• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.305-309
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• 2008

This experimental study has been conducted to investigate the installation of the vertical flame holder shape in ramjet combustor, which affects on the film cooling effectiveness. All slot position, the film cooling effectiveness decreases because of the shear layer and high turbulence intensity between separated flows and coolant flows. When the flame holder is installed, film cooling effectiveness decreases abruptly on the beginning of the slot exit region due to the mixing effect. As the blowing rate increases, the film cooling effectiveness is increased for all cases due to the augmented momentum of injected coolant from the slot.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.95-101
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• 2004

Stability rating of KSR-III rocket engine is conducted based on stability rating tests in the course of development of KSR-III rocket engine. Rocket engine is approved to have combustion stabilization ability when it can suppress the external perturbation or pressure oscillation with finite amplitude and recover the original stable combustion. Rocket engine in flight may be perturbed by unexpectedly large-amplitude pressure oscillation and thus a designer should not only assure combustion stabilization ability of the engine but also quantify the stabilization capacity. For this, principal quantitative parameters and their evaluation are introduced. To verify dynamic stability of KSR-III rocket engine, six stability rating tests have been conducted. Based on these test results, such parameters are quantified and thereby, the stabilization capacity of KSR-III rocket engine is evaluated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.142-151
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• 2004

A method for the determination of concrete armor unit weights with hydraulic stability and structural stability may be formulated in this paper. The hydraulic stability is analyzed by using Hudson's formula, the structural stability is also studied by evaluation of maximum flexural tensile stresses in armor unit induced by the impact loads and by comparison of those with the tensile resistance strength directly. The applicable criteria for concrete armor units can be represented as a function of design wave heights with return period, armor weights, and tensile strengths for the practical uses. In addition, reliability analyses for two failure modes are carried out to take into account some uncertainties. Finally, a series system for two-failure mode analysis can be made up straightforwardly, by which the optimal weights of armor units can be estimated with the various relative breakages, given the specific target probability of failure under the concepts of reliability-based design method.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.3
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• pp.337-342
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• 2009

This paper concerns delay-range-dependent robust stability and stabilization for time-delay nonliner system via T-S fuzzy model approach. The time delay is assumed to be a time-varying continuous function belonging to a given range. On the basis of a novel Lyapunov-Krasovskii functional, which includes the information of the range, delay-range-dependent stability criteria are established in terms of linear matrix inequality. It is shown that the new criteria can provide less conservative results than some existing ones. Moreover, the stability criteria are also used to design the stabilizing state-feedback controllers. Numerical examples are given to demonstrate the applicability of the proposed approach.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.181-190
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• 2013

In this study, a total of 51 cases of hydraulic model tests has been conducted for various wave conditions and slope angles of breakwater to develop a stability formula for Rakuna-IV armoring a rubble-mound breakwater. The stability number of the formula is expressed as a function of relative damage, number of waves, structural slope, and surf similarity parameter. The stability formula is derived separately for plunging and surging waves, the greater of which is used. The transitional surf similarity parameter from plunging waves to surging waves is also presented. Lastly, to explain the stability of Rakuna-IV to the engineers who are familiar with the stability coefficient in the Hudson formula, the required weight of Rakuna-IV is calculated for varying significant wave height for typical plunging and surging wave conditions, which is then compared with those of the Hudson formula using several different stability coefficients.

• Korean Journal of Childcare and Education
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• v.9 no.5
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• pp.229-249
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• 2013

This study aims to analyze the effects of infants' attachment to their mother and child care teacher on their adaptation to child care. Data were collected in a purposive sample involving 100 infants and toddlers at age one and two, their mothers, and 36 teachers were analyzed with two-way ANOVA. The results showed that the effects of infants' attachment to their mother and teacher varied by subfactors of adaptation. 'Social Relationships' and 'Positive Emotion' were significantly different only among infants who established insecure attachment with their mother. Second, the level of 'Social Relationships' and 'Positive Emotion' were significantly high when teacher-infant attachment was secure among infants who established insecure attachment with their mother. Third, there were significant effects of mother-infant attachment on 'Aggressive Behavior' as infants who established insecure attachment with their mother showed a significantly higher level of 'Aggressive Behavior' than infants having secure attachment with their mother.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.271-280
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• 2002

