• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.93-96
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• 2002

Instrumented impact tests and compression-after-impact(CAI) tests have been used to evaluate the effect of temperature on the low-velocity impact characteristics of phenolic matrix composites reinforced with various woven glass fabric. Impact characteristics and damage area in laminates are evaluated by C-scan. It is shown that the extent of damage and residual compressive strength of the laminates vary with energy level and impact test temperature. The damage area increases with increasing impact energy and temperature. All these observations indicate reduced impact damage resistance and damage tolerance of the laminates at elevated temperature.

• 대한의용생체공학회:의공학회지
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• 제7권2호
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• pp.169-182
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• 1986

Pulsed ultrasonic Doppler system is a useful diagnostic instrument to measure blood-flow-velocity, velocity profile, and volume-blood-flow. This system is more powerful compare with 2-dimensional B-scan tissue image. A system has been deve- loped and ii being evaluated using TMS 32010 DSP. We use this DSP for the purpose of real-time spectrum analyzer to obtain spectrogram in singlegate pulsed Doppler system and for the serial comb filter to cancel clutter and zero crossing counter to estimate Doppler mean frequency in multigate pulsed Doppler system. The Doppler shift of the backscattered signals is sensed in a phase detector. This Doppler signal corresponds to the mean velocity over a some region in space defined by the ultrasonic beam dimensions, transmitted pulse duration, and transducer ban(iwidth. Multi- gate pulsed Doppler system enable the transcutaneous and simultaneous assessment of the velocities in a number of adjacent sample volumes as a continuous function of time. A multigate pulsed Doppler system processing the information originating from presented.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.27-30
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• 2005

This paper studied the PVDF(polyvinylidene fluoride) and Acoustic Emission sensors characteristics of the laminated composite panels under the low velocity impact. The various impact test by changing impact height is performed on the instrumented drop weight impact tester. The STFT(short time Fourier transform) and WT(wavelet transform) are used to decompose the each sensor signals. A ultrasonic C-scan and digital scope are used to define damaged area in each case. The test result indicated that the individual sensor signals involve the damage initiation and development.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.86-91
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• 2002

Glass/phenolic composite laminates have been used in the field of non-flammable light rail transit and their applications have expanded more widely. Low velocity impact tests have been used to evalute the effect of temperature and acceleration aging on low velocity impact response of phenolic matrix composites reinforced with woven E-glass fabric. The damage of matrix cracking and delamination are suddenly reduced the compressive strength after impact. The damage area increases with increasing temperature and impact energy. UT C-scan is used to determine damage areas by impact loading. Therefore, all this observations indicate reduced impact damage resistance and damage tolerance of the laminates at elevated temperature.

• 대한물리의학회지
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• 제15권4호
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• pp.67-74
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• 2020

PURPOSE: The progression of the center of pressure (COP) velocity of the stance phase may have important roles for predicting gait speed in older adults with cognitive decline. This study was conducted to identify the correlation between gait speed and the velocity of COP progression during the stance phase in older adults with cognitive decline. METHODS: Forty adults aged 65 years or older (twenty participants without cognitive decline, 20 participants with cognitive decline) were recruited. The COP progression velocity was measured using an F-scan pressure-sensitive insole system. The stance phase was divided into four sub-stages. (loading response, mid-stance, terminal stance, and pre-swing). Gait speed, double support phase, and cadence were also measured. Correlations and multiple regression analyses were performed. RESULTS: Gait speed was associated with the COP progression velocity in midstance (r = .719, p < .05), cadence (r = .719, p < .05) and the COP progression velocity in loading response velocity (r = .515, p < .05) in older adults with cognitive decline. However, no correlation was found in older adults without cognitive decline. In multiple regression analysis using gait speed as a dependent variable, the COP progression velocity in midstance and cadence were significant predictors of gait speed, with the COP progression velocity being the most significant predictor. CONCLUSION: The COP progression velocity is an important factor for predicting gait speed in older adults with cognitive decline, suggesting that the cognitive function influences gait speed and the velocity of COP progression.

• 대한전자공학회논문지SP
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• 제38권2호
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• pp.191-198
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• 2001

HD ProjectionTV에서 CRT의 전자총 및 투영되는 스크린 상에서의 빔 프로파일에 의한 화질의 열화를 개선시키기 위한 방법으로는 영상신호의 진폭 변화량에 따라 수평 편향 속도를 선형적으로 변조시키는 SVM(Scan Velocity Modulation)방식이 있다. 그런데, 선형 SVM방식에서의 화질 개선은 입력 영상신호의 진폭변화에 대해 균일하지 않다. 본 논문에서는 HD Projection TV에서의 빔 프로파일의 특성을 분석하여 모델링하고, 고역의 HD 신호가 입력될 때 SVM효과를 모의실험을 통해 해석하였다. 그리고, 이를 근거로 영상신호에 따라 SVM량을 비선형적으로 조절하는 비선형 SVM방식이 HD Projection TV에서도 필요함을 이론적으로 제시하였다. 이를 바탕으로 SVM 회로를 직접 하드웨어로 제작하여 실제 TV에 장착하여 실험하였다. 실험 결과 영상 신호의 진폭이 작은 영역과 큰 영역의 경계부분에서 발생하는 화질의 열화를 거의 일정하게 개선시킬 수 있음을 확인 하였다.

