• 한국과학교육학회지
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• 제16권4호
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• pp.340-350
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• 1996

Knowledge is composed through the interaction between the concept structure already held by students and their experience, and learning can be said to be the active process of solving the cognitive conflict caused by this interaction. Therefore, this study consists in showing the effective learning method and finding out the elements which the teacher has to own, through examining several forms of pre-conception or mis-conception of the inertia, the force-equilibrium, the action and reaction, the heat, and the electric current, and then finding out their solution and studying student's change in science concepts. For this study, the types of concept on the five above-mentioned materials which students have were examined through the concept-classifying question paper, and the classes to which the class mode for the change of concepts applied, were practised in each different classroom by each different instructor - a professor, a scientist, a teacher, and two students, respectively. And the effect of the teaching strategy based on these classes, and each different instructor' influence on the change of concept in students. were examined. The result of my study is as follows; 1. Students have various types of pre-conception which are different from science concept, and these types of pre-conception tend to last even after learning in class. 2. The thoughts on the correct science concept of the high school third-grade students who learned the physics in the traditional teaching method, and the second grade students who don't learn the physics yet, were nearly equal those of the second grade students by receiving the physics class through the cognitive conflict course were greatly changed especially that students showed the distinct change on mechanics and electric current. 3. Students didn't show the remarkable change of the science concept on the five materials in the four kinds of experimental classes by each different instructor but in the part of mechanics, there was the distinct change between the class by professor and those by the students. This was due to the difference of the authority and the attitude of the concept demonstrator. 1) The authority, the kind attitude, and the responsibility of the expert played an important role in the correct concept-formation of mechanics part - especially in the case of the mis-conception caused by the intuitive belief. 2) In the class by instructor with the democratic teaching method, the change of concept took place more easily, because in his class students could discuss the subject freely, so that they might experience the thought course to give them the confidence on the science concept.

• 전자공학회논문지B
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• 제29B권10호
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• pp.59-68
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• 1992

In this paper, we proposed coordinator description and ambiguity on the hybrid controller for position/force control of robot manipulator. When the hybrid controller is desiged based on the PID control conception, the parameter sharing problem must be considered. However, selection problem of coordinate system on n-DOF robot manipulator control is unsolved. Moreover, contact force on object and change of shape make another problems. And it is very difficult to figure out the accurate mathematical model of manipulator on account of ambiguity and nonlinearity of actuator. Therfore, we design a new hybrid controller, FPID(Fuzzy PID). For verifying the validity of the controller, we tried computer simulation of this system. As a result, we can get remarkable improvement of overdamping and overshooting. Also we can solve compicance problem effectively. Furthermore, ambiguity problem is solved by adding control knowledge based compensator. So robust controller can be acheived, too.

• 한국과학교육학회지
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• 제24권6호
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• pp.1049-1062
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• 2004

이 연구에서는 물체의 운동에 대한 과학사적 변천을 아리스토텔레스 시대부터 뉴턴의 관점까지 다양하게 구분하고, 이를 토대로 설문지를 개발하였다. 설문지는 운동의 원인, 운동의 형태, 운동에서 보존되는 양의 개념을 포함하며, 이를 예비 중등 과학 교사들에게 투입하여 이들의 응답을 과학사적 관점으로 분석하였다. 연구 대상은 물리 교육을 전공하는 대학교 2학년생 20명과 다른 과학관련 교육을 전공하는 대학교 2학년생 34명이었다. 연구 결과, 물리교육을 전공하는 중등 예비교사들은 다른 과학관련 교육을 전공하는 예비교사들보다 운동의 원인이나 운동의 형태에 관련된 개념에서는 관성과 뉴턴의 힘 개념을 가지고 있는 비율이 높았다. 그러나 이들은 전공에 상관없이 운동에서 보존되는 양에 대한 개념을 알아보는 설문지에서 운동량을 속력에 비례하는 것으로 이해한 데카르트의 관점이나 운동 에너지가 보존된다는 호이겐스의 관점을 가지는 비율이 매우 높았으며, 상대적으로 운동량을 속도에 비례하는 것으로 이해하는 뉴턴의 관점을 가지고 있지 못하였다.

