• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1404-1408
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• 2008

The migration and proliferation of vascular endothelial cells (VEC), which play an important role in vascular remodeling, are known to be regulated by hemodynamic forces in the blood vessels. When shear stresses of 2, 6, 15 dynes/$cm^2$ are applied on mouse micro-VEC in vitro, cells surprisingly migrate against the flow direction at all conditions. While higher flow rate imposes more resistance against the cells, reducing their migration speed, the horizontal component of the velocity parallel to the flow increases with the flow rate, indicating the higher alignment of cells in the direction parallel to the flow at a higher shear stress. In addition, cells exhibit substrate stiffness and calcium dependent migration behavior, which can be explained by polarized remodeling in the mechanosensitive pathway under shear stress.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.177-183
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• 1993

본 연구에서는 범용 구조 해석 패키지인 MSC/NASTRAN을 이용하여 대형 구조물인 안테나 각 분계의 동특성을 파악하고, 부분구조합성법을 이용하여 구조물 전체의 동특성을 파악하였다. 또한 구조물의 주파수 응답 함수를 이 용하여 지배적인 고유모드를 구하였고, 각 분계의 변형 및 운동 에너지를 산 출하여 전체 고유모드에 대한 분계의 에너지 기여도 파악하였으며, 이와 같 은 진동 요인 분석에 따른 진동 대책으로, 변형 및 운동 에너지 기여도가 높 은 분계의 질량 및 강성 변경에 따른 구조물의 동특성 변화를 예측함으로 구조물의 동특성 개선의 방향을 제시하였다.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.633-644
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• 2016

The purpose of this study was to examine the effect of phytoncide Aroma inhalation and exercise combination therapy on the college life stress, mood state and sleep pattern of the university students. Participants were 72 college students of four groups of Phytoncide Aroma Inhalation group(n=18), Exercise group(n=17), Phytoncide Aroma Inhalation and exercise combination therapy group(n=17), control group(n=20). Research subjects pre-test(0week), mid-test(6week), post-test(12week) measurement was made equally on college life stress, mood state and sleep pattern. As a result, mood status, college life satisfaction and sleep scores were improved in all groups except the control group. Especially, phytoncide inhalation and exercise combination therapy group showed the greatest change in scores.

• Geotechnical Engineering
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• v.5 no.3
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• pp.5-18
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• 1989

The ground input motions used for seismic analysis of structures are studied in this paper, The one-dimensional wave propagation theory, the simple transfer function by Elsabee and Morray, and the finite element method that can account for the effect of scattering field, respectively, are used to get the ground input motions, and the results by these methods are compared among others. The responses of structures are also computed by both finite element analysis and elastic half space analysis, using the ground input motions obtained by the different methods mentioned above, and the computed results are analyzed. In addition, the parameteric study Is performed to analyze the effect of the increase of soil stiffness on the response of structures, and on that of the ground input motions. The responses of structures obtained are compared with the results obtained using the Building Code on seismic analysis for structures in Korea. The results of this study show that the ground input motions obtained without considering the effect of scattering field was 2 times larger than those with scattering effect, concluding that the effect of scattering field may not be ignored when obtains the ground input motion.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.109-116
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• 2023

The purpose of this study was to investigate the influence of gender and load carriage difference on the lower extremity kinetics during stair descent. Ten healthy males and 10 healthy females were recruited (n=20). In the Maximum resultant velocity, it showed more velocity was decreased with difference by the change of gender (males>females) and load carriage (30%, 20%, 10%> 10%). And, resultant velocity showed interaction between gender and a load (load>gender). Main effect by gender during stair descent showed leg length was decreased in females than that of males at initial contact phase. Also, main effect by gender during stair descent showed more hip, knee flexed and plantar flexion of ankle joint in females than that of males. In the kinetics variables, main effect by gender during stair descent showed more higher reaction force of medial-lateral direction, and leg stiffness in males than that of females. We found that females successfully accommodated a load during stair descent by decreasing the range of motion of the hip joint angle and resultant velocity of movement. Males, on the other hand, require greater medial-lateral, vertical reaction force, and leg stiffness to accommodate a load, and control of momentum.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.75-86
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• 1999

