PMDYN-CFD 모델을 이용한 계절별 도로 이격거리에 따른 자동차 배기 및 비배기 입자 기여도 분석

김연욱,곽경환,이현호,이승복 한국대기환경학회 2022 한국대기환경학회 학술대회논문집 Vol.2022 No.10

증례발표 : Calcium Sulfate(Capset(R), Lifecore)를 이용한 골유도 재생술

김연욱,유형근,신형식 대한치주과학회 2003 대한치주과학회 학술대회자료집 Vol.2003 No.1

플라즈마 용사한 Cr₂O₃및 Cr₂O₃-WC 피복층의 마찰계수 특성

김연욱 啓明大學校 産業技術硏究所 1999 産業技術硏究所 論文報告集 Vol.22 No.2

Microstructures and mechanical properties of HXPA(Cr₂O₃) and HXPB(Cr₂O₃-WC-Co) coating layers made by plasma spray coating method have been examined by means of scanning electron microscopy, X-ray diffraction, microvickers hardness test and ball-on-plate friction test. At the conditions of high power and external powder ejection, the splat is relatively wavy shape with the boundary in coated layers. This microstructual results are effective in reducing splat delamination during friction and wear process. The axis ratio of hexagonal structure in the coated layers of Cr₂O₃and WC is reduced according to the analysis of X-ray diffraction. Because of this reasons, the friction coefficient of HXPB spray coated layer is smaller than SiC which is the material of choice for high speed rotating seal.

다층원소박판에서 $TiAl_3$의 고온자전합성에 미치는 승온속도의 영향

김연욱,김병관,남태운,허보영,김영직,Kim, Yeon-Uk,Kim, Byeong-Gwan,Nam, Tae-Un,Heo, Bo-Yeong,Kim, Yeong-Jik 한국재료학회 1998 한국재료학회지 Vol.8 No.11

Ti 과 AI의 고순도 원소 박판을 이용하여 열간프레스장치에서 고온자전합성법으로 TiAI계 금속간화합물을 제조하였다. 원소 박판에서 $TiAl_3$ 금속간화합물을 제조하는 데 승온속도, 압력, 온도 등의 변수가 고온자전합성에 영향을 미치는 중요한 인자다. 특히 승온속도는 반응합성온도를 결정하는 인자로서 본 실험에서 DTA 분석을 이용하여 공정변수를 결정하였다. DTA 분석결과에 따르면, Ti와 AI의 계면에서 반응합성은 AI의 용융점 이하와 이상의 온도에서 두 번 발생함을 알 수 있다. 또한 승온속도가 증가할수록 두 반응합성온도는 증가하였다. 10층의 Ti 박판과 9층의 AI 박판을 $20^{\circ}C$/min의 승온속도로 고온자전합성시킨 후, $810^{\circ}C$와 240MPa의 압력에서 4시간 동안 열처리한 결과 $700\mu\textrm{m}$ 두께의 TiAI계 금속간화합물 판재를 제조하였으며, XRD 회절과 SEM으로 확인하였다. Titanium aluminide intermetallic compound was formed from high purity elemental Ti and A1 foils by selfpropagating, high-temperature synthesis(SHS1 in hot press. Formation of $TiAl_3$ intermetallics at the interface between Ti and Al foil was observed to be controlled by temperature, pressure and heating rate. Especially, the heating rate is the most important role to form intermetallic compound by SHS reaction. According to DTA experiment, the SHS reactions appeared at two different temperatures below and above the melting point of Al. It was also observed that both SHS reaction temperatures increased with increasing the heating rate. After the SHS reaction of alternatively layered 10 Ti and 9 A1 foils at the heating rate of $20^{\circ}C$/min, the $700\mu\textrm{m}$ thick titanium aluminide sheet was formed by heat treatment at $810^{\circ}C$ for 4hours.

