• Proceedings of the KSME Conference
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• 2001.06d
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• pp.66-70
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• 2001

The combustion characteristics have been investigated to develop the low $NO_{x}$ gas turbine combustor. The lean premixed combustion technology was applied to reduce the $NO_{x}$ emission. Also, the conventional combustor was designed and tested for the baseline of low $NO_{x}$ combustor performance. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of 500K were supplied to the combustor through the air preheater. The temperature and emissions of $NO_{x}$ and CO were measured at the exit of combustor. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The $NO_{x}$ was decreased with decreasing the equivalence ration. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.45. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The $NO_{x}$ was decreased slightly and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. The low $NO_{x}$ combustor has lower values of $NO_{x}$ and CO compared with conventional one. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1679-1683
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• 2018

Polycrystalline $BaSrCo_2(Fe_{1-x}Al_x)_{12}O_{22}$ (x = 0.00, 0.01, 0.05, and 0.10) samples were synthesized by polymerizable complex method. Based on the Rietveld refinement, crystal structures of the samples were found to be single-phased and determined to be rhombohedral with space group of R-3m. The hysteresis curves of the samples were measured under 15 kOe at various temperatures ranging from 4.2 and 295 K. It shows that they were not saturated with increasing Al ion contents due to the reduction of magnetic anisotropy. $M_{15kOe}$ was decreased with increasing Al ions contents. We expect that non-magnetic Al ions preferentially occupy the up-spin site of $18h_{VI}$, $3b_{VI}$, and $3a_{VI}$. The $M{\ddot{o}}ssbauer$ spectra of the samples were obtained at 295 K, and analyzed with sixsextets for Fe sites corresponding to the Y-type hexaferrite crystallography sites. The <$E_Q$> shows abrupt changes, and the <$H_{hf}$> shows abrupt decreases around x = 0.05 due to the coexistence of magnetic secondary phases.

• Bulletin of the Korean Mathematical Society
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• v.45 no.1
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• pp.59-66
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• 2008

Keskin and Harmanci defined the family B(M,X) = ${A{\leq}M|{\exists}Y{\leq}X,{\exists}f{\in}Hom_R(M,X/Y),\;Ker\;f/A{\ll}M/A}$. And Orhan and Keskin generalized projective modules via the class B(M, X). In this note we introduce X-local summands and X-hollow modules via the class B(M, X). Let R be a right perfect ring and let M be an X-lifting module. We prove that if every co-closed submodule of any projective module P contains Rad(P), then M has an indecomposable decomposition. This result is a generalization of Kuratomi and Chang's result [9, Theorem 3.4]. Let X be an R-module. We also prove that for an X-hollow module H such that every non-zero direct summand K of H with $K{\in}B$(H, X), if $H{\oplus}H$ has the internal exchange property, then H has a local endomorphism ring.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.572-580
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• 2003

Synthesizing behavior and microstructural evolution of $CaZrO_3$and $m-ZrO_2$in a thermal reaction process of $ZrSiO_4$-$xCaCO_3$mixtures, where x is 7 and 19, were investigated to determine the addition amount of CaO in CaO:$ZrO_2$:$SiO_2$ternary composition. CaZrO$_3$-Ca$_2$SiO$_4$precursor prepared by the mixture of $ZrSiO_4$and CaCO$_3$in aqueous suspending media was controlled to the acidic (pH=4.0) condition with HCI solution to enhance the thermal reaction. The addition amount of dispersant into the $ZrSiO_4$-$xCaCO_3$slip increased with increasing mole ratio of $CaCO_3$, which was associated with the viscosity of slip. Decarbonation reaction was activated with an increase of the addition amount of $CaCO_3$, showing different final temperatures in $ZrSiO_4$-$7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures as about 980 and 116$0^{\circ}C$, respectively, for finishing decarbonation reaction. The grain morphology was changed to spherical shape for all samples with an increase of sintering temperature. The grain size and phase composition of the synthesized composites depended on the mixture ratio of Zrsi04 and CacO3 powders, indicating that the main crystals were m-ZrO2 ($\leq$3 $\mu\textrm{m}$) and $CaZrO_3$ ($\leq$ 7 $\mu\textrm{m}$) in $ZrSiO_4$$>-7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures, respectively.

• Clean Technology
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• v.23 no.1
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• pp.80-89
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• 2017

The bubbling fluidized bed (BFB) reactor with a diameter of 0.1 m and a height of 1.2 m was used for experimental study of co-firing and emission characteristics fueled by sewage sludge (SS) and wood pellet (WP). The facility consists of a fluidized bed reactor, feeding system, cyclone, condenser and gas analyzer, The mean particle diameter and minimum fluidization velocity are $460{\mu}m$ and $0.21ms^{-1}$ respectively. SS produced from Korea and WP from Canada were examined. The various mixing ratios of WP were 20, 50, and 80% based on HHV. The equivalence ratio of 1.65, reactor temperature of $800^{\circ}C$, air flow rate of $100Lmin^{-1}$, and fluidization number of 4 were fixed in the BFB experiment. In TGA, the range of combustion temperature of SS was wider than that of WP. It represents that the combustibility of WP is higher than that of SS. The BFB reactor temperature was maintained between 800 and $900^{\circ}C$. CO emission of SS was high because of lower combustibility. $NO_X$ and $SO_X$ formation of SS were higher than that of WP since high nitrogen and sulfur contents of SS. CO, $NO_X$, and $SO_X$ formation were suppressed as the mixing ratio of WP was increased. The slagging and fouling tendencies show high in all test conditions.

