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Solvent and Structural Fluctuations Induced Symmetry-Breaking Charge Transfer in a Porphyrin Triad
Kim, Taeyeon,Kim, Woojae,Mori, Hirotaka,Osuka, Atsuhiro,Kim, Dongho American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.34
<P>This study aims to show that the symmetry-breaking charge transfer (SBCT) in a donor-acceptor-donor (DAD) porphyrin triad occurs via solvent and structural fluctuations measured by using femtosecond broadband fluorescence upconversion spectroscopy, which can directly trace the origin of the emitting state by monitoring its emission dipole moment as a function of time. While the emission dipole moment of the triad in the excited state remains nearly unchanged in nonpolar solvents such as cyclohexane and toluene, it is significantly reduced in polar solvents such as benzonitrile due to a change in the emitting state from quadrupolar (the exciton coupled state) to dipolar symmetry (the relaxed S<SUB>1</SUB> state). The latter state is formed by the SBCT process of DAD via a combination of solvent and structural fluctuations.</P> [FIG OMISSION]</BR>
김태연(Kim. Taeyeon),김창남(Kim. Chang-Nam),홍구표(Hong. Gu-Pyo),김광호(Kim. Kwang-Ho),노지웅(Rho. Ji-Woong),김병선(Kim. Byung-Seon) 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1
The Purpose of this study was to analyze the smoke elimination performance and evacuation time in an arcade of traditional market. In this study, the effect of the opening for the ventilation about the smoke eliminating performance was analyzed using CFD (Computational Fluid Dynamics) method. And also the evacuation time was analyzed according to the height of the building. The opening of the arcade is very important design factor to control the smoke movement.
Hyun Jung Kim(Hyun Jung Kim),Taeyeon Hwang(Taeyeon Hwang) 한국영어평가학회 2022 영어평가 Vol.17 No.2
Washback has been of interest in the field of second and foreign language teaching as well as testing; indeed, it has been widely discussed as one of the key test qualities. While multifaceted aspects of washback have been proposed and examined, there still remain many more unanswered questions because washback should be evaluated in relation to a specific testing and teaching/learning situation. It is therefore worth reviewing prior research and identifying gaps in the literature to address future research on washback, especially in the Korean context. This article first reviews seminal theoretical contributions to the current understanding of washback. It then introduces prior empirical research on two test types: largescale testing and classroom/school-based assessments used in both international and Korean contexts. Whereas the washback effects of representative international large-scale tests have been widely examined worldwide, there have been a limited number of studies on washback involving large-scale and classroom assessments in the Korean context. The primary focus of prior research has been on the perceptions of teachers and learners, while empirical evidence in teaching and learning is still lacking. These comprehensive, critical reviews illustrate washback effects on a range of stakeholders at different stages of teaching and learning, which contribute to addressing the need for future research on washback.
Kim, Tae-Kyoung,Kim, Taeyeon,Jo, Areum,Park, Suhyun,Choi, Kyungho,Zoh, Kyung-Duk Elsevier 2018 CHEMOSPHERE - Vol.208 No.-
<P><B>Abstract</B></P> <P>In this study, we developed a UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> system to remove cyanide, which is typically present in metal electroplating wastewater. The results showed the synergistic effects of UV-LED, H<SUB>2</SUB>O<SUB>2</SUB>, and Cu<SUP>2+</SUP> ions on cyanide removal in comparison with UV-LED photolysis, H<SUB>2</SUB>O<SUB>2</SUB> oxidation, UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>, and H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> systems. Cyanide was removed completely in 30 min in the UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> system, and its loss followed pseudo-first order kinetics. Statistically, both H<SUB>2</SUB>O<SUB>2</SUB> and Cu<SUP>2+</SUP> ions showed positive effects on cyanide removal, but Cu<SUP>2+</SUP> ions exhibited a greater effect. The highest cyanide removal rate constant (<I>k</I> = 0.179 min<SUP>−1</SUP>) was achieved at pH 11, but the lowest was achieved at pH 12.5 (<I>k</I> = 0.064 min<SUP>−1</SUP>) due to the hydrolysis of H<SUB>2</SUB>O<SUB>2</SUB> (pK<SUB>a</SUB> of H<SUB>2</SUB>O<SUB>2</SUB> = 11.75). The presence of dissolved organic matter (DOM) inhibited cyanide removal, and the removal rate constant exhibited a negative linear correlation with DOM (<I>R</I> <SUP>2</SUP> = 0.987). The removal rate of cyanide was enhanced by the addition of Zn<SUP>2+</SUP> ions (from 0.179 to 0.457 min<SUP>−1</SUP>), while the co-existence of Ni<SUP>2+</SUP> or Cr<SUP>+6</SUP> ion with Cu<SUP>2+</SUP> ion reduced cyanide removal. The formation of OH radicals in the UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> system was verified using an aminophenyl fluorescence (APF) probe. Cyanate ions and ammonia were detected as the byproducts of cyanide decomposition. Finally, an acute toxicity reduction of 64.6% was achieved in the system within 1 h, despite a high initial cyanide concentration (100 mg/L). In terms of removal efficiency and toxicity reduction, the UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> system may be an alternative method of cyanide removal from wastewaters.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cyanide completely removed in 30 min of UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> reaction. </LI> <LI> UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> reaction exhibited highest removal rate at pH 11. </LI> <LI> Cyanate and ammonia were detected as organic and inorganic byproducts. </LI> <LI> More than 64% of acute toxicity during reaction decreased within 60 min. </LI> <LI> UV-LED/H<SUB>2</SUB>O<SUB>2</SUB>/Cu<SUP>2+</SUP> reaction showed significantly lower energy consumption. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>