기 · 고계유동층의 Scale up 에 관하여

정우창,하백현,남궁식,문세기 한국화학공학회 1967 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.5 No.1

Fixed and fluidized bed were compared with their reaction rate constant by the ammonium catalytic dissociation reaction. There was almost same reaction rate constant on both unit column fluidized reactor (5㎝φ) and scaled up fluidized reactor (10㎝ × 10㎝ × 60㎝) which is scaled up by inserting internal wall with hole into four compartments, but scaled up reactor without compartment shows lower value of its reaction rate constant than with compartment.

도로 교차로에서의 흐름 특성에 관한 수치적 연구: 경사진 네 개의 도로가 대칭으로 연결된 교차로의 경우

정우창,이진우,조용식 한국방재학회 2010 한국방재학회논문집 Vol.10 No.6

In this study, the characteristics of flow within and around a crossroad connected symmetrically with four roads are numerically analyzed by using a two-dimensional well-balanced HLLC finite volume model. As results of simulations and analyses, the numerical model employed in this study describes relatively well the complex water surface in a crossroad according to the conditions of inflow and road slope. Moreover, the predicted temporal and spatial variations of water depths in a crossroad and outflows at two downstream boundaries agree relatively well with laboratory measurements. 본 연구에서는 네 개의 도로가 서로 대칭으로 연결된 교차로 근처 및 내에서의 흐름 특성에 대한 수치적 분석을 수행하였으며, 적용된 수치모형은 2차원 well-balanced HLLC 유한체적모형이다. 모의 및 분석결과 본 연구에서 적용된 모형은 유입유량 및 수로경사 조건에 따라 도로 교차로에서 변화되는 복잡한 수면양상을 비교적 잘 모의하는 것으로 나타났다. 또한 도로 교차로 내에서의 시간적 및 공간적 수심변화와 두 개의 하류경계에서의 유출유량에 대한 모의결과는 측정결과와 비교적 잘 일치하였다.

도시지역을 관통하는 홍수파의 특성에 관한 수치적 연구 (2) : 적용 및 분석

정우창,조용식,이진우 한국방재학회 2010 한국방재학회논문집 Vol.10 No.1

In this study, the effects of urban areas against flood waves due to a dam failure were numerically investigated based on the two laboratory experiments and the predicted water surface elevations at specific points showed good agreement with available measurements. In the first experiment, a relatively high water depth and the delay effect of flow at the front of urban areas are observed. The urban areas may become a large obstacle against smooth propagation of flood wave. In the second one, as the inflow increases, moreover, the water surface elevations can be classified into abruptly decreasing portion and slowly decreasing portion, and the first arrival time to the front of urban area is decreasing with the increasing inflow. 본 연구에서는 댐 붕괴로 인한 홍수파에 영향을 미치는 도시지역의 효과에 대해 두 가지 수리모형실험에 근거하여 수치적으로 분석되었으며, 계산된 지점별 수심은 측정결과와 비교적 잘 일치하였다. 첫 번째 수리모형실험에 대해 도시지역 전반부에서 상대적으로 높은 수심영역과 흐름의 지체현상이 발생하였으며, 홍수파의 원활한 전파에 큰 장애요소가 됨을 알 수 있었다. 두 번째 수리모형실험에 대해서는 유입량의 증가에 따라 도시지역의 전반부에서 후반부로 전파될 때 수심은 급격히 감소하는 구간과 느리게 감소하는 구간으로 구별되며, 도시지역 전반부에 도달하는 홍수파의 최초시간은 유입량이 증가함에 따라 감소되는 경향을 나타내었다.

3차원 수치모형을 이용한 댐 붕괴파 모의에 관한 연구

정우창,이진우,조용식 한국방재학회 2012 한국방재학회논문집 Vol.12 No.2

In this study, the simulation of the flood wave due to the dam failure is carried out using a three-dimensional numerical model. The applied numerical model is ANSYS CFX (Ver. 13.0) which is a commercial software developed by ANSYS Inc. This numerical model is applied to three different cases of hydraulic model experiments related to the analysis of the dam-break wave, and the results simulated from three-dimensional model are compared and analyzed with those from laboratory measurements and the two-dimensional numerical model. As results of comparison, the predicted results agree well with measured ones and are more slightly accurate than those from the two-dimensional numerical model. In particular, the peak water depth and its time agree almost accurately with measured ones. Therefore, we can expect that the three-dimensional numerical model applied in this study could be effectively applied to predict the peak water depth and its time after a dam failure. 본 연구에서는 3차원 수치모형을 이용하여 댐 붕괴파에 대한 모의를 수행하였다. 적용된 3차원 수치모형은 ANSYS Inc에서 개발한 ANSYS CFX (Ver. 13.0) 상용 프로그램이며, 댐 붕괴파의 전파양상 분석과 관련된 기존의 세 가지 수리모형실험에 대해 측정결과와 2차원 수치모형에 의한 결과와 비교 및 분석을 수행하였다. 비교 결과 3차원 수치모형은 2차원 수치모형에 비해 측정결과에 보다 따르는 경향을 나타냈으며, 특히 첨두수심과 발생시간은 거의 정확하게 일치하였다. 따라서 본연구에서 적용된 3차원 수치모형은 댐 붕괴에 따른 첨두수심 및 발생시간의 예측에 대해 효과적으로 적용될 수 있을 것으로기대된다.

