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새로운 Poly ( enaryloxynitriles ) 의 합성과 그 열적 성질
김병구,배장순,공명선 ( Byung Gu Kim,Jang Soon Bae,Myoung Seon Gong ) 한국공업화학회 1995 공업화학 Vol.6 No.4
주쇄에 다양한 화학 구조를 가진 새로운 poly(enaryloxynitriles)을 p-bis(1-chloro-2,2-dicyanovinyl)benzene (2)과 sulfide, sulfone, azo, acetal, imide, ether 그리고 ester 결합을 포함한 디 페놀 유도체의 나트륨 염과 계면중합에 의하여 합성하였다. 생성된 중합체는 고유 점도가 0.12∼0.45 dL/g이었으며 중량 평균 분자량은 9000∼12000이었다. 그들 중합체는 극성 반양자성 용매에 매우 잘 녹았으며 alkyl, acetal, ester를 가진 diphenol로부터 합성된 중합체는 THF나 aceton에도 매우 잘 녹았다. 그러나 중합체의 DMF 용액으로 부터 용매 증발후 단단하고 부서지시 쉬운 막이 형성되었다. 중합체들은 350℃에서 열경화 반응이 진행되어 불용성 물질이 형성되었다. 거의 모든 중합체가 350∼450℃사이에서 10% 중량 감량을 유지하였으며, 500℃에서 잔사량은 70∼85%로서 열안정성을 보여주었다. New poly(enaryloxynitriles) with a variety of chemical structure in the main chain were prepared by interfacial polymerization of p-bis(1-chloro-2,2-dicyanovinyl) benzene (2) with disodium salts of diphenol derivatives containing sulfide, sulfone, azo, acetal, imide, ether and ester group. The resulting polymers possess inherent viscosities of 0.12∼0.45 dL/g and Mw in the range 9000∼12000. They are easily soluble in polar aprotic solvents. The polymers derived from diphenols with alkyl, acetal and ester units were even soluble in common organic solvents such as THF and acetone. Brittle and hard films can be cast from DMF solutions. These polymers show a large exotherm in differnetial scanning calorimetry and undergo a curing reaction around 350℃ to form insoluble materials. Almost all the poly (enaryloxynitriles) retained a 10% weight loss being recorded between 350∼450℃ in nitrogen and displayed 70∼85% residual weight at 500℃.
김병구(Byung-Gu Kim),이창훈(Changhoon Lee) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
Large-eddy simulation has been conducted to simulate turbulent boundary-layer flows over an array of regularly distributed obstacles considering various cases of a wind incident angle. The effect of wind direction was investigated in the square cube array that periodic boundary condition was imposed. Characteristics of the turbulent flow over the obstacle array have been found to be very sensitive to the direction of prevailing wind or of mean wind or of mean pressure gradient. Velocity of planar average shows that the direction of the velocity is not always aligned with mean pressure gradient but varied with height, specially below the urban canopy. Turbulent statistics are changed sensitively with the direction of mean pressure gradient around 10 degree.
분자선에피택시에 의해 성장한 ZnO 나노결정 박막에 완충층 두께와 활성층 성장 온도가 미치는 효과
김병구 ( Byung Gu Kim ),남기웅 ( Gi Woong Nam ),박영빈 ( Young Bin Park ),박형길 ( Hyung Gil Park ),임재영 ( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.9
ZnO thin films were deposited on a Si (100) substrate by plasma-assisted molecular beam epitaxy (PA-MBE). Growth of ZnO thin films on a Si substrate is limited due to the large difference between the lattice constants of ZnO and Si. In this research, we studied the effects of the buffer-layer thickness and active-layer growth temperature on the structural and optical properties of ZnO thin films. Scanning electron microscopy, X-ray diffraction, and photoluminescence were carried out to investigate the structural and optical properties of the ZnO thin films. The structural and optical properties of the ZnO thin films were improved when the buffer layers were grown for 20 min and the active layers were grown at 800 ℃.(Received September 9, 2013)
기부금 지출이 기업가치에 미치는 영향: 유가증권시장 상장기업
김병구 ( Byung Gu Kim ),윤병섭 ( Byung Seop Yoon ) 한국재무관리학회 2016 財務管理硏究 Vol.33 No.2
