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Preparation and antimicrobial assay of ceramic brackets coated with TiO₂ thin films
Shuai Cao,Ye Wang,Lin Cao,Yu Wang,Bingpeng Lin,Wei Lan,Baocheng Cao 대한치과교정학회 2016 대한치과교정학회지 Vol.46 No.3
Objective: Different methods have been utilized to prevent enamel demineralization and other complications during orthodontic treatment. However, none of these methods can offer long-lasting and effective prevention of orthodontic complications or interventions after complications occur. Considering the photocatalytic effect of TiO₂ on organic compounds, we hoped to synthesize a novel bracket with a TiO₂ thin film to develop a photocatalytic antimicrobial effect. Methods: The sol-gel dip coating method was used to prepare TiO₂ thin films on ceramic bracket surfaces. Twenty groups of samples were composed according to the experimental parameters. Crystalline structure and surface morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively; film thickness was examined with a surface ellipsometer. The photocatalytic properties under ultraviolet (UV) light irradiation were analyzed by evaluating the degradation ratio of methylene blue (MB) at a certain time. Antibacterial activities of selected thin films were also tested against Lactobacillus acidophilus and Candida albicans . Results: Films with 5 coating layers annealed at 700°C showed the greatest photocatalytic activity in terms of MB decomposition under UV light irradiation. TiO₂ thin films with 5 coating layers annealed at 700°C exhibited the greatest antimicrobial activity under UV-A light irradiation. Conclusions: These results provide promising guidance in prevention of demineralization by increasing antimicrobial activities of film coated brackets.
Zhi Cao,Yunkai Huang,Baocheng Guo,Jianning Dong,Fei Peng 한국자기학회 2020 Journal of Magnetics Vol.25 No.2
This paper applies two different analytical methods, i.e., the perturbation method and superposition method, to calculate the magnetic flux density distribution and the magnetic force of the active magnetic bearing (AMB) with the rotor eccentricity. These two methods are thoroughly analyzed, compared and validated by the finite element model (FEM). The perturbation method is theoretically complex while the superposition method is intuitive. The valid range of the superposition method is larger than the perturbation method. However, the superposition method requires longer computation time. The main contribution of this paper is assessing the effectiveness of two analytical methods for predicting the AMB performance with the rotor eccentricity and giving a comprehensive guideline for engineers to choose the proper analytical method to design AMB.