• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.75-82
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• 2001

A dynamic interaction analysis of an adjacent surface fecundation on a layered half-space is performed in the frequency domain. A semi-analytical approach is employed to reduce the integration range of the wavenumber in the surface fundamental solution for a layered half-space in boundary element (BE) formulations. The present study then adopts a combined boundary and finite element method to analyze the dynamic behavior of a system of flexible surface foundations on an elastic homogeneous and layered half-space. Numerical examples are presented to demonstrate the accuracy of the developed method. The examples show the feasibility of an extended application fur the complicated dynamic interaction of foundations on layered media.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2009년도 학술대회 초록집
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• pp.139-143
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• 2009

• 비파괴검사학회지
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• 제9권2호
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• pp.25-36
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• 1989

This essay is a general review of the application of ultrasonic NDE techniques to the performance assessment and characterization of composite materials. A brief review of ultrasonic input-output characterization of a composite plate by shear waves is presented. A theoretical development of ultrasonic wave propagation in isotropic and anisotropic media excited, respectively, by a circular transducer and an oscillatory point source is summarized. Some experimental results are described in which ultrasonic velocity and attenuation measurements give insight into material degradation of fatigued composite laminates. Ultrasonic determination of the elastic constants of a composite plate and an experimental attempt at ultrasonic testing of an isotropic plate containing a crack are also included. A recent effort for the characterization of viscoelastic materials using the ultrasonic NDE technique is outlined. Finally, the reliability of ultrasonic NDE is briefly touched upon.

• Interaction and multiscale mechanics
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• 제6권1호
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• pp.1-14
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• 2013

The aim of this paper is to study the propagation of torsional surface waves in non-homogeneous isotropic layer of finite thickness placed over a homogeneous viscoelastic half-space, when both density and rigidity of the non-homogeneous medium are assumed to vary exponentially with depth. The frequency equations are obtained by using simple method of separation of variables. Further, it is seen that when viscoelastic parameter and non-homogeneity parameter is neglected, the dispersion equation gives the dispersion equations of Love waves in homogeneous, elastic and isotropic layer placed over homogeneous viscoelastic medium. The problem has been solved numerically and the effects of various inhomogeneities of the medium on torsional waves have been illustrated graphically.

• 대한토목학회논문집
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• 제11권3호
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• pp.47-58
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• 1991

본 논문에서는 무한요소를 이용한 지반-구조물 상호작용 해석에 대하여 연구하였다. 적층지반(Layered Soil)과 같이 여러 가지 응력파가 동시에 전파되는 탄성지반의 외부영역을 효과적으로 모형화할 수 있는 동적무한요소를 개발하였으며, 요소행렬 구성시 수반되는 무한대 방향으로의 적분을 효과적으로 수행하기 위하여 Gauss-Laguerre 적분방법을 기초로 하여 새로이 고안된 적분방법을 제시하였다. 이 방법의 타당성은 반무한 탄성지반과 적층된 반무한 탄성지반 위에 놓여 있는 원형강판의 임피던스(Impedance) 함수를 구하여 해석적으로 구한 값들과 비교함으로써 검토하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.25-32
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• 2006

We present a imaging method of seismic sources by time reversal propagation of seismic waves. Time-reversal wave propagation is actively used in medical imaging, non destructive testing and waveform tomography. Time-reversal wave propagation is based on the time-reversal invariance and the spatial reciprocity of the wave equation. A signal is recorded by an array of receivers, time-reversed and then back-propagated into the medium. The time-reversed signal propagates back into the same medium and the energy refocuses back at the source location. The increasing power of computers and numerical methods makes it possible to simulate more accurately the propagation of seismic waves in heterogenous media. In this work, a staggered-grid finite-difference solution of the elastic wave equation is employed for the wave propagation simulation. With numerical experiments, we show that the time-reversal imaging will enable us to explore the spatio-temporal history of complex earthquake.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.495-506
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• 2012

An elasto-dynamic model for pile-soil-pile interaction together with a simple plate model is used in this study to assess the effect of flexible foundation slabs on the dynamic response of pile groups. To this end, different pile configurations with various slab thicknessesare considered in two soil media with low and high elastic moduli. The analyses include dynamic impedances and seismic responses of pile-group foundations. The presented results indicate that the stiffness and damping of pile foundations increase with thickness of the foundation slab; however, the results approach those for rigid slab as the slab thickness approaches twice the pile diameter for the cases considered in this study. The results also reveal that pile foundations with flexible slabs may amplify the earthquake motions by as much as 10 percent in the low to intermediate frequency ranges.

