• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.126-131
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• 2003

A series of computational simulations have been carried out for supersonic flows in a scram jet engine with and without a cavity. Transverse injection of hydrogen, a simplest form of fuel supply, is considered in the present study with the injection pressure varying from 0.5 to 1.5 MPa. The corresponding equivalence ratios are 0.167 - 0.50. The work features detailed resolution of the flow dynamics in the combustor, which was not typically available in most of the Previous studies. In particular, oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between shock waves and shear layer may cause a large excursion of flow oscillation. The role of the cavity and injection pressure are examined systematically.

• 대한수학교육학회지:수학교육학연구
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• 제14권4호
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• pp.367-385
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• 2004

이 연구에서는 남북한 초등학교 교과서에서 분수를 도입하는 과정을 분할분수와 동치분수로 나누어 비교하여 차이점을 파악하고 그에 관해 반성적으로 논의를 전개하였다. 논의 결과, 남한 교과서는 사과와 같은 구체물을 등분할하는 활동의 소재로 사용하고 있으나, 북한 교과서에는 그와 같은 구체물을 실제로 등분할하는 활동은 제시되어 있지 않았다. 남한의 교과서는 연속량의 등분할과 이산량의 등분할을 시간 간격을 두고 다루는데 비해, 북한 교과서는 분수 도입 시점에서 같이 다룬다는 것도 확인하였다. 측정 단위가 붙은 양분수의 사용 측면에서도 남북한 교과서는 차이를 드러냈다. 또한 외연적 방법에 따라 분수를 도입한다는 점에서는 공통적이지만, 남한과 북한은 활동과 의미에 어느 정도 초점을 두는가에 있어서 차이를 보였다. 동치분수를 도입하는 방식을 비교한 결과, 세 가지 차이점을 확인하였다. 가장 큰 차이는 동치분수를 구하는 직접적인 방법을 제공하는가, 동치분수의 특성과 동치 분수를 구하는 방법에 대한 탐구를 자극하는가하는 측면에서 확인할 수 있었다.

• Child Health Nursing Research
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• 제7권1호
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• pp.21-34
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• 2001

The impact of childhood experience has lifelong significance on subsequent health and development. Especially, the experience of infant is mostly affected by the quality of parental care and rearing environment. But the new mothers usually do not know what to do because of the lack of experience in these days. Therefore, an educational program regarding maternal role would be necessary. This study was conducted to evaluate the effectiveness of the maternal role education program for mother-infant interaction, child-rearing environment, and infant development. Non-equivalent control group time-series design was used, and Barnard's mother-infant interaction model was used as a conceptual framework of this study. The subjects were the healthy infants weighing over 2,500gm at birth, whose gestational age was more than 37 weeks, and their mothers. The final sample consisted of 19 mother-infant dyads for intervention group and 18 dyads for control group. Data were collected from March 15th to September 3rd in 1999. For the intervention group, programmed education which focused on mother-infant interaction, breast feeding, and infant care was provided before discharge. Telephone counselling was provided within one week after discharge. Home visiting for maternal role education was provided twice, one month and three months postpartum. For the control group, home visiting was also conducted but only for data collection. The data were analyzed using chi-square test and t-test to test the equivalence of two groups, and the effectiveness of intervention program was determined with repeated measure ANCOVA and t-test. The results were as follows: 1. Significant differences were found in mother-infant interaction between two groups(p=.000). It indicates that intervention program was effective in improving mother- infant interaction. In subscale analysis, four out of six subscale showed significant differences between the groups: sensitivity to cues (p=.000), social-emotional growth fostering (p=.000), cognitive growth fostering(p=.000) in mothers, and responsiveness to caregiver (p=.019) in infants. 2. The difference in the mean score of childrearing environment (HOME) between the intervention group and control group was significant(p=.003). When each subscale of HOME was examined individually, intervention group showed significantly higher scores in the diversity of stimulation(p=.000), and mother's involvement(p=.001). 3. Three-month-Infants of the intervention group showed higher GQ in the Griffiths mental development scale(p=.026). In subscale analysis, significant differences were found in the personal-social(p=.005), and the hearing and speech(p=.003). In conclusion, the maternal role education program proved to be effective in promoting the mother-infant interaction, organizing the childrearing environment, and fostering the infant development. These results are very meaningful that we found maternal role education necessary for normal infants' mothers, and that nurses can make a great contribution in promoting health of infants and mothers.

• 한국유기농업학회지
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• 제24권3호
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• pp.369-383
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• 2016

Crop yield insurance program in Korea has rapidly grown not only in quantity but in quality for 15 years since it was introduced in 2001. Despite growth of Crop insurance, performance evaluation for crop yield insurance has not fully been evaluated at the farm, consumer and national level. The purpose of this study is to conduct the performance evaluation for crop yield insurance through estimating the effects of farm revenue stabilization and social welfare increase with three popular insurance items: apple, pear and sweet persimmon. Based on the analysis of social welfare effect, cost-benefit analysis of operating crop yield insurance was conducted at the national level. We found that crop yield insurance stabilizes farm revenue based on the estimated four risk indicators: Coefficient of Variation, Value at Risk, Certainty Equivalence, and Risk Premium. The result of cost-benefit analysis shows that crop yield insurance increases social net benefit by 44.1 billion won for the three items. As a result, crop yield insurance program has contributed remarkably on social welfare as well as farm management and its role will be more important in the future.

