• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.370-376
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• 2005

Magnesium alloys are becoming important material for light weight car body, due to their low specific density but high specific strength. However they have a poor weldability, caused high oxidization tendency and low vapor temperature. In this study, the welding performance of magnesium alloys was investigated for automobile application. The materials were rolled magnesium alloy sheet contains Al and Zn such as AZ3l , AZ6l and AZ9l. Three types of welding process were studied, that were GTAW, Laser beam welding and FSW. To evaluate the weldability, we examined the appearance of welding bead. Also we checked bead shape and internal defects such as crack and porosity on cross section of welding bead. The mechanical property was measured for welded specimen by tensile test. For determination of the strength change by welding process, the hardness profile across the welding center was measured. For the results, the tensile properties of welded specimen were decreased obviously on all welding process. For the fusion welding process such as GTAW and laser beam welding, the surface of the welding bead was covered with oxidized magnesium dust but it was removed by simple cleaning work as wipe-out with tissue. Also under cut, that caused vaporization of base metal was occurred. for the friction stir welding, there was no oxidation, under-cut or internal defects. However it had poor weld performance, the reason was cleavage fracture occurred at plastic deformation zone. For welding of magnesium alloy, the laser beam welding process was recommended.

• Journal of Microbiology and Biotechnology
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• 제24권4호
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• pp.440-446
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• 2014

The carbohydrate-binding module (CBM) is an important domain of most cellulases that plays a key role in the hydrolysis of cellulose. The neutral endoglucanase (EG1) gene was reconstructed. A redesigned endoglucanase, named EG2, was constructed with a CBM containing a linker from Corticium rolfsii (GenBank Accession No. D49448). The redesigned EG genes were expressed in Escherichia coli, and their characteristics are discussed. Results showed that the degradation of cellulose by EG2 was about double that by EG1. The specific activities of EG1 and EG2 were tested under optimal conditions, and EG2 had higher activity ($169.1{\pm}2.74$ U/mg) toward CMC-Na than did EG1 ($84.0{\pm}1.98$) in the process of cellulose degradation. The optimal pH and temperature, pH stability, and heat stability of EG1 and EG2 were similar. Results indicated that the CBM plays an essential role in the hydrolysis of cellulose. We can improve EG's catalytic power by adding the CBM from Corticium rolfsii.

• Fisheries and Aquatic Sciences
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• 제13권1호
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• pp.36-48
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• 2010

An agar-degrading Agarivorans sp. AG17 strain was isolated from the red seaweed Grateloupia filicina collected from Jeju Island. A beta-agarase gene from Agarivorans sp. AG17 was cloned and designated as agrA. agrA has a 2,985 bp coding region encoding 995 amino acids and was classified into the glycoside hydrolase family (GHF)-50. Predicted molecular mass of the mature protein was 105 kDa. His-tagged agrA was overexpressed in Escherichia coli and purified as a fusion protein. The enzyme showed 158.8 unit/mg specific activity (optimum temperature at $65^{\circ}C$ and pH 5.5 in acetate buffer) with unique biochemical properties (high thermal and pH stabilities). Enzyme produced neoagarohexaose, neoagarotetraose and neoagarobiose by degrading agar, and hydrolyzed neoagaro-oligosaccharides were biologically active. Hence the purified enzyme has potential for use in industrial applications such as the development of cosmetics and pharmaceuticals.

• BMB Reports
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• 제40권1호
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• pp.107-112
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• 2007

To study the functioning of HSP70 in Escherichia coli, we selected NtHSP70-2 (AY372070) from among three genomic clones isolated in Nicotiana tabacum. Recombinant NtHSP70-2, containing a hexahistidine tag at the amino-terminus, was constructed, expressed in E. coli, and purified by $Ni^{2+}$ affinity chromatography and Q Sepharose Fast Flow anion exchange chromatography. The expressed fusion protein, $H_6NtHSP70$-2 (hexahistidine-tagged Nicotiana tabacum heat shock protein 70-2), maintained the stability of E. coli proteins up to 90$^{\circ}C$. Measuring the light scattering of luciferase (luc) revealed that NtHSP70-2 prevents the aggregation of luc without ATP during high-temperature stress. In a functional bioassay (1 h at 50$^{\circ}C$) for recombinant $H_6NtHSP70$-2, E. coli cells overexpressing $H_6NtHSP70$-2 survived about seven times longer than those lacking $H_6NtHSP70$-2. After 2 h at 50$^{\circ}C$, only the E. coli overexpressing $H_6NtHSP70$-2 survived under such conditions. Our NtHSP70-2 bioassays, as well as in vitro studies, strongly suggest that HSP70 confers thermo-tolerance to E. coli.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2290-2298
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• 2020

The damage of first wall material in fusion reactor due to the bubbles caused by plasma has been studied by introducing a relation between the von Mises equivalent stress and the temperature field. The locations and shapes of the bubbles and the synergetic effect between the different bubbles under steady operational conditions have been studied using the finite elements method. Under transient heat loads, plastic deformations have been found to occur, and are significantly enhanced by the presence of the bubbles. The calculated concentration locations of von Mises equivalent stress are well consistent with the observed crack positions of the tungsten surface in many test experiments. Our simulations show that the damage of the bubbles is not severe enough to lead to catastrophic failure of the tungsten armor; however, it can cause local and gradual detachment of tungsten surface, which provides a reasonable explanation for the observed pits and rough or hairy surface morphology etc. Considering the transient heat loads, the lower bound of the security thickness of the tungsten tile is estimated to be greater than 2 mm.

• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.22-28
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• 2016

It is necessary to store and supply hydrogen isotopes for Tokamak operation. A storage and delivery system (SDS) is used for storing hydrogen isotopes as a metal hydride form. We designed and fabricated a depleted uranium (DU) bed to store hydrogen isotopes. The rapid storage of hydrogen isotopes is very important not only for safety reasons but also for the economic design and operation of the SDS. The delivery rate at the desorption temperatures without the operation of a dry pump was analyzed in comparison with that with the operation of the dry pump. The effect of the initial desorption temperatures on the dehydriding of the DU without the operation of the dry pump was measured. The effect of the initial desorption temperatures on the dehydriding of DU with the operation of the dry pump was also measured and analyzed. The primary pressure on the desorption temperatures without the operation of the dry pump was analyzed in comparison with that with the operation of the dry pump. The temperature gradient of the coil heater and the primary vessel was also analyzed. Our results will be used to develop pilot scale hydrogen isotope processes. It was confirmed that dehydriding of a medium-scale DU bed has enabled without the operation of the dry pump.

• 마이크로전자및패키징학회지
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• 제16권1호
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• pp.27-31
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• 2009

본 논문에서는 웨이퍼 레벨 기술을 이용한 CIS용 폴리머 접합 기술을 연구하고 접합 후의 warpage 분석과 개별 패키지의 신뢰성 테스트를 수행하였다. 균일한 접합 높이를 유지하기 위하여 glass 웨이퍼 상에 dam을 형성하고 접합용 폴리머 층을 patterning하여 Si과 glass 웨이퍼의 접합 테스트를 수행하였다. Si 웨이퍼의 접합온도, 접합 압력 그리고 접합 층이 낮을수록 warpage 결과가 감소하였으며 접합시간과 승온 시간이 짧을수록 warpage 결과가 증가하는 것을 확인하였다. 접합 된 웨이퍼를 dicing 하여 각 개별 칩 단위로 TC, HTC, Humidity soak의 신뢰성 테스트를 수행하였으며 warpage 결과가 패키지의 신뢰성 결과에 미치는 영향은 미비한 것으로 확인되었다.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.561-565
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• 2007

Because of a good wear resistance and a stable contact resistance, Ag-CdO is widely used as electrical contact material. But, the Cd-oxide mainly exists as a coarse particle and adversely affected to environment. As a reason, $Ag-SnO_2$ alloy has been developed. The Sn-oxide maintains stable and fine particle even at high temperature. In order to investigate the effect of Misch metal (Mm) additional that affects the formation of the oxide and the formation of fine matrix Ag, we studied the microstructures and properties of Ag-Sn-In(-Mm) material fabricated by rapid solidification process. The experimental procedure were melting using high frequency induction, melt spinning, and internal oxidation. The Mm addition makes Ag matrix more fine than no Mm addition. The reason is that the addition of Misch metal decreased a latent heat of fusion of alloy, as a result the rapid solidification effect of alloy is increased. The maximum hardness shows at 0.3 wt%Mm. after that the hardness is decreased until 0.4 wt% Mm, but still larger than no Mm addition alloy. At 0.5 wt% Mm alloy, the precipitation of Misch metal causes a decrease of hardness than no Mm addition alloy.

• 한국전기전자재료학회논문지
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• 제27권8호
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• pp.535-540
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• 2014

Because of the development of LED technology, products due to high output and compact, the material with high thermal conductivity has been developed. Now that heat radiating part of the LED lamp is currently used for die casting of aluminum. The development of aluminum with excellent thermal conductivity is required. In this study, we measured the thermal properties and compared them while we produced the alloy by changing the component of die casting aluminum. From this study, the thermal conductivity and thermal resistance of the developed alloy were superior to die casting aluminum.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.464-467
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• 1999

The undoped-InSe and Sn-doped InSe single crystals were grown by vertical Bridgman method and their properties were invesigated. The orientations and the crystallinites of these crystals were identified by X-ray diffraction(XRD), double crystal rocking curve(DCRC) and etch-pit density(EPD) measurements. From the Raman spectrum at room temperature, TO, LO modes and together with their overtones and combinations were observed. Optical properties were inves ated by PL at 12K and direct band gap of these crystals obtained from optical absorption spectrum. Compared with undo&-InSe, electrical properties of Sn-doped InSe were increased and the electrical conductivity type were n-type. But electrical properties along growth direction of crystals and radial direction of wafer showed nearly uniform distribution. The Zn diffusion mechanism in InSe could be explained by interstitial-substitutional and vacancy complex models and the activation energy of 1.15-3.01eV were needed for diffusion.fusion.