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Your search keyword '"Zhou, Yunong"' showing total 23 results
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23 results on '"Zhou, Yunong"'

1. Stochastic process model for interfacial gap of purely normal elastic rough surface contact

Author

Xu, Yang, Joe, Junki, Li, Xiaobao, and Zhou, Yunong

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

In purely normal elastic rough surface contact problems, Persson's theory of contact shows that the evolution of the probability density function (PDF) of contact pressure with the magnification is governed by a diffusion equation. However, there is no partial differential equation describing the evolution of the PDF of the interfacial gap. In this study, we derive a convection--diffusion equation in terms of the PDF of the interfacial gap based on stochastic process theory, as well as the initial and boundary conditions. A finite difference method is developed to numerically solve the partial differential equation. The predicted PDF of the interfacial gap agrees well with that by Green's Function Molecular Dynamics (GFMD) and other variants of Persson's theory of contact at high load ranges. At low load ranges, the obvious deviation between the present work and GFMD is attributed to the overestimated mean interfacial gap and oversimplified magnification-dependent diffusion coefficient used in the present model. As one of its direct application, we show that the present work can effectively solve the adhesive contact problem under the DMT limit. The current study provides an alternative methodology for determining the PDF of the interfacial gap and a unified framework for solving the complementary problem of random contact pressure and random interfacial gap based on stochastic process theory.

Published
2024
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17. Recyclable MoO3 nanobelts for photocatalytic degradation of Rhodamine B by near infrared irradiation.

Author

Hu, Chao, Xu, Minjie, Zhang, Jun, Zhou, Yunong, Hu, Bonian, and Yu, Gang

Subjects
RECYCLABLE material, NANOBELTS, PHOTOCATALYSIS, RHODAMINE B, NEAR infrared radiation
Abstract

Molybdenum trioxide (MoO3) represented an excellent photocatalytic performance with many applications, including degradation of organic contaminants and splitting of water. This paper presented a new route to synthesize MoO3 nanobelts with high aspect ratios and crystallinity by a hydrothermal technique. This work showed that the as‐synthesized nanobelts exhibited strong photocatalytic activity to degrade an organic dye of Rhodamine B (RhB) in aqueous solution under the exposure of the light source in the near infrared wavelength range, significantly improving the photocatalytic activity of the nanobelts. The results also showed that for a small concentration of RhB at 7.5 mg/L a complete photodegradation (for a given MoO3 nanobelts quantity of 0.1 g) can be reached after exposing for 60 min. For all concentrations of the RhB solution, the photodegradation exhibited an exponential dependence on the exposure time followed by a sudden shutdown, but no complete photodegradation can be reached. Also, the residual quantity of RhB in solution after the photocatalytic reaction was determined by the initial RhB concentration. The photocatalytic degradation can be interpreted by the pseudo–first‐order equation for the absorption of liquid/solid based on solid capacity; thus, photocatalytic degradation can be attributed to the interaction between the photoexcited electrons in the substrate and the antibonding orbital of the RhB in solution. The sudden shutdown was due to the inability of the photoexcited electrons in the substrate hopping to the antibonding orbital of RhB in the presence of the RhB intermediate products from the degraded RhB. In addition, this work showed that the photocatalytic reaction can be recovered after a thermal treatment of postreacted MoO3 nanobelts, enhancing the utilization efficiency of the catalysis. [ABSTRACT FROM AUTHOR]

Published
2019
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18. The Routledge Intermediate Chinese Reader

Author

Helen Shen, Zhou Yunong, Xiaoyuan Zhao, Helen Shen, Zhou Yunong, and Xiaoyuan Zhao

Subjects
Chinese language--Readers, Chinese language--English.--Textbooks for fore
Abstract

The Routledge Intermediate Chinese Reader is a comprehensive reader designed to provide varied, stimulating and up-to-date reading material for learners of Chinese at the intermediate level. The Chinese Reader provides a bridge between basic literacy skills and the ability to read full novels and newspapers in Chinese. It consists of forty readings, graded on the basis of complexity of vocabulary, grammar and syntax. These readings present a range of different text types representative of modern Chinese popular writing which will inspire students to continue reading independently in Chinese. It is ideal for learners who already possess a knowledge of essential grammar and vocabulary and who wish to expand their knowledge of the language through contextualized reading material. Key features include: Extracts from newspaper and internet articles Vocabulary annotation next to the reading paragraphs for quick reference Short grammar explanations of any complicated structures Comprehension and discussion questions Notes on culture and idioms Lesson structure maps to aid comprehension A companion website containing lesson audio and electronic vocabulary flash cards Full glossary at the back and answer key for reading questions Suitable for both class use and independent study, The Routledge Intermediate Chinese Reader is an essential tool for facilitating vocabulary learning and increasing reading proficiency.

Published
2013

22. Modelling contact mechanics with improved Green's function molecular dynamics

Author

Zhou, Yunong

Abstract

Green’s function molecular dynamics (GFMD) is frequently used to solve linear boundary-value problems using molecular-dynamics techniques. In this thesis, we first show that the convergence rate of GFMD can be substantially optimized. Improvements consist in the implementation of the so-called “fast inertial relaxation engine” algorithm as well as in porting the solution of the equations of motion into a Fourier representation and a shrewd assignment of inertia. GFMD was furthermore generalized to the simulation of finite-temperatures contact mechanics through the implementation of a Langevin thermostat. An analytical expression was derived for the potential of mean force, which implicitly describes the interaction between a hard wall and a thermally fluctuating elastomer. GFMD confirmed the correctness of the derived expression. A Hertzian contact was simulated as additional benchmark. Although the thermally induced shift in the displacement can be substantial, it turns out to be essentially independent of the normal load. A final application consisted in the test of the frequently made hypothesis that contact area and reduced pressure are linearly related for randomly rough surfaces. The relation was found to be particularly reliable if the pressure is undimensionalized with the root-mean-square height gradient.

Published
2020

23. Long-Range Electrostatic Adhesive Contact Between an Elastic Half-Space and a Rigid Indenter With Power-Law Profile

Author

Zhou, Yunong

Abstract

In this study, the electrostatic adhesive contact between a smooth indenter with a power-law geometry and an elastic half-space is studied using both a theoretical and numerical approach. Both the indenter and substrate are coated with an electrically insulating layer. The Maxwell stress and hard-wall constraint are applied to describe the interaction between the indenter and elastic counter face. By assuming electrostatic adhesion as a long-range interaction, we derived a theoretical relation between external load and contact radius. We show that the theoretical and numerical results are plausible when the Tabor parameter is small. However, when the Tabor parameter is large, the numerical results get closer to the Johnson–Kendall–Roberts (JKR) limit. The generalized Tabor parameter, which depends on the applied voltage and indenter shape, has been derived by following the technique of dimensional analysis.

Published
2025
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