• 한국산업융합학회 논문집
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• 제25권6_1호
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• pp.941-952
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• 2022

In this study, additive manufacturing technology was applied to restore a planner miller that was unusable due to aging. The drive spur gear of the planner miller was inoperable due to many defects in the teeth. The shape of the defective gear teeth was restored by deposition of the defective teeth using the DED method. However, as the location of the deposition head and the location of the set origin became farther, the deposition shape was different from the modeling shape. Nonetheless, since the modeling of the deposition part was designed to be larger than the tooth shape of the original gear, it was possible to completely restore all gear teeth through post-processing. The arrangement interval of the flow lines of the deposition part was narrower than that of the substrate. The hardness of the substrate was 172 HV, and that of the deposition part was 345 HV, which was twice as high as that of the substrate.

• 융합보안논문지
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• 제7권4호
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• pp.43-50
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• 2007

센서 노드들의 전기에너지 양은 극히 제한적이고, 밧데리 교체는 무선 센서 망에서는 매우 어렵다. 본 논문은 다른 라우터에서 에너지 손질에 대한 수학적 모델을 제안하며, 직접 Diffusion 기반에 에너지 소비를 근거로 하여 해석한다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2008년도 춘계학술발표대회
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• pp.1031-1034
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• 2008

최근 원하는 정보를 수집하기 위한 무선 센서 네트워크(WSN) 사용이 증가하고 있으며, 이때 여러개의 작은 센서들이 배터리의 용량에 한정되어 있기 때문에 가장 우선적으로 고려해야 할 부분은 에너지 효율성이다. Directed Diffusion(DD)은 데이터 중심 기반 라우팅 알고리즘으로 싱크는 모든 센서 노드에게 인터레스트(Interest)를 전송(Flooding)하면 Interest를 받은 노드들은 경사(Gradient)를 만들어서 그 경로들 중 최적화 경로를 강화(Reinforce)한다. 이 경로는 센서 네트워크 전체적으로 볼 때는 에너지를 최소화 하지만, 매 Flooding시 에너지 고갈과 시간 낭비의 문제점이 나타난다. 본 논문에서는 DD의 문제점을 개선하여 싱크가 Interest를 Flooding할 때 마다 여러 번의 Flooding으로 노드의 에너지 고갈과 시간 낭비가 심각해지는 것을 방지하기 위해 중간노드가 Interest를 기억하도록 Middle-Interest Node(MIN)를 두어 데이터를 전달하는 새로운 기법을 제안한다. 본 기법의 성능은 DD와 제안기법인 MIN에 대한 수학적 분석에 기반 하여 측정하였다.

• 한국분말재료학회지
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• 제28권6호
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• pp.491-496
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• 2021

The process optimization of directed energy deposition (DED) has become imperative in the manufacture of reliable products. However, an energy-density-based approach without a sufficient powder feed rate hinders the attainment of an appropriate processing window for DED-processed materials. Optimizing the processing of DED-processed Ti-6Al- 4V alloys using energy per unit area (E_eff) and powder deposition density (PDD_eff) as parameters helps overcome this problem in the present work. The experimental results show a lack of fusion, complete melting, and overmelting regions, which can be differentiated using energy per unit mass as a measure. Moreover, the optimized processing window (E_eff = 44~47 J/mm² and PDD_eff = 0.002~0.0025 g/mm²) is located within the complete melting region. This result shows that the Eeff and PDDeff-based processing optimization methodology is effective for estimating the properties of DED-processed materials.

• 한국실천공학교육학회논문지
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• 제2권2호
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• pp.42-48
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• 2010

이 연구에서는 PBL교육방법 및 교수법의 기초공학에 적용 예제로써 그 핵심 요구사항들인 높은 전공지식(the learner acquisition of critical knowledge), 고도의 문제해결 능력(problem solving proficiency), 학습자 중심의 학습전략 (self-directed learning strategies), 및 집단참여 기술(team participation skills)을 구현하기 위해 ET 헬스기구를 활용하여 물성과 생체 사이의 물리변수의 단위 통일, 실험 데이터의 오차범위 계산, 시스템이 물성과 생체를 포함하는 에너지보존법칙과 운동방정식 유도, 및 데이터의 패턴 해석 능력을 기르도록 하였다. 이 연구에서는 ET 기구가 PBL 교육방법과 교수법을 채택하는 좋은 예제가 될 수 있음을 보여준다. 수업계획은 한 학기용으로 준비되었으며 학습자가 주도적으로 그리고 창의적으로 실험수행을 하고 그 결과를 분석을 하도록 주어진 세 가지 PBL 프로젝트에 대해 얻어진 최종결과는 (1) 집단 A의 문제에 대해 얻어진 운동속도(km/s) 대 에너지 소비량(Cal) 도표의 기울기는 23.5o였으며, (2) 집단 B의 문제에 대해 얻어진 체중감량(kg) 대 에너지 소비량(Cal)의 도표의 각도범위는 15.0o ~ 26.5o 이었고, 마지막으로, (3) 집단 C의 문제에 대해서 운동 거리(km) 대 체중감량(kg) 도표의 각도변화는 51.0o 이였다.

