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Seung Youb Han,Seok Su Sohn,Sang Yong Shin,이성학,Yong Chan Suh 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.4
Effects of microstructural modification and microfracture mechanisms on fracture toughness of pearlitic graphite cast irons with different nodularity were investigated by in situ observation of microfracture process. Six pearlitic graphite cast irons were fabricated by adding a small amount of Mg as a nodularizing element for graphite, and their microstructures including pearlite, ferrite, graphite, and eutectic carbide were analyzed. Most of ferrites were observed in a layer shape around graphites because of carbon-depleted zones formed near graphites. As the nodularity and nodule count increased, fracture toughness linearly increased in the cast irons except the iron containing many fine graphites. According to in situ observation of microfracture process, cracks initiated at nodular graphites and carbides even at a small load, and then propagated readily through the adjacent graphites or carbides, thereby resulting in the lowest fracture toughness. The cast iron having widely spaced graphites and ferrite layers thickly formed around graphites showed the highest fracture toughness because of the blocking of crack propagation by ductile ferrite layers and the crack blunting and deflection by graphites, which was also confirmed by the R-curve analysis.
논문 : 탄소함량이 다른 경량철강판의 냉간 압연에 의한 파괴기구
한승엽 ( Seung Youb Han ),신상용 ( Sang Yong Shin ),이성학 ( Sung Hak Lee ),김낙준 ( Nack J. Kim ),곽재현 ( Jai Hyun Kwak ),진광근 ( Kwang Geun Chin ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.5
An investigation was conducted into the effects of κ-carbides on the cracking phenomenon, which often occurred in cold-rolled light-weight steel plates. Three kinds of steels were fabricated by varying the C content, and their microstructures and tensile properties were investigated. In the two steels that contained a high carbon content, the band structures of ferrites and κ-carbides that were severely elongated along the rolling direction were well developed, whereas continuous arrays of κ-carbides were formed in the steel that contained a low carbon content. Detailed microstructural analyses of the deformed region beneath the tensile fracture surface showed that the cracks initiated at arrays of κ-carbides or κ-carbides formed interfaces between the band structures, which initiated cleavage fractures in the ferrite bands, while the bands populated with a number of κ-carbides did not play an important role in propagating the cracks. Thus, the minimization of interfacial κ-carbides or κ-carbide arrays by increasing the carbon content was essential for preventing cracking from occurring during cold rolling.
논문 : 단상영역에서 압연된 API X80 라인파이프강의 인장 및 샤르피 충격 특성에 미치는 Mo, Cr, V의 영향
한승엽 ( Seung Youb Han ),신상용 ( Sang Yong Shin ),서창효 ( Chang Hyo Seo ),이학철 ( Hak Cheol Lee ),배진호 ( Jin Ho Bae ),김기수 ( Ki Soo Kim ),이성학 ( Sung Hak Lee ),김낙준 ( Nack J. Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 대한금속·재료학회지 Vol.46 No.12
This study is concerned with the effects of Mo, Cr, and V addition on tensile and Charpy impact properties of API X80 linepipe steels. Four kinds of steels were processed by varying Mo, Cr, and V additions, and their microstructures and tensile and Charpy impact properties were investigated. Since the addition of Mo and V promoted to form fine acicular ferrite and granular bainite, while prohibiting the coarsening of granular bainite, it increased the strength and upper shelf energy, and decreased the energy transition temperature. The Cr addition promoted the formation of coarse granular bainite and secondary phases such as martensite-austenite constituents, thereby leading to the increased effective grain size, energy transition temperature, and strength and to the decreased upper shelf energy. The steel containing 0.3wt.% Mo and 0.06wt.% V without Cr had the highest upper shelf energy and the lowest energy transition temperature because its microstructure was composed of fine acicular ferrite and granular bainite, together with a small amount of hard secondary phases, while its tensile properties maintained excellent.
Invar 36 합금 선재의 미세조직에 미치는 냉간 인발 및 열처리 공정의 영향
한승엽 ( seung Youb Han ),장선아 ( Seon Ah Jang ),은희철 ( Hee-Chul Eun ),최정훈 ( Jung-Hoon Choi ),이기락 ( Ki Rak Lee ),박환서 ( Hwan Seo Park ),안도희 ( Do-Hee Ahn ),김수영 ( Soo Young Kim ),김재열 ( Jea Youl Kim ),신상용 ( San 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.10
In this study, the effect of cold drawing and heat treatment on the microstructure of Invar36 alloy wire was investigated. Invar36 alloy wire is used as a transmission line core material, and is required to have high strength. The diameter of the Invar36 alloy wire specimens were reduced from 16 mm to 4.3 mm after three cold drawing and two heat treatment processed, thereby increasing tensile strength. Specimens were taken after each of the cold drawing and heat treatment processes, and their microstructure and tensile properties were analyzed. The Invar36 alloy γ-(Fe, Ni) phase matrix before the cold drawing and heat treatment processes. After the cold drawing processes, {220} and {200} textures were mainly achieved. After the heat treatment processes, a {220} recrystallization γ-(Fe, Ni)phase was formed with fine carbides. The recrystallization γ-(Fe, Ni) phase grains had low dislocation density, so they probably accommodated a large amount of deformation during the cold drawing processes.