• Molecules and Cells
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• 제25권2호
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• pp.172-177
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• 2008

Eukaryotic translation initiation factor 5B (eIF5B) plays a role in recognition of the AUG codon in conjunction with translation factor eIF2, and promotes joining of the 60S ribosomal subunit. To see whether the eIF5B proteins of other organisms function in Saccharomyces cerevisiae, we cloned the corresponding genes from Oryza sativa, Arabidopsis thaliana, Aspergillus nidulans and Candida albican and expressed them under the control of the galactose-inducible GAL promoter in the $fun12{\Delta}$ strain of Saccharomyces cerevisiae. Expression of Candida albicans eIF5B complemented the slow-growth phenotype of the $fun12{\Delta}$ strain, but that of Aspergillus nidulance did not, despite the fact that its protein was expressed better than that of Candida albicans. The Arabidopsis thaliana protein was also not functional in Saccharomyces. These results reveal that the eIF5B in Candida albicans has a close functional relationship with that of Sacharomyces cerevisiae, as also shown by a phylogenetic analysis based on the amino acid sequences of the eIF5Bs.

• Journal of Magnetics
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• 제20권3호
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• pp.284-289
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• 2015

This paper discusses general methods of modelling magnetic saturation in steady-state, two-axis (d & q) frame models of dual stator induction generators (DSIG). In particular, the important role of the magnetic coupling between the d-q axes (cross-magnetizing phenomenon) is demonstrated, with and without cross-saturation. For that purpose, two distinct models of DSIGs, with and without cross-saturation, are specified. These two models are verified by an application that is sensitive to the presence of cross-saturation, to prove the validity of these final methods and the equivalence between all developed models. Advantages of some of the models over the existing ones and their applicability are discussed. In addition, an alternative is given to evaluate all saturation factors (static and dynamic) by just calculating the static magnetizing inductance which is simply the magnitude of the ratio of the magnetizing flux to the current. The comparison between the simulation results of the proposed model with experimental results gives a good correspondence, especially at startup.

• 대한기계학회논문집
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• 제13권2호
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• pp.265-270
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• 1989

본 연구에서는 복사강도를 반구에 대하여 적분하여 비정상 미분방정식의 형태로 로 얻어지는 2-유속 회매질복사모델을 사용하여 복사전달방정식을 구성하고, 전술한 Yoshizawa 등의 가정을 배제하면서, 다공매질의 물리적 길이, 흡수계수 및 혼합기체의 당량비(equivalenceratio) 등을 변화시킴으로써 매질 내의 열적 구조를 분석하여 그들의 의 연구를 확장, 해석한다.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1366-1377
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• 2005

Experimental study was carried out in an atmospheric pressure, laboratory-scale dump combustor showing features of combustion instabilities. Flame structure and heat release rates were obtained from OH emission spectroscopy. Qualitative comparisons were made between line-integrated OH chemiluminescence image and Abel-transformed one. Local Rayleigh index distributions were also examined. Mean temperature, normalized standard deviation and temperature fluctuations were measured by coherent anti-Stokes Raman spectroscopy (CARS). To see the periodic behavior of oscillating flames, phase-resolved measurements were performed with respect to the pressure wave in the combustor. Results on system damping and driving characteristics were provided as a function of equivalence ratio. It also could be observed that phase resolved temperatures have been changed in a well-defined manner, while its difference between maximum and minimum reached up to 280K. These results would be expected to play an important role in better understanding of driving mechanisms and thermo-acoustic interactions.

• 한국어교육
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• 제28권4호
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• pp.87-119
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• 2017

The purpose of this study is to classify research methods used in Korean language education studies with a focus on identifying how and what quantitative research methods are utilized in these studies. Analyzing articles published in the Journal of Korean Language Education from 2005 to 2016, we found a trend that as a replacement for secondary research, primary research played a more prominent role after 2010, as the number of quantitative studies and studies using mixed methods increased. We also found that within quantitative studies of Korean language education, research themes and statistical analyses became diversified after 2010. In order for quantitative research to contribute continuously to Korean language education, the quality of research has to improve. In particular, quantitative researchers in this area should: (a) increase their general understanding of statistical methods, (b) conduct "power analysis" to determine the appropriate sample size for hypothesis testing, and (c) be aware of measurement issues such as measurement equivalence and DIF when measuring latent psychological constructs. It is also important to notice that these points above should be considered carefully in the planning and designing stage for researchers.

• 한국추진공학회지
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• 제15권4호
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• pp.26-34
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• 2011

스월러를 가진 천연가스 연료분사기가 장착된 희박 예혼합 연소기에서 화염구조의 일부분인 재순환 영역의 형성이 연소불안정에 미치는 영향에 대하여 실험적으로 연구를 진행하였다. PIV 계측기법으로 연소장에서의 화염의 안정화 그리고 불안정한 영역에서 유동장을 확인해본 결과 스월러에 의한 재순환 영역은 화염의 안정화 및 난류의 강도뿐만 아니라 재순환영역 형성의 크기에 따른 화염 재점화에도 영향을 미쳐 연소불안정 발생의 원인이 되는 열방출 섭동과 매우 밀접한 관계가 있음을 확인하였다.