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류재식,정용호,손장열 대한건축학회 2001 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.21 No.2
Air Conditioning Systems are an indispensable in modern buildings. Therefore Air filters playa main role in improving indoor air quality. However there is not enough information about air filters and any official maintenance standards or guidelines for air filters do not exist in Korea. In this study, arrestance, differential pressure and microorganisms between the upstream and the downstream of air filters were measured with digital dust indicators, a micro manometer and blood agar plates. Conditions were measured before and after rinsing out pre filters and they varied between 10%, 20% and 30% of the input of outdoor air under actual operating conditions. As for the results, arrestance increased depending on whether the input of outdoor air was added as in case of AHU 3. However arrestance was affected by the dust concentration rather than by the input of OA in the downstream of air filters in general. Differential pressure decreased depending on whether the input of outdoor air was added to AHUs which have built-out type return fans and vice versa in the built-in type but the range of fluctuation in differential pressure was hard to recognize as 1∼3mmAq. In contrast the colony counts of microorganisms increased in the downstream of air filters contrarily. The rates of increase dropped depending on the addition of the input of OA and after rinsing out pre filters.
(1-x)Mg<sub>4</sub>Ta<sub>2</sub>O<sub>9</sub>-xTiO<sub>2</sub>(x=0\sim0.9)세라믹스의 미세구조와 마이크로파 유전 특성
김재식,최의선,이문기,류기원,이영희 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.8
The microstructure and microwave dielectric properties of $(1-x){Mg}_4{Ta}_2{O}_9-xTi{O}_2(x=0\sim0.9)$ ceramics were investigated. The specimens were prepared by the conventional mixed oxide method with sintering temperature of 140$0^{\circ}C$∼150$0^{\circ}C$. To improve the quality factor and the temperature coefficient of resonant frequency,$ Ti{O}_2(\varepsilon\Gamma=100, Q\times f_\Gamma=40,000 GHz,\ta_f= +450 ppm\diagup^{\circ}C $ was added in ${Mg}_4{Ta}_2{O}_9$ceramics. The dielectric and structural properties were investigated. According to the XRD patterns, $(1-x){Mg}_4{Ta}_2{O}_9-xTi{O}_2(x=0\sim0.9)$ ceramics had the ${Mg}_4{Ta}_2{O}_9$ phase(hexagonal) and ${MgTi}_2{O}_5$phase(orthorhombic). The dielectric constant($\varepsilon_r$). quality($Qtimes{f}_r$</TEX) and temperature coeeficient of resonant frequency(${\tau}_f$) of the $(1-x){Mg}_4{Ta}_2{O}_9-xTi{O}_2(x=0\sim0.9)$ ceramics were 8.12∼18.59, 18,750∼186,410 GHz and -36.02∼+3.46 ppm/$^{\circ}C$, respectively.
김재식(Jae-Sik Kim),김상우(Sang-Woo Kim),류기원(Ki-Won Ryu),배선기(Seon-Gi Bae),이영희(Young-Hie Lee) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.11
The sintering behavior and high frequency properties of Ba-hexagonal ferrite were investigated. All samples of the Ba-hexagonal ferrite were prepared by the conventional mixed oxide method and sintered at 1150℃~1400℃. From the X-ray diffraction patterns of sintered Ba-hexagonal ferrite, the Ba₃Co₂Fe₂₄O₄₁ phase was represented as main phase in the almost sintering conditions. The bulk densities with sintering temperature and decreased at 1400℃. The bulk density of Ba₃Co₂Fe₂₄O₄₁ ceramics sintered at 1300℃ was 4.79 g/㎤. The permittivity (ε') of Ba₃Co₂Fe₂₄O₄₁ ceramics was increased and the permeability was decreased with sintering temperature, respectively. The permittivity and permeability of Ba₃Co₂Fe₂₄O₄₁ ceramics sintered at 1300℃ were 19.896 and 14.218 at 210 ㎒, respectively.
SnO 첨가에 따른 Ti-Te LTCC 재료의 소결 특성
김재식(Jae-Sik Kim),최의선(Eui-Sun Choi),류기원(Ki-Won Ryu),이영희(Young-Hie Lee) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10
In this study, low temperature sintering property of the 06TiTe₃O?-04MgTiO₃ ceramics with sintering adds were investigated for LTCC application which enable to cofiring with Ag electrode TiTe₃O? mixed with MgTiO₃ to improve the temperature property. In the X-ray diffraction patterns, the columbite structure of TiTe₃O? phase and ilmenite structure of MgTiO₃ phase were coexisted in all specimens. In the case of SnO addition, the bulk density and dielectric constant were increased but quality factor was decreased with amount of SnO additions. The TCRF of the 0.6TiTe₃O?-0.4MgTiO₃+xwt%SnO ceramics were shifted to negative direction. The dielectric constant, quality factor and TCRF of the 0.6TiTe₃O?-0.4MgTiO₃ ceramics with 2.5wt% addition of SnO ereinis at 830℃ for 1hr were 29.86, 35,800 ㎓, -0.58 ppm/℃, respectively.