수직면에서의 비등 열전달에 대한 실험적 연구

김재광,송진호,김신,김상백,김희동,Kim, Jae-Kwang,Song, Jin-Ho,Kim, Sin,Kim, Sang-Baik,Kim, Hee-Dong 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.9

An experimental study was carried out to identify the various regimes of natural convective pool boiling and to determine the boiling heat transfer curve and Critical Heat Flux(CHF) on a vertical square surface having a 70mm width and a 70mm height. The heater made of copper block with embedded cartridge heaters is submerged in a water tank at atmospheric pressure. As the heat flux increases from 100kW/㎡ to 1.2MW/㎡, the heat transfer regime migrates from the nucleate boiling to the film boiling. The boiling heat transfer data are fitted by Rohsenow type correlation. An explosive vapor generation on the heated surface, whose size and frequency are characterized by the heat flux, is visualized using a high speed digital imaging system.

간 실질세포주에서 니호채(泥胡菜) 분획물이 liver X receptor α 의존적 지방 생성 유전자의 발현에 미치는 효과

김재광,조일제,김은옥,정대화,구세광,김상찬,Kim, Jae Kwang,Cho, Il Je,Kim, Eun Ok,Jung, Dae Hwa,Ku, Sae Kwang,Kim, Sang Chan 대한한의학방제학회 2020 大韓韓醫學方劑學會誌 Vol.28 No.3

Objectives : Hemistepta lyrata Bunge (Bunge) is a wild herb that has been used for managing fever and wound in Korean Traditional Medicine. The present study explored the effects of H. lyrata extract on liver X receptor (LXR) α-dependent lipogenic genes in hepatocyte-derived cells. Methods : After HepG2 cells or Huh7 cells were pre-treated with 1-10 ㎍/mL of H. lyrata extract or its fractionated extract for 0.5 h, the cells were subsequently exposed to LXR ligand for 6-24 h. Cell viability, LXR response element (LXRE)-driven luciferase activity, sterol regulatory element binding protein-response element (SREBP-RE)-driven luciferase activity, SREBP-1c expression, and mRNA levels of LXRα and its-dependent target genes were determined. In addition, LC-MS/MS analysis was conducted to explore major compounds in H. lyrata-chloroform fractionated extract #4 (HL-CF4). Results : Of various H. lyrata extracts tested, chloroform extract and its fractionated extract #4, HL-CF4, significantly decreased T0901317-mediated SREBP-1c expression. In addition, HL-CF4 significantly reduced LXRE atransactivation and LXRα mRNA expression without any cytotoxicity. Moreover, HL-CF4 prevented the SREBP-RE-driven luciferase activity and mRNA levels of fatty acid synthase and stearoyl-CoA desaturase-1 induced by T0901317. Results from LC-MS/MS analysis at positive/negative mode indicated that HL-CF4 contained several compounds showing m/z 197.1176 (C₁₁H₁₇O₃), 693.2913/227.1069 (C₃₈H₄₅O₁₂/C₁₅H₁₅O₂), 203.1797 (C₁₅H₂₃), 181.1225 (C₁₁H₁₇O₂), 591.2957 (C₃₅H₄₃O₈), 379.1040 (C₁₈H₁₉O₉), 409.1509 (C₂₀H₂₅O₉), 309.1348 (C₁₆H₂₁O₆), 391.1404 (C₂₀H₂₃O₈), and 669.2924/389.1248 (C₃₆H₄₅O₁₂/C₂₀H₂₁O₈). Conclusion : Based on its inhibition of the LXRα-dependent signaling pathway, H. lyrata chloroform extract and HL-CF4 have prophylactic potentials for managing non-alcoholic fatty liver.