An analysis model is developed to evaluate the dynamic responses of a bridge system under seismic excitations, in which pounding actions between girders are considered in addition to other phenomena such as nonlinear pier motion, rotational and translational motions of foundations. The model also considers the abutment and restrainers connecting adjacent girders to prevent the unseating failures. Using the developed model, the longitudinal dynamic behaviors of a bridge system are examined for various peak ground accelerations, and the effects of the applied restrainers are investigated. It is found that the restrainers reduce the relative displacement with the shorter clearance length as well as the higher stiffness of the restrainers for moderate excitations. However, in the region with strong excitations the restrainers may yield due to the large relative displacement. Therefore, the extension of support length in addition to restrainers may need to prevent the unseating failure more effectively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.348-353
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• 1995

When cantilever beams rotate, their bending stiffnesses change due to the stretching caused by centrifugal inertia forces. Such phenomena result in variations of natural frequencies and mode shapes associated with constant speed rotational motions of the beams. These variations are important in many practical applications such as helicopter blades, turbomachines, and space structures. This paper presents the formulation of a set of linear equations governing the flapwise bending vibration of rotating cantilever beams. These equations can be used to provide accurate predictions of the variations of natural frequencies and mode shapes due to rotation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.101-107
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• 2014

Damage location and extent of structure could be detected by the inverse analysis on dynamic response properties such as frequencies and mode shapes. The dynamic response of building structures has many noise and affected by nonstructural members and, above all, the behavior of building structure is more complex than civil structure and this makes the damage detection difficult. In recent researches the damage is detected by the indirect index such as sensitivity or assumed values. However, for the more reasonable damage detection, it needs to use the damage index directly induced from dynamic equation. The purpose of this study is to provide the damage detection method on shear building structures by the damage index directly induced from dynamic equation. The provided damage index could be estimated from measured mode shape of undamaged structure and frequency difference between undamaged and damaged structure. The damage detection method is applied to numerical analysis model such as MATLAB and MIDAS GENw for the verification. The damage index at damaged story represents (-) sign and 15 times than other undamaged sories.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1989.06b
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• pp.35-47
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• 1989

누설방지를 목적으로 산업용 기계에서 많이 사용되고 있는 기계평면시일(mechanical face seal)은 기능상 높은 신뢰도를 요구하고 있다. 이를 위하여 동적 안정성이 커야되고, 밀봉된 유체의 누설을 최소화시킬 수 있는 정도에서 시일의 수명을 결정해야 한다. 이와같이 상반된 성질을 동시에 만족시키기 위하여 시일 성능에 영향을 미칠 수 있는 기하학적 요인들을 고려하여 해석해야 한다. 일반적으로 미끄럼 접촉운동을 하고 있는 시일에서 시일링 간극(sealing gap)이 수 micron 단위라는 점을 고려할때 시일 조립시 중심맞추기(alignnment) 정미\ulcorner 결여 및 회전축의 자중량 등에 의한 기계적 변형(mechanical distortion), 특히 고온의 분위기에서 작동되고 있는 시일의 열변형(thermal distortion)은 시일의 경사집에 커다란 영햐을 주고 있다. 또한 누설을 최소화시킬 목적으로 시일 링(seal ring) 을 시일의 경사짐에 커다란 영향을 주고 있는 스프링의 강성도를 증가시키면 상대 미끄럼 운동을 하고 있는 접촉명이 건조마찰에 의한 마멸이 진행되어 코닝(coning)현상이 생긴다. 시일 평면에서 코닝 현상은 시일의 축방향 분리력(axial separtating force)과 경사 모우면트(tilting moment)에 커다란 영향을 주고 있는 것으로 알여졌다. 이들의 연구는 주로 경사진 시일평판에 시일근사치이논(seal approximation bhoryl)을 이용하여 1차원 비압축성에 관한 시월 성능을 해석하였다. 본 연구에서는 비압축성 유체의 점성이 온도에 의하여 변화를 일으키는 조건하에서 경사진 회전시일에 코닝이 발생되었을때 시일링 각극에서의 압력분포를 ㅈ차원인 경우에 대하여 수치적으로 해석을 하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1521-1527
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• 2013

This study proposes a wearable master device that can measure the joint stiffness and the angular displacement of a human operator to enhance the adapting capability of a slave system. A lightweight inertial sensor and the exoskeleton mechanism of the master device can make an operator feel comfortable, and artificial pneumatic muscles having a working principle similar to that of human muscles improve the performance of the slave device on emulating what a human operator does. Experimental results revealed that the proposed master/slave system based on the muscle stiffness sensor yielded uniform tracking performance compared with a conventional position-feedback controller when the payload applied to the slave system changed.