• Proceedings of the KSME Conference
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• 2003.04a
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• pp.774-779
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• 2003

Arc-shaped line array slits have been used for the laser generation of focused Lamb waves. The spatially expanded Nd:YAG pulse laser was illuminated through the arc-shaped line array slit on the surface of a sample plate to generate the Lamb waves of the same pattern as the slit. Then the generated Lamb waves were focused at the point of which distance from the slit position is dependent on the curvature of slit arc. The proposed method showed better spatial resolution than the conventional linear array slit in the detection of laser machined linear defect and drill machined circular defect on aluminum plates of 1mm thickness.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.233-239
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• 1999

The feasibility of an ultrasonic technique using a pulse-echo method of normal-incident compressional waves was evaluated for its sensitivity to the worn surface and near surface damage due to wear. Worn surfaces were generated at various oscillation frequency under a given load and amplitude and these surface were in situ monitored using a ultrasonic wave detection system. Analysis of the ultrasonic waves received from the worn surface revealed a close relationship between the surface and near-surface damage and the maximum echo-amplitude of the compressional waves. The ultrasonic technique was successful in assessing the level of severity of the worn surface in real time during the wear process. It is also shown that the wear depth can be easily measured by the calculation of change of the specimen thickness based on the wave speed measured for the specimen medium.

• Tribology and Lubricants
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• v.16 no.5
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• pp.351-356
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• 2000

The feasibility of an ultrasonic technique using a pulse-echo method of normal-incident compressional waves was evaluated for its sensitivity to the worn surface and near surface damage due to wear. Worn surfaces were generated at various oscillation frequency under a given load and amplitude and these surface were in situ monitored using a ultrasonic wave detection system. Analysis of the ultrasonic waves received from the worn surface revealed a close relationship between the surface and near-surface damage and the maximum echo-amplitude of the compressional waves. The ultrasonic technique was successful in assessing the level of severity of the worn surface in real time during the wear process. It is also shown that the wear depth can be easily measured by the calculation of change of the specimen thickness based on the wave speed measured for the specimen medium.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.6
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• pp.1670-1675
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• 2007

The pulse diagnosis studies reported to date has mainly been performed to clinically reveal the pulse wave characteristics according to the specific diseases, whereas no attempts have been made to study the effects on the pulse wave characteristics of the daily activities such as taking meals, exercise, and sleep, etc. This work reports the effect of feeding stimulus on the healthy subjects on the pulse wave pattern which has quantitatively been analyzed using the objective model for the pulse diagnosis in oriental medicine. The pulse waves right before/after the meal and 30 minutes after the meal were measured using the pulse analyzing equipment (3D-Mac, Daeyo Medi, Korea) and at the same time oriental medicine doctors' diagnoses were given. The pulse parameters obtained from the equipment and clinical records on the subjects were statistically processed and the variables showing statistically significant differences were analyzed. The results indicate that the pulse pressure, the pulse rate, and the respiratory rate increase while the blood pressure decreases after the meal. For the floating/sinking and the deficient/excess coefficients characterizing the pulse states described in the oriental medicine, the floating/sinking coefficients were observed to decrease whereas the deficiency/excess coefficients increase after the meal. The results indicates that besides the standard bio-indicators like blood pressure and respiratory rate, etc., the pulse wave characterization in terms of the pulse classifications in the oriental medicine using the floating/sinking, deficient/excess pulse states provide an important piece of biomedical information.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.244-245
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• 2002

1 picosecond 보다 짧은 펄스길이를 갖는 초단파길이 레이저 펄스 (Ultrashort laser pulse, USLP)를 이용한 물질의 절제 (ablation)는 여타 nanosecond 영역의 레이저 절제와 많은 차이를 보인다(1). USLP는 순간 파워가 매우 높기 때문에 직접적으로 물질의 원자를 분리시켜 자유전자를 형성한다 이들 자유전자는 일반 선형흡수체 (linear absorbing chromophore)보다 흡수계수가 몇 십 배로 높아 대부분의 펄스 에너지가 표면 100-200 m 이내의 극히 작은 지역에 밀집되게 된다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.42-43
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• 2003

