Search

Your search keyword '"Wang, Yuchun"' showing total 64 results
Start Over Author "Wang, Yuchun" Publisher elsevier bv
64 results on '"Wang, Yuchun"'

6. Spatial variation of soil phosphorus in the water level fluctuation zone of the Three Gorges Reservoir: Coupling effects of elevation and artificial restoration

Author

Qin, Dongming, primary, Li, Shanze, additional, Wang, Jingfu, additional, Wang, Dengjun, additional, Liao, Peng, additional, Wang, Yuchun, additional, Zhu, Zhiqiang, additional, Dai, Zhihui, additional, Jin, Zuxue, additional, Hu, Xinping, additional, Qiu, Shuoru, additional, Ma, Yiming, additional, and Chen, Jingan, additional

Published
2023
Full Text
View/download PDF

24. Tracing the sources of nitrate in the rivers and lakes of the southern areas of the Tibetan Plateau using dual nitrate isotopes

Author

Li Yanhui, Aimin Cai, Yong Shui, Bao Yufei, Cong Lv, Pengcheng Du, Hu Mingming, Zhang Panwei, Shanze Li, and Wang Yuchun

Subjects
geography, Environmental Engineering, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Soil organic matter, Aquatic ecosystem, Drainage basin, chemistry.chemical_element, Wetland, 010501 environmental sciences, 01 natural sciences, Pollution, Nitrogen, Manure, chemistry.chemical_compound, chemistry, Nitrate, Environmental chemistry, Environmental Chemistry, Environmental science, Nitrification, Waste Management and Disposal, 0105 earth and related environmental sciences
Abstract

Based on a quantitative analysis of nitrate concentrations, the nitrate sources and temporal variability of the rivers, lakes, and wetlands of Tibet were assessed for the first time using dual isotope technology. Water samples were collected once in July 2017 for analysis of nitrate concentration and isotopic composition. The overall values of δ15N-NO3− and δ18O-NO3− ranged from +1.8‰ to +23.0‰, and from −6.3‰ to +22.2‰ respectively. Duel isotopic composition suggested that nitrification of soil organic nitrogen was the main source of nitrate in the Yalu Tsangpo River. Furthermore, anthropogenic nitrogen inputs become more important in downstream than upstream because of intensive agricultural activities and urban input. In the rivers of the Ngari District, nitrate is mainly derived from desert deposits, manure and sewage, and chemical fertilisers. Different rivers show different characteristics of nitrate sources depending on the location, topography, landform, and climate of the river basins. Animal manure, nitrification of soil organic matter, and desert deposits are mainly responsible for the shifting of nitrate isotopic signatures in lakes, which are minimally affected by human activities. In wetlands, biological nitrification and denitrification could be the main processes of nitrogen migration and transformation. These results provide useful information in revealing the fate of nitrate in different aquatic ecosystems and different areas of Tibet.

Published
2019

32. Effect of NH 4 + exchange on CuY catalyst for oxidative carbonylation of methanol

Author

Huayan Zheng, Wang Yuchun, and Zhong Li

Subjects
Thermal desorption spectroscopy, Inorganic chemistry, 02 engineering and technology, General Medicine, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Catalysis, chemistry.chemical_compound, chemistry, Anhydrous, Methanol, Temperature-programmed reduction, Dimethyl carbonate, 0210 nano-technology, Selectivity, Zeolite
Abstract

NaY and ion exchanged NaNH 4 Y zeolite with NH 4 NO 3 were used as the support to prepare CuY catalysts by a high temperature anhydrous interaction between the support and copper (ⅠⅠ) acetylacetonate Cu(acac) 2 . The catalysts were used for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) at atmospheric pressure. The textural and acidic properties of NaNH 4 Y zeolite and the CuY catalysts were investigated by X-ray diffraction, scanning electron microscopy, N 2 adsorption-desorption, temperature programmed reduction of H 2 , X-ray photoelectron spectroscopy and temperature programmed desorption of NH 3 . With increasing NH 4 NO 3 concentration, the NH 4 + exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH 4 + exchange degree of NaNH 4 Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH 4 + exchange degree of NaNH 4 Y, the content of surface bound Cu + active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu + content reached its maximum when the NH 4 + exchange degree of NaNH 4 Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/(g·h) space time yield of DMC, 6.9% conversion of methanol, 68.5% selectivity of DMC.

