• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.90-97
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• 2013

Oil booms are one of the most widely used types of equipment for the protection of coastal areas against oil spills. In some situations, however, there are several types of oil leaks from the oil boom. Important factors regarding these phenomena include the surrounding ocean environment, such as waves, the density and viscosity of oil, the length of the oil boom skirt, etc. To estimate the performance of the oil boom, it is necessary to predict the behavior of the spilled oil and oil boom. In the present study, the prediction of oil boom performance in waves was carried out using the Pusan-National-University-modified Moving Particle Semi-implicit (PNU-MPS) method, which is an improved version of the original MPS proposed by Koshizuka and Oka (1996). The governing equations, which consist of continuity and Navier-Stokes equations, are solved by Lagrangian moving particles, and all terms expressed by differential operators in the governing equations are replaced by the particle interaction models based on a kernel function. The simulation results were validated through a comparison with the results of Violeau et al. (2007)..

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.203-203
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• 2011

최근 들어 기후변화에 따른 강우패턴이 바뀌고 각종 하천개발이나 토목공사, 농경지, 경작지 등의 객토 등으로 인해 매년 탁수의 발생이 크게 증가하고 있는 추세이다. 특히 여름철 집중강우의 영향에 따라 상류지역 하천에서 발생하는 부유물질은 호수로 유입되어 장기간 체류하며 심각한 오염원으로서 수중생태계에 치명적인 영향을 주고 있다. 또한 하천과 호수의 상류지역의 농경지나 경작지에서 발생된 부유물질에는 과도한 비료의 사용으로 입자표면에 많은 인을 포함하고 있어 호수 수질악화 및 부영양화의 직접적 요인이 되고 있다. 이에 따라 세계 각국에서는 부유물질은 오염원뿐 아니라 생태계에 영향을 주는 인자로서 엄격히 규제하고 있으며, 특히 농업지역이 많은 하천에 대해서는 유역전체를 대상으로 부유물질에 대한 총량관리를 적용하고 있다. 그러나 우리나라의 경우 하천 수질기준 1급수의 부유물질 농도는 25 mg/l 로서 이는 선진국과 유사한 기준이나 실질적으로 규제가 어려운 실정이다. 수환경에서의 부유물질이란 수체 내 존재하는 유기성, 무기성 물질로써 입자 지름이 2mm 이하의 물에 용해되지 않는 물질을 말하는 것으로, 물의 탁도를 유발시키는 원인이 되며 빛을 차단하여 수생태계에 악영향을 초래한다. 국내 132개 하천을 대상으로 부유물질의 농도와 어류의 종 다양성간 상관성을 조사한 결과, 부유물질의 농도가 15 ~ 20 mg/l 이상에서 종 다양도는 1.0 이하로 급감하는 경향을 보였다(최재석 등, 2004). 한편, 대청호는 1975년부터 1980년에 걸쳐 건립된 저수 면적 $72.8km^2$, 저수량 15억톤의 인공호수로 우리나라 3번째 규모의 인공호수이다. 특히, 대전 및 청주지역의 식수는 물론, 생활용수 및 공업용수를 공급하는 중요한 수자원으로서 부유물질에 대한 모니터링 및 관리가 시급하나 저수 용량이 크고 체류시간이 길어 여름철 부영양화가 매년 반복되고 있다. 따라서 본 연구에서는 부유물질의 농도 변화에 따른 분광반사 특성을 조사하고, 이를 대청호의 Landsat 위성영상에 적용하여 대청호 내 부유물질의 농도변화를 추정하였다. 이와 함께 부유물질 농도 변화에 따른 탁수 환경 모니터링에 원격탐사 기법이 효과적임을 제시하고자 하였다.

• KSBB Journal
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• v.19 no.3
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• pp.178-186
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• 2004

The aim of this study was to investigate the skin-whitening effect of okyong-san and to develop new drug delivery carrier The extracts of okyong-san were found to have the whitening effect and Eudragit$\^$ⓡ/ L 100-55 (EUD) coated solid lipid nanoparticle (E-SLN) was prepared by solvent evaporation method and melt dispersion technique. As a result, E-SLN have a 144-170 nm of particle size, spherical shape, and 33-41% encapsulation efficiency, After release test in vitro, release profile of E-SLN depended on pH and temperature. Lastly, closed patch test and skin-whitening test was peformed clinically. In conclusion, test sample had non-stimulation and high % whiteness. The results suggest that okyong-san and E-SLN is useful as cosmeceuticals for whitening cosmetics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1229-1235
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• 2014

At the LPG vehicle air intake system, most of dust particles in the air cleaner are removed. However very small particles are not removed and accumulated. The accumulation of carbon in air intake system is going to affect the idle speed control and sensor signal. It also causes engine chattering and transmission troubles of automatic transmission. This is study about cleaning up intake system using cleaning chemical. We can clean up the intake system by spraying cleaning liquid onto intake device when the engine is idling after intake hose is removed from warmed up vehicle. We can obtain the following experimental results by cleaning up ISC, surge tank, intake manifold, intake valves and combustion chamber. According to this results, the stroll valve works correctly and power rate of engine is up to the standard, it is smoothy to control the idling speed when a vehicle pulls up. After cleaning up CO grow down about 0.15%, HC does about 20~100 ppm.

