Papers by Author: Ping Yang

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Authors: Wei Min Mao, Leng Chen, Ping Yang, Yong Ning Yu
Abstract: A new model describing the reaction stresses during plastic deformation of metals is proposed in which the reaction stresses among the grains and their accumulation are calculated. The model could overcome the shortages of the Sachs and Taylor deformation model. According to the model, the plastic strain tensor induced by activation of slip systems will produce certain elastic reaction stress in the surrounding matrix, which influences the choice of further activation of slip systems as well as the orientation evolution. The model gives more attention to both of the stress and strain compatibility among the grains. The simulation on the tensile deformation of pure copper indicates that the model could exhibit the main characteristics of the real deformation process.
Authors: An Sha Zhao, Ping Yang, Yong Xiang Leng, H. Sun, Jin Wang, Guo Jiang Wan, Nan Huang
Abstract: Platelet adhesion and activation restrict the clinical applicability of blood-contacting biomaterial because platelet-biomaterial interaction can result in the formation of a haemostatic plug or thrombus. In this study we used LDH (lactate dehydrogenase) tests to evaluate the adsorption behavior of platelets on material surfaces. Enzyme immunoassay (EIA) was applied to evaluate platelet activation using a special monoclonal antibody directly binding to the Pselectin on the activated platelet membrane. The results show compared with the conventional detecting tools of platelet adhesion / activation such as optical microscopy. LDH (lactate dehydrogenase) testing and EIA (enzyme immunoassay) are surface-sensitive methods for the investigation of various aspects of platelet adsorption and activation on different biomaterials.
Authors: Leng Chen, Wei Min Mao, Fan Xiu Lu, Ping Yang
Abstract: The residual stress and crystallographic texture of diamond films were investigated in the present work. The diamond films were synthesized on (100) silicon wafer by Microwave Plasma Chemical Vapor deposition (MPCVD). Then the residual stresses of the films were measured by X-ray diffractometer equipped with the two-dimensional detector. The residual stresses can be classified into two categories, i.e., the intrinsic stresses and the thermal stresses. It was shown that the thermal stresses were compressive in the temperature range studied and the intrinsic stresses were tensile. The crystallographic textures of the films were measured by X-ray diffractometer with the method of pole figure and orientation distribution function (ODF). The experimental results suggest that the crystallographic textures of the films depend upon the deposition temperature and methane flow rates, and the components and intensity of crystallographic textures have effect on the residual stresses in diamond films to a certain extent.
Authors: Nan Huang, Ping Yang, Yong Xiang Leng, Jin Wang, Jun Ying Chen, H. Sun, Guo Jiang Wan, An Sha Zhao, Pei Dao Ding
Abstract: In the present paper, the scientific basis, technique approaches, the present status and the development trends of surface modification for blood contacting materials are discussed briefly. The work in authors’ Lab. is also presented.
Authors: Ping Yang, Wang Yue Yang, Zu Qing Sun
Abstract: Texture evolutions are determined by XRD and EBSD techniques during ferrite refinement through deformation-enhanced ferrite transformation (DEFT) and dynamic recrystallization (DREX). Evidences of transformation texture, deformation texture and recrystallization texture during DEFT are provided and compared with the texture during DREX. The influence of pass-interval during DEFT on texture is illustrated. Results are discussed in terms of the influences of ferrite grain size and deforming temperature.
Authors: Ping Yang, Zude Zhao, Li Meng, Xueping Ren, Shao Dong Huang
Abstract: Depending on its initial texture and external strain condition differences in deformation mechanisms, kinetics of dynamic recrystallization or even superplastic behaviors may emerge in magnesium alloys leading to distinct microstructure and texture evolutions. When imposed strain condition is altered, e.g. from plane strain compression to rolling or uniaxial compression, the deformation anisotropy will decrease in different rates and basal slip and {1012} twinning will dominate deformation process. This work examines this strain sensibility by inspecting the σ-ε curves, microstructures and textures in a quasi plane-strain compressed ZK60 alloy and compares the results with those of AZ31 alloy compressed in channel die.
Authors: Yong Xiang Leng, Ping Yang, Ji Yong Chen, Lan Xin Xu, An Sha Zhao, H. Sun, Jin Wang, Nan Huang
Abstract: Surface modification has shown great potential for improving the hemocompatibility of biomedical materials and devices. In this paper we describe our work on improving blood compatibility with Ti–O thin films prepared by unbalanced DC magnetron sputtering. The structure and surface chemical and physical properties of the films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), SEM, sheet resistance tests, and Hall effect measurements. The sheet resistance of the titanium oxide samples increased with oxygen pressure and shows a sharp increase when only TiO2 exists in the films. The band gap, carrier density and sheet resistance of the titanium oxide films synthesized at different oxygen pressure are different. These properties affect blood compatibility significantly. We suggest that the semiconducting nature of n-type Ti–O films with bandgap 3.0~3.2 eV, sheet resistance greater than 1 Ω.cm and carrier density of about 1.17 x 1016cm-2 leads to their excellent blood compatibility.
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