시론 : 북한이 동시에 제시한 2개의 카드 합영법과 수재물자

윤동현 평화문제연구소 1984 통일한국 Vol.13 No.-

Fracture behavior of C/SiC composites at elevated temperature

윤동현,이정원,김재훈,신인철,임병주 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

The fracture behavior of carbon fiber-reinforced silicon carbide (C/SiC) composites used in rocket nozzles has been investigated under tension, compression, and fracture conditions at room temperature, 773 K and 1173 K. The C/SiC composites used in this study were manufactured by liquid silicon infiltration process at ~1723 K. All experiments were conducted using two types of specimens, considering fiber direction and oxidation condition. Experimental results show that temperature, fiber direction, and oxidation condition affect the behavior of C/SiC composites. Oxidation was found to be the main factor that changes the strength of C/SiC composites. By applying an anti-oxidation coating, the tensile and compressive strengths of the C/SiC composites increased with temperature. The fracture toughness of the C/SiC composites also increased with increase temperature. A fractography analysis of the fractured specimens was conducted using a scanning electron microscope.

정유공장에서 설비별 사고해석에 대한 연구

윤동현,김창은 한국경영공학회 2002 한국경영공학회지 Vol.7 No.2

Crack Band Model 기반 손상변수를 이용한 탄소섬유강화 복합재료 적층판의 점진적 파손 거동 예측 및 검증

윤동현,김상덕,김재훈,도영대 한국복합재료학회 2019 Composites research Vol.32 No.5

In this paper, a progressive failure analysis method was developed using the Hashin failure criterion and crack band model. Using the failure criterion, the failure initiation was evaluated. If the failure initiation is occurred, the damage variables at each failure modes (fiber tension & compression, matrix tension & compression) was calculated according to linear softening degradation behavior and the variables are used to derive the damaged stiffness matrix. The damaged stiffness matrix is reflected to damaged material and the progressive failure analysis is continued until the damage variables to be 1 that complete failure of material. A series of processes were performed using FE commercial code ABAQUS with user defined material subroutine (UMAT). To evaluate the proposed progressive failure model, the experimental results of open hole composite laminate tests was compared with numerical result. Using digital image correlation system, the strain behavior also was compared. The proposed numerical results were coincided well with the experimental results. 본 논문에서는 Hashin 파손 기준식과 crack band 모델이 접목된 손상변수를 이용하여 점진적파손해석 방법이 개발되었다. 파손기준식을 이용하여 파손의 개시 유무가 판단된다. 파손이 개시된 경우에는 각 파손모드(섬유 인장/압축, 기지 인장/압축)에서 손상변수가 선형 열화 거동에 따라 계산되고, 손상강성행렬을 계산하는데 사용된다. 손상강성행렬은 손상된 재료에 반영되고, 계산된 손상강성행렬을 이용하여 재료의 완전한 파괴를 의미하는 손상변수가 1인 시점이 되기까지 점진적 파손해석이 계속해서 반복적으로 수행된다. 일련의 과정들은 상용해석프로그램인 ABAQUS에 사용자 정의 부프로그램을 이용하여 수행되었다. 제안된 점진적파손해석 도구의 검증을 위하여, 원공을 가진 복합재료 적층판의 시험 결과와 비교를 수행하였으며, 시험 중 디지털 이미지 상관법을 이용하여 획득한 변형률 거동과 해석을 통해 획득한 변형률 거동을 비교하였다. 제안된 해석결과는 시험 결과와비교하여 유효한 일치를 보였다.

진실된 남북교류를 촉구한다

윤동현 북한연구소 1990 北韓 Vol.- No.217

Effect of chemical amendments on reduction of bioavailable heavy metals and ecotoxicity in soil

윤동현,최원석,홍영규,이영복,김성철 한국응용생명화학회 2019 Applied Biological Chemistry (Appl Biol Chem) Vol.62 No.5

Heavy metal pollution in soil has been concerned because of toxicity in ecosystem and adverse effect on human health. Main objective of this study was to examine reduction of bioavailable heavy metals and consequently, decrease of ecotoxicity to biota when chemical amendments were applied in soil. Three chemical amendments, acid mine drainage sludge (AMDS), lime stone (LS), and steel slag (SS) were applied with varied application ratio (1, 3, 5%) in heavy metal polluted soil and bioavailable fraction of heavy metal was monitored. In addition, ecotoxicity test using earthworm (Eisenia fetida) was conducted for 28 days examining mortality, weight increase, and bioaccumulation of heavy metal in the earthworm. Result showed that AMDS was the most efficient amendment for reducing bioavailable heavy metals in soil while SS showed the least efficiency. Reduction ratio of bioavailable-As, Cd, and Pb was ranged 39.0–92.0% depending on application ratio and heavy metal species for AMDS application. However, only bioavailable-Pb was reduced at the range between 39.1% and 56.5% when SS was applied in soil. In contrast, the lowest concentration of As, Cd, and Pb and ecotoxicity effect in the earthworm was observed in SS treatment indicating that exposure route of heavy metals or particle size of amendments might effect on uptake of heavy metals to the earthworm. Overall, ecotoxicity test in combination with chemical concentration monitoring is a useful tool for evaluating remediation efficiency of heavy metal polluted soil.

