• The korean journal of orthodontics
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• v.46 no.2
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• pp.73-80
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• 2016

Objective: The purpose of this study was to investigate the static (SFF) and kinetic frictional forces (KFF) in sliding mechanics of hybrid bracket systems that involve placing a conventional bracket (CB) or active self-ligating bracket (ASLB) on the maxillary anterior teeth (MXAT) and a passive SLB (PSLB) on the maxillary posterior teeth (MXPT). Methods: The samples consisted of two thoroughbred types (group 1, anterior-CB + posterior-CB; group 2, anterior-ASLB + posterior-ASLB) and four hybrid types (group 3, anterior-CB + posterior-PSLB-type 1; group 4, anterior-CB + posterior-PSLB-type 2; group 5, anterior-ASLB + posterior-PSLB-type 1; group 6, anterior-ASLB + posterior-PSLB-type 2) (n = 13 per group). After maxillary dentition alignment and maxillary first premolars removal in the stereolithographically-made typodont system, a $0.019{\times}0.025$-inch stainless steel wire was drawn through the right quadrant of the maxillary arch at 0.5 mm/min for 5 min. The SFF and KFF were measured with a mechanical testing machine and statistical analyses were performed. Results: Four different categories of SFF and KFF were observed among all groups (all p < 0.001). Group 1 demonstrated the highest SFF and KFF; groups 4 and 3 were second and third highest, respectively. The fourth category included groups 2, 5, and 6. Placing PSLBs on the MXPT resulted in significant SFF and KFF reductions in cases with CBs on the MXAT, but not in cases with ASLBs on the MXAT. Conclusions: These data might aid in the development of a hybrid bracket system that enables low-friction sliding of an archwire through the MXPT.

• Journal of architectural history
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• v.21 no.2
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• pp.7-20
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• 2012

As the corner of wooden pagoda forms the roof by closely bordering left and right eaves on the various purlins and angle rafters, it is designed for every face to be recognized as front whose structure system increases load to bear proportionally. The corner of wooden pagoda is inseparable with the corner bracket set as it becomes stable thanks to the corner bracket set structurally and load burden under restrained structure makes the corner bracket set really important. Accordingly, this study could figure out some facts by analyzing corner bracket sets of Palsangjeon of Beobjusa Temple in Korea, Seokgatap of Bulgungsa Temple in China and Ojungtap of Beobryungsa Temple in Japan which were constructed with pure wooden structure. This study demonstrated that corner bracket set played a pivotal role in keeping balance of concentrated load of corner (corner of opening) in each floor that contributed to the stability of wooden pagoda structurally despite multiple duplications of floors and also figured out the outfit of corner bracket set was subject to the floor type and the cross section of Gongpo installed on top of Pyeongju. Wooden pagodas in 3 countries were two floor types of octagon and square, and employed different connection method between upper and lower floors. The difference between floor and duplication method determines the method of corner, but even different methods were sufficient to have entirety in every side by completing dynamic principle of corner bracket set even though old method had to solve the problem of concentrated load and it also confirms that it was essential Gongpo to prevent any deformation of corner.

• The korean journal of orthodontics
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• v.26 no.1 s.54
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• pp.17-32
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• 1996

It is important to understand the operating mechanism and force system of fixed appliance that most effective for individual tooth movement in various orthodontic appliances. The archwire system of fixed appliance is devided into 3 types, which is continuous arch, segmented arch and sectional arch. The last two types have longer interbracket distance and simple force operating points, so it is easy to control force system by operator. But the continuous arch has shorter interbracket distance and various bracket geometry, so it is hard to control and anaylze the force system. The purpose of this study was three dimentional force and moment analysis of continuous arch system by finite element method, which is similar situation to three dimentional elastic beam in structural engineering. Several sample form of various bracket geometry and artificial lower crowding typodont made by author were constructed, analyzed and compared each other. The results were as follows : 1. The force magnitude is linear proportional to the degree of displacement or tilting of the bracket. 2. The force magnitude is inversely non-linear proportional to the interbracket distance. 3. In three dimensional typodont model, while the force can be compared with that of the sample form in the area where adjacent bracket geometry is simple, the force is much more than the expected value in the area where adjacent bracket geometry is complex.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.27-34
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• 2020