Metabolic Fingerprinting Study on the Substantial Equivalence of Genetically Modified (GM) Chinese Cabbage to Non-GM Cabbage

김재광,Jun Heong Kim,Sang Mi Chu,Chang Yeon Yu,Tae Hun Ryu,Soo In Sohn,Hyung Jin Baek 한국응용생명화학회 2009 Journal of Applied Biological Chemistry (J. Appl. Vol.52 No.2

Genetically modified (GM) Chinese cabbage containing the bar gene was compared to 24 non-GM Chinese cabbage varieties to evaluate unwanted changes in GM crops using HPLC-DAD-based metabolic fingerprinting to characterize polar metabolites containing flavonoids. No new compounds distinguishing GM crops from non-GM crops were observed using this technique. The GM crops had the similar flavonoid value as its nontransgenic counterpart (cv. Samjin). Moreover, the luteolin, quercetin, and kaempferol contents in GM Chinese cabbage were within the range of the 24 cultivars. The metabolome database included major 26 chemical species, which were analyzed with principal component analysis. The results clearly demonstrated that the time of sampling affects the metabolome. Moreover, the metabolic fingerprints showed a range of natural variability in the GM Chinese cabbage that was similar to that of the control at all times of sampling. Metabolic fingerprinting could potentially provide an innovative method for safety assessments of genetically modified organisms.

방전 플라즈마 소결법을 이용한 8YSZ-$Al_2O_3$ 고체 산화물 연료전지 전해질 제조

김재광,최봉근,양재교,좌용호,심광보,Kim Jae Kwang,Choi Bong Geun,Yang Jae Kyo,Choa Yong Ho,Shim Kwang Bo 한국결정성장학회 2005 한국결정성장학회지 Vol.15 No.1

고체 산화물 연료전지 전해질 재료인 8YSZ(yttria stabilized zirconia)세라믹 소재의 전기 전도도와 기계적 특성을 동시에 향상시키기 위하여 첨가제로서 Al₂O₃를 사용하고, 방전 플라즈마 소결법을 적용하였다. 제조된 소결체는 1200℃의 소결 온도에서 96% 이상의 밀도를 보이며, 1 ㎛ 이하의 균일한 크기의 결정립들로 구성된 미세구조를 보여주고 있다. 첨가된 Al₂O₃는 순수한 8YSZ의 결정립성장을 억제하여 파괴인성 및 굽힘강도 등 기계적 물성을 향상시키고, 또한 결정립 내부 전도도는 일정하게 유지한 채, 결정립계 전도도를 향상시켜 전체 이온 전도도를 증가시킴을 확인하였다. 이는 방전플라즈마 소결법이 비교적 낮은 온도에서 소결이 가능하여 기존의 소결 방법에서 문제시 되었던 8YSZ내로 Al₂O₃가 용해되는 것이 억제 되었을 뿐 아니라, 결정립계에 존재하는 SiO₂가 Al₂O₃와 반응하여 Al/sub 2-x/Si/sub l-y/O/sub 5/상으로 결정화되면서 결정립계 전도도를 향상시킨 결과로 사료된다. In order to improve electrical conductivity and mechanical properties of 8YSZ SOFC electrolyte material, we used Al₂O₃ as an additive and applied the spark plasma sintering (SPS) method. The sintered bodies were densified above 96 % of theoretical density at 1200℃ and possessed microstructures composed of homogeneous grains less than 1 ㎛ in size. The addition of Al₂O₃ improved fracture toughness and bending strength by inhibiting grain growth of 8YSZ and increased total ionic conductivity because grain interior conductivity appeared to remain constant and grain boundary conductivity increased. It was assumed that the dissolution of Al₂O₃ into 8YSZ which was inevitable problem at commercial sintering method was effectively prohibited by the SPS technique with a relatively low sintering temperature and the reaction between Al₂O₃ and SiO₂ present at grain boundary to produce the crystalline Al/sub 2-x/Si/sub l-y/O/sub 5/ phase, resulting in the increase of grain boundary conductivity.

