landslides》2021,18(6):2329-2333
Landslides - At about 12:00 a.m., on October 13, 2020, a rapid rotational landslide induced by rainfall swept over Ranger Station-7 in Phong Xuan commune, Phong Dien district, Thua Thien Hue... 相似文献
207.
Thi Thao Dinh To Quyen Nguyen Gia Co Quan Vo Dong Nghi Nguyen Hon Quoc Tran Tien Khoa Le 《International Journal of Environmental Science and Technology》2017,14(12):2613-2622
Magnetic photo-Fenton catalysts based on spinel CuFe2O4 were successfully prepared by the starch-assisted sol–gel method. Various synthetic conditions such as annealing temperatures (700, 800 and 900 °C) and molar ratios of Cu2+/Fe3+/C6H10O5 in the precursor solution (from 1:2:2 to 1:2:4) were, respectively, used in order to study the influences of annealing temperatures and precursor starch contents on the magnetic and catalytic properties of CuFe2O4 powders. The photo-Fenton catalytic activity was evaluated via the degradation of methylene blue under ultraviolet and visible irradiation with H2C2O4 as a new oxidizing agent. According to the results, when the annealing temperature increased to 800 °C, the spinel CuFe2O4 phase amount was increased, which strongly enhances the photo-Fenton catalytic performance. However, above 800 °C, the catalytic activity was reduced, due to the increase in particle size. The starch content also affected the surface Cu2+ content and the particle size of catalysts. The catalyst prepared at 800 °C with the molar Cu2+/Fe3+/C6H10O5 ratio of 1:2:3 presented the best photo-Fenton performance, owing to its highest surface Cu2+ content. This catalyst also exhibits ferromagnetic properties (saturation magnetization of 25.836 emu/g and coercivity of 1010.23 Oe), which allows them to be easily separated from the solution by a magnet. 相似文献
208.
Thanh Son Nguyen Suched Likitlersuang Hiroyasu Ohtsu Takafumi Kitaoka 《Arabian Journal of Geosciences》2017,10(16):369
Rainfall-induced landslides frequently occur in humid temperate regions worldwide. Research activity in understanding the mechanism of rainfall-induced landslides has recently focused on the probability of slope failure involving non-homogeneous soil profiles. This paper presents probabilistic analyses to assess the stability of unsaturated soil slope under rainfall. The influence of the spatial variability of shear strength parameters on the probability of rainfall-induced slope failure is conducted by means of a series of seepage and stability analyses of an infinite slope based on random fields. A case study of shallow failure located on sandstone slopes in Japan is used to verify the analysis framework. The results confirm that a probabilistic analysis can be efficiently used to qualify various locations of failure surface caused by spatial variability of soil shear strength for a shallow infinite slope failure due to rainfall. 相似文献
209.
Luong Duy Thanh Phan Van Do Nguyen Van Nghia Nguyen Xuan Ca 《Geophysical Prospecting》2018,66(4):753-766
Streaming potential is the result of coupling between a fluid flow and an electric current in porous rocks. The modified Helmholtz–Smoluchowski equation derived for capillary tubes is mostly used to determine the streaming potential coefficient of porous media. However, to the best of our knowledge, the fractal geometry theory is not yet applied to analyse the streaming potential in porous media. In this article, a fractal model for the streaming potential coefficient in porous media is developed based on the fractal theory of porous media and on the streaming potential in a capillary. The proposed model is expressed in terms of the zeta potential at the solid?liquid interface, the minimum and maximum pore/capillary radii, the fractal dimension, and the porosity of porous media. The model is also examined by using another capillary size distribution available in published articles. The results obtained from the model using two different capillary size distributions are in good agreement with each other. The model predictions are then compared with experimental data in the literature and those based on the modified Helmholtz–Smoluchowski equation. It is shown that the predictions from the proposed fractal model are in good agreement with experimental data. In addition, the proposed model is able to reproduce the same result as the Helmholtz–Smoluchowski equation, particularly for high fluid conductivity or large grain diameters. Other factors influencing the streaming potential coefficient in porous media are also analysed. 相似文献
210.
The paper presents a hysteretic damage model for the response simulation of structural components with strength and stiffness deterioration under cyclic loading. The model is based on 1D continuum damage mechanics and relates any 2 work‐conjugate response variables such as force‐displacement, moment‐rotation, or stress‐strain. The strength and stiffness deterioration is described by a continuous damage variable. The formulation uses a criterion based on the hysteretic energy and the maximum or minimum deformation for damage initiation with a cumulative probability distribution function for the damage evolution. A series of structural component response simulations showcase the ability of the model to describe different types of hysteretic behavior. The relation of the model's damage variable to the Park‐Ang damage index is also discussed. Because of its consistent and numerically robust formulation, the model is suitable for the large‐scale seismic response simulation of structural systems with strength and stiffness deterioration. 相似文献