• 대한한방내과학회지
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• 제19권2호
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• pp.392-410
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• 1998

In order to investigate the effect of Alismatis Lhizoma on hyperlipidemia, experimental studies were performed on hyperlipidemia rats. Hyperlipidemia model (controll group) was induced by 1% cholesterol fed-diet for 8 weeks. Sample I group fed with 1% cholesterol and 4% Alismatis Lhizoma diet for 8 weeks. Sample II group fed with 1% cholesterol and 8% Alismatis Lhizoma diet for 8 weeks. The contents of serum total cholesterol, triglyceride, free fatty acid, phospholipid, HDL-cholesterol and LDL-cholesterol were measured, and fat accumulation in liver and the change of elastic and collagenous fiber in aortic wall were observed. The results were summurized as follows ; 1. The content of total cholesterol in the serum compared with control group tended to be decreased in sample group, and then sample I group showed a significant value. 2. The content of triglyceride in the serum compared with control group tended to be decreased in sample group, and then sample I group showed a significant value. 3. The content of free fat acid in the serum compared with control group tended to be decreased in sample group, but did not show a significance. 4. The content of phospholipid in the serum compared with control group tended to be decreased in sample group, and then sample I group showed a significant value. 5. The content of HDL-cholesterol in the serum compared with control group tended to be increased in sample group, and then sample II group showed a significant value. 6. The content of LDL-cholesterol in the serum compared with control group tended to be decreased in sample group, and then sample I group showed a significant value. 7. The lipophagy in liver compared with control group tended to be repressed in sample group. 8. The change of elastic and collagenous fiber lesion in tunica media of aortic wall, compared with control group tended to be repressed in sample group. According to the above results, it is assumed that Alismatis Lhizoma has a valid effect on hyperlipidemia. And yet, it needs to make further researches that sample I group showed more significant value than sample II group.

• 대한한방내과학회지
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• 제19권2호
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• pp.347-366
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• 1998

In order to investigate the effect of Lycii Radicis Cortex on hyperlipidemia, experimental studies were performed on hyperlipidemia rats. Hyperlipidemia model (controll group) was induced by 1% cholesterol fed-diet for 8 weeks. Sample I group fed with 1% cholesterol and 4% Lycii Radicis Cortex diet for 8 weeks. Sample II group fed with 1% cholesterol and 8% Lycii Radicis Cortex diet for 8 weeks. The contents of serum total cholesterol, triglyceride, free fatty acid, phospholipid, HDL-cholesterol and LDL-cholesterol were measured, and fat accumulation in liver and the change of elastic and collagenous fiber in aortic wall were observed. The results were summurized as follows ; 1. The content of total cholesterol in the serum compared with control group tended to be decreased in sample group, but did not show a significance. 2. The content of triglyceride in the serum compared with control group tended to be decreased in sample group, and then sample II group showed a significant value. 3. The content of free fat acid in the serum compared with control group tended to be decreased in sample group, and then sample II group showed a significant value. 4. The content of phospholipid in the serum compared with control group tended to be decreased in sample group, but did not show a significance. 5. The content of HDL-cholesterol in the serum compared with control group tended to be increased in sample group, and then sample I group showed a significant value. 6. The content of LDL-cholesterol in the serum compared with control group tended to be decreased in sample group, and then sample I group showed a significant value. 7. The lipophagy in liver compared with control group tended to be decreased in sample group. 8. The change of elastic and collagenous fiber lesion in tunica media of aortic wall, compared with control group tended to be decreased in sample group. According to the above results, it is assumed that Lycii Radicis Cortex has a valid effect on hyperlipidemia. Therefore, it seems to be applicable to the diseases related to hyperlipidemia.

• 비파괴검사학회지
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• 제20권2호
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• pp.130-137
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• 2000

대표적인 비파괴 평가 기술들 중의 하나인 초음파응용 기술은 각종 구조물에 존재하는 내부결함에 의한 산란신호를 통해 건전성을 평가하는 기법이므로 결함의 신뢰성 높은 정량적 평가를 위해서는 결함으로부터의 초음파 산란신호특성에 대한 기본적 이해가 필수적이며 따라서 이를 위한 모델링 수치해석 연구가 요구된다. 모델링 기법들은 비파괴 평가기술에 있어서 중요한 역할을 하고 있고 많은 모델링 기법들이 결함의 탄성파 산란문제를 해석하기 위하여 사용되어 오고 있다. 본 연구에서는 다양한 수치기법들 중 탄성파 산란문제 해석에 있어 많은 장점을 가지고 있는 동탄성 경계요소법에 대하여 자세히 소개하고, 응용 예로서 경계요소법을 이용한 기공결함의 수평횡파 산란장 해석과 표면균열의 표면파 산란장 해석을 소개한다.