• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.445-452
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• 2011

The present work addresses structural characteristics of natural gas flames in a lean premixed swirl-stabilized combustor with an attention focused on the effect of the formation of recirculation zones on the combustion instability. It is known that the recirculation zone plays an important role in stabilizing a turbulent, premixed natural gas flames by providing a source of heat or radicals to the incoming premixed fuel and air. To improve our understanding of the role of recirculation zones, the flame structure was investigated for various mixture velocities, equivalence ratios and swirl numbers. The optically accessible combustor allowed for the application of laser diagnostics, and Particle Image Velocimetry(PIV) measurements was used to characterize the flame structure under both cold flow conditions and hot flow conditions. Dynamic pressures were also measured to investigate characteristics of combustion at the same time. The results indicates that the formation of recirculation zone is strongly related to the occurrence of thermo-acoustic instabilities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.423-430
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• 2017

This study examined the effects of role rotation experience on learning flow, self leadership and debriefing satisfaction in nursing students. A non-equivalence control group quasi-experimental study was used and included as participants 203 junior nursing students at Y University. The experimental group (n=103) participated in the teaching class using a role rotation experience, while the control group (n=100) received conventional practice education. The outcome measurements were learning flow, self leadership, and debriefing satisfaction. The collected data were analyzed using a chi-test, and at-test using the SPSS WIN 21.0 program. The total score of learning flow and self leadership were similar in the two groups. On the other hand, in the case of the debriefing satisfaction (t=-2.70, p=.008), the experimental group ($4.24{\pm}0.51$) was remarkably higher than the control group ($4.03{\pm}0.60$). Although the changes regarding the learning flow and self leadership could not be identified, the debriefing satisfaction had been affected by the practice education using the role rotation experience. Therefore, to identify the effects of simulation education for further details, more research with diversified subjects and varied durations is needed.

• Child Health Nursing Research
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• v.7 no.1
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• pp.96-107
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• 2001

Recent research indicates that the new mothers want to learn about childrearing, and have burden in care of infants. Also it indicates that the new mothers say the lack of confidence and knowledge about infant care. This study was a prospective longitudinal reseach developing parent role education program and evaluating the effectiveness of this program for mother-infant interaction, childrearing environment and infant development. Longitudinal quasi-experimental design was used. The subjects were the healthy infants weighing over 2,500gm at birth, whose gestational age was more than 37weeks, and their mothers. The sample consisted of 19 mother-infant dyads for intervention group and 18 dyads for control group. Data were collected from March 15th to December 14th in 1999. For the intervention group received programmed education that was consisted of discharge education, telephone counselling, and home visiting for maternal education. The data were analyzed using chi-square test and t-test to test the equivalence of two groups, and the effectiveness of intervention program. This study was focused on the results of six months time point. The results were as follows: 1. There was significant difference in the mean score of mother-infant interaction(NCAST) between two groups. Intervention group showed higher scores in the subscales of sensitivity to cues, cognitive growth fostering, and caregiver total. 2. There was no significant difference in the mean score of child rearing environment (HOME) between two groups of six-month-infants. But when each subscale of HOME was examined, intervention group showed higher scores in the dimensions of opportunities for variety in daily stimulation, maternal involvement with child, and emotional, verbal response. 3. Six-month-infants of the intervention group showed significantly higher GQ in the Griffiths mental development scale. In conclusion, the maternal education program was effective in promoting the mother-infant interaction, organizing the childrearing environment, and fostering the infant development. These results were very meaningful that we found parent role education necessary for normal infants' mothers, and nurses can make a great contribution in promoting health of infants and mothers.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.79-84
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• 2004

For the non-premixed interacting jet flames, it has been reported that if eight small nozzles are arranged along the circle of 40 $^{\sim}$ 72 times the diameter of single jet, the flames are not extinguished over 2oom/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, ${\Phi}$, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying Sand ${\Phi}$ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with ${\Phi}$ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of fuel through the centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was different from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.125-134
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• 2015

This is the third paper on the combustion characteristics of the landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine. It is the first in this series to discuss the effects of the torch device on combustion. The results show that an optimum orifice ratio exists regardless of the torch volume, and a few adverse effects on the combustion are observed for an excessively small orifice ratio. In addition, the torch ignition decreases the initial burn duration, and the decrease in the heat transfer caused by this decreased duration contributes to an increase in the peak combustion pressure. Finally, the torch mostly plays a positive role in shortening the main burn duration when the combustion condition is worsened by a lower methane fraction. Yet, the torch decreases the initial burn duration rather than the main burn as the methane fraction increases.

