• Journal of Welding and Joining
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• v.15 no.1
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• pp.101-108
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• 1997

In repaired weldment of ASTM A-470 class 8 high pressure stream turbine rotor steel, creep rupture life was studied in relation with carbide morphology. Carbides were identified using carbide extraction replica method. A retired rotor has molybdenum rich carbide $M_2C$, lndacochea vanadium rich carbide $M_4C_3$, and chromium rich carbides $M_{23}C_6$and $M_7C_3$. Weldments ruptured at ICHAZ showed that some of carbides have been transformed into spherical types of coarsened carbides at ruptured area. Those carbides were revealed as molybdenum rich $M_6C$ carbide and they provided cavitation sites due to molybdenum depletion around $(M_6C)$ carbide. However coarsened $M_6C$ and $M_{23}C_6$ carbides were observed at ruptured area in case of ruptured at CGHAZ.

• Microbiology and Biotechnology Letters
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• v.37 no.4
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• pp.333-339
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• 2009

Using a novel pine needle agar, fifteen bacterial species were isolated from pine litter. These bacteria were able to degrade aromatic hydrocarbons derived from lignin and utilize the ortho-cleavage of the $\beta$-ketoadipate pathway to degrade protocatechuate or catechol. A different utilization array of aromatic hydrocarbons by these bacteria was also determined. This study provides the information on bacterial species living in pine litter and suggests that these bacteria have metabolic abilities to utilize aromatic hydrocarbons derived from lignin biodegradation.

• The Korean Journal of Petroleum Geology
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• v.6 no.1_2 s.7
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• pp.37-43
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• 1998

Chemical components of water, chemical and isotopic compositions of extractable gases were analyzed to characterize the properties of the natural gases which are dissolved in ground water in the Pohang area. Amount of total extracted gases ranges from 27 ml/l to 50.1 ml/l. Hydrocarbon gases are composed of methane ($27{\~}376,420 ppm$) and ethane ($19{\~}127 ppm$). Amount of total hydrocarbon gases is related to the lithology and geological factors around the reservoir. Quantity of hydrocarbon gases tends to increase in the Tertiary reservoirs and in the reservoirs where the Tertiary formations are thick enough. According to the relationship between hydrocarbon gases and total solids in the ground water, it is believed that the hydrocarbon gases were dissolved in the Tertiary formation water. Based on the methane content ($>99.9\%$) and isotopic composition (${\delta}C^{13};-73.1\%_{\circ}{\~}-43.22\%_{\circ}$), we interpret the gases to be of predominantly biogenic origin which were generated by the methanogenic bacterial processes under the low temperature and anoxic conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.4 no.2
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• pp.11-19
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• 1988

대기오염물질 속에 함유되어 있는 다환방향족 탄화수소 (PAHs)는 분자식 구조가 비슷한 수십개의 이성질체가 여러 종류의 유기화합물과 혼합되어 존재한다. 본 연구에서는 환경오염 시료중의 PAHs를 분석하는데 있어서 분석방법과 결과를 비교하기 위하여 지침이 될 수 있는 환경표준 기준물을 개발할 목적으로 굴뚝 안쪽벽에서 긁어 채취한 검댕을 시료로 선책하여 액체/액체 용매 추출방법에 의해 PAHs 분류부분을 얻었다. Phenanthrene 이외의 30여종의 PAHs 화합물을 가스크로마토그라피의 머무른시간과 가스크로마토그라피/질량분석기에 의하여 분리, 판명하였고 5종의 주 PAHs 화합물을 정확하게 정량 분석하였다. 정량분석 결과의 신뢰도, 정확도, 정밀도는 미국 NBS의 표준기준물 1647을 분석하여 검정치와 비교함으로써 평가하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.250.2-250.2
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• 2010

