• Structural Engineering and Mechanics
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• 제51권4호
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• pp.643-650
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• 2014

A chaotic vibration isolation system is designed according to the chaotic vibration theory in this paper. The strong nonlinearity is generated by the system. Line spectra in the radiated noise maybe easily detected caused by marine vessels. It is Important to reduce the line spectra by improving the acoustic stealth of marine vessels. A multi-degree-freedom (MDF) nonlinear vibration isolation system (NVIS) system is setup by the experiment and finite element method. The model is established with finite element method. The results show that the behavior of the device gradually varies from period bifurcation into chaotic state and the line spectrum is changed from single spectral structure into broadband spectral structure. It is concluded that chaotic vibration isolation is preferable contrasted on line spectra isolation.

• 한국항공우주학회지
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• 제35권12호
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• pp.1082-1088
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• 2007

고속 및 고효율의 해양 수송수단에 대한 필요성이 점차 증가되면서 위그선(WIG: Wing in Ground effect)이 차세대 수송수단으로 관심이 집중되고 있다. 이러한 고속 해양 수송선의 구조설계 시 수면에 대한 충격하중은 중요하게 고려되어야 할 하중요소 중의 하나이며 착수하중에 의한 동적거동은 손상을 초래하는 중요한 요소이다. 본 연구에서는 위그선 착수 시 수면 충격하중에 대한 수치해석을 통해 선체의 동적거동을 평가하였다. 착수환경에서의 수면충격하중을 ALE (Arbitrary Lagrangian-Eulerian) 유한요소법을 적용하여 해석을 수행하였으며 3차원 쉘요소를 적용한 전기체 모델을 개발하여 위그선의 착수환경에서 선체의 동적거동을 모사하였다. 착수환경은 정상 착수조건과 측풍에 의한 비정상 착수조건 두 가지를 고려하여 해석을 수행하였으며 이러한 착수환경이 위그선 구조의 정적 구조 안정성에 미치는 영향을 평가하였다

• 한국어병학회지
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• 제28권2호
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• pp.99-107
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• 2015

Despite its economic importance as an aquaculture species, the molecular and genetic information regarding physiologically important elements in rock bream (Oplegnathus fasciatus) is not completely understood. Rab proteins play a vital role in cellular mechanisms and immunity as one of the key regulators of membrane trafficking. In this investigation, a Rab gene, named as RbRab-5C-like, was identified from Oplegnathus fasciatus. RbRab-5C-like protein exhibited high homology with Rab proteins of other species and possessed signature characteristics of Rab proteins with four conserved cysteine residues. Phylogenetic analysis showed that RbRab-5C-like clustered with other fish counterparts. The RbRab-5C-like genomic sequence possesses six exons and five introns. Transcriptional analysis revealed that RbRab-5C-like was ubiquitously expressed in all examined tissues with the highest expression occurring in the liver. While the structural and homologic characteristics of RbRab-5C-like suggest a strong conservation of this element in different species, its mRNA distribution implies a wide range of biological significance in rock bream.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.19-27
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• 2009

Globally, customer appreciation and demand for quieter products has driven noise control engineers to develop efficient and quieter products in a relatively short time. In the vehicles and ship industry, noise has become an important attribute because of the competitive market and increasing customer awareness. Noise reduction is often achieved through structural modifications by typical approaches. In the present paper, author describes a fundamental study on optimum design of curvature. Bezier curve. and rib attachment to reduce noise from simple panel using a genetic algorithm(GA). The acoustic optimization procedure employed p-FEM for structural analysis, the Rayleigh integral method for acoustic analysis and the GA for searching optimum design. In the optimization procedure. the objective function to be minimized is the average sound power radiated from an objective structure over a given frequency range $0{\sim}300$ Hz.

