• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.99-106
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• 2013

DME (Di-Methyl Ether) is synthetic product that is produced through dehydration of methanol or a direct synthesis from syngas. And it is able to save fossil fuel and reduce pollutants of emission such as PM and $CO_2$. In spite of its advantages it is difficult to design DME fuelled engine system because DME fuel may cause to severely generate cavitation and corrosion in fuel delivery system due to physical properties of DME. Therefore, in this study three-dimensional internal flow characteristics with consideration of cavitation were predicted in the DME injector using diesel and DME fuel. Moving grid technique was employed to describe needle motion and 1-D hydraulic simulation of injector was also simulated to obtain transient needle motion profiles. The results of simulation show that cavitations was generated at the inlet of nozzle near high velocity region both diesel and DME. And mass flow rate of DME is reduced by 4.73% compared to that of diesel at maximum valve lift because cavitation region of DME is much more larger. To increase flow rate of DME injector, internal flow simulation has been conducted to investigate the nozzle hole inner R-cut effect. The flow rates of diesel and DME increase as R-cut increases, and flow coefficient of DME fuel injector was increased by 6.3% on average compared with diesel fuelled injector. Finally, optimum shape of DME injector nozzle is suggested through the comparison of flow coefficient with variation of nozzle hole inner R-cut.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.824-829
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• 2002

New di-N-cyanomethylated tetraaza macrocycle 2.13-bis(cyanomethyl)-5.16-dimethyl-2,6,13,17-tetraazatricyclo[$16.4.0.0^7.12$]docosane $(L^2)$ has been prepared by the reaction of 3, 14-dimethyl-2,6,13,17-tetraazatricyclo $(L^1)$ with bromoacetonitrile. The square-planar complexes $[ML^2](ClO_4)_2(M=Ni(II)$ or Cu(II) can be prepared by the reaction of $L^2$ with the corresponding metal ion in acetonitrile. The cyanomethyl groups of $[ML^2](ClO_4)_2readily$ react with water to $yield[ML^3](ClO_4)_2$ containing pendant amide groups. The trans-octahedral complexes $[ML^4](ClO_4)_2$, in which two imidate ester groups are coordinated to the metal ion, can be also prepared by the reaction of $[ML^2](ClO_4)_2with$ methanol under mild conditions. The hydrolysis and alcoholysis reactions of $[ML^2](ClO_4)_2are$ promoted by the central metal ion, in spite of the fact that the cyanomethyl group is not involved in intramolecular coordination. The reactions are also promoted by a base such as triethylamine but are retarded by an $acid(HClO_4).Interestingly$, the imidate ester groups of $[ML^4]^2$ are unusually resistant to hydrolysis even in 0.1 M $HCIO_4$ or 0.1 M NaOH aqueous solution. Crystal structure of $[NiL^4](ClO_4)_2shows$ that the Ni-N (pendant imidate ester group) bond is rlatively strong; the Ni-N bond distance is shorter then the Ni-N(tertiary) distance and is similar to the Ni-N (secondary) distance.

• YAKHAK HOEJI
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• v.35 no.3
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• pp.154-164
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• 1991

These experiments were conducted to investigate the effects of Glycyrrhizae Radix extract(GR) on histamine synthesis, lymphocyte blastogenesis in C57BL/6J mice splenocytes, IL-1 production, $Ca^{2+}$ uptake by macrophage-like P388D$_{1}$ cells and plaque forming cell assay against SRBC. Histamine contents, lymphocyte blastogenesis, IL-1 activity, $Ca^{2+}$ uptake and plaque forming cell were determined by enzyme isotope method, [$^{3}$H]-thymidine incorporation, C3H/HeJ mouse thymocytes proliferation, the addition of 5 $\mu$Ci/ml $^{45}Ca^{2+}$ to P388D$_{1}$ cell suspension and assay to sheep red blood cell, respectively. Cytotoxicity, which was expressed as 50% mortality, was occurred by the addition of GR(10$^{-3}$g/ml). Histamine production in mouse spleen cell culture was significantly increased by 48 hour incubation added 0.25$\mu\textrm{g}$/ml of Con A. Con A-dependent T-lymphocyte proliferation was also enhanced by the addition of 0.25 $\mu\textrm{g}$/ml of Con A. GR depressed histamine contents at 10$^{-9}$~10$^{-4}$g/ml. and Con A (0.25 $\mu\textrm{g}$/ml) dependent T-lymphocyte proliferation at 10$^{-5}$~10$^{-4}$g/ml. IL-1 activity was significantly decreased by 10$^{-8}$~10$^{-4}$g/ml of GR. $Ca^{2+}$ uptake was not changed by GR, but antibody production markedly increased at 10.0~50.0 mg/kg of GR. From the above results, it is suggested that GR have immuno-regulatory action; GR decreased cell-mediated immune response and increased antibody production by B lymphocyte at high doses.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.3943-3949
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• 2012

