• Journal of Korean Elementary Science Education
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• v.41 no.4
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• pp.627-641
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• 2022

This study aims to help elementary school teachers increase their knowledge about the changes in the positions of the sun and moon during the day and the first time the moon observation begins in the Earth and Space section of the Earth and the Moon. The survey questions were grouped into four categories, namely, textbook explanation, inquiry activities, achievement of learning goals, and other opinions. The perception of each question differed according to advanced science majors and teaching careers and experiences of this unit. In addition, understanding the diverse views of the participants using descriptive questions was possible. The study recruited 67 teachers working at an elementary school in Gyeonggi-do. The conclusion is as follows. First, the teachers exhibited similar positive and negative perceptions about the description of the textbook on the changes in the positions of the sun and moon during the day. Second, the study found that majority of teachers used alternative methods when guiding students regarding the change in the positions. This trend was not correlated with the sun and the moon, and the study observed no difference in advanced majors and teaching careers and experience of this unit. Third, the majority of teachers responded that they could achieve their learning goals through this learning. However, many teachers complained of various difficulties in guiding students about the lesson, and the majority alternative methods. The results demonstrated the perception of teachers that students can achieve learning goals through alternative methods without direct observation.

• Journal of Korean Elementary Science Education
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• v.27 no.4
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• pp.385-398
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• 2008

The purpose of this study is to understand the effect of The Model of Phases of the Moon on conception changes for preservice teachers. The researcher interviewed two preservice teachers under the agreement with them on their participation in the research just before he performed a class using The New Model of Phases of the Moon. The post-interview with the same content as the pre-interview was preformed one month later. The main content of the interview is as follows; 'Explain the shape of the Moon by drawing it.', 'Explain the relative different position among the Sun, Earth, and Moon depending on phases of the Moon by drawing them.', 'What do you think of the cause of phases of the Moon?', 'Draw a picture to explain why we always see only one side of the moon.' The results of the research are as follows. First, the class with New Model of Phases of the Moon was able to perceive the relationship of Sun, Earth, and Moon in three-dimensions rather than in two-dimensions and it helped to change their misconception that the Moon's shadow causes the Moon's shape. Secondly, the class with New Model of Phases of the Moon helped preservice teachers understand better the different positional relationships among the Sun, Earth, and Moon depending on the Moon shapes. Third, the class adopting the New Model of Phases of the Moon help preservice teachers form scientific conceptions on the causes of phase change of the Moon. Fourth, the class with the New Model of Phases of the Moon is not appropriate for explaining the reason why only one face of the Moon is seen. Based upon the results above, the researcher realized the limitation of this model and suggested that this model would help learners understand phase change of the Moon and increase space perception ability.

• Journal of the Korean earth science society
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• v.27 no.4
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• pp.353-363
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• 2006

This study investigates how the lunar phases drawing module-applied instruction affects high school students' conceptual changes of the lunar phases. 46 juniors in a high school were given the module instruction on drawing the lunar phases, and then interviews were conducted to verify conceptual changes in subjects' recognition structures. The types of students' misconceptions of the lunar phases change before the instruction were as follows. Type S is that the Earth's shadow covers the moon. Type SR is that one has both misconception of Type S and a scientific concept at the same time according to the positional relationships. The scientific concept means that an observer sees a moon's part which reflects sunlight. Type SB is that the Earth's shadow covers the moon or the moon can be seen or not by the background's brightness according to the positional relationships. The last Type SRB includes all three above-mentioned types, and it explains the lunar phases at each position. As a result of the module-based instruction, 26 out of 36 subjects built up the scientific concept and 10 students did not. 7 out of the 11 Type S and 3 out of the 17 Type SR students did not, either. Especially, type S students did not change their preconception that the phases of moon change were done by the earth's shadow. Here, their preconception is too much strong; as they solve problems, their preconception is more beneficial, comparing to the method which it is presented from the module. This fact supports that it is difficult for students to discard preconception.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.1-6
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• 1998

손가락결합부재에 대한 정적휨시험 및 초음파 비파괴시험을 실시하였다. 발신 및 수신 변환기의 상대 위치와 두 변환기 사이의 거리에 따른 음전달속도의 변화를 분석하였으며 정적 휨시험으로 부터 구한 MOE 및 MOR과 비교하였다. MOR과 음전달속도는 손가락의 경사가 증가할수록 감소하였다. MOR은 음전달속도와 매우 밀접한 상관관계를 보였으나 MOE는 손가락의 경사도나 음전달속도에 큰 영향을 받지 않는 것으로 나타났다. 음전달속도는 섬유방향이 방사방향이나 접선방향에 비하여 더 높은 값을 나타내었다. 발신 및 수선 변환기를 동일면에 부착한 경우에 직각면 또는 반대면에 부착한 경우보다 더 높은 음전달속도를 나타내었다. 변환기 사이의 거리가 증가할수록 음전달속도는 양끝면에 변환기를 부착한 경우의 속도에 수렴하는 경향을 나타내었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.28-28
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• 1998

