• 한국결정성장학회지
• /
• 제14권5호
• /
• pp.193-198
• /
• 2004

$(TbBi)_3(FeAIGa)_5O_{12}(TbIG)$, $(EuBi)_3(FeAIGa)_5O_{12}(EuIG)$, $(EuTbBi)_3(FeAIGa)_5O_{12}(EuTbIG)$ 가네트 막을 $PbO-B_2O_3-Bi_2O_3$ 융제를 사용하여 $(GdCa)_3(GaMgZr)_5O_{12}(SGGG)$ 기판 위에 liquid phase epitaxy(LPE) 방법으로 성장시켰다. 성장된 TbIG, EuIG, EuTbIG 가네트 막의 포화자계값은 각각 150 Oe, 950 Oe, 170 Oe를 보였으며, magnetic force microscope(MFM) 분석을 측정 한 결과 TbIG 막에서는 단일 자구가 관찰되었으며, EuIG와 EuTbIG 막에서는 다 자구가 관찰되었다.

• Environmental Engineering Research
• /
• 제17권4호
• /
• pp.185-190
• /
• 2012

Rejection characteristics of perchlorate ($ClO_4^-$) were examined for commercially available reverse osmosis (RO) and nanofiltration (NF) membranes. A bench-scale dead-end stirred-cell filtration system was employed to determine the toxic ion rejection and the membrane flux. Model water solutions were used to prepare $ClO_4^-$ solutions (approximately, $1,000{\mu}g/L$) in the presence of background salts (NaCl, $Na_2SO_4$, and $CaCl_2$) at various pH values (3.5, 7, and 9.5) and solution ionic strengths (0.001, 0.01, and 0.01 M NaCl) in the presence of natural organic matter (NOM). Rejection by the membranes increased with increasing solution pH owing to increasingly negative membrane charge. In addition, the rejection of the target ion by the membranes increased with increasing solution ionic strength. The rejection of $ClO_4^-$ was consistently higher for the RO membrane than for the NF membrane and $ClO_4^-$ rejection followed the order $CaCl_2$ < NaCl < $Na_2SO_4$ at conditions of constant pH and ionic strength for both the RO and NF membranes. The possible influence of NOM on $ClO_4^-$ rejection by the membranes was also explored.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2006년도 춘계종합학술대회
• /
• pp.898-901
• /
• 2006

본 논문에서는 저손실 Mn-Zn 페라이트의 제조공정과 첨가제가 코어의 자기적 특성에 미치는 영향을 조사하였다. 통신부품재료로 Mn-Zn 페라이트 개발에는 필요한 높은 포화자속밀도 및 투자율을 가진 고주파 특성이 양호하고 자기손실도 적은 재료의 필요하다. 따라서, Mn-Zn 페라이트의 고주파 자기 특성의 개선을 위해서는 결정입자의 소경화와 입자계층의 고저항화에 따른 와전류 손실의 억제 및 미세 구조의 균일화에 따른 히스테리시스 손실의 저감이 중요하다. 본 논문에서는 고성능, 저손실의 자심재료를 위해 Mn-Zn Ferrite에 $V_2O_5$와 $CaCo_3$를 첨가하였다. 조성은 MnO : ZnO : $Fe_2O_3$ = 21 : 10 : 69 mol%로 하였다. 이 시료를 $1250^{\circ}C$에서 3시간 소결하였다. 측정은 0.1MHz에서 초투자율을 측정하였으며, 전력손실은 50mT에서 100kHz 및 온도를 변화시켜 측정하였다.

• Molecules and Cells
• /
• 제28권3호
• /
• pp.183-188
• /
• 2009

TSAd/Lad is a T cell adaptor molecule involved in $p56^{lck}$-mediated T cell activation. To investigate the functions of TSAd in T cells, we generated transgenic (TG) mice expressing the SH2 domain of TSAd (TSAd-SH2) under the control of the $p56^{lck}$ proximal promoter. In T cells from TSAd-SH2 TG mice, T cell receptor (TCR)-mediated early signaling events, such as $Ca^{2+}$ flux and ERK activation, were normal; however, late activation events, such as IL-2 production and proliferation, were significantly reduced. Moreover, TCR-induced cell adhesion to extracellular matrix (ECM) proteins and migration through ECM proteins were defective in T cells from TSAd-SH2 TG mice. Furthermore, the contact hypersensitivity (CHS) reaction, an inflammatory response mainly mediated by T helper 1 (Th1) cells, was inhibited in TSAd-SH2 TG mice. Taken together, these results show that TSAd, particularly the SH2 domain of TSAd, is essential for the effector functions of T cells.

