• 한국가시화정보학회지
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• 제8권1호
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• pp.31-38
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• 2010

An experimental study to evaluate dynamic structures of flow and turbulence characteristics in bubble-driven liquid flow in a rectangular tank with a varying flow rate of compressed air is conducted. Liquid flow fields are measured by time-resolved particle image velocimetry (PIV) with fluorescent tracer particles to eliminate diffused reflections, and by an image intensifier to acquire enhanced clean particle images. Instantaneous vector fields are investigated by using the two frame cross-correlation function and bad vectors are eliminated by magnitude difference technique. By proper orthogonal decomposition (POD) analysis, the energy distributions of spatial and temporal modes are acquired. When Reynolds number increases, bubble-induced turbulent motion becomes dominant rather than the recirculating flow near the side wall. The total kinetic energy transferred to the liquid from the rising bubbles shows a nonlinear relation regarding the energy input because of the interaction between bubbles and free surface.

• Applied Microscopy
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• 제38권2호
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• pp.135-140
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• 2008

본 연구에서 분만 중에 사망한 여성미라의 자궁 내에 있는 태아미라의 두피를 주사전자현미경과 투과전자현미경을 사용하여 관찰하였다. 주사전자현미경상에서 태아 두피의 표면은 잘 보존된 상태로 관찰되었으며, 각질층에 각화세포도 모양을 그대로 유지하고 있었다. 또한 땀샘과 모발도 원형 그대로 유지하고 있었으며 일부 두피표면에 모발이 빠져서 형성된 모공들이 다수 관찰되었다. 채취한 두피의 횡단면 두께는 약 1mm로 나타났으며 표피와 진피 및 피하조직이 뚜렷하게 존재하였다. 투과전자현미 경상에서 상피세포의 구조나 형태는 관찰되지 않았으며 또한, 세포의 형태를 그대로 유지하고 있는 어떠한 세포들도 전혀 관찰할 수 없었다. 그러나 진피의 교원섬유들은 잘 보존되어 있었고 이들 사이에 Clostridium 속으로 추정되는 부패세균들이 다수 관찰되었다.

• 한국전기전자재료학회논문지
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• 제21권4호
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• pp.354-361
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• 2008

The dielectric characteristics of low-k interlayer dielectric materials was fabricated by plasma enhanced chemical vapor deposition (PECVD). BTMSM precursor was evaporated and introduced with the flow rates from 16 sccm to 25 sccm by 1sccm step in the constant flow rate of 60 sccm $O_2$ in process chamber. Manufactured samples are analyzed components by measuring FT/IR absorption lines. Decomposition each Microscopic structures through two-dimensional correlation analysis about mechanisms for the formation of SiOCH in $SiOCH_3$, Si-O-Si and Si-$CH_3$ bonding group and analyzed correlation between the micro-structure of each group. It is a tendency that seems to be growing of Si-O-Ci(C) bonding group and narrowing of Si-O-$CH_3$ bonding group relative to the increasing flow-rate BTMSM. The order of changing sensitivity about changes of flow-rate in Si-O-Si(C) bonding group is cross link mode$(1050cm^{-1})$ $\rightarrow$ open link mode$(1100cm^{-1})\rightarrow$ cage link mode $(1140cm^{-1})$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1880-1884
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• 2000

The discrete wavelet transform is utilized as preprocessing of Neural Network(NN) to identify aging state of internal partial discharge in transformer. The discrete traveler transform is used to produce wavelet coefficients which are used for Classification. The statistical parameters (maximum of wavelet coefficients, average value, dispersion, skewness, kurtosis) using the wavelet coefficients are input into an back-propagation neural network. The neurons whose weights have obtained through Result of Cross-Validation. The Neural Network learning stops either when the error rate achieves an appropriate minimum or when the learning time overcomes a constant value. The networks, after training, can decide if the test signal is Early Aging State or Last Aging State or normal state.

• Corrosion Science and Technology
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• 제19권1호
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• pp.31-36
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• 2020

An efficient wet process approach to modifying natural graphite (NG) electrodes for Li-ion batteries is introduced in this paper. With homogeneous mixing and thermal decomposition of NG with diammonium phosphate ((NH₄)₂HPO₄), phosphorus and nitrogen were successfully incorporated into the surface layer of NG particles. Electron microscopy and X-ray photoelectron spectroscopy analyses demonstrated that the surface was well modified by this process. As a result, the treated NG electrodes exhibited much improved electrochemical performance over pristine NG at two different temperatures: 25 ℃ and 50 ℃. Excellent capacity retention of 95.6% was obtained after 100 cycles at 50 ℃. These enhanced properties were confirmed in a morphology analysis on the cross-sections of the NG electrodes after galvanostatic cycling. The improved cycle and thermal stabilities can be attributed to the surface treatment with phosphorus and nitrogen; the treatment formed a stable solid electrolyte interphase layer that performed well when undergoing Li insertion and extraction cycling.

