• 한국분말재료학회지
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• 제5권4호
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• pp.265-272
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• 1998

For the purpose of investigating the effect of sintering atmosphere and carbon addition on sintered density and microstructural characteristics, the M3/2 grade high speed steel powders with the addition of carbon are sintered in vacuum and $20%H_2/79%N_2/l%CH_4$ gas atmosphere. With the addition of 0 wt%C, 0.45wt%C and 1.15 wt%C the optimum sintering temperatures decrease down to $1260^{\circ}C$, $1210^{\circ}C$ and $1150^{\circ}C$ respectively for the vacuum sintered specimen, and also decrease down to $1130^{\circ}C$, $1120^{\circ}C$ and $1115^{\circ}C$ for the gas sintered specimen. The threshold temperatures for full densification decrease steeply with increasing carbon content of the sintered specimen, while this temperatures are slowly decreased at high carbon content. The vacuum sintered specimen shows the primary carbides of MC and $M_6C$ type at the optimum sintering temperature, and eutectic carbides of $M_2C$ and Fe-Cr type are produced in the oversintered specimen. The gas sintered specimen exhibits M6C and Fe-Cr type primary carbides at the optimum sintering temperature. The eutectic carbides of $M_6C$ and Fe-Cr type and MX type carbonitride are shown for the oversintered specimen in the gas atmosphere. The hardness of gas sintered specimen shows high value of 830-860 Hv due to the increment of carbide precipitation.

• 전기화학회지
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• 제7권2호
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• pp.89-93
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• 2004

설폰화된 폴리설폰 (sulfonated polysulfone, SPSF)과 Poly(phenylmethyl silsequioxane) (PPSQ)의 유무기 복합 전해 질막을 제조하여 이온전도도와 메탄을 투과 특성을 조사하였다 클로로트리메틸실란과 클로로설폰산의 반응 몰비와 반응시간를 변화시켜 설폰화도가 $37\~75\%$인 SPSF를 합성하였다. SPSF/PPSQ복합 전해막은 SPSF와 PPSQ를 DMF에 용해하여 캐스팅하는 방법으로 제조하였다 이 복합 전해질막의 수소 이온 전도도는 상온에서 $2.8\times10^{-3}\~4.9\times10^{-2}S/cm$이었으며 설폰화도가 증가할수록 전도도는 증가하였다. 제조된 설폰화된 폴리설폰 복합 전해질막의 메탄을 투과도는 이온전도도와 설폰화도에 비례하여 증가하였으며, PPSQ의 함량이 커질수록 메탄을 투과도가 비례적으로 감소하는 것을 확인할 수 있었다. 약 $5wt\%$ PPSO론 포함한 복합 전해질막의 이온전도도 및 메탄을 투과도는 SPSF에 비교하여 거의 동일하지만 함수율을 크게 감소시키는데 효과적이었다.

• The Plant Pathology Journal
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• 제27권4호
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• pp.372-377
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• 2011

A virus causing mottle and stunt symptom on Zea mays was observed around Ulleng-do, Korea and identified as Cucumber mosaic virus (CMV-ZM) based upon biological, serological, and molecular characteristics. In host range studies, the CMV-ZM isolate produced local lesions on Datura stramonium, Vigna unguiculata, Cucurbita moschata, Chenopodium amaranticolor, Ch. quinoa, whereas this isolate produced systemic mosaic on Nicotiana tabacum cv. 'Xanthi-nc', Capsicum annuum, Solanum lycopersicum, Solanum melongena, Cucurbita pepo, and Z. mays. In addition, chlorotic local rings on inoculated leaves along with severe mosaic, malformation, and fern leaf symptoms on upper systemic leaves were shown in N. glutinosa plants. Complete nucleotide sequences of each genomic RNA segment was determined and compared to those of the other CMV strains. Comparison of the nucleotide sequence of 1a open reading frame (ORF) revealed approximately 89.2-92.4% sequence identity with each CMV subgroup IA and IB strain, while showing only 78% sequence identity with CMV subgroup II. Nucleotide sequence analysis of RNA2 ORFs revealed 85.3-97.6% sequence identity with subgroup I. In ORFs of RNA3, levels of nucleotide sequence identities were higher than 92-99.2% with CMV subgroup I and lower than 82% with CMV isolates of subgroup II. These results suggest that CMV-ZM isolate is more closely related to subgroup I than subgroup II and therefore, CMV-ZM isolate might be classified into as CMV subgroup I based on biological and molecular analysis.

• 대한기계학회논문집B
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• 제27권10호
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• pp.1401-1411
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• 2003

A two-dimensional direct numerical simulation was performed to investigate the flame structure of CH$_4$$N_2$-air counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed chemistry were adopted in this simulation. The characteristic vortex and chemical time scales were introduced to quantify and investigate the extinction phenomenon during a flame-vortex interaction. The results showed that fuel- and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex was extinguished at much larger scalar dissipation rate than steady flame. It was also found that the air-side vortex extinguished a flame more rapidly than the fuel-side vortex. Furthermore, it was noted that the degree of unsteady effect experienced by a flame can be investigated by comparing the above two characteristic time scales, and this analysis could give an appropriate reason for the results of the previously reported experiment.