• The Korean Journal of Ceramics
• /
• 제4권2호
• /
• pp.146-150
• /
• 1998

The total conductivity and oxygen permeation in (Ce1-xZrxO2)0.9(CaO)0.1 solid solutions were measure das a function of temperature and oxygen partial pressure. Empirically, σ at given x and T was expressed essentially by σ=σo2+σeo Po2-1/4, where σo2 and σeo are constant. Applying a standard defect model in which major defects are Cace", Cece' and Vo in ideal solution, we can assign σo2 as the oxide ion conductivity decreases while the electronic conductivity increases with the increase in Zr content. Using the oxide ion and electronic conductivities thus determined, the oxygen permeation flux was calculated for respective Po2 and T conditions at which the measurements were made. The calculated values were found to agree with the observed ones.

• 한국대기환경학회지
• /
• 제13권5호
• /
• pp.371-381
• /
• 1997

Precipitation sampls were collected in Chonju-city during October 1994 to September 1995 and were analysed for major ions (N $a^{+}$, $K^{+}$, $Ca^{2+}$, $Mg^{2+}$, C $l^{[-10]}$ , NO/$_3$, S $O_4$$^{2-}$) and trace metals (Al, Cd, Ni, Pb, Sr, Zn) in addition to pH, in order to understand the chemical characteristics of acid rain and to estimate the origin of the determined ions. Most rain showed a neutral or alkaline character, and only 35% had a pH lower than 5.6. S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ are identified as the primary contributors to precipitation acidity in this region. Neutralization of precipitation acidity occurs as a result of the dissolution of alkaline compounds containing $Ca^{2+}$, $Mg^{2+}$ and $K^{+}$. S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ precipitation concentrations exhibit a seasonal pattern in which higher concentrations are observed during spring months and lower concentrations during summer months. However, the seasonal behavior of $H^{+}$ concentrations differs from this pattern, in that the highest concentrations occur during autumn months, owing to the different influence of neutralization processes. In all rain, S $O_4$$^{2-}$ concentration exceeded NO/$_3$$^{[-10]}$ concentration. The contribution of maritime sources to the total S $O_4$$^{2-}$ concentration was very low or negligible. For rain strongly affacted by yellow sand, $Ca^{2+}$, $Mg^{2+}$ and $K^{+}$ ions show a sharp increase in concentration, reflecting the increased amount of dust and soil suspended in atmosphere. At the same time, S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ concentrations are at their highest levels while $H^{+}$ values are not comparably elevated, presumably beacause much of the acidity has been neutralized by alkaline substances. The seasonal variance of trace metal concentrations in rainwater is similar to that of major cations. The annual wet flux of acidic pollutants and trace metals wat calculated to be as follows: N $O_3$$^{[-10]}$ ; 2.32 g/$m^2$, S $O_4$$^{2-}$, 5.34 g/$m^2$, Al; 6.30 mg/$m^2$, Cd; 0.62 mg/$m^2$, Ni; 4.08 mg/$m^2$, Pb: 9.76 mg/$m^2$, Sr; 5.94 mg/$m^2$, Zn; 111 mg/$m^2$./$m^2$.

• Environmental Engineering Research
• /
• 제25권2호
• /
• pp.230-237
• /
• 2020

Nitrogen flux release from organically enriched sediments into overlying water, which may have significantly influence on water quality and increasing continuous eutrophication. The purpose of this study is to evaluate the remediation efficiency of oyster shell powder and its treated product into organically enriched sediment in terms of nitrogen flux, organic matter, chlorophyll-a, pH and dissolved oxygen (DO). The TOSP was mainly composed of CaO2. The application of TOSP into the sediment has increased the pH, DO and significantly decreased the concentrations of NH₄⁺-N and T-N compared to other basins. On the other hand, nitrate was enriched with the addition of treated oyster powder, an oxygen releasing compound on both phases. Furthermore, chlorophyll-a was found to be increasing with time in the control basin meanwhile it dropped drastically with the addition of TOSP, which implied on the repression of algal growth owing to blockage of nitrogen source migrating from the sediment. This study has shown that the TOSP was effective to improve sediment-water quality, diminish eutrophication and control harmful algae blooms in a marine environment. Therefore, it is a good reference as an effective environmental remediation agent.