This paper examines the seismic performance and structural design of the ceiling bracket-type modular connection. The bracket-type system reduces the cross-sectional area loss of members and combines units using fitting steel plate, and it has been developed to be fit for medium-story and higher-story buildings. In particular, this study conducted the cyclic loading test for the performance of the C-type and L-type brackets, and compared the results. The test results were also compared with the commercial FEA program. In addition, the structural design process for the bracket-type modular connection was presented. The two connections, proposed as a result of the test results, were all found to secure the seismic performance level of the special moment steel frame. In the case of initial stiffness, the L-type bracket connection was found to be great, but in the case of the maximum moment or fully plastic moment, it was different depending on the loading direction.

• The korean journal of orthodontics
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• v.49 no.2
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• pp.73-80
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• 2019

Objective: The purpose of this study was to compare the static (SFF) and kinetic frictional forces (KFF) of a computer-aided design and computer-aided manufacturing lingual bracket (CAD/CAM-LB) with those of conventional LB (Con-LB) and Con-LB with narrow bracket width (Con-LB-NBW) under 3 tooth displacement conditions. Methods: The samples were divided into 9 groups according to combinations of 3 LB types (CAD/CAM-LB [Incognito], Con-LB [7th Generation, 7G], and Con-LB-NBW [STb]) with 3 displacement conditions (no displacement [control], maxillary right lateral incisor with 1-mm palatal displacement [MXLI-PD], and maxillary right canine with 1-mm gingival displacement [MXC-GD]; n = 6/group). While drawing a 0.016-inch copper or super-elastic nickel-titanium archwire with 0.5 mm/min for 5 minutes in a chamber maintained at $36.5^{\circ}C$, SFF and KFF were measured. The Kruskal-Wallis method with Bonferroni correction was performed. Results: The Incognito group demonstrated the highest SFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD, Stb-MXC-GD] < [7G-MXC-GD, 7G-MXLI-PD, 7G-control] < [Incognito-MXLI-PD, Incognito-control, Incognito-MXC-GD]; p < 0.001). However, there were no significant differences in SFF among the 3 displacement conditions within each bracket group. Within each displacement condition, the Incognito group demonstrated the highest KFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD] < Stb-MXC-GD < 7G-MXLI-PD < [7G-control, 7G-MXC-GD] < [7G-MXC-GD, Incognito-MXLI-PD, Incognito-control] < [Incognito-control, Incognito-MXC-GD]; p < 0.001). MXC-GD exhibited higher KFFs than MXLI-PD in the same bracket group. Conclusions: The slot design and ligation method of the CAD/CAM-LB system should be modified to reduce SFF and KFF during the leveling/alignment stage.

• Journal of Welding and Joining
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• v.16 no.6
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• pp.104-112
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• 1998

In the previous study, the countermeasure for welding deformation of bracket tilt is through up through experimental inspection for total process including welding process. For completeness of systematic examination of parts having sensitivity on welding deformation, the comparison and feedback between the result through simulation of welding process and experimental data is needed. In other words, it is necessary to control welding deformation that construct the prediction system for welding deformation through comparison and tuning with experimental data. In the present study, the application of FEA on welding process of bracket tilt with susceptibility to deformation is made and deformation behavior through change of welding sequence is focused on. It is used to improve the exactness of deformation analysis that three dimensional analysis for moving heat source, activated and deactivated bead element, and volume heat flux etc.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.4
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• pp.25-33
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• 2018

