• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.700-708
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• 2014

Jet engine modulation(JEM) is a frequency modulation phenomenon of the radar signal induced by electromagnetic scattering from a rotating jet engine turbine. Although JEM can be used as a representative radar target recognition method by providing unique information on the target, its recognition performance may be degraded in the observation range of weakly present JEM. Hence, this paper presents a method for extracting the JEM component by decomposing the radar signal into intrisic mode functions(IMFs) via complex empirical mode decomposition(CEMD) and by combining them based on signal eccentricity. Its application to various signals demonstrated that the proposed method improved the clarity of JEM analysis and could extend the effective observation range of JEM.

• Journal of Applied Biological Chemistry
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• v.62 no.4
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• pp.399-406
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• 2019

The roots of Scrophularia buergeriana were extracted with 80% aqueous Methanol and the concentrates were partitioned into EtOAc, n-BuOH, and H₂O fractions. The repeated silica gel or octadecyl SiO₂column, and medium pressure liquid chromatographies for the n-BuOH fraction led to isolation of phenylethanoid glycosides and iridoid glycosides. The chemical structures of these compounds were determined as harpagoside (1), angoroside C (2), aucubin (3) and acetoside (4) based on spectroscopic analyses including nuclear magnetic resonance and MS. A simple and efficient HPLC with UV detection method for the simultaneous determination of the four compounds (1-4) has been developed and applied to their content determination in the S. buergeriana. The roots were extracted by 80% methanol, and the contents of 1, 2, 3, and 4 were determined to 11.5, 7.6, 41.2, and 4.8 mg/g, respectively. Additionally, angoroside C (2) and acetoside (4) exhibited hepatoprotective effect against ethanol-induced hepatotoxicity in HepG2 cell line.

• Membrane Journal
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• v.8 no.3
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• pp.157-169
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• 1998

The effects of solvents (DMAc, NMP, 1,4-dioxane) and nonsolvents ($H_2O$, Methanol, n-hexane) on the morphology of 6FDA-p-TeMPD polyimide membrane, prepared by the wet phase inversion method, were studied. In the polymer/solvent/nonsolvent ternary system, the binodal curve, the coagulation value and the relative light transmission were measured, and the solubility parameter difference was calculated. The onset state and rate of liquid-liquid alemixing were predicted and the morphology of membrane was analyzed. It is found that the finger-like pores are formed within discontinuous polymer nodules when the binoclal curve is close to the polymer-solvent (P-S) axis, the coagulation value is small, the reduction of light transmission is easy to occur and the order of solubility parameter difference ($\Delta \delta_{i-j}$) is $\Delta \delta_{S-NS} > \Delta \delta_{P-NS} > \Delta \delta_{P-S}$. The dense skin with small nodules and the sponge type sublayer with macrovoid are formed in the case that the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is long and the order of $\Delta \delta_{i-j}$ is $\Delta \delta_{P-NS} >(\Delta \delta_{S-NS} < > \Delta \delta_{P-S})$. The thick layer of fine nodule coagulation and loosely grown sublayer of nodules appear when the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is very long and the order of $\Delta \delta_{i-j}$가 $\Delta \delta_{S-NS} > (\Delta \delta_{P-NS}$\lessgtr$ > (\Delta \delta_{P-NS} < >)\Delta \delta_{P-S}$ ).

