• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.211-218
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• 2021

This paper addressed the problems of controlling the coupled pitch-roll motions in a marine vessel exposed to the regular waves in the longitudinal and transversal directions. Stabilization of the pitch and roll motions can be regarded as the essential task to ensure the safety of a ship's navigation. One of the important features in the pitch-roll motions is the resonance phenomena, which result in unexpected large responses in terms of pitch and roll modes in some specific conditions. Besides, owing to its inherent characteristics of coupled combination and nonlinearity of restoring terms, the vessel shows various dynamical behaviors according to the system parameters, especially in the pitch responses. Above all, it can be seen that suppression of pitch rate remains the most significant challenge to overcome for ship maneuvering safety studies. To secure the stable upright condition, a quasi-sliding mode control scheme is employed to reduce the undesirable pitch and roll responses as well as chattering elimination. The Lyapunov theory is adopted to guarantee the closed stability of the pitch-roll system. Numerical simulations demonstrate the effectiveness of the control scheme. Finally, the control goals of state convergences and chattering reduction are effectively realized through the proposed control synthesis.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.142-144
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• 2002

전력계통망의 부하 구성에서 발생되는 갑작스런 변화는 계통의 부하 중심 사이에 전력 동요를 일으키게 되는데 계전기가 설치된 점에서 전압, 전류, 임피던스, 유효. 무효전력의 측정되는 전기량은 위상각 ${\delta}$의 함수로 변화한다. 그러한 조건에서 거리계전기의 오동작을 방지하기 위해 계통동요 방지 장치가 자주 이용된다. 종래의 계통동요 방지 장치는 이러한 전기량의 변화로 응동 되었다. 그러나 이런 방법은 빠른 계통 동요에 대처하지 못하고, 고저항 지락 같은 고장에는 장시간지연을 피할 수 없게 된다. 본 논문에서는 계통 동요시 여러고장 식별을 위해 계전기에 직교웨이브렛(WT)을 도입하여 동요시 고장을 구별하는 방법을 제시한다.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.4
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• pp.39-45
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• 1980

내항성이 우수한 선형을 개발하기 위해서는 초기설계단계에서 이미 그 배의 해상에서의 거동을 예측할 수 있어야만 한다. 이 보고서에서는 임의의 입사각을 갖는 규칙파중을 항주하는 선박이 겪게 되는 동요중에서 횡동요, 수평동요 그리고 선수동요의 연성운동방정식의 해를 Tassi-Takaki가 수정한 스트립이론을 적용하여 해석하였다. 제15차 ITTC의 내항성 위원회의 보고서에서 발표된 콘테이너선형에 대한 결과와 똑같이 선형에 대해 본 프로그램을 사용하여 계산한 수평동요, 횡동요 그리고 선수동요의 운동응답을 비교하여 보았으며, 상당히 만족스러운 결과를 얻었다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.138-143
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• 2004

This experimental paper deals with the performance of tanks that are turned the active A.R.T(Anti-Rolling Tank) when the fluid transfers from wing tank to the opposite tank by the power developed by the automatic control system (INTERING Stabilizer), which was installed in the fishery training ship T/S. A - RA (G/T:990 tons) of Cheju National University. In this paper, the author has tested the performance of INTERING Stabilizer for the signals obtained by the inclinometer in irregular waves and compared with the results obtained in passive mode operation at stop and at various ship speeds. The performances of the system were confirmed the results as follows through the tests: 1. The average amplitude and significant roll (${\pi}$1/3) of the passive and active mode operations in the condition of stoped engine and underway were obtained 8.30$^{\circ}$, 4.37$^{\circ}$, 8.30$^{\circ}$, 4.37$^{\circ}$, and 5.01$^{\circ}$, 4.36$^{\circ}$, 5.50$^{\circ}$, 5.10$^{\circ}$, respectively. 2. The rates of performance of active mode operations were carried out during a sea trial in the condition of stop engine and underway resulted in 47.5%, 12.7%, respectively, therefore the active mode operation estimated to be improved more than passive mode operation. 3. Active - A.R.T by INTERING Stabilizer didn't affect the amplitude of pitching.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.107-115
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• 1997

비성형 동력학계로 모델링된 부유수송체의 동적응답을 조사하고 그 운동의 안정성을 해석하였다. 종동요 모우드의 고유주파수가 횡동요 모우드의 고유주파수의 두배가 되는, 즉, 2:1 내부공진 혹은 자기계수공진인 조건하에서, 이부유수송체는 한 운동 모우드의 직접가진에 의해 간접가진된 다른 모우드가 대진폭 응답을 보일 수 있음을 밝혔다. 또항, 종동요 모우드의 감쇠력은 비교적 넓은 범위의 운동에 대해 선형적임에 반해, 횡동요 모우드의 감쇠력은 점성의 영향이 대단히 커서 비선형성이 대단히 강한 것으로 알려져 왔다. 이 문제를 수학적으로 모델링하기 위하여, 종동요 모우드의 운동방정식에는 선형및 제곱형의 합의 형태인 감쇠력 모형을 사용하였다. 다중척도법을 사용하여 이 두가지 운동 모우드의 주기적 응답및 그의 안정성에 미치는 제곱형 비선형 횡동요 감쇠력의 영향을 밝혔다. 조우주기가 횡동요 모우드의 고유주기와 근사한 경우에 대하여 이 비선형계의 응답을 구하고 주파수-응답 곡선으로 나타내었다.

