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Search Results: 1 - 10 of 7951 matches for " Jong-Geun Choi "
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Biodiesel Resistance of Thin Resin Cr-Free Steel Sheets for Fuel Tank  [PDF]
Dong-Joo Yoon, Kyung-Hwan Lee, Jong-Geun Choi, Sangkeol Noh, Jongsang Kim
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.35057
Abstract: The content of biodiesel mixed with diesel fuel were compared to inspect the fuel resistance of thin resin Cr-free steel sheets, which are widely used as steel sheets of automobile fuel tank. Some additives which can be presented during the process of biodiesel preparation were added for CCT (Cyclic Corrosion Test). These additives can accelerate the occurrence of corrosion. The corrosion was appeared on the coating and painting layer and in serious cases even substrate material was corroded. For methanol, mixing with blended fuel showed the reduction in corroded area as the additive concentration was reduced in the mixed fuel. Especially the peroxide hydrogen showed the strongest corrosiveness. It is known that formic acid has a tendency of weaker corrosiveness than peroxide hydrogen, but the corrosion is occurred throughout the specimen. Water is not mixed well with fuel, and does not seem to impact on corrosion significantly. However, water is easily mixed with other additives and is considered to facilitate the corrosion by other additives.
Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light
Meng Ze-Da,Zhu Lei,Choi Jong-Geun,Park Chong-Yeon
Nanoscale Research Letters , 2011,
Abstract: WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3.
RareEarthOxide-TreatedFullereneandTitaniaCompositeswithEnhancedPhotocatalyticActivityfortheDegradationofMethyleneBlue
MENG Zada,ZHU Lei,CHOI Jong-geun,PARK Chong-yeon,OH Won-chun
催化学报 , 2011, DOI: 10.1016/S1872-2067(10)60258-6
Abstract: ?Rareearthoxide-treatedfullereneandtitaniacomposites(Y-fullerene/TiO2)werepreparedbythesol-gelmethod.Theproductshadinterestingsurfacecompositions.X-raydiffractionpatternsofthecompositesshowedthattheY-fullerene/TiO2compositescontainedasingleandclearanatasephase.Thesurfacepropertieswereobservedbyscanningelectronmicroscopy,whichgaveacharacterizationofthetextureontheY-fullerene/TiO2compositesandshowedahomogenousdistributionoftitaniumparticles.Theenergy-dispersiveX-rayspectrashowedthepresenceofCandTiwithstrongYpeaks.ThecompositeobtainedwasalsocharacterizedwithtransmissionelectronmicroscopyandUV-Visspectroscopy.ThephotocatalyticresultsshowedthattheY-fullerene/TiO2compositeshadexcellentactivityforthedegradationofmethyleneblueundervisiblelightirradiation.ThiswasattributedtoboththeeffectsonthephotocatalysisofthesupportedTiO2bychargetransferbythefullerene,andtheintroductionofyttriumtoenhancephoto-generatedelectrontransfer.
Synthesis of Carbon Nanomaterials-CdSe Composites and Their Photocatalytic Activity for Degradation of Methylene Blue
Ming-Liang Chen,Ze-Da Meng,Lei Zhu,Chong-Yeon Park,Jong-Geun Choi,Trisha Ghosh,Kwang-Youn Cho,Won-Chun Oh
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/964872
Abstract: We use multi-walled carbon nanotube (MWCNT) and graphene as carbon nanomaterials to obtain carbon nanomaterilas-CdSe composites using a facile hydrothermal method. The intrinsic characteristics of resulting composites were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectrophotometer. The as-prepared carbon nanomaterilas-CdSe composites possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with carbon nanomaterilas-CdSe composites, compared to the CdSe compound.
Characteristics of primary and immortalized fibroblast cells derived from the miniature and domestic pigs
Ho-Yeon Oh, Xun Jin, Jong-Geun Kim, Myung-Joo Oh, Xumin Pian, Jun-Mo Kim, Moon-Seok Yoon, Chae-Ik Son, Young Lee, Ki-Chang Hong, Hyunggee Kim, Yun-Jaie Choi, Kwang Whang
BMC Cell Biology , 2007, DOI: 10.1186/1471-2121-8-20
Abstract: The in vitro lifespan of primary domestic pig fibroblast (PF) and miniature pig fibroblast (MPF) cells using a standard 3T3 protocol was determined. Both of the primary PF and MPF cells were shown to have a two-step replicative senescence barrier. Primary MPF cells exhibited a relatively shorter lifespan and slower proliferation rate compared to those of primary PF cells. Beyond senescence barriers, lifespan-extended PF and MPF cells were eventually established and indicated spontaneous cellular immortalization. In contrast to the immortalized PF cells, immortal MPF cells showed a transformed phenotype and possessed more frequent chromosomal abnormalities and loss of p53 regulatory function. The lifespan of primary MPF and PF cells was extended by inactivation of the p53 function using transduction by SV40LT without any detectable senescent phenotype.These results suggest that p53 signaling might be a major determinant for the replicative senescence in the MPF cells that have the shorter lifespan and slower growth rate compared to PF cells in vitro.Research using in vitro cell culture methods has a number of limitations to a complete understanding of biological systems in vivo. The primary somatic cells, however, are valuable tools to enable the study of a variety of cellular and biochemical functions under tightly controlled experimental conditions. One limitation to primary somatic cell use that must be managed is their finite proliferative capacity due to permanent growth arrest known as replicative senescence [1]. Replicative senescence is known to be triggered by two inter-dependent mechanisms; one is activation of two tumor suppressor pathways (p16INK4a/RB and ARF/p53, [2]), the second is a shortening of the telomeres due to an end-replication problem during chromosome replication [3,4]. To overcome these limitations, much effort has been put into the establishment of immortalized cell lines that have an unlimited replicative potential and normal cellular func
Filiform polyposis in the sigmoid colon: A case series
Chang Geun Lee, Yun Jeong Lim, Jong Sun Choi, Jin Ho Lee
World Journal of Gastroenterology , 2010,
Abstract: Filiform polyposis is a rare condition of uncertain pathogenesis that is usually found in association with Crohn’s disease, ulcerative colitis, intestinal tuberculosis or histiocytosis X. We report seven interesting cases of polyposis with various pathologic components, mainly located in the left side of the colon with no associated inflammatory bowel disease, intestinal tuberculosis or histiocytosis X. Multiple finger-like polypoid lesions with the appearance of stalactites were noted on the left side of the colon, especially in the sigmoid area, at the time of colonoscopy. The polyps had a variety of sizes and shapes and were shown to have various histopathologic components among the different patients. Although filiform polyposis localized in the sigmoid colon appears not to have high oncogenic potential, periodic follow-up seems to be needed.
