• Bulletin of the Korean Chemical Society
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• 제26권5호
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• pp.795-801
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• 2005

New PPV derivatives which contain electron-withdrawing trifluoromethyl ($CF_3$) group, poly[2-(2-ethylhexyloxy)-5-(4-trifluoro methylphenyl)-1,4-phenylenevinylene] (EH$CF_3$P-PPV), and poly[2-(2-ethylhexyloxy)-5-(3,5-bis(trifluoromethyl)-phenyl)-1,4-phenylenevinylene] (EHB$CF_3$P-PPV), have been synthesized by GILCH polymerization. As the result of the introduction of the electron-withdrawing $CF_3$ group to the phenyl substituent, the LUMO and HOMO energy levels of EH$CF_3$P-PPV (2.8, 5.1 eV) and EHB$CF_3$P-PPV (3.0, 5.3 eV) were lower than those of known poly[2-(2-ethylhexyloxy)-5-phenyl-1,4-phenylenevinylene] (EHP-PPV) (2.6, 4.9 eV). These polymers have been used as the electroluminescent (EL) layers in double layer lightemitting diodes (LEDs) (ITO/PEDOT/polymer/Al). EH$CF_3$P-PPV, and EHB$CF_3$P-PPV show maximum photoluminescence (PL) peaks at ${\lambda}_{max}$ = 550, 539 nm, and maximum EL peak at ${\lambda}_{max}$ = 545, 540 nm, respectively. The current-voltage-luminance (I-V-L) characteristics of the polymers show that turn-on voltages of EH$CF_3$P-PPV and EHB$CF_3$P-PPV are around 4.0 and 3.5 V, respectively.

• Bulletin of the Korean Chemical Society
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• 제18권3호
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• pp.296-300
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• 1997

The intracluster ion/molecule reactions within 1,1-difluoroethene homocluster have been studied by electron-impact quadrupole mass spectrometry. When CH2CF2 seeded in helium is expanded and ionized by electron impact, two different types of ion/molecule association (polymerization) reaction products, i.e., (CH2CF2)n+ (n≥l) and (CF2CH2)qX+ (X=fragment species, q≤n), are formed. The higher association products, (CH2CF2)n+ (n=3, 4), have shown stronger intensities over the lower association product, (CH2CF2)2+, in the low electron impact energy region ( < 39 eV). These stronger intensities are interpreted in terms of the stabilization of these ions due to the ring formations over the dimer ion in this energy region. The evidence of ring formation mechanism is on the basis of the intensity distribution of fragments at various electron impact energy. In another typical branched-chain growth reaction of these compounds, the F-shift reaction path is found to be more favorable energetically than the H-shift via the fragment patterns of clusters and semi-empirical calculation.

• 지능정보연구
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• 제22권3호
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• pp.113-127
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• 2016

협업 필터링(Collaborative Filtering)은 유용성과 정교성 면에서 가장 성공적인 추천 알고리즘으로 평가받으며 산업계나 학계에서 많이 활용 및 연구되고 있지만, 기본적으로 사용자들이 평가한 점수에만 기반하여 추천결과를 생성하는 한계점이 있다. 이에 본 연구는 사용자가 상품을 구매할 때 자신이 신뢰하는 타인의 추천을 더 적극적으로 수용할 것이라는 점에 착안하여, 사용자의 평점 외에 사용자 간 신뢰관계를 소셜네트워크분석으로 분석한 결과를 추가로 반영하는 추천 알고리즘들을 제안하였다. 구체적으로 본 연구에서는 소셜네트워크분석에서 네트워크 내의 중심적 위치를 나타내는 척도인 내향 및 외향 중심성을 활용하여 사용자 간 유사도를 산출하는 알고리즘들과 사용자 신뢰 네트워크를 탐색하여 추천 대상이 되는 사용자가 직접 간접적으로 신뢰하는 사용자의 평가점수를 보다 높게 반영하는 알고리즘을 제안한 뒤 그 성능을 비교해 보았다. 실제 데이터에 적용하여 분석한 결과, 사용자 신뢰 네트워크의 내향 중심성 지수를 조건 없이 적용한 경우에는 오히려 정확도의 감소만을 야기하는 것으로 나타났고, 일정 임계치 이상의 외향 중심성을 갖는 사용자에 한해 내향 중심성 지수를 고려한 추천 알고리즘은 전통적인 협업 필터링에 비해 약간의 정확도 개선이 이루어짐을 확인할 수 있었다. 아울러, 사용자 신뢰 네트워크를 기반으로 탐색하는 알고리즘이 가장 우수한 성능을 보이는 것을 알 수 있었으며, 전통적인 협업 필터링과 비교해서도 통계적으로 유의한 수준의 정확도의 개선이 이루어짐을 확인할 수 있었다.

