• 한국재료학회지
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• 제22권9호
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• pp.445-449
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• 2012

We investigate the effects of redox reaction on preparation of high purity ${\alpha}$-alumina from selectively ground aluminum dross. Preparation procedure of the ${\alpha}$-alumina from the aluminum dross has four steps: i) selective crushing and grinding, ii) leaching process, iii) redox reaction, and iv) precipitation reaction under controlled pH. Aluminum dross supplied from a smelter was ground to separate metallic aluminum. After the separation, the recovered particles were treated with hydrochloric acid(HCl) to leach aluminum as aluminum chloride solution. Then, the aluminum chloride solution was applied to a redox reaction with hydrogen peroxide($H_2O_2$). The pH value of the solution was controlled by addition of ammonia to obtain aluminum hydroxide and to remove other impurities. Then, the obtained aluminum hydroxide was dried at $60^{\circ}C$ and heat-treated at $1300^{\circ}C$ to form ${\alpha}$-alumina. Aluminum dross was found to contain a complex mixture of aluminum metal, aluminum oxide, aluminum nitride, and spinel compounds. Regardless of introduction of the redox reaction, both of the sintered products are composed mainly of ${\alpha}$-alumina. There were fewer impurities in the solution subject to the redox reaction than there were in the solution that was not subject to the redox reaction. The impurities were precipitated by pH control with ammonia solution, and then removed. We can obtain aluminum hydroxide with high purity through control of pH after the redox reaction. Thus, pH control brings a synthesis of ${\alpha}$-alumina with fewer impurities after the redox reaction. Consequently, high purity ${\alpha}$-alumina from aluminum dross can be fabricated through the process by redox reaction.

• 생명과학회지
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• 제21권5호
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• pp.678-683
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• 2011

본 연구에서는 울릉도 특산 약용 작물 추출물이 항염증에 대한 실험연구가 이루어져 있지 않은 것에 착안하여 LPS에 의해 활성화된 대식세포로부터 유도되는 염증반응에 대한 억제효과를 조사하였다. 울릉도 자생 식물인 곰취, 미역취, 삼나물의 세가지 식물 추출물을 이용하여 피부 염증에 대하여 연구를 하였다. 산화질소와 cytokine의 생산은 면역세포의 대표적인 염증인자이다. 세포는 LPS 처리 후 한 시간 뒤에 곰취, 미역취, 삼나물 70% 아세톤 추출물을 처리를 하였다. 세포 독성이 나타나지 않는 농도인 1, 10, 100 ug/ml를 사용하였다. 곰취, 미역취, 삼나물 70% 아세톤 추출물은 NO, $PGE_2$, TNF-${\alpha}$, IL-1${\beta}$, IL-6, iNOS, COX-2의 생성을 저해 시켰다. $PGE_2$는 100 ug/ml의 농도에서 60%에 가까운 저해율을 나타내었다. iNOS와 COX-2 역시 100 ug/ml의 농도에서 각각 54%, 65%가 저해가 되었다. 게다가 곰취, 미역취, 삼나물 70% 아세톤 추출물은 염증성 사이토 카인인 TNF-${\alpha}$, IL-1${\beta}$, IL-6의 생성을 감소 시켰다. 이러한 결과로 곰취, 미역취, 삼나물 추출물은 염증 예방과 치료에 효과적임을 확인할 수 있었다.

• 대한환경공학회지
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• 제38권5호
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• pp.269-278
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• 2016

수도권지역의 대기오염을 개선하기 위해 수도권 대기환경 개선에 관한 특별법이 제정되었고 2005년부터 시행되었다. 그 결과 수도권의 대기질은 개선되었으나 각 대책의 평가에 대한 연구는 부족하다. 이에, 본 연구는 도로이동오염원의 배출량 저감정책이 질소산화물의 농도저감에 미치는 영향을 정량적으로 분석하고자 하였다. 이를 위해 MM5-SMOKE-CMAQ 모델 시스템을 이용하여 수치모사를 수행하였다. 2007년 수도권 $NO_x$ 저감 배출량은 16,561톤으로서 4.7%의 저감률을 보였다. 여러 대책 중 제작차 배출허용기준강화 대책이 가장 효과적이었다. 지역별 삭감실적은 차이가 커서 서울의 삭감률은 인천과 경기의 약 2배에 달하였다. 결과적으로 $NO_x$ 저감의 효과는 서울 도심에 집중적으로 나타났다. 이동오염원 저감대책에 의하여 서울의 $NO_2$ 농도는 연평균 0.60 ppb (2.0%)저감되었고 인천과 경기는 각각 0.18 ppb (1.5%), 0.22 ppb (1.7%)가 저감되었다. 봄과 겨울의 저감농도는 여름과 가을에 비해 1.5~2.0배 정도 높았다. 도심과 풍하지역으로의 $NO_2$ 저감효과 분산때문에 도심지역의 $NO_x$ 배출량 저감이 직접적인 $NO_2$ 농도 저감에 효과적이지 않았다.

