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열전달 특성을 고려한 복합 초전도재료의 임계전류밀도 해석
고태국,최용환,이상진 연세대학교 대학원 1992 延世論叢 Vol.28 No.1
In the design of superconducting devices, stability in the present is the one of the most important factors. Stability is a mesure of the ability of a conductor or device to spontaneously return to the superconducting state after the passage of a disturbance that had either triggered or driven an excursion into the normal state ; this treatise made a study of one of the stability theories, flux jump stability. As a part of flux jump stabilization this treatise derived the stability parameter making use of superconducting theory and thermodynamics, and created the critical current density Jc on the formula. Consequently, the stability of superconductor was improved with considering the heat transfer effect. And this treatise reached the conclusion that the critical current density is uplifted in inverse proportion to the width of superconductor and the volumetric proportion of superconductor. For instance, Jc= 1.01×108 when a=0.018m, λ=0.3 but Jc=5.50×104 when a=0.019m, λ= 1
와전류 및 회전자극형상이 초전도 자속 PUMPING에 미치는 영향
고태국,문창욱 연세대학교 산업기술연구소 1991 논문집 Vol.23 No.2
The eddy current and the magnetic field in the normal region have been studied. The normal spot is a excitation part when it is connected fluxpump. Eddy currents rely on the shape of normal spot, the velocity of moving normal spot, and externally applied magnetic field. The critical current region begins to be formed at the leading corner of the spot once ?? is attained at that spot.
시변시 normal spot에 의해 초전도체에 발생되는 와전류의 효과
고태국,문창욱 연세대학교 산업기술연구소 1990 논문집 Vol.22 No.2
The Eddy current generated by the moving normal spot on superconductor depends on the shape of pole, the velocity of moving magnet, and the magnetic flux density. The Eddy Current that is taking place in a moving normal spot in a superconductor has been investigated in some detatils. The structure of the eddy current and magnetic field in the normal region has been studied.
회전 자계에 의해 초전도체에 발생되는 Eddy current 분포에 관한 연구
고태국,최진형,오윤상 연세대학교 산업기술연구소 1993 논문집 Vol.25 No.2
The distribution of magentic field and eddy current is analized to investigate the normal spot wihich plays a part in excitation. Magnetic Reynods Number has been introduced to explain the distribution of magnetic field and eddy current. Through the eddy current equation, we can predict where the quenching points are formed in superconductiong sheet. The part of zero-compression by motion. When the magnetic of the normal spot is large, the eddy current is increased in the side of normal spot and decreased in the left side. So the current reaches to the critical current, the superconductor begins to quench locally.
산소와 연소 단원에서 과학적 개념 형성을 위한 수업 전략의 효과
엄상수,고영환,백성혜,박국태 한국교원대학교 과학교육연구소 2000 청람과학교육연구논총 Vol.10 No.1
The purpose of this study was to investigate the effectiveness of teaching strategies for scientific conceptions in the units of oxygen and combustion in elementary school science textbook. 70 elementary school 6th grade students in Seoul participated. They were divided into experimental group and controlled group. Five scientific concepts were adopted from the units of oxygen and combustion in the 6th grade science textbook. Subjects' preconceptions were investigated by pre-questionnaires. A series of 6 instructional sessions based on the teaching strategy of cognitive confliction theory were given to the experimental group. By the end of the instructional session, a post-test was administered to both experimental and controlled groups. There was a statistically significant difference between post-test gains of the experimental and controlled groups. These results support the notion that the teaching strategy was effective for changing from preconceptions to scientific concepts.
외부전원 인가시 복합초전도체의 안정도 파라미터에 관한 연구
최용환,고태국 연세대학교 산업기술연구소 1992 논문집 Vol.24 No.1
Stability is a mesure of the ability of a device to spontaneously return to the superconducting state after the passage of a disturbance that had either triggered or driven an excursion into the normal state; this treatise made a study one of stability theories, flux jump stability. Consequently, the stability of superconductor with the condition of transport current flow was improved with considering the heat effect. And this treatise reached the conclusion that the critical current density is uplifted in inverse proportion to the width of superconductor and the volumetic proportion of superconductor.
산소와 연소 단원에서 과학적 개념 형성을 위한 수업 전략의 효과
엄상수,고영환,백성혜,박국태 한국초등과학교육학회 2000 초등과학교육 Vol.19 No.2
The purpose of this study was to investigate the effectiveness of teaching strategies for scientific conceptions in the units of oxygen and combustion in elementary school science textbook. 70 elementary school 6th grade students in Seoul participated. They were divided into experimental group and controlled group. Five scientific concepts were adopted from the units of oxygen and combustion in the 6th grade science textbook. Subjects' preconceptions were investigated by pre-questionnaires. A series of 6 instructional sessions based on the teaching strategy of cognitive confliction theory were given to the experimental group. By the end of the instructional session, a post-test was administered to both experimental and controlled groups. There was a statistically significant difference between post-test gains of the experimental and controlled groups. These results support the notion that the teaching strategy was effective for changing from preconceptions to scientific concepts.
주민석,배준한,고태국,강연일 연세대학교 산업기술연구소 1994 논문집 Vol.26 No.1
The transient one-dimensional heat conduction equation in a high Tc bulk superconductor with an localized hot zone has been analyzed numerically. After the heater energy is introduced in a few miliseconds, the development of the normal zone and full quench time are calculated with respect to distance as a fuction of three parameters including : transport current, heater current, heating time. The analysis of this model is performed using finite difference method under modified adiabatic condition. The results of computer simulation are also presented in this paper. Full quench occurs when transport currents exceed 1.15[A] in given heater current and heating time. A temperature of superconductor rises abruptly in heating region when heater energy is increased. If heater energy is same, heating time is dominant factor for quench. Given heater energy, ohmic heat dissipation is dominant part for quench. But, heating energy is dominant part for quench than conduction. When heater energy is large, quench is not affected by transport currents.
배준한,주민석,고태국 연세대학교 대학원 1994 延世論叢 Vol.30 No.1
This thesis is a study on the quench characteristics in epoxy impregnated superconducting magnet. Teh normal 3one propagation velocity, full quench time and full recovery time in a superconducting magnet during quench are simulated numerically. Propagation velocity is linearly proportional to the transport current and abruptly increases near the critical current. Longitudinal velocity is nearly 20 times of transverse velocity regardless of the transport current. The ratio of the transverse velocity to longitudinal velocity is about 0.04 regardless of the transport current and the full quench time is abruptly decreased near the minimum propagation current. Comparing superconducting composites composed of Cu matrix to the composites of Cu/CuNi matrix, the propagation velocity of the former is slower than the latter, while the full quench time of the former is longer under the same transport curent.