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.260-265
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• 2013

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via $CO_2$ laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In $CO_2$ laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the $CO_2$ laser matches the absorption cross section of silane. Silane absorbs the $CO_2$ laser energy at a wavelength of $10.6{\mu}m$. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.196-202
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• 2018

In this study, we investigated phosphate removal efficiency according to pretreatment (pyrolysis temperature, pyrolysis time, particle size) of oyster shells as a basic study for their recycling. And XAFS analysis and isothermal adsorption experiments were performed to investigate the phosphate removal characteristics of oyster shells. As a result, the removal efficiency was good at $600^{\circ}C$ pyrolysis temperature with 6 hour pyrolysis time and 0.355 ~ 0.075 mm particle size. Isothermal adsorption experiments showed that the Langmuir model is suitable for adsorption of oyster shells. XAFS analysis showed that calcium phosphate formed on the oyster shell pyrolyzed at $600^{\circ}C$. In other words, it was confirmed that the formation of calcium phosphate by the calcium ion elution of the oyster shell contributes to the decrease of phosphate concentration.

• Polymer(Korea)
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• v.28 no.6
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• pp.502-508
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• 2004

Cationic liposomes for cancer treatment have been developed in the field of chemotharpy. It was well combined on the surface of anionic tumor cell membrane by electrostatic interaction. Thus, the object of this study was to prepare the cationic liposomes capable of forming an ionic complex with the anionic cell membrane. To prepare the cationic liposomes, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) as a cationic lipid material and polyethylenimine (PEI) as a cationic polymer were synthesized. Ionic property on the surface of liposomes was determined by the zeta potential. The adsorption characteristics of plasma protein for liposome in bovine serum were determined by the particle size and turbidity change. To estimate the stability of liposome in buffered solution, the change of particle size was measured at room temperature for seven days. The cationic liposomes were absorbed a large amount of plasma protein in bovine serum because plasma protein having anionic charge was fixed on the surface of cationic liposomes. This result indicate that the modification on the surface of liposomes using cationic polyethylenimine enhances the protein adsorption in bovine serum. Additionaly, cationic liposomes showed good stability in buffered solution for seven days.

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.394-398
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• 1998

We have studied the effect of Ag additions on the microstructure and the related mechanical and supercon¬ducting properties of $ YBa_{2}$$Cu_{3}$$O_{7-\delta}$ (YBCO) superconductors. A 5-15 vol.% of Ag was added to YBCO in the forms of Ag and $AgNO_{3}$, powder and the resultant microstructural evolution was evaluated. It was observed that the strength and fracture toughness of YBCO increased with increasing Ag content. These improvements in strength and fracture toughness are believed to be due to the strengthening mechanisms caused by the presence of Ag. In addition, YBCO-Ag composite superconductors showed higher values of strength and fracture toughness when Ag was added in the form of AgNO, than those of which was added Ag. The higher mechanical properties of YBCO- Ag resulting from $AgNO_{3}$, addition are probably due to the microstructure of more finely and uniformly distributed Ag particles. The addition of Ag also showed slightly improved critical current density of YBCO superconductors.

• Polymer(Korea)
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• v.27 no.6
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• pp.569-575
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• 2003

The flame retardancy was investigated when the halogenated flame retardant, decabromodiphenyl oxide (DBDPO) and chlorinated paraffin wax (CPW), was added to the polypropylene (PP) / montmorillonite (MMT) nanocomposites. The flame retardancy of polymer resin could be improved not only by addition of flame retardant but also with nanoparticles compositions. The effect of the contents of flame retardant and nanoparticles on the flame retardancy of polypropylene/ montmorillonite nanocomposite systems was thoroughly examined in terms of limited oxygen index (LOI) and cone calorimetry. As a results of cone calorimetry, the heat release rate (HRR) was reduced by the flame retardant DBDPO and CPW, and CPW was a little better than DBDPO. The LOI increased from flammable region (LOI<19) to nonflammable region (LOI>20) for all the flame retardants used in this study. Especially, the improvement in flame retardancy by compounding with PP and MMT was better than that by adding flame retardant to polypropylene. So, the addition of flame retardant after compounding with montmorillonite was more efficient than simple addition of flame retardant.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.298-304
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• 1993

The effects of the substrate temperature and the Pd underlayer on the structure and the magnetic properties of Pd/Co multilayer films prepared by the thermal evaporation were studied. As the substrate temperature increases up to $150^{\circ}C$, the crystallinity of sublayers, (111) texture and the interface sharpness of Pd/Co multilayers were improved due to the enhanced mobility of adatoms. As results of that, the perpendicular and surface anisotropy energies were increased but the coercivity was decreased because the pinning sites of domain wall decreased due to the grain growth. The grain size of the multilayers increased with Pd underlyer thickness. Thermal degradation was enhanced at above $200^{\circ}C$ due to interdiffusion at the Pd/Co interface. The intensity of the main diffraction peak rapidly decayed in the initial stage of aging and then decreased slowly. The rapid change of the intensity in the initial stage was speculated to be due to the structural relaxation phenomena and the later stage change was due to the interdiffusion. The activation energy for the interdiffusion in Pd4/Co1 multilayers was 14.9 KCal/mole.K.