• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.86-92
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• 2008

AGT system is a kind of light railway train. AGT system use of concrete track and rubber tire, so it can be reduce the noise and vibration, compare to the normal train system. And, the dynamic responses of normal bridge are influenced by the dynamic characteristics of bridge, the speed of vehicle and the surface roughness of railway. But the AGT system bridge is influenced not only the above facts but also the guiderail unevenness, because, AGT vehicle steered by guiderail. So, in this study, optimized service condition is suggested for the design and operation of AGT system, by the means of experimental study. The experiments are executed for PSC bridge with length of 30m, at the AGT test line in Kyongsan. The test results are compared and investigated according to the prominence. In the test result, the guiderail prominence influenced on the dynamic response of bridge. It shows a increase as compared with no guiderail prominence in the dynamic response value acceleration, displacement, stain.

• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2094-2104
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• 2006

As demands for complex microstructures with high aspect ratios have increased, the existing methods, MEMS and LIGA, have had difficulties coping with the number of masks and fabricable heights. A microstereolithography technology can meet these demands because it has no need of masks and is capable of fabricating high aspect ratio microstructures. In this technology, 3D part is fabricated by stacking layers, 2D sections, which are sliced from STL file, and the Dynamic Image Projection process enables the resin surface to be cured by a dynamic image generated with $DMD^{TM}$ (Digital Micromirror Device) and one irradiation. In this paper, we address optical design process for implementing this microstereolithography system that takes the light path based on DMD operation and image-formation on the resin surface using an optical design program into consideration. To verify the performance of this implemented microstereolithography system, complex 3D microstructures with high aspect ratios were fabricated.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.974-987
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• 2021

This paper presents ductile fracture simulation of full-scale cracked pipe for nuclear piping materials using the cohesive zone model (CZM). The main objective of this study is to investigate the applicability of CZM to predict ductile fracture of cracked pipes with various crack shapes and under quasi-static/dynamic loadings. The transferability of the traction-separation (T-S) curve from a small-scale specimen to a full-scale pipe is demonstrated by simulating small- and full-scale tests. T-S curves are calibrated by comparing experimental data of compact tension specimens with finite element analysis results. The calibrated T-S curves are utilized to predict the fracture behavior of cracked pipes. Three types of full-scale pipe tests are considered: pipe with circumferential through-wall crack under quasistatic/dynamic loadings, and with 360° internal surface crack under quasi-static loading. Computational results using the calibrated T-S curves show a good agreement with experimental data, demonstrating the transferability of the T-S curves from small-scale specimen.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.440-445
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• 2011

Dynamic characteristic analysis is required in developing SMT mounter system with high installation speed and position precision, because of vibration source occurred by positioning head. This paper presents the method of improving dynamic characteristic of SMT(Surface Mount Technology) mounter with finite element method and modal test. The design direction is that natural frequencies of SMT mounter must be higher than the vibration source. In addition, the effect of input shaping on residual vibration reduction is investigated by simulating the response of a first-order system.

• 한국가시화정보학회지
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• 제16권3호
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• pp.35-39
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• 2018

In multiphase systems, surface wettability is one of dominant design parameters to enhance system performance. Since surface wettability can be maximized and minimized with micro-textured surfaces, therefore micro-textured surfaces are widely countered in various research and engineering fields. In this study, for better understanding of micrometer scaled surface wettability, spreading phenomena is experimentally investigated on the hydrophilic micro-textured surfaces. By photolithography and conventional dry etching method, there are prepared the surfaces with uniformly arrayed micro-pillars. The interfacial motions of a water droplet on the test sections are visualized by high speed camera in top view. On the basis of visualization data, it is analyzed the relation between dynamic coefficient and geometrical features on micro-textured surfaces.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.345-350
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• 2001

Dynamic behavior of high speed train is very important because the high speed train should be safe and satisfied with the ride comfort. An eddy current brake system is mounted on trailer bogie and wheelset. The eddy current braking force longitudinally exerts on the articulated trailer bogie and the attraction force vertically exerts on the wheelset. Because a frame of eddy current brake system is flexible, these forces generate the vertical vibration at middle point of the frame. Also, the vibration change the vertical clearance between an electromagnet and top of rail which affect the magnitude of braking and attracting forces. Therefore, the dynamic behavior of the eddy current braking system must be predicted for design the dynamic characteristic of its mounting system when normally operate on rail which have irregularity. Vampire program is used for prediction of the dynamic behavior of an eddy current braking system. Five design variables and five performance index are considered for optimization through D-optimal experimental design in this paper. Also model center is used to search the optimal point for sum of performance index with variational matric method.