• 대한환경공학회지
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• 제33권4호
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• pp.237-242
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• 2011

본 연구에서는 Mn-PC 촉매와 상압유통식 반응장치를 이용하여 $200{\sim}380^{\circ}C$ 범위에서 VOCs(아세트알데히드, 프로피온알데히드, 톨루엔) 연소반응을 수행하였다. 촉매 전처리(air, $450^{\circ}C$, 1 hr, 60 cc/min) 전 후의 물리화학적 특성변화 조사는 TGA (Thermogravimetric Analyzer), BET (Brunauer Emmett Teller), EA (Elemental Analyzer), XRD (X-ray Diffractometer) 및 SEM (Scanning Electronic Microscope)을 이용하여 파악하였다. TGA 분석결과 Mn-PC의 열중량(공기 분위기) 감소는 $419^{\circ}C$에서 88 wt.%를 나타내었으며, 전처리 후 비표면적은 크게 증가하는 것으로 확인되었다. EA 분석결과 전처리를 통해서 유기물 성분은 분해 또는 연소되어 거의 관찰되지 않는 것으로 파악되었다. 또한 XRD분석을 통해 Mn-PC 촉매가 전처리 후 새로운 형태의 산화물인 $Mn_3O_4$로 전이됨을 확인하였다. 그리고 SEM 분석결과 전처리 과정에서 많은 micropore가 생성된 것으로 관찰되었다. 프로피온알데히드 연소의 경우 전처리한 Mn-PC는 $Mn_3O_4$와 fresh한 Mn-PC 보다 우수한 촉매활성을 나타내었다. 전처리된 Mn-PC상에서 VOCs 연소 효과는 톨루엔 < 아세트알데히드 < 프로피온알데히드 순서로 나타났다.

• Progress in Superconductivity
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• 제12권2호
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• pp.118-123
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• 2011

The properties of $2^{nd}$ generation high temperature superconducting wire, coated conductor strongly depend on the quality of superconducting oxide layer and property of metal substrate is one of the most important factors affecting the quality of coated conductor. Good mechanical and chemical stability at high temperature are required to maintain the initial integrity during the various process steps required to deposit several layers consisting coated conductor. And substrate need to be nonmagnetic to reduce magnetization loss for ac application. Hastelloy and stainless steel are the most suitable alloys for metal substrate. One of the obstacles in using stainless steel as substrate for coated conductor is its difficulties in making smooth surface inevitable for depositing good IBAD layer. Conventional method involves several steps such as electro polishing, deposition of $Al_2O_3$ and $Y_2O_3$ before IBAD process. Chemical solution deposition method can simplify those steps into one step process having uniformity in large area. In this research, we tried to improve the surface roughness of stainless steel(SUS310). The precursor coating solution was synthesized by using yttrium complex. The viscosity of coating solution and heat treatment condition were optimized for smooth surface. A smooth amorphous $Y_2O_3$ thin film suitable for IBAD process was coated on SUS310 tape. The surface roughness was improved from 40nm to 1.8 nm by 4 coatings. The IBAD-MgO layer deposited on prepared substrate showed good in plane alignment(${\Delta}{\phi}$) of $6.2^{\circ}$.

• 치위생과학회지
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• 제14권2호
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• pp.140-149
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• 2014

본 연구에서는 지르코니아 에칭에 의한 표면변화가 지르코니아 코어와 도재 사이의 결합강도에 미치는 영향을 조사하기 위해 전단결합강도 실시하였고, 표면의 변화를 관찰하기 위한 SEM 측정, 에칭처리에 따른 지르코니아의 성분변화를 알아보기 위해 EDS 분석을 실시하였다. 그리고 구강상태에서 15~20년의 저온열화현상을 재현하기 위해 저온 열화 처리를 시행하여 전단결합강도 평가를 실시하여 다음과 같은 결과가 도출되었다. 1. 에칭처리를 시행하지 않은 시편과 에칭처리를 시행한 시편의 전단결합강도를 비교할 경우 에칭한 시편의 전단결합강도가 큰 것을 알 수 있다. 이는 에칭용액이 지르코니아코어 표면에 interlocking을 형성하여 기계적인 결합을 높여 주었을 것이라고 생각된다. 2. 전단결합강도의 결과(EZ>AEZ>NEZ>ANEZ)를 보았을 때 통계적으로는 유의한 차이를 보였으며, 저온열화처리를 하지 않고 에칭처리를 한 EZ군이 전단결합강도가 가장 큰 것을 알 수 있었다. 또한 파절 양상에서도 EZ군에서만 응집파절을 보여 가장 결합강도가 높다는 결과를 도출할 수 있다. 결론적으로 저온열화처리 여부에 관계없이 표면에칭처리를 한 시편의 전단결합강도가 큰 것으로 나타나 지르코니아 표면의 에칭처리로 인한 interlocking의 형성이 기계적인 결합을 향상시키는 요인이 되었다고 생각된다.