• Journal of Advanced Marine Engineering and Technology
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• 제29권2호
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• pp.202-208
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• 2005

Stress and fatigue life analyses are performed to enhance a fatigue life of a heating drum of the roller press for medium density fiberboard. The finite element method employing the submodel is used to analyze stress concentration in the journal of the heating drum. The fatigue life is evaluated by the stress-life theory. Two modified designs of the journal are suggested and evaluated to reduce the maximum stress and to increase the fatigue life Their structural reliabilities are verified in terms of the yield strength and the design life.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.160-168
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• 2020

Depending on the water depth and composition of seabed, there exist different alternatives for the wind turbine supporting structures. Among several types of the structures, the monopile foundation is the dominant solution for support structure, accounting for over 80% of the offshore wind turbines in Europe. To develop the monopile foundation suitable for domestic ocean environment, a basic design of a transition piece was carried out. This paper presents the design procedure of a flange connected transition piece and results of the structural safety assessment.

• Ocean Systems Engineering
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• 제5권4호
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• pp.301-318
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• 2015

The present investigations introduce the shell-finite element discretization for the dynamics of slender marine pipelines. A long catenary pipeline, corresponding to a particular Steel Catenary Riser (SCR), is investigated under long-standing cyclic loading. The long structure is divided into smaller tubular parts which are discretized with 8-node planar shell elements. The transient analysis of each part is carried out by the implicit time integration scheme, within a Finite Elements (FE) solver. The time varying external loads and boundary conditions on each part are the results of a prior solution of an integrated line-dynamics model. The celebrated FE approximation can produce a more detailed stress distribution along the structural surface than the simplistic "line-dynamics" approach.

• 해양환경안전학회지
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• 제19권3호
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• pp.290-301
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• 2013

The docking analysis of a global ship structure is requested to evaluate its structural safety against the reaction forces at supports during docking works inside a dry dock. That problem becomes more important recently as the size of ships is getting larger and larger. The docking supports are appropriately arranged in a dock to avoid their excessive reaction forces which primarily cause the structural damages in docking a ship and, up to now, the structural safety has been assessed against the support arrangement by the finite element analysis (FEA) of a global ship structure. However, it is complicated to establish the finite element model of the ship in the current structural design environment of a shipyard and it takes over a month to finish the work. This paper investigates a simple and fast approach to carry out a ship docking analysis by a simplified grillage model and to assign the docking supports position on the model. The grillage analysis was considered from the motivation that only the reaction forces at supports are sufficient to assess their arrangement. Since the simplified grillage model of the ship cannot guarantee its accuracy quantitatively, modeling strategies are proposed to improve the accuracy. In this paper, comparisons between the proposed approach and three-dimensional FEA for typical types of ships show that the results from the present grillage model have reasonably good agreement with the FEA model. Finally, an integrated program developed for docking supports planning and its evaluation by the proposed approach is briefly described.

• 동력기계공학회지
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• 제14권6호
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• pp.67-74
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• 2010

Many tanks are installed in ship and marine structures. They are often in contact with inner or outer fluid, like ballast, fuel and cargo tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine and propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tanks. Many authors have studied vibration of cylindrical and rectangular tanks containing fluid. Few research on dynamic interaction among tank walls through fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass have to be considered. In the previous report, A numerical tool of vibration analysis of a 3-dimensional tank is developed by using finite element method for plates and boundary element method for fluid region. In this paper, the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region and mode characteristics in accordance with changing breadth of the plates are investigated numerically and discussed.

• Structural Engineering and Mechanics
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• 제60권5호
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• pp.851-873
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• 2016

Helidecks are vital structures that act as a last exit in an emergency. They transport people and goods to and from ships and offshore plants. When designing the structure of a helideck, it is necessary to comply with loading conditions and design parameters specified in existing professional design standards and regulations. In the present study, finite element analysis (FEA) was conducted with regard to a steel helideck mounted on the upper deck of a ship considering the emergency landing of the helicopter. The superstructure and substructure were designed, and the influence of various design parameters was analyzed on the basis of the FEA results.