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정준기(Joon Ki Chung),김청균(Chung Kyun Kim) 한국가스학회 2015 한국가스학회지 Vol.19 No.4
본 연구에서는 여러 가지의 절단면 형상과 하중지지 용량을 높이기 위해 원판을 설치한 중공롤러의 변위거동 특성을 유한요소법으로 해석하였다. FEM 해석결과에 의하면, 중공롤러의 절단면 형상은 외측튜브, 중간튜브, 내측튜브와 이들 튜브들 사이를 연결하기 위해 X형 또는 Y형 컬럼을 설치한 경우는 중공롤러의 중간부에서 발생하는 최대 변위량을 줄여주는 효과가 있다. 여기에 중공롤러의 중간부 두께를 30~40mm 갖는 원판을 설치할 경우는 중공롤러의 최대 변위량을 줄이는데 효과가 크다는 해석결과를 제시하였다. 본 연구에서는 원통롤러의 전체 중량에 연계된 최대 변위량 비율을 고찰한 최적설계 데이터를 제하였다. FEM 해석결과에 의하면, 중공롤러에서 발생하는 최대 변위량과 전체 중량의 비율을 줄인 설계모델로는 4, 5와 6번을 추천할 수 있다. In this paper, the displacement behavior characteristic of hollow rollers with various cross sectional area profiles and circular plate for load supporting capacity increment has been presented using a finite element method. The FEM results present that the hollow roller with X-shaped or Y-shaped columns between outer tube, middle tube and inner tube reduces a maximum displacement at the middle length of hollow rollers. And the circular plate, which is inserted at the middle of the hollow roller, is very useful to reduce the maximum displacement of hollow rollers with the plate thickness of 30~40mm. This paper presents the weight vs the maximum displacement ratio in which is represented for the optimized design as a function of a hollow roller total weight. The FEM analyzed results recommend the design model 4, 5 and 6 of hollow rollers for decreasing the ratio of maximum displacement and total weight of hollow rollers.
정준기(Joon Ki Chung),정현도(Hyun Do Jeong),하재이(Jai Yi Ha),허민도(Min Do Huh) 한국어병학회 1992 한국어병학회지 Vol.5 No.2
The absorption and excretion times of oxolinic acid(OX) used in farms as new aquatic antibiotics commonly were evaluated with determination of the effects of water temperature and feeding to parameters by using the bioassay technique. On the same time, antibacterial activity and the complex formation of oxolinic acid with serum proteins of two different fishes were compared to those oxytetracycline(OTC). With more than 10 times lower MIC values than those of OTC in the strains among 13 analyzed fish pathogens. OX did not show the decresed antibacterial activity by the binding of serum proteins in carp and tilapia. It implies more powerful potential of OX as aquatic medicine OTC. The serum concentration of OX after different administrations the oral, i.m., i.v and dipping methods were compared. The higher beginning concentration in serum and faster excretion times were obserbed in i.m. and dipping methods respectively. In the oral and i.m. administration, peak serum concentration after 24-48 hrs and slow excretion times demonstrated in both methods. These pharmacokinetic characteristics similar at 30℃ and 20℃ water temperature conditions, however, beginning serum concentration of OX in fish dipped in 50㎎/ℓsol after starvation for 2 wks was appeared lower than those of fed fish. It suggests the importance of biological condition of the gill or skin for absorption of antibiotics after dipping administration.
흰쥐 적출 대동맥에서 alpha1-수용체 효능약과 alpha2-수용체 효능약의 혈관수축반응에 대한 내피세포의 영향
정준기(Joon Ki Chung),홍승철(Sung Cheul Hong),최수경(Su Kyung Choi),강맹희(Maeng Hee Kang),구미경(Mi Geong Ku),박상일(Sang Il Park),윤일(Il Yun) 대한약학회 1990 약학회지 Vol.34 No.3
A comparison was made of the effects of selective alpha1-adrenoceptor agonist phenylephrine and selective alpha2-adrenoceptor agonist clonidine on endothelium-containing and endothelium-denuded rings of the rat aorta. In the case of phenylephrine, removal of endothelium increased sensitivity 2.5 fold at EC50 level and maximum contractive response 1.4 fold. In the case of clonidine, which gave only 15% of maximum contractive response given to phenylephrine on endothelium-containing rings, removal of the endothelium increased sensitivity 5.6 fold at EC50 level and maximum contractive response 5 fold, which was about 55% of that given by phenylephrine. In endothelium-denuded ring, phenylephrine-induced contraction tended to be more increased in tonic contraction than in phasic contraction as compared to that in endothelium-containing ring, while clonidine-induced contraction was monophasic and was increased only in tonic contraction. In the calcium-free solution or in the presence, of verapamil, contraction stimulated by clonidine was almost abolished while that stimulated by phenylephrine produced only phasic contraction. The depression of sensitivity to these agonists in rings with endothelium appeared to be due to the vasodepressor action of endothelium derived relaxing factor(EDRF), because hemoglobin, a specific blocking agent of EDRF, abolished this depression. It is unlikely that the endothelium-dependent relaxation was due to stimulation of release of EDRF, because clonidine did not produce endothelium-dependent relaxation in 5-hydroxytryptamine-precontracted ring even when its contractile action was blocked by the alpha1-adrenoceptor antagonist, prazosin. When the efficacy of phenylephrine was reduced to about the initial efficacy of clonidine by pretreatment with dibenamine, the contraction-response curves for phenylephrine became very similar to the corresponding curves obtained for clonidine before receptor inactivation. In the dibenamine-treated rings, contraction of phenylephrine was abolished in calcium-free solution or in the presence of verapamil like that obtained for clonidine before receptor inactivation. These results suggest that EDRF spontaneously released from endothelium depress contraction more profoundly in a case of an agonist with low efficacy and the phenylephrine-induced contraction was totally dependent on extracellular calcium as was that obtained for clonidine when the efficacy of phenylephrine was reduced to that of clonidine by irreversible inactivation of alpha1-adrenoceptor with dibenamine.
이용복,정준기,박상흡,Lee, Yong-Bok,Chung, Joon-Ki,Park, Sang-Heup 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.4
The proportion of the welding in the production process of machinery, buildings and marine structures is increasing and the joining are mainly conducted by butt and fillet weld. In the case of fillet weld, the shape of structures is complicated depending on the constraint on the geometry of the structures, therefore, the full penetration is mostly difficult. Accordingly, it is necessary to establish safe and economical criteria of design of the structures through the strength based on the penetration state of the fillet weld. Patterns of fatigue failure in cruciform fillet weld jont appear in the form of the root, toe and mixed failure. In the case of toe and mixed failure, the fatigue strength is higher than root failure. Therefore, we have to make the enough depth of penetration or perform the welding work through improving the fatigue strength of cruciform joints in welded structures. So it is necessary to optimize the penetrated depth in the range of the possible mixed failure and find the way in the cost-effective design to lessen the amount of the welding work.