• 천문학논총
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• 제7권1호
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• pp.71-77
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• 1992

An axisymmetric, stationary electrodynamic model of the central engine of an active galactic nucleus has been well formulated by Macdonald and Thorne. In this model the relativistic region around the central black hole must be filled by highly conducting plasma and the equations of magnetohydrodynamics are then satisfied. In this paper we analyze magnetohydrodynamic wave propagation in this region. We find that there are three distinct types of waves - the Alfven wave and two magnetosonic waves. The wave equations turn out to be not very different from those in nonrelativistic case except they are redshifted.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.325-328
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• 2000

The effects of DO and pH on the mass production of pullulan with high-molecular weight from A. pullulans ATCC 42023 were evaluated. The maximum pullulan production yield (51%) was obtained at pH non control (initial pH 6.5) and DO control (above 50%) condition. The pullulan degrading enzyme was activated when the pH of broth reached lower than 5.0 and portion of low molecular weight pullulan was increased. The formation of a black pigment was observed at the initial stationary phase, 40hr of fermentation. Therefore, the fermentation should be carried out in pH non control and DO control condition and harvested before reaching stationary phase around 40h for the production of high molecular weight pullulan.

• 한국시스템다이내믹스연구
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• 제16권3호
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• pp.5-29
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• 2015

The importance of the concept of safety culture has increased in the security of high-risk facility after Chernobyl accident in 1986. This paper elaborated the concept of safety culture and its main factors by Causal Loop Diagram. Due to the decline of safety culture, the occurrence of incidents and accidents require more and more corrective actions to the members of high-risk facilities and thereby increasing their workloads. Employees who must complete the task within the given time have to have time pressures and don't comply with the rules and procedures. Also, a schedule pressure is a big stress for employees, causing mistakes in precision work. In order to improve these problems, CLD of the safety culture in this paper suggests hiring more workers, re-allocation of given workloads and strengthen the learning, communication capabilities and safety leadership. In addition, the two real accident cases were analyzed to test the feasibility of the System Dynamic simulation model through the process of structuring the fault trees on the stationary black out accident in Kori unit 1 in South Korea and Kleen Energy power station explosion in US. The simulation results show that the various safety factors cause the serious accident combined with mechanical failure and safety culture will reduce the possibility of the accidents in these high-risk organizations. This simulation model can contribute to analyzing the impact of the organizational and human factors of safety culture and can provide the alternatives in high-risk facilities.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.1-7
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• 2002

The effects of DO and pH on the mass production of pullulan with high molecular weight and the morphology of A. pullulans ATCC 42023 were evaluated. A. pullulans showed a maximum production of pullulan (11.98 g/l) when the initial pH of the culture broth was 6.5 in a shake-flask culture. In a batch culture, the mixture of a yeast-like and mycelial cell forms was found at a pH of 4.5, and the maximum production of pullulan (13.31 g/l) was obtained. However, a high proportion of high molecular weight pullulan (M.W.>2,000,000) was produced at a pH of 6.5, with a yeast-like morphology. The maximum pullulan production yield ($51\%$) was obtained at a pH noncontrol (initial pH 6.5) and DO control (above $50\%$) condition. Pullulan degrading enzyme was activated when the pH of the broth was lower than 5.0 and the portion of low molecular weight pullulan was increased. The formation of a black pigment was observed at an initial stationary phase, at 40 h of fermentation. Therefore, the fermentation should be carried out in a pH noncontrol (initial pH of 6.5) and DO control (above $50\%$) condition, and should be harvested before reaching the stationary phase (around 40 h) for the production of high molecular weight pullulan.

• The Korean Journal of Ecology
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• 제27권6호
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• pp.383-390
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• 2004