• 한국분말재료학회지
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• 제27권3호
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• pp.219-225
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• 2020

The directed energy deposition (DED) process of metal 3D printing technologies has been treated as an effective method for welding, repairing, and even 3-dimensional building of machinery parts. In this study, stainless steel 316L (STS316L) and Inconel 625 (IN625) alloy powders are additively manufactured using the DED process, and the microstructure of the fabricated STS316L/IN625 sample is investigated. In particular, there are no secondary phases in the interface between STS316L and the IN625 alloy. The EDS and Vickers hardness results clearly show compositionally and mechanically transient layers a few tens of micrometers in thickness. Interestingly, several cracks are only observed in the STS 316L rather than in the IN625 alloy near the interface. In addition, small-sized voids 200-400 nm in diameter that look like trapped pores are present in both materials. The cracks present near the interface are formed by tensile stress in STS316L caused by the difference in the CTE (coefficient of thermal expansion) between the two materials during the DED process. These results can provide fundamental information for the fabrication of machinery parts that require joining of two materials, such as valves.

• 한국기계가공학회지
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• 제20권10호
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• pp.27-37
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• 2021

The use of additive manufacturing processes for the repair and remanufacturing of mechanical parts has attracted considerable attention because of strict environmental regulations. Directed energy deposition (DED) is widely used to retrofit mechanical parts. In this study, finite element analyses (FEAs) were performed to investigate the influence of the substrate phase and inclination angle on the heat transfer characteristics in the vicinity of Hastelloy X regions deposited via DED. FE models that consider the bead size and hatch distance were designed. A volumetric heat source model with a Gaussian distribution in a plane was adopted as the heat flux model for DED. The substrate and the deposited powder were S45C structural steel and Hastelloy X, respectively. Temperature-dependent thermal properties were considered while performing the FEAs. The effects of the substrate phase and inclination angle on the temperature distributions and depth of the heat-affected zone (HAZ) in the vicinity of the deposited regions were examined. Furthermore, the influence of deposition paths on depths of the HAZ were investigated. The results of the analyses were used to determine the suitable phase and inclination angle of the substrate as well as the appropriate deposition path.

• 한국산업융합학회 논문집
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• 제25권4_2호
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• pp.699-706
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• 2022

In this study, Directed energy deposition (DED) among additive manufacturing is applied to repair damaged spindle key parts of planner miller. The material of the spindle key is SCM415, and the P21 Powder is used. In order to find the optimal deposition conditions for DED equipment, a single-line deposition experiment is conducted to analysis five parameters. The laser power affects the width, and the height is a parameter affected by coaxial gas and powder gas. In addition, laser power, powder feed rate, coaxial gas, and powder gas are parameters that affect dilution. Otimal deposition is that 400 W of laser power, 4.0 g/min of powder feed rate, 6.5 L/min of coaxial gas, 3.0 L/min of powder gas and 4.5 L/min of shield gas. By setting the optimum conditions, a uniform deposition cross section in the form of an ellipse can be obtained. Damage recovery process of spindle key consists of 3D shape design of the base and deposition parts, deposition path creation and deposition process, and post-processing. The hardness of deposited area with P21 powder on the SCM415 spindle key is 336 HV for the surface of the deposition, 260 HV for the boundary area, and 165 HV for the base material.

• Journal of Microbiology and Biotechnology
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• 제24권11호
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• pp.1551-1558
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• 2014

The esterase gene Est8 from the thermophilic bacterium Bacillus sp. K91 was cloned and expressed in Escherichia coli. The monomeric enzyme exhibited a theoretical molecular mass of 24.5 kDa and an optimal activity around $50^{\circ}C$ at pH 9.0. A model of Est8 was constructed using a hypothetical YxiM precursor structure (2O14_A) from Bacillus subtilis as template. The structure showed an ${\alpha}/{\beta}$-hydrolase fold and indicated the presence of a typical catalytic triad consisting of Ser-11, Asp-182, and His-185, which were investigated by site-directed replacements coupled with kinetic characterization. Asp-182 and His-185 residues were more critical than the Ser-11 residue in the catalytic activity of Est8. A comparison of the amino acid sequence showed that Est8 could be grouped into the GDSL family and further classified as an SGNH hydrolase. Est8 is a new member of the SGNH hydrolase subfamily and may employ a different catalytic mechanism.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.685-689
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• 2007

Ad-Hoc 통신 기술과 더불어 무선 센서 네트워크(Ubiquitous Sensor Networks) 기술은 최근 관심이 집중되고 있는 유비쿼터스 컴퓨팅 시대의 핵심 기반기술로서 그 중요성이 점차 대두되고 있다. 이러한 WSN환경에서 제한된 에너지로 얼마나 효율적으로 네트워크를 운용하느냐가 최근 많은 이슈로 등장하고 있다. 본 논문에서는 Large Scale Class Greenhouse를 배경으로 센서 노드 간에 Directed Diffusion과 Gossiping concept을 바탕으로 라우팅 경로를 생성하고, 에너지 효율(energy-efficient)적인 경로 설정(routing)을 통하여 센서노드의 에너지 소모를 최소화하여 전체 센서 네트워크의 life-time을 연장하는 방법을 제안한다.