• 한국산학기술학회논문지
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• 제16권12호
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• pp.8679-8683
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• 2015

세라믹은 고온에서 뛰어난 내마모성, 내부식성을 가지기 때문에 산업적 응용에 있어서 널리 사용된다. 세라믹은 금속과 비교해서 고온에서 더 큰 강도를 가지고 있고, 더 낮은 열전도도 및 열팽창 계수를 가진다. 그러나, 세라믹이 가진 취성의 성질은 전기전자산업과 고온에서의 구조적 적용에의 넓은 적용을 제한한다. Ti 활성금속과 STS304를 IBAD 기술을 이용해서 동시에 증착시켜 STS304 스테인레스강에 $Al_2O_3$(알루미나)의 브레이징 접합강도에 어떤 영향을 미치는지 알아보았으며, 시험편들은 Ti 타겟과 Ti+ STS304 타겟 두 종류를 이용하여 두께를 변화시켜가며 증착하였다. 브레이징 접합을 위한 삽입금속으로는 일반적으로 사용되는 Ag-Cu 공정조성의 합금이 사용되었다. 브레이징 접합품의 강도는 Ag-Cu 삽입금속과 알루미나 사이의 반응층의 두께와 반응 생성물 조직에 의해 결정되며, 본 실험에서는 계면 반응의 메커니즘을 보다 구체화하고 계면 반응에 의한 경사기능성의 접합계면을 더욱 향상시키는 결과를 얻고자 한다.

• Macromolecular Research
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• 제16권2호
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• pp.108-112
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• 2008

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of nonpolar polymeric materials is affected by the sample preparation as well as the matrix and cationizing agent. This study examined the influence of silver salt types on the MALDI analysis of polybutadiene (PB). Silver trifluoroacetate (AgTFA), silver benzoate (AgBz), silver nitrate ($AgNO_3$), and silver p-toluenesulfonate (AgTS) were used as the silver salts to compare the MALDI mass spectra of PB. The mixture solution of PB and 2,5-dihydroxybenzoic acid (DHB), as a matrix dissolved in THF, was spotted on the sample plate and dried. A droplet of the aqueous silver salt solution was placed onto the mixture. The mass spectrum with AgBz showed the clear $[M+Ag]^+$ ion distribution of PB while the mass spectrum with AgTFA did not show $[M+Ag]^+$ ions but only silver cluster ions. The mass spectra with $AgNO_3$ and AgTS did not show a clear $[M+Ag]^+$ ion distribution. The difference in the formation of $[M+Ag]^+$ ions of PB depending on the silver salts was attributed to the silver cation transfer reaction between the silver salt and the matrix (DHB). The mass spectrum showed a clear $[M+Ag]^+$ ion distribution of PB when the conjugate acid of the silver salt was less acidic than the matrix.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.844-847
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• 2001

The application of laser direct etching has been discussed, and believed that the process is a very powerful method for micro machining. This study is focused on the micro patterning technology using laser direct etching process with no chemical damage of the material surface. A new introduced concept of energy synergy effect for surface micro machining is the combination of chemically ion reaction and laser thermal process. The etchant can't etch the material in room temperature, and used Ar laser has not power enough to machine. But, the machining is occurred in local area of the material by the combined energy. Using this process, the material is especially prevented from chemical damage for electric property. We have tested this new concept, and achieved a line with $1{mu}m$ width. The Ar laser with 488nm wavelength was used. The material was Si(100) wafer, and etchant is KOH solution. The application and flexibility of this process is in great hopes for MEMS structures and fabrication of the micro electric device parts.

• 한국재료학회지
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• 제27권3호
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• pp.161-165
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• 2017

In this paper, synthesis of terephthalate intercalated Zn-Al: Layered double hydroxides (LDHs) was studied. We designed freestanding Zn-Al: carbonate LDH nanosheets for a facile exchange technique. The as-prepared Zn-Al carbonate LDHs were converted to terephthalate intercalated Zn-Al:LDHs by ion exchange method. Initially, Al-doped ZnO (AZO) thin films were deposited on p-Si (001) by facing target sputtering. For synthesis of free standing carbonate Zn-Al:LDH, we dipped the AZO thin film in naturally carbonated water for 3 hours. Further, Zn-Al: carbonate LDH nanosheets were immersed in terepthalic acid (TA) solution. The ion exchange phenomena in the terephthalate assisted Zn-Al:LDH were confirmed using FT-IR analysis. The crystal structure of terephthalate intercalated Zn-Al:LDH was investigated by XRD pattern analysis with different mole concentrations of TA solution and reaction times. The optimal conditions for intercalation of terephthalate from carbonated Zn-Al LDH were established using 0.3 M aqueous solution of TA for 24 hours.