졸-겔법에 의해 제조된 LiMPO₄(M = Fe, Mn) 양극 활물질의 전기화학적 특성

김재광,백동호,신용조,안주현,서양곤,김지수,윤석준,조명훈,Kim, Jae-Kwang,Baek, Dong-Ho,Shin, Yong-Jo,Ahn, Jou-Hyeon,Seo, Yang-Gon,Kim, Chi-Su,Yoon, Seok-Jun,Cho, Myung-Hun 한국전기화학회 2008 한국전기화학회지 Vol.11 No.2

리튬이차전지의 양극 활물질로 카본 코팅된 $LiFePO_4$와 $LiMn_{0.4}Fe_{0.6}PO_4$를 졸-겔방법으로 합성하였다. 제조된 양극 활물질을 X-선 회절분석과 주사전자현미경을 통하여 불순물이 존재하지 않으며 기공이 잘 발달되어 있다는 것을 확인하였다. 액체전해질을 사용하여 0.1 C-rate의 전류밀도에서 충방전하였을 경우 $LiFePO_4$는 132 mAH/g, $LiMn_{0.4}Fe_{0.6}PO_4$는 145 mAh/g의 방전용량을 각각 나타내었다. 전기방사에 의해 만들어진 겔 고분자 전해질을 사용하였을 경우에 $LiFePO_4$와 $LiMn_{0.4}Fe_{0.6}PO_4$는 각각 114, 130 mAh/g의 우수한 방전용량을 나타내었다. Carbon-coated $LiFePO_4$ and $LiMn_{0.4}Fe_{0.6}PO_4$ cathode materials for lithium batteries were synthesized by a sol-gel method. X-ray diffraction and scanning electron microscopy data showed that the cathode materials are pure crystalline and are surrounded by porous carbon. The initial discharge capacities of $LiFePO_4$ and $LiMn_{0.4}Fe_{0.6}PO_4$ with the liquid electrolyte of 1M $LiPF_6$ in EC/DMC are 132 mAh/g and 145 mAh/g, respectively, at current density of 0.1 C-rate. $LiFePO_4$ and $LiMn_{0.4}Fe_{0.6}PO_4$ with an electrospun polymer-based electrolyte exhibit initial discharge capacities of 114 and 130 mAh/g at 0.1 C-rate at room temperature, respectively.

가중치 보정 추정량에 대한 일반적인 분산 추정법 연구

김재광,Kim, Jae-Kwang 한국통계학회 2007 응용통계연구 Vol.20 No.2

Linear estimator, a weighted sum of the sample observation, is commonly adopted to estimate the finite population parameters such as population totals in survey sampling. The weight for a sampled unit is often constructed by multiplying the base weight, which is the inverse of the first-order inclusion probability, by an adjustment term that takes into account of the auxiliary information obtained throughout the population. The linear estimator using the weight adjustment is often more efficient than the one using only the bare weight, but its valiance estimation is more complicated. We discuss variance estimation for a general class of weight-adjusted estimator. By identifying that the weight-adjusted estimator can be viewed as a function of estimated nuisance parameters, where the nuisance parameters were used to incorporate the auxiliary information, we derive a linearization of the weight-adjusted estimator using a Taylor expansion. The method proposed here is quite general and can be applied to wide class of the weight-adjusted estimators. Some examples and results from a simulation study are presented. 유한 모집단에서 총계 추정에는 표본의 각 관측값으로 만들어지는 선형 추정량이 사용되는데 이때 사용되는 가중치는 표본 추출 확률의 역수를 사용한 기본 가중치를 모집단 전체에서 얻어지는 보조 정보를 이용하여 보정한 형태로 종종 사용된다. 이렇게 보정된 가중치를 사용한 추정량은 그렇지 않은 추정량보다 효율이 더 좋아질 수 있는 장점이 있으나 이러한 경우 분산 추정은 더 어려워지게 된다. 본 연구에서는 보정된 가중치를 사용한 추정량의 분산 추정을 다룬다. 가중치 보정의 일반적인 형태를 밝히고 이 경우 가중치 보정항은 유한개의 장애 모수(nuisance parameter)의 함수로 나타낼 수 있으므로 이 장애 모수에 대한 테일러 전개를 사용한 분산 추정식을 구한다. 이렇게 구현된 분산 추정식은 기존의 가중치 보정 추정량뿐만 아니라 보다 일반적인 경우에서도 적용될 수 있다는 장점이 있다. 몇가지 응용 사례와 모의 실험 결과를 소개한다.