• 한국과학교육학회지
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• 제25권5호
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• pp.583-594
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• 2005

이 연구에서는 진자에 대한 중학생들의 개념을 조사하고 그네를 타는 근운동 체험으로 불일치 자료를 제시하고 인지갈등 정도 및 개념변화를 살펴보았다. 다수의 학생들은 단진자에 작용하는 합력에 대해 진자 운동의 양 끝 주변에서는 운동궤도를 따라 표현하며 중심 부근에서는 힘이 없다고 하였다. 그 이유를 설명할 때 많이 고려하는 힘의 종류는 중력,운동방향으로의 힘, 그리고 장력이었다. 모든 학생들이 관찰 결과가 자신들의 예상과 다르다는 것을 인정하고 활동을 매우 즐거워하였지만 인지갈등 정도는 그다지 높지 않았다. 인지갈등 요소별로 보면 '흥미'가 가장 높았으며, '불안'이 현저하게 낮았다. 직후 사후 검사와 지연 사후 검사에서 대부분의 학생들이 관찰했던 합력의 방향은 잘 기억하게 되었으나 그 이유를 잘 이해하고 옳게 진술한 학생은 소수였다.

• 한국초등과학교육학회지:초등과학교육
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• 제19권1호
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• pp.131-143
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• 2000

The unit of a buoyant force included in the 7th national science curriculum for 6th grade students. On the contrary, it seldom that students' conception about buoyant phenomena is studied, even though there has been many studies of students' conceptions of basic science contents. The purpose of this study was to survey the elementary school students' conceptions of a buoyant force, to analyze their cognitive levels, and to explore the relationships between them. Sixth grade students (total numbers is 192) were selected .from 5 .lasses in two elementary schools in a local city of Kyungsangdo. They were asked to respond two kinds of test, which are the Logical Thinking Ability (GALT) to investigate students' cognitive levels and the Buoyant Force Questionnaire (BFQ). We developed BFQ test, based on the 7th national science curriculum for 6th grade and the previous researches of a buoyant force. We, qualitatively, analysed students' frequency of responses about a buoyant force and their types of explanation, and, quantitatively, analysed the relationships between cognitive levels and conceptions of a buoyant force with SPSS/ PC 7.0 programmes. The results of cognitive level showed that half of 6th grade students were in the concrete operational stage, 43.2% in the transitional stage, 6.8% in the formal stage. However, their sub-logical thinking abilities in a combinational, conservational, controlling variables, proportional, probability and correlational logic were very fluctuated from 91% to 8%. The results that only 4.8% of elementary students had correct conceptions of a buoyant force suggest that 6th grade students had great difficulties in understanding of that concept. Their difficulties would originated from the frequent common-sense explanations of a buoyant phenomena in terms of the weight or the unique properties or the contact area of an object or with/without air. Furthermore students' explanations, frequently, changed with context of problems of a buoyant force. Scheffe test of quantitative results that elementary students in the concrete level had 50.6% of concept formation in a buoyant force, the transitional level 54.5%, and in the formal operational level 62.8% showed significant differences of conceptions of a buoyant force with cognitive levels. Therefore the concrete operational elementary students had more difficulties of understanding of a buoyant force than the transitional and formal level, which is required to higher cognitive levels. This conclusion have implications that the unit of a buoyant force have to be presented with concrete activities for majority of students who are in concrete and transitional levels.

