• Title/Summary/Keyword: Pendulum 장치

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MAXILLARY MOLAR DISTALIZATION WITH A PENDULUM APPLIANCE (Pendulum 장치를 이용한 상악 대구치의 원심이동 증례)

  • Lee, H.J.;Kim, Y.J.;Kim, J.W.;Jang, K.T.;Lee, S.H.;Kim, C.C.;Hahn, S.H.
    • Journal of the korean academy of Pediatric Dentistry
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    • v.35 no.3
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    • pp.523-531
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    • 2008
  • Maxillary molar distalization is a treatment approach for patients with Class II malocclusions who do not require extractions and mesial movements of mandibular molars. The pendulum appliance is effective for distalization of the maxillary molars and independent of patient cooperation. This appliance can stabilize the maxillary premolars and use the palatal rugae area as an additional anchorage. However, caution is needed to control collateral effects, including increase of lower facial height, incisor protrusion and damage to the rugae area. This article reports the cases in which maxillary molar distalization achieved by pendulum appliance resolves the space problems and corrects the molar relationships.

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Experimental Study of Friction Pendulum System to Improve the Seismic Capacity of Transformer (변압기의 내진성능 향상을 위한 마찰진자 면진장치의 시험 연구)

  • Jang, Jung-Bum;Kim, Jeong-Ki;Hwang, Kyeong-Min;Ham, Kyung-Won;Park, Jin-Wan;Lee, Chan-Wook
    • Journal of the Earthquake Engineering Society of Korea
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    • v.12 no.2
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    • pp.1-8
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    • 2008
  • Friction pendulum system is developed to prevent the damage of transformer, which is the most important among the electric power facilities, due to the earthquake and its seismic capacity is verified through the shaking table test. The applicability of friction pendulum system is confirmed as test results of compressive capacity test and friction test. Especially, as a result of shaking table test with a large scale transformer model, friction pendulum system gives to the reduction of maximum response acceleration by 30% at anchorage of transformer and 59% at the top of porcelain bushing comparing with the existing anchorage type. In addition to the reduction of maximum response acceleration, natural frequency of transformer is shifted to long period due to the friction pendulum system. In case that friction pendulum system is applied to the transformer, the damage of transformer can be prevented effectively under the earthquake.

Performance Analysis of Friction Pendulum System using PVDF/MgO Friction Material (PVDF/MgO 마찰재를 이용한 마찰면진장치의 성능 분석)

  • Kim, Sung-Jo;Kim, Ji-Su;Han, Tong-Seok
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.34 no.4
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    • pp.213-219
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    • 2021
  • Polytetrafluoroethylene (PTFE) is a commercialized friction material in friction pendulum systems used for earthquake hazard mitigation in structures, and it has excellent chemical resistance and frictional performance. However, PTFE has a relatively low wear resistance for the friction pendulum systems in service. As an alternative to PTFE, a cost-effective frictional material, polyvinylidene fluoride (PVDF) strengthened by magnesium oxide (MgO), with enhanced wear resistance performance is proposed in this study. The frictional performance of the developed PVDF/MgO was evaluated through experiments and compared with that of PTFE. Accordingly, a friction pendulum system was designed using the measured friction coefficient. The performance of this friction pendulum system was evaluated via nonlinear time history analyses of bridges. Subsequently, the plausibility of using PVDF/MgO as an alternative to PTFE as a friction material for friction pendulum systems was discussed.

MAXILLARY MOLAR DISTALIZATION WITH THE BONE-SUPPORTED PENDULUM (Bone-supported pendulum을 이용한 상악대구치 원심이동)

  • Jang, Yong-Gul;Park, Ho-Won;Lee, Ju-Hyun;Seo, Hyun-Woo
    • Journal of the korean academy of Pediatric Dentistry
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    • v.36 no.3
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    • pp.464-474
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    • 2009
  • To distalize the maxillary molars, the traditional techniques such as extra-oral traction, Wilson distalizing arches, removable spring appliances and Schwarz plate-type appliances have been used. But, these need considerable patient cooperation. For minimal patient compliance, many practitioners use the pendulum appliances. Several clinical studies demonstrated pendulum is effective molar distalization appliance in the growing patient(using the premolars and the palate as anchorage). But unfortunately, maxillary anterior teeth also shift mesially as the molar moves distally. As a result anchorage loss is occurred. To overcome these disadvantages, we used bone-supported pendulum, combined the conventional pendulum with Skeletal Anchorage System(SAS). The miniscrew was implanted in the anterior paramedian region of the median palatal suture, which has comparatively sufficient bone thickness and is low risk to damage on the dental follicles. We report three cases, using bone-supported pendulum for the maxillary molar distalization in children. After treatment, we find out anchorage stability, minimal unfavorable anterior tooth movement and sufficient molar distalization.

