• 한국응용과학기술학회지
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• 제35권1호
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• pp.163-172
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• 2018

본 연구에서는 질소산화물 제거용 환원제로 사용하는 요소 수용액을 암모니아로 전환하는데 있어 SCR 상용촉매의 활용가능성을 확인하기위해 촉매조성에 따른 반응온도, 공간속도의 영향에 대한 연구를 수행하였다. 연구결과 SCR 촉매로 널리 사용되는 $V_2O_5/TiO_2$ 촉매는 $TiO_2$ 및 $WO_3-V_2O_5/TiO_2$ 촉매에 비해 암모니아 생성이 우수함을 보였다. 활성금속을 담지하지 않은 $TiO_2$ 촉매는 $V_2O_5$ 혹은 $WO_3-V_2O_5$를 담지 한 촉매에 비해 공간속도에 따른 암모니아 전환에 영향을 받지 않는 것으로 나타났으며, 활성금속을 담지 한 촉매는 공간속도가 증가함에 따라 암모니아 생성 농도가 감소됨을 확인하였다.

• 한국대기환경학회지
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• 제20권4호
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• pp.451-463
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• 2004

The performance of disk-type catalytic filters impregnated by TiO$_2$ or TiO$_2$-3Al$_2$O$_3$ㆍ 2SiO$_2$ supports and V$_2$O$_{5}$ catalyst was evaluated for selective catalytic reduction (SCR) of NO with ammonia as a reductant. XRD, FT -IR, BET and SEM were used to characterize the catalytic filters prepared in this work. Optimal V$_2$O$_{5}$ loading and reaction temperature for V$_2$O$_{5}$/TiO$_2$ catalytic filters were 3-6 wt.% and 350-40$0^{\circ}C$ at GHSV 14,300 $hr^{-1}$ in the presence of oxygen, respectively. With increasing the V$_2$O$_{5}$ loading from 0.5 to 6 wt%, NO conversion increased from 24 to 96% at 40$0^{\circ}C$ and 14.300$hr^{-1}$, and maintained at 80% over in the V$_2$O$_{5}$ loading range of 3-6 wt.% and then dropped at V$_2$O$_{5}$ loading of 7wt.% over. In comparing V$_2$O$_{5}$/ TiO$_2$ and V$_2$O$_{5}$/ TiO$_2$-3Al$_2$O$_3$ㆍ2SiO$_2$ catalytic fillers, which have same 3wt.% V$_2$O$_{5}$ loading, the V$_2$O$_{5}$/ TiO$_2$-3A1$_2$O$_3$ㆍ2SiO$_2$ catalytic filter showed higher activity than V$_2$O$_{5}$/ TiO$_2$ catalytic filter, but higher differential pressure drops owing to its low air permeability. low air permeability.

• 한국대기환경학회지
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• 제26권1호
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• pp.1-9
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• 2010

In this study, the selective catalytic reduction of $NO_x$ with ammonia was carried out in a filter bag support reactor. The experiments were performed by powder type $MnO_x$ and $V_2O_5$/$TiO_2$ catalyst at low temperature between 130 and $250^{\circ}C$. Also, the effect of $SO_2$ and $H_2O$ on the NO conversion was investigated under our test conditions. The powder type catalysts were analyzed by X-ray photoelectron spectrum (XPS), X-ray diffraction(XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was observed that NO removal efficiency of the powder type $V_2O_5$/$TiO_2$ catalyst was 85% at low temperature($200^{\circ}C$) under presence of oxygen and that of $MnO_x$ was 50% at the same condition. The powder type $V_2O_5$/$TiO_2$ catalyst, in conclusion, was found to be available for SCR reaction in a filter bag support system.

• 폴리머
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• 제25권3호
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• pp.311-317
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• 2001

본 연구에서는 반응성이 큰 친수성 단량체인 glycidylmethacrylate (GMA)를 이용하여 현탁중합법으로 bead type의 GMA-DVB 공중합체를 제조하고, 이들 공중합체를 trimethyl-ammonium chloride로 아민화하여 trimethylammonium기를 갖는 거대망상형 음이온 교환수지를 합성하였다. 여기서 지하수에 공존하는 음이온 중 $NO_3^-$ 제거에 가장 방해가 되는 $SO_4^{2-}$ 이 입체적으로 크다는 것에 착안하여 가교제인 divinylbenzene (DVB)의 양을 변화시켜 가교도에 따른 음이온에 대한 선택능을 확인하였고, 각각의 수지에 대한 물성과 $NO_3^-$ 에 대한 흡착능을 고찰하였다. 또한 FT-IR을 통하여 공중합체의 합성여부를 확인하였고, 또한 아민화 수율, 이온교환 용량 및 팽윤율을 평가하여 가교도에 따른 영향을 조사하였다. 여기서 DVB의 함량이 4wt%일 때 아민화 수율은 384.3%, 이온교환용량은 3.25 meq/g, 팽윤율은 77.1%로 가장 최적으로 나타났다.