• 대한환경공학회지
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• 제37권1호
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• pp.60-68
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• 2015

폐활성슬러지의 감량화 및 혐기성소화 효율 향상을 위한 가용화 기술로 microwave (MW)에 대한 연구가 활발히 진행되고 있다. MW에 의한 가용화는 유전가열에 의해 가열적, 비가열적 효과 및 이온성 전도를 유도하여 매우 짧은 시간에 반응이 일어나므로 폐활성슬러지의 가용화에 효과적으로 적용될 수 있다. 본 연구에서는 폐활성슬러지 가용화에 대해 전도 가열대비 MW의 우수성을 평가하였고, 고출력 조건에서 수행된 기존 연구들과 달리 저출력 조건에서 MW의 효율 향상을 위해 강산인 $H_2SO_4$ 및 이온성 물질인 $CaCl_2$, NaCl을 촉매로 이용하였다. 전도 가열 대비 MW를 이용한 폐활성슬러지의 가용화 효율은 $50^{\circ}C$ 조건에서 6.2배, $100^{\circ}C$ 조건에서 1.4배 높게 나타났으며, 본 연구의 MW 저출력 조건에서 최대 COD 가용화율은 10.0%로 나타났다. 동일한 MW 출력 및 반응시간 조건에서 촉매물질인 $H_2SO_4$ 및 NaCl의 첨가를 통해 폐활성슬러지의 COD 가용화율이 18.1%, 12.7%로 증가하였으며, $CaCl_2$를 첨가하였을 경우에는 COD 가용화율이 10.7%로 MW의 효율에 향상에 효과가 없는 것으로 나타났다. 이는 가용화 효율을 향상시킬 것으로 예상된 $Ca^{2+}$가 슬러지 가용화에 따라 발생하는 ${PO_4}^{3-}$와 반응하여 침전물 형성에 소모되었기 때문으로 판단된다. 본 연구에서 MW 효율 향상을 위한 가장 적합한 촉매물질은 $H_2SO_4$인 것으로 나타났으며, 0.2 M의 $H_2SO_4$를 첨가한 MW 조건이 폐활성슬러지의 가용화에 가장 효과적인 것으로 나타났다.

• 분석과학
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• 제20권4호
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• pp.331-338
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• 2007

한약과 기능성식품으로 널리 활용되는 감초의 지표물질인 glycyrrhizin과 liquiritin을 HPLC-MS/MS 로 정성, 정량분석을 실시하였다. 두 가지 지표성분 모두 positive ion mode에서 검출이 가능하였고, precursor ion과 product ion을 조합한 multiple-reaction monitoring (MRM) mode에서 liquiritin은 m/z $436.2{\rightarrow}257.0$로 관찰되었고, glycyrrhizin은 m/z $823.4{\rightarrow}453.4$ 로 각각 검지되었다. 감초 물 추출물을 분무건조기로 건조한 분말에서 glycyrrhizin의 경우 5.8%, liquiritin의 경우 2.3% 각각 함유되어 있었다. 회수율은 103-113%였고, 일간, 일내 정밀도 실험에서 상대표준편차는 0.95-1.8% 였다. 본 실험 조건에서 liquiritin과 glycyrrhizin의 검출한계는 각각 0.4 ng/mL과 0.01 ng/mL 이었다.

• Journal of Microbiology and Biotechnology
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• 제26권10호
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• pp.1781-1789
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• 2016

Glargine insulin is a long-acting insulin analog that helps blood glucose maintenance in patients with diabetes. We constructed the pPT-GI vector to express prepeptide glargine insulin when transformed into Escherichia coli JM109. The transformed E. coli cells were cultured by fed-batch fermentation. The final dry cell mass was 18 g/l. The prepeptide glargine insulin was 38.52% of the total protein. It was expressed as an inclusion body and then refolded to recover the biological activity. To convert the prepeptide into glargine insulin, citraconylation and trypsin cleavage were performed. Using citraconylation, the yield of enzymatic conversion for glargine insulin increased by 3.2-fold compared with that without citraconylation. After the enzyme reaction, active glargine insulin was purified by two types of chromatography (ion-exchange chromatography and reverse-phase chromatography). We obtained recombinant human glargine insulin at 98.11% purity and verified that it is equal to the standard of human glargine insulin, based on High-performance liquid chromatography analysis and Matrix-assisted laser desorption/ionization Time-of-Flight Mass Spectrometry. We thus established a production process for high-purity recombinant human glargine insulin and a method to block Arg (B31)-insulin formation. This established process for recombinant human glargine insulin may be a model process for the production of other human insulin analogs.

• 한국환경보건학회지
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• 제30권2호
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• pp.92-97
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• 2004

Three methods for VOCs emissions control in indoor air are reduction at the source, ventilation between indoor and outdoor, and removal. The best alternative should be to replace highly emitting sources with sources having low emissions, but the pertinent information on VOCs is not always available from manufactures. Other ways of improving indoor air quality are needed. It is to increase the outside fresh-air flow to dilute the pollutants, but this method would generally provide only a dilution effect without destruction in residence. An ideal alternative to existing technologies would be a chemical oxidation process able to treat large volumes of slightly contaminated air at normal temperature without additional oxidant such as ozone generator and ion generator. Photocatalytic oxidation(PCO) represents such a process. It is characterized by a surface reaction assisted by light radiation inducing the formation of superoxide, hydroperoxide anions, or hydroxyl radicals, which are powerful oxidants. In comparison with other VOCs removal methods, PCO offers several advantages. The purpose of this study was to explore the possibilities for photocatalytic purification of slightly contaminated indoor air by using visible light such as flurescent visible light(FVL). In this study, a PCO of relatively concentrated benzene using common FVL lamps was investigated as batch type and total volatile organic compounds(TVOCs) using a common FVL lamp and penetrated sun light over window. The results of this study shown the possibility of TiO$_2$ photocatalyst application in the area of indoor air quality control.