• Journal of Advanced Navigation Technology
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• v.16 no.5
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• pp.731-737
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• 2012

In the present study, a feasibility study on an innovative satellite attitude control actuator is performed. The actuator is specially designed to generate the reaction torque in an arbitrary axis, so that a satellite attitude can be controlled by using itself. It consists of a spherical flywheel and electromagnets for levitation and rotation control of the ball. As the earlier study, a rotating performance test on the spherical actuator is conducted in a single rotating axis and vertical levitation condition. From the test results, it can be confirmed that the maximum speed and torque of the innovative device are 7,200rpm and 0.7Nm, respectively. Using a velocity-voltage characteristic curve of the spherical motor, an open-loop control (V/f constant control) is performed, and the test results show excellent control performance in acceleration and deceleration phases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.283-284
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• 2014

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.183-187
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• 2012

In the present study, a feasibility study on an innovative satellite attitude control actuator is performed. The actuator is specially designed to generate the reaction torque in an arbitrary axis, so that a satellite attitude can be controlled by using itself. It consists of a spherical flywheel and electromagnets for levitation and rotation control of the ball. As the earlier study, a rotating performance test on the spherical actuator is conducted in a single rotating axis and vertical levitation condition. From the test results, it can be confirmed that the maximum speed and torque of the innovative device are 7,200rpm and 0.7Nm, respectively. Using torque-voltage characteristics of the spherical motor, an open-loop control (V/f constant control) is performed, and the test results show excellent control performance in acceleration and deceleration phases.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.215-224
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• 2003

This paper presents an electronic ballast using a novel complex modulation method for the metal halide lamp. The proposed modulation method, which has a modulating signal of swept complex frequency, can eliminate the acoustic resonance more effectively than the conventional modulation method, which has a modulating signal of constant frequency. For the purpose of future application specific integrated circuits (ASIC). the controller of the proposed ballast has been designed only with erasable programmable logic devices (EPLDs), but without a microprocessor. In this paper, detailed proposed modulation schemes are described and experimental results on the proto type 150W metal halide lamp ballast with the proposed modulation method ate discussed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.123-124
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• 2007

파력발전은 파랑에너지를 이용하여 유용한 에너지를 얻어내는 것인데, 본 논문에서는 그 가운데 진동수주 (Oscillating Water Column)형을 연구 대상으로 취하였다. 이는 외해에서의 파랑에너지를 공기실에 유입 집중시켜 공기실 내 수면의 승강운동을 증폭시키고 이로 인해 발생한 공기실 내의 공기 흐름을 터빈의 구동력으로 사용하는 것을 말한다. 적지 선정과정에서 채택된 곳의 설계파고를 바탕으로 원하는 정격출력인 500kW를 얻어낼 수 있도록 유량과 임펄스 터빈의 최적 직경을 산출하고자 하였는데 개념설계된 파력발전장치의 덕트가 쌍동형 형태를 취하고 있으므로 한 터빈당 250kW급을 목표 발전용량으로 하였다. 지난 연구를 통해서 기 작성된 터빈 성능도표를 활용하여, 본 연구에서는 1차적으로 임펄스 터빈의 개략적인 직경 및 유량을 구하고, 터빈의 자기 기동 특성을 고려하여 최종적인 형상을 구체적으로 도출하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.837-848
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• 2014

This paper describes the development of a walking assistive robot for effective self-rehabilitation for elderly people facing an inconvenience in walking. The main features of the developed robot are enhanced safety and mobility using the baby walker and electric wheelchair mechanisms and an accurate walking tracking control algorithm using potentiometers and stereo cameras. Specifically, a pelvis supporter is designed to prevent the user from falling down and reduce the burden on their legs, and electric motors are used for easy locomotion with low effort. Next, the walking intention and direction of the user are automatically recognized by using potentiometers attached at the pelvis supporter so that the robot can track the user, and the rapidity and accuracy of the tracking were increased by applying a lower-body motion analysis algorithm with stereo cameras. Finally, the user-tracking performance of the developed robot was experimentally verified through stepwise walking assistance experiments.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.449-458
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• 2001

This is a test report of system efficiency for the moving-actuator type Bi-ventricular assist device (AnyHear $t^{MT}$ ) Seoul National University). $AnyHeart^{TM}$), as an energy converter. utilities a brushless DC motor(S/M 566-26A. Sierracin/ Magnedyne, Carlsbad, CA. U.S.A.) generating their pendulous motion in the epicyclic gear train. It is necessary to know about the overall efficiency of the system. The system is subdivided into three parts: motor part, actuator part and blood sac part (including valves, etc.) according to system mechanism. The motor was operated with a variable range of torque. angular speed and width of voltage Pulse In this report. $AnyHeart^{TM}$ is focused on the efficiency of the motor and actuator parts. 4 $\ell/min$ pump output. which is normal condition of $AnyHeart^{TM}$ system, the total system efficiency is 8%, which is composed of 50%, 85% and 17% efficiency (motor Part, actuator Part and blood sac Part) respectively. In the analyzed result. applied input voltage on normal condition of $AnyHeart^{TM}$ is determined. Also speed Profile with considering filling state of blood sac is Provided. In the test of the in vitro mock circulation. some experimental results are Provided to demonstrate the effectiveness of the Presented approach.