단일 충돌제트의 경우 충돌면에서의 열전달 효과는 제트 출구와 충돌면 사이의 간격, 노즐 형상에 따른 제트출구의 초기조건, Re$_{D}$수 변화와 충돌면의 형상이나 표면거칠기 등에 따라 변화하게 된다. 그러나 수직 충돌제트의 경우 정체영역에서의 국소적인 열전달 향상은 용이하나 반경 방향으로 열전달이 점차 감소하게 된다. 따라서 충돌면의 전반적인 열전달 향상을 위해서는 열전달이 정체점보다 상대적으로 낮은 영역에서 열전달 향상이 필요하다. 또한, 실제 적용시 충돌면의 형상이나 협소한 공간에서 노즐위치의 제약으로 인하여 충돌제트가 수직으로 분사되는 경우보다 경사진 제트가 더욱 많이 응용된다. 더욱이, 수직충돌제트가 사용되는 많은 상황에서도 주위의 다른 공기 흐름의 영향으로 인하여 실제 제트가 경사각을 갖고 분사되어진다 이러한 경사충돌제트의 중요성에도 불구하고 경사충돌제트에 대한 연구는 수직충돌제트에 대한 연구보다 상대적으로 적게 이루어져 왔다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.271-278
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• 2015

The convective heat transfer of a crossflow fin-tube heat exchanger was studied numerically. In order to investigate the dependence of the heat transfer performance on the fan position, several cases with different blowing and suction types were selected for the fan position. A staggered tube arrangement was used for the heat exchanger, and the temperatures of the tube wall and air were $50^{\circ}C$ and $30^{\circ}C$, respectively. The three-dimensional flow structures were examined based on the results. In addition, the convective heat transfer coefficient and mean temperature difference between the inlet and outlet of the heat exchanger were analyzed for the various fan positions, and the heat transfer performance was investigated

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.100-108
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• 1995

Heat transfer plays a critical role in determining interface location and shape in ZMR process, which is used for the fabrication of silicon - on - insulator structure. In this work, the two - dimensional pseudo - steady - state ZMR model has been developed that can simulate the heat transfer process during ZMR process. It contains the radiation, convection and conduction heat transfer and determines the interface shapes. Numerical solutions from the model include flow field in the molten zone, temperature field in the full SOl structure and the location of solid/liquid interface in the silicon thin film and silicon substrate. We examined the effects of the various system parameters on the temperature profiles and the interface shape.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.99.1-99.1
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• 2012

Hapke의 양방향 분포 함수를 균일하게 입힌 실 크기 3차원 달표면 BRDF 모델을 이용한 달의 조도 수치모사 와 Big Bear Solar Observatory(BBSO)의 달빛 조도 관측 결과를 비교하였다. 1999년 9월 5일 UT9:30에서 UT12:30까지 지구상의 $34^{\circ}$ 15'30.04"N $116^{\circ}$ 55'16.49"W 위치에서 계산된 달의 조도가 관측된 조도와 1% 이내의 차이를 보이는 것을 확인하였다. 이후 검증된 달의 BRDF 모델과 램버시안 산란 지구 모델을 이용해 시간별 전 지구 알베도 추이를 광선 추적 수치 모사한 결과와 실제 BBSO에서의 측정결과 간 1% 이내의 차이를 보이는 것을 확인하여, .BRDF 모델과 광선추적 수치모사 기법의 타당성을 검증하였다.

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.69-78
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• 1999

We have developed an attitude sensing S/W system, one of modules of Mission Analysis System(MAS), which simulates attitude sensing data as almost the same as the real sensor of a satellite in orbit. When attitude elements($alpha,delta$) of a satellite and positions of Earth, Moon, and Sun are given, the S/W system calculates look angles and dihedral angles of each celestial bodies relative to the rotations axis of the satellite. It consists of two sub-modules : One is ephemeris service module which consider the perturbations of four planets(Venus, Mars, Jupiter, Saturn) for positions of Sun and Moon and 4 $\times$4 earth gravitational potential terms for a satellite's position. The other is attitude simulation module which generates attitude sensing data. Varying the rotational axis of a satellite and it's orbital elements, we simulated the generating attitude sensing data with this S/W system and discussed their results.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.507-516
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• 2009

In cases of high-level radioactive waste repositories, heat load is apparent by radioactive waste decay. The safety of a waste repository would be influenced by changing circumstances caused by heat transfer through rock. Thus, a ventilation system is necessary to secure the waste repository. The first priority for building an appropriate ventilation system is completing a computer simulation research with thermal rock properties and a heat transfer coefficient. In this study, the heat transfer coefficient in KURT was calculated using the measurement of inner circumstance factors that include dry bulb and wet bulb temperature, rock surface temperature, and barometric pressure. The heater that is 2 m in length and 5 kw in capacity heats the inside of rock in the research module by $90^{\circ}C$. As a result of determining the heat transfer coefficient in the heating section, the changes of heat transfer coefficient were found to be a maximum of 7.9%. The average heat transfer coefficient is approximately 4.533 w/$m^2{\cdot}K$.