• 한국자동차공학회논문집
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• 제14권1호
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• pp.167-175
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• 2006

Directional stability is important performance in vehicle and tire design. The current methods to analyze this is generally based on linear concept. Using the existing concept, it cannot realistically explain the subjective assessment at all because it is hard to practically represent the nonlinear behaviour of a complex vehicle system in reality. In this paper, new method to analyze directional stability is introduced. At first, directional stability of vehicle is categorized into yaw, rear axle, and roll stability. In order to objectify these items, driver perceptual parameters based on subjective assessment are used. Using the perceptual parameters, it can successfully explain the transient maneuver of vehicle and extract objective parameters for directional stability. Finally, these objective parameters are successfully validated through two handling tests, lane change and severe lane change. The correlation results show that there exists a good correlation between subjective assessment and the proposed objective parameters.

• 수산해양기술연구
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• 제40권1호
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• pp.65-72
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• 2004

This paper deals with an experimental study on the dynamical characteristics of ship motion during trawling job on the real sea. The experiments were carried out on the small stern trawler, and roll and pitch motion of the ship according to the wave directions were simultaneously recorded by P/C in the same sea conditions. From these data, the statistical properties and power spectra were obtained, and then the analysis of ship motion in trwal job was made. As a result, it was found that the pitch motions in trwal job were displayed low amplitudes on the whole, but the rolling motions were displayed high amplitudes relatively, and very high value on the beam and quartering sea especially. Also, the trial ship has a high extinction coefficient in the roll motion, compared with the rule of stability, but when wave height takes 2.5m over, it can induce the safety of ship to scare occasionally. Therefore, a usefull countermeasure for the safety of ship has to be made adequately.

• Structural Engineering and Mechanics
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• 제43권5호
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• pp.679-690
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• 2012

A new concept sea-floating port called mobile harbor has been introduced, in order to resolve the limitation of current above-ground port facilities against the continuous growth of worldwide marine transportation. One of important subjects in the design of a mobile harbor is to secure the dynamic stability against wave-induced excitation, because a relatively large-scale heavy crane system installed at the top of mobile harbor should load/unload containers at sea under the sea state up to level 3. In this context, this paper addresses a two-step sequential analytical-numerical method for analyzing the structural dynamic response of the mobile harbor crane system to the wave-induced rolling excitation. The rigid ship motion of mobile harbor by wave is analytically solved, and the flexible dynamic response of the crane system by the rigid ship motion is analyzed by the finite element method. The hydrodynamic effect between sea water and mobile harbor is reflected by means of the added moment of inertia.

• Ocean Systems Engineering
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• 제4권2호
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• pp.117-136
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• 2014

The increased interest in the design of energy efficient ships post IMO regulation on enforcing EEDI has encouraged researchers to reevaluate the numerical methods in predicting important hull design parameters. The prediction of added resistance and stability of ships in the rough sea environment dictates selection of ship hulls. A 3D panel method based on Green function is developed for vessel motion prediction. The effects of parametric instability are also investigated using the Volterra series approach to model the hydrostatic variation due to ship motions. The added resistance is calculated using the near field pressure integration method.

• 대한화학회지
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• 제16권3호
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• pp.193-199
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• 1972

국산 벤토나이트를 분자량이 큰 imidazolines과 반응시켜 벤톤을 만들었으며 벤토나이트의 양이온 교환율이 100meq/100g이상이 됨을 알았다. 제조한 벤톤은 윤활유에 분산시키고 three-roll mill로 milling 한 후 그리이스를 만들었다. 이들 그리이스의 주도 (microscale로), 정상상태에서의 산화 안정도, 내수성, 및 내 마모성은 ASTM방법에 의하여 시험하였고 매우 좋은 실험결과를 얻었다.