본 연구는 기부금 지출이 기업가치에 미치는 영향을 Pooled OLS로 분석하고 2단계 최소자승법(Two-Stage Least Squares: 2SLS)으로 강건성을 검증하였다. 2008년부터 2014년까지 7년의 연구기간동안 한국거래소 유가증권시장에 상장되어 있는 제조기업을 대상으로 2014년 12월 31일 현재 일정한조건을 만족하는 18개 업종, 74개 업체, 518개 연구표본을 선정하여 분석하였다. 연구 결과는 다음과 같다. 첫째, Pooled OLS 분석을 통해 기부금 지출 비율이 기업가치에 유의한 양(+)의 영향을 미치고 있음을 발견하였다. 그리고 기부금 지출 비율과 기업가치 사이 위로 볼록한 곡선 관계, 즉 역 U자형의 비선형관계가 있음을 밝혔다. 둘째, 매출액 대비 기부금 지출 비율은 Pooled OLS는 2.38%, 고정효과모형은 2.18%로 나타나분석방법에 따라 선형관계와 구조적 전환점이 다르게 나타난다는 점을 확인하였다. 고정효과모형기준으로 매출액 대비 기부금 지출 비율이 2.18% 영역까지는 기업가치가 증가하지만, 2.18% 영역을 지나면 기업가치가 다시 감소함을 시사한다. 셋째, 기부금을 한도 초과하여 과도하게 지출하면 주주와 경영자 사이 이해가 상충되는 대리인문제를 가져오므로 오히려 기업가치가 하락한다. 2SLS를 적용해 분석한 결과 기업가치가 높은 기업이 더욱 활발히 기부금을 지출한다는 주장은 지지되지 않았다. 다만, 기부금을 지출함으로써 기업가치가 변화한다는 주장은 밝혔다. 그리고 재벌기업과 비재벌기업 양 집단 사이 기부금 지출이 기업가치에 미치는 영향은 차별성이 없었다. This Study analyzed the effects of the level of contributions of the companies on the Enterprise Value. Models that were used on the research were Two-Stage Least Sqaures: 2SLS, which was used for robustness examination, and Lagrange Multiplier verification, Hausman verification and F-verification; we believe that fixed effects model is appropriate, hence 2SLS and Pooled OLS were used accordingly. From 2008 to 2014, we analyzed the manufacturing enterprises that are listed with Securities markets of KSE. The fundamental task was to analyze the experiment samples of 518, 18 business fields and 74 enterprises that are up-to-date of December 31st, 2014. The results of the research are following: Firstly, we observed the attentively positive effect of level of contribution’s ratio on the value of enterprises according to Pooled OLS analysis. Furthermore, the ratio of the level of contribution and the Enterprise Value represent the convex curve relation, that is, the reverse U shaped asymmetric relations. Secondly, we confirmed that different result was shown depending on the types of analysis with the structural turning point and linear relations of ratio between sales account and the level of contributions; Pooled OLS showed 2.38% and fixed effect model showed 2.18% respectively. Lastly, This would ultimately devalue the Enterprise Value, and according to 2SLS, the analysis showed that expenditure to contributions changes the Enterprise Value.
김병구(Byung-Gu Kim),이창훈(Changhoon Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
We investigated modification of inhomogeneous turbulent channel flow imposed on the thermal stratification using direct numerical simualtion. Typical length scale of vortical structures becomes smaller under stratification, whereas the length scale associated with temperature variation becomes larger. Both streamwise and spanwise components of baroclinic torque showed strongly intermittent behaviors. It was found that both increased small sized structures and changes in inclination angle of coherent structures are closely connected with the baroclinic torque. As the Richardson number increased, the angle of strong vortical structures make with the wall increased in buffer layer, while decreased in the outer layer.
김병구(Byung-Gu Kim),여경민(Kyeongmin Yeo),이창훈(Changhoon Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
We investigated modification of near-wall turbulence in the stably stratified turbulent channel flow by using direct numerical simulation. Detailed investigation revealed that the baroclinic torque plays an important role in generation and intensification of small-sized vortical structures. Thus typical length scale of vortical structures becomes smaller under stratification, whereas the length scale associated with temperature variation becomes larger. Both streamwise and spanwise component of baroclinic torque showed strongly intermittent behaviors. In addition to, streamwise baroclinic torque showed that it's non-gaussian behavior returned to like gaussian as stability was increased. As we increased stability, angle of strong vortical structure makes with the horizontal was increased in buffer layer, while decreased in the outer layer.