• 한국멀티미디어학회논문지
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• 제16권12호
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• pp.1465-1474
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• 2013

In this paper, air pollutant tracing models using perceptron neural network(PNN) and non-negative least square(NNLS) are proposed. When the measured values of the air pollution and the contribution concentration of each source by chemical transport modeling are given, they estimate and trace the amount of the air pollutants emission from each source. Two kinds of emissions data are used in the experiments : CH4 and N2O of Geumgo-dong landfill greenhouse gas, and PM10 of 17 areas in Northeast Asia and eight regions of the Korean Peninsula. Emission values were calculated using pseudo inverse method, PNN and NNLS. Pseudo inverse method could be used for the model, but it may have negative emission values. In order to deal with the problem, we used the PNN and NNLS methods. As a result, the estimation using the NNLS is closer to the measured values than that using PNN. The proposed tracing models have better utilization and generalization than those of conventional pseudo inverse model. It could be used more efficiently for air quality management and air pollution reduction.

• 한국수소및신에너지학회논문집
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• 제28권3호
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• pp.315-321
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• 2017

A combustion chamber is designed and fabricated for studying the combustion characteristics of counterflow flames at elevated pressure and establishing the fundamental combustion database of counterflow flames. The combustion chamber design aims to allow the maximum operating pressure of 11 bar and be able to conduct flame visualization and the measurements of flame extinction limits, flame temperature and combustion emissions at elevated pressure. Preliminary tests for counterflow nonpremixed $CH_4-NH_3-N_2$/air flames at 1-3 bar have been conducted, and the results confirm the proper operation of the designed chamber.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.99-100
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• 2005

We have grown carbon nanotubes (CNTs) with a microwave plasma chemical vapor deposition (MPECVD) method, which has been regard as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the low temperature and the large area growth. We use methane ($CH_4$) and hydrogen ($H_2$) gas for the growth of CNTs. 60 nm thick Ni catalytic layer were deposited on the TiN coated glass substrate by RF magnetron sputtering method. In this work, we report the effects of pressure on the growth of CNTs. We have changed pressure of processing (10 $\sim$ 20 Torr) deposition of CNTs. SEM (Scanning electron microscopy) images show diameter, length and cross section state CNTs.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1407-1416
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• 2004

A two-dimensional direct numerical simulation was performed to investigate the flame structure of CH$_4$/$N_2$-Air counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed chemistry were adopted in this computation. The results showed that an initially flat stagnation plane, on which an axial velocity was zero, was deformed into a complex-shaped plane, and an initial stagnation point was moved far away from a vortex head when the counterflow field was perturbed by the vortex. It was noted that the movement of stagnation point could alter the species transport mechanism to the flame surface. It was also identified that the altered species transport mechanism affected the distributions of the mixture fraction and the scalar dissipation rate.

• 공업화학
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• 제32권5호
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• pp.487-496
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• 2021

Microalgae is one of the promising biodiesel feedstock with high growth rates compared to those of terrestrial oil crops. Despite its numerous advantages, biodiesel production from microalgae needs to reduce energy demand and material costs further to go to commercialization. During solvent extraction of microalgal lipids, lipid-extracted algae (LEA) cell residue is generated as an organic solid waste, about 80-85% of original algal biomass, and requires an appropriate recycling or economic disposal. The resulting LEA still contains significant amount of carbohydrates, proteins, N, P, and other micronutrients. This review will focus on recent advancement in the utilization of LEA as: (i) utilization as nutrients or carbon sources for microalgae and other organisms, (ii) anaerobic digestion to produce biogas or co-fermentation to produce CH₄ and H₂, and (iii) conversion to other forms of biofuel through thermochemical degradation processes. Possible mutual benefits in the integration of microalgae cultivation-biodiesel production-resulting LEA with anaerobic digestion and thermochemical conversion are also discussed.

• 천문학회보
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• 제44권1호
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• pp.82.1-82.1
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• 2019

Recent analyses of spectro-images of Saturn observed by Visual and Infrared Mapping Spectrometer (VIMS)/Cassini revealed altitudinal distributions of the spectral structure of haze in Saturn's south-polar regions (Kim et al., 2018) and at $55^{\circ}N$ latitude (Kim et al., 2012). However, other regions of Saturn still have not been investigated. We derived series of high-spatial resolution VIMS images of Saturn's limb at various latitudes. Using our developed code, the altitudinal intensity profiles of $3.3-{\mu}m$ emission and H3+ through different latitudes were plotted. Then we obtained the averaged vertical spectra of $3.3-{\mu}m$ emission which is all blended with fluorescent methane and hydrocarbon haze. The vertically-resolved spectra were measured from the limb of Saturn in 50km intervals to see altitudinal variance. We will present a comparison of spectral structures of $3.3-{\mu}m$ emission with different latitudes. Further investigation using radiative transfer to extract adjacent fluorescent CH4, C2H6, and H3+ is needed to derive spectral structure of pure haze. We look forward to a better understanding of aging process in a global view.