• Journal of Advanced Marine Engineering and Technology
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• 제41권3호
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• pp.216-221
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• 2017

디젤엔진은 내연기관 중에 제동 열효율이 가장 높은 엔진이기 때문에 큰 동력을 필요로 하는 대형트럭과 같은 중 대형 운송 차량 및 선박 등의 수송분야 및 발전시스템 등의 다양한 분야에서 사용되어지고 있다. 하지만, 디젤엔진은 연소과정에서 질소산화물(이하 NOx) 발생량이 많은 단점을 가지고 있다. 따라서 본 연구에서는 선박용 디젤엔진의 NOx를 저감하기 위해서 습식 배기가스 처리 기술인 무격막식 해수 전기분해 방식을 이용하여 NOx 저감을 시도하였다. 실제 해수를 사용하여 디젤엔진에서 배출되는 유해가스에 전기 분해된 해수인 전해수를 분사하여 보았다. 전해수의 pH 농도 및 유효염소농도, 온도에 따른 NO 산화율 및 NOx 감소량을 조사하였다. 본 실험을 통해서 전해수의 pH가 약산성 영역일 경우가 중성일 경우보다 산화탑에서의 NO 산화율이 상승하였고, 유효염소농도가 높을수록 NO 산화율이 증가하는 것을 확인할 수 있었다. 또한, 전해수 온도는 NO 산화율에 영향이 없음을 추가적으로 확인할 수 있었으며 디젤엔진에서 생성된 배기배출물에 전해수를 분사함으로써 NOx가 저감됨을 확인할 수 있었다.

• 한국환경기술학회지
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• 제19권6호
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• pp.556-562
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• 2018

현재 하수종말처리장은 질소와 인의 방류수 수질기준 강화로 생물학적 처리 후 약품주입으로 잔류인의 처리를 하고 있는 실정에서 방류수 수질기준은 확보가 가능하나, 약품주입량의 과다와 발생되는 슬러지의 증대 및 발생슬러지의 탈수효율 저하로 슬러지처리과정에서 또 다른 문제가 발생하여 처리에 대한 신뢰성이 결여되어 있는 실정이다. 그러므로 본 연구는 기존 하수종말처리장에서 발생하고 있는 문제에 대하여 최소의 반응시간과 슬러지 발생량의 최소화를 토대로 생물학적 고도처리를 적용한 하수처리장에서 방류수 수질기준의 강화에 따라 생물학적 처리로 확보하기 어려운 안정적 처리방식과 처리수질변동에 대한 적응 및 질소와 인의 처리기준을 맞추기 위하여 기존 하수처리 방식에 Electro Coagulation and Oxidation system을 적용한 결과 다음과 같다. 1) Al-SUS(stainless steel)로 배치한 전극에서 반응시간대와 상관없이 $15mA/cm^2$의 전류밀도에서 BOD, TN 및 TP의 처리효율이 $5mA/cm^2$에서의 처리효율보다 높게 나타났으나, 전류밀도 $10mA/cm^2$ 이상만을 유지하여도 TP의 경우 대부분 0.1 mg/L 정도로 처리가 가능하며, 특히, 반응시간을 10 min으로 유지할 경우 TP농도는 전류밀도와 상관없이 0.06 mg/L 이하로 방류수 수질기준 0.1 mg/L 이하를 유지할 수 있었다. 2) TP농도의 변화는 전류밀도의 변화에 영향을 크게 받지 않으며, 오히려 반응시간에 따라 처리수의 농도가 변화하는 것으로 전기응집반응의 경우 수초~수분이 요구되나 전기산화와 동시에 반응이 일어나야 하므로 적절한 전기응집산화의 반응시간은 10 min 이상이 요구되는 것으로 연구되었다. 3) 결과적으로 본 연구에서 생활하수의 TN 및 TP처리를 위한 전기응집산화공정의 경제적인 전류밀도는 $15mA/cm^2$이하, 반응시간은 10 min을 유지하는 것이 적절한 것으로 연구되었다.

