• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.29-33
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• 1993

펄스레이저를 고체표면에 조사하면 광-음향효과에 의해 입사지점에서 음향파원이 형성되고 음향파원의 형태와 재료의 특성에 따라 여러 유형의 종파, 횡파 및 표면파의 음향에너지가 발생된다. 본 연구에서는 열탄성영역과 플라스마영역에서 종파와 횡파의 변위파형을 해석하여 모의실험을 수행하였다. 실험에서는 KrF엑시머레이저를 탄소강, 알루미늄, 황동에 조사하여 플라스마영역에서의 광-음향신호를 검출하였으며 이론과 비교하여 분석하였다.

• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.1-9
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• 1999

A study has been made on the fabrication of a dual mode(a longitudinal and shear mode) ultrasonic sensor using a single PZT piezoelectric ceramic element. We investigated the mechanism of the dual mode sensor that generated both of the longitudinal and the shear waves simultaneously with the single PZT element. Through the analysis of analytic wave propagation equations, all the possible crystal cuts have been examined to determine appropriate Euler transformation angles for efficient excitations of the dual modes. We studied the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves of equal strength. Experimental examination of the waveform on a delay line(STS303) setup confirms that the ultrasonic sensor can transmit and detect both longitudinal and shear waves simultaneously.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.4
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• pp.234-240
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• 1997

We studied the resolution enhancement of a novel scanning laser acoustic microscope (SLAM) using transverse waves. Mode conversion of the ultrasonic wave takes place at the liquid-solid interface and some energy of the insonifying longitudinal waves in the water will convert to transverse wave energy within the solid specimen. The resolution of SLAM depends on the size of detecting laser spot and the wavelength of the insonifying ultrasonic waves. Science the wavelength of the transverse wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution by using transverse waves. In order to operate SLAM in the transverse wave mode, we made wedge for changing the incident angle. Our experimental results with model 2140 SLAM and an aluminum specimen showed higher contrast of the SLAM image in the transverse wave mode than that in the longitudinal wave mode.

• Computational Structural Engineering
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• v.8 no.1
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• pp.137-146
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• 1995

Structural stress under shock or impact load is varied with the lapse of time and the structural stress is called stress wave. Propagating longitudinal stress wave is studied in a 2-dimensional plate. A finite element program for elastic stress wave propagation is developed in order to investigate the shape of stress field at time increment. The longitudinal stress wave is generated by unit step function. According to the finite element analysis results, the longitudinal stress wave propagates to the similar direction of impact load and the front of stress wave propagates with the same speed as analytic solution and the shape of stress field is similar to that of analytic solution. The shear wave is occurred after the longitudinal stress wave and declined at an angle of 45 degrees compared with longitudinal stress wave and the speed of shear wave is about a half of the longitudinal stress wave. The intensity of shear wave is larger than that of longitudinal stress wave.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.793-799
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• 2015

In this research, we study the propagation of longitudinal and transverse waves through a metal rod including a liquid layer using computational and experimental analyses. The propagation characteristics of longitudinal and transverse waves obtained by the computational and experimental analyses were consistent with the wave propagation theory for both cases, that is, the homogeneous metal rod and the metal rod including a liquid layer. The fluid-structure interaction modeling technique developed for the computational wave propagation analysis in this research can be applied to the more complex structures including solid-liquid interfaces.

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.51-58
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• 2017

The purpose of this study was to quantitatively evaluate the state of rocks in load steps by using the low-frequency ultrasonic flaw detection method. The initial Vp-velocities measured with a CND tester were in the order of Z-axis < X-axis < Y-axis, with 1687.5 m/s along the X-axis, 1690.7 m/s along the Y-axis, 1548.3 m/s along the Z-axis, and an average of 1642.2 m/s. The overall average of the Q vlaues, measured with a Silver Schmidt hammer, was 62.6, which corresponds to a uniaxial compressive strength of ~105 MPa. The Vp-velocity, measured with a low-frequency ultrasonic flaw detector at load steps of 50%, 60%, 70%, and 80%, typically decreases in the order of X-axis < Y-axis < Z-axis with increasing load steps. This oder contrasts with that of the initial Vp-velocities. As the load step increases the factors that reduce the Vp-velocity in the X-axis direction are more influential than those in the Y-axis or Z-axis directions. This indicates that the initial state of rocks can vary and is dependent on the stress state.

