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Fang M.,Nanjing University | Ju W.,Nanjing University | Liu X.,China University of GeosciencesBeijing | Yu Z.,Hangzhou Normal University | And 2 more authors.
Terrestrial, Atmospheric and Oceanic Sciences | Year: 2015

This study examines the spatio-temporal variations in the sea-surface chlorophyll-a (Chl-a) concentration and their associated underlying driving forces in the northern South China Sea (SCS) from 2004 - 2010. A stratified analysis method and the Moderate Resolution Imaging Spectroradiometer (MODIS) Chl-a product, the National Centers for Environmental Prediction (NCEP) reanalysis data, with maps of monsoon winds and current systems were used in this work. Validation indicated that the MODIS-derived Chl-a is in good agreement with in-situ measurements (R2 = 0.815), accurate enough for analyzing the temporal-spatial variations of Chl-a in the northern SCS. The results show that the spatial heterogeneity of the Chl-a concentration was lowest in winter and increased in spring. The seasonal Chl-a concentration dynamics varied spatially and depended predominantly on the distance from the coastline. The most important factors that affect the Chl-a concentration spatial variability were identified as the monsoon, surface current and sea surface temperature (SST). Source


Wang H.Z.,CAS Institute of Geology and Geophysics | Wang H.Z.,University of Chinese Academy of Sciences | Zhang H.F.,China University of GeosciencesBeijing | Zhai M.G.,CAS Institute of Geology and Geophysics
Acta Petrologica Sinica | Year: 2015

Metamorphism history of high-grade metamorphic rocks is an important clue to shed light on crust tectono-thermal events. However, intra-crystalline diffusion and recrystallization induced element re-distribution between rock-forming minerals, which have important influence on inversion of peak metamorphic history. On the contrary, intra-crystalline diffusion rates of trace elements are relatively slower than those of the major elements. Therefore, trace elements distribution and partition patterns in rock-forming minerals might be useful tools to shed light on metamorphic history of mafic high-pressure granulites. Major and trace elements of major rock-forming minerals in mafic high-pressure granulite are analyzed by in-situ LA-ICP-MS measurement to learn about trace element redistribution patterns between minerals and their indication of metamorphism. Our results show major elements (Mg, Fe, Ca) in peak stage minerals including garnet, clinopyroxene and plagioclase are homogenized by diffusion and recrystallization distribution, so P-T condition in peak stage can't get good inversion through minerals thermobarometry, but rare earth elements and trace elements distributed in garnet and clinopyroxene as bell shape to infer peak history recorded by trace elements and REE. Compiling major element thermobarometry and trace element thermometer results, we estimate P-T conditions of the peak and retrograde metamorphism of > 828°C and 1.27GPa, 810 ∼ 840°C and 0.6 ∼ 1.0GPa, respectively. Deduced amphibolite facies metamorphism took place after retrograde medium pressure granulite metamorphism. Integreting with previous data, we suggest that our mafic granulite experienced an ITD metamorphic history. Source


Wang G.,Petrochina | Cheng R.,Jilin University | Wang P.,Jilin University | Gao Y.,Jilin University | And 3 more authors.
Geoscience Frontiers | Year: 2015

The Sifangtai and Mingshui formations were continuously cored in the SK-1n borehole (China Cretaceous Continental Scientific Drilling-SongKe1-the north borehole). The core is 767.96 m long, and the recovery is 94.7%. The ages of the formations range from middle Campanian to Danian. The sequence and process of lithology-lithofacies and cyclic stratigraphy were described in detail. Eight litho-types compose the Sifangtai Formation, and 15 litho-types compose the Mingshui Formation. Deposition was predominantly in meandering river and lacustrine environments, including 10 microfacies in the Sifangtai Formation and 15 microfacies in the Mingshui Formation. The complete sequence is composed of 535 m-scale cycles (sixth-order cycle), 152 fifth-order cycles, 42 fourth-order cycles and five third-order cycles. The centimeter-scale description of the section revealed some previously unknown horizons such as a special type of mudstone, marl, volcanic ash and favorable sand reservoirs in the formations. The new-found evidence is very important for the interpretation of the evolution of the basin, conditions such as lake oxic events, the K/Pg boundary, tectonism in the late sag basin stage, and the reservoir-cap rock assemblages in the shallow stratigraphy. © 2015 China University of Geosciences (Beijing) and Peking University. Source


Huang S.,University of the Humanities | Huang S.,Key Laboratory of Carrying Capacity Assessment for Resource and Environment | An H.,University of the Humanities | An H.,Key Laboratory of Carrying Capacity Assessment for Resource and Environment | And 5 more authors.
Physica A: Statistical Mechanics and its Applications | Year: 2016

The nonlinear relationships among variables caused by the hidden frequency information complicate the time series analysis. To shed more light on this nonlinear issue, we examine their relationships in joint time-frequency domain with multivariate framework, and the analyses in the time domain and frequency domain serve as comparisons. The daily Brent oil prices, London gold fixing price and Shanghai Composite index from January 1991 to September 2014 are adopted as example. First, they have long-term cointegration relationship in time domain from holistic perspective. Second, the Granger causality tests in different frequency bands are heterogeneous. Finally, the comparison between results from wavelet coherence and multiple wavelet coherence in the joint time-frequency domain indicates that in the high (1-14 days) and medium frequency (14-128 days) bands, the combination of Brent and gold prices has stronger correlation with the stock. In the low frequency band (256-512 days), year 2003 is the structure broken point before which Brent and oil are ideal choice for hedging the risk of the stock market. Thus, this paper offers more details between the Chinese stock market and the commodities markets of crude oil and gold, which suggests that the decisions for different time and frequencies should consider the corresponding benchmark information. © 2015 Elsevier B.V. Source


Dai C.,China University of Petroleum - East China | Wu X.,China University of Petroleum - East China | Li W.,China University of Petroleum - East China | You Q.,China University of GeosciencesBeijing | And 4 more authors.
Soft Matter | Year: 2015

To understand the role of electrostatic interactions and hydrogen bonds in the formation of wormlike micelles with the aid of sodium salicylate, two quaternary ammonium surfactants with the headgroup decorated by one hydroxyethyl group N-cetyl-N-(2-hydroxyethyl)dimethylammonium bromide and two hydroxyethyl groups N-cetyl-N,N-di(2-hydroxyethyl)methylammonium bromide, abbreviated as CHEMAB and CDHAB, respectively, were synthesized in this work. Single crystal X-ray diffraction was used to study the intermolecular interactions of surfactants, and 1H NMR and rheological measurements were employed to investigate the molecular arrangement and morphology of the wormlike micelles. The synergistic interactions of hydrogen bonding and more effective shielding of electrostatic repulsion contribute to the formation and viscoelastic behavior of wormlike micelles. The results also revealed the aggregation behavior of surfactants with hydroxyethyl headgroups in aqueous solutions. © The Royal Society of Chemistry. Source

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