• Nuclear Engineering and Technology
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• 제1권1호
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• pp.17-22
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• 1969

English sole(가재미종) 어편을 Polymylar bag에 밀봉하여 500 Krad의 감마선에 조사한 후 36일간의 0-2$^{\circ}C$ 저장기간중 조사한 것과 조사하지 않은 어편내에 축적되는 부패표시 물질과 총 균수를 측정하였다. 단백질 분해균을 직접 계수하기 위하여 Casein agar Plate 법을 만들어 저장기간중의 총균수비 대한 단백질분해균의 비율을 측정하는데 사용하였다. 500 Krad 선량 조사결과 어편의 총 균수는 10분의 1로 감축되었고 저장중 조사하지 않은 어편의 총균수 보다 훨씬 적어 1000분의 1선까지 내려갔다. 이에 따라 TVB와 TMA 축적도 억제되어 부패선을 넘지 못했으며 단백질 분해균 역시 총균수의 1% 이하선으로 감축되었으며 저장 기간중 이 선을 넘지 못했다. 반면에 조사하지 않은 어편엔 총 균수에 대한 이들의 비율은 저장기간중 점차 상승하여 22일째까지 총균수의 85.5%를 차지하였다. 방사선 조사로 인한 이 단백질 분해균의 선택적인 제거는 그 어편의 단백질 분해 부진 현상을 초래했다.

• 청정기술
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• 제23권1호
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• pp.64-72
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• 2017

본 연구에서는, $150{\sim}400^{\circ}C$ 영역에서 $NO_x$를 제어하기 위한 ball mill 기법을 사용한 선택적 환원촉매(SCR)의 연구를 수행하였다. 제조된 촉매들의 구조적 특성 및 산화가 특성을 확인하기 위하여 XRD, BET, XPS 분석을 수행하였다. 다양한 ball mill 기법에 의해 제조된 촉매는 $250^{\circ}C$ 이하의 온도구간에서의 활성의 차이를 보였다. 이중 가장 우수한 탈질효율을 갖는 촉매를 기준으로, ball mill 시간이 3시간일 때 가장 높은 활성을 나타내었다. XPS 분석 결과, vanadium의 비 화학양론종의 존재 및 원자 수 증가가 활성증진에 유리하게 작용한 것으로 나타났다. 또한 $O_2$ on-off 실험을 통해 격자산소량의 양과 탈질 효율과의 상관관계를 나타내었고, 이는 서로 비례관계에 있음을 확인하였다.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1201-1207
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• 2020

This study explored whether MXene (Ti₃C₂T_x) could remove radioactive Cs⁺ from model nuclear wastewater. Various adsorption tests were performed and the physical aspects of the interaction were investigated. We varied the MXene dosage, Cs⁺ initial concentration, solution pH, solution temperature and exposure time. MXene adsorption exhibited very fast kinetics, based on the fact that equilibrium was achieved within 1 h. MXene exhibited an outstanding adsorption capacity (148 mg g^-1) at adsorbent and adsorbate concentrations of 5 and 2 mg L^-1, respectively, at neutral pH condition (i.e., pH 7). We explored Cs⁺ adsorption by MXene in the presence of four different ions (NaCl, KCl, CaCl₂ and MgCl₂) and three different organic acids (sodium oleate, oxalic acid, and citric acid). The Cs⁺ removal rate changed in the presence of these components; adsorption of Cs⁺ by MXene thus involved ion exchange, supported by both Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. We confirmed that MXene was re-usable for at least four cycles. MXene is cost-effective and practical when used to adsorb radionuclides (e.g., Cs⁺) in nuclear wastewater.

