• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.366-371
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• 2005

In this study treatment efficiencies of methylene blue were evaluated in term of BOD, COD, TOC, absorbance and initial decolorization rates. Ozonation of the dye in distilled water was performed in a laboratory scale cylindrical batch reactor. The decolorization process of methylene blue was carried out by bubbling ozone at the bottom of a bubble column reactor containing the dye solution. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the (${\lambda}_{max}$, 660 nm), was almost complete after 40 min with an ozone concentration of $50{\pm}10mg/L$. The $TOC/TOC_0$ ratio after ozonation was about 83.8%, the COD was diminished to 44.0% of the initial value. The $BOD_5/COD$ ratio was increased from 64.2% to about 90.8%, indicating an enhancement of biodegradable compounds in the ozonated solutions. The pseudo first-order rate constants of the ozonation was $3.30{\times}10^{-2}min^{-1}$ and the activation energy was $3.01kcal{\cdot}mol^{-1}$ at $30^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.26 no.5
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• pp.274-281
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• 1982

Ultraviolet spectrophotometric investigation have been carried out on the systems of pentamethylbenzene and hexamethylbenzene with iodine and iodine monochloride in carbon tetrachloride. The results reveal the formation of the one to one molecular complexes. The equilibrium constants were obtained in consideration of that absorption maxima due to the formation of the charge transfer complexes shift to blue with the increasing temperature. Thermodynamic parameters for the formation of the charge transfer complexes were calculated from these values. These results indicate that the complex formed between polymethylbenzene and iodine monochloride is more stable than that in the case of iodine. This may be a measure of their relative acidities toward polymethylbenzene, which is explained in terms of the relative electronegativities of halogen atoms. These results combined with previous studies of this series indicated that ${\lambda}_{max}$ shift to red with the increasing number of methyl groups on benezene ring and that the relative stabilities of these complexes increase in the order, Benzene < Toluene < Xylene < Durene < Mesitylene < Pentamethylbenzene < Hexamethylbenzene. The reason for the order found is thus additionally discussed.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.350-355
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• 1995

UV spectrophotometric investigation has been carried out on the system of charge-transfer (CT) complex with iodine and tetramethyltin in carbon tetrachloride solvent. The transient CT absorption spectrum can be observed in ${\lambda}_{max}=270nm$ and the subsequent disappearance of CT absorption spectrum was accompained by the cleavage of tetramethyltin with iodine (iododestannylation). From there, the rate constants for the iododestannylation were determined at 10, 20 and $35^{\circ}C$ up to 1200 bar and the reaction rates were increased with increasing temperature and pressure. From these rate constants, the values of the activation parameters (${\Delta}V^{\neq},\;{\Delta}{\beta}^{\neq},\;{\Delta}H^{\neq}\;and\;{\Delta}S^{\neq}$) were obtained and from these values discussed in terms of solvent structure variation of transition state and mechanism. From these results, it was found that the reaction is followed with $S_F2$ mechanism and weakened $S_F2$ mechanism nature by increasing pressure.

• Journal of electromagnetic engineering and science
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• v.11 no.2
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• pp.76-82
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• 2011

In this paper, a novel design for a dual-band negative group delay circuit (NGDC) is proposed. Composite right/left-handed (CRLH) ${\lambda}/4$ short stubs are employed as a dual-band resonator. A CRLH ${\lambda}/4$ short stub is composed of a typical transmission line element as the right-handed component and a high-pass lumped element section as the left-handed component. It is possible to simultaneously obtain open impedances at two separate frequencies by the combination of distinctive phase responses of the right/left-handed components. Negative group delay (NGD) can be obtained at two frequencies by using dual-band characteristics of the CRLH stub. In order to achieve a bandwidth extension, the proposed structure consists of a two-stage dual-band NGDC with different center frequencies connected in a cascade. According to the experiment performed, with wide-band code division multiple access (WCDMA) and worldwide interoperability for microwave access (WiMAX), NGDs of $-3.0{\pm}0.4$ ns and $-3.1{\pm}0.5$ ns are obtained at 2.12~2.16 GHz and 3.46~3.54 GHz, respectively.

