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( Sumin Pyo ),( Hanie Hakimian ),( Young-min Kim ),( Kyung-seun Yoo ),( Young-kwon Park ) 한국공업화학회 2021 공업화학 Vol.32 No.6
In the current research, thermal and catalytic thermogravimetric (TG) analysis of polyethylene terephthalate (PET) over natural zeolite (NZ), olivine, bentonite, HZSM-5, and HAl-MCM-41 were investigated using a TG analyzer and model-free kinetic analysis. Catalytic TG analysis of PET was carried out at multi-heating rates, 10, 20, 30, and 40 °C/min, under nitrogen atmosphere. Apparent activation energy (Ea) values for the thermal and catalytic pyrolysis of PET were calculated using Flynn-Wall-Ozawa method. Although natural catalysts, NZ, olivine, and bentonite, could not lead the higher PET decomposition efficiency than synthetic zeolites, HZSM-5 and HAl-MCM-41, maximum decomposition temperatures on the differential TG (DTG) curves for the catalytic pyrolysis of PET, 436 °C over olivine, 435 °C over bentonite, and 434 °C over NZ, at 10 °C/min, were definitely lower than non-catalytic pyrolysis. Calculated Ea values for the catalytic pyrolysis of PET over natural catalysts, 177 kJ/mol over olivine, 168 kJ/mol over bentonite, and 171 kJ/mol over NZ, were also not lower than those over synthetic zeolites, however, those were also much lower than the thermal decomposition, suggesting their feasibility as the proper and cost-effective catalysts on the pyrolysis of PET.
Kwon, Ji Eon,Lee, Sumin,You, Youngmin,Baek, Kyung-Hwa,Ohkubo, Kei,Cho, Jaeheung,Fukuzumi, Shunichi,Shin, Injae,Park, Soo Young,Nam, Wonwoo American Chemical Society 2012 Inorganic Chemistry Vol.51 No.16
<P>A new fluorescent zinc sensor (HNBO–DPA) consisting of 2-(2′-hydroxy-3′-naphthyl)benzoxazole (HNBO) chromophore and a di(2-picolyl)amine (DPA) metal chelator has been prepared and examined for zinc bioimaging. The probe exhibits zinc-induced fluorescence turn-on without any spectral shifts. Its crystal structure reveals that HNBO–DPA binds a zinc ion in a pentacoordinative fashion through the DPA and HNBO moieties. Steady-state photophysical studies establish zinc-induced deprotonation of the HNBO group. Nanosecond and femtosecond laser flash photolysis and electrochemical measurements provide evidence for zinc-induced modulation of photoinduced electron transfer (PeT) from DPA to HNBO. Thus, the zinc-responsive fluorescence turn-on is attributed to suppression of PeT exerted by deprotonation of HNBO and occupation of the electron pair of DPA, a conclusion that is further supported by density functional theory and time-dependent density functional theory (DFT/TD-DFT) calculations. Under physiological conditions (pH 7.0), the probe displays a 44-fold fluorescence turn-on in response to zinc ions with a <I>K</I><SUB>d</SUB> value of 12 pM. The fluorescent response of the probe to zinc ions is conserved over a broad pH range with its excellent selectivity for zinc ions among biologically relevant metal ions. In particular, its sensing ability is not altered by divalent transition metal ions such as Fe(II), Cu(II), Cd(II), and Hg(II). Cell experiments using HNBO–DPA show its suitability for monitoring intracellular zinc ions. We have also demonstrated applicability of the probe to visualize intact zinc ions released from cells that undergo apoptosis. More interestingly, zinc-rich pools in zebrafish embryos are traced with HNBO–DPA during early developmental stages. The results obtained from the <I>in vitro</I> and <I>in vivo </I>imaging studies demonstrate the practical usefulness of the probe to detect zinc ions.</P><P>The fluorescence sensor, constructed based on an excited-state intramolecular proton transfer (ESIPT) platform, displays zinc-selective turn-on response with <I>K</I><SUB>d</SUB> = 12 pM at pH 7.0. The fluorescence zinc response is attributed to suppression of photoinduced electron transfer exerted by deprotonation and occupation of the electron pair of the metal chelator. The zinc probe is capable of detection of endogenous free zinc ions in apoptotic mammalian cells and zebrafish embryos.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2012/inocaj.2012.51.issue-16/ic300476e/production/images/medium/ic-2012-00476e_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic300476e'>ACS Electronic Supporting Info</A></P>
Seoyeon Kwon,Sumin Kim,Haein Yim 한국물리학회 2020 Current Applied Physics Vol.20 No.1
In the present study, we investigated the effect of heat treatment on the magnetic properties of the Fe87- xSixB9Nb3Cu1 (x=1, 3, 5, 7, 9, and 13.5) alloy system. Ribbon samples with the width of 2mm and thickness of 20–30 μm were synthesized by melt spinning. Among the samples, only amorphous samples were nanocrystallized by annealing between 360 and 600 °C. The annealed alloys tended to have improved soft magnetic characteristics, including higher saturation magnetic flux density (Bs), while maintaining high relative permeability (μr), and low core loss (Pcv). A high saturation magnetic flux density of 1.51 T was obtained for the Fe78Si9B9Nb3Cu1 core sample after longitudinal magnetic field annealing at 520 °C. The sample had excellent soft magnetic properties as compared to the conventional value of FINEMET core (Bs=1.23 T), which is a significant improvement as compared to the as-spun ribbons (Bs=1.10-1.26 T).
박수민(Sumin Park),권재성(Jae-Sung Kwon) 한국가시화정보학회 2020 한국가시화정보학회지 Vol.18 No.3
The purpose of this study is to numerically evaluate the collection performance of an ultra-small Lapple cyclone separator for 1~10 ㎛ particles introduced at flow rate of 10 L/min. The numerical evaluation reveals that a static pressure drop occurs more dominantly inside of the cyclone separator than at the inlet and the vortex finder. Also a fluid flow in the cyclone separator is confirmed to have a helical structure heading upward in the center of cyclone separator and downward in the vicinity of wall. The investigation on dust collection efficiency of the Lapple cyclone separator shows that particles of 4~8 ㎛ diameters are collected at very lower efficiency than other sizes. Then, the cut-point diameter of the cyclone separator is 1.48 ㎛.