Search

Your search keyword '"Qu, Zhiguo"' showing total 204 results
Start Over Author "Qu, Zhiguo" Search Limiters Full Text
204 results on '"Qu, Zhiguo"'

25. Tuning Water Slip Behavior in Nanochannels using Self-Assembled Monolayers

Author

Huang, Dezhao, Zhang, Teng, Xiong, Guoping, Xu, Linji, Qu, Zhiguo, Lee, Eungkyu, and Luo, Tengfei

Subjects
Physics - Applied Physics, Condensed Matter - Soft Condensed Matter
Abstract

Water slip at solid surfaces is important for a wide range of micro/nano-fluidic applications. While it is known that water slip behavior depends on surface functionalization, how it impacts the molecular level dynamics and mass transport at the interface is still not thoroughly understood. In this paper, we use nonequilibrium molecular dynamics simulations to investigate the slip behavior of water confined between gold surfaces functionalized by self-assembled monolayer (SAM) molecules with different polar functional groups. We observe a positive-to-negative slip transition from hydrophobic to hydrophilic SAM functionalizations, which is found related to the stronger interfacial interaction between water molecules and more hydrophilic SAM molecules. The stronger interaction increases the surface friction and local viscosity, making water slip more difficult. More hydrophilic functionalization also slows down the interfacial water relaxation and leads to more pronounced water trapping inside the SAM layer, which both impede water slip. The results from this work will provide useful insights to the understanding of the water slip at functionalized surfaces and design guidelines for various applications.

Published
2019

35. Numerical Investigation of the Performance of a Proton Exchange Membrane Water Electrolyzer under Various Outlet Manifold Structure Conditions.

Author

Zhang, Guobin and Qu, Zhiguo

Subjects
*OXYGEN in water, *GAS flow, *LIQUEFIED gases, *PROTONS, *OXYGEN
Abstract

The oxygen discharge process significantly affects the electrochemical performance of a proton exchange membrane water electrolyzer (PEMWE), which requires an optimal structure of the flow field implemented in the bipolar plate (BP) component. In this study, we numerically investigated the two-phase (liquid water and oxygen) flow in the PEMWE's channel region with different outlet manifold structures utilizing the volume of fluid (VOF) model. Then, the oxygen volume fraction at the liquid/gas diffusion layer (L/GDL) surface, i.e., the interface of the channel and L/GDL, obtained by the liquid water and oxygen flow model was incorporated into a three-dimensional (3D) PEMWE model, which made it possible to predict the influence of the outlet manifold structure on the multiple transfers inside the whole electrolyzer as well as the electrochemical performance. The results indicate that the existence of oxygen in the flow field significantly decreased the electrolyzer voltage at a fixed operation current density and deteriorated the uniform distribution of the oxygen amount, current density (corresponding to the electrochemical reaction rate) and temperature in the membrane electrode assembly (MEA), indicating that the rapid oxygen removal from the flow field is preferred in the operation of the electrolyzer. Moreover, slight increases in the width of the outlet manifold were helpful in relieving the oxygen accumulation in the anode CL and, hence, improved the electrolyzer performance with more uniform distribution characteristics. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

40. Revealing Charpy Impact Toughness Variations of EH36 Shipbuilding Steel Weld Metals Processed by CaF2-Al2O3-TiO2 Fluxes under High Heat Input Submerged Arc Welding.

Author

Wang, Zhanjun, Gao, Junfeng, Zhong, Ming, Basu, Somnath, Wang, Dongming, Qu, Zhiguo, and Wang, Cong

Subjects
SUBMERGED arc welding, STEEL welding, METALS, SHIPBUILDING, WELDING, ALUMINUM alloys, ALUMINUM foam
Abstract

A series of CaF2-Al2O3-TiO2 welding fluxes with TiO2 content from 20 to 60 wt.% were applied to join EH36 shipbuilding steel under high heat input submerged arc welding. The effect of TiO2 content on Charpy impact energy, inclusion characteristics, microstructure features, and chemical compositions of weld metals were systematically investigated. A maximum Charpy impact energy of 81.67 J was detected for the weld metal treated by the flux with 50 wt.% TiO2. Such unusual behavior was consistent with the initially increased and subsequently decreased changing trend for the faction of acicular ferrite, which is closely related to the formation, number density, and size distribution of significantly populated TiO2-containing inclusions that were largely dictated by the transfer of O and Ti. Current findings may serve as a viable way of tuning weld metal properties enabled by optimized flux designs. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

45. FedSarah: A Novel Low-Latency Federated Learning Algorithm for Consumer-Centric Personalized Recommendation Systems

Author

Qu, Zhiguo, Ding, Jian, Jhaveri, Rutvij H., Djenouri, Youcef, Ning, Xin, and Tiwari, Prayag

Abstract

Data heterogeneity, insufficient scalability, and data privacy protection are the technological challenges of personalized recommendations. This study proposes a new federated learning algorithm (FedSarah) to address low scalability caused by data heterogeneity and uneven computing power in consumer-centric personalized recommendation systems while protecting data privacy of consumers. The algorithm updates the stochastic gradient estimates using a recursive framework on consumer clients. The outer loop calculates the entire gradient for updating global model, and the inner loop calculates the stochastic gradient based on the accumulated stochastic information for updating local models. To increase the stability of convergence, the inner loop modifies intrinsic parameters to change the number of training rounds and the direction of model update on consumer clients. The detailed mathematical analysis and experiments demonstrate that FedSarah has good convergence. In addition, it’s shown that the algorithm can achieve a performance improvement of nearly 5% in terms of accuracy compared to the traditional FedAvg and FedProx algorithms under the condition of heterogeneous data. Furthermore, under the condition of effective privacy protection on consumers’ data, the new algorithm can significantly lessen the impact of data heterogeneity on the real-time service of consumer-centric personalized recommendation systems with low communication latency. The code is available at https://github.com/DashingJ-82/FedSarah.git.

Published
2024
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results