생물전환(Bio-Conversion) 기술을 이용한 인삼사포닌 가공

김재광,Kim, Chi-Kwang 고려인삼학회 2012 고려인삼연구와 산업 Vol.6 No.1

Nuclear factor erythroid 2-related factor 2 활성화를 통한 해간전(解肝煎)의 간세포 보호 효능 및 분자기전을 활용한 해간전(解肝煎) 구성 약물의 최적화 연구

김재광,정지윤,박상미,박정아,구세광,변성희,조일제,김상찬,Kim, Jae Kwang,Jung, Ji Yun,Park, Sang Mi,Park, Chung A,Ku, Sae Kwang,Byun, Sung Hui,Cho, Il Je,Kim, Sang Chan 대한한의학방제학회 2018 大韓韓醫學方劑學會誌 Vol.26 No.3

Objectives : Present study investigated hepatoprotective effect of Haegan-jeon extract (HE) and tried to elucidate molecular mechanism involved. According to molecular mechanism, present study optimized herbal composition of HE (op-HE) and compared in vitro and in vivo hepatoprotective effects of op-HE to HE. Methods : For in vitro experiments, HepG2 cells were exposed to arachidonic acid (AA, $10{\mu}M$) and iron ($5{\mu}M$) for inducing oxidative stress. Cell viability, GSH contents, $H_2O_2$ production, mitochondrial membrane potential, immunoblot and reporter gene assay were performed to investigate cytoprotective effects and responsible molecular mechanisms. For in vivo experiments, hepatoprotective effect of HE and op-HE were assessed on $CCl_4-induced$ liver injury mice model. Results : HE pretreatment prevented AA+iron-mediated hepatocytes apoptosis. In addition, AA+iron-induced mitochondrial dysfunction, $H_2O_2$ production, glutathione depletion were reduced by HE pretreatment. In addition, nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation, antioxidant response element (ARE)-driven reporter gene activity, and antioxidant genes expression were increased by HE. Based on reporter gene and MTT assays, we found that op-HE consisting three medicinal herbs also significantly increased transactivation of Nrf2 and reduced the AA+iron-mediated cytotoxicity. Moreover, in $CCl_4-induced$ liver injury mice model, HE-op had an ability to ameliorate $CCl_4-mediated$ increases in serum alanine transferase and aspartate aminotransferase activity, hepatic degeneration, inflammatory cell infiltration, and collagen deposition. Hepatoprotective effects of op-HE were comparable to those of HE. Conclusions : Present study suggests that op-HE as well as HE exhibit hepatoprotective effect against oxidative stress-mediated liver injury via Nrf2 activation.

Unintended polar metabolite profiling of carotenoid-biofortified transgenic rice reveals substantial equivalence to its non-transgenic counterpart

김재광,박수연,이시명,Sun-Hyung Lim,Hyo Jin Kim,Sung-Dug Oh,Yunsoo Yeo,Hyun-Suk Cho,하선화 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.1

Substantial equivalence is a critical concept for biosafety assessment of genetically modified (GM) crops. To investigate substantial equivalence among carotenoidbiofortified GM rice and five conventional rice cultivars having common white (three) and red (two) grain colors, profiles of 52 polar metabolites were analyzed using gas chromatography time-of-flight mass spectrometry. The results were compared to evaluate the differences among GM and non-GM rice cultivars using principal components analysis. The GM rice is more comparable to its nontransgenic counterpart rice variety according to the closer co-separation than for other cultivars tested. This suggests that profiling of unintended polar metabolites could be a useful tool to reveal substantial equivalence of GM rice.

수소싸이클링 평가에 따른 수소용기밸브의 고무오링 거동 특성

김재광,김용기(Yonggi Kim),남충우(Chungwoo Nam),박장훈,이호길 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11