Tripod Polishing을 이용한 불균질 재료의 TEM 시편준비 방법과 미세조직 관찰

김연욱,조명주,Kim, Yeon-Wook,Cho, Myung-Ju 한국현미경학회 2004 Applied microscopy Vol.34 No.2

본 실험에서는 tripod polishing 방법을 이용하여 Pd/GaN/Sapphire 박막, PZT/MgO/Si 박막, 304 stainless steel 분말, $Mo_5Si_3/Mo_2B$ diffusion couple의 매우 다양한 물성이 포함된 불균질 재료의 TEM 시편을 제작하고 분석하였다. Tripod polishing을 사용하여 시편을 준비하면 시편의 종류에 관계없이 시편의 선단부에 매우 광범위한 전자빔 투과 영역을 지닌 TEM 시편을 얻을 수 있었으며, Pd/GaN/Sapphire 박막, PZT/MgO/Si 박막과 같이 기판이 경한 반도체 재료의 경우에는 연마 정도가 균일하며 연마과정 동안 오염이 심하지 않기 때문에 ion milling으로 cleaning 없이 TEM 관찰이 가능하다. 한편 304 stainless steel 분말과 같은 금속재료의 경우 짧은 시간의 ion milling 은 시편의 오염 제거에 도움된다. $Mo_5Si_3/Mo_2B$ diffusion couple에 형성된 실리사이드는 큰 취성 때문에 polishing 동안 시편이 깨지는 현상으로 전자가 투과할 수 있을 정도의 연마가 불가능하여 1시간 정도 ion milling 연마가 필요하다. Tripod polishing으로 TEM 시편을 준비하면 분석하고자 하는 지역을 정확하고도 넓게 연마할 수 있다. 또한 비교적 짧은 시간 내에 ion milling 없이 TEM 시편을 제작할 수 있기 때문에 ion milling에서 유발되는 여러 가지 문제점들을 해결할 수 있는 장점이 있었다. 그러나 tripod polishing은 전부 수작업으로 시편을 준비하기 때문에 시편을 제작하는 과정 동안 매우 세심한 주의가 요구되며 제작자의 숙련도와 경험을 필요로 하는 단점이 있다. The TEM samples prepared by ion milling have the advantage that thin area can be obtained from almost any materials. However, it has the disadvantage that the amount of thin area can often be quite limited. For the cross-sectioned samples and grossly heterogeneous materials, the thickness of less than $0.1{\mu}m$ can be achieved by mechanical grinding and polishing (tripod polisher) and then the TEM samples may be ion-milled for final thinning or cleaning. These approaches were described in this paper. Examples of TEM observations were taken from cross-section samples of thin films on silicon and sapphire, from diffusion layers between $Mo_5Si_3\;and\;Mo_2B$, and from rapidly solidified 304 stainless steel powders embedded in electroplated copper.

잇몸이 붓고 피가 날 때

김연욱 전남대학교 기업경영연구소 2006 經營情報 Vol.17 No.1

고온자전반응합성과 확산 열처리를 이용한 FeAl계 금속간화합물 복합판재의 제조

김연욱,윤영목,Kim, Yeon-Wook,Yun, Young-Mok 한국재료학회 2008 한국재료학회지 Vol.18 No.3

Fe-aluminides have the potential to replace many types of stainless steels that are currently used in structural applications. Once commercialized, it is expected that they will be twice as strong as stainless steels with higher corrosion resistance at high temperatures, while their average production cost will be approximately 10% of that of stainless steels. Self-propagating, high-temperature Synthesis (SHS) has been used to produce intermetallic and ceramic compounds from reactions between elemental constituents. The driving force for the SHS is the high thermodynamic stability during the formation of the intermetallic compound. Therefore, the advantages of the SHS method include a higher purity of the products, low energy requirements and the relative simplicity of the process. In this work, a Fe-aluminide intermetallic compound was formed from high-purity elemental Fe and Al foils via a SHS reaction in a hot press. The formation of iron aluminides at the interface between the Fe and Al foil was observed to be controlled by the temperature, pressure and heating rate. Particularly, the heating rate plays the most important role in the formation of the intermetallic compound during the SHS reaction. According to a DSC analysis, a SHS reaction appeared at two different temperatures below and above the metaling point of Al. It was also observed that the SHS reaction temperatures increased as the heating rate increased. A fully dense, well-bonded intermetallic composite sheet with a thickness of $700\;{\mu}m$ was formed by a heat treatment at $665^{\circ}C$ for 15 hours after a SHS reaction of alternatively layered 10 Fe and 9 Al foils. The phases and microstructures of the intermetallic composite sheets were confirmed by EPMA and XRD analyses.