• 한국분말재료학회지
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• 제18권6호
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• pp.532-537
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• 2011

Thermally stable $TiO_2$/Pt/$SiO_2$ core-shell nanocatalyst has been synthesized by chemical processes. Citrated capped Pt nanoparticles were deposited on amine functionalized silica produced by Stober process. Ultrathin layer of titania was coated on Pt/$SiO_2$ for preventing sintering of the metal nanoparticles at high temperatures. Thermal stability of the metal-oxide hybrid catalyst was demonstrated heating the sample up to $600^{\circ}C$ in air and by investigating the morphology and integrity of the structure by transmission electron spectroscopy. The surface analysis of the constituent elements was performed by X-ray photoemission spectroscopy. The catalytic activity of the hybrid catalysts was investigated by CO oxidation reaction with oxygen as a model reaction.

• Current Photovoltaic Research
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• 제1권2호
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• pp.115-121
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• 2013

ZnO film has been used for CIGS solar cells as a buffer layer as itself or by doping Mg and Sn; ZnO film also has been used as a transparent conducting layer by doping Al or B for solar cells. Since ZnO itself is a host material for many applications it is necessary to understand the electrical and optical properties of ZnO film itself with various preparation conditions. We prepared ZnO films by converting ZnS precursor into ZnO film by thermal annealing. ZnO film was formed at low temperature as low as $500^{\circ}C$ by annealing a ZnS precursor layer in air. In the air annealing, the electrical resistivity decreased monotonically with increasing annealing temperature; the intensity of the green photoluminescence at 505 nm increased up to $750^{\circ}C$ annealing. The electrical resistivity further decreased and the intensity of green emission also increased in reducing atmospheres. The results suggest that deep-level defects originated by oxygen vacancy enhanced green emission, which reduce light transmittance and enhance the recombination of electrons in conduction band and holes in valence. More oxidizing environment is necessary to obtain defect-free ZnO film for higher transparency.

• 한국재료학회지
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• 제13권4호
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• pp.233-238
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• 2003

Ferromagnetic tunnel junctions, Ta/Cu/Ta/NiFe/Cu/$Mn_{75}$ $Ir_{25}$ $Co_{70}$ $Fe_{30}$/Al-oxide, were fabricated by do magnetron sputtering and plasma oxidation process. The effect of annealing temperature on the local transport properties of the ferromagnetic tunnel junctions was studied using contact-mode Atomic Force Microscopy (AFM). The current images reflected the distribution of the barrier height determined by local I-V analysis. The contrast of the current image became more homogeneous and smooth after annealing at $280^{\circ}C$. And the average barrier height $\phi_{ave}$ increased and its standard deviation $\sigma_{\phi}$ X decreased. For the cases of the annealing temperature more than $300^{\circ}C$, the contrast of the current image became large again. And the average barrier height $\phi_{ave}$ decreased and its standard deviation $\sigma_{\phi}$ increased. Also, the current histogram had a long tail in the high current region and became asymmetric. This result means the generation of the leakage current that is resulted from the local generation of a low barrier height region. In order to obtain the high tunnel magnetoresistance(TMR) ratio, the increase of the average barrier height and the decrease of the barrier height fluctuation must be strictly controlled.led.

• 자원리싸이클링
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• 제29권6호
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• pp.114-124
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• 2020

시멘트 산업에서 질소산화물 배출은 중요한 문제로 인식되고 있으며 이를 저감하는 기술은 공정변경, 단계적 연소, 저 NOx 버너, SNCR, SCR로 나눌 수 있다. 이중 시멘트 산업에서 가장 많이 사용되고 있는 SNCR 운영만으로는 향후 강화될 배출허용기준을 만족시키기 어려울 것이 예상되며 SCR 등의 추가적인 장비 개선 및 기술 확보가 필요한 상황이다. 이에 따라 최근에는 국외를 중심으로 SNCR 및 SCR 동시 적용 기술, 분진 및 탈질 필터 기술과 NO 산화를 이용한 제거기술 등을 개발하고 있다.