• Korean Journal of Agricultural Science
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• v.5 no.2
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• pp.149-157
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• 1978

This study was carried out to obtain basic data for the type selection of furrow openers for the no-tillage soybean planter trailed by the two-wheel tractor from the standpoint of minimum draft and good performance of furrowing. For this study, two models of furrow opener, hoe and disc type, were tested on the artificial soil stuffed in the moving soil bin. The results obtained were as follows. In the case of disc furrow opener, the drafts were measured according to various diameters of discs under the condition of disc angle $8^{\circ}$ and $16^{\circ}$, working depth 3cm and 6cm, working speed 2.75cm/sec. Minimum draft appeared when the diameter of disc was about 28cm and the drafts increased as the diameter of discs became larger or smaller than this diameter. Specific draft showed almost same tendencies as above but showed the minimum when the diameter was about 30cm. For the purpose of controlling the seeding depth, the relationships between draft and working depths, 3cm and 6cm, were tested. The variations of draft concerning the various working depths showed linear changes and were affected in higher degree by depths than other factors. There were general tendencies at both working depths, 3cm and 6cm, that total draft showed the minimum with the disc diameter of about 28cm and specific draft showed it with the disc diameter of about 30cm regardless of disc angle and working speed. For the purpose of controlling the working width and speed, the relationships among drafts, disc angle and working speed were investigated and there were general tendencies that the draft increased as the angle and speed were increased and the draft was affected more by speed than by angle. To compare the hoe-type with disc-type opener, the specific drafts of hoe openers were compared with those of disc opener of $16^{\circ}$ angle and 30cm diameter. The specific draft of disc-type opener with the diameter of 30cm was $0.35{\sim}0.5kg/cm^2$, while $0.71{\sim}1.02kg/cm^2$ in the case of hoe type with the lift angle of $20^{\circ}$ which is 2 times as much as that of disc type in average value. And the furrows opened by disc openers were cleaner than those opened by hoe openers.

• Journal of Christian Education in Korea
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• v.71
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• pp.305-340
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• 2022

This study was started to suggest the direction of Christian educational development to revitalize North Korea's 'education' research. Since the two Koreas have experienced heterogeneity in almost all elements of society, such as politics, economy, society, culture, and education, during the period of division in 1977, true unification depends on laying the foundation for social integration that can overcome the sense of heterogeneity between the two Koreas. This is why North Korea's "education" research is needed. Education is the foundation for transferring culture and history, and for bringing about the survival, transformation, and community of society and since it is the mission of Korean churches and Christian educators to establish the direction of North Korean "education" research, North Korean "education" research is very important. Despite this importance, 'North Korean research' in the field of Christian education has not been properly conducted. Research on the "Christian Unification Education Program" that can be used in churches is actively taking place, but research on the macro level of presenting post-unification education blueprints is rare. This study was started to suggest the direction of Christian educational development to revitalize North Korea's 'education' research. For the study, the characteristics of 'North Korea Research' were analyzed according to generational classification. As a result of the study, recent research on North Korea has been expanding in research topics and methodologies, and recent studies have been differentiated into microscopic studies that deviate from existing research trends at a macro level and view North Korea's daily life. The characteristics of 'North Korean education research' are summarized by period. The research on North Korean education, which began in earnest in the 1970s, was divided into the period of start(70s), transition(80s), leap(90s), expansion(2000s), and development(2010s~). and research characteristics for each period were analyzed. Through this, early North Korean education research was also conducted in the policy aspect of the country, and the characteristics of political and social studies were strong, but recent studies have confirmed that the subjects and contents are diversifying. Based on these studies, the pending issues and issues of North Korean education research in the field of Christian education were analyzed. The study of North Korea in the field of Christian education, which began in the 1980s, has been conducted in the engineering aspect of 'development of unification education programs for churches'. However, studies on Christian unification education and North Korean education itself, which can be used in public education sites including Christian schools, have yet to be sufficient. Nevertheless, the diversification of research in the field of Christian education can be evaluated as a positive change. Based on these studies, it was proposed to establish a de-ideological research foundation, secure primary research data(Raw Data), activate research topics and research methodologies, and strengthen research capabilities in the direction of development to revitalize North Korean research in the field of Christian education. I hope this study will trigger various follow-up studies and help Korean churches that must achieve unification.