• 한국과학교육학회지
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• 제25권2호
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• pp.111-121
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• 2005

이 연구에서는 초등학교 6학년을 대상으로 변인통제 능력이 요구되는 문제해결 과정에서 실험설계와 증거제시의 특성 및 어려움을 분석하였다. 연구 결과 변인통제 문제 해결 과정에서의 실험설계 유형은 원인 변인과 통제 변인의 통제나 변화 여부에 따라 통제변인변화형, 원인변인통제형, 완전변인통제형, 불완전변인통제형, 모든변인변화형으로 구분되었으며, 실험설계 과정에서 선행신념에 포함된 원인 변인값을 포함시키려는 경향이 강하게 나타났다. 결론에 대한 증거제시 사례를 분석한 결과 원인변인의 변화 여부, 통제변인 통제 여부, 실험결과와 결론의 일치 여부에 따라 완전변인통제형, 원인변인통제형, 원인변인변화형으로 구분되었으며, 원인변인통제형이 가장 빈도가 높았다. 실험설계에 비해서 증거제시에서의 변인통제 정도는 훨씬 낮았는데, 이는 선행신념에 포함된 원인 변인값에 집착한 증거제시, 증거 실험에서의 실험 결과와 선행 신념의 불일치, 다중변인과제에 대한 잘못된 선입견 때문인 것으로 나타났다. 따라서, 선행신념을 극복할 수 있고, 탐구 과정 요소의 특성이 반영된 다양한 변인통제 발달 프로그램이 개발되어야 할 것이다.

• 한국과학교육학회지
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• 제22권3호
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• pp.571-585
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• 2002

형식적인 사고를 가능하게 하는 논리적 사고력의 형성 가능성에 대한 기초적인 연구 활동의 하나로, '생각하는 과학' 프로그램에 있는 변인통제 활동의 학습효과를 조사하였다. 초등학교 5학년 306명의 학생들이 연구에 참가하였으며, 같은 분량의 사간에 실험반에서는 교육과정에 따른 과학 교과 수업과 변인통제 활동을 병행하였고, 통제반에서는 과학교과 수업만을 수행하였다. 연구 초기에 논리적 사고력 검사와 변인통제 검사를 이용하여 사전 상태를 비교하고, 한 학기 동안 변인통제 활동 6개를 12차시에 걸쳐 진행하면서, 처치별, 성별, 인지수준별 학습효과를 알아보았다. 처치활동은 초등학교 5학년 학생들의 변인통제능력 신장에 매우 효과적인 것으로 나타났다. 변인통제능력의 하위요소별로 분석한 결과, 특별히 실험조건 통제, 변인측정과 결과변인 학습에 매우 효과적인 것으로 나타났고, 원인변인 학습효과도 다소 있는 것으로 나타났다. 남 여학생들의 사전 변인통제능력을 비교한 결과 여학생들이 월등히 높은 점수를 보였다. 변인통제 학습 후 남 여학생들 모두에게 거의 같은 정도로 우수한 학습효과가 나타났으며, 통제반에서 차이가 더 벌어진 반면, 실험반에서는 그 격차가 좁혀졌다. 학생들의 인지수준에 따란 변인통제 학습효과를 분석한 결과, 모든 인지수준에서 실험반 학생들의 변인 통제능력이 상당히 향상되었다. 특히 전기 구체적 조작기, 중기 구체적 조작기와 후기 구체적 조작기에 있는 학생들의 변인통제능력은 크게 향상되었다. 변인판별 능력은 전기 구체적 조작기, 중기 구체적 조작기와 후기 구체적 조작기에 있는 학생들이 거의 같은 정도의 우수한 발전을 보여주었으며, 실험설계 능력은 모든 수준에서 상당히 향상되었다. '생각하는 과학'의 변인통제 활동과 같은 형태의 학습내용을 현행 학교 과학교육에 적극적으로 도입해볼 필요가 있다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.222-224
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• 2002