A Practical Protection Coordination Strategy Applied to Secondary and Facility Microgrids
Dae-Geun Jin,Jong-Chan Choi,Dong-Jun Won,Hak-Ju Lee,Woo-Kyu Chae,Jung-Sung Park
Energies , 2012, DOI: 10.3390/en5093248
Abstract: In a conventional distribution system, protection algorithms are designed to operate on a unidirectional high fault-current level. In a microgrid, a fault current from distributed generation (DG) may bring about a relay malfunction because of the bidirectional and relatively small fault current. Therefore, the conventional protection scheme is not applicable to microgrids and a new protection method must be developed. In this paper, two protection coordination algorithms which can be applied for facility and secondary microgrids are proposed, respectively. The proposed protection algorithms eliminate faults not by the EMS signal but by directional relays. Moreover, this makes the algorithms flexible regardless of the types and numbers of DG. The proposed protection algorithms were simulated at the KEPCO RI Microgrid Demonstration Site.
Allelic Expression Imbalance of JAK2 V617F Mutation in BCR-ABL Negative Myeloproliferative Neoplasms
Hye-Ran Kim, Hyun-Jung Choi, Yeo-Kyeoung Kim, Hyeoung-Joon Kim, Jong-Hee Shin, Soon-Pal Suh, Dong-Wook Ryang, Myung-Geun Shin
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0052518
Abstract: The discovery of a single point mutation in the JAK2 gene in patients with BCR/ABL-negative myeloproliferative neoplasms (MPNs) has not only brought new insights and pathogenesis, but also has made the diagnosis of MPNs much easier. Although, to date, several mechanisms for the contribution of single JAK2V617F point mutation to phenotypic diversity of MPNs have been suggested in multiple studies, but it is not clear how a unique mutation can cause the phenotypic diversity of MPNs. In this study, our results show that allelic expression imbalance of JAK2 V617F mutant frequently occurs and contributes to phenotypic diversity of BCR-ABL-negative MPNs. The proportion of JAK2 V617F mutant allele was significantly augmented in RNA levels as compared with genomic DNA differently by distinct MPNs subtypes. In detail, preferential expression of JAK2 mutant allele showed threefold increase from the cDNA compared with the genomic DNA from patients with essential thrombocythemia and twofold increase in polycythemia vera. In conclusion, allelic expression imbalance of JAK2 V617F mutant proposes another plausible mechanism for the contribution of single JAK2 point mutation to phenotypic diversity of MPNs.
Successive spin-flop transitions of Neel-type antiferromagnet Li$_2$MnO$_3$ single crystal with honeycomb-lattice
K. Balamurugan,Sang-Hyun Lee,Jun-Sung Kim,Jong-Mok Ok,Youn-Jung Jo,Young-Mi Song,Shin-Ae Kim,E. S. Choi,Manh Duc Le,Je-Geun Park
Physics , 2014, DOI: 10.1103/PhysRevB.90.104412
Abstract: We have carried out high magnetic field studies of single-crystalline Li$_2$MnO$_3$, a honeycomb lattice antiferromagnet. Its magnetic phase diagram was mapped out using magnetization measurements at applied fields up to 35 T. Our results show that it undergoes two successive meta-magnetic transitions around 9 T fields applied perpendicular to the ab-plane (along the c*-axis). These phase transitions are completely absent in the magnetization measured with field applied along the ab-plane. In order to understand this magnetic phase diagram, we developed a mean-field model starting from the correct Neel-type magnetic structure, consistent with our single crystal neutron diffraction data at zero field. Our model calculations succeeded in explaining the two meta-magnetic transitions that arise when Li$_2$MnO$_3$ enters two different spin-flop phases from the zero field Neel phase.
Landscape Analysis of the Effects of Artificial Lighting around Wetland Habitats on the Giant Water Bug Lethocerus deyrollei in Jeju Island
Choi, Ho,Heungtae Kim,Jae Geun Kim
Journal of Ecology and Field Biology , 2009,
Abstract: We conducted a landscape analysis to investigate the possibility of adverse effects of anthropogeniclight sources, such as roads and residential buildings, on Lethocerus deyrollei on Jeju Island. Wetlandsinhabited by L. deyrollei had fewer anthropogenic structures within a 3 km radius that had the potential toproduce artificial light at night than wetlands not inhabited by L. deyrollei. In particular, the presence of artificiallights within a 1 km radius appears to reduce the probability of inhabitation by L. deyrollei. Our results suggestthat artificial light sources may be critical determinants of L. deyrollei inhabitation patterns in a landscape, andthat habitats that have a buffer area of at least 600~700 m radius free from residential buildings are the mostappropriate habitats for L. deyrollei.
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