• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1454-1457
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• 2003

This study was carried out to minimize the lifting force of a two hinge type stand mechanism. This unit is designed for the display devices in order to enhance the ergonomics for effective height adjustment and maintenance at any preferred position. The unit will be very useful for the mechanism fabricated with a coil spring and disc springs as a torque generator. The maximum and the minimum torque value should be calculated initially for the smooth lift. And the reasonable torque distribution is necessary to prevent any AUTO LIFT and AUTO Drooping at any position because the torque generated by coil spring is more sensitive than disc spring in tilting the position. Therefore, the analysis of the coil spring is requisite to issue the specific torque value depending on the distorted angle with securing reliability of a long time storage condition. After the theoretical torque value was calculated, the evaluation was carried out by making a proto-type sample, then distorted angle was updated by experiment. The result of this study can readily be applied to various units for the optimization of the smooth lift.

• Structural Monitoring and Maintenance
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• 제5권2호
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• pp.189-204
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• 2018

This paper examines the seismic responses of a reinforced concrete (RC) frame core-tube building with pre-pressed spring self-centering energy dissipation (PS-SCED) braces. The PS-SCED brace system consists of friction devices for energy dissipation, pre-pressed combination disc springs for self-centering and tube members as guiding elements. A constitutive model of self-centering flag-shaped hysteresis for PS-SCED brace is developed to better simulate the seismic responses of the RC frame core-tube building with PS-SCED braces, which is also verified by the tests of two braces under low cyclic reversed loading. Results indicate that the self-centering and energy dissipation capabilities are well predicted by the proposed constitutive model of the PS-SCED brace. The structure with PS-SCED braces presents similar peak story drift ratio, smaller peak acceleration, smaller base shear force and much smaller residual deformations as compared to the RC frame core-tube building with bucking-restrained braces (BRBs).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.181-185
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• 2001

This paper deals with the dynamic stability of a disc brake pad taking into account of its shear deformation and rotary inertia. A brake pad can be modeled as a beam like model subjected to distributed friction forces and having two translational springs. The study of this model is intended to provide a fundamental understanding of dynamic stability of drum brake pad. Governing equations of motion are derived from extended Hamilton's principle and their corresponding numerical solutions are obtained by applying the finite element formulation. The critical distributed friction force and the instability types are investigated bt changing two translational spring constants, rotary inertia parameter and shear deformation parameter. Also, the changes of eigen-frequencies of a beam determining instability types are investigated for various combinations of two translational spring constants.

• 한국육종학회지
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• 제40권4호
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• pp.499-502
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• 2008

A new gerbera variety 'Yellow Wing' was released by the National Horticultural Research Institute (NHRI) in 2007. A cross was made between 'Gold Finger' with yellow and single and 'Yellow Springs' with yellow and spider in 2004. After investigation of the characteristics for 4 years (from 2004 to 2007), it was selected specially for the use of cut-flower. 'Yellow Wing' is a vigorous cultivar with yellow (RHS YO14B), green center and spider type. The flower diameter is 10.6cm. And inner ray floret and disc diameter is 2.83cm and 2.03cm, respectively. It produces a large yield with continuous supply of flowers and has adequate peduncle height and brilliant color. We believe that 'Yellow Wing' has a great potential for expanding cultivated area of domestic gerbera cultivar and increasing farmers-income.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.54-63
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• 2022

이 연구는 구조물 내진보강 장치의 하나인 마찰댐퍼에 관한 것으로, 내부 마찰재를 복합재료의 일종인 초고분자량 폴리에틸렌으로 대체하여 댐퍼를 개발하였다. 또한 마찰력이 발생하는 내부 구조를 여러 층으로 적층하는 다중 마찰방식을 적용하였다. 개발된 다중 마찰댐퍼의 성능 검증을 위해서 재료에 대한 기초 물성과 마모 특성, 디스크 스프링에 대한 특성 분석 시험을 수행하였다. 마모시험 시험결과, UHMWPE의 질량 감소율은 0.003%로 복합재료 기반의 마찰재 중에서 가장 우수한 성능을 보였다. 디스크 스프링은 유한요소해석과 시험결과로부터 설계기초자료를 확보하였다. 또한 개발된 다중 마찰댐퍼의 품질 안정성을 확인하기 위해 토크값에 따른 마찰력 변화와 감쇠장치에 대한 지진하중 시험을 수행하였다. 품질성능 시험결과, 토크 값 조절에 따라 선형적인 마찰력 변화를 보였으며, 지진하중 시험 결과, 마찰댐퍼의 허용오차는 설계기준에서 요구하는 15% 미만으로 나타나 내진보강 장치로서의 요구조건을 만족하는 것으로 나타났다.

• Steel and Composite Structures
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• 제47권2호
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• pp.167-184
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• 2023

In this study, a new recentering friction device (RFD) to retrofit steel moment frame structures is introduced. The device provides both self-centering and energy dissipation capabilities for the retrofitted structure. A hybrid performance-based seismic design procedure considering multiple limit states is proposed for designing the device and the retrofitted structure. The design of the RFD is achieved by modifying the conventional performance-based seismic design (PBSD) procedure using computational intelligence techniques, namely, genetic algorithm (GA) and artificial neural network (ANN). Numerous nonlinear time-history response analyses (NLTHAs) are conducted on multi-degree of freedom (MDOF) and single-degree of freedom (SDOF) systems to train and validate the ANN to achieve high prediction accuracy. The proposed procedure and the new RFD are assessed using 2D and 3D models globally and locally. Globally, the effectiveness of the proposed device is assessed by conducting NLTHAs to check the maximum inter-story drift ratio (MIDR). Seismic fragilities of the retrofitted models are investigated by constructing fragility curves of the models for different limit states. After that, seismic life cycle cost (LCC) is estimated for the models with and without the retrofit. Locally, the stress concentration at the contact point of the RFD and the existing steel frame is checked being within acceptable limits using finite element modeling (FEM). The RFD showed its effectiveness in minimizing MIDR and eliminating residual drift for low to mid-rise steel frames models tested. GA and ANN proved to be crucial integrated parts in the modified PBSD to achieve the required seismic performance at different limit states with reasonable computational cost. ANN showed a very high prediction accuracy for transformation between MDOF and SDOF systems. Also, the proposed retrofit showed its efficiency in enhancing the seismic fragility and reducing the LCC significantly compared to the un-retrofitted models.