무한한 청정 에너지 자원 HDR(Hot Dry Rock) 국외 개발 현황

정우창,Jeong, U-Chang 한국수자원학회 2009 물과 미래(한국수자원학회지) Vol.42 No.11

이산 균열망 모형과 등가 다공성 매질 모형의 통합 모형

정우창,Jeong, U-Chang 한국수자원학회 2017 물과 미래(한국수자원학회지) Vol.50 No.5

차체 부품에 요구되는 Cold & Hot Stamping 금형 제조기술 동향

정우창 한국소성가공학회 2017 금형가공 심포지엄 Vol.2017 No.12

복합조직형 고강도 냉연강판의 기계적성질과 미세조직의 상관성 연구

정우창 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.10

An Investigation was made to determine the effects of annealing parameters on the mechanical properties of dual-phase steels with two different compositions: Fe-0.13% C-1.31% Si-1.91% Mn steel and Fe-0.13% C-1.11% Si-1.91% Mn-0.05% Nb steel. It was found that Nb retarded recrystallization of ferrite and refined the duplex microstructure of ferrite and martensite. Dual-phase properties were obtained in the former steel cooled at a rate of about 40℃/sec after intercritical annealing in the temperature range of 750℃ to 850℃ for 30 seconds. Nb-added steel showed higher strength and lower elongation than the steel without Nb. Good combinations of strength and elongation were obtained in specimens cooled at rates ranging from 10 to 20℃/sec in both steels. Overaging treatment at 400℃ resulted in the decrease in strength and increase in total elongation.

고강도 냉연강판에서 저온변태 페라이트의 조직적 특성 연구

정우창 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.5

The microstructural characteristics of the various low-temperature transformation ferrites such as quasi-polygonal ferrite (α_(B)), granular bainitic ferrite (α_(B)) and bainitic ferrite (α˚_(B)) have been investigated in an ultra-low carbon high strength cold-rolled steel. It was found that a grain of the aB and α˚_(B) comprised several subgrains with orientations of ND//<111> or ND//near <111>, but the aq grain consisted of several subgrains with orientations of ND/ /<001> or ND//near <001>. The EBSD result showed that the α˚_(B) and α_(B) were characterized by low angle grain boundaries whose misorientation angles are smaller than 15˚Even the very low angle grain boundaries with misorientation angle of 2-5˚or less were substantially observed in the α˚_(B) and a_(B) grains, resulting in the not well-etched grain boundaries in optical and scanning electron microscopy. The grain boundaries of the a_(q) were characterized by the high angle grain boundary with a winding shape. (Received September 23, 2004)

자동차 도어보강재의 경량화 및 충돌특성 향상을 위한 형상 최적화 연구

정우창 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.6

A study on shape optimization of a hot-stamped automotive door impact beam for lightweight design and improved crash performance was conducted using a static collision analysis based on FMVSS 214. An integral type one-piece door impact beam of bracket parts and pipe was realized using hot stamping technology. The method involves the heating in the austenite region and subsequent hot forming and quenching in a specially designed stamping tool with hydraulic system. A one-piece door impact beam is 6.8% lighter than a three-piece door impact beam because it eliminates two bracket parts. The one-piece door impact beam was hot-stamped with dies without cooling channels inside the dies, and revealed a Vickers hardness higher than 430 and a fully martensitic microstructure. Two one-piece door impact beams, with a straight pipe with circular cross section and a straight pipe with partially circular and partially elliptical cross section in the middle part of the pipe, were used for the collision analysis. The door impact beam with partially circular and partially elliptical cross section showed less plastic strain in the middle part of the pipe compared with the circular pipe, leading to better intrusion property. Intrusion analysis results also showed that the three-pieces door impact beam fractured at a 336 mm displacement due to excessive plastic strain in the welded part between the bracket and pipe. In contrast, the integral type one-piece door impact beam without welding did not show any fracture, even at a 457.2 mm displacement, confirming the better performance against lateral collision.