The nonlinear three-wave interaction is an interesting topic having various applications in nonlinear optics, hydrodynamics, acoustic waves, and plasma physics. The resonant interaction between two laser pulses and a plasma wave plays important roles in plasma heating, laser reflection in the inertial confinement fusion (ICF), plasma wakefield generation, and ultra-intense laser pulse amplification and pulse compression using stimulated Raman backscattering (RBS). (omitted)

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.6
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• pp.381-388
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• 2015

The speed and oscillation directions of elastic waves propagating in the [ab0] direction of a silicon single crystal were obtained by solving Christoffel's equation. It was found that the quasi waves propagate in the off-principal axis, and hence, the directions of the phase and group velocities are not the same. The maximum deviation of the two directions was $7.2^{\circ}$. Two modes of the pure transverse waves propagate in the [110] direction with different speeds, and hence, two peaks were observed in the pulse echo signal. The amplitude ratio of the two peaks was dependent on the initial oscillating direction of the incident wave. The pure and quasi-transverse waves propagate in the [210] direction, and the oscillation directions of these waves are perpendicular to each other. The skewing angle of the quasi wave was calculated as $7.14^{\circ}$, and it was measured as $9.76^{\circ}$. The amplitude decomposition in the [210] direction was similar to that in the [110] direction, since the oscillation directions of these waves are perpendicular to each other. These results offer useful information in measuring the crystal orientation of the silicon single crystal.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.118-122
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• 2003

Pulse tube refrigerator, which has no moving parts at its cold section, is attractive fer obtaining higher reliability, simpler construction and lower vibration than Stilting refrigerator or Gifford-McMahon refrigerator. Commonly used means to achieve optimum performance of Stilting type pulse tube refrigerator is an inertance tube. The use of inertance tube is a simple way to generate the phase shift needed to make pulse tube refrigerator operate as efficiently as Stilting refrigerator. In this study, the performance of the inertance pulse tube refrigerator (IPTR) was investigated experimentally. An in-line type IPTR consists of a linear compressor with two reciprocating pistons driven by linear motors, which makes pressure waves, a regenerator a pulse tube with the inertance tube, and a reservoir, The dynamic pressures (the compressor, pulse tube, reservior) and the temperature at the cold heat exchanger are measured to explore the dependence of the inertance tube on the performance of the IPTR. The experimental results show the dependency of cool-down characteristics, no-load temperature and amplitude of the pressures on the length and diameter of the inertance tube.

• Journal of Navigation and Port Research
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• v.29 no.4
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• pp.341-347
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• 2005

A unique technique to extract the phase in time domain is proposed in order to measure the time parameters such as speed and depth by transmitting sound and electric waves. In the signal analysis processing, the phase of pulse signal can be transformed and digitalized with local data in real time without the effect of direct current bias and Nyquist limits. This method is sensitive to base frequency of pulse signal with high spacial resolution and is effective to compare two signals which have different forms. It is expected that the phase analysis technique will be applied to the measurement of the speed and depth accurately by ultrasonic pulse signal in water.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.5
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• pp.65-70
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• 2004

In this paper, we present a new methodology to analyze the characteristic of artery by using 4 channels photoplethysmograpy. The proposed parameter is a time difference of pulse transit time(PTT) between Pulse waves at finger site and at toe site. To verify the usefulness of the developed system volume pulse waves on 4 sites were measured simultaneously for total 51 normal subjects (male 26 and female 25) aged from 9 to 83 years old. And then correlations between the analysis parameters and age were evaluated by using linear regression analysis method. As the result of experiments, the change of parameter was found according to ages. The result of regression analysis about relationships between the parameter and ages for n=51, the coefficient of correlation of non-normalized data has 0.79770 in left side and 0.80599 in right side and the coefficient of correlation of normalized data by height has 0.81345 in left side and 0.81605 in right side.