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Your search keyword '"Yuan, X.Z."' showing total 23 results
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23 results on '"Yuan, X.Z."'

8. A two-dimensional water-quality model for a winding and topographically complicated river

Author

Zeng, G.M., Yuan, X.Z., Yin, Y.Y., and Yang, C.P.

Subjects
Hunan, China -- Environmental policy, Stream conservation -- China, Water quality management -- Models, Stream ecology -- Models, Finite element method -- Usage, Environmental issues
Abstract

The article examines a two-dimensional, numerical calculation algorithm method for assessing water quality management at the Xiangjiang River in China's Hunan Province. The approach involves a finite element method and topographical map data of the river's course to project water quality.

Published
2001

14. Effect of solution pH on aging dynamics and surface structural evolution of mZVI particles: H2 production and spectroscopic/microscopic evidence

Author

Tang, F.L., Xin, J., Zheng, X.L., Zheng, T.Y., Yuan, X.Z., Kolditz, Olaf, Tang, F.L., Xin, J., Zheng, X.L., Zheng, T.Y., Yuan, X.Z., and Kolditz, Olaf

Abstract

A microscale zero-valent iron (mZVI)-based in situ reactive zone is a promising technology for contaminated groundwater remediation. Estimation of mZVI aging behavior after its injection into the subsurface is essential for efficiency and longevity assessments. In this study, batch tests were conducted to investigate the effect of initial pH on mZVI aging dynamics, as well as the formation and evolution of aging products over 112 days. Results indicated that mZVI aging accelerated with decreasing initial pH. Corrosion rates of mZVI particles under pH 6.0 and 7.5 were approximately two orders of magnitude higher than those observed at pH 9.0. The morphological, structural, and compositional evolution of mZVI particles in three systems (pH = 6.0, 7.5, and 9.0) were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In acidic and neutral solutions, a thick passivation layer with loosely and unevenly distributed aging precipitates was observed, and Fe3O4 was the final aging precipitate. Nevertheless, in alkaline solutions, minute aging precipitates were detected on the mZVI surface at 112 day. Characterization results suggested that mZVI was oxidized via the Fe0–Fe(OH)2–Fe3O4 route. These findings shed new light on mZVI aging mechanisms, particularly its physicochemical characteristics and the structural evolution of mZVI in field-scale groundwater remediation applications.

Published
2017

16. Co-operative project 'PEFC durability' of the Canadian National Research Council (NRC) and the German Helmholtz Gesellschaft (HGF)

Author

Friedrich, K. Andreas, Wang, Haijiang, Schulze, Mathias, Yuan, X.Z., and Haug, Andrea

Subjects
Degradation, Elektrochemische Energietechnik, PEFC
Abstract

The life-time of polymer electrolyte fuel cells (PEFC) is one of the crucial factors for commercialization in high volume markets. Consequently, the research on degradation processes and phenomena and the improvement of life-time is an important area. A German- Canadian collaboration is funded by the Helmholtz Foundation (Germany) and the National Research Council of Canada. The project is focussed on establishing the relationships between the MEA microstructure and fuel cell performance, identifying the primary causes of the major failure modes and the corresponding degradation mechanisms and degradation rates and providing the fundamental understanding of the influence of the operating conditions on the degradation of the MEA on spatial resolved level. For this purpose at the DLR spatial resolved measurements will be performed with in-situ and ex-situ methods. Current density measurements with a printed circuit board (PCB) as a bipolar plate will be performed in order to investigate the local operating conditions and performance. After operation the fuel cell components will be analyzed with various methods in order to detect and to identify the different degradation processes. The in-situ and ex-situ investigations will be competed by modelling activities.

Published
2009

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