• Clean Technology
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• v.12 no.3
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• pp.113-127
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• 2006

Waste lubricating oil(WLO)s have been recycled as energy source through direct fuel in cement kilns and fossil power plants, or as fuel oils, or re-refined lubricating base oils. In our country, they have been recycled as low grade fuel oil through chemical treatment process. In 2003, extended producer responsibility (EPR) system was adopted from deposit system on sale of lubricating oils in order to promote their recycleing rate. However, our recycling rate of WLOs have been stagnant(below 70%) for last 5 years. And there has been no research work on recycling of WLOs as re-refined base oil until now in this country. Stabilization technology of thermally cracked oils to reduce tar and malodor and to improve their color for production of high grade fuel oil, and a novel process production of high grade re-refined lubricating base oil from WLOs have been developed and commercialized recently in Canada and U.S.A., respectively. Several countries like Australia, Italy, Germany and U.S.A., etc. are encouraging recycling companies to recycle WLOs as re-refined lubricating oil by giving greater subsidies or benefits compared to other recycling methods. They also adopt a policy to purchase re-refined lubricating oil preferentially in the federal or local governments and to recommend consumers to purchase it willingly. Based on the facts that several advanced countries have adopted a policy to recycle WLOs as re-refined base oil for saving of petroleum resource and reduction of environmental pollution, it is right time to be considered that our present policy for recycling of WLOs should be reevaluated and the new policy of their environmental-friendly and sustainable recycling should be established.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.244-254
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• 1999

폐윤활유 재생용 TiO2 한외여과막은 정밀영과용 지르코니아 복합막(즉, 복층담채) 및 알루미나 단층 담체(기공크기 0.1$mu extrm{m}$)상에 졸-겔 코팅법에 의하여 TiO2 분리막 층을 코팅하여 제조 하였다. TiO2 졸의 특성 분석을 통하여 봉입침지(sealed dip-coating) 및 가압 코팅(pressurized coating)법으로 결함이 없는 TiO2 복합막을 제조할 수 있는 코팅조건을 최적화 하였다. 합성 TiO2 한외여과막의 분리막층 두께는 1$\mu\textrm{m}$이하의 범위에서 조절되었으며,기공값을 보여주었으며 75$0^{\circ}C$까지 열처리하여도 80%정도의 용질배제율(기공크기 22.5nm)을 유지하는 점으로 봐서 고온 공정을 요하는 폐윤활유 재생막으로서 충분한 열적 안정성을 갖고 있었다.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.59-59
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• 1996

막분리에 의한 폐윤활유 재생공정을 개발하기 위한 기초 연구로써 폐윤활유 분리/재생용으로 적합한 복층(multilayer)세라믹 복합막의 제조와 합성막의 폐유 분리 효율등이 연구되었다. 결함이 없고 두께가 균일한 지르코니아 복합막 (기공크기 0.07 $\mu$m 이하)은 압출 성형법으로 제조한 튜브형 $\alpha$-알루미나 담체 (외경 7.8 mm, 두께 0.6 mm, 기공크기 0.7 $\mu$m)내부표면에 역침지 인상법(reverse dip-drawing technique)에 의하여 지르코니아 슬러리를 코팅 한 후 950$\circ$C에서 1시간 열처리하여 제조 되었다. 또한 지르코니아 복합막 위에 니타니아 졸-겔 코팅을 한 후 450$\circ$C에서 2시간 열처리하여 기공크기가 15 nm정도인 3층 복합막을 제조 하였다. SEM, Bubble Point Test, Mercury Porosimeter 그리고 분획 분자량 측정등에 의하여 복합막의 코팅층 두께, 결함유무 및 막의 기공크기등을 분석하였다.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.203-209
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• 2016

Purpose: Stimulating the proliferation and migration of periodontal ligament cells (PDLCs) has become the main goal of periodontal regeneration. To accomplish this goal, regeneration procedures have been developed, but results have not been predictable. Recently, tissue engineering using enamel matrix derivatives (EMDs) and growth factors has been applied to periodontal regeneration; however, the mechanism of EMDs is largely unknown. The aim of this study was to investigate the effects of EMDs on the proliferation and release of growth factors from PDLCs. Materials and methods: Human PDLCs were removed from individually extracted 3rd molars of healthy young adults, and cultured in the media containing EMDs (Emdogain, Biora, Malmo, Sweden) at concentration of 0, 12.5, 25, 50, 100, and $200{\mu}g/mL$ each. Cell proliferation and ALP (alkaline phosphatase) activity were measured. The evaluation of growth factors released by PDLCs was also performed by one-way analysis of variance (ANOVA) and Bonferroni's multiple comparison test. Results: Significantly increased proliferation and ALP activity were observed in PDLCs treated with over $25{\mu}g/mL$ and $50{\mu}g/mL$ EMDs, respectively. Additionally, treatment of PDLCs with $50{\mu}g/mL$ resulted in significantly increased release of vascular endothelial growth factor (VEGF) and transforming growth factor $(TGF)-{\beta}$ after 24 h and 48 h, respectively. Conclusion: EMDs enhance the proliferation and ALP activity of PDLCs, and promote the release of growth factors, including VEGF and $TGF-{\beta}$, from PDLCs. Therefore EMDs could be one of the effective methods for periodontal regeneration.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.37-46
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• 2018

