• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.10-17
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• 2004

The results of the combustion performance tests of gas generator which supplies hot gas into the turbine of turbo-pump for liquid rocket engine and uses LOx and kerosene as propellant are described. The gas generator consists of a injector head with F-O-F impinging injector, a water cooled combustion chamber, a gas torch igniter, a turbulence ring and an instrument ring. The effect of turbulence ring and combustion chamber length on performance of gas generator are investigated. The ignition and combustion at design point are stable and the pressure and gas temperature at gas generator exit meets the target. The turbulence ring installed at middle of chamber effectively mixes hot gas with cold gas and the effect of residence time of hot gas in gas generator on combustion efficiency is small. Test results show that the main parameter controlling the gas temperature at gas generator exit is overall O/F ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.435-438
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• 2001

Thin films of vanadium oxide(VO$\sub$x/) have been deposited by r.f. magnetron sputtering from V$_2$O$\sub$5/ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio is changed from 0% to 8%. Crystal structure, chemical composition and bonding properties of films sputter-deposited under different oxygen gas pressures are characterized through XRO, XPS, RBS and FTIR measurements. All the films prepared below 8% O$_2$ are amorphous, and those prepared without oxygen are gray indicating the presence of V$_2$O$\sub$$_4$/ phase in the films. V$_2$O$\sub$5/ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric V$_2$O$\sub$5/. The increase of O/V ratio with increasing oxygen gas pressure is attributed to the partial filling of oxygen vacancies through diffusion. It is observed that the oxygen atoms. located on the V-O plane of V$_2$O$\sub$5/ layer participate more readily in the oxidation process.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.765-772
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• 1993

Two-dimensional potassium tetratitanate ($K_2Ti_4O_9$) and three-dimensional potassium hexatitanate ($K_2Ti_6O_{13}$) fibers have been prepared by the combined method consisting of the flux melting (1150$^{\circ}C$)-slow cooling (cooling rate = 5$^{\circ}C$/h) process from the starting raw materials of $K_2CO_3$, and $TiO_2$ with the flux of $K_2MoO_4$. It was found that the fiber growth reaction is strongly dependent upon the mole ratio of flux (F) to raw material (R), which is 7 : 3 (F : R) as for the optimum growth condition. Relatively long fibers (average length ${\thickapprox}$ 4 mm) with a mixture of $K_2Ti_4O_9$ (major) and $K_2Ti_6O_{13}$ (minor) could be obtained when the reaction was carried out for the $K_2MoO_4-$K_2O{\cdot}4TiO_2$ (F : R = 7 : 3) system, but for the $K_2$MoO_4$-$K_2O{\cdot}6TiO_2$ (F : R = 7: 3) one, only the short fibers with ${\thickapprox}$ 2 mm long could be grown as the mixed phase of $K_2Ti_6O_{13}$ and $K_2Ti_4O_9$.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.37-46
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• 2007

In this study, combustion fields of the end-burning hybrid combustor with tangential oxidizer injectors are examined. Momentum ratio of oxidizer is used as a main parameter to analyse the combustion efficiency with temperature, pressure, swirl velocity and mixture fraction field. It was found that as momentum ratio decreases the overall combustion efficiency is enhanced with the pressure field being insensitive to momentum ratio keeping quasi-uniform distribution. Irrespective to the momentum ratio, annular hot region commonly occurred in the upper combustion chamber where this phenomenon was left for a future improvement to be followed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.605-608
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• 2002

In order to improve the microwave dielectric properties of ZnO+$TiO_2$ ceramic systems, we studied the relations among microstructures, phases, and microwave dielectric properties at various mole ratio and sintering temperatures. The optimum composition was found to be 0.2ZnO+0.8$TiO_2$ when sintered at $1100^{\circ}C$, at which we could obtain following results: $Q{\times}f_o$ = 22,500 GHz, ${\varepsilon}_r$ = 73, and $\tau_f=+210ppm/^{\circ}C$.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.42-47
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• 2006