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.175-182
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• 2016

In this study, we isolated aromatic compounds (lignin polymers) utilizing bacteria in humus layer of oak forest and investigated phylogenetic characteristics and correlation with major bacterial populations in the humus layer by pyrosequencing. Forty-two isolates using aromatic compounds such as p-anisic acid, benzoic acid, ferulic acid and p-coumaric acid were isolated and phylogentic analyses based on 16S rRNA gene sequences showed that the isolates belonged to the genus Rhizobium, Sphingomonas, Burkhorlderia, and Pseudomonas. Among these, Burkhorlderia species which belong to Betaproteobacteria class occupied 83% among the isolates. The bacterial populations in humus layer of oak forest were characterized by next generation pyrosequencing based on 16S rRNA gene sequences. The humus sample produced 7,862 reads, 1,821 OTUs and 6.76 variability index with 97% of significance level, respectively. Bacterial populations consist of 22 phyla and Betaproteobacteria were the major phylum consisting of 15 genera including Burkholderia, Polaromonas, Ralstoria, Zoogloea, and Variovorax. Approximately fifty percentage of them was Burkholderia. Burkholderia as the majority of population in the humus was considered to play a role in degrading lignin in humus layer of oak forest.

• Journal of Applied Biological Chemistry
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• v.61 no.4
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• pp.397-403
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• 2018

The leaves of Spiraea prunifolia were extracted with 80% aqueous MeOH and the concentrates were partitioned into EtOAc, n-BuOH, and $H_2O$ fractions. The repeated $SiO_2$ or ODS column, and medium pressure liquid chromatographies for the n-BuOH fraction led to isolation of two phenolic glucosides. The chemical structures of these compounds were determined as isosalicin (1) and crenatin (2) based on spectroscopic analyses including Nuclear magnetic resonance and MS. Extracts were analyzed using UPLC-MS/MS providing a short analysis time within 5 min using MRM technique. The concentration of crenatin was higher as 9.53 mg/g and isosalicin was lower as 0.65 mg/g. Neuroprotective effects of these compounds against hydrogen peroxide ($H_2O_2$)-induced neurotoxicity were evaluated. The results showed that exposure to $H_2O_2$ induced morphological changes, cell death and neurotoxicity in SK-N-MC cells. However, pretreatment with crenatin resulted in inhibition of morphological change, reduction of loss of cell viability and attenuation of neuronal damage. These results suggested that neuroprotective effect of crenatin isolated from S. prunifolia can be a good candidate for the development of health beneficial foods which can ameliorate the degenerative neuronal disease caused by oxidative stress.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.521-527
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• 2016

This paper is concerned with the numerical analysis of dynamic response of floating offshore wind turbine subject to underwater explosion using an effective non-reflecting technique. An infinite sea water domain was truncated into a finite domain, and the non-reflecting technique called the perfectly matched layer(PML) was applied to the boundary of truncated finite domain to absorb the inherent reflection of out-going impact wave at the boundary. The generalized transport equations that govern the inviscid compressible water flow was split into three PML equations by introducing the direction-wise absorption coefficients and state variables. The fluid-structure interaction problem that is composed of the wind turbine and the sea water flow was solved by the iterative coupled Eulerian FVM and Largangian FEM. And, the explosion-induced hydrodynamic pressure was calculated by JWL(Jones-Wilkins-Lee) equation of state. Through the numerical experiment, the hydrodynamic pressure and the structural dynamic response were investigated. It has been confirmed that the case using PML technique provides more reliable numerical results than the case without using PML technique.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.1-8
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• 2005

This paper describes a new objective methodology of seismic building damage assessment which is called Advanced Component Method(ACM). ACM is a major attempt to replace the conventional loss estimation procedure, which is based on subjective measures and the opinions of experts, with one that objectively measures both earthquake intensity and the response ol buildings. First, response of typical buildings is obtained analytically by nonlinear seismic static analysis, push-over analyses. The spectral displacement Is used as a measure of earthquake intensity in order to use Capacity Spectrum Method and the damage functions for each building component, both structural and non-structural, are developed as a function of component deformation. Examples of components Include columns, beams, floors, partitions, glazing, etc. A repair/replacement cost model is developed that maps the physical damage to monetary damage for each component. Finally, building response, component damage functions, and cost model were combined probabilistically, using Wonte Carlo simulation techniques, to develop the final damage functions for each building type. Uncertainties in building response resulting from variability in material properties and load assumptions were incorporated in the Latin Hypercube sampling technique. The paper also presents and compares ACM and conventional building loss estimation based on historical damage data and reported loss data.

