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Dongfeng Li,Bangwen Yin,Yue Lei,Shengdan Liu,Yunlai Deng,Xinming Zhang 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2
By means of the end-quenching technique, we investigated the relationship between quenching rate and hardness as well as exfoliation corrosion rating for Al-2.21 Zn-3.59 Mg-0.45 Cu-0.038 Zr (at%) alloy plate. In order to achieve an exfoliation corrosion rating of P or EA, the quenching rate must be greater than approximately 460 °C/min and 300 °C/min, respectively, and the drop degree in hardness should simultaneously be lower than approximately 2.0% and 3.5%, respectively. The results of microstructural and microchemical examination using a scanning transmission electron microscope indicate that a lower quenching rate leads to a higher content of Zn, Mg, and Cu in the grain-boundary particles and a greater width of precipitate-free zones near grain boundaries; therefore, grain-boundary particles with Zn and Mg contents less than approximately 13.39% and 10.23% (at%), respectively, and precipitate-free zones near grain boundaries with widths less than about 107 nm can contribute to an exfoliation corrosion rating better than EA. The amount of quench-induced η- phase particles, which lead to lower hardness, increases with decreasing quenching rate, and the area fraction of these particles is approximately 2.9% at a quenching rate of 300 °C/min.
Yin, Dongfeng,Chu, Cang,Ding, Xueying,Gao, Jing,Zou, Hao,Gao, Shen The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.1
In order to enhance the gene delivery efficiency and decrease the cytotoxicity of polyplexes, we synthesized Solutol-g-PEI by conjugating polyethyleneimine (PEI) to Solutol (polyoxyethylene (10) stearate), and evaluated its efficiency as a possible nonviral gene carrier candidate. Structural analysis of synthesized polymer was performed by using $^1H$-NMR. Gel retardation assay, particle sizes and zeta potential measurement confirmed that the new gene carrier formed a compact complex with plasmid DNA. The complexes were smaller than 150 nm, which implicated its potential for intracellular delivery. It showed lower cytotoxicity in three different cell lines (Hela, MCF-7, and HepG2) than PEI 25 kDa. pGL3-lus was used as a reporter gene, and the transfection efficiency was in vitro measured in Hela cells. Solutol-g-PEI showed much higher transfection efficiency than unmodified PEI 25 kDa.
Tribo-Design of Coating/Substrate System
DIAO Dongfeng ENGINEERING TRIBOLOGY RESEARCH INSTITUTE KYUNGPOOK 1999 INTERNATIONAL SYMPOSIUM ON HIGH PERFORMANCE OF TRI Vol.1999 No.-
The design of coatings in tribo -system able to perform well in different wear conditions without lubricants requires a combination of adequate hardness and toughness, good adhesion, a low friction coefficient and a low wear rate. Recently introduced hard coating with interlayers or lubricative particles can be a major step towards the achievement of such coatings in practical usage is their high yielding, Failure and spalling tendency. Therefore, the inhibiting factors in using these coatings for tribo-application are our limited knowledge on the critical stress for the plastic deformation or the fracture. In this paper, three kind of coating/substrate systems(coating without interlayer, coating with an interlayer and coating with particles) in tribo-contact condition were introduced from the point of view of finite element analysis. A theoretical design method for coating/substrate system was given in a series of maps in which the positions of yield initiation and the effect of design factors(coating thickness, yield strenght), as well as, contact factors(contact width, friction coefficient) on the yielding behavior of the coating/substrate system will be pointed out.
Decheng Liu,Dongfeng Cao,Haixiao Hu,Yucheng Zhong,Shuxin Li 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.3
A new numerical model combining LaRC failure criterion and extended finite element method (XFEM) is created to describe the failure behavior in fiber-reinforced polymer (FRP) composites. In this model, the onset of intralaminar damages are predicted based on the LaRC failure criterion, and the crack propagation and stiffness degradation are described explicitly by the XFEM. The user subroutine UDMGINI of ABAQUS defines the initial damage criterion and a mixed-mode, energy-based fracture criterion is employed to describe the crack onset and propagation in the enriched region of XFEM. The proposed model is used to investigate the failure behavior of two sets of open-hole laminates under tension. It is demonstrated that the proposed numerical method can predict the experimental data well.