• Journal of the Korean institute of surface engineering
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• v.46 no.1
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• pp.36-41
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• 2013

Friction stir welding (FSW) is a relatively new joining technique particularly for magnesium and aluminum alloys that are difficult to fusion weld. In this study, AZ31 Mg alloys were joined by FSW with shoulder diameter 11, 19 mm and rotating speed 900, 1200, 1500, 1800 rpm. The shoulder diameter and welding speed depended on the heat input during FSW process. As a result, the microstructures of stir zone were a fine grain by dynamic recrystallization. According to the larger shoulder diameter and the higher rotating speed, refined grain sizes of stir zone were grown by higher heat input, and the microhardness of stir zone was lower. The tensile strength at the shoulder diameter 19 mm, rotating speed 900 rpm was obtained maximum value. This value compared with the base metal was over 93%.

• BMB Reports
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• v.40 no.1
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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.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.292-292
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• 2000

Since high-power CO$_2$ Laser can be make a high densed energy to Local processing area, manufacturing processes using the laser can be processed for very Localized areas at a very fast rate with minimal or no distortion. Accordingly, the laser has been widely used in the fields of thermal manufacturing processes such as welding, fusion cutting, grooving, and heat treatment of metals. In particular, interest in the laser heat treatment process has grown tremendously in the past few years. In this process, maintaining the uniform hardening depth is important problem to obtain good quality products and to reduce heat induced distortion and residual stress. For achieving this objective, we introduced a new design technique of a fuzzy logic controller that greatly simplified the design procedure by defining several simplified design parameters. In the design procedure, the major design parameters of the controller are characterized by identifying several common aspects. From a series of simulation results, we found that the proposed design technique can be effectively used to design of a fuzzy logic controller for the LASER surface hardening process.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.18-18
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• 2010

최근에 건조되는 선박이나 구조물들은 점차 대형화 되어가고, 이에 사용되는 판재들은 점차 고강도 극후판재화 되어가고 있다. 극후판재의 용접성을 향상시키기 위해서는 대입열 용접이 주로 적용되고 있는 실정인데, 30 mmt 이상의 후판을 1 pass로 용접하기 위해서는 EGW(Electro-gas welding) 기법을 사용한다. 대입열 용접은 용접입열(heat input)이 매우 높아 용착금속과 열영향부의 냉각속도가 매우 느려 용접열영향부에서 특히 fusion line 근처의 열영향부는 결정립 조대화 및 취약한 미세조직을 형성함으로서 저온인성을 크게 저하시키고, 연화 현상(softening effect)을 발생시켜 강도가 저하되는 문제점이 주로 발생하였다. 하지만 이런 문제점을 해결하기 위해 대입열용접에 사용된는 강재의 미세조직을 제어하여 AlN, TiN, $TiO_2$ 등의 석출물을 이용한 용접열영향부의 저온인성을 향상시켰다. 이러한 문제점이 발생하는 대입열용접에서 저온인성 시험은 주로 fuison line + 1, 2mm에서 수행한다. 하지만 대입열 용접시 용착금속의 냉각속도도 매우 느리기 때문에 용착금속의 위치에 따라 저온 인성 특성이 다르게 나타날 수 있다. 본 연구에서는 EGW 용착금속의 위치에 따른 저온인성 특성을 평가하기 위해 EH-36N, 40mmt 판재를 사용하여 1pole EG 용접 하였다. 용착금속의 저온인성 특성을 평가하기위해 충격 시편의 노치 위치가 fusion line - 2mm와 용접부 중앙을 기준으로 4곳을 선정하여 충격시험을 수행하였다. 또한 용착금속의 경도 분포를 알아보기 위해 micro vickers hardness tester(mitutoyo UR-501)을 사용해 hardness mapping 시험을 하였다. 용착금속의 저온인성은 미세조직과, 산소량에 따라 변화 할 수 있기 때문에 용착금속 위치를 달리하여 미세조직과 산소량도 각각 분석하였다. 용착금속의 저온인성을 향상시킬 수 있는 침상형페라이트와 비금속개재물의 상관관계에 관해 검토 하였다.

• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.3236-3241
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• 2024

Ion cyclotron resonance heating (ICRH) is an important auxiliary heating method applied to the China Fusion Engineering Test Reactor, which can effectively heat the ions and electrons in plasma. Owing to the harsh nuclear environment, neutronic analyses are required to verify tritium self-sufficiency and neutron-shielding requirements. In this study, a neutronics analysis of the ICRH antenna was conducted using the COre and System integrated engine for Reactor Monte Carlo (cosRMC) code to estimate the neutron flux, radiation damage, nuclear heating, gas generation rate of key components, and tritium breeding ratio (TBR), providing data support for the subsequent optimization of the shielding design. In addition, the neutron flux of the coils around the antenna was calculated to prevent the entry of neutrons that damage the magnetic field coils through the gaps between the port plugs and antenna, and the shielding effects of the port-plug antenna on the surrounding components were analyzed. Finally, the results obtained using the cosRMC and MCNP codes were compared, which and presented good agreement, thus verifying the reliability of the neutronic analysis using the cosRMC code.