최근 60년간 도시 및 농촌 지역의 국지적 기후변화 비교 분석

윤동현,남원호,홍은미,김태곤,허창회,Yoon, Dong-Hyun,Nam, Won-Ho,Hong, Eun-Mi,Kim, Taegon,Ho, Chang-Hoi,Hayes, Michael J. 한국농공학회 2018 한국농공학회논문집 Vol.60 No.3

Local climate characteristics for both urban and rural areas can be attributed to multiple factors. Two factors affecting these characteristics include: 1) greenhouse gases related to global warming, and 2) urban heat island (UHI) effects caused by changes in surface land use and energy balances related to rapid urbanization. Because of the unique hydrological and climatological characteristics of cities compared with rural and forested areas, distinguishing the impacts of global warming urbanization is important. In this study, we analyzed anthropogenic climatic changes caused by rapid urbanization. Weather elements (maximum temperature, minimum temperature, and precipitation) over the last 60 years (1955-2016) are compared in urban areas (Seoul, Incheon, Pohang, Daegu, Jeonju, Ulsan, Gwangju, Busan) and rural/forested areas (Gangneung, Chupungnyeong, Mokpo, and Yeosu). Temperature differences between these areas reveal the effects of urbanization and global warming. The findings of this study can be used to analyze and forecast the impacts of climate change and urbanization in other urban and non-urban areas.

Bone mineral density and specific physical performance in Korean national amateur male boxers

윤동현,송홍선,김광준 국민체육진흥공단 한국스포츠정책과학원 2019 International Journal of Applied Sports Sciences Vol.31 No.2

Background: The objective of this study was to investigate the relationships between bone mineral density, the level of anaerobic capacity and muscle strength in Korean national amateur male boxers. Methods: We carried out a cross-sectional population-based study where fifty-six Korean national amateur male boxers were enrolled. The participants’ whole-body bone and regional mineral density (BMD) and bone mineral content (BMC) were assessed using dual-energy X-ray absorptiometry as the main outcome. The anaerobic capacity was assessed using the Upper and lower Wingate test, and muscle strength was assessed using Isokinetic muscle strength and Maximal strength. Results: Of the fifty-six boxer, 37.5% were classified as LWC, 32.1% as MWC, and 30.3% as HWC. Linear regression analyses showed that the severity of bone variable was associated with upper and lower-body anaerobic capacity. Isokinetic muscle strength and Maximal strength were positively associated with bone variables. Conclusions: Within athletes of Korean national amateur male boxers, anaerobic capacity, and muscle strength measurements were positively associated with bone variables. Further research is needed to elucidate mechanisms underlying this positive association that is, undertaking studies involving effective exercise and nutrition supplements treatments, and developing the study designs to facilitate analysis of this relationship.

저 산너머 달보다 먼 세상 ; <분단 38년에서 본 오늘의 북한 실체상> : 북한의 교육 ; 귀신 등쳐먹을 구조적 세뇌술

윤동현 평화문제연구소 1983 통일한국 Vol.1 No.-

Hold time-Low Cycle Fatigue Behavior for Nickel Based Hastelloy X at Elevated Temperatures

윤동현,허인강,김재훈,장성영,장성호 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.1

Hastelloy X, a material used in gas turbines, is subject to complex damage because of creep and fatigue in a high temperature environment during the operation of gas turbines. Although the low cycle behavior of Hastelloy X has been widely investigated, the number of studies focusing on the actual operating conditions of the gas turbine is limited. In this study, the total strain range of the gas turbine at 760 °C and 870 °C was considered as a parameter of the actual gas turbine operation. In addition, tests were performed with a trapezoidal waveform of the total strain to reflect the operation—stop status of the gas turbine with frequent shutdown times. The results of the fatigue test were studied with the Coffin-Manson method and the lifetime prediction equation was derived based on the data. Fractography was performed using scanning electron microscopy (SEM) observation.