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Young‑Gil Jung,Wonseok Yang,Jae Ik Hyun,Shae K. Kim,Hyunkyu Lim,Do Hyang Kim 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12
Three alloys (Mg–6Zn–1.2Y, Alloy I; Mg–3.65Zn–1.65Y, Alloy II; and Mg–4.3Zn–1.4Y, Alloy III) with same volume fractionand grain size were designed to evaluate the effects of the I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2), which are themajor phases in Mg–Zn–Y alloys, on the mechanical properties. The tensile strength of Alloy I with the I-phase at roomtemperature was the highest among the tested alloys because the coherent interface between the I-phase and the α-Mg phasewas more resistant to cracking than the incoherent interface between the W-phase and the α-Mg phase. A cross-sectionalmicrostructure analysis of a sample that was tensile-tested at 423 K revealed that the morphology of the I-phase remainedrelatively stable. In contrast, the W-phase was broken and fragmented during the tensile test at 423 K because it had higherbrittleness under the test conditions. Therefore, the tensile and creep properties of Alloy I at 423 K were better than thoseof Alloys II and III containing the W-phase. According to the results, the I-phase in the Mg-Zn-Y alloy was more beneficialto the mechanical properties at room temperature and 423 K than the W-phase.
랜덤포레스트를 이용한 낙동강 본류의 남조류 발생 영향인자 분석
정우석(Jung, Woo Suk),김성은(Kim, Sung Eun),김영도(Kim, Young Do) 한국습지학회 2021 한국습지학회지 Vol.23 No.1
본 연구에서는 랜덤포레스트를 이용하여 8개 보 지점별 남조류 발생 주요 영향인자를 도출하고, 조류경보제 기반의범주형 예측모델을 개발하였다. 8개 보 지점의 랜덤포레스트의 변수 중요도를 살펴본 결과, 상류의 보 지점들은 남조류 발생에 있어 보 운영에 따른 영향을 직접적으로 받는 것으로 나타났다. 이는 효율적인 보 운영을 통한 남조류 관리가 가능할 수 있다는 것을 의미한다. 중류 구간은 DO와 E.C가 주요 영향인자로 도출되었다. 공간적으로 구미와 김천에 대규모 산업공단들이 밀집되어 있으며, 환경기초시설의 배출량이 큰 영향을 끼치는 구간이다. 따라서 폭염 및 가뭄 시기에 중류 유역에서 배출되는 환경기초시설의 방류는 본류의 E.C를 증가하게 하고 남조류 발생을 촉진 시키는것으로 나타났다. 중·하류에 위치한 보 지점들은 폭염 및 가뭄의 영향을 가장 많이 받는 지역으로 여름철 가뭄에 따른남조류 대발생에 대비하여 선제적인 관리가 필요한 지점으로 나타났다. 본 연구를 통해 지점별 남조류 발생 영향인자를 도출하였으며, 맞춤형 조류관리를 위한 정책적 의사결정의 기초자료로 제공될 수 있을 것으로 판단된다. In this study, the main influencing factors of the occurrence of cyanobacteria at each of the eight Multifunctional weirs were derived using a random forest, and a categorical prediction model based on a Algal bloom warning system was developed. As a result of examining the importance of variables in the random forest, it was found that the upstream points were directly affected by weir operation during the occurrence of cyanobacteria. This means that cyanobacteria can be managed through efficient security management. DO and E.C were indicated as major influencers in midstream. The midstream section is a section where large-scale industrial complexes such as Gumi and Gimcheon are concentrated as well as the emissions of basic environmental facilities have a great influence. During the period of heatwave and drought, E.C increases along with the discharge of environmental facilities discharged from the basin, which promotes the outbreak of cyanobacteria. Those monitoring sites located in the middle and lower streams are areas that are most affected by heat waves and droughts, and therefore require preemptive management in preparation for the outbreak of cyanobacteria caused by drought in summer. Through this study, the characteristics of cyanobacteria at each point were analyzed. It can provide basic data for policy decision-making for customized cyanobacteria management
정영화,김경진,원치문,심도식 江原大學校 産業技術硏究所 1995 産業技術硏究 Vol.15 No.-
In this paper, the importance of the size effects on the strength ratio is demonstrated by numerical results. The rate of decrease of tensile strength is for glass fiber, based on the experience of a composite manufacturing specialist. For other material, similar procedure may be used until detailed test result on such material is available. The strength criteria used is that of Tsai-Wu for stress space. The factors influencing the ratio are, reducing the tensile strength alone or both tensile and compression strengths, selection of the normalized interaction term, that is, the generalized Von Mises criterion or the Hill's criterion, and the status of applied stresses. Some of the numerical results are presented for a guideline for the furture study.
