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Seismic Performance of Friction Dampers installed at Coupling Beams between Shear Walls
Moon, Byoung-Wook,Min, Kyung-Won 단국대 부설 리모델링연구소 2011 리모델링 연구소 논문집 Vol.9 No.1
Friction dampers using the flexural deformation of shear walls can be installed as coupling beam system between two adjacent walls of shear wall structures. To verify the seismic control performance of proposed friction dampers, numerical nonlinear analysis of shear walls governed by flexural behavior is conducted. Control effectiveness of shear walls connected by beams with the proposed dampers are compared for single shear wall with same flexural rigidity. Average responses of the shear walls with the dampers are found with seven scaled-downed earthquakes based on KBC 2005 design spectrum. Slip load is the most important design parameter. It is designed to be 5, 10, 20, 30, 60, 90% of total vertical shear force at damper location to prevent damper slip in specific stories. Nonlinear time-history analysis is conducted by using SeismoSturct analysis program. Seismic control performance of the dampers is evaluated for base shear, energy dissipation and top-floor displacement. Results show that the dampers are the most effective in reducing the responses when their total slip load is 30% of total vertical shear force.
송전선에 의해 송전철탑에 전달되는 풍하중 저감을 위한 회전형 점탄성감쇠기
문병욱(Moon, Byoung-Wook),민경원(Min, Kyung-Won) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.4
In this study, wind loads transmitted to a transmission tower from transmission lines are mitigated using rotational viscoelastic dampers. First, the wind load characteristics in a transmission tower is investigated considering the effect of the transmission lines through stochastic analysis. The assemblage of the transmission line and insulator are modeled as a double pendulum system connected to the SDOF model of the tower. From the result of the stochastic analysis, the background component of the overturing moment caused by the wind loads acting on the transmission lines are found to have considerable portion in the total overturning moment. Based on this observation result, a strategy Installing rotational viscoelastic damper (VED) between tower arm and transmission line is proposed for the mitigation of the transmission line reactions, which play a role as dynamic loads on a transmission tower. For the purpose of verification, time history analysis is conducted for different wind velocities and VED parameters. The analysis result shows that the rotational VED is effective for the mitigation of the background component rather than the resonance component of the transmission line reactions and achieves the reduction ratio of 50% even for higher wind speed.
지진특성에 따른 MR감쇠기가 설치된 단자유도 구조물의 등가감쇠비
문병욱(Moon, Byoung-Wook),박지훈(Park, Ji-Hun),이성경(Lee, Sung-Kyung),민경원(Min, Kyung-Won) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.1
Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.
Link Voltage Adjustment Converter Employing Load Power Estimator for Notebook Computer Adaptor
Seong-Wook Choi,Byoung-Hee Lee,Keun-Wook Lee,Byoung-Woo Ryu,Gun-Woo Moon 전력전자학회 2008 전력전자학술대회 논문집 Vol.- No.-
A link voltage adjustment converter employing load power estimator for notebook computer adaptor is proposed. It is consisted of the boost converter as a power factor correction stage and the LLC resonant converter as a DC/DC conversion stage with a newly introduced link voltage adjustment method employing load power estimator, which helps to reduce the transformer size and peak of output voltage ripple, maintaining high efficiency over all the load condition. Experimental results with 85W converter are given to verify the validity of the proposed circuit.
Effect of milling on the soft magnetic behavior of nanocrystalline alloy cores
Moon, Byoung-Gi,Sohn, Keun Yong,Park, Won-Wook,Lee, Taek-Dong Elsevier 2007 Materials science & engineering. properties, micro Vol.449 No.-
<P><B>Abstract</B></P><P>The variation of soft magnetic properties of nanocrystalline Fe<SUB>73</SUB>Si<SUB>16</SUB>B<SUB>7</SUB>Nb<SUB>3</SUB>Cu<SUB>1</SUB> (numbers indicate at.%) alloy powder cores as a function of milling time has been investigated. Amorphous ribbons were pulverized using a hammer mill after crystallization heat treatment at 550°C for 1h. Ball milling was carried out for the pulverized flake powder at room temperature for up to 36h. The powders were classified into 53–75μm and under 45μm particles and mixed with a binder for consolidation into a toroidal shape. The consolidated powder was annealed at 450°C for 1h for stress relief. Results show that the consolidation density of the flake-shaped nanocrystalline alloy powder increased by 2.5–5% in theoretical density (0.2–0.4g/cm<SUP>3</SUP>) by the ball milling process. The density increase is attributed mainly to the morphological change due to the milling, which yields smoothened particle edges. Excess milling induced fracture of particles, resulting in reduced density due to the reappearance of sharp edges. In coarse flake powder the permeability is mainly controlled by the density of the consolidates whereas it is dominated by the size distribution of particles in finer powder. The intrinsic coercivity of the powder was significantly influenced by the residual stress and demagnetization effect arising from the change in morphology.</P>
AC/DC Notebook Adapter With 22㎽ No-Load Power Consumption
Byoung-Hee Lee,Byoung-Woo Ryu,Seong-Wook Choi,Gun-Woo Moon 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
An AC/DC notebook adapter with reduced no-load power consumption is proposed in this paper. During no-load condition, a lower limit of the output voltage is further lowered to reduce feedback circuit loss at the secondary side. Moreover, control-IC on/off scheme is employed to reduce power consumption of control-IC. As a result, the proposed AC/DC adapter of 65 W/17.5 V prototype can reduce the no-load power consumption under 30 ㎽. Operational principles and experimental results are presented to verify the feasibility of the proposed AC/DC adapter. Moreover, loss analysis of AC/DC adapter at no-load condition is also provided.