빛과 공기 중의 이산화탄소를 고정화하여 생성되는 바이오매스(biomass)로부터 다양한 에너지 및 물질을 생산하는 연구는 석유고갈과 환경문제 해결의 한 방안으로서 활발히 진행되어 왔으며, 앞으로도 그 지속 가능성과 환경 친화성에 의해 바이오에너지 이용 및 보급은 꾸준한 증가세를 보일 것으로 전망된다. 바이오디젤, 바이오에탄올의 경우는 미국, 브라질, EU, 한국 등에서 상용화되어 사용되고 있으며 그 생산량이 계속적으로 증가하고 있다. 하지만, 바이오연료의 보급 증가는 식량 자원과의 충돌과 열대우림 파괴 등의 부작용을 일으키고 있다. 이러한 문제 해결의 일환으로 단위면적당 생산성이 대두, 유채보다 월등한 것으로 보고되는 미세조류에 대한 관심이 증가하고 있으며 우수 미세조류종 개발, 미세조류 고속배양 및 수확, 미세조류로부터 에너지 및 유용물질, 소재 생산에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 미세조류로부터 바이오디젤 원료유를 생산하기 위해 Soxhlet을 이용한 추출 방법을 이용하였다. 추출되는 오일은 사용 용매의 극성에 따라 물성과 추출 효율에 차이가 큰 것으로 나타났다. 강한 극성의 용매일 경우, 엽록소와 단백질이 같이 추출되는 문제가 있으며 약한 극성 용매는 세포벽의 방해로 용매가 세포내부로 흡수되지 못하는 문제가 있다. 추출 효율이 높은 극성용매의 경우 불순물을 제거해야 고순도의 바이오디젤의 생산이 가능하고 비극성 용매는 추출 오일의 물성은 좋으나 수율이 매우 낮게 측정되었다. 이러한 동시추출을 방지함과 동시에 추출 효율을 높이기 위해 본 연구에서는 세포벽 파괴 후 용매추출하는 방법으로서 미세조류를 Microwave에 노출시켜 오일 추출율을 증가시키는 전처리 연구를 수행하였다. 전처리시, Microwave에 의한 열 발생은 미세조류를 탄화시키기 때문에 열매체로서 물을 혼합하여 탄화를 방지하고 세포벽 내외부의 가열효과로 세포벽을 파괴하고자 하였다. Microwave에 의한 에너지 손실을 줄이며 세포벽 파괴에 효과적인 수분혼합비를 조사하였으며 Microwave에 노출 후 잔류수분을 건조하고 효율적으로 용매를 접촉시키기 위해 분쇄를 수행하였다. 모든 전처리 반응을 거친 미세조류에서 약 2배 증가된 추출수율을 얻을 수 있었으며, SEM을 통해 전처리 미세조류와 미전처리 미세조류를 분석해본 결과 전처리 미세조류의 다공성이 증가함을 확인하였다. 또한, 90%의 메탄올에 미세조류를 녹여 엽록소 함유량을 측정한 결과, 전처리 미세조류의 엽록소가 미전처리 미세조류보다 약 7배가량 감소함을 확인할 수 있었다.

• Resources Recycling
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• v.31 no.4
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• pp.19-25
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• 2022

In this study, tungsten carbide (WC) powder was prepared using a novel recycling process for hard metal sludge that does not use ammonium paratungstate. Instead of ammonia, acid was used to remove the sodium and crystallized tungstate, resulting in the formation of tungstic acid (H₂WO₄). The WC powder was successfully synthesized by the carbothermal reduction of tungstic acid through H₂O decomposition, reduction of WO₃ to W, and formation of WC. The carbon content and holding time at the carbothermal reduction temperature were optimized to remove free carbon from the WC powder. As a result, most of the free carbon in the WC powder prepared from sludge was removed, and the content of free carbon in the synthesized WC powder was lower than that in commercial WC powder. Moreover, the crystallite size of WC prepared from H₂WO₄ was much smaller than that of commercial micron-sized WC powder produced from APT. The small crystallite size of WC induces grain growth during the sintering of the WC-Co composite; thus, a WC-Co composite with large WC grains was fabricated using the WC powder prepared from H₂WO₄. The large WC grains affected the mechanical properties of the WC-Co composite. Further, due to the large grain size, the WC-Co composite fabricated from H₂WO₄ exhibited a higher toughness than that of the WC-Co composite prepared from commercial WC powder.