A probabilistic approach to identify the effects of uncertainties of soil strength parameters on searching a critical slip surface with the lowest reliability is introduced. In general construction field, it is impossible for the engineer to always gather a variety of statistical information of soil strength parameters for which lots of laboratory and in-situ soil testing are required and to use it with enough statistical knowledge. Thus, in order that the engineer may easily understand the probabilistic concept for the slope stability analysis, this study proposes a combined procedure to incorporate the engineering probabilistic tools into the existing deterministic slope stability analysis methods. Using UTEXAS 3, a slope stability analysis computer program developed by U.S. Army Corps of Engineers (U.S. COE), this study provides the results of this probabilistic slope stability analysis in terms of probability of failure or reliability index. This probabilistic method f3r slope stability analysis appears to yield more comprehensive results of slope reliability than does existing deterministic methods with safety factors alone.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.537-544
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• 2009

This paper concerns analysis technique on determining of attitude control gain in the low frequency region using stability area. The stability area is defined by the D-Decomposition method, which was designed by Neimark. In this paper, it is introduced D-Decomposition method from reference paper and design attitude control gain of generic launch vehicle during first stage flight phase. For selecting PD control gain, it is considered the system parameter uncertainty about whole first-stage flight phase, represented the stability area boundary on each case. After deciding the PD control gain using stability area method, it is applied to launch vehicle linear model, and checking the stability margin requirement, frequency response characteristics.

• Applied Biological Chemistry
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• v.38 no.3
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• pp.254-258
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• 1995

Various artificial casein micelle systems were prepared from dephosphorylated whole casein, ${\beta}$- or ${\kappa}$-casein and their stabilities towards ethanol were assessed. Ethanol stability was lower in the micelle systems with dephesphorylated whole casein as compared to the artificial micelles prepared from native whole casein, and the stability decreased with the extent of dephosphorylation. The casein micelles with partially dephosphorylated ${\kappa}$-casein had a lower ethanol stability than those with native ${\kappa}$-casein. Ethanol stability of the micelle system with dephosphorylated ${\beta}$-casein decreased as the degree of dephosphorylation increased. Progressive dephosphorylation of caseins in skim milk system resulted in a decrease of the stability towards ethanol. The decrease was less than that in the system with dephosphorylated individual caseins. Increase in pH of the artificial casein micelle systems in the range of $6.3{\sim}7.2$ led to an increased ethanol stability manifesting that the presence of serine phosphates contributes significantly to the stability towards ethanol.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.74-74
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• 2000

낮은 유전상수(k$\leq$3)와 높은 열적안정성(>4$25^{\circ}C$)은 초고집적회로(ULSI)기술에서 RC 지연을 해결하기 위한 금속배선의 중간 절연층으로서의 2개의 가장 중요한 특성이다. 본 연구에서는 cyclohezane을 precursor로 사용하여 plasma enhanced chemical vapor deposition(PECVD)방법으로 유기박막을 성장시켰으며 낮은 유전상수와 높은 열적안정성을 동시에 확보하기 위하여 열적안정성은 좋지 않지만 유전상수가 낮은 박막(soft layer)위에 유전상수는 다소 높지만 열적안정성이 좋은 박막(hard layer)을 얇게 증착하여 hard layer/soft layer의 2층 구조를 형성하여서 구조적, 전기적 특성을 조사하였다. 유기박막은 5$0^{\circ}C$로 유지된 reactor 내부에서 argon(Ar) plasma에 의해 증착되었으며 platinum(Pt)기판과 silicon 기판위에 동시에 증착하였다. Pt 기판위에 증착한 시편으로 유전상수, I-V 등 전기적 특성을 측정하였고, silicon 기판위에 증착한 시편으로 열적안정성과 구조적 특성등을 분석하였다. 증착압력 0.2Torr에서 plasma power를 5W에서90W로 증가할 때 유전상수는 2.36에서 3.39로 증가하였으며 열적안정성은 90W에서 180W로 증가하였을 때 유전상수는 2.42에서 2.79로 증가하엿고 열적안정성은 모두30$0^{\circ}C$이하였다. 단일층 구조에서는 유전상수가 낮은 박막은 열적으로 불안정하고 열적 안정성이 좋은 박막은 유전상수가 다소 높은 문제가 나타났다. 이런 문제를 해결하기 위하여 2 Torr, 120W에서 증착한 유전상수가 2.55이고 열적으로 불안정한 박막을 soft layer로 5150 증착하고 그 위에 0.2Torr, 90W에서 증착한 유전상수가 3.39이고 열적으로 45$0^{\circ}C$까지 안정한 박막을 hard layer로 360 , 720 , 1440 증착하였다. 증착된 2층구조 박막의 유전상수는 각각 2.62, 2.68, 2.79이었으며 열적안정성 측정에서는 40$0^{\circ}C$까지 두께 감소가 보이지 않았다. 그러나 SEM 측정에서 열처리 후 표면이 거칠어지는 현상이 발견되었다.