• 한국세라믹학회지
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• 제42권1호
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• pp.16-21
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• 2005

The effect of additive composition, using AlN and $Er_{2}O_{3}$ as sintering additives, on the mechanical properties of liquid-phase-sintered, and subsequently annealed SiC ceramics was investigated. The microstructures developed were quantitatively analyzed by image analysis. The average thickness of SiC grains increased with increasing the $Er_{2}O_{3}/(AlN + Er_{2}O_{3})$ ratio in the additives whereas the aspect ratio decreased with increasing the ratio. The mechanical properties versus $Er_{2}O_{3}/(AlN + Er_{2}O_{3})$ ratio curve had a maximum; i.e., there was a small composition range at which optimum mechanical properties were realized. The best results were obtained when the ratio ranged from 0.4 to 0.6. The flexural strength and fracture toughness of the SiC ceramics were $550\~650\;MPa$ and $5.5\~6.5$ MPa${\cdot}m^{1/2}$, respectively.

• 한국기후변화학회지
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• 제6권2호
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• pp.105-111
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• 2015

With PV market extension, Operation & Maintenance (O&M) went on the floor as an effective method so solve the reduction phenomenon of Performance Ratio (PR) of PV power plant and as a new business model of photovoltaic industry. This study chose institutionalization of O&M to vitalize domestic photovoltaic industry improving level of photovoltaic technology and dominate the market in advance. The result of analyzing advanced researches and domestic cases indicates that O&M is essential of operating PV power plant, therefore, now is the time for a systematic approach to establish O&M policy.

• 한국전기전자재료학회논문지
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• 제18권10호
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• pp.909-916
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• 2005

The structural and electrical property of RF magnetron sputtered ZnO thin film have been studied as a function of RF power, substrate temperature, oxygen/argon gas ratio and film thickness at constant sputtering power, sputtering working pressure and target-substrate distance. To analyze a crystallo-graphic properties of the films, $\theta$/2$\theta$ mode X-ray diffraction, SEM, and AFM analyses. C-axis preferred orientation, resistivity and surface roughness highly depended on oxygen/argon gas ratio. The resistivity of ZnO thin film(6000 ${\AA}$) rapidly increased with increasing oxygen ratio and the resistivity value of $9 {\ast} 10^7 {\Omega}cm$ was obtained at a working pressure of 10 mTorr with the same oxygen/argon gas ratio. The surface roughness was also improved with increasing oxygen ratio and the ZnO films deposited with the same oxygen/argon gas ratio showed the excellent roughness value of 28.7 ${\AA}$. With increase of the substrate temperature, The C-axis preferred orientation of ZnO thin film increases and the resistivity decreases due to deviation from the stoichiometric ZnO due to oxygen deficiency.

• Journal of Magnetics
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• 제17권2호
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• pp.83-85
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• 2012

Magnetic particles in a novel, wound-healing ointment were studied using M$\ddot{o}$ssbauer spectroscopy and VSM to estimate the stability of the properties of the magnetic particles. The isomer shifts of $Fe_3O_4(A)$ were found to be 0.49-0.56 mm/s relative to iron metal, this indicates that the iron ions in $Fe_3O_4(A)$ are $Fe^{3+}$. On the other hand, the isomer shifts of $Fe_3O_4(B)$ were found to be 0.91-1.13 mm/s relative to iron metal, this shows that the ion state of $Fe_3O_4(B)$ is a mixed state of $Fe^{2+}$ and $Fe^{3+}$. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (${\sim}10\;{\AA}$), differs from the stoichiometric one. It was found that the area ratio of the M$\ddot{o}$ssbauer subspectra of $Fe_3O_4(A)$ / $Fe_3O_4(B)$ taken at 87 and 181 K linearly increased in comparison to the initial pure magnetic particles, but the rate of increase of the area ratio at 181 K was about two times that at 87 K. From the magnetic hyperfine field, despite their small size, the particles exhibit no superparamagnetism.