호텔 객실판매 예측에 관한 실증적 연구 - 서울지역 특급호텔을 중심으로 -
한승엽(Seung Youb Han) 한국산학경영학회 1991 산학경영연구 Vol.4 No.-
Nothing is more incorrect than forecasting. Nevertheless, forecasting is one of the most important business activities for the effective management. There has been rapid changes of the growth rate in every respect of the Korean hospitaity industry, especially the hotel industry, before and after the 88 Olympic Games. Therefore, the hoteliers shall be in need of more-than-ever accourate demand forecasting for the more systematic management and control. Under the above circumstances, this study suggested the best forecasting technique and method for the better sales and operations of the hotel rooms. The number of rooms sold is selected as a dependent variable of this study which is regarded as the best representative factor of measuring the growth rate of the rooms division performance of the hotels. The first step was to select the most verifiable independent variable diferently from the other countries or other areas of Korea. As a result, the number of foreign visitors was chosen. Empirical research, i.e. correlation and multiple regression analysis, shows that this independent variable has a strong relationship with the dependent variable told above. The second procedure was to estimate the number of rooms will be sold in 1991 on the basis of the formula calculated through the multiple regression analysis. Time series technique was conducted using the data of the number of foreign visitors by purpose of travel from 1987 to 1990. For the more correct forecasting, however, it would be desirable to adopt the data from 1989 considering the product or the industry life cycle. In addition, deeper analysis for the monthly or seasonal forecasting method is needed as a future research.
API X80 라인파이프강의 미세조직과 기계적 특성에 미치는 냉각조건의 영향
한승엽 ( Seung Youb Han ),신상용 ( Sang Yong Shin ),이성학 ( Sung Hak Lee ),배진호 ( Jin Ho Bae ),김기수 ( Ki Soo Kim ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.9
In this study, four API X80 linepipe steel specimens were fabricated with varying cooling rates and finish cooling temperatures, and their microstructures and crystallographic orientations were analyzed to investigate the effects of cooling conditions on their tensile and Charpy impact properties. All the specimens consisted of acicular ferrite, granular bainite, and secondary phases such as martensite and martensiteaustenite constituent. The volume fraction of secondary phases increased with increasing cooling rate, and the higher finish cooling temperature resulted in the reduction in volume fraction and grain size of secondary phases. According to the crystallographic orientation analysis data, the effective grain size and unit crack path decreased as fine acicular ferrites having a large amount of high-angle grain boundaries were homogeneously formed, thereby leading to the improvement of Charpy impact properties. The specimen fabricated with the higher cooling rate and lower finish cooling temperature had the highest upper shelf energy and the lowest energy transition temperature because it contained a large amount of fine secondary phases homogeneously distributed inside fine acicular ferrites, while its tensile properties well maintained.
공익법인의 회계정보가 기부자의 기부의사결정에 미치는 영향 : 예산집행 정보와 회계품질을 중심으로
한승엽 ( Seung-youb Han ),최세라 ( Sera Choi ),양승희 ( Seunghee Yang ),윤소은 ( So-eun Yoon ) 한국회계학회 2019 회계학연구 Vol.44 No.3
본 연구는 공익법인의 예산집행 정보와 회계품질을 중심으로 공익법인의 회계정보가 기부자의 기부의사결정에 미치는 영향을 분석한다. 2014년부터 2017년까지 사회복지사업을 영위하는 공익법인을 대상으로 분석한 결과, 전체 비용에서 고유목적사업에 지출된 비용의 비중(즉, 고유목적사업비율)이 높을수록 기부자가 예산집행 적정성을 보다 긍정적으로 평가해 차기 기부금이 유의하게 늘어나는 것으로 확인된다. 다만 회계품질이 낮은 경우 이러한 고유목적사업비율과 차기 기부금 간의 양(+)의 관계가 약화되는 것으로 관측되는 바, 동일한 회계정보라 하더라도 해당 정보의 신뢰성 수준에 따라 기부자의 정보의존도에 편차가 발생하는 것으로 나타난다. 본 연구의 결과는 국내 공익법인의 회계투명성 수준에 대한 그간의 우려에도 불구하고 공익법인의 회계정보가 기부자의 기부의사결정에 유용하게 활용됨으로써 효율적 자원배분을 촉진하는 정보체계로서 효과적으로 기능하고 있음을 시사한다. This study investigates whether accounting information of Korean nonprofit organizations (hereinafter NPO) influences donors’ subsequent-period donation decisions. Analyzing NPOs running social-welfare businesses which account for the largest portion of total donation revenues in Korea for the period 2014-2017, we find that donors perceive NPOs reporting higher program ratios (i.e., the ratio of program expenses to total expenses) as more efficient in budget usage and thus, increase the amount of subsequent-period donation. However, the positive association between program ratio and subsequent-period donation is attenuated for NPOs with low accounting quality, suggesting that donors’ reliance on NPOs’ accounting information varies with the credibility of the information contents. Collectively, our findings indicate that despite the increasing concerns on accounting transparency of Korean NPOs, donors incorporate the two attributes of accounting information - contents and quality - in their decision-making and that the accounting information system functions effectively, contributing to the efficient resource allocation in the nonprofit sector.