• Journal of Korea Soil Environment Society
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• v.1 no.1
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• pp.89-102
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• 1996

An integrated model is presented to describe underground flow and mass transport, using a multicomponent multiphase approach. The comprehensive governing equation is derived considering mass and force balances of chemical species over four phases(water, oil, air, and soil) in a schematic elementary volume. Compact and systemati notations of relevant variables and equations are introduced to facilitate the inclusion of complex migration and transformation processes, and variable spatial dimensions. The resulting nonlinear system is solved by a multidimensional finite element code. The developed code with dynamic array allocation, is sufficiently flexible to work across a wide spectrum of computers, including an IBM ES 9000/900 vector facility, SP2 cluster machine, Unix workstations and PCs, for one-, two and three-dimensional problems. To reduce the computation time and storage requirements, the system equations are decoupled and solved using a banded global matrix solver, with the vector and parallel processing on the IBM 9000. To avoide the numerical oscillations of the nonlinear problems in the case of convective dominant transport, the techniques of upstream weighting, mass lumping, and elementary-wise parameter evaluation are applied. The instability and convergence criteria of the nonlinear problems are studied for the one-dimensional analogue of FEM and FDM. Modeling capacity is presented in the simulation of three dimensional composite multiphase TCE migration. Comprehesive simulation feature of the code is presented in a companion paper of this issue for the specific groundwater or flow and contamination problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.99-105
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• 2009

Crack detection method of a rotating blade was suggested in this paper. A rotating blade was modeled with a cantilever beam connected to a hub undergoing rotating motion. The existence and the location of crack were able to be recognized from the vertical response of end tip of a rotating cantilever beam by employing Discrete Hidden Markov Model (DHMM) and Empirical Mode Decomposition (EMD). DHMM is a famous stochastic method in the field of speech recognition. However, in recent researches, it has been proved that DHMM can also be used in machine health monitoring. EMD is the method suggested by Huang et al. that decompose a random signal into several mono component signals. EMD was used in this paper as the process of extraction of feature vectors which is the important process to developing DHMM. It was found that developed DHMMs for crack detection of a rotating blade have shown good crack detection ability.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.822-826
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• 2009

홍수터에 식재된 수목에 의한 운동량 교환은 흐름의 추가적인 흐름저항으로 작용한다. 따라서 수목으로 인한 통수능의 감소로 부분적인 유속 상승이 발생하기도 하지만, 전반적으로 평균유속이 감소하며 수위는 상승하게 된다. 실무적 사용목적으로 홍수터 수목의 저항은 통합 매개변수인 합성조도계수가 사용되고 있으나, 정량적인 조도계수의 추정은 매우 어려운 문제이다. 본 연구에서는 경험적으로 추정되는 비정량적 합성조도 계수의 한계를 극복하고, 실무적으로 사용이 용이하도록 수목에 의한 흐름저항 항을 분리한 1차원 상류이송 음해기법이 개발되었다. 개발된 기법의 평가를 위하여 균일한 단면에서 수행된 수리실험에 적용하였으며, 다양한 유량규모 및 식재조건에서 제안된 기법의 적용성 및 정확성을 확인하였다. 불규칙한 단면형상을 가진 실제 하천의 홍수터에 식재된 수목군의 경우를 가정하여 1/25 정상축척의 수리실험을 실시하였고, 100년 빈도 홍수량에서 수목식재 전후의 실측결과를 개발된 수치기법으로 계산하여 비교하였다. 개발된 기법은 모든 경우에서 사용자의 주관적인 판단 없이 정확하면서 안정적인 해를 제공하였으므로, 흐름의 2차원 효과가 상쇄될 수 있는 광폭의 자연하천에서 수목의 식재기준 분석을 위한 대안으로 사용될 수 있을 것이다.