• 천문학회보
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• 제43권2호
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• pp.46.1-46.1
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• 2018

The Fast Imaging Solar Spectrograph (FISS) on the Goode Solar Telescope (GST) at Big Bear Solar Observatory is the imaging Echelle spectrograph developed by the Solar Astronomy Group of Seoul National University and the Solar and Space Weather Group of Korea Astronomy and Space Science Institute. The instrument takes spectral data from a region on the Sun in two spectral bands simultaneously. The imaging is done by the organization of intensity data obtained from the fast raster scan of the slit over the field of view. Since the scan repeats many times, the whole set of data can be used to construct the movies of monochromatic intensity at arbitrary wavelengths within the spectral bands, and those of line-of-sight velocity inferred from different spectral lines. So far there are two standard observing configurations: one recording the $H{\alpha}$ line and the Ca II 8542 line simultaneously, and the other recording the Na I D2 line and Fe I 5435 line simultaneously. We have developed the procedures to produce the standard data for each observing configuration. The procedures include the spatial alignment, the correction of spectral shift of instrumental origin, and the lambdameter measurement of the line wavelength. The standard data include the movie of continuum intensity, the movies of intensity and velocity inferred from a chromospheric spectral line, the movies of intensity and velocity inferred from a photospheric line. The processed standard data will be freely available online (fiss.snu.ac.kr) to be used for research and public outreach. Moreover, the IDL procedures will be provided on request as well so that each researcher can adapt the programs for their own research.

• 한국의류산업학회지
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• 제15권4호
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• pp.613-619
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• 2013

This study compares the gait characteristics of elderly women during barefoot walking and walking with sneakers. We measured foot angles, max foot pressure, peak plantar pressure of each plantar region, velocity of Center of Pressure(COP), and axis shifting of COP with an RS-scan system. Elderly women's foot angles were narrower when walking with sneakers than when barefoot walking. We found that the subtalar joint angle (representing ankle joint flexibility) affected walking stability. Regarding the peak plantar pressure of each foot region, pressures were high in the medial regions and the pressures greatly varied depending on the region measured during barefoot walking. The COP moved significantly faster when walking with sneakers than barefoot walking and suggests that elderly women walked faster in sneakers. Axis shifting of the COP decreased during walking with sneakers and indicated that gait balance improved when walking with sneakers. The findings of the present study can be utilized as foundational data for elderly women's gait characteristics as well as data for the production of functional footwear. Future research that focuses on various types of shoes, age groups, and gender are recommended for the development of more functional footwear for stable gaits.

• 한국의학물리학회지:의학물리
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• 제24권4호
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• pp.243-252
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• 2013

본 연구는 표적이 규칙적으로 움직일 때 생기는 4DCT 영상의 모션 아티팩트(motion artifact) 관련된 원인들인 partial volume effect (PVE), partial projection effect (PPE), 각각의 프레임의 시작점 사이에 불일치(MMimph)의 원인들은 조사 및 분석을 목적으로 했다. 본 기관에서 제작된 흉부팬텀과 아크릴의 두개의 원기둥팬텀(반지름: 2 cm, 길이: 0.5 cm/ 반지름: 2 cm, 길이: 10 cm)이 규칙적인 움직이는 동안 CT을 이용하여 4D 영상을 획득했다. 촬영은 자동시작과 각각의 프레임의 시작점을 일치시키기 위해 매뉴얼로 두 가지 방법으로 시작하였다. 첫번째 실험에서는 CT 캔트리 rotation time은 5초와 8초가 이용되었다. 각 프레임은 다른 위상으로 시작되었다. 두번째 실험에서는 각 프레임에서 같은 위상으로 시작되게 하기 위해 매뉴얼로 시작했다. 세번째 실험에서는 원기둥팬텀을 2초와 6초를 주기로 움직였다. 각각의 4DCT의 영상에서 표적의 부피를 구했다. 영상으로부터 구한 표적의 부피와 표적의 실제 부피와 비교를 통해 관계를 분석했다. 흉부팬텀 실험에서는 CT의 갠트리 속도가 팬텀의 움직임보다 빠를수록 PVE와 PPE의 영향이 적어짐에 따라 영상에서 얻은 표적부피는 실제에 근접했다. 각각의 프레임의 시작점이 일치할수록 움직임의 속도와 표적의 부피와 상관관계가 높았다. 원기둥팬텀에서는 흉부팬텀의 경우와 같이 갠트리 속도가 팬텀의 움직임보다 빠를수록 영상으로부터 구한 표적부피는 실제 표적부피에 근접했다. 특히 한 slice의 두께가 2.5 mm을 고려 할 때 axial방향의 PVE, PPE, 각각의 프레임의 시작점이 일치가 되는 상태를 시뮬레이션한 길이 10 cm의 원기둥팬텀 실험에서는 영상에서 얻은 표적부피는 표적이 정지되었을 때 영상에서 얻은 부피와 거의 일치했다. 팬텀이 느리게 움직일수록, CT 갠트리의 rotation 시간이 짧을수록 영상에서 얻은 표적부피는 실제 부피에 근접했다. CT 촬영 시 각각의 프레임의 시작점이 같을수록 표적의 속도와 영상에서 의한 표적의 부피는 상관관계가 높게 나타났다. CT 갠트리의 rotation 속도를 팬텀의 움직임보다 빠르게 하고, CT 촬영시 각의 프레임의 시작점을 일치시킬수록 실제의 팬텀부피에 근접하리라고 예상된다.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.1
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• pp.167-172
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• 2006

High-yield Pinus radiate kraft pulps with various Kappa number were produced from flow-through laboratory pulping. The samples were prepared and scanned using a rapid scan photoacoustic Fourier transform infrared (PAS-FTIR) spectrometer. A partial-least-squares (PLS) model was established based on the spectral data collected at different mirror velocities. The model was used to predict the Kappa number of the pulps and its robustness was statistically evaluated. The outcomes indicate that the PLS model can be used to predict the Kappa number of Pinus radiata kraft pulps with a high degree of accuracy provided that the moving mirror velocity is ${\leq}\;0.5cm/s$.