유한요소법을 이용한 볼트결합 구조부의 조건에 따른 동적변화 해석
鄭泳都,朴世蔓,朴明均 明知大學校 産業技術硏究所 2003 産業技術硏究所論文集 Vol.22 No.-
To join structure together, various methods and processes are available including welding, riveting, bonding with industrial adhesives and fastening by bolts. Analysis of the common areas formed by joining between the structure are significant in that their results can provide critical information for understanding the dynamic behavior of the whole structure. The structural factors affecting the dynamic behavior of the joined structures are usually believed to be materials composing the bolts, bolt sizes and the number of bolts as well as the strength of applied torque and the extent of overlap between the structures joined together. This paper analyzes the impacts of the structural factors such as the bolt sizes, the extent of overlap and the materials composing the structures on the dynamic behavior of the joined structures.
탄성반력의 영향에 따른 직교 이방성 복합판의 고유 진동 해석
정영화,심도식,김경진,이세진 江原大學校 産業技術硏究所 1997 産業技術硏究 Vol.17 No.-
In this paper, the result of application of vibration method to the orthotropic plates with free edges supported on elastic foundation and with a pair of opposite edges under axial forces is presented. Such plates represent the concrete highway slab and hybrid composite pavement of bridges. The reinforced concrete slab can be assumed as a special orthotropic plate, as a close approximation. The highway slab is supported on elastic foundation, with free boundaries. Sometimes, the pair of edges perpendicular to the traffic direction amy be subject to the axial forces. The plate is subject to the concentrated load/loads, in the form of traffic loads, or the test equipments. Finite difference method is used to obtain the deflection influence surfaces needed for vibration analysis. The influence of the modulus of the foundation, the aspect ration of the plate, and the magnitudes of the axial forces and the concentrated attached mass on the plate, under the natural frequency is thoroughly studied.
유한요소해석을 통한 iTECH의 전단 성능에 관한 해석적 연구
정재오,김도현,주영규,이재홍,김상대 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)
Experimental evaluations for the iTECH beam System, which is invented for the purpose of making a lower height in steel structures, have been studied a lot for many years. In addition, they show the possibility of being developed as a new system when the iTECH beam system is applied in construction fields. However, the experiments were carried out without preceding theoretical analyses. Thus, it is intended to supplement some parts of the experiments by analyses and to provide the basis on future studies. iTECH Beam evaluated structural function through moment, shear, joint experiment and proposed formula. While this experiment, shear formula proposed assuming that steel web is all shown similar shear behavior about shear component element. This paper tries to verify assumption for analyzing shear behavior through FEA method.
토당귀 종자의 형태적 특성과 발아와 입모율에 대한 저장방법,생장조절제 및 프라이밍 처리 효과
안희정,안복주,·김도현,·안영섭,·김영국,박춘근,이상원,·박충범·차선우,·송범헌, 忠北大學校 農業科學硏究所 2015 農業科學硏究 Vol.31 No.1
This study was conducted to have basic and applied informations to establish the cultivation method and to improve the cultivation techniques of Angelica gigas Nakai through investigating the rates of germination and seedling establishment with treatment of plant growth regulator and seed priming. The germination rates of round shape seed were about 0.3~12% higher than those of parallel shape. The germination rates with different storage durations were increased at the level of 25oC and 4oC with the storage days, while they were clearly higher at -20oC compared to those at 4oC and 25oC without the storage durations. With the results of germination rates with treating of plant growth regulator and seed priming, their rates with the round shape seeds were comparatively higher about 6% than those with parallel shape seed and they were increased with increasing of the storage durations. The germination rates were generally appeared higher with GA3 than did those with seed priming. The highest germination rate was appeared at 50 ppm GA3 of plant growth regulator and at -0.5 MPa PEG6000 of seed priming. The germination rates?ㅤ ?ㅤ of Angelica gigas were different with different temperature, storage durations and the treatments of plant growth regulator and seed priming. These results could be used according to different cultivating conditions.