• Korean Journal of Childcare and Education
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• v.8 no.5
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• pp.253-274
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• 2012

The purpose of this study is to make establishing criteria for Korea traditional nursery rhyme suitable for children and apply them effectively in early child education. The researchers of this study are firstly concerned with establishing criteria for Korean traditional nursery rhymes suitable for children. Secondly, they are concerned with establishing Korean traditional nursery rhymes suitable for children which are selected by following the established criteria. A Delphi survey was performed with early childhood educators and 30 related professionals to establish criteria for Korean traditional nursery rhymes suitable for children. The SPSS 12.0 program was used to calculate the standard deviation and average. Through this process the final seven criteria selected are: 'traditional play spaces and fun of play language is showed', 'lifestyles and emotions of children in the past is expressed', 'easy to understand story', 'the content is interesting', 'assisting in the development of children', 'easy to sing melody', and 'simple and repetitive in rhythm'. And 112 songs appropriate to the children were selected based on these criteria. The lyrics of the songs mainly expressed 'the joy of play.' it means songs need to combine with play to succeed to the next generation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.5
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• pp.595-602
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• 2024

This paper analyzes serviceability guidelines and index related to the motion of floating structures concerning human comfort. The guidelines for the motion of floating structures regarding human comfort must meet requirements such as including frequency range of floating structure and providing index for vertical direction, which is a major component of human discomfort. Therefore, ISO 2631-1:1997 was found to be applicable. The evaluation of serviceability of the floating structure showed that the frequency-weighted RMS acceleration, due to the characteristics of frequency weighting function, is significantly influenced by the period of the floating structure. Additionally, the frequency-weighted RMS acceleration presented lower values compared to the general RMS acceleration. These results are expected to contribute to the establishment of reasonable guidelines for human activities to the motion of floating structures.

• Journal of the Korean Data and Information Science Society
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• v.20 no.3
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• pp.527-539
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• 2009

The purpose of this study was to evaluate the influence of ankle joint mobilization on equilibrium ability of supinated foot. Both Joint mobilization group(n=20) and control group(n=20) were measured an equilibrium ability by Balance performance monitor at pre-test, post-test in 2 weeks, post-test in 4 weeks and follow-up test in 2 weeks. The sway area, sway path length and sway maximum velocity of the joint mobilization group were significantly reduced among the experimental period (p<.05). The reduction of sway area, sway path length and sway maximum velocity were significantly different between the joint mobilization group and the control group at in 2 weeks, 4 weeks and follow-up test(p<.05). In conclusion, we were found that ankle joint mobilization could reduce sway area, sway path length and sway max velocity and improve a balance for the individuals with supinated foot.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.299-304
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• 2021

The purpose of the study was to examine the repertoires of children's songs that early childhood teachers used for new-song-learning activities and to analyze the characteristics of frequently used songs. 120 early childhood teachers in South Korea were recruited to gather the repertoires of children's songs during January and February, 2021. And then, 20 most frequently used songs were selected and analyzed in genre, theme, tonality, meter, musical form, and tone range. SPSS ver. 25.0 was used to calculate the means, standard deviations, frequencies, and percentages. As results, the most frequently used five songs were 'Autumn Road,' 'Winter Wind,' 'Scarecrow Man,' 'Watermelon Party,' and 'Cosmos.' The results of analyses of 20 frequently used songs revealed that the creative songs as genre, seasons as theme, C major as tonality, 4/4 as meter, and ternary form as musical form, and c' - c" along with c' - d" as tone range were the mostly used.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.3
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• pp.116-127
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• 2024

The floating pier is a representative type of floating structure installed along the coast, primarily used as a facility for berthing and mooring ships. Additionally, ongoing attempts have been made to utilize it for various purposes, such as wave control and wave energy conversion structures. In this study, we experimentally investigated the reflection and motion characteristics of a pile-moored floating pier, which allows heave and limited roll motion, with respect to the presence of perforated structures and the attachment of submerged plates. The hydraulic experiment results indicated that the reflection and motion characteristics of the pile-moored floating pier were significantly influenced by the presence and installation depth of the submerged plates, rather than the presence of perforated structures on the floating body. In particular, the installation of submerged plates increased the reflection coefficient in short-period waves and effectively reduced the heave and roll motions of the floating body.