• 상하수도학회지
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• 제32권1호
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• pp.19-25
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• 2018

The objectives of this study were to evaluate the removal characteristics of total nitrogen, the influence factor of denitrification and the optimum operating condition in the pigment wastewater treatment using PAC-A/O process. The operating conditions of PAC-A/O process were mean BOD volumetric loading $0.86kgBOD/m^3/day$, mean F/M ratio 0.072~0.13 kgBOD/kgMLVSS/day and mean C/N ratio 3.47, respectively. The conditions of anoxic process in the field plant test were mean pH 8.3~8.7 and mean temperature $34.1{\sim}44.0^{\circ}C$. The ORP bending point knee was eventually appeared in the ORP -107 mV and $NO_3{^-}-N$ removal efficiency was increased according to the ORP decrease. In the ORP -107 mV below condition, the removal efficiency of T-N and $NO_3{^-}-N$ was 92.3~95.0% and 98.5~99.7%. Denitrification rate was calculated to be 1.581~1.791 mg $NO_3{^-}-N/gMLSS/hr$. The experimental results showed that the ORP control in the PAC-A/O process could be an effective method for treatment of pigment wastewater.

• 한국토양비료학회지
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• 제12권3호
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• pp.153-167
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• 1979

수도(水稻)의 생산능력(生産能力)을 최대(最大)한 발현(發顯)시키는데 필요(必要)한 시비량(施肥量) 결정방법(決定方法)을 시도(試圖)했다. 이 시도(試圖)에서는 양분(養分)의 균형적(均衡的) 공급(供給)을 토양특성(土壤特性)과 품종(品種)의 특성(特性)에 바탕을 두어 공식화(公式化)하고저 했으며, 과거(過去)에 실시(實施)된 시험성적(試驗成績)들을 이용(利用)하여 그 타당성(妥當性)을 검토(檢討)했다. 그 요지(要旨)는 다음과 같다. 1. 다수확(多收穫)을 도모(圖謀)할 경우(境遇), 양분(養分)의 균형적(均衡的) 공급(供給)이 매우 중요(重要)하다. 2. 규산(珪酸)은 시용(施用)된 질소(窒素)를 고수량(高收量)으로 연결(連結)시키는데 중요(重要)한 역할(役割)을 한다. 3. 수량(收量)에 가장 결정적(決定的)인 몫을 하는 질소(窒素)의 시용량(施用量)은 토양중(土壤中) 유기물(有機物) 및 유효규산(有效珪酸)의 비(比) 즉(卽) $SiO_2$/O.M. 비(比)를 참작(參酌)함이 타당하다. 4. $SiO_2$/OM. 비(比)를 근거(根據)로 질소시용량(窒素施用量)을 결정(決定)코저 할 경우(境遇), 수도(水稻)의 품종적(品種的) 특성(特性)이 고려(考慮)돼야한다. 그 까닭은 품종별(品種別)로 토양중(土壤中) 유기물(有機物) 함량(含量)에 영향(影響)받는 정도(程度)가 상이(相異)하기 때문이다. 5. 토양(土壤)에 규산질(珪酸質) 비료(肥料) 혹(或)은 유기물(有機物)의 시용(施用)으로 $SiO_2$/O.M. 비(比)를 변화(變化)시킬 수 있으며 이에 따라 질소량(窒素量)도 변동(變動)시킬 수 있다. 이 때에 수도품종(水稻品種)의 특성(特性)이 고려(考慮)돼야 한다. 6. 질소시용량(窒素施用量)을 이와 같이 결정(決定)한 다음 가리(加里)의 시용량(施用量)은 질소량(窒素量)과 토양중(土壤中) K/Ca+Mg 비(比)를 토대(土台)로 산출(算出)할 수 있다.

• 멤브레인
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• 제20권2호
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• pp.87-96
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• 2010

세공 크기가 2.6 ${\mu}m$인 SPG (Shirasu porous glass) 막이 설치된 실험실 규모의 막유화 장치를 사용하여 막유화 에멀젼-겔 공정의 변수 조절을 통해 구형상의 실리카 입자를 제조하였다. 막유화 에멀젼-겔 공정의 변수로는 분산상 압력, 연속상 내 안정제 및 유화제의 농도, $H_2O$/TEOS 비율 및 연속상에 대한 분산상의 비율로 설정하고, 이들 변수가 제조된 실리카 입자의 크기와 분포에 미치는 영향을 검토하였다. 막유화의 공정변수들 중에서 분산상 압력과 연속상에 대한 분산상의 비가 증가할수록 실리카 입자의 크기가 증가하였다. 반면 안정제 및 유화제의 농도, $H_2O$/TEOS 비가 증가할수록 입자의 크기가 감소하였다. 막유화 에멀젼-겔 공정변수의 조절을 통해 최종적으로 평균 입자 크기가 3 ${\mu}m$인 비교적 입도분포가 균일한 구형상의 실리카 입자 제조가 가능하였다.