• Resources Recycling
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• v.16 no.5
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• pp.46-50
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• 2007

Blue phosphor calcium aluminate, $CaAl_2O_4:Eu^{2+}$ co-doped with $Nd^{3+}$ was prepared by solid state synthesis method. Phosphor materials with 1 mol% $Eu^{2+}$ and varying compositions of $Nd^{3+}$ show high brightness and long persistent luminescence. The synthesized phosphor materials were investigated by powder x-ray diffraction (XRD), SEM, TEM, photoluminescence excitation and emission studies. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}:Nd^{3+}$ was observed in the blue region (${\lambda}_{max}=440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. $Nd^{3+}$ ion doping in the phosphor results in long afterglow phosphorescence when the excitation light is cut off.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.377-384
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• 1988

Carotenoprotein from Salmo Salar eggs was purified and characterized by CM-cellulose, 50% $(NH_4)_2SO_4$, DEAE-cellulose and sephadex G-75 column. The chromoprotein had a spectrum with ${\lambda}_{max}$ 409, 540 and 580nm in p-buffer (pH 7.0) at initial step. Molecular weights by sephadex G-200 gel filtration were 50, 200 and 26,000 daltons. SDS-PAGE analysis showed a structure with four identical subunits (12,500 daltons). Its sample retained a small amount of carbohydrates and lipids. Amino acids were analyzed, and mannose, galactose and glucosamine also were identified. Carotenoid extacted with acetone was found to be astaxanthin ester by partition test, epoxy test, iodine test, allylic test, reduction, acetylation, uv/vis, ir and nmr datas. Stearate (47.9%) and palmitate (21.4%) were predominant fatty acids in the astaxanthin ester.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1309-1315
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• 1997

Yields of enzyme-resistant starch (RS) from three kinds of maize starches (Amioca, normal starch and Amylomaize VII) which were treated with 1 N HCl for 24 hr and physicochemical characteristics were investigated. Hydrolysis rate of maize starches decreased with increasing amylose content. Maximum wavelength $({\lambda}_{max})$ and iodine affinity were decreased by the acid treatment. The yields of RS increased with acid treatment up to 12 hr and then decreased. The yield of for 12 hr acid-treated Amioca increased 8 times more than untreated sample, but those of normal starch and Amylomaize VII slightly increased. Using SEM, acid-treated and autoclaved maize starches showed gel like structure, but RS had round and rod shape small particles. X-ray diffraction patterns of autoclaved starches showed amorphous structure in Amioca and B-type in normal starch and Amylomaize VII, and those of RS showed all completely crystalline structure.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.12
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• pp.71-78
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• 2008

The paper proposes a chaotic double tent mapping PWM scheme for mitigation the acoustic noise of a motor chive. The chaos area ${\lambda}=0.99$ in bifurcation tree of the double tent mapping is used for generating the chaotic numbers. A 80C196 micro-controller is employed for generation of chaotic numbers, and the triangular carrier with chaotic frequency is obtained by using a 80C196 micro-controller and a MAX038 frequency modulator. The experiments are executed with a 1.5[kw] induction motor chive under the 2.5[A] load condition. As results, the experimental results show that the carrier, voltage and 3-D switching noise spectra of the proposed scheme is spread over the chaotic frequency range with no specific frequency concentration. Thereby, the shrill acoustic noise radiated from a motor chive is reduced by the proposed scheme.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.539-545
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• 2012

3-(2-benzotriazolovinyl)thiophene (BVT) was synthesized by the connection of the thiophene with the electron-withdrawing group, benzotriazole, through the vinylene. Its structure was confirmed by FT-IR, $^1H$-NMR, $^{13}C$-NMR and 2D hetero-cosy spectroscopy. Both BVT and 3-octylthiophene (OT) were copolymerized and showed an average molecular weight of 12000 (PDI 2.67) and 15000 (PDI 2.55), respectively. The copolymers were dissolved in the organic solvent such as chloroform, THF, TCE, etc. The mole ratios of BVT and OT in the synthesized copolymers were confirmed as 1 : 1.8 and 1 : 2.8 from $^1H$-NMR spectra. The UV-vis maximum absorption of copolymers appeared at the wavelength of 470 nm and 465 nm and the photoluminescence at ${\lambda}_{max}$ = 662 nm and 641 nm correspond to red-orange light. The band gaps of copolymers at 1.96 eV and 2.02 eV were found to be higher than those of poly(3-octylthiophene). The HOMO energy levels of the copolymers decreased overall in comparison with those of poly(3-octylthiophene), but the overall LUMO energy level increased.

• Journal of the Korean Chemical Society
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• v.63 no.3
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• pp.151-159
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• 2019

The TADF properties for carbazol-dicyanobenzene, carbazol-diphenyl sulfone, carbazol-benzonitrile derivatives as OLED candidate materials are theoretically investigated using density functional theory (DFT) with $6-31G^{**}$, cc-pVDZ, and cc-pVTZ basis sets. The optimized geometries, harmonic vibrational frequencies, and HOMO-LUMO energy separations are predicted at the B3LYP/$6-31G^{**}$ level of theory. The harmonic vibrational frequencies of the molecules considered in this study show all real numbers implying true minima. The time dependent density functional theory (TD-DFT) calculations have been also applied to investigate the absorption and emission wavelength (${\lambda}_{max}$), energy differences (${\Delta}E_{ST}$) between excited singlet ($S_1$) and triplet ($T_1$) states of candidate materials.