• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.6
• /
• pp.1547-1555
• /
• 1993

An experimental study on convection heat transfer characteristics from a heated tube to an oscillating flow has been carried out, . This problem is of particular interest in the design of heat exchangers in Stirling cycle machines. Experimental system has been developed to measure temporal variations of temperature inside a heater tube during oscillating modes in a Stirling cycle machine. The dependence of temperature distributions and heat transfer rates on the oscillating frequency as well as the swept volume ratio and the mean pressure of a Stirling cycle machine is investigated in detail. The experimental results indicate that the measured temporal variations of temperature become nearly sinusoidal. The amplitude of temperature variation in the core of the tube is much more substantial than that near the tube wall, whereas the reverse is true for pulsating flows. It is also found that the heat transfer rate is increased significantly as the oscillating frequency or oscillating amplitude or the mean pressure in a tube is increased.

• Journal of the Korean earth science society
• /
• v.25 no.7
• /
• pp.519-531
• /
• 2004

The purpose of this study was to ascertain high school student ideas on the motion of the Earth and moon by cognitive level. For this study, five students determined to be of high, middle and low cognitive level selected from 73 10th-grade students at a high school located in Suwon, Gyeonggido. The results of this study were as follows: first, students at the high cognitive level had comparatively more logical and scientific conception on the revolution and rotation of the Earth and moon. second, students at the middle cognitive level, generally had a passive learning attitude to unconditionally memorize learned contents, so they were apt to forget learned contents, also their recognized conception was not enlarged. In addition, they had native theories, intuitive ideas and misconceptions as well as made logical errors in the course of explanation for the motion of the Earth and moon. In the course of explanation for the phases of the moon and the cause of change of season, because of their scientific conception, the students made more and more errors in conception. finally students at the low cognitive level were not willing to think logically and positively and were very passive in the attitude to recognize conception. In addition, they have learned helplessness on the grounds that they have low scholastic achievement specially in science.

• Journal of The Korean Association For Science Education
• /
• v.13 no.1
• /
• pp.1-11
• /
• 1993

1980년 이래로 자연현상에 관한 유년적 사고에 관한 연구가 국내,외에 활발히 보고되어 왔지만, 그 근원에 관한 연구는 다소 소홀히 다루어져 왔다. 연구는 천문학에 관한 학생들의 유년적 사고와 그 사고의 근원을 조사한 것이다. 이의 대상은 국민학교 6학년 5명, 중학교 2학년 5명, 고등학교 1학년 5명으로 하였다. 연구방법으로는 질문지법(Open-ended Written Questions)과 면접법(Interview)을 이용하였다. 이 연구에서는 계절 변화, 달 위상 변화의 원인에 관하여, 국민학생에서 고등학생에 이르기까지 대다수의 학생들이 유년적 사고를 지니고 있는 것으로 밝혀졌고, 이들 유년적 사고의 근원으로는 '학교 교사'와 '교과서' 라고 대답하는 학생이 대부분으로 나타났다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.3
• /
• pp.809-823
• /
• 1991

본 연구에서는 Wiener 필터링 이론에 의하여 소음원의 입력신호에 대한 최적 한 예측을 할 수 있는 최적예측기(optimal predictor)로써 부가적인 음을 발생시키고 입력신호 및 출력신호 간의 차인 오차를 최소화시키도록 하는 적응신호처리방법에 대 해 설명하고 이러한 적응 신호처리 방법을 이용한 능동 소음 제어 방법을 제시하였다. 이와 아울러 제어계의 환경 변화에 따른 파라메타의 변화에 적응적으로 응답이 가능해 야 하는 적응 소음 제어계에서, 음향궤환과 함께 필히 고려해야하는 부가적인 전달함 수-모델과 스피커를 포함하는 보조경로 및 오차미이크로폰을 포함하는 오차경로의 전 달함수의 영향을 고려한 능동소음제어에 대해 연구하였다.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.18 no.4
• /
• pp.374-380
• /
• 1985

The annual variations of sea surface temperature (SST), air temperature (AT), and sea-air temperature separation (SST-AT) in the East Sea (Japan Sea) are studied by harmonic analysis of the monthly data in 2 by 2 degree rectangles. In the Tsushima Current region of the Japan Sea, the annual means of SST and AT are high due to warm water advection by the current, and the annual amplitudes of SST and AT are small because the annual variations of heat advection the the current and of the incoming solar radiation are almost out of phase each other. In summer the SST and the AT in the Japan Sea are almost the same, but in winter the SST is $6{\sim}10^{\circ}C$ higher than the AT. The physical processes responsible for the observed SST-AT in the Japan Sea and their consequences in the sea-air thermal interactions are discussed in this paper.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.10a
• /
• pp.118-124
• /
• 2003

응축기, 증발기, 전열관에 사용되는 Fin Tube는 열전달효율 향상을 위하여 Fin의 높이 를 증가시키고, Tube의 최소두께를 얇게 가공하는 경향으로 발전하고 있다. 따라서, Fin Tube의 와전류탐상(ECT; Eddy Current Testing)에 의한 결함검출에 더욱 어려움이 예상된다. 본 연구에서는 Fin Tube의 Fin 높이를 3단계로 변화시켜 Tube를 제작하고, Tube에 축 방향결함, 원주방향결함, 원형결함을 각각 Fin Tube의 안쪽에 최소두께의 20%, 40%, 60% 의 동일결함율을 갖는 인공결함 시험편을 제작하였다. 제작한 원형결함시험편에 와전류탐상을 수행하여 Fin 높이에 따른 최적주파수의 변화를 연구하였다. Fin높이가 다른 원형결함 시험편에 1~20KHz 주파수를 적용한 결과 최적주파수는 12KHz로 Fin높이에 크게 영향을 받지 않음을 밝혔다 또한 Fin높이에 따른 최적주파수변화는 크지 않으나 Fin 높이가 높을수록 100%관통결함의 위상각(40')에 근접하여 나타났다. 축방향결함, 원주방향결함, 원형결함을 갖는 시험편에 와전류탐상을 수행한 결과 원형결함을 갖는 시험편의 신호 감도가 축방향결함, 원주방향결함보다 좋게 나타났다.