• 한국응용과학기술학회지
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• 제21권4호
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• pp.359-363
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• 2004

Reaction conditions and catalysts were investigated for direct $CF_3I$ synthesis. Optimum reaction temperature was determined by pyrolysis of $CF_3H$ and catalytic reactions. Reactions with changing oxygen concentration were performed. As a result, yield of $CF_3I$ increased with decreasing oxygen concentration. Catalytic activity was changed with the weight ratio of the used metal salts. This result was stemmed from the change in the pore size of activated carbon by the metal salts. The optimum reaction conditions were: $600^{\circ}C$, space velocity of $45hr^{-1}$, and with 7wt% KF/AC catalyst.

• Bulletin of the Korean Chemical Society
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• 제13권2호
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• pp.158-162
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• 1992

Hydrocarbon solution of $(PPh_3)_2(CO)MOSO_2CF_3(M=Rh$, Ir)reacts rapidly with Pyrazine or 4,4'-bipyridyl to yield dinuclear metal complexes $[(PPh_3)_3(CO)M({\mu}-pyrazine)M(CO)(PPh_3)_2](SO_3CF_3)_2$ (I: M= RhH; III: M=Ir) or [$(PPh_3)_2$(CO)M(${\mu}$-44'-bipyridyl)M(CO)$(PPh_3)_2](SO_3CF_3)_2$, (II: M=Rh; IV: M=Ir), respectively. Compounds, I, II, III, and IV were characterized by $^1H-NMR$, $^{13}C-NMR$, $^{31}P-NMR$, and infrared spectrum. Ethanol solution of $(PPh_3)_2(CO)MOSO_2CF_3$ (M=Rh, Ir) also reacts with $(TBA)_2$M'$(CN)_4$ (M'=Pd, Pt) to yield trinuclear metal complexes [$(PPh_3)_2$(CO)dM-NCM'$(CN)_2$CN-M(CO)$(PPh_3)_2]$ (V : M=Rh, M'=Pd; VI : M=Rh, M'=Pt; VII: M=Ir, M'=Pd; VIII: M=Ir, M'=Pt). The trinuclear metal complexes V, VI, VII, and VIII are bridged by the cyanide groups. The infrared spectrum of V, VI, VII, and VIII supports the presence of the bridged cyanide and terminal cyanide group.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.291-294
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• 2002

The reactions of triplet oxygen atom with halomethanes as a potential fire extinguisher were studied by a discharge flow-chemiluminescence imaging method. The experiments were carried out under second order conditions. The bimolecular atom-molecule reaction rate constants were determined in terms of the initial rate method. The initial concentration of oxygen atom was also determined under second order rate law instead of the pseudo-first order conditions with $[O(^3P)]_0{\ll}[sample]_0$. The second order conditions were more reliable than pseudo-first order conditions for the determinations of rate constants. The rate constants of the reactions $CF_3I\;+\;O(^3P)$, $CH_3PI\;+\'O(^3P)$, and $CHBrCl_2\;+\;O(^3P)$ were determined to be $5.0\;{\times}\;10^{-12}$ , $1.1\;×\;0^{-11}$ , and $1.9\;{\times}\;10^{-14}cm^3molecule^{-1}s^{-1}$, respectively.