• 대한치과보철학회지
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• 제38권2호
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• pp.129-146
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• 2000

An increasing demand for esthetic restorations has led to the development of new ceramic systems. In-Ceram, a glass-infiltrated alumina ceramic has three to few times greater flexural strength than other ceramic glass material. Because of its high strength, In-Ceram has been suggested as inlay, crown, laminate veneer and core material for resin bonded fixed partial dentures. This clinical application requires a stable resin bond to In-Ceram core. The purpose of this study was to evaluate the shear bond strength between In-Ceram core and resin cements according to various surface treatments and storage conditions. The surface of each In-Ceram core sample was subjected to one of the following treatments and then bonded to Panavia 21 or Variolink II resin cement. ; (1) sandblasting with $110{\mu}m$ aluminum oxide powder, (2) sandblasting and silanization, (3) sandblasting and Siloc treatment, (4) sandblasting and Targis link application. Each of eight bonding groups was tested in shear bond strengths after the following storage times and thermocycling. ; A) 24 hours storage in distilled water at $37^{\circ}C$, B) 5 weeks storage in distilled water at $37^{\circ}C$ C) 5 weeks storage in distilled water at $37^{\circ}C$ and thermocycled 2,000 thormocycling for every 10 days(totally 10,000 thermocycting) in $5^{\circ}C-55^{\circ}C$ bath. The bond failure modes were observed with scanning electron microscope(SEM). The results were as fellows : 1 The shear bond strengths of sandblasting group were significantly lesser than the other groups after 24 hours water storage. No significant difference of bonding strengths was found between storage time conditions(24 hours and 5 weeks). The shear bond strengths showed a tendency to decrease in Variolink II bonding groups and to increase in Panavia 21 bonding groups. 3. After thermocycling, the shear bond strengths of all groups were significantly decreased(p<0.01) and Targis link group exhibited significantly greater strengths than the other groups(p<0.05). 4. Panavia 21 bonding groups exhibited significantly greater bonding strengths in sandblasting group(p<0.01) and silane group(p<0.05) than Variolink II bonding groups. 5. In observation of bond failure modes, Targis link group showed cohesive failure in resin part and silane group and Siloc group showed complex failure and sandblasting group showed adhesive failure between In-Ceram and resin.

• 콘크리트학회논문집
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• 제15권4호
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• pp.529-540
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• 2003

최근 콘크리트 내구성설계에 관한 연구가 활발히 진행되고 있으며, 사용수명 예측이 핵심인 내구성 평가모델 개발이 그 좋은 예이다. 본 연구에서는 콘크리트 구조물의 잔존수명예측 모델을 개발하여 적정시기의 유지보수를 통한 경제적 구조물 사용을 목적으로 하였다. 육지 콘크리트 구조물인 저수지의 콘크리트 구조물 부분을 대상으로 전국 70개 지구를 선정하고, TG/DTA 법과 페놀프탈레인 지시약법으로 중성화를, pH메타법으로 pH 값을 측정하여 탄산칼슘함량 대비 사용연수, pH값, 콘크리트 피복 두께의 관계함수를 각각 유도한 후 가능한 최소의 자료측정으로 잔존수명을 예측할 수 있는 모델을 개발하였다. 개발된 잔존수명예측 모델은 탄산가스등의 고정변수에 의한 실내촉진실험 자료기반 모델과 달리 동결융해작용, 중성화, 철근 부식 등 복합적인 열화작용이 동시에 일어나는 현장의 환경적 영향을 받은 구조물에서 측정한 자료를 기반으로 개발되었다. 이러한 점에서 그 신뢰성을 높게 평가 받을 수 있을 것이며, 시설물 유지관리자에게 적정 보수보강 시점을 제공하여 경제적인 구조물 사용에 도움을 줄 수 있을 것으로 판단된다.