Published
2016

33. Influence of the surface oxygenated groups of activated carbon on preparation of a nano Cu/AC catalyst and heterogeneous catalysis in the oxidative carbonylation of methanol

Author

Guoqiang Zhang, Yubo Ju, Tingjun Fu, Wang Yuchun, Zhong Li, and Huayan Zheng

Subjects
Process Chemistry and Technology, Inorganic chemistry, Heterogeneous catalysis, Catalysis, chemistry.chemical_compound, Adsorption, chemistry, Nitric acid, Chemisorption, Specific surface area, Methanol, Dimethyl carbonate, General Environmental Science
Abstract

Coconut shell activated carbon (AC) is treated by nitric acid and used as a support to prepare nano-copper heterogeneous catalysts for oxidative carbonylation of methanol to dimethyl carbonate. AC supports and their corresponding catalysts are characterized intensively by BET, XPS, XRD, TEM, N 2 O chemisorption, CO adsorption, and TPR. The results show that the concentrations of nitric acid do not significantly changes the specific surface area and textural property of AC. But the oxygenated groups which result in acidic properties, such as lactone, carboxyl and phenol groups, are formed on AC surface during the acid treatment process and increase with the increasing concentration of nitric acid. The increased surface oxygenated groups not only influence the dispersion but also the valence distributions of copper species. When copper supported on the AC treated by 4 M HNO 3 , the Cu/AC catalyst shows the optimal catalytic performance for oxidative carbonylation of methanol to dimethyl carbonate, which might be ascribed to the highest dispersion of Cu + and Cu 0 species. The average conversion of methanol and space-time yield of DMC (STY DMC ) within 10 h for the catalyst have reached 9.2% and 229 mg g −1 h −1 , respectively. The deactivation of Cu/AC catalysts is attributed to the agglomeration of copper species. Besides, the STY DMC of per S(Cu + + Cu 0 ) for the acid treated Cu/AC catalysts is very similar and less than that of the original Cu/AC catalyst which may be induced by the AC surface oxygenated groups itself but not the ratio of Cu + /Cu 0 .

Published
2015

46. Magnetostratigraphy of the Baoji loess-paleosol section in the north-central China Loess Plateau

Author

Wang Yuchun, Ding Zhongli, Nat Rutter, and Mike Evans

Subjects
Paleontology, Section (archaeology), North central, Loess, Loess plateau, Quaternary, Paleosol, Geology, Magnetostratigraphy, Earth-Surface Processes
Abstract

The Baoji Section is judged to be the most complete, accessible Quaternary loess-paleosol section in the north-central China Loess Plateau; it is located 5 km north of the city of Baoji. It contains 37 paleosols and was recently named the type-pedostratigraphic section. The pedostratigraphic units (geosols) of the Baoji Section can be correlated throughout the Loess Plateau by a combination of magnetostratigraphy, and character, position and association of pedostratigraphic units. Magnetic properties were determined from 483 samples taken from 159 m of loess that overlies the Red Clay formation. All major reversals that occurred in the last 2.5 Ma were recorded. The Brunhes/Matuyama boundary occurs at a depth of 58.5 m within loess unit L8, the Jaramillo Subchron between 72.0 m in loess unit L10 and 76.4 m in paleosol S11, the Olduvai Subchron between 125.5 m in loess unit L25 and 131.5 m in loess unit L27, and the Gauss/Matuyama boundary at 157.8 m within loess unit L33, just above the contact with the Red Clay formation. This is the only known site where all major magnetic reversals are clearly defined in distinct field identifiable loess-soil units in one section. The magnetostratigraphy of the Baoji Section is thus recommended as the type section for the Loess Plateau.

Published
1990

50. A novel I293MP mutation within BCR-ABL kinase domain in a Ph-positive acute lymphoblastic leukemia patient presenting resistant to imatinib but sensitive to nilotinib

Author

Kuang, Pu, primary, Liu, Ting, additional, Huang, Qi, additional, Ye, Yuanxin, additional, Xiang, Bing, additional, Huang, Jie, additional, Diwu, Lei, additional, Wang, Yuchun, additional, Meng, Wentong, additional, Dong, Tian, additional, Yang, Shengyong, additional, and Lu, Xiaojun, additional

Published
2012
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results