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Analysis of effects from usage of skeletal anchorage-assisted Pendulum appliance on vertical component of craniofacial structure (골격고정원을 이용한 Pendulum 장치가 두개 안면의 수직적 요소에 미치는 효과 분석)

  • Lee, Jin-Woo
    • Journal of Dental Rehabilitation and Applied Science
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    • v.34 no.1
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    • pp.10-16
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    • 2018
  • Purpose: The purpose of this study was to evaluate distalizing effects from the Pendulum appliance on vertical component of craniofacial structures. Materials and Methods: 20 Patients who visited for orthodontic treatments are assigned to two groups. Group I, SN-MP > 37 degrees are showing hyperdivergent pattern. Group II, 29 < SN-MP < 37 degrees are showing mesocephalic pattern. Each group are consisted of 10 people. Results and Conclusions: Differences between skeletal classifications result in significant differences at labioversion of lower incisors and distalized amount, which is larger at Group I (P <.05). Group II has only shown significant distalized molars (P < .05). Labioversion of lower incisors has not shown significant change. Skeletal anchorage-assisted Pendulum appliance doesn't deteriorate vertical component nor significantly improve.

Performance Analysis of Wave Energy Converter Using a Submerged Pendulum Plate (몰수형 진자판을 이용한 파력발전장치의 성능해석)

  • Cho, Il Hyoung
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.20 no.2
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    • pp.91-99
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    • 2017
  • The parametric study was performed for performance enhancement of wave energy converter(WEC) using a submerged pendulum plate. The wave exciting moment and hydrodynamic moment were obtained by means of eigenfunction expansion method based on the linear potential theory, and then the roll response of a pendulum plate and time averaged extracted power were investigated. The optimal PTO damping coefficient was suggested to give optimal extracted power. The peak value of optimal extracted power occurs at the resonant frequency. The resonant peak and it's width increase, as the height and thickness of a pendulum plate increase. The mooring line installed at the end of the pendulum plate is effective for extracting wave energy because it can not only induce the resonance with the waves of the installation site but also increase the restoring moment in case of PTO-on. The WEC using a rolling pendulum plate suitable for the shallow water acts as breakwater as well as energy extraction device.

Dynamic Analysis of a Pendulum Automatic Dynamic Balancer (펜들럼 자동 평형 장치의 동특성 해석)

  • Lee, Jin-Woo;Sohn, Jin-Seung;Cho, Eun-Hyoung;Park, No-Cheol;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.994-999
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    • 2002
  • The Pendulum Automatic Dynamic Balancer is a device to reduce the unbalanced mass of rotors. For the analysis of dynamic stability and behavior, the nonlinear equations of motion for a system including the Pendulum Balancer are derived with respect to polar coordinate by Lagrange's equations. And the perturbation method is applied to find the equilibrium positions and to obtain the linear variation equations. Based on the linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue problem. Furthermore, in order to confirm the stability, the time responses for the system are computed from the nonlinear equations of motion.

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Dynamic Analysis of a Pendulum Automatic Dynamic Balancer (펜들럼 자동 평형 장치의 동특성 해석)

  • Lee, Jin-Woo;Sohn, Jin-Seung;Joseph Cho;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.396.2-396
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    • 2002
  • Dynamic stability and behavior are analyzed fur Pendulum Automatic Dynamic Balancer which is a device to reduce an unbalanced mass of rotors. The nonlinear equations of motion for a system including a Pendulum Balancer are derived with respect to polar coordinate by Lagrange's equations. The perturbation method is applied to find the equilibrium positions and to obtain the linear variation equations. Based on linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue problem. (omitted)

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A Study on the Application of Friction Pendulum System in Main Control Room of Nuclear Power Plant (마찰진자를 이용한 면진장치의 원전 주 제어실 적용에 관한 연구)

  • Kim, Woo Bum;Lee, Kyung Jin
    • Journal of Korean Society of Steel Construction
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    • v.17 no.4 s.77
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    • pp.407-417
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    • 2005
  • An experimental and analytical study was performed to apply the friction pendulum system (FPS) to the main control room of a nuclear power plant. A friction pendulum bearing was fabricated, and the dynamic response of the bearing was evaluated. A partial model of a main control room attached to the FPS was tested on the shake table. The model consisted of a cabinet, a $3m\times3m$ access floor, and four friction pendulum bearings. The artificial time history based on the floor response spectrum of the main control room was used as the earthquake input signal in the test. Comparisons between the analytical study and the experimental study were conducted to verify the results and to extend the experimental study to the range of parameters that could not be experimentally studied.