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이용호,신용돌,김병걸,민복기,송재성 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-
자왜 또는 자기이방성의 측정에 사용되는 전사석의 여자전류를 측정에 필요한 수초간만 흘려서 에너지 소모 및 측정시의 최대난점인 시료의 온도변화의 문제를 극소화하였다. 따라서 전자석의 냉각장치는 생략되고 크기와 전원의 용량도 극소화되었다. 공기간격 22㎜, 자극의 단면적 40 × 25㎟에서 0.5 T의 자장발생에는 180 W의 전원으로 족하였다. 시료의 자왜와, 자기이방성에 의한 토크를 전기용량센서에 의하여 측정하여 10^-8의 자왜분해능과 1 nJ의 토크 분해능을 얻었다. 0.02× 0.8× 10㎟의 연자성 리본의 형상이방성을 이용하여 이방성 측정시의 토크값을 교정하였다. A high efficiency small electromagnet(22㎜ air gap and 40 × 25㎟ core's cross section) suitable for measuring magnetostriction and magnetic anisotropy was built. The magnet could be miniaturized by reducing the measuring space and time. The excitation current of the electromagnet was supplied for only a few second of small. An 0.5 T magnetic field was generated with 180 W power consumption. The values of magnetostriction and magnetic anisotropy were measured with a very sensitive capacitance cell with resolution of 10^-8 and 1 no. The torque was calibrated using a soft magnetic ribbon's shape anisotropy.
Jae-Dol Kim,Hoo-Kyu Oh,Jung-In Yoon 대한설비공학회 2000 International Journal Of Air-Conditioning and Refr Vol.8 No.1
The frequency response characteristics of a condenser were numerically studied for the control of refrigeration and air conditioning systems. The important parameters, such as the refrigerant flow rate, refrigerant temperature, air velocity, and air temperature at the condenser inlet, were analyzed. Superheated vapor, two phase, and subcooled liquid domain in condenser can be described by using the energy balance equation and the mass balance equation in refrigerant and tube wall, the basic equation for describing the dynamic characteristics of condenser can be derived. The transfer function for describing dynamic response of the condenser to disturbances can be obtained from using linearizations and Laplace transformations of the equation. From this transfer function, analytical investigation which affects the frequency responses of condenser has been made. Block diagrams were made based on the analytic transfer function; dynamic responses were evaluated in Bode diagrams on the frequency response.<br/> Through this study, it became possible that the information about the dynamic characteristics of air-cooled condenser is offered. The results may be used for determining the optimum design parameters in actual components and entire systems. Also, the mathematical models, frequency response may be used to help understanding, evaluate optimum design parameters, design control systems and determine on setting the best controller for the refrigeration and air-conditioning systems.