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김연욱 계명대학교 산업기술연구소 1993 産業技術硏究所 論文報告集 Vol.16 No.1
The glass forming ability (GFA) concept has been one of the challening topics in the field of rapid solidification because of the existing need for developing some useful guiding principles in the search for new stable metallic glasses (amorphous solid). In general, consideration is given to glass formation to be the consequence of crystallization difficulties during freezing of liquids. Therefore, this approach stems from the recognition that glass formation from a liquid occurs when the usual crystallization processes can be suppressed, allowing a supercooled liquid to undergo a glass transition at some temperature, Tg (glass transition temperature). In simple term, the situation can be depicted as a "competition" between the crystallization temperature, TN and the glass transition temperature, Tg. Based on the results of experimental findings using small droplet processing (Electrohydrodynamic Atomization), the glass transition temperature can be estimated by a correlation of the observed fraction of amorphous spheres with an analytical model using homogenous nucleation theory. In spite of many useful properties of amorphous alloys, serious limitations for the commercial use of these materials is, at the moment, that it is not possible to produce amorphous alloys of large sizes (the need for rapid quenching), that they crystallize at relatively low temperatures. Therefore, it is necessary that glass transition temperature should be studied experimentally to develop new quenching techniques and to design the new materials. Then amorphous alloys represent a most intriguing group of materials and with further work a new family of materials will become available for commercial applications.
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.
김연욱 啓明大學校 産業技術硏究所 1992 産業技術硏究所 論文報告集 Vol.15 No.1
Submicron droplets of pure silicon and germanium have been sprayed by electrohydrodynamic atomization. The submicron droplets of pure materials were produced and cooled in free flight through a vacuum chamber. Because they are very small, the surface area - to - volume ration is very high and the droplets cooled at 10bK/S. Furthermore, the volume of liquid in each droplet is extremely small. This combination of high cooling rate and very small liquid volume makes it difficult for a nucleation event to occur even in very fluid metals and an amorphous phase solidify in small droplets. A systemic study has been conducted for silicon and germanium of the distribution of the amorphous phase with droplet size. When the effect of droplet size was considered in pure semiconductor materials that amorphous phase was observed, the amorphous phase is formed predominantly in the smaller droplets and a transition between amorphous spheres and crystalline spheres clearly exists with increasing droplet size for each element. these transitions occur about 45 and 50 nm for Si and Ge.
김연욱,신만균 한국동물분류학회 2006 Animal Systematics, Evolution and Diversity Vol.22 No.2
Two rare ciliates from soil under the oak tree and mosses in the top of mountain in Korea were identified asGonostomum algicolaGellrt, 1942 and G. gonostomoida(Hemberger, 1985), respectively. There is littleinformation on their morphological features, therefore their detailed redescriptions are needed. Thedescription was based on the observation of living and protargol impregnated specimens, and biometricanalysis. Their diagnostic characteristics are as follows. Gonostomum algicola; 88-113× 30-40 m in vivo,colourless cortical granules, 20-31 adoral membranelles, two fronto-terminal cirri, five fronto-ventral cirri, nomid-ventral cirri, two transverse cirri, two to three micronuceli. Gonostomum gonostomoida; 60-121× 21-40m in vivo, no cortical granules, 27-34 adoral membranelles, no fronto-terminal cirri, two fronto-ventral cirralrows with each row bearing three cirri, midventral cirral row with 1-14 cirri, two to three transverse cirri,Gonostomumhave been recorded fromKorea by the present study.
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.