• Journal of the Korean Ceramic Society
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• v.37 no.10
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• pp.962-967
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• 2000

산소 결핍 페라이트 (oxygen deficient ferrites, ODF) MF $e_2$ $O_{4-}$$\delta$/는 약 30$0^{\circ}C$의 낮은 온도에서 온실가스중 하나인 $CO_2$를 C와 $O_2$로 분해시킨다. 본 연구에서는 $CO_2$분해 촉매로서 3원계 초미세 페라이트 N $i_{x}$Z $n_{1-x}$F $e_2$ $O_4$와 N $i_{x}$ $Co_{1-x}$F $e_2$ $O_4$를 수열합성법과 공침법 등의 습식 합성법으로 각각 합성하여 이들 분말의 특성과 $CO_2$분해 특성을 고찰하였다. 페라이트의 XRD 결과, 결정구조는 모두 전형적인 스피넬 구조로 동일하게 나타났다. BET 비표면적은 수열합성법으로 제조한 3원계 페라이트의 경우 110$m^2$/g 이상으로 공침법으로 제조한 페라이트보다 비교적 큰 값을 나타냈고 분말 입자크기 또한 약 10nm의 매우 미세한 분말을 얻을 수 있었다. 3원계 산소 결핍 페라이트의 $CO_2$분해 효율은 공침법으로 합성한 것보다 수열합성법으로 합성한 것이 더 우수하게 나타났으며, N $i_{x}$ $Co_{1-x}$F $e_2$ $O_{4-}$$\delta$/보다 N $i_{x}$Z $n_{1-x}$F $e_2$ $O_{4-}$$\delta$/가 우수한 것으로 나타났다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.784-785
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• 2006

Co-based amorphous powder was produced by a new atomization process "Spinning Water Atomization Process (SWAP)", having rapid super-cooling rate. The composition of the alloys was ($(Co_{0.95}Fe_{0.05})_{1-x}Cr_x$)$_{75}Si_{15}B_{10}$ (x=0, 0.025, 0.05, 0.075). The powders became the amorphous state even if particle size was up to about $500{\mu}m$. The coercive force of powders was about 0.35 - 0.7 Oe. Furthermore, Co-based amorphous powder cores with glass binders were made by cold-pressing and sintering methods. The initial permeability of the core in the frequency range up to 100 kHz was about 110, and the core loss at 100 kHz for Bm = 0.1 T was $350kW/m^3$.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.325-331
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• 2017

Adsorption experiments of carbon dioxide were performed on ZSM5 and Molecular Sieve 13X (MS13X) impregnated with Monoethanol Amine (MEA). Adsorption efficiency of $CO_2$ was investigated in a U type packed column with GC/TCD. The adsorption capacities of adsorbents are estimated in the temperature range of $30-80^{\circ}C$. The modified adsorbents was characterized by BET surface area, $N_2$ adsorption/desorption isotherms, X-ray diffraction and FT-IR. Surface analysis results showed that the impregnation method did not affect the crystallinity of any adsorbents. BET surface area of the MS13X impregnated amine decreased to $19.945m^2/g$ from $718.335m^2/g$. These reults showed that amine molecules were filled with the pore volume in MS13X, as a results restricting access of nitrogen into the pores. The MEA modified MS13X showed improvement in $CO_2$ adsorption capacity over the ZSM5 impregnated with MEA. The MS13X-MEA showed the highest adsorption capacity due to physical adsorption and chemical adsorption by amino-group content. This results also showed that adsorption capacity of MS13X-MEA increases with the temperature range of $60-80^{\circ}C$ compared with pristine MS13X.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1613-1618
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• 2014

Perovskite-type oxides are promising oxygen carriers in producing oxygen-enriched $CO_2$ gas stream for oxyfuel combustion. In this study, a new series of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ (x = 0.2, 0.4, 0.6, 0.8) was prepared and used to produce $O_2/CO_2$ mixture gas. The phase, crystal structure, and morphological properties of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ were investigated through X-ray diffraction, specific surface area measurements, and environmental scanning electron microscopy. The oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ was studied in a fixed-bed reactor system. Results showed that the different x values of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ have no obvious effects on crystalline structure. However, the oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ is improved by Co doping. Moreover, $SrCo_{0.8}Fe_{0.2}O_{3-{\delta}}$ synthesized via a new EDTA method has a larger BET surface area ($40.396m^2/g$), smaller particle size (48.3 nm), and better oxygen production performance compared with that synthesized through a liquid citrate method.

• Bulletin of the Korean Chemical Society
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• v.13 no.4
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• pp.391-395
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• 1992

Rhodium(I) and iridium(II) complexes, M(Cl$O_4$)(CO)$(PPh_3)_2$ and [M(CO)$(PPh_3)_3$]Cl$O_4$ (M = Rh, Ir), and RhX(CO)$(PPh_3)_2$ (X = Cl, Br, OH) catalyze the carbonylation of benzyl alcohols to produce phenylacetic acids under 6 atm of CO at $110^{\circ}C$ in deuterated chloroform. Benzyl alcohols initially undergo dehydration to give dibenzyl ethers which are then carbonylated to benzyl phenylacetates, and the hydrolysis of benzyl phenylacetate produces phenylacetic acids and benzyl alcohols. The carbonylation is accompanied with dehydrogenation followed by hydrogenolysis of benzyl alcohols giving benzaldehydes and methylbenzenes which are also produced by CO2 elimination of phenylacetic acids. Phenylacetic acid is also produced in the reactions of benzyl bromide with CO catalytically in the presence of Rh(Cl$O_4$)(CO)$(PPh_3)_2$ and $H_2O$, and stoichiometrically with Rh(OH)(CO)$(PPh_3)_2$ in the absence of $H_2O$.