In regard to modular systems, new methods, as well as middle and high-story unit design ideas, are currently being studied. These studies need to focus on the enhanced stiffness and seismic performance of these connections, and see that the development of fully restrained moment connections can improve the seismic performance. For this reason, this study evaluates the performance of the connections of the ceiling bracket-typed modular system through repeated loading tests and analyses. In order to compare them with these modular units, new unit specimens with the bracket connection being different from that of the traditional modular unit specimens were designed, and the results of repeated loading tests were analyzed. In the traditional units, the structural performances of both welding connection and bolt connection were evaluated. In regard to the testing results, the initial stiffness of the hysteresis curve was compared with the theoretical initial stiffness, and the features of all specimens were also analyzed with regard to the maximum moment. In addition, the test results were examined with regard to the connection flexural strength of the steel special moment frame specified under the construction criteria KBC2016. The connections, which were proposed in the test results, were found to be fully restrained moment connections for designing strong column-weak beams and meeting the requirements of seismic performance of special moment frames.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.283-289
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• 2015

In this study, the lightweight design of a brake bracket for a composite bogie was studied by considering two brake bracket models with thicknesses of 12t and 9t, respectively. For achieving this goal, finite element analysis and topology optimization were conducted. Firstly, the largest cross-sectional areas of the vertical and horizontal plates of the brake bracket were selected as the design variables. As the constraint, the Z-axis displacement of the brake bracket was increased by 2.5 units from the initial displacement value. The minimum volume fraction of the design regions was chosen as the objective function. The full model comprised a composite bogie frame and brackets attached together. However, to reduce the analysis time, 1D beam elements were used instead of the composite bogie frame by ensuring its equivalence with the full model. The result revealed that the weights of the 12t and 9t models of the brake bracket were reduced to 60 kg and 31 kg, respectively.

• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.47-54
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• 2011

Purpose: To investigate shear bonding strength between dental zirconia ceramics with different surface treatment and metal bracket. Methods: Zirconia ceramics(LAVA, 3M ESPE, USA) were divided to 4 groups according to their surface treatment; no surface treatment(G1), sand blasting(G2), silane coating(G3), and sand blasting+silane coating(G4). Specimens were bonded to metal bracket using resin bond($Transbond^{TM}XT$, 3M Unitek, USA). Shear bond strength was measured using universal test machine(3366 INSTRON. U.S.A) with cross head speed of 1 mm/min. Microstructural investigation for fracture surface was performed after shear test. Results: Shear bonding strengths of single surface treatment groups (G2 and G3) were higher than no treatment group(G1). Combined Treatment Group (G4) showed the highest shear bond strength of 9.15MPa. Microstructural observation shows that higher shear bonding strength was obtained when debonding was occurred at metal bracket/resin interface rather than zirconia ceramic/resin interface. Conclusion: Surface treatment of zirconia is necessary to obtain higher bonding strength. Combined treatment can be more effective when surface the surfaces are kept clean and homogeneous.

• Journal of architectural history
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• v.29 no.1
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• pp.39-49
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• 2020

A dapo type bracket system which consists of chuganpo(柱間包) and chusangpo(柱上包) with a fake-beam adopted a nemok-dori member to cope with oemok-dori member in order to obtain balance between the outer-side and the inner-side of the bracket system. The middle part of the longest rater in the dapo system is supported by three points made by oemok-dori, jusim-dori and nemok-dori members and the area between the rafer supporting points forms a supporting area. The increase of rafter supporting points and supporting area leads to heightening the structural stability and the efficiency of load delivery. In the eave of dapo system the portion where the three supporting points formed by oemok-dori, jusim-dori and nemok-dori members shows as 33% in the early period, 71% in the middle period and 78% in the later period. On the contrary the portion where more than one of the three dori members were omitted shows as 67% in the early period, 29% in the middle period and 22% in the later period. This is the result of the increase of the number and the distance of steps in the dapo bracket system as time goes on. This is because the structural role of three supporting points becomes important as the increase of distance between the dori members leads to the increase of load which burdens on each dori member.