김연욱,전해정 한국디지털정책학회 2022 디지털융복합연구 Vol.20 No.3
This study empirically analyzed the effect of complex commercial facilities on the price of nearby apartments in a Hedonic price model. The spatial range of this study was the walking area of H Department Store located in Pangyo among the second new towns suburb of Seoul, and the time range was 2020. The dependent variable was the real transaction price of the apartment, and independent variable were the characteristics of the housing, the characteristics of the complex, and the characteristics of the region. As a result of the analysis, the area of exclusive use space, the transaction floor, and the highway accessibility had a positive effect on the price of the apartment, and the elapsed year had a negative effect on the price of the apartment. However, the size of the apartment had little effect on apartment prices, and the distance from the complex commercial facilities was shown to be related to apartment prices, indicating that apartment prices declined as it moved away from the complex commercial facilities. Therefore, this is much more influential than the influence of distance from subway stations on apartment price. This confirms that the effect factors of apartment prices and the size of their influence appear differently in the new town area and the existing metropolitan area. 본 연구는 복합상업시설이 인근 아파트 가격에 미치는 영향을 헤도닉 가격모형으로 실증분석하였다. 연구의 공간적 범위는 수도권 2기 신도시 중 판교에 위치한 H 백화점의 도보 생활권역으로 하였고, 시간적 범위는 2020년, 1년간으로 하였다. 종속변수는 아파트 실거래 가격이며, 독립변수는 주거 특성과 단지 특성 및 지역 특성으로 하였다. 분석 결과, 전용면적과 거래 층, 고속도로 진입로와의 거리는 아파트의 가격에 정(+)의 영향을 미치며, 경과년도는 부(-)의 영향을 미쳤다. 그러나, 대단지 여부는 아파트 가격에 거의 영향을 미치지 않았고, 복합상업시설에서의 거리는 아파트 가격과 부(-)의 관계로 나타나 복합상업시설에서 멀어질수록 아파트 가격이 감소함을 보였는데, 그 영향력이 지하철역과의 거리가 아파트 가격에 미치는 영향력에 비하여 훨씬 크게 나타났다. 이는 아파트 가격 영향요인과 그 영향력의 크기가 신도시 지역과 기존의 대도시 지역에서 서로 다르게 나타난다는 점을 확인해준다.
고온자전합성과 확산 열처리를 이용한 V 이 첨가된 TiAl계 금속간화합물 복합판재의 제조
김연욱,Kim, Yeon-Wook 한국재료학회 2002 한국재료학회지 Vol.12 No.9
The Ti-aluminide intermetallic compound was formed from high purity elemental Ti and Al foils by self-propagating, high-temperature synthesis(SHS) in hot press. formation of $TiAl_3$ at the interface between Ti and Al foils was controlled by temperature, pressure, heating rate, and so on. According to the thermal analysis, it is known in this study that the heating rate is the most important factor to form the intermetallic compound by this SHS reaction. The V layer addition between Al and Ti foils increased SHS reaction temperatures. The fully dense, well-boned inter-metallic composite($TiA1/Ti_3$Al) sheets of 700 m thickness were formed by heat treatment at $1000^{\circ}C$ for 10 hours after the SHS reaction of alternatively layered 10 Ti and 9 Al foils with the V coating layer. The phases and microstructures of intermetallic composite sheets were confirmed by EPMA and XRD.
인공치근용 CP - Ti 과 Ti 합금의 기계적 성질 및 내식성
김연욱,정종평 ( Yeon Wook Kim,Chong Pyoung Chung ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.5
N/A Commercially pure titanium(cp-Ti) and Ti-15wt%Zr-4wt%Nb-4wt%Ta alloy were melted in vacuum induction furnace. According to the chemical analysis, the content of carbon was above ASTM standard in the cast ingots because of using graphite crucible. The TEM micostructures of cp-Ti and Ti alloy shows that chemically stable TiC precipitates distribute in α-Ti matrix. In order to examine the properties of cp-Ti and Ti-Zr-Nb-Ta alloy for dental applications, mechanical properties and corrosion resistance were investigated. The anodic polarization properties of Ti-Zr-Nb-Zr alloy were almost same as that of cp-Ti in 1% lactic acid. However, as the results of the anodic polarization test in 5% HCl, it was known that Ti-Zr-Nb-Zr alloy showed a rapid decrease in current density at higher potential in comparison with cp-Ti. The yield stress and tensile strengh in Ti-Zr-Nb-Ta were σ_0.2=623 MPa, σ_T.S.=708 MPa and these results showed 30% increase in yield stress in comparison with cp-Ti. (Received August 4, 1998)