• Journal of Astronomy and Space Sciences
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• 제6권2호
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• pp.127-135
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• 1989

연세대학교 천문대의 60cm와 40cm 반사망원경을 이용하여 1982년 4월 부터 1985년 5월까지 Epsilon Aurigae를 UBV 관전측광하여 총 1065 관측점을 얻었다. 우리의 광도곡선에 다른 천문대들의 관측자료를 합하여 제1극심의 광도곡선을 완성하였다. 이 광도곡선에서 2차적인 광도변화, 폭발현상, 식중심의 밝아짐 등에 관하여 자세히 조사하고, 제1그심의 각 접촉시각들과 중심식 시각을 결졍하여 다른 연국자들이 정한 값들과 비교하였다. 과거의 식들에서 구한 값들과 비교한 결과, 식이 일어나는 전체기간은 계속 감소하는 반면 완전식의 기간은 계속 증가하였다. 현재 가장 널리 통용되는 디스크 모델에 위의 여러 현상들을 적용하여 보았으나 명확히 설명되지 않았다. 그래서 새로운 모델인 혜성 모델을 만들어 광도곡선에 나타난 현상들을 해석하여 보았다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.511-514
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• 2004

Proposed about new inverter that can use in PV system in this paper. Multi_level inverter that used inverter makes use of 4 transformers is basis, primary winding of each transformer voltage as can do step_up or step_down to appropriate voltage space tap lake. Put circuit that tap that turn in transformer connects properly according to inhibit signal that sense change of input voltage (output voltage of solar cell place) and transformer secondary voltage controls point of contact of relay so that get into fixed output voltage. As a result, can minimise relative harmonic content despite change width of input voltage are wide because number of output voltage level of multi_level inverter does not decrease. Because proposed circuit manufactures is easy and control is easy and is no burden of cost price rise economically, commercialization expected to do easily and this study examined propriety of action as that compose and experiments proposed circuit.

• 한국과학교육학회지
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• 제8권1호
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• pp.57-72
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• 1988

It is very important for a teacher to know what his students know and what they do not; however, it seems not true for the most Korean secondary school science techers. This study tried to find students' misconception Newton's third law and the sources of the misconceptions. The researcher examined 609 students from middle schools, high schools, and college. In this study, students' understanding on Newton's third law were examined by school level, sex, stream (science and liberal arts), and departments. The following results were obtained by this study. 1. Students' understanding seemed to be improved continuously from middle school to university; however, their misconception (the most frequent incorrect selection of options of the test items) did not changed very much. 2. Students' answers were significantly affected by size of objects, existence of physical contact and the existence of life in the objects. 3. The answer were significantly affected by the source of attraction. 4. The answer to Newton's third law were affected by the magnitude of potential force which the target bodies have, state of motion, velocity, weight, friction and acceleration. This study could show the sources of the misconception on Newton's third law. The identified sources could be very useful for designing an instruction to teach Newton's third law in schools and universities.

• 제어로봇시스템학회논문지
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• 제14권4호
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• pp.385-391
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• 2008

To effectively cope with a complexity of kinematic metrology due to workspace enlargement of the planar stage, the linear induction motor is suggested as its new driving source. Especially, the linear induction motor under uniform plate type of secondary doesn't inherently have a periodical force ripple which is generally shown in the brushless DC motor. But, it presents a poor transient characteristic at zero or low speed zone owing to time delay of flux settling, resulting in slow response. To improve the servo property of linear induction motor and apply successfully it to the precision stage, this paper discusses a modified vector control methodology. The controller has a novel input form, fixed d-axis current, q-axis current and forward-fed DC current, to control thrust force and normal force of the linear induction motor independently. Influence of the newly introduced input and the feasibility of controller are validated experimentally.

• 한국소음진동공학회논문집
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• 제16권9호
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• pp.904-911
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• 2006

A modified energy method for the fretting wear of the steam generator tube is proposed to calculate the wear-out depth between the nuclear steam generator tube and its support. Estimation of fretting-wear damage typically requires a non-linear dynamic analysis with the information of the gap velocity and the flow density around the tube. This analysis is very complex and time consuming. The basic concept of the energy method is that the volume wear rate due to the fretting-wear phenomena Is related to work rate which is time rate of the product of normal contact force and sliding distance. The wearing motion is due to dynamic interaction between vibrating tube and its support structure, such as tube support plate and anti-vibration bar. It can be assumed that the absorbed work rate would come from turbulent flow energy around the vibrating tube. This study also numerically obtains the wear-out depth with various wear topologies. A new dissection method is applied to the multi-span tubes to represent the vibrational mode. It turns out that both the secondary side density and the normal gap velocity are important parameters for the fretting-wear phenomena of the steam generator tube.