A series of aromatic hydrazides 3a-j were prepared by refluxing esters 2a-j with hydrazine hydrate in methanol, which were prepared by the esterification of 1a-j. Acetohydrazides 3a-j upon treatment with carbon disulfide and methanolic potassium hydroxide yielded potassium dithiocarbazate salts 4a-j, which on refluxing with hydrazine hydrate yielded substituted 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones 5a-j. The target compounds 6a-j were synthesized by condensing furan-3-carboxylic acid in the presence of polyphosphoric acid under reflux. The structures of newly synthesized compounds were characterized by IR, $^1H$ NMR, $^{13}C$ NMR, elemental analysis and mass spectrometric studies. All the synthesized compounds were screened for their urease, acetylcholine esterase inhibition, antioxidant and alkaline phosphatase inhibition activity. Almost all of the compounds 6a-j showed good to excellent activities against urease and acetylcholine esterase more than the reference drugs. Compounds 6f and 6g were more potent scavenger of free radicals than the reference n-propyl gallate. Compound 6b and 6h showed excellent activities of alkaline phosphatase as compare to the reference $KH_2PO_4$.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3617-3622
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• 2010

The reaction of stoichiometric amount of $FeCl_2{\cdot}4H_2O$, (2-pyridylmethyl, 3-pyridylmethyl)amine (2,3-pyma) and sodium azide/sodium thiocyanate in methanol under aerobic conditions affords the dinuclear Fe(III) complexes, [(2,3-pyma) $(N_3)_2Fe({\mu}-OCH_3)_2Fe(N_3)_2$(2,3-pyma)]${\cdot}CH_3OH$ (1) and [(2,3-pyma)$(NCS)_2Fe({\mu}-OCH_3)_2Fe(NCS)_2$(2,3-pyma)] (2) in good yield. Two bis-methoxy-bridged diiron(III) complexes are isolated and characterized. The coordination geometries around iron(III) ions in 1 and 2 are the same tetragonally distorted octahedron. The iron(III) ions are coordinated by two nitrogens of a 2,3-pyma, two nitrogens of two azide/thiocyanate ions, and two oxygens of two methoxy groups. Both compounds are isomorphous. The structures of 1 and 2 display the C-$H{\cdots}\pi$ and/or $\pi-\pi$ stacking interactions as well as hydrogen bonding interactions, respectively. Compounds 1 and 2 show significant antiferromagnetic couplings through the bridged methoxy groups between the iron(III) ions in the temperature range from 5 to 300 K ($H=-2JS_1{\cdot}S_2$, J=-19.1 and $-13.9\;cm^{-1}$ for 1 and 2).

• Journal of the Korean Chemical Society
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• v.29 no.3
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• pp.257-264
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• 1985

Dioxobis(3-methoxysalicyaldehydato)molybdeum(VI) complex has been synthesized by reactions of 3-methoxysalicylaldehyde and ammonium paramolybdate in methanol solution. With appropriate primary amine, the resulting complex gave schiff-base complexes, MoO$_2$(CH$_3$O-sal-N-R)$_2$ in which C=O oxide ligands had been replaced by nitrogen. The properties and possible molecular structure of these complexes were discussed by elemental analysis, spectroscopic studies and electric conductivities measurements. It was found that the Mo(VI) complexes contain a cis-MoO$_2$ group since their infrared spectra two Mo=O band at about 900cm$^{-1}$ and the combining ratios for MoO$_2$-ligand are 1 : 2. Also, electronic spectra of molybdenyl complexes assigned to ligand-to-metal charge transfer transition. All of these complexes are yellow or orange, depolar compound and slightly soluble in alcohol, dichloromethane, chloroform and N,N-dimethylformamide.