• 한국결정성장학회지
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• 제13권1호
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• pp.24-30
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• 2003

The preparation of $PbTiO_3$ powder was carried out using the oxide starting material by hydrothermal method. The powder of a crystalline phase with perovskite structure was synthesized. The optimum conditions for the preparation of powder were as follows; hydrothermal solvent; 8M-KOH or 8M-NaOH, reaction temperature; 250~$270^{\circ}C$, run time; 10 h. The ,shape of synthesized powders were well developed crystalline faces with specific surface area of about 2.3 $\textrm m^2$/g in KOH solution and about 5.0 $\textrm m^2$/g in NaOH solution. The cell parameters of powder were a = 3.90$\AA$, c = 4.14 $\AA$ and cell volume was 57.30 $\AA^3$. The cell ratio (c/a) of powder was the same as the theoretical ratio with c/a = 1.06 and the phase transition temperature(Tc) of the powders was about $470^{\circ}C$.

• 환경위생공학
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• 제10권3호
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• pp.105-114
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• 1995

There has been increasing awareness on the importance of not only removal of organic materials but also sterilization of microbial cell in the drinking water purification research, so there has been many researches on that area. This study has been designed to analyze the effects of $TiO_{2}$ and ZnO coated on activated carbon on Escherichia coli. In this study, the sterilization power was analyzed by (1) variation of $TiO_{2}$ and ZnO concentration coated on activated carbon (2) variation of UV intensity. In addition, the kinetics between exposure time and sterilization velocity was viewed by the method of Chick. The results are as follows. 1. Survival ratio of E. coli decreased as time goes on in application of $TiO_{2}$, ZnO and $TiO_{2}{\cdot}ZnO$. In $TiO_{2}$ and ZnO, the effect increased upto certain concentration, but decreased there-after. In $TiO_{2}{\cdot}ZnO$, the effect of sterilization was in similar way among 3 combinations. 2. Survival ratio of E. coli decreased proportionately to an increase of light intensity in ZnO and $TiO_{2}{\cdit}ZnO$. In $TiO_{2}$, the survival ratio differed over extent of irradiation but the difference over the light intensity was not significant. 3. When Chick's law of sterilization was applied, m values of three concentrations of $TiO_{2}$ were 1.57,0.98, 1.96 respectively. M values of three concentration of ZnO were 1.10, 1.18,0. 11 respectively and those of three combination of $TiO_{2}{\cdot}ZnO$ were 1.17, 1.24, 1.74 respectively.

• 공업화학
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• 제10권1호
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• pp.73-79
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• 1999

초격자 구조의 $Li_{4/3}Ti_{5/3}O_4$를 lithium acetate (LA)와 titanium n-butoxide (TNB)의 혼합 용액을 이용한 졸겔법으로 합성하였다. 이때 얻어진 겔상은 TNB/LA 몰비 5/4에 AA/TNB의 몰비 0.125를 혼합한 clear sol 용액에 $NH_4OH/TNB$ 몰비 0.35와 $H_2O/TNH$ 몰비 3.5를 첨가하여 얻었으며, $Li_{4/3}Ti_{5/3}O_4$는 xerogel을 $600^{\circ}C$에서 30시간 동안 열처리하여 제조하였다. 그리고 합성된 $Li_{4/3}Ti_{5/3}O_4$는 0.5~3.0 V의 전위 영역에서 $0.15mA/cm^2$의 전류밀도로 Li/1M $LiClO_4(in\;PC)/Li_{4/3}Ti_{5/3}O_4$를 구성하여 실험한 결과 174 mAh/g의 초기 용량을 나타냈으며, 25 cycle 동안 27.3%의 용량 감소를 나타냈다.