본 연구는 1999년 3월부터 2002년 9월에 걸쳐 경기도 시화호, 경기도 웅진군 동${\cdot}$서만도, 장구엽도 3곳에서 검은머리물떼새의 번식기전 행동, 텃세권 행동, 번식생태, 주요 섭식지역과 섭식행동, 종내와 종간번식 및 먹이경쟁에 대해 조사하였다. 검은머리물떼새의 번식 시작은 지역에 따라 차이를 보여 시화호 지역은 4월 중순부터, 동${\cdot}$서만도와 장구엽도의 경우 5월 중순 번식을 시작하였다. 번식에 들어가기 전 짝간의 유대를 강화하기 위한 행동으로 암수짝간의 섭식행동(foraging behavior)과 추적행동(male-female chasing behavior)을 보인다. 교미행동에 들어가기 전 암수는 함께 섭식행동을 하며, 다른 쌍이나 개체들이 섭식장소로 접근해 오면 삑- 삑- 하는 울음소리(piping calling)와 함께 공격적 행동을 보이며 침입자를 쫓아내거나, 침입자 추적비행을 하기도 한다. 연속적 행동양상을 관찰하지 않으면 암수 추적비행과 침입자 추적비행을 구별하기 어렵다. 텃세권 행동은 나비비행(butterfly flight), 음성행동(calling behavior), 침입자 추적행동(chasing behavior), 싸움행동(fight behavior)의 4가지 타입으로 분류하였다. 시화호 지역의 중요 취식 지역은 대부도 선착장 앞쪽, 방어머리 갯벌, 시화방조제 오이도 초입부의 정치망이 설치되어 있는 갯벌, 공단의 조류 조망대 앞쪽 북측 간석지 등 크게 4지역으로 구분된다. 섬지역 중 동${\cdot}$서만도는 썰물시 갯벌에서, 만조시에는 섬 주변에서 취식하였고, 밀${\cdot}$썰물의 차가 없는 장구엽도의 경우 섬 주변에서 주로 취식하였다. 섭식행동 중 종내(intraspecific)와 종간 (interspecific) 경쟁이 이루어졌다. 취식지역에서 검은머리물떼새 개체간에는 먹이를 빼앗기 위해 쫓아가는 행동이 관찰되기도 하고, 중요 취식지역에 다른 개체가 들어올 경우 침입자 추적행동을 하며 쫓아내기도 하였다. 종간 섭식 경쟁은 주로 괭이갈매기와 일어난다. 괭이갈매기와 먹이경쟁이 이루어질 경우에 검은머리물떼새는 먹이를 갈취 당하거나 공격을 받아 다른 지역에서 먹이를 취식하는 개체보다 먹이 섭취율이 상대적으로 떨어지는 것이 관찰되었다. 종간 경쟁이 심하면 섭식지역을 떠나 다른 지역으로 이동하였다.

• 임산에너지
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• 제17권1호
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• pp.56-70
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• 1998

This study was carried out to investigate the structural characteristics of kraft lignin and the wood degrading characteristics, the productivity of ligninolytic enzymes and the enzymatic degradation of kraft lignin by white-rot fungi. To purify kraft lignin, precipitation of kraft pulping black liquors of pitch pine meal was done by titration with lN $H_{2}SO_{4}$ reaching to pH 2, and isolation of the precipitates done by centrifugation. The isolated precipitates from pitch pine were redissloved in lN NaOH, reprecipitated by titration with lN $H_{2}SO_{4}$, washed with deionized water, and kept ofr analysis after freeze drying. Fractionation of the precipitates in solution by successive extraction with $CH_{2}Cl_{2}$ and MeOH, and the fractionates were named SwKL, SwKL I, SwKL II, and SwKL III for pitch pine kraft lignin. The more molecular weights of kraft lignin increased, the less phenolic hydroxyl groups and the more aliphatic hydroxyl groups. Because as the molecular weights increased, the ratio of etherified guaiayl/syringyl(G/S ratio) and the percentage were increased. The spectra obtained by 13C NMR and FTIR assigned by comparing the chemical shifts of various signals with shifts of signals from autherized ones reported. The optimal growth temperature and pH of white-rot fungi in medium were $28^{\circ}C$ and 4.5-5.0, respectively. Especially, in temperature and pH range, and mycelial growth, the best white-rot fungus selected was Phanerochaete chrysosporium for biodegradation. For the degradation pathways, the ligninolytic fungus jcultivated with stationary culture using medium of 1% kraft lignin as a substrate for 3 weeks at $28^{\circ}C$. The weight loss of pitch pine kraft lignin was 15.8%. The degraded products extracted successively methoanol, 90% dioxane and diethyl ether. The ether solubles were analyzed by HPLC. Kraft lignin degradation was initiated in $\beta$-O-4 bonds of lignin by the laccase from Phanerochaete chrysosporium and the degraded compounds were produced from the cleavage of $C\alpha$-$C\beta$ linkages at the side chains by oxidation process. After $C\alpha$-$C\beta$ cleavage, $C\alpha$-Carbon was oxidized and changed into aldehyde and acidic compounds such as syringic acid, syringic aldehyde and vanilline. And the other compound as quinonemethide, coumarin, was analyzed. The structural characteristics of kraft lignin were composed of guaiacyl group substituted functional OHs, methoxyl, and carbonyl at C-3, -4, and -5 and these groups were combinated with $\alpha$ aryl ether, $\beta$ aryl ether and biphenyl. Kraft lignin degradation pathways by Phanerochaete chrysosporium were initially accomplished cleavage of $C\alpha$-$C\beta$ linkages and $C\alpha$ oxidation at the propyl side chains and finally cleavage of aromatic ring and oxidation of OHs.