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      • KCI등재

        Cone-beam computed tomography-guided threedimensional evaluation of treatment effectiveness of the Frog appliance

        Mujia Li,Xiaoxia Su,Yang Li,Xianglin Li,Xinqin Si 대한치과교정학회 2019 대한치과교정학회지 Vol.49 No.3

        Objective: To evaluate the effectiveness of the Frog appliance in three dimensions by using cone-beam computed tomography (CBCT) images. Methods: Forty patients (21 boys and 19 girls), averaged 11.7 years old, with an Angle Class II division 1 malocclusion were included in our study. They had either late mixed dentition or early permanent dentition, and the maxillary second molars had not yet erupted. All patients underwent CBCT before and after the treatment for measuring changes in the maxillary first molars, second premolars, central incisors, and profile. Paired-samples t-test was used to compare the mean difference in each variable before treatment and after the first phase of treatment. Results: The maxillary first molars were effectively distalized by 4.25 mm (p < 0.001) and 3.53 mm (p < 0.05) in the dental crown and root apex, respectively. The tipping increased by 2.25o, but the difference was not significant. Moreover the teeth moved buccally by 0.84 mm (p < 0.05) and 2.87 mm (p < 0.01) in the mesiobuccal and distobuccal cusps, respectively, whereas no significant changes occurred in the root apex. Regarding the anchorage parts, the angle of the maxillary central incisor’s long axis to the sella-nasion plane increased by 2.76o (p < 0.05) and the distance from the upper lip to the esthetic plane decreased by 0.52 mm (p = 0.01). Conclusions: The Frog appliance effectively distalized the maxillary molars with an acceptable degree of tipping, distobuccal rotation, and buccal crown torque, with only slight anchorage loss. Furthermore, CBCT image demonstrated that it is a simple and reliable method for three-dimensional analysis.

      • KCI등재

        Behavior of Steel-Concrete Composite Cantilever Box Beams under Negative Moment

        Xianglin Gu,Tao Chen,Hua Li,Weiping Zhang,Hongliu Wang 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.4

        Four steel-concrete composite cantilever beam specimens were tested to investigate their mechanical behavior under negative moment induced by concentrated loads at the ends of the beams. The failure modes, serviceability and ultimate bearing capacities of the composite beams with full shear connection were studied. The crack initiation and propagation were investigated with consideration of two types of shear connectors. Three kinds of longitudinal reinforcement ratios were also examined. The experimental results indicate that an increase in the reinforcement ratio is beneficial to the bearing capacity of the composite beams to some extent and that the shear stud connector is superior to the steel block connector with regards to the serviceability of the beams. Two numerical models, which were based on a concrete material model and an elasto-plastic material model, were employed to simulate the behavior of steel-concrete composite beams. The numerical calculation results show that the combination of the two models can be used to predict the longitudinal cracking load and ultimate bearing capacity of composite cantilever beams. Based on the experimental and numerical results, it was found that the ultimate bearing capacity of a steel-concrete composite beam under negative moment can be significantly affected by longitudinal cracks in the concrete slabs. An equation to predict the longitudinal cracking load of a composite cantilever beam under negative moment by concentrated load was proposed and found to have good accuracy.

      • KCI등재

        Behavior of Steel-concrete Composite Cantilever Beams with Web Openings under Negative Moment

        Tao Chen,Xianglin Gu,Hua Li 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.1

        The effect of web openings on the mechanical behavior of composite beams under negative moment was studied through monotonically loading tests. Nonlinear finite element method based analysis was also conducted for cantilever composite beams. The test and the finite element analysis results indicated that the initial cracking loads of composite beams with web opening are lower than that without web opening. The first crack initiated from the concrete slab on the top of the opening. The beams with web opening failed due to shear failure of concrete slab upon the opening. It was also found that the load carrying capacity of beam decreases with the increase of the moment-to-shear ratio at the central line of the opening and the mechanical behavior of beam can be improved significantly by applying stiffening steel plates around the opening. To quantify the reduction of load carrying capacity, a method for calculating the load carrying capacity of beams with web openings under negative moment was derived with consideration of the interaction between moment and shear. Good consistency was obtained between the proposed method, the finite element method and the test results.

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        Three-Dimensional Graphene/MnO2 Nanowalls Hybrid for High-Efficiency Electrochemical Supercapacitors

        Chuanyin Xiong,Tiehu Li,Tingkai Zhao,Alei Dang,Xianglin Ji,Hao Li,Mohammad Etesami 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.1

        In this paper, a facile method is designed to fabricate three-dimensional (3D) graphene (GR)/ manganese dioxide (MnO2) nanowall electrode material. The 3D GR/MnO2 hybrid is prepared by a combination of electrochemical deposition (ELD) and electrophoresis deposition (EPD), followed by thermal reduction (TR). Firstly, the 3D graphene oxide (GO)/MnO2 hybrid is obtained by the ELD–EPD method. Secondly, the 3D GR/MnO2 hybrid is obtained through hydrogen reduction at a certain temperature. The as-fabricated hybrid has been characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy. The electrochemical properties have been also measured by cyclic voltammetry. The results showed that the 3D GR/MnO2 nanowalls hybrid has a high specific capacitance of 266.75 Fg -1 and a high energy density of 25.36 Whkg -1. Moreover, a high specific capacitance (240.15 Fg -1) at a high scan rate of 200 mVs -1 (90% capacity retention) has been also obtained. Additionally, the hybrid can serve directly as the electrodes of supercapacitor without adding binder. This work provides a novel road to fabricate a binder-free 3D GR-based hybrid for high performance energy storage devices.

      • An External Parameter Optimize Method for 3D Optical Measurement System

        Heyao Ma,Wantao He,Xianglin Meng,Dan Li 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.5

        A simple and effective external parameter calibration and optimize method based on epipolar geometry for improving the accuracy and stabilization of 3D optical measurement system are present. First, the internal parameters of two cameras are calibrated using the planar calibration method. Then using the parameters as initial value calibrates the external parameter of the 3D optical measurement system in every view. Optimization result is computed through minimizing epipolar line error of the same pair of points in every view. Experimental results show that the measurement precision is high and stable in the measurement volume.

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