• 대한토목학회논문집
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• 제28권1A호
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• pp.39-49
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• 2008

본 연구에서는 교량의 노면조도 및 교량과 차량 사이의 상호작용을 고려한 수치해석방법을 사용하여 여러 매개변수에 대한 강판형교의 동적응답을 연구하였다. 대상교량은 건설교통부에서 제정한 "도로교 상부구조 표준도"에 수록되어 있는 지간이 20 m, 30 m와 40 m인 단순 강판형교를 사용하고, 여러 종류의 도로에 대하여 생성시킨 노면조도를 사용하였다. 차량은 2축과 3축 덤프트럭 및 5축 트랙터-트레일러인 표준트럭(DB-24)을 3차원으로 모델링하고, 교량은 주형을 보요소로, 콘크리트 바닥판은 쉘요소로 이상화시켰으며 주형과 콘크리트 바닥판 사이는 Rigid Link를 사용하여 3차원으로 모델링하였다. 이와 같은 차량 및 노면조도를 사용하여 강판형교의 지간별, 통행 차종별 및 노면조도별 충격계수와 DLA를 구하고 각국의 설계기준과 비교 검토하였다.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2006년도 춘계학술발표대회 논문집
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• pp.131-134
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• 2006

This study aims to inspect changes of physical expression in surfaces of both building interior and exterior in contemporary architecture. Nowadays society has transformed into more complicated framework with the development of the new media and digital technology in 21 century. Surface's expressivity has been changed with design trend and material development. Although surface study has been mainly concentrated on properties of materials and structure characters, new technology and cultural acceptance enables it extend itself to a new area with various design methods, taking its place as an important contemporary architectural element. Interior surface design is expressed with several unique methods such as optical illusion, surface exposure and spacial depth and volume, and it created dynamic space within the surface itself. In case of exterior surface, whole space seems to be designed to be coordinated with structured optical illusion as well as symbolic expression. Surface's area is extends itself with the stream of the times. This study explored the nature of surfaces with categorizing and comparing them in a various views and methods.

• 국제물리치료학회지
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• 제10권2호
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• pp.1756-1762
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• 2019

Background: Functional ankle instability (FAI) indicating a decrease in muscle strength, proprioception, neuromuscular control, balance and postural control function. Objective: To investigate the effect of jumping exercise on the supporting surface on the ankle muscle thickness, proprioceptive sensation, and balance in adults with FAI. Design: Randomized Controlled Trial. Methods: Twenty young people with FAI were randomly assigned to the unstable supporting surface jump group (N=10) and the stable supporting surface jump group (N=10). The intervention was conducted three times a week for eight weeks, and for 30 minutes per session. Trampoline was used as an unstable support surface and the stable support surface was carried out on a regular floor. The thickness of the tibialis anterior muscle and medial gastrocnemius muscle was measured by ultrasonography, and the proprioception of dorsiflexion and plantarflexion was measured using an electrogoniometer. The dynamic balance was also measured with a balance meter. Results: The the muscle thickness of the medial gastrocnemius muscle was significantly higher in the stable supporting surface jump group than in the unstable supporting surface jump group (p<.05). Furthermore, the plantar flexion proprioception and dynamic balance were significantly improved in the unstable supporting surface jump group than in the stable supporting surface jump group in the intergroup comparison (p<.05). Conclusions: The conclusion has been reached in this study that the jumping exercise on the unstable supporting surface could be a more effective in improving FAI than the regular surface.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.214-220
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• 2009

The spindle is the main component in machine tools. The static and dynamic stiffness of the spindle directly affect the machining productivity and surface integrity of the workpiece. The static and dynamic stiffness of the spindle depend on the shaft size, bearing arrangement, bearing span length, and so on. Therefore, the selection of shaft size and bearing span length are important to improve the spindle stiffness. This paper presents the determination of shaft size and bearing span length in spindle design step. In order to select the optimal bearing and built-in motor locations with constraint conditions, the extreme vertices design was applied. The results show that extreme vertices design is usable for spindle design with design constraints.