• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.391-394
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• 1999

제작되어진 LFB PVDF 초음파트랜스듀서를 이용하여 누설탄성표면파(Leaky Surface Acoustic Wave : LSAW)측정을 하였다. 시료로서는 $SiO_2$, Al, Cu등을 사용하였고, 측정방법으로써는 초점면에 위치한 시료를 트랜스듀서 쪽으로 접근시켰을 때 LSAW가 트랜스듀서의 중심축을 통과한 후 시료표면에서 반사되어오는 종파와 분리되어지는 현상을 이용하였다. 실험결과는 Campbell and Jones의 이론에 의한 해석결과와 비교 분석하였는데 매우 잘 일치됨을 알 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.17 no.1
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• pp.17-23
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• 1998

본 논문은 높은 전기 역학적 결합 계수를 갖고 있는 64°LiNbO3기판에 leaky표면 탄성파를 이용하여 종 결합 형태의 대역이 넓고, 손실이 적은 필터의 제작을 위한 연구이다. 이 기판 위에 1차 모드와 2차 모드를 이용하고 입력 IDT와 출력IDT사이의 거리, 그리고 전 극의 두께 및 전극 개수를 적절하게 조절하므로서 통과 대역 폭이 15MHz이상, 삽입 손실 1.28dB 및 저지대역 50dB인 특성을 얻을 수 있었다. 아울러, 전극의 두께는 파장과의 비를 고려해 2500Å으로 할 때 최적의 결과를 얻을 수 있었으며, IDT와 IDT 사이의 거리는 0.25 λ, IDT와 반사기 사이의 거리는 0.46λ로 할 때 가장 이상적인 결과를 얻을 수 있었다. 제 작한 필터는 329.3MHz의 중심 주파수를 갖고 있는 소자로서 소형이고 낮은 삽입 손실을 갖 고 있으며, 무선 호출기에 사용 가능하다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.183-183
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• 2010

최근 고밀도 플라즈마(High Density Plasma, HDP)를 이용하여 STI (shallow trench Isolation) 공정에 사용하기 위한 높은 종횡비를 가지는 갭을 공극 없이 절연물질로 채우는 HDP CVD 법이 개발되어 사용되고 있으며, HDP 공정에서는 그 증착 과정 중에 스퍼터링(Sputtering)에 의한 식각이 동시에 발생하기 때문에 높은 종횡비를 가지는 갭을 공극 없이 채우는 것이 가능하게 되었다. 이러한 특성을 이용하여 HDP CVD 공정은 주로 STI 와 알루미늄 배선간의 갭을 실리콘 산화막 ($SiO_2$)의 절연막으로 채우는 데 주로 사용되고 있다. 이 논문에서는 새로 개발된 HDP CVD 법을 적용하여 300 mm Si 웨이퍼에 $SiO_2$ 절연막을 증착하여 웨이퍼의 중심과 가장자리의 deposition uniformity를 nano-indenter system을 이용하여 연구하였으며, 그 결과 300 mm 웨이퍼에서 균일한 탄성계수 값이 측정되었다. 또한 HDP CVD로 제작된 SiO2 박막의 탄성계수 값이 99 - 107 GPa로 측정되어 기존 PECVD-$SiO_2$ 박막보다 약 10 - 20% 향상된 것을 확인하였다.

• Journal of KSNVE
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• v.9 no.5
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• pp.984-990
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• 1999

This paper presents the geometrical methodology to decouple the vibration modes of an elastically supported single rigid body in three-dimensional space. It is shown that the vibration modes can be decoupled by placing the center of elasticity at suitable locations and thereby yielding the plane(s) of symmetry for the given stiffness matrix. The developed methodology has been applied to the actuator supported by the 4-wire suspensions in optical discs, which has one plane of symmetry. For this numerical example, the axes of vibrations have been computed and illustrated with the natural frequencies. The forced response at the objective lens is represented and its geometrical interpretation has been explained as the mutual moment between the axis of vibration and the applied wrench times the line coordinates of the axis of vibration.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.93-105
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• 2001

해성토층(풍화토 및 모래질 충적토가 암반 위에 쌓인) 위에 준설매립된 수도권 해안매립지역에서 원형의 대심도 굴착공사로 인하여 발생하는 지중연속벽의 수평변위에 대한 현장계측을 중심으로 연구를 수행하였다. 현장측정으로는 지중연속벽의 8방향에서 벽체수평변위와 철근응력, 토압, 간극수압 등이 측정되었고, 정확한 측정결과를 얻기 위하여 합리적인 해석 및 보정방법이 연구되었다. 현장측정결과 굴착시공단계에 따라서 벽체수평변위가 증가하였으며, 일정깊이에 존재하는 점토층을 굴착함으로써 간극수압의 급격한 변화가 측정되었다. 한편, 굴착전후의 구속압감소에 따른 지반물성치의 변화를 정리하였다. 굴착전후의 탄성계수는 일정깊이까지 상당한 정도로 감소됨을 알 수 있었고 굴착전후 여러 가지 시험방법에 따른 탄성계수의 차이들을 비교하였다.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.759-767
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• 2000

