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속도-응력 변분식을 이용한 3차원 SEM 탄성파 수치 모사에 대한 ADE-PML경계조건의 적용
조창수 ( Chang Soo Cho ),손민경 ( Min Kyung Son ) 한국지구물리·물리탐사학회 2012 지구물리와 물리탐사 Vol.15 No.2
Various numerical methods in simulation of seismic wave propagation have been developed. Recently an innovative numerical method called as the Spectral Element Method (SEM) has been developed and used in wave propagation in 3-D elastic media. The SEM that easily implements the free surface of topography combines the flexibility of a finite element method with the accuracy of a spectral method. It is generally used a weak formulation of the equation of motion which are solved on a mesh of hexahedral elements based on the Gauss-Lobatto-Legendre integration rule. Variational formulations of velocity-stress motion are newly modified in order to implement ADE-PML (Auxiliary Differential Equation of Perfectly Matched Layer) in wave propagation in 3-D elastic media, because a general weak formulation has a difficulty in adapting CFS (Complex Frequency Shifted) PML (Perfectly Matched Layer). SEM of Velocity-Stress motion having ADE-PML that is very efficient in absorbing waves reflected from finite boundary is verified with simulation of 1-D and 3-D wave propagation.
Anti-bacterial effect of Dendropanax morbifera L. Leaf extract against Porphyromonas gingivalis
조창수(Chang-Soo Cho),황혜정(Hye-Jung Hwang),조영인(Young-In Cho),손송이(Song-Ee Son),김석(Suk Kim),이후장(Hu-Jang Lee) 한국예방수의학회 2021 예방수의학회지 Vol.45 No.4
The present study is designed to investigate the antibacterial effect of the hot-water and various ethanol extracts from the leaves of Dendropanax morbifera L. (DML) against Porphyromonas gingivalis (P. gingivalsis). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 30, 50 and 70% ethanol extract of DML against P. gingivalis decreased in a concentration-dependent manner. However, MIC and MBC of hot-water and 30% ethanol extract against P. gingivalis were the same as 3.13 and 6.25 mg/mL, respectively. In the bacterial growth inhibition test, the growth of P. gingivalis in the group treated with MBC and 2×MBC of DML hot-water extract was statistically significantly decreased from 6 h after incubation compared to the control group (p<0.001). From the results portrayed above, aqueous extract from DML at the concentration of 6.25 mg/mL can be usefully used to suppress infection of P. gingivalis, a major causative agent of periodontal disease.
지진기록계 보정과 힐버트 변환 적용에 의한 센서 주파수 응답 계산
조창수 ( Chang Soo Cho ) 한국지구물리·물리탐사학회 2016 지구물리와 물리탐사 Vol.19 No.2
The validation of performance test for newly developed or old-used sensor is very important in the earthquake monitoring and seismology using earthquake data. Especially the frequency response of the sensor is mainly used to correct the earthquake data. The technique of the calculation of phase and amplitude with Hilbert transformation for earthquake data that is filtered with band limited frequency in time domain is applied to calculate the frequency response of the sensor. This technique was tested for the acceleration sensors, CMG-5T of 1g and 2g installed on the vibration table at the laboratory and we could obtain satisfactory result. Tohoku large earthquake in 2011 observed at the station SNU that has accelerometer, ES-T and seismometer, STS-2 operated by KIGAM was also used to test the field data applicability. We could successfully get the low frequency response of broad band sensor, STS-2. The technique by using band limited frequency filter and Hilbert transformation showed the superior frequency response to the frequency spectrum ratio method for noisy part in data.