• 한국환경과학회지
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• 제21권12호
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• pp.1455-1462
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• 2012

The vertical distributions of nitrifying bacteria in aerobic fixed biofilm were investigated to evaluate the relationship between nitrification performance and microbial community at different HRT. Fluorescent in situ hybridization (FISH) and portable ion selective microelectrode system were adopted to analyze microbial communities and ions profiles according to the biofilm depth. Cilia media packed MLE (Modified Ludzack-Ettinger) like reactor composed of anoxic, aerobic I/II was operated with synthetic wastewater having COD 200 mg/L and $NH_4{^+}$-N mg/L at HRT of 6 hrs and 4 hrs. Total biofilm thickness of aerobic I, II reactor at 4 hrs condition was over two times than that of 6 hrs condition due to the sufficient substrate supply at 4 hrs condition (6 hrs; aerobic I 380 ${\mu}m$ and II 400 ${\mu}m$, 4 hrs; aerobic I 830 ${\mu}m$ and II 1040 ${\mu}m$). As deepen the biofilm detection point, the ratio of ammonia oxidizing bacteria (AOB) was decreased while the ratio of nitrite oxidizing bacteria (NOB) was maintained similar distribution at both HRT condition. The ratio of AOB was higher at 4 hrs than 6 hrs condition and $NH_4{^+}$-N removal efficiency was also higher at 4 hrs with 89.2% than 65.4% of 6 hrs. However, the ratio of NOB was decreased when HRT was reduced from 6 hrs to 4 hrs and $NO_2{^-}$-N accumulation was observed at 4 hrs condition. Therefore, it is considered that insufficient HRT condition could supply sufficient substrate and enrichment of AOB in all depth of fixed biofilm but cause decrease of NOB and nitrite accumulation.

• 구강회복응용과학지
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• 제21권1호
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• pp.69-81
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• 2005

The objective of this study was to evaluate the toothbrush abrasion characteristics of class V restorations. Thirty extracted human premolars, which were collected from oral surgery clinics were used. We mounted five teeth in a metal ring mold of 50 mm in diameter and 15 mm in height using chemically cured acrylic resin. Class V cavities were prepared in lingual cervical root surfaces and restored using one of following restorative materials : Dentin Conditioner/Fuji II LC (Group FL), All Bond II/Z-250 (Group ZT), One-up Bond F/Palfigue Estelite (Group PE), F2000 Primer/Adhesive (Group FT), and Prime & Bond 2.1/Dyract AP (Group DR). They were stored under distilled water at $37^{\circ}C$ for seven days. The toothbrush abrasion test was conducted using a wear testing machine of pin-on disk type under a load of 1.5 N for 100,000 cycles. We have examined the bonded interfaces, the changes of surface roughness and color of abraded surfaces. From this experiment, the following results were obtained. 1. The change of surface roughness showed high degree: RMGIC>compomer>composite resin (p<0.05). 2. Because of the protrusion and missing of filler particles, SEM observation of abraded surfaces of RMGIC and compomers revealed the increase of surface roughness due to the selective removal of matrix resin. 3. The color change by toothbrush abrasion was affected in large part by the change of $L^*$ and $b^*$ of resin composites (p<0.05). 4. The color change by toothbrush abrasion was so small to detect by human eyes. 5. SEM observation of abraded surfaces revealed the interface bonding was the best in the FT group.

• 한국기계가공학회지
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• 제14권4호
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• pp.62-72
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• 2015

Interest in three-dimensional (3D) printing processes has grown significantly, and several types have been developed. These 3D printing processes are classified as Selective Laser Sintering (SLS), Stereo-Lithography Apparatus (SLA), and Fused Deposition Modeling (FDM). SLS can be applied to many materials, but because it uses a laser-based material removal process, it is expensive. SLA enables fast and precise manufacturing, but available materials are limited. FDM printing's benefits are its reasonable price and easy accessibility. However, metal printing using FDM can involve technical problems, such as suitable component supply or the thermal expansion of the heating part. Thus, FDM printing primarily uses materials with low melting points, such as acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) resin. In this study, an FDM process for enabling metal printing is suggested. Particularly, the nozzle and heatsink for this process are focused for stable printing. To design the nozzle and heatsink, multi-physical phenomena, including thermal expansion and heat transfer, had to be considered. Therefore, COMSOL Multiphysics, an FEM analysis program, was used to analyze the maximum temperature, thermal expansion, and principal stress. Finally, its performance was confirmed through an experiment.