• The Journal of Korean Physical Therapy
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• 제22권1호
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• pp.47-51
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• 2010

Purpose: The purpose of this study was to determine whether there are any differences, with and without a toe spreader (TS), in dynamic foot pressure distribution in children with spastic diplegic cerebral palsy. Methods: Dynamic foot pressure recording using the RSscan system were obtained during walking in 12 participants (male=7, female=5) with and without TS. Mean force was measured for four different plantar regions; great toe, forefoot, midfoot, hindfoot. Displacement of center of pressure (COP), velocity of COP displacement and stance time were also measured during gait. Results: TS walking exhibited statistically significant decrease of mean force under great toe and forefoot (p<0.05), compared with a barefoot walking. Also, TS walking exhibited statistically significant increase of antero-posterior displacement of COP (p>0.05). Conclusion: These findings indicate the potential clinical utility of toe spreader to correct dynamic foot pressure during stance phase in children with spastic diplegic cerebral palsy.

• 한국안전학회지
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• 제11권2호
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• pp.25-32
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• 1996

This paper describes an experimental study of growing ductile crack-tip behaviors by means of computer image processing technique and finite element method. Here, the displacement field near a crack-tip is first measured by the computer image processing technique. Combined with the finite element technique, strain and stress fields are evaluated from the measured displacement. Then, crack-tip parameters such as J-integral are evaluated using the obtained displacement, strain and stress fields. The present technique Is applied to a growing crack problem of tensile CT specimen made of 304 stainless steel. The ductile crack growth behaviors accompanied by unloading are discussed in detail through the comparison between the experimental and the theoretical results.

• 한국산학기술학회논문지
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• 제8권5호
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• pp.1007-1012
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• 2007

되먹임 회로로 제어하는 새로운 Michelson형 레이저 간섭계를 제작하여 특성을 평가하였다. 새로운 Michelson형 레이저 간섭계는 압전 특성이 잘 알려진 PZT에 인가된 되먹임 회로의 인가전압을 직접적으로 측정함으로써 미세변위를 측정할 수 있는 간편한 측정 장치이다. 본 연구에서 제작한 Michelson형 레이저 간섭계의 신뢰성과 정밀도를 평가하기 위하여 실리콘 membrane의 단차를 측정한 결과 SEM으로 관찰한 값과 잘 일치함을 알 수 있었다.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.337-343
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• 2006

Numerical calculations are made in order to find a possible correlation between the J-integral and the crack mouth opening displacement(CMOD) in dynamic nonlinear fracture experiments of 3-point bend(3PB) specimens. Both elastic-plastic and elastic-viscoplastic materials are considered at different impact velocities. The J-integral may be estimated from the crack mouth opening displacement which can be measured directly from photographs taken during dynamic experiments.

• 한국소음진동공학회논문집
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• 제24권9호
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• pp.716-723
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• 2014

Vibration measurement using image processing is a fully non-contact measurement method and has many application fields. The resolution of vibration data measured by image processing depends on the camera performance and is lower than that measured by accelerometers. This work discusses the method to increase resolution of vibration signal measured by image processing based on the image mosaic technique with a high-power lens. The working principle of resolution enhancement was explained theoretically and verified by several experiments. It was shown that the proposed method can measure vibrations of relatively large scale structures with increased resolutions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1049-1050
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• 2013

• 한국지반환경공학회 논문집
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• 제12권4호
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• pp.33-41
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• 2011

연약지반상에 설치되는 항만구조물의 경우 편재하중에 의해 지반내의 과잉간극수압이 증가하게 되고, 토립자의 소성화로 인한 측방변형이 발생된다. 본 연구는 부산 ${\bigcirc}{\bigcirc}{\bigcirc}$현장에 설치되는 케이슨의 측방변위 및 침하 계측 데이터와 유한요소 해석 프로그램인 Plaxis를 이용한 수치해석 결과를 비교 분석하였다. 수치해석 시 실제 현장의 지반 물성치와 시공단계 및 기간 설정은 지반 조사 보고서 및 실시설계 보고서를 참고하여 적용하였으며, 현장 계측 단면 1개소 단면을 선정하여 수치해석하였다. 측방변위는 S.C.P.로 지반개량된 구간에 거치된 케이슨 전면부에 설치되어 있는 지중 경사계의 위치를 지점으로 측정하였고, 침하는 케이슨 배후의 여성토부의 중심에 설치되어 있는 지표 침하판의 위치를 지점으로 선정하여 현장계측하였다. 수치해석 결과 측방 변위의 해석 값은 실측치보다 크게 나타났으며, 실측값은 지속적인 완만한 증가양상을 보였지만 해석값은 단계 성토 때마다 큰 변위를 나타내는 계단식 증가를 보였다. 반면에 침하량 변화 양상은 측방변위 양상과 비슷한 거동을 보였고 변화량은 비슷하게 나타났다.

• Wind and Structures
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• 제20권2호
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• pp.315-326
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• 2015

To overcome the drawbacks of the traditional contact-type sensor for structural displacement measurement, the vision-based technology with the aid of the digital image processing algorithm has received increasing concerns from the community of structural health monitoring (SHM). The advanced vision-based system has been widely used to measure the structural displacement of civil engineering structures due to its overwhelming merits of non-contact, long-distance, and high-resolution. However, seldom currently-available vision-based systems are capable of realizing the synchronous structural displacement measurement for multiple points on the investigated structure. In this paper, the method for vision-based multi-point structural displacement measurement is presented. A series of moving loading experiments on a scale arch bridge model are carried out to validate the accuracy and reliability of the vision-based system for multi-point structural displacement measurement. The structural displacements of five points on the bridge deck are measured by the vision-based system and compared with those obtained by the linear variable differential transformer (LVDT). The comparative study demonstrates that the vision-based system is deemed to be an effective and reliable means for multi-point structural displacement measurement.

• 대한기계학회논문집A
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• 제31권8호
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• pp.880-888
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• 2007

This article describes the load capability of bending piezoelectric actuators with a thin sandwiched PZT plate in association with the stored elastic energy induced by an increased dome height after a curing process. The stored elastic energy within the actuators is obtained via a flexural mechanical bending test. The load capability is evaluated indirectly in terms of an actuating displacement with a load of mass at simply supported and fixed-free boundary conditions. Additionally, a free displacement under no load of mass is measured for a comparison with an actuating displacement. The results reveal that an actuator with a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators in terms of free displacement as well as actuating displacement due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at AC voltage, the actuating displacement is rather higher than the free displacement for the same actuating conditions. In addition, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric composite actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling the performance.

• 한국기계가공학회지
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• 제12권1호
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• pp.97-103
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• 2013

A new precision positioning mechanism for stage was been developed by Displacement Magnification Device(DMD) in this paper. The DMD was composed of the beam and multilayer piezoelectric actuators. The theoretical and experimental analysis of DMD to enlarge displacement more then 50times were discussed. And the 2-axis stage by using displacement amplification apparatus was added in the new DMD, and it was able to do it through finite element analysis and experiment. As the results, the magnification of DMD can be obtained about $100{mu}m$ displacement to the 10V input voltage($1.5{mu}m$). And the about 50nm of linearity error in the $30{mu}m$ measurement range and 20times of the amplification in displacement can be measured. In addition, the experimental results are confirmed the possibility of millimeter displacement characteristics and correspond to finite element analysis results.