In proton and heavy ion radiotherapy, compensators are required to modify the energy of heavy ion, to compensate the local difference of tumor depth. Conventional compensators have to be created, exchanged, and stored for each patient and for each irradiation directions. A Cylinder Type Liquid Variable Compensator is and is under development. Hexagonal cylinders will be arranged in honeycomb structure. In which air and fluid are divided by hexagonal pistons. The position of each piston will be changed in each cylinder for adjusting the thickness of fluid for variable compensator. The location of each hexagonal piston is determined by each controlling cylinder connected to the hexagonal cylinder by inlet pipes of fluid. Each controlling cylinder includes controlling a piston, which is moved mechanically. Each controlling cylinder is to be moved by a motor driven by a computer.

• 한국초등과학교육학회지:초등과학교육
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• 제28권2호
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• pp.154-160
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• 2009

Correlational reasoning is used to analyze results from an experiment and create meaningful relationships among variables. Although there were many recognition development studies, not a single study found the optimal period for the development of logical thinking. Therefore, the purpose of this study is to find the optimal period for students whose logic for variable controlling and correlational reasoning are poor. This study made a logic program treatment subject for students between the 4th and 8th grade whose recognition in reasoning has not been developed in general in order to find the optimal period for their development. The variable-controlling reasoning was performed the program of voice survey and sugared-water melting in subsection survey and sugared-water melting in subsection. And, the correlation reasoning was performed the program of rat's size and tail color, treatment, and effect. As a result of research, students, who were not formed variable controlling and correlational reasoning, could be known to be enhanced through learning, but to fail to be formed the qualitative change like the cognitive development. In other words, the optimal period couldn't be found that is grown the formation of students, who are not formed the variable controlling and correlational reasoning, through learning. It is expected that this research can contribute to the improvement of students' cognitive level and there would be more active researches in different fields to improve the cognitive level.

• 한국과학교육학회지
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• 제31권4호
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• pp.587-599
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• 2011

이 연구에서는 '생각하는 과학' 활동을 경험한 중학생들이 이를 경험하지 못한 통제집단과 비교하여 변인 통제 전략의 적용과 변인의 효과를 추론하는 능력에 대해 분석하였다. 연구 결과 변인 통제 전략 유형은 조작변인의 인식과 변인 통제의 여부에 따라 변인 통제전략 성공형, 변인 통제전략 미완성형, 부분통제형, 통제 불가능형, 변인 통제전략 실패형으로 구분하였다. 실험집단이 통제집단에 비해 변인 통제 전략을 보다 정화하고 효과적으로 사용하였다. 직관적으로 알 수 있는 변인의 효과 추론 능력을 분석한 결과 가역적 사고가 가능한지의 여부와 변인의 효과를 추론할 수 있는지에 따라 변인효과 추론 가능형, 변인효과 추론 불가능형, 가역적 사고 불가능형으로 구분하여 유형화하였다. 실험집단 학생들이 변인효과 추론 가능형에서 통제집단보다 두 배 이상 많았다. 보상논리 조작을 포함하는 가역적 사고가 가능한 학생들은 형식적 조작기 이상의 학생들에게서 가능하였다. 직관적으로 얻기 힘든 변인의 효과를 추론하는 능력은 두 집단 모두 형식적 조작기 후기에 도달한 인지 수준의 비율과 비슷하였으며, 추론에 성공한 학생들의 비율은 실험집단이 통제집단 학생들 보다 1.5배 정도 더 많았다. 따라서 변인 통제능력과 변인을 추론하는 능력을 향상시키기 위해서는 '생각하는 과학' 활동 프로그램이 큰 영향을 미치고 있음을 알 수 있다.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1221-1226
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• 2015

This paper proposes a multiple switch mode power supply (SMPS) system based on the wireless network which controls variable load. The system enables power supply of up to 600W using 200W SMPS as a unit module and provides a controlling function of output power based on variable load and a monitoring function based on wireless network. The controlling function for output power measures the variation of output power and facilitates efficient power supply by controlling output power based on the measured variation value. The monitoring function guarantees a stable power supply by observing the multiple SMPS system in real time via wireless network. The performance of the proposed system was examined by various experiments. In addition, it was verified through standardized test of Korea Testing Certification. The results were given and discussed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.249-252
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• 1997

In this paper the sway-control problem of a container crane is investigated in the perspective of controlling an underactuated mechanical system. For fast loading/unloading of containers from the ship, quick suppression of the remaining swing motion of the container at the end of each trolley stroke is crucial. Known nonlinearities are fully incorporated by feedback linearization. Robustness is enhanced by variable structure control. Compared with the linear LQ control, much better performance can be obtained.