• The Journal of the Korea Contents Association
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• v.18 no.9
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• pp.623-632
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• 2018

Both investors and researchers are attentive to the prediction of stock price movement directions since the accurate prediction plays an important role in strategic decision making on stock trading. According to previous studies, taken together, one can see that different factors are considered depending on stock markets and prediction periods. This paper aims to analyze what data mining techniques show better performance with some representative index and stock price datasets in the Korea stock market. In particular, extreme gradient boosting technique, proving itself to be the fore-runner through recent open competitions, is applied to the prediction problem. Its performance has been analyzed in comparison with other data mining techniques reported good in the prediction of stock price movement directions such as random forests, support vector machines, and artificial neural networks. Through experiments with the index/price datasets of 12 years, it is identified that the gradient boosting technique is the best in predicting the movement directions after 1 to 4 days with a few partial equivalence to the other techniques.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.602-610
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• 2001

In the MPLS(Multiprotocol Label Switching) forwarding paradigm, once a packet is assigned to a FEC(Forwarding Equivalence Class), no further header analysis is done by subsequent routers; all forwarding is driven by the labels. This has a number of advantages over conventional network layer forwarding. The MPLS LER(Label Edge Router) is located at the boundary of MPLS domain and plays a role in connecting with the existing Internet as an ingress or an egress router. That is, the MPLS LER as an ingress router assigns a label to a packet which enters the MPLS network from the Internet by analyzing its header and forwards to a corresponding next router in MPLS domain. As an egress router, the MPLS LER turns the packets out of the MPLS network by performing the reverse operation. In this paper, we analyze the traffic performance of an MPLS LER system and estimate the IP(Internet Protocol) packet processing capacity of the system using queueing model and simulation. It is found that the maximum IP packet processing capacity of the system is estimated by 420,000 through 460,000 packets/sec.

• Journal of Korean Academy of Nursing
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• v.42 no.7
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• pp.974-983
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• 2012

Purpose: The purpose of this study was to translate the Spiritual Perspective Scale (SPS) and Self-transcendence Scale (STS) into Korean and test the psychometric properties of the instruments with Korean elders. Methods: A cross-sectional survey design was used to implement the three stages of the study. Stage I consisted of translating and reviewing the scales by six experts. In Stage II, equivalence was tested by comparing the responses between the Korean and English versions among 71 bilingual adults. Stage III established the psychometric properties of the Korean versions SPS-K and STS-K among 154 Korean elders. Results: Cronbach's alpha of the SPS-K and the STS-K .97, and .85 respectively with Korean elders. Factor analysis showed that the SPS-K had one factor; the STS-K had four factors with one factor clearly representing self-transcendence as theorized. Both scales showed good reliability and validity for the translated Korean versions. However, continued study of the construct validity of the STS-K is needed. Conclusion: Study findings indicate that the SPS-K and the STS-K could be useful for nurses and geriatric researchers to assess a broadly defined spirituality, and to conduct research on spirituality and health among Korean elders. Use of these scales within a theory-based study may contribute to further knowledge about the role of spirituality in the health and well-being of Korean people facing health crises.

• Education of Primary School Mathematics
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• v.14 no.3
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• pp.261-275
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• 2011

We observed the process for solving linear equations of two 5th grade elementary students, who do not have any pre-knowledge about solving linear equation. The way of students' usage of fractional schemes and manipulations are closely observed. The change of their scheme adaptation are carefully analyzed while the coefficients and constants become complicated. The results showed that they used various fractional scheme and manipulations according to the coefficients and constants. Noticeably, they used repeating fractional schemes to establish the equivalence relation between unknowns and the given quantities. After establishing the relationship, equivalent fractions played important role. We expect the results of this study would help shorten the gap between the arithmetic and the algebraic thinking.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.71-79
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• 2005

For the non-premixed interacting jet flames, it has been reported that if eight small nozzles are arranged along the circle of $40{\sim}72$ times the diameter of single jet, the flames are not extinguished even in 200m/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, ${\phi}$, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying S and ${\phi}$ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with ${\phi}$ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of fuel through the centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was different from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.