• 대한한의학방제학회지
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• 제11권2호
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• pp.159-171
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• 2003

This study was done to investigate effects of SR, CF and AR to angiogenesis of cerebral tissues, protecting damage of cerebral neurons and activating them in cerebral contusion-induced rats. I observed these conclusions as follows ; 1. Observation of VEGF-immunoreactive cells : Groups of administered AR were not meaningful in increasing VEGF-immunoreactive cells for 3 days and 7 days, groups of administered SR meaningfully increased them to control groups in all groups, and groups of administered CF meaningfully increased them to control groups in all groups, too, interestingly, increased double to control group for 7 days. 2. Observation on cerebral neurons by Cresyl violet stain : Dendrites and axons of groups of administered SR, AR for 3 days were clearly observed to control group. Cerebral neurons of groups of administered CF for 3days and 7 days were increased a little, but were not meaningful. In conclusion, AR will be careful of being used in cerebral contusion. CF and SR were effective to activating cerebral hemokinesis by inducing angiogenesis in trauma of tissue, but weakly to protecting trauma of cerebral neurons and activating them. I think more studies will be done in these facts.

• Bulletin of the Korean Chemical Society
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• 제24권5호
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• pp.641-644
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• 2003

• Journal of the korean society of oceanography
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• 제31권3호
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• pp.144-149
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• 1996

I investigated the predation impact by the heterotrophic dinoflagellate Protoperidinium cf. divergens on copepod eggs in the presence of co-occurring phytoplankton prey (a preferred red-tide dinoflagellate Gonyaulax polyedra) and the selective feeding on mixtures of both prey. The ingestion rates of P. cf. divergens on Egg N (unidentified round copepod eggs with a smooth surface, about 80 in diameter) decreased by only 1.7-2 times when mean G. polyedra concentration increased by 57-115 times. In mixed prey experiments, P. cf. divergens preferred Egg N over G. polyedra even at 1.1 ${\mu}g$C $ml^{-1}$ or 470 cells $ml^{-1}$ of the latter. A strong preference of P. cf. divergens for Egg N over G. polyedra can be responsible for this relatively small effect. Protoperidinium may sometimes have a considerable predation impact on the populations of Egg N even during phytoplankton blooms or red-tide periods.

• Preventive Nutrition and Food Science
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• 제15권3호
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• pp.206-212
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• 2010

Codium fragile (CF) is an edible green alga consumed as a traditional food source in Korea. In this study, the ethanol extract of CF was evaluated to determine if it has anti-inflammatory activity. Lipopolysaccharide (LPS), a toxin from bacteria, is a potent inducer of inflammatory cytokines, such as tumor necrosis factor (TNF)-$\alpha$ and interleukin (IL)-6. Therefore, we studied whether CF extracts have an anti-inflammatory effect in LPS-induced murine macrophage cell lines (RAW 264.7). In the present study, IL-6 production was measured using an enzyme-linked immunosorbent assay (ELISA), prostaglandin $E_2$($PGE_2$) production was measured using the EIA kit, and cyclooxygenase (COX)-2 and mitogen-activated protein kinase (MAPK) activation were determined by Western blot analysis. IL-6 mRNA, COX-2 mRNA and iNOS mRNA expression were measured using reverse transcription-polymerase chain reaction (RT-PCR). The results indicated that CF extracts inhibit LPS-induced IL-6, NO and PGE2 production in a dose-dependent manner, as well as expression of iNOS and COX-2. CF extracts significantly inhibited LPS-induced c-Jun N-terminal kinase (JNK) 1/2 phosphorylation. Taken together, these findings may help elucidate the mechanism by which CF modulates RAW 264.7 cell activation under inflammatory conditions.