• 한국물환경학회지
• /
• 제36권2호
• /
• pp.137-147
• /
• 2020

A direct contact membrane distillation (DCMD) was applied to treat strong nitrogenous wastewater of anaerobic digestion supernatant (ADS) and human urine (HU). The ammonia transfer was evaluated in terms of specific ammonia transfer (SAT) value, which is the ratio of total ammoniacal nitrogen divided by the amount of water transferred. The acidification resulted in low SAT values and high quality of produced water. The ammonia transfer control in the acidic condition was stronger for HU than ADS due to higher alkalinity (pH 8.8) and ammonia concentration (5700 mg-N/L) of HU. Acidified HU at pH 4 exhibited a SAT value of 1.64 × 10^-5, which was significantly smaller than the SAT value of 3.00 × 10^-3 for the original HU. The low pH enhanced the water flux for ADS, but HU showed a steep decrease in water flux due to enhanced fouling. It was considered that the fouling intensity in acidic conditions depends on the characteristics of the wastewater source. The major foulants on the MD membrane were NaCl, CaCO₃ and CuSO₄ as recognized by the SEM-EDS. Acidified ADS and HU at pH 4 showed relatively high N content of 8.18 % and 28.03 %, respectively, as organic fouling.

• 한국대기환경학회지
• /
• 제22권4호
• /
• pp.459-467
• /
• 2006

This study was carried out to characteristics and distributions of acid deposition in Korea. Precipitation was collected by acid deposition monitoring networks and analyzed for pH, conductivity, and following major ionic components $SO_4^{2-}$, $CI^-$, $NO_3^-$, $NH_4^+$, $Na^+$, $K^+$, $Ca^{2+}$, $Mg{2+}$. During the investigation period, Volume weighted annual mean pH of precipitation in Korea is 4.8, showing slightly acidic level. The amount of rainfall in the range of pH 5.1$\sim$5.5 charged approximately 28% of annual precipitation,23.4% in pH 4.6$\sim$5.0, and contributed 16.2% under pH 4.5. Among seasons, alkaline precipitation has occurred more often in spring, meanwhile acidic precipitation in which pH is under 4.5 has frequently occurred in autumn. Volume weighted annual mean concentrations of $SO_4^{2-}$, $NO_3^-$, $CI^-$ are 2.558 mg/L, 1.590 mg/L, 1.286 mg/L respectively, and provided that $SO_4^{2-}$, is the major contributor, followed by $NO_3^-$, $CI^-$. In case of cation, annual mean concentration for $NH_4^+$, $Na^+$, $K^+$, $Ca^{2+}$, $Mg{2+}$, $H^+$ are 0.693 mg/L, 0.528 mg/L, 0.439 mg/L, 0.455 mg/L, 0.089 mg/L,0.015 mg/L, and $NH_4$ were decided as the main contributor, followed by $Na^+$, $K^+$, $Ca^{2+}$, $Mg{2+}$, $H^+$. Annual wet deposition rate for sulfate, nitrate and ammonia are $3.316gm^{-2}yr^{-1}$, $2.057gm^{-2}yr{-1}$, $0.894gm^{-2}yr{-1}$, respectively, and it was founded that the deposition flux in summer contributes about 38.42% to 67.62% to total deposition.

• 대한환경공학회지
• /
• 제38권1호
• /
• pp.34-41
• /
• 2016

UF (ultrafiltration)-SWRO (seawater reverse osmosis) 공정을 이용하여 해수와 기수의 유입수 블렌딩(pre-blending)이 보론(boron)과 휴믹산(humic acid)의 제거에 미치는 영향을 조사하였다. 유입수 블렌딩은 TDS (total dissolved solids) 농도를 기준으로 15,000 mg/L~27,000 mg/L까지 설정하였으며, RO에서의 보론 제거특성을 분석하였다. 또한, 동일한 TDS 농도범위에서 휴믹산을 주입하여 유기물 제거 특성을 알아보았다. 보론은 TDS 농도가 높아질수록 제거율은 76.60% - 83.27%로 높게 나타났지만, 최종 생산된 생산수의 보론 농도는 0.48 mg/L-0.69 mg/L로 높아져 유입수 내 보론 농도가 다량 유입될 시 유입수 블렌딩이 필요할 것으로 판단된다. 휴믹산의 경우 10 mg/L 수준일 경우 TDS 농도 22,500 mg/L가 27,000 mg/L 보다 제거율이 높게 나타났지만, 휴믹산이 5 mg/L 수준일 경우 TDS 농도 18,000 mg/L가 15,000 mg/L보다 높게 나타났다. 한편, 휴믹산이 주입되었을 때 UF-SWRO 공정에서는 오히려 플럭스(flux)와 회수율(recovery rate)이 증가하는 효과를 나타내었는데, 이는 파울링 물질이 $Ca^{2+}$와 휴믹산의 결합에 의해 대부분 제거되어 나타난 것으로 판단된다. 따라서 UF-SWRO를 이용한 해수 담수화 시 보론 농도와 휴믹산 제거측면에서 TDS 농도가 낮을수록 유리하다고 판단된다.