• 한국통신학회논문지
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• 제29권9A호
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• pp.1091-1100
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• 2004

본 논문은 최적 모듈 선택 아키텍쳐 합성을 위한 천력 감소 Force-directed 스케줄링을 제안한다. 제안한 전력 강소 스케줄링은 행위 수준 언어를 업력으로 스위칭 활동-(switching activity) 을 고려하여 기존의 FDS 스케쥴링을 저 전력으로 고려한 FDS_LP 앙고리듬을 수행한다. 제안한 FDSL LP 알고리듬은 스위칭 활동을 최소로 하는 동적 파워를 포스 개념에 적용하여 전력 감소를 수행한다. 모듈 선택에서는 전력, 면적, 지연의 매개 변수를 고려하여 최척 모율 성택 RT 라이브러리를 구축한다. 구축한 RT 라이브러리에서 최적 파라메터를 구하기 위해서 프렌치 앤드 바운드 방법을 사용한 최걱 요율 선택 방법을 제안한다. 비교 실험에서는 최적 모율 선택을 고려한 제안한 FDS LP 앙고리듬과 기존의 FDS 알고리듬간의 전력 차이를 비교하여 최대 23.9 % 까지 전력 감소를 얻을 수 있다.

• 한국과학교육학회지
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• 제36권3호
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• pp.423-434
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• 2016

이 연구의 목적은 연구자가 개발한 전향력 실험 장치를 통해 예비 지구과학 교사들이 가진 정신모형의 변화를 알아보는 것이다. 예비 지구과학 교사 5명을 대상으로 전향력에 대하여 질문지에 제시된 그림 그리기와 면담을 통해 전향력 실험 장치를 활용한 활동을 수행하기 전과 후의 정신모형을 조사하고 그 변화를 비교하였다. 정신모형 수준이 낮은 단계인 소박한 정신모형이었던 두 학생은 개발된 전향력 실험 장치를 통한 활동을 통해 정적 불안정 모형과 동적 불안정 모형으로 향상되었다. 그리고 활동 전 정적 불안정 모형을 보여주었던 두 학생은 활동 후 모두 동적 불안정 모형으로 변화하였다. 마지막으로 활동 전 동적 불안정 모형을 보여주었던 학생은 활동 후에도 동적 불안정 모형에 남아있었지만 이미 가지고 있었던 선개념이 과학적 개념으로 많이 변화한 모습을 보여주었다. 이 연구를 통해 개발된 전향력 실험 장치 활용이 학생들의 전향력 개념의 학습에서 안정적이고 과학적인 개념 형성에 효과적이었음을 확인할 수 있었다. 개발된 전향력 실험 장치가 학교 현장에서 전향력과 관련된 수업에 효과적으로 사용될 필요가 있으며 나아가 위의 예비 지구과학 교사들이 교사가 되어 학교 현장에서 학생들을 가르치는 동안 나타나는 정신모형의 변화에 대해서도 알아볼 필요가 있다.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.1-30
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• 2008

When the stagnation temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this temperature. The gas remains perfect; its state equation remains always valid, except, it is named in more by calorically imperfect gas. The aim of this work is to trace the profiles of the supersonic axisymmetric Minimum Length Nozzle to have a uniform and parallel flow at the exit section, when the stagnation temperature is taken into account, lower than the dissociation threshold of the molecules, and to have for each exit Mach number and stagnation temperature shape of nozzle. The method of characteristics is used with the algorithm of the second order finite differences method. The form of the nozzle has a point of deflection and an initial angle of expansion. The comparison is made with the calorically perfect gas. The application is for air.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.867-869
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• 2004

A smart blade conception has been proposed by the authors. With stretching-twisting coupling effect, the blade is twisted by centrifugal load or ambient temperature change. In this paper, the blades, made by three kinds of anti-symmetric laminates, are investigated by rotational tests. The results show the angle of smart blade tips increases in proportion to the 2nd power of a rotating speed and is well in agreement with the numerical results by FEM.

• 한국정밀공학회지
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• 제12권8호
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• pp.27-38
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• 1995

For solving troubles happened during the drilling process with carbon fiber epoxy composite materials(CFRP) by using HSS drill, a few types of diamond gift electroplated drills are manufactured, and machinability of these drills is experimented with a variety of cutting speed and feed rate. These drills have some advantages of good wear resistant and the conception of grinding process. As a result, using of these drills improves both troubles being caused by tool wear and damage of exit surface depending on fiber stacking angle. It is desirable that cutting conditions for the cutting thickness per revolution must be set under 0.01mm when the size of a diamond grit is # 60 .approx. 80.