• Bulletin of the Korean Chemical Society
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• 제1권1호
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• pp.35-39
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• 1980

A vacuum ultraviolet photolysis of ethyl bromide was studied in the pressure range of 0.5-19.9 torr and at 123.6 nm krypton resonance line. The pressure effect on the reaction was studied by increasing the reactant pressure and by adding an inert gas, e.g., He. In the observation the monatomic gas is found to be no effect in the reaction. A scavenger effect of the reaction was also performed by adding NO gas as a radical scavenger and was found to be quite efficient to scavenge a radical product $C_2H_6$. The observation of the major reaction product $C_2H_6$ was interpreted in terms of a molecular elimination. Nontheless the decreasing phenomenon of ${\phi}_{C_2H_4}/{\phi}_{C_2H_6}$ with pressure rise was attributed to the existence of the two electronically excited states. One state proceeds to the molecular elimination and the other to carbon-bromine bond fission. The excitation and the decomposition mechanisms between two excited states and the reaction products were interpreted in terms of the first excitation which proceeds the molecular elimination, and the second excitation which resulted from the first excited state by collisional cross over decomposes by carbon-bromine bond fission.

• Elastomers and Composites
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• 제57권3호
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• pp.100-106
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• 2022

Waterborne polyurethane-acrylate(WPUA) dispersions were prepared by surfactant-free emulsion polymerization in a two-step process. In the first step, polytetrahydrofuran, isophorone diisocyanate, dimethylol proponic acid, and 2-hydroxyethyl methacrylate were used to synthesize a vinyl-terminated polyurethane prepolymer. In the second step, styrene, methyl methacrylate, butyl acrylate, and different multi-functional crosslinkers were copolymerized. 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate were used as the crosslinkers, and their effect on the mechanical and thermal properties of WPUA was investigated. Overall, as the number of functional groups of the cross-linker increased, the gel fraction improved to 79.26%, the particle size increased from 75.9 nm to 148.7 nm, and the tensile strength was improved from 5.86 MPa to 12.40 MPa. In thermal properties, the glass transition temperature and decomposition temperature increased by 9.9℃ and 18℃, respectively. The chemical structures of the WPUA dispersions were characterized by Fourier-transform infrared spectroscopy. The synthesized WPUA has high potential for applications such as coatings, leather coatings, adhesives, and wood finishing.

• 한국수소및신에너지학회논문집
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• 제34권3호
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• pp.307-315
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• 2023

The physical and chemical changes exhibited by high density polyethylene (HDPE) after treatment with hydrogen at a pressure of 90 MPa followed by rapid release of the hydrogen were studied. X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, and attenuated total reflectance (ATR)-fourier transform infrared (FTIR) were used for this purpose. As a result, it was found that the degree of crystallinity of HDPE decreased after hydrogen pressure treatment, while the average thickness of lamellae that constitute the crystals and the melting temperature of the crystalline region actually increased. The decomposition temperature also increased by about 3℃. In addition, it was found that the hydrogen bonding network between -OH groups in the HDPE sample was strengthened and partial chain scission occurred. These cut chains were found to be terminated by oxidative degradation such as cross-linking between chains, -C=O, -C-O, and -CHO, or by the formation of -CH₃ at the chain ends, as confirmed by ATR-FTIR.

• 대한토목학회논문집
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• 제28권5A호
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• pp.641-647
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• 2008

본 논문은 상시진동데이터로부터 구조물의 고유진동수 및 감쇠비를 추정하는 기법을 소개한다. 제안된 기법은 TDD기법에서 추출된 모드형상과 상호상관신호로부터 직교 잡음이 제거된 자유진동함수를 추출하고 시스템 인식기술을 적용하여서 각 모드별 고유진동수와 감쇠비를 추정한다. 제안 알고리즘의 정확도는 수치적으로 기존의 기법과 비교분석 되었다. 제안 알고리즘의 현장 적용성 검토는 서해대교 보강형의 수직방향 가속도에 대한 상시진동데이터를 통하여 검증되었으며, 총 24개의 저차모드가 추출되었다.

• East Asian Economic Review
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• 제27권3호
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• pp.243-269
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• 2023

The multidimensional poverty index is an indicator system established for defining and evaluating poverty, to understand poverty in dimensions beyond just monetary scarcity. Based on income, education, health, living standards, and social dimensions, this article measures and analyzes the level of multidimensional poverty in Xinjiang using the AlkireFoster method, with cross-sectional data obtained from a 2022 survey. Probit model is constructed for regression analysis, further considering the impact of education on enhancing feasible capabilities and alleviating multidimensional poverty at the post-poverty alleviation era. The data shows that many people still face significant challenges from the perspective of multidimensional poverty; the decomposition results of each dimension show that education contributes more to the multidimensional poverty; the regression analysis results show that the higher the education level, the lower the multidimensional poverty; heterogeneity analysis revealed that the inhibitory effect of education on multidimensional poverty is greater for females than males, and the poverty reduction effect of education mainly concentrates on middle-aged and older individuals. This article is meaningful for exploring strategies to alleviate multidimensional poverty in ethnic minority regions in frontier areas in the new era, accelerating regional economic development, and achieving shared prosperity.