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- 저자 : Guocai Wang (검색결과 3 건)
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Synthesis and Excellent Microwave Absorption Properties of ZnO/Fe3O4/MWCNTs Composites
Lei Wang,Honglong Xing,Zhenfeng Liu,Ziyao Shen,Xiang Sun,Guocai Xu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.12
ZnO nanocrystals were introduced into Fe3O4/MWCNTs composites to improve the impedance matching and electromagnetic (EM) wave attenuation of the system. The as-synthesized ZnO/ Fe3O4/MWCNTs composites were characterized by X-ray diffraction, vibrating sample magnetometer, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy. SEM and TEM images showed that Fe3O4 microspheres 100–200 nm in size connected MWCNTs. Analysis of EM parameters revealed that the impedance matching of the ZnO/Fe3O4/MWCNTs composites was considerably improved after ZnO nanocrystals were introduced. The ZnO/Fe3O4/MWCNTs composites exhibited a highly efficient microwave absorption (MA) capacity within the tested frequency range of 2–18 GHz. The optimal reflection loss of EM waves was -38.2 dB at 6.08 GHz with an absorber thickness of 3.5 mm. The excellent MA properties of the composites could be attributed to the improved impedance matching, interfacial polarization, and combined effects of dielectric and magnetic losses.
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Case Study: Slope Stability Assessment Considering 3D Nonlinear Shear Strength
Kai Liu,Guocai Wang,Peng Yuan,Huijian Zhang 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.1
In this paper, factor of safety (FOS) considering three-dimensional (3D) and nonlinear shear strength of geomaterials is formulated based on the modified spatial mobilized plane (MSMP) model. The MSMP model has the desirable features of considering 3D strength and the nonlinear shear behavior of soils, compared with the widely used Mohr-Coulomb (M-C) model. The MSMP model is developed from the spatial mobilized plane model by relating the internal friction angle to the mean effective stress within the framework of critical state soil mechanics. Based on the developed MSMP model and the geometric relationships in the mobilized effective normal-shear stress plane, the nonlinear 3D FOS is defined as the ratio of mobilized shear strength to shear stress. The developed nonlinear 3D FOS is applied to slope parametric and case studies. The parametric studies show significant differences between the nonlinear 3D FOS by the MSMP model and the traditional linear two-dimensional (2D) FOS by the M-C model. The case study shows that the MSMP model and nonlinear 3D FOS can better capture the developed failure slope zone than the M-C model and linear 2D FOS.
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Zhenfeng Liu,Honglong Xing,Lei Wang,Dexin Tan,Ying Gan,Xiaoli Ji,Guocai Xu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.8
In this study, Zn-doped Fe3O4 nanoparticles were successfully synthesized by a facile solvothermal method in the presence of sodium dodecyl sulfate (SDS). The morphology, magnetic properties and electromagnetic wave absorbing properties of these materials were characterized. Results showed that Zn2+ played a significant role in the formation of Zn-doped Fe3O4. With the protection of SDS, highly dispersed Fe3O4 nanoparticles were obtained. The nanoparticle size decreased after Zn2+ doping, and the dispersity deteriorated with increasing Zn2+ doping concentration. Zndoped Fe3O4 exhibited excellent electromagnetic wave absorbing property, which resulted in magnetic loss and dielectric loss at an appropriate doping concentration. The minimum reflection loss (RL) was approximately -27.2 dB at 16.9 GHz. As the coating layer thickness increased to 4.0 mm, the bandwidth was approximately 5.0 GHz corresponding to RL below -10 dB, which nearly covered the entire S band (2–4 GHz) and C band (4–8 GHz). The peak frequency of RL and the number of peaks matched the quarter-wave thickness criteria. It was believed that the Zndoped Fe3O4 could be a potential electromagnetic wave absorbing material in S and C bands.
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