In this study, the time dependent internal stress changes of a Concrete Filled Steel Tube(CFT) column during a fire test were quantitatively analyzed. The strain ratio of a CFT column on the different loads was measured by tensile strength tests in terms of yield strength, tensile strength average extensibility and elasticity modulus. To understand the internal material properties change of concrete in CFT column damaged due to a fire, the compressive strength and elastic modulus tests were measured on a core sample from the center of the steel tube after the fire test. The elastic modulus test measured the strain from the stress. To determine the fire temperature of the test material, a differential thermal analysis was done. From the tested result, the gained data were conducted and an analysis method was suggested. The purpose of this work is to suggest a basic data for structure regulation enactments of the internal fire design of CFT.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.174-183
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• 2022

Acoustic radiation from a submerged elastic shell with an internal fluid surrounded by the bubble layer is studied with the modal theory. An omni-directional point source located on the center of the internal fluid is used as acoustic noise source. The unknown coefficients of modal solutions are solved using the interface conditions between media. To preserve the stability of the modal solution over wide frequency ranges, the scaled technique of modal solution is used. The bubble layer is modeled with four kinds of bubble distribution; uni-modal distribution, uniform distribution, normal distribution, and power-law distribution, based on the effective medium theory of Commander and Prosperetti. For each bubble distribution, the insertion losses are mainly calculated for the frequency. In addition, the numerical simulations are performed depending in the bubble void fraction, the material property of elastic shell, and the gap between the bubble layer and the elastic shell.

• Journal of Conservation Science
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• v.20
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• pp.43-54
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• 2007

The Muryangsa temple five-storied stone pagoda (Treasure No. 185) was geographically located in the area of the Baekje Kingdom. The architectural style of the Muryangsa temple five-storied stone pagoda is the pagoda at the early Goryeo Dynasty that was succeeded technique of the Baekje Kingdom and form of the Shilla Kingdom. Because this pagoda is located outside during old time that it received serious petrological and biological weathering in rock blocks and occurred the center subsidence in the upper capstone. This study executed ground stability interpretation in order to know what central subsidence in the upper capstone occurred for soft ground. The ground stability interpretation used seismic survey, electrical resistivity survey and GPR survey by non-destructive method. As the result, the ground appeared in the condition which is good. Specially, high resistance zone appeared from electric resistivity survey which come to seem with ground reinforcement harden. Consequently, central subsidence condition in the upper capstone is not by the instability of ground, and is judged with the thing by the structure instability in rock blocks over the upper capstone. This will be applied basic data with the long-term monitoring or preservation countermeasure of the pagoda.

• Geophysics and Geophysical Exploration
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• v.14 no.2
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• pp.127-132
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• 2011

We acquired and interpreted more than 650 km of high-resolution seismic reflection profiles in the Hupo Basin, offshore east coast of Korea at $37^{\circ}N$ in the East Sea (Japan Sea) to image shallow and basement deformation. The seismic profiles reveal that the main depocenter of the Hupo Basin in the study area is bounded by the large offset Hupo Fault on the east and an antithetic fault on the west; however, the antithetic fault is much smaller both in horizontal extension and in vertical displacement than the Hupo Fault. Sediment infill in the Hupo Basin consists of syn-rift (late Oligocene. early Miocene) and post-rift (middle Miocene.Holocene) units. The Hupo Fault and other faults newly defined in the Hupo Basin strike dominantly north and show a sense of normal displacement. Considering that the East Sea has been subjected to compression since the middle Miocene, we interpret that these normal faults were created during continental rifting in late Oligocene to early Miocene times. We suggest that the current ENE direction of maximum principal compressive stress observed in and around the Korean peninsula associated with the motion of the Amurian Plate induces the faults in the Hupo Basin to have reverse and right-lateral, strike-slip motion, when reactivated. A recent earthquake positioned on the Hupo Fault indicates that in the study area and possibly further in the eastern Korean margin, earthquakes would occur on the faults created during continental rifting in the Tertiary.

• Geophysics and Geophysical Exploration
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• v.22 no.4
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• pp.177-185
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• 2019

Ground roll is a surface wave which is usually observed in the land seismic data. It is one of the typical coherent noise. During the reflection data processing, ground roll is removed because it is considered as noise. This removal process often causes the loss of reflection signals if the ground roll overlaps reflection signals. In this study, we look over Karhunen-Loeve Transform (KLT) and analyze its effects to suppress the ground roll appropriately while reducing the reflection loss. Numerical tests in homogeneous elastic media show that the ground roll has been properly rejected. However, the field data application reveals that there is no significant suppression of ground roll when compared to band-pass filtering. This can be considered that it is hard to calculate horizontally aligned gathers in the field data because the ground roll contains a wide range of frequency bands. On the contrary, the result of singular value decomposition (SVD) filtering shows that the ground roll has been significantly reduced. It is thought that the SVD filtering performs better in the ground roll suppression than KLT because it is easy to calculate the horizontally aligned gathers in the SVD filtering.