• Korean Journal of Remote Sensing
• /
• v.35 no.2
• /
• pp.265-278
• /
• 2019

Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) data help to enable rapid emergency responses through detection of the artificial and natural disasters occurring at night. The DNB data without correction of lunar irradiance effect distributed by Korea Ocean Science Center (KOSC) has advantage for rapid change detection because of direct receiving. In this study, radiance differences according to the phase of the moon was analyzed for urban and mountain areas in Korean Peninsula using the DNB data directly receiving to KOSC. Lunar irradiance correction algorithm was proposed for the change detection. Relative correction was performed by regression analysis between the selected pixels considering the land cover classification in the reference DNB image during the new moon and the input DNB image. As a result of daily difference image analysis, the brightness value change in urban area and mountain area was ${\pm}30$ radiance and below ${\pm}1$ radiance respectively. The object based change detection was performed after the extraction of the main object of interest based on the average image of time series data in order to reduce the matching and geometric error between DNB images. The changes in brightness occurring in mountainous areas were effectively detected after the calibration of lunar irradiance effect, and it showed that the developed technology could be used for real time change detection.

• Journal of the Korean Society of Earth Science Education
• /
• v.8 no.1
• /
• pp.56-65
• /
• 2015

The purpose of this study is to investigate how elementary school student understands or students understand the illustrations on the phase change of the Moon in science textbook and to find out how textbook illustration helps students form the conception of the phase change of the Moon. To identify this purpose, we selected illustrations on the phase change of the Moon in the science textbook revised in 2007 and 2009 revised science textbook. For this study we selected and interviewed 20 students in the fifth grade. We integrated all data collected through interviews and created a transcription and a protocol and then, confirmed scientific conceptions related to the phase change of the Moon in students' illustration reading. The result are as followings: First, students read more scientific conceptions related to the phase change of the Moon in illustration of the 2009 revised science textbook which is presented with the universal observer's view point and the earth observer's view point. Second, students who find meaning in the various elements of the illustration and interpret with the integration of the various elements, get a lot of relevant information from illustration. All students have no differences recognizing the elements presented in illustration. But there are differences of contents of illustration reading depending on how students interpret the illustrations with integration of the various elements and if students cannot figure out the four scientific concepts needed to understand the phase change of the Moon, they ignore the information provided by illustration or analysis in their own way according to information provided by illustration. So misconception appears in this process.

• Journal of the Korean association of regional geographers
• /
• v.12 no.6
• /
• pp.656-670
• /
• 2006

In Gcochang-Gun, the population decrease, due to a rural exodus phenomenon, has led to the absolute decline in the numbers of both primary and secondary schools and students. However, the high schools in Geochang-Gun show an unusual characteristic that the students from other areas outside Geochang-Gun cover about 25% of the total students studying in Geochang-Gun. This is quite contrary to the contention that one of the major factors hindering the development of rural areas is generally the inferior condition of education. In this context, this paper aims to explore the spatio-temporal changes in the sphere of influence of the secondary education with special reference to Geochang-Gun, Gyeongnam. Most importantly Geochang High School and Geochang Daesung High School account for over 98% of the students coming from other areas outside Geochang-Gun's cross-border counties. This means that the sphere of influence of the Geochang's secondary education is dependent largely upon the two private academic high schools.

• Proceedings of the KSRS Conference
• /
• 2007.03a
• /
• pp.177-182
• /
• 2007

한반도 주변해역에서의 해수면 고도는 1993년부터 2005년까지의 기간 동안 연평균 3.89 mm $yr^{-1}$ 상승하였으며， 이는 전세계 해수면 상승률의 1.3배에 해당한다. 본 연구에서는 AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic data)에서 제공하는 복합위성자료 (Topex/Poseidon, Jason-1, ERS, Envisat)인 DT-MSLA (Delayed Time - Maps of Sea Level Anomalies)를 이용하여 동해와 황해, 남해, 한국해협에서의 해수면 고도 변화를 연구하였다. 해수면 고도의 평균적인 변화는 증가하는 경향을 보임과 동시에, 여름에는 $4{\sim}5$년，겨울에는 3년의 주기성을 가지고 진동하였다. 조화분석을 통하여 해수면 고도와 해수면 온도의 연주기 모드와 반년주기 모드의 진폭과 위상을 나타내었다. 해수면 고도의 연주기 진폭은 한반도 주변해역에서 남동쪽이 높게，북서쪽이 낮게 나타나는 반면, 해수면 온도는 이와는 반대의 분포를 보였다. 월별 해수면 고도와 해수면 온도의 상관을 구한 결과，$6{\sim}8$월에 동해와 남해에서 1 / 2달 시간지연 일 때，상관계수가 0.7정도로 높게 나타났다. 이러한 결과를 통해 여름철 동해와 남해가 쿠로시오 해류의 영향을 크게 받고 있음을 짐작할 수 있다.