• Journal of Powder Materials
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• v.31 no.2
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• pp.137-145
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• 2024

In order to predict the process window of laser powder bed fusion (LPBF) for printing metallic components, the calculation of volumetric energy density (VED) has been widely calculated for controlling process parameters. However, because it is assumed that the process parameters contribute equally to heat input, the VED still has limitation for predicting the process window of LPBF-processed materials. In this study, an explainable machine learning (xML) approach was adopted to predict and understand the contribution of each process parameter to defect evolution in Ti alloys in the LPBF process. Various ML models were trained, and the Shapley additive explanation method was adopted to quantify the importance of each process parameter. This study can offer effective guidelines for fine-tuning process parameters to fabricate high-quality products using LPBF.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2141-2152
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• 2024

Tungsten is the most promising plasma facing material for fusion reactors. Rolled W-Y₂(Zr)O₃ bulk material has been successfully produced in this study for future fusion engineering applications. The introduction of Zr is conducive to the refinement of the second phase particles. Nano-sized Y-Zr-O particles are observed in the powder and bulk samples. Related results show that the Y-Zr-O particle dispersion distribution improves the heat load resistance of W-Y₂(Zr)O₃ composite material. For four-point bend experiments in the same sampling direction, the DBTT of W-Y₂(Zr)O₃ composite materials is lower compared to the pure tungsten. For the same material, the DBTT of the material was selected for testing along the RD direction is lower compared to the material was selected for testing along the TD direction. Findings of this study provide suggestions for the subsequent industrial preparation of nanoscale particle-doped tungsten materials.

• KSBB Journal
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• v.26 no.3
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• pp.243-247
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• 2011

Using Bacillus subtilis spore display system, with cotG as an anchoring motif, levansucrase from Zymomonas mobilis, was displayed on the outer surface of Bacillus subtilis spore. Flow cytometry of DB104 (pSDJH-cotG-levU) spore, proved the surface localization of CotG-LevU fusion protein on the spore compared to that of DB104. Enzymatic activity of DB104 (pSDJH-cotG-levU) spore showed more than 1.5 times higher levansucrase specific activity compared to that of the host spore, which is a remarkable increase of enzymatic activity considering the existence of sacA (sucrase) and sacB (levansucrase) in the Bacillus subtilis chromosome. The spore integrity, revealed by sporulation frequency test after heat and lysozyme treatment of spore, did not changed at all in spite of the CotG-LevU fusion protein incorporation into the spore coat layer during spore formation process. These data prove again that Bacillus subtilis spore could be considered as good live immobilization vehicle for efficient bioconversion process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.3
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• pp.230-236
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• 2014

Wafer level package technology is added to the surface of wafer circuit packages to create a semiconductor technology that can minimize the size of the package. However, in conventional packaging, warpage and fracture are major concerns for semiconductor manufacturing. We optimized the wafer dam design using a finite element method according to the dam height and heat distribution thermal properties. The dam design influences the uniform deposition of the image sensor and prevents the filling material from overflowing. In this study, finite element analysis was employed to determine the key factors that may affect the reliability performance of the dam package. Three-dimensional finite element models were constructed using the simulation software ANSYS to perform the dam thermo-mechanical simulation and analysis.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.78-82
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• 2010

The feeder pipe of Main Primary Heat Transfer System in Wolsong Nuclear Power Plant was inspected by the Ultrasonic Phase Array technique in 2010. It is the first time to apply this method to the construction at Nuclear Power Plant in Korea. The time required for UT technique is less than RT method. The UT method doesn't need to evacuate personnel who works nearby inspecting area and doesn't need to wait developing of film. For these reasons, the UT method is the fastest method among the volumetric inspections. As a result of the examination, it became clear that main defect of the feeder pipe is the Lack of fusion in the welded area. Moreover, the rate of defect was reduced gradually as improvement of welder's skill. If welding machine has problem, the defect has tended to same pattern(occurred same position in the welding area) but these defects were founded without specific rules. For these reasons, the creation of defect is dependent on the skill of worker not on the automatic welding machine. This evaluation of defect signal and collecting data would be useful to further examination in ISI.