적엽작업을 반영하기 위한 시설토마토 생육모형(GreenTom) 개선 및 검증

김연욱,김진현,이변우 한국농림기상학회 2019 한국농림기상학회지 Vol.21 No.4

Smart-farm has been spreading across Korea to improve the labor efficiency and productivity of greenhouse crops. Although notable improvements have been made in the monitoring technologies and environmental-controlling systems in greenhouses, only a few simple decision-support systems are available for predicting the optimum environmental conditions for crop growth. In this study, a tomato growth model (GreenTom), which was developed by Seoul National University in 1997, was calibrated and validated to examine if the model can be used as a decision-supporting system. The original GreenTom model was not able to simulate artificial defoliation, which resulted in overestimation of the leaf area index in the late growth. Thus, an algorithm for simulating the artificial defoliation was developed and added to the original model. The node development, leaf growth, stem growth, fruit growth, and leaf area index were generally well simulated by the modified model indicating that the model could be used effectively in the decision-making of smart greenhouse. 스마트팜은 원예작물의 생산성과 품질을 제고하기 위한 생력화 방법으로 최근 많은 주목을 받고 있다. 하지만 국내의 스마트팜은 단순한 환경 모니터링과 환경제어만 가능한 초기단계에 머물고 있으며, 작물 생육에 최적화된 환경을 모의하는 의사결정도구의 개발은 미흡한 상태이다. 본 연구에서는 의사결정도구로써의 작물생육모형의 활용가능성을 확인하기 위해 국내에서 개발된 GreenTom모형의 품종모수를 추정하고 모형의 모의 성능을 검증하였다. 적엽은 시설토마토 재배에서 흔히 행해지는 농작업이지만 기존 모형은 이를 모의하지 않아 지상부 생육 모의에 문제를 나타냈다. 이를 해결하기 위해 적엽 알고리즘을 개발하여 기존 모형에 추가하고 모의 성능을 검증한 결과, 개선된 모형은 시설재배 토마토의 발달과 생육을 비교적 잘 모의하여 본 모형이 의사결정도구로 활용될 수 있음을 확인하였다.

진공가스분무한 AZ31+1%MM 합금 분말 압출재의 기계적 성질

김연욱,도달현 한국주조공학회 2000 한국주조공학회지 Vol.20 No.2

In this study, the powders of Mg-3wt%Al-lwt%Zn-lwt%MM alloy were produced under vacuum condition by the inert gas atomization and the rapidly solidified powders were consolidated by the vacuum hot extrusion. Then the structural change of powders during extrusion was investigated. The effects of misch metal addition to AZ31 on mechanical properties of extruded bars were also examined. During extrusion of the rapidly solidified powders, their dendrite structure was broken into fragments and remained as grains of 2㎛ size in extruded bar. The Mg-Al-Ce intermetallic compounds formed in the interdendritic regions of powders were broken finely, too. The yield stress, tensile strength and ductility obtained in as-extruded Mg-3wt%Al-lwt%Zn-lwt%MM alloy were σ_(0.2)=325㎫, σ_(T.S.)=417㎫ and ε=16.8%. All of these improvements on mechanical properties result from the refined micostructure and second-phase dispersions.

Synthesis and Photophysical Studies of Luminescent Lanthanide(Ⅲ)-cored Complexes Based on Alkyne Substituted Diphenylquinoxaline Dendritic Derivatives

김연욱,엄유경,김환규 한국고분자학회 2012 한국고분자학회 학술대회 연구논문 초록집 Vol.2012 No.4