• Journal of Life Science
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• v.27 no.5
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• pp.561-566
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• 2017

Dendropanax morbifera Lev. is known in Korea for its golden sap and medicinal properties. The many biological activities of the leaf and stem extracts suggest that this tree could be a valuable source of medicinal compounds for the treatment of various ailments such as dermatitis, migraines, dysmenorrhea, muscle pain, and infectious diseases. However, there is little information on the composition and biological activity of the volatile fraction of D. morbifera. Therefore, in this study, the volatile compounds in leaves, stems, and sap of D. morbifera were isolated using solvent and supercritical fluid extraction (SFE), and analyzed by gas chromatography/mass spectrometry to reveal their chemical composition and identify potential compounds of interest. Fifteen compounds were identified in the leaf extracts, whereas 29 and 3 compounds were identified in the stem and sap extracts, respectively. The volatile profiles obtained using solvent and SFE differed. Esters and aromatic hydrocarbons predominated in the solvent extract of leaves and SFE extract of stems, whereas the solvent extract of stems and SFE extract of leaves contained terpenoids. Limonene, ${\alpha}$-pinene, and ${\beta}$-myrcene were identified in the volatile extract of sap, with limonene representing 96.30% of the total peak area. In addition, the antiproliferative effects of the solvent extracts of leaves and stems were evaluated, revealing that these solvent extracts were particularly effective in decreasing the proliferation of HepG2 cells.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.105-109
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• 1986

Volatile components of pinenut were identified. Pinenut was extracted by simultaneous distillation and extraction method after Soxhlet extraction. The odor profile of the extract was very similar to that of pinenut. This extract was then fractionated into four fractions by Preparative TLC. These all fractions were analyzed by a combination of glass capillary gas chromatography (FTD, FID capillary GC) and mass spectrometry. One hundred and nine components, including 26 hydrocarbons,17 esters,16 aldehydes,12 ketones,31 alcohols, 11 bases, 2 acids and 3 miscellaneous components were identified.

• Korean Journal of Food Science and Technology
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• v.39 no.2
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• pp.109-113
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• 2007

Adenophora remotiflora (Mosidae) is a perennial plant in the Campanulaceae family and a wild plant that only inhabits in Korea. This research analyzed the volatile compounds in Mosidae and their antioxidant activities. The volatile compounds in fresh, shady air-dried, and freeze-dried Mosidae were isolated by steam-distillation extraction (SDE) method using diethylether as a solvent. Volatile compounds were analyzed by gas chromatography-mass spectrometry (GC/MS). Antioxidant activities were determined using the linoleic acid system and 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Sixty and seventy-two volatile compounds were identified from fresh and shady air-dried Mosidae, respectively. In fresh Mosidae, the most abundant compounds were ethyl acetate and heptyl acetate, while ethyl acetate and limonene were the most abundant in the shady air-dried sample. Inhibition of peroxide formation by fresh Mosidae was higher than that of ${\alpha}-tocopherol$, and inhibition by shady air-dried Mosidae was same as that of ${\alpha}-tocopherol$. Furthermore, volatile compounds from shady air-dried Mosidae had higher free radical scavenging activity than ${\alpha}-tocopherol$. The freeze-dried sample showed lower antioxidant activity in both the linoleic acid system and DPPH method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.99-100
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• 2009

탄화규소를 이용한 1200V급 MOSFET 소자 제작을 위하여 특성 simulation을 수행하였다. 1200V 내압을 얻기 위해서 불순물 농도가 5E15/cm3이고 에피층의 두께가 12um인 상용 탄화규소 웨이퍼를 기준으로 하였으며 채널 저항을 줄이기 위해 채널길이를 $0.5{\mu}m$로 하였다. 게이트전압이 13V, 드레인 전압이 4V에서 specific on-resistance 값은 $12m\;{\Omega}cm^2$로 매우 우수한 특성을 보이고 있다. P-body의 표면 농도를 5E16/cm3 에서 1E18/cm3으로 변화시키면서 소자의 전기적 특성을 예측하였으며 실험 결과와 비교하여 특성 변수를 추출하였다.