• Journal of the Korean Chemical Society
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• v.47 no.1
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• pp.59-66
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• 2003

The comb-type grafted polymer hydrogels, which composed of N-isopropylacrylamide monomer and oligo(N-isopropylacrylamide-co-tert-butylacrylamide) [oligo(NIPAAm-co-t-BAM)], were synthesized by redox polymerization in 5~10% methanol aqueous solution using ammonium peroxodisulfate (APS) at 4 oC for 24h. The lower critical solution temperatures (LCSTs) of the comb-type grafted hydrogels were decreased with increase of t-BAM content in the grafted copolymer. We observed the effect of crosslinker and concentration of oligo(NIPAAm-co-t-BAM) on the shrinking/swelling ratio of hydrogels. Changes of shrinking/swelling ratio were decreased with increase of concentration of crosslinker. The increase of grafted oligo(NIPAAm-co-t-BAM) in the hydrogel shows an fast changes of shrinking/ swelling rate. The comb-type grafted hydrogels are expected to be valuable for the sensing materials of time-temperature labels(TTLs).

• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.284-290
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• 2019

Ternary MoS₂/graphene (G)-TiO₂ photocatalysts were prepared by a simple hydrothermal method. The morphology, phase structure, band gap, and catalytic properties of the prepared samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-vis spectrophotometry, and Brunauer-Emmett-Teller surface area measurement. The H₂ production efficiency of the prepared catalysts was tested in methanol-water mixture under visible light. MoS₂/G-TiO₂ exhibited the highest activity for photocatalytic H₂ production. For 5 wt.% and 1 wt.% MoS₂ and graphene (5MT-1G), the production rate of H₂ was as high as 1989 µmol^-1h^-1. The catalyst 5MT-1G showed H₂ production activity that was ~ 11.3, 5.6, and 4.1 times higher than those of pure TiO₂, 1GT, and 5MT, respectively. The unique structure and morphology of the MoS₂/G-TiO₂ photocatalyst contributed to its improved hydrogen production efficiency under visible light.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.867-874
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• 2000

Two new azobenzene crown ether calix[4]arenes, 10 and 11, were synthesized by two pathways. In the first pathway,two ethoxy nitrobenzene groups were attached to t-butylcalix[4]arenes in a 1,3 position. Subsequent reduction ofthe nitrobenzene group s by metallic zinc in an alkaline solution afforded 10 and 11 in8% and 12%,respectively. In the second pathway,an azobenzene containing two glycolic units was prepared prior connect-ing to t-butylcalix[4]arenes. The yields from the second approach (5%, 8% for 10 and 11, respectively) were lower than those from the former approach. Single crystals of 10 suitable for X-ray crystallography was ob-tained by recrystallization in methanol.Both the X-ray structure and the 1H-NMR spectrum of 10 indicated that the stereoisomer of the azobenzene moiety was trans and the calixarene platform was in cone conformation. 1H NMR spectroscopy suggested that 10 underwent an observable cis-trans isomerization in CDCl3 under room light and upon UV irradiation with cis:trans ratios of 33:67 and 36:64,respectively. Compound 6 which was the precursor of 11showed fluxional behavior and was found to have mixed conformations ofcone and partial cone with a ratio of 47:53 at -30 $^{\circ}C.$ 1H NMR spectrum of 11 suggested that 11 was initially isolated as cis azobenzene with calix[4]arene in cone conformation and underwent conformational interconversion through calix[4]arene annulas in a similar fashion to 6 upon exposing to light. The complexation studies of 10 with picrate salts of Na+ and K+ using 1H NMR spectroscopysuggested that Na+ preferred to bind the cis form of 10 while K+ preferred to bind the trans form. The stereoisomer of the azobenzene unit in 11 changed partially from cis to trans upon complexing with K+.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.86-92
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• 2019

Although perylene bisimide derivatives have advantages such as excellent thermal stability and high luminance efficiency, they have poor solubility characteristics in organic solvents. In this research, in order to improve the solubility characteristics, we prepared perylene bisimide derivatives (1C) and (2C) with swallow-tail substituted imide, which is known to lead to excellent solubility. The structures and properties of swallow-tail perylene bisimide (1C) and (2C) were analyzed by $^1H-NMR$, FT-IR, UV/Vis spectroscopy, and thermogravimetric analysis (TGA). The maximum absorption wavelengths of (1C) and (2C) in the UV/Vis spectrum were 558 nm and 556 nm, respectively, and the maximum emission wavelengths were 602 nm and 600 nm, respectively. In the TGA, (1C) demonstrated good thermal stability with less than 5 wt% weight loss up to $242^{\circ}C$. In the solubility test, (1C) and (2C) exhibited solubilities of more than 5 wt% in chloroform, ethyl acetate, and dimethylformamide, but not in methanol. When the compounds (1C) and (2C) were mixed with PMMA (polymethyl methacrylate), thin films showed peaks at 679 nm and 677 nm, respectively, in the photoluminescence spectra. (1C) was found to be a possible candidate as red organic phosphor for hybrid LEDs.