• 아동학회지
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• 제31권3호
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• pp.51-66
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• 2010

This study examined the effects of parental attachment and peer attachment in elementary school children upon early adolescent delinquency. The participants were 2,844 taken from data from the Korean Youth Panel Survey (KYPS). Data from secondary questionnaires data on parent and peer attachment, problem behavior, delinquent peers, and delinquency were used for this study. Data were analyzed by means of a Structural Equation Model using AMOS 5.0. Our results indicated that, firstly, parental attachment was negatively related to problem behavior for both male and female adolescents, whereas peer attachment was positively related to problem behavior only for males, but not for females. Secondly, problem behavior in childhood has a direct effect on adolescent delinquency, which also can be indirectly mediated by contact with delinquent peers. In conclusion, the path model from parental and peer attachment in early childhood to adolescent delinquency was supported only in the case of males.

• 성인간호학회지
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• 제28권6호
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• pp.659-668
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• 2016

Purpose: This study utilized secondary data and investigated the factors associated with life satisfaction by living arrangements among community-dwelling adults aged 65 years or older in Korea. Methods: A total of 2,134 participants were selected from the 2014 Korean Longitudinal Study of Aging (KLoSA). Univariable and multivariable logistic regression were used for data analysis. Results: The significant factors associated with life satisfaction in older adults living with others were education level (odds ratio [OR] 1.73, 95% confidence interval [CI] 1.41~2.11), place of residence in medium-size city (OR 1.57, 95% CI 1.25~1.97), place of residence in rural town(OR 1.52, 95% CI 1.19~1.95), depression (OR 2.99, 95% CI 2.43~3.68), frequency of contact with neighbors (OR 1.39, 95% CI 1.10~1.76), and social participation (OR 1.48, 95% CI 1.14~1.93). In contrast, factors associated with life satisfaction among older adults living alone were education level (OR 1.93, 95% CI 1.15~3.24) and depression (OR 2.49, 95% CI 1.48~4.19). Conclusion: These findings indicated that nursing interventions for improving life satisfaction among older adults should take into account their specific living arrangements.

• Tribology and Lubricants
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• 제4권1호
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• pp.43-55
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• 1988

A Study on the effect of the additives in lubricating oil was investigated on the basis of the thermal activated wear theory in terms of their wear behaviours, using four ballwear machine. The sample oils, which included diethyl-3, 5-di-t-butyi-4-hydroxy-benzyl phosphonate (DEP), ZDDP and TCP additives respectively, showed distinct wear characteristics depending upon the bulk oil temperature and the sliding velocity. The newly synthesized additive, viz., DEP showed excellent antiwear performance cornpared with the conventional additives, ZDDP and TCP. On the basis of the experimental results, it is reduced that the wear mechanism of the conventional additives, viz., ZDDP and TCP is the protective film formation and their antiwear capability is depending upon the shearing strength of the film formed. On the other hand, the new additive, DEP showed that the secondary activation energy was much eliminated and so, the thermal instability was reduced by the hydrogen scavenging reaction of the new additive, which was virtually an endothermic reaction process.In conclusion, a new concept of antiwear mechanism is estabilished and testified. And new chemical, which showed the function of hydrogen and free radical scavenging role, is synthesized and introduced as the new, highly antiwear effective lubricating oil additive.

• 대한기계학회논문집
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• 제10권5호
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• pp.593-600
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• 1986

본 연구에서는 베어링과 같은 기계 회전부품의 정밀진동분석을 위한 구동장치 로서 평판 자기결합기를 갖는 회전장치를 제작하였다. 이 회전장치의 진동특성을 고 찰하기 위해 Weinmann 등의 연구결과에 따라 자기 결합기의 전달 토오크가 그대로 피 동축에 전달됨을 이용하여 이론전개를 하였으며 이 결과를 실험치와 비교하였다.

• Animal Systematics, Evolution and Diversity
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• 제32권2호
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• pp.105-111
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• 2016

The genetic structure of marine animals that inhabit the seashore is affected by numerous factors. Of these, gene flow and natural selection during recruitment have strong influences on the genetic structure of seashore-dwelling species that have larval periods. Relative contributions of these two factors to the genetic structure of marine species would be determined mainly by the duration of larval stage. The relationship between larval period and genetic structure of population has been rarely studied in Korea. In this study, genetic variations of cytochrome oxidase subunit I (COI) were analyzed in two dominant species on rocky shore habitats in the Korean peninsula: periwinkle Littorina brevicula and acorn barnacle Fistulobalanus albicostatus. Both species are not strongly structured and may have experienced recent population expansion. Unlike periwinkle, however, barnacle populations have considerable genetic variation, and show a bimodal pattern of mismatch distribution. These results suggest that barnacle populations are more affected by local adaptation rather than gene flow via larval migration. The bimodal patterns of barnacle populations observed in mismatch distribution plots imply that they may have experienced secondary contact. Further studies on seashore-dwelling species are expected to be useful in understanding the evolution of the coastal ecosystem around Korean waters.