• International Journal of Precision Engineering and Manufacturing
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• 제8권2호
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• pp.85-89
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• 2007

Linear ball guideways have been used recently in precision or ultra-precision positioning devices. However, when the inner balls begin to roll or the moving direction reverses, these guideways are subject to rolling friction or nonlinear spring behavior. An ultra-precision device with a linear motor, referred to as a 'tunnel actuator' (TA), has been constructed to measure these phenomena. The application of a TA is beneficial for two reasons: it mostly cancels the attractive magnetic force between the stator and mover (armature), and its magnetic flux leakage is very low. The influence of the nonlinear spring behavior in ball guideways was investigated in this study using the pure driving force from a TA. The equilibrium between the driving force from the TA and the nonlinear spring force provided great accuracy for a positioning stage using a linear ball guideway.

• 대한안전경영과학회지
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• 제22권1호
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• pp.45-50
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• 2020

The number of elevators in Korea has surpassed 700,000 units in 2019, which is the 8th in the world by number of installed units and 3rd in the world by new units. The word 'lift' is a representative word, and the category includes elevators, escalators, dumb waiters, and moving walks. Those who live in the city will experience using elevators once or twice a day, and these elevators are becoming an indispensable means of transportation when using high-rise apartments or subways. However, such a convenient elevator also has a lot of risks that threaten the safety of the user and actually cause many accidents every year. In particular, escalators (including moving walks), which account for as little as 5% of all elevators, account for 70% of all elevator accidents. According to Heinrich's chain of thought theory, accidents are caused by a combination of factors, which are divided into five stages: Stage 1: Genetic Factors and Social Environment, Stage 2: Individual Defects, Stage 3: Unsafe behavior and Unsafe conditions, Stage 4: Accident, Stage 5: Injury. Heinrich said that three of these five phases, unsafe behavior and unsafe conditions, require safety management and efforts to prevent accidents. In escalator accidents, the analysis of accident cases that have occurred so far will be related to unsafe behaviors and unsafe conditions, and the effective management of these causes of accidents will enable safer and more convenient use of escalators. This study analyzed accident cases of elevator users, focusing on escalator accidents over the last 10 years (2010 ~ 2019), and safety management to prevent safety accidents of elevator users by analyzing the behavior of actual users and questionnaires of experts in related fields. The method was studied.

• 수산해양기술연구
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• 제55권2호
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• pp.129-137
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• 2019

This study was conducted to investigate the effects of underwater noise caused by pile driving during marine construction on fish. In this study, the three gray rockfish were released about 1 km away from the construction site of wind power generation on July 18, 2018 and traced using two acoustic telemetry techniques. The behavior of the fish was analyzed by calculating the moving distance, swimming speed and direction of the gray rockfish. In the results of the acoustic tracking using the ship, the rockfish moved about 2.11 km for about two hours at a speed of $0.28{\pm}0.14m/s$ (0.94 TL/s). The bottom depth of the trajectory of the rockfish was $1.0{\pm}0.6m$ on average. There was a significant directionality in swimming direction of the gray rockfish, and there was no significant correlation between the swimming direction and tidal current direction. Moving distance during 5 minutes (5MD) during pile driving and finishing operations between rock surface and bedrock were 0.94-0.96 times (76.0-77.0 m) and 1.81-2.73 times (146.0-219.5 m), respectively, compared with no pile driving. This study is expected to be used as a basic data of fish behavior research on underwater noise.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.818-823
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• 2011

일반적인 강체의 동역학 해석방법은 지면에 고정된 좌표계에서 강체의 절대적 병진 위치좌표와 회전 각도 좌표의 6개 좌표계를 이용하여 기술된다. 그러나 철도차량의 경우 트랙의 중심과 같이 이동하는 트랙 좌표계에서 강체의 운동을 기술하는 방법이 이용될 수 있다. 트랙 좌표계는 트랙을 기준으로 강체의 운동이 기술되므로 트랙 좌표의 변위의 구속조건이 쉽게 설정될 수 있는 장점이 있다. 본 연구에서는 트랙 좌표계를 이용한 철도차량 운동방정식의 유도 방법과 시뮬레이션 결과를 제시하고자 한다.