• 소음진동
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• 제7권2호
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• pp.239-246
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• 1997

This paper presents an active suspension control algorithm to improve the suspension performance trade-offs between riding comfort and handling stability. In this paper, a hybrid control scheme is proposed, the idea of which is that sliding mode control is used for nonlinear hydraulic system and the skyhook control is applied to control the vehicle behavior. The parameter variations in hydraulic system are considered for the robust controller design. The performance of the proposed control method is evaluated by simulation and experiments based on a half car roll model which can reveal both heave and roll behavior.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.733-736
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• 2007

We have proposed novel bonding technique of substrates for developing the flexible LCD with high quality. The gel type mixture of agarose and UV curable epoxy developed to obtain tight bonding ability and enhanced electro-optical characteristic simultaneously. This technique can be used to roll-to-roll process for fabricating the flexible LCDs.

• 해양환경안전학회지
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• 제28권7호
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• pp.1244-1251
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• 2022

지난 10년간 선박의 횡동요 복원력 상실에 의한 해양사고가 지속해서 증가하고 있어, 횡동요 운동을 효과적으로 줄일 수 있는 장치가 필요한 실정이다. 횡동요 감쇄 탱크는 단순한 설치만으로 횡동요 저감을 가져오는 대표적인 수동형 제어장치로 그 장점이 널리 알려져 있다. 따라서 본 연구에서는 U-튜브형 횡동요 감쇄 탱크의 수치해석 기법을 개발하고자 한다. 특히, 해석기법의 검증을 위해 자유수면 높이를 실험을 통해 계측하였다. 수치해석기법은 메쉬 의존성, 난류모델 (k-𝜖, k-𝜔, Reynolds Stress Model), 시간 간격 크기 및 반복횟수 등의 영향을 비교하여 개발하였다. 최종적으로 개발된 해석기법은 Realizable k-𝜖이 난류 모델에 10-2s 수준의 시간 간격 크기와 15회의 반복횟수를 적용하였다. 2가지의 U-튜브형 감쇄 탱크의 조건에서 계측된 자유수면 높이를 이용하여 개발된 해석기법을 검증하였다. 본 연구의 수치해석은 RANS 기반 상용 해석 Solver인 STAR-CCM+ (ver. 17.02)을 이용하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.478-492
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• 2021

In this study, hull dimensions of an FPSO were optimized to maximize its operability at Brazil field. In contrast with the previous works which have used simplified models to evaluate some indicators related to stability and hydrodynamic performances of FPSOs for its own optimal design, we developed a generic hull and compartment modeler and sophisticated stability and hydrodynamic calculation modules. With the aid of the developed tools, the hull optimization was performed with initial dimensions of an FPSO originally designed for west Africa field. The optimization results indicated the relative importance of hydrodynamic performances compared with stability performances for the FPSO hull dimensioning by showing that there were 3 active constraints related to them, which were the natural periods of heave and roll and the maximum pitch angle under 1-year return period waves at full load condition. To the author's knowledge, this study is the first attempt to combine altogether the hull and compartment modeling and full set of stability and hydrodynamic calculations precisely to optimize an FPSO's hull dimensions within 30 min. Also, it is worthwhile to mention that the developed methods are generic enough to be applied to all types of ship-shaped offshore platforms.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2023년도 추계학술대회
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• pp.242-243
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• 2023

소형선박 운항은 해양 환경 및 기상조건에 따라 선박이 파도에 대해 다양한 방향으로 입사각을 가지게 된다. 특히 소형선박의 경우 입사각에 따라 운동의 특성이 크게 달라지며 이는 안정성과 밀접한 관계가 있다. 본 연구는 불규칙파에서 소형선박이 운항 중일 때 입사각에 따른 운동특성을 시뮬레이션과 실험을 통하여 비교분석 하였다. 불규칙파는 실제 소형선박이 운항하는 연안의 파랑 데이터를 바탕으로 만들었다. 선속에 따라 선박의 횡요동요를 분석하였으며 선속이 느릴 때에는 선수사파에서 가장 큰 횡요동요가 발생하였으며 선속이 빨라짐에 따라 선수사파의 횡요동요는 감소하나 선미사파의 횡요동요가 커지는 것을 알 수 있다. 따라서 선속에 따른 입사파 각도를 변경하여 선박의 운항할 경우 선박의 안정성과 운항 효율성을 개선할 수 있을 것이다.