• 제어로봇시스템학회논문지
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• 제21권11호
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• pp.1027-1033
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• 2015

For the attitude control of spacecraft, two variable-speed control moment gyros are proposed as main actuators in the article. Since a variable-speed control moment gyro (VSCMG) makes two control torques (gyroscopic torque and reaction torque), two VSCMGs are sufficient for controlling 3-axes attitude. Additionally, there are no singular conditions for two non-parallel VSCMGs. Since gyroscopic torque is usually much greater than reaction torque, the control performances of approximately 3 axes may not be the same. However, several missions can be accomplished by controlling two axes. For such missions, a selective axes control method is proposed. The method selects two axes for a certain task and controls the attitude of the selected axes. For the remaining axis, angular speed is controlled for stabilization. A hardware-in-the-loop simulation has been used to test VSCMG modules and to verify the proposed method. Two VSCMGs can be alternative actuators for small satellites.

• Smart Structures and Systems
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• 제9권2호
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• pp.189-206
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• 2012

This paper focuses on the actuation system combined with a piezoelectric transducer and an electric circuit, which leads to a new insight; the electric actuation system is equivalent to mechanical variable-stiffness actuation systems. By controlling the switch in the circuit, the electric status of the piezoelectric transducer is changed, and consequently a variable-stiffness mechanism is achieved on the electric actuator. This proposed actuator features a shift in the equilibrium point of force, while conventional electrically-induced variable-stiffness actuators feature the variation of the stiffness value. We intensively focus on the equilibrium shift in the actuation system, which has been neglected. The stiffness of the variable-stiffness actuator is periodically modulated by controlling the switch, to suppress the vibration of the system in an open-loop way. It is proved that this electric actuator is equivalent to its mechanical counterpart, and that the electrical version has some practical advantages over the mechanical one. Furthermore, another kind of electrically-induced variable-stiffness actuator, using an energy-recycling mechanism is also discussed from the viewpoint of open-loop vibration control. Extensive numerical simulations provide comprehensive assessment on both electrically-induced variable-stiffness actuators employed for open-loop vibration control.

• 대한임베디드공학회논문지
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• 제15권3호
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• pp.149-157
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• 2020

Regarding previously-developed drone simulators, it was easy to check their flight stability or controlling functions based on the condition that their weight was fixed from the design. However, the drone is largely classified into two types that is the one with the fixed weight whose purpose is recording video with camera and racing and another is whole weight-variable during flight with loading the articles for delivery and spraying pesticide though the weight of airframe is fixed. The purpose of this thesis is to analyze the structure of drone and its flight principle, suggest dynamics-model-based simulator that is capable of simulating weight-variable drone and develop the simulator that can be used for designing main control board, motor and transmission along the application of weight-variable drone. Weight-variable simulator was developed by using various calculation to apply flying method of drone to the simulator. First, ground coordinate system and airframe-fixing coordinate system were established and switching matrix of those two coordinates were made. Then, dynamics model of drone was established using the law of Newton and moment balance principle. Dynamics model was established in Simulink platform and simulation experiment was carried out by changing the weight of drone. In order to evaluate the validity of developed weight-variable simulator, it was compared to the results of clean flight public simulator against existing weight-fixed drone. Lastly, simulation test was performed with the developed weight-variable simulation by changing the weight of drone. It was found out that dynamics model controlled various flying positions of drone well from simulation and the possibility of securing the optimum condition of weight-variable drone that has flying stability and easiness of controlling.