• Journal of Korean Orthopaedic Sports Medicine
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• v.9 no.2
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• pp.91-97
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• 2010

Purpose: The purpose of this study was to evaluate the results of treatment for longitudinal meniscal tear in ACL rupture patients by clinical evaluation and $2^{nd}$ look arthroscopy. Materials and Methods: Among the patients who underwent surgery due to ACL rupture and longitudinal meniscal tear between 2002~2009, 32 patients were selected for the study. The patients were devided into three groups; group 1 had repair, group 2 had partial menisectomy due to impossible to repair, group 3 had conservative treatment due to stable meniscus. Comparative retrospective analysis was applied with KT 1000 arthrometer, Lysolm' score, Tegner activity score, IKDC subjective score, and $2^{nd}$ look arthroscopy. Results: Lysolm' score, Tegner activity score, IKDC subjective score showed no statistical difference in all three groups. KT-1000 side to side difference improved from 6.2, 6.15, 6.38 before surgery to 2.56, 2.49, 2.58 after surgery in group 1, 2, and 3, respectively. In group 1, second-look arthroscopy revealed complete healing in 12 patients, incomplete healing without any clinical symptoms in 2, and healing failure in 1. In group 2, second-look arthroscopy showed partial regeneration on margin of meniscectomy. In group 3, second-look arthroscopy revealed complete healing in 2 patients, while 4 showed incomplete healing so that have repaired. Conclusion: In the study, the outcome was better when the stable longitudinal meniscal tear on posterior horn with ACL rupture had active treatment.

• (The)Study of the Eastern Classic
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• no.59
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• pp.325-357
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• 2015

Max Weber claimed that the clans as a self-sufficient community in traditional China had limited market development. His statement can be applied to the lineage groups of $Chos{\breve{o}}n$ dynasty, however, it also could be criticized as an example of oversimplifying clans. Starting from this question, in this article, I examined the lineage movement of the P'ap'yong Yun's Nojongp'a branch. Through this research, I tried to investigate the reality of the lineage group communities of $Chos{\breve{o}}n$. My issues are following. First, the Nojongp'a clan promoted the solidarity movement of their lineage in the name of practicing human morality, which belonged to their family learning. Second, the Nojongp'a clan made preparations for their own 'righteous rice fields and grains', through which they tried to establish the base structure for the clan activities. This, however, had its own limitations in aiding the starved suffering from famines and did not last long. Third, the lineage could not function as a community for living that was actively involved in the reproduction of life, and was not an exclusive self-sufficient community, either.

• Journal of KSNVE
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• v.8 no.6
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• pp.1172-1180
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• 1998

Elastic wave scattering from an acoustically rigid or soft object is studied and compared with the acoustic wave scattering. The behavior of phases as well as magnitudes of partial waves and their total summation of scattered wave are numerically analyzed and discussed. The effect of mode conversion, which occurs between longitudinal and transversal waves in elastic wave scattering. on the magnitudes and phases of scattered waves is identified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.928-933
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• 2007

In this research, we investigated active vibration control based on wave-viewpoint using the longitudinal wave separation method. The control strategy is the one of active vibration control technique for generating vibration reduced zone and uses wave information including the directivity as the cost function. In order to get the wave information from the measured values, we proposed and examined the time-domain longitudinal wave separation method proper to real time application like active vibration control. Using the proposed method, we examine the performance and feasibility of active vibration control based wave view-point through the simulation. The related experimental verification and application is going to be expected in a near future.