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심미 브라켓의 종류와 브라켓-호선 각도에 따른 마찰 저항에 대한 연구
제영지,장민희,임용규,이동렬 대한치과교정학회 2007 대한치과교정학회지 Vol.37 No.5
본 실험은 마찰력을 줄이고 물리적 성질을 개선하여 최근에 개발된 수 종의 심미 브라켓들과 교정 탄선간에 발생하는 마찰력의 크기를 측정, 비교해 보고자 하였다. 일반 슬롯의 세라믹 브라켓인 Inspire, Signature III와 Cristaline V, 스테인레스 스틸 (SS) 슬롯을 가진 세라믹 브라켓인 Clarity, 골드 슬롯을 가진 Luxi II, Polyoxymethylene 계열의 플라스틱 브라켓인 Brillant, SS 슬롯을 가진 컴파짓 브라켓인 Spirit MB, 금속 브라켓인 Integra를 사용하여 018″ 원형의 교정 탄선에 0˚, 4˚, 8˚의 tip angulation을 부여하고 elastic module로 결찰한 뒤 인공 타액 상태에서 활주이동할 때의 운동 마찰력을 측정하였다. 연구 결과 슬롯에 silica 처리된 세라믹 브라켓 (CR)이 유의하게 낮은 마찰력을 보였고 (P < 0.05), 단결정 세라믹 브라켓이 (IN) 유의하게 큰 마찰력을 보였다 (P < 0.05). 플라스틱 브라켓인 polyoxymethylene계열의 BR이 낮은 마찰력 양상을 보였고 이는 금속 브라켓과 유사하였다. 모든 브라켓에서 브라켓-탄선 각도가 증가함에 따라 유의하게 마찰력이 증가하였으나 주사전자현미경상에서 탄선이나 브라켓에 손상은 발견되지 않았다. 마찰력의 양상이 브라켓의 재질로 추측할 수 있는 것과는 다르게 나타난 결과로 보건대 심미 브라켓이 스테인레스 스틸 브라켓에 비해 마찰력 면에서는 오히려 우수하거나 큰 차이가 없으므로 임상적으로는 마찰력은 크게 고려하지 않아도 되겠다. Objective: The purpose of this study was to evaluate how the friction that occurs during the sliding movement of the archwire through esthetic brackets is differently affected by bracket materials, slot designs, and tip angulations of the archwire. Methods: Eight types of brackets with 0.018 inch slots (composite: Brillant (BR); composite with metal slot: Spirit MB (SP); ceramic: Inspire (IN), Signature (SI), Cristaline V (CR); ceramic with metal slot: Clarity (CL), Luxi II (LU); and metal bracket: Integra (IT)), and placed into groups of 20 brackets in each group, were tested in artificial saliva with 0.018 inch stainless steel wire. The wire tip angulations were given as 0, 4 and 8 degrees. Results: CR group significantly showed the lowest frictional force with all wire tip angulations of 0, 4, and 8 degrees. IN significantly showed the highest frictional force (P < 0.001). BR (Polyoxymethylene) had significantly less frictional force than SP (Polycarbonate) (P < 0.001) and showed no significant difference between metal brackets. Friction was increased as the wire tip angulations were increased, but no notches were observed on any parts of the archwire. Conclusions : According to the results of this study, esthetic brackets are superior or similar to SS brackets from a frictional point of view.
THE RELATION BETWEEN MOLECULE AND VISUAL EXTINCTION IN DARK CLOUDS
Minn, Y.K. The Korean Astronomical Society 1991 Journal of The Korean Astronomical Society Vol.24 No.2
We have compared the column densities of $H_2CO$, $^{13}CO$, $C^{18}O$, $^{12}CO$, CS, and $HCO^+$ to the visual extinctions derived from star counts in eight dark clouds, L1317, B1, L1551, L1535, L1544, L134, L134N, and B335. We examined the degree of correlation between molecules and extinctions. The contours of $^{13}CO$, $H_2CO$, and CS distributions show an excellent coincidence with those of the visual extinction. Even though the plots of molecule brightness temperature or column density as a function of the visual extinction show a considerable scatter, a good correlation is found between the two quantities. The turnover of the ratios of $^{13}CO$ and $H_2CO$ column densities to the visual extinction at high extinctions observed in several clouds is not apparent in this work. The ratios seem to maintain constant values within the range of $A_V$ we studied. The slopes of the relations between the molecule column density and extinction, and the threshold values of extinction for detection of molecules are comparable to the other works. The cause of the slope difference is discussed. We derived, for the first time, the relations of CS and $HCO^+$ column densities and the visual extinction. The ratio of CS column density to extinction is at least two orders of magnitude lower than the mean value for $^{13}CO$, but the threshold for detection of CS is comparable to that of $^{13}CO$. The ratio of the $HCO^+$ column density to extinction is one to two orders of magnitude lower than the mean ratio for $H_2CO$.
DISTRIBUTION OF $H_2CO$, CO, AND EXTINCTION IN THE DARK CLOUD B5
MINN Y. K.,LEE Y. B.,GREENBERG J. M. The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1
We have made observations of the dark cloud, B5 in the transitions of $H_2CO$, J = $1_{10} {\leftarrow} 1_{11}$, and $2_{12} {\to} 1_{11}$. We compared the $H_2CO$ result with the observational results of CO and with the visual extinction. There exists an overall correspondence of molecules and extinction. However, a detailed agreement is lacking. We discussed the kinematics and the spatial relationship of molecules and extinction in this cloud.
Pulsed Energy Dependent Neutron Transport Theory
Minn, Hokee Korean Nuclear Society 1970 Nuclear Engineering and Technology Vol.2 No.4
고 에너지 영역에서 비탄성핵을 가진 충격중성자 전도문제에서 시간과 에너지의 과도적인 특성은 연속 에너지 전도연산자로서 면밀히 해결했다. 점근적으로 가장 우세한 하나의 고정된 시간고유치를 발견했다. 완전한 해는 다음 세 부분으로 되어 있다. 1. 점근적으로 가장 우세한 시간과 에너지의 분리 가능형. 2. 과도적으로 감속하는 순 에너지에 의해서 결정된 분리 불가능형. 3. 점근적으로 무시할 수 있는 시간과 에너지의 혼합에 의하여 결정된 분리 불가능형.
Lagrangian and Hamiltonian in quantum field theory.
Minn, Jooha 목포대학교 기초과학연구소 2000 基礎科學硏究誌 Vol.18 No.-
There is subtle difference between Lagrangian and Hamiltonian formalism. More precisely Lagrangian and Hamiltonian are not always convertible into each other without ambiguity. We will mainly discuss these matters with quantum field theory. There is the issue of imposing gauge fixing constraint before or after quantization. Why and how does this matter?