• Geomechanics and Engineering
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• 제16권4호
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• pp.341-353
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• 2018

A reinforced concrete pedestrian tunnel is constructed under a four-track surface railway. Heavy rainfall and soil exposure to drying lead to soil with different water content throughout the year. A railway is an open utility that is subject to rainfall without control on the quantity of the water on it and when there is a tunnel under a railway, the water content of the soil around the tunnel is very influential. This research shows the effects of change of water content in the soil around a pedestrian tunnel under a four-track surface railway. The pedestrian tunnel and the soil block around the tunnel are modeled in 3D by the FEM and are studied under the vibrations induced by the moving trains on the four-track surface railway for different soil water contents and the effects of the soil water content on the dynamic behavior of the tunnel and the surrounding soil are demonstrated.

• 아동학회지
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• 제28권1호
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• pp.17-35
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• 2007

This study examined whether sequential transition patterns of social play differed by children's social competence. The social competence of sixty 5-year-old children was rated by their teachers using the Social Competence Scale(NICHD Early Child Research Network, 1996). Children's social play was observed during free play and coded by criteria developed by Robinson et al(2003). Results showed differences in children's social play behaviors by social competence and differences in the transition patterns of children's social play level by social competence. Children with higher social competence showed a transition pattern moving toward cooperative-social interaction, whereas children with lower social competence showed a transition pattern moving backward to solitary or onlooker behavior.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.195-205
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• 2001

The mechanical properties of aluminum honeycomb on the direction of axial crushing under quasistatic loading test was investigated. The crushing process was simulated numerically by full-scale finite element models. Simulations reproduce the experimental results both qualitatively as well as quantitatively. From the investigation, we suggested the constitutive model of energy absorbing honeycomb structure for large scale impact analysis. Real impact test of the WB(Moving Deformable Barrier) was carried and compared with finite element simulation. Constitutive model used in the numerical simulation had a good correlation with experiment. By suggesting the optimizing method fur honeycomb cell configuration design, relationship between cell configuration and crush strength is studied.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 춘계 학술대회논문집
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• pp.127-139
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• 2000

Transient aerodynamic response of an airfoil to a rapidly deploying spoiler is numerically investigated using a two-dimensional turbulent compressible Navier-Stokes flow model. The spoiler moving relative to a stationary airfoil is treated by an overset grid bounded by a 'dynamic domain-dividing line' the concept of which is developed first..in this paper. The fluid-dynamic mechanism of the adverse lift due to the rapidly deploying spoiler is analyzed. Also the effect of spoiler deploying rate on the initial behavior of the aerodynamic response is expounded, which is of interest in view of active control technology and controller design for the spoiler. The results of present computation about the stationary as well as moving spoilers are relatively in good agreement with the existing experimental data.

• Tribology and Lubricants
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• 제18권3호
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• pp.219-227
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• 2002

A linear elastic fracture mechanics analysis of double subsurface cracks propagation in a half-space subjected to moving thermomechanical surface traction was performed using the finite element method. The effect of frictional heat at the sliding surface on the crack growth behavior is analyzed in terms of the thermal load and peclet number. The crack propagation direction is predicted in light of the magnitudes of the maximum shear and tensile stress intensity factor ranges. When moving thermomechanical surface traction exists, subsurface horizontal cracks are propagation in-plane crack growth rate at the beginning but they are propagation out-of-plane crack growth rate by the frictional heat which is occurrence by the repeated sliding contact.

• 한국멀티미디어학회논문지
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• 제17권1호
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• pp.15-25
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• 2014

본 논문에서는 지능형 감시 시스템을 위해 공간적 확률 분포와 방향 서술자를 이용하여 다양한 배회행위를 검출하는 방법을 제안한다. 적응적 배경 모델링 기법을 이용하여 움직이는 객체를 검출하고, 검출된 객체로부터 움직임의 정보를 추출한다. 추출된 객체의 움직임 정보는 이동 궤적과 방향에 대해 특징벡터를 생성한다. 생성된 특징벡터는 k-Nearest Neighbor를 통해 최종적으로 배회행위를 검출하게 된다. 제안한 방법을 실내외 다양한 환경에서 테스트하여 배회 행위를 검출하는 결과를 나타내었으며 이는 실시간으로 검출되는 것을 확인하였다.