• 한국습지학회지
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• 제17권2호
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• pp.155-162
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• 2015

정수처리공정에서 미량유기물질과 맛 냄새물질인 2-methylisoborneol (2-MIB)와 geosmin의 제거특성을 파악하기 위하여 오존 및 advanced oxidation process (AOP)와 입상활성탄으로 구성된 biological activated carbon (BAC)공정과 활성탄 단독공정인 granular activated carbon (GAC)공정에 대한 pilot plant를 수행하였다. 운전 결과, 2-MIB 159 ng/L, geosmin 371 ng/L의 고농도에서 오존 1.0 mg/L 주입시 42%, 86%의 제거율을 나타냈으며 $H_2O_2$ 0.5 mg/L를 추가주입한 AOP 공정에서 각각 58%, 90%의 제거율 상승을 나타냈다. 또한 BAC공정에서 99.8%의 제거율을 나타냈으며 GAC 공정에서 2 ng/L이하의 처리성능을 보였다. 따라서 미량유기물질 및 맛 냄새 물질의 지속적인 제거를 위해서는 오존/AOP와 활성탄의 처리효과를 조합한 BAC 공정이 효과적으로 나타났으며, 활성탄지의 흡착능을 지속적으로 유지하기 위해서 유입농도에 따른 오존/AOP 공정의 최적화가 필요한 것으로 판단된다.

• Corrosion Science and Technology
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• 제4권6호
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• pp.217-221
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• 2005

In the present investigation, holographic interferometry was utilized for the first time to monitor in situ the thickness of the oxide film of aluminium samples during anodization processes in boric acid solutions. The anodization process (oxidation) of the aluminium samples was carried out by the technique of the electrochemical impedance spectroscopy(EIS), in different concentrations of boric acid (0.5-5.0% $H_3BO_3$) at room temperature. In the mean time, the real-time holographic interferometry was used to measure the thickness of anodized (oxide) film of the aluminium samples in solutions. Consequently, holographic interferometry is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film of the aluminium samples can be determined without any physical contact. In addition, measurements of electrochemical values such as the alternating current (A.C) impedance(Z), the double layer capacitance($C_{dl}$), and the polarization resistance(Rp) of anodized films of aluminium samples in boric acid solutions were made by the electrochemical impedance spectroscopy(EIS). Attempts to measure electrochemical values of Z, Cdl, and Rp were not possible by holographic interferometry in boric acid especially in low concentrations of the acid. This is because of the high rate of evolutions of interferometric fringes during the anodization process of the aluminium samples in boric acid, which made measurements of Z, Cdl, and Rp are difficult.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2003년도 Challenges and Achievements in Environmental Health
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• pp.123-127
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• 2003

This experiment was performed to investigate the characteristics of sonolytic reaction as the basic data for development of the ultrasonic AOP(Advanced Oxidation Process) process from which the refractory organic compounds in aqueous solution which are not readily removed by the existing conventional wastewater treatment processes can be destructed and removed. Trichloroethylene (TCE), benzene, and 2,4-dichlorophenol(DCP) were used as the samples, and their destruction efficiency were measured in terms of experimental parameters of the initial solution concentration, initial solution pH, reaction temperature, acoustic frequencies and intensities. Results showed that the destruction efficiencies of all of the sample materials were above 80% within 120 minutes of sonolytic reaction in all reaction condition. The reaction order of these three compounds was verified as Pseudo first order. From the fore-mentioned results, it can be concluded that the refractory organic compounds could be removed by the ultrasonic irradiation with radicals, such as H$.$and OH$.$causing the high increase of pressure and temperature. Finally, it appears that the new AOP technology using ultrasonic irradiation can be applied to the treatment of refractory substances which are difficult to be decomposed by the conventional methods.

• Journal of Advanced Marine Engineering and Technology
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• 제34권7호
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• pp.963-970
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• 2010

This study makes an estimate of the laser-assisted machining (LAM) of an economically viable process for manufacturing precision silicon nitride ceramic parts using a high-power diode laser (HPDL). The surface is locally heated by an intense laser source prior to material removal, and the resulting softening and damage of the workpiece surface simplify the machining of the ceramics. The most important advantage of LAM is its ability to produce much better workpiece surface quality compared to conventional machining. Also important are its larger material removal rates and longer tool life. The cutting force and surface temperature were measured on-line using a pyrometer and a dynamometer, respectively. Tool wear, chips and the surface of the workpiece were measured using optical microscopy, and the surface and fractured cross-section of $Si_3N_4$ were measured by SEM. During the LAM process, the cutting force and tool wear were reduced and oxidation of the machined surface was increased according to the increase in the laser power. Moreover, the more the feed rate increased, the more the cutting force and tool wear increased.