• 자원환경지질
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• 제29권5호
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• pp.545-559
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• 1996

Rare metal (Nb-Zr-REE) ore deposits are located in the Chungju area. Geotectonically, the rare metal ore deposits are situated in the transitional zone between Kyeonggi massif and Okcheon belt. The rare metal deposits are distributed in Kyemyeongsan Formation which consist of schist and alkaline igneous rocks. Alkali granite has suffered extensive post-magmatic metasomatism and hydrothermal processes. The ore contains mainly Ce-La, Ta-Nb, Y, Y-Nd, Nd-Th group minerals. More than 15 RE and REE minerals are found in the ore deposits. Allanite, one of the Ce-La rich REE minerals belonging to the epidote group, is the most common mineral in the studied area. The allanite- bearing rocks may be devided into seven types by features of occurrence and mineral associations; zircon type (ZT), allanite-vein type (AT), feldspar type (KT), fluorite type (FT), quartz-mica type (QT), iron-oxide type (MT), and amphibole type (HT). The allanite veins (AT) and zircon rich rocks (ZT) contain the highest total REE contents. Differences in REE abundance can be interpreted in terms of varying portions of magmatic hydrothermal fluid. Petrographical and chemical data are presented for allanites which were collected from different types. The allanites show wide variations in optical properties, due in part to differences in their chemical composition (depending on the types) and to the degree of crystallinity of the individual specimens. Allanite metamicts in biotite are generally surrounded by well developed pleochroic haloes. Usually, allanite is accompanied by zircon and other REE-bearing minerals. CaO and total REE contents $({\sum}RE_2O_3)$ range from 9.29 to 18.79% and 11.66 to 26.31%, respectively. Also, SiO, (28.87~32.61%), $Al_2O_3$ (8.30~16.88%), and $Fc_2O_3$ (16.74~24.38%) contents show varying contents from type to type. The ${\sum}RE_2O_3$ of allanite has positive relationships with $Fe_2O_3$ and negative relaton with CaO, $SiO_2$, and $Al_2O_3$ Backscattered electron microscope images (BEl) of allanite shows that the its mineral composition and texture is very complex. The allanite-bearing hosts show distinct light REE enrichment with strong negative Eu anomaly except for HI. The HT has an almost flat REE distribution pattern with a small negative Eu anomaly. The chemical variation of the allanites with occurrences and mineral association can be related to condition of temperature and oxidation states in precipitation environment.

• Asian Pacific Journal of Cancer Prevention
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• 제15권15호
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• pp.6227-6232
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• 2014

Background: Oral squamous cell carcinoma (OSCC) remains as one of the most difficult malignancies to control because of its high propensity for local invasion and cervical lymph node dissemination. The aim of present study was to evaluate the efficacy of novel pH and temperature sensitive doxorubicin-methotrexate-loaded nanoparticles (DOX-MTX NP) in terms of their potential to change the VEGF-C expression profile in a rat OSCC model. Materials and Methods: 120 male rats were divided into 8 groups of 15 animals administrated with 4-nitroquinoline-1-oxide to induce OSCCs. Newly formulated doxorubicin-methotrexate-loaded nanoparticles (DOX-MTX NP) and free doxorubicin were IV and orally administered. Results: Results indicated that both oral and IV forms of DOX-MTX-nanoparticle complexes caused significant decrease in the mRNA level of VEGF-C compared to untreated cancerous rats (p<0.05). Surprisingly, the VEGF-C mRNA was not affected by free DOX in both IV and oral modalities (p>0.05). Furthermore, in DOX-MTX NP treated group, less tumors characterized with advanced stage and VEGF-C mRNA level paralleled with improved clinical outcome (p<0.05). In addition, compared to untreated healthy rats, the VEGF-C expression was not affected in healthy groups that were treated with IV and oral dosages of nanodrug (p>0.05). Conclusions: VEGF-C is one of the main prognosticators for lymph node metastasis in OSCC. Down-regulation of this lymph-angiogenesis promoting factor is a new feature acquired in group treated with dual action DOX-MTX-NPs. Beside the synergic apoptotic properties of concomitant use of DOX and MTX on OSCC, DOX-MTX NPs possessed anti-angiogenesis properties which was related to the improved clinical outcome in treated rats. Taking together, we conclude that our multifunctional doxorubicin-methotrexate complex exerts specific potent apoptotic and anti-angiogenesis properties that could ameliorate the clinical outcome presumably via down-regulating dissemination factor-VEGF-C expression in a rat OSCC model.