The biological nutrient treatment is formed with repetition and rearrangement of anaerobic, anoxic and oxic tank. In this case, VFAs is generated in the anaerobic tank and the anoxic tank. The VFAs is an important factor for removal of nitrogen and phosphate and SVI. So, in this study I investigated to find a relationship among the generation rate of the VFAs according to the change of F/M ratio and the characteristic which can eliminate organic matter and nitrogen according to the change of residual concentration of the VFAs and the efficiency of the process and also SVI in wastewater treatment. $A^2/O$ process was used for wastewater treatment. F/M ratio was under the control of the change of MLSS concentration. When the F/M ratio was changed from 0.16 to 0.08 kg-BOD/kg-MLSS/day, the VFAs's production volume increased based on the reduction of F/M ratio in batch reaction. And the residual concentration of the VFAs decreased at first and then increased later. SVI and SS were high when F/M ratio was $0.16kg/kg{\cdot}d$ and showed stable status when F/M ratio decreased $0.11{\sim}0.13kg/kg{\cdot}d$. However, SVI and SS continuously increased with decrease of F/M ratio and were high at $0.08kg/kg{\cdot}d$. In the result of comparison between residual concentration of the VFAs and denitrification rate in anoxic tank, the less residual volume of the VFAs was in anoxic tank, the higher denitrification ratio became. The optimal residual-concentration of the VFAs considering SVI and removal efficiency of nitrogenwas $1.4{\sim}2.2mg/L$. At that time F/M ratio was $0.11{\sim}0.13$ kg-BOD/kg-MLSS/day.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.506-508
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• 2000

Oxide of the form $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ present properties that make them useful as multilayer chip NTC thermistor for mobile phone NTC thermistor electric properties of $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ system has been measured as a function of temperature and composition. In $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ composition, it can be seen that resistivity and B-constant were increased as the ratio of $Mn_{3}O_{4}/F_{2}O_{3}$ and $Mn_{3}O_{4}$/NiO was increased. In particular, resistance change ratio (${\Delta}R$), the important factor for reliability varied within ${\pm}1%$, indicating the compositions of these products could be available for mobile phone.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.843-846
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• 2000

The (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.02∼0.08) ceramics were fabricated by conventional mixed oxide method. The sintering temperature and time were 1250$^{\circ}C$∼1400$^{\circ}C$, 2hr., respectively. The structural and microwave dielectric properties were investigated by varying sintering temperature and composition ratio. In the (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.02) ceramics, the cubic SrTiO$_3$and hexagonal MgTiO$_3$phases were coexisted. The dielectric constant was increased and the temperature coefficient of resonant frequency( $\tau_f$) was decreased with addition of SrTiO$_3$. The temperature coefficient of resonant frequency($\tau_f$) was gradually varied from negative value to positive value with increasing the SrTiO$_3$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.8
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• pp.675-680
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• 2000

In this study the temperature coefficient of resonant frequency(TC $F_{r}$) dielectric and piezoelectric properties of Pb[(S $b_{1}$2//N $b_{1}$2/)$_{0.065}$)-(Z $r_{x}$, $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics were investigated with Zr/Ti ratio. The compositions near the morphotropic phase boundary (MPB) appeared when Zr/Ti ratio was 49.5/50.5 The dielectric constant and electromechanical coupling factor( $k_{p}$) also showed the highest values of 1,257, 0.653 respectively when the Zr/Ti ratio was 49.5/50.5 Moreover the mechanical quality factor( $Q_{m}$) showed th lowest value of 713 when the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) abruptly change at the morphotropic phase boundary(MPB) which existed between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio varied from 50/50 to 49.5/50.5.50.5..50.5.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.459-459
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• 2012

Recently, the discharge of global warming gases in dry etching process of TFT-LCD display industry is a serious issue because perfluorocarbon compound (PFC) gas causes global warming effects. PFCs including CF4, C2F6, C3F8, CHF3, NF3 and SF6 are widely used as etching and cleaning gases. In particular, the SF6 gas is chemically stable compounds. However, these gases have large global warming potential (GWP100 = 24,900) and lifetime (3,200). In this work, we chose C3F6O gas which has a very low GWP (GWP100 = <100) and lifetime (< 1) as a replacement gas. This study investigated the effects of the gas flow ratio of C3F6O/O2 and process pressure in dual-frequency capacitively coupled plasma (CCP) etcher on global warming effects. Also, we compared global warming effects of C3F6O gas with those of SF6 gas during dry etching of a patterned positive type photo-resist/silicon nitride/glass substrate. The etch rate measurements and emission of by-products were analyzed by scanning electron Microscopy (SEM; HITACI, S-3500H) and Fourier transform infrared spectroscopy (FT-IR; MIDAC, I2000), respectively. Calculation of MMTCE (million metric ton carbon equivalents) based on the emitted by-products were performed during etching by controlling various process parameters. The evaluation procedure and results will be discussed in detail.