A design study on the cooling channel configuration in a regeneratively cooled supersonic combustor was performed. The flow parameters on the hot- and cold-side channels were calculated using a quasi-one-dimensional model. The heat transfer between these two sides was estimated as a part of the flow calculation. For the reference configuration, the total amount of heat exchanged was 10.7 kW, the heat flux was $566kW/m^2$, and the fuel temperature increase between the inlet and outlet was 153 K. Seven designs of the heat exchanger channel were compared for their heat transfer performance.

• Clean Technology
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• v.22 no.4
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• pp.274-280
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• 2016

In this study, it was to develop a chemical method that can recycle the cutting oil which accounts for about 25% of the cost of the process among containing materials of silicon waste sludge generated in the process for producing a solar cell wafer. The 7 types of reagents have been used, including acetone, HCl, NaOH, KOH, $Na_2CO_3$, HF, $CH_2Cl_2$, etc. for this experiment. And It was carried out at a speed of 3000 rpm for 60 minutes centrifugation after performing a reaction with a waste sludge at various concentrations. As a result, the best reagents and conditions for separating the solid such as a silicon powder and a metal powder and liquid cutting oil were identified as 0.3 N NaOH. It is found to be pH 6.05 in a post-processing recycled cutting oil with 0.3 N NaOH after reaction of waste sludge and 0.1 N HCl which is effective to remove metal powder in order to adjust the pH to suit the properties of the weak acid is a commercially available cutting oil and it showed excellent turbidity than when applied to sludge with 0.3 N NaOH alone. The results of FT-IR analysis which can compare the properties of the commercially available cutting oil shows it has a possibility of recycling oil. The cutting oil recovery rate obtained through the experiment was found to be 86.9%.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1371-1380
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• 2007

Study on the instability of waste plastic's thermal pyrolysis oil was carried out for the purpose of improving its quality. The reaction of pyrolysis oil with ozone changed double bonds into aldehydes and ketone, estimated that HDPE pyrolysis oil contained $\sim45$ wt% 1-alkene type olefins, and PP pyrolysis oil did $\sim73$ wt% olefins, which consisted of $\sim47$ wt% secondary and $\sim20$ wt% primary alkenes. The dark brown color and odor of pyrolysis oil were improved by eliminating double bonds, indicated that they were directly related to unsaturated hydrocarbons. Container test showed that metal can affected oil quality worse than the brown glass bottle. Antioxidant added into pyrolysis oil was consumed up to 90% within $2\sim3$ days and the wt. composition of unsaturated hydrocarbons in pyrolysis oil was not changed within 50 days, inferring that instability of pyrolysis oil due to unsaturated bonds can be stabilized by antioxidants. Adsorption test on silica gel, activated carbon and alumina to remove precipitates in oil produced a good result, but not enough to remove moisture. However, cheap anhydrous sodium carbonate showed the best removal efficiency of moisture as well as precipitates in oil. Therefore the pyrolysis oil quality improvement was accomplished by applying anhydrous $Na_2CO_3$ into the production plant.

• 대한치주과학회:학술대회논문집
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• 1999.11a
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• pp.32-33
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• 1999

• The Journal of the Korean dental association
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• v.36 no.7 s.350
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• pp.497-502
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• 1998

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.405-413
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• 2005

본 연구에서는 3톤/일의 플라스틱 투입량을 기준으로 혼합폐플라스틱으로부터 대체연료유를 생산할 수 있는 소용량 중심의 폐플라스틱 유화설비를 설계 제작하였으며 장기간에 걸친 시운전을 통하여 유화설비의 운전성 평가에 대한 실증연구를 수행하였다. 대상 폐플라스틱으로는 플라스틱 재활용 업체에서 분리 선별된 폴리에틸렌과 폴리프로필렌 그리고 이들을 혼합한 폐플라스틱을 각각 적용하였으며 $400\sim420^{\circ}C$의 분해 운전온도에서 폐플라스틱의 종류에 따른 시운전 평가를 하였다. 본 실증연구로부터 폴리에틸렌의 경우에 있어서는 79%의 재생유 회수율을 그리고 폴리프로필렌의 경우에 있어서는 80%의 재생유 회수율을 각각 얻을 수 있었으며 플라스틱 종류별 안정적인 운전조건을 확보할 수 있었다. 또한 폐플라스틱 투입량에 대한 설계용량과 운전용량과의 비교로부터 약 40$\sim$50%의 설계오차가 발생한 것으로 평가되었으며 이는 유화설비의 설계를 위하여 사용된 혼합폐플라스틱의 부정확한 물성 값에 기인한 것으로 판단된다. 따라서 본 연구로부터 얻은 시운전결과를 바탕으로 설계인자들을 확립하는 과정이 반드시 필요할 것으로 판단된다.